Biological motion during inflammation in humans

Locomotor and gait changes in the LPS model of neuroinflammation are correlated with inflammatory cytokines in blood and brain

Lipopolysaccharide (LPS) challenge in mice has been used to identify the mechanisms and therapeutics for neuroinflammation. In this study, we aimed to comprehensively evaluate the behavioral changes including locomotion, exploration, and memory, correlating them with a panel of thirteen inflammatory cytokines in both blood and brain.We found that acute LPS administration (0.83 mg/Kg i.p.) reduced body weight, food intake, and glucose levels compared to the saline-injected mice, concomitant with decreased activity in home cage monitoring. Locomotion was significantly reduced in Open Field, Introduced Object, and Y-Maze tests. Decreased exploratory behavior in the Y-Maze and Introduced Object tests was noticed, by measuring the number of arms explored and object interaction time, respectively. Additionally, in rotarod, LPS administration led to a significant decrease in the distance achieved, while in the MouseWalker, LPS led to a reduction in average velocity.LPS induced a decrease in microglia ramification index in the motor cortex and the striatum, while surprisingly a reduction in microglia number was observed in the motor cortex.The concentrations of thirteen cytokines in the blood were significantly altered, while only CXCL1, CCL22, CCL17, G-CSF, and IL-12p40 were changed in the brain. Correlations between cytokine levels in blood and brain were found, most notably for CCL17 and CCL22. TGFβ was the only one with negative correlations to other cytokines. Correlations between cytokines and behavior changes were also disclosed, especially for CCL17, CCL22, G-CSF, and IL-6 and negatively for TGFβ and IL-10.In summary, our study employing acute LPS challenge in mice has revealed a comprehensive profile of behavioral alterations alongside significant changes in inflammatory cytokine levels, both in peripheral blood and brain tissue. These findings contribute to a deeper understanding of the interplay between inflammation and behavior, with possible implications for identifying prognostics and therapeutic targets for neuroinflammatory conditions.

Back morphology and walking patterns mean 13.8 years after surgery for lumbar disk herniation in adolescents

Introduction

In many pain conditions, there is lingering pain despite healed tissue damage. Our previous study shows that individuals who underwent surgery for lumbar disk herniation (LDH) during adolescence have worse health, more pain, and increased disk degeneration mean 13 years after surgery compared with controls. It is unclear if walking patterns segregate surgically treated LDH adolescents and controls at mean 13-year follow-up.

Objectives

Here, we analyzed the relationship between gait, back morphology and other health outcomes in a cohort of individuals treated surgically because of lumbar disk herniation compared with controls.

Methods

We analyzed gait during a walking paradigm, back morphology at the site of surgery, and standardized health outcomes, among individuals who received surgery for LDH as adolescents, "cases" (n = 23), compared with "controls" (n = 23).

Results

There were gait differences in head (P = 0.021) and trunk angle (P = 0.021) between cases and controls in a direction where cases exhibited a posture associated with sickness. The gait variance was explained by subjective pain and exercise habits rather than objective disk degeneration.

Conclusion

Over a decade after surgery for LDH during adolescence, health among cases is worse compared with controls. The head and trunk angles differ between cases and controls, indicating that the residual pain lingers and may cause changes in movement patterns long after a painful episode in early life. Gait may be a useful target for understanding maintenance of pain and disability among individuals treated surgically for LDH during adolescence.

The walking sick: Perception of experimental sickness from biological motion

Identification of sick conspecifics allows for avoidance of infectious threats, and is therefore an important behavioral defense against diseases. Here, we investigated if humans can identify sick individuals solely from biological motion and posture (using point-light displays). Additionally, we sought to determine which movements and sickness parameters would predict such detection. We collected video clips and derived point-light displays (one stride presented in a loop) of sick walkers (injected with lipopolysaccharide at 2.0 ng/kg body weight) and the same walkers when healthy (injected with saline). We then presented these displays to two groups, one group classified each walker as sick or healthy (study 1, n = 106), and the other group scored the walkers' health on a visual analogue scale (study 2, n = 106). The raters were able to identify sick individuals above chance, and rated sick walkers as having worse health, both from observing video clips and point-light displays. Furthermore, both sickness detection and worse apparent health were predicted by inflammation-induced increase in rigidity and slower walking, but not other cues. Altogether, these findings indicate that biological motion can serve as a sickness cue, possibly allowing humans to identify sick conspecifics from a distance, and thereby allowing for disease avoidance.

