Stress response pathways, appetite regulation, and drug addiction

Sugar Beverage Habitation Relieves Chronic Stress-Induced Anxiety-like Behavior but Elicits Compulsive Eating Phenotype via vLSGAD2 Neurons

Chronically stressed individuals are reported to overconsume tasty, palatable foods like sucrose to blunt the psychological and physiological impacts of stress. Negative consequences of high-sugar intake on feeding behavior include increased metabolic disease burdens like obesity. However, the neural basis underlying long-term high-sugar intake-induced overeating during stress is not fully understood. To investigate this question, we used the two-bottle sucrose choice paradigm in mice exposed to chronic unpredictable mild stressors (CUMS) that mimic those of daily life stressors. After 21 days of CUMS paralleled by consecutive sucrose drinking, we explored anxiety-like behavior using the elevated plus maze and open field tests. The normal water-drinking stressed mice displayed more anxiety than the sucrose-drinking stressed mice. Although sucrose-drinking displayed anxiolytic effects, the sucrose-drinking mice exhibited binge eating (chow) and a compulsive eating phenotype. The sucrose-drinking mice also showed a significant body-weight gain compared to the water-drinking control mice during stress. We further found that c-Fos expression was significantly increased in the ventral part of the lateral septum (vLS) of the sucrose-treated stressed mice after compulsive eating. Pharmacogenetic activation of the vLS glutamate decarboxylase 2(GAD2) neurons maintained plain chow intake but induced a compulsive eating phenotype in the naïve GAD2-Cre mice when mice feeding was challenged by flash stimulus, mimicking the negative consequences of excessive sucrose drinking during chronic stress. Further, pharmacogenetic activation of the vLS^GAD2 neurons aggravated anxiety of the stressed GAD2-Cre mice but did not alter the basal anxiety level of the naïve ones. These findings indicate the GABAergic neurons within the vLS may be a potential intervention target for anxiety comorbid eating disorders during stress.

Early life adversity and appetite hormones: The effects of smoking status, nicotine withdrawal, and relapse on ghrelin and peptide YY during smoking cessation

There is evidence suggesting that ghrelin and peptide YY (PYY) modulate stress responses and the rewarding effects of drugs, although no research has examined the impact of exposure to early life stress on these hormones in smokers nor during smoking cessation. This study examined the relationships between early life adversity (ELA) and circulating ghrelin and PYY during ad libitum smoking and early withdrawal in tobacco smokers (N = 98) who were interested in cessation. We also included a comparison group of nonsmokers (N = 36). We prospectively compared levels of hormones between smokers who were successful in quitting within a 2-week period, smokers who relapsed during that period, and nonsmokers. Results showed that ELA was positively associated with elevated ghrelin in nonsmokers. Among those reporting no ELA, successful quitters had higher ghrelin levels than nonsmokers during ad libitum smoking, while relapsers had higher ghrelin levels than nonsmokers during withdrawal. In addition, having no ELA was associated with a decline in ghrelin from the ad libitum to abstinence sessions in successful quitters; this withdrawal-related decline was not found in relapsers. Although effects of ELA, smoking group, and time on PYY were not significant, greater PYY was associated with reduced urges to smoke during withdrawal. These findings suggest the importance of considering changes in appetite-related hormones in individuals who are dependent on tobacco. This research provides additional indications for effects of ELA on appetite-stimulating hormones.

Cannabis use and stressful life events during the perinatal period: cross-sectional results from Pregnancy Risk Assessment Monitoring System (PRAMS) data, 2016

AIMS

We aimed to determine the association between stressful life events (SLEs) in the year prior to childbirth with (1) pre-pregnancy cannabis use, (2) cessation of cannabis use during pregnancy and (3) postpartum relapse to cannabis use.

DESIGN

We used data from the Pregnancy Risk Assessment Monitoring System (PRAMS) 2016, a cross-sectional, population-based surveillance system.

SETTING

Mailed and telephone surveys conducted in five states-Alaska, Colorado, Maine, Michigan and Washington-in the United States.

PARTICIPANTS

Women (n = 6061) who delivered a live infant within the last 6 months and had data on cannabis use.

MEASUREMENTS

Self-reported data included SLEs (yes/no response for 14 individual events in the 12 months prior to childbirth) and cannabis use [yes/no prior to pregnancy, during pregnancy, and at the time of the survey (approximately 2-6 months postpartum)]. The associations between SLEs and cannabis use (primary outcomes) were examined in logistic regression models adjusted for maternal demographics (e.g. age, race, education), geography (i.e. state of residence) and cigarette smoking.

FINDINGS

Pre-pregnancy, 16.4% (997/6061) of respondents endorsed using cannabis, with 36.4% (363/997) continuing cannabis use during pregnancy. Among the 63.6% (634/997) who did not report use during pregnancy, 23.2% (147/634) relapsed to cannabis use during the postpartum. Nine of the 14 possible SLEs were associated with increased odds of pre-pregnancy cannabis use [e.g. husband/partner or mother went to jail, adjusted odds ratio (aOR) = 2.16, 95% confidence interval (CI) = 1.30-3.62] and four were associated with increased odds of continued cannabis use during pregnancy (e.g. husband/partner lost job, aOR = 2.19, 95% CI = 1.21-3.96). The odds of postpartum relapse to cannabis were significantly associated with two SLEs (husband/partner said they did not want pregnancy, aOR = 2.86, CI = 1.10-7.72; husband/partner or mother went to jail, aOR = 0.37, 95% CI = 0.13-1.00).

