The International Society for Mannosidosis & Related Diseases, Inc. presents
why diet is not a "cure" for alpha mannosidosis
 |
by Ole-Kristian
Tollersrud Associate professor Department of Medical Biochemistry Institute of Medical Biology University of Tromsoe, Norway |
as published in Pathways
Spring/Summer 1999 edition (vol. 1, no 1)
see also our comprehensive section on Alpha-Mannosidosis
Alpha-mannosidosis is a lysosomal storage disorder. This group of disorders is characterized by an accumulation of partially degraded biomolecules, usually oligosaccharides or glycolipids, within the lysosomes. Lysosomes are membrane enclosed bags that are localized in every cell and in which degradation of waste biomolecules takes place. This degradation results in the formation of small units of biomolecules that slip out of the bag and are reused in a big recycling system. The lysosomal degradation is carried out by biomolecules called "enzymes". More than 100 different enzymes take part in this degradation. In alpha-mannosidosis one of these enzymes, called lysosomal alpha-mannosidase, does not function. This causes the accumulation of partially degraded oligosaccharides within the cells. The accumulated material causes the formation of gigantic lysosomes and subsequent leakage into the circulation. Ultimately the excess oligosaccharides appear in the urine.
The compounds that are degraded in the lysosomes have been synthesized by the organism itself after serving functions that are vital for sustaining the everyday needs. Thus, the lysosomal degradation is independent of the diet. A consequence is that it is unlikely that lysosomal storage disorders, such as Alpha-mannosidosis, can be cured by the diet. This is in contrast to some other metabolic disorders like PKU (phenylketonuria, Føllings's disease) in which there is a defect in the degradation of a dietary compound.
Since the newborn child is apparently healthy and the genetic defect in Alpha-mannosidosis is known, one might envisage the possibility of a cure. The only way to obtain this is through investigation of the causes the clinical symptoms, like the recurrent infections of childhood, the hearing impairment, the mental retardation and the skeletal changes. With the present knowledge there is pitily no clear answer how to treat patients affected with Alpha-mannosidosis. A major obstacle will be to convince the funding authorities that research into the cure of such a rare disease as Alpha-mannosidosis is worth while.
There are four animal models of Alpha-mannosidosis (cattle, cat, mouse and guinea pig). Possibly the investigation of these models might lead us closer to an effective treatment. Furthermore, bone marrow replacement therapy has been initiated on a few patients. The clinical progress of these patients may give valuable information about the possibilities of finding a cure. Indeed, these and other ongoing projects give some hopes for a future therapy of Alpha-mannosidosis.
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