NEW YORK, May 07 (Reuters Health) - A rare disorder that leads to unusual fat distribution and causes the body to lose responsiveness to the sugar-processing hormone insulin increases the risk of early heart disease, a study in Canada has found.

The discovery may lead to improved understanding of the connection between heart disease and the more common types of insulin resistance, which have been linked to heart disease, the study's author told Reuters Health in an interview.

"There are other instances where studying a rare form of a condition has led to some understanding that has then had wider implications," said Dr. Robert A. Hegele of the Robarts Research Institute in London, Ontario.

He pointed out that the development of statins--the widely prescribed cholesterol-lowering drugs--grew out of research in families with a genetic disorder that raises LDL ("bad") cholesterol levels.

Sometimes "the zebra can teach you about the horse," according to Hegele.

The genetic disorder that Hegele studies, Dunnigan-type familial partial lipodystrophy (FPLD), interferes with the body's normal metabolism. At puberty, the distribution of fat begins to change in people with FPLD. They lose weight in their arms, legs and buttocks and gain weight in the abdomen, chest and face. The disorder causes insulin resistance and may also lead to diabetes, high blood pressure, high triglycerides and low HDL ("good") cholesterol.

"It had been assumed that those patients had a tendency to early vascular disease," Hegele noted, but he added that the link between FPLD and artery disease had not been studied systematically.

The current study included 23 people aged 35 and older who had FPLD and a "control" group of 17 of their relatives who did not have the disorder.

Participants with FPLD were more likely to have type 2 diabetes, high blood pressure, insulin resistance and blood-fat abnormalities, Hegele reports in the May 8th issue of Circulation: Journal of the American Heart Association.

Carriers of the trait were significantly more likely to develop heart disease than people in the study who did not have the gene. The risk of developing heart disease at any age was about six times greater in people with FPLD, according to the report. And the risk was even greater for early heart disease. About 26% of patients with FPLD developed heart disease before age 55, compared to none of the people without the gene.

Hegele found that FPLD appeared to have a greater impact on women's risk of heart disease. Four out of the 14 women (about 28%) with FPLD underwent bypass surgery before age 55. Hegele points out that the corresponding rate of bypass surgery in the overall population of Canadian women is 1 out of 7,350.

In the interview, Hegele said that the reasons for the increased risk in women are unknown. He cautioned that more study is needed to confirm the extra risk in women.

The next step, Hegele said, is to try to find out how FPLD increases the risk of early heart disease. A better understanding of this link may have wider implications, he added.

"Studying individuals with a genetic condition showing this complex interaction may lead to treatments directed at the underlying causes before heart disease becomes evident," according to Dr. Richard W. Nesto, a member of the American Heart Association's diabetes committee.

"Since patients with diabetes and heart disease have a high death rate if they have a heart attack, any knowledge that leads to more effective primary prevention of heart disease is noteworthy," Nesto, who is the chairman of cardiovascular medicine at Lahey Clinic Medical Center in Burlington, Massachusetts, said in a statement.

　　From Reutershealth