Pre-type 1 diabetes dysmetabolism: maximal sensitivity achieved with both oral and intravenous glucose tolerance testing

OBJECTIVE

To determine the relationship of intravenous (IVGTT) and oral (OGTT) glucose tolerance tests abnormalities to diabetes development in a high-risk pre-diabetic cohort and to identify an optimal testing strategy for detecting preclinical diabetes.

STUDY DESIGN

Diabetes Prevention Trial-Type 1 Diabetes (DPT-1) randomized subjects to oral (n = 372) and parenteral (n = 339) insulin prevention trials. Subjects were followed with IVGTTs and OGTTs. Factors associated with progression to diabetes were evaluated.

RESULTS

Survival analysis revealed that higher quartiles of 2-hour glucose and lower quartiles of first phase insulin response (FPIR) at baseline were associated with decreased diabetes-free survival. Cox proportional hazards modeling showed that baseline body mass index (BMI), FPIR, and 2-hour glucose levels were significantly associated with an increased hazard for diabetes. On testing performed within 6 months of diabetes diagnosis, 3% (1/32) had normal FPIR and normal 2-hour glucose on OGTT. The sensitivities for impaired glucose tolerance (IGT) and low FPIR performed within 6 months of diabetes diagnosis were equivalent (76% vs 73%).

CONCLUSIONS

Most (97%) subjects had abnormal IVGTTs and/or OGTTs before the development of diabetes. The highest sensitivity is achieved using both tests.

Effects of hunger state on flavour pleasantness conditioning at home: Flavour–nutrient learning vs. flavour–flavour learning

This study examined acquired liking of flavour preferences through flavour-flavour and flavour-nutrient learning under hungry or sated conditions in a naturalistic setting. Each participant consumed one of three versions of a test drink at home either before lunch or after lunch: minimally sweetened (

CONTROL

3% sucrose, 40 kcal), artificially sweetened (3% sucrose 40 kcal plus artificial sweeteners ASPARTAME) and sucrose-sweetened (SUCROSE: 9.9% sugar, 132 kcal). The test drink was an uncarbonated peach-flavoured iced tea served in visually identical drink cans (330 ml). Participants preselected as "sweet likers" evaluated the minimally sweetened flavoured drink (conditioned stimulus, CS) in the same state (hungry or sated) in which they consumed the test drink at home. Overall, liking for the CS flavour increased in participants who consumed the SUCROSE drink, however, this increase in liking was significantly larger when tested and trained hungry than sated, consistent with a flavour-nutrient model. Overall increases in pleasantness for the CS flavour in participants who consumed the SUCROSE drink when sated or the ASPARTAME drink independent of hunger state, suggest that flavour-flavour learning also occurred. These results are discussed in light of current learning models of flavour preference.

Threshold for Transitory Diarrhea Induced by Ingestion of Xylitol and Lactitol in Young Male and Female Adults

The ingestion of a sufficiently large amount of non-digestible and/or non-absorbable sugar substitutes causes overt diarrhea. The objective is to estimate the non-effective dosage that does not cause transitory diarrhea for xylitol, lactitol, and erythritol in healthy subjects. Twenty-seven males and 28 females gave informed and written consent to participate, were selected, and participated in the study. The oral dose levels of xylitol were 10, 20, 30, 40 and 50 g, while those of lactitol were 10, 20, 30, and 40 g. Those of erythritol were 20, 30, 40 and 50 g. The test substance was ingested in 150 mL of water 2-3 h after a meal. The ingestion order progressed from the smallest to larger amounts, and stopped at the dose that caused diarrhea, or at the largest dose level to be set up. The non-effective dose level of xylitol was 0.37 g/kg B.W. for males and 0.42 g/kg B.W. for females. That of lactitol was 0.25 g/kg B.W. for males and 0.34 g/kg B.W. for females, and that of erythritol was 0.46 g/kg B.W. for males and 0.68 g/kg B.W. for females. These results appear reasonable, because xylitol is poorly absorbed from the small intestine, and the absorption rate is less than that of erythritol, while lactitol is not hydrolyzed. Non-digestible and/or non-absorbable sugar alcohols and oligosaccharides with beneficial health effects inevitably cause overt diarrhea. The estimation of the non-effective dose level of these sugar substitutes is essential and important to produce processed foods that the consumer can use safely and with confidence.

