IL-6, but not TNF-α, increases plasma YKL-40 in human subjects.

Plasma levels of YKL-40 are elevated in patients with systemic infection, inflammatory disorders and cancer. Both monocytes/macrophages, neutrophils, and cancer cells have the capacity to produce YKL-40, but the regulation during the inflammatory response is unknown. To study the possible role of interleukin-6 (IL-6) and tumor necrosis factor (TNF)-α in the regulation of YKL-40 plasma levels, we included healthy men, who received either recombinant human (rh)IL-6 (n=6), rhTNF-α (n=8) or vehicle (n=7) for 3h. The plasma levels of IL-6 and TNF-α reached ∼ 150 and ∼ 18 pg/ml, respectively, during the infusions. Following the IL-6 infusion, the plasma level of YKL-40 increased from ∼ 30 to ∼ 57 ng/ml (p<0.05) at 24h, and returned to normal values after 48 h. The plasma level of YKL-40 did not change during TNF-α infusion or infusion of vehicle. These data demonstrate that IL-6, but not TNF-α, has a key-role in the regulation of plasma YKL-40 levels during inflammation.

Cerebral FDG-PET scanning abnormalities in optimally treated HIV patients.

BACKGROUND: The long-term neurological consequences of HIV infection and treatment are not yet completely understood. In this study we examined the prevalence of cerebral metabolic abnormalities among a cohort of neurologically intact HIV patients with fully suppressed HIV viral loads. Concomitant analyses of circulating brain derived neurotrophic factor (BDNF) were performed to correlate these abnormalities with potential signs of neuro-regenerating/protective activity, and concomitant analyses of circulating tumour necrosis factor (TNF) alpha, interleukin (IL) 6, and soluble urokinase plasminogen activator receptor (suPAR) were performed to correlate these abnormalities with potential signs of neurodegenerative processes. METHODS: The study population consisted of HIV-positive patients known to be infected for more than 5 years and on antiretroviral (ARV) treatment for a minimum of three years with no history of virological failure, a CD4 count above 200 x 106 cells/l and no other co-morbidities. The distribution of the regional cerebral metabolic rate of glucose metabolism was measured using fluorine-18-flourodeoxyglucose positron emission tomography (FDG-PET) scanning. The PET scans were evaluated for individual pathology using Neurostat software and for group pathology using statistical parametric mapping (SPM). Circulating levels of BDNF, TNF alpha, IL-6 and suPAR were measured by ELISA techniques. RESULTS: More than half (55%) of the patients exhibited varying severities of mesial frontal reduction in the relative metabolic rate of glucose. Compared to healthy subjects, the patients with abnormal FDG-PET scanning results had a shorter history of known HIV infection, fewer years on antiretroviral therapy and higher levels of circulating TNF alpha and IL-6 (p = 0.08). CONCLUSION: A large proportion of optimally treated HIV patients exhibit cerebral FDG-PET scanning abnormalities and elevated TNF alpha and IL-6 levels, which may indicate imminent neuronal damage. The neuroprotective effect of early ARV treatment should be considered in future prospective follow-up studies.

Role of exercise-induced brain-derived neurotrophic factor production in the regulation of energy homeostasis in mammals.

Brain-derived neurotrophic factor (BDNF) has been shown to regulate neuronal development and plasticity and plays a role in learning and memory. Moreover, it is well established that BDNF plays a role in the hypothalamic pathway that controls body weight and energy homeostasis. Recent evidence identifies BDNF as a player not only in central metabolism, but also in regulating energy metabolism in peripheral organs. Low levels of BDNF are found in patients with neurodegenerative diseases, including Alzheimer's disease and major depression. In addition, BDNF levels are low in obesity and independently so in patients with type 2 diabetes. Brain-derived neurotrophic factor is expressed in non-neurogenic tissues, including skeletal muscle, and exercise increases BDNF levels not only in the brain and in plasma, but in skeletal muscle as well. Brain-derived neurotrophic factor mRNA and protein expression was increased in muscle cells that were electrically stimulated, and BDNF increased phosphorylation of AMP-activated protein kinase (AMPK) and acetyl coenzyme A carboxylase-beta (ACCbeta) and enhanced fatty oxidation both in vitro and ex vivo. These data identify BDNF as a contraction-inducible protein in skeletal muscle that is capable of enhancing lipid oxidation in skeletal muscle via activation of AMPK. Thus, BDNF appears to play a role both in neurobiology and in central as well as peripheral metabolism. The finding of low BDNF levels both in neurodegenerative diseases and in type 2 diabetes may explain the clustering of these diseases. Brain-derived neurotrophic factor is likely to mediate some of the beneficial effects of exercise with regard to protection against dementia and type 2 diabetes.

Prognostic impact of hs-CRP and IL-6 in patients with persistent atrial fibrillation treated with electrical cardioversion.

