Genetic African Ancestry and Markers of Mineral Metabolism in CKD.

BACKGROUND AND OBJECTIVES: Disorders of mineral metabolism are more common in African Americans with CKD than in European Americans with CKD. Previous studies have focused on the differences in mineral metabolism by self-reported race, making it difficult to delineate the importance of environmental compared with biologic factors. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: In a cross-sectional analysis of 3013 participants of the Chronic Renal Insufficiency Cohort study with complete data, we compared markers of mineral metabolism (phosphorus, calcium, alkaline phosphatase, parathyroid hormone, fibroblast growth factor 23, and urine calcium and phosphorus excretion) in European Americans versus African Americans and separately, across quartiles of genetic African ancestry in African Americans (n=1490). RESULTS: Compared with European Americans, African Americans had higher blood concentrations of phosphorus, alkaline phosphatase, fibroblast growth factor 23, and parathyroid hormone, lower 24-hour urinary excretion of calcium and phosphorus, and lower urinary fractional excretion of calcium and phosphorus at baseline (P<0.001 for all). Among African Americans, a higher percentage of African ancestry was associated with lower 24-hour urinary excretion of phosphorus (Ptrend<0.01) in unadjusted analyses. In linear regression models adjusted for socio-demographic characteristics, kidney function, serum phosphorus, and dietary phosphorus intake, higher percentage of African ancestry was significantly associated with lower 24-hour urinary phosphorus excretion (each 10% higher African ancestry was associated with 39.6 mg lower 24-hour urinary phosphorus, P<0.001) and fractional excretion of phosphorus (each 10% higher African ancestry was associated with an absolute 1.1% lower fractional excretion of phosphorus, P=0.01). CONCLUSIONS: A higher percentage of African ancestry was independently associated with lower 24-hour urinary phosphorus excretion and lower fractional excretion of phosphorus among African Americans with CKD. These findings suggest that genetic variability might contribute to racial differences in urinary phosphorus excretion in CKD.

Role of dietary therapies in the prevention and treatment of hypertension.

Blood pressure naturally rises with increasing age. The rate of change in blood pressure with age is regulated in part by genetic factors, but can also be altered through sustained dietary modification. Dietary approaches to modify blood pressure remain an important part of cardiovascular health promotion, which is especially important given the aging of the general population coupled with the increasing prevalence of obesity and metabolic disturbances. Specific modification of dietary components such as macronutrients and micronutrients could be helpful to lower blood pressure and alter the slope of blood pressure change whereas nutritional supplements are less likely to have a substantial beneficial effect. Population-wide generalizations regarding diet are impractical as individualized strategies are more likely to be successful in facilitating long-term benefits in improving blood-pressure control. Consequently, more effort needs to be focused on evaluating data from large-scale observational and interventional studies and interpreting their information in a clinically relevant manner, which is likely to be helpful for individual patients. Providing education on the relationship between diet and blood pressure from an early age is most likely to produce tangible benefits.