Artificial sweeteners and cancer risk in a network of case–control studies

BACKGROUND

The role of sweeteners on cancer risk has been widely debated over the last few decades. To provide additional information on saccharin and other sweeteners (mainly aspartame), we considered data from a large network of case-control studies.

METHODS

An integrated network of case-control studies has been conducted between 1991 and 2004 in Italy. Cases were 598 patients with incident, histologically confirmed cancers of the oral cavity and pharynx, 304 of the oesophagus, 1225 of the colon, 728 of the rectum, 460 of the larynx, 2569 of the breast, 1031 of the ovary, 1294 of the prostate and 767 of the kidney (renal cell carcinoma). Controls were 7028 patients (3301 men and 3727 women) admitted to the same hospitals as cases for acute, non-neoplastic disorders. Odds ratios (ORs), and the corresponding 95% confidence intervals (CIs), were derived by unconditional logistic regression models.

RESULTS

The ORs for consumption of saccharin were 0.83 (95% CI 0.30-2.29) for cancers of the oral cavity and pharynx, 1.58 (95% CI 0.59-4.25) for oesophageal, 0.95 (95% CI 0.67-1.35) for colon, 0.93 (95% CI 0.60-1.45) for rectal, 1.55 (95% CI 0.76-3.16) for laryngeal, 1.01 (95% CI 0.77-1.33) for breast, 0.46 (95% CI 0.29-0.74) for ovarian, 0.91 (95% CI 0.59-1.40) for prostate and 0.79 (95% CI 0.49-1.28) for kidney cancer. The ORs for consumption of other sweeteners, mainly aspartame, were 0.77 (95% CI 0.39-1.53) for cancers of the oral cavity and pharynx, 0.77 (95% CI 0.34-1.75) for oesophageal, 0.90 (95% CI 0.70-1.16) for colon, 0.71 (95% CI 0.50-1.02) for rectal, 1.62 (95% CI 0.84-3.14) for laryngeal, 0.80 (95% CI 0.65-0.97) for breast, 0.75 (95% CI 0.56-1.00) for ovarian, 1.23 (95% CI 0.86-1.76) for prostate and 1.03 (95% CI 0.73-1.46) for kidney cancer. A significant inverse trend in risk for increasing categories of total sweeteners was found for breast and ovarian cancer, and a direct one for laryngeal cancer.

CONCLUSION

The present work indicates a lack of association between saccharin, aspartame and other sweeteners and the risk of several common neoplasms.

Effects of intravenous glucose on dopaminergic function in the human brain in vivo

Dopamine is known to regulate food intake by modulating food reward via the mesolimbic circuitry of the brain. The objective of this study was to compare the effects of high energy input (i.v. glucose) on striatal and thalamic dopamine release in overweight and lean individuals. We hypothesized that glucose would induce dopamine release and positive ratings (e.g., satiety) in Behavioral Analog Scales, particularly in food-deprived lean subjects. [(11)C]raclopride PET was performed for 12 lean (mean BMI = 22 kg/m(2)) and 12 overweight (mean BMI = 33 kg/m(2)) healthy subjects. Each subject was imaged twice in a blinded counter-balanced setting, after 300 mg/kg i.v. glucose and after i.v. placebo. Dopamine D2 receptor binding potentials (BPs) were estimated. The voxel-based analysis of the baseline scans indicated lower striatal BPs in the overweight group and a negative correlation between BMIs and BPs. Intravenous glucose did not have a significant effect on BPs in overweight or lean subjects (male and female groups combined). However, BP changes were opposite in the two gender groups. In male subjects, significant BP reductions after glucose were seen in the right and left caudate nucleus, left putamen, and right thalamus. In female subjects, increases in BP secondary to glucose were seen in the right caudate nucleus and right and left putamen. The sexually dimorphic effect of glucose was seen in both overweight and lean subjects. Although gender differences were not among the a priori hypotheses of the present study and, therefore, they must be considered to be preliminary findings, we postulate that this observation is a reflection of an interaction between glucose, sex steroids (estrogen), leptin, and dopamine.

