Abstract
In the literature, the relationship between appetite regulating peptides and alcohol craving is on the debate. Aim: This study aims to investigate serum level of NUCB2/nesfatin-1, which is discovered as appetite-related neuropeptide, in patients with alcohol dependence who were in craving and abstaining phase and to compare with healthy controls. Settings and Design: Research, Treatment, and Training Center for Alcohol and Substance Dependence, (AMATEM) Bakirkoy Training and Research Hospital for Psychiatry Neurology and Neurosurgery, Istanbul, case-control and prospective study design were used. Statistical Analysis: Chi-square, Mann-Whitney U, paired samples, independent samples t-and Pearson correlation tests were used for analysis. Materials and Methods: Forty-three patients with alcohol dependence who have been admitted for detoxification and thirty healthy controls were included in the study. The blood samples were drawn after the 1 st day of admission and postdetoxification treatment in inpatients who reached to abstinence period and from 30 healthy controls. The Penn Alcohol Craving Scale and the Obsessive Compulsive Drinking Scale were applied to detect craving scores. Results: Initial serum NUCB2/nesfatin-1 levels in patients were significantly lower than in the healthy control group (P < 0.001). The NUCB2/nesfatin-1 level of initial phase was significantly lower than abstinence phase (P = 0.027). No correlation was found between craving scores and NUCB2/nesfatin-1 level (P > 0.05). Conclusion: This study is the first that showed significant differences of serum NUCB2/nesfatin-1 level according to different stages of alcohol dependence. Plasma NUCB2/nesfatin-1 levels were lower in highest craving phase and tended to normalize after abstinence. Since we could not find a correlation between craving and NUCB2/nesfatin-1 levels, the increase of NUCB2/nesfatin-1 in abstinence phase might have been resulted from other reasons apart from craving.
INTRODUCTION
There is growing interest in literature about the relationship between appetite regulating peptides and alcohol dependence and/or craving. In several studies, altered serum leptin [1] [2] [3] or ghrelin [4] [5] [6] levels have been shown during alcohol craving, and in chronic alcohol consumption and evidence for the association between serum leptin levels and alcohol, craving has been detected in a power-based analysis study. [7] However, a debate is ongoing about the exact role of these appetite regulatory neuropeptides on alcohol craving. NUCB2/nesfatin-1 is an appetite-related neuropeptide that includes 82 amino acids [8, 9] which is widely present throughout the whole brain as hypothalamic paraventricular nuclei, amygdala, locus coeruleus, etc. [10] NUCB2/nesfatin-1 level is proposed to be relatively stable in peripheral circulating blood. [11] It was shown that NUCB2/nesfatin-1 has an appetite reducing effect after peripheral administration in mice. [12] In addition, decreased plasma levels of NUCB2/nesfatin-1 in case of fasting has increased after refeeding. [13] Thus, it was suggested that NUCB2/nesfatin-1 could play a role in satiety regulation and energy homeostasis. [13] Although NUCB2/nesfatin-1 has been investigated in some psychiatric disorders, such as major depressive disorder, [14] bipolar disorder, [15] and anxiety disorders, [16, 17] no study has been found about the relationship between alcohol craving and NUCB2/nesfatin-1 level.
INTRODUCTION
In this study, we hypothesized that (i) serum NUCB2/nesfatin-1 level in patients with alcohol dependence would be different than healthy controls, (ii) serum NUCB2/nesfatin-1 level would be altered after 10 days of abstaining, and (iii) serum NUCB2/nesfatin-1 level might be related to the severity of craving.
MATERIALS AND METHODS

Participants
Eighty-seven male inpatients with alcohol dependence according to the diagnostic criteria of DSM-IV-TR [18] have participated to study in Research, Treatment, and Training Center for Alcohol and Substance Dependence (AMATEM), which is subunit in Bakirkoy Training and Research Hospital for Psychiatry Neurology and Neurosurgery, from June 2013 to September 2014. The patients have been admitted for detoxification purposes and were included in the study on the day of following admission (12-24 h after last alcohol consumption). The inclusion criteria were (i) aged between 18 and 65 years, (ii) being psychopharmacologic agents free for at least 6 months, (iii) meeting the criteria of alcohol dependence according to DSM-IV-TR, and (iv) being literate. The exclusion criteria were (i) axis 1 disorder other than alcohol dependence or, (ii) drug naive or being drug free at least 6 months, (iii) having medical disease (diabetes mellitus, thyroid, Cushing, and other endocrinological disease), (iv) any extraordinary state needed to change the treatment protocol (i.e., inadherence to treatment, inability to stand under detoxification treatment protocol until 10 days), and (v) participants who did not eat dinner given at 18:00. All patients underwent a detailed physical examination, routine laboratory testing, and urine drug screening tests. Of 87 patients, 43 have been included to the study while 44 of them were excluded from the study because of earlier volunteered discharge (<10 days). Thus, the data of 43 patients were performed for the study.
