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Abstract

The present investigations were aimed to identify the possible association between genetic polymorphism in interleukin-6 (IL-6) G-174C gene, which confers susceptibility to metabolic syndrome, and serum level of resistin in North Indian women. The study population comprised 370 unrelated Indian women (192 having abdominal obesity and 178 controls). Polymorphism in genotype (CC+GC) of IL-6 G-174C gene was determined using a combination of polymerase chain reaction (PCR) and sequence-specific primer with restriction fragment length polymorphism (RFLP) technology. Insulin resistance (IR) and serum resistin level were also analyzed along with metabolic risk factors. Of 192 abdominal obese women, 147 (76.56%) were found to have mutant CC+GC (p = 0.001) genotype and allele frequency (p = 0.001), which was significantly higher 45 (23.44%) than non-obese and their respective wild type. The mutant genotype (CC+GC) of IL-6 gene was found to be associated significantly with high triglyceride (p = 0.025) and resistin level (p < 0.001), when compared with respective wild genotype (GG) in obese women. Non-obese women with no signs of metabolic risk factors were found to have significantly low level of serum resistin and IR in comparison to obese women having genetic polymorphism for IL-6 G-174C gene. Study suggests that IL-6 G-174C gene is one among the susceptibility loci for metabolic syndrome in North Indian women. Genotype for this polymorphism may prove informative for prediction of genetic risk for metabolic syndrome. Further, high level of serum resistin molecules may be targeted to correlate with metabolic syndrome risk factors and could be used as early prediction marker.

Keywords

interleukin-6 gene resistin metabolic risk factors abdominal obesity

Introduction

Metabolic syndrome is a constellation of abnormalities characterized by abdominal obesity, high triglycerides, hypertension, low high-density lipoprotein (HDL) cholesterol and high fasting glucose.¹ The clustering of these features into a single entity has been speculated to increase the risk for developing type 2 diabetes mellitus (T2DM) as well as increased cardiovascular morbidity and mortality.²

Adipose tissue is a very active endocrine organ that secretes various adipokines, which play an important role in body energy metabolism, biological effect of insulin on target tissue, and in development of insulin resistance (IR).^3–5 Serum adipocytokines level has been shown to be increased in obese or insulin-resistant subjects or in subjects with high cardiovascular risk.⁶

Resistin, an adipokine, is the product of the RSTN gene, a peptide hormone belonging to the class of cysteine-rich secreted proteins, which is termed the RELM family.⁷ Human resistin gene is located in No. 19 chromosome. Resistin gene was mainly expressed in various kinds of adipose tissue with its expression being regulated by many factors.⁸ Resistin is believed to play an important role in several metabolic pathways and inflammatory responses.^9,10 Resistin is also expressed in macrophages and may be a novel link between inflammation and IR.¹¹ Resistin suppresses the ability of insulin to stimulate glucose uptake.¹² One study suggested that resistin is present at elevated levels in blood of obese mice and is down-regulated by fasting and anti-diabetic drugs, whereas another study had found that resistin expression is severely suppressed in abdominal obesity and is stimulated by several anti-diabetic drugs.¹³ Resistin is considered to be the linkage between obesity and IR, but its role in humans is still controversial.

Interleukin-6 (IL-6), a pro-inflammatory cytokine that regulates the acute-phase response and inflammation cascade, influences adipose tissue function, endothelial function, and plasma lipid levels.^14,15 Adipose tissue contributes up to one-third of the circulating IL-6 in healthy human subjects, and this is closely related to the pattern and degree of adiposity.^6,16 An IL-6 level seems to be increased in obese subjects; on the other hand, IL-6 deficient mice develop obesity.^17,18 The IL-6 gene maps to chromosome 7p21 and contains a promoter polymorphism, −174G/C, that has been reported to alter transcription rate as well as serum IL-6 levels.^19,20

Recent study has shown the regulation of pro-inflammatory cytokine expression by resistin. Resistin strongly up-regulate IL-6 and tumor necrosis factor α (TNF-α) in human peripheral blood mononuclear cells (PBMC) via NF-κB pathway.²¹ Lipopolysaccharide (LPS) was reported to induce resistin gene expression in primary human macrophages via a cascade involving the secretion of inflammatory cytokines.¹⁰

However, to our knowledge, the studies have been conducted to evaluate the association of IL-6 -174 G/C gene polymorphism with metabolic risk factors and serum resistin level in abdominal obese women who are in their virgin stage, and no conclusive study is available in north India. Therefore, the aim of the present study was to investigate the association of IL-6 G-174C (rs 1800795) gene polymorphism with metabolic risk factors and circulating resistin in North Indian adult women.

