Title:Body Fat Distribution Contributes to Defining the Relationship between
Insulin Resistance and Obesity in Human Diseases
Volume: 20
Issue: 5
Author(s): María M. Adeva-Andany*, Alberto Domínguez-Montero, Lucía Adeva-Contreras, Carlos Fernández-Fernández, Natalia Carneiro-Freire and Manuel González-Lucán
Affiliation:
- Nephrology Division, Department of Internal Medicine, Hospital General Juan Cardona, c/ Pardo Bazán s/n, 15406
Ferrol, Spain
Keywords:
Bardet Biedl syndrome, insulin sensitivity , lipodystrophy, cardiovascular disease, obesity, visceral fat.
Abstract: The risk for metabolic and cardiovascular complications of obesity is defined by body
fat distribution rather than global adiposity. Unlike subcutaneous fat, visceral fat (including hepatic
steatosis) reflects insulin resistance and predicts type 2 diabetes and cardiovascular disease. In humans,
available evidence indicates that the ability to store triglycerides in the subcutaneous adipose
tissue reflects enhanced insulin sensitivity. Prospective studies document an association between
larger subcutaneous fat mass at baseline and reduced incidence of impaired glucose tolerance.
Case-control studies reveal an association between genetic predisposition to insulin resistance and
a lower amount of subcutaneous adipose tissue. Human peroxisome proliferator-activated receptorgamma
(PPAR-γ) promotes subcutaneous adipocyte differentiation and subcutaneous fat deposition,
improving insulin resistance and reducing visceral fat. Thiazolidinediones reproduce the effects
of PPAR-γ activation and therefore increase the amount of subcutaneous fat while enhancing
insulin sensitivity and reducing visceral fat. Partial or virtually complete lack of adipose tissue
(lipodystrophy) is associated with insulin resistance and its clinical manifestations, including essential
hypertension, hypertriglyceridemia, reduced HDL-c, type 2 diabetes, cardiovascular disease,
and kidney disease. Patients with Prader Willi syndrome manifest severe subcutaneous obesity
without insulin resistance. The impaired ability to accumulate fat in the subcutaneous adipose
tissue may be due to deficient triglyceride synthesis, inadequate formation of lipid droplets, or defective
adipocyte differentiation. Lean and obese humans develop insulin resistance when the capacity
to store fat in the subcutaneous adipose tissue is exhausted and deposition of triglycerides is
no longer attainable at that location. Existing adipocytes become large and reflect the presence of
insulin resistance.