Replication of SARS-CoV-2 in adipose tissue determines organ and systemic lipid metabolism in hamsters and humans

Adult Long Coronavirus Disease 2019: Definition, Prevalence Pathophysiology, and Clinical Manifestations

Long coronavirus disease 2019 (COVID-19) is a multisystem disorder with variable manifestations and duration. One in 10 people with a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection will develop some manifestation of long COVID-19. Currently, there is no one single etiologic factor for the symptoms and signs of long COVID-19 beyond exposure to the SARS-CoV-2 virus. There are multiple theories about the pathophysiology ranging from viral persistence, reactivation, autoimmunity, and immune depletion. Certain risk factors have been identified including female sex, severe acute/hospitalized COVID-19, previous infections with SARS-CoV-2, and absence of vaccinations.

Pre-existing adipose tissue signaling profile related to obesity determines disease outcome of COVID-19: addressing obesity should be a priority for future pandemic preparedness

Objectives

Obesity is associated with COVID-19 severity and mortality. We investigated relationships between adipokines, cytokines and redox parameters with obesity, human immunodeficiency virus (HIV), severity and outcome.

Methods

In the exploratory study, adipose tissue (AT) was sampled in patients with COVID-19 on admission. Concentrations of leptin, adiponectin, resistin, interleukin 1 beta (IL-1b), IL-2, IL-6, IL-10, IL-17, tumor necrosis factor alpha (TNF-a), monocyte chemoattractant protein 1 (MCP-1), Trolox equivalent antioxidant capacity (TEAC), oxidative stress (H202) and malonaldehyde (MDA) were determined.

Results

Thirty-eight biopsies of subcutaneous adipose tissue were obtained (prevalence of HIV was 39% and of obesity 61%). Higher IL-6 serum concentrations (p=0.03) were associated with more severe COVID-19, and higher serum IL-10 concentrations, (p=0.03) with mortality. People with obesity had higher leptin concentrations (p=0.03, and p<0.01), lower adiponectin/leptin (p=0.03 and p<0.01), and higher leptin/resistin ratios (p=0.09 and p<0.01) in both AT and serum respectively. Higher leptin/resistin (p=0.04) and lower adiponectin/resistin (p=0.05) ratios in AT, but not serum, were predictive of mortality. HIV was not associated with any differences. Relationships between resistin and redox indicators, TEAC and MDA, suggest a dysregulation of metabolic vs immune-relevant effect of resistin, which differentially predicted severity and mortality. SARS-CoV-2 RNA was detected in the subcutaneous AT in 3/8 patients who demised, but only in 1/30 who survived.

Conclusion

Given the significant link demonstrated between leptin dysregulation in obesity and mortal severity of COVID-19, addressing obesity should be a priority therapeutic target in terms of future pandemic preparedness. Mechanistic studies are recommended to further elucidate the importance of metabolic vs immune modulation by resistin in COVID-19, to identify future therapeutic targets.

Diabetes exacerbates SARS-CoV-2 replication through ineffective pulmonary interferon responses, delayed cell-mediated immunity, and disruption of leptin signaling

Comorbidities, including obesity and type 2 diabetes mellitus (T2DM), are associated with increased disease severity and mortality following SARS-CoV-2 infection. Here, we investigated virus-host interactions under the effects of these comorbidities in diet-induced obesity (DIO) and leptin receptor-deficient (T2DM) mice following infection with SARS-CoV-2. DIO mice, as well as their lean counterparts, showed limited susceptibility to SARS-CoV-2 infection. In contrast, T2DM mice showed exacerbated pulmonary SARS-CoV-2 replication and delayed viral clearance associated with down-regulation of innate and adaptative immune gene signatures, ineffective type I interferon response, and delayed SARS-CoV-2-specific cell-mediated immune responses. While T2DM mice showed higher and prolonged SARS-CoV-2-specific immunoglobulin isotype responses compared to their lean counterparts, neutralizing antibody levels were equivalent. By silencing the leptin receptor in vitro using a human alveolar epithelial cell line, we observed an increase in SARS-CoV-2 replication and type I interferons. Altogether, our data provides for the first time evidence that disruption of leptin receptor signaling leading to obesity and T2DM induces altered type I interferon and cell-mediated responses against SARS-CoV-2, mediating increased viral replication and delayed clearance. These data shed light on the alteration of the innate immune pathway in the lung using in-depth transcriptomic analysis and on adaptive immune responses to SARS-CoV-2 under T2DM conditions. Finally, this study provides further insight into this risk factor aggravating SARS-CoV-2 infection and understanding the underlying cellular mechanisms that could help identify potential intervention points for this at-risk population.

FABP4 as a therapeutic host target controlling SARS-CoV-2 infection

Host metabolic fitness is a critical determinant of infectious disease outcomes. Obesity, aging, and other related metabolic disorders are recognized as high-risk disease modifiers for respiratory infections, including coronavirus infections, though the underlying mechanisms remain unknown. Our study highlights fatty acid-binding protein 4 (FABP4), a key regulator of metabolic dysfunction and inflammation, as a modulator of SARS-CoV-2 pathogenesis, correlating strongly with disease severity in COVID-19 patients. We demonstrate that loss of FABP4 function, by genetic or pharmacological means, reduces SARS-CoV-2 replication and disrupts the formation of viral replication organelles in adipocytes and airway epithelial cells. Importantly, FABP4 inhibitor treatment of infected hamsters diminished lung viral titers, alleviated lung damage and reduced collagen deposition. These findings highlight the therapeutic potential of targeting host metabolism in limiting coronavirus replication and mitigating the pathogenesis of infection.

The COVID-19 thrombus: distinguishing pathological, mechanistic, and phenotypic features and management

A heightened risk for thrombosis is a hallmark of COVID-19. Expansive clinical experience and medical literature have characterized small (micro) and large (macro) vessel involvement of the venous and arterial circulatory systems. Most events occur in patients with serious or critical illness in the hyperacute (first 1-2 weeks) or acute phases (2-4 weeks) of SARS-CoV-2 infection. However, thrombosis involving the venous, arterial, and microcirculatory systems has been reported in the subacute (4-8 weeks), convalescent (> 8-12 weeks) and chronic phases (> 12 weeks) among patients with mild-to-moderate illness. The purpose of the current focused review is to highlight the distinguishing clinical features, pathological components, and potential mechanisms of venous, arterial, and microvascular thrombosis in patients with COVID-19. The overarching objective is to better understand the proclivity for thrombosis, laying a solid foundation for screening and surveillance modalities, preventive strategies, and optimal patient management.

Ubiquitylomics: An Emerging Approach for Profiling Protein Ubiquitylation in Skeletal Muscle

Skeletal muscle is a highly adaptable tissue, finely tuned by various physiological and pathological factors. Whilst the pivotal role of skeletal muscle in overall health is widely acknowledged, unravelling the underlying molecular mechanisms poses ongoing challenges. Protein ubiquitylation, a crucial post-translational modification, is involved in regulating most biological processes. This widespread impact is achieved through a diverse set of enzymes capable of generating structurally and functionally distinct ubiquitin modifications on proteins. The complexity of protein ubiquitylation has presented significant challenges in not only identifying ubiquitylated proteins but also characterising their functional significance. Mass spectrometry enables in-depth analysis of proteins and their post-translational modification status, offering a powerful tool for studying protein ubiquitylation and its biological diversity: an approach termed ubiquitylomics. Ubiquitylomics has been employed to tackle different perspectives of ubiquitylation, including but not limited to global quantification of substrates and ubiquitin linkages, ubiquitin site recognition and crosstalk with other post-translational modifications. As the field of mass spectrometry continues to evolve, the usage of ubiquitylomics has unravelled novel insights into the regulatory mechanisms of protein ubiquitylation governing biology. However, ubiquitylomics research has predominantly been conducted in cellular models, limiting our understanding of ubiquitin signalling events driving skeletal muscle biology. By integrating the intricate landscape of protein ubiquitylation with dynamic shifts in muscle physiology, ubiquitylomics promises to not only deepen our understanding of skeletal muscle biology but also lay the foundation for developing transformative muscle-related therapeutics. This review aims to articulate how ubiquitylomics can be utilised by researchers to address different aspects of ubiquitylation signalling in skeletal muscle. We explore methods used in ubiquitylomics experiments, highlight relevant literature employing ubiquitylomics in the context of skeletal muscle and outline considerations for experimental design.

