Multiple Roles of Sms2 in White and Brown Adipose Tissues from Dietinduced Obese Mice

Background/Objectives: Adipose tissue (AT) has an important role in energy homeostasis. The dysfunction of AT or the hyper-accumulation of neutral lipids leads to various metabolic diseases. Recent studies indicate that sphingo lipid metabolism associates with the development of metabolic diseases. Sphingomyelin, a major sphingolipid in mammals, requires sphingomyelin synthase (SMS) for biosynthesis. Previously, we reported that Sms2 deficiency inhibited diet-induced obesity, fatty liver, and insulin resistance in mice. However, the contribution of Sms2 to obesity and insulin resistance in AT is largely unknown. In this study, we investigated whether Sms2 deficiency in ATs affects obesity and insulin resistance.Subjects/Methods: Wild-type and Sms2 knockout (KO) mice were fed a high-fat for 12 weeks. Body and AT weights, and the food intake, were recorded. The AT status and macrophage infiltration were evaluated by histological analysis. The expression levels of genes and proteins involved in adipogenesis, inflammation, energy expenditure, and fatty acid metabolism were examined.Results: In white adipose tissue (WAT) from Sms2 KO mice, the number of small adipocytes increased but the adipocyte size decreased. In epididymal WAT, Sms2 deficiency inhibited inflammation and macrophage infiltration. Moreover, adipogenesis was moderately suppressed. In subcutaneous WAT from Sms2 KO mice, the expression of genes involved in energy expenditure and browning (Ucp1, Cidea, Tbx1) was elevated. In brown adipose tissue (BAT) from Sms2 KO mice, the lipid droplet surface area was lower than that of WT mice and the expression of genes involved in fatty acid synthesis (Fasn, Scd1) decreased.Conclusion: These results demonstrate that Sms2 deficiency leads to moderate adipogenesis and inflammatory suppression in epididymal WAT, increased energy expenditure by the browning of subcutaneous WAT, and suppression of fatty acid synthesis in BAT, suggesting that these synergetic effects in ATs from Sms2 KO mice contribute to the suppression of diet-induced obesity and insulin resistance.