Novel polymorphism of the human ob gene promoter in lean and morbidly obese subjects.

OBJECTIVE

Leptin, the circulating product of the human ob gene, may play role in control of appetite and metabolic rate. We screened the proximal promoter area of the ob gene for mutations and common polymorphisms in order to find out whether genetic variation in the regulatory area of this gene plays a role in human obesity.

DESIGN

The technique of single-strand-conformation polymorphism (SSCP) was applied to screen for the promoter area of the ob gene for genetic alterations in morbidly obese patients.

SUBJECTS

A total of 249 morbidity obese (present or past body mass index [BMI] > or = 40 kg/m2) and 141 lean (BMI < or = 25 kg/m2) subjects.

MEASUREMENTS

DNA analysis was carried out using a single-strand conformation polymorphism (SSCP) technique and PCR followed by digestion with the restriction enzyme BssHll. Leptin was determined by radioimmunoassay in obese subjects. Serum lipids, glucose and insulin concentrations in the obese subjects were also determined.

RESULTS

A new polymorphism C(-188)A was identified in the promoter region of the ob gene. This polymorphism was detected with allelic frequencies of 0.06 in morbidly obese subjects and 0.09 in lean controls (P = 0.28). Initial studies failed to show an association of this polymorphism with serum leptin, response to treatment for obesity, history and extent of weight gain, or serum insulin, glucose of lipid concentrations.

CONCLUSIONS

We have identified a common polymorphism in the promoter area of the human ob gene which appears to be very useful for genetic association and linkage studies. Further studies are needed to elucidate its potential role in the regulation of the human ob gene and in human metabolic disorders.