Targeting energy metabolism in Huntington's disease

IKKβ signaling mediates metabolic changes in the hypothalamus of a Huntington disease mouse model

Huntington disease (HD) is a neurodegenerative disorder caused by a CAG repeat expansion in the huntingtin (HTT) gene. Metabolic changes are associated with HD progression, but underlying mechanisms are not fully known. As the IKKβ/NF-κB pathway is an essential regulator of metabolism, we investigated the involvement of IKKβ, the upstream activator of NF-κB in hypothalamus-specific HD metabolic changes. We expressed amyloidogenic N-terminal fragments of mutant HTT (mHTT) in the hypothalamus of mice with brain-specific ablation of IKKβ (Nestin/IKKβ^lox/lox) and control mice (IKKβ^lox/lox). We assessed effects on body weight, metabolic hormones, and hypothalamic neuropathology. Hypothalamic expression of mHTT led to an obese phenotype only in female mice. CNS-specific inactivation of IKKβ prohibited weight gain in females, which was independent of neuroprotection and microglial activation. Our study suggests that mHTT in the hypothalamus causes metabolic imbalance in a sex-specific fashion, and central inhibition of the IKKβ pathway attenuates the obese phenotype.

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Mutant huntingtin in the hypothalamus causes sex-specific metabolic imbalance

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CNS-specific inactivation of the IKKβ pathway prevents the obese phenotype

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IKKβ inactivation leads to an increased number of mutant huntingtin inclusions

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IKKβ inactivation does not prevent orexin or A13 TH neuron loss

Neuroendocrine Coordination of Mitochondrial Stress Signaling and Proteostasis

During neurodegenerative disease, the toxic accumulation of aggregates and misfolded proteins is often accompanied with widespread changes in peripheral metabolism, even in cells in which the aggregating protein is not present. The mechanism by which the central nervous system elicits a distal reaction to proteotoxic stress remains unknown. We hypothesized that the endocrine communication of neuronal stress plays a causative role in the changes in mitochondrial homeostasis associated with proteotoxic disease states. We find that an aggregation-prone protein expressed in the neurons of C. elegans binds to mitochondria, eliciting a global induction of a mitochondrial-specific unfolded protein response (UPR(mt)), affecting whole-animal physiology. Importantly, dense core vesicle release and secretion of the neurotransmitter serotonin is required for the signal's propagation. Collectively, these data suggest the commandeering of a nutrient sensing network to allow for cell-to-cell communication between mitochondria in response to protein folding stress in the nervous system.

Coenzyme Q10 depletion in medical and neuropsychiatric disorders: potential repercussions and therapeutic implications

Coenzyme Q10 (CoQ10) is an antioxidant, a membrane stabilizer, and a vital cofactor in the mitochondrial electron transport chain, enabling the generation of adenosine triphosphate. It additionally regulates gene expression and apoptosis; is an essential cofactor of uncoupling proteins; and has anti-inflammatory, redox modulatory, and neuroprotective effects. This paper reviews the known physiological role of CoQ10 in cellular metabolism, cell death, differentiation and gene regulation, and examines the potential repercussions of CoQ10 depletion including its role in illnesses such as Parkinson's disease, depression, myalgic encephalomyelitis/chronic fatigue syndrome, and fibromyalgia. CoQ10 depletion may play a role in the pathophysiology of these disorders by modulating cellular processes including hydrogen peroxide formation, gene regulation, cytoprotection, bioenegetic performance, and regulation of cellular metabolism. CoQ10 treatment improves quality of life in patients with Parkinson's disease and may play a role in delaying the progression of that disorder. Administration of CoQ10 has antidepressive effects. CoQ10 treatment significantly reduces fatigue and improves ergonomic performance during exercise and thus may have potential in alleviating the exercise intolerance and exhaustion displayed by people with myalgic encepholamyletis/chronic fatigue syndrome. Administration of CoQ10 improves hyperalgesia and quality of life in patients with fibromyalgia. The evidence base for the effectiveness of treatment with CoQ10 may be explained via its ability to ameliorate oxidative stress and protect mitochondria.

The effects of topical coenzyme Q10 and vitamin E D-α-tocopheryl polyethylene glycol 1000 succinate after cataract surgery: a clinical and in vivo confocal study

PURPOSE

To evaluate the postoperative effects of topical coenzyme Q(10) + vitamin E D-α-tocopheryl polyethylene glycol 1000 succinate (CoQ(10)) after cataract surgery.

METHODS

40 consecutive patients were randomized to receive CoQ(10) or saline solution (SS) twice daily for 9 months after uneventful cataract surgery with a temporal port. Before surgery, on day 14 and at months 3, 6 and 9, they underwent non-invasive break-up time (NIBUT) testing, Schirmer test, BUT, aesthesiometry as well as in vivo confocal microscopy of the subbasal nerve plexus of the cornea (SBP). The density of the subbasal nerves was calculated in the central (CFD) and temporal (TFD) cornea (number of fibres per field).

RESULTS

On day 14, surgery reduced CFD and TFD, respectively, by 25-35 and 50%; indices of ocular surface stability were all impaired. The treatment with CoQ(10) was associated with faster nerve regeneration than SS (at month 3, CFD +1.5 ± 1.9 vs. +0.2 ± 1.8, p = 0.04, and TFD +2.5 ± 1.7 vs. +1.0 ± 1.6, p = 0.007; at month 6, TFD +2.7 ± 1.9 vs. +1.4 ± 1.5, p = 0.02) and better stability of ocular surface (NIBUT and BUT) throughout the study. No relevant side effects were found, apart from occasional burning in 10% of CoQ(10) patients.

