#2227 Exploring the interplay between gut microbiome, fecal metabolomics and ambulatory blood pressure in white-coat hypertensive patients
Authors: Ozbek Deniz Aral , Koc Neriman Sila , İnal Neşe , Kablan Sevilay Erdogan , Kaygusuz Yunus , Karahan Sevilay , Uyaroğlu Oğuz Abdullah , Yildirim Tolga , Ergunay Koray , Nemutlu Emirhan , Akyön Yakut , Altun Bulent 
Published: May 2024

Abstract

Background and Aims
Recent evidence showed the relationship between gut microbiota with hypertension. Few studies also demonstrated that ambulatory blood pressure monitoring variables such as dipping status and linear variability are associated with fecal microbiota and metabolomics. However, the relationship between gut microbiota and metabolomic composition of white-coat hypertensive patients has not been studied yet. In addition, although the link between gut microbiota, blood pressure variability and high salt intake has been shown, none of the studies addressed these changes simultaneously in the same study population. Here, we aimed to investigate the interplay between the gut microbiome, fecal metabolites and 24-hour urine sodium levels between hypertensive, white-coat hypertensive (WCH) and healthy participants diagnosed with ambulatory blood pressure monitoring.

Method
The study included 18 newly diagnosed hypertensive, 8 WCH, and 21 healthy participants from our tertiary center. Ambulatory blood pressure (BP) monitoring was performed in all participants and nighttime dipping, morning BP surge (MBPS), pre-wake MBPS and linear BP variability were calculated. 16S rRNA sequencing was performed using Illumina MiSeq sequencer. DeSeq2 and linear discriminant analysis effect size (LEfSe) were performed with R. Fecal metabolite levels were analyzed by GC-MS. A partial least squares-discriminant analysis (PLS-DA) model was constructed for the feature selector and classifier. The variable importance in the projection (VIP) coefficient was calculated based on the PLS-DA model.

Results
ANOVA and post-hoc Tukey test showed WHC and hypertensive groups had higher blood pressure variability and morning-thorough MBPS than normotensive patients (p = 0.02 and 0.04, respectively), whereas 24-h urine Na levels were statistically similar between WCH and hypertensive groups (p = 0.11). There were no significant differences in α- and β-diversity metrics of gut microbiome between study groups. Select taxa were specific to WHC patients, notably Rikenellaceae family and Mitsuokella were higher in WHC against normotensive patients, whereas Ruminococcus callidus, Roseburia, Clostridium, Lactobacillus ruminis, Sutterall, Lachospiraceae and Muribaculaceae were decreased in WHC against normotensive patients in DeSeq2 analysis. Dialister was increased, whereas Bacteroides genus and Bacteroides fragilis were decreased in WHC against hypertensive patients. LEfSe analysis showed positive enrichment in Proteobacteria phylum and negative enrichment in Mitsuokella genus in WHC against hypertensive group. Enterococcus, Lachnobacterium, Odoribacter and Pseudomonas genera had positive; whereas Lactobacillus and Clostridium had negative correlations with 24-h urine Na levels. Positive correlations were shown between linear BP variability and Bacteroides and Paraprevotella genera. Several genera and species were enriched in Q3-4 against Q1-2 quartiles of pre-wake and sleep-thorough MBPS in LEfSe analyzes (Fig. 1). Normotensive and essential hypertensive groups could also be differentiated based on fecal metabolomic composition. Specifically, metabolites with the highest VIP values discriminating WCH from normotensive and hypertensive groups were methyl-palmitoleate, oxalic acid and phenyl β-D-glucopyranoside, respectively (Fig. 2).

Conclusion
In conclusion, we performed the first study focusing on the fecal microbiome and metabolomic characteristics of white-coat hypertensive patients. Urine Na levels and ambulatory blood pressure variables of the WCH group are different than those of the normotensive and similar to the hypertensive group. Comparative and correlation analyses revealed novel relationships between ambulatory blood pressure variables and gut microbiome of both WCH and hypertensive patients. Fecal metabolomic differences between study groups imply possible mechanisms underlying the effects of gut microbiome on blood pressure. Gut microbiota and metabolites may become valuable targets for interventions of both white-coat and essential hypertension in the near future.