Akkermansia muciniphila supplementation improves glucose tolerance in intestinal Ffar4 knockout mice during the daily light to dark transition.

Disruption of blood glucose utilization may lead to diabetes mellitus, which has complex genetic and environmental aspects, and free fatty acid receptors (FFARs) may bridge the genetic and dietary aspects. FFAR4 has been identified as a new target for diabetes treatment, and it is essential to investigate how FFAR4 affects glucose homeostasis. FFAR4 knockout mice have been shown to cause severely impaired glucose tolerance under high-fat feeding conditions; however, the findings in FFAR4 knockout mice under chow diet conditions seem to be contradictory. Blood glucose utilization in mice under chow diet conditions is thought to show diurnal rhythmicity. In this study, we aim to investigate the role of FFAR4 in glucose utilization rhythm and explore the possible mechanism. Total Ffar4 and gut-specific Ffar4 knockout mice both showed a clear diurnal rhythm in glucose tolerance. However, deletion of total Ffar4 and gut-specific Ffar4 both deteriorate glucose tolerance at the daily light to dark transition (ZT12) in mice. We show that intestinal FFAR4 deficiency leads to significant changes in fecal microbiota at different ZTs. 16S rRNA sequencing results suggested that Akkermansia muciniphila was the main target of intestinal FFAR4 at ZT12. Akkermansia muciniphila supplementation significantly improved the impaired glucose tolerance at ZT12 in mice with gut-specific Ffar4 deletion and was accompanied by recovery of serum hormone level and transcripts of key genes in glucose metabolism. IMPORTANCE Alterations in the intestinal environment are associated with various diseases, and FFAR4 is abundantly enriched in the intestine, where it has been shown to have the ability to regulate intestinal hormone secretion and intestinal microbiota; here, we confirmed previous reports. Meanwhile, we found that intestinal FFAR4 regulates glucagon-like peptide 1 secretion by decreasing Akkermansia muciniphila abundance and show that such change is associated with the level of glucose utilization at ZT12 in mice. Intestinal FFAR4 deficiency leads to severely impaired glucose tolerance at the ZT12 moment in mice, and Akkermansia muciniphila supplementation ameliorates the abnormal glucose utilization at the ZT12 moment caused by FFAR4 deficiency, which is very similar to the dawn phenomenon in diabetic patients. Collectively, our data suggest that intestinal Ffar4 deteriorates glucose tolerance at the daily light to dark transition by affecting Akkermansia muciniphila .