Carbohydrate inborn errors

This chapter deals with the assays used for the diagnosis of three groups of inborn errors of metabolism of carbohydrates, i.e. ... 

In mitochondria, there are four fatty acyl CoA dehydrogenase species, each of which has a specificity for either short-, mediurr-long-, or very-long-chain fatty acids. MCAD deficiency, an autos mal, recessive disorder, is one of the most common inborn errors of metabolism, and the most common inborn error of fatty add oxidation, being found in 1 in 12,000 births in the west, and 1 in 40,000 worldwide. It causes a decrease in fatty acid oxidation and severe hypoglycemia (because the tissues cannot obtain full ener getic benefit from fatty acids and, therefore, must now rely on glu cose). Treatment includes a carbohydrate-rich diet. [Note Infants are particularly affected by MCAD deficiency, because they rely for their nourishment on milk, which contains primarily MCADs. 

Various inborn errors of metabolism (Table 25-1) result from deficiencies or absence of some of the enzymes listed in Figure 25-9. Some of these are discussed later in the chapter. The relationship of carbohydrate metabolism to the production of lactate, ketone bodies, and triglycerides is also depicted in Figure 25-9. The pentose phosphate pathway, also known as the hexose monophosphate shunt, is an alternative pathway for glucose metaboUsm that generates the reduced form of nicotinamide-adenine dinucleotide phosphate (NADPH), which is used in maintaining the integrity of red blood cell membranes, in lipid and steroid biosynthesis, in hydroxylation reactions, and in other anabolic reactions. The complete picture of intermediary metabolism of carbohydrates is rather complex and interwoven with the metabolism of lipids and amino acids. For details, readers should consult a biochemistry textbook. 

Description. Also known as vitamin Bg or H, this vitamin is of great importance for the biochemistry of the human organism. Biotin is the cofactor for a small group of enzymes that catalyze carboxyla-tion, decarboxylation, and transcarboxylation reactions in carbohydrate and fatty acid metabolism. Deficiency of this vitamin is rare in humans, but can be induced in special circumstances in individuals with inborn errors of biotin metabolism, in individuals taking certain medications, and in some women during pregnancy. ... 

Keir, G, Winchester, B.G, and Clayton, R, Carbohydrate-deficient glycoprotein syndromes inborn errors of protein glycosylation, Ann. Clin. Biochem., 36, 20, 1999. 

A two part compendium in the Monographs in Human Genetics series deals with inborn errors of metabolism in man and covers carbohydrate, amino-acid, and lipid metabolism and connective tissues and purine metabolism and endocrinology. ... 

The kidneys act to filter toxins out of the blood for excretion in the urine. There are complex mechanisms to recover electrolytes, carbohydrates, and amino acids. The kidney is also an endocrine organ, regulating vitamin D metabolism and signaling red blood cell proliferation through erythropoietin. While each of these unique roles is not specifically tied to an inborn error of metabolism, the kidneys are affected by several disorders and may be the source of chronic complications of disease. Symptoms of chronic kidney disease include osteoporosis, hypertension, anemia, and electrolyte abnormalities with the primary means of therapy being hemodialysis or transplant (Box 4.5). 

Inborn Errors of Carbohydrate Metabolism 163 Glycogen Storage Disease Glycogen Metabolism Von Gierke s Disease... 

Malnutrition may also result from disease of the gastrointestinal tract. Among the malabsorption syndromes, carbohydrate malabsorption due to inborn errors of metabolism, the dumping syndrome resulting from gastrectomy, and steatorrhea will be discussed [136]. 

A review dealing with cell-surface phenomena, the structures and biosynthesis of tissue proteoglycans, the regulation of glycogen metabolism, and inborn errors of carbohydrate metabolism has appeared. ... 

Tables 1-1 to 1-5 outline the specific defects, characteristic features, and treatment (particularly dietary management), of some of the more important inborn errors in the metabolism of amino acids, carbohydrates, lipids, nucleic... 

This is a rare inborn error in the metabolism of carbohydrates. The most common symptom is diarrhea. In this disease the enzymes invertase and isomaltase are missing Both enzymes are disaccharidases. Invertase splits sucrose (sugar) and isomaltase splits isomaltose, a product of starch digestion. Therefore, sources of sucrose and isomaltose—wheat and potatoes—should be omitted from the diet to control the disease. 

Also see INBORN ERRORS OF METABOLISM, Table 1-2, Inborn Errors of Carbohydrate Metabolism, "Carbohydrate Intolerance.")... 

INBORN ERRORS OF THE METABOLISM. At times the metabolism of the nutrients cannot proceed normally due to some defect in the genetic information that exists at birth or shortly thereafter. These defects can affect the metabolism of carbohydrates, proteins, and fats hence, they are referred to as inborn errors of metabolism. Often they are due to production of a nonfunctional enzyme or complete lack of an enzyme involved in the metabolic scheme. Since enzymes are protein, their production relies upon correct genetic information. Many of these inborn errors have serious consequences, but fortunately most are rare. Familiar examples of errors in carbohydrate metabolism include lactose intolerance and galactosemia. Familiar examples of errors in protein metabolism include albinism, maple syrup urine disease, and phenylketonuria. The hyperlipoproteinemias are familiar examples of inborn errors of fat metabolism. 

Note-. (1-9) Organic acid disorders, (10-14) fatty acid oxidation disorders, (15-20) amino acid disorders, (21-23) hemoglobinopathies, (24 and 25) endocrinopathy, (26) other inborn error of metabolism, (27) carbohydrate disorders, (28) miscellaneous genetic conditions, and (29) infectious diseases. MS/MS tandem mass spectrometry, HPLC high pressure hquid chromatography, lEF isoelectrofocusing, RIA radioimmuno assay, and ELISA enzyme-linked immunosorbent assay. 

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