Humans can detect axillary odor cues of an acute respiratory infection in others

Background and objectives

Body odor conveys information about health status to conspecifics and influences approach-avoidance behaviors in animals. Experiments that induce sickness in otherwise healthy individuals suggest that humans too can detect sensory cues to infection in others. Here, we investigated whether individuals could detect through smell a naturally occurring acute respiratory infection in others and whether sickness severity, measured via body temperature and sickness symptoms, was associated with the accuracy of detection.

Methodology

Body odor samples were collected from 20 donors, once while healthy and once while sick with an acute respiratory infection. Using a double-blind, two-alternative forced-choice method, 80 raters were instructed to identify the sick body odor from paired sick and healthy samples (i.e. 20 pairs).

Results

Sickness detection was significantly above chance, although the magnitude of the effect was low (56.7%). Raters' sex and disgust sensitivity were not associated with the accuracy of sickness detection. However, we find some indication that greater change in donor body temperature, but not sickness symptoms, between sick and healthy conditions improved sickness detection accuracy.

Conclusion and implications

Our findings suggest that humans can detect individuals with an acute respiratory infection through smell, albeit only slightly better than chance. Humans, similar to other animals, are likely able to use sickness odor cues to guide adaptive behaviors that decrease the risk of contagion, such as social avoidance. Further studies should determine how well humans can detect specific infections through body odor, such as Covid-19, and how multisensory cues to infection are used simultaneously.

The association of dietary inflammatory potential with sarcopenia in Chinese community-dwelling older adults

BACKGROUND

Dietary-induced inflammation is potentially associated with sarcopenia. Nevertheless, few studies have investigated the structure of the inflammatory diet and its correlation with muscle function and performance in both the upper and lower limbs. This study was performed to explore the association of the dietary inflammatory index (DII) with sarcopenia and its diagnostic parameters.

METHODS

We conducted a cross-sectional survey on a sample of 515 Chinese community-dwelling older adults selected through multistage cluster sampling from three districts in Shanghai. DII scores were calculated using a validated food frequency questionnaire. Sarcopenia and its diagnostic parameters were determined based on the definition set by the Asian Working Group on Sarcopenia (AWGS).

RESULTS

The mean age of study participants was 71.31 ± 4.71 years. The prevalence of sarcopenia in the cohort was 12.4%. Older adults in the highest DII quartile had a 3.339 times increased risk of sarcopenia compared to those in the lowest quartile (OR _Quartile4vs1:3.339, 95%CI: 1.232, 9.052, p-trend: 0.004) after adjusting for confounding factors. Additionally, a more pro-inflammatory diet was associated with lower appendicular skeletal muscle index (ASMI) (OR _Quartile4vs1: 3.005, 95%CI: 1.275, 7.318, p-trend: 0.005), a higher 5-times sit-stand test time score (OR _Quartile4vs1: 4.942, 95%CI: 1.745, 13.993, p-trend: 0.005), and lower gait speed (OR _Quartile4vs1: 2.392, 95%CI: 1.104, 5.185, p-trend: 0.041) after adjusting for confounding factors. However, there was no significant association between DII, handgrip strength, and Short Physical Performance Battery (SPPB) score in either the unadjusted or adjusted model.

CONCLUSION

This study found that the association between consuming a more pro-inflammatory diet and sarcopenia in Chinese community-dwelling older adults was mainly due to underlying low intakes of dietary energy, protein, and anti-inflammatory foods, and not due to the high intake of pro-inflammatory foods. Meanwhile, DII was more highly correlated with lower limb muscle strength and performance compared to upper limb muscle strength.

