Epigenetics of the molecular clock and bacterial diversity in bipolar disorder.

Objectives The gut microbiome harbors substantially more genetic material than our body cells and has an impact on a huge variety of physiological mechanisms including the production of neurotransmitters and the interaction with brain functions through the gut-brain-axis. Products of microbiota can affect methylation according to preclinical studies. The current investigation aimed at analyzing the correlation between gut microbiome diversity and the methylation of the clock gene ARNTL in individuals with Bipolar Disorder (BD). Methods Genomic DNA was isolated from fasting blood of study participants with BD (n = 32). The methylation analysis of the ARNTL CG site cg05733463 was performed by bisulfite treatment of genomic DNA with the Epitect kit, PCR and pyrosequencing. Additionally, DNA was extracted from stool samples and subjected to 16S rRNA sequencing. QIIME was used to analyze microbiome data. Results Methylation status of the ARNTL CpG position cg05733463 correlated significantly with bacterial diversity (Simpson index: r= -0.389, p = 0.0238) and evenness (Simpson evenness index: r= -0.358, p = 0.044). Furthermore, bacterial diversity differed significantly between euthymia and depression (F(1,30) = 4.695, p = 0.039). Discussion The results of our pilot study show that bacterial diversity differs between euthymia and depression. Interestingly, gut microbiome diversity and evenness correlate negatively with methylation of ARNTL, which is known to regulate monoamine oxidase A transcription. We propose that alterations in overall diversity of the gut microbiome represent an internal environmental factor that has an epigenetic impact on the clock gene ARNTL which is thought to be involved in BD pathogenesis.

Gut microbiota, dietary intakes and intestinal permeability reflected by serum zonulin in women.

PURPOSE: Increased gut permeability causes the trespass of antigens into the blood stream which leads to inflammation. Gut permeability reflected by serum zonulin and diversity of the gut microbiome were investigated in this cross-sectional study involving female study participants with different activity and BMI levels. METHODS: 102 women were included (BMI range 13.24-46.89 kg m-2): Anorexia nervosa patients (n = 17), athletes (n = 20), normal weight (n = 25), overweight (n = 21) and obese women (n = 19). DNA was extracted from stool samples and subjected to 16S rRNA gene analysis (V1-V2). Quantitative Insights Into Microbial Ecology (QIIME) was used to analyze data. Zonulin was measured with ELISA. Nutrient intake was assessed by repeated 24-h dietary recalls. We used the median of serum zonulin concentration to divide our participants into a "high-zonulin" (> 53.64 ng/ml) and "low-zonulin" (< 53.64 ng/ml) group. RESULTS: The alpha-diversity (Shannon Index, Simpson Index, equitability) and beta-diversity (unweighted and weighted UniFrac distances) of the gut microbiome were not significantly different between the groups. Zonulin concentrations correlated significantly with total calorie-, protein-, carbohydrate-, sodium- and vitamin B12 intake. Linear discriminant analysis effect size (LEfSe) identified Ruminococcaceae (LDA = 4.163, p = 0.003) and Faecalibacterium (LDA = 4.151, p = 0.0002) as significantly more abundant in the low zonulin group. CONCLUSION: Butyrate-producing gut bacteria such as Faecalibacteria could decrease gut permeability and lower inflammation. The diversity of the gut microbiota in women does not seem to be correlated with the serum zonulin concentration. Further interventional studies are needed to investigate gut mucosal permeability and the gut microbiome in the context of dietary factors.

The role of tryptophan metabolism and food craving in the relationship between obesity and bipolar disorder.

BACKGROUND & AIMS: Individuals with bipolar disorder (BD) have a significantly increased risk of obesity-related conditions. The imbalance between food intake and energy expenditure is assumed to be a major risk factor for obesity in BD. This study analyzed food craving in relation to anthropometric, metabolic, and neurobiological parameters in a well-characterized cohort of euthymic individuals with BD. METHODS: One-hundred-thirty-five patients completed the Food-Craving Inventory assessing four categories of food craving (fat, fast-food, sweets and carbohydrate craving). Additionally, clinical, metabolic and anthropometric parameters were assessed. RESULTS: Higher levels of fat craving were observed in males, versus females, with BD. High levels of carbohydrate craving positively correlated with kynurenine and the kynurenine-to-tryptophan ratio. Higher serum nitrite and neopterin levels were related to fat craving. Parameters of fat metabolism (triglycerides, high-density lipoprotein) were associated with fat and fast-food craving. Anthropometric measures of obesity (e.g. body mass index, waist-to-hip-ratio) were not related to food craving. CONCLUSIONS: Overweight/obese individuals with BD show an increased driving of tryptophan down the kynurenine pathways, as indicated by an increase in the serum kynurenine-to-tryptophan ratio. The driving of tryptophan down the kynurenine pathway is mediated by immune-inflammatory activity and stress. The correlation of increased kynurenine with food craving, especially carbohydrate craving, probably indicates a regulatory deficit in the maintenance of chronic inflammatory processes in obesity and BD. Food craving seems to be of clinical importance in the treatment of metabolic disturbances in BD, although not associated with anthropometric measures of obesity. Rather, food craving correlates with blood metabolic parameters and an increased activation of the kynurenine pathway, both of which are linked to higher affective symptomatology and the development of cardiovascular diseases.

