Ceramide Synthases Regulate Myristate-Induced Intestinal IRE1α Activation
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Background & Aims
High-fat diets (HFDs) are a major modifiable risk factor for intestinal health. Current research focuses primarily on palmitate (C16:0); however, myristate (C14:0, rich in dairy products) has been minimally investigated. HFDs increase ceramide generation which drives endoplasmic reticulum (ER) stress; with both sphingolipids and ER stress being key contributors to intestinal biology. Whether different fatty acids uniquely impact sphingolipid metabolism and ER stress in intestinal biology has not been well defined.
Methods
Human colon epithelial cells were utilized to determine the role of ceramide synthases (CerS) 5 and 6 on myristate-induced ER stress using pharmacologic inhibitors and siRNA. Intestinal epithelial cell specific CerS5 and/or CerS6 knockout mice of both sexes were fed a control, high milk-fat, or high lard-fat diet for 16 weeks. Cells and colon tissues were analyzed for lipids, mRNA, and protein.
Results
Myristate treatment increased C14:0-ceramide and induced IRE1α-dependent ER stress. Inhibition of CerS suppressed these effects, yet knockdown of CerS5/6, the primary enzymes generating C14:0-ceramide, unexpectedly exacerbated IRE1α activation both in vitro and in vivo , potentially due to depletion of dihydro(dh)sphingosine.
Conclusions
CerS are required for myristate-induced IRE1α activation and restoration of the sphingoid base pool provides partial protection from intestinal ER stress.
SYNOPSIS
This study identifies a new mechanism linking dietary fats to intestinal cell stress. Ceramide synthases drive ER stress triggered by myristate, a dairy-derived fat, while restoring sphingoid bases partially protects cells, revealing a new role for sphingolipids in shaping intestinal responses to diet.
