The Impact of MicroRNA 23/27 on Muscle Atrophy in Diabetic Mice

Diabetic nephropathy is the one of the major causes of morbidity and mortality in diabetes mellitus. Muscle atrophy is a serious consequence of diabetic nephropathy and other catabolic diseases. This study tests whether microRNA‐23/27 can moderate muscle atrophy in streptozotocin (STZ)‐induced diabetic mice. Recombinant of adeno‐associate virus (rAAV‐miR‐23/27) was injected into the skeletal muscle of diabetic and normal mice (C57BL/6J, 6–8 weeks). Mice were divided into four groups: control/AAV‐ctrl, control/AAV‐miR‐23/27, diabetes/AAV‐ctrl and diabetes/AAV‐miR‐23/27 (n=12/group). STZ (175 mg/kg) was injected on 2 consecutive days. Muscle and kidney samples were harvested 8 weeks after the injection. Muscle weight was significantly decreased in diabetic mice versus control mice. The expression of both miR‐23a‐3p and miR‐27a‐3p increased 15.3‐ and 13.8‐fold, respectively, in muscle from control mice, and increased 12.5‐fold (miR‐23) and 10.9‐fold (miR‐27) in diabetic muscle following AAV injections. AAV‐miR‐23/27 ameliorated the diabetes‐induced decrease of tibialis anterior (TA) muscle weight and the TA muscle to body weight ratio. Muscle function was measured using a grip strength meter at the end of experiment. Diabetic mice treated with AAV‐miR‐23/27 exhibited increased muscle grip capacity compared with diabetic mice (diabetes: 3.2± 0.9 KGF‐2; diabetes/miR‐23/27: 4.1 ± 0.8 KGF‐2; p<0.05). Protein metabolism markers were measured by Western blot and mRNA expression by PCR. Exogenous miR‐23‐27 blunted the increase in diabetes‐induced FoxO1, increased phosphorylation of Akt, and reduced PTEN protein. The protein abundance of two E3 ubiquitin ligases, TRIM63/MuRF1 and FBXO32/atrogin‐1, both direct targets of miR23 in the insulin pathway, were attenuated by miR‐23/27/24‐2. Additionally, it was found that AAV‐miR‐23/27 lessened myostatin mRNA and protein levels and the downstream signaling of phosphorylated pSmad2/3. In conclusion, AAV‐miR‐23/27 can prevent diabetes‐induced muscle loss by a multi‐faceted mechanism. MiR‐23 inhibits PTEN, TRIM63/MuRF1 and FBXO32/atrogin‐1, thus upregulating insulin‐like growth factor and limiting muscle protein loss. MiR‐27 directly targets myostatin, resulting in increased myogenesis. This combination can mitigate accelerated proteolysis‐related signaling, resulting in prevention of muscle loss induced by diabetes. These results suggest that miR23 and miR27 may serve as effective therapeutic targets for the treatment of diabetes‐induced muscle atrophy. Future studies will examine the impact of miR‐23/27 on renal fibrosis on diabetes‐induced nephropathy. Support or Funding Information This work was supported by: STEP‐UP 1R25DK095492‐01; NIH/NIAMS R01AR060268; NIH National Institute of Diabetes and Digestive Diseases; The American Physiological Society; and, Dr. Bin Wang, and Dr. Aiqing Zhang at the Emory University School of Medicine.Insulin signaling pathwaymiR23/27 attenuates the STZ‐induced decline in insulin signaling as evidenced by Western blot.miR23/27 attenuates the STZ‐induced decline in insulin signaling as found by qPCR.Exogenous miR‐23/27 decrease myostatin amount in normal and STZ.Myostatin mRNA was reduced by miR‐23/27, as shown by qPCR.Muscle function was increased by miR23/27/24.Average T.A. muscle weight to body weight ratio after tissue extraction.