Feeding neurons integrate metabolic and reproductive states in mice.

Balance between metabolic and reproductive processes is important for survival, particularly in mammals that gestate their young. How the nervous system coordinates this balance is an active area of study. Herein, we demonstrate that somatostatin (SST) neurons of the tuberal hypothalamus alter feeding in a manner sensitive to metabolic and reproductive states in mice. Whereas chemogenetic activation of SST neurons increased food intake across sexes, ablation decreased food intake only in female mice during proestrus. This ablation effect was only apparent in animals with low body mass. Fat transplantation and bioinformatics analysis of SST neuronal transcriptomes revealed white adipose as a key modulator of these effects. These studies indicate that SST hypothalamic neurons integrate metabolic and reproductive cues by responding to varying levels of circulating estrogens to modulate feeding differentially based on energy stores. Thus, gonadal steroid modulation of neuronal circuits can be context dependent and gated by metabolic status.

Long wavelength light reduces the negative consequences of dim light at night.

Many patients with autism spectrum disorders (ASD) show disturbances in their sleep/wake cycles, and they may be particularly vulnerable to the impact of circadian disruptors. We have previously shown that a 2-weeks exposure to dim light at night (DLaN) disrupts diurnal rhythms, increases repetitive behaviors and reduces social interactions in contactin-associated protein-like 2 knock out (Cntnap2 KO) mice. The deleterious effects of DLaN may be mediated by intrinsically photosensitive retinal ganglion cells (ipRGCs) expressing the photopigment melanopsin, which is maximally sensitive to blue light (480 nm). In this study, the usage of a light-emitting diode array enabled us to shift the spectral properties of the DLaN while keeping the intensity of the illumination at 10 lx. First, we confirmed that the short-wavelength enriched lighting produced strong acute suppression of locomotor activity (masking), robust light-induced phase shifts, and cFos expression in the suprachiasmatic nucleus in wild-type (WT) mice, while the long-wavelength enriched lighting evoked much weaker responses. Opn4DTA mice, lacking the melanopsin expressing ipRGCs, were resistant to DLaN effects. Importantly, shifting the DLaN stimulus to longer wavelengths mitigated the negative impact on the activity rhythms and 'autistic' behaviors (i.e. reciprocal social interactions, repetitive grooming) in the Cntnap2 KO as well as in WT mice. The short-, but not the long-wavelength enriched, DLaN triggered cFos expression in in the basolateral amygdala (BLA) as well as in the peri-habenula region raising that possibility that these cell populations may mediate the effects. Broadly, our findings are consistent with the recommendation that spectral properties of light at night should be considered to optimize health in neurotypical as well as vulnerable populations.

Uninterrupted CAG repeat drives striatum-selective transcriptionopathy and nuclear pathogenesis in human Huntingtin BAC mice.

In Huntington's disease (HD), the uninterrupted CAG repeat length, but not the polyglutamine length, predicts disease onset. However, the underlying pathobiology remains unclear. Here, we developed bacterial artificial chromosome (BAC) transgenic mice expressing human mutant huntingtin (mHTT) with uninterrupted, and somatically unstable, CAG repeats that exhibit progressive disease-related phenotypes. Unlike prior mHTT transgenic models with stable, CAA-interrupted, polyglutamine-encoding repeats, BAC-CAG mice show robust striatum-selective nuclear inclusions and transcriptional dysregulation resembling those in murine huntingtin knockin models and HD patients. Importantly, the striatal transcriptionopathy in HD models is significantly correlated with their uninterrupted CAG repeat length but not polyglutamine length. Finally, among the pathogenic entities originating from mHTT genomic transgenes and only present or enriched in the uninterrupted CAG repeat model, somatic CAG repeat instability and nuclear mHTT aggregation are best correlated with early-onset striatum-selective molecular pathogenesis and locomotor and sleep deficits, while repeat RNA-associated pathologies and repeat-associated non-AUG (RAN) translation may play less selective or late pathogenic roles, respectively.