Methods

Subject (study population)

It was a case control study conducted in 370 North Indian adult women aged between 20 and 40 years. Women were considered obese if their waist-to-hip ratio (WHR) was ≥0.85 (n = 192) and considered non-obese (n = 178) if it was <0.85.²² We excluded the subjects who were having any kind of addiction to any kind of drugs and suffering from any kind of cardiac, respiratory, inflammatory, endocrinal, and metabolic diseases. Pregnant, lactating women and women with any kind of gynecological or obstetrical problems or on medication including hormonal replacement therapy were excluded from the study. The study was approved by the ethical committee of our institute and by the Indian Council of Medical Research (ICMR), New Delhi, and ‘we certify that all applicable institutional and governmental regulations concerning the ethical use of human volunteers were followed during this research.’ Written informed consent was obtained from all the participants. A structured performa was also filled to collect the information regarding menstrual, medical, and personal history.

Laboratory analysis

Anthropometric measurements

All subjects were evaluated for body mass index (BMI), waist circumference (WC), and hip circumference (HC). From WC and HC, WHR was calculated, which is a good indicator for measuring abdominal obesity (WC was measured at the narrowest point superior to the hip and was divided by the circumference of the hip measured at its greatest gluteal protuberance).

Biochemical measurements

Blood samples were drawn (for biochemical parameters) in the morning after overnight fast on the 10th day of menstruation in all the women. Total 6.0 mL blood was drawn from each volunteer and plasma serum was separated as per the requirement of the experiment. Estimation of blood plasma glucose and serum lipid profile was done by GOD-POD and enzymatic method, respectively (Randox Laboratories Ltd, Antrim, UK). Circulating resistin (Human Resistin Version 16 190607 15, Biovendor, Czech Republic; sensitivity 0.1 ng/mL, intra- and inter-assay coefficient of variation were 3.4% and 6.9%, respectively) and IL-6 level (Human IL-6 ELISA 950 030 096/192, Diaclone, France; sensitivity <2.0 pg/mL, intra- and inter-assay coefficient of variation were 4.2% and 7.7%, respectively) was detected by sandwich enzyme-linked Immunosorbant Assay (ELISA) method. Plasma insulin was estimated by immuno-radiometric assay method (Immunotech Radiova, Prague). IR was calculated by homeostasis model assessment index-II (HOMA Index) using the equation (A)²³:

HOMA Index = [fasting insulin (µU / I) \times fasting glucose (mmol / L) / 22.5]

If subjects had no clinical and biological criteria of IR, a laboratory diagnosis of IR is made when the value of HOMA Index is ≥3.6.

For DNA extraction, 3.0 mL of venous blood from each study subject was collected in an EDTA vial. Genomic DNA was extracted using a commercially available genomic DNA purification kit (Qiagen, Valencia, CA, USA) and stored at −20°C.

Genotyping of IL-6 G-174C gene

The genotyping was performed using PCR-RFLP technique. To improve the genotyping quality and validation, all mutant and heterozygous samples were re-genotyped in duplicate and results were noted only for those samples that were reproducible and with no discrepancy.

IL-6 -174 G/C gene polymorphism was detected by PCR on the Thermo Cycler instrument (Bio-Rad Inc. Hercules, CA, USA) with subsequent restriction analysis of PCR products (RFLP). Forward and reverse primer sequences as well as PCR and RFLP conditions are shown in (Table 1 and Figure 1 ).²⁴

Table 1.

Detection details of SNP IL-6 -174 G/C (rs1800795) gene polymorphism

Forward primer^a	5′-GGAGTCACACACTCCACCT-3′
Reverse primer^a	5′-GTGGGGCTGATTGGAAACC-3′
PCR conditions	95°C / 5 min	1 cycle
	94°C / 45 sec	29 cycle
	64.2°C / 60 sec	29 cycle
	72°C / 1 min	29 cycle
	72°C / 8 min	1 cycle
	15°C / infinite
PCR product length	532 bp
Restriction enzyme	SfaNI/ LweI
RFLP conditions	37°C/ 24 h
RFLP products length	Wild type GG	532 bp
	Heterozygous GC	532/474/58 bp
	Homozygous CC	474/58 bp

^a Primer sequences from Schotte et al., 2001; Genscript, The Biology CRO, USA.

Figure 1.