Behavioral and physiological sensitivity to natural sick faces

The capacity to rapidly detect and avoid sick people may be adaptive. Given that faces are reliably available, as well as rapidly detected and processed, they may provide health information that influences social interaction. Prior studies used faces that were manipulated to appear sick (e.g., editing photos, inducing inflammatory response); however, responses to naturally sick faces remain largely unexplored. We tested whether adults detected subtle cues of genuine, acute, potentially contagious illness in face photos compared to the same individuals when healthy. We tracked illness symptoms and severity with the Sickness Questionnaire and Common Cold Questionnaire. We also checked that sick and healthy photos were matched on low-level features. We found that participants (N = 109) rated sick faces, compared to healthy faces, as sicker, more dangerous, and eliciting more unpleasant feelings. Participants (N = 90) rated sick faces as more likely to be avoided, more tired, and more negative in expression than healthy faces. In a passive-viewing eye-tracking task, participants (N = 50) looked longer at healthy than sick faces, especially the eye region, suggesting people may be more drawn to healthy conspecifics. When making approach-avoidance decisions, participants (N = 112) had greater pupil dilation to sick than healthy faces, and more pupil dilation was associated with greater avoidance, suggesting elevated arousal to threat. Across all experiments, participants' behaviors correlated with the degree of sickness, as reported by the face donors, suggesting a nuanced, fine-tuned sensitivity. Together, these findings suggest that humans may detect subtle threats of contagion from sick faces, which may facilitate illness avoidance. By better understanding how humans naturally avoid illness in conspecifics, we may identify what information is used and ultimately improve public health.

From Low-Grade Inflammation in Osteoarthritis to Neuropsychiatric Sequelae: A Narrative Review

Nowadays, osteoarthritis (OA), a common, multifactorial musculoskeletal disease, is considered to have a low-grade inflammatory pathogenetic component. Lately, neuropsychiatric sequelae of the disease have gained recognition. However, a link between the peripheral inflammatory process of OA and the development of neuropsychiatric pathology is not completely understood. In this review, we provide a narrative that explores the development of neuropsychiatric disease in the presence of chronic peripheral low-grade inflammation with a focus on its signaling to the brain. We describe the development of a pro-inflammatory environment in the OA-affected joint. We discuss inflammation-signaling pathways that link the affected joint to the central nervous system, mainly using primary sensory afferents and blood circulation via circumventricular organs and cerebral endothelium. The review describes molecular and cellular changes in the brain, recognized in the presence of chronic peripheral inflammation. In addition, changes in the volume of gray matter and alterations of connectivity important for the assessment of the efficacy of treatment in OA are discussed in the given review. Finally, the narrative considers the importance of the use of neuropsychiatric diagnostic tools for a disease with an inflammatory component in the clinical setting.

The Relationships of Fibrinogen and C-Reactive Protein With Gait Performance: A 20-Year Longitudinal Study

Background

Gait speed, a central marker of aging, has been linked to various health outcomes, such as cognitive and physical functions in middle-aged adults. Although long-term systemic low-grade inflammation is considered a mechanism underlying a variety of aging-related risk factors, the longitudinal associations between inflammation markers and gait speed are yet to be fully investigated.

Objective

To explore the associations of CRP and fibrinogen levels, measured two decades ago, with gait speed among community dwelling adults, considering the contribution of cardio-metabolic factors and cognition.

Methods

Study participants took part in two phases of the of the “Kibbutzim Family Study” (i.e., Phase II, 1999–2000 and Phase III, 2017–2019). Blood samples collected in Phase II (baseline) were used to determine level of inflammatory markers. Gait speed was assessed under single-task (ST) and dual-task (DT) conditions in Phase III. Demographic, anthropometric and clinical data were collected in both phases. Linear regression models were used to assess the adjusted associations of inflammation and gait speed.

