Interleukin-6 and risk of cognitive decline: MacArthur studies of successful aging

Inflammation and Nutritional Science for Programs/Policies and Interpretation of Research Evidence (INSPIRE)

An increasing recognition has emerged of the complexities of the global health agenda—specifically, the collision of infections and noncommunicable diseases and the dual burden of over- and undernutrition. Of particular practical concern are both 1) the need for a better understanding of the bidirectional relations between nutritional status and the development and function of the immune and inflammatory response and 2) the specific impact of the inflammatory response on the selection, use, and interpretation of nutrient biomarkers. The goal of the Inflammation and Nutritional Science for Programs/Policies and Interpretation of Research Evidence (INSPIRE) is to provide guidance for those users represented by the global food and nutrition enterprise. These include researchers (bench and clinical), clinicians providing care/treatment, those developing and evaluating programs/interventions at scale, and those responsible for generating evidence-based policy. The INSPIRE process included convening 5 thematic working groups (WGs) charged with developing summary reports around the following issues: 1) basic overview of the interactions between nutrition, immune function, and the inflammatory response; 2) examination of the evidence regarding the impact of nutrition on immune function and inflammation; 3) evaluation of the impact of inflammation and clinical conditions (acute and chronic) on nutrition; 4) examination of existing and potential new approaches to account for the impact of inflammation on biomarker interpretation and use; and 5) the presentation of new approaches to the study of these relations. Each WG was tasked with synthesizing a summary of the evidence for each of these topics and delineating the remaining gaps in our knowledge. This review consists of a summary of the INSPIRE workshop and the WG deliberations.

C-reactive protein plays a marginal role in cognitive decline: a systematic review and meta-analysis

OBJECTIVE

The objective of the study was to investigate the association between peripheral levels of C-reactive protein (CRP) and cognitive decline that is defined by 2-5 years of cognitive change in general cognitive function or specific cognitive domain.

METHODS

We searched PubMed and Google for prospective/longitudinal studies that report the association between peripheral levels of CRP and risk of cognitive decline in the nondementia population.

RESULTS

Out of 479 related articles from PubMed and Google, four studies with a total of 5255 non-demented subjects that report odds ratio (OR)/relative risk/hazard ratio of CRP levels and decline in general cognition met our criteria for meta-analysis. The association between higher levels of CRP and risk of global cognitive decline was weak but significant (OR, 1.27 [95% CI, 1.02 to 1.58]). However, the systematic review from six other articles that were not suitable for meta-analysis revealed a marginal association between CRP and cognitive decline in certain domains.

CONCLUSION

Our analysis demonstrated a weak association between peripheral CRP level and global cognitive decline. Because of the small number of included studies and varied methodologies that they applied, caution should be taken when generalizing our finding to the full range of cognitive changes in different cognitive domains observed in non-demented people.

Development and validation of risk index for cognitive decline using blood-derived markers

OBJECTIVE

We sought to develop and validate a risk index for prospective cognitive decline in older adults based on blood-derived markers.

METHODS

The index was based on 8 markers that have been previously associated with cognitive aging: APOE genotype, plasma β-amyloid 42/40 ratio, telomere length, cystatin C, glucose, C-reactive protein, interleukin-6, and albumin. The outcome was person-specific cognitive slopes (Modified Mini-Mental State Examination) from 11 years of follow-up. A total of 1,445 older adults comprised the development sample. An index based on dichotomized markers was divided into low-, medium-, and high-risk categories; the risk categories were validated with the remaining sample (n = 739) using linear regression. Amyloid was measured on a subsample (n = 865) and was included only in a secondary index.

RESULTS

The risk categories showed significant differences from each other and were predictive of prospective cognitive decline in the validation sample, even after adjustment for age and baseline cognitive score: the low-risk group (24.8%) declined 0.32 points/y (95% confidence interval [CI]: -0.46, -0.19), the medium-risk group (58.7%) declined 0.55 points/y (95% CI: -0.65, 0.45), and the high-risk group (16.6%) declined 0.69 points/y (95% CI: -0.85, -0.54). Using the secondary index, which included β-amyloid 42/40 (validation n = 279), the low-risk group (26.9%) declined 0.20 points/y (95% CI: -0.42, 0.01), the medium-risk group (61.3%) declined 0.55 points/y (95% CI: -0.72, -0.38), and the high-risk group (11.8%) declined 0.83 points/y (95% CI: -1.14, -0.51).

CONCLUSIONS

A risk index based on 8 blood-based markers was modestly able to predict cognitive decline over an 11-year follow-up. Further validation in other cohorts is necessary.

Differential susceptibility of white matter tracts to inflammatory mediators in schizophrenia: an integrated DTI study

BACKGROUND

The pathophysiological underpinnings of impaired anatomical and functional connectivity are not precisely known. Emerging data suggest that immune mediators may underlie such dysconnectivity. We examined anatomical brain connections using diffusion tensor imaging (DTI) data in relation to interleukin-6 (IL-6) and C-reactive protein (CRP) levels among early-course clinically stable schizophrenia subjects compared to healthy controls (HC).

METHODS

DTI data were acquired in 30 directions with 2 averages. Fractional anisotropy (FA) and radial diffusivity (RD) maps were separately processed using FSL4.1.9 and Tract-Based Spatial Statistics (TBSS). Threshold free cluster enhancements (TFCE) were examined employing familywise error (FWE) corrections for multiple testing within linear regression models including age, sex and socioeconomic status as covariates. IL-6 and CRP were assayed using highly sensitive and specific sandwich immunosorbent assays.

RESULTS

The groups did not differ in age and sex as well as in the IL-6 and CRP levels. IL-6 levels were negatively correlated with the FA and positively correlated with RD among schizophrenia subjects but not HC. The voxel clusters that showed significant correlations were localized to the forceps major, the inferior longitudinal fasciculus and the inferior fronto-occipital fasciculus. CRP levels showed similar pattern except for lack of correlation with RD on any cluster that corresponded to the forceps major.

DISCUSSION

Our results suggest that the IL-6 and CRP contribute to impaired anisotropy of water diffusion in selected pathways that have been previously associated with schizophrenia suggesting differential susceptibility of selected neural pathways to immune mediators.

DHEA and cognitive function in the elderly

The adrenal prohormone dehydroepiandrosterone (DHEA) and its sulphate conjugate (DHEAS) steadily decrease with age by 10% per decade reaching a nadir after the age of 80. Both DHEA and DHEAS (DHEA/S) exert many biological activities in different tissues and organs. In particular, DHEA and DHEAS are produced de novo in the brain, hence their classification as neurosteroids. In humans, the brain-to-plasma ratios for DHEA and DHEAS are 4-6.5 and 8.5, respectively, indicating a specific neuroendocrine role for these hormones. DHEA/S stimulates neurite growth, neurogenesis and neuronal survival, apoptosis, catecholamine synthesis and secretion. Together with antioxidant, anti-inflammatory and anti-glucocorticoid properties, it has been hypothesized a neuroprotective effect for DHEA/S. We conducted an accurate research of the literature using PubMed. In the period of time between 1994 and 2013, we selected the observational human studies testing the relationship between DHEA/S and cognitive function in both sexes. The studies are presented according to the cross-sectional and longitudinal design and to the positive or neutral effects on different domains of cognitive function. We also analysed the Clinical Trials, available in the literature, having cognitive domains as the main or secondary outcome. Although the cross-sectional evidence of a positive association between DHEA/S and cognitive function, longitudinal studies and RCTs using DHEA oral treatment (50mg/day) in normal or demented adult-older subjects, have produced conflicting and inconsistent results. In summary, the current data do not provide clear evidence for the usefulness of DHEA treatment to improve cognitive function in adult-older subjects. This article is part of a Special Issue entitled 'Essential role of DHEA'.

