Age-related Changes in Intestinal Sphingolipid Metabolism and Microbiota-dependent Lipid Absorption

Aging is a degenerative process linked to increased inflammation and dysfunction of the intestinal epithelial barrier, which may impact nutrient absorption in the rapidly growing elderly population. Emerging evidence suggests that disruptions in intestinal host-microbiota crosstalk sphingolipids (SLs) may precede the decline in immune function and intestinal nutrient absorption observed with aging, but the mechanisms associated with this disruption remain poorly defined. Given the pivotal role of intestinal SL in regulating lipid metabolism and inflammation, we propose that age-related inflammation and reduced barrier integrity are linked to alterations in host-microbiota SL metabolism. Here, we utilized Liquid Chromatography/Mass Spectrometry (LC/MS)-based lipidomics to identify colonic digesta lipid alterations with aging in C57BL/6 mice (young= 3-4 m.o. vs. aged= 18-20 m.o.). First, we revealed that gut SL metabolism is robustly altered with age, hallmarked by the accumulation of numerous SLs and ceramides (Cer). Next, we investigated small intestinal expression of fatty acid (FA) synthesis and trafficking genes ( Fasn, Acc2, Elovl6, Cd36 , ApoB ) but did not observe significant differences. However, among SL metabolism genes ( Sptlc1, 2, Cers2 ,4, 6, Kdsr , Degs1,2 ), Cers6 was significantly higher ( p <0.01) in small intestine of young mice, which may indicate a greater synthesis of barrier ceramides that declines with age. Further, higher accumulation of SLs in digesta are strongly associated with signs of immune cell infiltration like calprotectin ( p <0.0001) and ex vivo immune toll-like receptor TLR4 reactivity of intestinal mucosa ( p <0.05) and feces ( p <0.001). Given that aging is associated with reduced intestinal resilience, we examined the effect of broad-spectrum antibiotic cocktail (ABX) challenge in young and aged mice. Following a one-week of ABX, mice were allowed to recover for 1 week washout period. Expression of FA and SL metabolism genes in the ileum was unaltered by ABX treatment after washout. Despite this, ABX exposure led to a robust accumulation of digesta triglycerides (TG) in aged mice after washout, indicating a heightened lipid malabsorptive phenotype with aging. Moreover, ABX-induced TG accumulation in the colon of aged mice is associated with an inability to recover their microbiome structure and persistent TLR4 immunogenicity of the digesta. Our findings are in line with a previous aged germ-free (GF) mouse (vs. specific pathogen-free mice; SPF) lipidomic analysis by Tsugawa, et al. ( Nature Aging, 2024), which shows greater SL accumulation in small intestine tissue during aging, with non-glycosylated SLs dominating in SPF mice and glycosylated SLs in GF mice, highlighting the role of gut microbiota in intestinal lipid homeostasis. Altogether, we show that aging and ABX disrupt intestinal lipids which may underlie the chronic inflammatory milieu and reduced barrier integrity. Future studies are needed to understand how aging disrupts intestinal host-microbiota lipid metabolism and nutrient absorption. Funding was provided by Vision 20/20 at the University of Illinois Urbana-Champaign This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.