Developmental Trajectory of Height, Weight, and BMI in Children and Adolescents at Risk for Huntington's Disease: Effect of mHTT on Growth

BACKGROUND

The gene (Huntingtin or HTT) causing Huntington's disease (HD) is vital for development and is expressed throughout the brain and body lifelong. The mutant form (mHTT) may influence growth and development.

OBJECTIVE

To determine the impact of mHTT on human measures of growth, including height, weight, and body mass index (BMI), between child and adolescent carriers of mHTT and control peers.

METHODS

Children ages 6-18 years of age (n = 186) at risk for HD were enrolled in the KidsHD study. For research purposes only, genetic testing was performed to classify participants as Gene-Expanded (GE = 78) or as Gene Non-Expanded (GNE = 108). Outcome measures included height, weight, and body mass index (BMI). Mixed models were used to determine if non-linear age trends differed between groups for BMI, height, and weight.

RESULTS

Differences were seen in the trajectory of BMI in which the GE group reached a plateau in late adolescence with no further increase, compared with a nearly linear increase in the GNE group. There was a significant sex interaction pattern where GE males were taller than GNE males in adolescence, in the presence of similar weight. In contrast, GE females weighed significantly less than their GNE counterparts in adolescence, in the presence of similar height.

CONCLUSION

Measures of growth are abnormal in child and adolescent carriers of mHTT, decades before HD onset. Although further studies are needed for replication, the current findings suggest that developmental aberrations may be systemic and a vital part of disease pathology.

Brain structure in juvenile-onset Huntington disease

OBJECTIVE

To assess brain morphometry in a sample of patients with juvenile-onset Huntington disease (JOHD) and several mouse models of Huntington disease (HD) that likely represent the human JOHD phenotype.

METHODS

Despite sharing the mutation in the Huntingtin gene, adult-onset HD characteristically presents as a hyperkinetic motor disorder, while JOHD typically presents as a hypokinetic motor disease. The University of Iowa Kids-JHD program enrolls individuals 5 to 25 years of age who have already received the clinical diagnosis. A total of 19 children with juvenile HD (JHD) (mean CAG = 72) were studied. Patients with JHD were compared to healthy controls (n = 234) using a cross-sectional study design. Volumetric data from structural MRI was compared between groups. In addition, we used the same procedure to evaluate brain morphology of R6/2, zQ175, HdhQ250 HD mice models.

RESULTS

Participants with JHD had substantially reduced intracranial volumes. After controlling for the small intracranial volume size, the volumes of subcortical regions (caudate, putamen, globus pallidus, and thalamus) and of cortical white matter were significantly decreased in patients with JHD. However, the cerebellum was proportionately enlarged in the JHD sample. The cerebral cortex was largely unaffected. Likewise, HD mice had a lower volume of striatum and a higher volume of cerebellum, mirroring the human MRI results.

CONCLUSIONS

The primary pathology of JOHD extends beyond changes in the striatal volume. Brain morphology in both mice and human patients with JHD shows proportional cerebellar enlargement. This pattern of brain changes may explain the unique picture of hypokinetic motor symptoms in JHD, which is not seen in the hyperkinetic chorea-like phenotype of adult-onset HD.

Effect of Trinucleotide Repeats in the Huntington's Gene on Intelligence

Background

Huntington's Disease (HD) is caused by an abnormality in the HTT gene. This gene includes trinucleotide repeats ranging from 10 to 35, and when expanded beyond 39, causes HD. We previously reported that CAG repeats in the normal range had a direct and beneficial effect on brain development with higher repeats being associated with higher cognitive function. The current study now expands this line of inquiry to evaluate the effects of CAG repeat throughout the entire spectrum of repeats from 15 to 58.

Methods

We evaluated brain function in children ages 6–18 years old. DNA samples were processed to quantify the number of CAG repeats within HTT. Linear regression was used to determine if number of CAG repeats predicted measures of brain function.

Findings

The number of repeats in HTT, had a non-linear effect on a measure of general intelligence with an inverted U shape pattern. Increasing repeat length was associated with higher GAI scores up until roughly 40–41 repeats. After this peak, increasing repeat length was associated with declining GAI scores.

Interpretation

HTT may confer an advantage or a disadvantage depending upon the repeat length, playing a key role in the determination of intelligence, or causing a uniquely human brain disease.

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The HTT gene includes trinucleotide repeats ranging from 10 to 35 in the normal population.

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Huntington’s disease is caused when the trinucleotide repeats in the HTT gene expand beyond the normal range.

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The gene is vital for brain growth in which each repeat contributes to the development of brain function, measured as intelligence.

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Increasing repeats are beneficial to a certain point, then becomes detrimental to intelligence, forming an inverted U relationship.