Diet-induced obesity attenuates endotoxin-induced cognitive deficits

Activation of the immune system can impair cognitive function, particularly on hippocampus dependent tasks. Several factors such as normal aging and prenatal experiences can modify the severity of these cognitive deficits. One additional factor that may modulate the behavioral response to immune activation is obesity. Prior work has shown that obesity alters the activity of the immune system. Whether diet-induced obesity (DIO) influences the cognitive deficits associated with inflammation is currently unknown. The present study explored whether DIO alters the behavioral response to the bacterial endotoxin, lipopolysaccharide (LPS). Female C57BL/6J mice were fed a high-fat (60% fat) or control diet (10% fat) for a total of five months. After consuming their respective diets for four months, mice received an LPS or saline injection and were assessed for alterations in spatial learning. One month later, mice received a second injection of LPS or saline and tissue samples were collected to assess the inflammatory response within the periphery and central nervous system. Results showed that LPS administration impaired spatial learning in the control diet mice, but had no effect in DIO mice. This lack of a cognitive deficit in the DIO female mice is likely due to a blunted inflammatory response within the brain. While cytokine production within the periphery (i.e., plasma, adipose, and spleen) was similar between the DIO and control mice, the DIO mice failed to show an increase in IL-6 and CD74 in the brain following LPS administration. Collectively, these data indicate that DIO can reduce aspects of the neuroinflammatory response as well as blunt the behavioral reaction to an immune challenge.

Alzheimer's disease and chronic periodontitis: is there an association?

Alzheimer's disease, an affliction of old age, is one of the leading causes for dementia worldwide. Various risk factors including family history, genetics and infections have been implicated in its pathogenesis. The cognitive decline in this condition is mainly a result of the formation of amyloid deposits that provoke neuroinflammation, ultimately resulting in cell death. Recently, an association between peripheral inflammation and Alzheimer's disease was hypothesized. It was suggested that chronic systemic inflammation worsened the inflammatory processes in the brain. This was mainly attributed to increased levels of pro-inflammatory mediators, such as interleukin-1, interleukin -6 and tumor necrosis factor-α in the plasma. As chronic periodontitis is a widespread peripheral immunoinflammatory condition, it has been proposed to play a significant role in the aggravation of Alzheimer's disease. With this background, the current review focuses on the relationship between Alzheimer's disease and chronic periodontitis, and its therapeutic implications.

Whole blood gene expression and interleukin-6 levels

BACKGROUND

Circulating interleukin-6 levels increase with advancing age and are a risk factor for various diseases and mortality. The characterization of gene expression profiles associated with interleukin-6 levels might suggest important molecular events underlying its regulation.

METHODS AND RESULTS

We studied the association of transcriptional profiles with interleukin-6 levels in 2422 participants from the Framingham Heart Study Offspring Cohort using Affymetrix Human Exon 1.0 ST Array. We identified 4139 genes that were significantly associated with interleukin-6 levels (FDR<0.05) after adjusting for age, sex and blood cell components. We then replicated 807 genes in the InCHIANTI study with 694 participants. Many of the top genes are involved in inflammation-related pathways or erythrocyte function, including JAK/Stat signaling pathway and interleukin-10 signaling pathway.

CONCLUSION

We identified and replicated 807 genes that were associated with circulating interleukin-6 levels. Future characterization of interleukin-6 regulation networks may facilitate the identification of additional potential targets for treating inflammation-related diseases.

Interleukin-6 predicts short-term global functional decline in the oldest old: results from the BELFRAIL study

The chronic inflammatory state at old age may contribute to the pathophysiology of or reflect chronic conditions resulting in loss of physical and mental functioning. Therefore, our objective was to examine the predictive value of a large battery of serum inflammatory markers as risk indicators for global functional decline and its specific physical and mental determinants in the oldest old. Global functional decline and specific aspects of physical and mental functional decline were assessed during an average of 1.66 years (±0.21) in a sample of 303 persons aged 80 years or older of the BELFRAIL study. Serum levels of 14 inflammatory proteins, including cytokines, growth factors, and acute phase proteins, were measured at baseline. Almost 20 % of the participants had a significant global functional decline over time. Interleukin (IL)-6 serum levels were uniquely positively associated with global functional decline, even after correcting for multiple confounders (odds ratio 1.51). Odds ratios for the individual aspects (physical dependency, physical performance, cognition, and depression) of functioning were lower, and composite scores of physical or mental decline were not significant. The proportion of global functional decline exhibited a dose-response curve with increasing levels of IL-6. Thus, IL-6 is an independent risk indicator for accelerated global functional decline in the oldest old. Our results suggest that simple serum levels of IL-6 may be very useful in short-term identification or evaluation of global functional status in the oldest old.

BioAge: toward a multi-determined, mechanistic account of cognitive aging

The search for reliable early indicators of age-related cognitive decline represents a critical avenue for progress in aging research. Chronological age is a commonly used developmental index; however, it offers little insight into the mechanisms underlying cognitive decline. In contrast, biological age (BioAge), reflecting the vitality of essential biological systems, represents a promising operationalization of developmental time. Current BioAge models have successfully predicted age-related cognitive deficits. Research on aging-related cognitive function indicates that the interaction of multiple risk and protective factors across the human lifespan confers individual risk for late-life cognitive decline, implicating a multi-causal explanation. In this review, we explore current BioAge models, describe three broad yet pathologically relevant biological processes linked to cognitive decline, and propose a novel operationalization of BioAge accounting for both moderating and causal mechanisms of cognitive decline and dementia. We argue that a multivariate and mechanistic BioAge approach will lead to a greater understanding of disease pathology as well as more accurate prediction and early identification of late-life cognitive decline.

Inflammatory co-morbidities in HIV+ individuals: learning lessons from healthy ageing

Increased life expectancy due to improved efficacy of cART has uncovered an increased risk of age-related morbidities in HIV+ individuals and catalyzed significant research into mechanisms driving these diseases. HIV infection increases the risk of non-communicable diseases common in the aged, including cardiovascular disease, neurocognitive decline, non-AIDS malignancies, osteoporosis, and frailty. These observations suggest that HIV accelerates immunological ageing, and there are many immunological similarities with the aged, including shortened telomeres, accumulation of senescent T cells and altered monocyte phenotype/function. However, the most critical similarity between HIV+ individuals and the elderly, which most likely underpins the heightened risk of non-communicable diseases, is chronic inflammation and associated immune activation. Here, we review the similarities between HIV+ individuals and the aged regarding the pathogenesis of inflammatory diseases, the current evidence for mechanisms driving these processes and discuss current and potential therapeutic strategies for addressing inflammatory co-morbidity in HIV+ infection.

