POTASSIUM, URINARY METABOLOMICS, BLOOD PRESSURE AND GLUCOSE METABOLISM: THE AFRICAN-PREDICT STUDY

Abstract

Objective: A potassium deficient diet is associated with a higher risk of type 2 diabetes and hypertension. Both conditions occur more frequently in Black populations, who consume less potassium-rich foods than what is typically observed in White populations. Metabolomics is a useful tool in nutritional epidemiology and may help identify metabolic pathways involving potassium and its relationship with diabetes and cardiovascular disease. Recognizing metabolic pathways that may be dysregulated by potassium deficiency could help procure more accurate entry points for prevention and intervention strategies involving diet. Design and method: This study included 440 White and 350 Black adults from the African-PREDICT study (aged 20-30 years). We measured 24-hour BP and collected 24-hour urine samples to determine potassium and sodium concentrations. Fasting plasma glucose levels were determined. Amino acids and acylcarnitines were measured in spot urine using liquid chromatography-tandem mass spectrometry. Results: Black participants had lower urinary potassium than Whites (36.6 vs. 51.1 mmol/day) (p<0.001). In the total group 24-hour urinary potassium associated positively with 2-aminoadipic acid (r = 0.111; p = 0.002), C3-[propionylcarnitine] (r = 0.091; p = 0.014), C4-[butyrylcarnitine] (r = 0.094; p = 0.009) and C5-[valerylcarnitine] (r = 0.072; p = 0.043) after Pearson (q <0.05) and partial correlations adjusting for sex, ethnicity, age, and waist circumference. With ethnic stratification these relationships remained statistically significant only in White participants. In accordance, Na/K+ ratio was inversely related to 2-amino adipic acid (r = -0.085; p = 0.018), C3- (r = -0.077; p = 0.038), C4- (r = -0.125; p<0.001) and C5-carnitine (r = -0.104; p = 0.004) in the total group. In the total group, 2-aminoadipic acid (r = 0.086; p = 0.031) and C4-carnitine (r = 0.088; p = 0.026) in turn were positively associated with 24-hour SBP and negatively with fasting plasma glucose [2-aminoadipic acid (r = -0.139; p<0.001), C3-carnitine (r = -0.083; p = 0.044), C4-carnitine (r = -0.115; p = 0.004) and C5- (r = -0.124; p = 0.002)]. Conclusions: Our study highlights the important consideration of ethnic differences when investigating nutrient-metabolome relationships. Only in White adults did we observe a positive association of urinary potassium, with 2-aminoadipic acid and short chain acylcarnitines, which in turn related positively to blood pressure and negatively with plasma glucose levels. In White adults, early metabolomic changes related to potassium intake may contribute to BP regulation and glucose homeostasis.