Activation of NMDA receptor by elevated homocysteine in chronic liver disease contributes to encephalopathy

Homocysteine May Decrease Glucose Uptake and Alter the Akt/GSK3β/GLUT1 Signaling Pathway in Hippocampal Slices: Neuroprotective Effects of Rivastigmine and Ibuprofen

Homocysteine (Hcy) is a risk factor for neurodegenerative diseases, such as Alzheimer's Disease, and is related to cellular and tissue damage. In the present study, we verified the effect of Hcy on neurochemical parameters (redox homeostasis, neuronal excitability, glucose, and lactate levels) and the Serine/Threonine kinase B (Akt), Glucose synthase kinase-3β (GSK3β) and Glucose transporter 1 (GLUT1) signaling pathway in hippocampal slices, as well as the neuroprotective effects of ibuprofen and rivastigmine alone or in combination in such effects. Male Wistar rats (90 days old) were euthanized and the brains were dissected. The hippocampus slices were pre-treated for 30 min [saline medium or Hcy (30 µM)], then the other treatments were added to the medium for another 30 min [ibuprofen, rivastigmine, or ibuprofen + rivastigmine]. The dichlorofluorescein formed, nitrite and Na+, K+-ATPase activity was increased by Hcy at 30 µM. Ibuprofen reduced dichlorofluorescein formation and attenuated the effect of Hcy. The reduced glutathione content was reduced by Hcy. Treatments with ibuprofen and Hcy + ibuprofen increased reduced glutathione. Hcy at 30 µM caused a decrease in hippocampal glucose uptake and GLUT1 expression, and an increase in Glial Fibrillary Acidic Protein-protein expression. Phosphorylated GSK3β and Akt levels were reduced by Hcy (30 µM) and co-treatment with Hcy + rivastigmine + ibuprofen reversed these effects. Hcy toxicity on glucose metabolism can promote neurological damage. The combination of treatment with rivastigmine + ibuprofen attenuated such effects, probably by regulating the Akt/GSK3β/GLUT1 signaling pathway. Reversal of Hcy cellular damage by these compounds may be a potential neuroprotective strategy for brain damage.

Does Risk of Hyperhomocysteinemia Depend on Thiol-Disulfide Exchange Reactions of Albumin and Homocysteine?

Significance: Increased plasma concentrations of total homocysteine (tHcy; mild-moderate hyperhomocysteinemia: 15-50 μM tHcy) are considered an independent risk factor for the onset/progression of various diseases, but it is not known about how the increase in tHcy causes pathological conditions. Recent Advances: Reduced homocysteine (HSH ∼1% of tHcy) is presumed to be toxic, unlike homocystine (∼9%) and mixed disulfide between homocysteine and albumin (HSS-ALB; homocysteine [Hcy]-albumin mixed disulfide, ∼90%). This and other notions make it difficult to explain the pathogenicity of Hcy because: (i) lowering tHcy does not improve pathological outcomes; (ii) damage due to HSH usually emerges at supraphysiological doses; and (iii) it is not known why tiny increments in plasma concentrations of HSH can be pathological. Critical Issues: Albumin may have a role in Hcy toxicity, because HSS-ALB could release toxic HSH via thiol-disulfide (SH/SS) exchange reactions in cells. Similarly, thiol-disulfide exchange processes of reduced albumin (albumin with free SH group of Cys34 [HS-ALB]) or N-homocysteinylated albumin are plausible alternatives for initiating Hcy pathological events. Adverse effects of albumin and other data reviewed here suggest the hypothesis of a role of albumin in Hcy toxicity. Future Directions: HSS-ALB might be involved in disruption of the antioxidant/oxidant balance in critical tissues (brain, liver, kidney). Since homocysteine-albumin mixed disulfide is a possible intermediate of thiol-disulfide exchange reactions, we suggest that homocysteinylated albumin could be a new pathological factor, and that studies on the redox role of albumin and mixed disulfide production via thiol-disulfide exchange reactions could offer new therapeutic insights for reducing Hcy toxicity.

