until a few years ago, a taco metabolic myopathy is would have been limited to the glycogen storage diseases in the last few years, however, the field has considerably expanded to include not only some variants of glycogen storage diseases, but also some newly recognize disorders of lipid metabolism. The first slide shows a very schematic overview of glycogen metabolism. Once glucose has been transferred into the cell, it is fast food related to glucose six fostered by an enzyme, an enzyme known as exogenous forceful glue commutes then converts glucose six phosphate to glucose one phosphate. At this point, like a gin, the process of glycogen synthesis starts and this is the only an obligatory process for glycogen synthesis. It takes place essentially in three steps. First. An enzyme known as you redeem defaults for glucose Piros for Elise convert glucose one fast fit to your eddine die fast food dye, phosphate, glucose. This is the substrate for the main glycogen of synthetic enzyme known as glycogen center days this enzyme attaches glucose units to the peripheral chains of glycogen molecule In an alpha 1, 4 glucose citic link and this process goes on until the glycogen peripheral chain has reached a certain length. At this point, a third enzyme has to come into action and this is known as the branch er And what this enzyme does. It attach is a glucose unit in an alpha 1/6 position. And after this the sentences can then resume its action Elevating this new chain by adding glucose units in Alpha 1 4 links. Yeah. While this is, as I said, the only an obligatory synthetic pathway as far as it is known, there are several glycogen, analytic or degrade active pathways for the energetic metabolism of the cell. Certainly the most important is the first Farrell is the branch or pathway. The first end the enzyme to act is force Farrell is and what it does in the presence of inorganic phosphate it falls for politically splits off stepwise glucose units from the peripheral change of glycogen. With liberation of glucose one phosphate, This enzyme can proceed until it has uh split off glucose units Up to about three or 4 units from the branching point. And at this point they partially chewed up glycogen if you want is known as a phosphorus limited. Extreme Now a second enzyme has to come into action and this is known as a deep Rancher. This enzyme, in a two step reactions reaction uh splits off the glucose unit in the alpha 1/6 position and therefore phosphorus can again act on a new uh peripheral chain of glycogen with further liberation of glucose. One fasted. The branch is a hydrologic enzyme and liberates glucose and glucose one phosphate. But this is of course a very small amount as compared to the glucose. One faster liberated by first parallels the other two pathways that I mentioned that I indicated here or anonymously are less important. Certainly for the sell one of them is catalyzed by alpha amylase. Although this enzyme is certainly present in all tissues and muscle as well. Its function is totally unknown. The biochemical action is known what it does. It randomly split alpha 14 glucose, citic links except the ones in maltose with liberation of olive, osaka, right small toes and glucose. But the function, as I mentioned is totally unknown. This other final pathway, which is indicated here Schematically wants to represent two enzymes. The neutral and the acid alpha glucose days is neutral because alpha glucose, it is is apparently linked to the cytoplasmic particular. Um while uh and its function is again completely unknown. While acid alpha 14 glue cause it is actually it is an alpha 14 and 16 because it is, as you will see better known as acid maltese is Eliza Zuma enzyme and we'll talk about its function later on in the in this presentation. The next slide represents a uh summary of the glycogen storage diseases. There are eight, as you see known glycogen oh sis of these. However, type one like oh, gino sis or fungal disease and type type six glycogen Oh sis hers disease and type eight click on geonosis or hooks disease do not affect muscle Type one is due to a defect of glucose six phosphate days. An enzyme which is not present in muscle Types six is due to a defect of liver force Farrelly's and enzyme different genetically different from from muscle force Farrelly's and type eight Geico geonosis is due to A defect of one of the enzymes involved in the activation of Liverpool's Farrelly's. Again, this does not involve muscle, so when we exclude these, we are left with five glycogen storage diseases, all of which affect muscle Again. However, type three glycogen Asus and type four glycogen oh, sis do, respectively, respectively, to a defect of the deep branch er and the branch er enzyme are dominated by the liver involvement and muscle symptoms and signs are generally minimal. So we will ignore these for this time and concentrate on The residual three glycogen storage diseases. Type To type five and type seven, which indeed cause a major major neuromuscular disorder and the muscle disorder. Really, the clinical picture pictures fall basically into two groups, one which is dominated by muscle cramps and myoglobin urea, and the other which is dominated by muscle weakness, progressive muscle weakness. It is I think historically correct to start the description with glycogen Asus, type five because this