Adiponectin in Cerebrospinal Fluid from Patients Affected by Multiple Sclerosis Is Correlated with the Progression and Severity of Disease.

Adiponectin exerts relevant actions in immunity and is modulated in several disorders, such as multiple sclerosis (MS). In this study, we characterized adiponectin expression and profiles in cerebrospinal fluid (CSF) from MS patients to investigate its potential relationship with the severity and progression of the disease. Total adiponectin in CSF was measured by ELISA in 66 unrelated CSF MS patients and compared with 24 age- and sex-matched controls. Adiponectin oligomer profiles were analysed by Western blotting and FPLC chromatography. Total CSF adiponectin was significantly increased in MS patients compared with controls (9.91 ng/mL vs 6.02 ng/mL) (p < 0.001). Interestingly, CSF adiponectin positively correlated with CSF IgG, and CSF/serum albumin directly correlated with CSF/serum adiponectin. Our data demonstrated that CSF adiponectin predicts a worse prognosis: patients with the progressive form of MS had higher levels compared with the relapsing remitting form; patients with higher EDSS at baseline and a higher MS severity score at 4.5-year follow-up had significantly elevated adiponectin levels with respect to patients with a less severe phenotype. Finally, the adiponectin oligomerization profile was altered in CSF from MS patients, with a significant increase in HMW and MMW. The correlation of CSF adiponectin with the severity and prognosis of MS disease confirmed the role of this adipokine in the inflammatory/immune processes of MS and suggested its use as a complementary tool to assess the severity, progression and prognosis of the disease. Further studies on larger MS cohorts are needed to clarify the contribution of adiponectin to the etiopathogenesis of MS.

Association of Cerebrospinal Fluid Adiponectin Levels With Cerebral Glucose Metabolism In Mild Cognitive Impairment: A Pilot Study.

BACKGROUND: Adiponectin has been implicated in the pathophysiology of dementia, especially Alzheimer's disease. However, the association between cerebrospinal fluid (CSF) adiponectin levels and positron emission tomography (PET) imaging remains unclear. OBJECTIVE: To explore whether CSF adiponectin levels are associated with 11C-Pittsburgh compound B (PiB) or 18F-fluorodeoxyglucose (FDG) uptake in amnestic mild cognitive impairment (MCI) subjects. METHODS: Thirty-four amnestic MCI subjects underwent PiB-PET, FDG-PET, and CSF analysis. The CSF adiponectin levels were measured using the Bio-Plex 200 suspension array system. PET uptake was assessed for the frontal and temporoparietal lobes and posterior cingulate gyrus, referenced against the cerebellar cortex. The increased brain amyloid burden was defined as a mean uptake value ratio greater than 1.4. Spearman's rank correlation analysis and a multiple regression model were used to examine the association between CSF adiponectin levels and PiB or FDG uptake. RESULTS: The mean age was 76.3 years; 38.2% were men, and 61.8% were women. A high amyloid burden was identified in 18 (52.9%) subjects. CSF adiponectin levels positively correlated with global FDG uptake (ß = 0.45; 95% confidence interval (CI), 0.13 to 0.76, p < 0.01), especially in the parietotemporal lobe and posterior cingulate gyrus (ß = 0.70; 95% CI, 0.41 to 0.99, p<0.01, ß = 0.33; 95% CI, 0.03 to 0.63, p = 0.03, respectively) after adjusting for covariates, including age, sex, education years, body mass index, vascular risk factors, ApoEε4 status, and PiB status in all amnestic MCI subjects. CONCLUSION: CSF adiponectin levels were associated with cortical glucose metabolism, particularly in the specific regions that connect with the medial temporal, but not brain amyloid burden in amnestic MCI subjects.

Effects of running on adiponectin, insulin and cytokines in cerebrospinal fluid in healthy young individuals.

