Adipose tissue, obesity, and Covid-19
individuals, the release of PAI-1 is upregulated. Over-secretion of PAI-1 results in impaired fibrinolysis. 34 This means that clots that have been formed are broken down less well.
Obesity therefore results in a pro-thrombotic state. I have only explored three reasons for this but there are numerous other associations. Research has found that, in obese individuals, there are higher levels of vonWildebrand factor, factor VII, factor VIII and fibrinogen: these are all involved in the coagulation cascade and coagulation of the blood. 35 It is said that platelets in obese people are ‘angrier’ because it has been reported that their size and volume is increased. 36 Finally, insulin resistance also leads to increased thrombosis and increased platelet activation.
Obesity as a risk factor for Covid-19
Recently, it has been made apparent that obesity is a risk factor for Covid-19 and by analysing the complications brought on by this coronavirus it is apparent that people with a larger BMI are more at danger if infected. Exposure to the virus leaves patients vulnerable to thrombotic complications both in the venous and atrial circulations. This is as a result of excessive inflammation, endothelial dysfunction and enhanced platelet aggregation all of which are elevated in obese individuals. A study done in the Netherlands by Bikdeli et al found that thrombotic complications were frequent in Covid- 19 infected patients, 31% out of 184 critically ill patients had severe thrombosis. 37 Furthermore, the cytokine storm associated with this pathogen leads to a severe inflammatory response (inwhich IL-6 plays a central role). Zhou et al (2020) and Ruan et al (2020) both identified high levels of IL-6 as a prediction of a fatal response to the infection. 38 D-dimer is a breakdown product of thrombosis and D-dimer levels have also been associated with severe disease and mortality (Tang et al- February 2020). 39 Obese individuals naturally have higher levels of IL-6 and inflammatory cytokines in their blood plasma. The strong inflammatory response can lead to organ failure in different areas of the body. Although no clinical studies have confirmed these pathways as risk factors for obesity in COVID- 19, it seems that obese individuals are more likely to develop severe symptoms as a result of a chronic state of inflammation and a pro-thrombotic state.
Conclusion
Obesity directly leads to AT dysfunctionality. This in turn causes an upregulation of pro-inflammatory adipokines secreted from AT and surrounding macrophages. The inflammatory state is an initiator for the coagulation cascade and a pro-thrombotic state with a decreased ability to break down clots. It is known that all these factors increase the risk of developing various cardiovascular diseases, insulin resistance, type 2 diabetes and cancer. It appears that obese people are more at risk from COVID-19.
34 Vilahur et al. (n.4). 35 Vilahur et al. (n.4).
36 Park et al, 2009 available at https://www.tandfonline.com/doi/abs/10.1080/095371002220148332. Coban et al, 2005 available at https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1742-1241.2005.00500.x. 37 Bikdeli et al, 2020 available at https://www.sciencedirect.com/science/article/pii/S0735109720350087. 38 Zhou et al, 2020 available at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7151347/. Ruan et al, 2020 available at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7272974/. 39 Tang et al. (n. 29).
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