Effects Of Dietary Carbohydrate Research Articles

Effect of dietary carbohydrates and ethanol on expression of genes encodingsn-glycerol-3-phosphate dehydrogenase, aldolase, and phosphoglycerate kinase inDrosophila larvae

The genes encoding glycolytic enzymes in Drosophila form a group of functionally related genes that may be coordinately regulated and thus controlled by common factors. We have examined the effect of dietary carbohydrates and ethanol on expression of the genes encoding glycerol-3-phosphate dehydrogenase (GPDH), aldolase (ALD), and phosphoglycerate kinase (PGK) in D. melanogaster larvae. GPDH activity and transcript abundance increased in response to ethanol and additional amounts of several different carbohydrates. In addition, the levels of two alternatively processed Gpdh transcripts were differentially regulated by the treatments. The nutritional conditions tested had little or no effect on the activities and transcript levels of ALD and PGK. These results indicate that changes in dietary conditions affect expression of specific genes and do not evoke a general response from genes involved in cellular metabolism. The observation that dietary carbohydrates and ethanol increase Gpdh expression without affecting expression of Ald and Pgk reinforces previous suggestions that dietary carbon can be diverted by GPDH from glycolytic catabolism into lipid biosynthesis.

Insulin Rapidly Induces Rat Liver S14 Gene Transcription

We evaluated the role insulin plays in the regulation of hepatic S14 gene transcription using the streptozotocin-induced diabetic rat model. Nuclear run-on activity and mRNAS14 levels were reduced by more than 85% in diabetic rats compared to those in intact animals. After the administration of insulin, both S14 run-on activity and mRNAS14 levels were rapidly induced. Within 1 h of insulin administration, S14 run-on activity and mRNAS14 were induced 5- and 8-fold, respectively. S14 gene expression was restored to intact levels within 4 h, with overall increases in run-on activity and mRNAS14 of 7- and 20-fold, respectively. The full induction of mRNAS14 cannot be accounted for solely by activation of S14 gene transcription, implicating insulin effects at the posttranscriptional level. However, our results show that the principal target for insulin action on the S14 gene is transcriptional. Administration of dibutryl cAMP and theophylline fully blocked the insulin-mediated increase in S14 gene transcription, indicating that hepatic cAMP levels play a dominant negative role in regulating S14 gene transcription in vivo. Fructose administration to starved diabetic rats induced only a marginal 60% increase in mRNAS14 and S14 run-on activity within 4 h, while insulin plus fructose or insulin plus glucose fully restored S14 gene expression to intact levels within the same time period. Thus, dietary fructose or a metabolite generated from fructose alone cannot induce S14 gene transcription or mRNAS14 to intact levels in the starved diabetic rat. Acute effects of dietary carbohydrate on hepatic S14 gene transcription are insulin dependent.(ABSTRACT TRUNCATED AT 250 WORDS)

Copper‐Carbohydrate Interaction: Part I

Recent studies have shown that the type of dietary carbohydrate consumed greatly affects copper homeostasis. Simple sugars such as sucrose and fructose exacerbate the signs associated with the deficiency, and the consumption results in the mortality of the animal. In contrast, complex carbohydrates such as starch ameliorates the deficiency and protects against the morbidity and mortality of copper deficiency. This is the first of a two‐part article in which the effects of dietary carbohydrates on metabolic, biochemical and physiological pathways associated with copper deficiency in experimental animals and humans are summarised. In the first part of the review the effects that dietary carbohydrates exert on copper absorption, distribution and excretion are discussed. In addition, the role that copper plays in carbohydrate metabolism, insulin secretion and binding, glucose tolerance and the complications of diabetes (retinopathy and glomerular nephropathy) is reviewed. In the second part, the attention is focused on the cardiovascular system, sexual differences in copper‐carbohydrate interaction and copper deficiency during pregnancy and lactation. The mechanisms that may play a role in this interaction are discussed.

Effects of dietary carbohydrates on cholesterol metabolism in rats of different ages.