Exercise can prevent the sedentary lifestyle-related risk of metabolic and cognitive decline, but mechanisms and mediators of exercise effects on human brain are relatively unexplored. We measured acute exercise-induced changes in adiponectin, insulin and other bioactive molecules in cerebrospinal fluid (CSF) and serum from young lean individuals. Samples of serum and CSF were obtained before and 1-h after the 90-min run (75-80% HRmax; maximal heart rate), additional serum was taken at finish-line. Body composition, physical fitness, metabolic rate, cognitive functions, food preference, glucose, insulin and albumin were measured. The spectrum of 174 cytokines was assessed by protein arrays, adiponectin was also determined by ELISA and immunoblotting. CSF adiponectin decreased post-exercise by 21.3% (arrays) and 25.8% (ELISA) (p < 0.009). Immunoblotting revealed reduction in a low-molecular-weight-adiponectin (p < 0.005). CSF adiponectin positively correlated with CSF/serum albumin ratio (p < 0.022), an indicator of blood-brain-barrier permeability. CSF and serum adiponectin were positively associated with memory and running-induced changes in insulinemia and CSF insulin. Additionally, running modulated CSF levels of 16 other cytokines. Acute running reduced CSF adiponectin and modulated insulin and albumin in CSF and serum. Associations of adiponectin with memory and metabolism indicate the potential role of this bioactive molecule in mediating exercise-induced adaptive response in human brain.

Association between Adipokines and Biomarkers of Alzheimer's Disease: A Cross-Sectional Study.

BACKGROUND: Adipose tissue dysfunction has been implicated in the pathophysiology of Alzheimer's disease. However, the involvement of adipokines, particularly adiponectin, remains unclear. OBJECTIVE: To compare serum and cerebrospinal fluid (CSF) levels of adiponectin, leptin and leptin-to-adiponectin ratio in patients within the spectrum of Alzheimer's disease and evaluate their relationship with classical biomarkers and their value as markers of progression. METHODS: Amnestic mild cognitive impairment (MCI, n = 71) and Alzheimer's dementia (AD, n = 53) subjects were consecutively recruited for serum and CSF adiponectin and leptin determination using an analytically validated commercial enzyme-linked immunosorbent assay (ELISA). Correlations were explored using adjusted Spearman's correlation coefficients. A logistic regression model and ROC analysis were performed to evaluate the staging predictive value of adipokines. RESULTS: Serum adiponectin was 33% higher in AD when compared to MCI patients. Adiponectin CSF levels, similar in both groups, were positively correlated with Aß42 and cognitive function, though only in women. The area under the ROC curve was 0.673 (95% CI:0.57-0.78) for serum adiponectin as predictor of dementia stage and the cut-off 10.85µg/ml maximized the sum of specificity (87%) and sensitivity (44%). CONCLUSION: Although longitudinal studies are required, we hypothesize that higher serum adiponectin in AD patients constitutes a strategy to compensate possible central signaling defects. In addition, adiponectin might be specifically assigned to neuroprotective functions in women and eventually involved in the female-biased incidence of Alzheimer's disease.

CSF concentrations of adipsin and adiponectin in patients with amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) is described as a neurodegenerative disorder. However, neuroinflammation and chemokine expression are prominent pathological finding at sites of injury. Adipsin and adiponectin are molecules that are implicated in the pathogenesis of neurodegenerative and neuroimmune disorders. Adipsin and adiponectin concentrations were determined in the CSF of ALS patients and controls and the relationship of these chemokines with clinical severity and disease duration in ALS was determined. Seventy-seven ALS patients (mean age 49.5 ± 10.4 years) (mean body mass index 23.5 ± 4.5) were included. Twenty patients had bulbar, 53 spinal, and four bulbospinal onset ALS. Median adipsin CSF level was 12,650.94 pg/ml in ALS patients and 3290.98 pg/ml in controls (p < 0.001). Median adiponectin CSF level was 4608 pg/ml in ALS patients and 3453 pg/ml in controls (p = 0.1). No differences were observed in disease duration, progression rate or disease severity. There was a significant positive correlation between adipsin and adiponectin concentrations (r = 0.379, p = 0.01). No correlation with age, body mass index or ALFRS-R score was found. Adipsin was significantly elevated in CSF, suggesting that this chemokine might have a role in ALS pathogenesis. Adiponectin showed a trend towards higher concentrations, but failed to reach statistical significance. Due to the clinical heterogeneity in our cohort, these chemokines do not appear to be associated with disease duration or severity.

CSF and plasma adipokines after tonic-clonic seizures.

