Dataset Information

Absence of MyD88 from Skeletal Muscle Protects Female Mice from Inactivity-Induced Adiposity and Insulin Resistance.

ABSTRACT: OBJECTIVE:Inactivity and inflammation are linked to obesity and insulin resistance. It was hypothesized that MyD88 (mediates inflammation) knockout from muscle (MusMyD88-/- ) would prevent, whereas miR146a-/- (MyD88 inhibitor) would exacerbate, inactivity-induced metabolic disturbances. METHODS:Cre-control, MusMyD88-/- , and miR146a-/- mice were given running wheels for 5 weeks to model an active phenotype. Afterward, half were placed into a small mouse cage (SMC) to restrict movement for 8 days. Body composition, muscle (3 H)2-deoxyglucose uptake, visceral fat histology, and tissue weight (hind limb muscles, visceral fat, and liver) were assessed. In skeletal muscle and visceral fat, RNA sequencing and mitochondrial function were performed on female MusMyD88-/- and Cre-control SMC mice. RESULTS:The SMC induced adiposity, hyperinsulinemia, and muscle insulin-stimulated glucose uptake, which was worsened in miR146a-/- mice. In females, MusMyD88-/- mice were protected. Female MusMyD88-/- mice during the SMC period (vs. Cre-control) exhibited higher Igf1 and decreased Ip6k3 and Trim63 muscle expression. Visceral fat transcript changes corresponded to improved lipid metabolism, decreased adipose expansion (Gulp1?, Anxa2?, Ehd1?) and meta-inflammation (Hmox1?), and increased beiging (Fgf10?). Ralgapa2, negative regulator of GLUT4 translocation, and inflammation-related gene 993011J21Rik2 were decreased in both muscle and fat. CONCLUSIONS:Whole-body miR146a-/- exacerbated inactivity-induced fat gain and muscle insulin resistance, whereas MusMyD88-/- prevented insulin resistance in female mice.

SUBMITTER: Mahmassani ZS

PROVIDER: S-EPMC7093260 | biostudies-literature | 2020 Apr

REPOSITORIES: biostudies-literature

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Absence of MyD88 from Skeletal Muscle Protects Female Mice from Inactivity-Induced Adiposity and Insulin Resistance.

Mahmassani Ziad S ZS Reidy Paul T PT McKenzie Alec I AI Petrocelli Jonathan J JJ Matthews O'Connor O de Hart Naomi M NM Ferrara Patrick J PJ O'Connell Ryan M RM Funai Katsuhiko K Drummond Micah J MJ

Obesity (Silver Spring, Md.) 20200228 4

<h4>Objective</h4>Inactivity and inflammation are linked to obesity and insulin resistance. It was hypothesized that MyD88 (mediates inflammation) knockout from muscle (MusMyD88<sup>-/-</sup> ) would prevent, whereas miR146a<sup>-/-</sup> (MyD88 inhibitor) would exacerbate, inactivity-induced metabolic disturbances.<h4>Methods</h4>Cre-control, MusMyD88<sup>-/-</sup> , and miR146a<sup>-/-</sup> mice were given running wheels for 5 weeks to model an active phenotype. Afterward, half were placed in ...[more]

PMID: 32108446

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Project description:CONTEXT:Obesity is associated with insulin-resistance (IR), the key feature of type 2 diabetes. Although chronic low-grade inflammation has been identified as a central effector of IR development, it has never been investigated simultaneously at systemic level and locally in skeletal muscle and adipose tissue in obese humans characterized for their insulin sensitivity. OBJECTIVES:We compared metabolic parameters and inflammation at systemic and tissue levels in normal-weight and obese subjects with different insulin sensitivity to better understand the mechanisms involved in IR development. METHODS:30 post-menopausal women were classified as normal-weight insulin-sensitive (controls, CT) and obese (grade I) insulin-sensitive (OIS) or insulin-resistant (OIR) according to their body mass index and homeostasis model assessment of IR index. They underwent a hyperinsulinemic-euglycemic clamp, blood sampling, skeletal muscle and subcutaneous adipose tissue biopsies, an activity questionnaire and a self-administrated dietary recall. We analyzed insulin sensitivity, inflammation and IR-related parameters at the systemic level. In tissues, insulin response was assessed by P-Akt/Akt expression and inflammation by macrophage infiltration as well as cytokines and I?B? expression. RESULTS:Systemic levels of lipids, adipokines, inflammatory cytokines, and lipopolysaccharides were equivalent between OIS and OIR subjects. In subcutaneous adipose tissue, the number of anti-inflammatory macrophages was higher in OIR than in CT and OIS and was associated with higher IL-6 level. Insulin induced Akt phosphorylation to the same extent in CT, OIS and OIR. In skeletal muscle, we could not detect any inflammation even though I?B? expression was lower in OIR compared to CT. However, while P-Akt/Akt level increased following insulin stimulation in CT and OIS, it remained unchanged in OIR. CONCLUSION:Our results show that systemic IR occurs without any change in systemic and tissues inflammation. We identified a muscle defect in insulin response as an early mechanism of IR development in grade I obese post-menopausal women.

Project description:BackgroundLeucine supplementation might have therapeutic potential in preventing diet-induced obesity and improving insulin sensitivity. However, the underlying mechanisms are at present unclear. Additionally, it is unclear whether leucine supplementation might be equally efficacious once obesity has developed.Methodology/principal findingsMale C57BL/6J mice were fed chow or a high-fat diet (HFD), supplemented or not with leucine for 17 weeks. Another group of HFD-fed mice (HFD-pairfat group) was food restricted in order to reach an adiposity level comparable to that of HFD-Leu mice. Finally, a third group of mice was exposed to HFD for 12 weeks before being chronically supplemented with leucine. Leucine supplementation in HFD-fed mice decreased body weight and fat mass by increasing energy expenditure, fatty acid oxidation and locomotor activity in vivo. The decreased adiposity in HFD-Leu mice was associated with increased expression of uncoupling protein 3 (UCP-3) in the brown adipose tissue, better insulin sensitivity, increased intestinal gluconeogenesis and preservation of islets of Langerhans histomorphology and function. HFD-pairfat mice had a comparable improvement in insulin sensitivity, without changes in islets physiology or intestinal gluconeogenesis. Remarkably, both HFD-Leu and HFD-pairfat mice had decreased hepatic lipid content, which likely helped improve insulin sensitivity. In contrast, when leucine was supplemented to already obese animals, no changes in body weight, body composition or glucose metabolism were observed.Conclusions/significanceThese findings suggest that leucine improves insulin sensitivity in HFD-fed mice by primarily decreasing adiposity, rather than directly acting on peripheral target organs. However, beneficial effects of leucine on intestinal gluconeogenesis and islets of Langerhans's physiology might help prevent type 2 diabetes development. Differently, metabolic benefit of leucine supplementation is lacking in already obese animals, a phenomenon possibly related to the extent of the obesity before starting the supplementation.

Dataset Information

Absence of MyD88 from Skeletal Muscle Protects Female Mice from Inactivity-Induced Adiposity and Insulin Resistance.

Publications

Absence of MyD88 from Skeletal Muscle Protects Female Mice from Inactivity-Induced Adiposity and Insulin Resistance.

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