Biology subjects

Dinakis, E.

Publications and source records attributed to Dinakis, E..

6 recordsLinked to original sources

bioRxiv2023

Dietary fibre reverses adverse post-stroke outcomes in mice via short-chain fatty acids and its sensing receptors GPR41, GPR43 and GPR109A

Dietary fibre intake is associated with fewer cases of ischaemic stroke. This is likely via the microbiota-gut-brain axis, where fibre is fermented by the gut microbiota, releasing short-chain fatty acids (SCFAs). However, whether fibre or SCFAs can reverse adverse post-stroke outcomes remains unknown. Here, we demonstrated that a low fibre diet exacerbates post-stroke outcomes in mice. This was reversed by a high fibre diet or direct supplementation with SCFAs (delivered either in the water or a high SCFA-releasing diet) immediately after stroke. These modulated the gut microbiome and improved the gut epithelial barrier integrity, which was associated with fewer activated neutrophils and more neuroblast cells in the brain. We then investigated the SCFA-receptors GPR41/43/109A using a triple knockout mouse model, which exhibited poorer stroke outcomes and recovery. These results show that post-stroke interventions using dietary fibre and/or SCFA supplementation, acting via GPR41/43/109A signalling, may represent new therapeutic strategies for stroke-induced brain injury.

neuroscience↗

bioRxiv2023

Experimental Factors Influence Diversity Metrics of the Gut Microbiome in Laboratory Mice

IntroductionAnimal models are regularly used to test the role of the gut microbiome in hypertension. Small-scale pre-clinical studies have investigated changes to the gut microbiome in the angiotensin II hypertensive model. However, the gut microbiome is influenced by internal and external factors not regularly considered in the study design. Once these factors are accounted for, it is unclear if microbiome signatures are reproduceable. We aimed to determine the influence of angiotensin II treatment on the gut microbiome using a large and diverse cohort of mice and to quantify the magnitude by which other factors contribute to microbiome variations. Methods and ResultsWe conducted a retrospective study to establish a diverse mouse cohort resembling large human studies. We sequenced the V4 region of the 16S rRNA gene from 538 samples across the gastrointestinal tract of 303 male and female C57BL/6J mice randomised into sham or angiotensin II treatment from different genotypes, diets, animal facilities, and age groups. Analysing over 17 million sequencing reads, we observed that angiotensin II treatment influenced -diversity (P=0.0137) and {beta}-diversity (i.e., composition of the microbiome, P<0.001). Bacterial abundance analysis revealed patterns consistent with a reduction in short-chain fatty acid-producers, microbial metabolites that lower blood pressure. Furthermore, animal facility, genotype, diet, age, sex, intestinal sampling site, and sequencing batch had significant effects on both - and {beta}-diversity (all P<0.001). Sampling site (6.8%) and diet (6%) had the largest impact on the microbiome, while angiotensin II and sex had the smallest effect (each 0.4%). ConclusionsOur large-scale data confirmed findings from small-scale studies that angiotensin II impacted the gut microbiome. However, this effect was modest relative to most of the other factors studied. Accounting for these factors in future pre-clinical hypertensive studies will increase the likelihood that microbiome findings are replicable and translatable.

microbiology↗

bioRxiv2023

Gut bacteria translocation to the brain after ischaemic stroke occurs via the sympathetic nervous system

We provide evidence that stroke-induced gut breakdown results in bacteria translocation to the ischaemic mouse brain. Inhibition of sympathetic tone reduced bacterial load in the post-stroke brain and reduced functional deficits without altering cerebral apoptosis, neuroinflammation or infarct volume. These findings indicate that the activation of the sympathetic nervous system after stroke promotes gut-derived bacteria to enter to the brain, and this process worsens motor function in mice. Abstract Figure O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=106 SRC="FIGDIR/small/535309v1_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@1e78ca0org.highwire.dtl.DTLVardef@c1886forg.highwire.dtl.DTLVardef@1e45ae1org.highwire.dtl.DTLVardef@10aa224_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2023

GPR41/43 regulates blood pressure by improving gut epithelial barrier integrity to prevent TLR4 activation and renal inflammation