PURPOSE: Adipokines, especially leptin and adiponectin, have gained increasing importance in pathophysiology of various neurological diseases including epilepsy. There are experimental data suggesting a role for leptin in the genesis of seizures and neuroprotection related to seizures. However there are no clinical studies on the effects of epileptic seizures on adipokines. METHODS: We measured cerebrospinal fluid (CSF) and plasma levels of leptin, adiponectin and adipsin after provoked or unprovoked primary or secondarily generalized tonic-clonic seizures in 13 female patients and seven controls. The samples were taken within 24h after the seizure onset. RESULTS: Leptin plasma levels correlated negatively with the time to sample withdrawal, i.e. the longer the time interval between the seizure and the sample the lower the leptin levels in the patients. Interestingly, plasma adiponectin levels were significantly increased after the seizure episode. CONCLUSION: This study provides further evidence that there are seizure-induced acute changes in adipokine metabolism. Leptin concentrations seem to decrease during the first 24h after the seizure whereas adiponectin levels increase. The meaning of this response is far from clear, but it might be an endogenous attempt to prevent harmful effects of epileptic seizures in the central nervous system.

Possible Involvement of Adiponectin, the Anti-Diabetes Molecule, in the Pathogenesis of Alzheimer's Disease.

Adiponectin (APN) is protective in animal models of neurodegenerative diseases, but the role of APN in human brain has not been established. Using an enzyme-linked immunosorbent assay, we found that APN was significantly decreased in cerebrospinal fluid (CSF) of patients with Alzheimer's disease (AD), compared to those in patients with mild cognitive impairment (MCI) and in normal controls (NC), despite elevation of APN in serum of patients with MCI and AD compared to that in NC. The discrepancy of CSF APN from serum APN in AD may suggest some critical actions of APN in the pathogenesis of AD. Indeed, it was histologically observed that APN was co-localized with tau in neurofibrillary tangles and immunoblot analysis showed that the functional trimers of APN were significantly decreased in AD compared to those in NC. Collectively, a loss of function of APN may be involved in the pathogenesis of AD.

Serum and CSF adiponectin, leptin, and interleukin 6 levels as adipocytokines in Egyptian children with febrile seizures: a cross-sectional study.

BACKGROUND: A febrile seizure (FS) is the most common convulsive disorder in children. Activation of cytokine network is involved in FS pathogenesis. Adiponectin, leptin and IL-6 are the major adipocytokines secreted by fat cells. To date, only a few studies concerned the association of adipocytokines with febrile seizures. In this study, we tried to investigate serum and CSF levels of adiponectin, leptin, and interleukin-6 (IL-6); as adipocytokines, for the first time in Egyptian children with febrile seizures. METHODS: This was a prospective cross-sectional study included one hundred patients with febrile seizure, and matched with age, gender, 100 children with febrile illness without seizures (febrile control, FC) and 100 healthy control group (HC). Serum and cerebrospinal fluid (CSF) levels of adiponectin, leptin, and (IL-6) were measured by enzyme-linked immunosorbent assay (ELISA) method. RESULTS: Serum adiponectin was significantly higher in children with FS (16.8 ± 3.7 ug/ml) and the FC group (18.3 ± 4.3 ug/ml) compared to the HC group (9.5 ± 2.2 ug/ml); P < 0.05, respectively. Serum leptin was significantly lower in children with FS (0.9 ± 0.3 ng/ml) compared to both the FC group (4.7 ± 1.2 ng/ml) and the HC group (1.8 ± 0.4 ng/ml); P < 0.01, respectively. Children with FS had significantly higher serum IL-6 levels (43.7 ± 11.7 ng/ml) than the FC group (21.9 ± 4.5 ng/ml) and the HC group (6.5 ± 1.8 ng/ml); P < 0.01, respectively. Patients with simple febrile seizures (SFS) had serum and CSF adiponectin levels similar to those with complex febrile seizures (CFS); (P > 0.05). Serum and CSF leptin levels were significantly lower in patients with CFS compared to the SFS group (P < 0.05). Serum and CSF IL-6 levels were significantly higher in patients with CFS compared to the SFS group (P < 0.01). On multivariate logistic regression analysis, the high serum IL-6 levels was the most significant risk factor associated with febrile seizures among studied children (OR: 6.2; 95 % CI: 3.58 -10.57; P = 0.0001). CONCLUSION: Our data brought a novel observation that some adipocytokines like leptin and IL-6 could be, at least in part, an aetiopathogenetic factor in the manifestation of febrile seizures in susceptible Egyptian children. Moreover, we observed a significant association between high CSF IL-6 levels and susceptibility to complex febrile seizures as did the low CSF leptin levels.

