Serum and urinary zinc level and erythrocyte superoxide dismutase activity in type 2 diabetic patients with different albuminuria categories Htun, Y.W 1 , Kyaw, M.P 1 , Thidar, A 1 , Maung, K.K 2 1 Department of Biochemistry, University of Medicine 2, Yangon. 2 Department of Biochemistry, University of Medicine 1, Yangon.
Introduction 2 Dr. YWH Oxidative stress is critically the essential component of pathogenic mechanism involving in the development and progression of diabetic vascular complications. Aside from increased production of free radicals, oxidative stress in pathogenesis of diabetic complications can also be due to impaired antioxidant defense mechanisms. Among the different antioxidant micronutrients, zinc is an essential antioxidant trace element due to its diverse roles in antioxidant defense mechanisms. Zinc is specifically required for proper protein folding to maintain the functional conformation and stability of antioxidant enzyme copper-zinc superoxide dismutase.
Introduction 3 Dr. YWH Body zinc status could be affected by the possible increased urinary zinc excretion in diabetic patients and might be related to albuminuria status. Assessment of albuminuria is recognized as a clinically useful tool for detection of early stage of diabetic nephropathy and it also reflects higher risk of development of other diabetic vascular complications. This study aimed to identify the differences in the serum zinc level and erythrocyte superoxide dismutase (SOD) activity among different albuminuria categories of type 2 diabetic patients as well as to demonstrate the correlation between the serum zinc level and erythrocyte superoxide dismutase activity in the study groups.
Materials and Methods 4 Dr. YWH Type of study – cross-sectional descriptive study Subjects Total 127 type 2 diabetic patients were categorized into normoalbuminuria (n=41) and albuminuria (n=86) groups. Albuminuria group was subdivided into microalbuminuria (n=53) and macroalbuminuria (n=33) groups. Laboratory method Serum and urinary zinc level was determined by atomic absorption spectrophotometry. Erythrocyte SOD activity was determined by Ransod SOD assay. Urine albumin creatinine ratio was calculated from urine albumin level determined by immunoturbidimetric method and urine creatinine level measured by enzymatic method. Statistical analysis Parameters were expressed as mean ± standard deviation. Difference in erythrocyte SOD activity, serum and urinary zinc level among the study groups were analyzed by using unpaired ‘t’ test. A value of p ≤ 0.05 was considered as statistically significant. Pearson correlation coefficient was used to analyze the correlation between different parameters among the study groups.
Result and Discussion 5 Dr. YWH Table 1. Comparison of erythrocyte superoxide dismutase activity, serum zinc and urinary zinc level between type 2 diabetic patients with normoalbuminuria and those with albuminuria Normoalbuminuria (n=41) Albuminuria (n=86) p value (t test) Mean ± SD Mean ± SD Erythrocyte SOD (U/g Hb) 1955.95 ± 493.91 1480.33 ± 552.84 <0.001* Serum zinc ( μg /dL) 108.39 ± 54.27 93.03 ± 55.89 0.146 Urinary zinc (mg/g creatinine) 0.72 ± 0.51 0.86 ± 0.66 0.262 Although the present study demonstrated the mean serum zinc status changes in different albuminuria categories were insignificant, previous studies showed that serum zinc concentration was significantly lower in diabetic patients with increased albuminuria status. 1 In the present study, mean erythrocyte SOD activity was significantly lower in albuminuria group as compared to normoalbuminuria group. It supported the hypothesis of reduced antioxidant defense activity found with increased risk of vascular complications in diabetes as reflected by albuminuria status. 2