Manipulation of Host Cholesterol by SARS-CoV-2

SARS-CoV-2 infection is associated with alterations in host lipid metabolism, including disruptions in cholesterol homeostasis. However, the specific mechanisms by which viral proteins influence cholesterol remain incompletely understood. Here, we report that SARS-CoV-2 infection induces cholesterol sequestration within lysosomes, with the viral protein ORF3a identified as the primary driver of this effect. Mechanistically, we found that ORF3a interacts directly with the HOPS complex subunit VPS39 through a hydrophobic interface formed by residues W193 and Y184. A W193A mutation in ORF3a significantly rescues cholesterol egress and corrects the mislocalization of the lysosomal cholesterol transporter NPC2, which is caused by defective trafficking of the trans-Golgi network (TGN) sorting receptor, the cation-independent mannose-6-phosphate receptor (CI-MPR). We further observed a marked reduction in bis(monoacylglycero)phosphate (BMP), a lipid essential for lysosomal cholesterol egress, in both SARS-CoV-2-infected cells and ORF3a-expressing cells, suggesting BMP reduction as an additional mechanism of SARS-CoV-2-caused cholesterol sequestration. Inhibition of lysosomal cholesterol egress using the compound U18666A significantly decreased SARS-CoV-2 infection, highlighting a potential viral strategy of manipulating lysosomal cholesterol to modulate host cell susceptibility. Our findings reveal that SARS-CoV-2 ORF3a disrupts cellular cholesterol transport by altering lysosomal protein trafficking and BMP levels, providing new insights into virus-host interactions that contribute to lipid dysregulation in infected cells.

Long-term health outcome and quality of life in children with multisystem inflammatory syndrome: findings from multidisciplinary follow-up at an Italian tertiary-care paediatric hospital

Multisystem inflammatory syndrome is a severe complication of SARS-CoV-2 infection in children (MIS-C). To date, data on long-term sequelae mainly concern cardiac outcomes. All ≤ 18 year olds consecutively admitted to the Buzzi Children's Hospital with a diagnosis of MIS-C between October 1, 2020, and May 31, 2022, were followed up for up to 12 months by a dedicated multidisciplinary team. They underwent laboratory tests, multi-organ clinical and instrumental assessments, and psychosocial evaluation. 56/62 patients, 40 M, mean age 8.7 years (95% CI 7.7, 9.7), completed the follow-up. Cardiological, gastroenterological, pneumological, and neurological evaluations, including IQ and EEG, were normal. Alterations of HOMA-IR index and/or TyG index, observed in almost all patients during hospitalisation, persisted in about a third of the population at 12 months. At 6 and 12 months respectively, impairment of adaptive functions was observed in 38/56 patients (67.9%) and 25/56 (44.6%), emotional and behavioural problems in 10/56 (17.9%) and 9/56 (16.1%), and decline in QoL in 14/56 (25.0%) and 9/56 (16.1%). Psychosocial well-being impairment was significantly more frequent in the subgroup with persistent glycometabolic dysfunction at 12 months (75% vs. 40.9% p < 0.001).

CONLUSION

The mechanisms that might explain the long-term persistence of both metabolic alterations and neuro-behavioural outcomes and their possible relationship are far from being clarified. Our study points out to the potential long-term effects of pandemics and to the importance of a multidisciplinary follow-up to detect potential negative sequelae in different areas of health, both physical and psychosocial.

WHAT IS KNOWN

• Multisystem inflammatory syndrome in children (MIS-C) is a severe complication of SARS-CoV-2 infection. • Few data exist on the medium- and long-term outcomes of MIS-C, mostly focused on cardiac involvement. Emerging evidence shows neurological and psychological sequelae at mid- and long-term follow-up.

WHAT IS NEW

• This study reveals that MIS-C may lead to long-term glycometabolic dysfunctions joined to impairment in the realm of general well-being and decline in quality of life, in a subgroup of children. • This study highlights the importance of a long-term multidisciplinary follow-up of children hospitalised with MIS-C, in order to detect the potential long-term sequelae in different areas of health, both physical and psychosocial well-being.

Obesity-compromised immunity in post-COVID-19 condition: a critical control point of chronicity

Post-COVID-19 condition is recognized as a multifactorial disorder, with persistent presence of viral antigens, discordant immunity, delayed viral clearance, and chronic inflammation. Obesity has emerged as an independent risk factor for both SARS-CoV-2 infection and its subsequent sequelae. In this study, we aimed to predict the molecular mechanisms linking obesity and post-COVID-19 distress. Viral antigen-exposed adipose tissues display remarkable levels of viral receptors, facilitating viral entry, deposition, and chronic release of inflammatory mediators and cells in patients. Subsequently, obesity-associated inflammatory insults are predicted to disturb cellular and humoral immunity by triggering abnormal cell differentiation and lymphocyte exhaustion. In particular, the decline in SARS-CoV-2 antibody titers and T-cell exhaustion due to chronic inflammation may account for delayed virus clearance and persistent activation of inflammatory responses. Taken together, obesity-associated defective immunity is a critical control point of intervention against post-COVID-19 progression, particularly in subjects with chronic metabolic distress.

Obesity and age are transmission risk factors for SARS-CoV-2 infection among exposed individuals

The coronavirus disease (COVID-19) pandemic has occurred in Massachusetts in multiple waves led by a series of emerging variants. While the evidence has linked obesity with severe symptoms of COVID-19, the effect of obesity on susceptibility to SARS-CoV-2 infection remains unclear. Identification of intrinsic factors, which increase the likelihood of exposed individuals succumbing to productive SARS-CoV-2 infection could help plan mitigation efforts to curb the illness. We aim to investigate whether obese individuals have a higher susceptibility to developing productive SARS-CoV-2 infection given comparable exposure to nonobese individuals. This case-control study leveraged data from the Mass General Brigham's (MGB) electronic medical records (EMR), containing 687,813 patients, to determine whether obesity at any age increases the proportion of infections. We used PCR results of 72,613 subjects who tested positive to SARS-CoV-2 or declared exposure to the virus independently of the result of the test. For this study, we defined susceptibility as the likelihood of testing positive upon suspected exposure. We demonstrate evidence that SARS-CoV-2 exposed obese individuals were more prone to become COVID positive than nonobese individuals [adjusted odds ratio = 1.34 (95% CI: 1.29-1.39)]. Temporal analysis showed significantly increased susceptibility in obese individuals across the duration of the pandemic in Massachusetts. Obese exposed individuals are at a higher risk of getting infected with SARS-CoV-2. This indicates that obesity is not only a risk factor for worsened outcomes but also increases the risk for infection upon exposure. Identifying such populations early will be crucial for curbing the spread of this infectious disease.

Sex-specific biphasic alpha-synuclein response and alterations of interneurons in a COVID-19 hamster model

BACKGROUND

Coronavirus disease 2019 (COVID-19) frequently leads to neurological complications after recovery from acute infection, with higher prevalence in women. However, mechanisms by which SARS-CoV-2 disrupts brain function remain unclear and treatment strategies are lacking. We previously demonstrated neuroinflammation in the olfactory bulb of intranasally infected hamsters, followed by alpha-synuclein and tau accumulation in cortex, thus mirroring pathogenesis of neurodegenerative diseases such as Parkinson's or Alzheimer's disease.