SERUM ADIPONECTIN AND INSULIN-LIKE GROWTH FACTOR 1 IN PREDOMINANTLY FEMALE PATIENTS WITH THYROID CANCER: ASSOCIATION WITH THE HISTOLOGIC CHARACTERISTICS OF THE TUMOR.

OBJECTIVE: Insulin-like growth factor (IGF)-1 and adiponectin have been proposed to contribute to the pathogenesis of different malignancies. However, data regarding their association with histologic characteristics of thyroid cancer are scarce. The main aims of the present study were the comparative evaluation of IGF-1, IGF-binding protein 3 (BP3), and adiponectin serum levels between different histologic types of thyroid cancer, as well as within specific histologic characteristics of the tumors. METHODS: A total of 179 thyroid cancer patients (126 [70.4%] women) were recruited. A total of 129 (72.1%) had papillary thyroid carcinoma (including variants), 26 had follicular thyroid carcinoma (14.5%), and 24 had medullary thyroid carcinoma (13.4%). Parameters from history, physical examination, and thyroid histology were selected. Serum adiponectin, IGF-1, and IGF-BP3 were measured in fasting morning samples. RESULTS: IGF-1, IGF-BP3, and adiponectin levels were similar among different histologic types of thyroid carcinoma, with a trend towards higher IGF-1 and IGF-BP3 levels in patients with intrathyroid invasion, compared to those without. In addition, ratios of IGF-1 to adiponectin (P = .012) and IGF-1 to (adiponectin × IGF-BP3) (P = .003), as well as type 2 diabetes (P = .001), were positively associated with tumor size. CONCLUSION: Although IGF-1, IGF-BP3, and adiponectin were not separately different between groups or within specific histologic lesions, when they were combined to produce IGF-1 to adiponectin and IGF-1 to (adiponectin × IGF-BP3) ratios, they were independently associated with tumor size. Future prospective studies are needed to evaluate whether these ratios could serve as prognostic markers of thyroid tumor aggressiveness.

Neurogenesis-independent antidepressant-like effects of enriched environment is dependent on adiponectin.

Environmental enrichment (EE) that combines voluntary physical exercise, sensory and social stimuli, causes profound changes in rodent brain at molecular, anatomical and behavioral levels. Here, we show that EE efficiently reduces anxiety and depression-like behaviors in a mouse model of depression induced by long-term administration of corticosterone. Mechanisms underlying EE-related beneficial effects remain largely unexplored; however, our results point toward adiponectin, an adipocyte-secreted protein, as a main contributor. Indeed, adiponectin-deficient (adipo(-/-)) mice did not benefit from all the EE-induced anxiolytic and antidepressant-like effects as evidenced by their differential responses in a series of behavioral tests. Conversely, a single intravenous injection of exogenous adiponectin restored the sensitivity of adipo(-/-) mice to EE-induced behavioral benefits. Interestingly, adiponectin depletion did not prevent the hippocampal neurogenesis induced by EE. Therefore, antidepressant properties of adiponectin are likely to be related to changes in signaling in the hypothalamus rather than through hippocampal-neurogenesis mechanisms. Additionally, EE did not modify the plasma levels of adiponectin but may favor the passage of adiponectin from the blood to the cerebrospinal fluid. Our findings provide advances in the understanding of the anxiolytic and antidepressant-like effects of EE and highlight adiponectin as a pivotal mediator.

Adiponectin activates endothelial nitric oxide synthase through AMPK signaling after subarachnoid hemorrhage.