was the first muscle glycogen noses uh studied biochemically by bryan McArdle in England in 1951 and um Accardo very elegantly described. They the metabolic block If not the enzyme defect, which was discovered about eight years later. There are about 50 cases reported in the literature and Uh most of them affect males, as you see in the proportion of about 4-1. Type five. Black vaginosis is do as I mentioned before, to a defect of muscle force Farrellys in view of the central role played by this enzyme in glycogen metabolism. As I pointed out in the first slide, it is somewhat surprising that the symptoms symptom a theology in this disease, is not very dramatic. The symptoms consist mainly in exercise intolerance soon after starting vigorous exercise. These patients experience muscle stiffness and egg. Most patients soon learn what their limits are and if they do not overdo, they can enjoy a reasonably normal life. However, when they exceed their limits, they experience painful cramps, which electro maya graphically appear to be silent and therefore fit the definition of contractors. In some instances, contractors are followed by muscle breakdown, and this is reflected muscle necrosis, and this is reflected by myoglobin urea. We have seen two cases who presented with renal shutdown requiring him on dialysis and in whom the diagnosis of McArdle disease was made. Uh Subsequently McArdle disease. Patients with McArdle disease have rarely problems in childhood. While on the other hand, permanent myopathy with weakness has been described either as a late uh consequence of the disease or as a late onset form of this disease. Most patients with McArdle disease experience a characteristic second wind phenomenon. If they take a brief rest after muscle pain and weakness occur during strenuous exercise, they can then resume physical activity more vigorously and for a longer period of time without any problem. two factors apparently are responsible for this phenomenon. One an increased mobilization of free fatty acids to provide muscle with alternative fuel and the second and increased blood flow to the exercising muscles. The pathogenesis of contracture and myoglobin. Urea in McArdle disease Is generally attributed to a critical shortage of 80 p during strenuous exercise. When most of the energy for muscle contraction derives from glycogen breakdown and black colleges. A defect of 80P could impair muscle relaxation by affecting the energy dependent calcium uptake of the cytoplasmic, ridiculous, more severe or prolonged the ATP depletion could alter the integrity of muscle membranes and cause necrosis and myoglobin O'Ryan. This better genetic mechanism, however, has not been verified experimentally and in one study shown here in the old the results of which are shown in this slide in one study by DR. Roland and his colleagues, um the concentrations of adenine nucleotides creating phosphate, creating an inorganic phosphate were all found to be normal in two patients before in the muscle from two patients before and after or during contracture. The possibility was also considered that a compartmentalized as it were the effect of ATP may cause irreversible damage of circa plastic articular membranes responsible for the sometime rather prolonged contractors. However, no defect of calcium uptake nora Tps activity in cytoplasmic critical um vesicles isolated from a muscle was found in dr Brodus lab or in our own lab in a patient before and during contractor McArdle disease is not a single genetic entity, although in most cases the mode of inheritance appears to be autism. A recessive autos normal dominant inheritance was observed in one family, and the genetic basis for the large prevalence of male patients remain to be explained. A more striking example of genetic heterogeneity is the finding that in some patients, no enzyme protein is detectable by immunological methods, while in others, enzyme protein seems to be present. Although inactive or at least partially active, the relative proportion of patients and the mode of transmission will have to be determined for each of these conditions. This has not been done yet. Another genetic puzzle is the finding in dr king angles laboratory that force formulas activity was demonstrable. His to chemically at least in regenerating and cultured muscle fibers from three patients with McArdle disease. The fact that symptoms and signs of McArdle disease are intermittent and in most cases transitory as I mentioned, makes the need of effective therapy less dramatic for this disorder than for other progressively crippling metabolic diseases. However, because of the severe limitation of exercise in otherwise healthy people and the risk of extensive muscle necrosis and myoglobin urea several therapeutic measures have been tried in McArdle disease. Initial attempts to bypass the metabolic block, and here, let me point out again here is where the metabolic block is this is glycogen breakdown. This is like colleges. Initial attempts were aimed at bypassing this metabolic block by providing muscle with glucose or fructose. This was based on some observations that both glucose and fructose seems to prolong or to uh to prolong the capacity to exercise for these patients. Uh Another alternative therapy would consist in administration of uh drugs that would cause hyper glossy mia. Um like