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Chronic Exposure to Palmitic Acid Downregulates AKT in Beta-Cells through Activation of mTOR

ABSTRACT: High circulating lipids occurring in obese individuals and insulin resistant patients are considered a contributing factor to Type 2 Diabetes (T2D). Exposure to high lipids is proposed to both protect and damage beta-cells under different circumstances. By feeding mice high fat diet (HFD) for 2 weeks up to 14 months, we showed that HFD initially causes the beta-cells to expand in population whereas long-term exposure to HFD is associated with failure of beta-cells and the inability of animals to respond to glucose challenge. To prevent the failure of beta-cells and the development of T2D, we explored the molecular mechanisms that underlie this biphasic response of beta-cells to lipid exposure. Using palmitic acid (PA) in cultured beta-cells and islets, we demonstrated that chronic exposure to lipids leads to reduced viability and inhibition of cell cycle progression concurrent with downregulation of a pro-growth/survival kinase AKT, independent of glucose. To explore the mechanism further, we performed RNA-seq analysis in WT and AKT1-/- mice fed HFD for 4 months. The data here is the results of this study.

ORGANISM(S): Mus musculus

PROVIDER: GSE183778 | GEO | 2021/09/11

REPOSITORIES: GEO

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Project description:The incidence of type 2 diabetes (T2D) is increasing globally, with long-term implications for human health and longevity. Heart disease is the leading cause of death in T2D patients, who display an elevated risk of an acute cardiovascular event and worse outcomes following such an insult. The underlying mechanisms that predispose the diabetic heart to this poor prognosis remain to be defined. This study developed a pre-clinical model (Rattus norvegicus) that complemented caloric excess from a high-fat diet (HFD) and pancreatic β-cell dysfunction from streptozotocin (STZ) to produce hyperglycaemia, peripheral insulin resistance, hyperlipidaemia and elevated fat mass to mimic the clinical features of T2D. Ex vivo cardiac function was assessed using Langendorff perfusion with systolic and diastolic contractile depression observed in T2D hearts. Cohorts representing untreated, individual HFD- or STZ-treatments and the combined HFD+STZ approach were used to generate ventricular samples (n=9 per cohort) for sequential and integrated analysis of the proteome, lipidome and metabolome by liquid chromatography-tandem mass spectrometry. This study found that in T2D hearts, HFD treatment primed the metabolome, while STZ treatment was the major driver for changes in the proteome. Both treatments equally impacted the lipidome. Our data suggest that increases in β-oxidation and early TCA cycle intermediates promoted rerouting via 2-oxaloacetate to glutamate, γ aminobutyric acid and glutathione. Furthermore, we suggest that the T2D heart activates networks to redistribute excess acetyl-CoA towards ketogenesis and incomplete β-oxidation through the formation of short-chain acylcarnitine species. Multi-omics provided a global and comprehensive molecular view of the diabetic heart, which distributes substrates and products from excess β-oxidation, reduces metabolic flexibility and impairs capacity to restore high energy reservoirs needed to respond to and prevent subsequent acute cardiovascular events.

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Chronic Exposure to Palmitic Acid Downregulates AKT in Beta-Cells through Activation of mTOR

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