The effect of malnutrition on transferin isoforms pattern in childhood

Protein glycosylation, a result of many complex reactions in golgi and endoplasmic reticulum, is closely related to physiological processes such as cell adhesion, migration, cell surface recognition and cell membran antigenity. Therefore, defects in glycosylation is associated with several pathological conditions including inflammation, rheumatoid arthritis, cancer, liver diseases, galactosemia, sepsis and chronic alcohol abuse in addition to congenital disorders of glycosylation. Moreover some studies suggested that catabolic diseases may effect protein glycosylation, yet this issue needs further clarification. The aim of this study has been to evaluate the effect of malnutrition on glycosylation by investigating the possible changes in transferin isoform (glycoform) pattern in malnutrition and its relationship to the degree of malnutrition and other nutritional parameters.The study group included 42 malnourished patients (n=24 mild, n=12 moderate, n=6 severe) and 30 healthy controls (age range: 6 months- 5 years) who were evaluated according to Waterlow classification. In both groups prealbumin, insulin like growth factor-1, ferritin, iron, total iron-binding capacity, transferrin and zinc levels were measured. Transferrin isoform analysis was performed by isoelectric focusing, the reference method, to demonstrate the changes in glycosylation. The method was applied and evaluated on two different systems (Mutiphor II and Phastsystem). Statistical analyses were performed by "SPSS 16.0 for Windows" program. The comparison between the groups was done using t test or Mann-Whitney U test. For all analyses p value less than 0.05 was considered to be stastically significant. Correlations between parameters were evaluated using "Pearson" and "Spearman" tests.In isoelectric focusing method by Multiphor II system the coefficients of variation (CV) were determined to be < 3.5 % for within run (n=7) and < 7 % for between run (n=20) imprecision considering di- and tetrasialotransferrin isoforms in two levels of control material. The same values for Phastsystem were < 7 % (n=8) and < 6 % (n=10) respectively. The bias of Multiphor II system against Phast system was 9.69% and 9.27% for disialotransferrin and 1.33% and 2.15% for tetrasialotransferrin using low and high levels of control material respectively. A-,mono-, di-, tri-, tetra-, penta-, hexa- and heptasialotransferrin isoforms (%) showed no significant difference between the two systems (n=40) and coefficients of correlation for di- ve tetrasialotransferrin isoforms were determined to be 0.85 ve 0.64 respectively.Considering the biochemical nutritional parameters, insulin like growth factor-1 and iron were determined to be significantly lower (p= 0.009 and p= 0.006 respectively) in the patient group in comparison to the control group. Significantly lower values were observed for IGF-1, iron and transferrin (p= 0.007, p= 0.036 and p= 0.018 respectively ) and higher values were observed for ferritin (p= 0.010) in moderately and severely malnourished patient group (n= 18) compared to controls.Insulin like growth factor-1 was correlated positively with iron (p= 0.000, r= 0.562), transferrin (p= 0,001, r= 0,421) and prealbumin (p= 0.001, r= 0.420) while negatively with ferritin (p= 0.001, r= -0.446). Iron was correlated positively with transferrin (p= 0.027, r= 0.276), prealbumin (p= 0.006, r= 0.340) and zinc (p=0.041, r= 0.254) along with insulin like growth factor-1. Ferritin showed a negative correlation with transferrin (p=0.000, r= -0.484) along with insulin like growth factor-1.For transferrin isoforms and for "carbohydrate deficient transferin" described as the sum of a-, mono- and disialotransferrin, no significant difference existed between patients and controls. Significantly higher values were observed for asialotransferrin and disialotransferrin (p= 0.040 and p= 0.036 respectively ) in moderately and severely malnourished patients compared to controls."Weight for Height" was positively correlated with insulin like growth factor-1 (p= 0.006, r= 0.359) and iron (p= 0.006, r= 0.339) while negatively correlated with disialotransferrin (p= 0.017, r= -0.292) and CDT (p= 0.007, r= -0.328).Transferrin was positively correlated with disialotransferrin (p= 0.022, r= 0.283) and CDT (p= 0.009, r= 0.323) while negatively correlated with tetrasialotransferrin (p= 0.025, r= -0.278). As to the relationship of transferrin isoforms to other biochemical parameters, a positive correlation was observed only between asialotransferrin and prealbumin (p= 0.021, r= 0.287).In conclusion, the results of this study point out that malnutrition is a disease status which may effect glycosylation. Although insignificant, higher values were observed for "carbohydrate deficient transferin" and for the isoforms constituting it in malnourished patients compared to the control group and the monosialotransferrin isoform was significantly higher in severely malnourished patients compared to mildly malnourished and the control group. The significantly negative correlation between "Weight for Height" and disialotransferrin and "carbohydrate deficient transferin" further support this opinion. In a larger patient group with severe malnutrition and in other disease states with markedly increased catabolism, transferrin isoform analysis with isoelectric focusing may reveal the alterations in protein glycosylation. The mechanisms underlying the alterations in glycosylation during catabolic process and its outcomes need to be elucidated with further studies.Keywords: Glycosylation, malnutrition, transferrin isoforms, isoelectric focusing