Introduction

A metabolic syndrome is a group of risk factors that includes high blood pressure, high blood sugar, unhealthy cholesterol levels, obesity and increased levels of abdominal fat. At present, one of the fastest-growing pandemics of chronic diseases is obesity. It carries a 39% global prevalence among children and adults. The pathophysiology of obesity is complex associated with hyperplasia and hypertrophy of the adipose tissue.  The COVID-19 pandemic is associated with increased hospitalization and mortality. It is predominantly seen in the elderly population and patients with underlying conditions such as obesity and related comorbidities.

Pathophysiology of COVID-19 in obesity

The risk of complications and mortality in COVID – 19 is high in patients with obesity. This increased risk of developing complications can be attributed to multiple potential mechanisms such as the delayed immune response, impaired metabolic response and chronic basal inflammatory state.

It has been suggested that the SARS-CoV-2 infection targets the alveolar macrophages expressing angiotensin-converting enzyme 2 (ACE2). These activated macrophages may play a major role in the cytokine storm. The expression of ACE2 receptors level is higher in adipose tissue than that in lung tissue. As individuals with obesity have more adipose tissue, this translates into an increased number of ACE2 expressing cells and this adipose tissue constitutes a reservoir for SARS-CoV-2 increasing the viral load.

Adipose tissue is also a source of many pro-inflammatory mediators and hormones. The chronic low-grade inflammatory state in obesity is associated with high serum baseline CRP in overweight individuals.

Fat Inflammation in Obesity:

Adipose tissue in the body stores the energy provided by food, and it represents an independent endocrine organ. Adipose tissues release a great quantity of bioactive peptides named “adipokines,” which play a central role in both immunity and vascular homeostasis. These molecules modulate a wide variety of functions, from appetite control to inflammatory response and can exert pro-inflammatory actions (such as leptin) or anti-inflammatory actions, such as adiponectin. The crucial step in increased obesity-related inflammation is the massive infiltration of adipose tissue by mediators such as monocyte chemoattractant protein-1 (MCP-1). These circulating levels are elevated in obesity and the mediators recruit monocytes and macrophages into the adipose tissue and blood vessels.  This process contributes to cardiovascular events, which are frequent complications in COVID-19 patients.

Clinical Course of Obese COVID-19 Patients

There have been various studies done worldwide on obese patients to analyse the severity of COVID 19 illness. Patients with metabolic syndrome and infected with COVID 19 were associated with greater risks of adverse events.

One recent international multicenter retrospective meta-analysis has extracted data from health care records and regional databases of hospitalized adult patients with COVID-19 (published in the International Diabetes Consortium in April 2021) from 18 sites in 11 countries. The Society of Critical Care Medicine conducted a multicenter cohort study, which gathered data from the Discovery Viral Respiratory Illness Universal Study (collected from 181 hospitals across 26 countries over one year period February 2020 – 2021).

The studies compared data from COVID 19 patients with and without metabolic syndrome. From the analysis, it was concluded that patients with metabolic syndrome were associated with increased risk of ICU admission,  invasive mechanical ventilation, ARDS, mortality and prolonged hospital and ICU length of stay.

 Conclusion

Metabolic syndrome is a chronic low-grade inflammatory state characterized by subtly elevated acute-phase reactant levels and endothelial dysfunction. The combined characteristics of metabolic syndrome–associated comorbidities may be linked with driving COVID-19 mortality through its systemic inflammation and endothelial dysfunction. This chronic inflammatory state in obese individuals is considered as the source for initiating the cytokine storm in COVID-19 patients. There is an established association between obesity and the severity of COVID-19.  People with increased visceral adipose tissue significantly raise the possibility of a more severe course of COVID-19 and have been associated with increased risks of ARDS and death in patients hospitalized with COVID-19. The proportion of patients who required invasive mechanical ventilation increased with obese patients, and it was the greatest in patients with a BMI above 35 kg/m2.

People worldwide should be encouraged to improve their lifestyle to reduce risks during the current pandemic of COVID-19 to improve both short and long-term COVID-19 outcomes.

Dr. Karishma Puthanpura
Department of Critical Care
Kauvery Hospital Chennai