They say that study participants receiving daily doses of metformin had essentially no progression of coronary artery calcification during the year-long study period, while participants receiving a placebo had calcium increases of up to 50 per cent. The study also found that lifestyle modification – participation in regular exercise and dietary counseling sessions – did not have a significant effect on calcification, although it did improve several cardiovascular risk factors.
"HIV-infected patients are known to have higher rates of cardiovascular disease and elevations in traditional risk factors – such as insulin resistance, abdominal obesity, high triglyceride levels and hypertension," says Doctor Steven Grinspoon of MGH. "This is the first demonstration of a therapy that is effective in preventing progression of coronary calcium in patients infected with HIV."
Several large epidemiologic studies have found that HIV-infected individuals have approximately twice the rate of cardiovascular disease as non-infected individuals in the same demographic groups. Between 20 and 40 per cent of HIV-infected patients meet the diagnostic definition for metabolic syndrome – a cluster of symptoms including abdominal obesity, abnormal HDL cholesterol and triglyceride levels, insulin resistance and abnormal glucose levels, and elevated blood pressure – which is known to increase the risk of heart attack, stroke and type 2 diabetes. Factors behind these symptoms probably include side effects of antiviral medications and the effects of HIV itself on fat distribution, cholesterol levels and inflammatory factors.
A long-established treatment for type 2 diabetes, metformin is proven to reduce the incidence of cardiovascular disease associated with diabetes and is also used to treat insulin resistance caused by polycystic ovary syndrome. In 2000, Grinspoon led a pilot study finding that metformin reduced insulin levels in HIV patients with insulin resistance, abnormal fat distribution, and elevated cholesterol and triglyceride levels. The current study enrolled 50 participants – receiving antiviral therapy for HIV infection and diagnosed with metabolic syndrome – who were randomised into four groups. One group received standard daily doses of metformin and lifestyle modification classes; another received metformin only; a third received a placebo and lifestyle modification, and the fourth, placebo only.
At the end of the 12-month study period, participants taking metformin showed little change in coronary artery calcification – a standard measure to assess atherosclerosis – while those receiving neither intervention had an average calcium increase of 56 per cent. Metformin treatment also reduced a standard measure of insulin resistance.
MEDICA.de; Source: Massachusetts General Hospital (MGH)