The mean age in male subjects and in female subjects was 51.9 and 52.7 (Table 1). Diabetes patients were about 8.9% of the subjects; 37.3% of males and 3.9% of females were current smokers of the sample dataset. Cardiovascular disease patients were 44.7% of men and 35.9% of women. Table 2 shows the p values from a linear regression model for FBS levels when age and sex were included as covariates. The rs17782313 SNP in the MC4R gene was related to mean FBS level and BMI (effect per allele, 1.542 mg/dL, p = 0.0057, and 0.227 mg/dL, p = 0.0018). For healthy individuals, the rs17782313 SNP in the MC4R gene was related to mean FBS level and BMI (effect per allele, 1.477 mg/dL, p = 0.0205, and 0.237 mg/dL, p = 0.0096).
The relationship between diabetes and the MC4R gene SNP rs17782313 was examined (Table 3). Individuals with the TC/CC genotype had a 1.29-fold higher risk of diabetes than did those with the TT genotype when adjusting for age, sex, and BMI (OR, 1.29; 95% CI, 1.04-1.60). When analyzed by sex, the relationship between MC4R and diabetes was significant only for men (OR, 1.33; 95% CI, 1.04-1.70), not women (OR, 1.10; 95% CI, 0.70-1.75). For healthy subjects, individuals with the TC/CC genotype had a 1.40-fold higher risk of diabetes than did those with the TT genotype when for adjusting age, sex, and BMI (OR, 1.40; 95% CI, 1.01-1.95). However, the association was stronger in females (OR, 1.99; 95% CI, 1.01-3.93), and the association of MC4R with diabetes was not found in males (OR, 1.24; 95% CI, 0.85-1.81).
The relationship of the MC4R gene SNP rs17782313 to cardiovascular disease was also examined (Table 4). Male subjects with the TC/CC genotype had a 1.21-fold (range, 1.04–1.41-fold) higher risk of cardiovascular disease than did those with the TT genotype when for adjusting age, sex, BMI (OR, 1.21; 95% CI, 1.04-1.41). In contrast, the relationship of MC4R with cardiovascular disease was not found in females.
Table 5 shows the analysis by BMI for male subjects. The relationship between MC4R and cardiovascular disease was stronger in males with BMI < 24.75 (OR, 1.40; 95% CI, 1.12–1.74, p = 0.0028) than in subjects with BMI >= 24.75 (p = 0.6461). However, the interaction between BMI and MC4R (rs17782313) genotype for cardiovascular disease was not significant (p for interaction = 0.0753).