Laurent Lagrost, Research Director at Inserm (National Institute of Health and Medical Research) at the University of Burgundy in Dijon, was among the first to warn of the coronavirus epidemic’s impending arrival in France. He was interviewed by La Ligue contre l’obésité (League Against Obesity). According to his research, obesity is a major risk factor for a dangerous form of the coronavirus. Immune memory, particularly BCG or tuberculosis, could aid in the reduction of severe or critical forms of Covid-19.
Obesity a major risk factor
Laurent Lagrost suggests that obesity is a major risk factor for critical and fatal forms of Covid-19. This risk must therefore be taken very seriously. When asked, “Does obesity necessarily have to be linked to diabetes or hypertension to be considered a major risk factor for Covid-19?” He explains that in fact, diabetes, high blood pressure, and metabolic syndrome seem to add to the risk of overweight itself. These different risk factors very often coexist and it is, for the time being, difficult to distinguish between things. However, he remains convinced that hypertrophy, the accumulation of adipose tissue has its own inflammatory properties and consequences.
Numerous studies carried out in the United Kingdom, the United States, China, and even in France, for example with the first data from the REVA network, have fairly quickly demonstrated an obvious link between obesity and the severe form of the coronavirus.
How do the cellular and molecular composition of adipose tissue determine the risk associated with obesity? Several explanations seem to be emerging today, all of which are related to the nature, composition, and inflammatory response of adipose tissue. As a result, it appears necessary to recall that obesity is characterized by adipose tissue hypertrophy. It is a real reservoir of energy fuel that is stored in large cells known as adipocytes. Because the SARS-CoV-2 virus has a high affinity for ACE2, an enzyme that acts as a receptor to allow the virus to enter cells, adipose tissue could serve as a potential reservoir for the virus.
Inserm team in Dijon recently succeeded in modeling two types of adipose tissue in mice. One, inflammatory and immunocompetent cell-rich in obese mice fed a diet high in fat and sugars was associated with decreased lifespan compared to lean control mice. The other, without infiltrated immunocompetent cells and with little oxidation and inflammation in mice subjected to the same obesogenic diet but supplemented with a complex formulation of antioxidants based on plant polyphenols was associated with a normal lifespan ( work published in Scientific Reports in June 2019). For an equal mass, adipose tissue does not always show the same dangerousness. It was thus possible to avoid colonization of adipose tissue by macrophages and when this was the case, they were able to improve the health and lifespan of the animals.
In mouse models, they have succeeded in preventing the accumulation of macrophages in adipose tissue through long-term nutritional supplementation. When dealing with macrophages already resident in adipose tissue, it would be illusory to eliminate them. The objective here would rather be to control them and to extinguish their proinflammatory properties. The trick? By applying the concept of vaccination and trained or educated immunity, the famous ” trained immunity”. Or how to educate the resident macrophages of adipose tissue in order to obtain a proportionate inflammatory response and limit the inflammatory boost and the dreaded cytokine storm. So, blocking the deleterious consequences of obesity on resistance and survival against SARS-CoV-2 and Covid-19 by controlling the inflammatory response of immunocompetent cells residing in numbers in the tissue adipose.
BCG Vaccine reduces the severity of COVID-19
BCG vaccination could help reduce severe and fatal forms of Covid-19. Why? The education of our immune system could be possible, thanks in particular to BCG which is composed of attenuated and living bovine bacilli. They could help contain the exacerbated inflammatory response of macrophages, especially and possibly those residing in adipose tissue. The most recent studies suggest that the learning capacities, following vaccination, would be very real for monocytes and macrophages. So, why not the macrophages of adipose tissue, and why not thus control the inflammatory response in obese patients by suppressing this storm, this so dreaded inflammatory boost and at the origin of the most critical and potentially fatal forms of Covid-19 disease?
As the WHO regularly reminds us, obesity is a public health problem. But, the stigma and discrimination of overweight people often feeds on risk factors, real or suspected, that are linked to obesity. We can only regret that adipose tissue is still too often considered an unsightly, superfluous, potentially dangerous and ultimately useless mass of fat. So it would be time to focus not only on the quantitative aspect but on the qualitative aspect. Adipose tissue is in fact a complex organ made up of several cell types with well-defined and essential functions.
Source and Related Articles:
- Pasquarelli-do-Nascimento G, Braz-de-Melo HA, Faria SS, Santos IO, Kobinger GP, Magalhães KG. Hypercoagulopathy and Adipose Tissue Exacerbated Inflammation May Explain Higher Mortality in COVID-19 Patients With Obesity. Front Endocrinol (Lausanne). 2020 Jul 28;11:530. doi: 10.3389/fendo.2020.00530. PMID: 32849309; PMCID: PMC7399077.
- Ryan, P.M. and Caplice, N.M. (2020), Is Adipose Tissue a Reservoir for Viral Spread, Immune Activation, and Cytokine Amplification in Coronavirus Disease 2019?. Obesity, 28: 1191-1194. https://doi.org/10.1002/oby.22843
- Malavazos, A.E., Corsi Romanelli, M.M., Bandera, F. and Iacobellis, G. (2020), Targeting the Adipose Tissue in COVID‐19. Obesity, 28: 1178-1179. https://doi.org/10.1002/oby.22844