Low Copper Intake Research Articles

Blood glucose and insulin are modified by levels of dietary iron in copper-deficient rats

The present study was designed to test the hypothesis that lowering of hepatic iron in copper-deficient rats fed fructose will modify plasma insulin and glucose. One hundred ninety-two weanling male rats were randomly assigned to eight dietary groups. These diets contained either starch or fructose, adequate or inadequate copper and adequate or low iron. Rats were fed their respective diets for 2 weeks. Following an overnight fast rats were given oral glucose loads (250 mg glucose/100 g body weight). Blood was collected at fasting and at 30, 60 and 120 min post-load. Rats that had been fed the low-iron diet tolerated oral glucose load better than those fed the adequate-iron diet. These responses, however, were not due solely to decreased iron intake, but to a combination of low-iron and low copper intake and/or fructose feeding with low iron intake. The reduced levels of hepatic and pancreatic iron were accompanied by elevations of copper levels. Fructose-fed, copper-deficient rats benefited from these changes by improving insulin efficiency. © 1997 Wiley-Liss, Inc. This article is a US Government work and, as such, is in the public domain in the United States of America.

Blood glucose and insulin are modified by levels of dietary iron in copper‐deficient rats

The present study was designed to test the hypothesis that lowering of hepatic iron in copper-deficient rats fed fructose will modify plasma insulin and glucose. One hundred ninety-two weanling male rats were randomly assigned to eight dietary groups. These diets contained either starch or fructose, adequate or inadequate copper and adequate or low iron. Rats were fed their respective diets for 2 weeks. Following an overnight fast rats were given oral glucose loads (250 mg glucose/100 g body weight). Blood was collected at fasting and at 30, 60 and 120 min post-load. Rats that had been fed the low-iron diet tolerated oral glucose load better than those fed the adequate-iron diet. These responses, however, were not due solely to decreased iron intake, but to a combination of low-iron and low copper intake and/or fructose feeding with low iron intake. The reduced levels of hepatic and pancreatic iron were accompanied by elevations of copper levels. Fructose-fed, copper-deficient rats benefited from these changes by improving insulin efficiency. © 1997 Wiley-Liss, Inc. This article is a US Government work and, as such, is in the public domain in the United States of America.

The Effects of Low Dietary Copper Intake During Pregnancy on Physiological Fluids and Reproductive Performance of First-litter Gilts

Seven pairs of first littermate gilts were used to study the influence of low copper supply and pregnancy on physiological fluids and reproductive performance of first-litter gilts. They were fed semi-purified diets containing either 2.13 or 12.25 micrograms/kg of Cu from 30 days of gestation through two weeks of lactation. Low-Cu gilts had lower plasma Cu in early- and mid- gestation and farrowed piglets with lower plasma Cu and higher plasma Zn concentrations (p < 0.05). Plasma Fe and Mn concentrations were not affected by Cu supply (p > 0.05). Plasma Cu and Fe levels of newborn piglets were lower than those of their dams (p < 0.05) but this was not true for plasma Zn and Mn (p > 0.05). Low-Cu gilts had lower Cu and higher Zn content in colostrum and also lower Cu in milk than control gilts (p < 0.05). No significant differences were found in Fe and Mn levels in colostrum and milk between the two treatments (p > 0.05). Colostrum was richer in Cu and Zn than milk (p < 0.05) but not in Fe and Mn (p > 0.05). The low-Cu diet did not affect (p > 0.05) weight changes during pregnancy. The duration of parturition was shorter for low-Cu than for control gilts (3.19h vs. 5.71h, p < 0.05). Control gilts farrowed larger litters than low-Cu gilts (9.71 vs. 7.57 piglets, p < 0.05). There were no significant differences in live litter weights at birth, one wk. or two wks. of age (p > 0.05). The results indicated that a low-Cu diet and pregnancy had some effect on plasma, colostrum and milk mineral concentrations, as well as on litter size of gilts. An interaction between Cu and Zn was found.

