4-hydroxy-2-nonenal and Insulin-Resistance

Since the landmark discovery of α,β-unsaturated 4-hydroxyalkenals by Esterbauer and colleagues most studies have addressed the consequences of the tendency of these lipid peroxidation products to form covalent adducts with macromolecules and modify cellular functions. Many studies describe detrimental and cytotoxic effects of 4-hydroxy-2E-nonenal (4-HNE) in myriad tissues and organs and many pathologies. Other studies similarly assigned unfavorable effects to 4-hydroxy-2E-hexenal (4-HHE) and 4-hydroxy-2E,6Z-dodecadienal (4-HDDE). Nutrient overload (e.g., hyperglycemia, hyperlipidemia) modifies lipid metabolism in cells and promotes lipid peroxidation and the generation of α,β-unsaturated 4-hydroxyalkenals. Advances glycation- and lipoxidation end products (AGEs and ALEs) have been associated with the development of insulin resistance and pancreatic beta cell dysfunction and the etiology of type 2 diabetes and its peripheral complications. Less acknowledged are genuine signaling properties of 4-hydroxyalkenals in hormetic processes that provide defense against the consequences of nutrient overload. This review addresses recent findings on such lipohormetic mechanisms that are associated with lipid peroxidation in pancreatic beta cells. This article is part of a Special Issue entitled SI: LIPID OXIDATION PRODUCTS, edited by Giuseppe Poli.

Topics: Aldehydes; Animals; Diabetes Mellitus, Type 2; Diabetic Neuropathies; Glycation End Products, Advanced; Hormesis; Humans; Hyperglycemia; Hyperlipidemias; Insulin Resistance; Insulin-Secreting Cells; Lipid Peroxidation; Oxidative Stress; Phospholipases A2

Skeletal muscle is a major tissue that utilizes blood glucose. A single bout of exercise improves glucose uptake in skeletal muscle through insulin-dependent and insulin-independent signal transduction mechanisms. However, glucose utilization is decreased in muscle damage induced by acute, unaccustomed, or eccentric exercise. The decrease in glucose utilization is caused by decreased insulin-stimulated glucose uptake in damaged muscles with inhibition of the membrane translocation of glucose transporter 4 through phosphatidyl 3-kinase/Akt signaling. In addition to inflammatory cytokines, reactive oxygen species including 4-hydroxy-2-nonenal and peroxynitrate can induce degradation or inactivation of signaling proteins through posttranslational modification, thereby resulting in a disturbance in insulin signal transduction. In contrast, treatment with factors that attenuate oxidative stress in damaged muscle suppresses the impairment of insulin sensitivity. Muscle-damaging exercise may thus lead to decreased endurance capacity and muscle fatigue in exercise, and it may decrease the efficiency of exercise therapy for metabolic improvement.

Topics: Aldehydes; Biological Transport, Active; Exercise; Glucose; Glucose Transporter Type 4; Humans; Insulin; Insulin Resistance; Muscle Fatigue; Muscle, Skeletal; Oxidative Stress; Phosphatidylinositol 3-Kinases; Physical Endurance; Proto-Oncogene Proteins c-akt; Signal Transduction

The role of zinc (Zn) in hepatic steatosis of patients with HCV-related chronic liver disease (CLD-C) remains uncertain, although persistent HCV infection often evokes hepatic steatosis. The primary purpose of this study was to elucidate the contribution of Zn deficiency to hepatic steatosis in patients with CLD-C. Fifty nondiabetic patients with CLD-C were enrolled. Hepatic 4-hydroxy-2-nonenal (4-HNE) expression was examined using an immunohistochemical procedure as a marker for lipid peroxidation. Serum ferritin levels were assessed for iron overload. Insulin resistance was evaluated using the values of the homeostasis model for assessment of insulin resistance (HOMA-IR). The severity of hepatic steatosis was graded on the classification system proposed by Brunt and colleagues. Serum Zn levels were inversely correlated with serum ferritin levels in the patients with CLD-C (r = -0.382, p = 0.0062). Serum ferritin levels were strongly associated with the HOMA-IR values (r = 0.476, p = 0.0005). Therefore, Zn deficiency resulted in insulin resistance through iron overload. Moreover, serum Zn levels were significantly decreased in proportion to the level of hepatic 4-HNE expression, which was enhanced as hepatic steatosis developed. Then, Zn deficiency eventually seemed to exacerbate hepatic steatosis by way of an increase in lipid peroxidation. However, the serum Zn levels were not associated with either loads of HCV-RNA or HCV genotypes. These data suggest that, in patients with CLD-C, Zn deficiency promotes insulin resistance by exacerbating iron overload in the liver and induces hepatic steatosis by facilitating lipid peroxidation.

Topics: Adult; Aged; Aldehydes; Fatty Liver; Female; Ferritins; Hepatitis C, Chronic; Humans; Insulin Resistance; Lipid Peroxidation; Liver; Male; Middle Aged; Zinc

The relationships among skeletal muscle lipid peroxidation, intramyocellular lipid content (IMCL), and insulin sensitivity were evaluated in nine insulin-sensitive (IS), 13 insulin-resistant (IR), and 10 adults with type 2 diabetes (T2DM).. Insulin sensitivity was assessed by hyperinsulinemic-euglycemic clamp [glucose disposal rate (GDR)]. Lipid peroxidation was assessed by 4-hydroxynonenal (HNE)-protein adducts and general oxidative stress by protein carbonyl content. All patients were sedentary.. Protein-HNE adducts were elevated 1.6-fold in T2DM compared with IS adults, whereas IR showed intermediate levels of HNE-modified proteins. Protein-HNE adducts correlated with GDR, waist circumference, and body mass index. IMCL was increased by 4.0- and 1.9-fold in T2DM and IR patients, respectively, compared with IS, and was correlated with GDR and waist circumference but not BMI. Protein carbonyls were not different among groups and did not correlate with any of the measured variables. Correlations were detected between IMCL and protein-HNE.. Our data show for the first time that skeletal muscle protein-HNE adducts are related to the severity of insulin resistance in sedentary adults. These results suggest that muscle lipid peroxidation could be involved in the development of insulin resistance.

