Overweight/obesity as the potentially most important lifestyle factor associated with signs of pneumonia in COVID-19

PLOS
  • Published: November 18, 2020

Abstract

Objective

The occurrence of pneumonia separates severe cases of COVID-19 from the majority of cases with mild disease. However, the factors determining whether or not pneumonia develops remain to be fully uncovered. We therefore explored the associations of several lifestyle factors with signs of pneumonia in COVID-19.

Methods

Between May and July 2020, we conducted an online survey of 201 adults in Germany who had recently gone through COVID-19, predominantly as outpatients. Of these, 165 had a PCR-based diagnosis and 36 had a retrospective diagnosis by antibody testing. The survey covered demographic information, eight lifestyle factors, comorbidities and medication use. We defined the main outcome as the presence vs. the absence of signs of pneumonia, represented by dyspnea, the requirement for oxygen therapy or intubation.

Results

Signs of pneumonia occurred in 39 of the 165 individuals with a PCR-based diagnosis of COVID-19 (23.6%). Among the lifestyle factors examined, only overweight/obesity was associated with signs of pneumonia (odds ratio 2.68 (1.29–5.59) p = 0.008). The observed association remained significant after multivariate adjustment, with BMI as a metric variable, and also after including the antibody-positive individuals into the analysis.

Conclusions

This exploratory study finds an association of overweight/obesity with signs of pneumonia in COVID-19. This finding suggests that a signal proportional to body fat mass, such as the hormone leptin, impairs the body’s ability to clear SARS-CoV-2 before pneumonia develops. This hypothesis concurs with previous work and should be investigated further to possibly reduce the proportion of severe cases of COVID-19.

For More Information: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0237799

Hyperglycemia in Acute COVID-19 is Characterized by Adipose Tissue Dysfunction and Insulin Resistance

Authors: Reiterer MRajan MGómez-Banoy NLau JDGomez-Escobar LGGilani AAlvarez-Mulett SSholle ETChandar VBram YHoffman KRubio-Navarro AUhl SShukla APGoyal PtenOever BRAlonso LCSchwartz RESchenck EJSafford MM

Abstract 


COVID-19 has proven to be a metabolic disease resulting in adverse outcomes in individuals with diabetes or obesity. Patients infected with SARS-CoV-2 and hyperglycemia suffer from longer hospital stays, higher risk of developing acute respiratory distress syndrome (ARDS), and increased mortality compared to those who do not develop hyperglycemia. Nevertheless, the pathophysiological mechanism(s) of hyperglycemia in COVID-19 remains poorly characterized. Here we show that insulin resistance rather than pancreatic beta cell failure is the prevalent cause of hyperglycemia in COVID-19 patients with ARDS, independent of glucocorticoid treatment. A screen of protein hormones that regulate glucose homeostasis reveals that the insulin sensitizing adipokine adiponectin is reduced in hyperglycemic COVID-19 patients. Hamsters infected with SARS-CoV-2 also have diminished expression of adiponectin. Together these data suggest that adipose tissue dysfunction may be a driver of insulin resistance and adverse outcomes in acute COVID-19.

The deadly COVID-19 pandemic is underscored by the high morbidity and mortality rates seen in certain vulnerable populations, including patients with diabetes mellitus (DM), obesity, cardiovascular disease, and advanced age, with the latter associated with many chronic cardiometabolic diseases 14 . Hyperglycemia with or without a history of DM is a strong predictor of in-hospital adverse outcomes, portending a 7-fold higher mortality compared to patients with well-controlled blood glucose levels 5 . Hyperglycemia may be seen as a biomarker that predicts poor prognosis. A retrospective study that compared hyperglycemic patients that were treated with insulin against those who were not showed increased mortality in those receiving insulin 6 . However, it remains unclear whether insulin treatment is a surrogate for increased hyperglycemia and overall morbidity, or whether it is an actual causative factor for death. There is thus uncertainty regarding specific treatments for hyperglycemia in acute COVID-19 7 .

