Glyoxalase 1 (GLO1) Inhibition or Genetic Overexpression Does Not Alter Ethanol's Locomotor Effects: Implications for GLO1 as a Therapeutic Target in Alcohol Use Disorders

Genome-Wide Association Studies of Coffee Intake in UK/US Participants of European Ancestry Uncover Gene-Cohort Influences

Coffee is one of the most widely consumed beverages. We performed a genome-wide association study (GWAS) of coffee intake in US-based 23andMe participants (N=130,153) and identified 7 significant loci, with many replicating in three multi-ancestral cohorts. We examined genetic correlations and performed a phenome-wide association study across thousands of biomarkers and health and lifestyle traits, then compared our results to the largest available GWAS of coffee intake from UK Biobank (UKB; N=334,659). The results of these two GWAS were highly discrepant. We observed positive genetic correlations between coffee intake and psychiatric illnesses, pain, and gastrointestinal traits in 23andMe that were absent or negative in UKB. Genetic correlations with cognition were negative in 23andMe but positive in UKB. The only consistent observations were positive genetic correlations with substance use and obesity. Our study shows that GWAS in different cohorts could capture cultural differences in the relationship between behavior and genetics.

The expanding impact of methylglyoxal on behavior-related disorders

Methylglyoxal (MGO) is a reactive dicarbonyl compound formed as a byproduct of glycolysis. MGO is a major cell-permeant precursor of advanced glycation end products (AGEs), since it readily reacts with basic phospholipids and nucleotides, as well as amino acid residues of proteins, such as arginine, cysteine, and lysine. The AGEs production induced by MGO are widely associated with several pathologies, including neurodegenerative diseases. However, the impact of MGO metabolism and AGEs formation in the central nervous system (particularly in neurons, astrocytes and oligodendrocytes) on behavior and psychiatric diseases is not fully understood. Here, we briefly present background information on the biological activity of MGO in the central nervous system. It was gathered the available information on the role of MGO metabolism at the physiological processes, as well as at the neurobiology of psychiatry diseases, especially pain-related experiences, anxiety, depression, and cognition impairment-associated diseases. To clarify the role of MGO on behavior and associated diseases, we reviewed primarily the main findings at preclinical studies focusing on genetic and pharmacological approaches. Since monoamine neurotransmitter systems are implicated as pivotal targets on the pathophysiology and treatment of psychiatry and cognitive-related diseases, we also reviewed how MGO affects these neurotransmission systems and the implications of this phenomenon for nociception and pain; learning and cognition; and mood. In summary, this review highlights the pivotal role of glyoxalase 1 (Glo1) and MGO levels in modulating behavioral phenotypes, as well as related cellular and molecular signaling. Conclusively, this review signals dopamine as a new neurochemical MGO target, as well as highlights how MGO metabolism can modulate the pathophysiology and treatment of pain, psychiatric and cognitive-related diseases.

Methylglyoxal in the Brain: From Glycolytic Metabolite to Signalling Molecule

Advances in molecular biology technology have piqued tremendous interest in glycometabolism and bioenergetics in homeostasis and neural development linked to ageing and age-related diseases. Methylglyoxal (MGO) is a by-product of glycolysis, and it can covalently modify proteins, nucleic acids, and lipids, leading to cell growth inhibition and, eventually, cell death. MGO can alter intracellular calcium homeostasis, which is a major cell-permeant precursor to advanced glycation end-products (AGEs). As side-products or signalling molecules, MGO is involved in several pathologies, including neurodevelopmental disorders, ageing, and neurodegenerative diseases. In this review, we demonstrate that MGO (the metabolic side-product of glycolysis), the GLO system, and their analogous relationship with behavioural phenotypes, epigenetics, ageing, pain, and CNS degeneration. Furthermore, we summarise several therapeutic approaches that target MGO and the glyoxalase (GLO) system in neurodegenerative diseases.

