How the intestine microbiome might have an effect on COVID-19 severity

As of September 27, 2022, the coronavirus illness 2019 (COVID-19) has been liable 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 medical severity.

In consequence, many efforts have been made to find out the elements that improve a person’s threat of extreme or deadly COVID-19. A current Pathogens journal examine evaluations the potential position of the intestine microbiome in figuring out extreme COVID-19.

Study: Gut Microbiota and COVID-19: Potential Implications for Disease Severity. Image Credit: nobeastsofierce /

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. Because of its widespread communication with different organs and programs 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. Nevertheless, the reverse was additionally true, during which sufferers with fewer intestine signs had decrease possibilities of medical deterioration.

Dysbiosis triggers irritation

SARS-CoV-2 features 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 an important position within the renin-angiotensin-aldosterone system (RAAS), which regulates blood stress. Subsequently, the downregulation of ACE2 throughout SARS-CoV-2 an infection can influence RAAS operate.

The cytokine storm, characterised by the extreme launch of cytokines, typically 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 comparable 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 issues, pulmonary edema, and multi-organ failure. Important and deadly outcomes are extra probably when these happen in individuals with different threat elements 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 belly 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 probably produces intestine harm by this inflammatory setting.

Some COVID-19 sufferers with diarrhea exhibit greater serum cytokine ranges, probably as a result of viral protein binding to epithelial cell proteins that assist kind tight junctions. The ensuing disruption of the intestine epithelial barrier perturbs intracellular ion stability, thus inflicting colitis and infected intestine partitions. As well as, this may increasingly 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 vital to making sure a steady and wholesome microbiome composition and performance. Conversely, when ACE2 expression is diminished, sodium and amino acid uptake are additionally diminished, thus rising 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 leads to 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 medical 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 extremely 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 comparable to short-chain fatty acids (SCFAs) that originate from the bacterial fermentation of dietary fiber is also related to homeostasis. Butyrate is especially necessary 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 rising their threat 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 improve.

Elevated indicators of irritation, comparable 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 modifications continued even one month after viral clearance.

Probiotics cut back COVID-19 severity

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

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

ACE and COVID-19 severity

A number of research have recognized sufferers with pre-existing lung illness, most cancers, strong transplants, older age (70 years or above), weight problems, heart problems, and metabolic syndrome as having the next threat of extreme and deadly COVID-19. This may very well be as a consequence of modifications in ACE2 exercise involving RAAS. For instance, lung most cancers or diabetes sufferers specific ACE2 at the next baseline stage.

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.

Vitamin 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 danger of cytokine storm after viral an infection, additional exacerbated by the accompanying intestine dysbiosis and stress on the lungs.

East Asian nations, a lot 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 rising anti-inflammatory molecules like IL-10 and its motion on innate immune operate. Supplementation with vitamin D might cut back the danger of extreme an infection and demise 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 varied pathways. Sustaining omega-3 fatty acids at an ample stage whereas preserving their ratio with omega-6 fatty acids at 1:5, respectively, is a doubtlessly essential protecting measure. General, a plant-based weight loss plan enriched with practical meals and dietary supplements might assist defend 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 might be thought of a threat issue for and the results of extreme COVID-19.

It’s clear that interventions aiming to re-establish an accurate microbiota composition are necessary for growing a extra holistic strategy to managing a collection of ailments, together with COVID-19….methods aimed toward life-style and dietary modifications might 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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