Adipose tissue biology and HIV-infection.

HIV-1/highly active antiretroviral therapy-associated lipodystrophy syndrome (HALS) is an adipose tissue redistribution disorder characterized by subcutaneous adipose tissue lipoatrophy, sometimes including visceral adipose tissue hypertrophy and accumulation of dorsocervical fat ('buffalo hump'). The pathophysiology of HALS appears to be multifactorial and several key pathophysiological factors associated with HALS have been identified. These include mitochondrial dysfunction, adipocyte differentiation disturbances, high adipocyte lipolysis, and adipocyte apoptosis. These alterations in adipose tissue biology expand to involve systemic metabolism through alterations in endocrine functions of adipose tissue (via disturbed adipokine release), enhanced production of pro-inflammatory cytokines and excessive free fatty-acid release due to lipolysis. The deleterious action of some antiretroviral drugs is an important factor in eliciting these alterations in adipose tissue. However, HIV-1 infection-related events and HIV-1-encoded proteins also contribute directly to the complex development of HALS through effects on adipocyte biology, or indirectly through the promotion of local inflammation in adipose tissue.