Diffusion of brain metabolites highlights altered brain microstructure in type C hepatic encephalopathy: a 9.4 T preliminary study

Introduction

Type C hepatic encephalopathy (HE) is a decompensating event of chronic liver disease leading to severe motor and cognitive impairment. The progression of type C HE is associated with changes in brain metabolite concentrations measured by 1H magnetic resonance spectroscopy (MRS), most noticeably a strong increase in glutamine to detoxify brain ammonia. In addition, alterations of brain cellular architecture have been measured ex vivo by histology in a rat model of type C HE. The aim of this study was to assess the potential of diffusion-weighted MRS (dMRS) for probing these cellular shape alterations in vivo by monitoring the diffusion properties of the major brain metabolites.

Methods

The bile duct-ligated (BDL) rat model of type C HE was used. Five animals were scanned before surgery and 6- to 7-week post-BDL surgery, with each animal being used as its own control. 1H-MRS was performed in the hippocampus (SPECIAL, TE = 2.8 ms) and dMRS in a voxel encompassing the entire brain (DW-STEAM, TE = 15 ms, diffusion time = 120 ms, maximum b-value = 25 ms/μm2) on a 9.4 T scanner. The in vivo MRS acquisitions were further validated with histological measures (immunohistochemistry, Golgi-Cox, electron microscopy).

Results

The characteristic 1H-MRS pattern of type C HE, i.e., a gradual increase of brain glutamine and a decrease of the main organic osmolytes, was observed in the hippocampus of BDL rats. Overall increased metabolite diffusivities (apparent diffusion coefficient and intra-stick diffusivity-Callaghan's model, significant for glutamine, myo-inositol, and taurine) and decreased kurtosis coefficients were observed in BDL rats compared to control, highlighting the presence of osmotic stress and possibly of astrocytic and neuronal alterations. These results were consistent with the microstructure depicted by histology and represented by a decline in dendritic spines density in neurons, a shortening and decreased number of astrocytic processes, and extracellular edema.

Discussion

dMRS enables non-invasive and longitudinal monitoring of the diffusion behavior of brain metabolites, reflecting in the present study the globally altered brain microstructure in BDL rats, as confirmed ex vivo by histology. These findings give new insights into metabolic and microstructural abnormalities associated with high brain glutamine and its consequences in type C HE.

Inhibition of urease-mediated ammonia production by 2-octynohydroxamic acid in hepatic encephalopathy

Hepatic encephalopathy is a neuropsychiatric complication of liver disease which is partly associated with elevated ammonemia. Urea hydrolysis by urease-producing bacteria in the colon is often mentioned as one of the main routes of ammonia production in the body, yet research on treatments targeting bacterial ureases in hepatic encephalopathy is limited. Herein we report a hydroxamate-based urease inhibitor, 2-octynohydroxamic acid, exhibiting improved in vitro potency compared to hydroxamic acids that were previously investigated for hepatic encephalopathy. 2-octynohydroxamic acid shows low cytotoxic and mutagenic potential within a micromolar concentration range as well as reduces ammonemia in rodent models of liver disease. Furthermore, 2-octynohydroxamic acid treatment decreases cerebellar glutamine, a product of ammonia metabolism, in male bile duct ligated rats. A prototype colonic formulation enables reduced systemic exposure to 2-octynohydroxamic acid in male dogs. Overall, this work suggests that urease inhibitors delivered to the colon by means of colonic formulations represent a prospective approach for the treatment of hepatic encephalopathy.

Lessons on brain edema in HE: from cellular to animal models and clinical studies

Brain edema is considered as a common feature associated with hepatic encephalopathy (HE). However, its central role as cause or consequence of HE and its implication in the development of the neurological alterations linked to HE are still under debate. It is now well accepted that type A and type C HE are biologically and clinically different, leading to different manifestations of brain edema. As a result, the findings on brain edema/swelling in type C HE are variable and sometimes controversial. In the light of the changing natural history of liver disease, better description of the clinical trajectory of cirrhosis and understanding of molecular mechanisms of HE, and the role of brain edema as a central component in the pathogenesis of HE is revisited in the current review. Furthermore, this review highlights the main techniques to measure brain edema and their advantages/disadvantages together with an in-depth description of the main ex-vivo/in-vivo findings using cell cultures, animal models and humans with HE. These findings are instrumental in elucidating the role of brain edema in HE and also in designing new multimodal studies by performing in-vivo combined with ex-vivo experiments for a better characterization of brain edema longitudinally and of its role in HE, especially in type C HE where water content changes are small.

Abnormal brain oxygen homeostasis in an animal model of liver disease

Background & Aims

Increased plasma ammonia concentration and consequent disruption of brain energy metabolism could underpin the pathogenesis of hepatic encephalopathy (HE). Brain energy homeostasis relies on effective maintenance of brain oxygenation, and dysregulation impairs neuronal function leading to cognitive impairment. We hypothesised that HE is associated with reduced brain oxygenation and we explored the potential role of ammonia as an underlying pathophysiological factor.

Methods

In a rat model of chronic liver disease with minimal HE (mHE; bile duct ligation [BDL]), brain tissue oxygen measurement, and proton magnetic resonance spectroscopy were used to investigate how hyperammonaemia impacts oxygenation and metabolic substrate availability in the central nervous system. Ornithine phenylacetate (OP, OCR-002; Ocera Therapeutics, CA, USA) was used as an experimental treatment to reduce plasma ammonia concentration.

Results

In BDL animals, glucose, lactate, and tissue oxygen concentration in the cerebral cortex were significantly lower than those in sham-operated controls. OP treatment corrected the hyperammonaemia and restored brain tissue oxygen. Although BDL animals were hypotensive, cortical tissue oxygen concentration was significantly improved by treatments that increased arterial blood pressure. Cerebrovascular reactivity to exogenously applied CO2 was found to be normal in BDL animals.

Conclusions

These data suggest that hyperammonaemia significantly decreases cortical oxygenation, potentially compromising brain energy metabolism. These findings have potential clinical implications for the treatment of patients with mHE.

