Strojek K et al. (2005) Salt-sensitive blood pressure—an intermediate phenotype predisposing to diabetic nephropathy? Nephrol Dial Transplant 20: 2113–2119

A recent study has investigated the salt sensitivity of blood pressure among offspring of patients with type 2 diabetes and diabetic nephropathy. The results indicate that these individuals are more likely to be 'salt sensitive' than the offspring of diabetic patients without diabetic nephropathy. This might suggest, say the researchers, that salt sensitivity of blood pressure represents an 'intermediate phenotype' in individuals genetically predisposed to diabetic nephropathy.

The study included two groups of 15 healthy, adult participants, all of whom had a parent with type 2 diabetes with (DN+) or without (DN−) diabetic nephropathy. The control group comprised 15 staff members with no family history of diabetes. Each participant underwent a low-salt and then a high-salt regimen, with each diet lasting for five days.

During the high-salt period, systolic blood pressure was significantly higher among the offspring of DN+ patients than among the offspring of DN− individuals. The former group also had a significantly greater salt-induced difference in mean blood pressure between the two diets, and the proportion of salt-sensitive individuals was greater in this group than among offspring of DN− patients (67% vs 20%; P <0.05). Changes in plasma renin activity, plasma aldosterone and atrial natriuretic peptide were similar in both groups, although 11β-hydroxysteroid dehydrogenase type 2 activity appeared to be lower among salt-sensitive subjects.

In summary, the relationship between salt intake and blood pressure appeared to differ according to the presence or absence of diabetic nephropathy in the diabetic parents of these study participants. These differences might correspond to an individual's risk of developing diabetic nephropathy in future.