Adipocyte ceramides regulate subcutaneous adipose browning, inflammation, and metabolism
Chaurasia, B and Kaddai, VA and Lancaster, GI and Henstridge, DC and Sriram, S and Galam, DLA and Gopalan, V and Prakash, KNB and Velan, SS and Bulchand, S and Tsong, TJ and Wang, M and Siddique, MM and Yuguang, G and Sigmundsson, K and Mellet, NA and Weir, JM and Meikle, PJ and Bin M Yassin, MS and Shabbir, A and Shayman, JA and Hirabayashi, Y and Shiow, S-ATE and Sugii, S and Summers, SA, Adipocyte ceramides regulate subcutaneous adipose browning, inflammation, and metabolism, Cell Metabolism, 24, (6) pp. 820-834. ISSN 1550-4131 (2016) [Refereed Article]
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.