Male Sprague-Dawley rats aged 1 month (young) and 9 months (adult) were fed diets containing sucrose, glucose or corn starch as a carbohydrate source for 4 weeks. Dietary sucrose increased (a) the liver size in rats of both ages, (b) the serum cholesterol level in adult rats, (c) the serum triglyceride level, especially in young rats, and (d) the liver cholesterol and triglyceride levels in adult rats. Consequently, there were age-related increases in serum and liver cholesterol in rats fed sucrose. No significant difference was found in the activity of liver 3-hydroxy-3-methylgIutaryI coenzyme A reductase due to the diets in age-matched rats, whereas an age-related decrease was observed in rats fed simple sugars. Rats fed sucrose, especially adult rats, excreted more fecal steroids than ones fed glucose or corn starch. Sucrose tended to enhance the metabolism of linoleate to arachidonate, as judged from the fatty acid composition of liver microsomal phosphatidylcholine. Thus, sucrose exerts a peculiar effect on cholesterol metabolism in relation to age.

Effects of dietary carbohydrate and phenotype on thyroid hormones and brown adipose tissue locularity in adult LA/N-cp rats

1. 1. Groups of lean and corpulent LA/N-cp rats were fed isoenergetic diets containing, 54% carbohydrate as maize starch (MS) or sucrose (SU), 20% protein, 16% mixed fats, plus other essential nutrients and fiber from 1.5–9 months of age. Final body weights of corpulent rats were 2–3 times those of their lean littermates, and were greater with SU than MS diet in both phenotypes. 2. 2. Interscapular brown adipose tissue (IBAT) mass was greater in corpulent than lean and was greater with SU than MS diet in lean but not corpulent rats. IBAT cell diameters and adipocyte volumes were generally similar in both phenotypes, and were not markedly affected by dietary carbohydrate type. 3. 3. Brown adipocyte locularity profiles were qualitatively similar in both phenotypes, and were morphologically indicative of thermogenic activity in both phenotypes. Locule profiles of corpulent animals contained a greater proportion of thermogenically less active types IV and V brown adipocytes than similarly fed lean animals, however, and locule distribution profiles were not influenced by diet. 4. 4. Serum T 3 concentrations were similar in both phenotypes, were greater in SU than MS lean rats and were not influenced by diet in the corpulent phenotype. In contrast, serum thyroxine concentrations and percent thyroxine uptake were not influenced by diet or phenotype. 5. 5. These results are consistent with a partial impairment in BAT-mediated thermogenic activity in the corpulent phenotype and suggest that obesity in this strain may be due to factors other than biochemically defective brown adipose tissue thermogenesis.

Total body content of copper and other essential metals in rats fed fructose or starch

The effects of dietary carbohydrate and copper on whole body levels of copper and other essential minerals were investigated. Weaned male rats were pair-fed diets containing 62% fructose or cornstarch with either adequate (6–7 mg/kg) or deficient (0.5–0.7 mg/kg) copper (Cu) for 32–33 days. Recommended levels of other minerals were present in all diets. Total copper in whole body was approximately 2-fold higher in rats fed copper-supplemented diets than copper-deficient diets and was independent of the type of dietary carbohydrate. Whole body levels of zinc, iron, manganese and magnesium were independent of dietary copper and carbohydrate. Selenium content of rats fed copper-deficient diet with fructose was 35% higher than in those fed copper-adequate diet with fructose. Rats fed the copper-deficient diet containing starch had a whole body calcium level 17–23% lower than that of the other dietary groups. These results demonstrate that the copper-carbohydrate interaction is not a result of carbohydrate-dependent effects on the retention of dietary copper and other essential minerals.

