Pancreastatin induces islet amyloid peptide aggregation in the pancreas, liver, and skeletal muscle: An implication for type 2 diabetes

Chromogranin A-derived peptides pancreastatin and catestatin: emerging therapeutic target for diabetes

Chromogranin A (ChgA) is an acidic pro-protein found in neuroendocrine organs, pheochromocytoma chromaffin granules, and tumor cells. Proteolytic processing of ChgA gives rise to an array of biologically active peptides such as pancreastatin (PST), vasostatin, WE14, catestatin (CST), and serpinin, which have diverse roles in regulating cardiovascular functions and metabolism, as well as inflammation. Intricate tissue-specific role of ChgA-derived peptide activity in preclinical rodent models of metabolic syndrome reveals complex effects on carbohydrate and lipid metabolism. Indeed, ChgA-derived peptides, PST and CST, play a pivotal role in metabolic syndrome such as obesity, insulin resistance, and diabetes mellitus. Additionally, supplementation of specific peptide in ChgA-KO mice have an opposing effect on physiological functions, such as PST supplementation reduces insulin sensitivity and enhances inflammatory response. In contrast, CST supplementation enhances insulin sensitivity and reduces inflammatory response. In this review, we focus on the tissue-specific role of PST and CST as therapeutic targets in regulating carbohydrate and lipid metabolism, along with the associated risk factors.

E96V Mutation in the Kdelr3 Gene Is Associated with Type 2 Diabetes Susceptibility in Obese NZO Mice

Type 2 diabetes (T2D) represents a multifactorial metabolic disease with a strong genetic predisposition. Despite elaborate efforts in identifying the genetic variants determining individual susceptibility towards T2D, the majority of genetic factors driving disease development remain poorly understood. With the aim to identify novel T2D risk genes we previously generated an N2 outcross population using the two inbred mouse strains New Zealand obese (NZO) and C3HeB/FeJ (C3H). A linkage study performed in this population led to the identification of the novel T2D-associated quantitative trait locus (QTL) Nbg15 (NZO blood glucose on chromosome 15, Logarithm of odds (LOD) 6.6). In this study we used a combined approach of positional cloning, gene expression analyses and in silico predictions of DNA polymorphism on gene/protein function to dissect the genetic variants linking Nbg15 to the development of T2D. Moreover, we have generated congenic strains that associated the distal sublocus of Nbg15 to mechanisms altering pancreatic beta cell function. In this sublocus, Cbx6, Fam135b and Kdelr3 were nominated as potential causative genes associated with the Nbg15 driven effects. Moreover, a putative mutation in the Kdelr3 gene from NZO was identified, negatively influencing adaptive responses associated with pancreatic beta cell death and induction of endoplasmic reticulum stress. Importantly, knockdown of Kdelr3 in cultured Min6 beta cells altered insulin granules maturation and pro-insulin levels, pointing towards a crucial role of this gene in islets function and T2D susceptibility.

Pancreastatin induces hepatic steatosis in type 2 diabetes by impeding mitochondrial functioning

AIMS

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.

MAIN METHODS

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).

KEY FINDINGS

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.

SIGNIFICANCE

Collectively, the aforementioned data suggested the alteration in mitochondrial function induced by PST is responsible for hepatic steatosis in T2D.

Ethanolic extract of Cissus quadrangularis improves vasoreactivity by modulation of eNOS expression and oxidative stress in spontaneously hypertensive rats

BACKGROUND

Endothelial dysfunction is related to the reduced bioavailability of nitric oxide (NO) and plays a significant role in developing hypertension. The intake of a diet rich in antioxidants decreases the threat of hypertension. Cissus quadrangularis possesses antioxidant, anti-inflammatory, and hypocholesterolemic activities. However, to date, no studies have been performed to explore this plant's antihypertensive and vasorelaxant activity. Herein, we investigated the chronic effect of C. quadrangularis on blood pressure as well as vascular function in hypertensive rats.

METHODS

Male spontaneously hypertensive rats (SHR) were randomly divided into two groups. Normotensive Wistar rats were taken as the control group. The treatment was done using ethanolic extract of C. quadrangularis (EECQ) at a dose of 200 mg/kg.

RESULTS

The administration of EECQ for six weeks reduced the systolic blood pressure, mean arterial blood pressure, and heart rate. It also alleviated the cardiac and renal hypertrophy indices. Supplementation of EECQ improved the endothelium-dependent aortic vasodilation induced by acetylcholine. It restored the NO level and endothelial NO synthase expression in the aorta. Subsequently, the extract alleviates the oxidative stress and inflammatory markers in SHR rats.

CONCLUSION

Thus, in the present study, the chronic treatment of EECQ to genetically hypertensive rats improved endothelium-dependent relaxation in addition to its antihypertensive effect by eNOS activation and inhibition of ROS production, inflammation.