Role of Ghrelin polymorphisms in obesity based on three different studies

Objective: Associations between preproghrelin DNA variants and obesity-related phenotypes were studied in 3004 subjects from the Québec Family Study (QFS), the HERITAGE Family Study (HERITAGE), and the Swedish Obese Subjects (SOS) Study. Research Methods and Procedures: Body mass index (BMI), fat mass (FM) from underwater weighing, and abdominal fat from computerized tomography were measured. The ghrelin polymorphisms were identified by polymerase chain reaction. Results: Arg51Gln QFS subjects (n = 6) had lower ghrelin concentrations (p = 0.007) than Arg51Arg subjects (n = 14). White preproghrelin Met72Met subjects in HERITAGE had the lowest BMI (p = 0.020), and those in the QFS cohort had the lowest FM (p < 0.001). Met72 carrier status (Met72+) was associated with lower FM (p = 0.026) and higher insulin-like growth factor-1 levels (p = 0.019) among blacks. Met72Met QFS subjects had less visceral fat (p = 0.002) and a lower fasting respiratory quotient (p = 0.037). HERITAGE Met72+ white subjects also showed lower exercise respiratory quotient (p = 0.030) and higher maximal oxygen uptake (p = 0.023). Furthermore, the prevalence of Met72+ was higher (19.2%; p < 0.05) in SOS subjects whose BMI was ≤ 25 kg/m² than in those with BMI > 25 kg/m² (14.8%). SOS Met72+ obese women had a lower (11.4%; p = 0.032) prevalence of hypertension than noncarriers (23.9%). Discussion: Arg51Gln mutation was associated with lower plasma ghrelin levels but not with obesity. The preproghrelin Met72 carrier status seems to be protective against fat accumulation and associated metabolic comorbidities.