Plasma obestatin levels are lower in obese and post-gastrectomy subjects, but do not change in response to a meal

Objective: To investigate a potential role for obestatin in humans by examining response to a fixed energy meal. Context: A new anorectic peptide hormone, obestatin has recently been isolated from rat stomach. The significance of this peptide in humans is unknown. Study design: Case-control study. Setting: Hospital-based study. Patients: Nine healthy controls, nine morbidly obese subjects and eight post-gastrectomy subjects. Intervention: Subjects attended after an overnight fast and were given a fixed energy meal (1550 kJ). Main outcome measure: The response of obestatin to a meal in the different groups. Results: Fasting obestatin was significantly lower in obese subjects as compared to lean subjects (27.8 +/- 4 vs 17.2 +/- 2 pg/ml, P = 0.03). Obestatin was also decreased in gastrectomy subjects but this did not reach statistical significance (27.8 +/- 4 vs 21.9 +/- 3 pg/ml, P = 0.3). Obestatin did not change significantly from baseline in response to the meal. Lean and obese subjects had a similar obestatin/ghrelin ratio (0.04 +/- 0.003 vs 0.05 +/- 0.009, P = 0.32), but this was higher in the gastrectomy group (0.04 +/- 0.003 vs 0.1 +/- 0.01, P < 0.001). Conclusions: Obestatin does not vary significantly with a fixed energy meal, but is significantly lower in morbidly obese subjects as compared to lean subjects supporting a possible role for obestatin in long-term body weight regulation. Obestatin tended to be lower in gastrectomy subjects and their obestatin/ghrelin ratio differed from healthy controls. Hence, the expression of obestatin is altered following gastrectomy, suggesting other sites outside the stomach may also secrete obestatin.