Lay summary

Brain dysfunction is a serious complication of cirrhosis and affects approximately 30% of these patients; however, its treatment continues to be an unmet clinical need. This study shows that oxygen concentration in the brain of an animal model of cirrhosis is markedly reduced. Low arterial blood pressure and increased ammonia (a neurotoxin that accumulates in patients with liver failure) are shown to be the main underlying causes. Experimental correction of these abnormalities restored oxygen concentration in the brain, suggesting potential therapeutic avenues to explore.

Overview of oxidative stress findings in hepatic encephalopathy: From cellular and ammonium-based animal models to human data

Oxidative stress is a natural phenomenon in the body. Under physiological conditions intracellular reactive oxygen species (ROS) are normal components of signal transduction cascades, and their levels are maintained by a complex antioxidants systems participating in the in-vivo redox homeostasis. Increased oxidative stress is present in several chronic diseases and interferes with phagocytic and nervous cell functions, causing an up-regulation of cytokines and inflammation. Hepatic encephalopathy (HE) occurs in both acute liver failure (ALF) and chronic liver disease. Increased blood and brain ammonium has been considered as an important factor in pathogenesis of HE and has been associated with inflammation, neurotoxicity, and oxidative stress. The relationship between ROS and the pathophysiology of HE is still poorly understood. Therefore, sensing ROS production for a better understanding of the relationship between oxidative stress and functional outcome in HE pathophysiology is critical for determining the disease mechanisms, as well as to improve the management of patients. This review is emphasizing the important role of oxidative stress in HE development and documents the changes occurring as a consequence of oxidative stress augmentation based on cellular and ammonium-based animal models to human data.

Central nervous system and systemic oxidative stress interplay with inflammation in a bile duct ligation rat model of type C hepatic encephalopathy

The role and coexistence of oxidative stress (OS) and inflammation in type C hepatic encephalopathy (C HE) is a subject of intense debate. Under normal conditions the physiological levels of intracellular reactive oxygen species are controlled by the counteracting antioxidant response to maintain redox homeostasis. Our previous in-vivo¹H-MRS studies revealed the longitudinal impairment of the antioxidant system (ascorbate) in a bile-duct ligation (BDL) rat model of type C HE. Therefore, the aim of this work was to examine the course of central nervous system (CNS) OS and systemic OS, as well as to check for their co-existence with inflammation in the BDL rat model of type C HE. To this end, we implemented a multidisciplinary approach, including ex-vivo and in-vitro electron paramagnetic resonance spectroscopy (EPR) spin-trapping, which was combined with UV-Vis spectroscopy, and histological assessments. We hypothesized that OS and inflammation act synergistically in the pathophysiology of type C HE. Our findings point to an increased CNS- and systemic-OS and inflammation over the course of type C HE progression. In particular, an increase in the CNS OS was observed as early as 2-weeks post-BDL, while the systemic OS became significant at week 6 post-BDL. The CNS EPR measurements were further validated by a substantial accumulation of 8-Oxo-2'-deoxyguanosine (Oxo-8-dG), a marker of oxidative DNA/RNA modifications on immunohistochemistry (IHC). Using IHC, we also detected increased synthesis of antioxidants, glutathione peroxidase 1 (GPX-1) and superoxide dismutases (i.e.Cu/ZnSOD (SOD1) and MnSOD (SOD2)), along with proinflammatory cytokine interleukin-6 (IL-6) in the brains of BDL rats. The presence of systemic inflammation was observed already at 2-weeks post-surgery. Thus, these results suggest that CNS OS is an early event in type C HE rat model, which seems to precede systemic OS. Finally, our results suggest that the increase in CNS OS is due to enhanced formation of intra- and extra-cellular ROS rather than due to reduced antioxidant capacity, and that OS in parallel with inflammation plays a significant role in type C HE.

Probiotics combined with rifaximin influence the neurometabolic changes in a rat model of type C HE

Type C hepatic encephalopathy (HE) is a neuropsychiatric disease caused by chronic liver disease. Management of type C HE remains an important challenge because treatment options are limited. Both the antibiotic rifaximin and probiotics have been reported to reduce the symptoms of HE, but longitudinal studies assessing their effects on brain metabolism are lacking and the molecular mechanisms underpinning their effects are not fully understood. Therefore, we evaluated in detail the effects of these different treatments on the neurometabolic changes associated with type C HE using a multimodal approach including ultra-high field in vivo ¹H MRS. We analyzed longitudinally the effect of rifaximin alone or in combination with the probiotic Vivomixx on the brain metabolic profile in the hippocampus and cerebellum of bile duct ligated (BDL) rats, an established model of type C HE. Overall, while rifaximin alone appeared to induce no significant effect on the neurometabolic profile of BDL rats, its association with the probiotic resulted in more attenuated neurometabolic alterations in BDL rats followed longitudinally (i.e. a smaller increase in Gln and milder decrease in Glu and Cr levels). Given that both rifaximin and some probiotics are used in the treatment of HE, the implications of these findings may be clinically relevant.

Synchronous nonmonotonic changes in functional connectivity and white matter integrity in a rat model of sporadic Alzheimer's disease

Brain glucose hypometabolism has been singled out as an important contributor and possibly main trigger to Alzheimer's disease (AD). Intracerebroventricular injections of streptozotocin (icv-STZ) cause brain glucose hypometabolism without systemic diabetes. Here, a first-time longitudinal study of brain glucose metabolism, functional connectivity and white matter microstructure was performed in icv-STZ rats using PET and MRI. Histological markers of pathology were tested at an advanced stage of disease. STZ rats exhibited altered functional connectivity and intra-axonal damage and demyelination in brain regions typical of AD, in a temporal pattern of acute injury, transient recovery/compensation and chronic degeneration. In the context of sustained glucose hypometabolism, these nonmonotonic trends - also reported in behavioral studies of this animal model as well as in human AD - suggest a compensatory mechanism, possibly recruiting ketone bodies, that allows a partial and temporary repair of brain structure and function. The early acute phase could thus become a valuable therapeutic window to strengthen the recovery phase and prevent or delay chronic degeneration, to be considered both in preclinical and clinical studies of AD. In conclusion, this work reveals the consequences of brain insulin resistance on structure and function, highlights signature nonmonotonic trajectories in their evolution and proposes potent MRI-derived biomarkers translatable to human AD and diabetic populations.

