Ghrelin for Alcohol Use in Non-Treatment-Seeking Heavy Drinkers

Objective:

Ghrelin is a 28-amino acid peptide acting as the endogenous ligand for the growth hormone secretagogue receptor (GHS-R). Ghrelin stimulates appetite by acting on the hypothalamic arcuate nucleus (ARC), a region that controls the intake of food and other substances, including alcohol. In addition to the ARC, GHS receptors (GHS-Rs) are also highly expressed in the caudal brain stem, the ventral tegmental area (VTA), hippocampus, substantia nigra, and dorsal and medial raphe nuclei. The expression of the GHS-R in the mesolimbic dopamine (DA) pathway suggests that ghrelin could play a role in reward processing. The role of ghrelin in the DA reward processing and the role of the DA reward system in alcoholism suggest a role of ghrelin in alcoholism. Consistent with this hypothesis, preclinical studies demonstrate that both ghrelin and ethanol activate the cholinergic-dopaminergic reward link, implying neurochemical analogies between ghrelin and ethanol. This supports the hypothesis that ghrelin is involved in mediating the rewarding properties of ethanol. Additional animal experiments demonstrate that the central ghrelin action not only stimulates the reward processing but is also required for stimulation of that system by alcohol. Human studies show reduced ghrelin levels in actively drinking alcoholics; increased ghrelin levels during alcohol abstinence; and a positive correlation between ghrelin level and alcohol craving scores. More recently, a study conducted at Brown University by the PI demonstrated the safety of the administration IV of human ghrelin to non-treatment seeking alcohol-dependent heavy drinking individuals. Furthermore, a preliminary interim analysis shows that IV ghrelin administration may lead to a temporary significant increase in alcohol craving. The primary objective of this protocol is to investigate whether IV ghrelin, as compared to placebo, will increase motivation for alcohol reward, as measured by a progressive ratio (PR) schedule paradigm with IV alcohol self-infusion (primary aim). We will also assess a number of secondary aims. Specifically, we will also assess whether IV ghrelin, as compared to placebo, will also alter urges to drink and the subjective response to IV alcohol. Adverse events will also be assessed to ensure the safety of the IV coadministration of ghrelin and alcohol. During an fMRI/alcohol clamp session, fMRI will be used to see whether ghrelin affects the activation of the ventral striatum induced by acute IV alcohol administration and the incentive salience of cues associated with alcohol administration.

Study Population:

Male and female participants will be non-treatment seeking heavy drinking volunteers.

Design:

The study is designed as a within-subject, double-blind, placebo-controlled study of ghrelin. The first visit will be the initial screening visit. The second and third visits will be PR sessions with IV ethanol, during which each participant will also receive IV ghrelin (or matched placebo). The fourth and fifth visits will combine an fMRI session with an alcohol clamp session (i.e. a fixed dose of alcohol will be administered) and subjects will participate in a modified version of the monetary incentive delay (MID) task in which they will respond to cues that indicate the opportunity to press a button to gain a reward. On some trials the reward will be points that can be exchanged for snack foods while on other trials the reward will be points that will determine how much intravenous alcohol a subject will be given during the alcohol clamp procedure which will immediately follow the modified MID task. After the modified MID task is complete subjects will have a short break and then begin the alcohol IV infusion.

Outcome measures:

The primary measure of this study will be the breakpoint, which is the schedule (number of button presses) at which the individual stops to work for more alcohol. Also, the BrAC exposure measures will be determined. Alcohol craving in response to ghrelin will be measured using the Alcohol Visual Analogue Scale (A-VAS) and the Alcohol Urge Questionnaire (AUQ) during the PR sessions. Sensitivity to alcohol will be measured using the Drug Effects Questionnaire (DEQ), Biphasic Alcohol Effects Scale (BAES), and the Profile of Mood States (POMS), repeatedly during the PR sessions and the CASE Experience Questionnaire (CEQ) at the end of all sessions. fMRI BOLD signal in brain areas associated with incentive salience and areas associated with reward circuitry (including the ventral striatum) will be measured during the fMRI/alcohol clamp session. This study may facilitate the identification of a novel neuropharmacological target, thus facilitating the development of novel pharmacological treatments for alcoholism.