Adiponectin is produced from fatty tissue and has been reported to be involved with metabolic syndrome. Recently, adiponectin has been demonstrated to play a neuroprotective role against cerebral ischemia. In this study, we explored the time-course serial expression changes of adiponectin in cerebrospinal fluid (CSF) after subarachnoid hemorrhage (SAH) and the effects of adiponectin on cerebral arteries. The concentrations of adiponectin were measured serially until day 14 in CSF of 8 patients with SAH. The CSF samples obtained from 6 patients suffering from an unruptured aneurysm were used as controls. Serum samples were collected from 6 healthy adult volunteers. Rat cerebral arteries were incubated with adiponectin (2µg/ml). Western blot analysis using AMP-activated protein kinase α (AMPKα), phosphorylated (p)-AMPKα at Thr(172), endothelial nitric oxide synthase (eNOS), p-eNOS at Ser(1177) and actin antibodies was then performed. The adiponectin concentrations in serum and control CSF were 17,670±3748ng/ml and 9.2±3.0ng/ml, respectively. After SAH, the concentration of adiponectin in the CSF significantly increased on the first post-SAH day and gradually decreased thereafter. Adiponectin significantly phosphorylated both the AMPKα and eNOS of the cerebral arteries. Our findings suggest that adiponectin is significantly increased in the CSF after SAH, resulting in the activation of AMPKα and eNOS. Adiponectin plays an important role against cerebral vasospasm via the AMPK/eNOS signaling pathway.

Adiponectin in plasma and cerebrospinal fluid in MCI and Alzheimer's disease.

BACKGROUND AND PURPOSE: Life style-related disorders such as hypertension, diabetes, dyslipidemia, and obesity are reported to be a great risk of dementia. Adipocytokines released from adipose tissue are thought to modulate some brain functions including memory and cognition. We here analysed adiponectin, one of the most important adipocytokines, in plasma and cerebrospinal fluid (CSF) from cognitive normal controls (NC), mild cognitive impairment (MCI) subjects, and patients with Alzheimer's disease (AD) and discussed if/how adiponectin could relate to the pathogenesis of AD. METHODS: Normal controls (n = 28), MCI (n = 18), and AD (n = 27) subjects were recruited at Tohoku University Hospital. The diagnosis of AD was based on NINCDS-ADRDA criteria. All the blood and CSF samples were obtained from each fasted subject. Adiponectin was assayed using a sandwich ELISA system. RESULTS: The levels of adiponectin between in plasma and in CSF showed a positive correlation. Plasma adiponectin was significantly higher in MCI and AD compared to NC, whereas CSF adiponectin was significantly higher in MCI compared to NC. CONCLUSION: It is possible that the level of adiponectin in plasma reflects its level in CSF. The tendency to have higher adiponectin in plasma and CSF from MCI and AD suggests that this molecule plays a critical role in the onset of AD.

Elevated cerebrospinal fluid adiponectin and adipsin levels in patients with multiple sclerosis: a Finnish co-twin study.

BACKGROUND AND PURPOSE: The aim of this study was to investigate the levels of three adipocytokines: leptin, adiponectin and adipsin, in serum and cerebrospinal fluid (CSF) of twins discordant for multiple sclerosis (MS). Adipose tissue is an important component connecting immune system and several tissues and organs including CNS. Fat cells produce adipocytokines, which seem to have a role in various autoimmune disorders including MS. METHODS: Plasma samples were collected from twelve twins and CSF samples from four twins discordant for MS. The concentrations of interleukine (IL)-6, adiponectin, adipsin and leptin in plasma and CSF samples were determined by enzyme immuno assay. RESULTS: A significant difference was seen in the adipocytokine levels in CSF samples. Twins with MS had higher concentrations of adiponectin (P = 0.039) and adipsin (P = 0.039), than their asymptomatic co-twins. CONCLUSION: As adiponectin and adipsin levels in CSF did not correlate with their levels in plasma, it seems that there could be a secondary intrathecal synthesis of these adipocytokines in MS.

Detection of adiponectin in cerebrospinal fluid in humans.

