A group of Brazilian researchers discovered one of the most serious causes of Covid-19 in diabetic patients. As laboratory experiments have shown, the highest blood glucose content is captured by a type of defense cell known as a monocyte and serves as an extra energy source that allows the new coronavirus to replicate more than in an organism healthy. In response to the increasing viral load, monocytes start to release a large amount of cytokines (proteins with inflammatory action), which cause a series of effects, such as the death of lung cells.
The study, supported by the São Paulo State Research Support Foundation (Fapesp), is led by Pedro Moraes-Vieira, professor at the Institute of Biology at the State University of Campinas (IB-Unicamp), and by researchers who are part of the force – task against the university’s covid-19, coordinated by Marcelo Mori, also a professor at IB-Unicamp and co-author of the work.
The article is under review at Cell Metabolism, but is now available in preprint version, not yet peer reviewed.
“The work shows a causal relationship between increased glucose levels with what has been seen in the clinic: greater severity of covid-19 in patients with diabetes”, says Moraes-Vieira, a researcher at the Experimental Medicine Research Cluster (EMRC) and the Center on Obesity and Comorbidities (OCRC), a Research, Innovation and Dissemination Center (CEPID) supported by Fapesp, headquartered at Unicamp.
Using bioinformatics tools, the researchers initially analyzed public lung cell data from patients with medium and severe covid-19. An overexpression of genes involved in the so-called alpha and beta interferon signaling pathway was observed, which is linked to the antiviral response.
The researchers also observed in the lungs of critically ill patients with covid-19 a large amount of monocytes and macrophages, two defense cells and control of the body’s homeostasis.
Monocytes and macrophages were the most abundant cells in the samples and the analyzes showed that the so-called glycolytic pathway, which metabolizes glucose, was greatly increased.
The bioinformatics analyzes were carried out by researchers Helder Nakaya, professor at the Faculty of Pharmaceutical Sciences at the University of São Paulo (FCF-USP), and Robson Carvalho, professor at the Botucatu Biosciences Institute at the Universidade Estadual Paulista (IBB-Unesp).
Glucose and viruses
The Unicamp group then carried out a series of tests with monocytes infected with the new coronavirus, in which they were grown in different concentrations of glucose. The experiments were carried out at the Laboratory for Emerging Virus Studies (Leve), which has biosafety level 3 – one of the highest – and is coordinated by José Luiz Proença Modena, professor at IB-Unicamp supported by FAPESP and co-author of the work.
“The higher the concentration of glucose in the monocyte, the more the virus replicated and the more the defense cells produced molecules such as interleukins 6 and 1 beta and the tumor necrosis factor alpha, which are associated with the phenomenon known as cytokine storm, in that not only the lung, but the whole organism, is exposed to this uncontrolled immune response, triggering several systemic changes observed in critically ill patients and that can lead to death “, says Moraes-Vieira.
The researchers then used, in the infected cells, a drug known as 2-DG, used to inhibit the flow of glucose. They observed that the treatment completely blocked the replication of the virus, as well as increased expression of the cytokines previously observed and the ACE-2 protein, the one by which the coronavirus invades human cells.
In addition, they used a drug that is being tested on patients with some cancers. Like some analogues, 3-PO inhibits the action of a gene involved in increasing the flow of glucose into cells. The result of its application was the same as that of 2-DG: less viral replication and less expression of inflammatory cytokines.
The results that indicated greater activity of the glycolytic pathway against infection were obtained through proteomic analyzes of the infected monocytes, carried out in collaboration with Daniel Martins-de-Souza, professor at IB-Unicamp supported by Fapesp.
Finally, the analyzes showed that the mechanism was mediated by the factor induced by hypoxia 1 alpha. As it is studied in several diseases, it is known that this pathway is kept stable, in part by the presence of reactive oxygen species in the mitochondria, the cells’ power plant.
The researchers then used antioxidants in the infected cells and saw that hypoxia 1 alpha decreased its activity and thus failed to influence glucose metabolism. As a consequence, it stopped the virus from replicating in the monocytes, the infected defense cells, which no longer produced cytokines toxic to the organism.
“When we intervene in the monocyte with antioxidants or with drugs that inhibit glucose metabolism, we reverse the replication of the virus and also the dysfunction in other defense cells, the T lymphocytes. With this, we also prevent lung cell death”, says Moraes -Scallop.
The studies with T lymphocytes and the analysis of the expression of hypoxia 1 alfa in patients were carried out in collaboration with Alessandro Farias, professor at IB-Unicamp and co-author of the work.
Since the drugs used in cell experiments are currently in clinical trials for some types of cancer, they could be tested in the future with patients with covid-19.
The first authors of the work are Ana Campos Codo, Fapesp master’s scholarship holder; Gustavo Gastão Davanzo, who has a doctoral scholarship from Fapesp and Lauar de Brito Monteiro, also a doctoral fellow, all at IB-Unicamp under the guidance of Moraes-Vieira.
“This work was only possible due to collaborations, the commitment of graduate students, who have been working night and day on this project, and the fast financing of FAEPEX [Fundo de Apoio ao Ensino, à Pesquisa e à Extensão] Unicamp and Fapesp “, says Moraes-Vieira.