Results

A total of 373 individuals aged 34–99 (mean 64 ± 13 years) in Phase III were included in the study. Gait speed under ST was negatively associated with baseline levels of fibrinogen (b per standard deviation (SD) = −0.053, p = 0.0007) and CRP (b per SD = −0.043, p = 0.010), after adjusting for baseline and concurrent cardiometabolic risk factors. Accounting for executive functions, associations of fibrinogen with gait under ST were somewhat attenuated, yet associations remained statistically significant (p < 0.05). Associations with CRP were attenuated to the null. In contrast, there were no associations between inflammation markers and gait under DT.

Conclusion

Our findings demonstrate that in a sample including younger to older adults, higher systemic inflammatory activity was linked with gait 20 years later, beyond age and cardiometabolic health, and to a certain extent, beyond executive functions. Thus, systemic inflammation may serve as an early marker to identify individuals at risk for gait decline.

A Survey of Human Gait-Based Artificial Intelligence Applications

We performed an electronic database search of published works from 2012 to mid-2021 that focus on human gait studies and apply machine learning techniques. We identified six key applications of machine learning using gait data: 1) Gait analysis where analyzing techniques and certain biomechanical analysis factors are improved by utilizing artificial intelligence algorithms, 2) Health and Wellness, with applications in gait monitoring for abnormal gait detection, recognition of human activities, fall detection and sports performance, 3) Human Pose Tracking using one-person or multi-person tracking and localization systems such as OpenPose, Simultaneous Localization and Mapping (SLAM), etc., 4) Gait-based biometrics with applications in person identification, authentication, and re-identification as well as gender and age recognition 5) “Smart gait” applications ranging from smart socks, shoes, and other wearables to smart homes and smart retail stores that incorporate continuous monitoring and control systems and 6) Animation that reconstructs human motion utilizing gait data, simulation and machine learning techniques. Our goal is to provide a single broad-based survey of the applications of machine learning technology in gait analysis and identify future areas of potential study and growth. We discuss the machine learning techniques that have been used with a focus on the tasks they perform, the problems they attempt to solve, and the trade-offs they navigate.

Qigong Training Positively Impacts Both Posture and Mood in Breast Cancer Survivors With Persistent Post-surgical Pain: Support for an Embodied Cognition Paradigm

Theories of embodied cognition hypothesize interdependencies between psychological well-being and physical posture. The purpose of this study was to assess the feasibility of objectively measuring posture, and to explore the relationship between posture and affect and other patient centered outcomes in breast cancer survivors (BCS) with persistent postsurgical pain (PPSP) over a 12-week course of therapeutic Qigong mind-body training. Twenty-one BCS with PPSP attended group Qigong training. Clinical outcomes were pain, fatigue, self-esteem, anxiety, depression, stress and exercise self-efficacy. Posture outcomes were vertical spine and vertical head angles in the sagittal plane, measured with a 3D motion capture system in three conditions: eyes open (EO), eyes open relaxed (EOR) and eyes closed (EC). Assessments were made before and after the Qigong training. The association between categorical variables (angle and mood) was measured by Cramer's V. In the EO condition, most participants who improved in fatigue and anxiety scales also had better vertical head values. For the EOR condition, a moderate correlation was observed between changes in vertical head angle and changes in fatigue scale. In the EC condition, most of the participants who improved in measures of fatigue also improved vertical head angle. Additionally, pain severity decreased while vertical spine angle improved. These preliminary findings support that emotion and other patient centered outcomes should be considered within an embodied framework, and that Qigong may be a promising intervention for addressing biopsychosocially complex interventions such as PPSP in BCSs.

Back to the future of psychoneuroimmunology: Studying inflammation-induced sickness behavior

What do we know about sickness behavior? In this article, I guide you through some of the complexity of sickness behavior occurring after an immune challenge. I highlight the many features of behavioral and affective changes induced during experimental endotoxemia in humans, and describe how little we know about many of these features. I argue that we need to dismantle the components of inflammation-induced sickness behavior, and study each component in detail. I also point out the large inter-individual differences in inflammation-induced behavioral and affective changes, and the fact that psychosocial factors likely interact with inflammation to shape inflammation-induced sickness behavior. PNI clearly lacks investigations of the vulnerability and resilient factors underlying the inter-individual variability in sickness behavior. Throughout the article, I base my argument on my published articles, and provide concrete examples from my experience and the data that I have collected over the past 10 years. Given the relevance of inflammation-induced sickness behavior for inflammation-associated depression and for how people react to infections, I encourage current and future psychoneuroimmunologists to return towards basic science of sickness behavior.

