Are serum leptin levels predicted by lipoproteins, vitamin D and body composition?

Table 1 Demographics, body composition and biochemical parameters and comparison amongst genders and obese vs non obese

Description	Overall	Males	Females	P value	Overweight and obese (BMI > 23 kg/m2)	Non obese (BMI < 23 kg/m2)	P value
n	167	74	93		76 (50% Females)	91 (60.4% Females)
Anthropometric parameters
Median age (IQR) in yr	20 (27-20)	21(29-20)	20(23-20)	0.136	21 (35.5-20)	20 (21-20)	< 0.01
Mean height (SD) in cm	168 (9.2)	172 (8.2)	164.8 (8.7)	< 0.01	167.9 (9.7)	168.1 (8.8)	0.837
Mean weight (SD) in kg	65.0 (4.4)	70.2 (14.9)	60.9 (12.6)	< 0.01	75.1 (14.1)	56.6 (7.7)	< 0.01
Mean BMI (SD) in kg/m2	23 (4.6)	23.7 (5.1)	23.7 (5.1)	0.056	26.6 (4.3)	19.9 (1.8)	< 0.01
Mean waist circumference (SD) in cm	79.1 (12.8)	83.3 (13.3)	75.7 (11.3)	< 0.01	86.9 (12.4)	72.5 (8.8)	< 0.01
Body composition
Mean total body fat % (SD)	22.1 (8.7)	19.7 (9.0)	23.9 (8.0)	< 0.01	27.5 (7.5)	17.5 (6.8)	< 0.01
Under fat n (%)	44 (26.3)	5 (6.8)	39 (41.9)	< 0.01	3 (3.9)	41 (45)	< 0.01
Healthy n (%)	78 (46.7)	38 (51.4)	40 (43)	< 0.01	33 (43.4)	45 (49.4)	< 0.01
Over fat n (%)	21 (12.6)	11 (14.9)	10 (10.8)	< 0.01	19 (25)	2 (2.1)	< 0.01
Obese n (%)	24 (14.4)	20 (27)	4 (4.3)	< 0.01	21 (27.6)	3 (3.2)	< 0.01
Mean total body water %	55.7 (6.1)	57.8 (6.3)	54.1 (5.4)	< 0.01	52.3 (4.9)	58.6 (5.5)	0.255
Ideal body water n (%)	142 (85)	61 (82.4)	81 (87.1)	0.235	68 (89.4%)	74 (81.3%)	< 0.01
Mean muscle mass (SD) in kg	45.7 (7.9)	50.2 (8.4)	42 (5.1)	< 0.01	46.3 (8.7)	45.1 (7.2)	0.357
Median BMR (IQR) in kcal	1501 (1750-1336)	1732 (1875-1551)	1377 (1525-1300)	< 0.01	1690 (1892.5-1421.5)	1417 (1612-1308)	< 0.01
Median bone mass (IQR) in kg	2.5 (3-2.1)	2.9 (3.2-2.6)	2.2 (2.4-2)	< 0.01	2.9 (3.2-2.3)	2.2 (2.8-2.0)	< 0.01
Healthy bone mass n (%)	71 (42.5)	31 (41.9)	40 (43)	0.884	36 (47.3%)	35 (38.4%)	0.273
Biochemical parameters
Median leptin (ng/mL)	2.2 (4.5-1.0)	1.3 (3.60-0.54)	2.71 (4.76-1.66)	< 0.01	3.0 (5.8-1.5)	1.7 (3.4- -0.7)	< 0.01
Elevated serum leptin n (%)	17 (10.2)	7 (9.5)	10 (10.8)	0.784	9 (11.8%)	8 (8.8%)	0.61
Median 25OHD (IQR) in ng/mL	12.1 (16.1-7.7)	12.5 (16-8.5)	11.5 (16.6-7.5)	0.877	12.1 (16.8-8.5)	12 (15.9-7.1)	0.479
25OHD status: Deficiency n (%)	149 (89.2)	69 (93.2)	80 (86)		67 (88.1%)	82 (90.1%)
25OHD status: Insufficiency n (%)	10 (6)	5 (6.8)	5 (5.4)	0.03	4 (5.2%)	6 (6.5%)	0.585
Sufficiency n (%)	8 (4.8)	-	8 (8.6)		5 (6.5%)	3 (3.2%)
Mean total cholesterol (SD) in mg/dL	175.8 (46.3)	172 (49.4)	178.8 (43.7)	0.345	180.8 (48.6)	171 ± 44	0.199
Mean HDL (SD) in mg/dL	41.1 (9.6)	40.4 (10)	41.6 (9.2)	0.44	40.5 (9.4)	41.540.5 ± 9.49.7	0.498
Mean non-HDL (SD) in mg/dL	134.7 (47.2)	131.5 (52.4)	137.2 (42.8)	0.446	14040.5 (9.450.1)	13040.5 ± 9.444.4	0.163