Residual hip dysplasia in children: osseous and cartilaginous acetabular angles to guide further treatment-a pilot study

PURPOSE

In case of residual hip dysplasia (RHD) in children, pelvic radiographs are sometimes insufficient to precisely evaluate the entire coverage of the femoral head, when trying to decide on the need for further reconstructive procedures.

METHODS

This study retrospectively compares the bony and the cartilaginous acetabular angle of Hilgenreiner (HTE) of 60 paediatric hips on pelvic MRI separated in two groups. Group 1 included 31 hips with RHD defined by a bony HTE > 20°. Group 2 included 27 hips with a HTE < 20°. They were compared by introducing a new ratio calculated from the square of cartilaginous HTE above the bony HTE on frontal MRI. The normal upper limit for this acetabular angle ratio was extrapolated from the published normal values of cartilaginous HTE and bony HTE in children.

RESULTS

The acetabular angle ratio was statistically significantly increased in the hips with RHD with a mean value of 7.1 ± 4.7 compared to the hips in the control group presenting a mean value of 2.1 ± 1.9 (p < 0.00001).

CONCLUSIONS

This newly introduced ratio seems to be a helpful tool to orientate the further treatment in children presenting borderline RHD.

Longitudinal neurometabolic changes in the hippocampus of a rat model of chronic hepatic encephalopathy

BACKGROUND & AIMS

The sequence of events in hepatic encephalopathy (HE) remains unclear. Using the advantages of in vivo 1H-MRS (9.4T) we aimed to analyse the time-course of disease in an established model of type C HE by analysing the longitudinal changes in a large number of brain metabolites together with biochemical, histological and behavioural assessment. We hypothesized that neurometabolic changes are detectable very early, and that these early changes will offer insight into the primary events underpinning HE.

METHODS

Wistar rats underwent bile-duct ligation (BDL) and were studied before BDL and at post-operative weeks 2, 4, 6 and 8 (n = 26). In vivo short echo-time ¹H-MRS (9.4T) of the hippocampus was performed in a longitudinal manner, as were biochemical (plasma), histological and behavioural tests.

RESULTS

Plasma ammonium increased early after BDL and remained high during the study. Brain glutamine increased (+47%) as early as 2-4 weeks post-BDL while creatine (-8%) and ascorbate (-12%) decreased. Brain glutamine and ascorbate correlated closely with rising plasma ammonium, while brain creatine correlated with brain glutamine. The increases in brain glutamine and plasma ammonium were correlated, while plasma ammonium correlated negatively with distance moved. Changes in astrocyte morphology were observed at 4 weeks. These early changes were further accentuated at 6-8 weeks post-BDL, concurrently with the known decreases in brain organic osmolytes.

CONCLUSION

Using a multimodal, in vivo and longitudinal approach we have shown that neurometabolic changes are already noticeable 2 weeks after BDL. These early changes are suggestive of osmotic/oxidative stress and are likely the premise of some later changes. Early decreases in cerebral creatine and ascorbate are novel findings offering new avenues to explore neuroprotective strategies for HE treatment.

LAY SUMMARY

The sequence of events in chronic hepatic encephalopathy (HE) remains unclear, therefore using the advantages of in vivo proton magnetic resonance spectroscopy at 9.4T we aimed to test the hypothesis that neurometabolic changes are detectable very early in an established model of type C HE, offering insight into the primary events underpinning HE, before advanced liver disease confounds the findings. These early, previously unreported neurometabolic changes occurred as early as 2 to 4 weeks after bile-duct ligation, namely an increase in plasma ammonium and brain glutamine, a decrease in brain creatine and ascorbate together with behavioural and astrocyte morphology changes, and continued to progress throughout the 8-week course of the disease.

Early Perfusion Computed Tomography Scan for Prediction of Vasospasm and Delayed Cerebral Ischemia After Aneurysmal Subarachnoid Hemorrhage

OBJECTIVE

We investigated the ability of early alteration of cerebral perfusion-computed tomography (PCT) parameters to predict the risk of vasospasm, delayed cerebral ischemia (DCI), and clinical outcome in patients with aneurysmal subarachnoid hemorrhage (aSAH).

METHODS

A retrospective cohort study of 38 aSAH patients investigated with PCT within 48 hours after hemorrhage. Cerebral blood flow (CBF), cerebral blood volume, and mean transit time (MTT) values were recorded. Mean values were compared with clinical data. Vasospasm and DCI were determined by imaging and clinical criteria. Neurologic outcome was assessed by the modified Rankin Scale at discharge and 1-year follow-up visit.

RESULTS

More than a third (39.5%) of patients developed DCI, of whom 86.7% presented moderate-severe vasospasm. There was a significant correlation between perfusion parameters in the early phase and occurrence of DCI and vasospasm. The occurrence of DCI and vasospasm correlated significantly with lower mean early PCT values. DCI was correlated with lower mean early CBF values (P = 0.049) and vasospasm with lower mean CBF (P = 0.01) and MTT (P < 0.00001) values. MTT values of 5.5s were shown to have 94% specificity and 100% sensitivity for predicting the risk of developing vasospasm. The severity of the SAH according to the Barrow Neurological Institute scale correlated significantly with the risk of developing DCI and vasospasm, both significantly associated with unfavorable neurologic outcome (modified Rankin Scale score 3-6) (P = 0.0002 and P = 0.02, respectively).

CONCLUSIONS

Early alterations in PCT parameters and high Barrow Neurological Institute grade may identify a subgroup of patients at high risk of developing DCI and vasospasm after aSAH, thus prompting more robust preventative measures and treatment in this subgroup.

