Brain-derived neurotrophic factor (Val66Met) polymorphism and olfactory ability in young adults

Variant brain-derived neurotrophic factor val66met polymorphism engages memory-associated systems to augment olfaction

The neurogenetic basis of variability in human olfactory function remains elusive. This study examined olfactory performance and resting-state functional neuroimaging results from healthy volunteers within the context of the brain-derived neurotrophic factor (BDNF) val66met polymorphism with the aim of unraveling the genotype-associated intrinsic reorganization of the olfactory network. We found that the presence of the Met allele is associated with better olfactory identification and additional engagement of semantic memory system within the olfactory network, in an allele dosage-dependent manner. This suggests that the Met allele may promote adaptive neural reorganization to augment olfactory capacity.

ERRγ ligand HPB2 upregulates BDNF-TrkB and enhances dopaminergic neuronal phenotype

Brain derived neurotrophic factor (BDNF) promotes maturation of dopaminergic (DAergic) neurons in the midbrain and positively regulates their maintenance and outgrowth. Therefore, understanding the mechanisms regulating the BDNF signaling pathway in DAergic neurons may help discover potential therapeutic strategies for neuropsychological disorders associated with dysregulation of DAergic neurotransmission. Because estrogen-related receptor gamma (ERRγ) is highly expressed in both the fetal nervous system and adult brains during DAergic neuronal differentiation, and it is involved in regulating the DAergic neuronal phenotype, we asked in this study whether ERRγ ligand regulates BDNF signaling and subsequent DAergic neuronal phenotype. Based on the X-ray crystal structures of the ligand binding domain of ERRγ, we designed and synthesized the ERRγ agonist, (E)-4-hydroxy-N'-(4-(phenylethynyl)benzylidene)benzohydrazide (HPB2) (K_d value, 8.35 μmol/L). HPB2 increased BDNF mRNA and protein levels, and enhanced the expression of the BDNF receptor tropomyosin receptor kinase B (TrkB) in human neuroblastoma SH-SY5Y, differentiated Lund human mesencephalic (LUHMES) cells, and primary ventral mesencephalic (VM) neurons. HPB2-induced upregulation of BDNF was attenuated by GSK5182, an antagonist of ERRγ, and siRNA-mediated ERRγ silencing. HPB2-induced activation of extracellular-signal-regulated kinase (ERK) and phosphorylation of cAMP-response element binding protein (CREB) was responsible for BDNF upregulation in SH-SY5Y cells. HPB2 enhanced the DAergic neuronal phenotype, namely upregulation of tyrosine hydroxylase (TH) and DA transporter (DAT) with neurite outgrowth, both in SH-SY5Y and primary VM neurons, which was interfered by the inhibition of BDNF-TrkB signaling, ERRγ knockdown, or blockade of ERK activation. HPB2 also upregulated BDNF and TH in the striatum and induced neurite elongation in the substantia nigra of mice brain. In conclusion, ERRγ activation regulated BDNF expression and the subsequent DAergic neuronal phenotype in neuronal cells. Our results might provide new insights into the mechanism underlying the regulation of BDNF expression, leading to novel therapeutic strategies for neuropsychological disorders associated with DAergic dysregulation.

Brain-Derived neurotrophic factor Val66Met induces female-specific changes in impulsive behaviour and alcohol self-administration in mice

Substance use disorders are a debilitating neuropsychiatric condition, however it remains unclear why some individuals are at greater risk of substance use disorders than others and what genetic factors determine such individual differences. Impulsivity appears a promising candidate endophenotype to bridge the gap between genetic risk and addiction. Brain-derived neurotrophic factor (BDNF), and in particular the BDNF^Val66Met polymorphism, has been suggested to be involved in both impulsivity and substance use disorders, however results so far have been inconsistent. To investigate the role of BDNF, and more specifically the BDNF^Val66Met polymorphism, in both impulsivity and operant alcohol self-administration using the same animal model. Separate cohorts of humanized Val66Met transgenic mice were assessed for either trait impulsivity in the 5-choice serial reaction time (5-CSRT) touchscreen task, or propensity towards obtaining ethanol in an operant paradigm. It was found that female hBDNF^Val/Val mice exhibited both greater impulsivity compared to hBDNF^Met/Met mice of the same sex as shown by a higher number of premature responses at one of three increased inter-trial intervals tested in the 5-CSRT task, and a greater propensity toward stable ethanol self-administration relative to male mice of the same genotype in the operant paradigm. By contrast, male mice showed no difference between genotypes in impulsivity or stable ethanol self-administration. The hBDNF^Met/Met genotype appears to sex-specifically alter aspects of both impulsive behaviour and addiction propensity. These results suggest that impulse behaviour may be a possible predictor of addiction risk.