Peripheral inflammation acutely impairs human spatial memory via actions on medial temporal lobe glucose metabolism

BACKGROUND

Inflammation impairs cognitive performance and is implicated in the progression of neurodegenerative disorders. Rodent studies demonstrated key roles for inflammatory mediators in many processes critical to memory, including long-term potentiation, synaptic plasticity, and neurogenesis. They also demonstrated functional impairment of medial temporal lobe (MTL) structures by systemic inflammation. However, human data to support this position are limited.

METHODS

Sequential fluorodeoxyglucose positron emission tomography together with experimentally induced inflammation was used to investigate effects of a systemic inflammatory challenge on human MTL function. Fluorodeoxyglucose positron emission tomography scanning was performed in 20 healthy participants before and after typhoid vaccination and saline control injection. After each scanning session, participants performed a virtual reality spatial memory task analogous to the Morris water maze and a mirror-tracing procedural memory control task.

RESULTS

Fluorodeoxyglucose positron emission tomography data demonstrated an acute reduction in human MTL glucose metabolism after inflammation. The inflammatory challenge also selectively compromised human spatial, but not procedural, memory; this effect that was independent of actions on motivation or psychomotor response. Effects of inflammation on parahippocampal and rhinal glucose metabolism directly mediated actions of inflammation on spatial memory.

CONCLUSIONS

These data demonstrate acute sensitivity of human MTL to mild peripheral inflammation, giving rise to associated functional impairment in the form of reduced spatial memory performance. Our findings suggest a mechanism for the observed epidemiologic link between inflammation and risk of age-related cognitive decline and progression of neurodegenerative disorders including Alzheimer's disease.

Inflammatory markers and risk of hip fracture in older white women: the study of osteoporotic fractures

Hip fractures are the most devastating consequence of osteoporosis and impact 1 in 6 white women leading to a two- to threefold increased mortality risk in the first year. Despite evidence of inflammatory markers in the pathogenesis of osteoporosis, few studies have examined their effect on hip fracture. To determine if high levels of inflammation increase hip fracture risk and to explore mediation pathways, a case-cohort design nested in a cohort of 4709 white women from the Study of Osteoporotic Fractures was used. A random sample of 1171 women was selected as the subcohort (mean age 80.1 ± 4.2 years) plus the first 300 women with incident hip fracture. Inflammatory markers interleukin-6 (IL-6) and soluble receptors (SR) for IL-6 (IL-6 SR) and tumor necrosis factor (TNF SR1 and TNF SR2) were measured, and participants were followed for a median (interquartile range) of 6.3 (3.7, 6.9) years. In multivariable models, the hazard ratio (HR) of hip fracture for women in the highest inflammatory marker level (quartile 4) was 1.64 (95% confidence interval [CI], 1.09-2.48, p trend = 0.03) for IL-6 and 2.05 (95% CI, 1.35-3.12, p trend <0.01) for TNF SR1 when compared with women in the lowest level (quartile 1). Among women with 2 and 3-4 inflammatory markers in the highest quartile, the HR of hip fracture was 1.51 (95% CI, 1.07-2.14) and 1.42 (95% CI, 0.87-2.31) compared with women with zero to one marker(s) in the highest quartile (p trend = 0.03). After individually adjusting for seven potential mediators, cystatin-C (a biomarker of renal function) and bone mineral density (BMD) attenuated HRs among women with the highest inflammatory burden by 64% and 50%, respectively, suggesting a potential mediating role. Older white women with high inflammatory burden are at increased risk of hip fracture in part due to poor renal function and low BMD.

Interleukin 6 and cognitive dysfunction

The interleukin-6 (IL-6) is a pleiotropic cytokine that plays a key role in interaction between immune and nervous system. Although IL-6 has neurotrophic properties and beneficial effects in the CNS, its overexpression is generally detrimental, adding to the pathophysiology associated with CNS disorders. The source of the increase in peripheral IL-6 remains to be established and varies among different pathologies, but has been found to be associated with cognitive dysfunction in several pathologies. This comprehensive review provides an update summary of the studies performed in humans concerning the role of central and peripheral IL-6 in cognitive dysfunction in dementias and in other systemic diseases accompained by cognitive dysfuction such as cardiovascular, liver disease, Behçet's disease and systemic lupus erythematosus. Further research is needed to correlate specific deficits in IL-6 and its receptors in pathologies characterized by cognitive dysfunction and to understand how systemic IL-6 affects high cerebral function in order to open new directions in pharmacological treatments that modulate IL-6 signalling.

Interleukin-6 and C-Reactive Protein Levels and 9-Year Cognitive Decline in Community-Dwelling Older Women: The Women's Health and Aging Study II

BACKGROUND

Elevated inflammation is a proposed mechanism relating chronic diseases to cognitive dysfunction. The objective of this study was to test the hypothesis that greater levels of inflammation, as measured by the proinflammatory cytokine interleukin-6 (IL-6) and C-reactive protein, are associated with faster rates of cognitive decline among cognitively intact community-dwelling older women.

METHODS

We analyzed 336 women from the Women's Health and Aging Study II. Cognitive assessments were performed at baseline and every 18-36 months, and included the following domains: immediate and delayed memory (Hopkins Verbal Learning Test), psychomotor speed (Trail Making Test, Part A), and executive function (Trail Making Test, Part B). Aggregate measures of IL-6 and C-reactive protein, based on the average from visits one and two, were analyzed categorically. Random effects models were employed to test the relationship between tertiles of each inflammatory marker and changes in cognitive domain scores over 9 years.

RESULTS

Moderate and high levels of IL-6 predicted early declines in psychomotor speed by 1.0 connection/min per year. There were no differences in baseline scores or rates of change across tertiles of IL-6 in memory or executive function. No differences were observed across tertiles of C-reactive protein for all cognitive domains.

CONCLUSIONS

Higher levels of serum IL-6 were associated with greater declines in psychomotor speed over 9 years. This finding could suggest that elevated IL-6 may result in microvascular changes that may lead to damage of myelin sheaths that line neuronal axons, leading to decreased neuron propagation and impaired processing speed; however, mechanistic studies are needed to evaluate these hypotheses.

Longitudinal inflammation, cognitive decline, and Alzheimer's disease: a mini-review

The role of inflammation in cognitive decline has generated considerable interest, although few longitudinal evaluations have been conducted. A review of the literature yields mixed findings but suggests that inflammatory dysregulation is evident and may be related to clinical outcomes. The directionality, magnitude, and progression of these associations remain unclear. Future studies employing multiple time points of inflammatory data along with Alzheimer's disease (AD) biomarkers are critical for explication of longitudinal inflammation in cognitive decline.

Interleukin-6 and C-reactive protein as predictors of cognitive decline in late midlife

Objective:

Peripheral inflammatory markers are elevated in patients with dementia. In order to assess their etiologic role, we examined whether interleukin-6 (IL-6) and C-reactive protein (CRP) measured in midlife predict concurrently assessed cognition and subsequent cognitive decline.

Methods:

Mean value of IL-6 and CRP, assessed on 5,217 persons (27.9% women) in 1991–1993 and 1997–1999 in the Whitehall II longitudinal cohort study, were categorized into tertiles to examine 10-year decline (assessments in 1997–1999, 2002–2004, and 2007–2009) in standardized scores (mean = 0, SD = 1) of memory, reasoning, and verbal fluency using mixed models. Mini-Mental State Examination (MMSE) was administered in 2002–2004 and 2007–2009; decline ≥3 points was modeled with logistic regression. Analyses were adjusted for baseline age, sex, education, and ethnicity; further analyses were also adjusted for smoking, obesity, Framingham cardiovascular risk score, and chronic diseases (cancer, coronary heart disease, stroke, diabetes, and depression).