Correlative study of defective cartilage and bone growth in foals fed a low‐copper diet

SummaryA blind randomised study using two groups of age‐ and sex‐matched Quarter Horse foals was conducted by feeding a low copper diet containing 8 ppm of copper (Cu) and a control diet containing 25 ppm. Foals in the low‐Cu group had declining liver Cu values and developed osteochondritis (OCD), epiphysitis and limb deformities over a 6‐month period. Erosion and separation of cartilage from the subchondral bone in the dorsal facets of the cervical spine were the most consistent post‐mortem lesions. Foals fed the high‐Cu diet had no significant musculoskeletal lesions. Scoring of standing lateral cervical radiographs was a moderately sensitive (0.68) and specific (0.70) test and had moderate agreement with post‐mortem findings (κ = 0.35). Technetium scintigraphy of the limbs and cervical spine failed to detect occult or known lesions in the limbs and cervical spine. Microscopic examination of growth plates and metaphyseal bone from affected foals showed that fractures disrupted or displaced the normal growth plate architecture and interfered with orderly bone growth, similar to Cu deficiency in cattle. Bone morphometry indicated there was less subchondral bone volume in the distal cannon bone (P&lt;0.005). Similarly, there were fewer newly formed trabeculae in the primary spongiosa (P&lt;0.02) and metaphysis (P&lt;0.07) of the distal tibia in the Cu‐deficient foals. Biochemical studies were limited to 4 control and 6 low‐Cu foals. Of the 6 low‐Cu foals, 4 were severely affected with multiple lesions. These assays showed significantly reduced collagen cross‐linking in the cartilage and bone articular cartilage of severely affected foals. The control group foals had articular and growth plate cartilage explants in tissue culture released increased amounts of gelatinase and proteoglycanase, reflecting increased matrix remodelling. Traditional concepts of osteochondritis have implicated a non‐specific defect in endochondral ossification. This study proposes a relationship between low copper intakes in fast‐growing horses, inferior collagen quality, biomechanically weak cartilage and OCD lesions. While all foals in the low‐Cu group were affected, only 5 of the 9 developed clinically significant lesions. This indicates that factors other than nutrition, such as individual variation in growth rate or genetic potential, still influence the expression of this syndrome.

Low and marginal copper intake by postweanling rats: Effects on copper status and resistance to carbon tetrachloride hepatotoxicity

Copper feeding studies in rats are generally initiated at weaning. This study examined whether a 6-week feeding of low or marginal Cu levels (0.2 or 2.5 ppm) to rats initially weighing 135 g produced deleterious effects. Controls were fed 8 ppm Cu. Liver Cu-Zn superoxide dismutase activities paralleled Cu intake. Plasma ceruloplasmin activities were very low for both low and marginal Cu consumption. Low but not marginal Cu intake caused a low body weight, high plasma cholesterol level, anemia, cardiac hypertrophy, and a high degree of hepatic plasma membrane injury 24 hours after CCI 4 injection (150 μL/kg intraperitoneally [IP]). In summary, low and marginal Cu intakes produced low Cu enzyme activities, while low Cu intake produced pathological symptoms and poor resistance to an oxidative stress.

Effects of low copper intake on dimethylhydrazine-induced colon cancer in rats.

Rats fed low copper show a high incidence of dimethylhydrazine (DMH)-induced colon tumors compared with rats fed very high Cu. The difference could be due to Cu deficiency in the low group or to Cu toxicity in the high group. In the present study, rats fed low Cu (0.2 ppm) showed greater DMH-stimulated colon tumorigenesis than rats fed adequate Cu (8 ppm). Differences were seen in the number of rats developing tumors (5 of 11 vs 1 of 10), total tumors (7 vs 2), and average tumor mass (1.02 g vs 0.29 g). Low Cu intake did not cause any general DMH toxicity as assessed by body weight gain. To prevent Cu deficiency-induced mortality, low Cu feeding was begun in postweanling rats (weight, about 80 g) housed in groups of five to six, rather than individually. This limited the effects of low Cu feeding to only a moderate Cu deficiency based on several parameters, including three Cu antioxidant enzyme activities. Group-housed rats fed marginal Cu levels (2.5 ppm) showed normal Cu status, and DMH produced only one tumor in 10 rats. In conclusion, high DMH-induced colon tumorigenesis can be found in rats with low activities of Cu antioxidant enzymes.

