Project description:Over 40 % of microRNAs are located in introns of coding genes, and many intronic microRNAs are co-regulated with their host genes. In such cases of co-regulation, the products of host genes and their intronic microRNAs can cooperate to coordinately regulate biologically important pathways. Therefore, we screened intronic microRNAs dysregulated in liver of obese mouse models to identify previously uncharacterized coding host genes that may contribute to the pathogenesis of obesity-associated insulin resistance and type 2 diabetes mellitus. Our approach identified that expression of both Ectodysplasin A (Eda), the causal gene of X-linked hypohidrotic ectodermal dysplasia (XLHED; MIM 305100) and its intronic microRNA, miR-676, was strongly increased in liver of obese mouse models. Moreover, hepatic EDA expression is increased in obese human subjects, reduced upon weight loss, and its hepatic expression correlates with systemic insulin resistance. Eda expression in murine liver is controlled via PPARg activation, increases in circulation and promotes JNK activation and inhibitory serine phosphorylation of IRS1 in skeletal muscle. Consistently, bi-directional modulation of hepatic Eda expression in mouse models affects systemic glucose metabolism with alterations of muscle insulin signaling, revealing a novel role of EDA as an obesity-associated hepatokine, which impairs insulin sensitivity in skeletal muscle.
Project description:We screened intronic microRNAs dysregulated in liver of obese mouse models to identify previously uncharacterized coding host genes that may contribute to the pathogenesis of obesity-associated insulin resistance and type 2 diabetes mellitus. Our approach identified the expression of Ectodysplasin A (Eda), the causal gene of X-linked hypohidrotic ectodermal dysplasia (XLHED; MIM 305100) was strongly increased in liver of obese mouse models both in rodents and humans.Eda expression in murine liver is controlled via PPARγ activation, increases in circulation and promotes JNK activation and inhibitory serine phosphorylation of IRS1 in skeletal muscle. Consistently, bi-directional modulation of hepatic Eda expression in mouse models affects systemic glucose metabolism with alterations of muscle insulin signaling, revealing a novel role of EDA as an obesity-associated hepatokine, which impairs insulin sensitivity in skeletal muscle.
Project description:Obesity is a metabolic disease caused by environmental, genetic, and epigenetic factors. However, the epigenetic mechanisms of obesity are incompletely understood. The aim of our study was to identify skeletal muscle DNA methylation patterns in obesity. Muscle biopsies were obtained basally from lean (n=11) and obese (n=9) participants in combination with euglycemic hyperinsulinemic clamps to assess insulin sensitivity. We performed reduced representation bisulfite sequencing next generation methylation analysis on DNA isolated from vastus lateralis muscle biopsies.
Project description:Insulin resistance not compensated by secretion reduces energy storage, but little is known about its effect upon energy expenditure (EE). Insulin receptor substrates Irs1 and Irs2 mediate signaling in all tissues, resulting in the inhibition of FoxO transcription factors. We found that hepatic disruption of Irs1 and Irs2 (LDKO mice) attenuated high-fat diet (HFD)-induced obesity and increased whole-body EE in a FoxO1-dependent manner. Hepatic disruption of Fst (follistatin), a FoxO1-regulated hepatokine, normalized EE in LDKO mice and restored adipose mass during HFD consumption. Moreover, hepatic Fst disruption alone increased fat mass accumulation, whereas hepatic overexpression of Fst attenuated high HFD-induced obesity. Excess circulating Fst in overexpressing mice neutralized Mstn (myostatin), activating mTORC1-promoted pathways of nutrient uptake and EE in skeletal muscle. Similar to Fst overexpression, direct activation of muscle mTORC1 also reduced adipose mass. We conclude that Fst-promoted EE in muscle attenuates obesity during hepatic insulin resistance.
Project description:Obesity is a metabolic disease caused by environmental, genetic, and epigenetic factors. However, the epigenetic mechanisms of obesity are incompletely understood. The aim of our study was to identify skeletal muscle DNA methylation patterns in combination with transcriptomic changes in obesity. Muscle biopsies were obtained basally from lean (n=10) and obese (n=10) participants in combination with euglycemic hyperinsulinemic clamps to assess insulin sensitivity. We performed microarray (SurePrint G3 Human Gene Expression 8x60K v2) analysis on RNA isolated from vastus lateralis muscle biopsies. This represents the expression profiling component only.
