Gain Of Metabolic Benefit With Ablation Of MiR-149-3p From Subcutaneous Adipose Tissue In Diet-induced Obese Mice

The global rise in obesity has become a public health crisis.Excess body fat can increase risk for many chronic diseases,like type 2 diabetes,cardiovascular diseases,liver diseases,and other metabolic syndrome.Since weight gain is almost always caused by chronic energy imbalance.Overweight and obesity develop when energy intake exceeds energy expenditure,storing excess calories in the adipose tissue in the form of triglyceride.The global burden of suffering due to overnutrition outpaces that due to undernutrition for the first time in human history,with 1.7 billion people classified as obese.Nonsurgical therapy for obesity must reduce energy intake and/or increase energy expenditure.Hence,feasible strategies to reduce adiposity are urgently needed,nonsurgical therapy to increase energy expenditure could be efficient approach to overcome obesity.Studies on the developmental,functional,and pathophysiological aspects of adipose tissue have expanded markedly.The main function of white adipocytes is to store excess energy as triglycerides,whereas brown and beige adipocytes are specialized to oxidize chemical energy to produce heat,which considered as a natural defence against hypothermia and obesity.It has been reported that activation of the smaller beige adipocytes in subcutaneous adipose tissue(SAT)c ould protect mice and human from diet-induced obesity and related metabolic complications,such as insulin resistance.Therefore,activating the beige adipocytes in SAT,may open the way to improved therapeutic strategies for helping combat metabolic disorders.Although β-adrenergic agonists and other hormone like stimuli were shown to be able to induce subcutaneous adipose tissue(SAT)"browning",physiological cold stress is still the most prominent way to activate the multilocular beige adipocytes.PR-domain-containing 16(Prdm 16)is a critical transcriptional factor that powerfully regulate beige adipocytes differentiation and thermogenic gene program in SAT-.Increased expression of Prdm16 markedly promoted beige development in SAT,which protected mice against diet-induced metabolic disease.By contrast,ablation of Prdm 16 caused a profound loss of beige cell function in SAT,leading to aggravated obesity and hepatic steatosis.Thus,identify signalling molecules that transcriptional or post-transcripitional regulate Prdm 16 may offer new targets for clinical applications.MicroRNAs(miRNAs)are small non-coding RNA molecules that negatively regulate gene expression through targeting the 3’untranslated regions(UTR)of mature mRNA.several miRNAs have been found to play essential roles in classic brown as well as beige cell adipogenesis.According to our previous study,we identified miR-149-3p,which negatively regulated PRDM 16 expression by targeting a conserved site of its 3’UTR,was significantly up-regulated in mice SAT when exposed to chronic HFD.Here,we showed that chronic high-fat feeding caused a sharp decrease in the expression of thermogenic genes and acquisition of partial deleterious features of visceral fat in SAT.Our results showed that long-term high-fat feeding caused the SAT of mice acquired partial key properties of visceral fat,including the increased lipogenesis and average cell volume,and the significantly elevated WAT-selective and visceral-signature genes.We found that the PRDM 16 protein level was sharply decreased in SAT upon HFD via Western blotting and gene expression,indicating that the down-regulated PRDM16 might account for the lost beneficial effect of SAT.We have demonstrated that Prdm 16 is a direct target of miR-149-3p.The anti-miR-149-3p was directly introduced into the subcutaneous inguinal depot by employing a lentiviral vector,we showed that the inhibition of miR-149-3p in SAT of mice with an HFD resulted in a significant increase in PRDM16 protein level as well as SAT thermogenesis and whole-body energy expenditure,without much alteration in food intake and physical activity.More importantly,depletion of miR-149-3p led to improved glucose tolerance and insulin sensitivity,while decreasing the infiltration of macrophage in SAT and liver steatosis in mice fed on HFD.In summary,we showed that down-regulation of miR-149-3p efficiently induces thermogenesis while suppressed the obesity-induced ’visceralization’ in SAT,consequently improved whole body energy expenditure and hepatic steatosis in obese mice.We have provided direct evidence of the anti-obese and anti-diabetic effect of Prdm16 in the obese background for the first time.Our study also revealed an important mechanism of miR-149-3p and Prdm 16-dependent regulation of energy expenditure upon chronic high-fat feeding,indicating that SAT miR-149-3p can serve as a therapeutic target to defend against diet-induced obesity and metabolic dysfunctions.