Sucrose-based Diet Research Articles

Smooth Muscle Cells from a Rat Model of Obesity and Hyperleptinemia Are Partially Resistant to Leptin-Induced Reactive Oxygen Species Generation

The aim of this study was to evaluate the effect of leptin on reactive oxygen species' (ROS) generation of smooth muscle cells (SMCs) from a rat model of obesity and hyperleptinemia. Obesity and hyperleptinemia were induced in rats by a sucrose-based diet for 24 weeks. ROS generation was detected by using dichloro-dihydrofluorescein (DCF), a fluorescent ROS probe in primary SMCs culture. An increase in plasma leptin and oxidative stress markers was observed in sucrose-fed (SF) rats. At baseline SMCs from SF rats showed a more than twofold increase in fluorescence intensity (FI) compared to that obtained in control (C) cells. When the C cells were treated with 20 ng leptin, the FI increased by about 250%, whereas the leptin-induced FI in the SF cells increased only by 28%. In addition, sucrose feeding increased the levels of p22phox and gp91phox, subunits of Nox as an O2•- source in SMCs. Treatment of cells with leptin significantly increased p22phox and gp91phox levels in C cells and did not affect SF cells. Regarding STAT3 phosphorylation and the content of PTP1B and SOCS3 as protein markers of leptin resistance, they were found to be significantly increased in SF cells. These results suggest that SF aortic SMCs are partially resistant to leptin-induced ROS generation.

Fructooligosaccharides (FOS) enhance beneficial effects of a flavonoid, quercetin‐3‐glucoside (Q3G), on insulin sensitivity in rats fed high sucrose diet

An enhancement FOS on improvement of glucose tolerance and insulin sensitivity by a flavonoid glycoside, Q3G, and their mechanisms were studied. Rats were fed a sucrose‐based diet with or without 0.3% Q3G, 5% FOS, or 0.3% Q3G+5% FOS, while dextrin‐based diet was used for a normal reference group. OGTTs were conducted on day 14, 28, 45. Flavonoid levels in the aortic blood were measured by LC/MS. Body weight gain was lowered in Q3G+FOS group without changes in food intake. Abdominal fat weights and cecal pH were reduced in both the FOS‐fed groups without any effects of Q3G. Combination of Q3G and FOS only reduced blood glucose levels at 60 min in all OGTTs. HOMA‐IR showed an improvement in the Q3G+FOS group on day 14 and 28. On day 45, the value was improved in the individual FOS or Q3G group, and was further improved in the FOS+Q3G group. A much higher blood level of quercetin was observed in the FOS+Q3G group compared with the Q3G group, which may contribute the combination effects of Q3G and FOS. Secretion of GLP‐1 observed in the small intestinal loops of anesthetized rats and in vivo experiment were increased by addition of quercetin to luminal fluid containing FOS. This may involve in the improvement of glucose tolerance. In conclusion, FOS increases bioavailability of Q3G, and enhanced beneficial effects of Q3G on glucose tolerance and insulin sensitivity, which have a potential for prevention of type 2 diabetes.Grant Funding Source : Graduate School of Agriculture, Hokkaido University

Enhancing male sexual success in a lekking fly ( Anastrepha suspensa Diptera: Tephritidae) through a juvenile hormone analog has no effect on adult mortality

While defending lek-territories, male Anastrepha suspensa (Loew) produce chemical, acoustic and visual courtship signals. In the laboratory and under semi-natural conditions, topical application of the juvenile hormone analog methoprene doubles pheromone production and subsequently doubles sexual success. However, sexual signals and interactions are likely to be physiologically expensive and so result in higher male mortality. Comparison of males kept in isolation for 35 days, but provided daily with a potential mate or a rival male, revealed that both male- and female-interactors shortened focal-male lifespan. In addition, focal males were either treated with methoprene or not, then either provided with protein in their sucrose-based diet or not. Protein proved to similarly double sexual success and also resulted in longer male life spans in all of the interactor-categories. However, there was no evidence that methoprene induced hypersexuality resulted in higher rates of mortality, i.e., the longevity of males treated with methoprene did not significantly differ from untreated males in the same interactor/diet categories. This apparent lack of costs to a putatively sexually selected signal is unexpected but presents an opportunity to increase the sexual competence of sterile flies with few consequences to their survival following mass-release.