[The genetic predictors of cognitive impairment in Parkinson's disease]

Parkinson's disease (PD) is a common neurodegenerative disorder that can be both sporadic and familial. A number of studies are devoted to the study of non-motor symptoms in PD today. Cognitive deficits, and especially dementia, are one of the most severe and disabling non-motor symptoms of PD. More than a quarter of patients in the early stages of PD have a moderate cognitive impairment, more than half of patients with PD develop dementia within 10 years from the date of diagnosis. Using genome-wide association studies (GWAS), a number of genes associated with cognitive impairment have been identified based on a comparison of genetic and clinical phenotypes. These genes can be divided into three groups: genes that lead to the development of PD and are inherited according to the laws of Mendel (SNCA), genes that are risk factors for PD development (GBA, MAPT) and genes associated with the development of cognitive impairment, but not with PD (COMT, APOE, BDNF). This review examines the effect of genetic variants in the above-mentioned genes on cognitive functions in patients with PD. The elucidation of the genetic basis of cognitive deficits in PD could help in choice of treatment tactics and in development of new therapeutic strategies.

Olfactory disturbances in ageing with and without dementia: towards new diagnostic tools

BACKGROUND

Olfactory disorders increase with age and often affect elderly people who have pre-dementia or dementia. Despite the frequent occurrence of olfactory changes at the early stages of neurodegenerative disorders such as Alzheimer's disease, olfactory disorders are rarely assessed in daily clinical practice, mainly due to a lack of standardised assessment tools. The aims of this review were to (1) summarise the existing literature on olfactory disorders in ageing populations and patients with neurodegenerative disorders; (2) present the strengths and weaknesses of current olfactory disorder assessment tools; and (3) discuss the benefits of developing specific olfactory tests for neurodegenerative diseases.

METHODS

A systematic review was performed of literature published between 2000 and 2015 addressing olfactory disorders in elderly people with or without Alzheimer's disease or other related disorders to identify the main tools currently used for olfactory disorder assessment.

RESULTS

Olfactory disorder assessment is a promising method for improving both the early and differential diagnosis of Alzheimer's disease. However, the current lack of consensus on which tests should be used does not permit the consistent integration of olfactory disorder assessment into clinical settings.

CONCLUSION

Otolaryngologists are encouraged to use olfactory tests in older adults to help predict the development of neurodegenerative diseases. Olfactory tests should be specifically adapted to assess olfactory disorders in Alzheimer's disease patients.

Antioxidant and inflammatory biomarkers for the identification of prodromal Parkinson's disease

OBJECTIVES

We explored the role of oxidative stress and inflammatory molecules as potential Parkinson (PD) biomarkers and correlated biological with non-motor abnormalities (olfactory impairment and dysautonomia), in patients with idiopathic REM behavior disorder (iRBD) (prodromal PD) and established PD.

METHODS

We recruited 11 iRBD and 15 patients with idiopathic PD (Hohen&Yahr 1-3, on L-DOPA and dopamine agonists combination therapy) and 12 age- and sex-matched controls (CTRL). We measured total olfactory score (TOS), autonomic function [deep breathing (DB), lying to standing (LS) and Valsalva manoeuvre (VM) ratios], blood reduced glutathione (Br-GSH), oxidative stress and inflammatory markers (neopterin).

RESULTS

Anosmia was similarly prevalent in iRBD (36%) and PD (33%) patients, but absent in CTRL. Orthostatic hypotension was more common among iRBD (73%) and PD (60%) than in CTRL (25%). By univariable ordinal logistic regression, TOS, Br-GSH, LS and VM ratio worsened from CTRL to iRBD and PD groups. Only reduced Br-GSH levels (p=0.037, OR=0.994; 95%CI 0.988-1.000) were independently associated to PD. TOS correlated with Br-GSH (R=0.34, p=0.037), VM ratio (R=0.43, p=0.015), and neopterin (rho=0.39, p=0.016).

CONCLUSIONS

Reduced systemic antioxidant capacity is found in prodromal and overt PD and may represent, in association with olfactory loss and cardiovascular dysautonomia, a useful biomarker for an integrative, early diagnosis of PD.

A Novel Application for Cognitive Evaluation in Mountain Ultramarathons: Olfactory Assessment

OBJECTIVE

Olfactory function, a cognitive impairment biomarker, was evaluated in mountain ultramarathon (MUM) runners during the Tor des Géants race (332.5 km with an overall altitude gain of 24,000 m; altitude range 330-3296 m above the sea).

METHODS

An Odor Identification Test was administered before (T0; n = 53), at 148.7 kms (T1; n = 32) and after the race (T2; n = 28). The effect of dehydration and sleep deprivation on olfactory function was assessed. Olfactory function was also assessed in non-MUM athletes and sedentary controls (C) at rest.

RESULTS

A majority of the athletes completed the olfactory test at all time intervals. Olfactory function decreased throughout the race (T0: 13.8 ± 1.9, T1: 13.7 ± 1.6, T2: 13.1 ± 1.8; T0 vs T2 P = .01). There was no relationship with race time or sleep deprivation on the sense of smell throughout the competition. However, there was a combined effect with decreased olfaction during the second half of the race, while a poor relationship was seen between olfaction and total body water at midterm (T1: rs = -0.427; P = .019), but not at baseline or after the race. MUM athletes had similar olfactory scores to C (13.8 ± 1.9 vs 13.7 ± 1.4) and non-MUM (13.8 ± 1.9 vs 13.9 ± 1.6) athletes.

