Quantitative trait loci associated with short-term intake of sucrose, saccharin and quinine solutions in laboratory mice.

The goal of this study was simultaneously to map two genetic loci which, collectively, have a large effect on intake of sucrose, saccharin and quinine solutions in mice. These loci had been previously identified using long-term measurements with the traditional two-bottle test, but the present study used a short-term, one-bottle test. Intake of distilled water, 100 mM sucrose, 10 mM sodium saccharin and 1.1 mM quinine HCl over 6 h was measured on two occasions from a non-deprived group of 61 male and 72 female F2 mice derived from a cross of the C57BL/6J and DBA/2J mouse strains and used to detect quantitative trait loci (QTL). DNA from each animal was typed for polymorphisms in anonymous microsatellite markers on mouse chromosomes 4 and 6. Saccharin and sucrose relevant QTL were detected on distal chromosome 4 and a quinine relevant QTL was detected on medial/distal chromosome 6 in the region of Prp. The location of these QTL and the proportion of phenotypic variance they accounted for were similar to those arrived at following previous determinations using the two-bottle test. Measurement stability for the three gustatory phenotypes was high, product-moment correlation coefficients between first and second determinations varying between approximately 0.80 for sucrose and saccharin and 0.73 for quinine. QTL parameters assessed independently for first and second presentations of sucrose and saccharin were stable, but the location of the quinine QTL differed between presentations. The present experiment illustrates the utility of a 6 h fluid intake test in the mapping of Sac and Qui loci. The short duration of the test provides a simple means of measuring variation in gustatory processes and the discovery that these loci influence short-term as well as long-term fluid intake extends understanding of the mechanism of gene action.     

A moment-by-moment comparsion of sucrose and saccharin drinking by the rat

Comparisons were made between the ingestion patterns in ratsto a 0.2% sodium saccharin solution and to a 32% sucrose solutionin both short-term (30 min, one solution only) and long-term(23 h, solution versus water) tests. The resolution of measurementin the short- and long-term tests was 0.5 and 30 s respectively.Analysis programs for both procedures allowed for a quantificationof the ingestion patterns over time, showing details of thelick bursts in the short-term tests and ingestion bouts in the23-h tests. Although the quantities of sucrose and saccharinconsumed in the long-term tests were equal, the drinking patternsfor water, saccharin and sucrose were markedly different duringthe three testing periods, (i) There were fewer drinking boutsto the sucrose than to the saccharin or water, (ii) The averagebout of sucrose was much larger than the saccharin or waterbouts, (iii) The inter-bout intervals for sucrose were muchlonger than those for saccharin, (iv) Nearly half of the sucroseintake occurred during the ‘lights-on’ portion ofthe 23-h drinking period as compared to less than one-thirdfor saccharin or water, (v) Food intake when saccharin was presentwas equal to normal food intake when only water was available.However, in the presence of sucrose, the number and the sizeof feeding bouts decreased resulting in a 36% reduction in foodintake. Similar results were found in the short-term tests whencomparing sucrose and saccharin ingestion in that the quantitiesconsumed were not reliably different, but the ingestion patternswere, (i) The rats had many more bursts of licking saccharinthan sucrose, (ii) The saccharin bursts were much shorter thanthose for sucrose, (iii) Saccharin licking occurred off andon throughout the 30-min testing period while sucrose was consumedat a rapid rate at first and then terminated in 10–15min from the period onset. Inferences about the different tastesof saccharin and sucrose to the rat arc drawn from the detailedpattern analyses.     

