Interleukin-18 polymorphism as an inflammatory index in metabolic syndrome: A preliminary study

Table 1 Biophysical and biochemical data of the study subjects

Variables	Normal weight (18-22.9 kg/m2) (n = 60)	Overweight (23-25.9 kg/m2) (n = 60)	Obese (>26 kg/m2) (n = 60)	P value
Age (yr)	26.21 ± 3.876	25.76 ± 4.059	27.30 ± 5.389	NS
BMI (kg/m2)	20.48 ± 1.30	24.20 ± 0.911	28.59 ± 3.341,2	< 0.001
Body fat (%)	19.26 ± 7.17	28.70 ± 9.101	34.89 ± 4.471,2	< 0.001
Waist circumference (cm)	88.03 ± 10.53	88.46 ± 7.69	1.9.26 ± 11.47	< 0.001
Hip circumference (cm)	77.69 ± 11.78	84.43 ± 0.69	100.41 ± 12.89	< 0.001
WHR (cm)	0.87 ± 0.05	0.871 ± 0.054	0.91 ± 0.073	< 0.001
Fasting blood glucose (mg/dL)	89.31 ± 15.23	105.59 ± 12.501	119.00 ± 25.711	< 0.001
Insulin (uIU/mL)	20.48 ± 7.95	34.96 ± 4.471	41.13 ± 7.811,2	< 0.001
HOMA-IR	4.70 ± 2.66	9.05 ± 1.341	11.88 ± 2.811,2	< 0.001
QUICKI	0.31 ± 0.02	0.27 ± 0.001	0.27 ± 0.011	< 0.001
Cholesterol (mg/dL)	145.72 ± 30.08	147.44 ± 37.91	209.06 ± 55.511,2	< 0.001
Triglyceride (mg/dL)	124.82 ± 43.92	137.58 ± 65.60	167.03 ± 55.991,2	< 0.001
HDL(mg/dL)	39.96 ± 9.38	38.37 ± 8.00	36.40 ± 6.40	NS
LDL(mg/dL)	75.43 ± 30.03	79.57 ± 40.01	134.78 ± 58.991,2	< 0.001
TNFα (pg/mL)	810 ± 1233	4455 ± 23901	4581 ± 21321	< 0.001
IL-18 (ng/L)	25.34 ± 6.57	41.96 ± 4.501	58.87 ± 8.591,2	< 0.001

Values are expressed as mean ± SD. Comparison between groups was tested by One way analysis of variance followed by Tuckey’s post hoc test.

¹Statistically significant as compared to normal weight;

²Statistically significant as compared to overweight. Significance set at P value < 0.05. HOMA-IR: Homeostasis model of insulin resistance; QUICKI: Quantitative insulin sensitivity check index; HDL: High density lipoprotein; LDL: Low density lipoprotein; TNF: Tumor necrosis factor; WHR: Waist to hip ratio.

Table 2 Correlation of interleukin-18 with metabolic syndrome phenotypes

Variable	Unadjusted r	Adjusted r (age, BMI and body fat %)
Age (yr)	0.302	--
BMI (kg/m2)	0.751	--
Body fat (%)	0.518	--
Waist circumference (cm)	0.333	0.413
Hip circumference (cm)	0.695	-0.110NS
Fasting blood glucose (mg/dL)	0.559	0.376
Insulin (uIU/mL)	0.655	0.205NS
HOMA-IR	0.699	0.344
QUICKI	-0.600	-0.496
Cholesterol (mg/dL)	0.514	0.265
LDL(mg/dL)	0.464	0.245
TNFα	0.577	0.491

Pearson Correlation was applied. All associations remained significant after adjustment except insulin (^NSnon-significant), statistically significant P value < 0.01. HOMA-IR: Homeostasis model of insulin resistance; QUICKI: Quantitative insulin sensitivity check index; LDL: Low density lipoprotein; TNF: Tumor necrosis factor.

Table 3 Genotype frequency among study subjects

Genotype distribution
	CC	AC	AA	P value
Normal weight	27	23	10	< 0.001
Overweight	11	25	24
Obese	12	24	24
Allele frequency
	A allele	C allele	OR (95%CI)	P value
Normal weight	42 (35.0)	78 (65.0)	-	-
Overweight	47 (39.17)	73 (60.83)	2.81 (1.66-4.68)1	< 0.001
Obese	48 (40.00)	72 (60.00)	2.91 (1.72-4.94)2

In all divisions the HWE was > 0.05.

¹Normal weight vs overweight and

²normal weight vs obese calculated by Pearson’s χ² test. Allele frequencies are given as absolute values with percentage given in parentheses.

Table 4 Stratification of study subjects according to genotype distribution

Variables	CC (n = 57)	AC (n = 72)	AA (n = 51)	P value
BMI (kg/m2)	23.36 ± 4.05	24.60 ± 4.137	25.25 ± 3.351	0.05
Body fat (%)	24.70 ±10.30	28.70 ± 8.592	29.31 ± 9.461	< 0.001
Waist circumference(cm)	92.78 ± 16.61	96.48 ± 13.21	97.32 ± 13.82	0.085
Hip circumference (cm)	74.18 ± 4.23	67.40 ±3.99	64.51 ± 4.84	0.694
WHR (cm)	0.88 ± 0.069	0.88 ± 0.061	0.89 ± 0.06	0.490
Fasting blood glucose (mg/dL)	103.41 ± 23.43	101.79 ± 21.01	110.32 ± 21.97	> 0.05
Insulin (uIU/mL)	28.83 ± 11.91	32.76 ± 11.392	34.67 ± 9.611	0.002
HOMA-IR	7.75 ± 4.34	8.44 ± 3.71	9.47 ± 3.001	0.007
QUICKI	0.29 ± 0.02	0.28 ± 0.02	0.28 ± 0.011	0.046
Cholesterol (mg/dL)	161.01 ± 39.01	165.12 ± 55.03	177.42 ± 60.72	> 0.05
Triglyceride (mg/dL)	135.66 ± 42.29	145.61 ± 61.45	146.78 ± 64.08	> 0.05
HDL(mg/dL)	38.29 ± 8.84	38.48 ± 56.32	37.17 ± 6.75	> 0.05
LDL(mg/dL)	88.99 ± 5.38 (SEM)	94.73 ± 6.63 (SEM)	107.77 ± 7.89 (SEM)	> 0.05
TNFα (pg/mL)	2521 ± 353.9 (SEM)	3403.08 ± 313.25 (SEM)	3760.35 ± 336.551 (SEM)	0.008
IL-18 (ng/L)	37.16 ± 19.35	43.00 ± 13.192	46.311 ± 13.071	0.001

¹AA vs CC;

²AC vs CC. HDL: High density lipoprotein; LDL: Low density lipoprotein; TNFα: Tumor necrosis factor alpha; IL-18: Interleukin-18.