broken down. However, these drugs have been tried and have not proven to be very effective. The sugars tend to cause weight gain without much clinical response and the blue bag on the parental administration of glucose gonna certainly impractical other potential therapeutic approaches remain to be evaluated. one is suggested by the studies on the second Wind phenomenon that I briefly mentioned before and that would consist in raising the concentration of serum free fatty acid and ketone bodies either by dietary regimen like a ketogenic diet or by pharmacological means, for instance, by sublingual eyes. Oprah Torino Glycogen noses type seven or to Ruiz disease is due to an effect of muscle foster flew to kindness and this is shown here schematically. So as you see, the defect is lower down in the psychologist. six cases have been reported and we have recently started to more, the clinical picture is identical to that of macarthur's disease and consists of exercise intolerance, cramps and myoglobin area, muscle morphology and the degree of glycogen accumulation are also very similar in these two disorders. Differential diagnosis may be suggested by Eritrea's side studies because a partial defect of red blood cell fossil fuel to kindness has been shown consistently in all cases of fossil fuel to kindness deficiency. Mhm. No therapy has been attempted so far in this disease and as the metabolic block is at the level of like colleges and not of glycogen policies, there is of course no rationale for the use of glucose or fructose in this disease. However, dietary regiments or drugs causing increase of increased levels of plasma free fatty acids and ketone bodies again could prove beneficial in this disorder as well as in McArdle disease. A valuable lab test for the diagnosis of both glycogen oh sis type five and type seven is the response of venus blood lactate to ischemic exercise. And this is schematically shown here if the patient is asked to exercise, generates forearm exercise uh in ischemia. What happens is that either through the action of various hormones like epinephrine or more directly by a shift of calcium from the inside of the cytoplasmic article. Um Into the site is all there is a cascading of reactions of activating reactions of force foreigners from the less active form to the more active form. This in turn activates glycogen breakdown and psychologists and in ischemic conditions there is a production of lactate which results in an increase of venus lactate in normal individuals. In patients with a block either at the level of phosphoric or foster filter kindness. This X. S. Chemical exercise results in no increase in venus lock date. A very different picture is offered by like a geonosis, type two or acid maltese deficiency in the classical or infantile or generalized form. The disease is rapidly progressive and death occurs before a year of age. This is indicated here old tissues are affected, but particularly there is a massive accumulation of glycogen in the heart, skeletal muscle and both central and peripheral nervous system. The clinical picture is dominated by profound weakness and really floppy nous and uh and sometimes macro close to recently. However, a more benign form of the disease has been recognized onset is either in childhood or in adult life, and the clinical picture, with very few exceptions is really limited to skeletal muscle involvement and consist of a progressive, generally approximate limb muscle weakness, simulating muscular dystrophy or polymer anxieties sometimes, however, and rather often in about 50% of these patients, respiratory muscles are involved and this may result in severe ventilatory insufficiency serum, creating fast for kindness is consistently elevated in all of these patients with late onset as in motors deficiency, as well as in the infantile cases and characteristically, the electro maya electro my ah graffiti shows milestone is discharged. My Tony discharges without clinical my antonia. The history pathological features are those of a vascular myopathy and glycogen is variably increased in this late onset forms, but this may escape routine histological observation. It is therefore of great importance to consider late onset as emotive deficiency in the differential diagnosis of my pathetic syndromes 1963 hers in Belgium described the absence of acid maltese in tissues of patients with the generalist or infantile form of the disease and formulated the concept of the inborn listeners normal disease. As far as Guy Pacino's, this type two is concerned. This concept is based on the phenomenon of tautology in the course of the physiological renewal of the cell portions of the cytoplasm are surrounded by vesicles and form what is known as an automatic vacuum or auto fake ozone. In the terminology of DR airs, the merging of primary lizzo zones containing a whole battery of acid idolizes with this automatic vacuums transforms or forms what is known as a digestive vacuum or auto Liz ozone. Again, in the terminology of daughter earth, after all, the appropriate substrates have been digested by the specific hydrologists, The residual building blocks or smaller molecules that may be formed through this process are either released into the cell and re utilized like glucose from glycogen for instance, or if larger molecules and digestible structures are