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12.5 kDa cystatin could be used to diagnose multiple sclerosis

12.5 kDa cystatin could be used to diagnose multiple sclerosis

Johns Hopkins researchers found that a protein found only in cerebrospinal fluid ( CSF ) that they say might be useful in identifying a subgroup of patients with multiple sclerosis or identifying those at risk for the debilitating autoimmune disorder.

Multiple sclerosis strikes over 10,000 Americans each year, most of whom are women, and causes weakness, numbness, a loss of muscle coordination, and problems with vision, speech, and bladder control. It is a disorder in which the immune system destroys myelin, the covering of nerves that helps transmit signals.

. According to Hopkins researchers, the study, published in the Annals of Neurology, is important because unlike other autoimmune diseases in which the body attacks its own tissues, multiple sclerosis cannot be diagnosed with a simple blood or other test.

“ There is the possibility now that the protein we identified, 12.5 kDa cystatin, can be used to diagnose multiple sclerosis, perhaps in its earliest stages, and also to monitor treatment by measuring its levels in CSF," says Avindra Nath, at The Johns Hopkins University School of Medicine and lead author of the study.

Working with human CSF, the Hopkins team showed that 12.5 kDa cystatin is a breakdown product of a larger protein called cystatin C or 13.4kDa, which in turn blocks activity of some enzymes, including cathepsin B.
Cathepsin B has been linked to demyelination.

" In fact, those patients who had more of the breakdown product of 12.5 kDa cystatin also seemed to have the highest cathepsin B inhibition," Nath said.

The investigators made their finding using a sophisticated technique called SELDI-time-of-flight mass spectroscopy that can find one specific protein in a complex mixture based on its weight.
They used it to examine CSF samples from 29 patients with multiple sclerosis or pre-multiple sclerosis symptoms such as numbness on one side; 27 patients with transverse myelitis; 50 infected with the AIDS virus ( which can cause nerve damage ); and 27 with other neurological diseases. The Hopkins researchers analyzed CSF instead of blood samples because CSF better represents local events in the brain than does blood, according to Nath. And the high concentrations of many proteins in the blood can mask proteins that might be biomarkers for multiple sclerosis, he added.

The team found that the 12.5kDa fragment of cystatin C occurred in CSF samples from two-thirds of patients with multiple sclerosis or the pre-multiple sclerosis conditions. Moreover, although total cystatin C levels in multiple sclerosis patients were not different from control patients without the disease, patients with multiple sclerosis had a larger proportion of the 12.5 kDa compared to 13.4 kDa cystatin C than did other patients. Thus, the presence of the 12.5 kDa fragment might identify a subgroup of multiple sclerosis patients.

Source: Johns Hopkins Medical Institutions, 2006



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