Caffeine as a flavor additive in soft-drinks

Over 60% of soft-drinks sold in the United States contain caffeine, a mildly addictive psycho-active chemical, as a flavor additive. Using sweeteners as controls, we assessed whether caffeine has flavor activity in a cola soft-drink. A forced-choice triangle discrimination methodology was used to determine detection thresholds of caffeine in sweeteners and a cola beverage. The subjects (n=30, 28 female, 23+/-4 years old) were trained tasters and completed over 1600 discrimination tests during the study. The mean detection thresholds for caffeine in the sweet solutions were: 0.333+/-0.1mM sucrose; 0.467+/-0.29 mM aspartame; 0.462+/-0.3mM sucralose, well below the concentration in common cola beverages (0.55-0.67 mM). A fixed concentration of caffeine, corresponding to the concentration of caffeine in a common cola beverage (0.67 mM) was added to the sweeteners and a non-caffeinated cola beverage. Subjects could distinguish between caffeinated and non-caffeinated sweeteners (p<0.001), but all subjects failed to distinguish between caffeinated and non-caffeinated cola beverage (p=1.0). Caffeine has no flavor activity in soft-drinks yet will induce a physiologic and psychologic desire to consume the drink.

[Restless legs due to ingestion of 'light' beverages containing saccharine; results of an N-of-1 trial]

OBJECTIVE

To determine whether there was a connection between the complaint of restless legs and the ingestion of artificial sweeteners in a patient with these symptoms after drinking certain 'light' beverages.

DESIGN

Randomised, double-blind, placebo-controlled N-of-1 trial with a cross-over design.

METHOD

During a period of 48 days, the patient took 4 capsules per day containing either 150 mg of cyclamate, 22.5 mg of saccharine, both sweeteners, or placebo on two successive days. Between each of these 2-day periods there was a 2-day rest period during which no capsules were taken. The hospital pharmacist had prepared the capsules and determined the sequence of the 2-day periods on a random basis. The patient did not know which capsules he was taking. Every day on arising, starting 3 weeks before the trial period, the patient noted the intensity and duration of the symptoms in the late evening and previous night. For this notation he used an 11-point scale, from 0 (= no restless legs) to 10 (= almost total inability to sleep because of restless legs).

RESULTS

A score of 1-3 corresponded to mild symptoms that had no effect on the patient's sleep; at a score of 4-6 his sleep was disturbed and at a score of 7-10 the patient hardly slept at all. The patient had symptoms more often while using saccharine or the combination of saccharine and cyclamate than when taking the placebo (4 and 4 versus 2 ofthe 6 nights); moreover, the average score was then statistically significantly higher (5.2 and 5.8 versus 3.3).

CONCLUSION

There was a connection between the patient's complaints of restless legs and the use of saccharine, but not the use of cyclamate.

Results of long-term carcinogenicity bioassay on Sprague-Dawley rats exposed to aspartame administered in feed

Aspartame (APM) is one of the most widely used artificial sweeteners in the world. Its ever-growing use in more than 6000 products, such as soft drinks, chewing gum, candy, desserts, etc., has been accompanied by rising consumer concerns regarding its safety, in particular its potential long-term carcinogenic effects. In light of the inadequacy of the carcinogenicity bioassays performed in the 1970s and 1980s, a long-term mega-experiment on APM was undertaken at the Cesare Maltoni Cancer Research Center of the European Ramazzini Foundation on groups of male and female Sprague-Dawley rats (100-150/sex/group), 8 weeks old at the start of the experiment. APM was administered in feed at concentrations of 100,000, 50,000, 10,000, 2,000, 400, 80, or 0 ppm. Treatment lasted until spontaneous death of the animals. The results of the study demonstrate that APM causes: (a) an increased incidence of malignant tumor-bearing animals, with a positive significant trend in both sexes, and in particular in females treated at 50,000 ppm (P < or = 0.01) when compared to controls; (b) an increase in lymphomas-leukemias, with a positive significant trend in both sexes, and in particular in females treated at doses of 100,000 (P < or = 0.01), 50,000 (P < or = 0.01), 10,000 (P < or = 0.05), 2000 (P < or = 0.05), and 400 ppm (P < or = 0.01); (c) a statistically significant increased incidence, with a positive significant trend, of transitional cell carcinomas of the renal pelvis and ureter in females and particularly in those treated at 100,000 ppm (P < or = 0.05); and (d) an increased incidence of malignant schwannomas of the peripheral nerves, with a positive trend in males (P < or = 0.05). The results of this mega-experiment indicate that APM, in the tested experimental conditions, is a multipotential carcinogenic agent.