Parametric variables are reported as mean ± SD and non-parametric as median (interquartile ranges 75^th-25^th). Coefficients (r) and P values are calculated using Pearson's correlation analysis. P-value less than 0.05 was considered as significant and < 0.001 as highly significant. BMI: Body mass index; BMR: Basal metabolic rate; 25OHD: 25-hydroxy vitamin D; HDL: High density lipoprotein.

Table 2 Correlation of metabolic and biochemical factors with serum log leptin according to gender distribution

Gender	n	BMI (kg/m2)	Waist circumference (cm)	Total body fat %	Total body water %	Muscle mass (kg)	BMR (kcal)	Bone mass (kg)	Total cholesterol (mg/dL)	Mean HDL(mg/dL)	Mean non-HDL(mg/dL)	Log 25OHD (ng/mL)
Male	74	0.2561	0.2561	0.472	-0.3312	-0.4992	-0.018	-0.206	-0.053	-0.139	-0.023	-0.4792
Female	93	0.3772	0.3622	0.3222	-0.2712	0.02	-0.332b	0.247a	-0.169	-0.176	-0.135	-0.102
Overall	167	0.2392	0.1811	0.4452	-0.3642	-0.4262	-0.047	-0.137	-0.72	-0.127	-0.045	-0.2752

¹Correlation is significant at the 0.05 level (2-tailed);

²Correlation is significant at the 0.01 level (2-tailed). Univariate analysis was conducted and variables that had significant association with leptin in univariate analysis at P < 0.2 were considered in multivariable analysis. Coefficients (r) and P values are calculated using Pearson's correlation analysis. P-value less than 0.05 was considered as significant and < 0.001 as highly significant. BMI: Body mass index; BMR: Basal metabolic rate; 25OHD: 25-hydroxy vitamin D; HDL: High density lipoprotein.

Table 3 Multiple regression analysis of serum leptin determinants

Independent variables	Standardized β	T value	P value	95%CI for B	Collinearity statistics
					Tolerance	VIF
BMI	0.017	1.057	0.292	-0.015-0.049	0.238	4.208
BMR	0.000	2.281	0.024	0.000-0.001	0.396	2.526
Muscle mass	-0.265	-2.995	0.003	-0.032-0.007	0.530	1.885
Body water (%)	0.308	1.875	0.063	-0.002-0.060	0.147	6.792
Body fat (%)	0.488	2.588	0.011	0.008-0.058	0.129	7.751
Bone mass	-0.191	-2.137	0.034	-0.032-0.007	0.523	1.912
Waist Circumference	-0.022	-0.201	0.841	-0.011-0.009	0.468	2.138
Log 25OHD	-0.253	-3.816	0.000	-0.720-0.232	0.944	1.060
Male gender	-0.186	-2.155	0.033	-0.419-0.018	0.522	1.916

Dependent variable: was log leptin. Univariate analysis was conducted and variables that had significant association with leptin in univariate analysis at P < 0.2 were entered in multivariable analysis shown above. Coefficients (r) and P values are calculated using Pearson's correlation analysis. BMI: Body mass index; BMR: Basal metabolic rate; 25OHD: 25-hydroxy vitamin D; HDL: High density lipoprotein.