Despite our early recognition of the association between hyperglycemia and perilous outcomes, the pathophysiological mechanisms that underlie hyperglycemia in COVID-19 remain undefined 8,9 . Hypotheses have included a broad range of pathologies from direct infection of islets leading to beta cell failure (BCF) and to inflammation and glucocorticoids leading to insulin resistance (IR). Although COVID-19 is primarily a respiratory tract infection, SARS-CoV-2 is known to infect other cell types and often leads to extrapulmonary consequences 10,11 ACE2 and other entry receptors for SARS-CoV-2 can be expressed on pancreatic islet cells and endocrine cells differentiated from human pluripotent stem cells are permissive to infection 12 . Early reports of unexpected diabetic ketoacidosis (DKA) in COVID-19 patients fuelled concerns for a novel form of acute onset beta cell failure. For example, one case described a patient with new onset diabetic ketoacidosis (DKA) who was found to be autoantibody negative for type 1 DM (T1DM) but showed evidence of prior SARS-CoV-2 infection based on serology results, suggesting the possibility of pancreatic beta cell dysfunction or destruction as a result of COVID-19 13 . However, given the high rates of COVID-19 during this pandemic coupled with low background rates of new onset T1DM, the connection between these two events in this case could be “true, true, and unrelated.” Recent studies disagree on whether ACE2 is expressed on pancreatic beta cells or whether the SARS-CoV-2 virus is found in pancreatic beta cells of deceased individuals with COVID-19 1416 . Conversely, the well-known connection between obesity and insulin resistance might lead to impaired immunity and more severe SARS-CoV-2 infection 17 . In fact, population level studies have reported higher risk of complications in obese patients with COVID-19 1820 . Viral infection may lead to systemic insulin resistance and worsened hyperglycemia. In sum, despite much attention, the pathophysiology of hyperglycemia in COVID-19 remains unknown.

Dexamethasone substantially reduces mortality in patients with severe COVID-19 infection requiring oxygen or invasive mechanical ventilation 21 . Glucocorticoids can also provoke hyperglycemia by inducing insulin resistance and beta cell dysfunction. The widespread usage of dexamethasone in severe SARS-CoV-2 infection is sure to exacerbate both the incidence and severity of hyperglycemia in COVID-19.

For More Information: https://europepmc.org/article/PPR/PPR303316

Pathophysiology of COVID-19:

Mechanisms Underlying Disease Severity and Progression

Authors: Mary Kathryn Bohn,1,2, Alexandra Hall,1 Lusia Sepiashvili,1,2, Benjamin Jung,1,2 Shannon, Steele,1 and Khosrow Adeli1,2,3

The global epidemiology of coronavirus disease 2019 (COVID-19) suggests a wide spectrum of clinical severity, ranging from asymptomatic to fatal. Although the clinical and laboratory characteristics of COVID-19 patients have been well characterized, the pathophysiological mechanisms underlying disease severity and progression remain unclear. This review highlights key mechanisms that have been proposed to contribute to COVID-19 progression from viral entry to multisystem organ failure, as well as the central role of the immune response in successful viral clearance or progression to death.