Fermentation of dietary fibre by the gut microbiota leads to the production of metabolites called short-chain fatty acids (SCFAs), which have emerged as potent regulators of immune, metabolic, and tissue barrier functions. More recently, a high fibre diet and SCFA supplementation were shown to lower blood pressure and be cardio-protective. SCFAs activate host signalling responses via the receptors GPR41 and GPR43, which have redundancy in their signalling pathways. Whether these receptors play a role in hypertension or mediate the cardio-protective effects of fibre remains unknown. Using an experimental model that lacks both GPR41 and GPR43, we show that lack of signalling via these receptors increases risk to high blood pressure and leads to cardiorenal fibrosis and hypertrophy. Moreover, we demonstrate that GPR41/43 signalling is essential in maintaining gut epithelial barrier, which prevents the translocation of the bacterial toxins lipopolysaccharides (LPS) from entering the peripheral circulation. In the absence of GPR41/43, this is accompanied by macrophage infiltration to the kidneys, resulting in pro-inflammatory cytokine production. Using an antagonist against the LPS receptor, TLR4, a potent pro-inflammatory signalling pathway, we were able to rescue the cardiovascular phenotype in GPR41/43 knockout mice. We also demonstrate that GPR41/43 are, at least partially, responsible for the blood pressure- lowering and cardio-protective effects of a high fibre diet; however, improvements of gut barrier integrity and macrophages in the kidney were independent of GPR41/43 signalling. Finally, using the UK Biobank, we provide translational evidence that variants associated with lower expression of both GPR41/43 are more prevalent in hypertensive patients. Our findings highlight that lack of SCFA-receptor signalling via both GPR41/43 increases risk of high blood pressure, suggesting these receptors could be targeted as a new treatment.

physiology↗

bioRxiv2022

Dietary fibre controls blood pressure and cardiovascular risk by lowering large intestinal pH and activating the proton-sensing receptor GPR65

High blood pressure (BP) is the most common cause of death globally, due to increasing the risk of cardiovascular diseases. Dietary fiber regulates BP through gut microbial production of acidic metabolites known as short-chain fatty acids (SCFAs). The specific mechanisms of how SCFAs regulate BP are still emerging. In a phenome-wide association study, we identified that the proton-sensing G-protein-coupled receptor GPR65 gene is associated with hypertension and its associated end-organ damage phenotypes. We hypothesized that acidic metabolites produced from the gut microbiota may activate GPR65, thus conferring BP regulating effects. We found that dietary fiber levels determined the luminal and interstitial tissue pH in the large intestine through production of SCFAs by the gut microbiota. We identified that low pH produced by high fiber intake, acting via GPR65 signaling, increased cAMP production and phosphorylation of CREB, and restricted the production of hypertension-promoting inflammatory cytokines by CD8+ T cells. Gpr65-/- mice spontaneously developed higher BP, cardiac and renal hypertrophy and fibrosis. We showed that the benefits of a diet high in fiber, which prevented hypertension and associated end-organ damage, were decreased in Gpr65-/- mice. Finally, adoptive transfers revealed that GPR65 deficiency in CD8+ T cells causally explained this phenotype. In conclusion, we showed that pH sensing by GPR65 in CD8+ T cells mediates much of the cardiovascular benefits of dietary fiber. pH sensing represents a novel gene-by-environment interaction of gut microbiota-to-host biological effects and may form the basis for new therapeutic strategies for hypertension.

molecular biology↗

bioRxiv2022

Maternal diet and gut microbiota influence predisposition to cardiovascular disease in the offspring

Cardiovascular disease is one of the most significant causes of death globally, especially in regions where unhealthy diets are prevalent and dietary fibre intake is low.1,2 Fibre, particularly prebiotic types that feed gut microbes, is essential for maintaining healthy gut microbial ecosystems.3 One assumption has been that cardiovascular health relates directly to lifestyle choices in adult life. Here, we show in mice that some of these benefits operate from the prenatal stage and relate to the diet and gut microbiome of the mother. Intake of fibre during pregnancy shaped the mothers gut microbiome, which had a lasting founding effect on the offsprings microbial composition and function. Maternal fibre intake during pregnancy significantly changed the cardiac cellular and molecular landscape in the offspring, protecting them against the development of cardiac hypertrophy, remodelling, and inflammation. These suggest a role for foetal exposure to maternal-derived gut microbial metabolites, which are known to cross the placenta and drive epigenetic changes. Maternal fibre intake led to foetal epigenetic reprogramming of the atrial natriuretic peptide gene (Nppa), protective against heart failure. These results underscore the importance of dietary intake and the gut microbiome of the mother during pregnancy for cardiovascular disease in the offspring.

microbiology↗