Participants
In addition, 30 healthy male controls who have no previous and/or current psychiatric disorders including alcohol-/ drug-related disorders were enrolled in the study. Healthy controls ate dinner with the same amount of calories as the patients at the same time. They were stated not to eat anything and not to drink sugary beverage until drawing blood sample and were obtained written consent that they understood the conditions. Body mass index (BMI) of each participant was calculated as body weight divided by the squared body height (kg/m 2 ).
Serum sample for NUCB2/nesfatin-1 level
The blood samples were drawn on the 1 st day after admission and postdetoxification treatment in inpatients who reached to abstinence period. Blood samples for NUCB2/nesfatin-1 were drawn in the morning around 8 a.m. from a forearm vein of the participants at the end of an overnight fasting period range of 8-12 h. The first blood samples were drawn in patients who had used 20-30 mg diazepam orally. Tubes with 5 ml capacity and containing EDTA were used to collect blood. Before the centrifuge, the centrifuge tubes were gently rocked several times to inhibit the activity of proteinases. After the centrifuge process at 1600 ×g rate for 15 min at 4°C, the serum was obtained and stored at −80°C until the time of assay. Serum NUCB2/nesfatin-1 levels were measured using a commercial ELISA kit (Uscn Life Science, Wuhan, P. R. China). Some previous studies in the literature have used ELISA method for measuring NUCB2/nesfatin-1 peptide level. [14, 15] The intra-assay coefficients of variation (CV) value was <10% for NUCB2/nesfatin-1. The inter-assay CV values were as follows for glucose (<1.7%), for cholesterol (<1.7%), for low-density lipoprotein (LDL)-cholesterol (<1.03%), for high-density lipoprotein (HDL)-cholesterol (<1.3%), and for triglyceride (<1.8%).
Serum sample for NUCB2/nesfatin-1 level
This study was approved by a local ethical committee of Bakirkoy Training and Research Hospital for Psychiatry Neurology and Neurosurgery, and all participants gave written informed consent before the enrollment in the study.
Psychometric assessment
All patients were asked to fulfill the following inventories at initial phase and abstinence phase.
Penn Alcohol Craving Scale
The Penn Alcohol Craving Scale (PACS) is a self-reported scale consisting of 5 items which was performed to measure the desire of alcohol intake as intensity, frequency, duration, resistance to intake, average craving scores for the last week by Flannery et al. [19] Each sub-item evaluated between 0 and 6 points while the maximum craving score is 30 points. The Turkish reliability and validity of this scale in male inpatients with alcohol dependence was performed by Evren et al. [20] Obsessive Compulsive Drinking Scale The Obsessive Compulsive Drinking Scale (OCDS) is a reliable and validated self-rating questionnaire which is consisting of 14 items and was designed as a screening tool for craving in alcoholism. [21] This scale gives the opportunity to patients for self-rating of their obsessive thoughts about drinking and their compulsive use of alcohol. The Turkish reliability and validity of this scale was performed by Evren et al. [22] 
Statistical analysis
The data were analyzed using the Statistical Package for Social Sciences version 16.00. Frequencies, percentages, means, and standard deviations were given for sociodemographic variables. Chi-square test was used to detect differences between categorical variables. The normality distribution of the data was made by Kolmogorov Smirnov test. Mann-Whitney U-test was used when normal distribution was not satisfied. In patients, the initial and postdetoxification data were analyzed by paired samples test as data distribution was normally. The initial data of patients were compared with the data of healthy controls by independent samples t-test. The relationship between the NUCB2/nesfatin-1 levels and PACS and OCDS scores in the patient group was analyzed using Pearson correlation test. Internal consistency of PACS and OCDS was assessed using Cronbach's alpha. Statistical significance level was accepted as P < 0.05.
