Association of the Sweet-Liking Phenotype and Craving for Alcohol With the Response to Naltrexone Treatment in Alcohol Dependence: A Randomized Clinical Trial

Identification of moderators of the response to naltrexone hydrochloride treatment for alcohol dependence could improve clinical care for patients with alcohol use disorders. To investigate the preliminary finding that the sweet-liking (SL) phenotype interacts with a high level of craving for alcohol and is associated with an improved response to naltrexone in alcohol dependence. This 12-week double-blind, randomized, placebo-controlled clinical trial was conducted from February 1, 2010, to April 30, 2012, in an academic outpatient medical center. Eighty actively drinking patients were randomized by the SL (n = 22) or the sweet-disliking (SDL) (n = 58) phenotype and by pretreatment high (n = 40) or low (n = 40) craving for alcohol, with high craving defined as greater than the median. Patients and staff were blinded to categorization. Patients were excluded for unstable medical or psychiatric illness, including dependence on drugs other than nicotine. Four patients (2 in the placebo arm and 2 in the naltrexone arm) stopped medication therapy because of adverse effects. Data were analyzed from January 15, 2013, to May 15, 2016, based on intention to treat. Oral naltrexone hydrochloride, 50 mg/d, or daily placebo with weekly to biweekly brief counseling. The a priori hypothesis tested SL/SDL phenotype, pretreatment craving, and their interaction as moderators of frequency of abstinent and heavy drinking days during treatment, assessed with the timeline follow-back method. Eighty patients were randomized (57 men [71%]; 23 women [29%]; mean [SD] age, 47.0 [8.6] years). A nonsignificant effect of naltrexone on heavy drinking was noted (4.8 fewer heavy drinking days; Cohen d = 0.45; 95% CI, -0.01 to 0.90; F1,67 = 3.52; P = .07). The SL phenotype moderated the effect of naltrexone on heavy drinking (6.1 fewer heavy drinking days; Cohen d = 0.58; 95% CI, 0.12-1.03; F1,67 = 5.65; P = .02) and abstinence (10.0 more abstinent days; Cohen d = 0.57; 95% CI, 0.11-1.02; F1,67 = 5.36; P = .02), and high craving moderated heavy drinking (7.1 fewer heavy drinking days; Cohen d = 0.66; 95% CI, 0.20-1.11; F1,67 = 7.37; P = .008). The combination of the SL phenotype and high craving was associated with a strong response to naltrexone, with 17.1 fewer heavy drinking days (Cohen d = 1.07; 95% CI, 0.58-1.54; F1,67 = 19.33; P < .001) and 28.8 more abstinent days (Cohen d = 0.72; 95% CI, 0.25-1.17; F1,67 = 8.73; P = .004) compared with placebo. The SL phenotype and a high craving for alcohol independently and particularly in combination are associated with a positive response to naltrexone. The SL/SDL phenotype and a high craving for alcohol merit further investigation as factors to identify patients with alcohol dependence who are responsive to naltrexone. clinicaltrials.gov Identifier: NCT01296646

Unipolar depression does not moderate responses to the Sweet Taste Test

The Sweet Taste Test (STT) measures hedonic responses to sweet tastes and has been linked to both alcoholism and to a family history of alcoholism. However, STT response profiles in unipolar major depressive disorder (MDD), a disorder characterized by anhedonia, have been minimally investigated

The Ghrelin Signalling System Is Involved in the Consumption of Sweets

The gastric-derived orexigenic peptide ghrelin affects brain circuits involved in energy balance as well as in reward. Indeed, ghrelin activates an important reward circuit involved in natural- as well as drug-induced reward, the cholinergic-dopaminergic reward link. It has been hypothesized that there is a common reward mechanism for alcohol and sweet substances in both animals and humans. Alcohol dependent individuals have higher craving for sweets than do healthy controls and the hedonic response to sweet taste may, at least in part, depend on genetic factors. Rat selectively bred for high sucrose intake have higher alcohol consumption than non-sucrose preferring rats and vice versa. In the present study a group of alcohol-consuming individuals selected from a population cohort was investigated for genetic variants of the ghrelin signalling system in relation to both their alcohol and sucrose consumption. Moreover, the effects of GHS-R1A antagonism on voluntary sucrose- intake and operant self-administration, as well as saccharin intake were investigated in preclinical studies using rodents. The effects of peripheral grelin administration on sucrose intake were also examined. Here we found associations with the ghrelin gene haplotypes and increased sucrose consumption, and a trend for the same association was seen in the high alcohol consumers. The preclinical data show that a GHS-R1A antagonist reduces the intake and self-administration of sucrose in rats as well as saccharin intake in mice. Further, ghrelin increases the intake of sucrose in rats. Collectively, our data provide a clear indication that the GHS-R1A antagonists reduces and ghrelin increases the intake of rewarding substances and hence, the central ghrelin signalling system provides a novel target for the development of drug strategies to treat addictive behaviours

Efficacy and Safety of Baclofen for Alcohol Dependence: A Randomized, Double-Blind, Placebo-Controlled Trial

Recent clinical trials and case-reports indicate that baclofen, a GABAB agonist, may have efficacy for alcohol dependence. Baclofen has been shown to enhance abstinence, to reduce drinking quantity, to reduce craving, and to reduce anxiety in alcohol dependent individuals in two placebo-controlled trials in Italy. However, the clinical trial data with baclofen is limited. The purpose of the present study was to test the efficacy and tolerability of baclofen in alcohol dependence in the United States