Effects of dietary carbohydrates and temperatures on slow growing juvenile eels Anguilla anguilla

The influence of the level of carbohydrate in a purified diet on the growth of slow-growing Anguilla anguilla maintained at different temperatures was examined. The average weight increase of eels maintained at temperatures of 25° or 27° C and fed a diet containing 20% or 30% glucose, was significantly higher than the mean weight increase of eels maintained at the same temperature but fed a diet containing soluble corn starch, at the same percentages. There was no significant difference in the mean weight of slow growing eels fed 10%, 20% and 30% soluble corn starch or 10% glucose. There was no significant difference in protein content (wet weight) among the experimental groups. However, elvers that were fed a high percentage of carbohydrates (glucose or starch) and maintained at 27° C had a higher percentage of lipids in body weight compared with the other experimental groups.

Effects of sucrose and cornstarch on the development of copper deficiency in rats fed high levels of zinc

The effects of dietary carbohydrate and zinc on the development of copper deficiency were investigated. Male Sprague-Dawley rats (n=48) were fed one of eight diets in a 2×2×2 factorial design for 21 days. Two levels of copper (0.94 or 10 μg/g diet) and zinc (22 or 197 μg/g diet), and two types of carbohydrate (sucrose or cornstarch, 62% of the diet) were fed. Compared to copper-adequate rats, copper-deficient rats had lower hematocrit, hemoglobin, ceruloplasmin, and tissue copper levels, and higher hepatic iron levels. Sucrose and high dietary zinc promoted the development of copper deficiency. Copper-deficient rats fed 197 μg Zn/g diet with sucrose had significantly lower hematocrit and hemoglobin levels, hepatic copper levels, and tibia iron levels compared to all other copper-deficient rats. In copper-deficient rats, high dietary zinc significantly decreased copper and iron absorption, tibia iron levels, and hepatic iron accumulation. It appears that sucrose and high dietary zinc alter the development of copper deficiency through changes in both copper and iron metabolism.

Gender-Linked Differences in Dietary Induction of Hepatic Glucose-6-Phosphate Dehydrogenase, 6-Phosphogluconate Dehydrogenase and Malic Enzyme in the Rat

The objective of these studies was to determine how alterations in dietary carbohydrate affect hepatic glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphogluconate dehydrogenase (6PGDH) and malic enzyme (ME) activities in adult female rats. Rats were either 1) starved 2 d and then refed a nonpurified diet or a purified 65% carbohydrate diet (glucose, sucrose, fructose or cornstarch) for 3 d, or 2) switched from nonpurified to purified diets for 3 d. Liver G6PDH, 6PGDH and ME activities were determined. In males, enzyme activities were 8- to 12-fold and 3-fold higher when starved and refed purified diets and nonpurified diets, respectively, whereas in females, activities were 2- to 3-fold higher only when refed purified diets. Both genders had higher enzyme activities when shifted to purified diets. Females responded less dramatically than males. Of the higher enzyme activities observed during starvation-refeeding studies, in females 58–65% of the change is a function of switching rats from nonpurified to purified diets. In contrast, in males only 24–40% of the higher activities could be attributed to diet shifting. Results of these studies indicate that the effects of dietary carbohydrates on hepatic G6PDH, 6PGDH and ME activities are gender dependent.

Aortic lesions in copper deficiency: Modification by dietary carbohydrates

Copper deficiency can cause cardiovascular lesions in experimental animals. Previous experiments have shown that the biochemical and itDrphologic lesions induced by deprivation of dietary copper can be suppressed by feeding diets containing starch or can be magnified by a high sucrose diet. In a recent study it was found that the more severe signs of copper deficiency in rats fed sucrose as compared to starch were due to the fructose moiety of sucrose. Although fructose as compared to starch markedly enhanced the symptoms of copper deficiency, the possibility that an effect of dietary carbohydrates due to the nature of the simple carbohydrate (fructose vs glucose) cannot be excluded. The present study was designed to determine if the severity of copper deficiency in rats fed sucrose as compared to starch is due to the glucose as well as the fructose moiety of sucrose. This portion of the study assessed the morphologic changes in aortas of seventy weanling male rats who were fed, for 9 weeks, copper deficient or copper supplemented diets containing either 62% starch, fructose or glucose. The starch-fed copper supplemented group served as the most normal controls. Rats were sacrificed after 9 weeks of dietary treatments. Copper deficiency was verified by reduced serum ceruloplasmin activity and serum and hepatic copper concentration.

