Association of serum uric acid levels to inflammation biomarkers and endothelial dysfunction in obese prepubertal children.

BACKGROUND: High serum uric acid (SUA) levels are present in patients with metabolic syndrome (MetS), when the latter is associated with endothelial dysfunction, inflammation, and hypertension. This increase in SUA levels may have a key role in cardiovascular diseases. OBJECTIVE: We aim to quantify the differences in inflammation biomarkers, endothelial dysfunction, and parameters associated with MetS in obese prepubertal children compared to non-obese children, and determine if there is a relationship between uric acid levels and these variables. METHODS: A cross-sectional study was carried out on obese children (6-9 yr old). The study included 43 obese children and the same number of non-obese children (control group), matched by age and sex. SUA, C-reactive protein (CRP), interleukin-6 (IL-6), soluble intercellular adhesion molecule-1 (sICAM-1), glucose, insulin, lipid profile, and blood pressure were all measured. RESULTS: SUA levels, CRP, and sICAM-1 were significantly higher in obese children. In the obese group, SUA levels showed a positive correlation with body mass index (BMI), insulin, homeostasis model assessment for insulin resistance (HOMA-IR), CRP, IL-6, sICAM-1, and triglycerides (TGs), and correlated negatively with high-density lipoprotein cholesterol (HDL-C) and Apo-AI, but not with Apo-B. When adjusted for age, sex, and creatinine, it was noted that SUA levels are independent predictive factors for sICAM-1, CRP, and IL-6. CONCLUSIONS: Inflammation biomarkers, endothelial dysfunction, and parameters associated with MetS are elevated in obese prepubertal children and correlate to uric acid levels.

Long-term corticosterone exposure decreases insulin sensitivity and induces depressive-like behaviour in the C57BL/6NCrl mouse.

Chronic stress or long-term administration of glucocorticoids disrupts the hypothalamus-pituitary-adrenal system leading to continuous high levels of glucocorticoids and insulin resistance (IR). This pre-diabetic state can eventually develop into type 2 diabetes mellitus and has been associated with a higher risk to develop depressive disorders. The mechanisms underlying the link between chronic stress, IR and depression remains unclear. The present study aimed to establish a stress-depression model in mice to further study the effects of stress-induced changes upon insulin sensitivity and behavioural consequences. A pilot study was conducted to establish the optimal administration route and a pragmatic measurement of IR. Subsequently, 6-month-old C57BL/6NCrl mice were exposed to long-term oral corticosterone treatment via the drinking water. To evaluate insulin sensitivity changes, blood glucose and plasma insulin levels were measured at different time-points throughout treatment and mice were behaviourally assessed in the elevated zero maze (EZM), forced swimming test (FST) and open field test to reveal behavioural changes. Long-term corticosterone treatment increased body weight and decreased insulin sensitivity. The latter was revealed by a higher IR index and increased insulin in the plasma, whereas blood glucose levels remained unchanged. Corticosterone treatment induced longer immobility times in the FST, reflecting depressive-like behaviour. No effects were observed upon anxiety as measured in the EZM. The effect of the higher body weight of the CORT treated animals at time of testing did not influence behaviour in the EZM or FST, as no differences were found in general locomotor activity. Long-term corticosterone treatment via the drinking water reduces insulin sensitivity and induces depressive-like behaviour in the C57BL/6 mouse. This mouse model could thus be used to further explore the underlying mechanisms of chronic stress-induced T2DM and its association with increased prevalence of major depressive disorder on the short-term and other behavioural adaptations on the longer term.

Short-term effects of GH treatment on coagulation, fibrinolysis, inflammation biomarkers, and insulin resistance status in prepubertal children with GH deficiency.