A Faustian Bargain: Could the key to the evolution of the human brain be found in a dreadful disease? Huntington's Disease is a fatal progressive brain disease caused by a single gene. Results from the current study show that the same gene is important for brain development and intelligence. Therefore, this gene may have a simultaneous advantage and disadvantage: a role in the evolution of a superior human brain, yet the disadvantage of a uniquely human brain disease.

Sex-specific effects of the Huntington gene on normal neurodevelopment

Huntington disease is a neurodegenerative disorder caused by a gene (HTT) with a unique feature of trinucleotide repeats ranging from 10 to 35 in healthy people; when expanded beyond 39 repeats, Huntington disease develops. Animal models demonstrate that HTT is vital to brain development; however, this has not been studied in humans. Moreover, evidence suggests that triplet repeat genes may have been vital in evolution of the human brain. Here we evaluate brain structure using magnetic resonance imaging and brain function using cognitive tests in a sample of school-aged children ages 6 to 18 years old. DNA samples were processed to quantify the number of CAG repeats within HTT. We find that the number of repeats in HTT, below disease threshold, confers advantageous changes in brain structure and general intelligence (IQ): the higher the number of repeats, the greater the change in brain structure, and the higher the IQ. The pattern of structural brain changes associated with HTT is strikingly different between males and females. HTT may confer an advantage or a disadvantage depending on the repeat length, playing a key role in either the evolution of a superior human brain or development of a uniquely human brain disease. © 2016 Wiley Periodicals, Inc.

A survey-based study identifies common but unrecognized symptoms in a large series of juvenile Huntington's disease

AIM

The symptoms of Huntington's disease are well known, yet the symptoms of juvenile Huntington's disease (JHD) are less established due to its rarity. The study examined a cluster of symptoms considered to be common, but under-recognized in JHD: pain, itching, sleeping difficulties, psychosis and tics.

MATERIALS & METHODS

A symptom survey was constructed using the online tool Qualtrics and dispersed to JHD caregivers through websites.

RESULTS

A total of 33 surveys were completed. Disrupted sleep was the most prevalent symptom (87%), followed by tics (78%), pain (69%), itching (60%) and psychosis (39%).

CONCLUSION

Despite limitations, the study supports that there are symptoms in the JHD population that are not considered classic, however, are common and significant for patients and caregivers.

A randomized, double-blind, placebo-controlled trial of coenzyme Q10 in Huntington disease

OBJECTIVE

To test the hypothesis that chronic treatment of early-stage Huntington disease (HD) with high-dose coenzyme Q10 (CoQ) will slow the progressive functional decline of HD.

METHODS

We performed a multicenter randomized, double-blind, placebo-controlled trial. Patients with early-stage HD (n = 609) were enrolled at 48 sites in the United States, Canada, and Australia from 2008 to 2012. Patients were randomized to receive either CoQ 2,400 mg/d or matching placebo, then followed for 60 months. The primary outcome variable was the change from baseline to month 60 in Total Functional Capacity score (for patients who survived) combined with time to death (for patients who died) analyzed using a joint-rank analysis approach.

RESULTS

An interim analysis for futility revealed a conditional power of <5% for the primary analysis, prompting premature conclusion in July 2014. No statistically significant differences were seen between treatment groups for the primary or secondary outcome measures. CoQ was generally safe and well-tolerated throughout the study.

CONCLUSIONS

These data do not justify use of CoQ as a treatment to slow functional decline in HD.

CLINICALTRIALSGOV IDENTIFIER

NCT00608881.

CLASSIFICATION OF EVIDENCE

This article provides Class I evidence that CoQ does not slow the progressive functional decline of patients with HD.

Measures of growth in children at risk for Huntington disease

OBJECTIVE

The effect of mHTT on human development was examined by evaluating measures of growth in children at risk for Huntington disease (HD).

METHODS

Children at risk for HD with no manifest symptoms (no juvenile HD included) were enrolled and tested for gene expansion for research purposes only. Measurements of growth (height, weight, body mass index [BMI], and head circumference) in children tested as gene-expanded (n = 20, 7-18 years of age, CAG repeats ≥39) were compared to those of a large database of healthy children (n = 152, 7-18 years of age).

RESULTS

Gene-expanded children had significantly lower measures of head circumference, weight, and BMI. Head circumference was abnormally low even after correcting for height, suggesting a specific deficit in brain growth, rather than a global growth abnormality.

CONCLUSIONS

These results indicate that, compared to a control population, children who were estimated to be decades from HD diagnosis have significant differences in growth. Further, they suggest that mHTT may play a role in atypical somatic, and in particular, brain development.

