Replication of the pharmacogenetic effect of rs678849 on buprenorphine efficacy in African-Americans with opioid use disorder.

Many patients with opioid use disorder do not have successful outcomes during treatment but the underlying reasons are not well understood. An OPRD1 variant (rs678849) was previously associated with methadone and buprenorphine efficacy in African-Americans with opioid use disorder. The objective of this study was to determine if the effect of rs678849 on opioid use disorder treatment outcome could be replicated in an independent population. Participants were recruited from African-American patients who had participated in previous studies of methadone or buprenorphine treatment at the outpatient treatment research clinic of the NIDA Intramural Research Program in Baltimore, MD, USA between 2000 and 2017. Rs678849 was genotyped retrospectively, and genotypes were compared with urine drug screen results from the previous studies for opioids other than the one prescribed for treatment. Genotypes were available for 24 methadone patients and 55 buprenorphine patients. After controlling for demographics, the effect of rs678849 genotype was significant in the buprenorphine treatment group (RR = 1.69, 95% confidence interval (CI) 1.59-1.79, p = 0.021). Buprenorphine patients with the C/C genotype were more likely to have opioid-positive drug screens than individuals with the C/T or T/T genotypes, replicating the original pharmacogenetic finding. The effect of genotype was not significant in the methadone group (p = 0.087). Thus, the genotype at rs678849 is associated with buprenorphine efficacy in African-Americans being treated for opioid use disorder. This replication suggests that rs678849 genotype may be a valuable pharmacogenetic marker for deciding which opioid use disorder medication to prescribe in this population.

Assessment of pioglitazone and proinflammatory cytokines during buprenorphine taper in patients with opioid use disorder.

BACKGROUND: Preliminary evidence suggested that the PPARγ agonist pioglitazone reduces opioid-withdrawal symptoms, possibly by inhibiting increases in proinflammatory cytokines. METHODS: A randomized, placebo-controlled clinical trial was conducted utilizing two different study designs (entirely outpatient, and a combination of inpatient and outpatient) to evaluate the safety and efficacy of pioglitazone as an adjunct medication for people with opioid physical dependence undergoing a buprenorphine taper. Participants were stabilized on buprenorphine/naloxone (sublingual, up to 16/4 mg/day), then randomized to receive oral pioglitazone (up to 45 mg/day) or placebo before, during, and after buprenorphine taper. Outcome measures included the Subjective Opiate Withdrawal Scale (SOWS) and Clinical Opiate Withdrawal Scale, use of rescue medications to alleviate opioid withdrawal symptoms, and opioid-positive urine specimens. Cerebrospinal fluid (CSF) and plasma were collected during the taper in a subset of participants for measurement of proinflammatory cytokines. RESULTS: The clinical trial was prematurely terminated due to slow enrollment; 40 participants per group were required for adequate statistical power to test study hypotheses. Twenty-four participants enrolled; 17 received at least one dose of study medication (6 pioglitazone, 11 placebo). SOWS scores were higher in the pioglitazone arm than in the placebo arm after adjusting for use of rescue medications; participants in the pioglitazone arm needed more rescue medications than the placebo arm during the post-taper phase. SOWS scores were positively correlated with monocyte chemoattractant protein-1 (MCP-1) in CSF (r = 0.70, p = 0.038) and plasma (r = 0.77, p = 0.015). Participants having higher levels of plasma MCP-1 reported higher SOWS, most notably after the buprenorphine taper ended. CONCLUSIONS: Results from this study provide no evidence that pioglitazone reduces opioid withdrawal symptoms during buprenorphine taper. High correlations between MCP-1 and opioid withdrawal symptoms support a role of proinflammatory processes in opioid withdrawal. TRIAL REGISTRATION: clinicaltrials.gov identifier: NCT01517165.

Altered behavioral development in Nrf2 knockout mice following early postnatal exposure to valproic acid.

Early exposure to valproic acid results in autism-like neural and behavioral deficits in humans and other animals through oxidative stress-induced neural damage. In the present study, valproic acid was administered to genetically altered mice lacking the Nrf2 (nuclear factor-erythroid 2 related factor 2) gene on postnatal day 14 (P14). Nrf2 is a transcription factor that induces genes that protect against oxidative stress. It was found that valproic acid-treated Nrf2 knockout mice were less active in open field activity chambers, less successful on the rotorod, and had deficits in learning and memory in the Morris water maze compared to the valproic acid-treated wild type mice. Given these results, it appears that Nrf2 knockout mice were more sensitive to the neural damage caused by valproic acid administered during early development.

Differential sensitivity of Pak5, Pak6, and Pak5/Pak6 double-knockout mice to the stimulant effects of amphetamine and exercise-induced alterations in body weight.

OBJECTIVES: PAK5 and PAK6 are protein kinases highly expressed in the brain. Previously, we observed that Pak6 knockout mice gained significantly more weight during development than Pak5 knockout mice as well as wild-type controls and double-knockout mice lacking both Pak5 and Pak6. In this study, we assessed the effects of exercise on food intake and weight gain of these mice as well as their sensitivity to the stimulant effects of amphetamine. METHODS: Mice of each genotype were placed in cages with free access to run wheel exercise or in cages without run wheels for a total of 74 days. Food and fluid intake as well as body weight of each mouse were measured on a weekly basis. Finally, mice were given a high dose of amphetamine and activity levels were observed immediately thereafter for 90 minutes. Brains and testes of mice were assayed for protein levels of the estrogen alpha and progesterone receptors. RESULTS: While run wheel mice consumed significantly more food, they weighed less than non-run wheel mice. In addition, although Pak6 knockout mice consumed the same amount of food as wild-type mice, they were significantly heavier regardless of run wheel condition. Pak5 knockout mice were found to be more active than other genotypes after amphetamine treatment. Finally, protein levels of the progesterone and estrogen alpha receptors were altered in brain and testes of the Pak6 knockout mice. DISCUSSION: Collectively, these data suggest that PAK6 play a role in weight gain unrelated to exercise and caloric intake and that Pak5 knockout mice are more sensitive to the stimulant effects of amphetamine.

Functional deficits in PAK5, PAK6 and PAK5/PAK6 knockout mice.

The p21-activated kinases are effector proteins for Rho-family GTPases. PAK4, PAK5, and PAK6 are the group II PAKs associated with neurite outgrowth, filopodia formation, and cell survival. Pak4 knockout mice are embryonic lethal, while Pak5, Pak6, and Pak5/Pak6 double knockout mice are viable and fertile. Our previous work found that the double knockout mice exhibit locomotor changes and learning and memory deficits. We also found some differences with Pak5 and Pak6 single knockout mice and the present work further explores the potential differences of the Pak5 knockout and Pak6 knockout mice in comparison with wild type mice. The Pak6 knockout mice were found to weigh significantly more than the other genotypes. The double knockout mice were found to be less active than the other genotypes. The Pak5 knockout mice and the double knockout mice performed worse on the rotorod test. All the knockout genotypes were found to be less aggressive in the resident intruder paradigm. The double knockout mice were, once again, found to perform worse in the active avoidance assay. These results indicate, that although some behavioral differences are seen in the Pak5 and Pak6 single knockout mice, the double knockout mice exhibit the greatest changes in locomotion and learning and memory.