OBJECTIVE: The aims of this study was to determine whether prepubertal GH deficiency (GHD) children showed any impairment in coagulation- and fibrinolysis-related parameters and in inflammatory and insulin resistance markers and to evaluate the effect of short-term GH therapy on these parameters. DESIGN: This was a 6-month, prospective, observational, case-control study (36 prepubertal children with GHD and 38 healthy prepubertal children with no differences in BMI). Comparison of study parameter values in GHD AND control groups at baseline and after 6 months of GH treatment in the GHD group. The following were analyzed: glucose, insulin, fibrinogen, absolute plasminogen activator inhibitor type 1 (aPAI-1), von Willebrand factor (vWF), homeostasis model assessment for insulin resistance (HOMA-IR) index, C-reactive protein (CRP), and interleukin 6 (IL6) levels. RESULTS: Children with GHD showed higher baseline levels of aPAI-1 and fibrinogen and lower levels of glucose, insulin, and HOMA-IR index than healthy controls. No intergroup differences were found for vWF. After 6 months of treatment, aPAI-1 levels were lower but no changes were observed in fibrinogen or vWF levels, which were similar to those of controls. Glucose levels increased, though not significantly, while insulin levels and HOMA-IR index rose to normal levels. A positive correlation was found between changes in insulin status/HOMA-IR index and levels of aPAI-1, fibrinogen, vWF, CRP, and IL6. CONCLUSIONS: At early ages, GH therapy appears to exert beneficial effects on the amount of aPAI-1. At the same time, it increases the state of insulin resistance (HOMA-IR index) without modifying the levels of fibrinogen, vWF, CRP, and IL6.

Does acute tryptophan depletion affect peripheral serotonin metabolism in the intestine?

BACKGROUND: Serotonin (5-hydroxytryptamine; 5-HT), a tryptophan metabolite, plays an important regulatory role in the human central nervous system and in the gastrointestinal tract. Acute tryptophan depletion (ATD) is currently the most widely established method to investigate 5-HT metabolism. OBJECTIVE: The aim of this study was to assess the effect of an acute decrease in the systemic availability of tryptophan on intestinal 5-HT metabolism and permeability. DESIGN: Thirty-three healthy volunteers (17 with ATD, 3 of whom dropped out; 16 placebo) participated in this randomized placebo-controlled study. Plasma and duodenal mucosal concentrations of 5-HT, 5-hydroxyindoleacetic acid (5-HIAA), and kynurenic acid (KA) were measured by HPLC-mass spectrometry. Intestinal barrier function was assessed with a multisugar plasma test, and analysis of tight junction transcription was performed in duodenal biopsy samples obtained by gastroduodenoscopy. RESULTS: Mucosal 5-HT, 5-HIAA, and KA concentrations remained unaltered by ATD. In contrast, ATD significantly decreased plasma 5-HT (P < 0.05) and 5-HIAA (P < 0.0001) concentrations. After endoscopy, a significant increase in plasma 5-HT concentrations was observed in the placebo group (P = 0.029) compared with the ATD group. Moreover, a significant increase in plasma KA concentrations over time was found in the placebo group (P < 0.05). No changes in intestinal barrier function were observed. CONCLUSIONS: An acute decrease in precursor availability does not affect mucosal concentrations of serotonergic metabolites, in contrast with systemic concentrations. ATD alters biochemical responses to acute stress from the endoscopic examination reflected by lower 5-HT concentrations. Changes in 5-HT concentrations were paralleled by alterations in KA concentrations, which suggest competition between the 2 metabolic pathways for the mutual precursor. This trial was registered at clinicaltrials.gov as NCT00731003.

Effects of tryptophan depletion and tryptophan loading on the affective response to high-dose CO2 challenge in healthy volunteers.

RATIONALE: It has been reported that in panic disorder (PD), tryptophan depletion enhances the vulnerability to experimentally induced panic, while the administration of serotonin precursors blunts the response to challenges. OBJECTIVES: Using a high-dose carbon dioxide (CO(2)) challenge, we aimed to investigate the effects of acute tryptophan depletion (ATD) and acute tryptophan loading (ATL) on CO(2)-induced panic response in healthy volunteers. METHODS: Eighteen healthy volunteers participated in a randomized, double-blind placebo-controlled study. Each subject received ATD, ATL, and a balanced condition (BAL) in separate days, and a double-breath 35% CO(2) inhalation 4.5 h after treatment. Tryptophan (Trp) manipulations were obtained adding 0 g (ATD), 1.21 g (BAL), and 5.15 g (ATL) of l-tryptophan to a protein mixture lacking Trp. Assessments consisted of a visual analogue scale for affect (VAAS) and panic symptom list. A separate analysis on a sample of 55 subjects with a separate-group design has also been performed to study the relationship between plasma amino acid levels and subjective response to CO(2). RESULTS: CO(2)-induced subjective distress and breathlessness were significantly lower after ATD compared to BAL and ATL (p < 0.05). In the separate-group analysis, ΔVAAS scores were positively correlated to the ratio Trp:ΣLNAA after treatment (r = 0.39; p < 0.05). CONCLUSIONS: The present results are in line with preclinical data indicating a role for the serotonergic system in promoting the aversive respiratory sensations to hypercapnic stimuli (Richerson, Nat Rev Neurosci 5(6):449-461, 2004). The differences observed in our study, compared to previous findings in PD patients, might depend on an altered serotonergic modulatory function in patients compared to healthy subjects.