Berberine and plant stanols synergistically inhibit cholesterol absorption in hamsters

The present study was conducted to determine the efficacy and underlying mechanism of berberine (BBR), plant stanols (PS) and their combination on plasma lipids. Male Golden Syrian hamsters were randomly divided into 4 groups (n=15/group) and fed a cornstarch–casein–sucrose-based diet containing 0.15% cholesterol and 5% fat. Three treatment groups were supplemented with 0.17% (equivalent to 100mgkg−1d−1) BBR, 1% PS, or a combination of both (BBRPS) for 4wk. At the end of the study, plasma lipids were analyzed with enzymatic methods, cholesterol absorption and synthesis using stable isotope tracer methodology, and gene and protein expressions in the liver and small intestine using real-time PCR and Western blot, respectively. BBR and PS significantly lowered plasma total- and nonHDL-cholesterol levels, and BBRPS markedly improved cholesterol-lowering efficacy compared to BBR or PS alone. Further examinations revealed that BBR and PS both inhibited cholesterol absorption and by contrast, increased cholesterol synthesis, and exerted a synergistic action when they were combined. Plasma total or nonHDL-cholesterol levels were significantly correlated with cholesterol absorption rates. BBR upregulated sterol 27-hydroxlase gene expression and BBRPS increased both cholesterol-7α-hydroxylase and sterol 27-hydroxlase gene expressions. BBR and PS also synergistically decreased plasma triacylglycerides. These findings suggest that the cholesterol-lowering action of BBR might involve a combination of inhibition of cholesterol absorption and stimulation of bile acid synthesis. The combination of BBR and PS improves cholesterol-lowering efficacy through a synergistic action on cholesterol absorption, in addition to synergistically reducing plasma triacylglycerols in hamsters.

Influence of honey versus sucrose on satiety and postprandial metabolism in healthy subjects

We recently demonstrated that rats consuming a honey‐based diet gained less body weight and fat and ate less food versus rats consuming a sucrose‐based diet. The objectives of this study were to assess the effects of honey compared to sucrose on satiety and plasma concentrations of glucose, insulin and ghrelin in healthy humans. Thirteen healthy (BMI: 23.2±3.3) participants (6 men, 7 women) aged 21‐40 y fasted overnight (10 hours) then consumed isocaloric beverages (240 kcal) sweetened with sucrose, clover honey, or glucose in a randomized, crossover design where glucose served as a control. Fingerprick blood samples were collected and satiety ratings were assessed prior to beverage consumption and 15, 30, 45, 60, 90 and 120 minutes following the start of ingestion. Plasma was analyzed for concentrations of glucose, insulin and ghrelin, and area under the curve (AUC) or over the curve was calculated for all variables. Satiety was not different between sucrose and honey. Lower (p<0.05) AUCs for plasma glucose were detected for honey (‐35±28%) and sucrose (‐27±29%) relative to glucose consumption. No differences in insulin or ghrelin responses were detected among groups. Honey promoted a potentially healthier response than glucose but not sucrose with regard to postprandial glucose metabolism, but no differences in the satiating effects of the sweeteners were detected.Supported by the American Heart Association.

