The p66Shc redox adaptor protein is induced by saturated fatty acids and mediates lipotoxicity-induced apoptosis in pancreatic beta cells

Abstract

Aims/hypothesis The role of the redox adaptor protein p66 Shc as a potential mediator of saturated fatty acid (FA)-induced beta cell death was investigated. Methods The effects of the FA palmitate on p66 Shc expression were evaluated in human and murine islets and in rat insulinsecreting INS-1E cells. p66 Shc expression was also measured in islets from mice fed a high-fat diet (HFD) and from human donors with different BMIs. Cell apoptosis was quantified by two independent assays. The role of p66 Shc was investigated using pancreatic islets from p66 Shc−/− mice and in INS-1E cells with knockdown of p66 Shc or overexpression of wildtype and phosphorylation-defective p66 Shc . Production of reactive oxygen species (ROS) was evaluated by the dihydroethidium oxidation method. Results Palmitate induced a selective increase in p66 Shc protein expression and phosphorylation on Ser 36 and augmented apoptosis in human and mouse islets and in INS-1E cells. Inhibiting the tumour suppressor protein p53 prevented both the palmitate-induced increase in p66 Shc expression and beta cell apoptosis. Palmitate-induced apoptosis was abrogated in islets from p66 Shc−/− mice and following p66 Shc knockdown in INS-1E cells; by contrast, overexpression of p66 Shc , but not that of the phosphorylation-defective p66 Shc mutant, enhanced palmitate-induced apoptosis. The pro-apoptotic effects of p66 Shc were dependent upon its c-Jun N-terminal kinasemediated phosphorylation on Ser 36 and associated with generation of ROS. p66 Shc protein expression and function were also elevated in islets from HFD-fed mice and from obese/ overweight cadaveric human donors. Conclusions/interpretation p53-dependent augmentation of p66 Shc expression and function represents a key signalling response contributing to beta cell apoptosis under conditions of lipotoxicity.

p66Shc deletion or deficiency protects from obesity but not metabolic dysfunction in mice and humans

“…In addition, p66Shc may have divergent, and possibly antagonistic, effects in the different organs and tissues involved in the metabolic response to overfeeding, an issue that could be addressed only with tissue-specific p66Shc knockout. For instance, obese p66Shc −/− mice become glucose intolerant despite p66Shc −/− beta cells being resistant to lipotoxicity-induced apoptosis [22]. Therefore, further studies are still needed to dissect the role of p66Shc in whole body metabolism.…”

Molecular mechanisms underlying metabolic syndrome: the expanding role of the adipocyte

“…P66Shc is a redox enzyme that generates ROS and, according to the free radical theory of aging, may promote senescence (169,170); however, whereas the role of p66Shc in regulating lifespan-at least in mice-has been recently debated (171), p66Shc gene has a prominent role in fat accumulation and in setting the condit i o n sf o rm e t a b o l i cd i s e a s e s ;t h i se v i d e n c ei sq u i t e strong in animal models of metabolic and cardiovascular pathologies (172)(173)(174)(175). In the adipocyte, insulin activates p66Shc and the absence of p66Shc impairs insulin-induced lipogenesis in adipocytes in vitro (176).…”

Anti-Aging Genes Improve Appetite Regulation and Reverse Cell Senescence and Apoptosis in Global Populations

“…Repression of p66Shc expression by Sirt 1 has been shown to be involved with liver injury and hyperglycemia induced endothelium dysfunction [73]. Palmitic acid is an inhibitor of Sirt 1 and palmitate has been shown to increase p66Shc (Ser phosphorylation) in pancreatic beta cells [74]. p53 is closely involved with the palmitate-induced increase in p66Shc expression and beta cell apoptosis.…”

“…To maintain the cell anti-aging gene mechanisms and prevent early programmed cell death diets that are very low carbohydrate diets need to be ingested to avoid the intestinal absorption of LPS into the blood that is found in various foods [14]. The low calorie diet will maintain the nuclear Sirt 1 activity with relevance to p66Shc mechanisms that are sensitive to the ingestion of high palmitic acid and leads to cell cycle dysregulation with cell apoptosis [74] [126]. Short chain fatty acids (SCFA) have become important to appetite regulation with the consumption ofacetate, propionic acid and butyric acid at therapeutic doses applicable to central appetite regulation [127] [128].…”