Topics: Adiposity; Adult; Aldehydes; Blood Glucose; Body Mass Index; Diabetes Mellitus, Type 2; Female; Glucose Clamp Technique; Humans; Insulin Resistance; Lipid Peroxidation; Male; Middle Aged; Muscle, Skeletal; Young Adult

Metabolic syndrome (MetS) is a predictor of cardiovascular diseases, commonly associated with oxidative stress and inflammation. However, the pathogenic mechanisms are not yet fully elucidated. The aim of the study is to evaluate the oxidative status and inflammation in the heart of obese Zucker rats (OZRs) and lean Zucker rats (LZRs) at different ages. Morphological and morphometric analyses were performed in the heart. To study the oxidative status, the malondialdehyde (MDA), 4-hydroxynonenal (4-HNE), protein oxidation, and antioxidant enzymes were measured in plasma and heart. To elucidate the inflammatory markers involved, immunohistochemistry and Western blot were performed for cellular adhesion molecules and proinflammatory cytokines. OZRs were characterized by hypertension, hyperlipidemia, hyperglycemia, and insulin resistance. The obesity increased MDA and decreased the activities of superoxide dismutase (SOD) in plasma as well as in the heart, associated with cardiomyocytes hypertrophy. OxyBlot in plasma and in heart showed an increase of oxidativestate proteins in OZRs. Vascular cell adhesion molecule-1, interleukin-6, and tumor necrosis factor-α expressions in OZRs were higher than those of LZRs. However, these processes did not induce apoptosis or necrosis of cardiomyocytes. Thus, MetS induces the lipid peroxidation and decreased antioxidant defense that leads to heart tissue changes and coronary inflammation.

Topics: Aldehydes; Animals; Antioxidants; Cardiovascular System; Cytokines; Disease Models, Animal; Heart; Hyperglycemia; Hyperlipidemias; Hypertension; Inflammation; Insulin Resistance; Male; Malondialdehyde; Metabolic Syndrome; Obesity; Oxidative Stress; Rats; Rats, Zucker; Superoxide Dismutase

The prevalence of obesity is increasing worldwide. Oxidative stress plays an etiological role in a variety of obesity-related metabolic disorders. 4-hydroxynonenal (4-HNE) is the most abundant and reactive aldehydic product derived from the peroxidation of n-6 polyunsaturated fatty acids with diverse biological effects that are not well detailed. Obesity is associated with decreased plasma adiponectin concentrations and increased production of lipid peroxidation products, including 4-HNE, in adipose tissue. There may be some association between the level of adipokines and 4-HNE.. To analyze the associations between 4-HNE and classical adipokines, namely, adiponectin and leptin in a Chinese population, the plasma 4-HNE, adiponectin and leptin levels of 160 non-diabetic obese (NDO) patients and 160 healthy subjects were determined by ELISA, and their associations with adiposity, glucose, lipid profiles, insulin secretion and insulin sensitivity were studied.. Plasma 4-HNE levels were significantly increased in patients with NDO compared with healthy controls (p < 0.01). 4-HNE was negatively correlated with adiponectin and positively correlated with leptin. The plasma levels of 4-HNE were significantly correlated to several parameters involved in body mass index (BMI) and insulin resistance (IR). The 4-HNE levels were positively correlated with BMI and negatively correlated with insulin sensitivity.. We conclude that 4-HNE is associated with the secretion of adiponectin and leptin and is correlated with IR in NDO humans. These findings indicate a pro-inflammatory role of 4-HNE in NDO patients, which supports the potential role of 4-HNE in the development of obesity-related disorders.

Topics: Adipokines; Adiponectin; Adult; Aged; Aldehydes; Asian People; Biomarkers; China; Female; Humans; Insulin Resistance; Leptin; Male; Middle Aged; Obesity

Increased adipose production of 4-hydroxynonenal (4-HNE), a bioreactive aldehyde, directly correlates with obesity and insulin resistance. The aim of this study was to elucidate the impact of 4-HNE in mediating adipocyte differentiation and function in two metabolically distinct obese groups; the insulin sensitive (IS) and the insulin resistant (IR).. Subcutaneous (SC) adipose tissues were obtained from eighteen clinically well characterized obese premenopausal women undergoing weight reduction surgery. Cellular distribution of 4-HNE in the form of protein adducts was determined by immunohistochemistry in addition to its effect on oxidative stress, cell growth, adipogenic capacity and insulin signaling in preadipocytes derived from the IS and IR participants.. 4-HNE was detected in the SC adipose tissue in different cell types with the highest level detected in adipocytes and blood vessels. Short and long-term in vitro treatment of SC preadipocytes with 4-HNE caused inhibition of their growth and increased production of reactive oxygen species (ROS) and antioxidant enzymes. Repeated 4-HNE treatment led to a greater reduction in the adipogenic capacity of preadipocytes from IS subjects compared to IR and caused dephosphorylation of IRS-1 and p70S6K while activating GSK3α/β and BAD, triggering an IR phenotype.. These data suggest that 4-HNE-induced oxidative stress plays a role in the regulation of preadipocyte growth, differentiation and insulin signaling and may therefore contribute to adipose tissue metabolic dysfunction associated with insulin resistance.

Topics: Adipocytes; Adipogenesis; Adult; Aldehydes; Animals; Blood Vessels; Cell Proliferation; Female; Humans; Insulin Resistance; Mice; Obesity; Oxidative Stress; Reactive Oxygen Species

The aim of the current study was to evaluate the possible protective effect of allopurinol (Allo) on experimentally induced insulin resistance (IR) and vascular complications. Rats were divided into four groups: control, IR, allopurinol-treated IR (IR-Allo), and allopurinol-treated control (Allo). IR was induced by adding fructose and high fat, high salt diet for 12 weeks. The results showed that Allo has alleviated the increased level of TNF-α and the systolic, diastolic, mean, and notch pressure observed in IR with no change in pulse pressure. In addition, Allo decreased the heart rate in the treated group compared to IR rats. On the other hand, it has no effect on increased levels of insulin, glucose, fructosamine, or body weight gain compared to IR group, while it increased significantly the insulin level and body weight without hyperglycemia in the control group. Moreover, Allo treatment ameliorated increased level of 4HNE, Ang II, and Ang R1. In conclusion, the results of the current study show that Allo has a protective effect on vascular complications of IR which may be attributed to the effect of Allo on decreasing the TNF-α, 4HNE, Ang II, and Ang R1 as well as increasing the level of insulin secretion.