Introduction

Coronavirus disease 2019 (COVID-19) is caused by a novel beta-coronavirus known as Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). As of June 15, 2020, the number of global confirmed cases has surpassed 8 million, with over 400,000 reported mortalities. The unparalleled pathogenicity and global impact of this pandemic has rapidly engaged the scientific community in urgently needed research. Preliminary reports from the Chinese Center for Disease Control and Prevention have estimated that the large majority of confirmed SARS-CoV-2 cases are mild (81%), with ~14% progressing to severe pneumonia and 5% developing acute respiratory distress syndrome (ARDS), sepsis, and/or multisystem organ failure (MOF) (144). Although more data is urgently needed to elucidate the global epidemiology of COVID-19 (80), a wide spectrum of clinical severity is evident, with most patients able to mount a sufficient and appropriate immune response, ultimately leading to viral clearance and case resolution. However, a significant subset of patients present with severe clinical manifestations, requiring life-supporting treatment (51). The pathophysiological mechanisms behind key events in the progression from mild to severe disease remain unclear, warranting further investigation to inform therapeutic decisions. Here, we review the current literature and summarize key proposed mechanisms of COVID-19 pathophysiological progression (FIGURE 1). Key Pathophysiological Mechanisms: Our Current Understanding Viral Invasion The first step in COVID-19 pathogenesis is viral invasion via its target host cell receptors. SARSCoV-2 viral entry has been described in detail elsewhere (138). In brief, SARS-CoV-2 consists of four main structural glycoproteins: spike (S), membrane (M), envelope (E), and nucleocapsid (N). The M, E, and N proteins are critical for viral particle assembly and release, whereas the S protein is responsible for viral binding and entry into host cells (33, 76, 89, 143, 148). Similar to SARS-CoV, several researchers have identified human angiotensin converting enzyme 2 (ACE2) as an entry receptor for SARS-CoV-2 (75, 99, 148, 156). SARSCoV-2 is mostly transmissible through large respiratory droplets, directly infecting cells of the upper and lower respiratory tract, especially nasal ciliated and alveolar epithelial cells (161). In addition to the lungs, ACE2 is also expressed in various other human tissues, such as the small intestine, kidneys, heart, thyroid, testis, and adipose tissue, indicating the virus may directly infect cells of other organ systems when viremia is present (77). Interestingly, although the S proteins of SARS-CoV-2 and SARSCoV share 72% homology in amino acid sequences, SARS-CoV-2 has been reported to have a higher affinity for the ACE2 receptor (18, 21, 143). Following host cell binding, viral and cell membranes fuse, enabling the virus to enter into the cell (89). For many coronaviruses, including SARS-CoV, host cell binding alone is insufficient to facilitate membrane fusion, requiring S-protein priming or cleavage by host cell proteases or transmembrane serine proteases (9, 10, 90, 94, 108). Indeed, Hoffman and colleagues demonstrated that S-protein priming by transmembrane serine protease 2 (TMPRSS2), which may be substituted by cathepsin B/L, is required to facilitate SARS-CoV-2 entry into host cells (58). In addition, unlike other coronaviruses, SARS-CoV-2 has been reported to possess a furin-like cleavage site in the S-protein domain, located between the S1 and S2 subunits (31, 138). Furin-like proteases are ubiquitously expressed, albeit at low levels, indicating that S-protein priming at this cleavage site may contribute to the widened cell tropism and enhanced transmissibility of SARS-CoV-2 (123). However, whether furin-like protease-mediated cleavage is required for SARS-CoV-2 host entry has yet to be determined. Blocking or inhibiting these processing enzymes may serve as a potential antiviral target (130). Interestingly, SARS-CoV-2 has developed a unique S1/S2 cleavage site in its S protein, characterized by a four-amino acid insertion, which seems to be absent in all other coronaviruses (4). This molecular mimicry has been identified as an efficient evolutionary adaptation that some viruses have acquired for exploiting the host cellular machinery. Once the nucleocapsid is deposited into the cytoplasm of the host cell, the RNA genome is replicated and translated into structural and accessory proteins. Vesicles containing the newly formed viral particles are then transported to and fuse with the plasma membrane, releasing them to infect other host cells in the same fashion (33, 89, 105). Although much progress has been made in our understanding of the mechanisms underlying SARS-CoV-2 invasion, additional research is needed to delineate exactly how cleavage of the S proteins by TMPRSS2 confers viral particle entry as well as how S-protein cleavage by membrane proteases contributes to viral penetration.

For More Information: https://journals.physiology.org/doi/pdf/10.1152/physiol.00019.2020