Adiponectin circulates in the body in high concentrations, and 100-fold lower amounts were described in the cerebrospinal fluid (CSF) of mice, whereas in humans, contradictory results have been published. To clarify whether adiponectin is present in human CSF and is derived from the circulation, it was determined in human CSF and plasma of 52 nonselected patients. Adiponectin was detected by immunoblot in CSF and was quantified in CSF and serum by ELISA. CSF adiponectin was positively correlated to systemic levels, and the CSF/serum adiponectin ratio was correlated to the CSF/serum albumin ratio. Furthermore, disturbed function of the blood-brain barrier (BBB) was associated with an elevated CSF/serum adiponectin ratio. Adiponectin mRNA was not found in the brain, indicating that adiponectin crosses the BBB and/or the blood-cerebrospinal fluid barrier (BCB). Rat adiponectin with a COOH-terminal tag was injected into the tail vein of rats and was detected 3 h later in CSF. However, CSF adiponectin in humans and rats was approximately 0.1% of the serum concentration and therefore was below the 0.5% expected in the CSF because of the residual leakage of an undisturbed BBB/BCB. Taken together, data from the present study show that adiponectin in human CSF is far below the level expected by the baseline BBB/BCB permeability, indicating that adiponectin enters the brain much less efficiently than albumin, thus supporting recent data that exclude adiponectin transport to the CSF. Additional studies are needed to reveal whether these low levels of adiponectin in CSF have a physiological function.

Adiponectin: starving for attention.

Maintaining energy balance involves the dynamic control of appetite and energy expenditure. A new study from the Kadowaki laboratory (Kubota et al., 2007) shows that the adipocyte-derived hormone adiponectin increases appetite and reduces energy expenditure by stimulating AMPK in the hypothalamus.

Adiponectin stimulates AMP-activated protein kinase in the hypothalamus and increases food intake.

Adiponectin has been shown to stimulate fatty acid oxidation and enhance insulin sensitivity through the activation of AMP-activated protein kinase (AMPK) in the peripheral tissues. The effects of adiponectin in the central nervous system, however, are still poorly understood. Here, we show that adiponectin enhances AMPK activity in the arcuate hypothalamus (ARH) via its receptor AdipoR1 to stimulate food intake; this stimulation of food intake by adiponectin was attenuated by dominant-negative AMPK expression in the ARH. Moreover, adiponectin also decreased energy expenditure. Adiponectin-deficient mice showed decreased AMPK phosphorylation in the ARH, decreased food intake, and increased energy expenditure, exhibiting resistance to high-fat-diet-induced obesity. Serum and cerebrospinal fluid levels of adiponectin and expression of AdipoR1 in the ARH were increased during fasting and decreased after refeeding. We conclude that adiponectin stimulates food intake and decreases energy expenditure during fasting through its effects in the central nervous system.

Improved ELISA for selective measurement of adiponectin multimers and identification of adiponectin in human cerebrospinal fluid.

BACKGROUND: Human serum adiponectin exists in 3 multimer forms: high molecular weight (HMW), middle molecular weight, and low molecular weight (LMW), with some of the latter bound to albumin (Alb)-LMW. Some studies have suggested that adiponectin crosses the blood-brain barrier and plays a central role in energy homeostasis. METHODS: To determine cerebrospinal fluid (CSF) adiponectin at extremely low concentrations, we modified the protocol of the ELISA system used to assay serum adiponectin. The 3 multimers of adiponectin were measured separately by pretreating CSF with 2 proteases. We measured the CSF adiponectin concentrations in anonymous human samples (n = 19). The molecular sizes of adiponectin in CSF pretreated with proteases or untreated were determined by use of native PAGE and immunoblotting. RESULTS: The ELISA system measured adiponectin in the range of 1.0-167 microg/L. The between-assay imprecision estimates (CVs) were 6%-17% for the 3 forms. The mean total CSF adiponectin concentration (7.2 microg/L) was approximately 1/1000 of the mean concentration in serum. Unlike serum adiponectin, the LMW and Alb-LMW forms predominated in all of the CSF samples. Immunoblotting analysis revealed that most LMW forms were bound to Alb, although the HMW form was detected in some samples. CONCLUSIONS: The modified ELISA system measures the 3 multimers separately and is sufficiently sensitive to measure adiponectin in CSF.

Adiponectin and resistin in human cerebrospinal fluid and expression of adiponectin receptors in the human hypothalamus.

