Dietary Fructose Alters Duodenal Mucin Glycosylation and Mucus Production in High-Fat Diet-Fed Mice

Fructose, a key component of modern diets, is closely linked to the growing prevalence of pediatric obesity and metabolic alterations. Although numerous studies highlight its systemic consequences, including altered carbohydrate and lipid metabolism and increased cardiovascular risk, the direct impact of fructose, particularly its role in modulating mucin composition, a key determinant of the mucosal barrier, remains poorly explored. This study investigated whether fructose supplementation modifies high-fat diet (HFD)-induced changes in duodenal mucin production and whether these effects vary depending on age in animals. To this end, young and adult mice were fed a normal diet (ND), HFD, or an HFD supplemented with 30% fructose (w/v) in drinking water (HFD+Fru) for 16 weeks. Brunner's glands and villus goblet cells were then analyzed using conventional histochemistry and a panel of lectins to evaluate possible alterations in intestinal mucus glycosylation. Results showed that both HFD and HFD+Fru significantly increased body weight. In young mice, HFD+Fru induced a compensatory mucosal phenotype characterized by increased villus PAS (Periodic Acid-Schiff) reactivity (2% vs. ND), elevated sialylated mucin secretion rate (SSR) in Brunner's glands (25% vs. ND) and villi (17% vs. ND), and higher SNA (up to 46% vs. ND) and PNA (up to 39% vs. ND) in villus goblet cells. In contrast, adult mice receiving HFD+Fru exhibited a maladaptive response, characterized by a reduction in villus PAS-positive mucins (6% vs. ND), decreased villus SSR (5% vs. ND), diminished sialylation (up to 43% SNA vs. ND) and GlcNAc (up to 50% reduction in WGA vs. ND) in villus goblet cells, and marked loss of fucosylation in Brunner's glands (81% vs. ND) and villus goblet cells (66% vs. ND). These results reveal that fructose-enriched HFD remodels duodenal mucin O-glycosylation in an age-dependent manner, suggesting that while young mice exhibit transient adaptive responses, prolonged exposure can deplete these mechanisms, leading to a compromised adult epithelial barrier. This age-specific vulnerability may significantly contribute to the pathogenesis of diet-related intestinal disorders and obesity-related complications in later life, highlighting the need for early dietary interventions.