Topics: Aldehydes; Allopurinol; Animals; Blood Pressure; Body Weight; Cardiovascular Diseases; Diet, High-Fat; Enzyme Inhibitors; Fructose; Heart Rate; Insulin Resistance; Male; Rats; Rats, Wistar; Receptor, Angiotensin, Type 2; Sodium Chloride, Dietary; Tumor Necrosis Factor-alpha

General overnutrition but also a diet rich in certain macronutrients, age, insulin resistance and an impaired intestinal barrier function may be critical factors in the development of nonalcoholic fatty liver disease (NAFLD). Here the effect of chronic intake of diets rich in different macronutrients, i.e. fructose and/or fat on liver status in mice, was studied over time. C57BL/6J mice were fed plain water, 30% fructose solution, a high-fat diet or a combination of both for 8 and 16 weeks. Indices of liver damage, toll-like receptor 4 (TLR-4) signaling cascade, macrophage polarization and insulin resistance in the liver and intestinal barrier function were analyzed. Chronic exposure to a diet rich in fructose and/or fat was associated with the development of hepatic steatosis that progressed with time to steatohepatitis in mice fed a combination of macronutrients. The development of NAFLD was also associated with a marked reduction of the mRNA expression of insulin receptor, whereas hepatic expressions of TLR-4, myeloid differentiation primary response gene 88 and markers of M1 polarization of macrophages were induced in comparison to controls. Bacterial endotoxin levels in portal plasma were found to be increased while levels of the tight junction protein occludin and zonula occludens 1 were found to be significantly lower in the duodenum of all treated groups after 8 and 16 weeks. Our data suggest that chronic intake of fructose and/or fat may lead to the development of NAFLD over time and that this is associated with an increased translocation of bacterial endotoxin.

Topics: Aldehydes; Animals; Body Weight; Diet, High-Fat; Endotoxins; Energy Intake; Female; Fructose; Insulin Resistance; Intestinal Mucosa; Intestines; Liver; Mice, Inbred C57BL; Myeloid Differentiation Factor 88; Nitric Oxide Synthase Type II; Non-alcoholic Fatty Liver Disease; Tight Junction Proteins; Toll-Like Receptor 4

The lipid peroxidation end-product and oxidant 4-hydroxynonenal (4-HNE) impairs cell function. However, the impact of 4-HNE on the glucose transport system in mammalian slow-twitch skeletal muscle is not known.. We assessed the effects of 4-HNE on insulin signalling and glucose transport activity in slow-twitch muscle by incubating soleus strips from lean Zucker rats with 4-HNE (50 µM) in the absence or presence of insulin (5 mU/ml) for up to 6 hr.. Insulin-stimulated glucose transport activity was significantly (p<0.05) decreased by 4-HNE at 2 hr. AS160 Thr(642) phosphorylation was decreased at 2 hr, whereas Akt Ser473 phosphorylation and IRS-1 protein expression were not substantially changed until 4 hr. IRS-2 protein expression was slightly decreased only at 6 hr.. The lipid peroxidation end-product and oxidant 4-HNE induces insulin resistance of glucose transport activity in rat slow-twitch skeletal muscle, initially associated with impaired phosphorylation of AS160.

Topics: Aldehydes; Animals; Biological Transport; Female; Gene Expression Regulation; Glucose; GTPase-Activating Proteins; In Vitro Techniques; Insulin Receptor Substrate Proteins; Insulin Resistance; Lipid Peroxidation; Muscle, Skeletal; Oxidants; Phosphorylation; Proto-Oncogene Proteins c-akt; Rats; Rats, Zucker; Signal Transduction

The rising prevalence of type-2 diabetes is becoming a pressing issue based on emerging reports that T2DM can also adversely impact mental health. We have utilized the UCD-T2DM rat model in which the onset of T2DM develops spontaneously across time and can serve to understand the pathophysiology of diabetes in humans. An increased insulin resistance index and plasma glucose levels manifested the onset of T2DM. There was a decrease in hippocampal insulin receptor signaling in the hippocampus, which correlated with peripheral insulin resistance index along the course of diabetes onset (r=-0.56, p<0.01). T2DM increased the hippocampal levels of 4-hydroxynonenal (4-HNE; a marker of lipid peroxidation) in inverse proportion to the changes in the mitochondrial regulator PGC-1α. Disrupted energy homeostasis was further manifested by a concurrent reduction in energy metabolic markers, including TFAM, SIRT1, and AMPK phosphorylation. In addition, T2DM influenced brain plasticity as evidenced by a significant reduction of BDNF-TrkB signaling. These results suggest that the pathology of T2DM in the brain involves a progressive and coordinated disruption of insulin signaling, and energy homeostasis, with profound consequences for brain function and plasticity. All the described consequences of T2DM were attenuated by treatment with the glucagon-like peptide-1 receptor agonist, liraglutide. Similar results to those of liraglutide were obtained by exposing T2DM rats to a food energy restricted diet, which suggest that normalization of brain energy metabolism is a crucial factor to counteract central insulin sensitivity and synaptic plasticity associated with T2DM.

Topics: Aldehydes; Animals; Biomarkers; Blood Glucose; Brain; Crosses, Genetic; Diabetes Mellitus, Type 2; Disease Models, Animal; Energy Metabolism; Glucagon-Like Peptide 1; Hippocampus; Homeostasis; Hypoglycemic Agents; Immunoblotting; Insulin Resistance; Liraglutide; Male; Neuronal Plasticity; Obesity; Rats; Rats, Sprague-Dawley; Rats, Zucker; Receptor, Insulin

