BACKGROUND: Alcohol use disorder (AUD) is a relapsing disease described as excessive use of alcohol. Evidence of the role of DNA methylation in addiction is accumulating. Ghrelin is an important peptide known as appetite hormone and its role in addictive behavior has been identified. Here we aimed to determine the methylation levels of two crucial genes (GHRL and GHSR) in ghrelin signaling and further investigate the association between methylation ratios and plasma ghrelin levels.
METHODS: Individuals diagnosed with (n = 71) and without (n = 82) AUD were recruited in this study. DNA methylation levels were measured through methylation-sensitive high-resolution melting (MS-HRM). Acylated ghrelin levels were detected by ELISA. The GHRL rs696217 polymorphism was analyzed by the standard PCR-RFLP method.
RESULTS: GHRL was significantly hypermethylated (P < 0.0022) in AUD between 25 and 50% methylation than in control subjects but no significant changes of GHSR methylation were observed. Moreover, GHRL showed significant positive correlation of methylation ratio between 25 and 50% with age. A significant positive correlation between GHSR methylation and ghrelin levels in the AUD group was determined (P = 0.037). The level of GHRL methylation and the ghrelin levels showed a significant association in the control subjects (P = 0.042).
CONCLUSIONS: GHSR and GHRL methylation levels did not change significantly between control and AUD groups. However, GHRL and GHSR methylations seemed to have associations with plasma ghrelin levels in two groups. This is the first study investigating the DNA methylation of GHRL and GHSR genes in AUD.

There has been considerable interest in transforming peptides into small molecules as peptide-based molecules often present poorer bioavailability and lower metabolic stability. Our studies looked into building machine learning (ML) models to investigate if ML is able to identify the \'bioactive\' features of peptides and use the features to accurately discriminate between binding and non-binding small molecules. The ghrelin receptor (GR), a receptor that is implicated in various diseases, was used as an example to demonstrate whether ML models derived from a peptide library can be used to predict small molecule binders. ML models based on three different algorithms, namely random forest, support vector machine, and extreme gradient boosting, were built based on a carefully curated dataset of peptide/peptidomimetic and small molecule GR ligands. The results indicated that ML models trained with a dataset exclusively composed of peptides/peptidomimetics provide limited predictive power for small molecules, but that ML models trained with a diverse dataset composed of an array of both peptides/peptidomimetics and small molecules displayed exceptional results in terms of accuracy and false rates. The diversified models can accurately differentiate the binding small molecules from non-binding small molecules using an external validation set with new small molecules that we synthesized previously. Structural features that are the most critical contributors to binding activity were extracted and are remarkably consistent with the crystallography and mutagenesis studies.

Ghrelin has been found to be expressed in the human endometrium. Emerging evidence links ghrelin and its receptor with the reproductive system. Certain associations between ghrelin and angiogenesis have also been established. The aim of this small case-control study was to quantify and compare the expression of mRNA encoding ghrelin, ghrelin receptor (GHS-R), vascular endothelial growth factor A (VEGF A) and its receptors (VEGFR1-3) in the endometrium of women with recurrent miscarriage compared to parous controls. Correlations between the expression of particular genes were also investigated. Endometrial samples were obtained during the secretory phase of the menstrual cycle from 15 women with a history of recurrent miscarriage (first trimester pregnancy loss without a known cause) and 10 healthy parous controls. Ghrelin, GHS-R, VEGF A and VEGFR1-3 mRNA expression was analyzed by quantitative RT-PCR. The expression of mRNA for ghrelin and VEGF A was significantly higher in the study group than the control group. In the control group, the expression of ghrelin mRNA was positively correlated with the expression of VEGF A and VEGFR1 mRNA. In the study group, no such associations were observed. These results show that the expression of mRNA for ghrelin and VEGF A may be increased in the endometrium of women with recurrent miscarriage thus suggesting that ghrelin may play a role in the pathogenesis of recurrent miscarriage.

Components of the brain reward system, i.e. the mesolimbic dopamine, laterodorsal cholinergic and ghrelin signaling systems, have been implicated in alcohol reward in preclinical studies. Genetic variants of these systems have previously been linked to alcohol dependence. Here, we genotyped 31 single nucleotide polymorphisms (SNPs): 1 SNP in the dopamine D₂ receptor (DRD2) gene, 20 SNPs in 5 different nicotinic acetylcholine receptor subunit (CHRN*) genes, and 10 SNPs in the genes encoding pro-ghrelin (GHRL) and its receptor (GHSR), in a pilot study of type 1 alcoholics (n = 84) and healthy controls (n = 32). These individuals were characterized using the Temperament and Character Inventory. None of the SNPs were associated with risk of alcohol dependence in this population. The GG genotype of SNP rs13261190 in the CHRNB3 was associated with increased novelty seeking, while SNPs of the ghrelin signaling system were associated with decreased self-directedness (AA of rs495225, GHSR) and alterations in self-transcendence (AA of both rs42451 and rs35680, GHRL). In conclusion, this pilot study suggests that reward-related genes are associated with altered personality scores in type 1 alcohol dependence, which warrants future studies of these associations in larger study samples.

BACKGROUND: Ghrelin, an endogenous ligand for the growth hormone secretagogue receptor (GHSR), has two major functions: the stimulation of the growth hormone production and the stimulation of food intake. Accumulating evidence also indicates a role of ghrelin in cancer development.
METHODS: We conducted a case-control study to examine the association of common genetic variants in the genes coding for ghrelin (GHRL) and its receptor (GHSR) with colorectal cancer risk. Pairwise tagging was used to select the 11 polymorphisms included in the study. The selected polymorphisms were genotyped in 680 cases and 593 controls from the Czech Republic.
RESULTS: We found two SNPs associated with lower risk of colorectal cancer, namely SNPs rs27647 and rs35683. We replicated the two hits, in additional 569 cases and 726 controls from Germany.
CONCLUSIONS: A joint analysis of the two populations indicated that the T allele of rs27647 SNP exerted a protective borderline effect (Ptrend = 0.004).

Ghrelin, an endogenous ligand for the growth hormone secretagogue receptor, has two major functions: the stimulation of the growth hormone production and the stimulation of food intake. Accumulating evidence also suggests a role of ghrelin in cancer development. We conducted a case-control study on 1359 breast cancer cases and 2389 matched controls, nested within the European Prospective Investigation into Cancer and Nutrition, to examine the association of common genetic variants in the genes coding for ghrelin (GHRL) and its receptor (GHSR) with anthropometric measures, circulating insulin growth factor I (IGF-I) and insulin-like growth factor-binding protein 3 and breast cancer risk. Pair-wise tagging was used to select the 15 polymorphisms that represent the majority of common genetic variants across the GHRL and GHSR genes. A significant increase in breast cancer risk was observed in carriers of the GHRL rs171407-G allele (odds ratio: 1.2; 95% confidence interval: 1.0-1.4; P = 0.02). The GHRL single-nucleotide polymorphism rs375577 was associated with a 5% increase in IGF-I levels (P = 0.01). A number of GHRL and GHSR polymorphisms were associated with body mass index (BMI) and height (P between <0.01 and 0.04). The false-positive report probability (FPRP) approach suggests that these results are noteworthy (FPRP < 0.20). The results presented here add to a growing body of evidence that GHRL variations are associated with BMI. Furthermore, we have observed evidence for association of GHRL polymorphisms with circulating IGF-I levels and with breast cancer risk. These associations, however, might also be due to chance findings and further large studies are needed to confirm our results.