Dr.Ehab Fathy Gabr Aboueladab (PhD in Biochemistry), Associate Prof.Dr. of Biochemistry, Damietta University, Faculty of Specific Education Damietta, New Damietta City, P.O.Box.34517, Egypt, Tel :002-057-2224444(HOME), 002-057-2403085(WORK), 002-0100-7834123(MOBIEL or HANDY), Email:ehab10f@gmail.com, ChatYahoo:ehababoueladab@yahoo.com, http://www.labhoo.com, http://www.citeulike.org,http://vadlo.com,www.thesciencejobs.com, http://medicalppt.blogspot.com,http://www.medbio.info,worldcat.org
Sunday, October 28, 2012
Road Train Elphinstone Easyloader
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Folding Log Trailer
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Transport Schmiedepresse / forging press Bohnet Schwertransporte
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Amazing Future Truck
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Arrivée du premier tram-train Avanto à Mulhouse et déchargement.
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Nadměrný náklad Hradec Králové - Mělník
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Ditched Kenworth Log Truck Recovery
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Overview of sphingolipidosis (Lipid storage Diseases)
he sphingolipidosis (lipid storage diseases) are a group of inherited diseases that are caused by a genetic defect in the catabolism of lipids containing sphingosine. They are part of a larger group of lysosomal disorders and exhibit several constant features:
(1) Complex lipids containing ceramide accumulate in cells, particularly neurons, causing neuro degeneration and shortening the life span.
(2) The rate of synthesis of the stored lipid is normal.
(3) The enzymatic defect is in the lysosomal degradation pathway of sphingolipids.
(4) The extent to which the activity of the affected enzyme is decreased is similar in all tissues.
There is no effective treatment for many of the diseases, although some success has been achieved with enzyme replacement therapy and bone marrow transplantation in the treatment of Gaucher’s and Fabry’s diseases. Other promising approaches are substrate deprivation therapy to inhibit the synthesis of sphingolipids and chemical chaperone therapy. Gene therapy for lysosomal disorders is also currently under investigation.
Disease | Enzyme Deficiency | Lipid Accumulating | Clinical Symptoms |
Tay Sach’s Disease | Hexosaminidase A | GM2 Ganglioside | Mental retardation, blindness, muscular weakness |
Fabry’s disease | α-Galactosidase | Globotriaosylceramide | Skin rash, kidney failure (full symptoms only in males; X-linked recessive). |
Metachromatic leukodystrophy | Arylsulfatase A | Sulfogalactosylceramide | Mental retardation and Psychologic disturbances in adults; demyelination. |
Krabbe’s disease | β-Galactosidase | Galactosylceramide | Mental retardation; myelin almost absent. |
Gaucher’s disease | β -Glycosidase | Glucosyl ceramide | Enlarged liver and spleen, erosion of long bones, mental retardation in infants. |
Niemann-Pick disease | Sphingomyelinase | Sphigomyelin | Enlarged liver and spleen, mental retardation; fatal in early life. |
Farber’s disease | Ceramidase | Ceramide | Hoarseness, dermatitis, skeletal deformation, mental retardation; fatal in early life |
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Hyperlipoproteinemia
A) Primary Hyperlipoproteinemia
TYPE | CLASSIFICATION | BIOCHEMICAL DEFECT | INHERITANCE | PLASMA LIPIDS AND LIPOPROTEINS | CLINICAL FEATURES |
I. | Familial lipoprotein lipase deficiency(Hyperchylomicronemia) | Deficiency of lipoprotein lipase. A variant of this diseases can be produced by deficiency of apo CII. | Autosomal recessive | TG↑, cholesterol may also be increased, Chylomicrons ++, VLDL↑, HDL and LDL ↓.Refrigeration test confirms the presence of chylomicrons in serum | Present in early childhood, Eruptive xanthomas, Recurrent abdominal pain, no premature cardiovascular disease |
II. | Familial Hypercholesterolemia(FHC) | No enzyme deficiency but there is increased synthesis of apo- B protein and there is impaired degradation of LDL | Autosomal dominant | LDL ↑, total cholesterol ↑, VLDL and TG are also raised | Xanthomas, corneal arcus, increased risk of premature Cardiovascular disease. |
III. | Familial Dysbeta lipoproteinemiaAlso called- Broad beta disease , ‘Remnant removal disease” | Increase concentration of apo-E, increased synthesis of Apo B, conversion of normal VLDL to IDL and its degradation without conversion to LDL. Defect in Remnant removal. | Autosomal dominant | LDL↑, VLDL↑, actual rise in IDL which appears as Broad beta band on electrophoresis. TG↑, cholesterol may also be increased. | Tuberous and Palmar xanthomas, increased risk of premature Cardiovascular disease and peripheral vascular disease. |