Activation of angiotensin receptor type 1 (AT1) contributes to NADPH oxidase (Nox)-derived oxidative stress during metabolic syndrome. However, the specific role of AT1 in modulating redox signaling, mitochondrial function, and oxidative stress in the heart remains more elusive. To test the hypothesis that AT1 activation increases oxidative stress while impairing redox signaling and mitochondrial function in the heart during diet-induced insulin resistance in obese animals, Otsuka Long Evans Tokushima Fatty (OLETF) rats (n = 8/group) were treated with the AT1 blocker (ARB) olmesartan for 6 wk. Cardiac Nox2 protein expression increased 40% in OLETF compared with age-matched, lean, strain-control Long Evans Tokushima Otsuka (LETO) rats, while mRNA and protein expression of the H₂O₂-producing Nox4 increased 40-100%. ARB treatment prevented the increase in Nox2 without altering Nox4. ARB treatment also normalized the increased levels of protein and lipid oxidation (nitrotyrosine, 4-hydroxynonenal) and increased the redox-sensitive transcription factor Nrf2 by 30% and the activity of antioxidant enzymes (SOD, catalase, GPx) by 50-70%. Citrate synthase (CS) and succinate dehydrogenase (SDH) activities decreased 60-70%, whereas cardiac succinate levels decreased 35% in OLETF compared with LETO, suggesting that mitochondrial function in the heart is impaired during obesity-induced insulin resistance. ARB treatment normalized CS and SDH activities, as well as succinate levels, while increasing AMPK and normalizing Akt, suggesting that AT1 activation also impairs cellular metabolism in the diabetic heart. These data suggest that the cardiovascular complications associated with metabolic syndrome may result from AT1 receptor-mediated Nox2 activation leading to impaired redox signaling, mitochondrial activity, and dysregulation of cellular metabolism in the heart.

Topics: Aldehydes; Angiotensin II Type 1 Receptor Blockers; Animals; Catalase; Citrate (si)-Synthase; Disease Models, Animal; Gene Expression Regulation, Enzymologic; Glutathione Peroxidase; Imidazoles; Insulin Resistance; Male; Membrane Glycoproteins; Mitochondria, Heart; Myocardium; NADPH Oxidase 2; NADPH Oxidase 4; NADPH Oxidases; NF-E2-Related Factor 2; Obesity; Oxidation-Reduction; Oxidative Stress; Rats; Rats, Inbred OLETF; Receptor, Angiotensin, Type 1; RNA, Messenger; Signal Transduction; Succinate Dehydrogenase; Superoxide Dismutase; Tetrazoles; Time Factors; Tyrosine

Although well-established, the underlying mechanisms involved in obesity-related plasma adiponectin decline remain elusive. Oxidative stress is associated with obesity and insulin resistance and considered to contribute to the progression toward obesity-related metabolic disorders. In this study, we investigated the effects of 4-hydroxynonenal (4-HNE), the most abundant lipid peroxidation end product, on adiponectin production and its potential implication in obesity-related adiponectin decrease. Long-term high-fat diet feeding led to obesity in mouse, accompanied by decreased plasma adiponectin and increased adipose tissue 4-HNE content. Exposure of adipocytes to exogenous 4-HNE resulted in decreased adiponectin secretion in a dose-dependent manner, which was consistent with significantly decreased intracellular adiponectin protein abundance. In contrast, adiponectin gene expression was significantly elevated by 4-HNE treatment, which was concomitant with increased peroxisome proliferator-activated receptor gamma (PPAR-γ) gene expression and transactivity. The effect was abolished by T0070907, a PPAR-γ antagonist, suggesting that PPAR-γ activation plays a critical role in this process. To gain insight into mechanisms involved in adiponectin protein decrease, we examined the effects of 4-HNE on adiponectin protein degradation. Cycloheximide (CHX)-chase assay revealed that 4-HNE exposure accelerated adiponectin protein degradation, which was prevented by MG132, a potent proteasome inhibitor. Immunoprecipitation assay showed that 4-HNE exposure increased ubiquitinated adiponectin protein levels. These data altogether indicated that 4-HNE enhanced adiponectin protein degradation via ubiquitin-proteasome system. Finally, we demonstrated that supplementation of HF diet with betaine, an antioxidant and methyl donor, alleviated high-fat-induced adipose tissue 4-HNE increase and attenuated plasma adiponectin decline. Taken together, our findings suggest that the lipid peroxidation product 4-HNE can differentially regulates adiponectin gene expression and protein abundance and may play a mechanistic role in obesity-related plasma adiponectin decline.

Topics: 3T3-L1 Cells; Adiponectin; Adipose Tissue; Aldehydes; Animals; Benzamides; Diet, High-Fat; Dose-Response Relationship, Drug; Gene Expression; Insulin Resistance; Leupeptins; Lipid Peroxidation; Male; Mice; Mice, Inbred C57BL; Obesity; Oxidative Stress; PPAR gamma; Proteasome Endopeptidase Complex; Proteasome Inhibitors; Proteolysis; Pyridines; Ubiquitin; Up-Regulation

The current study was designed to test the hypothesis that inducible nitric oxide synthase (iNOS)-mediated lipid free radical overproduction exists in an insulin-resistant rat model and that reducing the accumulation of toxic metabolites is associated with improved insulin signaling and metabolic response. Lipid radical formation was detected by electron paramagnetic resonance spectroscopy with in vivo spin trapping in an obese rat model, with or without thiazolidinedione treatment. Lipid radical formation was accompanied by accumulation of toxic end products in the liver, such as 4-hydroxynonenal and nitrotyrosine, and was inhibited by the administration of the selective iNOS inhibitor 1400 W. The model showed impaired phosphorylation of the insulin signaling pathway. Ten-day rosiglitazone injection not only improved the response to an oral glucose tolerance test and corrected insulin signaling but also decreased iNOS levels. Similar to the results with specific iNOS inhibition, thiazolidinedione dramatically decreased lipid radical formation. We demonstrate a novel mechanism where a thiazolidinedione treatment can reduce oxidative stress in this model through reducing iNOS-derived lipid radical formation. Our results suggest that hepatic iNOS expression may underlie the accumulation of lipid end products and that reducing the accumulation of toxic lipid metabolites contributes to a better redox status in insulin-sensitive tissues.

