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Highs and lows of cannabinoid-dopamine interactions: effects of genetic variability and pharmacological modulation of catechol-O-methyl transferase on the acute response to delta-9-tetrahydrocannabinol in humans. Psychopharmacology (Berl) 2019; 236:3209-3219. [PMID: 31187152 DOI: 10.1007/s00213-019-05273-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Accepted: 05/10/2019] [Indexed: 12/15/2022]
Abstract
RATIONALE The catechol-O-methyl transferase (COMT) enzyme has been implicated in determining dopaminergic tone and the effects of delta-9-tetrahydrocannabinol (THC) in the human brain. OBJECTIVE This study was designed to evaluate the effect of (1) a functional polymorphism and (2) acute pharmacological inhibition of COMT on the acute response to THC in humans. METHODS Sub-study I: The effect of intravenous (IV) THC (0.05 mg/kg) was investigated in 74 healthy subjects genotyped for the COMT rs4680 (Val/Met) polymorphism in a 2-test-day double-blind, randomized, placebo-controlled study. Sub-study II: COMT rs4680 homozygous subjects (Val/Val and Met/Met) from sub-study I received the COMT enzyme inhibitor tolcapone (200 mg) followed by IV THC or placebo on two additional test days. Subjective, behavioral, and cognitive data were obtained periodically on each test day. RESULTS Sub-study I: Val/Val individuals were most sensitive to THC-induced attention and working memory deficits. In contrast, the psychotomimetic and subjective effects of THC were not influenced by COMT genotype. Sub-study II: Tolcapone reduced THC-induced working memory deficits, but not THC's psychotomimetic effects. Tolcapone and COMT genotype (met/met) were associated with an increased report of feeling "mellow." CONCLUSIONS The interaction between COMT rs4680 polymorphisms and tolcapone on the cognitive, but not on the psychotomimetic and overall subjective effects of THC, suggests that modulation of dopaminergic signaling may selectively influence specific cannabinoid effects in healthy individuals. The role of dopaminergic signaling in the cognitive effects of cannabinoids should be considered in drug development efforts targeting these effects. CLINICALTRIALS.GOV REGISTRATION: https://clinicaltrials.gov/ct2/show/NCT00678730?term=NCT00678730&rank=1 ClinicalTrials.gov Identifier: NCT00678730.
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Fassini PG, Das SK, Suen VMM, Magerowski G, Marchini JS, da Silva Junior WA, Changyu S, Alonso-Alonso M. Appetite effects of prefrontal stimulation depend on COMT Val158Met polymorphism: A randomized clinical trial. Appetite 2019; 140:142-150. [PMID: 31095973 DOI: 10.1016/j.appet.2019.05.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Revised: 04/22/2019] [Accepted: 05/12/2019] [Indexed: 12/13/2022]
Abstract
The regulation of appetite is supported by dopamine-modulated brain circuits. Recent studies have shown that transcranial direct current stimulation (tDCS) aimed at increasing the excitability of the dorsolateral prefrontal cortex can reduce appetite, but the underlying mechanisms remain unknown, and response variability is large. The aim of this study was to determine whether individual differences in Catechol-O-methyl transferase (COMT) Val158Met polymorphism can influence tDCS effects on appetite. Thirty-eight adult women with obesity, classified as carriers or non-carriers of the Met allele, underwent a randomized, double-blind, sham-controlled tDCS intervention involving three phases: Phase I, target engagement (immediate effects of tDCS on working memory performance), Phase II, tDCS only (10 sessions, two weeks), and Phase III, tDCS + hypocaloric diet: (6 sessions, two weeks, 30% energy intake reduction, inpatient). Data were analyzed using linear mixed-effects models and mixed ANCOVA. Appetite was evaluated using visual analogue scales. We found that Met-carriers receiving active tDCS were the only participants who experienced a significant reduction of appetite over time. Conversely, Met non-carriers maintained high levels of appetite during the intervention; this effect was driven by a delayed paradoxical rise in appetite after stimulation. Working memory task performance at phase I correlated with subsequent appetite change in a COMT-dependent manner: speed improvements during the task predicted appetite increase in Met carriers and appetite reduction in Met non-carriers. Our findings suggest that genotype differences impacting dopamine levels influence prefrontal tDCS effects on appetite. This source of variability should be considered in the design of future studies.
