The bidirectional interaction of COVID-19 infections and lipoproteins

The biogenesis and transport of triglyceride-rich lipoproteins

Triglyceride-rich lipoproteins (TRLs) play essential roles in human health and disease by transporting bulk lipids into the circulation. This review summarizes the fundamental mechanisms and diverse factors governing lipoprotein production, secretion, and regulation. Emphasizing the broader implications for human health, we outline the intricate landscape of lipoprotein research and highlight the potential coordination between the biogenesis and transport of TRLs in physiology, particularly the unexpected coupling of metabolic enzymes and transport machineries. Challenges and opportunities in lipoprotein biology with respect to inherited diseases and viral infections are also discussed. Further characterization of the biogenesis and transport of TRLs will advance both basic research in lipid biology and translational medicine for metabolic diseases.

HDL-based therapeutics: A promising frontier in combating viral and bacterial infections

Low levels of high-density lipoprotein (HDL) and impaired HDL functionality have been consistently associated with increased susceptibility to infection and its serious consequences. This has been attributed to the critical role of HDL in maintaining cellular lipid homeostasis, which is essential for the proper functioning of immune and structural cells. HDL, a multifunctional particle, exerts pleiotropic effects in host defense against pathogens. It functions as a natural nanoparticle, capable of sequestering and neutralizing potentially harmful substances like bacterial lipopolysaccharides. HDL possesses antiviral activity, preventing viruses from entering or fusing with host cells, thereby halting their replication cycle. Understanding the complex relationship between HDL and the immune system may reveal innovative targets for developing new treatments to combat infectious diseases and improve patient outcomes. This review aims to emphasize the role of HDL in influencing the course of bacterial and viral infections and its and its therapeutic potential.

Anti-inflammatory mechanism of Apolipoprotein A-I

Apolipoprotein A-I(ApoA-I) is a member of blood apolipoproteins, it is the main component of High density lipoprotein(HDL). ApoA-I undergoes a series of complex processes from its generation to its composition as spherical HDL. It not only has a cholesterol reversal transport function, but also has a function in modulating the inflammatory response. ApoA-I exerts its anti-inflammatory effects mainly by regulating the functions of immune cells, such as monocytes/macrophages, dendritic cells, neutrophils, and T lymphocytes. It also modulates the function of vascular endothelial cells and adipocytes. Additionally, ApoA-I directly exerts anti-inflammatory effects against pathogenic microorganisms or their products. Intensive research on ApoA-I will hopefully lead to better diagnosis and treatment of inflammatory diseases.

Lower serum LDL-C levels are associated with poor prognosis in severe fever with thrombocytopenia syndrome: a single-center retrospective cohort study

Background

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease triggered by a novel bunyavirus (SFTSV). Characterized by fever, thrombocytopenia, leukocytopenia, and multiple organ dysfunction manifestations, its primary mode of transmission is through tick bites. Despite the critical role of lipid metabolism in viral infections, the role of lipids in SFTS remains unclear.

Methods

This retrospective study analyzed 602 patients with SFTS treated at the Shandong Public Health Clinical Center from January 2021 to December 2023. Based on the endpoint events, patients were classified into survival (S) and death (D) groups. The S group was further classified into non-critical (non-C) and critical (C) groups based on symptoms. All patients were followed up for at least 28 days after admission. Propensity score matching, multivariable logistic regression, survival analysis, time trend analysis, and mediation analysis were conducted to assess the association between LDL-C levels and prognosis in SFTS.

Results

The serum LDL-C levels on admission were significantly lower in the D and C groups than in the S and non-C groups. The logistic regression models indicated a potential association between LDL-C levels and a poor prognosis in SFTS. The restricted cubic spline showed a unidirectional trend between LDL-C levels and mortality, with a cutoff value of 1.59 mmol/L. The survival analysis revealed higher and earlier mortality in the low-LDL-C group than in the high-LDL-C group. The trends over 28 days post-admission showed that the serum LDL-C levels gradually increased in SFTS, with a favorable prognosis. Finally, the mediation analysis indicated that low LDL-C levels are associated with mortality through poor hepatic, cardiac, and coagulation functions.

Conclusion

Low LDL-C levels are potentially associated with a poor prognosis in SFTS.

Effect of IL-6R blockade on plasma lipids and clinical outcomes among hospitalized patients with COVID-19 infection

Plasma lipid levels are modulated by systemic infection and inflammation; it is unknown whether these changes reflect inflammatory responses or caused directly by pathogen presence. We explored the hypothesis that anti-inflammatory intervention via interleukin 6 receptor (IL-6R) blockade would influence plasma lipid levels during severe infection and evaluated the association of plasma lipid changes with clinical outcomes. Sarilumab (monoclonal antibody blocking IL-6R) efficacy was previously assessed in patients with coronavirus disease 2019 (COVID-19) (NCT04315298). This analysis determined whether strong inflammatory reduction by sarilumab in patients with COVID-19 pneumonia of increasing severity (severe, critical, multisystem organ dysfunction) affected plasma lipid changes between day 1 and day 7 of study therapy. Baseline lipid levels reflected the presence of acute systemic infection, characterized by very low HDL-C, low LDL-C, and moderately elevated triglycerides (TGs). Disease severity was associated with progressively more abnormal lipid levels. At day 7, median lipid levels increased more in the sarilumab versus placebo group (HDL-C +10.3%, LDL-C +54.7%, TG +32% vs. HDL-C +1.7%, LDL-C +15.4%, TG +8.8%, respectively). No significant association between lipid changes and clinical outcomes was observed. In conclusion, severe-to-critical COVID-19 pneumonia causes profound HDL-C depression that is only modestly responsive to strong anti-IL-6R inflammatory intervention. Conversely, LDL-C depression is strongly responsive to IL-6R blockade, with LDL-C levels likely returning to the predisease set point. These results advance our understanding of the complex relationship between serum lipids and infection/inflammation and suggest that HDL-C depression during acute contagious disease is driven by infection and not IL-6-mediated inflammation.

