[Leptin, body composition and bone mineralization in children after treatment for Wilms tumor]. / Leptyna, skladowe masy ciala oraz mineralizacja ukladu kostnego u dzieci po zakonczonym leczeniu guza Wilmsa.

UNLABELLED: Advances in diagnosis and improved methods of treatment have resulted in increasing number of long-term survivors in children with Wilms tumor. Growth and puberty are important for accumulation of bone mass; chemotherapy nad radiotherapy used in treatment for Wilms tumor can influence bone structure and physical development. Leptin plays an important role in metabolism of adipose tissue and bone mineralization. Considering that neoplasm and its treatment can affect normal development in childhood, we analysed the influence of antineoplastic treatment on bone mineralization and the correlations between serum leptin levels, body composition and bone mineral density in survivors of Wilms tumor. Twenty subjects (12 boys) treated for Wilms tumor at the mean age of 10.9 (range 3-20 years) participated in this study. Mean follow up period after discontinuation of therapy was 5.6 years (range 2 months - 13.5 years). Mean age of diagnosis was 3.9 years (range 1 month - 12.6 years). 18 patients received chemotherapy, 7 - additionally radiotherapy and 2 infants had only surgery treatment. We measured fat mass - FM, fat free mass - FFM, bone mineral density - BMD total and BMD spine using dual energy x-ray absorptiometry (DXA) and compared to the results obtained for healthy references (SD score). Leptin levels were measured with RIA method. RESULTS: 1. No difference was found in leptin levels, body mass index, FM, FFM, BMD total and spine in relation to sex. 2. Means of SDS BMI, FM, FFM, BMD and leptin were in the normal range for the age and sex matched controls. 3. We found the correlation between leptin level and BMI, FM, FFM and BMD total and spine, no correlation was found between SDS values. 4. We observed a positive correlation between SDS BMD and SDS BMI, FM, FFM, BMD spine. 5. BMI, FM and leptin levels were higher in children treated with radiotherapy and chemotherapy than in children treated with only chemotherapy. However, the SDS values were comparable with the healthy controls. 6. SDS BMD total was decreased in 5/20 subjects (25% of all studied patients) compared with healthy controls. CONCLUSIONS: The results demonstrated the risk of osteopenia in the group of children treated for Wilms tumor and the necessity for long-term monitoring of bone mineralization.

Gly511 to Ser substitution in the COL1A1 gene in osteogenesis imperfecta type III patient with increased turnover of collagen.

Osteogenesis imperfecta (OI) is a result of heterozygous mutations in the COL1A1 or COL1A2 genes, encoding type I procollagen chains. Here we described the molecular and biochemical defects detected in a case of severe type III OI. Cultured skin fibroblasts from the proband produced both normal and mutant type I collagen which was secreted into the medium. The mutation site was localized in alpha 1(I)-CB3 by CNBr cleavage of collagen chains. Subsequent reverse transcription-PCR amplification and direct sequencing of single-stranded PCR product led to identification of G to A transition in the COL1A1 gene, resulting in Gly511Ser substitution in the a1 chain of type I collagen. The new mutation conforms to the chain-specific non-lethal microdomain of Gly to Ser substitutions in the genotype-phenotype map. We have found that biosynthesis of collagen was increased in OI cells to about 160% of the control value. However, the amount of collagen deposed to the insoluble matrix was decreased as compared to the control. This suggests increased degradation of collagen, since the collagenolytic activity of OI cells was increased. Furthermore, the activity of prolidase, which is a marker of collagen turnover, was increased in OI cells. In regulation of activity of the enzyme are involved beta1 integrin and insulin-like growth factor (IGF) receptors. Western immunoblot analysis showed that the expressions of both receptors were markedly increased in OI cells. These results suggest that increase in activity of prolidase can be associated with increase in intensity of collagen metabolism in type III OI patient with identified new G511S mutation.

Studies on type I collagen in skin fibroblasts cultured from twins with lethal osteogenesis imperfecta.

Studies on type I procollagen produced by skin fibroblasts cultured from twins with lethal type II of osteogenesis imperfecta (OI) showed that biosynthesis of collagen (measured by L-[5-(3)H]proline incorporation into proteins susceptible to the action of bacterial collagenase) was slightly increased as compared to the control healthy infant. SDS/PAGE showed that the fibroblasts synthesized and secreted only normal type I procollagen. Electrophoretic analysis of collagen chains and CNBr peptides showed the same pattern of electrophoretic migration as in the controls. The lack of posttranslational overmodification of the collagen molecule suggested a molecular defect near the amino terminus of the collagen helix. Digestion of OI type I collagen with trypsin at 30 degrees C for 5 min generated a shorter than normal alpha2 chain which melted at 36 degrees C. Direct sequencing of an asymmetric PCR product revealed a heterozygous single nucleotide change C-->G causing a substitution of histidine by aspartic acid in the alpha2 chain at position 92. Pericellular processing of type I procollagen by the twin's fibroblasts yielded a later appearance of the intermediate pC-alpha1(I) form as compared with control cells.