Loneliness Gets Under the Skin: A Scoping Review Exploring the Link Between Loneliness and Biological Measures of Inflammation

BACKGROUND

Research suggests that systemic inflammation may link loneliness to adverse health outcomes, yet there is a gap in comprehensively reviewing recent evidence on the relationship between loneliness and biological measures of inflammation in adults. This scoping review synthesizes current research to address the question: Is there a definitive link between loneliness and biological markers of inflammation in adults?

METHODS

Following the methods outlined by Arksey and O'Malley, we developed a protocol, defined our research question, and systematically searched PubMed, CINAHL, Embase, and Scopus for English-language studies conducted from 2018 to 2023 exploring the relationship between loneliness and biomarkers of inflammation in adults.

RESULTS

Twelve studies meeting the inclusion criteria displayed heterogeneity in terms of sample characteristics, loneliness scales, and inflammatory biomarkers. The UCLA Loneliness Scale, in various forms, emerged as the predominant tool for measuring loneliness, while C-reactive protein and interleukin-6 were the most frequently evaluated inflammatory biomarkers. Notably, all 12 studies reported an association between loneliness and at least 1 biological marker of inflammation.

CONCLUSION

Research consistently associates loneliness with poor health outcomes in aging adults, but the underlying mechanisms remain unclear. This scoping review suggests that inflammation may serve as a pathway linking loneliness to adverse health outcomes. However, the variability across studies highlights the need for standardized measurement methods and a consideration of both the duration and extent of loneliness. Enhancing our understanding of how loneliness affects systemic inflammation may help clarify why loneliness is associated with negative health outcomes.

Body composition markers are associated with changes in inflammatory markers but not vice versa: A bi-directional longitudinal analysis in a population-based sample

BACKGROUND AND AIM

Growing body of evidence consistently link obesity and inflammation, Although the direction of the association is still unclear. We aimed to investigate longitudinal associations of body anthropometric, composition and fat distribution parameters with inflammatory markers and vice versa.

METHOD AND RESULTS

We used data from 2464 individuals of the SHIP-TREND cohort with a median follow-up of 7 years. Linear regression models adjusted for confounders were used to analyze associations of standardized body composition markers derived from classic anthropometry, bioelectrical impedance analysis (BIA) and magnetic resonance imaging (MRI) at baseline with changes in inflammatory markers (C-reactive protein (CRP), white blood cell (WBC), fibrinogen) and vice versa. Higher level of anthropometric markers at baseline were associated with an increase in the change of inflammatory markers. A 13.5 cm higher waist circumference (WC), 16.0 kg body weight and 7.76 % relative fat mass (FM) at baseline was associated with a change in CRP of 0.52 mg/L (95 % confidence interval [CI]: 0.29 to 0.74), 0.51 mg/L (95 % CI: 0.29; 0.74) and 0.58 mg/L (95 % CI: 0.34; 0.82) respectively. Absolute FM showed the strongest association with changes in serum fibrinogen levels (β for 8.69 kg higher FM: 0.07 g/L; 95 % CI: 0.05; 0.09). Baseline inflammatory markers were only associated with changes in hip circumference.

CONCLUSION

Our study indicates the importance of anthropometric, body composition and fat distribution markers as a risk factor for the development of inflammation. To prevent inflammatory-related complications, important is to take measures against the development of obesity.

The Role of Major Inflammatory Biomarkers in the Pathogenesis of Atrial Fibrillation

Many studies have reported a relationship between inflammation and atrial fibrillation (AF). According to the literature, inflammation is the key component in pathophysiological processes during the development of AF; the amplification of inflammatory pathways triggers AF, and, at the same time, AF increases the inflammatory state. The plasma levels of several inflammatory biomarkers are elevated in patients with AF; therefore, inflammation might contribute to both the maintenance and occurrence of AF and its thromboembolic complications. Numerous inflammatory markers have been linked to AF, including CD40 ligand, fibrinogen, matrix metalloproteinase (MMP)-9, monocyte chemoattractant protein-1, myeloperoxidase, plasminogen activator inhibitor-1, and serum amyloid A. There are many pathophysiological aspects of AF that are linked to these inflammatory biomarkers, including atrial structural remodeling and atrial dilatation, increased atrial myocyte expression, fluctuations in calcium cycling, cardiac remodeling promotion, increased cardiac myocyte proliferation and terminal differentiation, production of several MMPs, the pathogenesis of atherosclerosis and cardiomyocyte apoptosis, an increased degree of fibrosis in atrial myocardium, and the progression and development of atherogenesis and atherothrombosis. The present review article aims to provide an updated overview and focus on the basic role of different biomarkers of inflammation in the pathophysiological aspects of the pathogenesis of AF.