Abdominal obesity is associated with impaired cognitive function in euthymic bipolar individuals.

OBJECTIVES: Overweight/obesity has been implicated to play a role in cognitive deficits in bipolar disorder (BD). This study aims to identify the relationship between body fat distribution and different domains of cognition in BD during euthymia. METHODS: A sample of 100 euthymic individuals with BD was measured with a cognitive test battery (i.e., Trail Making Test-A-B/TM-A/B, d2 Test of Attention, Stroop test, California Verbal Learning Test/CVLT) and an anthropometric measures set (body mass index, waist circumference, hip circumference, waist-to-hip-ratio, waist-to-height-ratio, and lipometry). Patient data were compared with a healthy control group (n = 64). RESULTS: Results show that overweight patients with BD exhibit lower performance in the TMT-A/B as well as in the free recall performance of the CVLT compared to normal-weight patients with BD and controls. In bipolar individuals, (abdominal) obesity was significantly associated with a poor cognitive performance. In bipolar females, associations with measures of verbal learning and memory were found; in bipolar males, associations with poor performance in the TMT-A/B and in the Stroop interference task were demonstrated. In controls, no associations were found. CONCLUSIONS: There are several possible pathways moderating the association between obesity and cognition in BD. Anthropometric and lipometry data underline the substantial mediating impact of body fat distribution on cognition in BD.

Impaired probabilistic classification learning with feedback in patients with major depression.

BACKGROUND: The function of basal ganglia (BG) in the pathophysiology of major depression (MD) is still unclear. Recent research found changes in BG regarding size, structure and cerebral perfusion in patients with MD. Neuroimaging shows recruitment of the striatum during feedback (FB) based incidental learning of probabilistic classification learning, while the medial temporal lobe (MTL) is associated with paired associate (PA) based incidental learning. The purpose of this study was to evaluate whether FB-based incidental learning is affected in MD. METHODS: The FB and PA versions of the weather prediction task (WPT), a task of incidental probabilistic classification learning, were completed by patients with MD (n=44) and healthy controls (n=44). In FB-learning the participants received either a "thumbs-up" or "thumbs-down" message according to their right or wrong classification of cards to a certain kind of weather (either rainy or fine), while in PA learning no classification was required. Severity of MD was rated on the Beck Depression Inventory and Hamilton Rating Scale for depression. RESULTS: Patients with MD were selectively impaired on the FB task relative to controls (p<0.05), while no significant difference was found for PA learning between the two groups. Furthermore, there were no significant differences between FB and PA-learning within the patient and control groups. CONCLUSION: Our results indicate a distinct impairment on the FB-based version of the weather prediction task. These findings implicate disturbed reinforcement learning in this group of patients.

[Predictors of mental and physical quality of life in Huntington's disease]. / Prädiktoren der psychischen und physischen Lebensqualität beim Morbus Huntington.

BACKGROUND: The assessment of health-related quality of life (hrQoL) is an important tool in therapy studies and in the treatment of patients with Huntington's disease (HD). In the absence of causal interventions, HD therapy targets the alleviation of symptoms aiming to improve impaired hrQoL. The aim of this study was to determine the impact of disease characteristics on hrQoL in HD. METHODS: A total of 80 genetically confirmed HD patients underwent an assessment using the Unified Huntington's Disease Rating Scale, the Beck Depression Inventory, the Hamilton Rating Scale and the SF-36, a scale for the assessment of physical and mental QoL. RESULTS: Multiple regression analysis revealed that health-related physical and mental QoL was considerably influenced by the functional capacity. The mental QoL also correlated with the degree of depressive symptoms, age and the number of CAG repeats. However, there was no statistical relation between QoL and motor and cognitive abilities. DISCUSSION: This study underlines the relationship between function capacity and depressive symptoms with mental and physical QoL. This is the first time that hrQoL has been investigated in a German speaking cohort. The results are in accordance with previous studies of hrQoL in HD.

[Verbal memory in patients with major depression]. / Das verbale Gedächtnis bei depressiven Patienten.

INTRODUCTION: Patients with major depression commonly report memory deficits but studies on this topic have shown inconsistent results. The aim of this study was to determine whether patients with major depression showed any differences in explicit verbal memory compared to healthy controls. MATERIAL AND METHODS: We used the California verbal learning test (CVLT) in order to compare the explicit verbal memory of 30 patients (21 women and 9 men) to a healthy control group (23 women and 10 men). RESULTS: The results showed no significant differences between verbal memory performance of patients with major depression and healthy controls. DISCUSSION: Verbal memory of depressive patients with antidepressant pharmacotherapy showed no significant differences compared to a healthy control group. It can be assumed that verbal memory in depression depends on variable parameters (e.g. age, severity and duration of depression and medication). More studies with a larger number of patients should be conducted to obtain reliable results about explicit verbal memory in depression.