Melatonin treatment of repetitive behavioral deficits in the Cntnap2 mouse model of autism spectrum disorder.

Nighttime light pollution is linked to metabolic and cognitive dysfunction. Many patients with autism spectrum disorders (ASD) show disturbances in their sleep/wake cycle, and may be particularly vulnerable to the impact of circadian disruptors. In this study, we examined the impact of exposure to dim light at night (DLaN, 5 lx) in a model of ASD: the contactin associated protein-like 2 knock out (Cntnap2 KO) mice. DLaN was sufficient to disrupt locomotor activity rhythms, exacerbate the excessive grooming and diminish the social preference in Cntnap2 mutant mice. On a molecular level, DLaN altered the phase and amplitude of PER2:LUC rhythms in a tissue-specific manner in vitro. Daily treatment with melatonin reduced the excessive grooming of the mutant mice to wild-type levels and improved activity rhythms. Our findings suggest that common circadian disruptors such as light at night should be considered in the management of ASD.

The circadian clock is disrupted in mice with adenine-induced tubulointerstitial nephropathy.

Chronic Kidney Disease (CKD) is increasing in incidence and has become a worldwide health problem. Sleep disorders are prevalent in patients with CKD raising the possibility that these patients have a disorganized circadian timing system. Here, we examined the effect of adenine-induced tubulointerstitial nephropathy on the circadian system in mice. Compared to controls, adenine-treated mice showed serum biochemistry evidence of CKD as well as increased kidney expression of inflammation and fibrosis markers. Mice with CKD exhibited fragmented sleep behavior and locomotor activity, with lower degrees of cage activity compared to mice without CKD. On a molecular level, mice with CKD exhibited low amplitude rhythms in their central circadian clock as measured by bioluminescence in slices of the suprachiasmatic nucleus of PERIOD 2::LUCIFERASE mice. Whole animal imaging indicated that adenine treated mice also exhibited dampened oscillations in intact kidney, liver, and submandibular gland. Consistently, dampened circadian oscillations were observed in several circadian clock genes and clock-controlled genes in the kidney of the mice with CKD. Finally, mice with a genetically disrupted circadian clock (Clock mutants) were treated with adenine and compared to wild type control mice. The treatment evoked worse kidney damage as indicated by higher deposition of gelatinases (matrix metalloproteinase-2 and 9) and adenine metabolites in the kidney. Adenine also caused non-dipping hypertension and lower heart rate. Thus, our data indicate that central and peripheral circadian clocks are disrupted in the adenine-treated mice, and suggest that the disruption of the circadian clock accelerates CKD progression.

Sleep/Wake Disruption in a Mouse Model of BLOC-1 Deficiency.

Mice lacking a functional Biogenesis of Lysosome-related Organelles Complex 1 (BLOC-1), such as those of the pallid line, display cognitive and behavioural impairments reminiscent of those presented by individuals with intellectual and developmental disabilities. Although disturbances in the sleep/wake cycle are commonly lamented by these individuals, the underlying mechanisms, including the possible role of the circadian timing system, are still unknown. In this paper, we have explored sleep/circadian malfunctions and underlying mechanisms in BLOC-1-deficient pallid mice. These mutants exhibited less sleep behaviour in the beginning of the resting phase than wild-type mice with a more broken sleeping pattern in normal light-dark conditions. Furthermore, the strength of the activity rhythms in the mutants were reduced with significantly more fragmentation and lower precision than in age-matched controls. These symptoms were accompanied by an abnormal preference for the open arm in the elevated plus maze in the day and poor performance in the novel object recognition at night. At the level of the central circadian clock (the suprachiasmatic nucleus, SCN), loss of BLOC-1 caused subtle morphological changes including a larger SCN and increased expression of the relative levels of the clock gene Per2 product during the day but did not affect the neuronal activity rhythms. In the hippocampus, the pallid mice presented with anomalies in the cytoarchitecture of the Dentate Gyrus granule cells, but not in CA1 pyramidal neurones, along with altered PER2 protein levels as well as reduced pCREB/tCREB ratio during the day. Our findings suggest that lack of BLOC-1 in mice disrupts the sleep/wake cycle and performance in behavioural tests associated with specific alterations in cytoarchitecture and protein expression.

