Relationship of obesity and visceral adiposity with serum concentrations of CRP, TNF-α and IL-6

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Abstract

Objective:

To investigate the relationship between serum concentrations of the cytokines C-reactive protein (CRP), tumor necrosis factor (TNF)-α, and interleukin (IL)-6, and obesity and visceral adiposity.

Methods:

A cross-sectional study of 100 Korean adults free from pre-existing inflammatory disease or cancer was performed. Body mass index (BMI), waist circumference, and serum concentrations of CRP, TNF-α and IL-6 were measured. In 46 obese subjects, fat mass was assessed by bioimpedance analysis and abdominal fat distribution was determined by computerized tomography scan.

Results:

Overall, serum concentrations of CRP, TNF-α and IL-6 were significantly correlated with weight, BMI, waist circumference, hip circumference, and waist-hip ratio. In obese subjects, CRP and IL-6 were significantly correlated with BMI, waist circumference and visceral adipose tissue. Multiple regression analysis showed that CRP was significantly associated with BMI, whereas IL-6 was significantly related with visceral adiposity in obese subjects.

Conclusions:

The positive associations of obesity and visceral adiposity with elevated cytokine levels suggest the importance of reducing obesity and visceral adiposity to prevent elevations in cytokine levels.

Introduction

Inflammation is thought to play a key role in the pathophysiology of cardiovascular disease [1], [2], [3] as well as in diabetes mellitus [4], [5]. Three of the most important proinflammatory cytokines are serum C-reactive protein (CRP), tumor necrosis factor (TNF)-α, and interleukin (IL)-6, all of which have been implicated in atherogenesis [1], [2]. CRP has been shown to be an important marker of vascular inflammation and a predictor of atherosclerosis [6], [7], [8]; TNF-α activates the transcription factor nuclear factor-κβ, which organizes inflammatory changes in vascular tissue [9], [10]; and IL-6 has intrinsic proinflammatory activity and increases the levels of TNF-α [3].

Adipose tissue is an important source of cytokines, and adiposity contributes to the proinflammatory milieu [11], [12]. Serum cytokine levels are elevated in humans and animals with excess adiposity [12], [13], and there are differences in the level of mRNA encoding proteins secreted by adipocytes between human subcutaneous and visceral adipose tissues [14], [15], [16], [17]. Moreover, the relationship between adiposity and CRP has been reported to differ according to ethnic group [18].

Obesity-related cardiovascular disease occurs in Asian people with lower body mass index (BMI) than is observed in Western people [19], [20], [21]. Although Asians are less obese, they tend to have larger amounts of visceral fat than Caucasians [22]. The relationship between TNF-α and IL-6 levels and precise measures of fat distribution (i.e. visceral and subcutaneous adiposity) has not yet been determined in Asian people. We therefore assayed serum concentrations of the cytokines CRP, TNF-α and IL-6 in obese and non-obese Korean individuals in order to determine the relationship between cytokine levels and obesity and visceral adiposity.

Section snippets

Recruitment of subjects

We recruited 46 obese (BMI ≥ 25 kg/m2) and 54 non-obese (BMI < 25 kg/m2) individuals, aged 20–60 years (30 males and 70 females), who visited the Department of Family Medicine at Asan Medical Center, Seoul, Korea, for their periodic health examinations. All participants gave written informed consent, and the study was approved by the Institutional Review Board of Asan Medical Center.

Excluded from this study were individuals with severe inflammatory or infectious diseases, cancers, secondary causes of

Cytokine concentrations in non-obese and obese individuals

Table 1 shows the baseline characteristics of the non-obese and obese subjects. Age and sex distribution did not differ between these two groups. The median concentrations of CRP, TNF-α and IL-6 were all significantly higher in the obese group than in the non-obese group.

Correlations between anthropometric measurements and cytokine concentrations in total subjects

The correlations between anthropometric measurements and cytokine concentrations in the entire subject cohort (100 individuals) are shown in Table 2. CRP, TNF-α and IL-6 concentrations were significantly correlated with weight,

Discussion

We have shown here that CRP, TNF-α and IL-6 concentrations were higher in obese than in non-obese individuals. In obese individuals, obesity measured by BMI was significantly correlated with CRP concentration, whereas visceral adiposity was significantly associated with IL-6 concentration. These results may be related to the finding that adipose tissue is a dynamic endocrine organ that secretes a number of factors that contribute to systemic inflammation [26].

Our finding of a significant

Acknowledgements

This study was supported by a Grant from the Asan Institute for Life Science 2002-106 and a SRC fund to IRC at the University of Ulsan from the KOSEF and the Korean Ministry Science and Technology.

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