Fructose triggers DNA modification and damage in an Escherichia coli plasmid.

The nonenzymatic reaction between reducing sugars and amino groups of long-lived macromolecules results in an array of chemical modifications that may account for several physiological complications. The characteristics of the reaction are directly related to the type of the reducing sugars involved, whether aldoses or ketoses, phosphorylated or non-phosphorylated, and these in turn determine the consequences of the induced modifications. So far, most studies have been focused on the nonenzymatic reaction between glucose and proteins, while the reaction with fructose, a faster glycating agent, attracted only a minor attention. We have recently demonstrated that long-term fructose consumption induces age-related changes in collagen from skin and cortical bones faster than glucose. In the present study we provide evidence that fructose and its phosphate metabolites can modify DNA faster than glucose and its phosphate metabolites under in vitro conditions. Incubating the plasmid pBR322 with fructose and glucose phosphate metabolites induced DNA modifications and damage that were verified by gel electrophoresis and transformation capacity of the plasmid into an Escherichia coli host. The intensity of the tested sugars to modified and damage DNA after incubation for 15 days increased significantly in the following order: glucose 1-phosphate < glucose < glucose 6-phosphate < fructose 1-phosphate < fructose < fructose 6-phosphate. The data suggest that fructose should deserve more attention as a factor that may influence glycation and induce physiological complications.

Hepatic fructose-metabolizing enzymes and related metabolites: role of dietary copper and gender.

The purpose of this study was to further examine the hypothesis that variations in hepatic fructose-metabolizing enzymes between males and females might account for the differences in the severity of copper (Cu) deficiency observed in fructose-fed male rats. Weanling rats of both sexes were fed high-fructose diets either adequate or deficient in copper for 45 days. Cu deficiency decreased sorbitol dehydrogenase activity and dihydroxyacetone phosphate levels and increased glyceraldehyde levels in both sexes. Gender effects were expressed by higher activities of glycerol 3-phosphate dehydrogenase and aldehyde dehydrogenase in male than in female rats and higher levels of dihydroxyacetone phosphate and fructose 1,6-diphosphate (F1,6DP) in female than in male rats. The interactions between dietary Cu and gender were as follows: alcohol dehydrogenase activities were higher in female rats and were further increased by Cu deficiency in both sexes; aldehyde dehydrogenase activities were decreased by Cu deficiency only in male rats; sorbitol levels were higher in male rats and were further increased by Cu deficiency in male rats; fructose 1-phosphate (F1P) levels were increased by Cu deficiency in both sexes, but to a greater extent in male rats; glyceraldehyde 3-phosphate levels were higher in female rats, but were decreased by Cu deficiency in female and increased in male rats. Though most of the examined hepatic fructose-metabolizing enzymes and metabolites showed great differences between rats fed diets either adequate or deficient in Cu, it is the activity of fructokinase and aldolase-B, and the concentrations of their common metabolites, F1P and notably F1,6DP, that could be in part responsible for differences in the severity of pathologies associated with Cu deficiency observed between female and male rats.

Availability and antiperoxidative effects of beta-carotene from Dunaliella bardawil in alcohol-drinking rats.

The present study demonstrated the high bioavailability and antiperoxidative capacity of the natural beta-carotene isomer mixture of Dunaliella bardawil compared with synthetic beta-carotene under alcohol-induced oxidative stress. Weanling rats were adapted to ethanol by increasing ethanol levels in their drinking water to 30% at 5% intervals per week; other rats received water with no added ethanol. One water-drinking group and one alcohol-drinking group with no dietary carotene were used as controls. Two water-drinking groups were supplemented with 1 g/kg diet beta-carotene either from Dunaliella or a synthetic source, and due to reduced food intake, two ethanol-fed groups received 2 g beta-carotene per kilogram of diet from each source. Following 3 months of ethanol consumption, both carotene sources were found to prevent ethanol-induced lipid peroxidation as expressed by the hepatic conjugated oxidized dienes level. However, in the algal-fed rats, hepatic carotene and vitamin A levels were higher. In addition to a lower performance of the group fed ethanol and synthetic beta-carotene, there were three deaths in this group.

Long-term fructose consumption accelerates glycation and several age-related variables in male rats.

