Genetic evidence of causal relation between intestinal glucose absorption and early postprandial glucose response: a Mendelian randomization study

The post-prandial glucose response is an independent risk factor for type 2 diabetes. Observationally, early glucose response after an oral glucose challenge has been linked to intestinal glucose absorption, largely influenced by the expression of sodium-glucose-co-transporter-1 (SGLT1). This study utilizes Mendelian randomization (MR) to estimate the causal effect of intestinal SGLT1 expression on early glucose response. Involving 1547 subjects with class II/III obesity from the ABOS cohort, the study employs SGLT1 genotyping, oral glucose tolerance tests, and jejunal biopsies to measure SGLT1 expression. A loss-of-function SGLT1 haplotype served as the instrumental variable, with intestinal SGLT1 expression as the exposure and the change in 30-minute post-load glycemia from fasting glycemia (∆30 glucose) as the outcome. Results showed that 12.8% of the 1,342 genotyped patients carried the SGLT1 loss-of-function haplotype, associated with a mean ∆30 glucose reduction of -0.41 mmol/L and a significant decrease in intestinal SGLT1 expression. The observational study linked a one standard deviation decrease in SGLT1 expression to a ∆30 glucose reduction of -0.097 mM/L. MR analysis paralleled these findings, associating a statistically significant reduction in genetically instrumented intestinal SGLT1 expression with a ∆30 glucose decreases of -0.353. In conclusion, the MR analysis provides genetic evidence that reducing intestinal SGLT1 expression causally lowers early post-load glucose response. This finding has a potential translational impact on managing early glucose response in type 2 diabetes