METHODS

To uncover the sex-specific spatiotemporal profiles of neuroinflammation and neuronal dysfunction following intranasal SARS-CoV-2 infection, we quantified microglia cell density, alpha-synuclein immunoreactivity and inhibitory interneurons in cortical regions, limbic system and basal ganglia at acute and late post-recovery time points.

FINDINGS

Unexpectedly, microglia cell density and alpha-synuclein immunoreactivity decreased at 6 days post-infection, then rebounded to overt accumulation at 21 days post-infection. This biphasic response was most pronounced in amygdala and striatum, regions affected early in Parkinson's disease. Several brain regions showed altered densities of parvalbumin and calretinin interneurons which are involved in cognition and motor control. Of note, females appeared more affected.

INTERPRETATION

Our results demonstrate that SARS-CoV-2 profoundly disrupts brain homeostasis without neuroinvasion, via neuroinflammatory and protein regulation mechanisms that persist beyond viral clearance. The regional patterns and sex differences are in line with neurological deficits observed after SARS-CoV-2 infection.

FUNDING

Federal Ministry of Health, Germany (BMG; ZMV I 1-2520COR501 to G.G.), Federal Ministry of Education and Research, Germany (BMBF; 03COV06B to G.G.), Ministry of Science and Culture of Lower Saxony in Germany (14-76403-184, to G.G. and F.R.).

The interplay of aging, adipose tissue, and COVID-19: a potent alliance with implications for health

Obesity has emerged as a significant public health challenge. With the ongoing increase in life expectancy, the prevalence of obesity is steadily growing, particularly among older age demographics. The extension of life expectancy frequently results in additional years of vulnerability to chronic health issues associated with obesity in the elderly.The concept of SARS-CoV-2 directly infecting adipose tissue stems from the fact that both adipocytes and stromal vascular fraction cells express ACE2, the primary receptor facilitating SARS-CoV-2 entry. It is noteworthy that adipose tissue demonstrates ACE2 expression levels similar to those found in the lungs within the same individual. Additionally, ACE2 expression in the adipose tissue of obese individuals surpasses that in non-obese counterparts. Viral attachment to ACE2 has the potential to disturb the equilibrium of renin-angiotensin system homeostasis, leading to an exacerbated inflammatory response.Consequently, adipose tissue has been investigated as a potential site for active SARS-CoV-2 infection, suggesting its plausible role in virus persistence and contribution to both acute and long-term consequences associated with COVID-19.This review is dedicated to presenting current evidence concerning the presence of SARS-CoV-2 in the adipose tissue of elderly individuals infected with the virus. Both obesity and aging are circumstances that contribute to severe health challenges, heightening the risk of disease and mortality. We will particularly focus on examining the mechanisms implicated in the long-term consequences, with the intention of providing insights into potential strategies for mitigating the aftermath of the disease.

Precision nutrition to reset virus-induced human metabolic reprogramming and dysregulation (HMRD) in long-COVID

SARS-CoV-2, the etiological agent of COVID-19, is devoid of any metabolic capacity; therefore, it is critical for the viral pathogen to hijack host cellular metabolic machinery for its replication and propagation. This single-stranded RNA virus with a 29.9 kb genome encodes 14 open reading frames (ORFs) and initiates a plethora of virus-host protein-protein interactions in the human body. These extensive viral protein interactions with host-specific cellular targets could trigger severe human metabolic reprogramming/dysregulation (HMRD), a rewiring of sugar-, amino acid-, lipid-, and nucleotide-metabolism(s), as well as altered or impaired bioenergetics, immune dysfunction, and redox imbalance in the body. In the infectious process, the viral pathogen hijacks two major human receptors, angiotensin-converting enzyme (ACE)-2 and/or neuropilin (NRP)-1, for initial adhesion to cell surface; then utilizes two major host proteases, TMPRSS2 and/or furin, to gain cellular entry; and finally employs an endosomal enzyme, cathepsin L (CTSL) for fusogenic release of its viral genome. The virus-induced HMRD results in 5 possible infectious outcomes: asymptomatic, mild, moderate, severe to fatal episodes; while the symptomatic acute COVID-19 condition could manifest into 3 clinical phases: (i) hypoxia and hypoxemia (Warburg effect), (ii) hyperferritinemia ('cytokine storm'), and (iii) thrombocytosis (coagulopathy). The mean incubation period for COVID-19 onset was estimated to be 5.1 days, and most cases develop symptoms after 14 days. The mean viral clearance times were 24, 30, and 39 days for acute, severe, and ICU-admitted COVID-19 patients, respectively. However, about 25-70% of virus-free COVID-19 survivors continue to sustain virus-induced HMRD and exhibit a wide range of symptoms that are persistent, exacerbated, or new 'onset' clinical incidents, collectively termed as post-acute sequelae of COVID-19 (PASC) or long COVID. PASC patients experience several debilitating clinical condition(s) with >200 different and overlapping symptoms that may last for weeks to months. Chronic PASC is a cumulative outcome of at least 10 different HMRD-related pathophysiological mechanisms involving both virus-derived virulence factors and a multitude of innate host responses. Based on HMRD and virus-free clinical impairments of different human organs/systems, PASC patients can be categorized into 4 different clusters or sub-phenotypes: sub-phenotype-1 (33.8%) with cardiac and renal manifestations; sub-phenotype-2 (32.8%) with respiratory, sleep and anxiety disorders; sub-phenotype-3 (23.4%) with skeleto-muscular and nervous disorders; and sub-phenotype-4 (10.1%) with digestive and pulmonary dysfunctions. This narrative review elucidates the effects of viral hijack on host cellular machinery during SARS-CoV-2 infection, ensuing detrimental effect(s) of virus-induced HMRD on human metabolism, consequential symptomatic clinical implications, and damage to multiple organ systems; as well as chronic pathophysiological sequelae in virus-free PASC patients. We have also provided a few evidence-based, human randomized controlled trial (RCT)-tested, precision nutrients to reset HMRD for health recovery of PASC patients.

Diving into the proteomic atlas of SARS-CoV-2 infected cells

The COVID-19 pandemic was initiated by the rapid spread of a SARS-CoV-2 strain. Though mainly classified as a respiratory disease, SARS-CoV-2 infects multiple tissues throughout the human body, leading to a wide range of symptoms in patients. To better understand how SARS-CoV-2 affects the proteome from cells with different ontologies, this work generated an infectome atlas of 9 cell models, including cells from brain, blood, digestive system, and adipocyte tissue. Our data shows that SARS-CoV-2 infection mainly trigger dysregulations on proteins related to cellular structure and energy metabolism. Despite these pivotal processes, heterogeneity of infection was also observed, highlighting many proteins and pathways uniquely dysregulated in one cell type or ontological group. These data have been made searchable online via a tool that will permit future submissions of proteomic data ( https://reisdeoliveira.shinyapps.io/Infectome_App/ ) to enrich and expand this knowledgebase.

Diabetes Mellitus, Energy Metabolism, and COVID-19

Obesity, diabetes mellitus (mostly type 2), and COVID-19 show mutual interactions because they are not only risk factors for both acute and chronic COVID-19 manifestations, but also because COVID-19 alters energy metabolism. Such metabolic alterations can lead to dysglycemia and long-lasting effects. Thus, the COVID-19 pandemic has the potential for a further rise of the diabetes pandemic. This review outlines how preexisting metabolic alterations spanning from excess visceral adipose tissue to hyperglycemia and overt diabetes may exacerbate COVID-19 severity. We also summarize the different effects of SARS-CoV-2 infection on the key organs and tissues orchestrating energy metabolism, including adipose tissue, liver, skeletal muscle, and pancreas. Last, we provide an integrative view of the metabolic derangements that occur during COVID-19. Altogether, this review allows for better understanding of the metabolic derangements occurring when a fire starts from a small flame, and thereby help reducing the impact of the COVID-19 pandemic.