Development of Anemia in Copper-Deficient Rats Fed High Levels of Dietary Iron and Sucrose

The effects of dietary carbohydrate and iron on the development of copper deficiency were examined. Male Sprague-Dawley rats (n = 48) were limit-fed one of eight diets in a 2 × 2 × 2 factorial design for 19 d. Two levels of copper (0.85 or 8.6 µg Cu/g diet) and iron (54 or 226 µg Fe/g diet) and two types of carbohydrate (sucrose or cornstarch, 65.3%) were fed. Compared with control rats, copper-deficient rats had lower hematocrits, lower ceruloplasmin levels, lower tissue levels of copper and increased hepatic iron levels. Copper-deficient rats fed sucrose had significantly lower hematocrits, lower apparent absorption of copper, lower liver iron levels and higher plasma triglyceride levels than copper-deficient rats fed cornstarch. Copper-deficient rats fed sucrose with 226 µg Fe/g diet had hematocrit levels that were 15% lower than all other copper-deficient levels and 23% lower than control levels. Tissue levels of copper among copper-deficient rats were not affected by the type of carbohydrate or by the level of dietary iron. These data indicate that both high iron and sucrose can affect the development of the copper deficiency.

Interaction of Dietary Carbohydrate, Ascorbic Acid and Copper with the Development of Copper Deficiency in Rats

The effects of dietary carbohydrate and ascorbic acid on the development of copper deficiency were investigated. Male Sprague-Dawley rats (n = 48) were fed one of eight diets in a 2 × 2 × 2 factorial design for 21 d. These diets varied in copper (1.11 or 8.96 µg Cu/g diet), carbohydrate (sucrose or cornstarch, 62.3%) and ascorbic acid (0 or 1%). Compared to controls, copper-deficient rats had lower hematocrit and ceruloplasmin levels, lower levels of copper and iron in several tissues, higher heart weights and lower spleen weights. During copper deficiency, liver iron levels were higher than control levels when cornstarch, but not sucrose, was the carbohydrate source, while liver and gastrointestinal tract weights were higher with sucrose compared to cornstarch. Copper-deficient rats fed ascorbic acid had significantly (P < 0.05) lower hematocrits when fed sucrose compared to starch [29.6 ± 1.2 vs. 36.8 ± 1.2 g/dl (mean ± SEM), respectively]. In copper-deficient rats, sucrose tended to lower the apparent absorption of copper compared to cornstarch, while ascorbic acid reduced the apparent absorption of iron. Thus, sucrose and ascorbic acid appeared to reduce hematocrit levels through effects on mineral absorption.

Changes in bone and muscle constituents during dieting for obesity

The effects of dietary carbohydrate (CHO) content and of tri-iodothyronine (T3) administration on calcium, zinc and phosphate balances and on urinary hydroxyproline output were examined in eight obese subjects undergoing therapy with low energy (2741-3301 kJ/day), high calcium (28.9-35.1 mmol/day) diets. Calcium balances were generally positive at the high levels of intake used, but significantly more calcium was retained when dietary CHO intake (as proportion of total energy intake) was increased. Zinc balances were more positive when the proportion of dietary CHO was high and correlated both with nitrogen balance and with daytime insulin concentration. Urinary hydroxyproline output generally increased with dieting irrespective of dietary CHO content. Administration of T3 (30-80 micrograms/day) markedly increased zinc loss without affecting calcium balance.

