A double- blind, cross over clinical trial was designed to evaluate the efficacy of zinc supplements on renal function, albuminuria and erectile dysfunction of men with type 2 DM. The subjects were randomly selected from patients who referred to diabetes clinic of vali-e-Asr hospital, a referral academic hospital in Zanjan.
Fifty men with type 2 DM whose albuminuria has been detected newly by two times measurement of 24-h urinary albumin excretion was enrolled in this study. Albuminuria more than 30 mg/24h in double checking and reconfirmation with ACR>=30µg/mg in the absence of other causes of albuminuria defined as diabetic nephropathy in this study. Coexistence of erectile dysfunction, using international index of erectile function -5 (IIEF-5), made the patients eligible for this study.
All the subjects with history of any forms of supplement therapy in the previous 6 months and those who suffered from active urinary tract infection based on urinary analysis test were excluded .We also excluded all the participants with glomerular filtration rate (GFR) less than 30mL/min, other causes of albuminuria and hypogonadism , acute or chronic inflammation or active liver disease . Patients who are not satisfied to participate or not to pursue a regular observe or medication allergies happened for them, were excluded from the study.
The details of the study were explained to the participants and informed-consent was obtained. A local ethical committee approved the study. This clinical trial was approved in the Iran registry of clinical trial (IRCT code: IRCT138806091179N3 ).
Before and at the end of first and second phase of the study, the measurements were done. We recorded demographic, anthropometric and clinical information of patients. Blood pressure was measured by a mercury barometer after 10 min resting in sitting position; weight was measured in minimum dressing by Seca scale with the accuracy of 0.1kg. Height of the subjects was measured by standard methods and body mass index (BMI) was calculated.
All the subjects had laboratory measurements including FPG, HbA1C, lipid profile (total cholesterol,HDL-c, LDL-c and triglyceride), serum creatinine (Cr), serum zinc and testosterone level and also albumin to creatinine ratio(ACR) at the first and after the end of first and second phase of the study. Two different urine samples were obtained to measure ACR and mean of them was reported as final ACR result at the two stages of the study.
All the laboratory examinations were done in one laboratory center and the assays were unchanged during the study period. Creatinine was measure by Jaff method and glomerular filtration rate was calculated using Cockcroft_gault formula; GFR= ([140-age (years)] ×Weight (kg)/72×Pcr) ×0.085.
HemoglobinA1c levels were measured using Ione exchange method by DS5 device set. Lipid profiles were determined by the colorimetric enzymatic method and by auto analyzer; Cubas Mira. Urine Albumin was checked by nephelometry method and by using Binding Site kits (UK). The inter-assay CV of the kit was 4.1% for higher levels of albumin and 3.1% for lower levels of it. Intra-assay CV for the kit was 2.6% for upper levels and 2.2% for lower levels of albumin.
Detection sensitivity of zinc kit was also 3µmol/L and normal zinc ranges from 4.1 up to 4.16µmol/L.
International Index of Erectile Function -5 (IIEF-5) was used to detect erectile function of the subjects. IIEF-5 is a sexual function questionnaire contains 15 questions with 5 or 6 choices. Score between 0-5 awards to each of the items. Impairment of erectile function is assessing by 6 questions of 15 with a maximum score of 30 and score of 20 or less than that is considered to erectile dysfunction.
A randomized two- phase, double blind study was assigned. At first, participants were categorized randomly and equally into two zinc-experimental and placebo-control groups and received zinc or placebo for a three- month period. Then they were undergone 1 month (4 weeks) of wash out period. Finally, reverse placebo or zinc intervention was conducted as second phase for additional three months. Any documented side effects of the medications were recorded.
Twenty-five men in experimental group received one capsule of zinc –sulfate per day containing 30 mg elemental zinc (made by Iran_Al-havi Company) for 3months. The other twenty-five subjects in control group received placebo in similar designed to zinc capsules. The medications were distributed and checked by a third person. Patients advised to continue their previous medications with the same dose throughout the study. To ensure the drug taking, patients were asked to have two controlling visits during the study and bring their medication cartridge. In every visit, subjects were reassessed for their blood pressure, weight, BMI and the medication side effects.
All data are showed as mean (± SD). The comparison between the groups of patients was performed using Student t tests for quantitative independent variables and Chi square test for qualitative one. Paired T test was used to evaluate the changes in variables in one group. For nonparametric data, mann_Witney Test and Wilcoxon Signed Ranks test were applied. Log transformation was done for ACR to change it to a normal distributed variable. For emission of confounding variables effect, we used multivariate linear regression analysis.
For determination of normal distribution of variables, Komogorov_Sminrnov test was applied. Collected data were analyzed by SPSS version 16. Significance was defined as P<0.05.