Restriction fragments length polymorphism (RFLP) distribution pattern of IL-6 G-174C gene. This gel picture showing band pattern of IL-6 gene: RFLP result digested by restriction enzyme SfaN1, separated on 2% agarose gel and visualized under UV light. Lane 1 = GG (wild type = W) - 474/58 bp. Lane 2,4,7,8 = CC (homozygous mutation = M) - 532 bp. Lane 3,6 = GC (heterozygous mutation = H) - 532/474/58 bp. Lane 5 = Ladder (L; 100 bp).

Statistical analysis

The power analysis for the calculation of sample size was calculated with 95% confidence interval (CI), 5% expected error, and 12% prevalence. The number of participating subjects was investigated by Third National Family Health Survey (NFHS) on the prevalence of obesity in different states of India.²⁵

Data were summarized as means ± standard deviation (SD) and subjected to Student’s t-test and χ² (chi-square) test. The continuous data were compared by two-sample Student’s t-test while discrete (categorical) data was analyzed by χ² test with Yates correction. The genotypic frequencies of control group were tested by Hardy–Weinberg equilibrium (HWE). The normality of variables was tested by Kolmogorov-Smirnov test. A two-tailed (α = 2) probability (p) value p < 0.05 was considered statistically significant. STATISTICA (version 6.0) was used for the analysis.

Results

Study population

There were total 370 North Indian adult women. The age of all subjects ranged from 20 to 40 years. Out of 370 women, 178 were non-obese with WHR <0.85 (control group) and 192 were obese ≥0.85 (study group).

Demographic characteristics and biochemical parameters of non-obese and obese women

The demographic characteristics and biochemical parameters of two groups were summarized in Table 2 . The observations in Table 2 showed that the mean level of all demographic characteristics and biochemical parameters of obese were found to be significantly (p < 0.05 or p < 0.001) different and higher than that of non-obese except age, height, TC/HDL-C ratio, and LDL-C/HDL-C ratio, which were found similar (p > 0.05) in two groups.

Table 2.

Demographic characteristics and biochemical parameters summary (mean ± SD) of non-obese and obese women

Variables	Non-obese (n = 178)	Obese (n = 192)	p-Value
Age (years)	28.04 ± 5.86	29.12 ± 6.51	0.094
Height (cm)	154.16 ± 6.01	153.86 ± 5.98	0.633
Weight (Kg)	49.64 ± 8.24	67.69 ± 8.76	<0.001
WC (cm)	69.88 ± 8.61	88.16 ± 11.08	<0.001
HC (cm)	87.25 ± 8.80	99.30 ± 10.86	<0.001
WHR	0.80 ± 0.04	0.89 ± 0.03	<0.001
BMI (kg/m²)	20.87 ± 3.09	28.64 ± 3.81	<0.001
SBP (mmHg)	119.10 ± 10.02	126.35 ± 13.21	<0.001
DBP (mmHg)	80.57 ± 7.34	84.47 ± 8.59	<0.001
PR (per/min)	78.27 ± 6.21	79.92 ± 6.52	0.013
FPG (mg/dL)	91.75 ± 14.96	96.14 ± 14.00	0.004
Serum TC (mg/dL)	150.03 ± 35.25	161.04 ± 31.01	0.002
Serum TG (mg/dL)	112.89 ± 39.84	124.89 ± 41.18	0.005
Serum VLDL (mg/dL)	22.58 ± 7.97	24.98 ± 8.24	0.005
Serum HDL (mg/dL)	46.11 ± 11.71	43.06 ± 8.68	0.005
Serum LDL (mg/dL)	81.35 ± 34.92	93.00 ± 26.78	<0.001
TC/HDL ratio	3.55 ± 2.14	3.85 ± 0.97	0.075
HDL/LDL ratio	0.69 ± 0.58	0.51 ± 0.28	<0.001
LDL/HDL ratio	2.01 ± 1.88	2.25 ± 0.82	0.105
FPI (μU/mL)	8.39 ± 5.75	13.05 ± 7.98	<0.001
IR (HOMA Index)	1.96 ± 1.52	3.12 ± 1.97	<0.001
Serum resistin (ng/mL)	8.12 ± 3.94	17.23 ± 12.29	<0.001
Serum IL-6 (pg/mL)	4.12 ± 2.36	6.11 ± 4.40	<0.001

Abbreviations: SBP: systolic blood pressure, DBP: diastolic blood pressure, WC: waist circumference, HC: hip circumference, WHR: waist to hip ratio, BMI: body mass index, PR: pulse rate; FPG: fasting plasma glucose; TC: total cholesterol; TG: triglyceride; VLDL: very low density lipoprotein; HDL: high density lipoprotein; LDL: low density lipoprotein; FPI: fasting plasma insulin; IR: insulin resistance; HOMA: homeostatic model assessment; IL-6: interleukin-6.