RESULTS
There were 43 patients with alcohol dependence and 30 healthy controls in the study. The whole groups were consisted of male individuals to support the homogeneity of the data. There was significant difference according to mean age between patients and controls 46.37 ± 9.29 years versus 30.96 ± 7.66 years, respectively and P < 0.001. The BMI between patients and healthy controls was insignificant (23.30 ± 2.74 kg/m 2 vs. 24.17 ± 3.08 kg/m 2 , respectively and P = 0.287). The education level and marital status were insignificant between patient and control groups (P = 0.316 and P = 0.069, respectively). The mean fasting glucose level was significantly lower in patients than healthy controls (86.49 ± 9.65 vs. 91.87 ± 11.86, P = 0.037). In addition, mean total cholesterol (214.41 ± 51.28 vs. 164.66 ± 31.18) and mean HDL levels (66.93 ± 33.50 vs. 37.33 ± 7.64) were significantly higher in patients than healthy controls (for both, P < 0.0001), while mean LDL (114.22 ± 29.29 vs. 102.09 ± 28.36, P = 0.082) and mean triglyceride levels (154.35 ± 121.69 vs. 125.17 ± 73.77, P = 0.246) were insignificant. Characteristics of sociodemographics, BMI scores, lipid profiles, and fasting glucose were shown in Table 1 . The mean onset age of alcohol consumption, duration of alcohol consumption 21.16 ± 6.23, 21.63 ± 9.66 years, respectively and the mean beverage of consumption was 14.56 ± 6.80 unit/day. Internal consistency for the PACS (coefficient α =0.914) and for the OCDS (coefficient α =0.937) examined by Cronbach's alpha were high. The PACS at initial phase was significantly higher than abstinence phase (25.72 ± 4.07 vs. 3.32 ± 2.80 points, Table 2 ].
RESULTS
Initial serum NUCB2/nesfatin-1 levels in patients were significantly lower than in healthy control group (P < 0.001) [ Table 3 ]. The NUCB2/nesfatin-1 level of initial phase was significantly lower than abstinence phase (P = 0.027). These data are shown in Table 4 . There was no significant correlation between serum NUCB2/nesfatin-1 level and initial craving scores according to OCDS (r = −0.079; P = 0.613) and PACS (r = −0.022; P = 0.888). The correlations between serum NUCB2/nesfatin-1 level and abstinence craving score were also insignificant according to OCDS (r = −0.113; P = 0.472) and PACS (r = −0.019; P = 0.905). In addition, no correlation between NUCB2/nesfatin-1 level and duration of alcohol consumption (r = −0.137, P = 0.382), mean beverage of alcohol consumption (r = 0.172, P = 0.274 in craving phase and abstinence phase (r = −0.215, P = 0.166 and r = −0.50, P = 0.751, respectively).
DISCUSSION
In last two decades, shared pathophysiological mechanisms were extensively considered between addictive behaviors and neuroendocrine pathways as energy consumption, appetite regulation, and food craving. [7] Alcohol was accounted for 10% of total energy consumption in alcohol consumers and for more than 50% of dietary intake in alcohol-dependent individuals. [23] In the present study, we have found decreased serum NUCB2/nesfatin-1 level in chronic alcohol consumers who have higher craving scores than healthy controls and increased serum NUCB2/nesfatin-1 level after 10 days abstinence phase with lower craving scores. In literature, there is no study dealing with the relation between serum NUCB2/nesfatin-1 level and alcohol-related issues as craving, withdrawal, or abstinence. The NUCB2/nesfatin-1 is a potent anorexigenic peptide which leads to satiety and inhibits energy intake [24] and reported to be reduced by fasting. [13] Thus, in the light of the literature, we considered that the lower NUCB2/nesfatin-1 level in the 1 st day of the admission might be resulted from alcohol withdrawal while the mean craving scores were the highest according to OCDS and PACS. On the other hand, the chronic consumption of alcohol as an energy source might be an outcome of lower NUCB2/nesfatin-1 levels in patients with alcohol dependence. In literature, leptin is a relatively well-known anorexigenic peptide in association with alcohol-related issues. Interestingly, increased serum leptin level was reported to be associated with increased alcohol craving in preclinical and clinical studies. [3, [25] [26] [27] In literature, the leptin level was informed to be associated with alcohol craving first in females [28] and then in males. [7] There is no study about the relation between gender differences and NUCB2/ nesfatin-1 level in patients with alcohol dependence. In this study, for the first time, we have shown significant differences in NUCB2/nesfatin1 level in male patients with alcohol dependence. Serum leptin levels were widely accepted to normalize during withdrawal and abstinence [29] and we have found that NUCB2/nesfatin-1 level tended to normalize by increasing in abstinence phase which is in line with