Metabolism of gamma hydroxybutyrate in human hepatoma HepG2 cells by the aldo-keto reductase AKR1A1

Acute Sodium Oxybate Intoxication: A Case Report and Review of the Literature

PURPOSE

Despite a better safety profile than illicit γ-hydroxybutyric acid (GHB) and other GHB analogs, sodium oxybate continues to raise serious concerns regarding clinical safety. In this study, the authors report the case of near-fatal intoxication involving sodium oxybate-alcohol combination in a 40-year-old woman. In addition, a review of the literature on published cases of intoxication involving this pharmaceutical form of GHB was conducted. A 40-year-old woman was admitted to the intensive care unit in a coma after voluntary ingestion of 18 g of sodium oxybate and alcohol.

METHODS

The GHB plasma concentration was quantified to be 146 mg/L using liquid chromatography coupled with tandem mass spectrometry. An English literature search was performed using PubMed without any limiting period to identify all available scientific publications involving cases of sodium oxybate intoxication.

RESULTS

Six cases were identified. Five involved fatal intoxication cases, with GHB postmortem blood concentrations ranging from 11.5 to 3500 mg/L. One involved a nonfatal intoxication case with a GHB serum concentration of 569 mg/L 7 hours postingestion.

CONCLUSIONS

In the present case, the estimated elimination half-life was 154 minutes. The risk of acute poisoning seems to be high considering the pharmacokinetic properties of sodium oxybate. Physicians and toxicologists must take such properties into account.

Long non-coding RNAs in <i>Sus scrofa</i> ileum under starvation stress

Objective

In this study, we aimed to identify long non-coding RNAs (lncRNAs) that play important roles in starvation stress, analyze their functions, and discover potential molecular targets to alleviate starvation stress to provide a theoretical reference for subsequent in-depth research.

Methods

We generated a piglet starvation stress animal model. Nine Yorkshire weaned piglets were randomly divided into a long-term starvation stress group (starved for 72 h), short-term starvation stress group (starved for 48 h), and the control group. LncRNA libraries were constructed using high-throughput sequencing of piglet ileums.

Results

We obtained 11,792 lncRNAs, among which, 2,500 lncRNAs were novel. In total, 509 differentially expressed (DE)lncRNAs were identified in this study. Target genes of DElncRNAs were predicted via cis and trans interactions, and functional and pathway analyses were performed. Gene ontology functions and Kyoto encyclopedia of genes and genomes analysis revealed that lncRNA-targeted genes mainly participated in metabolic pathways, cellular processes, immune system processes, digestive systems, and transport activities. To reveal the mechanism underlying starvation stress, the interaction network between lncRNAs and their targets was constructed based on 26 DElncRNAs and 72 DEmRNAs. We performed an interaction network analysis of 121 DElncRNA–DEmRNA pairs with a Pearson correlation coefficient greater than 0.99.

Conclusion

We found that MSTRG.19894.13, MSTRG.16726.3, and MSTRG.12176.1 might play important roles in starvation stress. This study not only generated a library of enriched lncRNAs in piglets, but its outcomes also provide a strong foundation to screen key lncRNAs involved in starvation stress and a reference for subsequent in-depth research.

Pleiotropic Actions of Aldehyde Reductase (AKR1A)

We provide an overview of the physiological roles of aldehyde reductase (AKR1A) and also discuss the functions of aldose reductase (AKR1B) and other family members when necessary. Many types of aldehyde compounds are cytotoxic and some are even carcinogenic. Such toxic aldehydes are detoxified via the action of AKR in an NADPH-dependent manner and the resulting products may exert anti-diabetic and anti-tumorigenic activity. AKR1A is capable of reducing 3-deoxyglucosone and methylglyoxal, which are reactive intermediates that are involved in glycation, a non-enzymatic glycosylation reaction. Accordingly, AKR1A is thought to suppress the formation of advanced glycation end products (AGEs) and prevent diabetic complications. AKR1A and, in part, AKR1B are responsible for the conversion of d-glucuronate to l-gulonate which constitutes a process for ascorbate (vitamin C) synthesis in competent animals. AKR1A is also involved in the reduction of S-nitrosylated glutathione and coenzyme A and thereby suppresses the protein S-nitrosylation that occurs under conditions in which the production of nitric oxide is stimulated. As the physiological functions of AKR1A are currently not completely understood, the genetic modification of Akr1a could reveal the latent functions of AKR1A and differentiate it from other family members.

γ-Hydroxybutyric Acid: Pharmacokinetics, Pharmacodynamics, and Toxicology

Gamma-hydroxybutyrate (GHB) is a short-chain fatty acid present endogenously in the brain and used therapeutically for the treatment of narcolepsy, as sodium oxybate, and for alcohol abuse/withdrawal. GHB is better known however as a drug of abuse and is commonly referred to as the "date-rape drug"; current use in popular culture includes recreational "chemsex," due to its properties of euphoria, loss of inhibition, amnesia, and drowsiness. Due to the steep concentration-effect curve for GHB, overdoses occur commonly and symptoms include sedation, respiratory depression, coma, and death. GHB binds to both GHB and GABAB receptors in the brain, with pharmacological/toxicological effects mainly due to GABAB agonist effects. The pharmacokinetics of GHB are complex and include nonlinear absorption, metabolism, tissue uptake, and renal elimination processes. GHB is a substrate for monocarboxylate transporters, including both sodium-dependent transporters (SMCT1, 2; SLC5A8; SLC5A12) and proton-dependent transporters (MCT1-4; SLC16A1, 7, 8, and 3), which represent significant determinants of absorption, renal reabsorption, and brain and tissue uptake. This review will provide current information of the pharmacology, therapeutic effects, and pharmacokinetics/pharmacodynamics of GHB, as well as therapeutic strategies for the treatment of overdoses. Graphical abstract.