Results:

In cross-sectional analysis, reasoning was 0.08 SD (95% confidence interval [CI] −0.14, −0.03) lower in participants with high compared to low IL-6. In longitudinal analysis, 10-year decline in reasoning was greater (ptrend = 0.01) among participants with high IL-6 (−0.35; 95% CI −0.37, −0.33) than those with low IL-6 (−0.29; 95% CI −0.31, −0.27). In addition, participants with high IL-6 had 1.81 times greater odds ratio of decline in MMSE (95% CI 1.20, 2.71). CRP was not associated with decline in any test.

Conclusions:

Elevated IL-6 but not CRP in midlife predicts cognitive decline; the combined cross-sectional and longitudinal effects over the 10-year observation period corresponded to an age effect of 3.9 years.

Serum high-mobility group box 1 protein correlates with cognitive decline after gastrointestinal surgery

BACKGROUND

Accumulating evidence has indicated that inflammation may act as a potential mechanism underlying post-operative cognitive dysfunction (POCD). High-mobility group box 1 (HMGB1), as a known late mediator of inflammation, is involved in the development of post-operative complications. Thus, we sought to determine the role of HMGB1 in reflecting POCD following major gastrointestinal surgery.

METHODS

Fifty-three elderly patients undergoing gastrointestinal surgery were recruited, and 50 patients completed the study. Serum HMGB1 and interleukin (IL)-6 levels were measured pre-operatively and at 6 h, day 1 and day 3 post-operatively. Neuropsychological tests were administered before and 1 week after surgery. POCD was determined using a Z score ≥ 1.96.

RESULTS

Seventeen (34%, 17/50) patients developed POCD at 1 week. The POCD group had higher serum HMGB1 levels at day 1 (12.15 ± 3.12 vs. 9.91 ± 3.15 ng/ml, P = 0.021) and day 3 (11.04 ± 2.88 vs. 8.52 ± 3.31 ng/ml, P = 0.011). IL-6 levels at 6 h (51.18 ± 15.22 vs. 39.20 ± 14.32 pg/ml, P = 0.009) and day 1 (41.59 ± 11.08 vs. 33.81 ± 11.42 pg/ml, P = 0.026) were significantly higher in POCD patients. Serum values of IL-6 at 6 h, HMGB1 at day 1 and levels of education showed positive correlations with Z scores. HMGB1 at day 3 and IL-6 at 6 h were independent risk factors.

CONCLUSIONS

Serum HMGB1 and IL-6 levels increase significantly after major gastrointestinal surgery in elderly patients and such elevations are associated with the occurrence of cognitive decline after surgery.

The negative effects of obesity and poor glycemic control on cognitive function: a proposed model for possible mechanisms

Obesity has reached epidemic proportions and is a contributor to many adverse health outcomes, including increased risk for dementia and adverse structural and functional brain changes. Milder forms of cognitive impairment in multiple domains can also be found in obese individuals of all ages that are believed to stem from brain abnormalities long prior to onset of neurologic conditions such as dementia. However, the mechanisms for adverse brain changes and subsequent cognitive dysfunction in obesity are complex and poorly understood. This paper proposes a possible etiologic model for obesity associated cognitive impairment with emphasis on the role of poor glycemic control and conditions like type 2 diabetes mellitus. Clinical implications associated with treatment of obesity in persons with cognitive deficits in addition to the cognitive promoting effects of weight loss surgery are also discussed.

Infection hospitalization increases risk of dementia in the elderly

OBJECTIVES

Severe infections, often requiring ICU admission, have been associated with persistent cognitive dysfunction. Less severe infections are more common and whether they are associated with an increased risk of dementia is unclear. We determined the association of pneumonia hospitalization with risk of dementia in well-functioning older adults.

DESIGN

Secondary analysis of a randomized multicenter trial to determine the effect of Gingko biloba on incident dementia.

SETTING

Five academic medical centers in the United States.

SUBJECTS

Healthy community volunteers (n = 3,069) with a median follow-up of 6.1 years.

INTERVENTIONS

None.

MEASUREMENT AND MAIN RESULTS

We identified pneumonia hospitalizations using International Classification of Diseases, 9th Edition-Coding Manual codes and validated them in a subset. Less than 3% of pneumonia cases necessitated ICU admission, mechanical ventilation, or vasopressor support. Dementia was adjudicated based on neuropsychological evaluation, neurological examination, and MRI. Two hundred twenty-one participants (7.2%) incurred at least one hospitalization with pneumonia (mean time to pneumonia = 3.5 yr). Of these, dementia was developed in 38 (17%) after pneumonia, with half of these cases occurring 2 years after the pneumonia hospitalization. Hospitalization with pneumonia was associated with increased risk of time to dementia diagnosis (unadjusted hazard ratio = 2.3; CI, 1.6-3.2; p < 0.0001). The association remained significant when adjusted for age, sex, race, study site, education, and baseline mini-mental status examination (hazard ratio = 1.9; CI, 1.4-2.8; p < 0.0001). Results were unchanged when additionally adjusted for smoking, hypertension, diabetes, heart disease, and preinfection functional status. Results were similar using propensity analysis where participants with pneumonia were matched to those without pneumonia based on age, probability of developing pneumonia, and similar trajectories of cognitive and physical function prior to pneumonia (adjusted prevalence rates, 91.7 vs 65 cases per 1,000 person-years; adjusted prevalence rate ratio = 1.6; CI, 1.06-2.7; p = 0.03). Sensitivity analyses showed that the higher risk also occurred among those hospitalized with other infections.

CONCLUSION

Hospitalization with pneumonia is associated with increased risk of dementia.

Hypoxia and inflammation in children with sickle cell disease: implications for hippocampal functioning and episodic memory

Children with sickle cell disease (SCD) suffer from systemic processes (e.g., chronic anemia, recurrent hypoxic-ischemic events, chronic inflammation) that have been associated with neurocognitive impairment in a range of clinical populations, but which have been largely understudied in relation to specific domains of cognitive functioning in children with SCD. This review focuses on episodic memory, as the hippocampus may be especially vulnerable to the systemic processes associated with SCD. The first part of the paper outlines the pathophysiology of SCD and briefly reviews the extant literature on academic and cognitive functioning in children with SCD, emphasizing the dearth of research on episodic memory. Next, the complex systemic processes of hypoxia and inflammation associated with SCD are reviewed, along with research that has associated these processes with hippocampal damage and memory impairment. The paper concludes with suggestions for future research that are informed, in part, by the literature on developmental amnesia.

Change in inflammatory markers and cognitive status in the oldest-old women from the Study of Osteoporotic Fractures

OBJECTIVES

To determine the association between interleukin-6 (IL-6), IL-6 soluble receptor (sR), and soluble tumor necrosis factor receptor-1 (sTNF-R1) and cognitive status in the oldest-old women.

DESIGN

Twenty-year longitudinal cohort study.

SETTING

Four clinical sites in the United States.

