Gut microbiota depletion with antibiotics enhances fructose induced salt‐sensitive hypertension in normal rats

Abstract

Introduction‐We reported that 20% fructose in drinking water induced salt‐sensitive hypertension in normal rats. High fructose (HF) or high salt (HS) intake reportedly alter the gut microbiota, which influences a variety of microbial‐regulated bioactive metabolites that can affect blood pressure and renal function. The contribution of the gut microbiota to fructose induced salt‐sensitive hypertension or renal function has not been studied. Aim‐ We hypothesized that gut microbiota depletion with antibiotics (ABX) would change fructose induced salt‐sensitive hypertension, renal excretory function and plasma levels of bacterial metabolites (lactate, β‐hydroxy‐butyrate).Methods‐Sprague Dawley rats were treated with a cocktail of antibiotics (ABX group, in g/L 1.0 ampicillin, 1.0 neomycin sulphate, 1.0 metronidazole, and 0.5 vancomycin in drinking water) for 4 weeks followed by a 0.33 fractional maintenance dose for up to 12 weeks) or control diet (no‐ABX). On week 5, all rats were given 20% fructose (HF) in drinking water and fed a diet with normal salt (NS, 0.4% Na) or high salt content (HS, 4% Na). Rats were divided as: Group 1 (HF + NS, no‐ABX, n= 6), Group 2 (HF + NS + ABX, n=6), Group 3 (HF + HS, no‐ABX, n= 8), Group 4 (HF + HS + ABX, n= 8). We trained rats and measured systolic blood pressure (SBP) for 12 weeks by tail‐cuff and collected feces before and after ABX, to measure gut c‐DNA content. On the 12th week, we collected 24‐ hour urine and plasma before the end of the protocol.Results‐ Antibiotics induced microbiome depletion (ABX) decreased fecal DNA content by 83%. Baseline SBP (in mmHg) or urine albumin excretion was not affected by ABX. Fructose with normal salt diet did not change SBP with (125±4) or without ABX (124±3). HS significantly increased SBP in rats fed fructose without ABX (from 123±3 to 141±4, p<.05) but the increase was greater in ABX rats (from 124±4 to 155±3, p<.05). Average increase on SBP was 26±2 in HF+HS with ABX, but only 15±2 without ABX (p<.001). In HF + HS groups, ABX decreased plasma lactate from 1657±259 to 905±144 µM (p<.01), and β‐hydroxy‐butyrate from 861±144 vs 220±53 µM (p<.001). Non‐fasted plasma insulin was also decreased by ABX in HF+HS rats (0.77±0.13 to 0.36±0.06 ng/mL, p<.03). The increase in body weight was similar in HF+HS rats with or without ABX.Conclusion‐ Chronic antibiotic treatment induced gut microbiota depletion and enhanced fructose induced salt‐sensitive hypertension in normal rats, an effect that was associated with decreased plasma beta‐hydroxy‐butyrate, lactate and insulin. Additional studies should focus on direct renal effects of ABX on salt handling.