ABSTRACT
Background: COVID-19 due to SARS-CoV-2 infection has had an enormous adverse impact on global public health. As the COVID-19 pandemic evolves, the WHO declared several variants of concern (VOCs), including Alpha, Beta, Gamma, Delta, and Omicron. Compared with earlier variants, Omicron, now a dominant lineage, exhibits characteristics of enhanced transmissibility, tropism shift toward the upper respiratory tract, and attenuated disease severity. The robust transmission of Omicron despite attenuated disease severity still poses a great challenge for pandemic control. Under this circumstance, its tropism shift may be utilized for discovering effective preventive approaches. Scope and approach: This review aims to estimate the potential of green tea epigallocatechin gallate (EGCG), the most potent antiviral catechin, in neutralizing SARS-CoV-2 Omicron variant, based on current knowledge concerning EGCG distribution in tissues and Omicron tropism. Key findings and conclusions: EGCG has a low bioavailability. Plasma EGCG levels are in the range of submicromolar concentrations following green tea drinking, or reach at most low µM concentrations after pharmacological intervention. Nonetheless, its levels in the upper respiratory tract could reach concentrations as high as tens or even hundreds of µM following green tea consumption or pharmacological intervention. An approach for delivering sufficiently high concentrations of EGCG in the pharynx has been developed. Convincing data have demonstrated that EGCG at tens to hundreds of µM can dramatically neutralize SARS-CoV-2 and effectively eliminate SARS-CoV-2-induced cytopathic effects and plaque formation. Thus, EGCG, which exhibits hyperaccumulation in the upper respiratory tract, deserves closer investigation as an antiviral in the current global battle against COVID-19, given Omicron's greater tropism toward the upper respiratory tract.
ABSTRACT
Diabetes mellitus is a metabolic disease that causes hyperglycemia. In COVID-19 patients the severity of the disease depends on myriad factors but diabetes mellitus is the most important comorbidity. The current review was conducted to investigate the virulence of SARS-CoV-2 and disease severity of COVID-19 in type 2 diabetes mellitus patients and relevant treatment. The literature published in PubMed, Scopus, Web of Science, and Google Scholar was reviewed up to September 2021. The keywords including SARS-CoV-2, type 2 diabetes mellitus in COVID-19, hyperglycemia in COVID-19, opportunistic infections in type 2 diabetes mellitus and COVID-19 were used in different combinations. Hyperglycemic individuals over-express ACE-2 receptors in the lungs thus increasing the SARS-CoV-2 susceptibility and replication. Although dipeptidyl peptidase-4 plays an important role in glucose homeostasis, additionally it also stimulates the production of proinflammatory cytokines such as IL-6 and TNF-α creating a cytokine storm. Cytokine storm might be responsible for respiratory insufficiency in severe COVID-19 patients. Type 2 diabetes mellitus is associated with immunosuppression and the patients are prone to get many opportunistic infections. Type 2 diabetes mellitus patients with severe COVID-19 have lymphopenia. Moreover, in type 2 diabetes mellitus patients the neutrophils exhibit decreased chemotaxis, hydrogen peroxide production, and phagocytosis. Reduction in lymphocyte count and defective neutrophil capacity renders them with COVID-19 susceptible to opportunistic bacterial and fungal infections increasing the mortality rate. The opportunistic bacterial infections in COVID-19 patients were due to Staphylococcus aureus, Streptococcus pneumonia, and coagulase-negative Staphylococci, E. coli, Pseudomonas aeruginosa, and Klebsiella sp. In COVID-19 patients with type 2 diabetes mellitus, mucormycosis was found to be the most common fungal infection with a higher predilection to males. Hyperglycemia in COVID-19 patients with type 2 diabetes mellitus enhances the SARS-CoV-2 replication with an adverse outcome. A strong correlation exists between the poor prognosis of COVID-19 and type 2 diabetes mellitus. Proper glycemic control in COVID-19 patients with diabetes mellitus might lessen the severity of the disease.
ABSTRACT
The occurrence of the novel severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), responsible for coronavirus disease 2019 (COVD-19), represents a catastrophic threat to global health. Protruding from the viral surface is a densely glycosylated spike (S) protein, which engages angiotensin-converting enzyme 2 (ACE2) to mediate host cell entry. However, studies have reported viral susceptibility in intra- and extrapulmonary immune and non-immune cells lacking ACE2, suggesting that the S protein may exploit additional receptors for infection. Studies have demonstrated interactions between S protein and innate immune system, including C-lectin type receptors (CLR), toll-like receptors (TLR) and neuropilin-1 (NRP1), and the non-immune receptor glucose regulated protein 78 (GRP78). Recognition of carbohydrate moieties clustered on the surface of the S protein may drive receptor-dependent internalization, accentuate severe immunopathological inflammation, and allow for systemic spread of infection, independent of ACE2. Furthermore, targeting TLRs, CLRs, and other receptors (Ezrin and dipeptidyl peptidase-4) that do not directly engage SARS-CoV-2 S protein, but may contribute to augmented anti-viral immunity and viral clearance, may represent therapeutic targets against COVID-19.