Intact hedonic responses to sweet tastes in autism spectrum disorder

The Sweet Taste Test (STT) is a standardized measure designed to index the ability to detect differences in sweet tastes (sweet taste sensitivity) and hedonic responses to sweet tastes (sweet taste liking). Profiles of response on the STT suggest enhanced hedonic responses to sweet tastes in psychiatric disorders characterized by dysfunctional reward processing systems, including binge-eating disorders and substance use disorders, and a putative mechanism governing STT responses is the brain opioid system. The present study examined STT responses in 20 adults with autism spectrum disorder (ASD) and 38 healthy control adults. There were no differences in sweet taste sensitivity or hedonic response to sweet tastes between the ASD and control groups. Within the ASD sample, ASD symptom severity was associated with sweet taste sensitivity, but not hedonic response to sweet taste. Results may ultimately shed light on brain opioid system functioning in ASD

Sweet taste pleasantness is modulated by morphine and naltrexone

Rodent models highlight the key role of µ-opioid receptor (MOR) signaling in palatable food consumption. In humans however, the effects of MOR stimulation on eating and food liking remain unclear. In a bidirectional psychopharmacological cross-over study, 49 healthy men underwent a sweet taste paradigm following double-blind administration of the MOR agonist morphine, placebo, and the opioid antagonist nalt rexone. We hypothesized that behaviors regulated by the endogenous MOR system would be enhanced by MOR agonism, and decreased by antagonism. The strongest drug effects were expected for the sweetest (high-calorie) sucrose solution, as reported in rodents. However, very sweet sucrose-water solutions are considered sickly and aversive by many people (called sweet dislikers). Since both sweet likers and dislikers were tested, we were able to assess whether MOR manipulations affect pleasantness ratings differently depending on both subjective and objective value. As hypothesized, MOR stimulation with morphine increased pleasantness of the sweetest of five sucrose solutions, without enhancing pleasantness of the lower-sucrose solutions. For opioid antagonism, an opposite pattern was observed for the sweetest drink only. This bidirectional effect of agonist and antagonist treatment is consistent with rodent findings that MOR manipulations most strongly affect the highest-calorie foods. Importantly, the observed drug effects on pleasantness of the sweetest drink did not differ between sweet likers and dislikers. We speculate that the MOR system promotes survival in part by increasing concordance between the objective (caloric) and subjective (hedonic) value of food stimuli, so that feeding behaviour becomes more focused on the richest food available

Behavioral genetics and taste

This review focuses on behavioral genetic studies of sweet, umami, bitter and salt taste responses in mammals. Studies involving mouse inbred strain comparisons and genetic analyses, and their impact on elucidation of taste receptors and transduction mechanisms are discussed. Finally, the effect of genetic variation in taste responsiveness on complex traits such as drug intake is considered. Recent advances in development of genomic resources make behavioral genetics a powerful approach for understanding mechanisms of taste

High locomotor reactivity to novelty is associated with an increased propensity to choose saccharin over cocaine: new insights into the vulnerability to addiction.

Drug addiction is associated with a relative devaluation of natural or socially-valued reinforcers that are unable to divert addicts from seeking and consuming the drug. Before protracted drug exposure, most rats prefer natural rewards, such as saccharin, over cocaine. However, a subpopulation of animals prefer cocaine over natural rewards and are thought to be vulnerable to addiction. Specific behavioral traits have been associated with different dimensions of drug addiction. For example, anxiety predicts loss of control over drug intake whereas sensation seeking and sign-tracking are markers of a greater sensitivity to the rewarding properties of the drug. However, how these behavioral traits predict the disinterest for natural reinforcers remains unknown. In a population of rats, we identified sensation seekers (HR) on the basis of elevated novelty-induced locomotor reactivity, high anxious rats (HA) based on the propensity to avoid open arms in an elevated-plus maze and sign-trackers (ST) that are prone to approach, and interaction with, reward-associated stimuli. Rats were then tested on their preference for saccharin over cocaine in a discrete-trial choice procedure. We show that HR rats display a greater preference for saccharin over cocaine compared with ST and HA whereas the motivation for the drug was comparable between the three groups. The present data suggest that high locomotor reactivity to novelty, or sensation seeking, by predisposing to an increased choice toward non-drug rewards at early stages of drug use history, may prevent the establishment of chronic cocaine use.This work was funded by an INSERM AVENIR and Agence Nationale de la Recherche (ANR) ANR12 SAMA00201 grant to DB, the région Poitou-Charentes, an AXA research fund fellowship to ABR, and a Ministère de la Recherche et de la Technologie grant to NV. AM was supported by the Behavioural and Clinical Neuroscience Institute of Cambridge.This is the accepted manuscript of a paper published in Neuropsychopharmacology (2015) 40, 577–589; doi:10.1038/npp.2014.204; published online 17 September 2014

Understanding sweet-liking phenotypes and their implications for obesity: narrative review and future directions

Building on a series of recent studies that challenge the universality of sweet liking, here we review the evidence for multiple sweet-liking phenotypes which strongly suggest, humans fall into three hedonic response patterns: extreme sweet likers (ESL), where liking increases with sweetness, moderate sweet likers (MSL), who like moderate but not intense sweetness, and sweet dislikers (SD), who show increasing aversion as sweetness increases. This review contrasts how these phenotypes differ in body size and composition, dietary intake and behavioural measures to test the widely held view that sweet liking may be a key driver of obesity. Apart from increased consumption of sugar-sweetened beverages in ESL, we found no clear evidence that sweet liking was associated with obesity and actually found some evidence that SD, rather than ESL, may have slightly higher body fat. We conclude that ESL may have heightened awareness of internal appetite cues that could protect against overconsumption and increased sensitivity to wider reward. We note many gaps in knowledge and the need for future studies to contrast these phenotypes in terms of genetics, neural processing of reward and broader measures of behaviour. There is also the need for more extensive longitudinal studies to determine the extent to which these phenotypes are modified by exposure to sweet stimuli in the context of the obesogenic environment