Plasma Proteomics Elucidated a Protein Signature in COVID-19 Patients with Comorbidities and Early-Diagnosis Biomarkers

Despite great scientific efforts, deep understanding of coronavirus-19 disease (COVID-19) immunopathology and clinical biomarkers remains a challenge. Pre-existing comorbidities increase the mortality rate and aggravate the exacerbated immune response against the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection, which can result in more severe symptoms as well as long-COVID and post-COVID complications. In this study, we applied proteomics analysis of plasma samples from 28 patients with SARS-CoV-2, with and without pre-existing comorbidities, as well as their corresponding controls to determine the systemic protein changes caused by the SARS-CoV-2 infection. As a result, the protein signature shared amongst COVID-19 patients with comorbidities was revealed to be characterized by alterations in the coagulation and complement pathways, acute-phase response proteins, tissue damage and remodeling, as well as cholesterol metabolism. These altered proteins may play a relevant role in COVID-19 pathophysiology. Moreover, several novel potential biomarkers for early diagnosis of the SARS-CoV-2 infection were detected, such as increased levels of keratin K22E, extracellular matrix protein-1 (ECM1), and acute-phase response protein α-2-antiplasmin (A2AP). Importantly, elevated A2AP may contribute to persistent clotting complications associated with the long-COVID syndrome in patients with comorbidities. This study provides new insights into COVID-19 pathogenesis and proposes novel potential biomarkers for early diagnosis that could be facilitated for clinical application by further validation studies.

Targeting host-specific metabolic pathways-opportunities and challenges for anti-infective therapy

Microorganisms can takeover critical metabolic pathways in host cells to fuel their replication. This interaction provides an opportunity to target host metabolic pathways, in addition to the pathogen-specific ones, in the development of antimicrobials. Host-directed therapy (HDT) is an emerging strategy of anti-infective therapy, which targets host cell metabolism utilized by facultative and obligate intracellular pathogens for entry, replication, egress or persistence of infected host cells. This review provides an overview of the host lipid metabolism and links it to the challenges in the development of HDTs for viral and bacterial infections, where pathogens are using important for the host lipid enzymes, or producing their own analogous of lecithin-cholesterol acyltransferase (LCAT) and lipoprotein lipase (LPL) thus interfering with the human host's lipid metabolism.

Why have SGLT2 Inhibitors Failed to Achieve the Desired Success in COVID-19?

The SARS-CoV-2 virus emerged towards the end of 2019 and caused a major worldwide pandemic lasting at least 2 years, causing a disease called COVID-19. SARS-CoV-2 caused a severe infection with direct cellular toxicity, stimulation of cytokine release, increased oxidative stress, disruption of endothelial structure, and thromboinflammation, as well as angiotensin-converting enzyme 2 (ACE2) down-regulation-mediated renin-angiotensin system (RAS) activation. In addition to glucosuria and natriuresis, sodium-glucose transport protein 2 (SGLT2) inhibitors (SGLT2i) cause weight loss, a decrease in glucose levels with an insulin-independent mechanism, an increase in erythropoietin levels and erythropoiesis, an increase in autophagy and lysosomal degradation, Na+/H+-changer inhibition, prevention of ischemia/reperfusion injury, oxidative stress and they have many positive effects such as reducing inflammation and improving vascular function. There was great anticipation for SGLT2i in treating patients with diabetes with COVID-19, but current data suggest they are not very effective. Moreover, there has been great confusion in the literature about the effects of SGLT2i on COVID-19 patients with diabetes . Various factors, including increased SGLT1 activity, lack of angiotensin receptor blocker co-administration, the potential for ketoacidosis, kidney injury, and disruptions in fluid and electrolyte levels, may have hindered SGLT2i's effectiveness against COVID-19. In addition, the duration of use of SGLT2i and their impact on erythropoiesis, blood viscosity, cholesterol levels, and vitamin D levels may also have played a role in their failure to treat the virus. This article aims to uncover the reasons for the confusion in the literature and to unravel why SGLT2i failed to succeed in COVID-19 based on some solid evidence as well as speculative and personal perspectives.

Eliminating COVID-19 as the immediate culprit for igniting pancreatitis

The impact of severe acute respiratory syndrome coronavirus 2 infection on the potential development of pancreatitis is a subject of ongoing debate within academic discourse. Establishing a causal link between COVID-19 and pancreatitis may not be fully supported by relying only on retrospective studies or case reports. This study examined the relationship between COVID-19 phenotypes and pancreatitis by Mendelian randomization (MR) method. The identification of instrumental variables (single nucleotide polymorphisms) that exhibit a robust association with the COVID-19 phenotypes was accomplished through a meticulous process of rigorous screening procedures. We included acute pancreatitis and chronic pancreatitis (CP) as the outcomes in the MR analysis, even though no definitive studies exist between COVID-19 and CP. A direct causal relationship between genetically predicted COVID-19 phenotypes and pancreatitis risk cannot be established. There is an ongoing debate over the designation of COVID-19 as a definitive cause of pancreatitis.