leptin literature. Although NUCB2/nesfatin-1 and leptin are both anorexigenic, we have found opposite directions between NUCB2/nesfatin-1 and leptin levels: in highest craving phase (decreased vs. increased) and in abstinence phase while craving was the lowest (increased vs. decreased). This conflict might be due to the food (energy) intake regulatory role of NUCB2/nesfatin-1 by independent from mechanism of leptin as shown in rats. [30] In the study of Kiefer et al. [25] self-rated visual analog scale has been used to assess craving severity at the beginning of alcohol withdrawal. Subsequently, studies have measured craving severity of patients with a validated and reliable scale as OCDS. [3, 7, 28] In all these studies, an association between leptin level and craving score was reported. Although we detected a significant increase in NUCB2/nesfatin-1 level after a significant decrease in craving score, we have not found a significant correlation between craving scores and serum NUCB2/nesfatin-1 level in the current study. One possible explanation of this noncorrelation might be relatively small sample size (n = 43) of our study. Furthermore, some studies showed implication of NUCB2/nesfatin-1 in the stress response, [31, 32] which might be an explanation for the results in the present study. Alcohol addicted patients might be stressed on the 1 st day of detoxification which alleviates after reaching abstinence but does not reach normal levels at this early stage as compared to healthy controls. Thus, this difference might be resulted from the involvement of NUCB2/nesfatin-1 in the stress response rather than alcohol addiction and craving.
DISCUSSION
This study has several limitations: in the calculation, although it is sufficient to take at least 26 participants from both groups, relatively small sample size compared to previous studies conducted with leptin which is another appetite regulator hormone [3, 33] and relatively small duration of prospective design seem to be important influences in our study. In a recent study, higher serum leptin levels have been found in longer duration of abstinence in female patients with alcohol dependence. [1] Thus, measuring serum NUCB2/nesfatin-1 level in the 3 rd month of abstinence and its possible influences on metabolic parameters as BMI or waist circumference would be interesting. Someone might ask the significant difference of age between patients and healthy controls in the current study on NUCB2/nesfatin-1 level. In a study that is published in January of 2014 in mice, no age-related change is detected on NUCB2/nesfatin-1 level. [34] This comparison may be controversial, but we have no data regarding the effects of aging on NUCB2/nesfatin-1 levels in human. The levels of NUCB2/nesfatin-1 were substantially lower than controls who were in the abstinence phase. Therefore, it would be useful to measure NUCB2/nesfatin-1 level baseline and few weeks later in healthy controls. In addition, an additional time point would be added to see if the levels continue to increase in patients with alcohol dependence. It was suggested that serum leptin level was associated with different alcohol craving types such as Lesch Type I and II while no association was proposed in Lesch Type III and IV. [33] In addition, acamprosate, which is an anti-craving agent, was found to be effective only in Lesch Type I and Type II patients. It might be valuable to separate the groups according to craving types while searching association between NUCB2/nesfatin-1 level and craving scores. Furthermore, in our study, the whole sample is consisted of male patients with alcohol dependence, which might be considered as a limitation. Preliminary findings have supported that a significant association is only present in female alcohol dependent patients between craving scores and leptin level. [28] Nevertheless, a significant association was informed in both genders or male alcohol-dependent patients. [7] Lenz et al. [35] have suggested that androgen receptor on craving in alcohol withdrawal in men is partially mediated by leptin. Thus, the relationship between craving scores and NUCB2/nesfatin-1 level according to gender seems to be unclear and needs to be studied further.
CONCLUSION
This is the first study that explore differences of serum NUCB2/nesfatin-1 level according to different stages of alcohol dependence (i.e., highest craving phase and abstinence phase). Although we could not find a relationship between craving and NUCB2/nesfatin-1 levels, since neuroendocrinological mechanisms of NUCB2/nesfatin-1 might be potentially involved in the neurobiology of alcohol craving, this relationship deserves further consideration with studies overcoming the limitations of the present study.

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