Risk Factor Analysis of Hepatic Encephalopathy and the Establishment of Diagnostic Model

To identify laboratory diagnostic indicators of hepatic encephalopathy (HE), the present study established a HE diagnostic model to explore the diagnostic value of serum homocysteine, lactic acid, procalcitonin, and bile acid levels in HE identification. 371 patients with liver cirrhosis were selected as research objects, who were admitted to the Department of Hepatic Diseases, Affiliated Hospital of Northwest Minzu University from August 2019 to August 2020. The Spearman correlation results indicated that between lactic acid, procalcitonin, bile acid, serum homocysteine, and HE, the coefficients were -0.15, 0.41, 0.29, and -0.19, respectively. Univariate and multivariate analysis methods were adopted for inpatient analysis to identify the influencing factors of HE occurrence, and the diagnosis of the HE identification model was subsequently constructed. The univariate logistic regression showed that risk of developing HE increased as bile acid level (P = 0.00434) and serum homocysteine (P = 0.058) increased. Multivariate logistic regression diagnostic model of bile acid level and serum homocysteine revealed that the AUC value of the area under the ROC curve was 0.7201, indicating that the diagnostic model produced a satisfactory evaluation effect. The model formula referred logistic (P) = -2.4544 + 0.0117 bile acid levels + 0.0198 serum homocysteine. In this study, the HE diagnostic model was established using logistic regression analysis, which could benefit patients in early HE differential diagnosis. Particularly, combined detection of serum homocysteine and bile acid levels was considered to be more significant.

Post-SSRI Sexual Dysfunction (PSSD): Biological Plausibility, Symptoms, Diagnosis, and Presumed Risk Factors

INTRODUCTION

Post-SSRI sexual-dysfunction (PSSD) is an iatrogenicsyndrome, the underlying neurobiological mechanisms of which areunclear. Symptom onset follows cessation of serotonergicantidepressants i.e. Selective Serotonin and Norepinephrine ReuptakeInhibitors (SSRI's, SNRI's), and Tricyclic antidepressants (TCA's). PSSDsymptoms include genital anesthesia, erectile dysfunction andorgasmic/ejaculatory anhedonia, and should be differentiated fromdepression-related sexual-dysfunction. Recently, accumulated data of numerous case-reports suggest additional non-sexual symptoms including, anhedonia, apathy, and blunted affect. PSSD gained official recognition after the European medical agency concluded that PSSD is a medical condition that persists after discontinuation of SSRI's and SNRI's.

OBJECTIVE

To review possible underlying neurobiological mechanisms ofthis syndrome, update information on the pathophysiology, present a listof potential risk-factors and discuss potential management options forPSSD.

METHODS

Extensive literature review on the main symptom-patterns ofthis disorder was undertaken using PubMed. It includes introductoryexplications of relevant neurobiology with the objective of generatinghypothesis.

RESULTS

Precipitating factors for PSSD include previous exposure to certain drugs, genetic predisposition, psychological stress or chemical stressful reaction to antidepressants along pre-existing medical conditions affecting neuroplasticity. Different theories have been proposed to explain the pathophysiology of PSSD: epigenetic gene expression, dopamine-serotonin interactions, serotonin neurotoxicity and hormonal changes. The diagnosis of PSSD is by excluding all other etiologies of sexual-dysfunction. Treatment is challenging, and many strategies have been suggested without definitive outcomes. We offerthe contours of a future neurobiological research agenda, and propose several underlying mechanisms for the various symptoms of PSSD which could be the foundation for a future treatment algorithm.

CONCLUSION

There is a need for well-designed neurobiological research in this domain, as well as in the prevalence, pathophysiology, and treatment of PSSD. Practitioners should be alert to the distinctive features of PSSD. Misdiagnosing this syndrome might lead to harmful Sexual Medicine Reviews. Peleg LC, Rabinovitch D, Lavie Y, et al. Post-SSRI Sexual Dysfunction (PSSD): Biological Plausibility, Symptoms, Diagnosis, and Presumed Risk Factors. Sex Med Rev 2021;XX:XXX-XXX.

