Hypertension and non-insulin-dependent diabetes mellitus (NIDDM) are c
haracterized by a strong genetic component and impaired ability to sto
re glucose as glycogen in skeletal muscle. Impaired insulin activation
and altered genetic control of muscle glycogen synthase, the rate-lim
iting enzyme for glucose storage in skeletal muscle, could provide an
explanation for this insulin resistance. We examined whether there is
an association between the glycogen synthase gene (Xba I polymorphism)
and hypertension in 304 nondiabetic subjects. We examined glucose tol
erance with an oral glucose tolerance test and glucose storage in skel
etal muscle with the euglycemic insulin clamp technique in combination
with indirect calorimetry. The Xba I A(2) allele of the glycogen synt
hase gene was enriched in subjects with hypertension and a family hist
ory of NIDDM (48%) compared with normotensive subjects without a famil
y history of NIDDM (6%, P<.0001). The presence of the A(2) versus the
A(1) allele was associated with decreased rates of insulin-stimulated
glucose storage in hypertensive subjects (11.2+/-2.3 versus 16.9+/-2.6
mu mol/kg lean body mass per minute, P=.029) but not in normotensive
subjects (28.0+/-4.6 versus 29.6+/-3.7 mu mol/kg lean body mass per mi
nute). In conclusion, Xba I polymorphism of the glycogen synthase gene
identifies a subgroup of hypertensive subjects with a family history
of NIDDM. The data suggest that a locus in the glycogen synthase gene
region on chromosome 19 may serve as a ''thrifty gene,'' increasing su
sceptibility for insulin resistance when exposed to other environmenta
l or genetic factors.