Genome wide search for genetic determinants of habitual alcohol, tobacco and coffee use, obesity-related traits, response to mental and physical stress and hemodynamic traits

Links among substance use, obesity, stress and related cardiovascular outcomes may be in part due to shared genetic factors. To investigate this hypothesis, we performed genome-wide linkage and association scans for genetic components of habitual alcohol, tobacco and coffee use, response to mental and physical stress, obesity related anthropometric traits and heart rate (HR) and blood pressure (BP) measurements in 119 multigenerational French Canadian families from founder population of Saguenay-Lac-St-Jean region using 58000 SNPs and 437 microsatellite markers and followed with functional annotation on resulted genes.  We found significant phenotypic correlations among substance use, obesity, stress and hemodynamic traits. For instance, alcohol and tobacco users had attenuated HR response to mental stress; moreover, tobacco users had lower BP compared to non users; Hypertensives had stronger HR and systolic blood pressure (SBP) response to mental stress and higher body mass index (BMI), compared to normotensives; Use of tobacco seemed to increase the epinephrine level in body and higher epinephrine level was correlated with lower BMI. Consistent with phenotypic relatedness, we found numerous shared genes associated / linked to substance use, obesity-related traits, response to mental and physical stress and hemodynamic traits including CAMK4, CNTN4, DLG2, DAG1, FHIT, GRID2, ITPR2, NOVA1, NRG3 and PRKCE forming protein interaction network, involved in synaptic plasticity and highly expressed in brain related tissues; moreover, pathway analysis on identified genes pointed (P = 0.03) to Long-Term Potentiation pathway. Large portions of variation of studied traits were explained by sex and hypertension status, focusing on tobacco use we noted that degree and the direction of correlations of obesity, hemodynamic and stress related traits with tobacco use vary according to sex and hypertension status; for instance, while in males, current tobacco users were slender compared to never or former tobacco users, there were no such differences in females; moreover, we found several obesity related traits that their correlations with smoking behavior seemingly root in genetic factors rather than smoking effect itself. Sex- and hypertension differences in heritabilities of many of these traits were also observed; meanwhile, specific subgroup genetic analyses uncovered additional shared synaptic genes among these traits including CAMK4, CNTN5, DNM3, KCNAB1 (Hypertension-specific), CNTN4, DNM3, FHIT, ITPR1 and NRXN3 (Sex-specific) having protein interactions with genes driven from general analysis; moreover, the results of pathway analysis and reported gene expression profiles of resulted genes from subgroup analyses revealed similar characteristics to those from general analysis.  The substantial overlap among genomic determinants of substance use, stress, obesity and hemodynamic traits supports the notion that the genetic variations in pathways of synaptic plasticity may be a common interface behind them as well as observed sex and hypertension genetic differences, we also think synaptic plasticity may underlie many complex phenotypes in which life style is a contributing factor; moreover, our findings indicate considering subgroup and network-based approaches enhance understanding of polygenic nature of complex phenotypes as well as shared molecular underpinnings among them.

Keyphrases: Stress, Synapse, Genetic mapping, Substance use, Obesity-related traits, Stress, Heart rate, Blood pressure, Synapse, Subgroup analysis, Gene network, Phenotype network