Metabolomics reveals tepotinib-related mitochondrial dysfunction in MET-activating mutations-driven models

Genetic aberrations in the hepatocyte growth factor receptor tyrosine kinase MET induce oncogenic addiction in various types of human cancers, advocating MET as a viable anticancer target. Here, we report that MET signaling plays an important role in conferring a unique metabolic phenotype to cellular models expressing MET-activating mutated variants that are either sensitive or resistant toward MET small molecule inhibitors. MET phosphorylation downregulated by the specific MET inhibitor tepotinib resulted in markedly decreased viability and increased apoptosis in tepotinib-sensitive cells. Moreover, prior to the induction of MET inhibition-dependent cell death, tepotinib also led to an altered metabolic signature, characterized by a prominent reduction of metabolite ions related to amino sugar metabolism, gluconeogenesis, glycine and serine metabolism, and of numerous TCA cycle-related metabolites such as succinate, malate, and citrate. Functionally, a decrease in oxygen consumption rate, a reduced citrate synthase activity, a drop in membrane potential, and an associated misbalanced mitochondrial function were observed exclusively in MET inhibitor-sensitive cells. These data imply that interference with metabolic state can be considered an early indicator of efficient MET inhibition and particular changes reported here could be explored in the future as markers of efficacy of anti-MET therapies.

Thyrotropin-secreting pituitary adenomas: a systematic review and meta-analysis of postoperative outcomes and management

PURPOSE

TSH-secreting pituitary adenomas are rare pituitary tumors. An efficient treatment is essential to limit the mortality and morbidity in untreated patients. The aim of this study is to summarize the evidence about the postoperative outcomes and management of this rare pathology.

METHODS

A systematic search and meta-analysis of surgical series was performed.

RESULTS

Our analysis included 23 articles (536 patients). No sex difference was observed and mean age at diagnosis was 45 years. Hyperthyroidism was reportedly clinical in 67% and biochemical in 90% of patients. Co-secretion of other pituitary hormones was present in 42% of cases. Macroadenomas were found in 79% of patients, showing in 44% and 30% of cases respectively extrasellar extension and cavernous sinus invasion. The pooled rate of postoperative biochemical remission was 69.7% and a gross total resection (GTR) was observed in 54% of patients. The extent of resection was significantly increased in microadenomas (p < 0.001) and cavernous sinus invasion was predictive of lower GTR rate (p < 0.001). A biochemical remission was achieved in 66% of patients after adjuvant radiation therapy and in 76% after adjuvant medical treatment. The combination of both allowed remission in 67% of cases. At final follow-up the overall biochemical remission rate was significantly improved (85.8%) when compared to the postoperative biochemical remission (p < 0.001).

CONCLUSION

When compared to the early postoperative period, at last follow-up biochemical remission was significantly greater (p < 0.001). GTR was achieved in half of patients; the size of tumor and cavernous sinus invasion determined the extent of resection.

Do intra-operative neurophysiological changes predict functional outcome following decompressive surgery for lumbar spinal stenosis? A prospective study

Background

To analyse the relation between immediate intraoperative neurophysiological changes during decompression and clinical outcome in a series of patients with lumbar spinal stenosis (LSS) undergoing surgery.

Methods

Twenty-four patients with neurogenic intermittent claudication (NIC) due to LSS undergoing decompressive surgery were prospectively studied. Intra operative trans-cranial motor evoked potentials (tcMEPs) were recorded before and immediately after surgical decompression. Lower limb normalised tcMEP improvement was used as primary neurophysiological outcome. Clinical outcome was assessed using the Zurich Claudication Questionnaire (ZCQ) self-assessment score, before surgery (baseline) and at an average of 8 and 29 months post-operatively.

Results

We found a moderate positive correlation between tcMEP changes and ZCQ at early follow-up (R=0.36). At late follow-up no correlation was found between intra-operative tcMEP and ZCQ changes. Dichotomizing the data showed a statistically significant relationship between tcMEP improvement and better functional outcome at early follow-up (P=0.013) but not at later follow-up (P=1).

Conclusions

Our findings suggest that intra-operative neurophysiological improvement during decompressive surgery may predict a better clinical outcome at early follow-up although this is not applicable to late follow-up possibly due to the observed erosion of functional improvement with time.

Calcium-phosphate metabolism in patients with multiple sclerosis

INTRODUCTION AND OBJECTIVES

The purpose of this study was to evaluate the concentration of 25-hydroxycholecalciferol and parameters of calcium-phosphate metabolism at different periods of relapsing-remitting multiple sclerosis (RRMS).

MATERIALS AND METHODS

Forty-five patients, residents of Poland (49°-50°, N), were enrolled in the study, i.e. 15 immediately after the diagnosis of RRMS, 15 at the early stage and 15 at the advanced stage of RRMS. The results were compared to values obtained in 20 age- and sex-matched controls.

RESULTS

Lower serum concentrations of 25-hydroxycholecalciferol and ionised calcium were found in patients compared to the control group. In patients with the disease duration of 5-6 years, concentrations of 25-hydroxycholecalciferol and ionised calcium were lower than in patients in the earlier period of RRMS. The inverse and clearer direction of changes was found in parathormone serum concentration in patients compared to the controls. In patients with a longer disease duration, a significantly lower 25-hydroxycholecalciferol concentration was found in female patients compared to male patients. In patients, more frequent 25-hydroxycholecalciferol and unsaturated fatty acids' supplementation was observed compared to the controls.

CONCLUSIONS

In RRMS patients, calcium-phosphate metabolism is disturbed which increases during disease progression.

Proopiomelanocortin but not vasopressin or renin-angiotensin system induces resuscitative effects of central 5-HT1A activation in haemorrhagic shock in rats

The aim of this study was to determine the effectory mechanisms: vasopressin, renin-angiotensin system and proopiomelanocortin-derived peptides (POMC), partaking in the effects of serotonin through central serotonin 1A receptor (5-HT1A) receptors in haemorrhagic shock in rats. The study was conducted on male Wistar rats. All experimental procedures were carried out under full anaesthesia. The principal experiment included a 2 hour observation period in haemorrhagic shock. Drugs used - a selective 5-HT1A agonist 8-OH-DPAT (5 μg/5 μl); V1a receptor antagonist [β-mercapto-β, β-cyclo-pentamethylenepropionyl(1),O-me-Tyr(2),Arg(8)]AVP (10 μg/kg); angiotensin type I receptor antagonist (AT1) ZD7155 (0.5 mg/kg, i.v.); angiotensin-converting-enzyme inhibitor captopril (30 mg/kg, i.v.); melanocortin type 4 (MC4) receptor antagonist HS014 (5 μg, i.c.v.). There was no influence of ZD715, captopril or blocking of the V1a receptors on changes in the heart rate (HR), mean arterial pressure (MAP), peripheral blood flow or resistance caused by the central stimulation of 5-HT1A receptors (P≥0.05). However, selective blocking of central MC4 receptors caused a slight, but significant decrease in HR and MAP (P<0.05). POMC derivatives acting via the central MC4 receptor participate in the resuscitative effects of 8-OH-DPAT. The angiotensin and vasopressin systems do not participate in these actions.

