Immunological Mechanisms of Sickness Behavior in Viral Infection

An IFNγ-dependent immune-endocrine circuit lowers blood glucose to potentiate the innate antiviral immune response

Viral infection makes us feel sick as the immune system alters systemic metabolism to better fight the pathogen. The extent of these changes is relative to the severity of disease. Whether blood glucose is subject to infection-induced modulation is mostly unknown. Here we show that strong, nonlethal infection restricts systemic glucose availability, which promotes the antiviral type I interferon (IFN-I) response. Following viral infection, we find that IFNγ produced by γδ T cells stimulates pancreatic β cells to increase glucose-induced insulin release. Subsequently, hyperinsulinemia lessens hepatic glucose output. Glucose restriction enhances IFN-I production by curtailing lactate-mediated inhibition of IRF3 and NF-κB signaling. Induced hyperglycemia constrained IFN-I production and increased mortality upon infection. Our findings identify glucose restriction as a physiological mechanism to bring the body into a heightened state of responsiveness to viral pathogens. This immune-endocrine circuit is disrupted in hyperglycemia, possibly explaining why patients with diabetes are more susceptible to viral infection.

Inflammageing mediated by cytotoxic lymphocytes is associated with diabetes duration

AIMS

Inflammageing, the age-related systemic increase of proinflammatory factors, has been linked to the development of cardiovascular disease, chronic kidney disease and cancer in the elderly. Chronic inflammation is believed to be a causative factor in the development of diabetic complications. However, exactly how type 2 diabetes impacts the inflammatory state of the immune system is incompletely characterised.

METHODS

Blood collection and anthropometric measurements were performed in patients with type 2 diabetes (n = 49) and control subjects (n = 30). The phenotype, proliferation capacity and cytokine production by cytotoxic lymphocytes were analysed using multiparametric flow cytometry.

RESULTS

Type 2 diabetes did not impact the phenotype or proliferation of the investigated cells. However, we observed a significantly increased production of tumour necrosis factor-α by CD8+ T cells and Granzyme B by natural killer cells and γδ T cells compared to controls. Hyperresponsiveness of cytotoxic blood lymphocytes did not correlate with glycaemia or body mass index, but instead was associated with older age and longer diabetes duration.

CONCLUSIONS

Type 2 diabetes is associated with an increased pro-inflammatory potential of cytotoxic blood lymphocytes correlating with age and diabetes duration. Further research is necessary to explore potential benefits of diabetes medications in reverting this effect.

Cognitive, neuropsychiatric and neurological alterations in mastocytosis: A systematic review

BACKGROUND

Mastocytosis manifests with multisystemic symptoms, often involving the nervous system. Numerous cognitive, neuropsychiatric and neurological alterations have been reported in multiple observational studies.

METHODS

We performed a qualitative systematic literature review of reported data consulting the electronic databases Medline, Scopus, Web of Science, Cochrane, and BASE until June 2023.

RESULTS

We selected 24 studies in which the majority showed that a high proportion of mastocytosis patients suffer cognitive, neuropsychiatric and neurological alterations. The most common disorders and estimated ranges of frequency observed in adults were depression (68%-75%), anxiety, high stress or irritability (27%-54%), cognitive impairment (27%-39%, primarily affecting memory skills), and headaches (55%-69%). Attention challenges and learning difficulties were reported in children at a rate of 13%, while neurodevelopmental disorders occurred at rates of 8%-12%. Frequent white abnormalities in mastocytosis patients with concomitant psychocognitive symptoms have been reported although neuroimaging studies have been performed rarely in this population.

CONCLUSION

Further studies with more comprehensive and homogeneous evaluations and neuroimaging and histological analysis should be performed for a better understanding of these manifestations. An earlier detection and proper management of these symptoms could greatly improve the quality of life of these patients.

Glucose metabolism disorder: a potential accomplice of SARS-CoV-2

Globally, 265,713,467 confirmed cases of SARS-CoV-2 (CoV-2), including 5,260,888 deaths, have been reported by the WHO. It is important to study the mechanism of this infectious disease. A variety of evidences show the potential association between CoV-2 and glucose metabolism. Notably, people with type 2 diabetes mellitus (T2DM) and other metabolic complications were prone to have a higher risk of developing a more severe infection course than people who were metabolically normal. The correlations between glucose metabolism and CoV-2 progression have been widely revealed. This review will discuss the association between glucose metabolism disorders and CoV-2 progression, showing the promoting effect of diabetes and other diseases related to glucose metabolism disorders on the progression of CoV-2. We will further conclude the effects of key proteins and pathways in glucose metabolism regulation on CoV-2 progression and potential interventions by targeting glucose metabolism disorders for CoV-2 treatment. Therefore, this review will provide systematic insight into the treatment of CoV-2 from the perspective of glucose metabolism.