A 4-wk high-fructose diet alters lipid metabolism without affecting insulin sensitivity or ectopic lipids in healthy humans

BACKGROUND

High fructose consumption is suspected to be causally linked to the epidemics of obesity and metabolic disorders. In rodents, fructose leads to insulin resistance and ectopic lipid deposition. In humans, the effects of fructose on insulin sensitivity remain debated, whereas its effect on ectopic lipids has never been investigated.

OBJECTIVE

We assessed the effect of moderate fructose supplementation on insulin sensitivity (IS) and ectopic lipids in healthy male volunteers (n = 7).

DESIGN

IS, intrahepatocellular lipids (IHCL), and intramyocellular lipids (IMCL) were measured before and after 1 and 4 wk of a high-fructose diet containing 1.5 g fructose . kg body wt(-1) . d(-1). Adipose tissue IS was evaluated from nonesterified fatty acid suppression, hepatic IS from suppression of hepatic glucose output (6,6-2H2-glucose), and muscle IS from the whole-body glucose disposal rate during a 2-step hyperinsulinemic euglycemic clamp. IHCL and IMCL were measured by 1H magnetic resonance spectroscopy.

RESULTS

Fructose caused significant (P < 0.05) increases in fasting plasma concentrations of triacylglycerol (36%), VLDL-triacylglycerol (72%), lactate (49%), glucose (5.5%), and leptin (48%) without any significant changes in body weight, IHCL, IMCL, or IS. IHCL were negatively correlated with triacylglycerol after 4 wk of the high-fructose diet (r = -0.78, P < 0.05).

CONCLUSION

Moderate fructose supplementation over 4 wk increases plasma triacylglycerol and glucose concentrations without causing ectopic lipid deposition or insulin resistance in healthy humans.

Nicotine does not produce state-dependent effects on learning in a Pavlovian appetitive goal tracking task with rats

Past research has shown that when rats received 0.4mg base/kg nicotine paired reliably with intermittent sucrose delivery that anticipatory sucrose-seeking behavior (i.e., goal tracking) was differentially displayed in the nicotine state relative to intermixed saline sessions in which no sucrose was delivered. The present research extended this observation to a lower dose of nicotine (i.e., 0.2mg base/kg) and tested a state-dependent learning account of differential conditioned responding. According to this account, the increase in goal tracking on nicotine sessions reflects a chamber-sucrose association that is only recalled when in the nicotine state. We used a 2x2 factorial design in which rats received sucrose deliveries in one drug state (nicotine or saline) and were then tested in the same state (Nic-->Nic or Sal-->Sal) or a different state (Nic-->Sal or Sal-->Nic) after acquiring the conditioned response. A state-dependency account predicts disruption in conditioned goal tracking for rats that receive a shift in drug state on the test day. This disruption did not occur suggesting that differential control of conditioned responding by nicotine is more likely due to a direct excitatory association between the interoceptive cueing effects of nicotine and the appetitive qualities of sucrose.

Sucrose analgesia: identifying potentially better practices

OBJECTIVE

The objectives of this study were to review the use of oral sucrose for procedural pain management in NICUs, develop potentially better practice guidelines that are based on the best current evidence, and provide ideas for the implementation of these potentially better practices.

METHODS

A collaboration of 12 centers of the Vermont Oxford Network worked together to review the strength of the evidence, clinical indications, dosage, administration, and contraindications and identify potential adverse effects for the use of sucrose analgesia as the basis of potentially better practices for sucrose analgesia guidelines. Several units implemented the guidelines.