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Inflammation-related sickness behavior is relevant for inflammation-associated depression

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The many features of sickness behavior should be investigated in detail

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There are large inter-individual variability in sickness behavior

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Vulnerability and resilient factors predicting sickness responses are little known

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I call for a return towards basic science of sickness behavior.

Regulation of emotions during experimental endotoxemia: A pilot study

Even though dysfunctional emotion regulation is prominent in depression and a link between depression and inflammation is well established, there is little knowledge about how inflammation affects the regulation of emotions. The aim of this pilot study was to explore the effect of experimentally induced inflammation on the cognitive reappraisal of emotions, and to assess domain specificity by comparing success in regulation of emotions towards two unpleasant stimuli classes (general negative stimuli and disgust stimuli). In a between-subject design, ten healthy participants were injected with an intravenous injection of lipopolysaccharide (2 ng/kg body weight) and eleven were injected with saline. Participants performed a cognitive reappraisal task, in which they had to down-regulate or up-regulate their emotions towards general negative stimuli and disgust stimuli, 5-6 h post-injection. Contrary to our hypotheses, participants injected with lipopolysaccharide reported greater success in down-regulating emotional responses towards unpleasant stimuli as compared to the saline group. In addition, both groups were poorer at down-regulating emotions towards disgust stimuli as compared to general negative stimuli. The current pilot study indicates that cognitive reappraisal of emotions is affected during experimental endotoxemia, and suggests that disgust stimuli might be difficult to reappraise.

Infection threat shapes our social instincts

We social animals must balance the need to avoid infections with the need to interact with conspecifics. To that end we have evolved, alongside our physiological immune system, a suite of behaviors devised to deal with potentially contagious individuals. Focusing mostly on humans, the current review describes the design and biological innards of this behavioral immune system, laying out how infection threat shapes sociality and sociality shapes infection threat. The paper shows how the danger of contagion is detected and posted to the brain; how it affects individuals’ mate choice and sex life; why it strengthens ties within groups but severs those between them, leading to hostility toward anyone who looks, smells, or behaves unusually; and how it permeates the foundation of our moral and political views. This system was already in place when agriculture and animal domestication set off a massive increase in our population density, personal connections, and interaction with other species, amplifying enormously the spread of disease. Alas, pandemics such as COVID-19 not only are a disaster for public health, but, by rousing millions of behavioral immune systems, could prove a threat to harmonious cohabitation too.

Acute Systemic Experimental Inflammation Does Not Reduce Human Odor Identification Performance

Olfactory dysfunction is a common symptom of various diseases, but the underlying pathophysiology has not been fully understood. Evidence from both animal and human studies suggests that local inflammation of the olfactory epithelium is linked to olfactory dysfunction. However, whether systemic inflammation causes olfactory dysfunction is yet to be determined. In the present behavioral study, we set out to test whether acute systemic inflammation impairs olfactory identification performance by inducing a transient and controlled state of systemic inflammation using an experimental endotoxemia model. We treated young healthy participants (N = 20) with a relatively high dose (2.0 ng/kg) of lipopolysaccharide (LPS) and a placebo treatment in a double-blind within-subject design, and assessed participants’ ability to identify odors using the MONEX-40, a reliable method for experimental assessment of odor identification ability in healthy and young individuals. Our results show that olfactory identification performance was not affected by the acute systemic inflammation triggered by the injection of LPS. Moreover, odor identification performance following the LPS injection was not associated with levels of circulating proinflammatory cytokines (interleukin-6, interleukin-8, and tumor necrosis factor-α). Because experimental LPS-induced systemic inflammation does not affect olfactory identification performance, our findings suggest that chronic, rather than transient, systemic inflammation is a more likely mechanism to explore in order to explain the olfactory deficits observed in inflammatory diseases.