Fructose intake has increased steadily during the past two decades. Fructose, like other reducing sugars, can react with proteins through the Maillard reaction (glycation), which may account for several complications of diabetes mellitus and accelerating aging. In this study, we evaluated the effect of fructose intake on some age-related variables. Rats were fed for 1 y a commercial nonpurified diet, and had free access to water or 250 g/L solutions of fructose, glucose or sucrose. Early glycation products were evaluated by blood glycated hemoglobin and fructosamine concentrations. Lipid peroxidation was estimated by urine thiobarbituric reactive substances. Skin collagen crosslinking was evaluated by solubilization in natural salt or diluted acetic acid solutions, and by the ratio between beta- and alpha-collagen chains. Advanced glycation end products were evaluated by collagen-linked fluorescence in bones. The ratio between type-III and type-I collagens served as an aging variable and was measured in denatured skin collagen. The tested sugars had no effect on plasma glucose concentrations. Blood fructose, cholesterol, fructosamine and glycated hemoglobin levels, and urine lipid peroxidation products were significantly higher in fructose-fed rats compared with the other sugar-fed and control rats. Acid-soluble collagen and the type-III to type-I ratio were significantly lower, whereas insoluble collagen, the beta to alpha ratio and collagen-bound fluorescence at 335/385 nm (excitation/emission) were significantly higher in fructose-fed rats than in the other groups. The data suggest that long-term fructose consumption induces adverse effects on aging; further studies are required to clarify the precise role of fructose in the aging process.

Opioid Peptides, Adrenocorticotrophic Hormone and Dietary Copper Intake in Humans.

Copper plays an important role in cardiac and brain function possibly through endocrine and neuroendocrine systems. The syndrome of copper deficiency is worsened by dietary fructose and other trace metals such as zinc. We investigated the effect of a low copper diet on plasma opioid peptides in 11 healthy young volunteers who were fed foods low in copper but adequate in all other nutrients. The study was divided into three dietary periods. Copper was added to the diet so that the diet contained 0.66 mg/day for 24 days (marginal Cu), 0.38 mg/day for 42 days (low Cu) and 2.49 mg/day for 24 days (adequate Cu). The indices of copper status, ceruloplasmin and plasma copper concentrations, declined and were significantly lower (p < 0.05) at the end of the low Cu period than at the beginning of the study and the end of the marginal Cu period. They increased significantly at the end of the adequate Cu diet to the levels of the marginal Cu diet. Plasma ß-endorphin (BEN), Leu-enkephalin (LE), Met-enkephalin (ME) and Adrenocorticotropic hormone (ACTH) were measured by radioimmunoassay at the beginning of the study and at the end of each dietary period. No significant differences were observed in BEN, LE or ME during any of the periods. There were only small increases in LE and ME at the end of marginal and low copper diet periods and no significant changes were observed on copper repletion. Plasma ACTH was significantly lower at the end of low copper compared to baseline value but was not lower after marginal copper. Copper repletion had no significant effect on ACTH. The data show that plasma opioid peptides did not respond significantly to differential copper intake.

Gender, dietary copper and carbohydrate source influence cardiac collagen and lysyl oxidase in weanling rats.

The present investigation was conducted to determine the effects of consumption of diets containing fructose or cornstarch on cardiac collagen metabolism in weanling male and female rats fed copper-deficient or copper-adequate diets for 5 wk. Although both male and female rats that consumed the copper-deficient diet containing fructose were similarly copper deficient, only the males showed severe cardiac pathologies and two died prematurely due to heart-related abnormalities. These pathologies were accompanied by a significant reduction of cardiac lysyl oxidase activity and elevated soluble and total cardiac collagen concentrations compared with rats fed copper-adequate diets. These abnormalities were less severe in copper-deficient rats fed cornstarch. The data show that the activity of the copper-containing enzyme lysyl oxidase is affected by both dietary carbohydrate and gender. The pathologies of heart tissue could be the result of abnormal crosslinking of collagen induced by the combination of copper deficiency, fructose feeding and the sex of the rats.

Opioid peptides, adrenocorticotrophic hormone, and idiopathic (orthostatic) edema.

