Study design and description
The NUTRIDOPE study is a randomized controlled trial with repeated measures, whose rationale is depicted in Fig. 1. Figure 2 illustrates the experimental design of the study. According to it, the participants will be randomly divided into the experimental and control groups. Regarding the randomization process, the volunteers using the unique code they obtain during entering the MAT programs of the Organization Against Drugs (OKANA, Greece), will be randomly divided in the study groups, matched-up based on their demographic characteristics. The randomization will be performed by an independent individual, who will not participate in the data collection and evaluation procedures. This individual will have access to interim results and decide to terminate the trial in case there is a need for that or check for any adverse effects before addresses to the appropriate expert. The volunteers will be informed about the group they have been allocated through a message in an opaque envelope. The participants of both groups will be further stratified into two subgroups, i.e., MMT and BMT, according to the maintenance treatment program they attend. Pomegranate juice, which is the examined nutritional intervention, will be administered to the participants of the experimental group, whereas their counterparts in the control group will not consume any similar beverage. Therefore, this is a double-blinded and not a triple-blinded design, since the researchers and analysts but not the participants will be blinded. The juice will be administered to the patients at the following dosage: 250 ml/day, seven days/week, for four months. According to the literature, administration of pomegranate juice at a similar dosage exerts beneficial effects on overweight patients with dyslipidemia, on patients with type 2 diabetes, and on patients at moderate risk for coronary heart disease (Davidson et al., 2009; Kojadinovic et al., 2021; Parsaeyan et al., 2012). Moreover, no adverse effects have been referred to, however parameters of the participants such as blood pressure, heart rate and concentrations of liver transaminases will be regularly measured. Specific validated self-reported instruments for the assessment of the effects of pomegranate juice on craving, quality of life (QoL), mood, fatigue level, bowel function, constipation and cognitive function will be completed by the participants at four timepoints, namely, before the start of the experiment (i.e., day 1), in the middle (i.e., day 60), at the end of the experiment (i.e., day 120) and six months following the end of the experiment (i.e., follow-up measurements). Furthermore, whole blood samples will be collected at the same timepoints where several established redox biomarkers, inflammation markers and hormones will be measured.
Supply of the pomegranate juice
The pomegranate juice that will be used in the experiment is a 100% natural product without conservatives. It will kindly be donated from the company Rodi Hellas SA, Pella, Greece. The product is in line with the quality assurance certificates ISO 22000:2005, Global Gap, Grasp and Kosher.
Participants
Patients under MAT that are active members of the OKANA therapeutic units will be recruited for this investigation. The inclusion and exclusion criteria are shown in Table 1. The patients will be informed about the objectives of the study, the risks, and difficulties as well as the expected benefits they will gain after the fulfillment of this investigation. Each patient will sign a written consensus form before the experimental procedure starts. This form will be collected by the aforementioned independent individual. The highest adherence rate is anticipated to be achieved through informing the volunteers regarding the putative beneficial role of the nutritional intervention on several parameters of their life. Furthermore, the patients will be allowed to follow their regular program in OKANA (i.e., accept psychiatric care and psychosocial support). All personal data and information obtained will be unequivocally confidential and the investigators only will strictly have access on them. Moreover, the data obtained will be kept in password protected computers that will stay within OKANA and will never be transferred outside the premises of this Institution.
Table 1
The inclusion and exclusion criteria of the study.
Inclusion criteria
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Exclusion criteria
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Over 20 years of age
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Severe psychopathology and other serious medical problems, such as infection by human immunodeficiency virus or hepatitis B virus
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Long-term heroin or other opioid drug use
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Current use of anti-inflammatory medication
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Suffering from physical and mental dependence due to chronic opioid use
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Relapse to other addictive substances (i.e., opioids, methamphetamine, benzodiazepines, cannabis, tetrahydrocannabinol, amphetamine)
- To rule out the use of such substances, all participants underwent weekly urine tests during the four-month period of the experiment
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Medication for addiction treatment (MAT)
The patients under MAT receive daily methadone hydrochloride solution (10 mg/ml) and buprenorphine/buprenorphine-naloxone pills (2 mg − 8 mg), according to the existing dose guidelines (National Organization for Medicines, 2007: 258–261).