Why Do They Fall? The Impact of Insomnia on Gait of Older Adults: A Case-Control Study

STUDY OBJECTIVES

To compare gait and cognitive performance conducted separately as a single- (ST) and simultaneously as a dual-task (DT), ie, when a cognitive task was added, among community-dwelling older adults with and without insomnia.

METHODS

Participants included: 39 (28 females) community-dwelling older adults with insomnia, 34 (21 females) controls without insomnia. Subject groups were matched for age, gender, and education. Sleep quality was evaluated based on two-week actigraphy. Gait speed and cognition were assessed as ST and DT performance. DT costs (DTCs) were calculated for both tasks. Outcomes were compared via independent samples t-tests or Mann-Whitney U-tests.

RESULTS

Older adults with insomnia demonstrated significantly slower gait speed during ST (1 ± 0.29 vs 1.27 ± 0.17 m/s, p<0.001) and DT (0.77 ± 0.26 vs 1.14 ± 0.20 m/s, p<0.001) and fewer correct responses in the cognitive task during ST (21 ± 7 vs 27 ± 11, p=0.009) and DT (19 ± 7 vs 23 ± 9, p=0.015) compared to control group. DTC for the gait task was higher among older adults with insomnia (18.32%, IQR: 9.48-30.93 vs 7.81% IQR: 4.43-14.82, p<0.001). However, no significant difference was observed in DTC for the cognitive task (14.71%, IQR: -0.89-38.84 vs 15%, IQR: -0.89-38.84%, p=0.599).

CONCLUSION

Older adults with insomnia have lower gait speed and poorer cognitive performance during ST and DT and an inefficient pattern of task prioritization during walking, compared to counterparts without insomnia. These findings may explain the higher risk of falls among older adults with insomnia. Geriatric professionals should be aware of potential interrelationships between sleep and gait.

Comparison of bacterial lipopolysaccharide-induced sickness behavior in rodents and humans: Relevance for symptoms of anxiety and depression

Increasing evidence from animal and human studies suggests that inflammation may be involved in mood disorders. Sickness behavior and emotional changes induced by experimental inflammatory stimuli have been extensively studied in humans and rodents to better understand the mechanisms underlying inflammation-driven mood alterations. However, research in animals and humans have remained compartmentalized and a comprehensive comparison of inflammation-induced sickness and depressive-like behavior between rodents and humans is lacking. Thus, here, we highlight similarities and differences in the effects of bacterial lipopolysaccharide administration on the physiological (fever and cytokines), behavioral and emotional components of the sickness response in rodents and humans, and discuss the translational challenges involved. We also emphasize the differences between observable sickness behavior and subjective sickness reports, and advocate for the need to obtain both subjective reports and objective measurements of sickness behavior in humans. We aim to provide complementary insights for translational clinical and experimental research on inflammation-induced behavioral and emotional changes, and their relevance for mood disorders such as depression.

Properties of the Sickness Questionnaire in an Australian sample with chronic medically unexplained symptoms

Sickness behavior including malaise, fatigue and increased pain sensitivity is thought to be adaptive and facilitate recovery from disease. However, it may also reduce functioning and health if symptoms persists, which is why validated instruments for its assessment are needed. We evaluated the English translation of the Sickness Questionnaire (SicknessQ) in an Australian population of 156 participants with high level of persistent musculoskeletal pain and/or gastrointestinal symptoms without an organic explanation. The SicknessQ total score had an adequate model fit and no other models were found to fit data better. The SicknessQ correlated most strongly with fatigue, stress, anxiety and depression, which explained 62% of the variance in SicknessQ, but not with physical functioning. The mean score (8.9; 95 %CI: 8.0-9.8) was in between those previously reported in a general population sample and in primary care patients. In conclusion, the evaluation of the English version of the SicknessQ in an Australian sample with significant, chronic unexplained medical symptoms supports the use of the English version of the total SicknessQ score as an overall measure of sickness behavior.