Influence of melatonin supplementation on serum antioxidative properties and impact of the quality of life in multiple sclerosis patients

The relationship between the prevalence of multiple sclerosis (MS) and sunlight's ultraviolet radiation was proved. Oxidative stress plays a role in the pathogenic traits of MS. Melatonin possesses antioxidative properties and regulates circadian rhythms. Several studies have reported that the quality of life is worse in patients with MS than in healthy controls, with a higher prevalence of sleep disturbances, depression and fatigue. The aim of study was to evaluate 5 mg daily melatonin supplementation over 90 days on serum malondialdehyde (MDA) concentration and superoxide dismutase (SOD) activity and its' influence on impact of the quality of life of MS patients. A case-control prospective study was performed on 102 MS patients and 20 controls matched for age and sex. The EDSS, MRI examinations and Multiple Sclerosis Impact Scale (MSIS-29) questionnaire was completed. Marked increase in serum MDA concentration in all MS patients groups was observed and after melatonin treatment decreased significantly in interferons-beta and glatiramer acetate-treated groups, but not in mitoxantrone-treated group. A significant increase in SOD activity compared to controls only in glatiramer acetate-treated group was observed. After 3 months melatonin supplementation the SOD activity increased compared to initial values in interferons beta-treated groups. A significant increase in both MSIS-29-PHYS and MSIS-29-PSYCH items mean scores only in the MX group as compared to other groups was observed. There were no significant differences in mean MSIS-29-PHYS was observed before and after melatonin therapy. Melatonin supplementation caused a decrease in mean MSIS-29-PSYCH scores compared to initial values in interferons beta-treated groups. Finding from our study suggest that melatonin can act as an antioxidant and improves reduced quality in MS patients.

Labeled [³H]--thymidine incorporation in the DNA of 3T3-L1 preadipocytes due to MT₂- and not MT₃- melatonin receptor

The discovery of MT₁, MT₂, and MT₃ melatonin receptors on adipose tissue cells gives grounds for considering the possibility of melatonin as a factor which influences energy storage through modulation of metabolism and adipocyte proliferation. To date only a few contradictory studies have been published on the influence of melatonin on preadipocytes. The aim of the present study is to evaluate the influence of melatonin at physiological and supraphysiological concentrations on the proliferation of 3T3-L1 murine preadipocytes after 3 and 24 hours of the experiment and to determine the participation of membrane melatonin MT₂ receptors, and for the first time--MT₃, in its melatonin action during a 24-hour experiment. The 3T3-L1 murine preadipocyte cell line were cultured with or without melatonin at 10⁻³ and 10⁻⁹ mol/L, with or without melatonin antagonists luzindole (10⁻⁴ mol/L) and prazosin (10⁻⁵ mol/L). Cell proliferation was determined by means of labeled [³H]-thymidine incorporation in the DNA of the cell. Melatonin at both physiological and supraphysiological concentrations has a stimulating effect on the number of 3T3-L1 preadipocytes. The application of luzindole inhibits the above effect of melatonin both at 10⁻³ mol/L and 10⁻⁹ mol/L concentrations (P<0.05). The presence of prazosin does not have a statistically significant influence on the effects of melatonin action. Summarizing, it has been proven that melatonin exerts a proproliferative effect on 3T3-L1 preadipocytes at physiological and supraphysiological concentrations, partially by MT₂, and not by MT₃ receptors.

The role of serotonergic 5-HT1A receptors in central cardiovascular regulation in haemorrhagic shock in rats

The bleeding and haemorrhage is strictly related with accidents and many medical procedures. In some conditions it leads to hypovolaemia and further to hypovolaemic shock. Under conditions of haemorrhagic shock, heart rate and blood pressure critically collapse. Reversing the sympathoinhibitory phase of hypovolaemia could be crucial for clinical management of injured patients after haemorrhage. Systemic administration of 5-HT1A agonists seams to produce resuscitating effects. The aim of this study was to investigate the participation of central serotonin and, in particular, 5-HT1A receptors in cardiovascular regulation in haemorrhagic shock in rats. Intracerebroventricular (i.c.v.) administration of serotonin (5-HT) increased the heart rate (HR), mean arterial pressure (MAP) and implicated that all haemorrhaged animals survived for the whole observation time (2 hours). Similar, although significantly more minor, effects were achieved after selective 5-HT1A activation. Moreover, the i.c.v. administration of selective 5-HT1A antagonist before i.c.v. 5-HT injection partially inhibited 5-HT induced changes. The results of the present work indicate that 5-HT plays an important role in the reversal of the haemorrhagic shock in rats. These effects are at least partially dependent on activation of 5-HT1A receptors.

Antioxidative enzymes activity and malondialdehyde concentration during mitoxantrone therapy in multiple sclerosis patients

Mitoxantrone (MX) is approved for the treatment of aggressive relapsing-remitting, secondary-progressive and progressive-relapsing form of multiple sclerosis (MS). The mechanism of its action is multiaxial, however, it is not free from side effects. The causes of the side effects are still unknown and require further investigation. The aim of this study was to investigate the influence of MX therapy on enzymatic parameters of endogenous antioxidative status: manganese and copper/zinc superoxide dismutase (MnSOD, Cu/ZnSOD), catalase (CAT), glutathione peroxidase (GSH-Px) and lipid peroxidation marker--malondialdehyde (MDA) in blood serum and cerebrospinal fluid (CSF) in patients suffering from MS. After the MX therapy serum and the CSF MDA concentrations increased significantly. We reported that MnSOD activities decrease in serum and the CSF, while, surprisingly, the serum Cu/ZnSOD activity increases after the MX therapy. We also noted a marked decrease in CSF CAT and GSH-Px activity after the MX treatment. Our results strongly suggest the influence of MX therapy on oxidation/antioxidation status of serum and the CSF. These findings open up new opportunities for a better understanding of underlying physiopathological events in MS and provide a new insight into MX's mechanisms of action, especially its potent side effects.