Consequences of COVID-19 on Adipose Tissue Signatures

Since the emergence of coronavirus disease-19 (COVID-19) in 2019, it has been crucial to investigate the causes of severe cases, particularly the higher rates of hospitalization and mortality in individuals with obesity. Previous findings suggest that adipocytes may play a role in adverse COVID-19 outcomes in people with obesity. The impact of COVID-19 vaccination and infection on adipose tissue (AT) is currently unclear. We therefore analyzed 27 paired biopsies of visceral and subcutaneous AT from donors of the Leipzig Obesity BioBank that have been categorized into three groups (1: no infection/no vaccination; 2: no infection but vaccinated; 3: infected and vaccinated) based on COVID-19 antibodies to spike (indicating vaccination) and/or nucleocapsid proteins. We provide additional insights into the impact of COVID-19 on AT biology through a comprehensive histological transcriptome and serum proteome analysis. This study demonstrates that COVID-19 infection is associated with smaller average adipocyte size. The impact of infection on gene expression was significantly more pronounced in subcutaneous than in visceral AT and mainly due to immune system-related processes. Serum proteome analysis revealed the effects of the infection on circulating adiponectin, interleukin 6 (IL-6), and carbonic anhydrase 5A (CA5A), which are all related to obesity and blood glucose abnormalities.

Neuroimmune interactions and their roles in neurodegenerative diseases

The nervous system possesses bidirectional, sophisticated and delicate communications with the immune system. These neuroimmune interactions play a vitally important role in the initiation and development of many disorders, especially neurodegenerative diseases. Although scientific advancements have made tremendous progress in this field during the last few years, neuroimmune communications are still far from being elucidated. By organizing recent research, in this review, we discuss the local and intersystem neuroimmune interactions and their roles in Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis. Unveiling these will help us gain a better understanding of the process of interplay inside the body and how the organism maintains homeostasis. It will also facilitate a view of the diseases from a holistic, pluralistic and interconnected perspective, thus providing a basis of developing novel and effective methods to diagnose, intervene and treat diseases.

Glucose oxidase-instructed biomineralization of calcium-based biomaterials for biomedical applications

In recent years, glucose oxidase (GOx) has aroused great research interest in the treatment of diseases related to abnormal glucose metabolisms like cancer and diabetes. However, as a kind of endogenous oxido-reductase, GOx suffers from poor stability and system toxicity in vivo. In order to overcome this bottleneck, GOx is encapsulated in calcium-based biomaterials (CaXs) such as calcium phosphate (CaP) and calcium carbonate (CaCO3) by using it as a biotemplate to simulate the natural biomineralization process. The biomineralized GOx holds improved stability and reduced side effects, due to the excellent bioactivity, biocompatibitliy, and biodegradability of CaXs. In this review, the state-of-the-art studies on GOx-mineralized CaXs are introduced with an emphasis on their application in various biomedical fields including disease diagnosis, cancer treatment, and diabetes management. The current challenges and future perspectives of GOx-mineralized CaXs are discussed, which is expected to promote further studies on these smart GOx-mineralized CaXs biomaterials for practical applications.

Mechanisms and pathophysiology of SARS-CoV-2 infection of the adipose tissue

Obesity is an independent risk factor for severe COVID-19, yet there remains a lack of consensus on the mechanisms underlying this relationship. A hypothesis that has garnered considerable attention suggests that SARS-CoV-2 disrupts adipose tissue function, either through direct infection or by indirect mechanisms. Indeed, recent reports have begun to shed some light on the important role that the adipose tissue plays during the acute phase of infection, as well as mediating long-term sequelae. In this review, we examine the evidence of extrapulmonary dissemination of SARS-CoV-2 to the adipose tissue. We discuss the mechanisms, acute and long-term implications, and possible management strategies to limit or ameliorate severe disease and long-term metabolic disturbances.

Thoracic adipose tissue contributes to severe virus infection of the lung

OBJECTIVE

Obesity is an independent risk factor for severe influenza virus and COVID-19 infections. There might be an interplay between adipose tissue and respiratory pathogens, although the mechanism is unknown. Proinflammatory factors secreted by the adipose tissue are often discussed to serve as indirect contributor to virus infection. However, the direct potential of adipose tissue to serve as a viral niche has not yet been investigated.

METHODS

Two murine obesity models (DIO and ob/ob) were infected with influenza A virus (IAV) and monitored for 3 weeks. p.i. Lung and adipose tissue were harvested, and the viral load was analysed. Direct replication of IAV in vitro was investigated in human derived primary adipocytes and macrophages. The indirect impact of the secretory products of adipocytes during infection was analysed in a co-culture system with lung fibroblasts. Moreover, lung and adipose tissue was harvested from deceased patients infected with SARS-CoV-2 omicron variant. Additionally, replication of SARS-CoV-2 alpha, delta, and omicron variants was investigated in vitro in adipocytes and macrophages.

RESULTS

Both murine obesity models presented high IAV titers compared to non-obese mice. Interestingly, adipose tissue adjacent to the lungs was a focal point for influenza virus replication in mice. We further detected IAV replication and antiviral response in human adipocytes. Co-cultivation of adipocytes and lung fibroblasts led to increased IL-8 concentration during infection. Though we observed SARS-CoV-2 in the thoracic adipose tissue of COVID-19 patients, no active replication was found in adipocytes in vitro. However, SARS-CoV-2 was detected in the macrophages and this finding was associated with increased inflammation.

CONCLUSIONS

Our study revealed that thoracic adipose tissue contributes to respiratory virus infection. Besides indirect induction of proinflammatory factors during infection, adipocytes and macrophages within the tissue can directly support viral replication.

Mechanisms and clinical relevance of the bidirectional relationship of viral infections with metabolic diseases

Viruses have been present during all evolutionary steps on earth and have had a major effect on human history. Viral infections are still among the leading causes of death. Another public health concern is the increase of non-communicable metabolic diseases in the last four decades. In this Review, we revisit the scientific evidence supporting the presence of a strong bidirectional feedback loop between several viral infections and metabolic diseases. We discuss how viruses might lead to the development or progression of metabolic diseases and conversely, how metabolic diseases might increase the severity of a viral infection. Furthermore, we discuss the clinical relevance of the current evidence on the relationship between viral infections and metabolic disease and the present and future challenges that should be addressed by the scientific community and health authorities.

Obesity negatively impacts maintenance of antibody response to COVID-19 vaccines

Severe obesity accelerates the decline of neutralizing antibodies to COVID-19 vaccines contributing to increased risk of hospitalization from breakthrough SARS-CoV-2 infections.¹ These findings have repercussion on the vaccination policy for SARS-CoV-2 variants and other infectious diseases like influenza in obese population.

SARS-CoV-2 infection and its effects on the endocrine system

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causing corona virus disease 2019 (COVID-19) can infect multiple tissues, including endocrine organs, such as the pancreas, adrenal, thyroid, and adipose tissue. The main receptor for SARS-CoV-2, ACE2, is ubiquitously expressed in the cells of the endocrine organs and accordingly, the virus has been detected in various amounts in all endocrine tissues in post-mortem samples from COVID-19 patients. The infection with SARS-CoV-2 may directly lead to organ damage or dysfunction, such as hyperglycaemia or in rare cases, new-onset diabetes. Furthermore, an infection with SARS-CoV-2 may have indirect effects affecting the endocrine system. The exact mechanisms are not yet completely understood and have to be further investigated. Conversely, endocrine diseases may affect the severity of COVID-19 and emphasis has to be laid on reducing the prevalence, or enhance the treatment, of these often non-communicable diseases in the future.