Effects of low copper and high zinc intakes and related changes in Cu,Zn-superoxide dismutase activity on DMBA-induced mammary tumorigenesis

The effect of low copper and high zinc intakes on Cu,Zn-superoxide dismutase (Cu,Zn-SOD) activity and mammary tumorigenesis induced by 9,10-dimethyl-1,2-benzanthracene (DMBA) was investigated. Groups of 40 weanling female Sprague-Dawley rats were fed a modified AIN-76 diet containing the following (/kg diet): 1 mg Cu (0.016 mmol) and 30 mg Zn (0.459 mmol); 6 mg Cu (0.094 mmol) and 30 mg Zn (0.459 mmol) (control); or 6 mg Cu (0.094 mmol) and 150 mg Zn (2.295 mmol) for 21 wk. At 5 wk, 30 rats/group were given 4 mg (15.6 mumol) DMBA in corn oil intragastrically, and controls (10/group) received corn oil alone. Erythrocyte Cu,Zn-SOD activity was measured at 3, 5 (just before DMBA), 9, 13, 17, and 21 wk. The group fed the high-Zn diet had a slightly lower weight gain and food consumption. DMBA treatment had no effect on these parameters. Plasma and liver Cu concentration decreased in the low-Cu group. Femur zinc was significantly elevated in the high-Zn group. Erythrocyte Cu,Zn-SOD activity was decreased in the low-Cu group from 3 to 21 wk and was significantly elevated in the high-Zn group at 3 and 5 wk. In the low-Cu group, there were 5 nonmalignant adenomas and 3 malignant adenocarcinomas; in the control group, there were 4 adenomas and 3 adenocarcinomas; in the high-Zn group, there were 5 adenomas and 3 adenocarcinomas. No relationship between Cu,Zn-SOD activity and the presence of tumors could be found.

Effects of Moderate Copper Deficiency on Carbon Tetrachloride-Induced Hepatotoxicity in Rats

Extreme copper deficiency has been shown to enhance CCl4-induced injury in rats. CCl4 hepatotoxicity was studied in rats with copper deficiency moderated by limiting deficiency periods to 5 or 6 weeks, using minimally adequate dietary zinc and including a marginal copper diet. Also, housing some rats in groups of six, rather than individually, was found to moderate the effects of low copper intake. Weanling male rats were fed copper at either 6, 2, or 0.2 mg/kg diet (adequate, marginal, deficient). Copper-zinc superoxide dismutase activity levels for singly and group-housed marginal rats were 80% and 93%, respectively, of adequate values. Values for deficient rats were 35% (singles) and 47% (group). In singly housed rats, a CCl4 dose of 400 microliters/kg intraperitoneally increased serum sorbitol dehydrogenase activities, indicators of cell membrane hepatotoxicity, in inverse proportion to dietary copper. A lower dose (100 microliters/kg) also produced smaller sorbitol dehydrogenase increases in adequate rats compared with deficients, but produced lowest increases in the marginals. The latter pattern also occurred in group-housed rats given the higher CCl4 dose, but the difference for adequate and marginal rats was not significant. The higher CCl4 dose, in singly housed rats, decreased liver glucose-6-phosphatase activities independently of copper intake. These activities are inversely proportional to microsomal lipid damage. In conclusion, moderate copper deficiency enhanced CCl4 hepatotoxicity, but the effect depended on injury criteria, CCl4 dose, and actual copper status as assessed by copper-zinc superoxide dismutase activities.