Frequency distribution of genotypes and alleles

The IL-6 -174 G/C polymorphism was genotyped in all subjects and summarized in Table 3 . The proportions of genotypes frequency of IL-6 -174 G/C polymorphism (χ² = 2.346; p = 0.1260) in controls was in Hardy–Weinberg equilibrium.

Table 3.

Frequency distribution of IL-6 G-174C genotypes and alleles in non-obese (n = 178) and obese (n = 192) women^a

Genotypes/ Alleles	Groups	Non-obese n (%)	Obese n (%)	p Value
Genotype	GG*	71 (39.89)	45 (23.44)	−
	GC	75 (42.13)	97 (50.52)	0.0049
	CC	32 (17.98)	50 (26.04)	0.0034
	GC+CC	107 (60.11)	147 (76.56)	0.0010
Allele	G**	217 (60.96)	187 (48.70)	−
Allele	C	139 (39.04)	197 (51.30)	0.0011

^a In comparison with wild genotypes GG* and wild alleles G**; taken as reference.

Table 3 shows that the IL-6 G-174C gene polymorphism, the genotype frequency of both heterozygous mutant GC (χ² = 7.898, p = 0.0049; OR = 2.04, 95% CI = 1.26−3.30) and homozygous mutant CC (χ² =8.603, p = 0.0034; OR = 2.47, 95% CI = 1.38−4.40) genotype differed significantly with wild GG genotype, while the frequency of wild type (GG) and mutant type (GC+CC) also differed significantly among non-obese and obese (χ² = 10.862, p = 0.0010; OR = 2.17, 95% CI = 1.38−3.40). Like genotypes, the allele frequency also differed significantly between 2 groups (χ² = 10.707, p = 0.0011; OR = 1.65, 95% CI = 1.23−2.20).

Differences in demographic and biochemical parameters on the basis of wild type and mutant type genotypes in non-obese and obese women

The demographic characteristics and biochemical parameters of wild type and mutant type non-obese women are summarized in Table 4 . The observations in Table 4 showed that in non-obese, the mean height, weight, pulse rate (PR), fasting plasma glucose (FPG), triglyceride (TG), very low density lipoprotein (VLDL), and IL-6 were higher in wild type while age, WC, HC, WHR, BMI, systolic blood pressure (SBP), diastolic blood pressure (DBP), total cholesterol (TC), high density lipoprotein (HDL), low-density lipoprotein (LDL), TC/HDL-C ratio, HDL-C/LDL-C ratio, LDL-C/HDL-C ratio, fasting plasma insulin (FPI), IR, and serum resistin were higher in mutant type. On comparing, the mean of level of all demographic characteristics and biochemical parameters in wild type and mutant type women were found to be the same (p > 0.05) except height and WHR, which differed significantly (p < 0.05) between the two groups.

Table 4.

Demographic characteristics and biochemical parameters summary (mean ± SD) of wild type and mutant type non-obese women (n = 178)

Variables	Wild type (n = 80)	Mutant type (n = 98)	p Value
Age (years)	27.49 ± 5.35	28.60 ± 6.48	0.074
Height (cm)	155.47 ± 5.15	153.08 ± 6.47	0.008
Weight (kg)	50.11 ± 9.38	49.26 ± 7.21	0.492
WC (cm)	68.71 ± 8.64	70.84 ± 8.50	0.102
HC (cm)	86.74 ± 8.88	87.67 ± 8.75	0.482
WHR	0.79 ± 0.04	0.81 ± 0.03	<0.001
BMI (kg/m²)	20.69 ± 3.43	21.02 ± 2.79	0.478
SBP (mmHg)	118.39 ± 9.48	119.68 ± 10.44	0.392
DBP (mmHg)	80.44 ± 7.97	80.68 ± 6.81	0.825
PR (per/min)	78.82 ± 6.33	77.82 ± 6.11	0.283
FPG (mg/dL)	92.30 ± 15.67	91.31 ± 14.42	0.663
Serum TC (mg/dL)	148.03 ± 40.06	151.67 ± 30.90	0.495
Serum TG (mg/dL)	115.21 ± 34.54	111.01 ± 43.77	0.486
Serum VLDL (mg/dL)	23.04 ± 6.91	22.20 ± 8.75	0.486
Serum HDL (mg/dL)	44.73 ± 11.02	47.23 ± 12.19	0.158
Serum LDL (mg/dL)	80.26 ± 37.67	82.24 ± 32.68	0.707
TC/HDL	3.48 ± 1.32	3.61 ± 2.63	0.701
HDL/LDL	0.65 ± 0.33	0.73 ± 0.73	0.370
LDL/HDL	1.93 ± 1.17	2.07 ± 2.30	0.613
FPI (μU/mL)	7.82 ± 4.53	8.86 ± 6.57	0.234
IR (HOMA Index)	1.83 ± 1.26	2.07 ± 1.71	0.296
Serum Resistin (ng/mL)	7.79 ± 4.01	8.40 ± 3.89	0.306
Serum IL-6 (pg/mL)	4.33 ± 2.40	3.95 ± 2.32	0.284

