[show abstract][hide abstract] ABSTRACT: Measurement of HbA1c is the most important parameter to assess glycemic control in diabetic patients. Different point-of-care devices for HbA1c are available. The aim of this study was to evaluate two point-of-care testing (POCT) analyzers (DCA Vantage from Siemens and Afinion from Axis-Shield). We studied the bias and precision as well as interference from carbamylated hemoglobin.
Bias of the POCT analyzers was obtained by measuring 53 blood samples from diabetic patients with a wide range of HbA1c, 4%-14% (20-130 mmol/mol), and comparing the results with those obtained by the laboratory method: HPLC HA 8160 Menarini. Precision was performed by 20 successive determinations of two samples with low 4.2% (22 mmol/mol) and high 9.5% (80 mmol/mol) HbA1c values. The possible interference from carbamylated hemoglobin was studied using 25 samples from patients with chronic renal failure.
The means of the differences between measurements performed by each POCT analyzer and the laboratory method (95% confidence interval) were: 0.28% (p<0.005) (0.10-0.44) for DCA and 0.27% (p<0.001) (0.19-0.35) for Afinion. Correlation coefficients were: r=0.973 for DCA, and r=0.991 for Afinion. The mean bias observed by using samples from chronic renal failure patients were 0.2 (range -0.4, 0.4) for DCA and 0.2 (-0.2, 0.5) for Afinion. Imprecision results were: CV=3.1% (high HbA1c) and 2.97% (low HbA1c) for DCA, CV=1.95% (high HbA1c) and 2.66% (low HbA1c) for Afinion.
Both POCT analyzers for HbA1c show good correlation with the laboratory method and acceptable precision.
Clinical Chemistry and Laboratory Medicine 02/2011; 49(4):653-7. · 3.01 Impact Factor
[show abstract][hide abstract] ABSTRACT: The aim of this study was to compare the use of glycated hemoglobin (HbA(1c)) and the oral glucose tolerance test (OGTT) in the diagnosis of impaired glucose tolerance in high-risk individuals.
A total of 713 patients with at least two risk factors for the development of type 2 diabetes were enrolled in the study. Fasting glucose and HbA(1c) were measured in all individuals. Patients whose fasting glucose concentrations were below 7.0 mmol/L underwent an OGTT.
From the 713 patients, 234 were euglycemic, 200 had impaired fasting glucose, 118 presented with impaired glucose tolerance and 161 met the diagnostic criteria for type 2 diabetes. OGTT was performed in a total of 596 patients (83.6%). Statistically significant differences were observed for HbA(1c) concentrations in all groups. Receiver operating characteristic curve analysis was performed to assess the capability of HbA(1c) to discriminate between normal glucose tolerance and impaired glucose tolerance. An HbA(1c) value of 36 mmol/mol (5.4%) gave an optimal sensitivity of 85% and a specificity of 73%, and a negative predictive value of 97% for identifying patients with impaired glucose tolerance.
HbA(1c) can be used to rule out patients at high-risk of developing type 2 diabetes.
Clinical Chemistry and Laboratory Medicine 12/2010; 48(12):1719-22. · 3.01 Impact Factor
[show abstract][hide abstract] ABSTRACT: Leptin, the LEP gene product, is produced in placenta where it has been found to be an important autocrine signal for trophoblastic growth during pregnancy. Thus, we have recently described the antiapoptotic and trophic effect of leptin on choriocarcinoma cell line JEG-3, stimulating DNA and protein synthesis. We have also demonstrated the presence of leptin receptor and leptin signaling in normal human trophoblastic cells, activating JAK-STAT, PI3K and MAPK pathways. In the present work we have employed dominant negative forms of MAPK and PKB constructs to find out the signaling pathways that specifically mediates the effect of leptin on protein synthesis. As previously shown, leptin stimulates protein synthesis as assessed by (3)H-leucine incorporation. However, both dominant negative forms of MAPK and PKB inhibited protein synthesis in JEG-3 choriocarcinoma cells. The inhibition of PKB and MAPK activity by transfection with the dominant negative kinases prevented the leptin stimulation of p70 S6K, which is known to be an important kinase in the regulation of protein synthesis. Moreover, leptin stimulation of phosphorylation of EIF4EBP1 and EIF4E, which allows the initiation of translation was also prevented by MAPK and PI3K dominant negative constructs. Therefore, these results demonstrate that both PI3K and MAPK are necessary to observe the effect of leptin signaling that mediates protein synthesis in choriocarcinoma cells JEG-3.
