South Asian Ancestry Raises
Risk of Diabetes
People of Asian Indian ancestry are at increased
risk for type 2 diabetes, even when they are thin, according
to articles in the December 2003 and June 2004 issues of the
Journal of Clinical Endocrinology and Metabolism. The researchers
found that people of Indian, Pakistani, or Bangladeshi ancestry
- all considered “Asian Indian” for these studies
-a re metabolically and genetically different from those of
European descent. (Traditionally, anthropologists have classified
Asian Indians as “Caucasians.” In these studies,
however, those descended from Europeans are referred to as
“Caucasians”). Scientists already knew that insulin
resistance and type 2 diabetes are common in India. The new
research studied people living in the United States.
In the December 2003 study, the research team looked at whether
two genes suspected to cause insulin resistance occur more
often among people of Asian Indian ancestry than among Caucasians.
They also investigated whether people who had these genes
were more insulin-resistant than those who didn’t.
There were 738 subjects of European ancestry and 638 subjects
of Asian Indian ancestry; some of the Asian Indians were recent
immigrants, and others had been born in the United States.
Genetic tests found that one of the two suspect genes, called
PC-1 121 Q, occurred significantly more often in the Asian
Indians. Blood tests also showed that Asian Indians with this
gene were less insulin sensitive than Asian Indians without
it. Among Caucasians, the gene did not affect insulin sensitivity
in this study.
The researchers concluded that the PC-1 121Q gene is strongly
associated with insulin resistance among Asian Indians in
the United States. Because insulin resistance raises the risk
of type 2 diabetes, people with this gene are likely more
prone to diabetes. In the June 2004 study, the researchers
compared insulin-resistant Asian Indian men with less-insulin-resistant
Caucasian men. They sought to find out whether the men’s
fat cells released similar amounts of leptin, adiponectin,
and none sterified fatty acids (NEFA). (Obese people produce
high levels of leptin and NEFA and low levels of adiponectin;
these abnormalities may help cause the insulin resistance
that often accompanies obesity.).
The Asian Indians’ higher levels of NEFA and leptin
and lower levels of adiponectin suggest that the bodies of
thin Asian Indians are metabolically similar in some ways
to those of overweight Caucasians. The researchers concluded
that Asian Indians may have a fat cell defect that makes them
produce the wrong quantities of these three substances and
so leads to insulin resistance, even when a person isn’t
overweight. Insulin resistance, in turn, presumably leads
to a higher risk of type 2 diabetes.
Together, these studies suggest that people of Asian Indian
ancestry are genetically more prone to type 2 diabetes. Thus,
it is extra important for people with such ancestry to stay
as thin as possible, to exercise regularly, and to be aware
of the symptoms of diabetes.