Relationship of leptin concentration to gender, body mass index and age in Saudi adults.

Objective: Leptin concentrations are highly correlated with body fat storage and exhibit sexual dimorphism, with women having higher concentrations at every level of relative or absolute adiposity. To test whether or not this relation is consistent across the Saudi population. This study aims to investigate the effect of gender, obesity related parameters, and age on leptin levels from representative samples of Saudi women and men.

Methods: This study was carried out at King Abdul-Aziz University, Jeddah, Kingdom of Saudi Arabia during the year 2003. Fasting leptin concentrations were determined after an overnight fast in 122 healthy subjects (57 women, 65 men; age 20-75 years; body mass index [BMI] 16-56 kg/m2). The subjects were separated into female and male groups. To clarify the age and BMI-related changes in leptin levels, each gender was divided into 3 BMI groups (lean 15-24, overweight 25-30 and obese >30 kg/m2), and 3 age groups (younger 20-34, middle-aged 35-49 and older 50-75 years); and they were treated separately. Anthropometrics measurements (weight, height, waist, and hip circumferences), blood pressure, and fasting glucose levels were taken at the time of the collection.

Results: In the whole group, leptin levels were between 0.16-21.72 ng/ml, and females had higher leptin concentration (6.04 +/- 4.71 ng/ml versus 1.72 +/- 0.95 ng/ml, p<0.0001) than males. Gender differences remained clear when leptin concentrations were divided by BMI or age. In comparing the pattern of changes between the 2 genders, leptin levels were low in lean individuals and rose with increased BMI in both genders. Age-related change in leptin levels showed a tendency toward a non-significant reduction in older women and a significant (p=0.05) rise in older men. Correlation analysis between leptin and BMI were highly significant in female (r=0.64; p=0.0001) and male (r=0.49; p=0.0001) groups independent of age and sex. The findings were further explored using stepwise multiple linear regression analysis with leptin concentrations as the dependent variable and age, BMI, waist hip ratio (WHR), waist, and hip measurements as independent variables. The analysis demonstrated that the determinants of leptin concentrations were BMI and age (r=0.69; p=0.015) in women and BMI, age and WHR (r=0.61; p=0.01) in men.

Conclusion: The present study demonstrates that there are gender-specific and age-dependent gender-specific differences in leptin concentrations in healthy Saudi individuals. However, this study indicates that there may be unknown variables that may also influence leptin levels in Saudi women and men.