CYP2D6 genotype may moderate measures of brain structure in methamphetamine users

Structural indices of brain aging in methamphetamine use disorder

BACKGROUND

Methamphetamine use is surging globally. It has been linked to premature stroke, Parkinsonism, and dementia, suggesting that it may accelerate brain aging.

METHODS

We performed a retrospective study to determine if structural indices of brain aging were more prevalent prior to old age (26 - 54 years) in individuals with Methamphetamine Use Disorder (MUD), who were in early abstinence (M ± SD = 22.1 ± 25.6 days) than in healthy control (HC) participants. We compared T1-weighted MRI brain scans in age- and sex-matched groups (n = 89/group) on three structural features of brain aging: the brain volume/cerebrospinal fluid (BV/CSF) index, volume of white matter hypointensities/lesions, and choroid plexus volume.

RESULTS

The MUD group had a lower mean BV/CSF index and larger volumes of white matter hypointensities and choroid plexus (p-values < 0.01). Regression analyses showed significant age-by-group effects, indicating different age trajectories of the BV/CSF index and choroid plexus volume, consistent with abnormal global brain atrophy and choroid plexus pathology in the MUD group. Significant age and group main effects reflected a larger volume of white matter hypointensities for older participants across groups and for the MUD group irrespective of age. None of the three measures of brain aging correlated significantly with recent use or duration of recent abstinence from methamphetamine.

CONCLUSIONS

Premature brain pathology, which may reflect cerebrovascular damage and dysfunction of the choroid plexus, occurs in people with MUD. Such pathology may affect cognition and thereby efficacy of behavioral treatments for MUD.

The Common Denominators of Parkinson's Disease Pathogenesis and Methamphetamine Abuse

The pervasiveness and mortality associated with methamphetamine abuse have doubled during the past decade, suggesting a possible worldwide substance use crisis. Epitomizing the pathophysiology and toxicology of methamphetamine abuse proclaims severe signs and symptoms of neurotoxic and neurobehavioral manifestations in both humans and animals. Most importantly, chronic use of this drug enhances the probability of developing neurodegenerative diseases manifolds. Parkinson's disease is one such neurological disorder, which significantly and evidently not only shares a number of toxic pathogenic mechanisms induced by methamphetamine exposure but is also interlinked both structurally and genetically. Methamphetamine-induced neurodegeneration involves altered dopamine homeostasis that promotes the aggregation of α-synuclein protofibrils in the dopaminergic neurons and drives these neurons to make them more vulnerable to degeneration, as recognized in Parkinson's disease. Moreover, the pathologic mechanisms such as mitochondrial dysfunction, oxidative stress, neuroinflammation and decreased neurogenesis detected in methamphetamine abusers dramatically resemble to what is observed in Parkinson's disease cases. Therefore, the present review comprehensively cumulates a holistic illustration of various genetic and molecular mechanisms putting across the notion of how methamphetamine administration and intoxication might lead to Parkinson's disease-like pathology and Parkinsonism.

Cortical thickness and related depressive symptoms in early abstinence from chronic methamphetamine use

Methamphetamine use is surging globally as a cause of morbidity and mortality. Treatment is typically sought in early abstinence, when craving and depressive symptoms are intense, contributing to relapse and poor outcomes. To advance an understanding of this problem and identify therapeutic targets, we conducted a retrospective analysis of brain structure in 89 adults with Methamphetamine Use Disorder who were in early abstinence and 89 healthy controls. Unlike most prior research, the participants did not significantly differ in age, sex and recent use of alcohol and tobacco (p-values ≥ 0.400). We analysed thickness across the entire cerebral cortex by fitting a general linear model to identify differences between groups. Follow-up regressions were performed to determine whether cortical thickness in regions showing group differences was related to craving, measured on a visual analogue scale, or to the Beck Depression Inventory score. Participants in early methamphetamine abstinence (M ± SD = 22.1 ± 25.6 days) exhibited thinner cortex in clusters within bilateral frontal, parietal, temporal, insular, and right cingulate cortices relative to controls (p-values < 0.001, corrected for multiple comparisons). Unlike craving (β = 0.007, p = 0.947), depressive symptoms were positively correlated with cortical thickness across clusters (β = 0.239, p = 0.030) and with thickness in the anterior cingulate cluster (β = 0.246, p = 0.027) in the methamphetamine-dependent group. Inasmuch as anterior cingulate pathology predicts response to antidepressants for Major Depressive Disorder, cingulate structure may also identify patients with Methamphetamine Use Disorder who can benefit from antidepressant medication.