Bat behavioral immune responses in social contexts: current knowledge and future directions

Animals often mount complex immune responses to infections. Aside from cellular and molecular defense mechanisms, animals can alter their behavior in response to infection by avoiding, resisting, or tolerating negative effects of pathogens. These behaviors are often connected to cellular and molecular immune responses. For instance, sickness behaviors are a set of behavioral changes triggered by the host inflammatory response (e.g., cytokines) and could aid in resisting or tolerating infection, as well as affect transmission dynamics if sick animals socially withdraw or are being avoided by others. To fully understand the group and population level transmission dynamics and consequences of pathogen infections in bats, it is not only important to consider cellular and molecular defense mechanisms, but also behavioral mechanisms, and how both interact. Although there has been increasing interest in bat immune responses due to their ability to successfully cope with viral infections, few studies have explored behavioral anti-pathogen defense mechanisms. My main objective is to explore the interaction of cellular and molecular defense mechanisms, and behavioral alterations that results from infection in bats, and to outline current knowledge and future research avenues in this field.

Physiological role of cytokines in the regulation of mammalian metabolism

The innate cytokine system is involved in the response to excessive food intake. In this review, we highlight recent advances in our understanding of the physiological role of three prominent cytokines, interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF), in mammalian metabolic regulation. This recent research highlights the pleiotropic and context-dependent functions in the immune-metabolic interplay. IL-1β is activated in response to overloaded mitochondrial metabolism, stimulates insulin secretion, and allocates energy to immune cells. IL-6 is released by contracting skeletal muscle and adipose tissue and directs energy from storing tissues to consuming tissues. TNF induces insulin resistance and prevents ketogenesis. Additionally, the therapeutic potential of modulating the activity of each cytokine is discussed.

Inflammation and severity of depressive symptoms in physically active individuals after COVID-19 – An exploratory immunopsychological study investigating the effect of inflammation on depressive symptom severity

Background

SARS-CoV-2 infection is a risk factor for the development of depressive symptoms such as lack of energy, loss of interest, and depressed mood. Inflammatory processes might underline this association. The aim of this study was to investigate the association between inflammatory markers and the severity of depression after SARS-CoV-2 infection, and the predictive effect of inflammatory markers on the severity of depressive symptoms. Lifestyle factors and lifestyle-related diseases can influence inflammation and depressive symptoms. As these lifestyle factors and lifestyle-related diseases are less common in physically active individuals, they are a suitable population for investigating this research question.

Methods

We investigated 61 at least moderate physically active individuals on average ∼6 months (SD = 4.22, range = 0.5–19 months) after SARS-CoV-2 infection (t₀) and performed a follow-up after 3 months (t₁). Depressive symptoms and biomarkers of inflammation (interleukin [IL]-1β, IL-8, IL-10, Ferritin, Lipopolysaccharide-binding-protein [LBP], neutrophil-to-lymphocyte ratio [NLR], platelet-to-lymphocyte ratio [PLR], lymphocyte-to-monocyte ratio [LMR]) and kynurenine [KYN] were measured at both time points. Concentrations of inflammatory markers at t₀ were used to predict the severity of depressive symptoms at t₀ and t₁.

Results

Concentrations of KYN were negatively related to the severity of depressive symptoms at t_0. Concentrations of LMR predicted higher depressive symptoms at t₀ as well as at t₁. Furthermore, individuals with lower concentrations of LBP at t₀ showed a higher severity of depressive symptoms at t₁. No correlation was found between severity of depressive symptoms and IL1β, IL-8, IL-10, ferritin, NLR, and PLR at both time points.

Conclusions

KYN, LBP and LMR might be useful as a predictive factor of depressive symptoms in physically active individuals after SARS-CoV-2 infection. While the results for KYN confirm the current scientific evidence, our results highlight the importance of the innovative inflammatory markers LMR and LBP. LMR and LBP might be interesting targets for predicting the development of depressive symptoms in SARS-CoV-2 infected populations and should be further investigated in future studies.

Reviving the mutual impact of SARS-COV-2 and obesity on patients: From morbidity to mortality

Obesity-related metabolic dysfunction, endothelium imbalance, chronic inflammation, immune dysregulation, and its comorbidities may all have a role in systemic inflammation, leading to the pulmonary fibrosis and cytokine storm, which leads to failure of lung function, which is a hallmark of severe SARS-CoV-2 infection. Obesity may also disrupt the function of mucociliary escalators and cooperation of epithelial cell's motile cilia in the airway, limiting the clearance of the coronavirus that causes severe acute respiratory syndrome (SARS-CoV-2). Adipose tissues in obese patients have a greater number of proteases and receptors for SARS-CoV-2 admittance, proposing that they could serve as an accelerator and reservoir for this virus, boosting immunological response and systemic inflammation. Lastly, anti-inflammatory cytokines such as anti-IL-6 and the infusion of mesenchymal stem cells could be used as a modulation therapy of immunity to help COVID-19 patients. Obesity, on the other hand, is linked to the progress of COVID-19 through a variety of molecular pathways, and obese people are part of the SARS-CoV-2 susceptible individuals, necessitating more protective measures.