Role of leptin, ghrelin, angiotensin II and orexins in 3T3 L1 preadipocyte cells proliferation and oxidative metabolism

There is now growing evidence that the reactive oxygen species have an influence on proliferation and antioxidative status of various cell types. The aim of the study was to investigate the effects of different concentrations of leptin, ghrelin, angiotensin II and orexins on proliferation, culture medium malondialdehyde (MDA) levels and antioxidative enzymes activities: superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) in 3T3 L1 preadipocytes cell culture. Cell proliferation was measured using [(3)H]tymidine incorporation. In 3T3-L1 cells leptin caused a significant reduction in proliferation (by 36%) compared to control. Ghrelin increased preadipocyte proliferation, and the effect was stronger in higher dose (by 39%), while proproliferatory effect of angiotensin II was stronger in lower doses (by 47%). All used doses of orexin A significantly increased 3T3 L1 cell proliferation (from 21% to 160%), while orexin B caused a marked reduction (from 35% to 70%) of this proliferation. The effects of both orexins were dose-dependent. Leptin and ghrelin increased activity of SOD, CAT, GSH-Px and decreased level of MDA. Angiotensin II treatment stimulated only SOD and CAT activities. Influence of orexins was different on various enzymes. Orexin A increased MDA levels, while orexin B caused a marked decrease in MDA levels. Our results strongly suggest the effects of appetite affecting hormones such as leptin and ghrelin on proliferation and antioxidative enzyme activities of preadipocyte cell lines. Orexin A was found to be the most efficient proliferative-signalling hormone, while orexin B revealed the most significant inhibitory effect on preadipocytes proliferation.

[Contemporary views on the pathogenesis of diabetic neuropathy]

The duration of diabetes, age and genetic predispositions are admitted agents of risk in diabetic neuropathy. The reasons of diabetic neuropathy are suspected in cooperation with various factors among which metabolic disturbances and ischaemia are the most important. The abnormal activation of sorbitol tract is very significant agent of development of diabetic neuropathy. The excess of sorbitol which is accumulating also in nervous tissue causes its damage in osmotic way. At the same time decreasing concentration of myoinositol reduces ATP-ase Na+/K+ activity which is important in impulse conduction. The overproduction of free oxygenic radical (oxidative lesion) and nitrogen oxide (vasodilator) deficiency is inducted by hyperglycaemia and the activation of aldolase reductase. Metabolic disturbances cause the decrease of carnitine concentration what deteriorates nerve sensitivity on growth factor. The activation of sorbitol tract leads to nonenzymatic proteins glycation which causes thickening of basement membrane and proliferation of endothelium cells. In this way increased vascular resistance decreases tissue perfusion and induces nerve hypoxia. The impairment of nerve blood supply depends on altered in diabetes rheological properties. They are inconveniently changed through hyperglycaemia, hyperlypidaemia, dysproteinaemia and excessive aggregation and rigidity of morphotic elements of blood.

Endogenous opioid peptide mediation of hypoalgesic response in long-term diabetic rats

This study was designed to examine the role of endogenous opioid peptide mediation of elevated pain threshold in adult male Sprague-Dawley rats with long-term diabetes mellitus induced by streptozotocin (STZ). Diabetes resulted in a significant elevation in pain threshold as measured by the tail-flick and/or hotplate latency tests. The hypoalgesic response in diabetic rats to hotplate testing developed gradually over a 4-6 week period after a transient hyperalgesia during the first two weeks of diabetes. The elevation of pain threshold achieved peak level by the fourth week after STZ administration, and remained at that level throughout the experimental period (up to 13 weeks). This hypoalgesic state in diabetic animals is thought to be mediated by opioid receptors (i.e. mu and delta). The involvement of the mu receptor is supported by the effect of naltrexone on the STZ-diabetic rats; naltrexone significantly attenuated the increase in tail-flick and hotplate latencies, compared to that of the non-diabetic controls. Furthermore, the concentration of native (free) Met-enkephalin in the spinal cord of STZ-diabetic rats was about 5-fold higher than that of non-diabetic animals. Such high levels of Met-enkephalin suggest the involvement of delta opioid receptors in the hypoalgesic response observed in STZ-diabetic rats. Seven weeks of insulin treatment, initiated after development of the hypoalgesic response, normalized not only plasma glucose level and body weight of diabetic rats, but also returned their antinociceptive latency toward normal. The results of this study showed that long-term diabetes is associated with altered pain threshold and further support the hypothesis for endogenous opioid peptide mediation of hypoalgesia in chronically diabetic rats that can be prevented by insulin treatment.

Plasma Met-enkephalin and catecholamine responses to intense exercise in humans

Native and cryptic Met-enkephalin and catecholamines are coreleased in response to stress. However, it is not known whether Met-enkephalin and catecholamines exhibit concurrent temporal relationships in response to exercise. The purpose of this investigation was to examine the corelease of catecholamines and Met-enkephalin in endurance-trained (n = 6) and untrained (n = 6) male subjects during a 6-min bout of exercise: 4 min at 70% of maximal O2 uptake (VO2max) followed by 2 min at 120% VO2max. Peak catecholamine levels were found at 1 min of recovery. In trained subjects, native Met-enkephalin peaked during exercise at 70% VO2max, declined during exercise at 120% VO2max, and returned to basal levels by 1 min of recovery. In the untrained subjects, native Met-enkephalin peaked at 120% VO2max (6 min) and returned to baseline by 5 min of recovery. In both groups, cryptic Met-enkephalin peaked at 70% VO2max and returned to basal levels during exercise at 120% VO2max. These data demonstrate that during exercise there is a temporal dissociation in plasma levels of Met-enkephalin and catecholamines.