Dietary patterns, gastrointestinal complaints, and nutrition knowledge of recreational triathletes

Dietary habits, nutrition knowledge, and gastrointestinal complaints were evaluated in 21 female and 50 male triathletes; 30 completed hemoccult slides to determine the frequency of gastrointestinal bleeding. Triathletes trained 11 h/wk with weekly distances of 5.3, 116.5, and 40.9 km for swimming, biking, and running, respectively. Mean daily energy intake averaged 9058 and 11,591 kJ for women and men, respectively; 53.8% of the energy was from carbohydrates. Mean intakes of vitamins and most minerals exceeded the Recommended Dietary Allowances (RDAs), but many had intakes below RDAs for some nutrients; greater than 60% had low zinc and copper intakes. Because 39% took a daily multivitamin-mineral supplement, some had intakes 200-600% above the RDA. Although there were notable misconceptions about nutrition, nutrition knowledge was high. Upper-gastrointestinal complaints, reported by 50%, included bloating and abdominal gas; the incidence of positive hemoccult slides was 27%. The relation among performance, dietary patterns, nutrition knowledge, and gastrointestinal function remains to be established.

Effects of various levels of dietary copper and zinc on channel catfish

Furified egg white diets containing 1 or 20 mg Cu/kg and 20, 100 or 200 mg Zn/kg in a factorial arrangement were fed to triplicate groups of fingerling channel catfish ( Ictalurus punctatus) in aquaria to investigate possible interactions between dietary copper and zinc. At the end of the 12-week feeding trial, weight gain and feed efficiency values of catfish fed the various diets were similar. Dietary zinc had a significant ( P < 0.01) effect on hematocrit, which was generally reduced at higher levels of zinc intake. However, such a response was not observed in hemoglobin from fish fed the various diets. Dietary zinc also had a significant ( P < 0.01) effect on catfish bone zinc and liver iron, but not liver zinc concentrations. Hepatic copper concentration and activities of heart cytochrome c oxidase and liver copper-zinc superoxide dismutase (SOD) were significantly ( P < 0.05) reduced in catfish fed 1 mg Cu/kg compared to those fed 20 mg Cu/kg, while manganese SOD showed a compensatory increase in activity at low copper intake. Based on these enzyme activities as well as hemoglobin and tissue mineral concentrations, increasing levels of dietary zinc did not affect copper bioavailability. Therefore, supplementation of high levels of zinc in practical diets should not impair the copper status of channel catfish.

Effects of ascorbic acid supplements and a diet marginal in copper on indices of copper nutriture in women

Biochemical indicators of copper status were studied in young women housed in a metabolic unit for 135 days. The women were fed a diet low in Cu (0.67 mg/d), that was supplemented with 1.5 g of ascorbic acid and variable amounts of copper. Copper balance was not significantly affected by diet. Plasma copper and monoamine oxidase, and erythrocyte superoxide dismutase were not affected by dietary copper or by ascorbic acid. Enzymatic (CpENZ), but not immunoreactive (CpRID), ceruloplasmin was lower at the end of low copper intake and high ascorbic acid intake periods. The specific activity of ceruloplasmin (CpENZ/CpRID) was significantly lower at the end of the ascorbic acid period (1.26) than at either the end of control (1.81) or repletion (1.80) periods, and slightly lower than after only low copper intake (1.44). Cytochrome-c oxidase activities in platelets and leukocytes were significantly affected by copper intake, but not ascorbic acid intake. These findings indicate that the specific activity of ceruloplasmin and cytochrome-c oxidase activity of platelets and white cells may be sensitive indicators of copper status, and that ascorbic acid supplements do not markedly affect commonly measured indices of copper metabolism, except for the specific activity of ceruloplasmin in young women.

Influence of Copper Intake and Inflammation on Rat Serum Superoxide Dismutase Activity Levels

Serum superoxide dismutase (SOD) activity concentrations, though small compared to tissue levels, could contribute to extracellular superoxide radical detoxification and act as indicators of copper status. The present study identified the response of rat serum SOD activity contents to marginal and deficient copper intakes and to inflammation. Rats fed copper-deficient diet (less than 0.2 mg/kg Cu) for 5 wk displayed serum SOD activity contents that were only about 20% of those found in rats fed copper-supplemented diet (6.0 mg/kg Cu). Activities in rats fed a marginal diet (1.5 mg/kg Cu) were about 55% of those in the adequate rats. Turpentine-induced inflammation lowered serum SOD in rats within each dietary group. However, the change in the marginal group was not statistically significant. Based on chromatographic characterizations and inhibitor studies, rat serum SOD activity seemed to result primarily from a copper protein other than ceruloplasmin, Cu-Zn SOD or the recently discovered tissue extracellular SOD. In conclusion, low copper intake and inflammation may compromise extracellular defenses against superoxide. In addition, serum SOD activities could provide a non-ceruloplasmin-related means of assessing copper status, but nondietary variables can also affect these SOD values.