left, they will remain indefinitely in what are known as residual or dense bodies in the cell now. Uh in like a generous this type to the absence of acid maltese, which has both alpha 14 and alpha 16 glucose. It is activity as we mentioned before and is therefore capable of digesting glycogen all the way to glucose results in continuous accumulation of undigested glycogen within lizzo zones until the cell is literally engorged with this and sometimes are called glycogen ISMs. While there is little doubt that this is the basic pathogenesis In type two black vaginosis, some observations remain difficult to explain. One question which probably merely merely reflects our ignorance of the functional role of lizards. Normal glycogen metabolism, normal muscle is why this tissue, which is normally, which normally appears to have very few lizzo soames is so severely affected in this disease. A more impor important question, however, is why such a large proportion of the accumulated glycogen is not internalize omo As one would expect from the theory, but rather free the cytoplasm, a phenomenon which is particularly apparent in infantile form of the disease and particularly muscle. And this is exemplified in the slide. As you see here, you can see only the first of all notice the great accumulation of glycogen. You can only see here some mile five brill's group here in one isolated here and but notice particularly how most of the glycogen is freeing the cytoplasm and only in certain areas. You can see one or two bodies or vesicles enclosing glycogen further irrespective of the mechanism by which the glycogen? The free glycogen accumulates? Another question is why is it not degraded by the normal, like a generalistic pathways of the cytoplasm. In other puzzling question, regards the biochemical basis for the clinical differences between infantile and late onset, as in motors deficiency. In a comparative study. Angelini and dangle found lower than normal neutral multi activity in several tissues from the infantile but not the late onset late onset AMG patients as emotive deficiency patients and suggested a possible compensatory role for neutral maltese. In our laboratory determination of acid maltese by a very sensitive floor O Matic asset using the artificial substrate for methylene Bellisario alpha, the glucose, glucose glucose side revealed the presence of some residual activity variable From between three and 12 in 15 cases in muscle from 15 cases with late onset as in motives deficiency, but no residual Activity in in muscle from three patients with infantile form of the disease. This phenomenon is even more apparent in Lucas sides where enzyme activity, acid motives activity is either normal or only partially reduced in late onset but undetectable in infantile forms of the disease. These observations, and the fact that no cases of infantile and late onset as emotive deficiency have been so far reported in the same family, suggest that these are two different genetic diseases affecting the same enzyme. Another example of genetic virginity. Several different therapeutic strategies have been tried, particularly the infantile form, including liberalization of liposomes, stimulation of glycogen analysis and enzyme replacement, vitamin A. Progesterone hyperbaric oxygen are among the list goes on liberalising agents used to make the trapped glycogen. This is the rationale behind it to make the trapped glycogen available to cytoplasmic digestion. These agents were clinically ineffective and the rationale of this approach may be questionable in infantile MD. where as I showed before, much extra lies omar glycogen is already present in most tissues stimulation of psychoanalysis by administration of epinephrine resulted in decrease of cytoplasmic but not centralized. Uzoma glycogen in liver. In one case this only demonstrates that astral is is normal. Glycogen breakdown is normal. In this disease administration of alpha glucose, it is prepared either from aspergillus *** or from human placenta was attempted in a few cases. In one patient centralizes omo glycogen decreased significantly in liver and the morphology. The infrastructure of this organ reverted essentially to normal. In no case, however, did the exotic, did exogenous enzyme enter either skeleton or cardiac muscle and the clinical course was unchanged by this treatment. In patients with the late onset form of the disease, ketogenic diet associated or not with epinephrine administration has been suggested as a means of slowing down glycogen accumulation in Mosul and its effectiveness is presently under investigation in several laboratories. While a great amount of work has been done over the past 25 years on glycogen metabolism of muscle and if disorders as I think became apparent from this presentation, relatively little attention has been directed to lipid metabolism. This is surprising because lipid metabolism is at least as important as glycogen metabolism as a source of energy for muscle contraction. While glycogen breakdown is an ideally suited metabolic system for the rapid provision of energy, which is crucial in flight or fly situations or in strenuous exercise in humans, it cannot sustain exercise for more than a few minutes. The energy for prolonged exercise derives mainly from lipid metabolism, which is largely an intra mitochondria process, as shown