MOTS-c Improves Metabolic Abnormalities And Prevents Ovariectomy-induced Bone Loss And In A Ovariectomy Mouse Model By Regulating Classical AMPK Pathways

Obesity and osteoporosis are two common diseases with an increasing prevalence and a high impact on morbidity and mortality which, during the last two decades, have become major health threats worldwide. It has been reported that age and female gender increase the risk of developing both obesity and osteoporosis.Sex hormone imbalance is causally related with visceral adipose tissue(AT) dysfunction and visceral obesity-an etiological component of metabolic syndrome(Met S), associated with high risk of both cardiovascular disease(C VD) and type 2 diabetes. Estrogen plays crucial roles for bone tissue homeostasis; the decrease in estrogen level at menopause is the main cause of bone loss and osteoporosis. several studies have shown that estrogen maintains bone homeostasis by inhibiting osteoblast and osteocyte apoptosis and preventing excessive bone resorption.Exciting recent studies indicate that AMPK may not only influence metabolism in adipocytes, but also act to suppress this pro- inflammatory environment, such that targeting AMPK in adipose tissue may be desirable to normalize adipose dysfunction and inflammation.Novel work demonstrates that the AMPK signaling pathway plays a role in bone physiology. Activation of AMPK promotes bone formation in vitro and the deletion of α or β subunit of AMPK decreases bone mass in mice. AMPK is also activated by antidiabetic drugs such as metformin and thiazolidinediones(TZDs), which also impact on skeletal metabolism.Lee et al. identify a novel bioactive mitochondrial-derived peptide(MO TS-c) encoded in the mitochondrial DN A that regulates metabolic homeostasis. MOTS-c regulates insulin sensitivity and metabolic homeostasis via AMPK, and prevents age-dependent and high- fat diet- induced insulin resistance, as well as diet- induced obesity. Aims(1)Investigate whether the MOTS-c in OVX mice improved lipid metabolic disorderand MO TS-c promotes metabolic homeostasis and reduces O VX induced obesity andinsulin resistance.(2)Investigate whether the MOTS-c in OVX mice reduce bone loss and exploreMOTS-c on osteoclast differentiation and the osteoblast differentiation.(3)To reveal the mechanism how MOTS-c plays a role in vivo and in vitro. Methods and Results(1)We first establish the postmenopausal mouse model. The results show that there was a marked reduction of the uterus in size and wet weight due to OVX, indicating that surgically induced estrogen deficiency caused uterine atrophy. Compared with OVX group, the mouse which injected MO TS-c decrease of body weight, feeding increased suggests MOTS-c play a role in the body.(2)MOTS-c attenuated body weight gain, fat accumulation, and serum free fatty acid and triglyceride levels in the mouse model of postmenopausal obesity.Moreover,MOTS-c improved glucose intolerance and attenuated hepatic steatosis in the mouse model of postmenopausal obesity.(3)Compared with controls, Phosphorylation of AMPK from OVX treated mice was significantly decreased in brown adipose tissue and subcutaneous fat. But Phosphorylation AMPK from MOTS-c treated mice was significantly increased. Compared with controls, Phosphorylation AMPK was significantly increased in MOTS-c treated MEF cell, but Phosphorylation AMPK was significantly decreased in Compound C treated MEF cell.In the present study, the phospho-Akt in the insulin- treated MEF was found to be increased in comparison with the control group. However, preincubation of the MEF cells with 150μM PA or 10 n M ICI significantly decreased insulin induced phospho-Akt.But pretreatment with 10μM MOTS-c for 8h,the phospho-Akt was found to be increased in comparison with the PA and ICI group. In addition, pretreatment with 10μM Compound C for 8h abrogated the phosphorylation of Akt completely.These results suggested that MOTS-c may be through activation of Akt signal pathways that increased insulin sensitivity.(4) In accordance with Micro-CT analysis results, significant bone loss was demonstrated in the OVX group in comparison with the sham group. MOTS-c also increased BV/TV, Tb.N, Tb.Th and decreased Tb.sp, BS/BV in comparison with those of the ovx group.(5)MOTS-c inhibits RANKL-induced osteoclast formation and osteoclast-specific gene expression, but MO TS-c does not affect Osteogenic differentiation in C3H10T1/2.(6)we investigated the effect of MOTS-c on RANKL induced phosphorylation of AMPK, MOTS-c strongly potentiates RANKL- induced phosphorylation of AMPK at a concentration of 50μM. MOTS-c, whereas in cells also treated with compound C, the impaired osteoclastogenesis was partially rescued and mature osteoclasts were ob served. ConclusionMOTS-c attenuated lipid accumulation in adipose tissue and the liver, and improved glucose and lipid metabolism. In addition,MOTS-c effectively decreased OVX induced bone loss in mice in vivo. MOTS-c also inhibited osteoclastic differentiation of BMMs via impaired RANK L signaling with decreased activations o f NFATc-1,TRAP, c-FOS, and CTSK and attenuated RANKL induced ROS production. Taken together, these results suggest that the MOTS-c may be a promising complementary therapeutic compound for the treatment postmenopausal osteoporosis and postmenopausal obesity by regulating classical AMPK pathways.