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:Purpose: To reveal the mechanism of mitochondrial DNA methylation in the progression of fatty liver and insulin resistance. Methods: Liver mitochondrial DNA bisulfite-sequencing of high-fat diet (HFD) and db/db diabetic mice were using Illumina 4000. Western blot, real-time PCR and confocal microscopy were used for further biochemical validation. Results: In the present study, we found increased mitochondrial localization of DNA methyltransferase 1 (DNMT1) in the liver of high-fat diet (HFD) and db/db diabetic mice. Whole genome bisulfite sequencing of mouse liver mtDNA revealed significant increase of cytosine methylation frequencies including CG, CHG and CHH on both L and H-strand in the diabetic mice comparing with normal control, and ND6 showed the most dramatic increase on the L-strand. Conclusions: Our present study suggests an epigenetic regulatory of mitochondrial homeostasis and insulin sensitivity by DNMT1, providing novel therapeutic targets for the prevention and treatment of fatty liver and type 2 diabetes.