Effect of diabetes on the levels of two forms of Met-enkephalin in plasma and peripheral tissues of the rat

Levels of native and cryptic or peptidase-derivable (after being digested with trypsin and carboxypeptidase) Met-enkephalin were measured by a specific radioimmunoassay method in plasma, anterior and neurointermediate lobes of pituitary and various peripheral tissues of streptozotocin (STZ) diabetic rats. The results show that the highest concentration of native and cryptic Met-enkephalin were found in the neurointermediate lobe of pituitary. Streptozotocine-induced diabetes alters the concentration of either or both forms of Met-enkephalin in plasma, the anterior and neurointermediate lobes of the pituitary, heart, lung, spleen, liver, seminal vesicle, vas deferens, kidney, bladder detrusor, and duodenum. One of the most pronounced effects of diabetes observed in this study is seen in the seminal vesicles where native Met-enkephalin was depleted to less than 10% of the control value. The uneven distribution of Met-enkephalin in peripheral tissues may suggest that these tissues process and/or metabolize Met-enkephalin to different degrees. Our data also suggest that STZ-induced diabetes alters the enkephalinergic activity in some of these tissues. It is suggested that some of the peripheral pathophysiological symptoms associated with diabetes may be attributed, in part, to altered activity of enkephalinergic systems.

Nicotine-induced alterations in peripheral tissue concentrations of native and cryptic Met- and Leu-enkephalin

This study examined the peripheral tissue distribution of native and cryptic Met- and Leu-enkephalin, and regulation of tissue enkephalins by nicotine. Met- and Leu-enkephalin concentrations showed widespread variation in tissue concentration and degree of processing. HPLC characterization of homogenate of spleen revealed that both native and cryptic immunoreactive Met-enkephalin are comprised of two peaks, one representing authentic Met-enkephalin pentapeptide and the other its sulfoxide. Subacute repeated administration of nicotine 0.1 mg/kg ip, six times at 30 min intervals, increased native Met- and Leu-enkephalin in adrenal medulla without affecting cryptic Met- and Leu-enkephalin concentrations, consistent with increased processing of larger peptides to Met- and Leu-enkephalin. Subacute nicotine decreased splenic concentrations of native and cryptic Met-enkephalin and native Leu-enkephalin, consistent with increased release of Met- and Leu-enkephalin from spleen and decreased synthesis of proenkephalin A or inadequate processing of larger peptides to enkephalin pentapeptides in spleen to compensate for the increased release during this period. HPLC characterization revealed that nicotine-induced decrease in native Met-enkephalin in spleen resulted from reductions in both pentapeptide and its sulfoxide. Nicotine also increased native Met-enkephalin in jejunum, decreased cryptic Met-enkephalin in heart atrium, increased native Leu-enkephalin in anterior pituitary and decreased cryptic Leu-enkephalin in jejunum. Nicotine may produce some of its effects through alterations in release of enkephalins from peripheral tissues.

Nicotine-induced alteration in Tyr-Gly-Gly and Met-enkephalin in discrete brain nuclei reflects altered enkephalin neuron activity

Nicotine acts in CNS, but the pathways and mechanisms of its actions are poorly understood. Recent studies suggest an interaction between brain nicotinic receptors and endogenous opioid peptides. Acute administration of nicotine may alter enkephalin release without affecting brain enkephalin level. Tyr-Gly-Gly has been shown previously to be an extraneuronal metabolite of opioid peptides derived from proenkephalin A. Concentrations of Tyr-Gly-Gly in brain were used to provide an index of enkephalin release in vivo. Thus we examined the thesis that nicotine alters brain neuronal enkephalin release, by measuring Tyr-Gly-Gly levels in specific brain nuclei from rats treated with nicotine 0.3 mg/kg SC 10 min before decapitation. Of 30 brain regions investigated, acute nicotine increased Tyr-Gly-Gly immunoreactivity in nucleus accumbens and in lower brain stem areas including dorsal raphe, pontine reticular formation, gigantocellular reticular formation, locus coeruleus, sensory trigeminal nucleus and the caudal part of ventrolateral medulla oblongata. Concomitantly, nicotine produced a significant decrease in native Met-enkephalin in central amygdala, flocculo-nodular lobe of cerebellum, caudal part of the ventrolateral medulla and intermediolateral cell column of the spinal cord. It is probable that the effects of nicotine to increase Tyr-Gly-Gly and alter Met-enkephalin concentration are mediated by nicotine-induced release of enkephalin at these brain sites. Furthermore, some of the physiologic and pharmacologic effects of nicotine may be mediated by such enkephalin release.

Source of Stress-Induced Increase in Plasma Met-Enkephalin in Rats: Contribution of Adrenal Medulla and/or Sympathetic Nerves*

Abstract The contribution of the adrenal medulla and/or the sympathetic nerves to the plasma levels of Met-enkephalin was investigated. Rats were divided into four groups: sham-operated/saline, sham-operated/guanethidine, adrenal-demedullated/saline, demedulla-ted/guanethidine. After 4 weeks of injection with either saline or guanethidine (25 mg/kg/day), animals were cannulated in the left carotid artery for blood sampling. Three days later, blood samples were taken before and at 2 and 30 min of restraint stress. Adrenal demedullation lowered basal plasma epinephrine levels markedly and prevented entirely the increase induced by restraint stress. Chronic guanethidine treatment lowered basal plasma norepinephrine levels and decreased the response to stress. Guanethidine treatment increased the basal plasma epinephrine level without affecting the response to stress. The combination of guanethidine plus adrenal demedullation lowered basal plasma concentrations of all three catecholamines and further attenuated the norepinephrine response. Restraint stress increased plasma native and peptidase-derivable Met-enkephalin. Adrenal demedullation, resulting in greater than 95% depletion of adrenal catecholamines and significant depletion of adrenal Met-enkephalin, did not inhibit the stress-induced increase in plasma Met-enkephalin, and in fact, was associated with a potentiated response to stress. Guanethidine treatment with or without demedullation increased baseline plasma native Met-enkephalin and abolished the stress-induced increase in plasma native and peptidase-derivable Met-enkephalin. Thus, the stress-induced increase in plasma Metenkephalin results from release from sympathetic nerves, rather than adrenal medulla. However, the sympathetic nerves and adrenal medulla together do not appear to account entirely for basal concentrations of circulating Met-enkephalin. Hepatic portal vein plasma concentration of native Met-enkephalin was greater than that in the carotid artery, suggesting contribution from the gastrointestinal tract; however, evisceration did not decrease plasma native Met-enkephalin. Some compensatory mechanism results in elevation of basal plasma native Met-enkephalin in sympathectomized rats. Also, in the absence of the adrenal medulla there is a compensatory increase in the amount of Met-enkephalin released into the circulation in response to stress.

