It is widely believed that the steps in the major metabolic pathways are known and that the control of flux through these pathways occurs at a very limited number of """"""""rate limiting"""""""" steps. This concept has lead to the design of drugs to alter the kinetics of these """"""""rate limiting enzymes"""""""". It has also led to attempts to alter metabolic pathways by altering the amounts of rate limiting enzymes using the techniques of molecular biology. To the dismay of many, such interventions often fail to alter the rates of the pathways under study. These failures have led to an increased awareness that """"""""control"""""""" of pathway flux is distributed among many enzymes of a metabolic pathway and can vary from enzyme to enzyme depending upon conditions. Metabolic control theory predicts distribution of control among many enzymes of a pathway (Veech RL & Fell DA: Cell Biochem & Function 1996;14:229-36). However, actual demonstration and testing of such theories was technically difficult. We were the first laboratory to make the required measurements of flux, kinetic and thermodynamic constants of each step, and the levels of all substrates and products required to make such a formal analysis of flux control in a major metabolic pathway (Kashiwaya, Y. et al: J Biol Chem 1994;269:25502-14). We went on to show that ketone bodies can act in heart to overcome insulin resistance in heart (Kashiwaya J et al: Am J Cardiol 1997;80:50A-64A). Since Dr. Kashiwaya left this laboratory, I have continued to collaborate with him and he, with others at the Department of Neurology of Tottori University in Yonago, Japan, have applied these insights from our previous work to investigate the effects of ketone bodies upon two neuronal culture models of the two most common degenerative neurological diseases. Alzheimer's disease was modeled by adding amyloid beta 1-42 to embryonic rat hippocampal neuronal cultures and Parkinson's disease was modeled by adding MPP+ to mesencephalic neuronal cultures. In both cases, ketone bodies protected neurons from death induced by these very different toxins. The ability of ketone bodies to protect neurons under these conditions offers the possibility of therapy of these very common diseases as well as other diseases resulting from failures in either glycolysis or mitochondrial energy generation. This work has now appeared in: Kashiwaya Y, Takeshima T, Mori N et al: Proc Natl Acad Sci (USA) 2000;97:5440-44. Discussions of the uses of ketone bodies in the treatment of neurological diseases including refractory epilepsy and insulin resistance such as Leprechaunism was held in a Rare Disease Meeting at NIH on May 3, 2000. Work on metabolic control was done in collaboration with the Dept of Biochemistry, U of Barcelona and the Harbor UCLA Research Institute and was directed this year toward the hexosemonophosphate pathway and the role of thiamine in certain cancers and appeared in Cascante M, Centelles JJ, Veech RL et al: Nutrition & Cancer 2000;36:150-4. As a result of this work, a meeting sponsored by the NIH Office of Rare Diseases was convened in May 2000 where the potential therapeutic uses of ketone bodies was discussed in a disparate group of diseases. These include: Alzheimer's disease, Parkinson's disease, Friedreich's ataxia, Leprechaunism and other forms of insulin resistance and in the prevention of apoptosis of lung and subsequent multiple organ failure subsequent to hemorrhage and resuscitation. The report has been published in Veech RL, Chance B, Kashiwaya Y et al: Ketone bodies, potential therapeutic uses, IUBMB Life, 2001;51:241-7. We are extending this work by examining the effects of ketone bodies upon cardiac function in the MDX mouse, an animal model of Duchenne's muscular dystrophy. This most common genetic disease, affecting about 1/1000 males results in immobility by about 10 years and death between 20-25, usually from heart failure. There is currently no therapy for this disease resulting from failure to synthesize dystrophin. Attempts to express dystrophin in patients and animals have failed. Using the the principles of metabolic control analysis, we have determined that lack of dystrophin results in a defect in glucose transport, similar to insulin resistance. Accordingly this defect should be treatable by mild ketosis. We are in the process of examining this hypothesis in the isolated working perfused heart. If our results are successful in this preparation, we shall proceed to try similar therapies in the MDX mouse model. The application of the principles of metabolic control analysis has been suggested as a fruitful approach to the analysis of the phenotype seen observed in a number of common polygenic disorders which have proven to be insoluble by the present method of human genetic analysis, see Strohman R: Science 2002;296:701-3. It was also the subject of meetings in October and November 2002. Ketosis has been used for about 100 years for the treatment of epilepsy, but aside from this use, there has been no systematic investigation of their therapeutic potential. However, examination in depth of the metabolic effects of ketosis (1;28) suggest significant therapeutic uses in 3 main disease phenotypes: 1) diseases of insulin resistance or substrate lack, 2) diseases of free radical damage and 3) hypoxic states. These broad phenotypes include a number of very common diseases including neurodegenerative diseases, insulin resistance and obesity as well as myocardial infarction and stroke. The possible therapeutic implications for ketosis have been reviewed (28-30). The problem has been that the only method for inducing ketosis has been the feeding of low carbohydrate high fat diets which have specific untoward effects, namely elevation of blood cholesterol and triglyceride leading to vascular damage and even more significantly, the elevation of blood free fatty acids, which lead to activation of the PPAR nuclear transcription factors which increase the transcription and activate the metabolic activity of uncoupling proteins. Increased uncoupling proteins can cause significant pathology in states associated with muscular weakness, such as muscular dystrophies or heart failure. Further lowering of the energy of ATP hydrolysis can lead to serious and potentially fatal cardiac arrythmias due to changes in inorganic ion distributions (31). We are attempting, in collaboration with DARPA to develop ketone esters which would induce ketosis after oral administration, without the above listed complications. During last year, and in collaboration with Dr. Roscoe Brady of NINDS we prepared applications in response to a DoD solicitation for therapeutic approaches in the areas of 1) epilepsy, 2) Duchenne?s muscular dystrophy, and 3) amyotrophic lateral sclerosis. Unfortunately these applications were not successful and no funds were made available. However, I believe the approach outlines was sound, and if our present program of ester synthesis with DARPA is successful, these applications and the approach outlined should be submitted to NIH for further consideration. This material has been the subject of 2 meetings sponsored by the NIH Office of Rare Disease over the past 2 years.
| Masuda, R; Monahan, J W; Kashiwaya, Y (2005) D-beta-hydroxybutyrate is neuroprotective against hypoxia in serum-free hippocampal primary cultures. J Neurosci Res 80:501-9 |
| Koh, Ho-Jin; Lee, Su-Min; Son, Byung-Gap et al. (2004) Cytosolic NADP+-dependent isocitrate dehydrogenase plays a key role in lipid metabolism. J Biol Chem 279:39968-74 |
| Veech, Richard L (2004) The therapeutic implications of ketone bodies: the effects of ketone bodies in pathological conditions: ketosis, ketogenic diet, redox states, insulin resistance, and mitochondrial metabolism. Prostaglandins Leukot Essent Fatty Acids 70:309-19 |
| Hopkins, James C A; Radda, George K; Veech, Richard L et al. (2004) Accumulation of 2-deoxy-D-glucose-6-phosphate as a measure of glucose uptake in the isolated perfused heart: a 31P NMR study. Metab Eng 6:36-43 |
| Cahill Jr, George F; Veech, Richard L (2003) Ketoacids? Good medicine? Trans Am Clin Climatol Assoc 114:149-61; discussion 162-3 |
