Prandial subcutaneous injections of glucagon-like peptide-1 cause weight loss in obese human subjects

Recombinant glucagon-like peptide-1 (7-36)amide (rGLP-1) was recently shown to cause significant weight loss in type 2 diabetics when administered for 6 weeks as a continuous subcutaneous infusion. The mechanisms responsible for the weight loss are not clarified. In the present study, rGLP-1 was given for 5 d by prandial subcutaneous injections (PSI) (76 nmol 30 min before meals, four times daily; a total of 302.4 nmol/24 h) or by continuous subcutaneous infusion (CSI) (12.7 nmol/h; a total of 304.8 nmol/24 h). This was performed in nineteen healthy obese subjects (mean age 44.2 (SEM 2.5) years; BMI 39.0 (SEM 1-2)kg/m(2)) in a prospective randomised, double-blind, placebo-controlled, cross-over study. Compared with the placebo, rGLP-1 administered as PSI and by CSI generated a 15% reduction in mean food intake per meal (P = 0.02) after 5 d treatment. A weight loss of 0.55 (SEM 0.2) kg (P< 0.05) was registered after 5 d with PSI of rGLP-1. Gastric emptying rate was reduced during both PSI (P<0.001) and CSI (P<0.05) treatment, but more rapidly and to a greater extent with PSI of rGLP-1. To conclude, a 5 d treatment of rGLP-1 at high doses by PSI, but not CSI, promptly slowed gastric emptying as a probable mechanism of action of increased satiety, decreased hunger and, hence, reduced food intake with an ensuing weight loss.