Glucagon-like peptide-1 (7-36) amide response to low versus high glycaemic index preloads in overweight subjects with and without type II diabetes mellitus

BACKGROUND AND OBJECTIVE

Glucagon-like-peptide-1 (7-36) amide (GLP-1) is an insulin secretagogue and potential treatment for type II diabetes mellitus. An alternative to GLP-1 administration is endogenous dietary stimulation. We described a greater GLP-1 release following ingestion of liquids versus solids. We add to this work studying the effect of fluid preloads with differing glycaemic indices (GI) on the metabolic response to a meal.

SUBJECTS AND DESIGN

GLP-1, insulin and glucose responses were measured in six overweight individuals and six subjects with type II diabetes on three occasions, after preload (milk, low GI; Ovaltine Light, high GI; or water, non-nutritive control) and meal ingestion.

RESULTS

In people with and without diabetes, the high GI preload produced the greatest glucose incremental area under the curve (IAUC)(0-20), followed by the low GI preload, and water (P<0.001). In both groups, insulin IAUC(0-20) was higher following high and low GI preloads compared with water (NS). In people without diabetes, the GLP-1 response was higher when high and low GI preloads were consumed compared with water (P=0.041), with no significant difference between nutritive preloads. GLP-1 response did not differ between preloads in people with diabetes. Despite initial differences, total IAUCs(0-200) for biochemical variables did not differ by preload.

CONCLUSION

We confirm that nutritive liquids stimulate GLP-1 to a greater extent than water in subjects without diabetes; however, this does not influence subsequent meal-induced response. The GI of preloads does not influence the degree of GLP-1 stimulation.

Ghrelin increases food intake in obese as well as lean subjects

OBJECTIVE

To investigate whether effects on food intake are seen in obese subjects receiving exogenous administration of ghrelin.

DESIGN

Randomised, double-blind, placebo-controlled study of intravenous ghrelin at doses 1 pmol/kg/min and 5 pmol/kg/min.

SUBJECTS

In all, 12 healthy lean subjects (mean body mass index (BMI) 20.5+/-0.17 kg/m(2)) and 12 healthy overweight and obese subjects (mean BMI 31.9+/-1.02 kg/m(2)).

MEASUREMENTS

Food intake, appetite and palatability of food, ghrelin and other obesity-related hormones, growth hormone.

RESULTS

Low-dose infusion of ghrelin increased ad libitum energy intake at a buffet meal in the obese group only (mean increase 36.6+/-9.4%, P<0.01.) High-dose ghrelin infusion increased energy intake in both groups (mean increase 20.1+/-10.6% in the lean and 70.1+/-15.5% in the obese, P<0.01 in both cases.) Ghrelin infusion increased palatability of food in the obese group.

CONCLUSION

Ghrelin increases food intake in obese as well as lean subjects. Obese people are sensitive to the appetite-stimulating effects of ghrelin and inhibition of circulating ghrelin may be a useful therapeutic target in the treatment of obesity.