Adipocyte Ceramides Regulate Subcutaneous Adipose Browning, Inflammation, and Metabolism

Adipocytes package incoming fatty acids into triglycerides and other glycerolipids, with only a fraction spilling into a parallel biosynthetic pathway that produces sphingolipids. Herein, we demonstrate that subcutaneous adipose tissue of type 2 diabetics contains considerably more sphingolipids than non-diabetic, BMI-matched counterparts. Whole-body and adipose tissue-specific inhibition/deletion of serine palmitoyltransferase (Sptlc), the first enzyme in the sphingolipid biosynthesis cascade, in mice markedly altered adipose morphology and metabolism, particularly in subcutaneous adipose tissue. The reduction in adipose sphingolipids increased brown and beige/brite adipocyte numbers, mitochondrial activity, and insulin sensitivity. The manipulation also increased numbers of anti-inflammatory M2 macrophages in the adipose bed and induced secretion of insulin-sensitizing adipokines. By comparison, deletion of serine palmitoyltransferase from macrophages had no discernible effects on metabolic homeostasis or adipose function. These data indicate that newly synthesized adipocyte sphingolipids are nutrient signals that drive changes in the adipose phenotype to influence whole-body energy expenditure and nutrient metabolism. [Display omitted] •Cold or β-adrenergic agonists selectively reduce adipose ceramides•Adipocyte-specific inhibition of ceramide synthesis induces adipose beiging•Ceramide effects on adipose metabolism are cell autonomous•Adipose sphingolipids increase in obesity and correlate with insulin resistance Chaurasia et al. show that whole-body and fat-specific inhibition of ceramide synthesis induces browning and increases M2 macrophages preferentially in subcutaneous WAT of obese mice. Adipose sphingolipids, increased by overnutrition and decreased by cold, modulate β-adrenergic-induced thermogenesis.