Demographic data
Before the start of the experimental procedures, demographic data will be collected by all participants. Information such as the sex, the age, the educational level, the nationality, the marital status, the professional status, the area of residence, the number of years attending a rehab program in OKANA, the age of onset, the duration of substance use before entering the MAT program and the chronic diseases they putatively suffer from will be obtained.
Outcomes
The primary outcome of the NUTRIDOPE study is craving, a psychosocial parameter that is of utmost important towards the trajectory of the patients to rehabilitation. Craving will be assessed through a validated and reliable self-reported questionnaire. Secondary outcomes comprise blood redox status, through measuring specific redox biomarkers in blood, and quality of life evaluated through another validated and reliable self-reported questionnaire. Further outcomes include physiological, psychosocial, and biochemical parameters that are analyzed in the following paragraphs. These outcomes are of high clinical relevance since they are fundamental factors for the maintenance of mental and organismal equilibrium of the patients. In case any protocol modification is needed, this will be communicated to relevant parties.
Description of the instruments
The main characteristics (outcome measured, title and description of the instruments) of the questionnaires that will be used in the study are shown in Table 2 and a detailed description can be found below. All instruments have been used after obtaining the appropriate permission by the researchers that introduced them.
Table 2
The questionnaires administered to the participants of the NUTRIDOPE study (days 1, 60, 120, and six months after the end of the experiments as a follow-up measurement).
Outcome
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Questionnaire
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Description
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Example
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Heroine craving
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Heroin Craving Questionnaire
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5 Dimensions: Desire to use heroin; Intentions and planning to use heroin; Anticipation of positive outcome; Relief from withdrawal or dysphoria; Lack of control overuse
45 Items
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For each question, please click between 1 (strongly disagree) to 7 (strongly agree)
E.g., I intend to use heroin as soon as possible
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Quality of life
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Nottingham Health Profile
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First part: Assessment of activity, pain, emotional reaction, sleep, social isolation, mobility
Second part: Evaluation of the effects of health or disease on the presence of the patients at the working environment and inside their household, social life, home life, sex life, interests, and vacations.
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Please provide yes-or-no answers
E.g., I experience unstable sleep; I am getting tired very easily
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Sleep quality and quantity
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Pittsburgh Sleep Quality Index
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7 Components: Subjective sleep quality; Sleep latency; Sleep duration; Habitual sleep efficiency; Sleep disturbances; Use of sleep medication; Daytime dysfunction
19 Items
Lower obtained scores indicate better sleep quality
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Please complete the following items based on the past
month:
E.g., Did you have bad dreams?
(never during the last month, less than once/week, once or twice/week, more than 3 times/week)
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Fatigue
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Fatigue Severity Scale
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9 Items
Higher obtained scores indicate worse experienced fatigue
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For each question, please click between 1 (strongly disagree) to 7 (strongly agree)
E.g., Fatigue is one out of three symptoms that make difficult my everyday routine
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Effect of constipation on quality of life
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Patient Assessment of Constipation - Quality of Life
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4 Dimensions: Physical discomfort; Psychosocial discomfort; Treatment satisfaction; Worries discomfort
28 Items
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Please click 1 (zero) to 5 (constantly)
E.g., How many times have you felt uncomfortable due to constipation when you meet other people?
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Faecal Evaluation
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Bristol Stool Form Scale
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Assessment of the type (types 1 to 7) of stools
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Please click the box that represents your situation
E.g., Your stools are of type 6 (pulpy)
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Faecal Colour Assessment
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Assessment of the colour (scale from 1 to 6) of faeces
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Please click the box that represents the colour of your faeces
1 for green to 6 for cherry red
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Mood states
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Profile of Mood States (POMS-short version)
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6 Dimensions: Tension; Depression; Anger; Vigour; Fatigue; Confusion
37 Items
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For each question, please click between 0 (not at all) to 7 (very much)
E.g., I am currently feeling desperate
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Heroin Craving Questionnaire (HCQ)
The HCQ will be used for the assessment of pomegranate juice effects on craving.consisted of 45 questions divided in 5 dimensions, namely desire to use heroin, intentions and planning to use heroin, anticipation of positive outcome, relief from withdrawal or dysphoria, and lack of control overuse. The score is calculated with a 7-point Likert scale ranging from 1 (i.e., strongly disagree) to 7 (i.e., strongly agree). Internal consistency reliability was accepted with Cronbach’s alpha equal to 0.90 (Leventelis et al., 2020a) .
