How the gut microbiome could affect COVID-19 severity


As of September 27, 2022, the coronavirus illness 2019 (COVID-19) has been answerable for over 6.5 million deaths worldwide. Attributable to the extreme acute respiratory syndrome coronavirus 2 (SARS-CoV-2), COVID-19 has been remarkably unpredictable in its scientific severity.

Because of this, many efforts have been made to find out the components that enhance a person’s danger of extreme or deadly COVID-19. A current Pathogens journal research opinions the potential position of the intestine microbiome in figuring out extreme COVID-19.

Research: Gut Microbiota and COVID-19: Potential Implications for Disease Severity. Picture Credit score: nobeastsofierce /


Earlier analysis has emphasised the significance of the intestine microbiome in regulating inflammatory processes at each native and systemic ranges. On account of its widespread communication with different organs and techniques inside the physique, the microbiome has additionally been known as the ‘second mind’ of the physique.

The danger of intestine dysbiosis has been proven to extend throughout SARS-CoV-2 an infection, in addition to post-acute COVID sequelae (PASC), the latter of which is extra generally often called ‘lengthy COVID.’ In these conditions, an elevated focus of opportunistic pathogenic species has been reported, whereas the variety of ‘good’ micro organism declined. Nonetheless, the reverse was additionally true, during which sufferers with fewer intestine signs had decrease possibilities of scientific deterioration.

Dysbiosis triggers irritation

SARS-CoV-2 positive aspects entry to the goal host cell by binding its receptor binding area (RBD) inside the viral spike protein S1 subunit to the angiotensin-converting enzyme 2 (ACE2) receptor.

The ACE2 receptor additionally has a significant position within the renin-angiotensin-aldosterone system (RAAS), which regulates blood stress. Subsequently, the downregulation of ACE2 throughout SARS-CoV-2 an infection can impression RAAS operate.

The cytokine storm, characterised by the extreme launch of cytokines, usually happens in extreme COVID-19. This arises following the detection of contaminated cells by innate immune cells, which subsequently triggers a hyperinflammatory immune response. Cytokines launch pro-inflammatory messenger molecules equivalent to interleukin-1 (IL-1), IL-6, IL-8, IL-12, tumor necrotic issue α (TNF-α), and interferon γ (IFN-γ) at excessive ranges into the circulation.

The cytokine storm then induces systemic vasodilation and will increase vascular permeability, thus resulting in thrombotic problems, pulmonary edema, and multi-organ failure. Essential and deadly outcomes are extra possible when these happen in folks with different danger components for heart problems or thrombosis. The systemic harm and multi-organ dysfunction characterize acute respiratory misery syndrome (ARDS).

Dysbiosis triggers systemic results

About one in 5 COVID-19 sufferers develop diarrhea, with or with out stomach discomfort or ache, sooner or later throughout the an infection. Viral RNA seems to persist within the intestine mucosa and stool of beforehand contaminated sufferers for over one month from symptom onset. Along with inflicting direct harm to the intestine cells, SARS-CoV-2 possible produces intestine harm by way of this inflammatory surroundings.

Some COVID-19 sufferers with diarrhea exhibit greater serum cytokine ranges, possible as a result of viral protein binding to epithelial cell proteins that assist type tight junctions. The ensuing disruption of the intestine epithelial barrier perturbs intracellular ion steadiness, thus inflicting colitis and infected intestine partitions. As well as, this will likely enable intestine micro organism to cross over into the systemic circulation, thereby contributing to systemic immune-mediated inflammatory injury.

Excessive ACE2 expression on the intestinal epithelium is essential to making sure a steady and wholesome microbiome composition and performance. Conversely, when ACE2 expression is lowered, sodium and amino acid uptake are additionally lowered, thus growing susceptibility to intestinal irritation.

Lowered ACE2 expression on intestinal epithelium weakens the mammalian goal of the rapamycin (mTOR) pathway, thus altering anti-microbial peptides (AMPs) expression with elevated autophagy. Interference with these interacting processes compromises enterocyte survival.

The weakened intestine barrier ends in power intestine dysfunction and altered absorption of amino acids like phenylalanine, tryptophan, glutamine, and leucine. These results can result in irritation, diarrhea, and dysbiosis.

Dysbiosis will increase vulnerability to respiratory an infection and its scientific severity. For instance, mice with antibiotic-induced intestine dysbiosis are extra vulnerable to influenza-induced lung irritation.

Dysbiosis will increase COVID-19 severity

A number of earlier research have proven that COVID-19 is prone to be much less extreme within the presence of an elevated abundance of seven bacterial lessons, notably Faecalibacterium prausnitzii and Alistipes onderdonkii. Each of those microorganism species regulate tryptophan metabolism and immune homeostasis. Faecalibacterium prausnitzii ranges are sometimes low in Western diets however excessive in Mediterranean diets.

Extreme COVID-19 has additionally been correlated with the presence of Coprobacillus, Clostridiumramosum, C.hathaway, and Erysipelotrichaceae. As well as, Coprobacillus is very correlated with diarrhea and irritation in irritable bowel illness (IBD).  