Mild Hyperhomocysteinemia Causes Anxiety-like Behavior and Brain Hyperactivity in Rodents: Are ATPase and Excitotoxicity by NMDA Receptor Overstimulation Involved in this Effect?

Mild hyperhomocysteinemia is a risk factor for psychiatric and neurodegenerative diseases, whose mechanisms between them are not well-known. In the present study, we evaluated the emotional behavior and neurochemical pathways (ATPases, glutamate homeostasis, and cell viability) in amygdala and prefrontal cortex rats subjected to mild hyperhomocysteinemia (in vivo studies). The ex vivo effect of homocysteine on ATPases and redox status, as well as on NMDAR antagonism by MK-801 in same structures slices were also performed. Wistar male rats received a subcutaneous injection of 0.03 µmol Homocysteine/g of body weight or saline, twice a day from 30 to 60th-67th days of life. Hyperhomocysteinemia increased anxiety-like behavior and tended to alter locomotion/exploration of rats, whereas sucrose preference and forced swimming tests were not altered. Glutamate uptake was not changed, but the activities of glutamine synthetase and ATPases were increased. Cell viability was not altered. Ex vivo studies (slices) showed that homocysteine altered ATPases and redox status and that MK801, an NMDAR antagonist, protected amygdala (partially) and prefrontal cortex (totally) effects. Taken together, data showed that mild hyperhomocysteinemia impairs the emotional behavior, which may be associated with changes in ATPase and glutamate homeostasis, including glutamine synthetase and NMDAR overstimulation that could lead to excitotoxicity. These findings may be associated with the homocysteine risk factor on psychiatric disorders development and neurodegeneration.

Endogenous toxic metabolites and implications in cancer therapy

It is well recognized that many metabolic enzymes play essential roles in cancer cells in producing building blocks such as nucleotides, which are required in greater amounts due to their increased proliferation. On the other hand, the significance of enzymes in preventing the accumulation of their substrates is less recognized. Here, we outline the evidence and underlying mechanisms for how many metabolites normally produced in cells are highly toxic, such as metabolites containing reactive groups (e.g., methylglyoxal, 4-hydroxynonenal, and glutaconyl-CoA), or metabolites that act as competitive analogs against other metabolites (e.g., deoxyuridine triphosphate and l-2-hydroxyglutarate). Thus, if a metabolic pathway contains a toxic intermediate, then we may be able to induce accumulation and poison a cancer cell by targeting the downstream enzyme. Furthermore, this poisoning may be cancer cell selective if this pathway is overactive in a cancer cell relative to a nontransformed cell. We describe this concept as illustrated in selenocysteine metabolism and other pathways and discuss future directions in exploiting toxic metabolites to kill cancer cells.

Methanolic extract of Tamarix Gallica attenuates hyperhomocysteinemia induced AD-like pathology and cognitive impairments in rats

Although few drugs are available today for the management of Alzheimer’s disease (AD) and many plants and their extracts are extensively employed in animals’ studies and AD patients, yet no drug or plant extract is able to reverse AD symptoms adequately. In the present study, Tamarix gallica (TG), a naturally occurring plant known for its strong antioxidative, anti-inflammatory and anti-amyloidogenic properties, was evaluated on homocysteine (Hcy) induced AD-like pathology and cognitive impairments in rats. We found that TG attenuated Hcy-induced oxidative stress and memory deficits. TG also improved neurodegeneration and neuroinflammation by upregulating synaptic proteins such as PSD95 and synapsin 1 and downregulating inflammatory markers including CD68 and GFAP with concomitant decrease in proinflammatory mediators interlukin-1β (IL1β) and tumor necrosis factor α (TNFα). TG attenuated tau hyperphosphorylation at multiple AD-related sites through decreasing some kinases and increasing phosphatase activities. Moreover, TG rescued amyloid-β (Aβ) pathology through downregulating BACE1. Our data for the first time provide evidence that TG attenuates Hcy-induced AD-like pathological changes and cognitive impairments, making TG a promising candidate for the treatment of AD-associated pathological changes.