Nottingham Health Profile (NHP)
The NHP questionnaire will be used for the assessment of the pomegranate juice effects on the QoL of the patients. The questionnaire consists of two parts; the first part assesses parameters such as activity, pain, emotional reaction, sleep, social isolation, and mobility, whereas the second part evaluates the effects of health or disease on the activities of daily living. The patients will complete the NHP questionnaire using yes-or-no answers. The questionnaire is highly valid and reliable in its version in the Greek language (i.e., test-retest reliability coefficients and Spearman’s R-value range between 0.77 and 0.86) (Leventelis et al., 2020b).
Pittsburgh Sleep Quality Index (PSQI)
PSQI is a 19-item self-reported questionnaire, which subjectively assesses sleep quality and quantity, sleep habits related to quality and occurrence of sleep disturbances in adults consisting of 7 components. Each component score is marked on a 0–3-scale, and the PSQI is calculated as the sum of the 7 components ranging between 0 and 21. The Cronbach’s alpha for global PSQI score was equal to 0.76 (Kotronoulas et al., 2011).
Fatigue Severity Scale (FSS)
FSS is a 9-item, self-administered questionnaire which assesses the magnitude of fatigue that the patients have experienced throughout the past weeks. Each item is scored on a 7-point Likert scale ranging from 1 (i.e., completely disagree) to 7 (i.e., completely agree). The Cronbach’s alpha for all FSS was 0.953 (Bakalidou et al., 2013).
Patient Assessment of Constipation - Quality of Life (PAC-QOL)
The PAC-QOL questionnaire consists of 28 self-reported items that assess the effects of constipation on the patient QOL in the last 2 weeks. The responses are scored on a Likert scale ranging from 0 to 5. Higher score indicates increase of severity of the negative effects of the intervention in question on QOL (Sason et al., 2021).
Bristol Stool Form Scale (BSFS)
The BSFS is a pictorial representation of each stool type ranging from the hardest (i.e., type 1) to the softest (i.e., type 7) related to specific bowel symptoms, such as constipation, diarrhea (Blake et al., 2016).
Faecal Colour Assessment
This is a tool for the evaluation of the colour of faeces using a 1–6 scale. There is a 6-colour scale for the faecal assessment comprising the colours green, brown, white, yellow, black and red indicating specific bowel symptoms and diaseases, as bilirubin deficiency, liver or gallbladder abnormalities, bleeding from gastrointestinal system (Ohno et al., 2019).
Profile of Mood States (POMS-short version)
The POMS questionnaire consists of 37 self-administered items and assesses current mood states in 6 dimensions, namely tension, depression, anger, vigour, fatigue, and confusion. Each item is scored on a 5-point Likert scale from 0 (i.e., not at all) to 4 (very much). The instrument has been validated in Greek and the Cronbach’s a is ranged between 0.72 and 0.93 (Zervas et al., 1993).
Blood collection and handling
Plasma and erythrocytes will be collected following a procedure that has been previously described (Veskoukis et al., 2016). In brief, whole blood samples from a forearm vein of seated individuals will be collected in vacutainers with ethylenediaminetetraacetic acid (EDTA) as an anticoagulant agent. The samples will be centrifuged, and the plasma will be collected and stored at -80°C until analyses. Then, distilled water will be added to the packed erythrocytes (1:1 v:v) and following a centrifugation, the red blood cell lysate (RBCL) will be collected and stored also at -80°C.
In vitro experiments - Evaluation of the antioxidant and antimutagenic activities of pomegranate juice in vitro
The capacity of pomegranate juice to reduce the DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), hydroxyl and superoxide radicals, as well as Fe+ 3 to Fe2+ using the reducing power assay will provide evidence regarding the antioxidant/reductive properties of the administered juice. Furthermore, the antimutagenic activity of the juice will be evaluated through measuring its ability to protect plasmid DNA from the oxidative action of peroxyl radicals (ROO•). Finally, the total polyphenolic content of the pomegranate juice will be measured through the Folin-Ciocalteau assay (Veskoukis et al., 2012a, 2019).
