Orphan receptor GPR50 attenuates inflammation and insulin signaling in 3T3-L1 preadipocytes

Evaluation of the Potential Hypoglycaemic Properties of Mimusops zeyheri Sond. and Aloe marlothii A.Berger, Two Plants Used by Traditional Healers in South Africa

Mimusops zeyheri Sond. And Aloe marlothii A.Berger are used traditionally in South Africa to manage many diseases, including diabetes mellitus. The mechanism through which these extracts exert blood glucose lowering is not well understood or reported. This study was aimed at assessing M. zeyheri and A. marlothii plant extracts for their potential to exhibit antidiabetic activity and their associated mechanisms. We evaluated the action of both extracts on major genes involved in the insulin signalling pathways in skeletal muscle cells. The in vitro cytotoxic effects of M. zeyheri and A. marlothii extracts were evaluated using the MTT assay and glucose uptake was evaluated using a glucose oxidase assay. The amount of translocated GLUT-4 was determined using the flow cytometry. Conventional PCR was used to determine the expression of GLUT-1 and GLUT-4 and RT-qPCR. IRS-1 total protein and Phospho-Akt were determined using ELISA. Plant extracts stimulated glucose absorption by skeletal muscle cells. M. zeyheri extract increased glucose absorption in muscle cells after 1 and 3 h of incubation. A 2-fold increase in translocated GLUT-4 was noted with M. zeyheri. The mRNA levels of GLUT-4 and GLUT-1 remained uniform in all treatments, while IRS-1, PI3K, Akt1, Akt2, and PPAR-γ were downregulated by both extracts. The expression of GLUT-4 was significantly increased by the action of insulin and M. zeyheri extract at 500 μg/mL. This study validates the traditional use of aqueous extracts of A. marlothii and M. zeyheri as hypoglycaemic plants and raises the assertion that the selected plant extracts utilise the IRS-1/PI3K/Akt pathway.

Deficiency of the lipid flippase ATP10A causes diet-induced dyslipidemia in female mice

Genetic association studies have linked ATP10A and closely related type IV P-type ATPases (P4-ATPases) to insulin resistance and vascular complications, such as atherosclerosis. ATP10A translocates phosphatidylcholine and glucosylceramide across cell membranes, and these lipids or their metabolites play important roles in signal transduction pathways regulating metabolism. However, the influence of ATP10A on lipid metabolism in mice has not been explored. Here, we generated gene-specific Atp10A knockout mice and show that Atp10A-/- mice fed a high-fat diet did not gain excess weight relative to wild-type littermates. However, Atp10A-/- mice displayed female-specific dyslipidemia characterized by elevated plasma triglycerides, free fatty acids and cholesterol, as well as altered VLDL and HDL properties. We also observed increased circulating levels of several sphingolipid species along with reduced levels of eicosanoids and bile acids. The Atp10A-/- mice also displayed hepatic insulin resistance without perturbations to whole-body glucose homeostasis. Thus, ATP10A has a sex-specific role in regulating plasma lipid composition and maintaining hepatic liver insulin sensitivity in mice.

Deficiency of the lipid flippase ATP10A causes diet-induced dyslipidemia in female mice

Genetic association studies have linked ATP10A and closely related type IV P-type ATPases (P4-ATPases) to insulin resistance and vascular complications, such as atherosclerosis. ATP10A translocates phosphatidylcholine and glucosylceramide across cell membranes, and these lipids or their metabolites play important roles in signal transduction pathways regulating metabolism. However, the influence of ATP10A on lipid metabolism in mice has not been explored. Here, we generated gene-specific Atp10A knockout mice and show that Atp10A-/- mice fed a high-fat diet did not gain excess weight relative to wild-type littermates. However, Atp10A-/- mice displayed female-specific dyslipidemia characterized by elevated plasma triglycerides, free fatty acids and cholesterol, as well as altered VLDL and HDL properties. We also observed increased circulating levels of several sphingolipid species along with reduced levels of eicosanoids and bile acids. The Atp10A-/- mice also displayed hepatic insulin resistance without perturbations to whole-body glucose homeostasis. Thus, ATP10A has a sex-specific role in regulating plasma lipid composition and maintaining hepatic liver insulin sensitivity in mice.