Obesity and Inflammation

Researchers at the US National Institute of Health recently reviewed the differences in the amount of chemicals associated with inflammation in overweight as compared with healthy weight people. In the overweight group the chemicals associated with inflammation were much higher than in the healthy weight group. Such findings have caused researchers to re-evaluate their view of fatty tissue. White adipose tissue (body fat) was once seen as nothing more than stored energy. It is now recognized, however, that adipose tissue is involved in a large number of physiological and metabolic functions. One of the processes that adipose tissue is involved in is the release of proteins that signal other bodily systems into operation. These proteins are called adipokines. Over 50 adipokines have been identified, including those that signal the immune system response. It is believed that fat cells secrete inflammatory factors such as cytokines and histamines, which bring on the inflammatory response. The result of this is that obesity is characterized by a state of chronic, low grade inflammation in which markers of inflammation are increased in the body’s circulation.

(The Journal of the American Medical Association, Vol. 282, No. 22, 2131–2135).

(Rayner D. V. & Trayhurn P. (2001) Regulation of leptin production sympathetic nervous system interactions. Journal of Molecular Biology 79, 8-20).

Researchers have long pondered the question as to why increased levels of adipose tissue should lead to the release of inflammatory markers. In a 2004 paper, Trayhurn and Wood have suggested that the secretion of inflammatory cytokines occurs because, as the fat mass increases in size, the system of blood vessels feeding the adipose tissue is insufficient to maintain a normal oxygen supply. This results in shortage of oxygen (localized hypoxia) and it is this that triggers the inflammatory response.

(Trayhurn P. & Wood I. S. (2004) Adipokines: inflammation and the pleiotropic role of white adipose tissue. British Journal of Nutrition 92, 347-55).

Obese people have a higher incidence of inflamed arteries as compared to healthy weight people putting them at far greater risk of a heart attack and stroke. As well as inflaming the arteries, the inflammation appears to damage the lining of the arteries, resulting in enhanced susceptibility to clot formation. Obese people are also 23 times more likely to have an active inflammation of the joints, bowel or respiratory tract.

(Yudkin J. S. (2003) Adipose tissue, insulin action and vascular disease: inflammatory signals. International Journal of Obesity 27, Suppl 3, 525-528).