Topics: Aldehydes; Animals; Body Composition; Free Radicals; Glucose Intolerance; Heart Failure; Hypertension; Insulin Resistance; Lipid Peroxidation; Liver; Male; Muscle, Skeletal; Nitric Oxide Synthase Type II; Nitrites; Oxidative Stress; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Thiazolidinediones; Tyrosine

Numerous oxidants are produced as by-products of aerobic cell metabolism, and there is growing evidence that they play key roles in the pathogenesis of insulin resistance. Under conditions of oxidative stress, lipid peroxidation of ω6-polyunsaturated fatty acids leads to the production of 4-hydroxy-2-nonenal (4-HNE). Several lines of evidence suggest that 4-HNE could be involved in the pathophysiology of metabolic diseases; therefore, in this study we assessed the direct effects of 4-HNE on skeletal muscle insulin sensitivity. Gastrocnemius muscle and L6 muscle cells were treated with 4-HNE. Insulin signaling was measured by Western blotting and glucose uptake using 2-deoxy-d-[3H]glucose. Carbonyl stress, glutathione content, and oxidative stress were assessed as potential mechanisms leading to insulin resistance. Protection of cells was induced by pretreatment with 3H-1,2-dithiole-3-thione, N-acetyl-cysteine, aminoguanidine, or S-adenosyl-methionine. 4-HNE induced a time- and dose-dependent decrease in insulin signaling and insulin-induced glucose uptake in muscle. It induced a state of carbonyl stress through adduction of proteins as well as a depletion in reduced glutathione and production of radical oxygen species. A pharmacological increase in glutathione pools was achieved by 3H-1,2-dithiole-3-thione and protected the cells against all deleterious effects of 4-HNE; furthermore, N-acetylcysteine, aminoguanidine, and S-adenosylmethionine prevented 4-HNE noxious effects. 4-HNE can impair insulin action in muscle cells through oxidative stress and oxidative damage to proteins, eventually leading to insulin resistance. These deleterious effects can be prevented by pretreatment with antioxidants, scavengers, or an increase in intracellular glutathione pools. Use of such molecules could represent a novel strategy to combat insulin resistance and other oxidative stress-associated pathologies.

Topics: Aldehydes; Animals; Cell Line; Cells, Cultured; Glutathione; Insulin; Insulin Resistance; Lipid Peroxidation; Male; Mice; Muscle, Skeletal; Oxidative Stress; Reactive Oxygen Species; Signal Transduction

To test the hypothesis that the inducible nitric oxide synthase (iNOS) is involved in mediating the toll-like receptor 4-dependent effects on the liver in the onset of fructose-induced steatosis, wild-type and iNOS knockout (iNOS(-/-)) mice were either fed tap water or 30% fructose solution for 8 weeks. Chronic consumption of 30% fructose solution led to a significant increase in hepatic steatosis and inflammation as well as plasma alanine-aminotransferase levels in wild-type mice. This effect of fructose feeding was markedly attenuated in iNOS(-/-) mice. Hepatic lipidperoxidation, concentration of phospho-IκB, nuclear factor κB activity, and tumor necrosis factor-α mRNA level were significantly increased in fructose-fed wild-type mice, whereas in livers of fructose-fed iNOS(-/-) mice, lipidperoxidation, phospho-IκB, nuclear factor κB activity, and tumor necrosis factor-α expression were almost at the level of controls. However, portal endotoxin levels and hepatic myeloid differentiation factor 88 expression were significantly higher in both fructose-fed groups compared to controls. Taken together, these data suggest that (i) the formation of reactive oxygen species in liver is a key factor in the onset of fatty liver and (ii) iNOS is involved in mediating the endotoxin/toll-like receptor 4-dependent effects in the development of fructose-induced fatty liver.

Topics: Aldehydes; Animals; Cells, Cultured; Coculture Techniques; Endotoxins; Fatty Liver; Fructokinases; Fructose; Glutathione; I-kappa B Proteins; Insulin Resistance; Kupffer Cells; Lipid Peroxidation; Liver; Mice; Mice, Inbred C57BL; Mice, Knockout; Myeloid Differentiation Factor 88; NF-kappa B; Nitric Oxide Synthase Type II; Organ Size; Toll-Like Receptor 4; Transcription, Genetic; Triglycerides; Tumor Necrosis Factor-alpha; Tyrosine; Weight Gain

The production of reactive aldehydes such as 4-hydroxy-2-nonenal (4-HNE) is a key component of the pathogenesis in a spectrum of hepatic diseases involving oxidative stress such as alcoholic liver disease (ALD). One consequence of ALD is increased insulin resistance in hepatocytes. To understand the effects of 4-HNE on insulin signaling in liver cells, we employed a model using hepatocellular carcinoma cell line HepG2. Previously, we have demonstrated an increase in the level of Akt phosphorylation is mediated by 4-HNE inhibition of PTEN, a direct regulator of Akt. In this work, we evaluated the effects of 4-HNE on insulin-dependent stimulation of the Akt2 pathway. We demonstrate that 4-HNE selectively leads to phosphorylation of Akt2. Although Akt2 is phosphorylated following 4-HNE treatment, the level of downstream phosphorylation of Akt substrates such as GSK3β and MDM2 is significantly decreased. Pretreatment with 4-HNE prevented insulin-dependent Akt signaling and decreased intracellular Akt activity by 87%. Using biotin hydrazide capture, it was confirmed that 4-HNE treatment of cells resulted in carbonylation of Akt2, which was not observed in untreated control cells. Using a synthetic GSK3α/β peptide as a substrate, treatment of recombinant human myristoylated Akt2 (rAkt2) with 20 or 40 μM 4-HNE inhibited rAkt2 activity by 30 or 85%, respectively. Matrix-assisted laser desorption ionization time-of-flight tandem mass spectrometry (MALDI-TOF/TOF) identified Michael addition adducts of 4-HNE with His196, His267, and Cys311 of rAkt2. Computation-based molecular modeling analysis of 4-HNE adducted to His196 and Cys311 of Akt2 suggests inhibition of GSK3β peptide binding by 4-HNE in the Akt2 substrate binding pocket. The inhibition of Akt by 4-HNE provides a novel mechanism for increased insulin resistance in ALD. These data provide a potential mechanism of dysregulation of Akt2 during events associated with sustained hepatocellular oxidative stress.