OBJECTIVE: The aim of this study was to assess the role of inflammatory processes in the development of atrial fibrillation (AF) and the prognostic impact of inflammatory markers in predicting long-term risk of AF recurrence after electrical cardioversion (CV). METHODS: High-sensitivity C-reactive protein (hs-CRP) and interleukin-6 (IL-6) were measured in 56 patients with persistent AF (lasting mean 128 days (range 14-960), mean age 65 years (34-84)), 19 healthy volunteers and 19 patients with permanent AF. Patients with persistent AF underwent CV. Blood samples were taken prior to CV and after 1, 30 and 180 days. RESULTS: The immediate success rate of CV was 88%, while the total recurrence rate after 180 days was 68%. Patients with permanent AF had significantly higher levels of hs-CRP and IL-6 than patients with persistent AF (p = 0.0011, p<0.001). Patients in sinus rhythm (SR) after 180 days had significantly lower baseline hs-CRP (1.25 mg/L (0.5-2.4) versus 2.0 mg/L (0.9-3.3), p<0.001) and IL-6 (1.96 pg/mL (1.35-2.7) versus 2.75 pg/mL (1.55-3.62), p<0.001) than patients with recurrent AF. Baseline IL-6 was the only independent predictor of recurrent AF (p = 0.04) in a multivariate Cox analysis. Patients in the lowest hs-CRP quartile (<0.8 mg/L) had significantly lower AF recurrence rates after 180 days (50% versus 74% in the other three quartiles combined; p = 0.0069). CONCLUSION: Patients with AF had elevated levels of inflammatory markers. Low hs-CRP and IL-6 prior to CV are associated with a lower risk of AF recurrence after CV.

Cholinergic status modulations in human volunteers under acute inflammation.

Cholinergic Status, the total soluble circulation capacity for acetylcholine hydrolysis, was tested for putative involvement in individual variabilities of the recruitment of immune cells in response to endotoxin challenge. Young (average age 26) and elderly (average age 70) volunteers injected with either Escherichia coli endotoxin or saline on two different occasions were first designated Enhancers and Suppressors if they showed increase or decrease, respectively, in plasma acetylcholinesterase (AChE) activity 1.5 h after endotoxin administration compared to saline. Enhancers showed significant co-increases in plasma butyrylcholinesterase (BChE) and paraoxonase (PON1) activities, accompanied by rapid recovery of lymphocyte counts. Young Enhancers alone showed pronounced post-exposure increases in the pro-inflammatory cytokine interleukin-6 (IL-6), and upregulation of the normally rare, stress-induced AChE-R variant, suggesting age-associated exhaustion of the cholinergic effects on recruiting innate immune reactions to endotoxin challenge. Importantly, IL-6 injected to young volunteers or administered in vitro to primary mononuclear blood cells caused upregulation of AChE, but not BChE or PON1, excluding it from being the sole cause for this extended response. Interestingly, Suppressors but not Enhancers showed improved post-exposure working memory performance, indicating that limited cholinergic reactions may be beneficial for cognition. Our findings establish Cholinergic Status modulations as early facilitators and predictors of individual variabilities in the peripheral response to infection.

Commonly studied polymorphisms in inflammatory cytokine genes show only minor effects on mortality and related risk factors in nonagenarians.

Systemic low-grade inflammation is consistently associated with functional status, cognitive functioning, multimorbidity, and survival in oldest olds. If inflammation is either a cause or a consequence of age-related pathology, genetic determinants of late-life survival can reside in cytokine genes polymorphisms, regulating inflammatory responses. The aim of this study was to test associations between commonly studied polymorphisms in interleukin (IL)6, IL10, IL15, and IL18, and tumor necrosis factor-alpha genes and late-life survival in a longitudinal cohort of nonagenarians: the Danish 1905 cohort. Additionally, associations were investigated between inflammatory markers and major predictors of mortality as cognitive and functional status. Modest sex-specific associations were found with survival, cognitive functioning, and handgrip strength. Evaluation of combined genotypes indicated that, in nonagenarian men, the balance of pro- and anti-inflammatory activity at IL18 and IL10 loci is protective against cognitive decline. In conclusion, in this large study with virtually complete follow-up, commonly studied polymorphisms in cytokine genes do not have a major impact on late-life survival or associated risk phenotypes.

Brain-derived neurotrophic factor predicts mortality risk in older women.

OBJECTIVES: To test the hypothesis that low circulating brain-derived neurotrophic factor (BDNF), a secretory member of the neurotrophin family that has a protective role in neurodegeneration and stress responses and a regulatory role in metabolism, predicts risk of all-cause mortality in 85-year-old men and women. DESIGN: Longitudinal study with 50- to 58-month follow-up. SETTING: The 1914 cohort, a population-based cohort established in 1964 by the Research Center for Prevention and Health at Glostrup Hospital. PARTICIPANTS: One hundred eighty-eight unselected 85-year-old Danes. MEASUREMENTS: BDNF was measured in plasma and serum. The Danish National Register of Patients was used to collect data on morbidity. The primary outcome in Cox regression analyses was all-cause mortality. RESULTS: Women with low plasma BDNF (lowest tertile) had greater all-cause mortality risk than women with high plasma BDNF (highest tertile) (hazard ratio=2.2, 95% confidence interval=1.1-4.7). Low plasma BDNF predicted mortality independently of activities of daily living; education; and a history of central nervous system disease, cerebrovascular accidents, cardiovascular disease, cancer, respiratory disease, and low-grade inflammation. No association was found between plasma BDNF and mortality in men, and serum BDNF did not influence mortality in either sex. CONCLUSION: Low plasma BDNF is a novel, independent, and robust biomarker of mortality risk in old women. BDNF may be a central factor in the network of multimorbidity in old populations.