Circadian-based Treatment Strategy Effective in the BACHD Mouse Model of Huntington's Disease.

Huntington's disease (HD) patients suffer from progressive neurodegeneration that results in cognitive, psychiatric, cardiovascular, and motor dysfunction. Disturbances in sleep-wake cycles are common among HD patients with reports of delayed sleep onset, frequent bedtime awakenings, and excessive fatigue. The BACHD mouse model exhibits many HD core symptoms including circadian dysfunction. Because circadian dysfunction manifests early in the disease in both patients and mouse models, we sought to determine if early interventions that improve circadian rhythmicity could benefit HD symptoms and delay disease progression. We evaluated the effects of time-restricted feeding (TRF) on the BACHD mouse model. At 3 months of age, the animals were divided into 2 groups: ad lib and TRF. The TRF-treated BACHD mice were exposed to a 6-h feeding/18-h fasting regimen that was designed to be aligned with the middle (ZT 15-21) of the period when mice are normally active (ZT 12-24). Following 3 months of treatment (when mice reached the early disease stage), the TRF-treated BACHD mice showed improvements in their locomotor activity and sleep behavioral rhythms. Furthermore, we found improved heart rate variability, suggesting that their autonomic nervous system dysfunction was improved. On a molecular level, TRF altered the phase but not the amplitude of the PER2::LUC rhythms measured in vivo and in vitro. Importantly, treated BACHD mice exhibited improved motor performance compared with untreated BACHD controls, and the motor improvements were correlated with improved circadian output. It is worth emphasizing that HD is a genetically caused disease with no known cure. Lifestyle changes that not only improve the quality of life but also delay disease progression for HD patients are greatly needed. Our study demonstrates the therapeutic potential of circadian-based treatment strategies in a preclinical model of HD.

Time-Restricted Feeding Improves Circadian Dysfunction as well as Motor Symptoms in the Q175 Mouse Model of Huntington's Disease.

Huntington's disease (HD) patients suffer from a progressive neurodegeneration that results in cognitive, psychiatric, cardiovascular, and motor dysfunction. Disturbances in sleep/wake cycles are common among HD patients with reports of delayed sleep onset, frequent bedtime awakenings, and fatigue during the day. The heterozygous Q175 mouse model of HD has been shown to phenocopy many HD core symptoms including circadian dysfunctions. Because circadian dysfunction manifests early in the disease in both patients and mouse models, we sought to determine if early intervention that improve circadian rhythmicity can benefit HD and delay disease progression. We determined the effects of time-restricted feeding (TRF) on the Q175 mouse model. At six months of age, the animals were divided into two groups: ad libitum (ad lib) and TRF. The TRF-treated Q175 mice were exposed to a 6-h feeding/18-h fasting regimen that was designed to be aligned with the middle of the time when mice are normally active. After three months of treatment (when mice reached the early disease stage), the TRF-treated Q175 mice showed improvements in their locomotor activity rhythm and sleep awakening time. Furthermore, we found improved heart rate variability (HRV), suggesting that their autonomic nervous system dysfunction was improved. Importantly, treated Q175 mice exhibited improved motor performance compared to untreated Q175 controls, and the motor improvements were correlated with improved circadian output. Finally, we found that the expression of several HD-relevant markers was restored to WT levels in the striatum of the treated mice using NanoString gene expression assays.

Possible use of a H3R antagonist for the management of nonmotor symptoms in the Q175 mouse model of Huntington's disease.

