Restricted feeding modulates the daily variations of liver glutamate dehydrogenase activity, expression, and histological location

Advanced Biomarkers of Hepatotoxicity in Psychiatry: A Narrative Review and Recommendations for New Psychoactive Substances

One of the factors that increase the effectiveness of the pharmacotherapy used in patients abusing various types of new psychoactive substances (NPSs) is the proper functioning of the liver. However, the articles published to date on NPS hepatotoxicity only address non-specific hepatic parameters. The aim of this manuscript was to review three advanced markers of hepatotoxicity in psychiatry, namely, osteopontin (OPN), high-mobility group box 1 protein (HMGB1) and glutathione dehydrogenase (GDH, GLDH), and, on this basis, to identify recommendations that should be included in future studies in patients abusing NPSs. This will make it possible to determine whether NPSs do indeed have a hepatotoxic effect or whether other factors, such as additional substances taken or hepatitis C virus (HCV) infection, are responsible. NPS abusers are at particular risk of HCV infection, and for this reason, it is all the more important to determine what factors actually show a hepatotoxic effect in them.

Daytime Dependence of the Activity of the Rat Brain Pyruvate Dehydrogenase Corresponds to the Mitochondrial Sirtuin 3 Level and Acetylation of Brain Proteins, All Regulated by Thiamine Administration Decreasing Phosphorylation of PDHA Ser293

Coupling glycolysis and mitochondrial tricarboxylic acid cycle, pyruvate dehydrogenase (PDH) complex (PDHC) is highly responsive to cellular demands through multiple mechanisms, including PDH phosphorylation. PDHC also produces acetyl-CoA for protein acetylation involved in circadian regulation of metabolism. Thiamine (vitamin B1) diphosphate (ThDP) is known to activate PDH as both coenzyme and inhibitor of the PDH inactivating kinases. Molecular mechanisms integrating the function of thiamine-dependent PDHC into general redox metabolism, underlie physiological fitness of a cell or an organism. Here, we characterize the daytime- and thiamine-dependent changes in the rat brain PDHC function, expression and phosphorylation, assessing their impact on protein acetylation and metabolic regulation. Morning administration of thiamine significantly downregulates both the PDH phosphorylation at Ser293 and SIRT3 protein level, the effects not observed upon the evening administration. This action of thiamine nullifies the daytime-dependent changes in the brain PDHC activity and mitochondrial acetylation, inducing diurnal difference in the cytosolic acetylation and acetylation of total brain proteins. Screening the daytime dependence of central metabolic enzymes and proteins of thiol/disulfide metabolism reveals that thiamine also cancels daily changes in the malate dehydrogenase activity, opposite to those of the PDHC activity. Correlation analysis indicates that thiamine abrogates the strong positive correlation between the total acetylation of the brain proteins and PDHC function. Simultaneously, thiamine heightens interplay between the expression of PDHC components and total acetylation or SIRT2 protein level. These thiamine effects on the brain acetylation system change metabolic impact of acetylation. The changes are exemplified by the thiamine enhancement of the SIRT2 correlations with metabolic enzymes and proteins of thiol-disulfide metabolism. Thus, we show the daytime- and thiamine-dependent changes in the function and phosphorylation of brain PDHC, contributing to regulation of the brain acetylation system and redox metabolism. The daytime-dependent action of thiamine on PDHC and SIRT3 may be of therapeutic significance in correcting perturbed diurnal regulation.

Vital Role of Glutamate Dehydrogenase Gene in Ammonia Detoxification and the Association Between its SNPs and Ammonia Tolerance in Sinonovacula constricta

Increasing evidence has revealed accumulated ammonia will cause adverse effects on the growth, reproduction, and survival of aquatic animals. As a marine benthic mollusk, the razor clam Sinonovacula constricta shows better growth and survival under high ammonia nitrogen environment. However, little is known about its adaptation mechanisms to high ammonia stress in an integrated mariculture system. In this study, we analyzed the association between the polymorphism of glutamate dehydrogenase gene (GDH), a key gene involved in ammonia nitrogen detoxification, and ammonia tolerance. The results showed that 26 and 22 single-nucleotide polymorphisms (SNPs) of GDH in S. constricta (denoted as Sc-GDH) were identified from two geographical populations, respectively. Among them, two SNPs (c.323T > C and c.620C > T) exhibited a significant and strong association with ammonia tolerance, suggesting that Sc-GDH gene could serve as a potential genetic marker for molecular marker–assisted selection to increase survival rate and production of S. constricta. To observe the histological morphology and explore the histocellular localization of Sc-GDH, by paraffin section and hematoxylin–eosin staining, the gills were divided into gill filament (contains columnar and flattened cells) and gill cilia, whereas hepatopancreas was made up of individual hepatocytes. The results of immunohistochemistry indicated that the columnar cells of gill filaments and the endothelial cells of hepatocytes were the major sites for Sc-GDH secretion. Under ammonia stress (180 mg/L), the expression levels of Sc-GDH were extremely significantly downregulated at 24, 48, 72, and 96 h (P < 0.01) after RNA interference. Thus, we can speculate that Sc-GDH gene may play an important role in the defense process against ammonia stress. Overall, these findings laid a foundation for further research on the adaptive mechanisms to ammonia–nitrogen tolerance for S. constricta.

