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Abstract: Glucagon-like peptide-1 (GLP-1) is an incretin hormone that decreases postprandial glycemic excursions by enhancing insulin secretion but with short half-life due to rapid inactivation by enzymatic N-terminal truncation. Therefore, efforts are being made to improve the stability of GLP-1 via modifying its structure or inhibiting dipeptidyl-peptidase IV (DPP IV), which is responsible for its degradation. Here we report a novel GLP-1 analog BPI3006 with –NHCO– of Ala8 replaced by –CH(CF3)NH– and features of its metabolic stability, GLP-1 receptor trans-activation and in vivo biological activity. BPI3006 is highly resistant to DPP IV-mediated degradation with 91.1% of parental peptide left after 24h exposure to the enzyme. BPI3006 also effectively activates its target gene promoter through GLP-1 receptor activation by measuring the transiently transfected reporter gene green fluorescence protein (GFP) expression in NIT-1 cells. Furthermore, BPI3006 could well restrain the glycemia variation in fasted normal ICR mice after a single administration followed by an oral glucose loading. In spontaneous type 2 diabetic KKAy mice, BPI3006 injected twice daily could significantly improve the oral glucose tolerance and hyperinsulinemia, as well as ameliorate the food and water consumption. In conclusion, BPI3006 has enhanced resistance to DPP IV leading to improved stability, and shows excellent in vivo biological activity. Thus it may be a new candidate for T2DM treatment and its novel modification may provide valuable guidance for the future development of long-acting GLP-1 analogs. [ABSTRACT FROM AUTHOR]

Abstract Recently, SIRT5 was reported to be a predominant desuccinylase and demalonylase in mitochondria. Ablation of SIRT5 enhances the systemic succinylation and malonylation of mitochondrial proteins, including various metabolic enzymes; however, its function in pancreatic β cells has not yet been clarified. In this study, we evaluated the effects of SIRT5 overexpression on glucolipotoxicity-induced apoptosis in β cell lines. Full-length SIRT5, which preferentially targeted to mitochondria and partially to the nucleus and cytoplasm, was overexpressed in NIT-1 cells. Chronic exposure to excess palmitate and glucose (High-PA-G) induced apoptosis and suppressed glucose-stimulated insulin secretion in β cells. SIRT5 overexpression significantly alleviated apoptosis under the High-PA-G condition, accompanied by suppressed Caspase 3 activity and reduced malondialdehyde levels. SIRT5 overexpression also improved β cell secretory capacity in response to glucose under the High-PA-G condition, suggesting its protective role in β cell function. Furthermore, SIRT5 overexpression reversed the decreasing trend of anti-apoptotic factors BCL-2 and BCL-XL expression under High-PA-G condition. Further regulation mechanisms between SIRT5 and these anti-apoptotic factors remains to be explored in future studies. Our data reveal that SIRT5 is a potentially protective factor for pancreatic β cells against glucolipotoxicity-induced apoptosis and cell dysfunction. Highlights • SIRT5 expression significantly diminished in the pancreas of T2DM animals. • SIRT5 reduced apoptotic cell mass and retained glucose-stimulated insulin secretion in β cell lines upon glucolipotoxicity. • SIRT5 plays an essential role in maintaining the β cell mass and function under glucolipotoxicity condition. [ABSTRACT FROM AUTHOR]