Sex Differences in Substance Use Disorders: A Neurobiological Perspective

Clinical studies provide fundamental knowledge of substance use behaviors (substance of abuse, patterns of use, relapse rates). The combination of neuroimaging approaches reveal correlation between substance use disorder (SUD) and changes in neural structure, function, and neurotransmission. Here, we review these advances, placing special emphasis on sex specific findings from structural neuroimaging studies of those dependent on alcohol, nicotine, cannabis, psychostimulants, or opioids. Recent clinical studies in SUD analyzing sex differences reveal neurobiological changes that are differentially impacted in common reward processing regions such as the striatum, hippocampus, amygdala, insula, and corpus collosum. We reflect on the contribution of sex hormones, period of drug use and abstinence, and the potential impact of these factors on the interpretation of the reported findings. With the overall recognition that SUD impacts the brains of females and males differentially, it is of fundamental importance that future research is designed with sex as a variable of study in this field. Improved understanding of neurobiological changes in males and females in SUD will advance knowledge underlying sex-specific susceptibility and the neurobiological impact in these disorders. Together these findings will inform future treatments that are tailor designed for improved efficacy in females and males with SUD.

4-Fluoromethamphetamine (4-FMA) induces in vitro hepatotoxicity mediated by CYP2E1, CYP2D6, and CYP3A4 metabolism

4-Fluoromethamphetamine (4-FMA) is an amphetamine-like psychoactive substance with recognized entactogenic and stimulant effects, but hitherto unclear toxicological mechanisms. Taking into consideration that the vast majority of 4-FMA users consume this substance through oral route, the liver is expected to be highly exposed. The aim of this work was to determine the hepatotoxic potential of 4-FMA using in vitro hepatocellular models: primary rat hepatocytes (PRH), human hepatoma cell lines HepaRG and HepG2, and resorting to concentrations ranging from 37 μM to 30 mM, during a 24-h exposure. EC₅₀ values, estimated from the MTT viability assay data, were 2.21 mM, 5.59 mM and 9.57 mM, for each model, respectively. The most sensitive model, PRH, was then co-exposed to 4-FMA and cytochrome P450 (CYP) inhibitors to investigate the influence of metabolism on the toxicity of 4-FMA. Results show that CYP2E1, CYP3A4 and CYP2D6 have major roles in 4-FMA cytotoxicity. Inhibition of CYP2D6 and CYP3A4 led to left-geared shifts in the concentration-response curves of 4-FMA, hinting at a role of these metabolic enzymes for detoxifying 4-FMA, while CYP2E1 inhibition pointed towards a toxifying role of this enzyme in 4-FMA metabolism at physiologically-relevant concentrations. The drug also destabilised mitochondrial membrane potential and decreased ATP levels, increased the production of reactive oxygen and nitrogen species and compromised thiol antioxidant defences. 4-FMA further affected PRH integrity by interfering with the machinery of apoptosis and necrosis, increasing the activity of initiator and effector caspases, and causing loss of cell membrane integrity. Potential for autophagy was also observed. This research contributes to the growing body of evidence regarding the toxicity of new psychoactive substances, in particular regarding their hepatotoxic effects; the apparent influence of metabolism over the resulting cytotoxicity of 4-FMA shows that there is a substantial degree of unpredictability of the consequences for users that could be independent of the dose.

Age Influences Loss Aversion Through Effects on Posterior Cingulate Cortical Thickness

Decision-making strategies shift during normal aging and can profoundly affect wellbeing. Although overweighing losses compared to gains, termed "loss aversion," plays an important role in choice selection, the age trajectory of this effect and how it may be influenced by associated changes in brain structure remain unclear. We therefore investigated the relationship between age and loss aversion, and tested for its mediation by cortical thinning in brain regions that are susceptible to age-related declines and are implicated in loss aversion - the insular, orbitofrontal, and anterior and posterior cingulate cortices. Healthy participants (n = 106, 17-54 years) performed the Loss Aversion Task. A subgroup (n = 78) provided structural magnetic resonance imaging scans. Loss aversion followed a curvilinear trajectory, declining in young adulthood and increasing in middle-age, and thinning of the posterior cingulate cortex mediated this trajectory. The findings suggest that beyond a threshold in middle adulthood, atrophy of the posterior cingulate cortex influences loss aversion.