leptin and acetovanillone

In the present study, we tested the effect of OS (oxidative stress) inhibition in rats fed on an FRD [fructose-rich diet; 10% (w/v) in drinking water] for 3 weeks. Normal adult male rats received a standard CD (commercial diet) or an FRD without or with an inhibitor of NADPH oxidase, APO (apocynin; 5 mM in drinking water; CD-APO and FRD-APO). We thereafter measured plasma OS and metabolic-endocrine markers, AAT (abdominal adipose tissue) mass and cell size, FA (fatty acid) composition (content and release), OS status, LEP (leptin) and IRS (insulin receptor substrate)-1/IRS-2 mRNAs, ROS (reactive oxygen species) production, NADPH oxidase activity and LEP release by isolated AAT adipocytes. FRD-fed rats had larger AAT mass without changes in body weight, and higher plasma levels of TAG (triacylglycerol), FAs, TBARS (thiobarbituric acid-reactive substance) and LEP. Although no significant changes in glucose and insulin plasma levels were observed in these animals, their HOMA-IR (homoeostasis model assessment of insulin resistance) values were significantly higher than those of CD. The AAT from FRD-fed rats had larger adipocytes, higher saturated FA content, higher NADPH oxidase activity, greater ROS production, a distorted FA content/release pattern, lower insulin sensitivity together with higher and lower mRNA content of LEP and IRS-1-/2 respectively, and released a larger amount of LEP. The development of all the clinical, OS, metabolic, endocrine and molecular changes induced by the FRD were significantly prevented by APO co-administration. The fact that APO treatment prevented both changes in NADPH oxidase activity and the development of all the FRD-induced AAT dysfunctions in normal rats strongly suggests that OS plays an important role in the FRD-induced MS (metabolic syndrome) phenotype.

Topics: Abdominal Fat; Acetophenones; Adipocytes; Animals; Antioxidants; Biomarkers; Body Weight; Eating; Fatty Acids; Fructose; Homeostasis; Leptin; Male; Metabolic Diseases; NADPH Oxidases; Oxidative Stress; Rats; Rats, Wistar; Sweetening Agents

The adipose tissue hormone leptin and homocysteine (Hcy)-thiolactone are linked to the pathogenesis of atherosclerosis through their interactions with the anti-atherogenic enzyme paraoxonase 1 that has the ability to hydrolyze Hcy-thiolactone and minimizes protein N-homocysteinylation. Here we examined the relationships between hyperleptinemia, Hcy-thiolactonase, and protein N-homocysteinylation in rats. Hyperleptinemia was induced in adult rats by administration of leptin for 7 days (0.25 mg/kg twice daily s.c). We found that serum Hcy-thiolactonase was lower in hyperleptinemic than in control animals (-41.0%, P<0.001). Leptin administration increased the level of N-linked Hcy in plasma proteins (+92.9%, P<0.01), but had no effect on plasma total Hcy. These effects were not reproduced by pair-feeding. We also found that the synthetic liver X receptor (LXR) agonist, T0901317 (1 mg/kg per day) normalized Hcy-thiolactonase and protein N-homocysteinylation levels in leptin-treated rats. However, leptin-induced increase in plasma isoprostane levels (a marker of oxidative stress) was not normalized by T0901317. The NADPH oxidase inhibitor apocynin prevented leptin-induced increase in isoprostane levels but did not normalize Hcy-thiolactonase and protein N-homocysteinylation levels. These results suggest that the decreased capacity to metabolize Hcy-thiolactone and concomitant increase in protein N-homocysteinylation contribute to pro-atherogenic effect of chronic hyperleptinemia, independently of oxidative stress. LXR agonists normalize Hcy-thiolactonase levels and decrease protein N-homocysteinylation, especially under conditions associated with excess leptin such as metabolic syndrome.