RESULTS

Through reviews and inputs from all centers of the evidence, consensus was reached and guidelines that included indication, dosage per painful procedure, age-related dosage over 24 hours, method of delivery, and contraindications were developed.

CONCLUSIONS

Guidelines now are available from a consensus group, and suggestions for implementation of guidelines, based on implementation of other pain management strategies, were developed.

Implementation and case-study results of potentially better practices to improve pain management of neonates

OBJECTIVE

Collaborative quality improvement techniques were used to facilitate local quality improvement in the management of pain in infants. Several case studies are presented to highlight this process.

METHODS

Twelve NICUs in the Neonatal Intensive Care Quality Improvement Collaborative 2002 focused on improving neonatal pain management and sedation practices. These centers developed and implemented evidence-based potentially better practices for pain management and sedation in neonates. The group introduced changes through plan-do-study-act cycles and tracked performance measures throughout the process.

RESULTS

Strategies for implementing potentially better practices varied between centers on the basis of local characteristics. Individual centers identified barriers to implementation, developed tools for improvement, and shared their experience with the collaborative. Baseline data from the 12 sites revealed substantial opportunities for improved pain management, and local potentially better practice implementation resulted in measurable improvements in pain management at participating centers.

CONCLUSIONS

The use of collaborative quality improvement techniques enhanced local quality improvement efforts and resulted in effective implementation of potentially better practices at participating centers.

Xylitol concentration in saliva and dental plaque after use of various xylitol-containing products

The study consisted of two sets of experiments, one in saliva and one in dental plaque. The xylitol concentration in saliva was determined enzymatically in 12 children (mean age 11.5 years) after a standardised use of various xylitol products: (A) chewing gums (1.3 g xylitol), (B) sucking tablets (0.8 g xylitol), (C) candy tablets (1.1 g xylitol), (D) toothpaste (0.1 g xylitol), (E) rinse (1.0 g xylitol), and (F) a non-xylitol paraffin. Unstimulated saliva was sampled 1, 3, 8, 16 and 30 min after use. The concentration in dental plaque was determined after mouthrinses with contrasting amounts of xylitol (LX = 2.0 g, HX = 6.0 g, and control) and supragingival plaque was collected and pooled after 5, 15 and 30 min. The mean xylitol concentration in saliva at baseline was approximately 0.1 mg/ml. All xylitol-containing products resulted in significantly increased levels (p < 0.05) immediately after intake and remained elevated for 8-16 min in the different groups. The highest mean value in saliva was obtained immediately after use of chewing gums (33.7 +/- 16.4 mg/ml) and the lowest was demonstrated after using toothpaste (8.2 +/- 4.9 mg/ml). No significant differences were demonstrated between chewing gums (A), sucking tablets (B), candy (C) and rinses (E). In dental plaque, the mean values were 8.6 +/- 5.4 and 5.1 +/- 4.0 mg/ml 5 min after HX and LX rinses. Concerning the higher concentration, the values remained significantly elevated (p < 0.05) during the entire 30-min follow-up. In conclusion, commonly advocated xylitol-containing products gave elevated concentrations of xylitol in unstimulated whole saliva and dental plaque for at least 8 min after intake.

Chronobiological disturbances with hyperthermia and hypercortisolism induced by chronic mild stress in rats

The chronic mild stress (CMS) model has been established as a realistic model of depressive disorder as it simulates anhedonia. In the present study, the consumption of sucrose solution was decreased in the rats exposed to CMS, which coincided with many published studies. Since depression is a multifaceted disorder, and a number of symptoms may be present, including circadian rhythm disturbances, we attempted to find the chronobiological abnormalities in CMS rats. After 4-week of the stress procedure, the rhythmic pattern of rectal temperature in the CMS group was extinguished. In particular, the temperature in the CMS group in the light phase was significantly higher than that in the control group. The plasma corticosterone levels in the CMS group were remarkably increased in the light phase compared to the control group, but not in the dark phase. It was concluded that the CMS procedure caused the disturbance of circadian rhythms with hyperthermia and hypercortisolism.

Acute hepatic failure and coagulopathy associated with xylitol ingestion in eight dogs

CASE DESCRIPTION

8 adult dogs were evaluated for treatment of lethargy and vomiting after ingestion of xylitol, a sugar alcohol used as a sweetener in various products.