Similarly, the demographic characteristics and biochemical parameters of wild type and mutant type obese women were summarized in Table 5 . The observation in Table 5 showed that in obese, the mean height, TC, TG, VLDL, HDL, and serum IL-6 level were higher in wild type while age, weight, WC, HC, WHR, BMI, SBP, DBP, PR, FPG, LDL-C, HDL-C/LDL-C ratio, LDL-C/HDL-C ratio, FPI, IR, and serum resistin were higher in mutant type. On comparing, the mean level of all demographic characteristics and biochemical parameters in wild type and mutant type women were found to be the same (p > 0.05) except WHR, TG, VLDL, and serum resistin which differed significantly (p < 0.05 or p < 0.001) between the two groups.

Table 5.

Demographic characteristics and biochemical parameters summary (mean ± SD) of wild type and mutated obese women (n = 192)

Variables	Wild type (n = 42)	Mutant type (n = 150)	p Value
Age (years)	28.60 ± 6.53	29.64 ± 7.41	0.154
Height (cm)	155.12 ± 6.23	153.51 ± 5.88	0.123
Weight (kg)	67.31 ± 8.52	67.79 ± 8.85	0.753
WC (cm)	86.21 ± 9.44	88.71 ± 11.47	0.198
HC (cm)	98.40 ± 9.82	99.55 ± 11.15	0.548
WHR	0.88 ± 0.02	0.89 ± 0.03	<0.001
BMI (kg/m²)	28.00 ± 3.32	28.82 ± 3.92	0.215
SBP (mmHg)	125.71 ± 14.99	126.53 ± 12.72	0.723
DBP (mmHg)	83.10 ± 8.34	84.85 ± 8.65	0.242
PR (per/min)	78.74 ± 6.14	80.25 ± 6.61	0.184
FPG (mg/dL)	95.41 ± 14.30	96.35 ± 13.96	0.701
Serum TC (mg/dL)	162.80 ± 30.09	160.55 ± 31.35	0.680
Serum TG (mg/dL)	137.45 ± 43.30	121.38 ± 40.02	0.025
Serum VLDL (mg/dL)	27.49 ± 8.66	24.28 ± 8.00	0.025
Serum HDL (mg/dL)	43.52 ± 8.77	42.93 ± 8.68	0.698
Serum LDL (mg/dL)	91.79 ± 25.90	93.35 ± 27.09	0.740
TC/HDL ratio	3.85 ± 0.94	3.85 ± 0.98	0.966
HDL/LDL ratio	0.51 ± 0.18	0.52 ± 0.30	0.945
LDL/HDL ratio	2.19 ± 0.78	2.27 ± 0.84	0.607
FPI (μU/mL)	11.11 ± 6.47	13.59 ± 8.29	0.074
IR (HOMA Index)	2.67 ± 1.72	3.25 ± 2.02	0.087
Serum Resistin (ng/mL)	11.65 ± 6.99	18.79 ± 13.00	<0.001
Serum IL-6 (pg/mL)	6.40 ± 4.51	5.61 ± 3.97	0.074

Discussion

In the present study, we observed the association of IL-6 G-174C gene polymorphism with high circulating resistin in abdominal obese women (WHR ≥ 0.85) of North India.

