Fructose deficiency

Inorganic iron is absorbed only in the (reduced) state, and for that reason the presence of reducing agents will enhance absorption. The most effective compound is vitamin C, and while intakes of 40-60 mg of vitamin C per day are more than adequate to meet requirements, an intake of 25-50 mg per meal will enhance iron absorption, especially when iron salts are used to treat iron deficiency anemia. Ethanol and fructose also enhance iron absorption. Heme iron from meat is absorbed separately and is considerably more available than inorganic iron. However, the absorption of both inorganic and heme iron is impaired by calcium—a glass of milk with a meal significantly reduces availabiUty. 

Deficiency of aldolase B, although this isozyme is not expressed in red blood cells, is responsible for hereditary fructose intolerance, an autosomal recessive dis-... 

The diagnosis of PK deficiency depends on the determination of quantitative enzyme activity or qualitative abnormalities of the enzyme. In 1979, the International Committee for Standardization in Haematology (ICSH) established methods for the biochemical characterization of red blood cell PK variants (M22). Since the establishment of these methods, many PK-deficient cases have been characterized, including 13 cases of homozygous PK deficiency. Residual red blood cell PK activity is not usually associated with phenotypic severity,whereas enzymatic characteristics such as decreased substrate affinity, thermal instability, or impaired response to the allosteric activator fructose-1,6-diphosphate (F-1,6-DP) correspond to a more severe phenotype. 

L The answer is a. (Hardman, p 922) Lactulose is a synthetic disaccharide (galactose-fructose) that is not absorbed. In moderate doses, it acts as a laxative. In higher doses, it is capable of binding ammonia and other toxins that form in the intestine in severe liver deficiency and that are believed to cause the encephalopathy. Loperamide is an antidiarrheal opioid lorazepam is a CNS depressant loxapine is a heterocyclic antipsychotic. 

Fructose-1,6-bisphosphatase deficiency, first describ ed by Baker and Winegrad in 1970, has now been reported in approximately 30 cases. It is more common in women and is inherited as an autosomal recessive disorder. Initial manifestations are not strikingly dissimilar from those of glucose-6-phosphatase deficiency. Neonatal hypoglycemia is a common presenting feature, associated with profound metabolic acidosis, irritability or coma, apneic spells, dyspnea, tachycardia, hypotonia and moderate hepatomegaly. Lactate, alanine, uric acid and ketone bodies are elevated in the blood and urine [11]. The enzyme is deficient in liver, kidney, jejunum and leukocytes. Muscle fructose-1,6-bisphosphatase activity is normal. 

Phosphoenolpyruvate carboxykinase (PEPCK) deficiency is distinctly rare and even more devastating clinically than deficiencies of glucose-6-phosphatase or fructose-1,6-bisphosphatase. PEPCK activity is almost equally distributed between a cytosolic form and a mitochondrial form. These two forms have similar molecular weights but differ by their kinetic and immunochemical properties. The cytosolic activity is responsive to fasting and various hormonal stimuli. Hypoglycemia is severe and intractable in the absence of PEPCK [12]. A young child with cytosolic PEPCK deficiency had severe cerebral atrophy, optic atrophy and fatty infiltration of liver and kidney. 

Genetic deficiency of fructokinase is benign and often detected incidentally when the urine is checked for glucose with a dipstick. Fructose 1-phosphate aldolase deficiency is a severe disease because of accumulation of fructose 1-phosphate in the liver and renal proximal tubules. Table 1-12-4 compares the two conditions. Symptoms are reversed after removing fructose and sucrose from the diet. 

Table 1-12-4. Comparison of Fructokinase and Fructose 1-Pho hate Aldolase Deficiencies...

Fnictokinase Defidenc)r (Essoitial Fnictosuria) Fructose l-Phoq>hate Aldolase (Aldolase B) Deficiency (Hereditary Iroctose Intolerance)... 

In a person with glucose 6-phosphatase deficiency, ingestion of galactose or fructose causes no increase in blood glucose, nor does administration of glucagon or epinephrine. 

The concentration of free Pj decreases as it may in galactosemia, hereditary fructose intolerance, and glucose 6-phosphatase deficiency. 

Hereditary fructose intolerance is due to aldolase B deficiency and is often diagnosed when babies are switched from formula or mother s milk to a diet containing fructose-based sweetening, such as sucrose or honey. 

Essential fructosuria is a benign, asymptomatic condition arising from deficiency of the enzyme fructokinase that causes a portion of fructose to be excreted in the urine. 

Diabetes - insulin dependent Methyl malonic, propionic or isovaleric acidaemias Pyruvate carboxylase and multiple carboxylase deficiency Gluconeogenesis enzyme deficiency glucose-6-phosphatase, fructose-1,6-diphosphatase or abnormality of glycogen synthesis (glycogen synthase) Ketolysis defects Succinyl coenzyme A 3-keto acid transferase ACAC coenzyme A thiolase... 

CDG-Ib is caused by PMI deficiency. This enzyme catalyses the conversion of fructose-e-phosphate to mannose-6-phosphate in the cytosol (Fig. 4.5.1). The IEF pattern of serum transferrin in CDG-Ib is comparable to that of CDG-Ia, although the clinical phenotype is completely different, with gastrointestinal bleedings and hepa-topathy. Determination of PMI activity is performed by a coupled optical test. 

Hereditary fructose intolerance (HFI), caused by the deficiency of fructaldolase, and fructose- 1,6-bisphosphatase deficiency. 

Fructose-bisphosphate aldolase, which also acts on fructose-1-phosphate, is the enzyme deficient in hereditary fructose intolerance (HFI, MIM 229 600). 

Fructose- 1,6-bisphosphatase is the enzyme deficient in fructose-1,6-bisphosphatase deficiency (MIM 229 700). 

Baker L, Winegrad AI (1970) Fasting hypoglycaemia and metabolic acidosis associated with deficiency of hepatic fructose-1,6-diphosphatase activity. Lancet ii 13 16... 

Cause and treatment of hereditary fructose intolerance A deficiency of fructokinase causes a benign condition, but a deficiency of aldolase B causes hereditary fructose intolerance, in which severe hypoglycemia and liver damage can lead to death if the amount of fructose (and, therefore, sucrose) in the diet are not severely limited. 

Carbohydrate abnormalities, such as renal glycosuria (a transport defect), pentosuria (enzyme deficiency, xylitol dehydrogenase I. lactase deficiencies, fructose intolerance, galactosemia, galacloki-nase deficiency, oxalosis, and several glycogenoses (von Gierke s, Forbes . Andersen s, Hers s. and Tarui s diseases). 

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