The effects of long-term honey, sucrose or sugar-free diets on memory and anxiety in rats

Sucrose is considered by many to be detrimental to health, giving rise to deterioration of the body associated with ageing. This study was undertaken to determine whether replacing sucrose in the diet long-term with honey that has a high antioxidant content could decrease deterioration in brain function during ageing. Forty-five 2-month old Sprague Dawley rats were fed ad libitum for 52 weeks on a powdered diet that was either sugar-free or contained 7.9% sucrose or 10% honey (which is the equivalent amount of sugar). Anxiety levels were assessed using an Elevated Plus Maze, whilst a Y maze and an Object Recognition task were used to assess memory. Locomotor activity was also measured using an Open Field task to ensure that differences in activity levels did not bias results in the other tasks. Anxiety generally decreased overall from 3 to 12 months, but the honey-fed rats showed significantly less anxiety at all stages of ageing compared with those fed sucrose. Honey-fed animals also displayed better spatial memory throughout the 12-month period: at 9 and 12 months a significantly greater proportion of honey-fed rats recognised the novel arm as the unvisited arm of the maze compared to rats on a sugar-free or sucrose-based diet. No significant differences among groups were observed in the Object Recognition task, and there appeared to be no differences in locomotor activity among groups at either 6 or 12 months. In conclusion, it appears that consumption of honey may reduce anxiety and improve spatial memory in middle age.

Adult nutrition and butterfly fitness: effects of diet quality on reproductive output, egg composition, and egg hatching success.

BackgroundIn the Lepidoptera it was historically believed that adult butterflies rely primarily on larval-derived nutrients for reproduction and somatic maintenance. However, recent studies highlight the complex interactions between storage reserves and adult income, and that the latter may contribute significantly to reproduction. Effects of adult diet were commonly assessed by determining the number and/or size of the eggs produced, whilst its consequences for egg composition and offspring viability were largely neglected (as is generally true for insects). We here specifically focus on these latter issues by using the fruit-feeding tropical butterfly Bicyclus anynana, which is highly dependent on adult-derived carbohydrates for reproduction.ResultsAdult diet of female B. anynana had pronounced effects on fecundity, egg composition and egg hatching success, with butterflies feeding on the complex nutrition of banana fruit performing best. Adding vitamins and minerals to a sucrose-based diet increased fecundity, but not offspring viability. All other groups (plain sucrose solution, sucrose solution enriched with lipids or yeast) had a substantially lower fecundity and egg hatching success compared to the banana group. Differences were particularly pronounced later in life, presumably indicating the depletion of essential nutrients in sucrose-fed females. Effects of adult diet on egg composition were not straightforward, indicating complex interactions among specific compounds. There was some evidence that total egg energy and water content were related to hatching success, while egg protein, lipid, glycogen and free carbohydrate content did not seem to limit successful development.ConclusionThe patterns shown here exemplify the complexity of reproductive resource allocation in B. anynana, and the need to consider egg composition and offspring viability when trying to estimate the effects of adult nutrition on fitness in this butterfly and other insects.

Hypocholesterolaemic effects of plant sterol analogues are independent of ABCG5 and ABCG8 transporter expressions in hamsters

The hypolipidaemic effects of plant sterols are well established. However, mechanisms by which plant sterols lower plasma cholesterol levels, particularly at the molecular level, have not been clearly elucidated. The objective of the present study was to determine whether different plant sterol analogues reduce plasma cholesterol levels by up regulating the sterol transporters ABCG5 and ABCG8 in the liver and/or small intestine. Male Golden Syrian hamsters were divided into eight groups. Groups 1 and 2 were fed a maize starch-casein-sucrose-based diet that did not contain cholesterol (control; Con) or the Con diet with the addition of 0.25 % cholesterol (Ch-Con). Groups 3-8 were fed the Ch-Con diet supplemented with 1 % plant sterols, 1 % plant stanols, 1 % of a plant sterol and stanol mixture (50:50), 1.76 % plant sterol-fish oil esters, or 0.71 or 1.43 % stanol-ascorbic acid esters, respectively. After 5 weeks, the Ch-Con diet up regulated the ABCG5 mRNA expression and tended (P = 0.083) to increase ABCG8 mRNA expression in the liver, but did not affect both genes' expression in the small intestine compared with the Con diet. Hamsters fed 0.7 % stanol esters showed lower plasma cholesterol levels (P < 0.001) and also lower liver ABCG5 mRNA expression (P < 0.05) compared with the Ch-Con diet. Plant stanols, stanol esters, and sterol esters did not affect the ABCG5 or ABCG8 mRNA expressions in the liver and intestine although they reduced plasma cholesterol levels. These results suggest that plant sterols and their derivatives reduce plasma cholesterol levels independently from the mRNA expression of ABCG5 and ABCG8 transporters.