PARTICIPANTS

Women from the Study of Osteoporotic Fractures (N = 905; mean age 88.3 ± 2.8 at cognitive status adjudication).

MEASUREMENTS

At Year 20, cognitive status was adjudicated as normal, mild cognitive impairment (MCI), or dementia. Inflammatory markers were measured from blood serum at Years 10 and 16 in a random sample of women.

RESULTS

Over 10 years, 199 (22.0%) women developed MCI and 145 (16.0%) dementia. There were no significant associations between IL-6 or sTNF-R1 and cognitive status. High IL-6-sR (≥ 37,401.36 pg/mL, highest tertile) at Year 16 was significantly associated with lower risk of dementia (odds ratio (OR) = 0.54, 95% confidence interval (CI) = 0.30-0.97) than in women with lower levels (<37,401.36 pg/mL, lower two tertiles). Women with high IL-6-sR at both time points (OR = 0.39, 95% CI = 0.17-0.89) or who transitioned to a high level (OR = 0.35, 95% CI = 0.14-0.88) had a lower risk of dementia.

CONCLUSION

In this cohort of white, high-functioning oldest-old women, a consistently high or an increasing level of IL-6-sR was associated with lower risk of dementia. Compared with other studies of younger-old adults, this suggests that the effect of inflammation on dementia may differ in younger-old and the oldest-old individuals. Understanding these differences will be crucial in interpreting results from ongoing clinical trials and in targeting therapeutic strategies to the oldest-old individuals.

Body fluid cytokine levels in mild cognitive impairment and Alzheimer's disease: a comparative overview

This article gives a comprehensive overview of cytokine and other inflammation associated protein levels in plasma, serum and cerebrospinal fluid (CSF) of patients with Alzheimer's disease (AD) and mild cognitive impairment (MCI). We reviewed 118 research articles published between 1989 and 2013 to compare the reported levels of 66 cytokines and other proteins related to regulation and signaling in inflammation in the blood or CSF obtained from MCI and AD patients. Several cytokines are evidently regulated in (neuro-) inflammatory processes associated with neurodegenerative disorders. Others do not display changes in the blood or CSF during disease progression. However, many reports on cytokine levels in MCI or AD are controversial or inconclusive, particularly those which provide data on frequently investigated cytokines like tumor necrosis factor alpha (TNF-α) or interleukin-6 (IL-6). The levels of several cytokines are possible indicators of neuroinflammation in AD. Some of them might increase steadily during disease progression or temporarily at the time of MCI to AD conversion. Furthermore, elevated body fluid cytokine levels may correlate with an increased risk of conversion from MCI to AD. Yet, research results are conflicting. To overcome interindividual variances and to obtain a more definite description of cytokine regulation and function in neurodegeneration, a high degree of methodical standardization and patients collective characterization, together with longitudinal sampling over years is essential.

Significance of serum immune markers in identification of global functional impairment in the oldest old: cross-sectional results from the BELFRAIL study

The large burden and coexistence of physical disability, cognitive impairment, and depression in the oldest old makes summary markers of global functioning of great value, allowing for risk stratification. Inflammation may be a common underlying cause or represents a final common pathway. The present study investigated the association between elevated serum inflammatory markers and global functioning and its underlying aspects. A representative sample of 415 community-dwelling elderly subjects participating in the BELFRAIL study, with a mean age of 85 years, was included in the present analysis. Data on physical performance, dependence, and mental aspects of functioning and serum levels of 15 inflammatory proteins, including cytokines, chemokines, and acute-phase proteins, were assessed. Interleukin (IL)-6 was negatively associated with global functioning (odds ratio (OR) 4.35). The odds ratios for C-reactive protein (CRP) (OR 2.37) and the combined score of IL-6 and CRP (OR 2.59) were lower or not significant. IL-6 was significantly associated with physical dependence and cognitive function, and only a highly elevated serum level was associated with physical performance. Physical dependence was associated with a highly elevated CRP serum level. The proportion of functionally impaired older persons with elevated IL-6 was 81.93 %, giving a low positive predictive value (0.38), but a high negative predictive value (0.87). So, IL-6 is strongly associated with global functioning and all of the individual aspects of functioning, except suspected depression, in community-dwelling persons 80 years and older.

Plasma cytokine concentrations in dogs with a congenital portosystemic shunt

Congenital portosystemic shunts (cPSS) are a well-recognised vascular anomaly in dogs. Recent studies have shown an association between inflammation and hepatic encephalopathy (HE), which is a common clinical syndrome in dogs with a cPSS. Pro-inflammatory cytokines such as interleukin (IL)-6 and tumour necrosis factor (TNF)-α are frequently increased in the plasma of human patients with liver disease and have been implicated in the development of HE. In the current study, plasma concentrations of IL-2, IL-6, IL-8 and TNF-α were measured using a multiplex electrochemiluminescence immunoassay in 36 dogs with a cPSS and compared to 25 healthy dogs. There were no significant differences in plasma IL-2, IL-8 and TNF-α concentrations between the two groups; however, plasma concentrations of IL-6 were significantly higher in dogs with a cPSS compared to healthy dogs (P=0.02).

A novel role for brain interleukin-6: facilitation of cognitive flexibility in rat orbitofrontal cortex

Cytokines, small proteins released by the immune system to combat infection, are typically studied under inflammatory conditions. However, these molecules are also expressed in the brain in basal, nonpathological states, where they can regulate neuronal processes, such as learning and memory. However, little is known about how cytokine signaling in the brain may influence higher-order cognitive functions. Cognitive flexibility is one such executive process, mediated by the prefrontal cortex, which requires an adaptive modification of learned behaviors in response to environmental change. We explored the role of basal IL-6 signaling in the orbitofrontal cortex (OFC) in reversal learning, a form of cognitive flexibility that can be measured in the rat using the attentional set-shifting test. We found that inhibiting IL-6 or its downstream JAK/STAT signaling pathway in the OFC impaired reversal learning, suggesting that basal IL-6 and JAK/STAT signaling facilitate cognitive flexibility. Further, we demonstrated that elevating IL-6 in the OFC by adeno-associated virus-mediated gene delivery reversed a cognitive deficit induced by chronic stress, thus identifying IL-6 and the downstream JAK/STAT signaling pathway as potentially novel therapeutic targets for the treatment of stress-related psychiatric diseases associated with cognitive dysfunction.

Central adiposity and the functional magnetic resonance imaging response to cognitive challenge

Background

Excessive adipose tissue, particularly with a centralized distribution, propagates hormonal and metabolic disturbance. The detrimental effects of adiposity may extend beyond the periphery and target the central nervous system, increasing vulnerability to cognitive decline. The aim of current study was to determine how central adiposity impacts the brain at midlife by examining the blood oxygen level-dependent (BOLD) response to a challenging cognitive task.

Methods

Seventy-three adults, aged 40-60 years, completed a 2-Back verbal working memory task during functional magnetic resonance imaging (fMRI). Central adiposity was assessed with waist circumference. The association between waist circumference and task-related activation in a priori regions of interest was modeled using bootstrapping regression models corrected for multiple-comparisons.

