LAUSR

Ceramides in focus Excess calorie intake can ultimately lead to a metabolic syndrome that interferes with fat or lipid metabolism. There are many different types of lipids, and it has been widely debated which are the true culprits underlying metabolic disorders. Chaurasia et al. report that ceramides are the major contributor to insulin resistance and fatty liver disease (see the Perspective by Kusminski and Scherer). This appears to be caused by the enzyme dihydroceramide desaturase 1 (DES1), which is normally involved in ceramide production by inserting a double bond into the backbone of the molecule. In mice fed a high-fat diet, deletion of DES1 improved glucose and lipid metabolism. Science, this issue p. 386; see also p. 319 Deletion of dihydroceramide desaturase 1 (DES1) resolves insulin resistance and fatty liver in mice. Ceramides contribute to the lipotoxicity that underlies diabetes, hepatic steatosis, and heart disease. By genetically engineering mice, we deleted the enzyme dihydroceramide desaturase 1 (DES1), which normally inserts a conserved double bond into the backbone of ceramides and other predominant sphingolipids. Ablation of DES1 from whole animals or tissue-specific deletion in the liver and/or adipose tissue resolved hepatic steatosis and insulin resistance in mice caused by leptin deficiency or obesogenic diets. Mechanistic studies revealed ceramide actions that promoted lipid uptake and storage and impaired glucose utilization, none of which could be recapitulated by (dihydro)ceramides that lacked the critical double bond. These studies suggest that inhibition of DES1 may provide a means of treating hepatic steatosis and metabolic disorders.