148-OR: Partial Knockout of Skeletal Muscle Dynamin-Related Protein 1 Improves Insulin Sensitivity in Diet-Induced Insulin Resistant Mice, but Not in Normal Control Mice

Abstract

Dynamin-related protein 1 (Drp1) is the key regulator of mitochondrial fission. We and others have reported excessive Drp1 activity in skeletal muscle from both animals and humans with insulin resistance, which is strongly correlated to impaired skeletal muscle insulin sensitivity. To examine whether Drp1 directly regulates skeletal muscle insulin sensitivity and whole-body glucose homeostasis, we generated tamoxifen-inducible skeletal muscle-specific heterozygous Drp1 partial knockout mice (mDrp1+/-) . Male mDrp1+/- and wildtype (WT) mice were fed with either a high-fat diet (HFD) or low-fat diet (LFD) for four weeks, received tamoxifen injections for five consecutive days, and remained on their respective diet for another four weeks. Improvements in whole-body glucose tolerance and insulin sensitivity were observed in HFD-fed mDrp1+/- mice (P<0.05) , but not in LFD-fed mDrp1+/- mice, when compared to their respective WT controls. Further, HFD-induced impairment in skeletal muscle insulin-stimulated Akt Ser473 phosphorylation (P<0.05) was mitigated in HFD-fed mDrp1+/- mice. In contrast, insulin-stimulated Akt Ser473 phosphorylation was reduced in LFD-fed mDrp1+/- mice compared to LFD-fed WT mice (P<0.05) . mDrp1+/- mice exhibited more fused and interconnected mitochondrial networks in skeletal muscle than WT mice. The examination of mitochondrial function revealed no change in mitochondrial respiration but reductions in mitochondrial Complex I and II and pyruvate dehydrogenase derived H2O2 production in HFD-fed mDrp1+/- mice compared to HFD-fed WT mice (P<0.05) . In conclusion, our data suggest that partial knockout of skeletal muscle Drp1 improves skeletal muscle insulin sensitivity and whole-body glucose homeostasis in diet-induced insulin-resistant mice but not in normal control mice. These improvements are, at least in part, due to reduced mitochondrial-derived H2O2 production. Disclosure B.A.Kugler: None. N.Lin: None. P.D.Nguyen: None. A.Ali: None. A.Sesay: None. B.Kalemba: None. H.Sesaki: None. K.Zou: None. Funding National Institutes of Health (R15DK131512) Diabetes Action Research and Education Foundation Grant (#505)