Biochemical and Biophysical Research Communications 06/2010; 396(4):956-60. · 2.41 Impact Factor
[show abstract][hide abstract] ABSTRACT: Leptin was originally considered as an adipocyte-derived signaling molecule for the central control of metabolism. However, pleiotropic effects of leptin have been identified in reproduction and pregnancy, particularly in placenta, where it may work as an autocrine hormone, mediating angiogenesis, growth, and immunomodulation. Leptin receptor (LEPR, also known as Ob-R) shows sequence homology to members of the class I cytokine receptor (gp130) superfamily. In fact, leptin may function as a proinflammatory cytokine. We have previously found that leptin is a trophic and mitogenic factor for trophoblastic cells. In order to further investigate the mechanism by which leptin stimulates cell growth in JEG-3 cells and trophoblastic cells, we studied the phosphorylation state of different proteins of the initiation stage of translation and the total protein synthesis by [(3)H]leucine incorporation in JEG-3 cells. We have found that leptin dose-dependently stimulates the phosphorylation and activation of the translation initiation factor EIF4E as well as the phosphorylation of the EIF4E binding protein EIF4EBP1 (PHAS-I), which releases EIF4E to form active complexes. Moreover, leptin dose-dependently stimulates protein synthesis, and this effect can be partially prevented by blocking mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3 kinase (PIK3) pathways. In conclusion, leptin stimulates protein synthesis, at least in part activating the translation machinery, via the activation of MAPK and PIK3 pathways.
Biology of Reproduction 07/2009; 81(5):826-32. · 4.03 Impact Factor
[show abstract][hide abstract] ABSTRACT: Introduction
The use of point of care techniques (POCT) has become the standard for the management of the diabetic patient. Nevertheless, the diagnosis of diabetes and glucose intolerance is based on Standard laboratory methods, even though continous improvement in glucose meters technology and quality control has led to better analytical performance, with more precise and accurate results. In the present work we evaluated the use of on-line controled glucose meters in oral glucose tolerante test (OGTT) in comparison with the Standard method.
We sought to analyze the performance of on-line controled glucose meters (PCx) in the OGTT for the diagnosis of diabetes and glucose intolerance by comparing results with those obtained in parallel by standard laboratory method.
Materials and methods
We studied 332 OGTT results obtained by PCx glucose meters and the Standard laboratory method (glucose oxidase) in 2007. After basal venoud blood sampling, subjects had 75 g glucose oral load, and a second venous blood sample was obtained after 120 min post-load. 664 whole blood samples were analyzed for glucose determination by the glucose meter and the Standard laboratory method measured serum glucose levels from the same blood samples in parallel. Cut-off values for diabetes diagnosis was 200 mg/dL, and the cut-off value for glucose intoleance was 140 mg/dL. Statistic analysis was performed using SPSS program.
Correlation of basal glucose determination by the glucose meters and the standard method yielded a Pearson coefficient of 0.798, p<0.0001 and the correlation of post-glucose determination was 0.974 (p<0.0001). Kappa coefficient, indicating agreement in the diagnosis of diabetes and glucose intolerance between both methods, indicated very good agreement (0.862, p<0001) between diagnosis carried out by glucose meter and the standard laboratoy method.
Data obtained in this study demmonstrate that the use of point-of-care-testing glucose meters (controled on-line by the laboratory) may be used in the OGTT for the diagnosis of diabetes and glucose intolerance.
Point of Care The Journal of Near-Patient Testing & Technology 08/2008; 7(3):158.
