Introduction
Adipose tissue is an active endocrine tissue, which secretes hormones, such as adiponectin, resistin and leptin, referred to as adipocytokines. Adipocytokines appear to contribute to inflammation and atherosclerosis and may be involved in the etiology of type 2 diabetes, possibly constituting the missing link between obesity and insulin resistance (IR) [1] .
Interleukin (IL)-6 and tumour necrosis factor-α (TNF-α) are two major pro-inflammatory cytokines, secreted in significant amounts by adipose tissue and, consequently, obese women (healthy and diabetic) have higher cytokine levels than healthy, lean women. Furthermore, increased levels of IL-6 and TNF-α are associated with deterioration of glycemic control, increased IR, and dyslipidemia, contributing to the dysfunctional metabolic status of obese and type 2 diabetic individuals [2] .
Chronic low-grade inflammation, characterized by abnormal production of adipokines and inflammatory mediators, has been implicated in the pathogenesis of obesity-related chronic diseases including what may be called the obesity – type 2 diabetes mellitus (T2DM) – cardiovascular disease (CVD) triad [3] .
Exercise suppresses the production of proinflammatory cytokines and enhances anti-inflammatory cytokines. Because proinflammatory cytokines IL-6 and TNF-α have cytotoxic actions, it can be proposed that regular exercise prevents further damage to insulin-producing β-cells by attenuating the production of these proinflammatory cytokines [4] .
Aerobic exercise decreases subclinical, chronic inflammation and improves endothelial function simply as a result of reducing obesity (particularly visceral obesity) and improving insulin sensitivity [5] and [6] .
Several studies suggest that training programmes that involve a resistive exercise component (ie, moderate intensity weight-lifting exercises) may be of particular benefit in type 2 diabetes due to an effect of increasing insulin action. An increase in muscle mass has been associated with benefits in terms of glycemic control as skeletal muscle represents the largest mass of insulin-sensitive tissue [7] , [8] and [9] .
Aerobic exercise intervention, but not flexibility/resistance exercise, reduces serum inflammatory cytokines including IL-18, CRP and IL-6 among older adults [10] .
Apart from the controversy surrounding the beneficial effects of exercise on glycemic control in type 1 diabetes patients, the question remains as to which type of activity is better: aerobic exercise or resistance training? This study was aimed at comparing the impact of aerobic versus resistance training on insulin resistance, adipocytokines and inflammatory cytokine in obese type 2 diabetic patients.