Meta-Analysis of the Effects of the Catechol-O-Methyltransferase Val158/108Met Polymorphism on Parkinson's Disease Susceptibility and Cognitive Dysfunction

Background: There is a continued debate and inconsistent findings in previous literature about the relationship of catechol-O-methyltransferase (COMT) and Parkinson’s disease (PD) susceptibility as well as cognitive dysfunction. To substantiate this existing gap, we comprehensively examine COMT genotype effects on the development of PD and test the hypothesis that the Met158 allele of the COMT gene is associated with cognitive dysfunction by conducting a meta-analysis review.

Methods: PubMed/MEDLINE, Embase, Cochrane databases search (18/30/08) yielded 49 included studies. Data were extracted by two reviewers and included COMT genotype, publication year, diagnostic status, ancestry, the proportion of male participants, and whether genotype frequencies were consistent with Hardy–Weinberg equilibrium. Unadjusted odds ratios (ORs) were used to derive pooled estimates of PD risk overall and in subgroups defined by ethnicity, gender, and onset of disease. Moreover, the association of certain cognitive domains in PD and COMT gene type was explored. Meta-analyses were performed using random-effect models and p value–based methods. All statistical tests were two-sided. The present study was registered with PROSPERO (CRD42018087323).

Results: In the current studies, we found no association between COMT Val158/108Met polymorphism and PD susceptibility. However, the gender-stratified analyses revealed marginally significant effects in heterozygote model analyses in women (P = 0.053). In addition, stratification according to onset of PD also shows significant effects of COMT Val158/108Met polymorphism on late-onset population both in recessive (P = 0.017) and allelic (P = 0.017) genetic models. For the intelligence quotient (IQ) score and Unified Parkinson Disease Rating Scale III (UPDRS III), there was no evidence for genetic association, except in subgroup analyses in Asian populations (IQ score, P = 0.016; UPDRS III, P < 0.001).

Conclusion: The COMT Val158/108Met polymorphism is associated with the risk for PD in female or late-onset PD. Methionine/methionine carriers of Asian population performed significantly worse than the valine allele carriers in IQ score and UPDRS III.

Moringa Oleifera Alleviates Homocysteine-Induced Alzheimer's Disease-Like Pathology and Cognitive Impairments

Alzheimer’s disease (AD) is multifactorial with unclear etiopathology. Due to the complexity of AD, many attempted single therapy treatments, like Aβ immunization, have generally failed. Therefore, there is a need for drugs with multiple benefits. Naturally occurring phytochemicals with neuroprotective, anti-amyloidogenic, antioxidative, and anti-inflammatory properties could be a possible way out. In this study, the effect of Moringa oleifera (MO), a naturally occurring plant with high antioxidative, anti-inflammatory, and neuroprotective effects, was evaluated on hyperhomocysteinemia (HHcy) induced AD-like pathology in rats. Homocysteine (Hcy) injection for 14 days was used to induce AD-like pathology. Simultaneous MO extract gavage followed the injection as a preventive treatment or, after injection completion, MO gavage was performed for another 14 days as a curative treatment. MO was found to not only prevent but also rescue the oxidative stress and cognitive impairments induced by Hcy treatment. Moreover, MO recovered the decreased synaptic proteins PSD93, PSD95, Synapsin 1 and Synaptophysin, and improved neurodegeneration. Interestingly, MO decreased the Hyc-induced tau hyperphosphorylation at different sites including S-199, T-231, S-396, and S-404, and at the same time decreased Aβ production through downregulation of BACE1. These effects in HHcy rats were accompanied by a decrease in calpain activity under MO treatment, supporting that calpain activation might be involved in AD pathogenesis in HHcy rats. Taken together, our data, for the first time, provided evidence that MO alleviates tau hyperphosphorylation and Aβ pathology in a HHcy AD rat model. This and previous other studies support MO as a good candidate for, and could provide new insights into, the treatment of AD and other tauopathies.