[show abstract][hide abstract] ABSTRACT: Leptin (Ob), the peripheral signal produced by the adipocyte to regulate energy metabolism, can also be produced by placenta, where it may work as an autocrine hormone. Recently, we have demonstrated that leptin promotes proliferation and survival of trophoblastic cells. In the present work we aimed to study the signal transduction pathways that mediate the trophic effect of leptin in placenta, by using the human placenta choriocarcinoma JEG-3 cell line, as well as trophoblastic cells from human placenta. We have assayed the early phase of apoptosis, triggered by serum deprivation, by using Annexin V-propidium iodide (PI) labeling and flow cytometric analysis, as well as the late phase of apoptosis by studying the activation of caspase-3. We have studied the major signalling pathways known to be triggered by the leptin receptor, and we have investigated the relative importance of these pathways in the effect of leptin by using pharmacological inhibitors. We have found that leptin stimulates Janus kinase (JAK)-signal transducers and activators of transcription (STAT) pathway by promoting JAK-2 and STAT-3 tyrosine phosphorylation. We have also demonstrated the activation of mitogen-activated protein kinase (MAPK) pathway by studying phosphorylation of extracellular-signal regulated kinase (Erk) kinase (MEK) and Erk1/2. PI3K pathway is also triggered by leptin stimulation as assessed by the study of protein kinase B (PKB) phosphorylation. These signaling pathways were confirmed in trophoblastic cells obtained from placenta of healthy donors. The effect of leptin on JEG-3 survival was completely reversed by blocking Erk1/2 activation employing the MEK inhibitor PD98059, whereas it was not affected by PI3K inhibition using wortmannin. These data suggest that the leptin antiapoptotic effect in placenta is mediated by the MAPK pathway.
Archives of Biochemistry and Biophysics 07/2008; 477(2):390-5. · 3.37 Impact Factor
[show abstract][hide abstract] ABSTRACT: Leptin (Ob) is a non-glycosylated peptide hormone that regulates energy homeostasis centrally, but also has systemic effects including the regulation of the immune function. We have reported previously that leptin activates human peripheral blood lymphocytes co-stimulated with phytohaemagglutinin (PHA) (4 microg/ml), which prevented the employment of pharmacological inhibitors of signalling pathways. In the present study, we used Jurkat T cells that responded to leptin with minimal PHA co-stimulation (0.25 microg/ml). The long isoform of leptin receptor is expressed on Jurkat T cells and upon leptin stimulation, the expression of early activation marker CD69 increases in a dose-dependent manner (0.1-10 nM). We have also found that leptin activates receptor-associated kinases of the Janus family-signal transucers and activators of transcription (JAK-STAT), mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3 kinase (PI3K) signalling pathways. Moreover, we sought to study the possible effect of leptin on cell survival and apoptosis of Jurkat T cells by culture in serum-free conditions. We have assayed the early phases of apoptosis by flow cytometric detection of fluorescein isothiocyanate (FITC)-labelled annexin V simultaneously with dye exclusion of propidium iodide (PI). As well, we have assayed the activation level of caspase-3 by inmunoblot with a specific antibody that recognizes active caspase-3. We have found that leptin inhibits the apoptotic process dose-dependently. By using pharmacological inhibitors, we have found that the stimulatory and anti-apoptotic effects of leptin in Jurkat T cells are dependent on MAPK activation, rather than the PI3K pathway, providing new data regarding the mechanism of action of leptin in T cells, which may be useful to understand more clearly the association between nutritional status and the immune function.
[show abstract][hide abstract] ABSTRACT: Human immunodeficiency virus (HIV) codes for a protein, Rev, that mediates the viral RNA export from the nucleus to the cytoplasm. Recently, it has been found that Sam68, the substrate of Src associated in mitosis, is a functional homologue of Rev, and a synergistic activator of Rev activity. Thus, it has been suggested that Sam68 may play an important role in the post-transcriptional regulation of HIV. Sam68 contains an RNA binding motif named KH [homology to the nuclear ribonucleoprotein (hnRNP) K]. Tyrosine phosphorylation of Sam68 and binding to SH3 domains have been found to negatively regulate its RNA binding capacity. Besides, tyrosine phosphorylation of Sam68 allows the formation of signalling complexes with other proteins containing SH2 and SH3 domains, suggesting a role in signal transduction of different systems in human lymphocytes, such as the T cell receptor, and leptin receptor, or the insulin receptor in other cell types. In the present work, we have found that Sam68 is tyrosine phosphorylated in peripheral blood mononuclear cells (PBMC) from HIV infected subjects, leading to the formation of signalling complexes with p85 the regulatory subunit of PI3K, GAP and STAT-3, and decreasing its RNA binding capacity. In contrast, PBMC from HIV infected subjects have lower expression levels of Sam68 compared with controls. These results suggest that Sam68 may play some role in the immune function of lymphocytes in HIV infection.
