Browsing Pathways

Spironolactone is a potassium-sparing diuretic. It acts by competing with aldosterone for its receptor inside the principal cells of the late distal tubule and collecting tubule. Aldosterone increases sodium reabsorption and potassium excretion by up-regulating the expression of basolateral sodium-potassium ATPases as well as luminal (apical) sodium and potassium channels. Sodium in the nephron lumen enters the principal cells through the luminal sodium channels, where it is then actively pumped out into the interstitium by sodium-potassium ATPases. This causes the interstitium to become hyperosmotic and establishes an osmotic gradient, facilitating water reabsorption through aquaporin channels. On the other hand, potassium is actively pumped from the interstitium into the principle cell. It then diffuses from inside the cell into the nephron lumen via potassium channel, driven by an electrochemical gradient established by sodium leaving the lumen. Potassium entering the nephron lumen is subsequently excreted in the urine. Spironolactone inhibits sodium and water reabsorption as well as potassium excretion by blocking the actions of aldosterone as described above.

Eplerenone is a potassium-sparing diuretic. It acts by competing with aldosterone for its receptor inside the principal cells of the late distal tubule and collecting tubule. Aldosterone increases sodium reabsorption and potassium excretion by up-regulating the expression of basolateral sodium-potassium ATPases as well as luminal (apical) sodium and potassium channels. Sodium in the nephron lumen enters the principal cells through the luminal sodium channels, where it is then actively pumped out into the interstitium by sodium-potassium ATPases. This causes the interstitium to become hyperosmotic and establishes an osmotic gradient, facilitating water reabsorption through aquaporin channels. On the other hand, potassium is actively pumped from the interstitium into the principle cell. It then diffuses from inside the cell into the nephron lumen via potassium channel, driven by an electrochemical gradient established by sodium leaving the lumen. Potassium entering the nephron lumen is subsequently excreted in the urine. Eplerenone inhibits sodium and water reabsorption as well as potassium excretion by blocking the actions of aldosterone as described above.

L-2-Hydroxyglutaric Aciduria (D-2-Hydroxyglutaric Aciduria ) is an autosomal recessive disease caused by a mutation in the L2HGDH gene which codes for L-2-Hydroxygluarate dehydrogenase. A deficiency in this enzyme results in accumulation of L-2-Hydroxyglutaric acid in plasma, spinal fluid, and urine; and L-lysine in plasma and spinal fluid. Symptoms, which present at birth, include ataxia, hypotonia, mental retardation, and seizures. Premature death often results. D-2-Hydroxyglutaric Aciduria is an autosomal recessive disease caused by a mutation in the D2HGDH gene which does for D-2-Hydroxygluarate dehydrogenase. A deficiency in this enzyme results in accumulation of D-2-Hydroxyglutaric acid in plasma, spinal fluid, and urine; oxoglutaric acid in urine; and gabba-aminobutyric acid in spinal fluid. Symptoms, which present at birth, include ataxia, hypotonia, mental retardation, and seizures. Premature death often results.

2-Methyl-3-hydroxybutyryl CoA dehydrogenase deficiency (Hydroxyl-CoA dehydrogenase deficiency; MHBD) is a rare inborn disease of metabolism caused by a mutation in the HSD17B10 gene which codes for 3-hydroxyacyl-CoA dehydrogenase type-2. A deficiency in this enzyme results in accumulation of L-lactic acid in blood, spinal fluid, and urine; 2-ethylhydracrylic acid, 2-methyl-3-hydroxybutyric acid, and tiglylglycine in urine. Symptoms include cerebal atrophy, motor and mental retardation, overactivity and behavior issues, seizures and progressive neurological defects leading to early death. Treatment includes a high carbohydrate and low protein diet.

3-Hydroxy-3-methylglutaryl-CoA lyase deficiency (3-Hydroxy-3-methylglutaric acidemia; Leucine metabolism, defect in, HMG-CoA lyase deficiency) is an autosomal recessive disease caused by a mutation in the HMGCL gene which codes for hydroxymethylglutaryl-CoA lyase. A deficiency in this enzyme results in accumulation of 3-hydroxymethylglutaric acid, 3-hydroxyisovaleric acid, 3-methylcrotonylglycine and 3-methylglutaconic acid (cis and trans form), and methylglutaric acid in urine; and ammonia in blood. Symptoms include cardiomyopathy, dehydration, hypotonia, lactic acidosis, and pancreatitis. Treatment includes a low-fat, low-protein, high-carbohydrate diet.

3-Methylglutaconic aciduria type 1 (3-Methylglutaconicaciduria; Aciduria, 3-methylglutaconic type I) is an autosomal recessive disease caused by a mutation in the AUH gene which codes for methylglutaconyl-CoA hydratase. A deficiency in this enzyme results in accumulation of 3-hydroxyisovaleric acid, 3-methylglutaconic acid, and methylglutaric acid in urine. Symptoms include hypoglycemia, low birth weight, coma, seizures, and mental retardation. Treatment includes a low protein diet.

3-Methylglutaconic aciduria type 3 (Costeff syndrome; Optic atrophy plus syndrome) is an autosomal recessive disease caused by a deficiency in the OPA3 code which does for optic atrophy 3 protein. A deficiency of this enzyme results in accumulation of 3-methylglutaconic acid and methylglutaric acid. Symptoms include ataxia, dysarthria, optic atrophy, and neurological deterioration.

3-Methylglutaconic Aciduria Type IV, also called MGA, Type IV and MGA4, is a rare inborn error of metabolism (IEM) and autosomal recessive disorder and caused by a defective methylglutaconyl-CoA hydratase. Methylglutaconyl-CoA hydratase catalyzes the conversion of 3-Methylglutaconyl-CoA into 3-Hydroxy-3-methylglutaryl-CoA which is the substrate of hydroxymethylglutaryl-CoA lyase. This disorder is characterized by increased urinary excretion of 3-methylglutaconic acid. Symptoms of the disorder include poor growth and neurological degression. Currently, there is no effective treatment for 3-MGA type IV.

5-Oxoprolinuria (5-Oxoprolinase deficiency) is a result of a defect in the gamma-glutamyl cycle due to either 5-oxoprolinase or glutathione synthetase deficiency. In the case of glutathione synthetase deficiency, the glycine is not incorporated into gamma-glutamylcysteine. In the case of 5-oxoprolinase, however, pyroglutamic acid accumulates. Symptoms include anemia, mental retardation, metabolic acidosis, respiratory distress and urolithiasis.

Adenosine deaminiase deficiency (immunodeficiency) is an autosomal recessive disease caused by a muation in the ADA gene which codes for adenosine deaminase. A deficiency in this enzyme results in immunodeficiency and a decreased concentration of lymphocytes in blood. Symptoms include diarrhea, severe or recurrent infections, vomiting and early onset in children, infants and newborns. Treatment includes bone-marrow transplants and enzyme replacement therapy.