Altered renal sodium handling and hypertension in men carrying the glucagon receptor gene (Gly40Ser) variant.

A higher prevalence of hypertension has been associated with the G-->A/GT (Gly40Ser) polymorphism of the glucagon receptor gene (GCGR) in two population studies. As the mutated receptor is less responsive to glucagon, it has been speculated that the increased susceptibility to hypertension is due to deprivation of the recognized natriuretic effect of the hormone. To test this hypothesis we determined the frequency of the polymorphic variant and evaluated the segmental renal sodium handling by the clearances of uric acid and of exogenous lithium in the Olivetti Heart Study participants (n=971). The polymorphic variant was present only in heterozygous form in 37 individuals (3.8\%). After controlling for age and body mass index, the carriers of the variant were twice more likely to be hypertensive and almost three times more likely to be on antihypertensive treatment at the time of examination. Compared to participants carrying the wild type, those carrying the Gly40Ser allele had higher serum uric acid and lower fractional excretion of uric acid and exogenous lithium, independently of age, body mass, and current pharmacological treatment. We conclude that the Gly40Ser polymorphism of the GCGR gene is associated with higher risk of hypertension and with enhanced proximal tubular sodium reabsorption, a factor possibly contributing to hypertension in this group.