“Long COVID-19” and viral “fibromyalgia-ness”: Suggesting a mechanistic role for fascial myofibroblasts (Nineveh, the shadow is in the fascia)

The coronavirus pandemic has led to a wave of chronic disease cases; “Long COVID-19” is recognized as a new medical entity and resembles “fibromyalgia” which, likewise, lacks a clear mechanism. Observational studies indicate that up to 30%–40% of convalescent COVID-19 patients develop chronic widespread pain and fatigue and fulfill the 2016 diagnostic criteria for “fibromyalgia.” A recent study suggested a theoretical neuro-biomechanical model (coined “Fascial Armoring”) to help explain the pathogenesis and cellular pathway of fibromyalgia, pointing toward mechanical abnormalities in connective tissue and fascia, driven by contractile myo/fibroblasts and altered extracellular matrix remodeling with downstream corresponding neurophysiological aberrations. This may help explain several of fibromyalgia’s manifestations such as pain, distribution of pain, trigger points/tender spots, hyperalgesia, chronic fatigue, cardiovascular abnormalities, metabolic abnormalities, autonomic abnormalities, small fiber neuropathy, various psychosomatic symptoms, lack of obvious inflammation, and silent imaging investigations. Pro-inflammatory and pro-fibrotic pathways provide input into this mechanism via stimulation of proto/myofibroblasts. In this hypothesis and theory paper the theoretical model of Fascial Armoring is presented to help explain the pathogenesis and manifestations of “long COVID-19” as a disease of immuno-rheumo-psycho-neurology. The model is also used to make testable experimental predictions on investigations and predict risk and relieving factors.

Novel clinical and immunological features associated with persistent post-acute sequelae of COVID-19 after six months of follow-up: a pilot study

BACKGROUND

Currently, there is scant information regarding the features associated to the persistence of post-COVID-19 syndrome, which is the main aim of the present study.

METHODS

A cohort study of 102 COVID-19 patients was conducted. The post-COVID-19 symptoms were assessed by a standardised questionnaire. Lymphocyte immunophenotyping was performed by flow cytometry and chemokines/cytokines, neutrophil extracellular traps, the tripartite motif 63, anti-cellular, and anti-SARS-CoV-2 IgG antibodies were addressed in serum. The primary outcome was the persistence of post-COVID-19 syndrome after six months follow-up.

RESULTS

Thirteen patients (12.7%) developed the primary outcome and had a more frequent history of post-COVID-19 syndrome 3 months after infection onset (p = .044), increased levels of IL-1α (p = .011) and IP-10 (p = .037) and increased CD57 expression in CD8⁺ T cells (p = .003). There was a trend towards higher levels of IFN-γ (p = .051), IL-1β (p = .062) and IL-6 (p = .087). The history of post COVID-19 in the previous 3 months, obesity, baseline serum MIP-1α and IP-10, and CD57 expression in CD8⁺ T cells were independently associated with the persistence of post-COVID-19 syndrome.

CONCLUSION

Our data suggest an important relationship between a pro-inflammatory state mediated through metabolic pathways related to obesity and increased cellular senescence as a key element in the persistence of post-COVID-19 syndrome at six months of follow-up.

Beyond energy balance regulation: The underestimated role of adipose tissues in host defense against pathogens

Although the adipose tissue (AT) is a central metabolic organ in the regulation of whole-body energy homeostasis, it is also an important endocrine and immunological organ. As an endocrine organ, AT secretes a variety of bioactive peptides known as adipokines - some of which have inflammatory and immunoregulatory properties. As an immunological organ, AT contains a broad spectrum of innate and adaptive immune cells that have mostly been studied in the context of obesity. However, overwhelming evidence supports the notion that AT is a genuine immunological effector site, which contains all cell subsets required to induce and generate specific and effective immune responses against pathogens. Indeed, AT was reported to be an immune reservoir in the host's response to infection, and a site of parasitic, bacterial and viral infections. In addition, besides AT's immune cells, preadipocytes and adipocytes were shown to express innate immune receptors, and adipocytes were reported as antigen-presenting cells to regulate T-cell-mediated adaptive immunity. Here we review the current knowledge on the role of AT and AT's immune system in host defense against pathogens. First, we will summarize the main characteristics of AT: type, distribution, function, and extraordinary plasticity. Second, we will describe the intimate contact AT has with lymph nodes and vessels, and AT immune cell composition. Finally, we will present a comprehensive and up-to-date overview of the current research on the contribution of AT to host defense against pathogens, including the respiratory viruses influenza and SARS-CoV-2.

Pulmonary recovery from COVID-19 in patients with metabolic diseases: a longitudinal prospective cohort study

The severity of coronavirus disease 2019 (COVID-19) is related to the presence of comorbidities including metabolic diseases. We herein present data from the longitudinal prospective CovILD trial, and investigate the recovery from COVID-19 in individuals with dysglycemia and dyslipidemia. A total of 145 COVID-19 patients were prospectively followed and a comprehensive clinical, laboratory and imaging assessment was performed at 60, 100, 180, and 360 days after the onset of COVID-19. The severity of acute COVID-19 and outcome at early post-acute follow-up were significantly related to the presence of dysglycemia and dyslipidemia. Still, at long-term follow-up, metabolic disorders were not associated with an adverse pulmonary outcome, as reflected by a good recovery of structural lung abnormalities in both, patients with and without metabolic diseases. To conclude, dyslipidemia and dysglycemia are associated with a more severe course of acute COVID-19 as well as delayed early recovery but do not impair long-term pulmonary recovery.

The intersection of obesity and (long) COVID-19: Hypoxia, thrombotic inflammation, and vascular endothelial injury

The role of hypoxia, vascular endothelial injury, and thrombotic inflammation in worsening COVID-19 symptoms has been generally recognized. Damaged vascular endothelium plays a crucial role in forming in situ thrombosis, pulmonary dysfunction, and hypoxemia. Thrombotic inflammation can further aggravate local vascular endothelial injury and affect ventilation and blood flow ratio. According to the results of many studies, obesity is an independent risk factor for a variety of severe respiratory diseases and contributes to high mechanical ventilation rate, high mortality, and slow recovery in COVID-19 patients. This review will explore the mechanisms by which obesity may aggravate the acute phase of COVID-19 and delay long COVID recovery by affecting hypoxia, vascular endothelial injury, and thrombotic inflammation. A systematic search of PubMed database was conducted for papers published since January 2020, using the medical subject headings of "COVID-19" and "long COVID" combined with the following keywords: "obesity," "thrombosis," "endothelial injury," "inflammation," "hypoxia," "treatment," and "anticoagulation." In patients with obesity, the accumulation of central fat restricts the expansion of alveoli, exacerbating the pulmonary dysfunction caused by SARS-CoV-2 invasion, inflammatory damage, and lung edema. Abnormal fat secretion and immune impairment further aggravate the original tissue damage and inflammation diffusion. Obesity weakens baseline vascular endothelium function leading to an early injury and pre-thrombotic state after infection. Enhanced procoagulant activity and microthrombi promote early obstruction of the vascular. Obesity also prolongs the duration of symptoms and increases the risk of sequelae after hospital discharge. Persistent viral presence, long-term inflammation, microclots, and hypoxia may contribute to the development of persistent symptoms, suggesting that patients with obesity are uniquely susceptible to long COVID. Early interventions, including supplemental oxygen, comprehensive antithrombotic therapy, and anti-inflammatory drugs, show effectiveness in many studies in the prevention of serious hypoxia, thromboembolic events, and systemic inflammation, and are therefore recommended to reduce intensive care unit admission, mortality, and sequelae.

