Noting emerging interest in the interaction between cannabinoids and orexins, a class of molecules involved in regulation of appetite, arousal, and energy regulation, Rotter and colleagues [113] examined a differences in Orexin A expression between cannabis dependent individuals, (tobacco) cigarette smokers, and non-smoking controls. Expression was measured by quantitative PCR in peripheral lymphocytes, and promoter methylation measured by methylation specific digestion and subsequent quantitative PCR. Cotinine, THC and metabolites of THC were not measured for comparison, nor were analyses adjusted for blood cell composition. Significant differences in Orexin A expression were found between all three groups. There was no difference found in mean Orexin A promoter methylation between groups, but their method precluded measurement of individual CpG methylation status to examine for differences between groups. Despite the lack of overall difference in methylation found, the differences in expression suggest that further investigation of this locus as a potential biomarker is warranted.