schematically in the slide. Once free fatty acids, which are the so to the lipid currency of the sale. For the sale have been transported into the cell. They are activated by an enzyme known as fatty acid coenzyme, a center days at the expense of ATP to form fatty acid coenzyme A. At this point in an enzyme known as car knitting performative transfers, one which is located on the outer face of the inner mitochondrial membrane mitochondrial membrane. And this this structure here is supposed to represent the mitochondria um attach is the fatty acid oil residue to a molecule of carnitine to form fatty acids. Carnegie in this form, and only this form long chain fatty acids can go across or penetrate into the mitochondria. Once inside the mitochondria in a second enzyme known as car knitting permitted transfers to which is attached to the interface or the inner mitochondrial membrane catalyze is the reverse reaction. Detaches the fatty acid residue or the long chain fatty acid residue from carnitine and reattach, is it to a coenzyme coenzyme a to form again fatty acid coenzyme a. This now can undergo within the mitochondria in the stepwise process of better oxidation at each step. In this process, there is liberation of a molecular velocity coenzyme A, which then can enter the Krebs cycle to disorders of lipid metabolism or to specific disorders of lipid metabolism have been affecting muscle have been reported, one of them causing intolerance to exercise if you want. Or intermittent myoglobin urea and the other causing progressive muscle weakness. Again, as you see, the muscle seems to have but a few ways of crime. 1973 at the University of Pennsylvania, we started two brothers 33 and 29 years old. As you see here, with a similar with similar syndromes in the syndrome, the clinical picture consisted really of recurrent myoglobin urea, convincing around puberty. Unlike muscle for foreigners and fossil fuel tokens deficiency, there was no history of painful cramps or intolerance to strangers, exercise of short duration myoglobin urea generally followed sustained exercise of about two hours duration, like mountain hiking, unloading lumber painting walls. Also, unlike McArdle disease, fasting contribute to the pierre. Myoglobin urea and the two most severe attacks were induced by were indeed precipitated by a combination of prolonged exercise and inadequate diet. The diagnosis of glycogen, Osi's type five Or seven was ruled out by the normal rise of Venus lactate after ischemic exercise and more directly by the normal level of glycogen and the normal activities of phosphorus and fossil fuel tokens in muscle biopsies morphology of muscle was essentially normal. The concentration of carnitine was slightly elevated in this patient as compared to normal and the activity of parliamentary coenzyme a center days and acetyl carnitine transfers were normal muscle. Carnitine. Parliamentary transfer is for the long chain. If you remember. Arsenal. Canada transfers was Measured by three methods, 2 of which are shown in this slide in both crude muscle or margin. It's and in mitochondria preparation and in the patients, the activities varied between undetectable to about 20% of normal at most the enzyme. The fact was also expressed in leukocyte. In both patients, where activities were below 20% of normal and intermediate activities were found in the leukocyte of their symptomatic mother. This pattern seems to suggest an auto xoma recessive model transmission, although at present, next link transmission cannot be excluded. Plasma free fatty acids were normal on a balanced diet, but cholesterol was slightly increased And tried illiterates were increased between three and five fold in the patient, Each patient then underwent a 72 hour fast without exercise. Both patients remained a symptomatic, but one of them had a marked increase of CPK after 72 hours of fasting, which was again present at a subsequent trial of fasting and myoglobin traces of myoglobin became apparent in both plasma, enduring in both patients. After fasting ketone bodies production was also abnormal. As you see Here, Ketone bodies did not rise in plasma until about the 3rd day of fasting. While administration of medium change like this right produced a very prompt increasing ketone bodies as in normal individuals. This would suggest that the side effect may affect the liver as well. Although this was not directly tested, how can we now tie all this data together? Well, long chain fatty acid oxidation in men at rest and on a regular diet provides more than 50%. Certainly of the energy required by muscle impairment of fatty acid utilization. By muscle may cause an increase of free fatty acids in the blood. And this would be the free fatty acids, which are potentially toxic substances would be handled by the liver, which would then s terrify them to triglycerides, and this may cause secondary hypercholesterolemia. The sequence of events would be magnified during fasting, which normally causes increased utilization of fatty acids released from multiple sides during normal activity. And on a normal diet, these patients can utilize muscle glycogen and blood glucose. Normal activity and moderate or short exercise are very well tolerated after unusual exercise. However, especially with some degree of fasting, glycogen stores are probably depleted and due to the