Intravenous administration of oxytocin in rats acutely decreases deprivation-induced chow intake,but it fails to affect consumption of palatable solutions

Despite its limited ability to cross the blood-brain barrier, peripherally administered oxytocin (OT) acutely decreases food intake, most likely via the brainstem and hypothalamic mechanisms. Studies performed to date have focused mainly on the effects of subcutaneous or intraperitoneal OT on the consumption of only solid calorie-dense diets (either standard or high-fat), whereas it is unknown whether, similarly to central OT, peripherally administered peptide reduces intake of calorie-dilute and non-caloric palatable solutions. In this project, we established that 0.1 μg/kg intravenous (IV) OT is the lowest anorexigenic dose, decreasing deprivation-induced standard chow intake by ca. 40% in rats and its effect does not stem from aversion. We then used this dose in paradigms in which effects of centrally acting OT ligands on consumption of palatable solutions had been previously reported. We found that IV OT did not change episodic intake of individually presented palatable solutions containing 10% sucrose, 0.1% saccharin, combined 10% sucrose-0.1% saccharin or 4.1%. Intralipid and it failed to affect daily scheduled consumption of a sucrose solution in non-deprived rats. In a two-bottle choice test, IV OT did not shift animals’ preference from sucrose to Intralipid. Finally, OT injected IV prior to the simultaneous presentation chow and a sucrose solution in food-deprived rats significantly decreased chow intake, whereas sugar water consumption remained unchanged. We conclude that IV OT reduces deprivation-induced chow intake without causing aversion, but the dose effective in decreasing energy-driven consumption of high-calorie food fails to affect consumption of palatable calorie-dilute solutions.     

Evidence in Female Rhesus Monkeys (Macaca mulatta) that Nighttime Caloric Intake is not Associated with Weight Gain

Objective: To evaluate the hypothesis that nighttime consumption of calories leads to an increased propensity to gain weight. Research Methods and Procedures: Sixteen female rhesus monkeys (Macaca mulatta) were ovariectomized and placed on a high‐fat diet to promote weight gain, and we examined whether monkeys that ate a high percentage of calories at night were more likely to gain weight than monkeys that ate the majority of calories during the day. Results: Within 6 weeks post‐ovariectomy, calorie intake and body weight increased significantly (129 ± 14%, p = 0.04; 103 ± 0.91%, p = 0.02, respectively). Subsequent placement on high‐fat diet led to further significant increases in calorie intake and body weight (368 ± 56%, p = 0.001; 113 ± 4.0%, p = 0.03, respectively). However, there was no correlation between the increase in calorie intake and weight gain (p = 0.34). Considerable individual variation existed in the percentage of calories consumed at night (6% to 64% total daily caloric intake). However, the percentage of calorie intake occurring at night was not correlated with body weight (r = 0.04; p = 0.87) or weight gain (r = 0.07; p = 0.79) over the course of the study. Additionally, monkeys that showed the greatest nighttime calorie intake did not gain more weight (p = 0.94) than monkeys that showed the least nighttime calorie intake. Discussion: These results show that eating at night is not associated with an increased propensity to gain weight, suggesting that individuals trying to lose weight should not rely on decreasing evening calorie intake as a primary strategy for promoting weight loss.     

The sweet-bitter taste of alcohol: aversion generalization to various sweet-quinine mixtures in the rat

Rats were trained to avoid a 5% alcohol solution and then testedwith either sweet + quinine hydrochloride solutions (Experiment1) or sweet + hydrochloric acid solutions (Experiment 2). Thesweet stimuli used were sucrose, glucose, fructose and saccharin.Significant aversion generalization was found only in Experiment1 where trained rats generalized to all four test stimuli, thussuggesting that alcohol has a sweet taste (in combination withbitter) not specific to one sweetener. No significant aversiongeneralization was noted in Experiment 2 when sweet + hydrochloricacid solutions were tested. In Experiment 3, rats were trainedto avoid 6% alcohol and tested with sucrose + quinine hydrochloridemixtures with varying concentrations of each component. In general,rats showed generalization of the alcohol aversions across thevarious concentrations of sucrose and quinine hydrochloridetested.     

