ReviewVisceral adipose tissue as a source of inflammation and promoter of atherosclerosis
Section snippets
Adipose tissue – a must have to survive
Adipose tissue is a type of connective tissue that plays important physiological roles in mammals. A 70 kg reference man has an average of 15 kg of adipose tissue that corresponds to 21% of body mass. This percentage is higher in women, the elderly, and overweight subjects [1]. Not all deposits of adipose tissue in the human body are composed of the same type of fat. Human adipose tissue is classically characterized as white and brown, although more recently beige adipose tissue has also been
Adipose tissue: a friend or foe for your health?
Obesity is accompanied by several adverse health effects such as hypertension, insulin resistance, franc diabetes, dyslipidemia and subclinical inflammation, all factors leading to atherosclerosis. Although adipocytes can increase in number (hyperplasia), they mostly grow in size (hypertrophy) accumulating lipids as body weight increases. In general, obesity results in a greater increase in visceral adipose tissue than in subcutaneous fat. However, it is well known that there is a “healthy
Visceral adipose tissue classification (Figs. 1 and 2)
The radiological classification of visceral adipose tissue is performed according to the body region where fat is deposited and it includes: intrathoracic (ITAT), intraabdominal (IAAT) and intrapelvic (IPAT) adipose tissue [1]. IAAT and IPAT are usually quantified together, as intraabdominopelvic (or abdominal) adipose tissue. Abdominal adipose tissue can be distinguished further into intraperitoneal and extraperitoneal adipose tissue (Fig. 1) [1]. For the purpose of this review intraabdominal
Visceral adipose tissue and atherosclerosis
Several studies explored the association of visceral adipose tissue with atherosclerosis; investigators used different methodologies for adipose tissue quantification and measured adipose tissue volume in different body regions. In the following paragraphs we will present some of the main findings according to the region where adipose tissue was quantified. Because there are discrepancies in the adipose tissue terminology used in the literature – for example the term “pericardial” adipose
Dynamic changes of visceral adipose tissue with pharmacological and non-pharmacological interventions
Interventional and observational studies have addressed the dynamic changes of visceral adipose tissue under different conditions. Weight loss was very effective in reducing abdominal VAT [76] and slightly less efficacious in reducing EAT [77], [78]. In one study, the regression of EAT volume was accompanied by a reduction in the serum level of the pro-inflammatory CD40 ligand [75]. Bariatric surgery in morbidly obese patients restored the anti-contractile activity of perivascular adipose
Pathophysiological mechanisms
The exact mechanisms by which visceral adipose tissue predisposes to atherosclerosis development are unknown, although several plausible mechanisms may be involved in this process. Large VAT volumes have been repeatedly associated with the presence of traditional cardiovascular risk factors, such as hyperlipidemia, arterial hypertension and diabetes mellitus or impaired glucose tolerance and the presence of the metabolic syndrome [82]. The endocrine, metabolic, and inflammatory activities of
Conclusion
Visceral adipose tissues (intra-abdominal and intra-thoracic) are metabolically active and are the source of humoral and cellular inflammation in obese patients and patients with established coronary artery disease. Whether the inflammation in these tissues predisposes to the development of arterial disease or is the consequence of such process is still speculative. However, the role of cellular inflammation in particular is increasingly being recognized in other cardiovascular disease states
Acknowledgments
This work was supported in part by a grant from the Stavros Niarchos Foundation (Nikolaos Alexopoulos, MD).
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