CONCLUSIONS

Stressful life events during the year prior to childbirth appear to be linked to greater odds of women's cannabis use during the perinatal period, especially during pre-pregnancy.

Biological underpinnings from psychosocial stress towards appetite and obesity during youth: research implications towards metagenomics, epigenomics and metabolomics

Psychosocial stress, uncontrolled eating and obesity are three interrelated epidemiological phenomena already present during youth. This broad narrative conceptual review summarises main biological underpinnings of the stress-diet-obesity pathway and how new techniques can further knowledge. Cortisol seems the main biological factor from stress towards central adiposity; and diet, physical activity and sleep are the main behavioural pathways. Within stress-diet, the concepts of comfort food and emotional eating are highlighted, as cortisol affects reward pathways and appetite brain centres with a role for insulin, leptin, neuropeptide Y (NPY), endocannabinoids, orexin and gastrointestinal hormones. More recently researched biological underpinnings are microbiota, epigenetic modifications and metabolites. First, the gut microbiota reaches the stress-regulating and appetite-regulating brain centres via the gut-brain axis. Second, epigenetic analyses are recommended as diet, obesity, stress and gut microbiota can change gene expression which then affects appetite, energy homeostasis and stress reactivity. Finally, metabolomics would be a good technique to disentangle stress-diet-obesity interactions as multiple biological pathways are involved. Saliva might be an ideal biological matrix as it allows metagenomic (oral microbiota), epigenomic and metabolomic analyses. In conclusion, stress and diet/obesity research should be combined in interdisciplinary collaborations with implementation of several -omics analyses.

The preliminary investigation of orexigenic hormone gene polymorphisms on posttraumatic stress disorder symptoms

Orexigenic hormones are a group of hormones that can up-regulate appetite. Current studies have shown that orexigenic hormones also play important roles in stress responses and may be implicated in regulation of fear memory. However, these conclusions lack evidence from human studies. In this study, we examined associations between orexigenic hormone genes and fear-related mental disorders by investigating main, G × E, and G × G effects of ghrelin and orexin gene single nucleotide polymorphisms (SNPs) on human posttraumatic stress disorder (PTSD) symptoms in 1134 Chinese earthquake survivors. SNPs Leu72Met of the GHRL gene (rs696217), Ile408Val of the HCRTR1 gene (rs2271933) and Val308Ile of the HCRTR2 gene (rs2653349) were genotyped. None of the SNPs showed significant main or G × E effects. However, a significant interaction effect between GHRL rs696217 and HCRTR1 rs2271933 was found to predict the PTSD Checklist (PCL-5) total score (P =  0.007). Further analysis revealed different interaction patterns in males and females. For females, the rs2271933 G allele was associated with an increased PCL-5 total score (B = 2.59, P =  0.024) when the rs696217 genotype TT/TG was present. For males, the rs696217 T allele is associated with an increased PCL-5 total score (B = 3.62, P =  0.040) when the rs2271933 genotype GG/GA was present. These current findings expand our knowledge of physiological function of the orexigenic hormone system, and suggest its involvement in development of fear-related mental disorders such as PTSD.

Neuroendocrine response to GABA-B receptor agonism in alcohol-dependent individuals: Results from a combined outpatient and human laboratory experiment

Gamma-aminobutyric acid (GABA), the main inhibitory neurotransmitter in the nervous system, plays an important role in biobehavioral processes that regulate alcohol seeking, food intake, and stress response. The metabotropic GABA-B receptor has been investigated as a potential therapeutic target for alcohol use disorder, by using orthosteric agonists (e.g., baclofen) and positive allosteric modulators. Whether and how pharmacological manipulation of the GABA-B receptor, in combination with alcohol intake, may affect feeding- and stress-related neuroendocrine pathways remains unknown. In the present randomized, double-blind, placebo-controlled study, thirty-four alcohol-dependent individuals received baclofen (30 mg/day) or placebo in a naturalistic outpatient setting for one week, and then performed a controlled laboratory experiment which included alcohol cue-reactivity, fixed-dose priming, and self-administration procedures. Blood samples were collected, and the following neuroendocrine markers were measured: ghrelin, leptin, amylin, glucagon-like peptide-1 (GLP-1), insulin, prolactin, thyroid-stimulating hormone, growth hormone, cortisol, and adrenocorticotropic hormone (ACTH). During the outpatient phase, baclofen significantly increased blood concentrations of acyl-ghrelin (p = 0.01), leptin (p = 0.01), amylin (p = 0.004), and GLP-1 (p = 0.02). Significant drug × time-point interaction effects for amylin (p = 0.001) and insulin (p = 0.03), and trend-level interaction effects for GLP-1 (p = 0.06) and ACTH (p = 0.10) were found during the laboratory experiment. Baclofen, compared to placebo, had no effect on alcohol drinking in this study (p's ≥ 0.05). Together with previous studies, these findings shed light on the role of the GABAergic system and GABA-B receptors in the shared neurobiology of alcohol-, feeding-, and stress-related behaviors.