defect of carnitine permitted transfers long chain fatty acids cannot enter muscle mitochondria to serve a source of energy. The pathogenesis of myoglobin urea is as Hypothetical as it is in like a diagnosis type five and 7. Again, in this disorder, it can be postulated that acute muscle necrosis, maybe related to the defect of ATP do in this case to a block of lipid rather than glycogen metabolism In 1972 Andrew Angle and Zeke Erred reported the case of a young woman, 19 year old woman with severe generalized muscle weakness, Which started apparently in childhood but became rapidly wars around 90 age 19. They main feature of this patient was in the morphology of her muscle, which showed tremendous accumulation of lipids, a real lipid storage myopathy and next slide, which is not from the same patient, but from a patient that we recently studied the Columbia University shows this phenomenon. As you see, these great accumulation of lipids in these three portions of these three fibers is remarkable in normal muscle. You could see just a few of these vacuums containing lipids originally here and there the following year angle and Angelini found that in vitro utilization of long chain fatty acids by the patient muscle was defective as compared to normal in the absence of of added Carnegie. But when carnitine was added to the medium, then utilization of fatty acids became essentially normal. This observation led them to measure the concentration of carnitine in the patient muscle in the patient's muscle and in several occasions they found that the carnitine levels were very low as compared to normal muscles. Mhm. Carnitine is sympathized exclusively or predominantly in the liver and then sort of exported through the blood to other tissues. The much higher concentration of carnitine in muscle than in plasma. Further suggests that the uptake of carnitine, maybe an active process depending on energy, possibly as serum carnitine levels. We are normal in the patient, the effect of this transport mechanism appear to be the most likely explanation for the defect of muscle carnitine. In the patient of Andrew Anglin Angelini, four more patients with this syndrome have been described and actually it is almost difficult to uh to keep Up with the literature. A 5th, a fifth patient or six patient in all, has been now described in Lancet and we have seen, as I mentioned in other patients that we're following. Now. In any event, there are several, some common features between these patients, namely, they all showed muscle weakness more or less generalized and all of them had lipid storage in their muscle lipid story picture of lipid storage myopathy. However, the disorders seem to be rather heterogeneous. As far as other parameters are concerned. Age of onset varied. The number of tissues involved varied very much in some cases. In some cases the disorder seems to be limited to skeletal muscle. In other it seemed to affect peripheral nerve, uh, leukocyte, it's on the most important difference uh is reflected by a patient described by car party and collaborators in Montreal. This was a child where carnitine was not only low in muscle, but it was only law in uh zero and in living and this would therefore suggest that in this case we are dealing with a defect in carnitine synthesis in the liver rather than an effect of carnitine transport. The genetic nature of the disease was demonstrated in one case, this is the pedigree of the patients studied by Dr van Dyke and his collaborators here in Rochester and as the numbers indicate carnitine levels, carnitine concentration in muscle and as you see, both parents of the pra positives and a maternal and all had definitely lower than normal levels of comedy, suggesting because this pattern strongly suggest an auto xoma recessive model transmission regardless of what the primary biochemical error or errors. Really, maybe these disorders, the effect of muscle committee, which is the indispensable carrier of fatty acids across the inner mitochondrial membrane, as I showed before in the scheme may easily account for the defect of lipid metabolism observed in these patients and for the lipid storage. What is not easily explained is why to biochemical defects affecting the same metabolic pathway, namely carnitine positive transference deficiency and carnitine deficiency should cause such dissimilar clinical pictures. Therapy with corticosteroids has been beneficial in Carnitine deficiency in two cases for reasons that are still largely unknown replacement therapy with oral carnitine has also been very effective in at least two patients and the rationale for such a therapy appears to be, of course, obvious particularly in the case in the cases with low serum Carnegie. However, in spite of the good clinical response, no increase of either liver or muscle carnitine was observed suggesting the defective sentences of carnitine in the liver may not be the sole biochemical abnormality, particularly this. This is true for the case of Car party and collaborators in Montreal, the area of lipid metabolism of muscle, and it's disorders is still largely uncharted territory, and it is likely that a number of different disease entities will be recognized in the near future, just as it happened for the glycogen storage diseases. And this is certainly a challenging and exciting perspective for the future.