Topics: Acetophenones; Animals; Aryldialkylphosphatase; Blood Proteins; Homocysteine; Hydrocarbons, Fluorinated; Leptin; Liver; Liver X Receptors; Male; NADPH Oxidases; Orphan Nuclear Receptors; Oxidative Stress; Rats; Rats, Wistar; Sulfonamides

Leptin, the obese gene product, plays an important role in the regulation of cardiac function. However, the mechanism behind leptin-induced cardiomyocyte contractile response is poorly understood. This study was designed to examine whether endothelin-1 receptor and NADPH oxidase play any role in leptin-induced cardiac contractile response. Isolated murine cardiomyocytes were exposed to leptin (5, 50, and 100 nmol/L) for 60 minutes in the absence or presence of the ETA receptor antagonist BQ123 (1 micromol/L), the ETB receptor antagonist BQ788 (1 micromol/L), or the NADPH oxidase inhibitor apocynin (100 micromol/L) before mechanical function was studied. Superoxide levels were measured by dihydroethidium fluorescent dye and the superoxide dismutase-inhibitable reduction of cytochrome c. NADPH oxidase subunit expression (p22phox, p47phox, p67phox, and gp91phox) was evaluated with Western blot. Leptin depressed peak shortening and maximal velocity of shortening/relengthening (+/-dL/dt), prolonged the duration of relengthening (TR90) without affecting the time-to-peak cell shortening. Consistent with the mechanical characteristics, myocytes treated with leptin displayed a reduced electrically stimulated rise in intracellular Ca2+ (change in fura-2 fluorescence intensity) associated with a prolonged intracellular Ca2+ decay rate. All of the abnormalities were significantly attenuated by apocynin, BQ123, or BQ788. Intracellular superoxide generation was enhanced after leptin treatment, which was partially blocked by apocynin, BQ123, or BQ788. Leptin had no effect on p22phox and gp91phox but upregulated protein expression of p67phox and p47phox, both of which were inhibited by apocynin, BQ123, or BQ788. These results suggest that leptin suppresses cardiac contractile function in ventricular myocytes through the endothelin-1 receptor and NADPH oxidase-mediated pathway.

Topics: Acetophenones; Animals; Calcium; Cyclic N-Oxides; Endothelin A Receptor Antagonists; Enzyme Inhibitors; Heart Ventricles; Intracellular Membranes; Leptin; Male; Mice; Mice, Inbred C57BL; Myocardial Contraction; Myocytes, Cardiac; NADPH Oxidases; Oligopeptides; Peptides, Cyclic; Piperidines; Receptor, Endothelin A; Receptors, Leptin; Spin Labels; Superoxides

1. Recent studies suggest that leptin, a peptide hormone secreted by white adipose tissue, is involved in the pathogenesis of arterial hypertension, in part by regulating renal sodium handling. Previously, we have demonstrated that in normal rats leptin has a time-dependent effect on renal Na(+)/K(+)-ATPase that drives tubular sodium reabsorption. Short-term leptin infusion results in a transient decrease in Na(+)/K(+)-ATPase activity, whereas prolonged administration stimulates the enzyme. 2. In the present study, we investigated whether these acute effects of leptin are preserved in rats with experimentally induced chronic hyperleptinaemia. 3. Hyperleptinaemia was induced by administration of exogenous leptin (0.25 mg/kg twice daily, s.c., for 7 days). Acute effects of leptin in anaesthetized control (normoleptinaemic) and hyperleptinaemic animals was investigated. Leptin was infused into the abdominal aorta proximally to the renal arteries for 0.5, 1, 2 or 3 h. 4. Leptin (1 microg/min per kg) had a time-dependent effect on renal Na(+)/K(+)-ATPase in both the control and hyperleptinaemic groups. The inhibitory effect observed after 0.5 h infusion was impaired in the hyperleptinaemic group. However, in both groups this effect was abolished by the Janus kinase inhibitor tyrphostin AG490 (100 nmol/min per kg), as well as by the phosphatidylinositol 3-kinase inhibitors wortmannin (10 nmol/min per kg) and LY294002 (1 micromol/min per kg). 5. The stimulatory effect of leptin on Na(+)/K(+)-ATPase activity was observed after 3 h of infusion and was of similar magnitude in control and hyperleptinaemic groups. In the control group, the stimulatory effect of leptin was abolished by the NADPH oxidase inhibitor apocynin (1 micromol/min per kg), the H(2)O(2) scavenger catalase (1 mg/min per kg) and the extracellular signal-regulated kinase (ERK) inhibitor PD98059 (100 nmol/min per kg). In contrast, in the hyperleptinaemic group, the stimulatory effect of leptin was abolished by the cGMP analogue 8-bromo-cGMP (100 nmol/min per kg) and by the superoxide dismutase mimetic tempol (100 micromol/min per kg) but was not affected by catalase or PD98059. 6. Leptin increased urinary H(2)O(2) excretion and ERK phosphorylation in the renal tissue only in the control group. 7. The results suggest that the acute stimulatory effect of leptin on renal Na(+)/K(+)-ATPase is mediated by divergent mechanisms depending on the chronic leptin level (i.e. by H(2)O(2)-dependent stimulation o

