Energy expenditure and protein metabolism in human immunodeficiency virus infection and cancer cachexia

Malnutrition and weight loss are clinically significant complications of both human immunodeficiency virus (HIV) infection and cancer. Over the last two decades, multiple abnormalities in energy and protein metabolism have been documented in patients with cancer and, more recently, in HIV infection. In HIV infection, studies of the components of energy balance have demonstrated that weight loss results primarily from decreased energy intake, coupled with a failure to consistently reduce resting energy expenditure. Although several studies have shown that resting energy expenditure is elevated in many patients with HIV infection, other studies have shown that not all patients with HIV infection are hypermetabolic. Likewise, protein turnover is increased, decreased, or unchanged in patients with HIV infection and varies with the physiologic state of the patient. In cancer patients, studies of resting energy expenditure have produced similarly varying results, depending in part on tumor type and dietary intake. Protein turnover studies in patients with cancer suggest that support of the tumor may occur at the expense of host skeletal muscle. Abnormalities of glucose and lipid metabolism have been noted as well. Thus, pharmacologic intervention may be needed to restore weight and lean tissue in patients with weight loss associated with either HIV infection or cancer.