Inulin attenuates atherosclerosis in apolipoprotein E-deficient mice

Effects of different inulin-type fructan fractions were studied on atherosclerotic plaque formation in male apo E-deficient mice. Thirty-two mice were randomly divided into four groups and received either a semi-purified sucrose-based diet (control group), or diets in which sucrose was replaced in part by various inulin-type fructans (10 g/100 g): long-chain inulin, oligofructose, or an oligofructose-enriched inulin for 16 weeks. The presence of atherosclerotic plaques was assessed by histomorphometry in the aortic sinus. The apo E-deficient mice fed long-chain inulin or an oligofructose-enriched inulin had about 35 % and 25 % less atherosclerotic lesion area compared with the control group, respectively. Feeding long-chain inulin significantly reduced plasma cholesterol concentrations (P<0.001), and the three inulin-type fructans reduced triacylglycerol (TAG) concentrations compared with the control group (P<0.001). Both the long-chain inulin and an oligofructose-enriched inulin significantly lowered hepatic cholesterol concentrations compared with the control diet (P<0.05). Hepatic TAG concentrations were significantly lower in all three groups fed the fructan-supplemented diets v. the control group (P<0.0001). The results of the present study suggest that inhibition of atherosclerotic plaque formation is more potent in the presence of long-chain inulin, either alone or in combination with oligofructose (an oligofructose-enriched inulin), and that this probably is related to changes in lipid metabolism.

Massive large bowel resection decreases bone strength and magnesium content but not calcium content of the femur in rats

We examined the effects of massive large bowel resection (cecocolonectomy) on calcium and magnesium absorption and bone characteristics in rats. Male Sprague-Dawley rats were divided into two groups: sham-operated and cecocolonectomized rats. The rats were fed a sucrose-based diet containing casein at 250 g/kg diet for 10 d after a 9- to 10-d postoperative recovery period. Apparent magnesium absorption but not calcium absorption was lower in the resection group than in the sham group. There was a tendency of lower serum magnesium concentration ( P = 0.070) but not calcium concentration ( P = 0.418) in the resection group compared with the sham group. The maximum breaking force and magnesium content but not the calcium content of the femur were lower in the resection group than in the sham group. These results suggest that massive large bowel resection influences magnesium kinetics and decreases bone strength through reduction of the magnesium content of the femur in rats. Femoral breaking force was positively correlated ( r = 0.617, P = 0.011) with only the magnesium content. We conclude that the changes in magnesium kinetics caused by cecocolonectomy could contribute to the fragility of bone.

Effects of dietary myo-inositol related compounds on sucrose-mediated hepatic lipid accumulation in rats

We have previously shown that dietary myo-inositol and phytic acid depress elevations of hepatic lipids and of hepatic lipogenic enzymes activities in rats fed a high-sucrose diet. In the present study, we examined whether dietary phytin (Calcium magnesium phytate) normalizes the enhancements of hepatic lipid parameters caused by sucrose feeding as well as dietary myo-inositol or phytate (sodium phytate), and whether this normalizing effect of phytate is caused by a mechanism involving reduced intestinal sucrase activity. Male Wistar rats were fed a sucrose-based diet (650g/kg diet) with supplementation of myo-inositol (1g/kg diet), phytate (sodium phytate, 5.13g/kg diet) or phytin (Calcium Magnesium phytate, 4.23g/kg diet). Phytin feeding reduced liver weight, hepatic concentrations of total lipids and triglyceride, and hepatic activities of glucose-6-phosphate dehydrogenase (G6PD, EC 1.1.1.49), malic enzyme (ME, EC 1.1.1.40) and fatty acid synthetase (FAS, EC 2.3.1.85) in rats fed the sucrose-based diet as well as myo-inositol or phytate. Dietary phytate had no influence on intestinal activities of enzymes including sucrase (EC 3.2.1.48). We speculated that the ameliorative effect of dietary myo-inositol, phytate or phytin on sucrose-induced fatty liver is not mediated through altering intestinal absorption of sucrose.