Topics: Aldehydes; Amino Acid Sequence; Down-Regulation; Glycogen Synthase Kinase 3; Glycogen Synthase Kinase 3 beta; Hep G2 Cells; Humans; Insulin Resistance; Molecular Sequence Data; Peptide Mapping; Peptides; Phosphorylation; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; Recombinant Proteins; Signal Transduction

Both insulin resistance and increased oxidative stress in the liver are associated with the pathogenesis of nonalcoholic fatty liver disease (NAFLD). Senescence marker protein-30 (SMP30) was initially identified as a novel protein in the rat liver, and acts as an antioxidant and antiapoptotic protein. Our aim was to determine whether hepatic SMP30 levels are associated with the development and progression of NAFLD.. Liver biopsies and blood samples were obtained from patients with an NAFLD activity score (NAS) < or = 2 (n = 18), NAS of 3-4 (n = 14), and NAS > or = 5 (n = 66).. Patients with NAS > or = 5 had significantly lower hepatic SMP30 levels (12.5 +/- 8.4 ng/mg protein) than patients with NAS < or = 2 (30.5 +/- 14.2 ng/mg protein) and patients with NAS = 3-4 (24.6 +/- 12.2 ng/mg protein). Hepatic SMP30 decreased in a fibrosis stage-dependent manner. Hepatic SMP30 levels were correlated positively with the platelet count (r = 0.291) and negatively with the homeostasis model assessment of insulin resistance (r = -0.298), the net electronegative charge modified-low-density lipoprotein (r = -0.442), and type IV collagen 7S (r = -0.350). The immunostaining intensity levels of 4-hydroxynonenal in the liver were significantly and inversely correlated with hepatic SMP30 levels. Both serum large very low-density lipoprotein (VLDL) and very small low-density lipoprotein (LDL) levels in patients with NAS > or = 5 were significantly higher than those seen in patients with NAS < or = 2, and these lipoprotein fractions were significantly and inversely correlated with hepatic SMP30.. These results suggest that hepatic SMP30 is closely associated with the pathogenesis of NAFLD, although it is not known whether decreased hepatic SMP30 is a result or a cause of cirrhosis.

Topics: Adult; Aged; Aldehydes; Calcium-Binding Proteins; Cholesterol, LDL; Cholesterol, VLDL; Disease Progression; Fatty Liver; Female; Homeostasis; Humans; Insulin Resistance; Intracellular Signaling Peptides and Proteins; Liver; Liver Cirrhosis; Male; Middle Aged; Platelet Count

Previous studies show that naringenin promotes insulin sensitivity in fructose-fed rats. This study investigates whether naringenin prevents oxidative events and apoptotic changes triggered in the rat liver by a high fructose diet. Male Wistar rats of body weight 150-180 g were fed either diet containing starch (60% carbohydrate) or fructose (60% fructose diet). From the 16th day of feeding, rats in each dietary group were divided into two, and treated or not with naringenin (50mg/kg b.w/day). After 60 days, oxidative and nitrosative damage and endothelial nitric oxide synthase (eNOS) expression and hepatocyte apoptosis were determined. To evaluate whether nitric oxide (NO) plays a role in naringenin action, insulin sensitivity indices, fasting plasma glucose and insulin were assessed in response to co-administration of L-nitro-arginine methyl ester (L-NAME), a NOS inhibitor. Fructose feeding caused oxidative damage to proteins and lipids and resulted in reduced antioxidant status, eNOS expression and nitrite level. Increased formation of 4-hydroxy nonenal (4-HNE), 2, 4-dinitrophenol (2, 4-DNP) and 3-nitrotyrosine (3-NT)-modified proteins and the presence of apoptotic nuclei were observed in the liver. Treatment with naringenin attenuated all these parameters to levels not significantly different from control. Treatment with naringenin improved insulin sensitivity. However, L-NAME plus naringenin administration abolished the insulin-sensitizing effects of naringenin in fructose-fed rats. Reduced oxidative events with simultaneous increase in NO bioavailability may be involved in the insulin-sensitizing and cytoprotective effects of naringenin in fructose-fed rats.

Topics: 2,4-Dinitrophenol; Aldehydes; Animals; Antioxidants; Apoptosis; Blood Glucose; Diet; Flavanones; Fructose; Hepatocytes; Insulin; Insulin Resistance; Liver; Male; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Oxidative Stress; Rats; Rats, Wistar; Tyrosine

Alzheimer's disease (AD) is associated with brain insulin resistance and insulin deficiency, whereas Type 2 diabetes mellitus (T2DM) is associated with peripheral insulin resistance. This study assesses the degree to which T2DM causes AD-type neurodegeneration. In a C57BL/6 mouse model of obesity and T2DM, we characterized the histopathology, gene expression, and insulin and insulin-like growth factor (IGF)-receptor binding in temporal lobe. High fat diet (HFD) feeding for 16 weeks doubled mean body weight, caused T2DM, and marginally reduced mean brain weight. These effects were associated with significantly increased levels of tau, IGF-I receptor, insulin receptor substrate-1 (IRS-1), IRS-4, ubiquitin, glial fibrillary acidic protein, and 4-hydroxynonenol, and decreased expression of beta-actin. HFD feeding also caused brain insulin resistance manifested by reduced BMAX for insulin receptor binding, and modestly increased brain insulin gene expression. However, HFD-fed mouse brains did not exhibit AD histopathology, increases in amyloid-beta or phospho-tau, or impairments in IGF signaling or acetylcholine homeostasis. Obesity and T2DM cause brain atrophy with insulin resistance, oxidative stress, and cytoskeleton degradation, but the absence of many features that typify AD suggests that obesity and T2DM may contribute to, but are not sufficient to cause AD.

Topics: Actins; Adaptor Proteins, Signal Transducing; Aldehydes; Alzheimer Disease; Amyloid beta-Peptides; Animals; Atrophy; Brain; Diabetes Mellitus, Type 2; DNA Primers; Enzyme-Linked Immunosorbent Assay; Gene Expression; Glial Fibrillary Acidic Protein; Insulin Receptor Substrate Proteins; Insulin Resistance; Insulin-Like Growth Factor I; Mice; Mice, Inbred C57BL; Nerve Degeneration; Obesity; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Ubiquitin

Beneficial effects of an antioxidant (N-acetyl-L-cysteine, NAC) and an angiotensin I-converting enzyme (ACE) inhibitor (ramipril) were assessed in a rat model of insulin resistance induced by 10% glucose feeding for 20 weeks. Treatments with NAC (2 g/kg per day) and ramipril (1 mg/kg per day) were initiated at 16 weeks in the drinking fluid. Systolic blood pressure, plasma levels of insulin and glucose, and insulin resistance were significantly higher in rats treated with glucose for 20 weeks. This was associated with a higher production of superoxide anion and NADPH oxidase activity in aorta and liver and with a marked reduction in protein expression of skeletal muscle insulin receptor substrate-1 (IRS-1) in the gastrocnemius muscle. NAC prevented all these alterations. Although ramipril also reversed high blood pressure, it had a lesser effect on insulin resistance (including IRS-1) and blocked superoxide anion production only in aorta. Ramipril, in contrast to NAC, did not reduce NADPH oxidase activity in aorta and liver or plasma levels of 4-hydroxynonenal and malondialdehyde. Results suggest that the inhibition of the oxidative stress in hypertensive and insulin-resistant states contributes to the therapeutic effects of NAC and ramipril. Whereas NAC exerts effective antioxidant activity in multiple tissues, ramipril appears to preferentially target the vasculature.