Acute tryptophan depletion in C57BL/6 mice does not induce central serotonin reduction or affective behavioural changes.

Acute tryptophan depletion is extensively used to investigate the implication of serotonin in the onset of depressive disorders. In rats, it lowers peripheral tryptophan and decreases central serotonin concentrations. We aimed to establish the rat model of acute tryptophan depletion in the mouse for potential application as serotonin challenge tool in genetic mouse models of depression. Pharmacokinetic and behavioural effects of a tryptophan-free diet were examined in Swiss and C57BL/6 mice. Peripheral amino acids were measured and central tryptophan and serotonin concentrations were compared with anxiety and depression-like behaviour in the elevated zero-maze, forced swimming test or tail suspension test. While acute tryptophan depletion resulted in a 74% reduction of the plasma ratio tryptophan to the sum of other large neutral amino acids in Swiss mice 1h after administration (2x10 ml/kg, 30 min interval), there was only a 40% reduction in C57BL/6 mice. The latter did not show anxiety in the elevated zero-maze or increased immobility in the forced swimming test or tail suspension test. A higher dose (2x20 ml/kg) with a longer interval (60 min) reduced the ratio with 68% in C57BL/6 mice, lowered hippocampal serotonin turnover and had no functional effect when tested in the elevated zero-maze and forced swimming test. These findings have important implications for the use of acute tryptophan depletion in general and in particular for its application in mice. Although in healthy mice no clear central serotonin or functional effects were observed, further research is indicated using mice with pre-existing serotonin dysfunction, as they might be more vulnerable to acute tryptophan depletion.

Acute tryptophan depletion potentiates 3,4-methylenedioxymethamphetamine-induced cerebrovascular hyperperfusion in adult male Wistar rats.

The serotonergic (5-hydroxytryptamine; 5-HT) dysfunction found in depression may affect not only brain function (mood) but also cerebrovascular control. Similar, but possibly occult, disturbances may also be induced by 3,4-methylenedioxymethamphetamine-induced neurotoxicity (MDMA, or "ecstasy"). Acute tryptophan depletion (ATD) is widely used to identify vulnerability to depression, and we hypothesized that repeated MDMA administration would increase the sensitivity of rats to this acute serotonergic challenge. In this study, male Wistar rats were injected with MDMA (20 mg kg(-1), twice daily for 4 days) and challenged 3 weeks later with ATD, induced by intragastric administration of a nutritional mixture with tryptophan (TRP) removed. Cerebral metabolism (CMRG) and blood flow (CBF) were measured in parallel groups of animals following ATD by using quantitative [(14)C]2-deoxyglucose and [(14)C]iodoantipyrine autoradiographic techniques, respectively. A significant reduction in paroxetine binding to 5-HT transporter sites in MDMA-treated rats indicated 5HT terminal depletion, whereas the plasma TRP/sum large neutral amino acids ratio was reduced by 40% following ATD. Under all experimental conditions, the normal close correlation between CBF and metabolic demand was maintained. However, a global analysis of all brain regions revealed a significant decrease in the overall ratio of CBF to CMRG after ATD in control animals, whereas a higher ratio was observed after ATD in the MDMA-treated group. This increase in blood flow relative to cerebral metabolism suggests an ATD-induced loss of cerebrovascular tone in MDMA-treated animals that could have pathophysiological consequences and might conceivably contribute to the behavioral dysfunction of depression.

Stress-mediated decreases in brain-derived neurotrophic factor as potential confounding factor for acute tryptophan depletion-induced neurochemical effects.