Acute Myocardial Infarction Biosensor: A Review From Bottom Up

Acute myocardial infarction (AMI) is a cardiovascular disease that is produced due to a deficiency of oxygen generating irreversible damage in the heart muscle. In diagnosis, electrocardiogram (ECG) investigation has been the main method but is insufficient, so approaches like the measurement of biomarkers levels in plasma or saliva have become one of the most commonly applied strategies for prognosis of AMI, as some of them are specifically related to a heart attack. Many tests are carrying on to determine biological markers changes, but usually, they present disadvantages related to time consumption and laborious work. To overcome the issues, researchers around the world have been developing different ways to enhance detection through the use of biosensors. These diagnostic devices have a biological sensing element associated to a physicochemical transducer that can be made from different materials and configurations giving place to different kinds of detection: Electrical/Electrochemical, Optical and Mechanical. In this review, the authors presents relevant investigations related to the most important biomarkers and biosensors used for their detection having in mind the nanotechnology participation in the process through the application of nanostructures as a good choice for device configuration.

C-Reactive Protein Level and its Relationship with Suicide Risk and Alexithymia among Newly Diagnosed, Drug-Naïve Patients with Non-Affective Psychosis

The aim of the present study was to evaluate C-Reactive Protein (CRP) levels in newly diagnosed drug-naïve patients with non-affective psychosis, testing the hypotheses that in such patients serum CRP levels would be higher than in healthy controls and related to more severe psychopathology, suicide risk and alexithymia. CRP levels of 30 adult patients and 30 sex- and age-matched healthy controls were evaluated. Patients were tested with the Scale of Suicide Ideation (SSI), the Toronto Alexithymia Scale (TAS-20), the Scale for the Assessment of Positive and Negative Symptoms (SAPS and SANS) and the Calgary Depression Scale for Schizophrenia (CDSS). Higher suicide risk patients showed higher CRP levels than lower suicide risk patients and healthy controls. Moreover, such patients showed higher SAPS, SANS and CDSS scores than lower suicide risk patients. In linear regression model, CRP was significantly associated with higher SSI and TAS-20 scores. The results of the present study support the notion that CRP, suicide risk and alexithymia are strictly linked in newly diagnosed, drug-naïve patients with non-affective psychosis, independently of depressive symptoms or general psychopathology. Limitations are discussed.

Impact and Neuropeptide Substance Pan Inflammatory Compound on Arachidonic Acid Compound Generation

There is much evidence that neuropeptide substance P is involved in neurogenic inflammation and is an important neurotransmitter and neurmodulator compound. In addition, substance P plays an important role in inflammation and immunity. Macrophages can be activated by substance P which provokes the release of inflammatory compounds such as interleukins, chemokines and growth factors. Substance P is involved in the mechanism of pain through the trigeminal nerve which runs through the head, temporal and sinus cavity. Substance P also activates mast cells to release inflammatory mediators such as arachindonic acid compound, cytokines/chemokines and histamine. The release of these chemical mediators is crucial for inflammatory response. Among these mediators there are prostoglandins and leukotrines. Here we review the impact of substance P on inflammatory compounds.

Endothelial cells, cholesterol, cytokines, and aging

It has been reported that high levels of cholesterol and triglycerides are associated with increased risk of developing atherosclerosis and shorter life. In fact, vascular endothelial dysfunction occurs during the human aging process. Accumulation of lipids in vascular endothelium activates leukocytes to produce cytokines and chemokines which recruit macrophages. On the other hand, macrophages augment inflammatory response and secrete vascular endothelial growth factor, a key cytokine that mediates angiogenesis and inflammatory response. In addition, hyperlipidaemia is one of the main risk factors for aging, hypertension and diabetes. Here, we review the interrelationship between endothelial cells, high level of cholesterol, and aging.

IL-37 (IL-1F7) the Newest Anti-Inflammatory Cytokine Which Suppresses Immune Responses and Inflammation

Cytokines such as interleukins, chemokines and interferons are immunomodulating and inflammatory agents, characterized by considerable redundancy, in that many cytokines appear to share similar functions. Virtually all nucleated cells, but especially epithelial cells and macrophages, are potent producers of cytokines. The objective of this study is to review the detailed mechanism of action and the biological profiles of IL-37, the newest anti-inflammatory cytokine. This review focuses on IL-37, a key cytokine in regulating inflammatory responses, mainly by inhibiting the expression, production and function of proinflammatory cytokines: IL-1 family pro-inflammatory effects are markedly suppressed by IL-37.