Topics: Acetylcysteine; Aldehydes; Angiotensin-Converting Enzyme Inhibitors; Animals; Aorta, Thoracic; Blood Pressure; Diet; Free Radical Scavengers; Glucose; Hypertension; Insulin Receptor Substrate Proteins; Insulin Resistance; Lipid Peroxidation; Liver; Male; Malondialdehyde; Muscle, Skeletal; NADPH Oxidases; Oxidative Stress; Oxygen Consumption; Ramipril; Rats; Rats, Wistar

Reduced insulin sensitivity is a key factor in the pathogenesis of type 2 diabetes and hypertension. Skeletal muscle insulin resistance is particularly important for its major role in insulin-mediated glucose disposal. Angiotensin II (ANG II) is integral in regulating blood pressure and plays a role in the pathogenesis of hypertension. In addition, we have documented that ANG II-induced skeletal muscle insulin resistance is associated with generation of reactive oxygen species (ROS). However, the linkage between ROS and insulin resistance in skeletal muscle remains unclear. To explore potential mechanisms, we employed the transgenic TG(mRen2)27 (Ren-2) hypertensive rat, which harbors the mouse renin transgene and exhibits elevated tissue ANG II levels, and skeletal muscle cell culture. Compared with Sprague-Dawley normotensive control rats, Ren-2 skeletal muscle exhibited significantly increased oxidative stress, NF-kappaB activation, and TNF-alpha expression, which were attenuated by in vivo treatment with an angiotensin type 1 receptor blocker (valsartan) or SOD/catalase mimetic (tempol). Moreover, ANG II treatment of L6 myotubes induced NF-kappaB activation and TNF-alpha production and decreased insulin-stimulated Akt activation and GLUT-4 glucose transporter translocation to plasma membranes. These effects were markedly diminished by treatment of myotubes with valsartan, the antioxidant N-acetylcysteine, NADPH oxidase-inhibiting peptide (gp91 ds-tat), or NF-kappaB inhibitor (MG-132). Similarly, NF-kappaB p65 small interfering RNA reduced NF-kappaB p65 subunit expression and nuclear translocation and TNF-alpha production but improved insulin-stimulated phosphorylation (Ser(473)) of Akt and translocation of GLUT-4. These findings suggest that NF-kappaB plays an important role in ANG II/ROS-induced skeletal muscle insulin resistance.

Topics: Aldehydes; Angiotensin II; Animals; Blotting, Western; Cells, Cultured; Enzyme-Linked Immunosorbent Assay; Fluorescent Antibody Technique; Glucose Transporter Type 4; Insulin Resistance; Male; Muscle, Skeletal; NADPH Oxidases; NF-kappa B; Oxidative Stress; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Reverse Transcriptase Polymerase Chain Reaction; RNA, Small Interfering; Transcription Factor RelA; Transfection; Tumor Necrosis Factor-alpha

The lipid peroxidation product 4-hydroxynonenal (4-HNE) is a signaling mediator with wide-ranging biological effects. In this paper, we report that disruption of mGsta4, a gene encoding the 4-HNE-conjugating enzyme mGSTA4-4, causes increased 4-HNE tissue levels and is accompanied by age-dependent development of obesity which precedes the onset of insulin resistance in 129/sv mice. In contrast, mGsta4 null animals in the C57BL/6 genetic background have normal 4-HNE levels and remain lean, indicating a role of 4-HNE in triggering or maintaining obesity. In mGsta4 null 129/sv mice, the expression of the acetyl-CoA carboxylase (ACC) transcript is enhanced several-fold with a concomitant increase in the tissue level of malonyl-CoA. Also, mitochondrial aconitase is partially inhibited, and tissue citrate levels are increased. Accumulation of citrate could lead to allosteric activation of ACC, further augmenting malonyl-CoA levels. Aconitase may be inhibited by 4-HNE or by peroxynitrite generated by macrophages which are enriched in white adipose tissue of middle-aged mGsta4 null 129/sv mice and, upon lipopolysaccharide stimulation, produce more reactive oxygen species and nitric oxide than macrophages from wild-type mice. Excessive malonyl-CoA synthesized by the more abundant and/or allosterically activated ACC in mGsta4 null mice leads to fat accumulation by the well-known mechanisms of promoting fatty acid synthesis and inhibiting fatty acid beta-oxidation. Our findings complement the recent report that obesity causes both a loss of mGSTA4-4 and an increase in the level of 4-HNE [Grimsrud, P. A., et al. (2007) Mol. Cell. Proteomics 6, 624-637]. The two reciprocal processes are likely to establish a positive feedback loop that would promote and perpetuate the obese state.