Result and Discussion 6 Dr. YWH Table 2. Correlation between serum zinc level and erythrocyte superoxide dismutase activity in different study groups Group r p Significance Whole study population (n =127) 0.298 0.001 Not significant Normoalbuminuria (n =41) 0.421 0.006 Significant Whole study population Albuminuria (n = 86) 0.210 0.053 Not significant Microalbuminuria (n = 53) 0.109 0.437 Not significant Albuminuria group Macroalbuminuria (n = 33) 0.311 0.039 Significant In the present study, significant correlation was found between serum zinc level and erythrocyte SOD activity only in normoalbuminuria and macroalbuminuria groups. Some studies reported significant positive correlation between serum zinc level and serum SOD activity in diabetic patients but some observed that there was no significant correlation between serum zinc level and erythrocyte SOD activity in diabetic patients. 3,4
Discussion 7 Dr. YWH The present study revealed that relationship between serum zinc level and erythrocyte SOD activity was indeterminate since the correlation between the two factors was seen only in some study groups (normoalbuminuria and macroalbuminuria groups). Such findings suggested that erythrocyte SOD activity changes in diabetes might be attributed by changes in serum zinc level but factors other than serum zinc level could also influence upon the activity of SOD enzyme. Body zinc status was thought to influence upon the progression of diabetic vascular complications as indicated by many studies. But serum zinc level changes might also be the consequence of the increased urinary zinc excretion in diabetes. 5
Result and Discussion 8 Dr. YWH Table 3. Correlation between urinary zinc level and serum zinc level in different study groups Group r p Significance Whole study population (n =127) - 0.0075 0.400 Not significant Whole study Normoalbuminuria (n =41) - 0.046 0.774 Not significant population Albuminuria (n = 86) - 0.069 0.525 Not significant Microalbuminuria (n = 53) - 0.029 0.417 Not significant Albuminuria group Macroalbuminuria (n = 33) - 0.09 0.309 Not significant Table 4. Correlation between urine albumin creatinine ratio and urinary zinc level in different study groups Group r p Significance Normoalbuminuria (n =41) - 0.046 0.774 Not significant Albuminuria (n = 86) - 0.069 0.525 Not significant
Discussion 9 Dr. YWH Although mean urinary zinc level was higher in albuminuria group as compared to normoalbuminuria group, it was not statistically significant in the study (Table 1). Moreover, correlation between urinary and serum zinc level as well as correlation between albuminuria level and urinary zinc level showed no significant correlation in different study groups (Table 3 and 4). In conclusion, according to the study, reduced antioxidant status as indicated by erythrocyte SOD activity changes in type 2 diabetic patients could be related to serum zinc status but factors other than serum zinc level should also be considered. Study also indicated that extent of urine zinc excretion alone could not explain the serum zinc level changes in type 2 diabetic patients.
References 10 Dr. YWH 1. Luo, Y.Y., Zhao, J., Han, X.Y., Zhou, X.H., Wu, J. and Ji, L.N. (2015) Relationship between serum zinc level and microvascular complications in patients with type 2 diabetes. Chinese Medical Journal: 128; p.3276-82. 2. Kornelia, Z., Kedziora-Kornatowska., Luciak, M., Blaszczyk, J. and Pawlak, W. (1998) Lipid peroxidation and activities of antioxidant enzymes in erythrocytes of patients with non-insulin dependent diabetes with or without diabetic nephropathy. Nephrology Dialysis Transplantation: 13; p.2829-2832. 3. Haddad, N.I.A., Nori, E. and Ali, S.H. (2016) The effect of type two diabetes mellitus on superoxide dismutase (SOD) activity and its correlation with HbA1c in Iraqi patients. International Journal of Engineering Research & Science: 2 (4); p.7-15. Salmonowicz, B., Krzystek-Korpacka, M. and Noczyńska , A. (2014) Trace elements, 4. magnesium, and the efficacy of antioxidant systems in children with type 1 diabetes mellitus and in their siblings. Advances in Clinical and Experimental Medicine Journal: 23 (2); p.259 – 268. 5. Sagara, M., Kudo, M., Yashiro, H., Makino, I. and Takebe, K. (1982) Urinary excretion and serum levels of zinc in diabetics, and its relationship to renal damage. Journal of Japan Diabetes Society: 25(6); p.697-704.
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