Humanized Diets Define Optimal Pressure Lowering Response to Dietary Potassium in Mice

Abstract

High potassium (K) diets are known to lower blood pressure (BP) in rodents and humans but can also raise BP when consumed in extreme. Interestingly, this response also appears to be influenced by dietary sodium (Na) such that when Na intake is high, high K lowers BP, whereas when sodium intake is lower, high K increases BP (Little et al, Hypertension, 2023). We recently reported (Little et al, JCI Insight, 2023) that the K-mediated BP lowering response, driven by the inactivation of the thiazide-sensitive sodium chloride cotransporter (NCC), is offset by an increase in ENaC (epithelial sodium channel) when an extremely high K diet is chronically consumed. Here, we define the optimal dietary K level needed to inactivate NCC without activating ENaC in the high Na setting and show this K level approximates the recommended level for humans by the DASH (Dietary Approaches to Stop Hypertension) trials. Mice were fed diets containing 6 different K contents, all with high Na (1.7%), so the effects of the control diet (1% K, 1.7% Na) could be compared to traditional extremes (0.1% and 5% K) and others (0.35%, 0.7%, 1.7%) that mimic typical variation in human diets (30-120 mEq/d) when mouse consumption is normalized for caloric intake relative to body mass. Metabolic cage and renal clearance studies were used to assess electrolyte and aldosterone (aldo) excretion as well as NCC- (hydrochlorothiazide (HCTZ) sensitive) and ENaC- (benzamil sensitive) dependent sodium handling. Blood potassium (PK) was measured using iSTAT. BP was measured hourly for 10 days using DSI telemetry probes in male mice (C57Bl6J). The BP response to the diuretics was also measured. PK levels changed significantly with each diet relative to the control diet from 3.2mM to 4.8mM. Systolic blood pressure (SBP; 12-hour active period average) also changed significantly with the different K diets. Extreme high or low K diets (0.1% and 5%) increased SBP by 7mmHg, 0.35% and 0.7% K diets increased SBP by 6 and 3mmHg, while the 1.7% K diet lowered SBP by 4mmHg relative to control (1% K, 132 mmHg). Thus, the relationship between SBP and PK is ‘U-shaped’. Diuretic studies revealed that HCTZ reduces SBP in the 0.1%, 0.35%, 0.7% K groups but had minimal effect in the 1.7% and 5% K groups. Conversely, inhibiting ENaC activity with benzamil normalized SBP in the 5% K group but had a minimal effect in the 1.7% group and no BP effect in the other groups. The BP-lowering effect of each diuretic correlated with increased natriuresis suggesting dietary K influences blood pressure by affecting distal nephron sodium transport. Lastly, urinary aldo levels increased with increasing dietary K, but compared to the control group, aldo levels were significantly lower in the 0.1%, 0.35%, and 0.7% groups, significantly higher in the 5% group, and not different in the 1.7% group. As previously reported, our results demonstrate that extremes in dietary intake can elevate blood pressure by stimulating distal nephron sodium transport proteins with low K inducing NCC activation and high K stimulating ENaC with elevated aldosterone. An optimal dietary K level (1.7%) that maximally reduces BP in mice was identified, suppressing NCC activity while limiting aldosterone production and ENaC activity. Remarkably, this diet mimics the human DASH diet in K content and further supports its effcacy as a blood pressure-lowering modality. DE (DK054231, DK51496); PW (DK054231, DK093501, DK110375): Leducq Foundation U54 DK137331-01. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.