Perceived stress in prodromal Huntington disease

This study examines perceived stress and its relationship to depressive symptoms, life changes and functional capacity in a large sample of individuals who are positive for the Huntington disease (HD) gene expansion but not yet diagnosed. Participants were classified by estimated proximity to HD diagnosis (far, mid, near) and compared with a non-gene-expanded comparison group. Persons in the mid group had the highest stress scores. A significant interaction between age and time since HD genetic testing was also found. Secondary analyses using data from a different data collection point and including a diagnosed group showed the highest stress scores in the diagnosed group. Possible explanations and implications are discussed.

Microbial sulfide oxidation in the oxic-anoxic transition zone of freshwater sediment: involvement of lithoautotrophic Magnetospirillum strain J10

The oxic-anoxic transition zone (OATZ) of freshwater sediments, where opposing gradients exist of reduced iron and sulfide with oxygen, creates a suitable environment for microorganisms that derive energy from the oxidation of iron or sulfide. Gradient microcosms incubated with freshwater sediment showed rapid microbial turnover of sulfide and oxygen compared with sterile systems. Microcosms with FeS as a substrate also showed growth at the OATZ and subsequent dilution series resulted in the isolation of three novel strains, of which strain J10 grows chemolithoautotrophically with reduced sulfur compounds under microaerobic conditions. All three strains are motile spirilla with bipolar flagella, related to the genera Magnetospirillum and Dechlorospirillum within the Alphaproteobacteria. Strain J10 is closely related to Magnetospirillum gryphiswaldense and is the first strain in this genus found to be capable of autotrophic growth. Thiosulfate was oxidized completely to sulfate, with a yield of 4 g protein mol(-1) thiosulfate, and autotrophic growth was evidenced by incorporation of (13)C derived from bicarbonate into biomass. A putative gene encoding ribulose 1,5-bisphosphate carboxylase/oxygenase type II was identified in strain J10, suggesting that the Calvin-Benson-Bassham cycle is used for autotrophic growth. Analogous genes are also present in other magnetospirilla, and in the autotrophically growing alphaproteobacterium magnetic vibrio MV-1.

Basic helix-loop-helix transcription factor NEUROG1 and schizophrenia: effects on illness susceptibility, MRI brain morphometry and cognitive abilities

Transcription factors, including the basic helix-loop-helix (bHLH) family, regulate numerous genes and play vital roles in controlling gene expression. Consequently, transcription factor mutations can lead to phenotypic pleiotropy, and may be a candidate mechanism underlying the complex genetics and heterogeneous phenotype of schizophrenia. Neurogenin1 (NEUROG1; a.k.a. Ngn1 or Neurod3), a bHLH transcription factor encoded on a known schizophrenia linkage region in 5q31.1, induces glutamatergic and suppresses GABAergic neuronal differentiation during embryonic neurodevelopment. The goal of this study is to investigate NEUROG1 effects on schizophrenia risk and on phenotypic features of schizophrenia. We tested 392 patients with schizophrenia or schizoaffective disorder and 226 healthy normal volunteers for association with NEUROG1. Major alleles on two NEUROG1-associated SNPs (rs2344484-C-allele and rs8192558-G-allele) were significantly more prevalent among patients (p<or=.0018). Approximately 80% of the sample also underwent high-resolution, multi-spectral magnetic resonance brain imaging and standardized neuropsychological assessment. There were significant rs2344484 genotype main effects on total cerebral gray matter (GM) and temporal GM volumes (p<or=.05). C-allele-carrier patients and healthy volunteers had smaller total cerebral GM and temporal GM volumes than their respective T-homozygous counterparts. rs2344484-C-allele was further associated with generalized cognitive deficits among schizophrenia patients but not in healthy volunteers. Our findings replicate previous association between NEUROG1 and schizophrenia. More importantly, this is the first study to examine brain morphological and neurocognitive correlates of NEUROG1. rs2344484-C-allele may affect NEUROG1's role in transcription regulation such that brain morphology and cognitive abilities are altered resulting in increased susceptibility to develop schizophrenia.

Oxygen gradients correlate with cell density and cell viability in engineered cardiac tissue

For clinical utility, cardiac grafts should be thick and compact, and contain physiologic density of metabolically active, differentiated cells. This involves the need to control the levels of nutrients, and most critically oxygen, throughout the construct volume. Most culture systems involve diffusional transport within the constructs, a situation associated with gradients of oxygen concentration, cell density, cell viability, and function. The goal of our study was to measure diffusional gradients of oxygen in statically cultured cardiac constructs, and to correlate oxygen gradients to the spatial distributions of cell number and cell viability. Using microelectrodes, we measured oxygen distribution in a disc-shaped constructs (3.6 mm diameter, 1.8 mm thickness) based on neonatal rat cardiomyocytes cultured on collagen scaffolds for 16 days in static dishes. To rationalize experimental data, a mathematical model of oxygen distribution was derived as a function of cell density, viability, and spatial position within the construct. Oxygen concentration and cell viability decreased linearly and the live cell density decreased exponentially with the distance from the construct surface. Physiological density of live cells was present only within the first 128 microm of the construct thickness. Medium flow significantly increased oxygen concentration within the construct, correlating with the improved tissue properties observed for constructs cultured in convectively mixed bioreactors.

