pancreastatin and Diabetes-Mellitus--Type-2

Chromogranin A is a member of the granin glycoprotein family that is expressed by the endocrine and neuroendocrine cells of different organs. Intracellularly, chromogranin A contributes to the regulation of secretion and gives several cleavage products after secretion. Some of its cleavage products modify the hormone functions in autocrine and paracrine ways, while the functions of others have not been fully understood yet. Serum chromogranin A level is most prominently used in neuroendocrine tumour diagnostics. In addition, recent studies have suggested that chromogranin A and some of its cleavage products (pancreastatin and WE-14) also play important roles in the pathogenesis of the various forms of diabetes mellitus, but their exact mechanisms still need to be clarified. Higher chromogranin A, pancreastatin, and WE-14 levels have been reported in type 1, type 2, and gestational diabetic patients compared to healthy controls. A notable connection has been inferred through the observation that type 1 diabetes mellitus is not at all or rarely developed in chromogranin A gene-knockout, non-obese diabetic model mice compared to non-knockout, non-obese diabetic mice. Pancreastatin inhibits insulin release in various cell and animal models, and WE-14 serves as an autoantigen for both CD4+ and CD8+ beta cell-destructive diabetogenic T-cell clones in type 1 diabetes. Chromogranin A contributes to the pathogenesis of diabetes mellitus according to the available literature. The current findings facilitate further investigation to unravel the deeper relationships between this glycoprotein and diabetes.

Topics: Animals; Chromogranin A; Diabetes Mellitus; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; Diabetes, Gestational; Female; Humans; Mice; Mice, Inbred NOD; Pregnancy

Chromogranin A (CgA) is an established plasma marker of neuroendocrine tumors and has been suggested to also have a role as biomarker in other diseases. Whether CgA has any role as biomarker in diabetes is, however, unresolved, but its widespread distribution in the secretory granules in endocrine tissues including β cells and α cells in pancreas, and the metabolic effects of its peptide fragments suggest that CgA may play a pathophysiological role in diabetes, and thus also be a potential diabetes biomarker. In this review, we summarize the available information on CgA and some of its functional post-translational cleavage products in diabetes, followed by a discussion of its potential as a plasma marker in diabetes and the methodological concerns involved.

Topics: Biomarkers; Chromogranin A; Diabetes Mellitus, Type 1; Diabetes Mellitus, Type 2; Humans; Insulin-Secreting Cells

Chromogranins or secretogranins (granins), present in secretory granules of virtually all neuroendocrine cells and neurones, are structurally related proteins encoded by different genetic loci: chromogranins A and B, and secretogranins II through VI. Compelling evidence supports both intracellular and extracellular functions for this protein family. Within the cells of origin, a granulogenic or sorting role in the regulated pathway of hormone or neurotransmitter secretion has been documented, especially for chromogranin A (CHGA). Granins also function as pro-hormones, giving rise by proteolytic processing to an array of peptide fragments for which diverse autocrine, paracrine, and endocrine activities have been demonstrated. CHGA measurements yield insight into the pathogenesis of such human diseases as essential hypertension, in which deficiency of the catecholamine release-inhibitory CHGA fragment catestatin may trigger sympathoadrenal overactivity as an aetiologic culprit in the syndrome. The CHGA dysglycaemic fragment pancreastatin is functional in humans in vivo, affecting both carbohydrate (glucose) and lipid (fatty acid) metabolism. Pancreastatin is cleaved from CHGA in hormone storage granules in vivo, and its plasma concentration varies in human disease. The pancreastatin region of CHGA gives rise to three naturally occurring human variants, one of which (Gly297Ser) occurs in the functionally important carboxy-terminus of the peptide, and substantially increases the peptide's potency to inhibit cellular glucose uptake. These observations establish a role for pancreastatin in human intermediary metabolism and disease, and suggest that qualitative hereditary alterations in pancreastatin's primary structure may give rise to interindividual differences in glucose disposition.

