Human amniotic mesenchymal stem cells-conditioned medium protects mice from high-fat diet-induced obesity.

Background: Obesity is a metabolic disorder syndrome characterized by excessive fat accumulation that is related to many diseases. Human amniotic mesenchymal stem cells (hAMSCs) have a great potential for cell-based therapy due to their characteristics such as pluripotency, low immunogenicity, no tumorigenicity, potent paracrine effects, and no ethical concern. Recently, we observed that both hAMSCs and their conditioned medium (hAMSCs-CM) efficiently repaired skin injury, inhibited hepatocellular carcinoma, and alleviated high-fat diet (HFD)-induced diabetes. However, the effects and the underlying mechanisms of hAMSCs-CM on high-fat diet (HFD)-induced obesity were not explored.

Methods: The characteristics of hAMSCs were confirmed by flow cytometry, RT-PCR, and immunofluorescence. Obese mice were induced by administrating HFD for 15 weeks and simultaneously, the mice were intraperitoneally injected with hAMSCs-CM weekly to evaluate the effects of hAMSCs-CM on HFD-induced obesity. GTT and ITT assays were used to assess the effects of hAMSCs-CM on HFD-induced glucose tolerance and insulin resistance. The lipid accumulation and adipocytes hypertrophy in mouse adipose tissues were determined by histological staining, in which the alterations of blood lipid, liver, and kidney function were also examined. The role of hAMSCs-CM in energy homeostasis was monitored by examining the oxygen consumption (VO), carbon dioxide production (VCO), and food and water intake in mice. Furthermore, the expressions of the genes related to glucose metabolism, fatty acid β oxidation, thermogenesis, adipogenesis, and inflammation were determined by western blot analysis, RT-PCR, and immunofluorescence staining. The roles of hAMSCs-CM in adipogenesis and M1/M2 macrophage polarization were investigated with 3T3-L1 preadipocytes or RAW264.7 cells in vitro.

Results: hAMSCs-CM significantly restrained HFD-induced obesity in mice by inhibiting adipogenesis and lipogenesis, promoting energy expenditure, and reducing inflammation. The underlying mechanisms of the anti-obesity of hAMSCs-CM might be involved in inhibiting PPARγ and C/EBPα-mediated lipid synthesis and adipogenesis, promoting GLUT4-mediated glucose metabolism, elevating UCP1/PPARα/PGC1α-regulated energy expenditure, and enhancing STAT3-ARG1-mediated M2-type macrophage polarization.

Conclusion: Our studies demonstrated that hAMSCs significantly alleviated HFD-induced obesity through their paracrine effects. Obviously, our results open up an attractive therapeutic modality for the prevention and treatment of obesity and other metabolic disorders clinically. The cytokines, exosomes, or micro-vesicles secreted from hAMSCs significantly inhibited HFD-induced obesity in mice by inhibiting lipid production and adipogenesis, promoting energy consumption, and reducing inflammation.