Effects of Shu Gan Jian Pi formula on rats with carbon tetrachloride‑induced liver fibrosis using serum metabonomics based on gas chromatography‑time of flight mass spectrometry

Liver fibrosis is a common stage in the majority of chronic liver diseases, regardless of the etiology, and its progression may lead to hepatic cirrhosis or hepatocellular carcinoma. Metabolomics, a powerful approach in systems biology, is a discipline used to qualitatively and quantitatively analyze the small molecule metabolites of cells at specific times and under certain conditions. The present study aimed to investigate serum metabolic changes following Shu Gan Jian Pi formula (SGJPF) treatment of carbon tetrachloride (CCl₄)-induced liver fibrosis in rats using gas chromatography-time of flight mass spectrometry (GC-TOFMS). In addition, the potential mechanisms were explored. Rat liver fibrosis was induced by twice-weekly subcutaneous CCl₄ injection for 12 continuous weeks. During the same period, the SGJPF group received 16.2 g/kg body weight SGJPF, diluted in water, once a day for 12 weeks. Rats in the control and model groups received oral administration of the same volume of saline solution. Serum samples from the control, model and SGJPF groups were collected after 12 weeks of treatment, and metabolic profile alterations were analyzed by GC-TOF/MS. Metabolic profile analysis indicated that clustering differed between the three groups and the following 12 metabolites were detected in the serum of all three groups: Isoleucine; L-malic acid; D-erythro-sphingosine; putrescine; malonic acid; 3,6-anhydro-D-galactose, α-ketoglutaric acid; ornithine; glucose; hippuric acid; tetrahydrocorticosterone; and fucose. The results demonstrated that SGJPF treatment mitigated the effects of CCl₄-induced liver fibrosis on biomarker levels, thus indicating that SGJPF may have a therapeutic effect on CCl₄-induced liver fibrosis in rats. The mechanism may involve the regulation of energy, amino acid, sphingolipid, cytochrome P450, glucose and water-electrolyte metabolism.

Altered postural control and stability in cirrhotic patients with minimal hepatic encephalopathy correlate with cognitive deficits

BACKGROUND & AIMS

Cognitive dysfunction in cirrhotic patients with minimal hepatic encephalopathy (MHE) is associated with falls. Alterations in postural control and stability could contribute to increase falls risk in these patients. We aimed to assess whether postural control and direction-specific limits of stability are altered in cirrhotic patients with MHE compared to patients without MHE and controls. We also assessed if alterations in postural control correlate with neurological impairment and/or blood biomarkers.

METHODS

Posturography analysis, attention Stroop test and bimanual and visuo-motor coordination tests were performed in 18 controls, 19 patients with cirrhosis without MHE and 17 with MHE, diagnosed by PHES. Posturography was assessed by NedSVE^® /IBV system under four sensory conditions. Limits of stability and rhythmic weight-shifting tests were also performed. Blood ammonia and serum interleukins were also measured. Falls were assessed after 12-24 months follow-up.

RESULTS

MHE patients show impaired balance, mainly on unstable surface with eyes open, with longer reaction and confinement times and lower success in Limits of Stability test compared to patients without MHE. Performance in attention and motor coordination tests correlated with most posturography parameters alterations. Logistic regression analysis shows that posturography parameters and bimanual coordination test are good predictors of falls.

CONCLUSION

Balance patterns and limits of stability in MHE patients are impaired compared to patients without MHE and controls. This seems to contribute to a higher falls risk. Attention and motor coordination deficits could contribute to balance impairment in patients with MHE.