Topic
Insulin
About: Insulin is a research topic. Over the lifetime, 124295 publications have been published within this topic receiving 5129734 citations. The topic is also known as: human insulin.
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TL;DR: It is postulate that this variability in the severity of insulin resistance varies greatly among obese people might reflect differences in levels of lipid-droplet proteins that promote the sequestration of fatty acids within adipocytes in the form of triglycerides, thereby lowering exposure of skeletal muscle to the inhibitory effects of fatty acid.
Abstract: Acquired resistance to the action of insulin to stimulate glucose transport in skeletal muscle is associated with obesity and promotes the development of type 2 diabetes. In skeletal muscle, insulin resistance can result from high levels of circulating fatty acids that disrupt insulin signalling pathways. However, the severity of insulin resistance varies greatly among obese people. Here we postulate that this variability might reflect differences in levels of lipid-droplet proteins that promote the sequestration of fatty acids within adipocytes in the form of triglycerides, thereby lowering exposure of skeletal muscle to the inhibitory effects of fatty acids.
1,980 citations
TL;DR: It is shown that expression of retinol binding protein-4 (RBP4) is elevated in adipose tissue of adipose-Glut4-/- mice and RBP4 is an adipocyte-derived ‘signal’ that may contribute to the pathogenesis of type 2 diabetes.
Abstract: In obesity and type 2 diabetes, expression of the GLUT4 glucose transporter is decreased selectively in adipocytes. Adipose-specific Glut4 (also known as Slc2a4) knockout (adipose-Glut4-/-) mice show insulin resistance secondarily in muscle and liver. Here we show, using DNA arrays, that expression of retinol binding protein-4 (RBP4) is elevated in adipose tissue of adipose-Glut4-/- mice. We show that serum RBP4 levels are elevated in insulin-resistant mice and humans with obesity and type 2 diabetes. RBP4 levels are normalized by rosiglitazone, an insulin-sensitizing drug. Transgenic overexpression of human RBP4 or injection of recombinant RBP4 in normal mice causes insulin resistance. Conversely, genetic deletion of Rbp4 enhances insulin sensitivity. Fenretinide, a synthetic retinoid that increases urinary excretion of RBP4, normalizes serum RBP4 levels and improves insulin resistance and glucose intolerance in mice with obesity induced by a high-fat diet. Increasing serum RBP4 induces hepatic expression of the gluconeogenic enzyme phosphoenolpyruvate carboxykinase (PEPCK) and impairs insulin signalling in muscle. Thus, RBP4 is an adipocyte-derived 'signal' that may contribute to the pathogenesis of type 2 diabetes. Lowering RBP4 could be a new strategy for treating type 2 diabetes.
1,961 citations
TL;DR: Data indicate that peripheral insulin resistance, increased fatty acid beta oxidation, and hepatic oxidative stress are present in both fatty liver and NASH, but NASH alone is associated with mitochondrial structural defects.
1,938 citations
TL;DR: Mice created with a neuron-specific disruption of the IR gene showed increased food intake, and both male and female mice developed diet-sensitive obesity with increases in body fat and plasma leptin levels, mild insulin resistance, elevated plasma insulin levels, and hypertriglyceridemia.
Abstract: Insulin receptors (IRs) and insulin signaling proteins are widely distributed throughout the central nervous system (CNS). To study the physiological role of insulin signaling in the brain, we created mice with a neuron-specific disruption of the IR gene (NIRKO mice). Inactivation of the IR had no impact on brain development or neuronal survival. However, female NIRKO mice showed increased food intake, and both male and female mice developed diet-sensitive obesity with increases in body fat and plasma leptin levels, mild insulin resistance, elevated plasma insulin levels, and hypertriglyceridemia. NIRKO mice also exhibited impaired spermatogenesis and ovarian follicle maturation because of hypothalamic dysregulation of luteinizing hormone. Thus, IR signaling in the CNS plays an important role in regulation of energy disposal, fuel metabolism, and reproduction.
1,932 citations
TL;DR: PCO women have significant insulin resistance that is independent of obesity, changes in body composition, and impairment of glucose tolerance, and PCO is associated with a unique disorder of insulin action.
Abstract: Hyperinsulinemia secondary to a poorly characterized disorder of insulin action is a feature of the polycystic ovary syndrome (PCO). However, controversy exists as to whether insulin resistance results from PCO or the obesity that is frequently associated with it. Thus, we determined in vivo insulin action on peripheral glucose utilization (M) and hepatic glucose production (HGP) with the euglycemic glucose-clamp technique in obese ( n = 19) and nonobese ( n = 10) PCO women and age- and body-composition-matched normal ovulatory women ( n = 11 obese and n = 8 nonobese women). None had fasting hyperglycemia. Two obese PCO women had diabetes mellitus, established with an oral glucose tolerance test; no other women had impairment of glucose tolerance. However, the obese PCO women had significantly increased fasting and 2-h glucose levels after an oral glucose load and increased basal HGP compared with their body-composition-matched control group. There were statistically significant interactions between obesity and PCO in fasting glucose levels and basal HGP ( P < .05). Steady-state insulin levels of ∼100 μU/ml were achieved during the clamp. Insulin-stimulated glucose utilization was significantly decreased in both PCO groups whether expressed per kilogram total weight ( P < .001) or per kilogram fat free mass ( P < .001) or when divided by the steady-state plasma insulin (I) level (M/I, P < .001). There was residual HGP in 4 of 15 obese PCO, 0 of 11 obese normal, 2 of 10 nonobese PCO, and 0 of 8 nonobese normal women. The metabolic clearance rate of insulin did not differ in the four groups. We conclude that 1 ) PCO women have significant insulin resistance that is independent of obesity, changes in body composition, and impairment of glucose tolerance, 2 ) PCO and obesity have a synergistic deleterious effect on glucose tolerance, 3 ) hyperinsulinemia in PCO is not the result of decreased insulin clearance, and 4 ) PCO is associated with a unique disorder of insulin action.
1,916 citations