Diurnal regulation of the function of the rat brain glutamate dehydrogenase by acetylation and its dependence on thiamine administration

Glutamate dehydrogenase (GDH) is essential for the brain function and highly regulated, according to its role in metabolism of the major excitatory neurotransmitter glutamate. Here we show a diurnal pattern of the GDH acetylation in rat brain, associated with specific regulation of GDH function. Mornings the acetylation levels of K84 (near the ADP site), K187 (near the active site), and K503 (GTP-binding) are highly correlated. Evenings the acetylation levels of K187 and K503 decrease, and the correlations disappear. These daily variations in the acetylation adjust the GDH responses to the enzyme regulators. The adjustment is changed when the acetylation of K187 and K503 shows no diurnal variations, as in the rats after a high dose of thiamine. The regulation of GDH function by acetylation is confirmed in a model system, where incubation of the rat brain GDH with acetyl-CoA changes the enzyme responses to GTP and ADP, decreasing the activity at subsaturating concentrations of substrates. Thus, the GDH acetylation may support cerebral homeostasis, stabilizing the enzyme function during diurnal oscillations of the brain metabolome. Daytime and thiamine interact upon the (de)acetylation of GDH in vitro. Evenings the acetylation of GDH from control animals increases both IC₅₀ ^GTP and EC₅₀ ^ADP . Mornings the acetylation of GDH from thiamine-treated animals increases the enzyme IC₅₀ ^GTP . Molecular mechanisms of the GDH regulation by acetylation of specific residues are proposed. For the first time, diurnal and thiamine-dependent changes in the allosteric regulation of the brain GDH due to the enzyme acetylation are shown.

High carbohydrate diet partially protects Nile tilapia (Oreochromis niloticus) from oxytetracycline-induced side effects

Antibiotics used in global aquaculture production cause various side effects, which impair fish health. However, the use of dietary composition such as carbohydrate, which is one of the dominant components in fish diets to attenuate the side effects induced by antibiotics, remains unclear. We determined the ability of high carbohydrate diet to protect Nile tilapia (Oreochromis niloticus) from oxytetracycline-induced side effects. Triplicate groups of thirty O. niloticus (9.50 ± 0.08 g) were fed on medium carbohydrate (MC; 335 g/kg) and high carbohydrate (HC; 455 g/kg) diets without and with 2.00 g/kg diet of oxytetracycline (80 mg/kg body weight/day) hereafter, MCO and HCO for 35 days. Thereafter, we assessed growth performance, hepatic nutrients composition and metabolism, microbiota abundance, immunity, oxidative and cellular stress, hepatotoxicity, lipid peroxidation and apoptosis. To understand the possible mechanism of carbohydrate protection on oxytetracycline, we assessed the binding effects and efficiencies of mixtures of medium and high starch with oxytetracycline as well as the MCO and HCO diets. The O. niloticus fed on the MCO and HCO diets had lower growth rate, nutrients utilization and survival rate than those fed on the MC and HC diets, respectively. Dietary HCO increased hepatosomatic index and hepatic protein content of O. niloticus than MCO diet. The O. niloticus fed on the HCO diet had lower mRNA expression of genes related to protein, glycogen and lipid metabolism compared to those fed on the MCO diet. Feeding O. niloticus on the HCO diet increased innate immunity and reduced pathogenic bacteria, pro-inflammation, hepatotoxicity, cellular stress and apoptosis than the MCO diet. The high starch with oxytetracycline and HCO diet had higher-oxytetracycline binding effects and efficiencies than the medium starch with oxytetracyline and MCO diet, respectively. Our study demonstrates that, high carbohydrate partially protects O. niloticus from oxytetracycline-induced side effects by binding the antibiotic. Incorporating high carbohydrate in diet formulation for omnivorous fish species alleviates some of the side effects caused by antibiotics.

Identification of serological markers for pre- and postoperative fasting periods

BACKGROUND & AIMS

Prolonged preoperative fasting periods lead to catabolic states and decelerate recovery after surgery. Valid plasma markers reflecting the patients' metabolic state may improve tailored nutrition support before surgery. Within this study, we sought to advance the knowledge on fasting time-sensitive plasma markers that allow the metabolic characterisation of surgical patients for an optimised preoperative metabolic preparation.

METHODS

Patients scheduled for elective surgery of the upper (n = 23) or lower (n = 27) gastrointestinal tract participated in a prospective observational study. Patients' charateristics and nutritional status were recorded and blood samples were drawn on the day of admission. Further blood samples were collected before skin incision of the surgical procedure, on postoperative day 3 and on the day of discharge. Values of clinical chemistry, electrolytes, hemograms and plasma amino acids were determined and correlated with fasting times.

RESULTS

Preoperative fasting times were positively correlated with plasma levels of valine, leucine, serine, α-amino butyric acid, free fatty acids, 3-hydroxy butyric acid and significantly negative correlated with chloride and glutamic acid. Postoperative fasting times were correlated with erythrocytes, leukocytes and plasma levels of albumin, CRP, HDL, asparagine and 3-methylhistidine. The multivariate regression analysis revealed glutamic acid and valine as significant independent predictors of preoperative fasting periods. The regression model showed best performance (sensitivity of 90.91% and specificity of 92.31%) to detect patients fasted for ≥20 h.

CONCLUSION

Valine and glutamic acid appear as independent metabolic markers for accurate prediction of prolonged fasting periods, independent of the overall nutritional status, age or BMI of patients.