Effects of dietary fat and protein on glucoregulatory hormones in adolescents and young adults with type 1 diabetes

CONTEXT Dietary fat and protein impact postprandial hyperglycaemia in people with type 1 diabetes, but the underlying mechanisms are poorly understood. Glucoregulatory hormones are also known to modulate gastric emptying and may contribute to this effect. OBJECTIVE Investigate the effects of fat and protein on glucagon like peptide (GLP-1), glucagon-dependent insulinotropic polypeptide (GIP) and glucagon secretion. DESIGN Two cross-over euglycaemic insulin clamp clinical trials. SETTING Two Australian paediatric diabetes centres. PARTICIPANTS 12-21years (n=21) with type 1 diabetes for ≥1year. INTERVENTION(S) Participants consumed a low protein (LP) or high protein (HP) meal in Study 1, and low protein/low fat (LPLF) or high protein/high fat (HPHF) meal in Study 2, all containing 30g carbohydrate. An insulin clamp was used to maintain postprandial euglycaemia and plasma glucoregulatory hormones were measured every 30 minutes for 5-hours. Data from both cohorts (n=11,10) were analysed separately. MAIN OUTCOME Area under the curve of GLP-1, GIP and glucagon. RESULTS Meals low in fat and protein had minimal effect on GLP-1, while there was sustained elevation after the HP (80.3±16.8pmol/L) vs LP (56.9±18.6), P=0.016, and HPHF (103.0±26.9) vs LPLF (69.5±31.9) meals, P=0.002. The prompt rise in GIP after all meals was greater after the HP (190.2±35.7pmol/L) vs LP (152.3±23.3), P=0.003, and HPHF (258.6±31.0) vs LPLF (151.7±29.4), P<0.001. A rise in glucagon was also seen in response to protein, HP (292.5±88.1pg/mL) vs LP (182.8±48.5), P=0.010. CONCLUSIONS The impact of fat and protein on postprandial glucose excursions may be mediated by the differential secretion of glucoregulatory hormones. Further studies to better understand these mechanisms may lead to improved personalised postprandial glucose management.