CLINICAL FINDINGS

In addition to vomiting and lethargy, 5 of the dogs had widespread petechial, ecchymotic, or gastrointestinal tract hemorrhages. Common clinicopathologic findings included moderately to severely high serum activities of liver enzymes, hyperbilirubinemia, hypoglycemia, hyperphosphatemia, prolonged clotting times, and thrombocytopenia. Necropsies were performed on 3 dogs and severe hepatic necrosis was found in 2. In the third dog, histologic examination revealed severe hepatocyte loss or atrophy with lobular collapse.

TREATMENT AND OUTCOME

Treatments varied among dogs and included IV administration of fluids; plasma transfusions; and, if indicated, administration of dextrose. Three dogs were euthanatized, 2 dogs died, 2 dogs made a complete recovery, and 1 dog was recovering but was lost to follow-up.

CLINICAL RELEVANCE

Although xylitol causes hypoglycemia in dogs, hepatic failure after ingestion has not previously been reported. Because an increasing number of consumer products contain xylitol, clinicians should be aware that ingestion of xylitol can have serious, life-threatening effects.

Forebrain structures specifically activated by conditioned taste aversion

This study investigates which forebrain structures show Fos protein expression during conditioned taste aversion (CTA) acquisition and whether Fos expression depends on the aversion strength. A novel taste paired with an intraperitoneal injection of a low dose of the malaise-inducing agent lithium chloride (LiCl) induced a weak CTA, whereas associating this novel taste with a high dose of LiCl induced a strong CTA. Increasing the strength of the gastric malaise alone enhanced Fos expression in central, basal, and lateral amygdala nuclei and decreased Fos expression in the nucleus accumbens core. Taste-malaise association induced specific Fos activation in the insular cortex (with both the low and the high doses of LiCl) and the nucleus accumbens shell (with the high LiCl dose only). No significant variation of Fos expression was measured in the perirhinal cortex. Several forebrain areas may be sites of taste-malaise convergence during CTA acquisition depending on the strength of the aversion.

Gastrointestinal tolerance of erythritol and xylitol ingested in a liquid

OBJECTIVES

To determine and compare the gastrointestinal (GI) responses of young adults following consumption of 45 g sucrose, 20, 35 and 50 g xylitol or erythritol given as a single oral, bolus dose in a liquid.

DESIGN

The study was a randomized, double-blind, placebo-controlled study.

SUBJECTS

Seventy healthy adult volunteers aged 18-24 years were recruited from the student population of the University of Salford. Sixty-four subjects completed the study.

INTERVENTIONS

Subjects consumed at home without supervision and in random order, either 45 g sucrose or 20, 35 and 50 g erythritol or xylitol in water on individual test days, while maintaining their normal diet. Test days were separated by 7-day washout periods. Subjects reported the prevalence and magnitude of flatulence, borborygmi, bloating, colic, bowel movements and the passage of faeces of an abnormally watery consistency.

RESULTS

Compared with 45 g sucrose, consumption of a single oral, bolus dose of 50 g xylitol in water significantly increased the number of subjects reporting nausea (P<0.01), bloating (P<0.05), borborygmi (P<0.005), colic (P<0.05), watery faeces (P<0.05) and total bowel movement frequency (P<0.01). Also 35 g of xylitol increased significantly bowel movement frequency to pass watery faeces (P<0.05). In contrast, 50 g erythritol only significantly increased the number of subjects reporting nausea (P<0.01) and borborygmi (P<0.05). Lower doses of 20 and 35 g erythritol did not provoke a significant increase in GI symptoms. At all levels of intake, xylitol produced significantly more watery faeces than erythritol: resp. 50 g xylitol vs 35 g erythritol (P<0.001), 50 g xylitol vs 20 g erythritol (P<0.001) and 35 g xylitol vs 20 g erythritol (P<0.05).