IV. | Familial Hypertriglyceridemia(FHTG) | Increased synthesis and decreased catabolism of endogenous TGs | Autosomal dominant | Hyper pre beta lipoproteinemia VLDL↑, TG and cholesterol also↑, α and β-lipoproteins are subnormal (HDL↓ and LDL↓). There is associated impaired Glucose Tolerance | Presents in early childhood, and is commonly associated with CHD, Diabetes Mellitus, Alcoholism and obesity |
V. | Combined Hyperlipidemia | Usually secondary to other disorders like obesity, excessive alcohol intake, renal failure and pancreatitis etc. Exact biochemical defect is not known | Autosomal dominant | Complex lipoprotein pattern, Increase in both chylomicrons and pre β-lipoproteins (VLDL), TG and cholesterol also↑↑, α and β-lipoproteins are subnormal (HDL↓ and LDL↓). | Xanthomas are frequently present impaired glucose tolerance, frequently found associated with CHD, Diabetes Mellitus, Alcoholism and obesity |
B) Secondary Hyperlipoproteinemia
S. .No | Disease | Serum total Cholesterol | Serum triglycerides |
1. | Diabetes Mellitus | Increased | Increased |
2. | Nephrotic syndrome | Increased | Increased |
3. | Hypothyroidism | Increased | Increased |
4. | Biliary obstruction | Increased | Normal |
5. | Pregnancy | Increased | Normal |
6. | Alcoholism | Normal | Increased |
7. | Oral contraceptives | Normal |
Hypolipoproteinemia
Disease | Biochemical defect | Inheritance | Laboratory findings | Clinical manifestations |
Familial Hypobetalipoproteinemia | Inability to synthesize ApoB100 and Apo-B48 | Autosomal dominant | LDL between 10 to 50 % of normal, Cholesterol low but Triglycerides and Chylomicrons normal. | Mostly asymptomatic, but there is decreased risk of CHD |
Abetalipoproteinemia | No synthesis or secretion of Apo B containing lipoproteins | Rare inherited disease | VLDL↓, LDL↓↓, B-100↓, B-48↓, decrease in TG and a marked ↓in Serum total cholesterol, prolonged prothrombin time. | Malabsorption, mental and physical retardation, acanthocytosis, Atypical retinitis pigmentosa, fatty infiltration of intestinal mucosal cells and liver. |
Hypoalphalipoproteinemia | Not known | Autosomal dominant | HDL↓, Cholesterol and TGs normal | Increased risk of CHD |
Familial Alpha lipoprotein deficiency(Tangier’s disease) | Deficiency of alpha lipoprotein. Cholesteryl esters are deposited in the reticulo endothelial system, but functions of major organs are not affected | Autosomal recessive | Low or absent HDL, Lack of Alpha band on electrophoresis. | Orange yellow tonsils and adenoids, muscle weakness, atrophy, recurrent peripheral neuropathies and depressed tendon reflexes. The pharyngeal and rectal mucosa is also orange colored.(The orange color is due to deposition of cholesteryl esters.) There is increased predisposition to Atherosclerosis. |
------------------------------------------ Best Wishes: Dr.Ehab Aboueladab, Tel:01007834123 Email:ehab10f@gmail.com,ehababoueladab@yahoo.com ------------------------------------------
Regulatory Mechanisms- Lipid Metabolism
Enzyme
|
Pathway
|
Effect of substrate concentration
|
Allosteric Modification/ Fed back Inhibition
|
Induction/ Repression
|
Clinical Significance
|
Acetyl co A Carboxylase
|
Fatty acid synthesis
|
Activity increases during well fed state
Activity decrease during fasting
|
Activator-
Citrate,
ATP
Acetyl co A
Insulin-by causing de phosphorylation by stimulating protein phosphatase
Inhibitors-
Long chain fatty acids, Epinephrine, Glucagon- via changes in phosphorylation state through c AMP mediated phosphorylation cascade
|
Induced byInsulin
Repressed byGlucagon
|
Activity decreases in diabetes Mellitus
|
Carnitine Acyl Transferase
|
Carnitine shuttle
|
Activity low in fed state, high during fasting
|
Activated byGlucagon through lipolysis and provision of fatty acids for oxidation
Inhibited by insulin and malonyl co A
|
Inherited CAT-I deficiencyaffects only the liver, resulting in reduced fatty acid oxidation and ketogenesis, with hypoglycemia.
| |
HMG co A Reductase
|
Cholesterol synthesis
|
Activity low in fasting state,
|
Activated by Insulin, Thyroid hormone
Inhibited by –Glucagon, Glucocorticoids,(By reversible phosphorylation)
Dietary cholesterol (Hepatic synthesis)
Mevalonate and cholesterol ,the products of pathway
|
Expression of HMG COA reductase is regulated by sterol regulatory element binding protein
Also induced by Insulin
|
Activity high in Diabetes mellitus die to availability of excess Acetyl co A.
Activity inhibited by Statins used as cholesterol lowering drugs.
|
------------------------------------------ Best Wishes: Dr.Ehab Aboueladab, Tel:01007834123 Email:ehab10f@gmail.com,ehababoueladab@yahoo.com ------------------------------------------
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