Oat β-glucans with different molecular weights modulate constipation through intestinal motility and gut microbiota metabolism

This study aimed to evaluate the efficacy and underlying mechanisms of oat β-glucans with different molecular weights in alleviating constipation. High molecular weight β-glucans (HMG) extracted directly from oats were enzymatically hydrolyzed using 60 U/g enzyme (medium molecular weight β-glucans, MMG) or 600 U/g enzyme (low molecular weight β-glucans, LMG). The molecular weight of HMG decreased by 44.09% and 83.32%, respectively, and showed significant alterations in water-holding capacity and viscosity. The constipated mice were employed to evaluate the laxative efficacy of oat β-glucans via oral gavage. Results demonstrated that HMG and MMG both significantly increased the frequency of bowel movements and intestinal propulsion rate, with HMG additionally shortening the time to the first defecation. Hematoxylin and eosin staining revealed that oat β-glucans alleviated colonic inflammation and damage in constipated mice, among which HMG and MMG further led to an increase in mucosal thickness and 5-hydroxytryptamine. Gut microbiota and short-chain fatty acids analysis indicated that only HMG significantly enhanced microbial diversity and the contents of butyric and acetic acid. Furthermore, HMG specifically increased the relative abundance of key bacterial genera relevant to acetic acid production ( Bacteroides ) and butyric acid production ( Odoribacter ). In summary, oat β-glucans with different molecular weights exhibited varying efficacy in alleviating constipation, with HMG showing the optimal performance. The superior water-holding capacity and viscosity of HMG contributed to the stimulation of intestinal motility, while its significant regulation of the gut microbiota-SCFA metabolism constituted a key mechanism. • Better effect of oat β-glucans with 15 kDa on alleviating constipation than lower molecular weights is confirmed. • Alleviating efficacy of HMG mainly depends on promoting intestinal peristalsis via its water-holding capacity. • HMG alleviated constipation via the gut microbiota-SCFA metabolic axis.