Topics: Amino Acid Sequence; Animals; Biological Transport; Blood Glucose; Catecholamines; Cattle; Chromogranin A; Diabetes Mellitus, Type 2; Humans; Metabolic Syndrome; Mice; Molecular Sequence Data; Pancreatic Hormones; Rats; Secretory Vesicles; Sequence Alignment

Pancreastatin (PST), a chromogranin A-derived potent physiological dysglycemic peptide, regulates glucose/insulin homeostasis. We have identified a nonsynonymous functional PST variant (p.Gly297Ser; rs9658664) that occurs in a large section of human populations. Association analysis of this single nucleotide polymorphism with cardiovascular/metabolic disease states in Indian populations (n = 4,300 subjects) displays elevated plasma glucose, glycosylated hemoglobin, diastolic blood pressure, and catecholamines in Gly/Ser subjects as compared with wild-type individuals (Gly/Gly). Consistently, the 297Ser allele confers an increased risk (∼1.3-1.6-fold) for type 2 diabetes/hypertension/coronary artery disease/metabolic syndrome. In corroboration, the variant peptide (PST-297S) displays gain-of-potency in several cellular events relevant for cardiometabolic disorders (e.g., increased expression of gluconeogenic genes, increased catecholamine secretion, and greater inhibition of insulin-stimulated glucose uptake) than the wild-type peptide. Computational docking analysis and molecular dynamics simulations show higher affinity binding of PST-297S peptide with glucose-regulated protein 78 (GRP78) and insulin receptor than the wild-type peptide, providing a mechanistic basis for the enhanced activity of the variant peptide. In vitro binding assays validate these in silico predictions of PST peptides binding to GRP78 and insulin receptor. In conclusion, the PST 297Ser allele influences cardiovascular/metabolic phenotypes and emerges as a novel risk factor for type 2 diabetes/hypertension/coronary artery disease in human populations.

Topics: Amino Acid Sequence; Animals; Cardiovascular Diseases; Catecholamines; Cell Line; Cell Line, Tumor; Chromogranin A; Coronary Artery Disease; Diabetes Mellitus, Type 2; Endoplasmic Reticulum Chaperone BiP; Genetic Association Studies; Genetic Predisposition to Disease; Hep G2 Cells; Humans; Hypertension; India; Metabolic Diseases; Peptides; Polymorphism, Single Nucleotide; Rats; Receptor, Insulin

Recent findings suggest that the accumulation of misfolded aggregates of islet amyloid peptide (IAPP) plays an essential role in pancreatic damage and type 2 diabetes (T2D). Pancreastatin (PST), a chromogranin derived peptide, instigates insulin resistance (IR) and promotes T2D. Here, we aimed to investigate whether PST induces IAPP aggregation in the pancreas, liver, and skeletal muscles. Foremost, we unraveled kinetics of fibril formation by ThT kinetic assay, ANS binding, turbidity, and far UV-CD. Subsequently, we checked the microarchitecture of fibril by TEM. Moreover, the PST action on IAPP expression was examined by immunocytochemistry, immunohistochemistry, western blotting, and real-time PCR. The outcome of spectral analysis and TEM demonstrated the fibril formation in the alone IAPP group but not in the alone PST; however, PST with IAPP produced stronger fibril. Moreover, PST was found to stimulate IAPP aggregation and expression more prominently in PANC1 and HepG2 cells, and pancreas and liver tissues than in L6 and skeletal muscle. Subsequently, pancreastatin inhibitor manifested a decline in the extent of the IAPP fibril formation and its expression. To conclude, PST upon combination induces the aggregation of IAPP in the pancreas, liver, and skeletal muscle, which may have the potential to generate IR and cause T2D.

Topics: Amyloid; Animals; Chromogranin A; Diabetes Mellitus, Type 2; Hep G2 Cells; Humans; Islet Amyloid Polypeptide; Liver; Male; Mice; Mice, Inbred C57BL; Muscle, Skeletal; Pancreas; Protein Aggregation, Pathological; Protein Folding

Mitochondrial dysfunction is among the key factors for the advancement of hepatic steatosis to NAFLD and NASH. Pancreastatin (PST: human ChgA250-301) is a dysglycemic hormone, previously reported to promote steatosis and inflammation in various animal models of metabolic disorders. Recently, we observed PST deregulates energy expenditure and mitochondrial functioning in perimenopausal rats. In the current study, we aimed to decipher the role of PST instigated altered mitochondrial functioning in hepatic steatosis.. The HepG2 cells were PST exposed and the Chga gene was knocked down using siRNA and lipofectamine. Parallelly, type 2 diabetes (T2D) was developed in C57BL/6 mice by HFD feeding and administered PST inhibitor (PSTi8).. The PST exposed cells and HFD fed mice depicted: enhanced CHGA expression detected by IF/IHC, WB, and ELISA; dysregulated cellular ROS, mitochondrial ROS, oxygen consumption rate, mitochondrial membrane potential, ATP level, and NADP/NADP ratio; enhanced apoptosis determined by MTT, TUNEL, Annexin-V FITC, and WB of Bax/bcl2 and caspase 3; hepatic lipid accumulation upon Nile Red, Oil Red O, H&E staining, and the expression of SREBP-1c, FAS, ACC, and SCD; inflammation based on expression and circulatory level of IL6, IL-1β, and TNF-α. However, Chga knocked down HepG2 cells and PSTi8 treated mice unveiled protection from all the above abnormalities.. Collectively, the aforementioned data suggested the alteration in mitochondrial function induced by PST is responsible for hepatic steatosis in T2D.