Results

Larger waist circumference was associated with diminished working-memory-related BOLD response in the right superior frontal gyrus (β=-0.008, p=0.001, 95% CI: -0.012 - -0.004) and left middle frontal gyrus (β=-0.009, p=0.002, 95% CI: -0.015 - -0.003), statistically adjusting for age, sex, systolic blood pressure, and total cholesterol. Reduced task-related activation in the right superior frontal gyrus (r=-0.369, p=0.002) and left middle frontal gyrus (r=-0.266, p=0.025) were related to slower reaction time on the task, controlling for age and education.

Conclusions

Larger waist circumference predicted alterations in the BOLD response that coupled with decrements in task performance. While future studies are necessary, the results suggest that similar to its role in the periphery, central adiposity may be a robust predictor of metabolic and hormonal alterations that impinge upon central nervous system functioning.

Endotoxin-induced experimental systemic inflammation in humans: a model to disentangle immune-to-brain communication

Systemic inflammation is among the most prominent and most frequently observed responses of the immune system. Over the past decades, it has become clear that inflammatory cytokines not only affect immune and metabolic functions but also cause a wide range of behavioral and mood changes. Based on experimental findings in animals and observations in clinical populations it has been hypothesized that inflammation-induced neurocognitive changes contribute to the pathophysiology of neuropsychiatric diseases. However, since certain aspects of human behavior cannot be modeled in laboratory animals, there is a need for human models of systemic inflammation. In this review, we summarize recent studies employing administration of endotoxin as a model to induce transient systemic inflammation in healthy human subjects.

Pre-Operative, High-IL-6 Blood Level is a Risk Factor of Post-Operative Delirium Onset in Old Patients

BACKGROUND

Post-operative delirium (POD) is a common complication in elderly patients undergoing surgery, but the underpinning causes are not clear. We hypothesized that inflammaging, the subclinical low and chronic grade inflammation characteristic of old people, can contribute to POD onset. Accordingly, we investigated the association of pre-operative and circulating cytokines in elderly patients (>65 years), admitted for elective and emergency surgery.

METHODS

This is a secondary analysis of a sub-cohort of patients belonging to a previous large case-control study, where 351 patients were clinically and cognitively thoroughly characterized, together with the assessment of POD (47 patients) by confusion assessment method and delirium rating scale. Seventy-four pre-operative plasma samples were selected from a larger bio-bank and they included 37 subjects with POD and 37 without POD. Inflammaging related cytokines, i.e., IL-1β, IL-2, IL-6, IL-8, IL-10, and TNF-α, were assayed by ELISA in pre-operative blood samples; univariate and multivariable analyses have been applied to identify cytokines independently associated to POD. Associations of cytokine levels with functional status, cognitive decline, intra-hospital mortality, and comorbidity were also analyzed independently of POD onset.

RESULTS

High IL-6 and low-IL-2 levels were significantly associated with POD. After adjustment for potential confounders in multivariate analysis, high level of pre-operative IL-6 was confirmed to be significantly associated with risk of POD onset. High level of IL-6 was also associated with several baseline features (including poor functional status, cognitive impairment, emergency admission, and higher comorbidity burden) and intra-hospital mortality.

CONCLUSION

Pre-operative, high-plasma level of IL-6 (≥9 pg/mL) was significantly associated with POD onset. We propose IL-6 as an additional risk factor of POD onset together with the previously identified factors. Discovery of all risk factors contributing to POD onset will permit to improve hospitalized patient management and the decrease of healthcare cost.

Association of serum dehydroepiandrosterone sulfate and cognition in older adults: sex steroid, inflammatory, and metabolic mechanisms

OBJECTIVE

Dehydroepiandrosterone sulfate (DHEAS) levels and cognitive function decline with age, and a role for DHEAS in supporting cognition has been proposed. Higher DHEAS levels may be associated with better cognitive performance, although potential mechanisms for this relationship are not well established.

METHOD

We performed a cross-sectional study of the relationship between serum DHEAS and three aspects of cognition--executive function, working memory, and processing speed--in 49 men and 54 women, aged 60-88 years, with low serum DHEAS levels. We examined three potential mechanisms of DHEAS action--sex hormone sufficiency, inflammatory status, and glucose regulation.

RESULTS

After adjustment for multiple covariates, higher serum DHEAS levels were associated with better working memory (standardized beta coefficient 0.50, p < .05), with a trend toward better executive function (standardized beta coefficient 0.37, p < .10) in men only. There was a nonsignificant trend toward a negative association between levels of tumor necrosis factor α (TNFα) and working memory in the combined population (standardized beta coefficient -0.22, p < .10). None of the glucoregulatory measures was associated with cognitive function.

CONCLUSIONS

The relationship between DHEAS and cognition is complex and differs by sex and cognitive domain. This study supports the need for further investigations of the sex-specific effects of DHEAS on cognition and its underlying mechanisms of action.

Microbial translocation, residual viremia and immune senescence in the pathogenesis of HIV-1 infection

The pathophysiological mechanisms that underlie the progression of human immunodeficiency virus-1 (HIV-1) disease to full-blown AIDS are not well understood. Findings suggest that, during HIV-1 infection, plasma lipopolysaccharide (LPS) levels, which are used as an indicator of microbial translocation (MT), are elevated throughout the acute and chronic phases of HIV-1 disease. The translocation of bacterial products through the damaged gastrointestinal barrier into the systemic circulation has been described as a driver of immune activation. In contrast, comorbidities that are associated with HIV-1 infection have been attributed to chronic inflammation and immune system dysfunction secondary to MT or low-level HIV-1 replication in plasma and cell reservoirs. Moreover, accelerated aging is significantly associated with chronic inflammation, immune activation, and immune senescence. In this review, we aimed to investigate the role of inflammation as a pivotal marker in the pathogenesis of HIV-1 disease. We will discuss the key features of chronic inflammation and immune activation that are observed during the natural course of the disease and those features that are detected in cART-modified infection. The review will focus on the following aspects of HIV-1 infection: (1) MT; (2) the role of residual viremia; and (3) “immune senescence” or “inflammaging.” Many questions remain unanswered about the potential mechanisms that are involved in HIV-1 pathogenesis. Further studies are needed to better investigate the mechanisms that underlie immune activation and their correlation with HIV-1 disease progression.

Evaluating the physiological reserves of older patients with cancer: the value of potential biomarkers of aging?

Aging of an individual entails a progressive decline of functional reserves and loss of homeostasis that eventually lead to mortality. This process is highly individualized and is influenced by multiple genetic, epigenetic and environmental factors. This individualization and the diversity of factors influencing aging result in a significant heterogeneity among people with the same chronological age, representing a major challenge in daily oncology practice. Thus, many factors other than mere chronological age will contribute to treatment tolerance and outcome in the older patients with cancer. Clinical/comprehensive geriatric assessment can provide information on the general health status of individuals, but is far from perfect as a prognostic/predictive tool for individual patients. On the other hand, aging can also be assessed in terms of biological changes in certain tissues like the blood compartment which result from adaptive alterations due to past history of exposures, as well as intrinsic aging processes. There are major signs of 'aging' in lymphocytes (e.g. lymphocyte subset distribution, telomere length, p16INK4A expression), and also in (inflammatory) cytokine expression and gene expression patterns. These result from a combination of the above two processes, overlaying genetic predispositions which contribute significantly to the aging phenotype. These potential "aging biomarkers" might provide additional prognostic/predictive information supplementing clinical evaluation. The purpose of the current paper is to describe the most relevant potential "aging biomarkers" (markers that indicate the biological functional age of patients) which focus on the biological background, the (limited) available clinical data, and technical challenges. Despite their great potential interest, there is a need for much more (validated) clinical data before these biomarkers could be used in a routine clinical setting. This manuscript tries to provide a guideline on how these markers can be integrated in future research aimed at providing such data.