[show abstract][hide abstract] ABSTRACT: Portable meters for blood glucose concentrations are used at the patients bedside, as well as by patients for self-monitoring of blood glucose. Even though most devices have important technological advances that decrease operator error, the analytical goals proposed for the performance of glucose meters have been recently changed by the American Diabetes Association (ADA) to reach <5% analytical error and <7.9% total error. We studied 80 meters throughout the Virgen Macarena Hospital and we found most devices with performance error higher than 10%. The aim of the present study was to establish a new system to control portable glucose meters together with an educational program for nurses in a 1200-bed University Hospital to achieve recommended analytical goals, so that we could improve the quality of diabetes care. We used portable glucose meters connected on-line to the laboratory after an educational program for nurses with responsibilities in point-of-care testing. We evaluated the system by assessing total error of the glucometers using high- and low-level glucose control solutions. In a period of 6 months, we collected data from 5642 control samples obtained by 14 devices (Precision PCx) directly from the control program (QC manager). The average total error for the low-level glucose control (2.77 mmol/l) was 6.3% (range 5.5-7.6%), and even lower for the high-level glucose control (16.66 mmol/l), at 4.8% (range 4.1-6.5%). In conclusion, the performance of glucose meters used in our University Hospital with more than 1000 beds not only improved after the intervention, but the meters achieved the analytical goals of the suggested ADA/National Academy of Clinical Biochemistry criteria for total error (<7.9% in the range 2.77-16.66 mmol/l glucose) and optimal total error for high glucose concentrations of <5%, which will improve the quality of care of our patients.
Clinical Chemistry and Laboratory Medicine 01/2005; 43(8):876-9. · 3.01 Impact Factor
[show abstract][hide abstract] ABSTRACT: Coronary angioplasty is known to mediate an inflammatory response. Recently, we have characterized the transient systemic inflammatory response after coronary stent implantation in patients with unstable angina by measuring different soluble protein markers. In the present study we have characterized the expression of various cellular activation markers in neutrophils, monocytes and lymphocytes from the same group of patients. Peripheral blood samples were taken before and 24 h, 48 h and 7 days after successful coronary stenting in 58 patients. Cell surface markers (CD11b/CD18 and CD38) were analyzed by flow cytometry to determine the activation of neutrophils, monocytes and T lymphocytes. We found that coronary angioplasty with stent implantation produces an increase in the cell surface expression of CD11b/CD18 in neutrophils and CD38 in monocytes, following a similar time-course with a peak after 24 h, returning to basal levels after 48 h and a second peak after 7 days. However, T lymphocytes were not found to be activated. These results suggest that coronary stent implantation induces a different pattern inducing soluble and cellular inflammation markers, and therefore, they should be taken into account in patients undergoing stent implantation to study clinical correlations.
Clinical Chemistry and Laboratory Medicine 04/2004; 42(3):273-8. · 3.01 Impact Factor
[show abstract][hide abstract] ABSTRACT: Leptin, the 16 kDa product of the ob gene, is a an adipocyte-secreted hormone that centrally regulates weight. However, the physiological role of leptin is not limited to the regulation of food intake and energy expenditure, and leptin has a variety of effects in peripheral tissues, such as a regulatory role modulating the immune system. Thus, leptin receptor is expressed in human peripheral blood mononuclear cells, mediating the leptin stimulation of proliferation and activation, the production of proinflammatory cytokines from cultured monocytes, and the prevention of apoptotic death in serum-deprived monocytes. Because leptin can stimulate monocytes and the production of reactive oxygen species (ROS) are the result of monocyte activation, we investigated the effect of leptin on ROS production by human monocytes in vitro. Oxidative burst was measured by oxidation of the redox-sensitive dye 2',7'-dichlorofluorescein diacetate, and analysed by flow cytometry. We have found that stimulation with leptin produces oxygen radical formation by monocytes. This effect is dependent on the dose and maximal response is achieved at 10 nM leptin. Because HIV infection induces the production of ROS, we next investigated the effect of leptin on ROS production in monocytes from HIV-positive (HIV+) subjects. We have also found that monocytes from HIV+ subjects spontaneously produced increased amounts of free radicals. In contrast, leptin stimulation of monocytes from these patients partially inhibited the production of ROS. This effect of leptin was also dependent on the dose and maximal effect was achieved at 10 nM. The effect of leptin stimulating the production of ROS is consistent with the proinflammatory role in the immune system. On the other hand, the inhibitory effect on monocytes from HIV+ subjects may be explained by the attenuation of the oxidative burst by a delayed activation of monocytes in a hyperinflammatory state.