Topics: Animals; Body Weight; Chromogranin A; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 2; Diet, High-Fat; Fatty Liver; Hep G2 Cells; Humans; Inflammation; Lipid Metabolism; Male; Mice, Inbred C57BL; Mitochondria, Liver

Pancreastatin (PST), a chromogranin A (CHGA) derived peptide connects obesity with insulin resistance by inducing inflammation. Previously, we have evaluated potential activity of PST inhibitor (PSTi8) in liver and adipose tissue in type 2 diabetic mice model. In this study we further explore the therapeutic effect of PSTi8 on glucose metabolism in skeletal muscle cells/tissue and its effect on energy homeostasis in diet induced diabetic mice model. In in-vitro studies, we found that PSTi8 increases glucose uptake via enhanced GLUT4 translocation in L6 cells. This positive effect of PSTi8 led us to proceed with in-vivo studies in diabetic mice. C57BL/6 mice were fed HFD or HFrD diet for 12 weeks along with single STZ induction at 4th week followed by PSTi8 treatment. We found that HFD and HFrD model showed increased fat mass, caused glucose intolerance and insulin resistance, with accompanying proinflammatory effect on epididymal white adipose tissue (eWAT) together leading to skeletal muscle insulin resistance. Administration of PSTi8 protects from diet induced inflammatory response and enhances glucose tolerance and insulin sensitivity. PSTi8 improves circulating adipokine and lipid parameters, along with switch in macrophage polarisation from M1 to M2 in stromal vascular fraction of adipose tissue. In addition, treatment of PSTi8 also improves energy homeostasis, decreases circulatory non-esterified fatty acids level and inhibits ceramide deposition in muscle tissue. Overall this increased muscle insulin sensitivity is mediated via AKT/AS160/GLUT4 pathway activation. Our results reveal that PSTi8 inhibits the obesity mediated inflammation which enhances glucose disposal in skeletal muscle.

Topics: Adipose Tissue, White; Adiposity; Animals; Biomarkers; Blood Glucose; Chromogranin A; Diabetes Mellitus, Experimental; Diabetes Mellitus, Type 2; Diet, High-Fat; Energy Metabolism; Glucose Transporter Type 4; GTPase-Activating Proteins; Humans; Hypoglycemic Agents; Inflammation Mediators; Insulin Resistance; Macrophages; Male; Mice, Inbred C57BL; Muscle, Skeletal; Obesity; Proto-Oncogene Proteins c-akt; Streptozocin; THP-1 Cells

The chromogranin A (CHGA) fragment pancreastatin (human CHGA250-301) impairs glucose metabolism, but the role of human pancreastatin in vivo remains unexplored.. We studied brachial arterial infusion of pancreastatin (CHGA273-301-amide at approximately 200 nm) on forearm metabolism of glucose, free fatty acids, and amino acids. Plasma pancreastatin was measured in obesity or type 2 diabetes. Systematic discovery of amino acid variation was performed, and the potency of one variant in the active carboxyl terminus (Gly297Ser) was tested.. Pancreastatin decreased glucose uptake by approximately 48-50%; the lack of change in forearm plasma flow indicated a metabolic, rather than hemodynamic, mechanism. A control CHGA peptide (catestatin, CHGA352-372) did not affect glucose. Insulin increased glucose uptake, but pancreastatin did not antagonize this action. Pancreastatin increased spillover of free fatty acids by about 4.5- to 6.4-fold, but not spillover of amino acids. Insulin diminished spillover of both free fatty acids and amino acids, but these actions were not reversed by pancreastatin. Plasma pancreastatin was elevated approximately 3.7-fold in diabetes, but was unchanged during weight loss. Proteolytic cleavage sites for pancreastatin in vivo were documented by matrix-assisted laser desorption ionization/time of flight mass spectrometry. Three pancreastatin variants were discovered: Arg253Trp, Ala256Gly, and Gly297Ser. The Gly297Ser variant had unexpectedly increased potency to inhibit glucose uptake.. The dysglycemic peptide pancreastatin is specifically and potently active in humans on multiple facets of intermediary metabolism, although it did not antagonize insulin. Pancreastatin is elevated in diabetes, and the variant Gly297Ser had increased potency to inhibit glucose uptake. The importance of human pancreastatin in vivo as well as its natural variants is established.