Growth, feed conversion, body composition and nutrient retention efficiencies in fingerling catfish, Heteropneustes fossilis (Bloch), fed different sources of dietary carbohydrate

Growth, conversion efficiency, body composition, nutrient retention and plasma glucose concentration were evaluated in fingerling catfish, Heteropneustes fossilis (Bloch), (3.25 ± 0.1 g) fed iso-nitrogenous (40% crude protein) and iso-caloric (4.7 kcal g–1 gross energy) test diets containing different sources of carbohydrates (i.e. glucose, fructose, maltose, sucrose, dextrin, pre-cooked corn-starch or α- cellulose) at the 20% level of inclusion. Each dietary treatment had three replicates of 20 fish each. The growth trial was conducted in 70-L high-density polyvinyl flow-through (1–1.5 L min–1) indoor circular troughs (water volume = 55 L). The catfish were fed to apparent satiation twice daily at 0800 and 1600 h for 6 days a week over ≈ 8 weeks. No significant (P > 0.05) differences were noted in the growth and feed conversion efficiencies when fish were fed the sucrose, dextrin and corn-starch diets. Similarly, growth and conversion efficiencies were similar (P > 0.05) in fish fed the glucose, fructose and maltose diets. The minimum growth and conversion efficiencies were found in fish fed the α-cellulose diet. Post-feeding glucose or maltose resulted in the maximum increase in plasma glucose, followed by sucrose, dextrin, fructose or corn-starch diets, over the 8-h sampling period. Post-feeding α-cellulose produced a relatively low (P > 0.05) variation in the plasma glucose level. Compared to the initial values, higher values of dry matter, crude protein, lipid and body energy, and lower percentages of ash were recorded in catfish fed different sources of carbohydrate. The maximum protein retention rate was seen in fish fed the dextrin diet, while a higher energy retention rate was observed in fish fed the sucrose-based diet. Dietary α-cellulose produced significantly (P < 0.05) lower values of protein and energy retention in fish. The present study indicates that utilization of complex carbohydrates in catfish is more successful with di- and monosaccharides, while dietary α-cellulose is poorly utilized.

A Sucrose-Based Maintenance Diet Increases Sensitivity to Appetite Suppressant Effects of Naloxone

Rats maintained under restricted access to food (but at 100% free-feeding weights) received one of two diets in their home cages: a palatable sucrose-based diet, or regular chow (grain based diet), and could respond for either sucrose- or grain-based reinforcers under an FR 40 reinforcement schedule (crossover design). Naloxone (0, 0.1,0.3, 1.0, and 3.0 mg/kg) was more potent in reducing operant-chamber responding in rats maintained on a sucrose-based diet in their home cages than those fed a grain-based diet, regardless of the type of pellets available in the operant chambers. Whereas naloxone decreased response rate over the session, it had no effect on initiation of responding. Results support the hypothesis that opioids are involved in the maintenance, but not the initiation of consummatory behavior. Furthermore, increased potency of naloxone following chronic ingestion of palatable food is similar to that observed following chronic opiate administration, suggesting a relationship between palatability and opioids.