Myristic acid as a checkpoint to regulate STING-dependent autophagy and interferon responses by promoting N-myristoylation

Stimulator of interferon gene (STING)-triggered autophagy is crucial for the host to eliminate invading pathogens and serves as a self-limiting mechanism of STING-induced interferon (IFN) responses. Thus, the mechanisms that ensure the beneficial effects of STING activation are of particular importance. Herein, we show that myristic acid, a type of long-chain saturated fatty acid (SFA), specifically attenuates cGAS-STING-induced IFN responses in macrophages, while enhancing STING-dependent autophagy. Myristic acid inhibits HSV-1 infection-induced innate antiviral immune responses and promotes HSV-1 replication in mice in vivo. Mechanistically, myristic acid enhances N-myristoylation of ARF1, a master regulator that controls STING membrane trafficking. Consequently, myristic acid facilitates STING activation-triggered autophagy degradation of the STING complex. Thus, our work identifies myristic acid as a metabolic checkpoint that contributes to immune homeostasis by balancing STING-dependent autophagy and IFN responses. This suggests that myristic acid and N-myristoylation are promising targets for the treatment of diseases caused by aberrant STING activation.

Proteome-wide Mendelian randomization implicates nephronectin as an actionable mediator of the effect of obesity on COVID-19 severity

Obesity is a major risk factor for Coronavirus disease (COVID-19) severity; however, the mechanisms underlying this relationship are not fully understood. As obesity influences the plasma proteome, we sought to identify circulating proteins mediating the effects of obesity on COVID-19 severity in humans. Here, we screened 4,907 plasma proteins to identify proteins influenced by body mass index using Mendelian randomization. This yielded 1,216 proteins, whose effect on COVID-19 severity was assessed, again using Mendelian randomization. We found that an s.d. increase in nephronectin (NPNT) was associated with increased odds of critically ill COVID-19 (OR = 1.71, P = 1.63 × 10-10). The effect was driven by an NPNT splice isoform. Mediation analyses supported NPNT as a mediator. In single-cell RNA-sequencing, NPNT was expressed in alveolar cells and fibroblasts of the lung in individuals who died of COVID-19. Finally, decreasing body fat mass and increasing fat-free mass were found to lower NPNT levels. These findings provide actionable insights into how obesity influences COVID-19 severity.

Adipocytes in obesity: A perfect reservoir for SARS-CoV-2?

Research evidence suggests that adipocytes in obesity might facilitate SARS-CoV-2 replication, for it was only found in adipose tissue of individuals with overweight or obesity but not lean individuals who died from COVID-19. As lipid metabolism is key to adipocyte function, and viruses are capable of exploiting and manipulating lipid metabolism of host cells for their own benefit of infection, we hypothesize that adipocytes could not only impair host immune defense against viral infection, but also facilitate SARS-CoV-2 entry, replication and assembly as a reservoir to boost the viral infection in obesity. The latter of which could mainly be mediated by SARS-CoV-2 hijacking the abnormal lipid metabolism in the adipocytes. If these were to be confirmed, an approach to combat COVID-19 in people with obesity by taking advantage of the abnormal lipid metabolism in adipocytes might be considered, as well as modifying lipid metabolism of other host cells as a potential adjunctive treatment for COVID-19.

SARS-CoV-2 infection induces persistent adipose tissue damage in aged golden Syrian hamsters

Coronavirus disease 2019 (COVID-19, caused by severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2)) is primarily a respiratory illness. However, various extrapulmonary manifestations have been reported in patients with severe forms of COVID-19. Notably, SARS-CoV-2 was shown to directly trigger white adipose tissue (WAT) dysfunction, which in turn drives insulin resistance, dyslipidemia, and other adverse outcomes in patients with COVID-19. Although advanced age is the greatest risk factor for COVID-19 severity, published data on the impact of SARS-CoV-2 infection on WAT in aged individuals are scarce. Here, we characterized the response of subcutaneous and visceral WAT depots to SARS-CoV-2 infection in young adult and aged golden hamsters. In both age groups, infection was associated with a decrease in adipocyte size in the two WAT depots; this effect was partly due to changes in tissue's lipid metabolism and persisted for longer in aged hamsters than in young-adult hamsters. In contrast, only the subcutaneous WAT depot contained crown-like structures (CLSs) in which dead adipocytes were surrounded by SARS-CoV-2-infected macrophages, some of them forming syncytial multinucleated cells. Importantly, older age predisposed to a unique manifestation of viral disease in the subcutaneous WAT depot during SARS-CoV-2 infection; the persistence of very large CLSs was indicative of an age-associated defect in the clearance of dead adipocytes by macrophages. Moreover, we uncovered age-related differences in plasma lipid profiles during SARS-CoV-2 infection. These data suggest that the WAT's abnormal response to SARS-CoV-2 infection may contribute to the greater severity of COVID-19 observed in elderly patients.

Circulating adipokine levels and COVID-19 severity in hospitalized patients

BACKGROUND

Obesity is a risk factor for adverse outcomes in COVID-19, potentially driven by chronic inflammatory state due to dysregulated secretion of adipokines and cytokines. We investigated the association between plasma adipokines and COVID-19 severity, systemic inflammation, clinical parameters, and outcome of COVID-19 patients.

METHODS

In this multi-centre prospective cross-sectional study, we collected blood samples and clinical data from COVID-19 patients. The severity of COVID-19 was classified as mild (no hospital admission), severe (ward admission), and critical (ICU admission). ICU non-COVID-19 patients were also included and plasma from healthy age, sex, and BMI-matched individuals obtained from Lifelines. Multi-analyte profiling of plasma adipokines (Leptin, Adiponectin, Resistin, Visfatin) and inflammatory markers (IL-6, TNFα, IL-10) were determined using Luminex multiplex assays.

RESULTS

Between March and December 2020, 260 SARS-CoV-2 infected individuals (age: 65 [56-74] BMI 27.0 [24.4-30.6]) were included: 30 mild, 159 severe, and 71 critical patients. Circulating leptin levels were reduced in critically ill patients with a high BMI yet this decrease was absent in patients that were administered dexamethasone. Visfatin levels were higher in critical COVID-19 patients compared to non-COVID-ICU, mild and severe patients (4.7 vs 3.4, 3.0, and 3.72 ng/mL respectively, p < 0.05). Lower Adiponectin levels, but higher Resistin levels were found in severe and critical patients, compared to those that did not require hospitalization (3.65, 2.7 vs 7.9 µg/mL, p < 0.001, and 18.2, 22.0 vs 11.0 ng/mL p < 0.001).

CONCLUSION

Circulating adipokine levels are associated with COVID-19 hospitalization, i.e., the need for oxygen support (general ward), or the need for mechanical ventilation and other organ support in the ICU, but not mortality.

SARS-CoV-2 fires up inflammation in adipose tissue

Obesity is an important risk factor for severe COVID-19 and, possibly, for breakthrough SARS-CoV-2 infections in fully vaccinated people. Novel findings highlight how SARS-CoV-2 infects adipose tissue and promotes subclinical inflammation. Thus, also based on knowledge about endocrine dysfunction facilitating SARS-CoV-2 infection, a vicious cycle involving obesity, impaired metabolic health and COVID-19 might exist.

B cell contribution to immunometabolic dysfunction and impaired immune responses in obesity

Obesity increases the risk of type 2 diabetes mellitus, cardiovascular disease, fatty liver disease, and cancer. It is also linked with more severe complications from infections, including COVID-19, and poor vaccine responses. Chronic, low-grade inflammation and associated immune perturbations play an important role in determining morbidity in people living with obesity. The contribution of B cells to immune dysregulation and meta-inflammation associated with obesity has been documented by studies over the past decade. With a focus on human studies, here we consolidate the observations demonstrating that there is altered B cell subset composition, differentiation, and function both systemically and in the adipose tissue of individuals living with obesity. Finally, we discuss the potential factors that drive B cell dysfunction in obesity and propose a model by which altered B cell subset composition in obesity underlies dysfunctional B cell responses to novel pathogens.

