hyperglycemia is caused by defects in insulin secretion , reduced glucose utilization and increased glucose production depending on the type of diabetes . end organ damage is the result of metabolic disorder in patients with diabetes , which is accompanied by other important problems for patients and health care system . in the usa , diabetes is the main cause of renal disease , also known as esrd , non - traumatic lower extremity amputation and adults ' blindness . it is the fourth reason of referring patients to physicians ( 1 - 5 ) . diabetes nephropathy occurs in both types 1 and 2 diabetes and also in genetic types of diabetes . it is the most common cause of esrd in developed countries and includes 30% of these cases . type 1 diabetes is usually easy to recognize and the epidemiology of diabetic nephropathy in type 1 has been more clarified . micro - albuminuria occurs in almost 20% - 30% of patients with type 2 diabetes after 15 years . less than a half of patients with micro - albuminuria would progress to end - stage renal disease ( 2 , 3 , 6 ) . zinc ( zn ) plays a functional act in nervous and immune systems , hormones activity , growth and development , taste and smells function and wound healing as well as proteins and nucleic acids synthesis ( 7 - 9 ) , sexual maturation , release of vitamin a from the liver and cell wall structure ( 10 ) . zn is an important micronutrient , which has a major role in synthesis , storage , secretion and function of insulin and its metabolism is altered in diabetes ( 11 , 12 ) . zn deficiency is correlated with insulin resistance ( 13 , 14 ) . in diabetic patients , chronic hyperglycemia due to glycosylation and peroxidation leads to increased oxidative stress and thereby proteins and lipids structure are changed ( 15 ) . lipid peroxidation produces toxic aldehydes ; malondialdehyde ( mda ) is one of the most poisonous molecules ( 16 ) . zn acts as a strong antioxidant ( 17 , 18 ) and may decrease lipid peroxidation and improve antioxidant status in patients with diabetes ( 19 , 20 ) . hyperglycemia is the most important sign of diabetes induced by increased oxidative stress , free radicals production and proteins glycosylation . copper ( cu ) ions have more desire to bind to these proteins ( 15 , 21 ) . cu binding glycosylated proteins can cause oxidative reactions , increased oxidative stress and free radicals production in diabetes ( 22 , 23 ) . the ceruloplasmin ( cu - carrying protein ) can stimulate glycation and release cu ions by accelerating oxidative stress in diabetes . therefore , plasma level of cu is increased ( 24 ) , which can induce oxidative activity . in contrast , antioxidant defense system reduces damages by decreasing oxidative stress ( 25 ) . the requirement of insulin would be reduced with sufficient dietary intake of cr , which is very critical to prevent adverse effects of diabetes . chromium supplementation has an anti - diabetic effect and improves fasting blood sugar ( fbs ) , insulin function , insulin - receptor binding , increased pancreas beta cells sensitivity and glucagon action ( 26 ) . cr plays a vital role in lipid and protein metabolism and regulation of water and also may decrease low density lipoprotein ( ldl ) and  lipoprotein . . it can also reduce the effect of free radicals in type 2 diabetes ( 27 , 28 ) . regarding trace element role in pathophysiology of renal dysfunction and their importance in diabetes , we measured these elements level ( zn , cu and cr ) in patients with diabetic nephropathy and control subjects . this study was performed at mazandaran university of medical sciences , sari city , during 2010 - 2011 . the number of samples was selected based on the previous studies ( 22 , 23 ) . after obtaining informed consents , all participants in this study were subjected to complete history taking and thorough clinical examination . in case group , there was no history of type 1 diabetes , proteinuria with other reasons , hypertension more than 140/90 , dialysis , transplantation , arf ( acute renal failure ) , malnutrition and use of supplementary such as zn or other evaluated elements in mineral or purified water . 24-hour urine samples were obtained from all subjects for evaluation of micro - albumin . eventually , the term microalbuminuria is determined by a lower and upper limit for the urinary albumin concentration . lower than 30 mg / day ( or 20 mg / l ) is assumed normal and above 300 mg / day ( or 200 mg / l ) considered as macroalbuminuria . after 12 hours overnight fasting , blood samples were taken through peripheral venous and serum was separated by centrifugation at 1500 rpm for 5 minutes and stored at 4c until assayed . serum fbs , hb , hba1c , uric acid , bun ( blood urea nitrogen ) and creatinine levels were measured by standard kits ( pars azmoon , iran ) using an auto analyzer ( prestige 24i , japan ) . immediately after separating serum , each tube was diluted ( 1:3 ) with diluted glycerol and serum zn , cu and cr were assessed using a varian atomic absorption spectrometer . the serum