Persisting inflammation and chronic immune activation but intact cognitive function in HIV-infected patients after long-term treatment with combination antiretroviral therapy

OBJECTIVES

Impaired cognitive function in HIV-infected patients has been suggested. Treatment with combination antiretroviral therapy (cART) restores CD4⁺ cell counts and suppresses viral replication, but immune activation and inflammation may persist. The aim of the study was to examine if cognitive function in HIV-infected patients was related to immune activation and inflammation.

METHODS

Sixty-one HIV-infected patients and 31 healthy controls were included. All patients were on treatment with cART, had suppressed viral replication, and had a mean CD4⁺ cell count of 522 cells/μL. Cognitive function was assessed using a test battery of neurocognitive tests. Plasma concentrations of interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and β-2-microglobulin were measured. Immune activation (CD8⁺HLR-DR⁺CD38⁺ cells) was determined using flow cytometry. Multiple linear regression analysis was performed to identify relationship between cognitive scores and markers of inflammation and immune activation.

RESULTS

HIV-infected patients had intact cognitive function compared with healthy controls. Higher levels of TNF-α, β-2-microglobulin, and chronic activated CD8⁺ cells were found in HIV-infected patients (P = 0.0002, P < 0.0001, and P = 0.021, respectively). Weak negative correlations were found between chronic activated CD8⁺ cells (β-coefficient = -0.277, P = 0.044), IL-6 (β-coefficient = -0.280, P = 0.014), and memory and learning.

CONCLUSIONS

HIV-infected patients on cART with undetectable viral load had an increased level of inflammation and immune activation. However, intact cognitive function was found, and only weak correlations were found between cognitive function and markers of inflammation and immune activation, indicating that peripheral inflammation and immune activation are not major drivers of cognitive decay in HIV-infected patients.

Systemic inflammation in non-demented elderly human subjects: brain microstructure and cognition

The purpose of this study was to test the hypothesis that higher levels of systemic inflammation in a community sample of non-demented subjects older than seventy years of age are associated with reduced diffusion anisotropy in brain white matter and lower cognition. Ninety-five older persons without dementia underwent detailed clinical and cognitive evaluation and magnetic resonance imaging, including diffusion tensor imaging. Systemic inflammation was assessed with a composite measure of commonly used circulating inflammatory markers (C-reactive protein and tumor necrosis factor-alpha). Tract-based spatial statistics analyses demonstrated that diffusion anisotropy in the body and isthmus of the corpus callosum was negatively correlated with the composite measure of systemic inflammation, controlling for demographic, clinical and radiologic factors. Visuospatial ability was negatively correlated with systemic inflammation, and diffusion anisotropy in the body and isthmus of the corpus callosum was shown to mediate this association. The findings of the present study suggest that higher levels of systemic inflammation may be associated with lower microstructural integrity in the corpus callosum of non-demented elderly individuals, and this may partially explain the finding of reduced higher-order visual cognition in aging.

The emerging role of dietary fructose in obesity and cognitive decline

The incidence of obesity has increased dramatically over the past several years, and in parallel, so has the prevalence of type 2 diabetes (T2D). Numerous studies have demonstrated that both obesity and T2D are associated with lower cognitive performance, cognitive decline, and dementia. Intake of dietary fructose has also increased. In fact, high-fructose corn syrup (HFCS) accounts for as much as 40% of caloric sweeteners used in the United States. Given the increase in the incidence of Alzheimer’s disease (AD), characterized by an age-related decline in memory and cognitive functioning, in this report we review the effects of obesity on cognitive performance and the impact of high fructose intake in promoting cognitive decline. The paper then considers the effects of omega-3 fatty acids (FAs), which have been linked to promising results in cognitive function including ameliorating the impact of a high-fructose diet.

A systematic analysis of the peripheral and CNS effects of systemic LPS, IL-1β, [corrected] TNF-α and IL-6 challenges in C57BL/6 mice

It is increasingly clear that systemic inflammation has both adaptive and deleterious effects on the brain. However, detailed comparisons of brain effects of systemic challenges with different pro-inflammatory cytokines are lacking. In the present study, we challenged female C57BL/6 mice intraperitoneally with LPS (100 µg/kg), IL-1β (15 or 50 µg/kg), TNF-α (50 or 250 µg/kg) or IL-6 (50 or 125 µg/kg). We investigated effects on core body temperature, open field activity and plasma levels of inflammatory markers at 2 hours post injection. We also examined levels of hepatic, hypothalamic and hippocampal inflammatory cytokine transcripts. Hypothermia and locomotor hypoactivity were induced by LPS>IL-1β>TNF-α>>IL-6. Systemic LPS, IL-1β and TNF-α challenges induced robust and broadly similar systemic and central inflammation compared to IL-6, which showed limited effects, but did induce a hepatic acute phase response. Important exceptions included IFNβ, which could only be induced by LPS. Systemic IL-1β could not induce significant blood TNF-α, but induced CNS TNF-α mRNA, while systemic TNF-α could induce IL-1β in blood and brain. Differences between IL-1β and TNF-α-induced hippocampal profiles, specifically for IL-6 and CXCL1 prompted a temporal analysis of systemic and central responses at 1, 2, 4, 8 and 24 hours, which revealed that IL-1β and TNF-α both induced the chemokines CXCL1 and CCL2 but only IL-1β induced the pentraxin PTX3. Expression of COX-2, CXCL1 and CCL2, with nuclear localisation of the p65 subunit of NFκB, in the cerebrovasculature was demonstrated by immunohistochemistry. Furthermore, we used cFOS immunohistochemistry to show that LPS, IL-1β and to a lesser degree, TNF-α activated the central nucleus of the amygdala. Given the increasing attention in the clinical literautre on correlating specific systemic inflammatory mediators with neurological or neuropsychiatric conditions and complications, these data will provide a useful resource on the likely CNS inflammatory profiles resulting from systemic elevation of particular cytokines.

Proinflammatory cytokines, aging, and age-related diseases

Inflammation is a physiological process that repairs tissues in response to endogenous or exogenous aggressions. Nevertheless, a chronic state of inflammation may have detrimental consequences. Aging is associated with increased levels of circulating cytokines and proinflammatory markers. Aged-related changes in the immune system, known as immunosenescence, and increased secretion of cytokines by adipose tissue, represent the major causes of chronic inflammation. This phenomenon is known as "inflamm-aging." High levels of interleukin (IL)-6, IL-1, tumor necrosis factor-α, and C-reactive protein are associated in the older subject with increased risk of morbidity and mortality. In particular, cohort studies have indicated TNF-α and IL-6 levels as markers of frailty. The low-grade inflammation characterizing the aging process notably concurs at the pathophysiological mechanisms underlying sarcopenia. In addition, proinflammatory cytokines (through a variety of mechanisms, such as platelet activation and endothelial activation) may play a major role in the risk of cardiovascular events. Dysregulation of the inflammatory pathway may also affect the central nervous system and be involved in the pathophysiological mechanisms of neurodegenerative disorders (eg, Alzheimer disease).The aim of the present review was to summarize different targets of the activity of proinflammatory cytokines implicated in the risk of pathological aging.

