clinical aspects of Metabolism of Acylglycerols & Sphingolipids
المؤلف:
Peter J. Kennelly, Kathleen M. Botham, Owen P. McGuinness, Victor W. Rodwell, P. Anthony Weil
المصدر:
Harpers Illustrated Biochemistry
الجزء والصفحة:
32nd edition.p244-245
2025-07-24
360
Lung surfactant is composed mainly of lipid with some proteins and carbohydrate and prevents the alveoli from collapsing. The phospholipid dipalmitoyl-phosphatidyl choline decreases surface tension at the air-liquid interface and thus greatly reduces the work of breathing, but other surfactant lipid and protein com ponents are also important in surfactant function. Deficiency of lung surfactant in the lungs of many preterm newborns gives rise to infant respiratory distress syndrome (IRDS). Administration of either natural or artificial surfactant is of therapeutic benefit.
Phospholipids & Sphingolipids Are Involved in Multiple Sclerosis & Lipidoses
Certain diseases are characterized by abnormal quantities of these lipids in the tissues, often in the nervous system. They may be classified into two groups: (1) true demyelinating dis eases and (2) sphingolipidoses.
In multiple sclerosis, which is a demyelinating disease, there is loss of both phospholipids (particularly ethanolamine plasmalogen) and of sphingolipids from white matter. Thus, the lipid composition of white matter resembles that of gray matter. The cerebrospinal fluid shows raised phospholipid levels.
The sphingolipidoses (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 neurodegeneration and shortening the life span. (2) The rate of synthesis of the stored lipid is normal. (3) The enzymatic defect is in the degradation pathway of sphingolipids in lysosomes. (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 dis eases, although some success has been achieved with enzyme replacement therapy and bone marrow transplantation in the treatment of Gaucher and Fabry 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. Some examples of the more important lipid storage diseases are shown in Table 1.
Multiple sulfatase deficiency results in accumulation of sulfogalactosylceramide, steroid sulfates, and proteoglycans owing to a combined deficiency of arylsulfatases A, B, and C and steroid sulfatase. Symptoms include abnormalities in neu rologic and metabolic functions, as well as in hearing, sight, and bone.Metachromatic leukodystrophyis characterized by a build-up of sulfatides in tissues caused by a defect in arylsulfatase A, and leads to irreversible damage to the myelin sheath.
Table1. Examples of Sphingolipidoses
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