[show abstract][hide abstract] ABSTRACT: Leptin is a an adipocyte-secreted hormone that regulates weight centrally. However, the leptin receptor is expressed not only in the central nervous system, but also in peripheral tissues, such as haematopoietic and immune systems. Therefore, the physiological role of leptin should not be limited to the regulation of food intake and energy expenditure. Moreover, the leptin receptor bears homology to members of the class I cytokine family, and recent data have demonstrated that leptin is able to modulate the immune response. Thus, the leptin receptor is expressed in human peripheral blood mononuclear cells, mediating the leptin effect on proliferation and activation. In vitro activation and HIV infection in vivo induce the expression of the long isoform of the leptin receptor in mononuclear cells. Also, leptin stimulates the production of proinflammatory cytokines from cultured monocytes and enhances the production of Th1 type cytokines from stimulated lymphocytes. Moreover, leptin has a trophic effect on monocytes, preventing apoptosis induced by serum deprivation. Leptin stimulation activates JAK-STAT, IRS-1-PI3K and MAPK signalling pathways. Leptin also stimulates Tyr-phosphorylation of the RNA-binding protein Sam68 mediating the dissociation from RNA. In this way, leptin signalling could modulate RNA metabolism. These signal transduction pathways provide possible mechanisms whereby leptin may modulate activation of peripheral blood mononuclear cells. Therefore, these data support the hypothesis regarding leptin as a proinflammatory cytokine with a possible role as a link between the nutritional status and the immune response. Moreover, these immunoregulatory functions of leptin could have some relevance in the pathophysiology of obesity.
[show abstract][hide abstract] ABSTRACT: Leptin, the Ob gene product, is an adipocyte hormone that centrally regulates weight control. In addition, other effects of leptin in peripheral tissues have been described. Thus, leptin has been found to regulate reproduction, haematopoiesis and immune function. We have found recently that leptin has a stimulatory effect on human peripheral blood mononuclear cells (PBMC). Monocytes are activated by leptin alone whereas T lymphocytes need a suboptimal stimulus of PHA or ConA before further activation by leptin. These effects are mediated by the long isoform of the leptin receptor, which has been shown to trigger signalling in PBMC. In fact, we have found that human leptin stimulates Janus kinase (JAK)-signal transducer and activator of transcription (STAT), phosphatidylinositol 3-kinase (PI3K) and mitogen-activated protein kinase (MAPK) pathways in PBMC. In order to assess possible regulation of the long isoform of the leptin receptor (Ob-R) in mononuclear cells upon activation, we have studied the expression of Ob-R by RT-PCR and Western blotting in PBMC activated in vitro by PHA or ConA and in vivo in HIV-infected patients. We have found that in vitro activation and in vivo HIV infection correlates with an increase in leptin receptor expression in PBMC. Moreover, the leptin receptor is tyrosine phosphorylated in PBMC from HIV-infected patients, suggesting that the leptin receptor is activated. These results are consistent with the suggested role of leptin in modulating the immune response.
[show abstract][hide abstract] ABSTRACT: Previous evidence has shown that coronary angioplasty leads to the release of inflammatory mediators. In this study, we sought to characterize the systemic inflammatory response after coronary stent implantation in patients with unstable angina by measuring different protein markers. Peripheral blood samples were taken before and 24 h, 48 h, and 7 days after successful coronary stenting in 58 patients. Several markers of acute-phase response were determined: C-reactive protein (CRP), alpha2-macroglobulin, haptoglobin, acid alpha1-glycoprotein, prealbumin and albumin. Besides, proinflammatory cytokines (tumor necrosis factor-alpha, IL-6, IL-8) and the anti-inflammatory cytokine IL-10 were also measured. We have found that coronary angioplasty with stent implantation produces a systemic inflammatory response with a rise in inflammation markers concentration. CRP plasma levels declined 1 week after the intervention, but the other marker levels were even higher after 7 days. IL-6 was the only cytokine whose plasma levels significantly increased in peripheral blood after stenting, with a rise after 24 h, maintained after 48 h, and decreased to near-basal levels after 1 week. There was a good correlation between CRP and IL-6 plasma levels (r=0.5, p<0.001). IL-10 levels were slightly decreased after 24 h. Although no significant differences in the means at different time points were found, there was a decrease in IL-10 in most patients 24 h after the intervention. These results indicate that coronary stent implantation induces a systemic inflammatory reaction, with a temporal increase in the concentration of the inflammation markers, especially CRP and IL-6. Since these markers had been previously used as prognostic markers, this needs to be taken into account in patients undergoing stent implantation.