Role of diabetes mellitus on hepatic encephalopathy

Hepatic encephalopathy is the main cognitive dysfunction in cirrhotic patients associated with impaired prognosis. Hyperammonemia plus inflammatory response do play a crucial role on hepatic encephalopathy. However, in some patients HE appeared without hyperammonemia and patients with increased levels of ammonia could not show cognitive dysfunction. This has led to investigate other factors that could act in a synergistic way. Diabetes mellitus and insulin resistance are characterized by releasing and enhancing these pro-inflammatory cytokines and, additionally, has been related to hepatic encephalopathy. Indeed, patients with diabetes showed raised risk of over hepatic encephalopathy in comparison with non-cirrhotics. Type 2 diabetes mellitus could impair hepatic encephalopathy by different mechanisms that include: a) increasing glutaminase activity; b) impairing gut motility and promoting constipation, intestinal bacterial overgrowth and bacterial translocation. Despite of insufficient clarity about the practicability of anti-diabetic therapy and the most efficacious therapy, we would have to pay a special attention to the management of type 2 diabetes mellitus and insulin resistance in cirrhotic patients.

Sevoflurane anesthesia in pregnant mice induces neurotoxicity in fetal and offspring mice

BACKGROUND

Each year, over 75,000 pregnant women in the United States undergo anesthesia care. The authors set out to assess the effects of the anesthetic sevoflurane on neurotoxicity in pregnant mice and on learning and memory in fetal and offspring mice.

METHODS

Pregnant mice (gestational day 14) and mouse primary neurons were treated with 2.5% sevoflurane for 2 h and 4.1% sevoflurane for 6 h, respectively. Brain tissues of both fetal and offspring mice (P31) and the primary neurons were harvested and subjected to Western blot and immunohistochemistry to assess interleukin-6, the synaptic markers postsynaptic density-95 and synaptophysin, and caspase-3 levels. Separately, learning and memory function in the offspring mice was determined in the Morris water maze.

RESULTS

Sevoflurane anesthesia in pregnant mice induced caspase-3 activation, increased interleukin-6 levels (256 ± 50.98% [mean ± SD] vs. 100 ± 54.12%, P = 0.026), and reduced postsynaptic density-95 (61 ± 13.53% vs. 100 ± 10.08%, P = 0.036) and synaptophysin levels in fetal and offspring mice. The sevoflurane anesthesia impaired learning and memory in offspring mice at P31. Moreover, interleukin-6 antibody mitigated the sevoflurane-induced reduction in postsynaptic density-95 levels in the neurons. Finally, environmental enrichment attenuated the sevoflurane-induced increases in interleukin-6 levels, reductions of synapse markers, and learning and memory impairment.

CONCLUSIONS

These results suggest that sevoflurane may induce detrimental effects in fetal and offspring mice, which can be mitigated by environmental enrichment. These findings should promote more studies to determine the neurotoxicity of anesthesia in the developing brain.

Inflammation and clinical presentation in neurodegenerative disease: a volatile relationship

A proposed immune mechanism that potentially modifies or exacerbates neurodegenerative disease presentation in older adults has received considerable attention in the past decade, with recent studies demonstrating a strong link between pro-inflammatory markers and neurodegeneration. The overarching aim of the following review is to synthesize recent research that supports a possible relationship between inflammation and clinical features of neurodegenerative diseases, including risk of development, cognitive and clinical correlates, and progression of the specified diseases. Specific emphasis is placed on providing a temporal context for the association between inflammation and neurodegeneration.

Cytokines: monitors of disease severity for the clinic

BACKGROUND

Cytokines communicate between the cells of the immune system and its targets to maintain homeostasis after injury or pathogenic events. They are involved in almost any pathological situation imaginable.

OBJECTIVE

To verify the importance of cytokines as biomarkers in current preclinical (aetiopathogenic, development of new therapies) and clinical studies (diagnosis, disease severity, prognosis and response to therapy).

METHOD/RESULTS

A Medline search with the query 'cytokine' AND 'biomarker' AND a variable for a variety of biomedical fields, followed by deeper-level searches, demonstrated the immense popularity of cytokines as biomarkers in almost any biomedical field.

CONCLUSION

As cytokines are not disease-specific they do not serve as single diagnostic biomarkers. The strength of the cytokines resides in monitoring disease severity, prognosis and response to treatment.

Inflammatory Markers and Their Association with Post Stroke Cognitive Decline

Background

Population-based studies have demonstrated the association of inflammation and cognitive impairment. However, few studies to date have examined this association in ischemic stroke patients.

Aims

The study aims to determine the association between inflammatory markers and cognitive impairment.

Methods

Ischemic stroke patients with baseline neuropsychological assessments at three-months poststroke were followed up with annual neuropsychological assessments for up to five-years. Inflammatory markers (C-reactive protein, interleukin 1β, interleukin 6, interleukin 8, interleukin 10, interleukin 12, and tumor necrosis factor-α) were assayed, and logistic regression analyses were performed to determine associations between inflammatory markers and both baseline cognitive status and subsequent cognitive decline.

Results

There were 243 ischemic stroke patients in the study. In multivariable ordinal logistic regression analysis, age, education, ethnicity, stroke subtype, and interleukin 8 (OR 1·23 CI 1·05–1·44) levels were independently associated with baseline cognitive status. In multivariable logistic regression analyses, age, gender, recurrent strokes, and interleukin 12 (OR 25·02 CI 3·73 to 168·03) were independent predictors of subsequent cognitive decline.

Conclusions

Following ischemic stroke, higher serum interleukin 8 is independently associated with baseline cognitive impairment while higher serum interleukin 12 is associated with subsequent cognitive decline.

Changes in body mass in later life and incident dementia

BACKGROUND

There is ongoing debate about whether a decline in body mass represents a true risk factor for dementia, whether it is a phenotypic marker of incipient dementia, or perhaps a marker of another process that increases dementia risk. This study was designed to determine if changes in body mass index (BMI) in later life are associated with hazard of incident dementia over a follow-up period of up to eight years.

METHODS

Method followed was a prospective cohort study of 4,181 men aged 65-84 years, resident in Perth, Australia. The exposure of interest was change in BMI measured between 1996-1998 and 2001-2004. The outcome was incident dementia, established using the Western Australia Data Linkage System until 2009. We used Cox regression models to establish crude and adjusted hazard of dementia for change in BMI.

RESULTS

Compared with men with a stable BMI, those with a decrease in BMI >1 kg/m2 had a higher adjusted hazard of dementia (hazard ratio (HR) = 1.89, 95% CI = 1.32-2.70). The cumulative hazard of dementia over follow-up for changes in BMI was greatest for men with a decrease in BMI >1 kg/m2; this trend was apparent for men in all BMI categories (underweight, normal, overweight, obese). A reverse "J-shaped" association between BMI change and incident dementia was observed, with the lowest dementia rate being for men whose BMI remained stable.

CONCLUSIONS

Men who maintained a stable body mass had the lowest incidence of dementia. Further studies are needed to clarify causality and assess feasibility of interventional studies to preserve body mass in aging men.