Metabolic Syndrome Phenotype in Very Obese Women

Adipose tissue and metabolic syndrome: too much, too little or neither

Obesity is strongly associated with metabolic syndrome. Recent research suggests that excess adipose tissue plays an important role in development of the syndrome. On the other hand, persons with a deficiency of adipose tissue (e.g. lipodystrophy) also manifest the metabolic syndrome. In some animal models, expansion of adipose tissue pools mitigates adverse metabolic components (e.g. insulin resistance, hyperglycaemia and dyslipidemia). Hence, there are conflicting data as to whether adipose tissue worsens the metabolic syndrome or protects against it. This conflict may relate partly to locations of adipose tissue pools. For instance, lower body adipose tissue may be protective whereas upper body adipose tissue may promote the syndrome. One view holds that in either case, the accumulation of ectopic fat in muscle and liver is the driving factor underlying the syndrome. If so, there may be some link between adipose tissue fat and ectopic fat. But the mechanisms underlying this connection are not clear. A stronger association appears to exist between excessive caloric intake and ectopic fat accumulation. Adipose tissue may act as a buffer to reduce the impact of excess energy consumption by fat storage; but once a constant weight has been achieved, it is unclear whether adipose tissue influences levels of ectopic fat. Another mechanism whereby adipose tissue could worsen the metabolic syndrome is through release of adipokines. This is an intriguing mechanism, but the impact of adipokines on metabolic syndrome risk factors is uncertain. Thus, many potential connections between adipose tissue and metabolic syndrome remain to unravelled.

The genetics of obesity and the metabolic syndrome

In this review, we discuss the genetic architecture of obesity and the metabolic syndrome, highlighting recent advances in identifying genetic variants and loci responsible for a portion of the variation in components of the metabolic syndrome, namely, adiposity traits, serum HDL and triglycerides, blood pressure, and glycemic traits. We focus particularly on recent progress from large-scale genome-wide association studies (GWAS), by detailing their successes and how lessons learned can pave the way for future discovery. Results from recent GWAS coalesce with earlier work suggesting numerous interconnections between obesity and the metabolic syndrome, developed through several potentially pleiotropic effects. We detail recent work by way of a case study on the cadherin 13 gene and its relation with adiponectin in the HyperGEN and the Framingham Heart Studies, and its association with obesity and the metabolic syndrome. We provide also a gene network analysis of recent variants related to obesity and metabolic syndrome discovered through genome-wide association studies, and 4 gene networks based on searching the NCBI database.

Increased expression and activity of hepatic lipase in the liver of morbidly obese adult patients in relation to lipid content

BACKGROUND

The types and sources of lipid deposition in the liver of most patients with morbid obesity, as well as the effects of bariatric surgery, are discussed.

METHODS

In 26 patients with morbid obesity who underwent bariatric surgery, we analyzed different kinds of lipids and hepatic lipase (HL) from both plasma and liver biopsies performed 12-18 months after surgery.

RESULTS

The HL activity and HL-mRNA in morbidly obese (MO) livers were high (258 +/- 17 mU/g, and 4.5-fold, respectively); after surgery, the activity decreased (137 +/- 15 mU/g, p < 0.001) but not the levels of HL-mRNA (4.3-fold). Plasma HL activity was also high (4.31 +/- 0.94 mU/mL plasma), and it decreased during weight loss (2.01 +/- 0.29 mU/mL, p < 0.01); moreover, it correlated (r = 0.3694, p < 0.05) with decreased liver HL activity. Adrenocorticotropic hormone in MO was higher (27 +/- 3 pg/mL) than after surgery (13 +/- 1 pg/mL, p < 0.001). All hepatic and plasma lipids were significantly increased in MO patients, but, after bariatric surgery, most of those parameters recovered or normalized. Liver HL activity correlated with total and esterified cholesterol (r = 0.4399, p < 0.001 and r = 0.4395, p < 0.01, respectively).

CONCLUSION

High HL in MO patients could allow for liver intake of cholesterol that could be re-exported to steroidogenic organs to synthesize steroidal hormones. A decrease of plasma HL during weight loss could be a good index for improvement of liver disease.