Acute tryptophan depletion (ATD) is extensively used to investigate the implication of serotonin (5-hydroxytryptamine; 5-HT) in the onset and treatment of depression and cognitive disorders. Brain-derived neurotrophic factor (BDNF) is strongly linked to the 5-HT system and plays an essential role in mood and memory processes. The present study investigated the effects of ATD upon BDNF in serum, hippocampus and prefrontal cortex in the rat to further explore the underlying mechanism of ATD. ATD significantly decreased peripheral tryptophan (TRP) levels and moderately interrupted 5-HT metabolism 4h after administration of the nutritional mixture. Although no direct effects of ATD upon serum or brain BDNF concentrations were found, a stress-mediated, decrease in BDNF was observed in the prefrontal cortex. Moreover, brain TRP levels correlated positively with BDNF in both the prefrontal cortex and hippocampus. Thus, BDNF-mediated mechanisms due to ATD and/or its application stress might underlie ATD-induced neurochemical and behavioural alterations.

Phosphodiesterase inhibitors enhance object memory independent of cerebral blood flow and glucose utilization in rats.

Phosphodiesterase (PDE) inhibitors prevent the breakdown of the second messengers, cyclic AMP (cAMP) and cyclic GMP (cGMP), and are currently studied as possible targets for cognitive enhancement. Earlier studies indicated beneficial effects of PDE inhibitors in object recognition. In this study we tested the effects of three PDE inhibitors on spatial memory as assessed in a place and object recognition task. Furthermore, as both cAMP and cGMP are known vasodilators, the effects of PDE inhibition on cognitive functions could be explained by enhancement of cerebrovascular function. We examined this possibility by measuring the effects of PDE5 and PDE4 inhibitor treatment on local cerebral blood flow and glucose utilization in rats using [14C]-iodoantipyrine and [14C]-2-deoxyglucose quantitative autoradiography, respectively. In the spatial location task, PDE5 inhibition (cGMP) with vardenafil enhanced only early phase consolidation, PDE4 inhibition (cAMP) with rolipram enhanced only late phase consolidation, and PDE2 inhibition (cAMP and cGMP) with Bay 60-7550 enhanced both consolidation processes. Furthermore, PDE5 inhibition had no cerebrovascular effects in hippocampal or rhinal areas. PDE4 inhibition increased rhinal, but not hippocampal blood flow, whereas it decreased glucose utilization in both areas. In general, PDE5 inhibition decreased the ratio between blood flow and glucose utilization, indicative of general oligaemia; whereas PDE4 inhibition increased this ratio, indicative of general hyperemia. Both oligaemic and hyperemic conditions are detrimental for brain function and do not explain memory enhancement. These results underscore the specific effects of cAMP and cGMP on memory consolidation (object and spatial memory) and provide evidence that the underlying mechanisms of PDE inhibition on cognition are independent of cerebrovascular effects.

Phosphodiesterase 2 and 5 inhibition attenuates the object memory deficit induced by acute tryptophan depletion.

The underlying mechanism of short-term memory improvement after inhibition of specific phosphodiesterases (PDEs) is still poorly understood. The present study aimed to reveal the ability of PDE5 and PDE2 inhibitors, that increase cyclic guanosine monophosphate (cGMP) and both cyclic adenosine monophosphate (cAMP) and cGMP, respectively, to reverse an object recognition deficit induced by acute tryptophan depletion. Acute tryptophan depletion is a pharmacological challenge tool to lower central serotonin (5-hydroxytryptamine; 5-HT) levels by depleting the availability of its dietary precursor tryptophan. Short-term object memory was tested in male Wistar rats by exposing them to the object recognition task. First, the effects of acute tryptophan depletion upon object recognition 2 h after administration of the nutritional mixture were established. Subsequently, acute tryptophan depletion was combined with the PDE5 inhibitor vardenafil (1, 3 and 10 mg/kg) or with the PDE2 inhibitor BAY 60-7550 (0.3, 1 and 3 mg/kg), 30 min prior to testing. Acute tryptophan depletion significantly lowered plasma tryptophan levels and impaired object recognition performance. Vardenafil (3 and 10 mg/kg) and BAY 60-7550 (3 mg/kg) were able to attenuate the acute tryptophan depletion induced object recognition impairment. Thus, both PDE5 and PDE2 inhibition improved short-term object recognition performance after an acute tryptophan depletion induced deficit. The underlying mechanisms, however, remain poorly understood and further studies are needed to determine whether the present findings can be explained by a direct effect of enhanced cAMP and cGMP levels upon 5-HT activity, or even other neurotransmitter systems, and possibly an interaction with synthesis of nitric oxide or effects upon cerebral blood flow function.