CONCLUSIONS

When consumed in water, 35 and 50 g xylitol was associated with significant intestinal symptom scores and watery faeces, compared to the sucrose control, whereas at all levels studied erythritol scored significantly less symptoms. Consumption of 20 and 35 g erythritol by healthy volunteers, in a liquid, is tolerated well, without any symptoms. At the highest level of erythritol intake (50 g), only a significant increase in borborygmi and nausea was observed, whereas xylitol intake at this level induced a significant increase in watery faeces.

Mutans streptococci dose response to xylitol chewing gum

Xylitol is promoted in caries-preventive strategies, yet its effective dose range is unclear. This study determined the dose-response of mutans streptococci in plaque and unstimulated saliva to xylitol gum. Participants (n = 132) were randomized: controls (G1) (sorbitol/maltitol), or combinations giving xylitol 3.44 g/day (G2), 6.88 g/day (G3), or 10.32 g/day (G4). Groups chewed 3 pellets/4 times/d. Samples were taken at baseline, 5 wks, and 6 mos, and were cultured on modified Mitis Salivarius agar for mutans streptococci and on blood agar for total culturable flora. At 5 wks, mutans streptococci levels in plaque were 10x lower than baseline in G3 and G4 (P = 0.007/0.003). There were no differences in saliva. At 6 mos, mutans streptococci in plaque for G3 and G4 remained 10x lower than baseline (P = 0.007/0.04). Saliva for G3 and G4 was lower than baseline by 8 to 9x (P = 0.011/0.038). Xylitol at 6.44 g/day and 10.32 g/day reduces mutans streptococci in plaque at 5 wks, and in plaque and unstimulated saliva at 6 mos. A plateau effect is suggested between 6.44 g and 10.32 g xylitol/day.

Different signal transduction cascades are activated simultaneously in the rat insular cortex and hippocampus following novel taste learning

Novel taste learning is a robust one-trial incidental learning process, dependent on functional activity of the insular (taste) cortex. In contrast to that of the cortex, the role of the hippocampus in taste learning is controversial. We set out to identify the time courses of the activation of mitogen-associated protein kinase (MAPK), transcription factor cAMP-response element-binding protein (CREB) and Akt/PKB (protein kinase B) in the insular cortex and hippocampus of rats subsequent to novel taste learning. Following taste learning, an early response (20 min) occurred at the same time in the insular cortex and the hippocampus. However, whereas MAPK was activated specifically in the insular cortex, CREB and Akt were phosphorylated in the hippocampus but not in the cortex. In addition, the immediate early gene, CCAAT/enhancer binding protein (C/EBPbeta) was induced in both the hippocampus and the insular cortex 18 h following taste learning. The results demonstrate, for the first time, correlative activation and gene expression in the hippocampus following novel taste learning. Moreover, the results suggest that different signal transduction cascades necessary for taste learning are activated in concert in different brain structures, to enable taste learning and consolidation.

Dissociation of conditioned and unconditioned factors in the running-induced feeding suppression

In adult rats, running wheel introduction induces a 7 to 10 day feeding suppression, either due to a learned conditioned taste avoidance or to the direct unconditioned effects of wheel running. The three experiments investigated the effects of wheel introduction on familiar (rat chow) and novel (24% sucrose solution) food consumption (Experiment 1), and then explored how alternate-day wheel access affected sucrose consumption when it was novel (Experiment 2) or familiar (Experiment 3). When paired with wheel introduction the consumption of a novel sucrose solution was completely suppressed for an extended period, whether the rats had continuous or alternate-day wheel access. In contrast, familiar food consumption was suppressed, for a limited period, only on wheel days. When rats were pre-exposed to the sucrose, consumption was suppressed only on wheel days. The results suggest that in addition to the direct unconditioned effects of wheel running on feeding, learning factors may influence the feeding suppression observed and thus wheel introduction supports a learned conditioned taste avoidance.

Effect of orally administered phenylalanine with and without glucose on insulin, glucagon and glucose concentrations

OBJECTIVE

As part of our studies of the metabolic effects of ingested proteins, we are currently investigating the effects of ingestion of individual amino acids. The objective of the present study was to determine whether ingested phenylalanine stimulates insulin and/or glucagon secretion, and if phenylalanine ingested with glucose modifies the insulin, glucagon or glucose response to the ingested glucose.