In vivo experiments - Measurement of biomarkers in blood
Redox biomarkers
Several well-established redox biomarkers will be measured for the assessment of the effects of pomegranate juice consumption on blood redox status of the patients (Veskoukis et al., 2019). In particular, the following three categories of redox biomarkers will be examined:
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Biomarkers of antioxidant profile comprising the antioxidant enzymes catalase, superoxide dismutase, glutathione peroxidase and glutathione reductase, and the reduced form of glutathione (GSH) as a crucial antioxidant molecule, which will be measured in RBCL, as well as total antioxidant capacity that will be assessed in plasma spectrophotometrically (Veskoukis et al., 2016, 2019).
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Biomarkers indicating the oxidative modification of biomolecules, namely protein carbonyls as a biomarker of protein oxidation and thiobarbituric acid reactive substances as a biomarker of lipid peroxidation that will be assessed in plasma spectrophotometrically (Veskoukis et al., 2016, 2019).
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Biomarkers evaluating the reductive capacity of plasma through measuring its ability to reduce the hydroxyl (OH•) and superoxide (O2-•) radicals, as well as Fe+ 3 to Fe2+ using the reducing power assay. All three assays are spectrophotometric (Veskoukis et al., 2019).
Biomarkers of inflammation
Pro-inflammatory cytokines namely interferon gamma (IFN-γ), interferon alpha-2 (IFN-a2), interleukin-1 betta (IL-1β), interleukin-1 alpha (IL-1a), interleukin-8 (IL-8), monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor alpha (TNF-a) will be measured in plasma through immunofluorescence.
Hormones
Melatonin and cortisol levels will be measured in plasma using enzyme-linked Immunosorbent Assay (ELISA).
Ethical considerations
The NUTRIDOPE study in terms of ethics and methodology has been approved by the Review Board of the OKANA (ref. number 44482-2/12/2020) and the implemented procedures are in accordance with the Declaration of Helsinki, as revised in 2013. The trial has also been registered in ClinicalTrials.gov (ID: NCT05861544).
Statistical analyses and power calculation
A preliminary statistical power analysis was performed using the online available sample size calculator ClinCalc.com. The primary outcome for this analysis will be the reduction of craving. The relevant literature has demonstrated that MAT induce a 30% reduction of craving in patients with OUDs (Fudala et al., 2003; Preston et al., 2000). We anticipate that pomegranate juice will lead to a further 10% craving reduction. On that basis, the statistical power analysis showed that at least 16 participants for each group (i.e., control and experimental) are needed to obtain statistically meaningful results. The input variables for the analysis were as follows: alpha error = 0.05; power = 0.90; enrollment ratio = 2 (for additional safety data). However, due to potential dropouts, the final number of the participants with a dropout rate equal to 10% is: n = 18 for the control group and n = 35 for the experimental group.
The results from the demographic data of the participants will be expressed as mean ± standard deviation. If the results obtained from the Kolmogorov-Smirnov test indicate that our data follows normality, parametric tests will be used for their evaluation. The effects of pomegranate juice consumption on the measured parameters in all four time points will be analyzed using 3-way ANOVA with repeated measures. The results from the psychosocial parameters obtained through the questionnaires will be correlated with the results from the biochemical parameters (i.e.., redox status, inflammation, hormones) through Spearman's rank correlation (R-value). Furthermore, to study the topological behavior of the data set and uncover hidden patterns, unsupervised learning methods will be utilized. Nonlinear visualization and clustering techniques able to handle mixed data, will allow us to examine groups of samples with similar characteristics (Tasoulis et al., 2020). The outcome will be validated through various internal clustering metrics along with visual investigation of 2-dimensional scatter plots. In the presence of a hierarchical clustering structure, additional machine learning methods will be used (tree-based methods) to provide the importance metrics that significantly discriminate groups of samples. Statistical analyses will be performed using the Statistical Package for the Social Sciences (SPSS) (version 21.0 (SPSS Inc., Chicago, IL) and the R Project for statistical computing (version 4.1.3, The R Foundation, Vienna, Austria). The source code for the machine learning and statistical analysis processes developed in R will be available under an open-source license.