To determine whether a low intraduodenal glucose load (1 kcal/min) has the capacity to stimulate GLP-1, and if so, the characteristics of the response.
Retrospective analysis of all studies in our laboratory involving healthy humans administered intraduodenal glucose at 1 kcal/min for 120 min.
Clinical research laboratory.
27 healthy subjects (24 male; age 36 ± 3 years; BMI 25.2 ± 0.7 kg/m2). Main outcome measures: Plasma GLP-1, GIP, insulin, and blood glucose concentrations, reported as mean ± SEM.
During intraduodenal glucose, plasma GLP-1 increased at 15 and 30 min (P < 0.001 for both) and returned to baseline thereafter. In contrast, there were sustained increases in plasma GIP (P < 0.001), insulin (P < 0.001), and blood glucose (P < 0.001).
In healthy subjects, there is early, transient stimulation of GLP-1 by glucose loads hitherto believed to be “sub-threshold”. The mechanisms underlying this effect, which could be attributed to initially rapid transit to jejunal L cells, or a duodeno-jejunoileal neural or hormonal loop, remain to be determined.