A mutant allele of glycoprotein M6-B (Gpm6b) facilitates behavioral flexibility but increases delay discounting

The neuronal membrane glycoprotein M6B (Gpm6b) gene encodes a membrane glycoprotein that belongs to the proteolipid protein family, and is enriched in neurons, oligodendrocytes, and subset of astrocytes in the central nervous system. GPM6B is thought to play a role in neuronal differentiation, myelination, and inactivation of the serotonin transporter via internalization. Recent human genome-wide association studies (GWAS) have implicated membrane glycoproteins (both GPM6B and GPM6A) in the regulation of traits relevant to psychiatric disorders, including neuroticism, depressed affect, and delay discounting. Mouse studies have implicated Gpm6b in sensorimotor gating and regulation of serotonergic signaling. We used CRISPR to create a mutant Glycoprotein M6B (Gpm6b) allele on a C57BL/6J mouse background. Because Gpm6b is located on the X chromosome, we focused on male Gpm6b mutant mice and their wild-type littermates (WT) in two behavioral tests that measured aspects of impulsive or flexible decision-making. We found that Gpm6b deletion caused deficits in a delay discounting task. In contrast, reward sensitivity was enhanced thereby facilitating behavioral flexibility and improving performance in the probabilistic reversal learning task. Taken together these data further delineate the role of Gpm6b in decision making behaviors that are relevant to multiple psychiatric disorders.

Fentanyl-induced acute and conditioned behaviors in two inbred mouse lines: Potential role for Glyoxalase

An increase in opioid-overdose deaths was evident before the COVID-19 pandemic, and has escalated since its onset. Fentanyl, a highly potent synthetic opioid, is the primary driver of these recent trends. The current study used two inbred mouse strains, C57BL/6 J and A/J, to investigate the genetics of behavioral responses to fentanyl. Mice were tested for conditioned place preference and fentanyl-induced locomotor activity. C57BL/6J mice formed a conditioned place preference to fentanyl injections and fentanyl increased their activity. Neither effect was noted in A/J mice. We conducted RNA-sequencing on the nucleus accumbens of mice used for fentanyl-induced locomotor activity. Surprisingly, we noted few differentially expressed genes using treatment as the main factor. However many genes differed between strains. We validated differences in two genes: suppressor APC domain containing 1 (Sapcd1) and Glyoxalase 1 (Glo1), with quantitative PCR on RNA from the nucleus accumbens and prefrontal cortex (). In both regions A/J mice had significantly higher expression of both genes than did C57BL/6 J. In prefrontal cortex, fentanyl treatment decreased Glo1 mRNA. Glyoxalase 1 catalyzes the detoxification of reactive alpha-oxoaldehydes such as glyoxal and methylglyoxal, is associated with anxiety and activity levels, and its inhibition reduces alcohol intake. We suggest that future studies assess the ability of Glo1 and related metabolites to modify opioid intake.

Phosphorylation of T107 by CamKIIδ Regulates the Detoxification Efficiency and Proteomic Integrity of Glyoxalase 1

The glyoxalase system is a highly conserved and ubiquitously expressed enzyme system, which is responsible for the detoxification of methylglyoxal (MG), a spontaneous by-product of energy metabolism. This study is able to show that a phosphorylation of threonine-107 (T107) in the (rate-limiting) Glyoxalase 1 (Glo1) protein, mediated by Ca²⁺/calmodulin-dependent kinase II delta (CamKIIδ), is associated with elevated catalytic efficiency of Glo1 (lower K_M; higher V_max). Additionally, we observe proteasomal degradation of non-phosphorylated Glo1 via ubiquitination does occur more rapidly as compared with native Glo1. The absence of CamKIIδ is associated with poor detoxification capacity and decreased protein content of Glo1 in a murine CamKIIδ knockout model. Therefore, phosphorylation of T107 in the Glo1 protein by CamKIIδ is a quick and precise mechanism regulating Glo1 activity, which is experimentally linked to an altered Glo1 status in cancer, diabetes, and during aging.