Haplotype-resolved and integrated genome analysis of the cancer cell line HepG2

HepG2 is one of the most widely used human cancer cell lines in biomedical research and one of the main cell lines of ENCODE. Although the functional genomic and epigenomic characteristics of HepG2 are extensively studied, its genome sequence has never been comprehensively analyzed and higher order genomic structural features are largely unknown. The high degree of aneuploidy in HepG2 renders traditional genome variant analysis methods challenging and partially ineffective. Correct and complete interpretation of the extensive functional genomics data from HepG2 requires an understanding of the cell line’s genome sequence and genome structure. Using a variety of sequencing and analysis methods, we identified a wide spectrum of genome characteristics in HepG2: copy numbers of chromosomal segments at high resolution, SNVs and Indels (corrected for aneuploidy), regions with loss of heterozygosity, phased haplotypes extending to entire chromosome arms, retrotransposon insertions and structural variants (SVs) including complex and somatic genomic rearrangements. A large number of SVs were phased, sequence assembled and experimentally validated. We re-analyzed published HepG2 datasets for allele-specific expression and DNA methylation and assembled an allele-specific CRISPR/Cas9 targeting map. We demonstrate how deeper insights into genomic regulatory complexity are gained by adopting a genome-integrated framework.

The Drug of Abuse Gamma-Hydroxybutyric Acid Exhibits Tissue-Specific Nonlinear Distribution

The drug of abuse γ-hydroxybutyric acid (GHB) demonstrates complex toxicokinetics with dose-dependent metabolic and renal clearance. GHB is a substrate of monocarboxylate transporters (MCTs) which are responsible for the saturable renal reabsorption of GHB. MCT expression is observed in many tissues and therefore may impact the tissue distribution of GHB. The objective of the present study was to evaluate the tissue distribution kinetics of GHB at supratherapeutic doses. GHB (400, 600, and 800 mg/kg iv) or GHB 600 mg/kg plus L-lactate (330 mg/kg iv bolus followed by 121 mg/kg/h infusion) was administered to rats and blood and tissues were collected for up to 330 min post-dose. K _p values for GHB varied in both a tissue- and dose-dependent manner and were less than 0.5 (except in the kidney). Nonlinear partitioning was observed in the liver (0.06 at 400 mg/kg to 0.30 at 800 mg/kg), kidney (0.62 at 400 mg/kg to 0.98 at 800 mg/kg), and heart (0.15 at 400 mg/kg to 0.29 at 800 mg/kg), with K _p values increasing with dose consistent with saturation of transporter-mediated efflux. In contrast, lung partitioning decreased in a dose-dependent manner (0.43 at 400 mg/kg to 0.25 at 800 mg/kg) suggesting saturation of active uptake. L-lactate administration decreased K _p values in liver, striatum, and hippocampus and increased K _p values in lung and spleen. GHB demonstrates tissue-specific nonlinear distribution consistent with the involvement of monocarboxylate transporters. These observed complexities are likely due to the involvement of MCT1 and 4 with different affinities and directionality for GHB transport.

Mechanisms for the Specific Properties of γ-Hydroxybutyrate in Brain

γ-Hydroxybutyrate (GHB) is both a natural brain compound with neuromodulatory properties at central GABAergic synapses (micromolar concentration range) and also a drug (Xyrem(R) ) clinically used for the treatment of various neurological symptoms (millimolar dose range). However, this drug has abuse potential and can be addictive for some patients. Here, we review the basic mechanistic role of endogenous GHB in brain as well as the properties and mechanisms of action for therapeutic clinical doses of exogenous GHB. Several hypotheses are discussed with a preference for a molecular mechanism that conciliates most of the findings available. This conciliatory model may help for the design of GHB-like drugs active at lower doses and devoid of major side effects.

Hypoxia and GABA shunt activation in the pathogenesis of Alzheimer's disease

We have previously observed that the conversion of mild cognitive impairment to definitive Alzheimer's disease (AD) is associated with a significant increase in the serum level of 2,4-dihydroxybutyrate (2,4-DHBA). The metabolic generation of 2,4-DHBA is linked to the activation of the γ-aminobutyric acid (GABA) shunt, an alternative energy production pathway activated during cellular stress, when the function of Krebs cycle is compromised. The GABA shunt can be triggered by local hypoperfusion and subsequent hypoxia in AD brains caused by cerebral amyloid angiopathy. Succinic semialdehyde dehydrogenase (SSADH) is a key enzyme in the GABA shunt, converting succinic semialdehyde (SSA) into succinate, a Krebs cycle intermediate. A deficiency of SSADH activity stimulates the conversion of SSA into γ-hydroxybutyrate (GHB), an alternative route from the GABA shunt. GHB can exert not only acute neuroprotective activities but unfortunately also chronic detrimental effects which may lead to cognitive impairment. Subsequently, GHB can be metabolized to 2,4-DHBA and secreted from the brain. Thus, the activation of the GABA shunt and the generation of GHB and 2,4-DHBA can have an important role in the early phase of AD pathogenesis.