The H19 lncRNA has been implicated in development and growth control and is associated with human genetic disorders and cancer. Acting as a molecular sponge, H19 inhibits microRNA (miRNA) let-7. Here we report that H19 is significantly decreased in muscle of human subjects with type-2 diabetes and insulin resistant rodents. This decrease leads to increased bioavailability of let-7, causing diminished expression of let-7 targets, which is recapitulated in vitro where H19 depletion results in impaired insulin signaling and decreased glucose uptake. Furthermore, acute hyperinsulinemia downregulates H19, a phenomenon that occurs through PI3K/AKT-dependent phosphorylation of the miRNA processing factor KSRP, which promotes biogenesis of let-7 and its mediated H19 destabilization. Our results reveal a previously undescribed double-negative feedback loop between sponge lncRNA and target miRNA that contributes to glucose regulation in muscle cells.

Endometriosis affects approximately 15% of reproductive aged women and is associated with chronic pelvic pain and infertility. However, the molecular mechanisms by which endometriosis impacts fertility are poorly understood. The developmentally regulated, imprinted H19 long noncoding RNA (lncRNA) functions to reduce the bioavailability of microRNA let-7 by acting as a molecular sponge. Here we report that H19 expression is significantly decreased in the eutopic endometrium of women with endometriosis as compared to normal controls. We show that decreased H19 increases let-7 activity, which in turn inhibits Igf1r expression at the post-transcriptional level, thereby contributing to reduced proliferation of endometrial stromal cells. We propose that perturbation of this newly identified H19/Let-7/IGF1R regulatory pathway may contribute to impaired endometrial preparation and receptivity for pregnancy in women with endometriosis. Our finding represents the first example of a lncRNA-based mechanism in endometriosis and its associated infertility, thus holding potential in the development of novel therapeutics for women with endometriosis and infertility.

Skeletal muscle insulin resistance has been implicated in the pathogenesis of nonalcoholic fatty liver disease (NAFLD) and atherogenic dyslipidemia associated with the metabolic syndrome by altering the distribution pattern of postprandial energy storage. We conducted a study to examine this hypothesis by reversing muscle insulin resistance with a single bout of exercise and measuring hepatic de novo lipogenesis and hepatic triglyceride synthesis after a carbohydrate-rich meal. We studied 12 healthy, young, lean, insulin resistant individuals in an interventional, randomized cross-over trial. The response to the ingestion of a carbohydrate-rich meal was studied at rest and after one 45-min bout of exercise on an elliptical trainer. Hepatic de novo lipogenesis was assessed by using 2 H 2 O, and changes in glycogen and fat content in liver and muscle were measured by 13 C and 1 H magnetic resonance spectroscopy, respectively. Exercise resulted in a greater than threefold increase in postprandial net muscle glycogen synthesis (P < 0.001), reflecting improved muscle insulin responsiveness, and a ≈40% reduction (P < 0.05) in net hepatic triglyceride synthesis. These changes in whole body energy storage were accompanied by a ≈30% decrease in hepatic de novo lipogenesis (P < 0.01) and were independent of changes in fasting or postprandial plasma glucose and insulin concentrations. These data demonstrate that skeletal muscle insulin resistance is an early therapeutic target for the treatment and prevention of atherogenic dyslipidemia and NAFLD in young insulin resistant individuals who are prone to develop the metabolic syndrome and type 2 diabetes.liver triglyceride | nuclear magnetic resonance spectroscopy T he metabolic syndrome is characterized by a clustering of risk factors for cardiovascular disease that include abdominal obesity, atherogenic dyslipidemia, hypertension, hyperuricemia, a prothrombotic state, a proinflammatory state, nonalcoholic fatty liver disease (NAFLD), and insulin resistance (1, 2). The metabolic syndrome is estimated to afflict 50 million Americans, and approximately half of all Americans are predisposed to it (1). Individuals with the metabolic syndrome are at increased risk for the development of coronary heart disease and other diseases related to plaque buildup in artery walls, such as stroke and peripheral vascular disease, as well as type 2 diabetes. However, the underlying mechanism(s) responsible for these cardiovascular risk factors associated with the metabolic syndrome are not fully understood and appear to be complex.In this regard, insulin resistance, localized to skeletal muscle, has been hypothesized to cause atherogenic dyslipidemia and NAFLD by changing the pattern of storage of ingested carbohydrate away from skeletal muscle glycogen synthesis into hepatic de novo lipogenesis, resulting in an increase in plasma triglyceride concentrations, reduction in plasma high-density lipoprotein concentrations and increased liver triglyceride synthesis in healthy, young, lean insulin r...

Aging is closely associated with muscle insulin resistance, hyperlipidemia, nonalcoholic fatty liver disease (NAFLD), and type 2 diabetes. We examined the hypothesis that muscle insulin resistance in healthy aging promotes increased hepatic de novo lipogenesis (DNL) and hyperlipidemia by altering the distribution pattern of postprandial energy storage. Healthy, normal weight, sedentary elderly subjects pair-matched to young subjects were given two high-carbohydrate meals followed by 13C/1H magnetic resonance spectroscopy measurements of postprandial changes in muscle and liver glycogen and lipid content, and assessment of DNL using 2H2O. Net muscle glycogen synthesis was reduced by 45% (P < 0.007) in the elderly subjects compared with the young, reflecting severe muscle insulin resistance. Net liver glycogen synthesis was similar between groups (elderly, 143 ± 23 mmol/L vs. young, 138 ± 13 mmol/L; P = NS). Hepatic DNL was more than twofold higher in the elderly than in the young subjects (elderly, 14.5 ± 1.4% vs. young, 6.9 ± 0.7%; P = 0.00015) and was associated with approximately threefold higher postprandial hepatic triglyceride (TG) content (P < 0.005) and increased fasting plasma TGs (elderly, 1.19 ± 0.18 mmol/L vs. young, 0.74 ± 0.11 mmol/L; P = 0.02). These results strongly support the hypothesis that muscle insulin resistance in aging promotes hyperlipidemia and NAFLD by altering the pattern of postprandial carbohydrate storage away from muscle glycogen and into hepatic DNL.