SARS-CoV-2 infection drives an inflammatory response in human adipose tissue through infection of adipocytes and macrophages

Obesity, characterized by chronic low-grade inflammation of the adipose tissue, is associated with adverse coronavirus disease 2019 (COVID-19) outcomes, yet the underlying mechanism is unknown. To explore whether severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection of adipose tissue contributes to pathogenesis, we evaluated COVID-19 autopsy cases and deeply profiled the response of adipose tissue to SARS-CoV-2 infection in vitro. In COVID-19 autopsy cases, we identified SARS-CoV-2 RNA in adipocytes with an associated inflammatory infiltrate. We identified two distinct cellular targets of infection: adipocytes and a subset of inflammatory adipose tissue-resident macrophages. Mature adipocytes were permissive to SARS-CoV-2 infection; although macrophages were abortively infected, SARS-CoV-2 initiated inflammatory responses within both the infected macrophages and bystander preadipocytes. These data suggest that SARS-CoV-2 infection of adipose tissue could contribute to COVID-19 severity through replication of virus within adipocytes and through induction of local and systemic inflammation driven by infection of adipose tissue-resident macrophages.

Cytokines and regulation of glucose and lipid metabolism in the obesity

The article presents data of the influence of cytokines of different directions of glucose and lipid metabolism in obesity. A change of the basic paradigm regarding adipose tissue has contributed to a number of recent discoveries. This concerns such basic concepts as healthy and diseased adipocytes, and, as a consequence, changes of their metabolism under the influence of cytokins. Distinguishing the concept of organokines demonstrates that despite the common features of cytokine regulation, each organ has its own specifics features of cytokine regulation, each organ has its own specific an important section of this concept is the idea of the heterogeneity of adipose tissue. Knowledge of the function of adipose tissue localized in different compartments of the body is expanding. There are date about the possibility of transition of one type of adipose tissue to another. A possible mechanism linking adipose tissue inflammation and the formation of insulin resistance (IR) is presented in this paper. The mechanism of IR development is closely connected with to proinflammatory cytokins disordering the insulin signal, accompanied by a decrease of the work of glucose transporters. A decrease of the income of glucose into cells leads to a change of glycolysis level to an increase of the fatty acids oxidation. Cytokins are able to participate in the process of the collaboration of some cells with others, that occurs both during physiological and pathological process.

Genuine selective caspase-2 inhibition with new irreversible small peptidomimetics

Caspase-2 (Casp2) is a promising therapeutic target in several human diseases, including nonalcoholic steatohepatitis (NASH) and Alzheimer's disease (AD). However, the design of an active-site-directed inhibitor selective to individual caspase family members is challenging because caspases have extremely similar active sites. Here we present new peptidomimetics derived from the VDVAD pentapeptide structure, harboring non-natural modifications at the P2 position and an irreversible warhead. Enzyme kinetics show that these new compounds, such as LJ2 or its specific isomers LJ2a, and LJ3a, strongly and irreversibly inhibit Casp2 with genuine selectivity. In agreement with the established role of Casp2 in cellular stress responses, LJ2 inhibits cell death induced by microtubule destabilization or hydroxamic acid-based deacetylase inhibition. The most potent peptidomimetic, LJ2a, inhibits human Casp2 with a remarkably high inactivation rate (k3/Ki ~5,500,000 M-1 s-1), and the most selective inhibitor, LJ3a, has close to a 1000 times higher inactivation rate on Casp2 as compared to Casp3. Structural analysis of LJ3a shows that the spatial configuration of Cα at the P2 position determines inhibitor efficacy. In transfected human cell lines overexpressing site-1 protease (S1P), sterol regulatory element-binding protein 2 (SREBP2) and Casp2, LJ2a and LJ3a fully inhibit Casp2-mediated S1P cleavage and thus SREBP2 activation, suggesting a potential to prevent NASH development. Furthermore, in primary hippocampal neurons treated with β-amyloid oligomers, submicromolar concentrations of LJ2a and of LJ3a prevent synapse loss, indicating a potential for further investigations in AD treatment.

SARS-CoV-2 infects adipose tissue in a fat depot- and viral lineage-dependent manner

Visceral adiposity is a risk factor for severe COVID-19, and a link between adipose tissue infection and disease progression has been proposed. Here we demonstrate that SARS-CoV-2 infects human adipose tissue and undergoes productive infection in fat cells. However, susceptibility to infection and the cellular response depends on the anatomical origin of the cells and the viral lineage. Visceral fat cells express more ACE2 and are more susceptible to SARS-CoV-2 infection than their subcutaneous counterparts. SARS-CoV-2 infection leads to inhibition of lipolysis in subcutaneous fat cells, while in visceral fat cells, it results in higher expression of pro-inflammatory cytokines. Viral load and cellular response are attenuated when visceral fat cells are infected with the SARS-CoV-2 gamma variant. A similar degree of cell death occurs 4-days after SARS-CoV-2 infection, regardless of the cell origin or viral lineage. Hence, SARS-CoV-2 infects human fat cells, replicating and altering cell function and viability in a depot- and viral lineage-dependent fashion.

Visceral adiposity is a risk factor for severe COVID-19, and infection of adipose tissue by SARS-CoV-2 has been reported. Here the authors confirm that human adipose tissue is a possible site for SARS-CoV-2 infection, but the degree of adipose tissue infection and the way adipocytes respond to the virus depend on the adipose tissue depot and the viral strain.

COVID-19 metabolism: Mechanisms and therapeutic targets

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) dysregulates antiviral signaling, immune response, and cell metabolism in human body. Viral genome and proteins hijack host metabolic network to support viral biogenesis and propagation. However, the regulatory mechanism of SARS-CoV-2-induced metabolic dysfunction has not been elucidated until recently. Multiomic studies of coronavirus disease 2019 (COVID-19) revealed an intensive interaction between host metabolic regulators and viral proteins. SARS-CoV-2 deregulated cellular metabolism in blood, intestine, liver, pancreas, fat, and immune cells. Host metabolism supported almost every stage of viral lifecycle. Strikingly, viral proteins were found to interact with metabolic enzymes in different cellular compartments. Biochemical and genetic assays also identified key regulatory nodes and metabolic dependencies of viral replication. Of note, cholesterol metabolism, lipid metabolism, and glucose metabolism are broadly involved in viral lifecycle. Here, we summarized the current understanding of the hallmarks of COVID-19 metabolism. SARS-CoV-2 infection remodels host cell metabolism, which in turn modulates viral biogenesis and replication. Remodeling of host metabolism creates metabolic vulnerability of SARS-CoV-2 replication, which could be explored to uncover new therapeutic targets. The efficacy of metabolic inhibitors against COVID-19 is under investigation in several clinical trials. Ultimately, the knowledge of SARS-CoV-2-induced metabolic reprogramming would accelerate drug repurposing or screening to combat the COVID-19 pandemic.

Obesity and COVID-19: What are the Consequences?

Obesity is an increasing health problem all over the world. In combination with the current COVID-19 pandemic, this has turned into a massive challenge as individuals with overweight and obesity at all ages show a significant increase in their risk of getting severe COVID-19. Around 20% of all patients that were hospitalized for COVID-19 suffered from obesity alone, whereas obesity in combination with other metabolic comorbidities, such as type 2 diabetes and hypertension, account for up to 60% of all hospitalizations in relation to COVID-19. Therefore, it is of immense importance to put the spotlight on the high incidence of obesity present already in childhood both by changing the individual minds and by encouraging politicians and the whole society to commence preventive interventions for achieving a better nutrition for all social classes all over the world. In the current review, we aim to explain the different pathways and mechanisms that are responsible for the increased risk of severe COVID-19 in people with overweight and obesity. Furthermore, we discuss how the pandemic has led to weight gains in many people during lockdown. At the end, we discuss the importance of preventing such an interface between a non-communicable disease like obesity and a communicable disease like COVID-19 in the future.