Huntington's disease (HD) is an autosomal dominant, neurodegenerative disorder characterized by motor as well as nonmotor symptoms for which there is currently no cure. The Q175 mouse model of HD recapitulates many of the symptoms identified in HD patients including disruptions of the sleep/wake cycle. In this study, we sought to determine if the daily administration of the histamine-3 receptor (H3R) antagonist/inverse agonist 6-[(3-cyclobutyl-2,3,4,5-tetrahydro-1H-3-benzazepin-7-yl)oxy]-N-methyl-3-pyridinecarboxamide hydrochloride (GSK189254) would improve nonmotor symptoms in the Q175 line. This class of drugs acts on autoreceptors found at histaminergic synapses and results in increased levels of histamine (HA). HA is a neuromodulator whose levels vary with a daily rhythm with peak release during the active cycle and relatively lower levels during sleep. H3Rs are widely expressed in brain regions involved in cognitive processes and activation of these receptors promotes wakefulness. We administered GSK189254 nightly to homozygote and heterozygote Q175 mice for 4 weeks and confirmed that the plasma levels of the drug were elevated to a therapeutic range. We demonstrate that daily treatment with GSK189254 improved several behavioral measures in the Q175 mice including strengthening activity rhythms, cognitive performance and mood as measured by the tail suspension test. The treatment also reduced inappropriate activity during the normal sleep time. The drug treatment did not alter motor performance and coordination as measured by the challenging beam test. Our findings suggest that drugs targeting the H3R system may show benefits as cognitive enhancers in the management of HD.

Blue light therapy improves circadian dysfunction as well as motor symptoms in two mouse models of Huntington's disease.

Patients with Huntington's disease (HD) exhibit movement disorders, psychiatric disturbance and cognitive impairments as the disease progresses. Abnormal sleep/wake cycles are common among HD patients with reports of delayed sleep onset, fatigue during the day, and a delayed pattern of melatonin secretion all of which suggest circadian dysfunction. Mouse models of HD confirm disrupted circadian rhythms with pathophysiology found in the central circadian clock (suprachiasmatic nucleus). Importantly, circadian dysfunction manifests early in disease, even before the classic motor symptoms, in both patients and mouse models. Therefore, we hypothesize that the circadian dysfunction may interact with the disease pathology and exacerbate the HD symptoms. If correct, early intervention may benefit patients and delay disease progression. One test of this hypothesis is to determine whether light therapy designed to strengthen this intrinsic timing system can delay the disease progression in mouse models. Therefore, we determined the impact of blue wavelength-enriched light on two HD models: the BACHD and Q175 mice. Both models received 6 h of blue-light at the beginning of their daily light cycle for 3 months. After treatment, both genotypes showed improvements in their locomotor activity rhythm without significant change to their sleep behavior. Critically, treated mice of both lines exhibited improved motor performance compared to untreated controls. Focusing on the Q175 genotype, we sought to determine whether the treatment altered signaling pathways in brain regions known to be impacted by HD using NanoString gene expression assays. We found that the expression of several HD relevant markers was altered in the striatum and cortex of the treated mice. Our study demonstrates that strengthening the circadian system can delay the progression of HD in pre-clinical models. This work suggests that lighting conditions should be considered when managing treatment of HD and other neurodegenerative disorders.

Cardiac Dysfunction in the BACHD Mouse Model of Huntington's Disease.

While Huntington's disease (HD) is classified as a neurological disorder, HD patients exhibit a high incidence of cardiovascular events leading to heart failure and death. In this study, we sought to better understand the cardiovascular phenotype of HD using the BACHD mouse model. The age-related decline in cardiovascular function was assessed by echocardiograms, electrocardiograms, histological and microarray analysis. We found that structural and functional differences between WT and BACHD hearts start at 3 months of age and continue throughout life. The aged BACHD mice develop cardiac fibrosis and ultimately apoptosis. The BACHD mice exhibited adaptive physiological changes to chronic isoproterenol treatment; however, the medication exacerbated fibrotic lesions in the heart. Gene expression analysis indicated a strong tilt toward apoptosis in the young mutant heart as well as changes in genes involved in cellular metabolism and proliferation. With age, the number of genes with altered expression increased with the large changes occurring in the cardiovascular disease, cellular metabolism, and cellular transport clusters. The BACHD model of HD exhibits a number of changes in cardiovascular function that start early in the disease progress and may provide an explanation for the higher cardiovascular risk in HD.