Background
Controversial findings exist on the role of leptin in obesity and its correlation with metabolic variables, with few data emanating from Nigerian-Africans. Plasma leptin was therefore determined in obese and non-obese. Its relationship with obesity indices and metabolic variables were further envisaged.
Materials and Methods
A cross-sectional comparative study on 87 randomly-selected non-diabetes Nigerians distributed into 3 groups (24 normal, 23 pre-obese and 40 obese). Obesity indices, fasting Insulin (FI) and homeostasis model assessment-insulin resistance (HOMA-IR) were determined. Plasma leptin was determined by sandwich enzyme-linked immunosorbent assay. Mann-Whitney
U
-test, Independent Kruskal-Wallis test, Spearman correlation and Step-wise Multivariate Logistic Regression analysis determined outcomes.
Results
Median+IQR leptin concentrations were higher in obese {61.8(40.8, 91.4) ng/mL,
p<0.001
} than pre-obese {42.7(28.0, 51.7) ng/mL,
p=0.003
} and normal {28.6(20.7, 39.8) ng/mL,
p=0.03
} BMI categories. Leptin was higher (
p<0.001
) in females than males {Median+IQR, 52.0 (35.0, 80.0) ng/mL versus 34.0(24, 65.0 ng/mL)}. Leptin was positively correlated with body fat percentage (BFP), r=0.57; waist circumference (WC), r=0.46 and body mass index (BMI), r=0.50,
p<0.001
, respectively in all subjects, with higher correlation coefficient in males than females. Leptin showed sex-specific correlations to age, FI and HOMA-IR. In the unadjusted models, central obesity/generalized obesity, WC, BMI, BFP, combined pre-obesity/obesity, younger age and female sex were significantly (
p<0.001
) associated with log-transformed leptin. WC (OR: 1.2, 95% CI, 1.05–1.38,
p=0.009
), BFP (OR: 1.41, 95% CI, 1.07–1.84,
p=0.013
) and BMI (OR: 1.6, 95% CI, 1.13–2.31,
p=0.008
) in men and all subjects, were independently associated with hyperleptinaemia following adjustments.
Conclusion
Plasma leptin concentrations, fasting insulin and insulin resistance are higher in obese and pre-obese than normal controls, with females showing higher leptin concentrations than males. Leptin is independently related to BMI, BFP, WC, female sex and generalized/central obesity in Nigerian-Africans especially males. It showed sex-specific relations to age, fasting insulin and HOMA-IR.