level of metals for each sample was obtained by calibration curve and dilution of samples . before collecting samples of drinking water , the water supply area of sari city , five points were chosen from each water distribution supply and samples ( 1 liter ) were taken from the house water tap at 8 am , 12 md and 4 pm . the samples were then transferred into a container of 3 liter and mixed . then 1 liter was taken from the mixed samples and ph was adjusted between 4.6 and 6.4 . , the samples were fixed by nitric acid 65% and stored in the refrigerator until analyzed . finally , the levels of mentioned metals were evaluated by an atomic absorption spectrophotometer model a100 . independent - samples t - test was used to compare data between the two groups . 24-hour urine samples were obtained from all subjects for evaluation of micro - albumin . eventually , the term microalbuminuria is determined by a lower and upper limit for the urinary albumin concentration . lower than 30 mg / day ( or 20 mg / l ) is assumed normal and above 300 mg / day ( or 200 mg / l ) considered as macroalbuminuria . after 12 hours overnight fasting , blood samples were taken through peripheral venous and serum was separated by centrifugation at 1500 rpm for 5 minutes and stored at 4c until assayed . serum fbs , hb , hba1c , uric acid , bun ( blood urea nitrogen ) and creatinine levels were measured by standard kits ( pars azmoon , iran ) using an auto analyzer ( prestige 24i , japan ) . immediately after separating serum , each tube was diluted ( 1:3 ) with diluted glycerol and serum zn , cu and cr were assessed using a varian atomic absorption spectrometer . the serum level of metals for each sample was obtained by calibration curve and dilution of samples . before collecting samples of drinking water , the water supply area of sari city , five points were chosen from each water distribution supply and samples ( 1 liter ) were taken from the house water tap at 8 am , 12 md and 4 pm . then 1 liter was taken from the mixed samples and ph was adjusted between 4.6 and 6.4 . , the samples were fixed by nitric acid 65% and stored in the refrigerator until analyzed . finally , the levels of mentioned metals were evaluated by an atomic absorption spectrophotometer model a100 . immediately after separating serum , each tube was diluted ( 1:3 ) with diluted glycerol and serum zn , cu and cr were assessed using a varian atomic absorption spectrometer . the serum level of metals for each sample was obtained by calibration curve and dilution of samples . before collecting samples of drinking water , the water supply area of sari city was detected coming from wells . , five points were chosen from each water distribution supply and samples ( 1 liter ) were taken from the house water tap at 8 am , 12 md and 4 pm . the samples were then transferred into a container of 3 liter and mixed . then 1 liter was taken from the mixed samples and ph was adjusted between 4.6 and 6.4 . , the samples were fixed by nitric acid 65% and stored in the refrigerator until analyzed . finally , the levels of mentioned metals were evaluated by an atomic absorption spectrophotometer model a100 . independent - samples t - test was used to compare data between the two groups . the study population included 70 patients ( 30 - 60 years old ) with type 2 diabetic nephropathy ( micro and macroalbuminuria ) ( cases ) and 70 healthy subjects ( controls ) matched for age and gender and other variables . both case and control groups were subjected to complete history taking and clinical examination ; individuals with complications mentioned above were excluded from the study . demographic data , duration of diabetes and findings of clinical and laboratory examination of both case and control groups are presented in table 1 . cu , cr and zn were assessed in both case and control groups using a varian atomic absorption spectrometer model a100 . trace elements in cases are significantly lower than controls ( * , p < 0.001 ) . urine protein in micro - albuminuria and macro - albuminuria were 113.43  41.38 mg / dl and 514.35  90.11 mg / dl , respectively . figure 2 illustrated the comparison of serum trace elements level in patients with micro- and macro - albuminuria . there was no significant difference in cr values in micro and macro albuminuria cases ( * , p < 0.05 ) . several studies indicated that imbalance of some fundamental metals can adversely affect pancreatic islet that cause diabetes . however , imbalance of essential metals induced generation of some reactive oxygen species ( ros ) during diabetes . hyperglycemia causes oxidative stress that can lead to a reduction of gene promoter activity and expression of mrna in pancreatic islet cells . assessment of trace elements such as zn , cu and cr in various diseases including diabetes remains contradictory with a lot of unanswered questions ( 6 , 29 ) . according to the results in the present study , patients with diabetic nephropathy had lower serum concentrations of zn , cu and cr than healthy individuals . study , which