Does intestinal dysbiosis contribute to an aberrant inflammatory response to SARS-CoV-2 in frail patients?

Abstract In few months, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has become the main health worldwide problem. Epidemiological studies revealed that population has different vulnerability to SARS-CoV-2: severe outcome of COVID-19, with an increased risk of death, is observed in patients with metabolic syndrome, diabetic and heart conditions (frail population). Excessive pro-inflammatory cytokine storm could be the main cause of enlarged vulnerability in frail population. In subjects with diabetes and/or heart disease, a low inflammatory state is often associated with gut dysbiosis. The increase of microbial metabolites (i.e. TMAO and LPS), generating an inflammatory microenvironment is probably associated with an improved risk of severe illness from COVID-19. Nutritional interventions aimed at restoring gut microbial balance could represent preventive strategies to protect frail population from COVID-19. This narrative review presents the possible molecular mechanisms by which intestinal dysbiosis, enhancing inflammatory state, could promote SARS-CoV-2 spreading infection. Some nutritional strategies to counteract inflammation state in frail patients are also analysed.