Background: Peptide YY (PYY) and glucagon-like peptide-1 (GLP-1) are cosecreted in the same enteroendocrine L-cells of the gut and reported to inhibit food intake additively. However, findings in human studies regarding these peptides are controversial. The aim of this study was to analyze the relationships between fasting PYY, GLP-1, and weight status in morbidly obese patients before and after surgically induced weight loss.
Methods: Fasting GLP-1, PYY, glucose, and insulin concentrations; blood pressure; and body-mass index (BMI) were determined in 30 morbidly obese adults (mean BMI 45.8, mean age 40 years) before bariatric surgery [Roux-en-Y gastric bypass (RYGB): n = 19; gastric banding (GB): n = 11] and after weight loss (mean 50% excess weight loss) in the course of mean 2 years.
Results: GLP-1 concentrations decreased (mean -20 pg/ml; mean -38%; p = 0.001) and PYY concentrations increased (mean +19 pg/ml; mean +19%, p = 0.036) after bariatric surgery. The weight loss and changes of GLP-1 were significantly (p < 0.05) more pronounced after RYGB as compared to GB, whereas the changes of PYY did not differ significantly between the patients who had undergone RYGB or GB.
Conclusions: In morbidly obese adults reducing their weight by bariatric surgery, fasting PYY levels increased and GLP-1 concentrations decreased independently of each other. Therefore, the relationship between PYY and GLP-1 seems more complicated than might be anticipated from animal and in vitro studies.