Integrative physiology of human adipose tissue

Abstract

Adipose tissue is now recognised as a highly active metabolic and endocrine organ. Great strides have been made in uncovering the multiple functions of the adipocyte in cellular and molecular detail, but it is essential to remember that adipose tissue normally operates as a structured whole. Its functions are regulated by multiple external influences such as autonomic nervous system activity, the rate of blood flow and the delivery of a complex mix of substrates and hormones in the plasma. Attempting to understand how all these factors converge and regulate adipose tissue function is a prime example of integrative physiology. Adipose tissue metabolism is extremely dynamic, and the supply of and removal of substrates in the blood is acutely regulated according to the nutritional state. Adipose tissue possesses the ability to a very large extent to modulate its own metabolic activities, including differentiation of new adipocytes and production of blood vessels as necessary to accommodate increasing fat stores. At the same time, adipocytes signal to other tissues to regulate their energy metabolism in accordance with the body's nutritional state. Ultimately adipocyte fat stores have to match the body's overall surplus or deficit of energy. This implies the existence of one (or more) signal(s) to the adipose tissue that reflects the body's energy status, and points once again to the need for an integrative view of adipose tissue function.

A computational model of adipose tissue metabolism: Evidence for intracellular compartmentation and differential activation of lipases

“…Adipose tissue is no longer considered a metabolically quiescent storage depot of lipids, but an active organ that regulates plasma fatty acid (FA) levels (Frayn, 2002;Frayn et al, 2003) and secretes various cytokines and hormones such as leptin, adiponectin, resistin, tumor necrosis factor (TNF)-α etc. (Trayhurn and Beattie, 2001;Frayn et al, 2003).…”

“…(Trayhurn and Beattie, 2001;Frayn et al, 2003). The understanding of adipose tissue metabolism and its regulation is underscored by the demonstration of its role in the development of insulin resistance, regulation of satiety, and other metabolic functions (Kahn et al, 2006;Frayn, 2001).…”

“…As an alternative, in vivo microdialysis has been applied to study adipose tissue metabolism in human, but it provides only qualitative data of several metabolites in the interstitium. In vitro studies of tissue explants or isolated cells do not provide comparable physiological data with respect to in vivo conditions (Frayn et al, 2003). Mathematical models and simulations of adipose tissue metabolism in vivo offer a method for quantitative analysis of control mechanisms for lipid mobilization and for prediction of physiological responses.…”

HSV vector-mediated transduction and GDNF secretion from adipose cells

“…In addition, numerous adipokines are secreted from fat cells into the bloodstream and these bioactive molecules influence a wide range of metabolic functions such as energy balance, glucose oxidation, insulin sensitivity, host defense and reproduction. 1 Adipose tissue is mainly composed of terminally differentiated adipocytes filled with lipid droplets. These mature cells arise from preadipocytes, a fibroblast-like precursor cell present in the stromal-vascular fraction of the tissue.…”

Association of adipose tissue blood flow with fat depot sizes and adipokines in women

“…1,2 Furthermore, post-prandial ATBF may facilitate signalling between AT and other tissues, such as the liver and skeletal muscle. 3 The dynamics of ATBF is related to the degree of obesity, and obese subjects respond less to a mixed meal than lean subjects. 4,5 Notably, an attenuated postprandial ATBF may decrease glucose and triglyceride (TG) uptake, leading to post-prandial hyperglycaemia, hyperinsulinemia and hyperlipidemia.…”