Circulating levels of all proglucagon-derived peptides are differentially regulated postprandially by obesity status and in response to high-fat meals vs. high-carbohydrate meals

Background & aims: We measured all proglucagon-derived peptides (PGDPs) levels in response to administration of three mixed meal tolerance tests (MMTs), examining differences in postprandial PGDP responses in subjects with leanness and obesity or between high-fat vs. high carbohydrate meals.

Methods: We designed three physiology interventional studies, administering MMTs over a 180-min period to individuals without diabetes after an overnight fast. In Study 1, a 450 kcal MMT was administered to n = 4 normal weight and n = 9 individuals with obesity. In Study 2, a 600 kcal high-fat MMT was administered to n = 15 normal-weight and n = 15 individuals with obesity. In Study 3, n = 32 participants with obesity were assigned to receive a 600-kcal high-fat (n = 15) or an isocaloric high-carbohydrate MMT (n = 17). Fasting and postprandial levels of c-peptide and PGDPs (proglucagon, GLP-1, GLP-2, glicentin, oxyntomodulin, glucagon, major proglucagon fragment [MPGF]) were assessed.

Results: In study 1, individuals with normal weight displayed elevated glicentin postprandial secretion compared with people with obesity (p = 0.002). Following a high-fat MMT with 33% higher energy content in study 2, all postprandial PGDPs levels were elevated (p-time<0.001), irrespective of weight status. In study 3, a prolonged postprandial upregulation of PGDPs during the high-fat MMT was observed in contrast with the acute, short-term (max 60 min) PGDP responses to a high-carbohydrate MMT (p-time∗meal<0.001). Across both studies 2 and 3, the postprandial responses of glucagon and MPGF were higher in subjects with male sex whereas glicentin was higher in subjects with female sex.

Conclusions: Fat and carbohydrate content of a meal can substantially affect the postprandial levels of PGDPs. Circulating levels of PGDPs are influenced by the energy content of the meal, and additionally, the presence of leanness or obesity affects circulating levels of select PGDPs. These results, which are to be confirmed by additional studies, expand our understanding of PGDP physiology in leanness and obesity.

Clinicaltrials: GOV REGISTRATION NUMBERS: (NCT04170010, NCT04430946, NCT04575194).