Effects of Changes in Dietary Zinc, Copper and Selenium Supply and of Endotoxin Administration on Metallothionein I Concentrations in Blood Cells and Urine in the Rat

These studies were designed to investigate the effects of low dietary zinc, copper or selenium intake of certain types of stress and of injection of zinc, copper or cadmium on metallothionein I (MT-I) concentrations in the blood and urine of rats. The aim was to establish whether such measurements could be of value in the diagnosis of zinc deficiency. Marginal zinc deficiency rapidly caused a major decrease in MT-I levels in the blood cells and to a lesser extent in urine. Injection of zinc and also of cadmium and copper had the opposite effect and increased MT-I concentrations in both samples, although the effects of zinc on blood cells and urine were relatively transient. The MT-I in the blood cells was associated mainly with the erythrocytes. No changes in blood or urine MT-I levels were found in copper- and selenium-deficient rats. Neither cold stress nor restriction of food intake for 24 h had any significant effect on MT-I levels in the blood cells or urine. Endotoxin injection increased urinary MT-I excretion in both zinc-adequate and zinc-deficient rats but did not affect blood cell MT-I levels in either group of animals. It appears therefore that assay of erythrocyte MT levels could be of particular value in the diagnosis of zinc deficiency, especially when it is accompanied by stress or infection.

Contrasting effects of low or high copper intake on rat tissue lipid essential fatty acid composition.

The effects of low copper intake or copper supplementation on the metabolism of stearic acid have been studied previously, but their effects on essential fatty acids have not been reported. Male Sprague-Dawley rats were fed for 12 weeks on pelleted semi-synthetic diets containing less than 1 mg/kg copper (low copper), 6 mg/kg (copper control), or 250 mg/kg copper (copper supplemented). The fatty acid composition of the total phopholipids and triglycerides of plasma, liver, heart and adipose tissue was analyzed by gas liquid chromatography. In low copper rats compared to controls, palmitic and oleic acids were decreased but stearic acid and docosahexaenoic acid were increased in plasma, liver and heart phopholipids. Arachidonic acid was also increased in plasma and liver phospholipids in low copper rats. In liver triglycerides, linoleic and arachidonic acids were increased but palmitic and oleic acid were decreased in low copper rats. Copper supplementation had the opposite effect; palmitic and oleic acids were increased in phospholipids and triglycerides whereas essential fatty acids were generally decreased. Hence, copper not only has a direct effect on the desaturation of stearic acid but also has significant effects on the tissue lipid composition of essential fatty acids.

Selected Features of Copper Metabolism in the Cat

In separate experiments, domestic short hair kittens were fed diets based on soy or egg white protein containing from 1.98 to 9.64 or 0.58 to 9.8 µg Cu/g diet, respectively. Moreover, kittens were also nursed from queens fed diets containing either 0.58 or 12 µg Cu/g of diet. In each experiment, copper was analyzed in liver, spleen, lung, heart, muscle and brain samples. The liver copper concentration was the most responsive to changes in dietary copper intake. For example, in weanling kittens fed 0.58 or 9.8 µg Cu/g diet, the liver copper concentration was 24 or 45 µg/g wet weight, respectively. Likewise, the levels of hepatic Cu,Zn-superoxide dismutase were reduced in kittens fed the low copper diet. However, the concentrations of zinc, iron and manganese in liver, lung, spleen, brain, muscle and kidney were not consistently changed in response to low copper intakes. Anemia was also not a consistent feature in the copper-deficient cat or kitten, but signs of connective tissue lesions were observed in kittens born to and weaned from queens fed diets containing < 1 µg Cu/g diet. Based on these observations and data for changes in growth in response to the differing levels of dietary copper, the copper requirement for the kitten was estimated to be 4–5 µg/g of diet (energy content approximately 5 kcal or 21 kJ per gram).