Microvascular
Processes Plays A Role in Development of Diabetes
Microvascular
damage may play a role in the initial development of diabetes.
Retinal
arteriolar narrowing is independently associated with the risk of
diabetes, according to results of the prospective Atherosclerosis Risk
in Communities study, which suggests that microvascular damage may
play a role in the initial development of the disease.
Dr.
Ronald Klein, of the University of Wisconsin-Madison, and associates
obtained retinal photographs from 7993 study participants between 1993
and 1995. High-resolution scanners measured the diameter of individual
arterioles and venules surrounding the optic disk, which were then
used to express arteriole-to-venule ratios (AVR).
Within
a median follow-up period of 3.5 years, 3.6% of participants developed
diabetes. The incidence increased from 2.4% to 5.2% with decreasing
quartiles of AVR. The relationship remained significant after
adjustment for age, sex, race, fasting glucose and insulin levels, and
family history of diabetes, with an odds ratio of 1.71 for those in
the lowest quartile versus those in the highest quartile of AVR.
The
association remained when individuals with signs of diabetic
retinopathy, such as microaneurysms and retinal hemorrhages, were
excluded, and was similar for those stratified according to risk. The
authors of the study, published in the May 15 issue of the Journal of
the American Medical Association, suggest that "arteriolar
narrowing precedes the onset of diabetes," and when
"resulting from hypertension, cigarette smoking, inflammation,
and other unmeasured processes, may be a common pathophysiological
link to diabetogenesis."
"The
fact that microvascular changes precede the onset of diabetes is
surprising," co-author Dr. A. Richey Sharrett, of the National
Heart, Lung, and Blood Institute in Bethesda, Maryland,” stated.
"However, there have been a number of things that previously were
thought to be markers of the presence of diabetes that are now known
to be predictors, for example, lipid abnormalities and low HDL
cholesterol."
"It's
as if part of the metabolic syndrome appears first," he added.
In
the article, the authors suggest that microvascular changes may reduce
the ability of insulin to mediate glucose uptake by skeletal muscles.
However, Dr. Sharrett pointed out, the arteriolar narrowing "is a
finding that begs explanation." He noted that researchers
involved in the MESA (Multiethnic Study of Atherosclerosis) study
should extend the findings by also evaluating retinal photographs.
JAMA
2002;287:2528-2533.