Tolerance and cross-tolerance to stress-induced increases in plasma Met-enkephalin in rats with adaptively increased resting secretion

Plasma concentrations of both native (pentapeptide plus its sulfoxide) and peptidase-derivable (trypsin followed by carboxypeptidase-B) Met-enkephalin showed brisk increases in response to the stresses of immobilization, hemorrhage, and electric footshock in conscious, freely moving, adult male rats. Daily exposure to 150-min periods of immobilization resulted in a maintained increase in baseline plasma concentrations of native Met-enkephalin 21.5 h after the sixth day and a further increase after 39 days. The plasma native Met-enkephalin response to acute immobilization was attenuated on day 7 and completely absent on day 40. Unstressed rats showed a plasma native Met-enkephalin response to hemorrhage of 15% blood volume and a further increase in response to 25% hemorrhage. Immediately after initial acute immobilization or 6 days of daily immobilization when plasma native Met-enkephalin was elevated but the response to acute immobilization was attenuated, plasma native Met-enkephalin responses to hemorrhage were also attenuated. Rats that had been immobilized daily for 40 days and showed no plasma native Met-enkephalin response to acute immobilization also showed no responses to hemorrhage. After 39 days of immobilization when there was no plasma native Met-enkephalin response to acute immobilization, there was also no response to footshock. Thus, development of tolerance or adaptive loss of plasma native Met-enkephalin response to immobilization with repeated exposure to this stressor is associated with cross-tolerance or adaptive loss of the responses to the stresses of hemorrhage or electric footshock. Development of tolerance and cross-tolerance of plasma responses of peptidase-derivable Met-enkephalin paralleled that of native Met-enkephalin. Thus, adaptation of plasma Met-enkephalin responses to repeated exposure to a stressor included both increased resting secretion and decreased acute responses to homotypic or novel stressors.

Plasma native and peptidase-derivable Met-enkephalin responses to restraint stress in rats. Adaptation to repeated restraint

Met-enkephalin and related proenkephalin A-derived peptides circulate in plasma at picomolar concentration as free, native pentapeptide and at nanomolar concentration in cryptic forms. We have optimized conditions for measurement of immunoreactive Met-enkephalin in plasma and for generation by trypsin and carboxypeptidase B of much greater amounts of total peptidase-derivable Met-enkephalin in plasma of rats, dogs, and humans. Free Met-enkephalin (11 pM) is constituted by native pentapeptide and its sulfoxide. Characterization of plasma total Met-enkephalin derived by peptidic hydrolysis revealed a small amount (38 pM) of Met-enkephalin associated with peptides of molecular mass less than 30,000 D, and probably derived from proenkephalin A, but much larger amounts of Met-enkephalin associated with albumin (1.2 nM) and with a globulin-sized protein (2.8 nM). Thus, plasma protein precursors for peptidase-derivable Met-enkephalin differ structurally and chemically from proenkephalin A. Met-enkephalin generated from plasma by peptidic hydrolysis showed naloxone-reversible bioactivity comparable to synthetic Met-enkephalin. Prolonged exposure of adult, male rats to restraint stress produced biphasic plasma responses, with peaks occurring at 30 s and 30 min in both free native and total peptidase-derivable Met-enkephalin. Repeated daily exposure to this 30-min stress resulted in adaptive loss of responses of both forms to acute restraint. Initial plasma responses of Met-enkephalin paralleled those of epinephrine and norepinephrine, but subsequently showed divergence of response. In conclusion, Met-enkephalin circulates in several forms, some of which may be derived from proteins other than proenkephalin A, and plasma levels of both free native, and peptidase-derivable Met-enkephalin are modulated physiologically.

Nicotine-induced alterations in brain regional concentrations of native and cryptic Met- and Leu-enkephalin

The distribution of cryptic forms (larger enkephalin-containing peptides) in neostriatum, hypothalamus, spinal cord T3-L1 and neurointermediate lobe of pituitary were determined by radioimmunoassay. Optimal conditions for enzymic hydrolysis of the cryptic enkephalins by trypsin and carboxypeptidase B were established. The proportion of total Met- and Leu-enkephalin represented by native pentapeptide varied markedly among these central nervous system regions. Also, the distributions of native and cryptic Met-enkephalin were distinct from that of Leu-enkephalin. Chromatographic separation by HPLC of immunoreactive Met-enkephalin peptides revealed only two peaks corresponding to Met-enkephalin and Met-enkephalin sulfoxide in rather equal amounts. Hydrolysis of cryptic Met-enkephalin also produced only two HPLC-separable peaks of immunoreactive Met-enkephalin, again corresponding to Met-enkephalin and Met-enkephalin sulfoxide. Bioactivity of cryptic striatal Met-enkephalin after hydrolysis was demonstrated by antinociception and catalepsy in rats following its intracerebroventricular injection. Repeated short-term administration of nicotine, 0.1 mg/kg IP six times at 30 min intervals, produced significant increases in native and cryptic Met-enkephalin in striatum, consistent with an increase in neuronal release of Met-enkephalin together with increases in synthesis and processing of proenkephalin A in this brain region. This regimen of nicotine also decreased levels of native Met-enkephalin and of both native and cryptic Leu-enkephalin in neurointermediate lobe, consistent with nicotine-induced release of both proenkephalin A- and prodynorphin-derived peptides from neurointermediate lobe.