Topics: Acetyl-CoA Carboxylase; Aconitate Hydratase; Aging; Aldehydes; Animals; Antigens, CD; Antigens, Differentiation, Myelomonocytic; Blood Glucose; Citric Acid; Female; Glucose Tolerance Test; Glutathione Transferase; Insulin Resistance; Lipid Peroxidation; Male; Malonyl Coenzyme A; Mice; Mice, Inbred C57BL; Obesity; Reactive Oxygen Species

Obesity is a state of mild inflammation correlated with increased oxidative stress. In general, pro-oxidative conditions lead to production of reactive aldehydes such as trans-4-hydroxy-2-nonenal (4-HNE) and trans-4-oxo-2-nonenal implicated in the development of a variety of metabolic diseases. To investigate protein modification by 4-HNE as a consequence of obesity and its potential relationship to the development of insulin resistance, proteomics technologies were utilized to identify aldehyde-modified proteins in adipose tissue. Adipose proteins from lean insulin-sensitive and obese insulin-resistant C57Bl/6J mice were incubated with biotin hydrazide and detected using horseradish peroxidase-conjugated streptavidin. High carbohydrate, high fat feeding of mice resulted in a approximately 2-3-fold increase in total adipose protein carbonylation. Consistent with an increase in oxidative stress in obesity, the abundance of glutathione S-transferase A4 (GSTA4), a key enzyme responsible for metabolizing 4-HNE, was decreased approximately 3-4-fold in adipose tissue of obese mice. To identify specific carbonylated proteins, biotin hydrazide-modified adipose proteins from obese mice were captured using avidin-Sepharose affinity chromatography, proteolytically digested, and subjected to LC-ESI MS/MS. Interestingly enzymes involved in cellular stress response, lipotoxicity, and insulin signaling such as glutathione S-transferase M1, peroxiredoxin 1, glutathione peroxidase 1, eukaryotic elongation factor 1alpha-1 (eEF1alpha1), and filamin A were identified. The adipocyte fatty acid-binding protein, a protein implicated in the regulation of insulin resistance, was found to be carbonylated in vivo with 4-HNE. In vitro modification of adipocyte fatty acid-binding protein with 4-HNE was mapped to Cys-117, occurred equivalently using either the R or S enantiomer of 4-HNE, and reduced the affinity of the protein for fatty acids approximately 10-fold. These results indicate that obesity is accompanied by an increase in the carbonylation of a number of adipose-regulatory proteins that may serve as a mechanistic link between increased oxidative stress and the development of insulin resistance.

Topics: Adipose Tissue; Aldehydes; Animals; Fatty Acid-Binding Proteins; Glutathione Transferase; Insulin Resistance; Mice; Mice, Inbred C57BL; Obesity; Protein Carbonylation; Proteomics; Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; Tandem Mass Spectrometry

Phosphatidylinositol 3-kinase signaling regulates the expression of several genes involved in lipid and glucose homeostasis; deregulation of these genes may contribute to insulin resistance and progression toward type 2 diabetes. By employing RNA arbitrarily primed-PCR to search for novel phosphatidylinositol 3-kinase-regulated genes in response to insulin in isolated rat adipocytes, we identified fatty aldehyde dehydrogenase (FALDH), a key component of the detoxification pathway of aldehydes arising from lipid peroxidation events. Among these latter events are oxidative stresses associated with insulin resistance and diabetes. Upon insulin injection, FALDH mRNA expression increased in rat liver and white adipose tissue and was impaired in two models of insulin-resistant mice, db/db and high fat diet mice. FALDH mRNA levels were 4-fold decreased in streptozotocin-treated rats, suggesting that FALDH deregulation occurs both in hyperinsulinemic insulin-resistant state and hypoinsulinemic type 1 diabetes models. Moreover, insulin treatment increases FALDH activity in hepatocytes, and expression of FALDH was augmented during adipocyte differentiation. Considering the detoxifying role of FALDH, its deregulation in insulin-resistant and type 1 diabetic models may contribute to the lipid-derived oxidative stress. To assess the role of FALDH in the detoxification of oxidized lipid species, we evaluated the production of reactive oxygen species in normal versus FALDH-overexpressing adipocytes. Ectopic expression of FALDH significantly decreased reactive oxygen species production in cells treated by 4-hydroxynonenal, the major lipid peroxidation product, suggesting that FALDH protects against oxidative stress associated with lipid peroxidation. Taken together, our observations illustrate the importance of FALDH in insulin action and its deregulation in states associated with altered insulin signaling.

Topics: Adenoviridae; Adipocytes; Adipose Tissue; Aldehyde Oxidoreductases; Aldehydes; Animals; Blotting, Northern; Blotting, Western; Cell Differentiation; Culture Techniques; Cysteine Proteinase Inhibitors; Diabetes Mellitus, Experimental; Gene Expression Regulation, Enzymologic; Hepatocytes; Humans; Insulin; Insulin Resistance; Lipid Metabolism; Lipid Peroxidation; Liver; Male; Mice; Mice, Inbred C57BL; Models, Biological; Oxidative Stress; Oxygen; Phosphatidylinositol 3-Kinases; Polymerase Chain Reaction; Rats; Rats, Wistar; Reactive Oxygen Species; RNA; RNA, Messenger; Signal Transduction; Streptozocin; Tissue Distribution

In order to assess the beneficial effect of the peroxisome proliferator-activated receptor-gamma (PPAR-gamma) agonist pioglitazone on reduction of mass and alteration of function of pancreatic beta cells under diabetic conditions, diabetic C57BL/KsJ db/db mice were treated with pioglitazone for 6 weeks, and insulin secretory capacity and insulin content of isolated pancreatic islets were evaluated. In addition, the expression of oxidative stress markers, 4-hydroxy-2-nonenal (HNE)-modified proteins and heme oxygenase-1, in endocrine pancreas was examined to measure reduction of oxidative stress in pancreatic beta cells. The capacity for glucose-induced insulin secretion from isolated islets and their insulin content were improved by pioglitazone treatment (P <.01). When beta cells were stained with anti-insulin antibodies, those of db/db mice treated with pioglitazone exhibited strong staining, as also observed in their lean littermates. The density of immunostaining for oxidative stress markers was significantly reduced in pancreatic islets of pioglitazone-treated db/db mice (P <.05). This study clearly demonstrates the benefit of long-term treatment with pioglitazone in decreasing hyperglycemia and improving glucose-induced insulin secretory capacity in diabetic db/db mice. The results of immunocytochemical examination suggest that this treatment reduces oxidative stress and thereby preserves beta-cell mass. Treatment with pioglitazone thus protects against beta-cell damage and would be useful for restoration of insulin secretory capacity in obese diabetes individuals.

Topics: Aldehydes; Animals; Blood Glucose; Diabetes Mellitus, Experimental; Glucose; Heme Oxygenase (Decyclizing); Heme Oxygenase-1; Hemostatics; Hypoglycemic Agents; Immunohistochemistry; Insulin; Insulin Resistance; Insulin Secretion; Islets of Langerhans; Male; Membrane Proteins; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Obesity; Oxidative Stress; Pioglitazone; Thiazolidinediones; Triglycerides