Effects of dietary carbohydrate on the nutritional physiology and blood sugar level of Trichoplusia ni parasitized by the insect parasite, Hyposoter exiguae

SUMMARYThe effects of parasitization by Hyposoter exiguae on the nutritional physiology of Trichoplusia ni were influenced by the dietary sucrose level. The results confirmed that host nutrition plays a significant role in the manifestation of parasitic infection during the insect parasite-host association. Increased dietary sucrose level resulted in an increase in haemolymph trehalose concentration in both control and parasitized insects, but the increase was greater in the latter group. However, when the sucrose level was increased without energetic compensation and the dietary casein level was maintained constant, the haemolymph trehalose concentration was affected very little in unparasitized individuals but was markedly elevated in parasitized hosts. This result suggests that the de novo synthesis of carbohydrate in parasitized T. ni may not be regulated by dietary sugar intake.

Effects of Dietary Carbohydrates on the Numbers of Streptococcus mutans and Actinomyces viscosus in Dental Plaque of Mono-infected Gnotobiotic Rats

Dietary sucrose and glucose are known to promote the accumulation of, respectively, Streptococcus mutans and Actinomyces viscosus in complex dental plaque microflora. In this study, we have investigated the effects of these carbohydrates on the numbers of S. mutans and A. viscosus colonizing the teeth of mono-infected gnotobiotic rats. Sucrose at a dietary concentration of between 0.25 and 0.5 percent (corresponding with 7-15 mM in the drinking water) caused an increase in the numbers of S. mutans. This result strongly suggested that the increase was due to extracellular polysaccharide (EPS) synthesis by glucosyltransferase, whose Km value (1.0-7.0 mM) is in the same concentration range. The numbers of A. viscosus increased three-fold when 10% glucose was added to the basal diet. It seems plausible that this was due to extracellular heteropolysaccharide produced by A. viscosus in the presence of excess glucose. Although in most microbial ecosystems provision of additional substrates leads to an increase in biomass, glucose had only a small effect on the numbers of S. mutans. Mechanical dislodging forces could be limiting the accumulation of dental plaque. EPS synthesis from dietary carbohydrates seems to enable the population to withstand mechanical dislodging at least partially by providing a matrix wherein cells are entrapped or to which the cells are firmly attached.

Effects of Dietary Carbohydrate on Mitochondrial Composition and Function in Two Strains of Rats

BHE and Wistar male, weanling rats were fed either a 65% sucrose or a 65% cornstarch diet. They were killed at 50 d of age; livers were excised and used for the determination of the fatty acids of mitochondrial phospholipid or used to determine the effect of such diets on the dependence on temperature of succinate-supported respiration. Neither diet nor strain affected either the total quantity of phospholipids or the quantities of the individual phospholipids. However, analysis of variance revealed strain and diet differences in the fatty acyl moieties of the phospholipids: sucrose-fed rats had more stearic (18:0) and less linoleic acid (18:2) than did starch-fed rats; BHE rats had more arachidonic acid (20:4) than did Wistar rats. There were no significant differences in either transition temperature or in the lower or upper activation energies determined from the biphasic Arrhenius plot. Although fatty acid compositional differences were observed, these differences had little effect on the membrane-associated, succinate-supported respiration.

Dietary induction of glucose-6-phosphate dehydrogenase synthesis

The effect of dietary carbohydrate on rat liver glucose-6-phosphate dehydrogenase synthesis has been determined by using a method which can accurately quantitate relative rates of synthesis as low as 0.001 percent of total protein synthesis. Hepatocytes were incubated with (3H) leucine for 60 min and G6PD was separated from all other proteins by immunoprecipitation and electrophoresis on two-dimensional O'Farrell gels. The relative rate of synthesis of G6PD increased 70-fold (from 0.0015 to 0.11% of total protein synthesis) in hepatocytes from fasted rats refed a high carbohydrate diet. We have concluded that the 20-30 fold dietary induction of G6PD is due to a 70 and 3 fold increase in synthesis and degradation, respectively.