• INCLUSION CRITERIA:

Male and female participants between 21-60 years of age.

Good health as determined by medical history, physical exam, ECG and lab tests.

Creatinine less than to 2 mg/dl.

Female must have a negative urine pregnancy (hCG) test at the start of each study session. Females of childbearing potential who are sexually active and have not been surgically sterilized must agree to use an adequate method of birth control during the study. Adequate methods of contraception for sexually active women are having a male sexual partner(s) who is surgically sterilized prior to inclusion; having a sexual partner(s) who is/are exclusively female; using oral contraceptives (either combined or progestrogen only) with a single-barrier method of contraception consisting of spermicide and condom or diaphragm; using double-barrier contraception, specifically, a condom plus spermicide and a female diaphragm or cervical cap plus spermicide; or using an approved intrauterine device (IUD) with established efficacy.

Participants must drink alcohol regularly at a heavy level, on average greater than 20 drinks per week for men, and greater than 15 drinks per week for women, and not be seeking help for alcohol-related problems.

Participant must be willing to receive two IV lines.

Exclusion criteria

Current or prior history of any clinically significant disease, including CNS, cardiovascular, respiratory, gastrointestinal, hepatic, renal, endocrine, or reproductive disorders.

Specific exclusion criteria related to the administration of ghrelin, are chronic inflammatory diseases (e.g., Crohn s disease, ulcerative colitis, celiac disease) diabetes, obesity (BMI greater than or equal 30 kg/m(2), weight greater than or equal to 120 Kg, high triglycerides level (> 350 mg/dL), history of clinically significant hypotension (e.g.: history of fainting and/or syncopal attacks) and/or resting systolic BP < 100 mmHg.

Positive hepatitis or HIV test at screening.

Current clinically significant major depression or anxiety; or prior clinically significant psychiatric problems, including eating disorders, schizophrenia, bipolar disorder, obsessive compulsive disorder.

Current diagnosis of substance dependence (other than alcohol or nicotine).

Currently seeking treatment for alcohol use disorder.

History of significant withdrawal symptoms or presence of clinically significant withdrawal symptoms (Clinical Institute Withdrawal Assessment (CIWA) score > 8) at screening.

Non-drinkers (alcohol-naive individuals or current abstainers) or no experience drinking 5 or more drinks on one occasion.

Unable to provide a negative urine drug screen.

Pregnancy or intention to become pregnant for women. Female participants will undergo a urine beta-hCG test to ensure they are not pregnant.

Use of prescription or OTC medications known to interact with alcohol within 2 weeks of the study. These include, but may not be limited to: isosorbide, nitroglycerine, benzodiazepines, warfarin, anti-depressants such as amitriptyline, clomipramine and nefazodone, anti-diabetes medications such as glyburide, metformin and tolbutamide, H2-antagonists for heartburn such as cimetidine and ranitidine, muscle relaxants, anti-epileptics including phenytoin and Phenobarbital codeine, and narcotics including darvocet, percocet and hydrocodone. Drugs known to inhibit or induce enzymes that metabolize alcohol should not be used for 4 weeks prior to the study. These include chlorzoxazone, isoniazid, metronidazole and disulfiram. Cough-and-cold preparations, which contain antihistamines, pain medicines and anti-inflammatories such as aspirin, ibuprofen, acetaminophen, celecoxib and naproxen, should be withheld for at least 72 hours prior to each study session.

Current or prior history of alcohol-induced flushing reactions.

Contraindications for MRI scanning, including metal in body that are contraindicated for MRI (such as implants, pacemaker, prostheses, shrapnel, irremovable piercings), left-handedness, and claustrophobia.