demonstrated a decrease in serum level of zn in male and female with type 2 diabetes compared to both genders in healthy group ( 30 ) . kazi et al . reported a significant reduction in zn level in blood and scalp hair samples and also its increase in urine of both genders in diabetic patients ( 31 ) . in a study performed by nasli - esfahani et al the level of elements in hair , nail , urine and serum were evaluated in type 2 diabetic patients ; their results indicated a meaningful decrease in serum level of zn in patients compared to healthy individuals ( 32 ) . in a research performed by adewumi et al . the serum level of cu in type 2 diabetic patients of both genders was significantly decreased in patient groups compared with healthy individuals ( 33 ) , which was in accordance with our study . study , in which type 2 diabetic patients had lower values of cr in blood and scalp hair samples in men and women compared with healthy subjects ( 31 ) . saboori et al . demonstrated low serum cr in diabetic patients compared to healthy individuals ( 32 , 34 ) , which is in accordance to our findings . our research displayed a significant difference in serum cu and zn levels between patients with macro and microalbuminuria ; as serum copper and zinc concentrations in patients with microalbuminuria were remarkably higher than patients with macroalbuminuria . as well , talaei et al . evaluated levels of proteinuria and cu in diabetes and a positive association between microalbuminuria and urine cu level has been found ; as higher levels of urinary copper have been shown in diabetics ( 35 ) . in diabetic patients with nephropathy , high levels of urinary copper may be associated with excretion of its carrier proteins , ceruloplasmin . copper excretion in urine may also be caused by dissociations from both copper - albumin and ceruloplasmin - copper complexes filtered through the disturbed glomerulus . high urinary copper can damage renal tubules and play an important function in the development of nephropathy ( 35 ) . a relationship between serum zinc and albuminuria has been detected in various researches for type 1 and type 2 diabetes ( 36 ) . decreased serum concentration of zinc assumed to be the result of increased urinary albumin excretion by microvascular injury . regarding our survey and other studies , low levels of these elements can be considered as a risk factor for diabetes . there are inconsistent findings about the association of serum cu level with diabetes incidence , which necessitates further investigations . in addition , results indicate that factors such as drinking water have no role in low serum levels of cu , zn and cr in patients with diabetic nephropathy and the reason should be studied in other causes such as urinary excretion , amount of these elements in each meal , intervention factors in absorption and utilization and individual conditions . the dietary minerals and their effects on diabetic persons need more research and interventional studies . excessive urination in diabetic subjects may be a potential cause fort these trace elements deficiency . regarding our study , serum zn , cu and cr levels were low in patients with diabetic nephropathy , whereas no association was found between drinking water and serum concentration of these trace elements in patients with diabetic nephropathy . the mentioned trace elements are cofactors of different enzymes playing a major role in the etiology of diabetes . it is recommended to perform future studies to investigate the association between serum levels of these enzymes and other metals including selenium , magnesium and iron .
background : diabetic nephropathy is the most common cause of end stage renal disease ( esrd ) in developed countries . 
 several trace elements were reported to be changed in diabetic nephropathy.objectives:the aim of this study was to investigate changes in serum levels of zinc , copper and chromium and their association with the incidence of esrd in patients with diabetes.patients and methods : this study was performed on 70 patients with type 2 diabetic nephropathy ( macro and micro - albuminuria ) and 70 healthy individuals . 
 samples were collected to survey metals by atomic absorption spectrophotometer . 
 data was analyzed by spss18 using descriptive and inferential analysis methods.results:mean  sd levels of zn , cu and cr were significantly decreased in blood samples of patients compared to healthy subjects ( p < 0.01 ) . 
 also the mean concentrations of cu , zn and cr in drinking water of sari were lower than the accepted limit . only in one case , cu was higher than the accepted limit , which was the possibility of contamination by water supply pipes.conclusions:cu , zn and cr play a specific role in the pathophysiology of diabetic nephropathy . 
 meanwhile in these patients , low serum levels of cu , zn and cr were not associated with factors such as drinking water . 
 possible causes should be sought in other factors like urine , intervention factors in absorption and utilization and individual conditions .