t0901317 and Hyperinsulinism

The nuclear liver X receptor (LXR) regulates multiple aspects of cholesterol, triacylglycerol (TG), and carbohydrate metabolism. Activation of LXR induces the expression of genes encoding enzymes involved in de novo lipogenesis (DNL) resulting in hepatic steatosis in mice. Pharmacological LXR activation has also been reported to improve insulin sensitivity and glucose homeostasis in diabetic rodents. The effects of pharmacological LXR ligands on insulin's action on hepatic lipid metabolism are not known. We evaluated secretion of VLDL during a hyperinsulinemic euglycemic clamp in mice treated with the LXR-ligand T0901317. In untreated mice, hyperinsulinemia reduced the availability of plasma NEFA for VLDL-TG synthesis, increased the contribution of DNL to VLDL-TG, reduced VLDL particle size, and suppressed overall VLDL-TG production rate by approximately 50%. Upon T0901317 treatment, hyperinsulinemia failed to reduce VLDL particle size or suppress VLDL-TG production rate, but the contribution of DNL to VLDL-TG was increased. In conclusion, the effects of LXR activation by T0901317 on lipid metabolism can override the normal control of insulin to suppress VLDL particle secretion.

Topics: Animals; Blood Glucose; Gene Expression; Glucose Clamp Technique; Hydrocarbons, Fluorinated; Hyperinsulinism; Lipoproteins, VLDL; Liver; Liver X Receptors; Male; Mice; Mice, Inbred C57BL; Orphan Nuclear Receptors; Particle Size; Sterol Regulatory Element Binding Protein 1; Sulfonamides; Triglycerides

Adipocytes release a variety of factors which deregulation could provide the basis for complications such as insulin resistance, an early defect on the onset of type 2 diabetes. Such insulin resistance can initially be overcome by compensatory hyperinsulinemia, but the prolonged presence of the hormone can be detrimental for insulin sensitivity.. The objective of the study was to dissect the molecular mechanisms that may regulate hyperinsulinemia-induced insulin resistance in a human liposarcoma cell line and its paracrine interactions with a human rhabdomyosarcoma cell line.. We studied glucose uptake, lipolysis, insulin signaling, and secretion pattern at different days of adipocyte differentiation in the presence of insulin.. Adipocytes differentiated for 14 d gain insulin sensitivity on glucose uptake and inhibition of lipolysis, but prolonged cultures develop an insulin-resistant state characterized by an increase in phosphatase and tensin homolog-deleted on chromosome 10 expression and defects in insulin signaling at the insulin receptor substrate-1/AKT level. The secretion pattern of nonesterified fatty acids, IL-6, adiponectin, leptin, and monocyte chemotactic protein-1 was in keeping with the changes in insulin sensitivity during differentiation. An inverse biphasic response was also observed in human myocytes when they were cultured with various adipocyte-conditioned media, although insulin resistance was detected earlier than in adipocytes. This behavior mimics hyperinsulinemia because insulin action was restored when adipocytes were cultured in the absence of the hormone. Pharmacological treatment of adipocytes with a liver X receptor agonist reestablishes insulin-stimulated glucose uptake, whereas treatment with a peroxisome proliferator-activated receptor-gamma agonist restored the antilipolytic action of insulin.. Hyperinsulinemia deregulates adipocyte secretion pattern, producing insulin resistance in adipocytes and myocytes, a situation that can be ameliorated with nuclear receptor agonists.

Topics: Adipocytes; Cell Differentiation; Cell Line; Chemokine CCL2; DNA-Binding Proteins; Fatty Acids, Nonesterified; Glucose; Humans; Hydrocarbons, Fluorinated; Hyperinsulinism; Insulin Resistance; Interleukin-6; Lipid Metabolism; Liver X Receptors; Muscle Cells; Muscle, Skeletal; Orphan Nuclear Receptors; Receptors, Cytoplasmic and Nuclear; Sulfonamides