Ghrelin in addictive behaviors: plenus venter non studet libenter

G-CuP: the effect of a forced oral glucose intake on alcohol craving and mesolimbic cue reactivity in alcohol dependence-study protocol of a randomized, double-blind, placebo-controlled crossover study

BACKGROUND

Multiple studies indicate that a lower plasma level of the acetylated form of the appetite-regulating hormone ghrelin and higher plasma levels of insulin lead to a reduction in subjective alcohol craving and a reduced mesolimbic cue reactivity in functional magnetic resonance imaging (fMRI) when being exposed to alcohol-associated stimuli. The ghrelin level can physiologically be reduced by the induction of stomach distension and the ingestion of glucose or lipids.

METHODS

A total of 108 alcohol-dependent patients aged between 18 and 65 years are examined in the randomized, double-blind, placebo-controlled crossover study. After collecting demographic and psychometric data, participants take part in an alcohol exposure session. Afterwards, the participants go through the intervention condition (oral glucose intake) and the control condition (placebo intake) in a randomized order on two examination days. Blood samples are taken repeatedly (every 10 min) during the study course on both measuring days to determine changes in acetylated and total ghrelin and insulin plasma levels. In parallel, subjective alcohol craving after the glucose or placebo intake as the primary outcome is assessed using the Alcohol Urge Questionnaire (AUQ) and a visual analog scale (VAS). To examine the mesolimbic cue reactivity as the secondary outcome, a fMRI measurement is conducted while being exposed to alcohol-related stimuli. Appropriate statistical analysis will be used for the evaluation of the outcomes.

DISCUSSION

If successful, the results of this study could offer alcohol-dependent patients a new potential option for acute short-term reduction of alcohol craving and thus prevent relapses and prolong periods of abstinence in the long term.

TRIAL REGISTRATION

German Clinical Trials Register DRKS00022419 (UTN: U1111-1278-9428). Retrospectively registered on September 15, 2020.

Ghrelin modulates mesolimbic reactivity to alcohol cues in alcohol-addicted subjects: a functional imaging study

Ghrelin has been shown to be involved in the pathophysiology of alcohol dependence, affecting alcohol self-administration and craving. However, the mechanism of action in alcohol dependence still has to be determined. We thus investigated whether ghrelin is associated with mesolimbic cue reactivity to alcohol cues and alcohol craving in recently detoxified alcohol-addicted subjects. We included 41 recently detoxified alcohol-dependent individuals. Functional magnetic resonance imaging (fMRI) was used to study mesolimbic cue reactivity during the presentation of alcohol-related pictures. Additionally, we assessed patients' alcohol craving using the Alcohol Urge Questionnaire and a visual analogue scale. Plasma concentrations of total and acylated (activated) ghrelin were measured in parallel to the fMRI session. The association between ghrelin plasma concentrations, mesolimbic cue reactivity and alcohol craving was assessed by performing correlation and mediation analyses. Alcohol-induced brain response in a network of brain clusters, including the right and left ventral striatum, showed a significant positive association with acylated ghrelin plasma concentration. Additionally, acylated ghrelin was significantly associated with craving. Mediation analyses showed that the association between acylated ghrelin plasma concentration and alcohol craving is mediated by a cue-induced brain response in the ventral striatum. Based on the finding that ghrelin modulates mesolimbic reactivity to alcohol cues, the following should be considered: If alcohol craving and the appetitive status were interrelated, this has to be taken into account when implementing fMRI studies for addictive disorders. Moreover, appetite regulation seems to represent a valid treatment target for reducing cue reactivity in addictive disorders.

Drinking water to reduce alcohol craving? A randomized controlled study on the impact of ghrelin in mediating the effects of forced water intake in alcohol addiction

BACKGROUND

Recent data suggest that ghrelin is involved in the pathophysiology of alcohol use disorders, affecting alcohol self-administration and craving. Gastric ghrelin secretion is reduced by stomach distension. We now tested the hypothesis whether the clinically well-known effects of high-volume water intake on craving reduction in alcoholism is mediated by acute changes in ghrelin secretion.

METHODS

In this randomized human laboratory study, we included 23 alcohol-dependent male inpatient subjects who underwent alcohol cue exposure. Participants of the intervention group drank 1000ml of mineral water within 10min directly thereafter, compared to the participants of the control group who did not. Craving and plasma concentrations of acetylated ghrelin were measured ten times during the 120min following the alcohol cue exposure session.

RESULTS

In the intervention group, a significant decrease in acetylated ghrelin in plasma compared to the control group was observed. This decrease was correlated to a reduction in patients' subjective level of craving. In the control group, no decrease of acetylated ghrelin in plasma and no association between alcohol craving and changes in plasma concentrations of acetylated ghrelin were observed.

CONCLUSIONS

Our results present new evidence that the modulation in the ghrelin system by oral water intake mediates the effects of volume intake with craving reduction in alcohol use disorders. Hence, in addition to pharmacological interventions with ghrelin antagonists, the reduction of physiological ghrelin secretion might be a target for future interventions in the treatment of alcohol craving.

The Role of the Ghrelin System in Drug Addiction

In the past years, a significant volume of research has implicated the appetitive hormone ghrelin in the mechanisms underlying drug use and addiction. From a neuroscientific standpoint, ghrelin modulates both reward and stress pathways, two key drivers of substance use behaviors. Previous investigations support a connection between the ghrelin system and alcohol, stimulants, and tobacco use in both animals and humans, while the research on opioids and cannabis is scarce. In general, upregulation of the ghrelin system seems to enhance craving for drugs as well as substances use. On the other hand, acute and chronic exposure to drugs of abuse influences the ghrelin system at different levels. This chapter summarizes the literature on the relationship between the ghrelin system and substance-related behaviors. We also review recent work investigating the ghrelin system as a potential pharmacological target for treating substance use disorders and discuss the need for additional research.