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Affiliation(s)
- Priscila Giacomo Fassini
- Laboratory of Bariatric and Nutritional Neuroscience, Center for the Study of Nutrition Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, Boston, MA 02215, United States
| | - Sai Krupa Das
- Energy Metabolism Laboratory, Jean Mayer USDA Human Nutrition Center on Aging, Tufts University, 711 Washington Street, Boston, MA 02111-1524, United States
| | - Vivian Marques Miguel Suen
- Department of Internal Medicine, Ribeirão Preto Medical School, University of São Paulo, Avenida Bandeirantes, 3900. Monte Alegre, CEP: 14049-900, Ribeirão Preto, São Paulo, Brazil
| | - Greta Magerowski
- Laboratory of Bariatric and Nutritional Neuroscience, Center for the Study of Nutrition Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, Boston, MA 02215, United States
| | - Júlio Sérgio Marchini
- Department of Internal Medicine, Ribeirão Preto Medical School, University of São Paulo, Avenida Bandeirantes, 3900. Monte Alegre, CEP: 14049-900, Ribeirão Preto, São Paulo, Brazil
| | - Wilson Araújo da Silva Junior
- Department of Internal Medicine, Ribeirão Preto Medical School, University of São Paulo, Avenida Bandeirantes, 3900. Monte Alegre, CEP: 14049-900, Ribeirão Preto, São Paulo, Brazil
| | - Shen Changyu
- Department of Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, Boston, MA 02215, United States
| | - Miguel Alonso-Alonso
- Laboratory of Bariatric and Nutritional Neuroscience, Center for the Study of Nutrition Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, Boston, MA 02215, United States.
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New Repeat Polymorphism in the AKT1 Gene Predicts Striatal Dopamine D2/D3 Receptor Availability and Stimulant-Induced Dopamine Release in the Healthy Human Brain. J Neurosci 2017; 37:4982-4991. [PMID: 28416594 DOI: 10.1523/jneurosci.3155-16.2017] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 03/31/2017] [Accepted: 04/05/2017] [Indexed: 12/21/2022] Open
Abstract
The role of the protein kinase Akt1 in dopamine neurotransmission is well recognized and has been implicated in schizophrenia and psychosis. However, the extent to which variants in the AKT1 gene influence dopamine neurotransmission is not well understood. Here we investigated the effect of a newly characterized variant number tandem repeat (VNTR) polymorphism in AKT1 [major alleles: L- (eight repeats) and H- (nine repeats)] on striatal dopamine D2/D3 receptor (DRD2) availability and on dopamine release in healthy volunteers. We used PET and [11C]raclopride to assess baseline DRD2 availability in 91 participants. In 54 of these participants, we also measured intravenous methylphenidate-induced dopamine release to measure dopamine release. Dopamine release was quantified as the difference in specific binding of [11C]raclopride (nondisplaceable binding potential) between baseline values and values following methylphenidate injection. There was an effect of AKT1 genotype on DRD2 availability at baseline for the caudate (F(2,90) = 8.2, p = 0.001) and putamen (F(2,90) = 6.6, p = 0.002), but not the ventral striatum (p = 0.3). For the caudate and putamen, LL showed higher DRD2 availability than HH; HL were in between. There was also a significant effect of AKT1 genotype on dopamine increases in the ventral striatum (F(2,53) = 5.3, p = 0.009), with increases being stronger in HH > HL > LL. However, no dopamine increases were observed in the caudate (p = 0.1) or putamen (p = 0.8) following methylphenidate injection. Our results provide evidence that the AKT1 gene modulates both striatal DRD2 availability and dopamine release in the human brain, which could account for its association with schizophrenia and psychosis. The clinical relevance of the newly characterized AKT1 VNTR merits investigation.SIGNIFICANCE STATEMENT The AKT1 gene has been implicated in schizophrenia and psychosis. This association is likely to reflect modulation of dopamine signaling by Akt1 kinase since striatal dopamine hyperstimulation is associated with psychosis and schizophrenia. Here, using PET with [11C]raclopride, we identified in the AKT1 gene a new variable number tandem repeat (VNTR) marker associated with baseline striatal dopamine D2/D3 receptor availability and with methylphenidate-induced striatal dopamine increases in healthy volunteers. Our results confirm the involvement of the AKT1 gene in modulating striatal dopamine signaling in the human brain. Future studies are needed to assess the association of this new VNTR AKT1 variant in schizophrenia and drug-induced psychoses.
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