Both Lipolysis and Hepatic Uptake of VLDL Are Impaired in Transgenic Mice Coexpressing Human Apolipoprotein E*3Leiden and Human Apolipoprotein C1

Transgenic mice overexpressing human APOE*3Leiden are highly susceptible to diet-induced hyperlipoproteinemia and atherosclerosis due to a defect in hepatic uptake of remnant lipoproteins. In addition to the human APOE*3Leiden gene, these mice carry the human APOC1 gene (APOE*3Leiden-C1). To investigate the possible effect of simultaneous expression of the human APOC1 gene, we examined the phenotypic expression in these APOE*3Leiden-C1 mice in relation to transgenic mice expressing the APOE*3Leiden gene without the APOC1 gene (APOE*3Leiden-HCR). APOE*3Leiden-C1 and APOE*3Leiden-HCR mice had comparable liver expression for the APOE*3Leiden transgene and high total cholesterol levels on a sucrose-based diet compared with control mice (4.3 and 4.3 versus 2.1 mmol/L). In addition, on this diet APOE*3Leiden-C1 mice displayed significantly higher serum triglyceride levels than APOE*3Leiden-HCR mice and control mice (4.4 versus 0.6 and 0.2 mmol/L). Elevated triglyceride and cholesterol levels were mainly in the VLDL-sized lipoproteins. In vivo turnover studies with endogenously triglyceride-labeled VLDL showed a reduced VLDL triglyceride fractional catabolic rate for APOE*3Leiden-C1 and APOE*3Leiden-HCR mice compared with control mice (3.5 and 11.0 versus 20.4 pools per hour). To study whether the difference in fractional catabolic rates between the two transgenic strains was due to an inhibiting effect of apoC1 on the extrahepatic lipolysis or hepatic-mediated uptake of VLDL, turnover experiments were performed in functionally hepatectomized mice. Strikingly, both APOE*3Leiden-C1 and APOE*3Leiden-HCR mice showed a decreased lipolytic rate of VLDL triglyceride in the extrahepatic circulation compared with control mice (1.5 and 1.8 versus 6.3 pools per hour). We conclude that next to an impaired hepatic uptake, overexpression of the APOE*3Leiden gene influences the extrahepatic lipolysis of VLDL triglycerides, whereas simultaneous overexpression of the APOC1 gene leads to a further decrease in hepatic clearance of VLDL.

Gut-specific genes from the black fly Simulium vittatum encoding trypsin-like and carboxypeptidase-like proteins.

In haematophagous insects digestion of the blood meal provides nutrients for survival and essential components for egg production. We have isolated and partially characterized two gut-specific genes from the black fly Simulium vittatum. Sequence analysis revealed that both are highly similar to digestive proteases, one to trypsins and the other to carboxypeptidases. RNA blot analysis indicates that the expression of these two genes is regulated in a sex-specific manner; when fed the same sucrose-based diet, expression in males is substantially lower than in females. In females, expression of both genes is strongly induced by a blood meal. At 6 h after the blood meal the trypsin-like gene product was immunolocalized to the midgut epithelium and to the outer layers of the peritrophic matrix.

Sucrose as an energy source for growing pigs: energy utilization for protein deposition

ABSTRACTAn experiment was conducted to determine the effect of sucrose as an energy source on energy utilization and protein retention by growing pigs. Growing pigs (20 to 50 kg live weight) were restrictively fed (three times maintenance) either a control wheat-based diet (14 MJ digestible energy (DE) per kg), a sucrose-based diet (15 MJ DE per kg) or a wheat-based diet made i so-energetic with the sucrose diet by the addition of oil. Net energy (NE) content of the diet, energy utilization, protein and fat deposition were measured.Both the sucrose- and the iso-energetic wheat-based diets improved energy utilization and increased NE retention. They also increased fat deposition (P &lt; 0·05) but had no effect on protein deposition (P &gt; 0·05) compared with the wheat-based control. Increased DE utilization in the sucrose-based diet appeared due to (i) lower dietary fibre, (ii) a better balance of amino acids, or possibly due to (iii) increased fat synthesis due to sucrose metabolism. The lack of effect of sucrose on protein deposition appeared due to either (i) an increased amino acid requirement as a result of the higher NE content of the diet or (ii) preferential use of sucrose for fat deposition.

