[Obesity, adipogenesis and insulin resistance]

Insulin resistance precedes the development of type 2 diabetes mellitus and is also a common denominator in the so-called metabolic syndrome. Although the cause of insulin resistance has not been fully elucidated, it seems clear that lifestyle changes, including little physical exercise and constant access to food, particularly in developed and economically emergent countries, as well as genetic factors, appear to have triggered the escalating incidence of diseases related to insulin resistance, including type 2 diabetes and metabolic syndrome. Obesity is considered as a risk factor for developing insulin resistance. Increased adipose tissue has been related to an increased production of pro-inflammatory cytokines which, together with fatty acids, appear to be responsible for the development of insulin resistance. Thus, a greater or lesser expansibility or ability of adipose tissue to store lipids also appears to play a significant role in the development of insulin resistance because overcoming of this capacity, which is variable in each case, would result in leaking of lipids to other tissues where they could interfere with insulin signaling. This article reviews various molecular mechanisms related to the development of insulin resistance and its relationship to expansibility of adipose tissue and obesity.