Clinical Chemistry and Laboratory Medicine 08/2002; 40(8):769-74. · 3.01 Impact Factor
[show abstract][hide abstract] ABSTRACT: Homocysteine has been associated with the oxidative stress in the pathogenesis of atherosclerosis. Oxidative stress caused by triglycerides and free fatty acids is known to cause insulin resistance and hyperinsulinemia. On the other hand, insulin resistance may increase homocysteine levels. Since obesity is associated with insulin resistance and hyperinsulinemia, we aimed to study the possible association of homocysteine with hyperinsulinemia in obese subjects. 20 obese male subjects (body mass index >29), aged 33--55 (mean 45 years old) were studied. A fasting blood sample was obtained for the study and the subjects undertook an oral glucose tolerance test with samples taken at 1 and 2 h after glucose. Subjects were divided in two groups according to the fasting insulin levels, < 9 &mgr;U/ml or normoinsulinemic (group 1) and >9 &mgr;U/ml or hyperinsulinemic (group 2). Glucose, insulin, homocysteine, folate, B(12,) total cholesterol, HDL-cholesterol and triglycerides levels were determined in fasting blood samples. In oral glucose tolerance test, glucose, insulin and homocysteine levels were measured. Hyperinsulinemic obese subjects (group 2) had higher levels of insulin and glucose at 1 h and 2 h postglucose, compared with group 1. Fasting total homocysteine and triglyceride levels were also increased in this group, whereas folate and B(12) levels were similar in both groups. Fasting homocysteine significantly correlated with fasting insulin (r = 0.6, p <0.01). Homocysteine levels slightly but significantly decreased after glucose loading in normoinsulinemic but not in hyperinsulinemic obese subjects. These results show that higher homocysteine levels are observed in the hyperinsulinemic obese subjects and suggest that homocysteine could play a role in the higher risk of cardiovascular disease in obesity.
The Journal of nutritional biochemistry 03/2002; 13(2):75-79. · 4.29 Impact Factor
[show abstract][hide abstract] ABSTRACT: Leptin is an adipocyte-secreted hormone that centrally regulates weight control. However, leptin receptor is expressed not only in the central nervous system, but also in other systems such as reproductive and hematopoietic tissues. Human leptin has previously been shown to enhance cytokine production by murine peritoneal macrophages and human circulating monocytes. In this paper we have assessed the presence of leptin receptors in peripheral human T lymphocytes and we have studied their functional role. Both CD4(+) and CD8(+) T lymphocytes express leptin receptors. Moreover, we show that human leptin dose-dependently enhances proliferation and activation of human circulating T lymphocytes when they are costimulated by PHA or Con A. Leptin alone was not able to activate T lymphocytes. To confirm a direct effect of leptin on T lymphocytes, monocytes were extracted by adhesion to culture flasks. The early activation surface marker CD69 was then induced in both CD4(+) and CD8(+) T lymphocytes after 8 h stimulation with PHA or Con A. Leptin dose-dependently enhanced stimulated CD69 expression. Moreover, leptin dose-dependently enhanced the expression of the late activation markers CD25 and CD71 in both CD4(+) and CD8(+) T lymphocytes after 48 h stimulation with PHA or Con A. Finally, we have found that leptin modulates CD4(+) T lymphocyte activation toward Th1 phenotype by stimulating the synthesis of IL-2 and IFN-gamma. These results demonstrate the presence of the leptin receptor in human circulating CD4(+) and CD8(+) T lymphocytes and a functional role of leptin as a modulator (enhancer) of lymphocyte stimulation with a shift toward Th1 cytokine-production profile. This function of leptin may have some relevance in the pathophysiology of immunologic alterations related to obesity.