Detection of SARS-CoV-2 in subcutaneous fat but not visceral fat, and the disruption of fat lymphocyte homeostasis in both fat tissues in the macaque

The well documented association between obesity and the severity of SARS-CoV-2 infection raises the question of whether adipose tissue (AT) is impacted during this infection. Using a model of SARS-CoV-2 infection in cynomolgus macaques, we detected the virus within subcutaneous AT (SCAT) but not in visceral AT (VAT) or epicardial AT on day 7 post-infection. We sought to determine the mechanisms responsible for this selective detection and observed higher levels of angiotensin-converting-enzyme-2 mRNA expression in SCAT than in VAT. Lastly, we evaluated the immunological consequences of SARS-CoV-2 infection on AT: both SCAT and VAT T cells showed a drastic reduction in CD69 expression, a standard marker of resident memory T cell in tissue, that is also involved in the migratory and metabolic properties of T cells. Our results demonstrate that in a model of mild infection, SCAT is selectively infected by SARS-CoV-2 although changes in the immune properties of AT are observed in both SCAT and VAT.

Subcutaneous fat tissue expresses higher angiotensin-converting-enzyme 2 mRNA than visceral fat tissue and is selectively infected by SARS-Cov-2, while both fat tissues show drastic reduction in CD69 expression in T cells.

Microgliosis and neuronal proteinopathy in brain persist beyond viral clearance in SARS-CoV-2 hamster model

BACKGROUND

Neurological symptoms such as cognitive decline and depression contribute substantially to post-COVID-19 syndrome, defined as lasting symptoms several weeks after initial SARS-CoV-2 infection. The pathogenesis is still elusive, which hampers appropriate treatment. Neuroinflammatory responses and neurodegenerative processes may occur in absence of overt neuroinvasion.

METHODS

Here we determined whether intranasal SARS-CoV-2 infection in male and female syrian golden hamsters results in persistent brain pathology. Brains 3 (symptomatic) or 14 days (viral clearance) post infection versus mock (n = 10 each) were immunohistochemically analyzed for viral protein, neuroinflammatory response and accumulation of tau, hyperphosphorylated tau and alpha-synuclein protein.

FINDINGS

Viral protein in the nasal cavity led to pronounced microglia activation in the olfactory bulb beyond viral clearance. Cortical but not hippocampal neurons accumulated hyperphosphorylated tau and alpha-synuclein, in the absence of overt inflammation and neurodegeneration. Importantly, not all brain regions were affected, which is in line with selective vulnerability.

INTERPRETATION

Thus, despite the absence of virus in brain, neurons develop signatures of proteinopathies that may contribute to progressive neuronal dysfunction. Further in depth analysis of this important mechanism is required.

FUNDING

Federal Ministry of Health (BMG; ZMV I 1-2520COR501), Federal Ministry of Education and Research (BMBF 01KI1723G), Ministry of Science and Culture of Lower Saxony in Germany (14 - 76103-184 CORONA-15/20), German Research Foundation (DFG; 398066876/GRK 2485/1), Luxemburgish National Research Fund (FNR, Project Reference: 15686728, EU SC1-PHE-CORONAVIRUS-2020 MANCO, no > 101003651).

Post-acute sequelae of COVID-19: A metabolic perspective

The SARS-CoV-2 pandemic continues to rage around the world. At the same time, despite strong public health measures and high vaccination rates in some countries, a post-COVID-19 syndrome has emerged which lacks a clear definition, prevalence, or etiology. However, fatigue, dyspnea, brain fog, and lack of smell and/or taste are often characteristic of patients with this syndrome. These are evident more than a month after infection, and are labeled as Post-Acute Sequelae of CoV-2 (PASC) or commonly referred to as long-COVID. Metabolic dysfunction (i.e., obesity, insulin resistance, and diabetes mellitus) is a predisposing risk factor for severe acute COVID-19, and there is emerging evidence that this factor plus a chronic inflammatory state may predispose to PASC. In this article, we explore the potential pathogenic metabolic mechanisms that could underly both severe acute COVID-19 and PASC, and then consider how these might be targeted for future therapeutic approaches.

The Shades of Grey in Adipose Tissue Reprogramming

The adipose tissue (AT) has a major role in contributing to obesity-related pathologies through regulating systemic immunometabolism. The pathogenicity of the AT is underpinned by its remarkable plasticity to be reprogrammed during obesity, in the perspectives of tissue morphology, extracellular matrix (ECM) composition, angiogenesis, immunometabolic homoeostasis and circadian rhythmicity. Dysregulation in these features escalates the pathogenesis conferred by this endometabolic organ. Intriguingly, the potential to be reprogrammed appears to be an Achilles’ heel of the obese AT that can be targeted for the management of obesity and its associated comorbidities. Here, we provide an overview of the reprogramming processes of white AT (WAT), with a focus on their dynamics and pleiotropic actions over local and systemic homoeostases, followed by a discussion of potential strategies favouring therapeutic reprogramming. The potential involvement of AT remodelling in the pathogenesis of COVID-19 is also discussed.

SARS-CoV-2 adipose tissue infection and hyperglycemia: A further step towards the understanding of severe COVID-19

Numerous studies have highlighted the prognostic significance of hyperglycemia in the outcomes of SARS-CoV-2 infection. A number of mechanisms have been proposed as potential drivers of this association, which were, however, up until recently based rather on speculation than on investigational evidence. It has been recently come to light that the development of insulin resistance in the frame of COVID-19 is likely the driving force behind the development of overt hyperglycemia. This results through the infectious insult of the adipose tissue, and is observed in conjunction with aberrant adipokine secretion by host adipocytes, such as decreased adiponectin, as well as a switch towards an antiviral immune secretory profile. These data could have a considerable relevance not only for the management of hyperglycemia in the course of the infection but also for the overall understanding of the pathogenesis of severe COVID-19.

Causal associations between body fat accumulation and COVID-19 severity: A Mendelian randomization study

Previous studies reported associations between obesity measured by body mass index (BMI) and coronavirus disease 2019 (COVID-19). However, BMI is calculated only with height and weight and cannot distinguish between body fat mass and fat-free mass. Thus, it is not clear if one or both of these measures are mediating the relationship between obesity and COVID-19. Here, we used Mendelian randomization (MR) to compare the independent causal relationships of body fat mass and fat-free mass with COVID-19 severity. We identified single nucleotide polymorphisms associated with body fat mass and fat-free mass in 454,137 and 454,850 individuals of European ancestry from the UK Biobank, respectively. We then performed two-sample MR to ascertain their effects on severe COVID-19 (cases: 4,792; controls: 1,054,664) from the COVID-19 Host Genetics Initiative. We found that an increase in body fat mass by one standard deviation was associated with severe COVID-19 (odds ratio (OR)_{body fat mass} = 1.61, 95% confidence interval [CI]: 1.28-2.04, P = 5.51 × 10^-5; OR_{body fat-free mass} = 1.31, 95% CI: 0.99-1.74, P = 5.77 × 10^-2). Considering that body fat mass and fat-free mass were genetically correlated with each other (r = 0.64), we further evaluated independent causal effects of body fat mass and fat-free mass using multivariable MR and revealed that only body fat mass was independently associated with severe COVID-19 (OR_{body fat mass} = 2.91, 95% CI: 1.71-4.96, P = 8.85 × 10^-5 and OR_{body fat-free mass} = 1.02, 95%CI: 0.61-1.67, P = 0.945). In summary, this study demonstrates the causal effects of body fat accumulation on COVID-19 severity and indicates that the biological pathways influencing the relationship between COVID-19 and obesity are likely mediated through body fat mass.