CONCLUSIONS

This pilot study showed the feasibility of olfactory evaluation as a minimally invasive cognitive impairment assessment. The test can be used in logistically difficult environments, adding scientific value to this promising method. Although olfaction decreased after prolonged physical activity, further studies are warranted to make the relationship between cognition and external factors (eg, sleep deprivation, dehydration) more clear.

Association Between Atopic Dermatitis and Autism Spectrum Disorders: A Systematic Review

BACKGROUND

Atopic dermatitis (AD) is an allergic disorder caused by both immunological dysregulation and epidermal barrier defect. Several studies have investigated the association between AD and mental health disorders. Autism spectrum disorders (ASD) are a heterogeneous group of neurodevelopmental conditions characterized by impairments in social communication and restricted, stereotyped interests and behaviors. The concurrent increased prevalence of AD and ASD in the last decades has led many scientists to investigate the relationship between the two diseases.

OBJECTIVE

The aim of this systematic review was to examine the association between AD and ASD.

METHODS

A systematic review was performed according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. PubMed and ScienceDirect were searched up to March 2015 for all reports examining the association between ASD and AD. Descriptive statistics of the studies are reported.

RESULTS

The review included 18 studies assessing the association between ASD and AD. Of these studies, two focused on ASD in relation to AD alone, 14 discussed ASD in relation to both AD and other atopic disorders, and two evaluated AD in parents of children with ASD. Most of these studies found a positive association between the two disorders, although there were some studies going in the opposite direction. The entity of the association is somewhat inconsistent among the different studies given that the frequencies of AD in ASD compared with a control group ranged from 7 to 64.2%. In addition, odds ratios (ORs) or hazard ratios (HRs) gave different results as three studies found a weak association with an OR below 2 and a nonsignificant p value, and three other studies found a moderate or strong association with an OR ranging from 1.52 to 7.17 and a significant p value. When all atopic disorders were considered when evaluating the risk of ASD, the association was strong with an HR of 3.4 or an OR of 1.24 and p < 0.001.

CONCLUSIONS

Overall, the results of this systematic review seem to reveal an association between ASD and AD, suggesting that subjects with ASD have an increased risk of presenting with AD compared with typically developing controls, and vice versa. This association is supported by clinical/epidemiological aspects, shared genetic background and common immunological and autoimmune processes. However, the variability in study population and design, and the presence of other risk factors acting as confounding factors, sometimes contribute to inconsistent results. Further studies are needed to clarify the underlying pathophysiologic mechanism explaining the association between ASD and AD and to explore the causal association between the two conditions.

Effect of Olfactory Stimulation in Agenesis of the Corpus Callosum: A Case Report

Objective: To evaluate the olfactory and psychophysical performances in a 13-year-old boy with intellectual disability and severe hypoplasia of the corpus callosum and of the olfactory bulbs, compared to controls.

Methods: The Sniffin’ Sticks Identification Test was administered to the patient and to a patient control child with cognitive delay, with the same mental (5 years) and chronological age, but normal brain magnetic resonance image. Two typically developing control participants, aged 13 and 5, were also evaluated. Psychophysical tests were performed during the olfactory assessment by smart portable sensors.

Results: A significant decrease in olfactory function and a different psychophysical response to stimuli were observed in the patient compared to control participants, suggesting absence of ‘odorous stress’. A higher olfactory score but a similar psychophysical trend was found in the patient control with cognitive delay, while the two other control participants showed a selective increase of the anxiety state depending on the odour presented.

Conclusions: Olfactory dysfunction is reported in children with neurodevelopmental disabilities. Low-cost, portable devices to assess olfactory function are proposed for use with children with intellectual disability. Stress monitoring by unobtrusive platforms provides discriminant information in this subset, as compared to controls.

Quantitative measurement of odor detection thresholds using an air dilution olfactometer, and association with genetic variants in a sample of diverse ancestry

Genetic association studies require a quantitative and reliable method for odor threshold assessment in order to examine the contribution of genetic variants to complex olfactory phenotypes. Our main goal was to assess the feasibility of a portable Scentroid air dilution olfactometer for use in such studies. Using the Scentroid SM110C and the SK5 n-butanol Sensitivity Kit (IDES Canada Inc.), n-butanol odor thresholds were determined for 182 individuals of diverse ancestry (mean age: 20.4 ± 2.5 years; n = 128 female; n = 54 male). Threshold scores from repeat participants were used to calculate a test–retest reliability coefficient, which was statistically significant (r = 0.754, p < 0.001, n = 29), indicating that the Scentroid provides reliable estimates of odor thresholds. In addition, we performed a preliminary genetic analysis evaluating the potential association of n-butanol odor thresholds to six single-nucleotide polymorphisms (SNPs) putatively involved in general olfactory sensitivity (GOS). The results of multiple linear regression analysis revealed no significant association between the SNPs tested and threshold scores. However, our sample size was relatively small, and our study was only powered to identify genetic markers with strong effects on olfactory sensitivity. Overall, we find that the Scentroid provides reliable quantitative measures of odor detection threshold and is well suited for genetic studies of olfactory sensitivity.