Topics: Acetophenones; Animals; Cyclic N-Oxides; Enzyme Inhibitors; Extracellular Signal-Regulated MAP Kinases; Free Radical Scavengers; Hydrogen Peroxide; Indicators and Reagents; Janus Kinases; Kidney; Leptin; Male; Nitric Oxide; Oxidants; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Phosphorylation; Rats; Rats, Wistar; Sodium-Potassium-Exchanging ATPase; Spin Labels; Stimulation, Chemical; Superoxide Dismutase; Superoxides

Recent studies suggest that adipose tissue hormone, leptin, is involved in the pathogenesis of arterial hypertension. However, the mechanism of hypertensive effect of leptin is incompletely understood. We investigated whether antioxidant treatment could prevent leptin-induced hypertension. Hyperleptinemia was induced in male Wistar rats by administration of exogenous leptin (0.25 mg/kg twice daily s.c. for 7 days) and separate groups were simultaneously treated with superoxide scavenger, tempol, or NAD(P)H oxidase inhibitor, apocynin (2 mM in the drinking water). After 7 days, systolic blood pressure was 20.6% higher in leptin-treated than in control animals. Both tempol and apocynin prevented leptin-induced increase in blood pressure. Plasma concentration and urinary excretion of 8-isoprostanes increased in leptin-treated rats by 66.9% and 67.7%, respectively. The level of lipid peroxidation products, malonyldialdehyde + 4-hydroxyalkenals (MDA+4-HNE), was 60.3% higher in the renal cortex and 48.1% higher in the renal medulla of leptin-treated animals. Aconitase activity decreased in these regions of the kidney following leptin administration by 44.8% and 45.1%, respectively. Leptin increased nitrotyrosine concentration in plasma and renal tissue. Urinary excretion of nitric oxide metabolites (NO(x)) was 57.4% lower and cyclic GMP excretion was 32.0% lower in leptin-treated than in control group. Leptin decreased absolute and fractional sodium excretion by 44.5% and 44.7%, respectively. Co-treatment with either tempol or apocynin normalized 8-isoprostanes, MDA+4-HNE, aconitase activity, nitrotyrosine, as well as urinary excretion of NO(x), cGMP and sodium in rats receiving leptin. These results indicate that oxidative stress-induced NO deficiency is involved in the pathogenesis of leptin-induced hypertension.

Topics: Acetophenones; Aconitate Hydratase; Aldehydes; Animals; Antioxidants; Blood Pressure; Body Weight; Creatine; Cyclic GMP; Cyclic N-Oxides; Drinking; Eating; Hypertension; Isoprostanes; Kidney; Leptin; Male; Malondialdehyde; Natriuresis; Nitric Oxide; Rats; Rats, Wistar; Reactive Nitrogen Species; Sodium; Spin Labels; Tyrosine