The effect of dextroamphetamine sulfate (Dexedrine) on plasma opioid peptides, hormones, and other metabolites was studied in eight female subjects with idiopathic (orthostatic) edema and five healthy females. All subjects were given 20 mg of dextroamphetamine sulfate, a drug widely used in the treatment of this disorder, and blood samples were collected before and 30, 60, and 90 minutes after treatment. Patients with idiopathic (orthostatic) edema had significantly lower plasma sodium levels but higher blood urea nitrogen, aldosterone, and renin levels. D-amphetamine decreased aldosterone and renin levels in both groups. Plasma adrenocorticotropin levels were lower whereas met-enkephalin levels were higher in idiopathic (orthostatic) edema subjects compared to control subjects. D-amphetamine had no significant effect on plasma beta-endorphin, adrenocorticotrophic hormone, or enkephalins. Our data indicate that opioid peptides, especially enkephalins, and adrenocorticotrophic hormone may be involved in the pathogenesis of idiopathic (orthostatic) edema syndrome, but they seem uninvolved in the aldosterone- and renin-lowering action of amphetamine. It is possible that amphetamine is acting further down the chain, either directly on the adrenal and kidney or the microvasculature, rather than at hypothalamus-pituitary axis.

Avocado oils and hepatic lipid metabolism in growing rats.

The effect of various avocado oils on liver metabolism was studied in growing female rats. The rats were fed diets containing 10% (w/w) avocado oil for 4 wk. In comparison with rats fed refined avocado oil obtained from cored fruit by centrifugal separation, rats fed unrefined avocado oil obtained by organic solvent extraction from intact fruit, or its unsaponifiable components, showed a significant increase in total liver lipogenesis as well as in phospholipid and triglceride synthesis. Rats fed avocado-seed oil exhibited enhanced [1-14C]acetate incorporation into total liver lipids but showed the same distribution of label in the three main lipid classes as that of rats fed refined avocado oil. In addition, a significant reduction of triglycerides and protein content of plasma very-low-density lipoprotein and high-density lipoprotein fractions was observed in rats fed avocado-seed oil as compared with rats fed refined oil. Electron micrographs suggested that the alterations in hepatic lipogenesis are related to the marked proliferation of the smooth endoplasmic reticulum, which is known to be associated with induction of enzymes involved with lipid biosynthesis. The differences between the animals fed seed oil and those fed the unrefined oils, in the distribution of label within the main lipid classes, indicate that more than one factor is involved in the alterations caused by these oils.

The effect of various avocado oils on skin collagen metabolism.

The effects of various avocado oils on collagen metabolism in skin were studied in growing rats fed diets containing 10% (w/w) of the tested oils. Rats fed the unrefined avocado oil extracted with hexane from the intact fruit, its unsaponifiables or the avocado seed oil, showed significant increases in soluble collagen content in skin, though total collagen content was not affected. The increased soluble collagen content appears to be a consequence of the inhibition of lysyl oxidase activity. The active factor was found to be present in the unrefined avocado oil and probably originated from the avocado seed, since collagen metabolism was affected only by fractions which contained lipids fraction from the seed. In comparison rats fed the refined or unrefined soybean oils showed no effects.

The effect of avocado oils on some liver characteristics in growing rats.

The effects of various avocado oils on some liver characteristics were studied in growing rats. The rats were fed diets containing 10% (w/w) avocado oil for 4 wk. In comparison with rats fed refined oil obtained from cored fruit by centrifugal separation, rats fed unrefined avocado oil obtained by solvent extraction from the intact fruit, or refined avocado oil containing avocado-seed oil, showed significant growth inhibition, an increase in the amount of hepatic lipids (identified as steatosis by histopathological examination), and a decrease in levels of triglycerides in blood. Rats fed the refined oil containing unsaponifiable material prepared from unrefined oil from the intact fruit showed similar responses. Fatty livers were not induced by feeding rats unrefined avocado oil obtained from intact fruit by centrifugal separation, although a significant decrease in blood triglycerides was observed. There were no significant differences between groups in serum total protein, albumin or bilirubin content or in alanine aminotransferase activity. However, serum alkaline phosphatase activity was increased in rats fed the seed oil, the unrefined solvent-extracted oil from intact fruit, or the unsaponifiables, and aspartate aminotransferase activity was significantly increased in the group fed avocado-seed oil. These data suggest that consumption of avocado oil extracted from intact fruit may cause changes in liver metabolism.