Topics: Amino Acid Sequence; Amino Acids; Base Sequence; Case-Control Studies; Chromogranin A; Diabetes Mellitus, Type 2; Fatty Acids, Nonesterified; Forearm; Genetic Variation; Glucose; Humans; Injections, Intra-Articular; Male; Middle Aged; Molecular Sequence Data; Obesity; Pancreatic Hormones; Polymorphism, Genetic; Weight Loss

The physiologic effects of the chromogranin A peptide fragment, pancreastatin, were studied in six healthy Caucasian men, ages 25-46 years. Synthetic pancreastatin (human chromogranin A(273-301)-amide) was infused into the brachial artery of each subject to achieve a local concentration of approximately 200 nM over 15 minutes. Forearm blood flow was measured by strain-gauge plethysmography while (A-V)(glucose) was monitored by arterial and venous sampling. Pancreastatin infusion significantly reduced forearm glucose uptake (mean reduction +/- 1 SEM, 54 +/- 15%; P = 0.028) but did not alter forearm blood flow-indicating a metabolic, rather than hemodynamic, effect. Simultaneous infusion of pancreastatin with insulin (0.1 mU/kg/min) did not diminish insulin-induced forearm glucose uptake, suggesting pancreastatin is not simply a negative insulin modulator. The results of this study suggest that pancreastatin may contribute to the dysglycemia associated with type 2 diabetes and essential hypertension, two common human disease states in which plasma pancreastatin levels are elevated.

Topics: Adult; Arm; Blood Flow Velocity; Blood Glucose; Chromogranin A; Diabetes Mellitus, Type 2; Glucose; Hemodynamics; Humans; Male; Middle Aged; Muscle, Skeletal; Pancreatic Hormones

Pancreastatin (PST) is known as the peptide which inhibits first phase of glucose-stimulated insulin secretion. Fasting plasma PST levels and responses of PST after oral glucose ingestion in patients with non-insulin-dependent diabetes mellitus (NIDDM) were studied with human PST-specific radioimmunoassay. Fasting plasma PST in NIDDM patients was not different from healthy controls, although a slightly higher level of PST was observed in patients treated with sulfonylurea among NIDDM patients. No significant increase in plasma PST was observed after a glucose ingestion in healthy controls. In contrast, plasma PST levels in NIDDM patients rose significantly after glucose ingestion. These results suggest a possible pathophysiological role for PST in NIDDM.

Topics: Administration, Oral; Blood Glucose; Chromogranin A; Diabetes Mellitus, Type 2; Glucose; Humans; Insulin; Insulin Secretion; Pancreatic Hormones; Sulfonylurea Compounds

The concentration and molecular form of pancreastatin-like immunoreactivity (PST-LI) in urine of normal subjects and patients with noninsulin-dependent diabetes mellitus or chronic renal failure were examined. PST-LI output (mean +/- SEM) in urine of normal subjects was 74.6 +/- 8.5 pmol/day and 87.1 +/- 11.7 pmol/g creatinine. That in patients with noninsulin-dependent diabetes mellitus was 78.1 +/- 9.0 (SEM) pmol/day and 85.6 +/- 9.0 pmol/g creatinine and was not significantly different from that in normal subjects. Gel filtration analysis showed that PST-LI molecules excreted in urine of these two groups were smaller than human pancreastatin (43-52) (hPST-10) of C-terminal fragment. The PST-LI molecular forms were deduced to be nonbioactive from the result that hPST-10 did not inhibit pancreatic exocrine secretion. PST-LI excretion in patients with chronic renal failure was 258.5 +/- 62.9 pmol/day and 713.2 +/- 219.6 pmol/g creatinine. A molecular form corresponding to hPST-52 and a larger form eluted in the high mol wt region (approximately mol wt 15 K) were detected by gel filtration of urine from these patients, indicating that PST-LI is excreted in urine without degradation in patients with chronic renal failure. These results support the suggestion that the kidney may play an important role in PST degradation or metabolism.

Topics: Chromatography, Gel; Chromogranin A; Diabetes Mellitus, Type 2; Humans; Kidney Failure, Chronic; Pancreatic Hormones; Peptide Fragments; Radioimmunoassay