CONTEXT: The adipokine leptin has critical importance in central appetite regulation. In contrast to some suggestion of adiponectin influencing energy homeostasis in rodents, there is no evidence for adiponectin or resistin entering the human blood-brain barrier. OBJECTIVE: The objective was to establish the presence of adiponectin or resistin in human cerebrospinal fluid (CSF) and to compare their distribution with leptin. Furthermore, we wished to examine the expression of the adiponectin receptors 1 and 2 (AdipR1, AdipR2) in the human hypothalamus. METHODS: For this purpose, serum and CSF samples were collected from 20 men and 19 women matched for age [men, 69.8 +/- 8.6 yr (mean +/- SD); women, 69.4 +/- 4.3 yr] and BMI (men, 29.4 +/- 3.4 kg/m(2); women, 27.3 +/- 4.8 kg/m(2)) undergoing elective surgery under spinal anesthesia. RESULTS: Adiponectin was identified in CSF with levels 1000-fold less than serum, whereas resistin and leptin levels were 100-fold less. Unlike their serum levels, adiponectin CSF levels showed no gender difference or correlation with insulin resistance, which is similar to resistin CSF levels. The adiponectin and leptin CSF/serum ratios in our study exhibit the same pattern of gender-specific BMI association with inverse correlation in women (r = -0.61; P = 0.02) and no correlation in men (r = 0.026; P = not significant). Furthermore, immunostaining established AdipR1 and -2 in the hypothalamus and increased AdipR2 expression in the paraventricular nucleus, which is involved in energy regulation. CONCLUSION: In summary, our findings show both the presence of adiponectin and resistin in human CSF, with no effect of insulin resistance on CSF levels. The CSF entry of adiponectin and leptin in women appears to be impaired in obesity.

Adiponectin complexes in human cerebrospinal fluid: distinct complex distribution from serum.

AIMS/HYPOTHESIS: Adiponectin is an adipocyte-derived secretory factor that is specifically produced in adipocytes. It exerts effects on energy homeostasis via peripheral and central mechanisms. However, it is not clear whether adiponectin crosses the blood-brain barrier in humans. In serum, adiponectin circulates in several different complexes, each of which has distinct functions. Here, we wanted to test whether adiponectin can be found in human cerebrospinal fluid (CSF) and whether specific adiponectin complexes are enriched in CSF compared with peripheral serum samples. We also wanted to establish whether there is a sex-related difference with regard to the distribution of adiponectin oligomers in CSF. MATERIALS AND METHODS: We studied 22 subjects (11 men, 11 women) in this study. Their average BMI was 28.0+/-4.7 kg/m2; average age was 70+/-7 years. RESULTS: Analysis of total adiponectin revealed that adiponectin protein is present in human CSF at approximately 0.1% of serum concentration. The distribution of adiponectin oligomers differs considerably in CSF from that of serum within matched samples from the same patients. Only the adiponectin trimeric and low-molecular-mass hexameric complexes are found in CSF, with a bias towards the trimeric form in most patients. Male subjects have a higher CSF:serum ratio of total adiponectin (p<0.05; n=20) and have slightly higher trimer levels in serum and CSF than female subjects. CONCLUSIONS/INTERPRETATION: We conclude that the adiponectin trimer is the predominant oligomer in human CSF.

Adiponectin does not cross the blood-brain barrier but modifies cytokine expression of brain endothelial cells.

Adiponectin has recently been reported to generate a negative energy balance by increasing energy expenditure. However, it is unclear whether such effects require the presence and direct action of the adiponectin protein in the central nervous system. In this study, neither radiolabeled nonglycosylated nor glycosylated globular adiponectin crossed the blood-brain barrier (BBB) in mice. In addition, adiponectin was not detectable in human cerebrospinal fluid using various established methods. Using murine cerebral microvessels, we demonstrated expression of adiponectin receptors, which are upregulated during fasting, in brain endothelium. Interestingly, treatment with adiponectin reduced secretion of the centrally active interleukin-6 from brain endothelial cells, a phenomenon that was paralleled by a similar trend of other proinflammatory cytokines. In summary, our data suggest that direct effects of endogenous adiponectin on central nervous system pathways are unlikely to exist. However, the identification of adiponectin receptors on brain endothelial cells and the finding of a modified secretion pattern of centrally active substances from BBB cells provides an alternate explanation as to how adiponectin may evoke effects on energy metabolism.