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      A Ketogenic Diet May Offer Neuroprotection in Glaucoma and Mitochondrial Diseases of the Optic Nerve

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          Abstract

          Glaucoma is a chronic optic nerve disease in which the primary damage occurs to the retinal ganglion cell axons. Therapies that prevent the death of retinal ganglion cells should be theoretically beneficial. Despite promising preclinical studies, however, almost all clinical studies with pharmacological approaches for neuroprotection in neurologic and eye diseases, including glaucoma, have so far failed to show efficacy. As the evidence supporting the neuroprotective efficacy of a ketogenic diet (KD) in a number of neurodegenerative diseases continues to grow, it is conceivable that this metabolic approach might be useful in chronic glaucoma. Putative cellular mechanisms underlying the neuroprotective activity of the KD have been identified in neurological studies, including effects on energy metabolism, the GABA system, glutamate-mediated toxicity, antioxidant mechanisms, programmed cell death, anti-inflammatory mechanisms, and the production of kynurenic acid. Of note, the same mechanisms are thought to be involved in glaucoma. Given these mechanistic similarities, testing the KD for its efficacy in neurodegenerative diseases of the eye is proposed.

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          Most cited references35

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          Treatment of Parkinson disease with diet-induced hyperketonemia: a feasibility study.

          Ketones may bypass the defect in complex I activity implicated in Parkinson disease (PD). Five of seven volunteers with PD were able to prepare a "hyperketogenic" diet at home and adhere to it for 28 days. Substituting unsaturated for saturated fats appeared to prevent cholesterol increases in four volunteers. Unified Parkinson's Disease Rating Scale scores improved in all five during hyperketonemia, but a placebo effect was not ruled out.
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            A ketogenic diet reduces amyloid beta 40 and 42 in a mouse model of Alzheimer's disease

            Background Alzheimer's disease (AD) is a progressive neurodegenerative disorder that primarily strikes the elderly. Studies in both humans and animal models have linked the consumption of cholesterol and saturated fats with amyloid-β (Aβ) deposition and development of AD. Yet, these studies did not examine high fat diets in combination with reduced carbohydrate intake. Here we tested the effect of a high saturated fat/low carbohydrate diet on a transgenic mouse model of AD. Results Starting at three months of age, two groups of female transgenic mice carrying the "London" APP mutation (APP/V717I) were fed either, a standard diet (SD) composed of high carbohydrate/low fat chow, or a ketogenic diet (KD) composed of very low carbohydrate/high saturated fat chow for 43 days. Animals fed the KD exhibited greatly elevated serum ketone body levels, as measured by β-hydroxybutyrate (3.85 ± 2.6 mM), compared to SD fed animals (0.29 ± 0.06 mM). In addition, animals fed the KD lost body weight (SD 22.2 ± 0.6 g vs. KD 17.5 ± 1.4 g, p = 0.0067). In contrast to earlier studies, the brief KD feeding regime significantly reduced total brain Aβ levels by approximately 25%. Despite changes in ketone levels, body weight, and Aβ levels, the KD diet did not alter behavioral measures. Conclusion Previous studies have suggested that diets rich in cholesterol and saturated fats increased the deposition of Aβ and the risk of developing AD. Here we demonstrate that a diet rich in saturated fats and low in carbohydrates can actually reduce levels of Aβ. Therefore, dietary strategies aimed at reducing Aβ levels should take into account interactions of dietary components and the metabolic outcomes, in particular, levels of carbohydrates, total calories, and presence of ketone bodies should be considered.
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              A ketogenic diet as a potential novel therapeutic intervention in amyotrophic lateral sclerosis

              Background The cause of neuronal death in amyotrophic lateral sclerosis (ALS) is uncertain but mitochondrial dysfunction may play an important role. Ketones promote mitochondrial energy production and membrane stabilization. Results SOD1-G93A transgenic ALS mice were fed a ketogenic diet (KD) based on known formulations for humans. Motor performance, longevity, and motor neuron counts were measured in treated and disease controls. Because mitochondrial dysfunction plays a central role in neuronal cell death in ALS, we also studied the effect that the principal ketone body, D-β-3 hydroxybutyrate (DBH), has on mitochondrial ATP generation and neuroprotection. Blood ketones were > 3.5 times higher in KD fed animals compared to controls. KD fed mice lost 50% of baseline motor performance 25 days later than disease controls. KD animals weighed 4.6 g more than disease control animals at study endpoint; the interaction between diet and change in weight was significant (p = 0.047). In spinal cord sections obtained at the study endpoint, there were more motor neurons in KD fed animals (p = 0.030). DBH prevented rotenone mediated inhibition of mitochondrial complex I but not malonate inhibition of complex II. Rotenone neurotoxicity in SMI-32 immunopositive motor neurons was also inhibited by DBH. Conclusion This is the first study showing that diet, specifically a KD, alters the progression of the clinical and biological manifestations of the G93A SOD1 transgenic mouse model of ALS. These effects may be due to the ability of ketone bodies to promote ATP synthesis and bypass inhibition of complex I in the mitochondrial respiratory chain.
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                Author and article information

                Journal
                Med Hypothesis Discov Innov Ophthalmol
                Med Hypothesis Discov Innov Ophthalmol
                mehdiophth
                Medical Hypothesis, Discovery and Innovation in Ophthalmology
                Medical Hypothesis, Discovery & Innovation Ophthalmology
                2322-4436
                2322-3219
                Autumn 2012
                : 1
                : 3
                : 45-49
                Affiliations
                [1 ] Chair of Ophthalmology, Medical University, Lublin, Poland
                [2 ] SANITAS Private Medical Center, Lublin, Poland
                [3 ] Department of Experimental and Clinical Pharmacology, Medical University, Lublin, Poland
                [4 ] Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelpia, USA
                Author notes
                Correspondence to: Prof. Tomasz Zarnowski, Chair of Ophthalmology, Medical University, Lublin, Poland, Tel: +48815324827, E-mail: zarnowskit@poczta.onet.pl
                Article
                mehdiophth-1-045
                3939735
                24600621
                e6d14440-159e-493a-9115-cc127fe553fb
                © 2012, Medical Hypothesis, Discovery & Innovation (MEHDI) Ophthalmology Journal

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License, ( http://creativecommons.org/licenses/by/3.0/) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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                Categories
                Hypothesis

                glaucoma,ketogenic diet,optic nerve diseases,neuroprotection,mitochondrial disease

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