Effect of dietary carbohydrates and copper status on blood pressure of rats

Copper deficiency was induced in rats by feeding diets containing either 62% starch, fructose or glucose deficient in copper for 6 weeks. All copper deficient rats, regardless of the dietary carbohydrate, exhibited decreased ceruloplasmin activity and decreased serum copper concentrations. Rats fed the fructose diet exhibited a more severe copper deficiency as compared to rats fed either starch or glucose. The increased severity of the deficiency was characterized by reduced body weight, serum copper concentration and hematocrit. In all rats fed the copper adequate diets, blood pressure was unaffected by the type of dietary carbohydrate. Significantly reduced systolic blood pressure was evident only in rats fed the fructose diet deficient in copper. When comparing the three carbohydrate diets, the physiological and biochemical lesions induced by copper deprivation could be magnified by feeding fructose.

Effects of carbohydrate intake on phenobarbital-, polychlorinated biphenyl- and 3-methylcholanthrene-induced enhancement of drug oxidation and conjugation in rat liver

The effects of dietary carbohydrate on phenobarbital (PB)-, polychlorinated biphenyl (PCB)- or 3-methylcholanthrene (MC)-induced increase in the activity of cytochrome P-450-linked monooxygenase, a UDP-glucuronyltransferase and a glutathione S-transferase in rats were studied. A low-carbohydrate diet increased the monooxygenase activity for all of the hydrocarbons studied (benzene, toluene, styrene, carbon tetrachloride, chloroform, 1, 2-dichloroethane, 1, 1-dichloroethylene and trichloroethylene) without affecting microsomal protein and cytochrome P-450 contents. On the other hand, though causing an increase both in microsomal protein and cytochrome P-450 contents, PB, PCB and MC each produced only a substrate-specific increase in the enzyme activity: PB enhanced the metabolism of toluene, styrene, chloroform and trichloroethylene, but not those of benzene, carbon tetrachloride, 1, 2-dichloroethane and 1, 1-dichloroethylene; PCB increased only the metabolism of toluene, styrene and trichloroethylene; MC did not affect the metabolism of any of the hydrocarbons. A low-carbohydrate diet potentiated the effects of these inducers on the protein and cytochrome P-450, but the augmentation was reflected only in the metabolism of toluene and styrene.Although PB, PCB and MC each increased both activites of UDP-glucuronyltransferase (substrate, p-nitrophenol) and glutathione S-transferase (3, 4-dichloronitrobenzene), the effect of dietary carbohydrate on these transferases was negligible. In addition, a low-carbohydrate diet failed to augment the enhancing effects of these inducers.These results indicate that dietary carbohydrate intake is likely to affect the first phase metabolism of volatile hydrocarbons (functionalization reaction) but is not likely to cause a significant influence on the second phase metabolism (conjugation reactions).

Effects of dietary carbohydrate, fat, and protein on norepinephrine turnover in rats

To investigate effects of diet composition on rates of norepinephrine (NE) turnover in sympathetically innervated organs, weanling rats were fed for 2 to 2 1 2 weeks diets varying in carbohydrate (74.2% to 7.4% of total metabolizable energy) and fat (5.2% to 72.0%), or diets varying in protein (9.9% to 39.6%) and carbohydrate (77.8% to 48.1%). Changing the proportions of carbohydrate and fat in the diet, while maintaining similar intakes of energy and all other essential nutrients did not affect rates of NE turnover in heart, white adipose tissue (WAT), liver or pancreas and only minimally affected NE turnover in interscapular brown adipose tissue (IBAT). Decreasing the proportion of protein in the diet from 39.6% to 9.9% accelerated rats of NE turnover in heart (52%), IBAT (20%), WAT (42%), and liver (37%). When rats fed a diet containing 19.8% protein were also given a 10% (wt/vol) sucrose solution to drink for three days, their rates of NE turnover increased in heart (45%), IBAT (17%), liver (71%), and pancreas (55%). This response to sucrose depended on the protein content of the diet, since rats fed a 9.9% protein diet in which rates of NE turnover was already accelerated had no further increase in NE turnover when given the sucrose solution to drink. These data demonstrate that diet composition can affect activity of the sympathetic nervous system, as indicated by changes in rates of NE turnover. Changing the proportion of protein in the diet was more effective in altering NE turnover than changing the proportion of carbohydrate or fat.