Project description:Insulin resistance represents a hallmark during the development of type 2 diabetes mellitus (T2D) and in the pathogenesis of obesity-associated disturbances of glucose and lipid metabolism 1,2,3. MicroRNA (miR)-dependent posttranscriptional gene silencing has recently been recognized to control gene expression in disease development and progression including that of insulin-resistant T2D. MiRs, whose deregulation alters hepatic insulin sensitivity include miR-143, miR-181 and miR-103/107. Here we report that expression of miR-802 is increased in liver of two obese mouse models and of obese human subjects. Inducible transgenic overexpression of miR-802 in mice causes impaired glucose tolerance and attenuates insulin sensitivity, while reduction of miR-802 expression improves glucose tolerance and insulin action. We identify Hnf1b as a target of miR-802-dependent silencing and shRNA-mediated reduction of Hnf1b in liver causes glucose intolerance, impairs insulin signaling and promotes hepatic gluconeogenesis. In turn, hepatic overexpression of Hnf1b improves insulin sensitivity in db/db mice. Thus, the present study defines a critical role for deregulated expression of miR-802 in the development of obesity-associated impairment of glucose metabolism via targeting Hnf1b and assigns Hnf1b an unexpected role in the control of hepatic insulin sensitivity.
Project description:substantial number of people at risk to develop type 2 diabetes could not improve insulin sensitivity by physical training intervention. We studied the mechanisms of this impaired exercise response in 20 middle-aged individuals who performed a controlled eight weeks cycling and walking training at 80 % individual VO2max. Participants identified as non-responders in insulin sensitivity (based on Matsuda index) did not differ in pre-intervention parameters compared to high responders. The failure to increase insulin sensitivity after training correlates with impaired up-regulation of mitochondrial fuel oxidation genes in skeletal muscle, and with the suppression of the upstream regulators PGC1α and AMPKα2. The muscle transcriptome of the non-responders is further characterized by an activation of TGFβ and TGFβ target genes, which is associated with increases in inflammatory and macrophage markers. TGFβ1 as inhibitor of mitochondrial regulators and insulin signaling is validated in human skeletal muscle cells. Activated TGFβ1 signaling down-regulates the abundance of PGC1α, AMPKα2, mitochondrial transcription factor TFAM, and of mitochondrial enzymes. Thus, increased TGFβ activity in skeletal muscle can attenuate the improvement of mitochondrial fuel oxidation after training and contribute to the failure to increase insulin sensitivity. We performed gene expression microarray analysis on muscle biopsies from humans before and after an eight weeks endurance training intervention
Project description:Myostatin is a negative regulator of muscle growth and metabolism and its inhibition in mice improves insulin sensitivity, increases glucose uptake into skeletal muscle, and decreases total body fat. A recently described mammalian protein called Mss51 is significantly downregulated with myostatin inhibition. In vitro disruption of Mss51 results in increased levels of ATP, β-oxidation, glycolysis and oxidative phosphorylation. To determine the in vivo biological function of Mss51 in mice, we disrupted the Mss51 gene by CRISPR/Cas9 and found that Mss51 KO mice have normal muscle weights and fiber-type distribution but reduced fat pads. Myofibers isolated from Mss51 KO mice showed an increased oxygen consumption rate compared to WT controls, indicating an accelerated rate of skeletal muscle metabolism. The expression of genes related to oxidative phosphorylation and fatty acid β-oxidation were enhanced in skeletal muscle of Mss51 KO mice compared to that of WT mice. We found that mice lacking Mss51 and challenged with a high fat diet were resistant to diet-induced weight gain, had increased whole-body glucose turnover and glycolysis rate, and increased systemic insulin sensitivity and fatty acid β-oxidation. These findings demonstrate that Mss51 modulates skeletal muscle mitochondrial respiration and regulates whole-body glucose and fatty acid metabolism, making it a potential target for obesity and diabetes.
