LAUSR

DESIGN The hormone secretin, best known for regulating pH in the duodenum, has anorectic properties in mice proposedly mediated via secretin-induced brown adipose tissue (BAT) activation. We investigated the effects of exogenous secretin on ad libitum food intake, BAT activity, and postprandial physiology in healthy male volunteers. METHODS In a randomized, placebo-controlled, double-blind, crossover study, 25 healthy men underwent two 5-hour i.v. infusions of secretin (1 pmol/kg/min) and placebo (saline), respectively, with an interposed two-month wash-out period. After 30 min of infusion, a standardized liquid mixed meal was ingested and after 5 hours, food intake and meal duration were assessed during an ad libitum meal test. BAT activity was assessed regularly by thermal imaging-measured supraclavicular skin temperature. RESULTS Compared to placebo, secretin significantly decreased ad libitum food intake by 173 ± 88 kcal [95% CI 0.76 to 0.99, P = 0.039], but did not alter ad libitum meal duration. Secretin acutely decreased BAT activity but increased it postprandially compared to placebo. Acetaminophen-assessed gastric emptying was not affected by exogenous secretin, but secretin increased gallbladder volume, bile acid synthesis, and circulating levels of lipase, amylase and triglycerides, while decreasing plasma Na+. Compared to placebo, secretin infusion was associated with 24.0 ± 10.8% (95% CI 0.3 to 1, P = 0.025) more adverse events (headache, nausea, diarrhoea, and vomiting). CONCLUSIONS In healthy men, secretin infusion decreased ad libitum food intake concomitantly with a postprandial increase in BAT activity as assessed by thermal imaging-measured supraclavicular skin temperature. TRIAL REGISTRATION Clinicaltrials.gov, NCT04613700.