The responses of photosynthesis and oxygen consumption to short-term changes in temperature and irradiance in a cyanobacterial mat (Ebro Delta, Spain)

We have evaluated the effects of short-term changes in incident irradiance and temperature on oxygenic photosynthesis and oxygen consumption in a hypersaline cyanobacterial mat from the Ebro Delta, Spain, in which Microcoleus chthonoplastes was the dominant phototrophic organism. The mat was incubated in the laboratory at 15, 20, 25 and 30 degrees C at incident irradiances ranging from 0 to 1,000 micromol photons m(-2) s(-1). Oxygen microsensors were used to measure steady-state oxygen profiles and the rates of gross photosynthesis, which allowed the calculation of areal gross photosynthesis, areal net oxygen production, and oxygen consumption in the aphotic layer of the mat. The lowest surface irradiance that resulted in detectable rates of gross photosynthesis increased with increasing temperature from 50 micromol photons m(-2) s(-1) at 15 degrees C to 500 micromol photons m(-2) s(-1) at 30 degrees C. These threshold irradiances were also apparent from the areal rates of net oxygen production and point to the shift of M. chthonoplastes from anoxygenic to oxygenic photosynthesis and stimulation of sulphide production and oxidation rates at elevated temperatures. The rate of net oxygen production per unit area of mat at maximum irradiance, J0, did not change with temperature, whereas, JZphot, the flux of oxygen across the lower boundary of the euphotic zone increased linearly with temperature. The rate of oxygen consumption per volume of aphotic mat increased with temperature. This increase occurred in darkness, but was strongly enhanced at high irradiances, probably as a consequence of increased rates of photosynthate exudation, stimulating respiratory processes in the mat. The compensation irradiance (Ec) marking the change of the mat from a heterotrophic to an autotrophic community, increased exponentially in this range of temperatures.

Dynamics of anoxygenic photosynthesis in an experimental green sulphur bacteria biofilm

The dynamics of sulphide oxidation in an experimental biofilm of the green sulphur bacterium, Prosthecochloris aestuarii, were studied using a newly developed light-dark cycling procedure. The biofilm was grown for 6 weeks in a benthic gradient chamber, in which gradients of light, sulphide and oxygen were imposed experimentally. The H2S concentrations and pH were measured with microsensors as a function of depth in the biofilm and of time after a change in illumination status. The sulphide oxidation rates were calculated as a function of time and depth in the biofilm using a numerical procedure to solve the non-stationary general diffusion equation. A close agreement was found between the areal rates of anoxygenic photosynthesis during the cycling procedure and the steady state before the cycling experiment. For the different layers of the biofilm, the maximum activity was observed after 10-12min of light exposure. After this maximum, sulphide oxidation decreased concomitantly with sulphide concentration, indicating sulphide limitation of anoxygenic photosynthesis. This lag time limits the application of the standard dark-light shift method with a brief light exposure of a few seconds and, therefore, the numerical procedure described in this study enables the depth distribution of anoxygenic photosynthesis rates in microbial mats to be determined more accurately.

Comparison of the chitinolytic properties of Clostridium sp. strain 9.1 and a chitin-degrading bacterium from the intestinal tract of the plaice, Pleuronectes platessa (L.)

The chitinolytic properties of a facultatively anaerobic bacterium isolated from the hindgut of plaice were compared with those of Clostridium sp. strain 9.1, a bacterium isolated from anoxic estuarine sediment. The chitinolytic enzyme systems of the gut isolate and strain 9.1 both released N,N'-diacetylchitobiose (NAG2) as the major hydrolysis end-product. During the hydrolysis of chitin, there was transient accumulation of a non-sedimentary chitin fraction which was not detectable by high-performance liquid chromatography. Growth on NAG2 repressed chitinase synthesis in the gut isolate but not in the Clostridium species. Thiol reagents were strongly inhibitory to the chitinase of the strict anaerobe but did not affect the hydrolytic enzymes of the gut isolate. When the two bacteria were cocultured with chitin as the sole carbon and energy source, Clostridium sp. strain 9.1 was always outcompeted. Experiments with batch and phauxostat cultures showed that the competitiveness of strain 9.1 could be improved dramatically by the inclusion in the cocultures of a non-chitinolytic bacterium capable of fermenting chitin oligomers. The cooperation between the oligomer-fermenting species and the Clostridium sp. is discussed in relation to the regulation of chitinolytic activity in the latter organism.