Serotonin transporter-linked polymorphic region (5-HTTLPR) genotype is associated with cortisol responsivity to naloxone challenge

Independent and Interactive Effects of OPRM1 and DAT1 Polymorphisms on Alcohol Consumption and Subjective Responses in Social Drinkers

BACKGROUND

The current study examined independent and interactive effects of polymorphisms of the mu opioid receptor gene (OPRM1, A118G) and variable number tandem repeats of the dopamine transporter gene (DAT1, SLC6A3) on alcohol consumption and subjective responses to alcohol in 127 young, healthy, social drinkers.

METHODS

Participants completed an in-person assessment, which included self-reported alcohol drinking patterns and blood sampling for DNA, and in a second visit, a cumulative alcohol dosing procedure with subjective ratings across multiple time points and breath alcohol contents (0.03 to 0.1%). DNA was analyzed for OPRM1 AA versus AG/GG (*G) genotypes, DAT1 10-repeat allele (A10) versus 9 or lesser alleles (A9), and ancestral informative markers.

RESULTS

There were significant epistatic interactions between OPRM1 and DAT1 genotypes. Subjective High Assessment Scale scores after alcohol consumption were highest in *G and A9 carriers, and lowest in *G and A10 carriers. Negative subjective effects were also highest in *G and A9 carriers. Effects were similar in a sensitivity analysis limited to Caucasian subjects. There were independent and epistatic interactions on drinking. The OPRM1 *G allele was independently associated with fewer heavy drinking days. The A9 allele was associated with a greater number of drinking days, which was attenuated in carriers of the *G allele.

CONCLUSIONS

These findings highlight the biological importance of interactions between these 2 genes and interactions between brain opioid and dopamine systems.

Genetic and environmental modulation of neurotrophic and anabolic stress response: Counterbalancing forces

The serotonin transporter genetic variant 5HTTLPR influences activation and feedback control of the hypothalamic-pituitary-adrenal axis, and has been shown to influence the effect of stressful life events on behavioral health. We recently reported that 5HTTLPR modulates cortisol response in healthy military men exposed to intense stress. Less is known of its combined effects with environmental factors in this context, or of its effect on neuroprotective stress responses. In this follow-up study, we examined the unique and combined effects of 5HTTLPR and prior trauma exposure on neuroprotective (salivary nerve growth factor [sNGF]), anabolic (dehydroepiandrosterone sulfate [DHEAS] and testosterone), and catabolic (cortisol) stress responses. Ninety-three healthy, active-duty military men were studied before, during, and 24h after a stressful 12-day survival course. Distinct and interactive effects of 5HTTLPR long allele carriage [L] versus homozygous short allele carriage [SS]) and prior trauma exposure (low versus high) were evaluated, after which a priori group comparisons were performed between hypothesized high resilience (L/low) and low resilience (SS/high) groups. For sNGF, L/low produced the greatest sNGF throughout stress exposure while SS/high demonstrated the smallest; L/high and SS/low bisected these two extremes and were nearly identical to each other (i.e., SS/high < SS/low = L/high < L/low). Thus, 5HTTLPR and prior trauma exposure demonstrated counterbalancing (additive) forces. Similar patterns were found for DHEAS. To our knowledge, this study is the first to report counterbalancing genetic and environmental effects on novel biomarkers related to resilience in humans exposed to real-world stress. These findings have profound implications for health, performance and training in high-stress occupational settings.

Evaluation of the promoter region polymorphism (5-HTTLPR) in the serotonin transporter gene in females with postpartum depression

The aim of the present study was to investigate the association between polymorphism in the serotonin transporter (5-HTT) gene-linked polymorphic region (5-HTTLPR) in the promoter region of the 5-HTT gene and the pathogenesis of postpartum depression (PPD). Blood samples were collected from 120 female patients with PPD and 140 age-matched normal controls. Polymerase chain reaction analysis was performed to detect the 5-HTTLPR polymorphism in these subjects, and the genotype and allele frequencies were compared between the two groups. The disease severity was evaluated using the Hamilton Depression Rating Scale (HAMD) score. The results showed that the frequency of the homozygous long/long (L/L) genotype was significantly lower in the PPD group than that in the control group; by contrast, the frequencies of the heterozygous long/short (L/S) and homozygous S/S genotypes were similar for the two groups, without significant differences. No significant differences were observed in the L and S allele frequencies between the two groups. Furthermore, compared with the L/S heterozygous and S/S homozygous genotypes, patients with PPD with the L/L homozygous genotype had a significantly lower HAMD score. The present results suggest that female patients with PPD carrying the homozygous L/L genotype may be less susceptible to depressive symptoms and that the L/L genotype may be associated with the reduced occurrence of PPD. These findings provide a theoretical basis for the clinical diagnosis and treatment of PPD.

Endogenous opiates and behavior: 2012

This paper is the thirty-fifth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2012 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).