Visceral adipose

PPARy White adipose tissue, atherosclerotic lesions Insulin-sensitizing and glucoselowering re-directs TG from non-adipose tissues and visceral adipose depots for storage in subcutaneous adipose tissue slowed progression of atherosclerosis Fatty acids, eico-sanoids Th iazolid i ned iones pioglitazone (Actos ), rosiglita-zone (Avandia ) Type 2 diabetes, (insulin resistance, metabolic syndrome)... 

Katoh S, Hata S, Matsushima M, Ikemoto S, Inoue Y, Yokoyama J, Tajima N. Troglitazone prevents the rise in visceral adiposity and improves fatty liver associated with sulfonylurea therapy—a randomized controlled trial. Metabolism 2001 50(4) 414-7. 

We have observed that suppression of elevated FFA levels is a very rapid (less than 12 hour) response to treatment of insulin-resistant rats with PPARy agonists (T. Doebber, unpublished data). Since PPARy agonists are known to promote adipose tissue uptake and storage of fatty acids, it is plausible that this effect constitutes a major mechanism of insulin sensitization, whereby elevated FFAs—a known cause of hepatic and muscle insulin resistance—can be alleviated. An additional effect of in vivo PPARy activation, shown to occur in rats, was an increase in the number of small white adipocytes, along with a relative shift in the size of visceral (decreased) versus subcutaneous (increased) adipose depots (73). This has important implications because visceral adiposity and larger fat cells are both associated with insulin resistance. 

Excess adiposity, particularly the abdominal obesity associated with increased waist circumference, is associated with insulin resistance, hypertension, and proinflammatory states. The prevalence of this complex of comorbidities associated with obesity, now referred to as the metabolic syndrome, is reaching epidemic proportions in the United States (Grundy et al., 2004 Roth et al., 2002). Indeed, increased abdominal adiposity is one of a cluster of factors that are used in the diagnosis of metabolic syndrome. Abdominal tissue in the trunk occurs in several compartments, including subcutaneous and intraperitoneal or visceral fat. Visceral fat in particular appears to contribute to perturbed fuel metabolism by at least two mechanisms. First, hormones and free fatty acids released from visceral fat are released into the portal circulation and impact directly on metabolism of the liver. Second, the visceral adipose depot produces a different spectrum of adipocytokines than that produced by subcutaneous fat (Kershaw and Flier, 2004). 

Conway, J. M., Vanovski. S. 7., Avila, N. A., and Hubbard, V (1995). Visceral adipose tissue differences in black and white women. Am. f- Clin. Nutr 61,765-771. 

Kvisi, H., Chowdhiiry, B-, Grangard, U-, Tylen, U-, and Sjostrom, L. (1988). Total and visceral adipose-tissue volumes derived from measurements with computed tomography in adult mon and women. Am. /. Clin. Nutr. 48,1351-1361. 

Schocn, R. L-, Evans, R. W.,Sankey, S. S., Weissfeld,]. L., and Kuller, L. (1996). Does visceral adipose tissue differ from subcutaneous adipose tissue in fatty acid content Int. J. Obesity 20,346-352. 

In detail, adipocytes from visceral adipose tissue are more resistant to insuhn-induced anti-lipolysis and re-esterification of NEFA than those from leg and non-visceral body fat both in vitro [503, 504] and in vivo [505]. Various functional differences in these ceUs have been identified at the level of the insuhn receptor and the post-receptor insulin signahng cascade [503, 504]. PDE3B involved in hpolysis regulation by insuhn (see above. Fig. 11.7) and protein tyrosine phosphatases de-phosphorylating fhe insuhn receptor, such as PTPlb, could be affected in differen-... 

To facilitate the discussion on the effects of catecholamines (below). Table 32-3 includes a list of the physiological ligand (i. e., neural NE or plasma E) for the adrenergic receptor subtype in some of the tissues, based on their efferent sympathetic nerve supply. The different tissue distribution of adrenergic receptor subtypes indicates the genetic influence on the kinds of receptors however, the density of the receptor subtypes also exhibits tissue variation. For example, although white adipose tissue contains both /I, and receptors, the latter is in greater quantity in visceral adipose tissue. 

Weight gain leads to insulin resistance, and obese nondiabetic individuals have the same degree of insulin resistance as lean type 2 diabetic patients. In 1,146 nondiabetic, normotensive individuals, Ferrannini and associates showed a progressive loss of insulin sensitivity when the BMI increased from 18 kg/m to 38 kg/m . The increase in insulin resistance with weight gain is directly related to the amount of visceral adipose tissue. ... 

The term visceral adipose tissue (VAT) refers to fat cells located within the abdominal cavity and includes omental, mesenteric, retroperitoneal, and perinephric adipose tissue. VAT has been shown to correlate with insuhn resistance and explain much of the variation in insuhn resistance seen in a population of African-Americans. Visceral adipose tissue represents 20% of fat in men and 6% of fat in women. This fat tissue has been shown to have a higher rate of lipolysis than subcutaneous fat, resulting in an increase in free fatty acid production. These fatty acids are released into the portal circulation and drain into the liver, where they stimulate the production of very-low-density lipoproteins and decrease insuhn sensitivity in peripheral tissues. VAT also produces a number of cytokines which cause insulin resistance. These factors drain into the portal circulation and reduce insulin sensitivity in peripheral tissues. ... 

UKPDS United Kingdom Prospective Diabetes Study VAT visceral adipose tissue... 

Montague CT, O Rahilly S. The perils of portliness Causes and consequences of visceral adiposity. Diabetes 2000 49 883-888. 

Banerji MA, Lebowitz J, Chaiken RL. Relationship of visceral adipose tissue and glucose disposal is independent of sex in black NIDDM subjects. Am J Physiol 1997 273 E425-E432. 

Waist circumference (WC) is the most practical method of characterizing central or visceral adiposity. Clinically, WC is the narrowest circumference measured in the area between the last rib and the top of the iliac crest. The current definition for high-risk WC is greater than 40 inches in males and greater than 35 inches in females. ... 

Park YW, AlUson DB, Heymslield SB, Gallagher D. Larger amounts of visceral adipose tissue in Asian Americans. Obes Res 2001 9 381-387. 

Fig. 1. Mechanism of the pleiotropic actions of the thiazolidinediones. Working via the PPAR-y receptor system in adipose tissue, the thiazolidinediones interrupt the pathogenic signaling between the expanded visceral adipose mass in obesity, which leads to improved insulin sensitivity in skeletal muscle and hver, enhanced pancreatic P-cell insulin secretion, and improved vascular endothelial function. The processes affected by the thiazolidinediones include redistribution of adipose stores, reduced circulating levels of FFA, diminished levels and tissue effects of cytokines (TNF-a), and increased circulating levels of the insulin-sensitizing, anti-atherogenic plasma protein adiponectin, which also arises from adipose tissue. The thiazohdinediones have also been shown to have direct effects in muscle and endothelial cells, which is likely to also contribute to some of their pharmacologic activity.

Curat, C., Wegner, V., Sengenes, C., Miranville, A., Tonus, C., Busse, R., and Bouloumie, A. (2006). Macrophages in human visceral adipose tissue Increased accumulation in obesity and a source of resistin and visfatin. Diabetohgia 49,744-747. 

Woo, M. N., Jeon, S. M., Shin, Y. C., Lee, M. K., Kang, M. A., and Choi, M. S. (2009). Anti-obese property of fucoxanthin is partly mediated by altering Upid-regulating enzymes and uncoupling proteins of visceral adipose tissue in mice. Mol. Nutr. Food Res. 53, 1603-1611. 

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