Role of Chromium in Barley in Modulating the Symptoms of Diabetes

In adult diabetic rats, a diet containing barley had a modulating effect on the symptoms of diabetes (blood glucose concentration and water consumption) when compared with a starch or sucrose-based diet. It was postulated that the beneficial effect of barley might be explained by its very high content of chromium (5.69 micrograms/g). Supplementation of the sucrose-based diet with an amount of trivalent inorganic chromium calculated to be equivalent to the available chromium in the barley-based diet abolished the differences in response to the diabetic state.

Modified behavioral and olfactory bulb responses to maternal odors in preweanling rats

Rat pups acquire an attraction for maternal odors, which can vary with maternal diet. In the two experiments reported here, maternal diet was modified and both pup behavioral responses and pup olfactory bulb neural responses ([ 14C]2-DG uptake) to maternal odors were examined. In experiment 1, pups were reared from birth to postnatal day 19 with either a dam fed normal rat chow or a dam fed a sucrose-based diet which suppressed her normal maternal odor. In experiment 2, pups were raised from birth to postnatal day 19 with either a dam fed the sucrose-based diet adulterated with peppermint, or the non-scented sucrose-based diet. Pups selectively expressed both a behavioral attraction and an enhanced olfactory bulb neural response to odors that they experienced in the nest.

Active hepatic glycogen synthesis from gluconeogenic precursors despite high tissue levels of fructose 2,6-bisphosphate.

When fasted rats ate regular lab chow there was a lag time of about 2 h before the concentration of fructose 2,6-bisphosphate (Fru-2,6-P2) in liver began to rise from its low basal level. By contrast, in animals refed on a sucrose-based diet hepatic [Fru-2,6-P2] increased 20-fold (to a value of approximately 12 nmol/g wet weight) during the first hour. These responses correlated with differences in the ability of the two diets to increase the circulating [insulin]/[glucagon] ratio and thus to elevate the ratio of 6-phosphofructo-2-kinase to fructose-2, 6-bisphosphatase. Liver glycogen was deposited briskly in both groups of rats. To assess its mechanism of synthesis (directly from glucose versus indirectly via the gluconeogenic pathway), animals eating the chow or sucrose diets received intravenous infusions of [14C]bicarbonate, [1-14C] fructose, and 3H2O. After isolation, the glycogen was subjected to positional isotopic analysis of its glucose residues. The results established that regardless of the diet the bulk of liver glycogen was gluconeogenic in origin. The fact that with sucrose feeding carbon flow through hepatic fructose-1,6-bisphosphatase remained active despite high levels of Fru-2,6-P2 (a potent inhibitor of this enzyme in vitro) presents a metabolic paradox. Conceivably, the suppressive effect of Fru-2, 6-P2 on hepatic fructose-1,6-bisphosphatase is overridden in vivo by some unknown factor or factors generated in response to sucrose feeding. Alternatively, metabolic zonation in liver might result in the coexistence of hepatocytes rich in Fru-2,6-P2 (high glycolytic, low gluconeogenic, low glycogenic capacitites) with cells depleted of Fru-2,6-P2 (low glycolytic, high gluconeogenic, high glycogenic capacities).

The relationship between the number of the bacterium Streptococcus mutans at discrete sites on the dentition of macaque monkeys ( Macaca fascicularis) and the subsequent development of dental caries

Sixteen consecutively-born monkeys were used in a longitudinal study to determine the changes occurring in the total number of bacteria in the palatal grooves of the upper left first deciduous molar teeth, following the introduction of a sucrose-based diet. The total number of bacteria recovered from the grooves increased significantly following the diet change. Twenty-nine days after the diet change, the number of Streptococcus mutons had increased from a median value of less than 10 2 to approx. 10 7 per groove, and the number of Streptococcus sanguis decreased. These changes in the number of Strep. mutans occurred prior to the detection of dental caries. Grooves that became carious harboured significantly more bacteria and more Strep, mutans than did grooves remaining caries-free six months after the diet change.