Obesity-Related Inflammation and Endothelial Dysfunction in COVID-19: Impact on Disease Severity

Abstract

The coronavirus disease 2019 (COVID-19) pandemic has put into evidence another pandemic - obesity. Currently, several studies have documented the association between obesity and COVID-19 severity. The mechanisms underlying the increased risk of complications and mortality in obese patients with COVID-19 are of diverse nature. Inflammation plays a central role in obesity. Metabolic alterations seen in obese patients are related to an inflammatory response, and several studies report elevated levels of circulating inflammatory cytokines in obese patients. Also, deregulated expression of adipokines, such as leptin and resistin, increase the expression of vascular adhesion molecule 1 and intercellular adhesion molecule 1 that contribute to increased vascular leukocyte adhesiveness and additional oxidative stress. Additionally, it is now recognized that the chronic impairment of systemic vascular endothelial function in patients with cardiovascular and metabolic disorders, including obesity, when intensified by the detrimental effects of SARS-CoV-2 over the endothelium, may explain their worse outcomes in COVID-19. In fact, vascular endothelial dysfunction may contribute to a unfavorable response of the endothelium to the infection by SARS-CoV-2, whereas alterations in cardiac structure and function and the prothrombotic environment in obesity may also provide a link to the increased cardiovascular events in these patients.

Keywords: COVID-19; endothelial dysfunction; inflammation; microcirculation; obesity.

Figure 1

The mechanisms underlying the increased risk of complications and mortality in obese patients with COVID-19 based on the association of low-grade inflammation, adipose tissue dysfunction and endothelial dysfunction: In obese patients with COVID-19 or SARS-CoV-2, as well as, the bacterial endotoxins (LPS) of the intestinal bacterial translocation promote the activation of TLR4 in favor of the MyD88-dependent pro-inflammatory pathway. The activation of NF-κB is linked to the production of TNF-α, IL-1β, IL-6, IL-12 and other cytokines, contributing to the activation of NLRP3 inflammasomes and increased expression of ECA2. In the adipose tissue of patients with COVID-19, there is an increase in the expression of ECA2, promoting greater entry of SARS-CoV-2, making this tissue a viral reservoir. Metabolic inflammation in obese patients is characterized by dysfunctional adipose tissue, with mitochondrial dysfunction and decreased fatty acid oxidation, causing an amount of inflammatory cells showing an increase in the influx of M1 macrophages and chemotactic signaling, via MCP-1 and release of IL-8 by adipocytes, associated with an increase in reactive oxygen species. Associated with this process of immune activation, obese patients with COVID-19 have systemic microvascular dysfunction and a predisposition to thrombus formation that is exacerbated by higher levels of circulating inflammatory cytokines, such as TNF-α, IL-1β and IL-6, worsening the outcomes in COVID-19.