Project description:Aims/hypothesis: While lipid deposition in skeletal muscle is considered to be involved in obesity-associated insulin resistance, neutral intramyocellular lipid (IMCL) accumulation per se does not necessarily induce insulin resistance. We previously demonstrated that overexpression of the lipid droplet coat protein perilipin 2 augments intramyocellular lipid content while improving insulin sensitivity. Another member of the perilipin family, perilipin 5 (PLIN5), is predominantly expressed in oxidative tissues like skeletal muscle. Here we investigated the effects of PLIN5 overexpression M-bM-^@M-^S in comparison with effects of PLIN2 M-bM-^@M-^S on skeletal muscle lipid levels, gene expression profiles and insulin sensitivity. Methods: Gene electroporation was used to overexpress PLIN5 in tibialis anterior muscle of rats fed a high fat diet. Eight days after electroporation, insulin-mediated glucose uptake in skeletal muscle was measured by means of a hyperinsulinemic euglycemic clamp. Electron microscopy, fluorescence microscopy and lipid extractions were performed to investigate IMCL accumulation. Gene expression profiles were obtained using microarrays. Results: TAG storage and lipid droplet size increased upon PLIN5 overexpression. Despite the higher IMCL content, insulin sensitivity was not impaired and DAG and acylcarnitine levels were unaffected. In contrast to the effects of PLIN2 overexpression, microarray data analysis revealed a gene expression profile favoring FA oxidation and improved mitochondrial function. Conclusions/interpretation: Both PLIN2 and PLIN5 increase neutral IMCL content without impeding insulin-mediated glucose uptake. As opposed to the effects of PLIN2 overexpression, overexpression of PLIN5 in skeletal muscle promoted expression of a cluster of genes under control of PPARM-NM-1 and PGC1M-NM-1 involved in FA catabolism and mitochondrial oxidation. Rats received a high fat diet for 3 weeks; 2 weeks after start of the diet intervention Plin5 (OXPAT) or Plin2 (ADRP) were overexpressed in either the right or left tibialis anterior muscle. One week later pooled tibialis anterior muscle samples were analysed on microarrays.
Project description:Insulin resistance represents a hallmark during the development of type 2 diabetes mellitus (T2D) and in the pathogenesis of obesity-associated disturbances of glucose and lipid metabolism 1,2,3. MicroRNA (miR)-dependent posttranscriptional gene silencing has recently been recognized to control gene expression in disease development and progression including that of insulin-resistant T2D. MiRs, whose deregulation alters hepatic insulin sensitivity include miR-143, miR-181 and miR-103/107. Here we report that expression of miR-802 is increased in liver of two obese mouse models and of obese human subjects. Inducible transgenic overexpression of miR-802 in mice causes impaired glucose tolerance and attenuates insulin sensitivity, while reduction of miR-802 expression improves glucose tolerance and insulin action. We identify Tcf2 as a target of miR-802-dependent silencing and shRNA-mediated reduction of Tcf2 in liver causes glucose intolerance, impairs insulin signaling and promotes hepatic gluconeogenesis. In turn, hepatic overexpression of Tcf2 improves insulin sensitivity in db/db mice. Thus, the present study defines a critical role for deregulated expression of miR-802 in the development of obesity-associated impairment of glucose metabolism via targeting Tcf2 and assigns Tcf2 an unexpected role in the control of hepatic insulin sensitivity. Adenoviruses (Ad5) encoding either GFP (Ad-Ctrl 1-3) or shTcf2 (Ad-shTcf2 1-4) were injected into the tail vein of C57BL/6 mice at 1x10E10 viral particles (VP) per gram bodyweight. Biotin-labeled cDNA was synthesized using GeneChip Whole Transcript Sense Labeling Assay (Affymetrix) according to vendorM-bM-^@M-^Ys instructions. After fragmentation, cDNAs were hybridized for 17h at 45M-BM-0C on Affymetrix Mouse Gene 1.0 ST Arrays. The Arrays were washed and stained in the GeneChip Fluidics Station 450 and scanned on a GeneChip Scanner 3000 7G (Affymetrix). Data intensities were log transformed and normalized with a quantile normalization method using Affymetrix Power Tools. Differentially expressed genes were identified according to statistical evidence indicated by Student's t-test and fold change statistics