Milk polar lipids and sphingomyelin attenuate DSS-induced colitis in mice fed high-fat diet: Mechanisms and microbiota modulation

Sphingomyelin (SM) is a component of milk polar lipids (MPLs) and may influence gut inflammation and the development of colitis. However, studies examining dose-dependent effects and mechanisms of action have been limited. We investigated the effects of MPLs and SM on mouse models of acute and chronic colitis induced by dextran sulfate sodium (DSS). Supplementation of a high-fat diet (HFD) in male C57BL/6J mice with 1% (w/w) MPLs (0.2% SM) or 2% (w/w) MPLs (0.4% SM) attenuated colitis disease activity index (DAI) scores following a single acute colitis protocol (10-day exposure to 1% DSS in water). MPL supplementation resulted in higher fecal levels of ceramide and sphingomyelin and altered the microbiota, with 2% MPLs increasing the relative abundance of short-chain fatty acid (SCFA)-producing bacteria such as Acetatifactor, Anaerotruncus, and Clostridiales vadinBB60 group. RNA-seq transcriptomics analysis of colons showed that mice fed with 2% MPLs had reduced expression of genes related to IL-17 signaling, TNF signaling, and cytokine-cytokine receptor interactions. Colonic mRNA expression of Itln1, which encodes the antimicrobial and anti-inflammatory protein intelectin-1, was markedly increased in 2% MPL-fed mice. In a Caco-2 cell model, exogenous SM significantly attenuated the loss of cellular barrier integrity when polarized cells were incubated with mixed micelles and lipopolysaccharide (LPS). We then performed a study testing purified dietary SM on chronic colitis development with three cycles of a 7-day treatment with 1% DSS, followed by 14 days of normal water for recovery. Dietary supplementation of 0.1% (w/w) SM and 0.3% (w/w) SM to HFD-fed male mice attenuated DAI scores after the first cycle, but this effect was not sustained after the second and third cycles. In summary, dietary sources of sphingomyelin increase fecal sphingolipids, alter the composition of the fecal gut microbiota, and enhance gut barrier markers, thereby protecting against the development of colitis.