Notably, a number of species of Bacteroides cut back ACE2 expression within the rat colon and are related to much less extreme COVID-19.

Bacterial metabolites equivalent to short-chain fatty acids (SCFAs) that originate from the bacterial fermentation of dietary fiber is also related to homeostasis. Butyrate is especially essential because it maintains the integrity of the intestine epithelial barrier whereas modulating immune and inflammatory pathways all through the physique.

SCFAs additionally act in lots of different methods to scale back irritation. For instance, intestine dysbiosis reduces SCFA manufacturing by decreasing the related bacterial taxa whereas selling the abundance of opportunistic pathogens. These organisms can penetrate the weakened intestine mucosal barrier, subsequently inflicting secondary an infection in an already weak particular person and growing their danger of extreme or deadly outcomes.

COVID-19 triggers dysbiosis

In COVID-19 sufferers, the intestine microbiome is altered, with fewer commensal micro organism of main species like Bacteroides, helpful Lachnospiraceae, and Bifidobacterium. Concurrently, opportunistic pathogens like Streptococcus, Rothia, and a few species of Clostridia like C. hathawayi enhance.

Elevated indicators of irritation, equivalent to C-reactive protein (CRP), lactate dehydrogenase (LDH), gamma-glutamyl transferase (GGT), and circulating IL-6, IL-10, IFN-γ, and TNF-α ranges, have additionally been reported. These adjustments endured even one month after viral clearance.

Probiotics cut back COVID-19 severity

Probiotics, particularly these containing Bifidobacterium species, shorten higher respiratory infections by way of their anti-inflammatory results which are mediated by their modulation of the intestine microbiome. Thus, analysis signifies that probiotic supplementation may cut back COVID-19 severity.

Beforehand, probiotics elevated virus-specific immunoglobulin M (IgM) and IgG with out inflicting a big change within the fecal microbiota profile. This means a direct motion of IgG on immunity slightly than by way of altered intestine microbiome composition.

ACE and COVID-19 severity

A number of research have recognized sufferers with pre-existing lung illness, most cancers, stable transplants, older age (70 years or above), weight problems, heart problems, and metabolic syndrome as having the next danger of extreme and deadly COVID-19. This could possibly be because of adjustments in ACE2 exercise involving RAAS. For instance, lung most cancers or diabetes sufferers categorical ACE2 at the next baseline degree.

SARS-CoV-2 an infection causes elevated ACE2 expression within the lungs and kidneys, particularly in aged sufferers and people with power lung illness, diabetes, and hypertension. This might result in extreme activation of the ACE-Angiotensin II-angiotensin 1 receptor axis.

The results of those actions embody vascular harm and dysfunction, irritation and fibrosis of the lungs and coronary heart muscle, kidney harm, and insulin resistance with elevated oxidative stress.

The involvement of the infection-induced dysregulation of ACE-2, comorbidities, and alterations in the gut microbiota during COVID-19 and the beneficial effects of dietary supplements in restoring the microbiota and immune homeostasis.The involvement of the infection-induced dysregulation of ACE-2, comorbidities, and alterations within the intestine microbiota throughout COVID-19 and the helpful results of dietary dietary supplements in restoring the microbiota and immune homeostasis.

Diet and COVID-19

Overweight people have power low-grade irritation with excessive inflammatory mediators produced by visceral fats deposits and innate immune cells. This enhances the chance of cytokine storm after viral an infection, additional exacerbated by the accompanying intestine dysbiosis and stress on the lungs.

East Asian nations, lots of which predominantly eat rice, reported a lot decrease COVID-19 mortality charges than wheat-eating nations in the remainder of the world.  

Vitamin D modulates T-cell operate, subsequently decreasing inflammatory mediators whereas growing anti-inflammatory molecules like IL-10 and its motion on innate immune operate. Supplementation with vitamin D may cut back the chance of extreme an infection and dying associated to COVID-19.

Nutritional vitamins C, E, and A, in addition to metals like zinc and iron, are potent anti-inflammatory and antioxidant compounds that act by way of varied pathways. Sustaining omega-3 fatty acids at an sufficient degree whereas preserving their ratio with omega-6 fatty acids at 1:5, respectively, is a probably essential protecting measure. Total, a plant-based eating regimen enriched with purposeful meals and dietary supplements may assist shield in opposition to respiratory infections.


The intestine microbiome composition considerably determines how the immune system responds to a number of pathogens, together with SARS-CoV-2. Moreover, dysbiosis could be thought-about a danger issue for and the results of extreme COVID-19.

It’s clear that interventions aiming to re-establish an accurate microbiota composition are essential for growing a extra holistic method to managing a sequence of illnesses, together with COVID-19….methods aimed toward way of life and dietary modifications may also help to positively modulate the intestine microbiome and play a preventive position in SARS-CoV-2 viral an infection.”

Journal reference:

  • Rocchi, G., Giovanetti, M., Benedetti, F., et al. (2022). Intestine Microbiota and COVID-19: Potential Implications for Illness Severity. Pathogens. doi:10.3390/pathogens11091050.
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