CONCLUSIONS

Changes of the corneal nerves occurring after cataract surgery may influence the integrity of the ocular surface. Treatment with topical CoQ(10) has a positive effect in restoring SBP anatomy and ocular surface stability.

Quantitative proteomic analysis of human substantia nigra in Alzheimer's disease, Huntington's disease and Multiple sclerosis

The substantia nigra plays important roles in the brain function and is critical in the development of many diseases, particularly Parkinson's disease. Pathological changes of the substantia nigra have also been reported in other neurodegenerative diseases. Using a quantitative proteomic approach, we investigated protein expressions in the substantia nigra of Alzheimer's disease, Huntington's disease, and Multiple sclerosis. The expression level of one hundred and four proteins that were identified in at least three samples of each group were compared with the control group, with nineteen, twenty-two and thirteen proteins differentially expressed in Alzheimer's diseases, Huntington's disease and Multiple sclerosis respectively. The result indicates that the substantia nigra also undergoes functional adaption or damage in these diseases.

Couples' attributions for work function changes in prodromal Huntington disease

People who have tested positive for the expanded Huntington disease (HD) gene who are not yet diagnosed (pre-HD) and their companions report subtle changes in ability of people with pre-HD to do their jobs. However, it is not known whether they attribute these changes to HD. Semi-structured telephone interviews were analyzed from seven persons with pre-HD at different estimated points from diagnosis and six companions. Data were analyzed using qualitative analysis methods. Participants made attributions related to health, work, and temperament. Only one participant attributed a change to HD. The process of forming attributions was demonstrated through symptom monitoring and comparison of participants with pre-HD to others with and without HD. Participants also expressed uncertainty regarding how to make attributions. Attributions influence coping procedures, including whether to seek and accept medical treatment. In persons with prodromal HD the relationship between attributions and use of coping strategies for symptoms that interfere with job functioning is unknown.

Therapeutic potential of fluoxetine in neurological disorders

The selective serotonin reuptake inhibitor (SSRI) fluoxetine, which is registered for a variety of psychiatric disorders, has been found to stimulate the cAMP-responsive element binding protein (CREB), increase the production of brain-derived neurotrophic factor (BNDF) and the neurotrophic peptide S100beta, enhance glycogenolysis in astrocytes, block voltage-gated calcium and sodium channels, and decrease the conductance of mitochondrial voltage-dependent anion channels (VDACs). These mechanisms of actions suggest that fluoxetine may also have potential for the treatment of a number of neurological disorders. We performed a Pubmed search to review what is known about possible therapeutic effects of fluoxetine in animal models and patients with neurological disorders. Beneficial effects of fluoxetine have been noted in animal models of stroke, multiple sclerosis, and epilepsy. Fluoxetine was reported to improve neurological manifestations in patients with Alzheimer's disease, stroke, Huntington's disease, multiple sclerosis, traumatic brain injury, and epilepsy. Clinical studies so far were small and often poorly designed. Results were inconclusive and contradictory. However, the available preclinical data justify further clinical trials to determine the therapeutic potential of fluoxetine in neurological disorders.

IGF-1 exacerbates the neurotoxicity of the mitochondrial inhibitor 3NP in rats

Insulin-like Growth Factor 1 (IGF-1) has broad-range neuroprotective effects and is a therapeutic candidate for Huntington's disease (HD). IGF-1 protects striatal neurons from the toxicity of mutated huntingtin in vitro and improves neuronal survival in vivo in a phenotypic model of HD involving excitotoxic cell death. Because HD is a multifactorial disease, it is important to evaluate the neuroprotective role of IGF-1 in other pathological situations involved in HD progression. We have evaluated the neuroprotective effects of IGF-1 in vivo, using the 3-nitropropionic acid (3NP) rat model which replicates the mitochondrial dysfunction observed in HD. Continuous intracerebroventricular infusion of recombinant IGF-1 at a low dose (0.025 microg/h for 5 days) did not alleviate motor impairment and weight loss induced by 3NP treatment. In addition, histological evaluation and quantification of DNA fragmentation evidenced no improvement in neuronal survival. Of interest, we found that a higher concentration of IGF-1 (0.25 microg/h) resulted in an exacerbation of 3NP toxicity on striatal neurons. These results suggest that intracerebral delivery of IGF-1 may not provide a fully effective therapeutic strategy for HD or other disorders involving mitochondrial impairment.

Coenzyme Q10: a review of its promise as a neuroprotectant

Coenzyme Q10 (CoQ10) is a powerful antioxidant that buffers the potential adverse consequences of free radicals produced during oxidative phosphorylation in the inner mitochondrial membrane. Oxidative stress, resulting in glutathione loss and oxidative DNA and protein damage, has been implicated in many neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, and Huntington's disease. Experimental studies in animal models suggest that CoQ10 may protect against neuronal damage that is produced by ischemia, atherosclerosis and toxic injury. Though most have tended to be pilot studies, there are published preliminary clinical trials showing that CoQ10 may offer promise in many brain disorders. For example, a 16-month randomized, placebo-controlled pilot trial in 80 subjects with mild Parkinson's disease found significant benefits for oral CoQ10 1,200 mg/day to slow functional deterioration. However, to date, there are no published clinical trials of CoQ10 in Alzheimer's disease. Available data suggests that oral CoQ10 seems to be relatively safe and tolerated across the range of 300-2,400 mg/day. Randomized controlled trials are warranted to confirm CoQ10's safety and promise as a clinically effective neuroprotectant.