Increased blood pressure and erythrocyte sodium/lithium countertransport activity are not inherited in diabetic nephropathy

Parental hypertension and proteinuria in Pima Indians with NIDDM

To determine if parental hypertension is associated with proteinuria in offspring with non-insulin-dependent diabetes mellitus (NIDDM), 438 diabetic Pima Indians (172 men, 266 women) aged 20 years or more and both of their parents were examined. Hypertension was defined as a systolic blood pressure 140 mm Hg or more, diastolic blood pressure 90 mm Hg or more, or treatment with antihypertensive medicine. Sixty-three percent of the fathers and 80% of the mothers had diabetes at the time their blood pressure was measured. Families in which either parent had proteinuria, defined as a urine protein-to-creatinine ratio > or = 0.5 g/g were excluded; 73 (16.7%) of the offspring had proteinuria. The prevalence rates of proteinuria in the offspring were similar if neither parent or only one parent had hypertension (8.9 and 9.4%, respectively), but was significantly higher if both parents had hypertension (18.8%), after adjustment for age, sex, duration of diabetes, and 2-h post-load plasma glucose concentration in the offspring and diabetes in the parents by logistic regression. The odds for proteinuria being present in the offspring if both parents had hypertension was 2.2 times (95% confidence interval, 1.2 to 4.2) that if only one parent had hypertension. When mean arterial pressure and blood pressure treatment in the offspring were added to the model the relationship remained (odds ratio = 2.2; 95% confidence interval, 1.1 to 4.3). Hypertension in both parents is associated with the development of proteinuria in offspring with NIDDM. This relationship was present even when controlled for the effects of blood pressure and its treatment in the offspring.

Predisposition to hypertension: risk factor for nephropathy and hypertension in IDDM

Less than a quarter of the patients with juvenile-onset IDDM develop diabetic nephropathy during the first 20 years of diabetes. To study the determinants of this complication, we selected patients who had come with newly diagnosed IDDM to the Joslin Clinic between 1967 to 1972, and we examined them in 1986 to 1988, that is, 15 to 21 years after onset of diabetes. Using a case control design we compared three groups of cases, that is, advanced nephropathy (N = 43), only microalbuminuria (N = 41), and hypertension alone (N = 17), with a group of controls who remained normoalbuminuric and normotensive despite the long duration of IDDM (N = 61). In comparison with controls, patients with advanced nephropathy had more parents with hypertension (odds ratio 3.8), higher Vmax values of Na/Li countertransport in red blood cells (odds ratio 10.0 for the highest tertile), and higher mean arterial pressure during adolescence and early adulthood (odds ratio 3.1 for those above the median). They also had significantly poorer glycemic control during their first 12 years of diabetes. Patients with hypertension alone were similar to those with advanced nephropathy with regard to markers of predisposition to hypertension but differed from them with regard to glycemic control, having the best glycemic control of all the study groups. Patients who developed only microalbuminuria during 15 to 21 years of IDDM (some of whom will progress to overt proteinuria later) did not differ significantly from controls with regard to predisposition to hypertension. In conclusion, predisposition to hypertension is a major risk factor for the development of advanced diabetic nephropathy and essential hypertension during the first 20 years of IDDM.