[show abstract][hide abstract] ABSTRACT: This work evaluates whether physiological concentrations of the pineal secretory product melatonin contribute to the total antioxidant status (TAS) of human serum. Day and nighttime serum samples were collected from healthy volunteers ranging from 2 to 89 years of age and used to measure melatonin and TAS. Results showed that both melatonin and TAS in human serum exhibited 24 hr variations with nocturnal peak values at 01:00 hr. Moreover, exposure of volunteers to light at night resulted in clear decreases of both TAS and melatonin. Furthermore, when melatonin was removed from sera collected at night, the TAS value of the sample was reduced to basal daytime values. In aging studies, it was found that nocturnal serum values of TAS and melatonin exhibited maximal values during the first four decades; thereafter, these values decreased as age advanced. In 60-year-old individuals, day/night differences in serum melatonin and TAS levels were clearly diminished, by more than 80%, with these differences being completely abolished in older individuals. Our results suggest that melatonin contributes to the total antioxidative capability of human serum. This antioxidant contribution of melatonin is reduced as age advances correlating with the age-related reduction of melatonin.
Journal of Pineal Research 09/1999; 27(1):59-64. · 7.30 Impact Factor
[show abstract][hide abstract] ABSTRACT: The Ob gene product, leptin, is an adipocyte-secreted hormone that centrally regulates weight control. However, leptin receptor is expressed not only in the central nervous system, but also in other systems such as reproductive and hematopoietic tissues. Human leptin has previously been shown to enhance cytokine production by murine peritoneal macrophages. In this paper we show that human leptin stimulates proliferation in a dose-dependent manner and functionally activates human circulating monocytes in vitro, by inducing the production of cytokines such as TNF-alpha and IL-6. Proliferation was assessed both by [3H]thymidine and bromodeoxyuridine incorporation at 48 h. We also checked the leptin stimulated monocyte expression of activation markers by flow cytometry: CD25, HLA-DR, CD38, CD71, CD11b, and CD11c expression increased after 72 h. Moreover, leptin increases the expression of the early activation marker CD69 in monocytes but not in lymphocytes. The stimulation produced by leptin is comparable to that produced by endotoxin [lipopolysaccharide (LPS)]. In addition, leptin can potentiate the stimulatory effect of LPS or PMA. Furthermore, we studied cytokine production (TNF-alpha and IL-6) simultaneously by flow cytometric detection of intracellular cytokines in the activated monocytes. Leptin produced a dose-dependent increase in the number of activated monocytes producing cytokines. These data indicate that leptin is a potent stimulatory hormone on human peripheral blood monocytes and suggest that it may have a role as a proinflammatory cytokine.
[show abstract][hide abstract] ABSTRACT: Many functional studies show that melatonin plays a fundamental role in neuroimmunomodulation. In this paper, we have extended our studies on the influence of melatonin on IL-2 and IL-6 production by human peripheral blood mononuclear cells (PBMCs) by comparing the effects of the specific membrane receptor agonist S 20098, the RZR/ROR(alpha) receptor agonist CGP 52608, and structurally related thiazolidinediones. Melatonin bound to membranes as well as to nuclei of human PBMCs with about the same affinity (IC50 values around 5 nM). S 20098 bound to PBMC membranes but not to PBMC nuclei, although the affinity was at least 100 times lower than that of melatonin; this compound did not stimulate cytokine production. In contrast, all four CGP compounds did not bind to PBMC membranes, while binding to nuclei exhibited IC50 values comparable to those of melatonin. The thiazolidinediones activating the RZR/ROR(alpha) receptor (CGP 52608, CGP 53079) also increased IL-2 and IL-6 production. CGP 55644 had no effect on cytokine production and antagonized the effects of CGP 52608 on IL-2 and IL-6 production; moreover, CGP 55644 decreased the enhanced IL-2 production caused by melatonin. Results obtained in monocyte cultures resembled closely those shown in PBMCs. The results reported in this paper confirm the involvement of a nuclear mechanism in the melatonin effects on cytokine production in human PBMCs. We have also shown a synergistic effect of S 20098 and CGP 52608, suggesting a possible link between nuclear and membrane melatonin receptors in PBMCs.
Journal of Neuroimmunology 01/1999; 92(1-2):76-84. · 3.03 Impact Factor