Relationship between the changes of plasma levels of leptin and obesity in patients with insulinoma

Objective To analyze the relationship between the changes of fasting plasma level of leptin and obesity in patients with insulinoma before operation. Methods From January 2003 to May 2008, 40 patients with insulinoma diagnosed at Peking Union Medical College Hospital were selected. Preoperative fasting plasma samples of them were collected. From January 2003 to May 2008, the plasma samples of 28 volunteers matched with age, gender and body weight matched with the patients were collected as the controls. All the subjects were divided into overweight-obesity group and normal weight group according to their body mass index (BMI). Plasma levels of leptin of all the subjects were measured by enzyme linked immunosorbent assay(ELISA). The Mann-Whitney U test and the correlation coefficient test were used for statistical analysis. Results The plasma leptin level of patients with insulinoma was 0.35 ng/mL (0.25 ng/mL to 1.13 ng/mL), which was higher than that of the control group (0.29 ng/mL, 0.25 ng/mL to 1.15 ng/mL), and the difference was statistically significant (U=324.50, P=0.003). In the normal-weight group, the plasma leptin level of the patients with insulinoma was 0.35 ng/mL (0.27 ng/mL to 0.62 ng/mL), which was higher than that of the control group (0.28 ng/mL, 0.25 ng/mL to 0.37 ng/mL), and the difference was statistically significant (U=28.000, P=0.001). While in the overweight-obesity group, the plasma leptin levels of the patients with insulinoma and the controls were 0.35 ng/mL (0.25 ng/mL to 1.13 ng/mL) and 0.34 ng/mL (0.26 ng/mL to 1.15 ng/mL), respectively, and the difference was not statistically significant (U=153.500, P=0.525). Plasma leptin levels in both the patients with insulinoma and the controls, were correlated with BMI (r=0.355, P=0.025; r=0.571, P=0.001, respectively). Conclusion Preoperative fasting plasma level of leptin increase in patients with insulinoma which is correlated with BMI. Key words: Insulinoma; Obesity; Leptin; Insulin; Body mass index; Pancreatic neuroendocrine tumor