DESIGN

Six healthy subjects were tested on 4 separate occasions. Plasma phenylalanine, glucose, insulin, glucagon, and total alpha amino nitrogen (AAN) (i.e., total amino acids) concentrations were measured at various times during a 2.5 h period after ingestion of 1 mmol phenylalanine/kg lean body mass, 25 g glucose, 1 mmol phenylalanine/kg lean body mass+25 g glucose, or water only, given in random order.

RESULTS

Following phenylalanine ingestion, the circulating phenylalanine concentration increased approximately 14 fold and remained elevated for the duration of the experiment. Glucagon and AAN increased, insulin increased modestly, and glucose was unchanged when compared to water ingestion. When glucose was ingested with phenylalanine, the circulating phenylalanine, glucagon, AAN, and insulin area responses were approximately the sum of the responses to phenylalanine alone and glucose alone. However, the plasma glucose area response was decreased 66% when phenylalanine was co-ingested with glucose.

CONCLUSION

In summary, phenylalanine in an amount moderately greater than that in a large protein meal stimulates an increase in insulin and glucagon concentration. It markedly attenuates the glucose-induced rise in plasma glucose when ingested with glucose.

Effects of neuropeptide Y on feeding microstructure: Dissociation of appetitive and consummatory actions

The effects of intracerebroventricular application of Neuropeptide Y (NPY) on licking microstructure for sucrose, saccharin, and water solutions were evaluated. In Experiment 1, NPY increased meal size for three sucrose concentrations (0.03 M, 0.3 M, and 1.0 M) by increasing licking burst number but not size and by extending meals more than four-fold in duration with a slow, sustained rate of ingestion in late phases of the meal. Results are consistent with the interpretation that NPY suppressed inhibitory postingestive feedback. Experiment 2 supported this conclusion. NPY significantly increased the number of meals initiated for water, 0.1% saccharin, and 1.0 M sucrose solutions, but meal size was only increased for 1.0 M sucrose. Therefore, NPY also increased appetitive feeding behaviors, but its consummatory effects were limited to caloric solutions. The results are discussed with regard to their potential to explain current discrepancies in the literature.

Effects of posture on gastric emptying, transpyloric flow, and hunger after a glucose drink in healthy humans

Previous studies suggest that posture has relatively little effect on gastric emptying of high-nutrient liquids; these studies have, however, only assessed overall rates of gastric emptying, whereas gastric emptying is known to be predominantly a pulsatile phenomenon. In healthy subjects perceptions of appetite, such as hunger, are inversely related to antral area and content; hence, changes in intragastric meal distribution induced by posture may affect appetite. Gastric emptying is a major determinant of postprandial glycemia. The aims of this study were to evaluate the effects of posture on patterns of transpyloric flow (TF), gastric emptying (GE), antral area (AA), hunger, and the glycemic response to oral glucose. Eight healthy young subjects (five males, three females; mean age, 24.0 +/- 2.4 years; BMI, 21.2 +/- 0.6 kg/m2) were studied twice in random order, once in the sitting position and once in the lying (supine) position. After consuming 600 ml water with 75 g glucose, labeled with 20 MBq 99mTc-sulfur colloid, subjects had simultaneous measurements of (i) TF during consumption of the drink by Doppler ultrasonography, (ii) GE with scintigraphy, (iii) AA at t = -5 and t = 30 min by ultrasonography, and (iv) perceptions of appetite with a visual analogue scale. During drink ingestion TF was greater in the sitting, compared with the lying, position (586 +/- 170 vs. 177 +/- 65 [cm/sec] x sec; P < 0.05). Posture affected intragastric distribution; more of the drink was retained in the distal stomach in the sitting position (e.g., at 30 min: sitting, 29 +/- 3%, vs. lying, 12 +/- 3%; P < 0.0001) but had no effect on the overall rate of GE or the blood glucose response. AA at t = 30 min (P < 0.005) was greater in the sitting position; there was an inverse relationship between hunger and AA at 30 min (r = -0.53, P < 0.05). We conclude that posture influences initial TF and intragastric distribution, but not the overall rate of GE of, or the glycemic response to, a large-volume nutrient liquid. The increases in AA and content in the sitting position are associated with a reduction in hunger.