We observed a significant association between IL-6 -174 G/C promoter gene polymorphism and abdominal obesity in study group and also high circulating IL-6 level in this group. Okuno et al. had observed a similar finding, i.e. circulating IL-6 level in obese individual is significantly higher with greater expression of gene in abdominal adipose tissue.²⁶ Some of the studies have suggested that serum concentrations of IL-6 are elevated in obesity and subsequent weight loss decreases the IL-6 concentration and correlate with BMI.^27,16 One more study on human population suggest that there is an interaction among BMI and the -174 G/C of IL-6 gene polymorphism on metabolic risk that is independent of IL-6 level and associated correlates of increased BMI.²⁸

The mechanisms that how IL-6 leads to the development of IR in obese women is that IL-6 reduces lipoprotein lipase activity and increases basal lipolysis in adipose tissue.²⁹ One of the study reports a reduction in adipocyte IRS-1 expression and tyrosine phosphorylase in response to IL-6 treatment.³⁰ Other study suggests that IL-6 may stimulate fat oxidation in adipocytes, thus leading to increased circulating non-esterified fatty acids.³¹

A common G/C polymorphism of the IL-6 promoter on position -174 increases the IL-6 expression in peripheral blood cells, and was found to be associated with abnormal circulating lipids.^19,15 Our results demonstrated that mutated CC+GC of IL-6 gene was high risk genotype for development of metabolic syndrome as the risk was increased up to 2.17-fold when compared with their non-obese counterpart. We also found significant differences between obese and non-obese women in the frequencies of IL-6 gene polymorphism, which were in accordance with the study of Wernstedt et al.³² We also found a significant higher WHR in women with mutated CC+GC genotypes than in those with the wild GG genotype.

The North Indian population (Aryans) and South Indians (Dravidians) are entirely different due to different socio-cultural diversity. South Indians are considered as the original inhabitants of Indian subcontinent and the North Indians are the migrant population having a mixed gene pool.³³ This fact supports our results of IL-6 gene polymorphism. Allele frequency of G allele in North Indians is 60.1% in our present study compared to 84.5% in South Indian population and that of C allele is 39.0% and 15.5%, respectively.³⁴

In this present study, there were no correlation found between serum IL-6 level and polymorphism at −174 G/C promoter region gene. However, −174 G/C genotype was found to be associated with high circulating resistin in abdominal obese women. Some other study also have quoted the similar finding.¹⁰ Resistin expression is not always altered in relation to weight, BMI, or insulin sensitivity.³⁵ Regarding serum resistin level, our present results are in agreement with previous studies showing significant increase in serum resistin levels only in obese subjects,^36,37 contrary to some other studies showing decreased resistin level in obesity.^38,39

Recent studies on resistin show that it exerts a tight control on the cytokine inflammatory cascade and, thereby, may provide an alternative pathway for activation of cytokine release.²¹ One study showed that the NF-κB transcription pathway mediates the stimulatory effect of resistin on cytokine release. These studies strongly support the pro-inflammatory regulatory properties of resistin. Because cytokine genetic variability leads to a wide diversity within the immune and inflammatory responses, a detailed analysis of polymorphisms in cytokine genes may be crucial for the understanding of the mechanisms underlying initiation and progression of metabolic syndrome in subjects with abdominal obesity.

We have also observed significant difference for serum TC, TG, HDL-C levels and plasma glucose, plasma insulin, and IR between obese and non-obese women. This observation suggests that the associated variants might be the factor involved in the causation and progression of metabolic syndrome.

Although, the observation shows a correlation of IL-6 gene polymorphism with circulating resistin and IL-6 level. However, the study would become more explanatory if we could be able the adipose tissue level (ex vivo or in vitro) of resistin and IL-6 level and would have correlated it with IL-6 174 G/C gene polymorphism.

In conclusion, our results suggest that the significant association of serum resistin level with IL-6 polymorphism might affect circulating IL-6 level in abdominal obesity that could lead to the development of metabolic syndrome. The relationship between circulating resistin and IL-6 with abdominal obesity and presence of CC+GC genotype of IL-6 G-174C promoter gene polymorphism suggests that they may take part in the development of metabolic syndrome. However, the role of other genetic and environmental factors has certainly been confirmed. Hence, further studies are required to precisely define the biochemical mechanism of action of IL-6 gene, which can help in the development of methods for the prediction, prevention, and treatment strategy of metabolic syndrome.

Footnotes

Acknowledgements

The authors would like to thank the participants for participating in this study; the participating physicians and residents of the Department of Medicine and Physiology, Chhatrapati Shahuji Maharaj Medical University Uttar Pradesh, Lucknow, India, for their generous support.

The authors and co-authors have declared no conflict of interest.

This study was supported by the ICMR (Grant No. 3/1/2/2/06-RHN) and Department of Biotechnology, Ministry of Science & Technology, New Delhi (Grant No. BT/PR9780/GBD/27/68/2007).

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