Sustained elevation of systemic blood pressure, affecting an estimated 1.3 billion adults worldwide and the leading modifiable risk factor for cardiovascular disease, stroke, and chronic kidney disease. The gut microbiome-blood pressure axis has emerged as a major research area, with short chain fatty acids, tmao, the mycobiome, and microbial metabolites all contributing to BP regulation. Heavy metals -- particularly lead and cadmium -- are established environmental risk factors operating through both direct vascular toxicity and microbiome-mediated pathways.
Gut Microbiome-Blood Pressure Axis
SCFA-Mediated BP Regulation
SCFAs regulate blood pressure through opposing receptor systems:
- GPR41 (FFAR3): Propionate and butyrate binding causes vasodilation and BP reduction via endothelial relaxation.
- Olfr78 (olfactory receptor 78, renal): Propionate and acetate binding on renal juxtaglomerular cells stimulates renin release, raising BP.
- At physiological SCFA concentrations, the vasodilatory GPR41 effect dominates, producing net BP reduction [hoffelner 2025 emerging therapy targets microbiome cvd].
- Dysbiosis-driven SCFA depletion removes this vasodilatory brake, contributing to hypertension.
- High-fiber diets increase colonic SCFA production and are consistently associated with lower BP.
TMAO and Vascular Remodeling
- Prolonged tmao elevation activates pro-inflammatory vascular remodeling pathways, contributing to arterial stiffness and increased peripheral resistance [zhen 2023 tmao cardiovascular diseases review].
- TMAO-associated Firmicutes/Bacteroidetes ratio elevation is characteristic of hypertensive microbiomes.
- TMAO promotes endothelial dysfunction via HMGB1/TLR4 signaling and tight junction destruction.
Bile Acid-FXR Axis
- FXR agonist CDCA reduces blood pressure in spontaneously hypertensive rat models through iNOS expression [ryan 2017 bile acids gut microbiome cardiometabolic interactions].
- FXR expression is downregulated in left ventricle of hypertensive rats with end-stage heart failure.
- Bile acid metabolism disruption may compound SCFA depletion in raising BP.
Mycobiome in Hypertension
A distinctive feature of hypertension research is the role of the gut fungal microbiome:
Malassezia Enrichment
- Malassezia increases progressively from normotensive to pre-hypertensive to hypertensive individuals (28.45% dominance in HTN vs lower in NT) [zou 2022 mycobiome dysbiosis hypertension light chains].
- Malassezia produces inflammatory lipases and activates immune cells; its enrichment compounds bacterial dysbiosis-driven inflammation.
- Malassezia positively associated with immunoglobulin light chain kappa in pre-HTN (r=0.510, P=0.044) and both kappa and lambda in HTN.
Mortierella Depletion
- Mortierella is depleted in both pre-HTN and HTN, paralleling loss of protective bacterial taxa [zou 2022 mycobiome dysbiosis hypertension light chains].
HTN+CKD Comorbidity
- HTN+CKD patients show the most severe mycobiome disruption: Malassezia (18.71%) dominant, with increased Apiotrichum, Cystobasidium, saccharomyces, and decreased Candida, Meyerozyma [qiu 2023 gut mycobiome hypertension ckd].
- HTN+CKD has higher IL2Ralpha, IL18, TNF-alpha; Candida negatively associated with TNF-alpha.
- Fungal dysbiosis occurs at the pre-hypertension stage, suggesting it precedes clinical disease.
FMT for Hypertension: First Human RCT
Fan et al. 2025 conducted the first multicenter, randomized, blinded, placebo-controlled trial of oral FMT for stage 1 hypertension (NCT04406129) [fan 2025 fmt hypertension rct]:
- 124 patients (mean age 43), 7 centers in China.
- Primary outcome: SBP change at day 30 was -6.28 mmHg (FMT) vs -5.77 mmHg (placebo), p=0.62 (not significant).
- Transient effect: At 1 week, FMT produced -4.34 mmHg between-arm SBP difference (p=0.024), but this did not persist.
- Age subgroup: Participants >48 years showed significant SBP reduction of 7.65 mmHg (p=0.029).
- Microbial shifts: Increased Parabacteroides merdae, Prevotella copri, Eubacterium sp.; decreased Eggerthella lenta, Streptococcus vestibularis.
- Metabolite associations: SBP-associated metabolites included tyrosine, glutamine, phenylalanine, methionine.
- Implication: microbial BP modulation is real but transient, suggesting repeated or sustained intervention is needed.
Metal Risk Factors
Lead
- Pb is among the most established environmental risk factors for hypertension.
- Mechanisms: inhibits endothelial NO synthase, increases oxidative stress, activates RAAS (renin-angiotensin-aldosterone system), promotes vascular smooth muscle contraction.
- Even low-level chronic Pb exposure (blood Pb <10 ug/dL) is associated with elevated BP.
- Pb accumulates in kidney, impairing renal BP regulation.
Cadmium
- Cd nephrotoxicity damages renal tubules, impairing sodium handling and BP regulation.
- Cd-induced oxidative stress in vascular endothelium promotes arterial stiffness.
- Cd accumulates in renal cortex over decades; renal Cd burden correlates with hypertension risk.
Renal Metal Accumulation
- The kidney is a primary target organ for both Pb and Cd accumulation.
- Metal-induced renal damage impairs the kidney's central role in long-term BP regulation (sodium excretion, RAAS modulation, prostaglandin synthesis).
- This creates a direct metal-to-hypertension pathway independent of the microbiome, though both pathways likely operate simultaneously.
Connections
- cardiovascular disease -- hypertension is the leading modifiable CVD risk factor
- short chain fatty acids -- SCFA-mediated vasodilation via GPR41 is a primary microbiome BP mechanism
- tmao -- promotes vascular remodeling and endothelial dysfunction
- bile acid metabolism -- FXR agonists reduce BP in hypertensive models
- dysbiosis -- both bacterial and fungal dysbiosis precede and associate with hypertension
- lead -- established environmental hypertension risk factor via renal and vascular toxicity
- cadmium -- renal accumulation impairs BP regulation
- chronic kidney disease -- HTN+CKD comorbidity shows most severe mycobiome disruption
- inflammation -- Malassezia-driven and LPS-driven inflammation contributes to vascular remodeling
- malassezia -- enriched in hypertension; correlates with immunoglobulin light chain dysregulation