Assessment of diet choice by the yellow fever mosquito Aedes aegypti

To investigate feeding‐related decisions in Aedes aegypti (L.), adults are presented with simple diets of paired gustatory stimuli conveying information concerning energy content, nutrient richness, osmotic balance and food toxicity in a two‐diet matrix assay. Assessment of mosquito gut contents indicates that both sexes accept single sugar diets in a dose‐dependent manner. When presented with a choice between two different yet equimolar sugar solutions, more individuals of both sexes accept the disaccharides, sucrose and trehalose, than the monosacharrides, fructose and glucose. The combination of pyranose and furanose sugars in solution, either physically associated (as in sucrose) or present as monomers (as glucose and fructose), is accepted over solutions containing a single sugar moiety. Using the two‐diet matrix assay, mosquito diet‐choice is also tested between two equimolar sucrose ‘driver’ solutions in which one is presented with various concentrations of another potential feeding cue ‘test’ compound (i.e. each of the 20 naturally‐occurring amino acids, sodium chloride, quinine or caffeine). Diet‐choice between the ‘driver’ sucrose‐only solution and the solution of the ‘driver’ sucrose containing a ‘test’ amino acid is influenced by sex, amino acid concentration and sucrose concentration. There is also an example of synergism between the diet components, leucine and sucrose. Mosquitoes demonstrate a dose‐dependent acceptance of sucrose‐only diets over sodium chloride‐containing sucrose when presented together. Interestingly, the sucrose‐only diet is accepted by more mosquitoes than all concentrations of the saline‐containing sucrose diets except those approximately isotonic to mosquito haemolymph, at which concentration mosquitoes show no clear choice between the diets. More individuals of both sexes accept sucrose‐only diets than the diets of caffeine‐containing sucrose in a dose‐dependent manner. Only females, however, respond to quinine‐containing sucrose diets and modulate this behaviour in relation to the energetic reward: more females imbibed quinine‐containing sucrose at the higher sucrose concentration (1 m ). A systematic characterization of diet selection behaviour of A. aegypti is presented for 27 putative feeding cues potentially involved in nectar/honeydew feeding. This study will be used as a basis from which to investigate further the mosquito's assessment of food quality and ultimately host choice.     

Preference for sucralose predicts behavioral responses to sweet and bittersweet tastants

Rats can be classified as either sucralose avoiders (SA) or sucralose preferrers (SP) based on their behavioral responses in 2-bottle preference, 1-bottle intake, and brief-access licking tests. The present study demonstrates that this robust phenotypic variation in the preference for sucralose predicts acceptance of saccharin, an artificial sweetener with a purported concentration-dependent "bitter" side taste and a 0.25 M sucrose solution adulterated with increasing concentrations of quinine hydrochloride (QHCl). Specifically, SA displayed decreased preference for and intakes of saccharin (≥41.5 mM) and sucrose-QHCl (>0.5 mM QHCl) solutions, relative to SP. In a second experiment involving brief-access (30-s) tests, SP and SA did not differ in their unconditioned licking responses across a range of sodium chloride or QHCl solutions (0.03-1 mM). However, the acceptability threshold for sucrose was lower in SA, relative to SP (0.06 and 0.13 M, respectively). Our findings suggest that phenotypic differences in sucralose preference are indicative of a more general difference in the hedonic processing of stimuli containing "bittersweet" or "sweet" taste qualities.     

Differential effects of dietary sodium intake on blood pressure and atherosclerosis in hypercholesterolemic mice

The amount of dietary sodium intake regulates the renin angiotensin system (RAS) and blood pressure, both of which play critical roles in atherosclerosis. However, there are conflicting findings regarding the effects of dietary sodium intake on atherosclerosis. This study applied a broad range of dietary sodium concentrations to determine the concomitant effects of dietary sodium intake on the RAS, blood pressure, and atherosclerosis in mice. Eight-week-old male low-density lipoprotein receptor ?/? mice were fed a saturated fat-enriched diet containing selected sodium concentrations (Na 0.01%, 0.1%, or 2% w/w) for 12 weeks. Mice in these three groups were all hypercholesterolemic, although mice fed Na 0.01% and Na 0.1% had higher plasma cholesterol concentrations than mice fed Na 2%. Mice fed Na 0.01% had greater abundances of renal renin mRNA than those fed Na 0.1% and 2%. Plasma renin concentrations were higher in mice fed Na 0.01% (14.2±1.7 ng/ml/30 min) than those fed Na 0.1% or 2% (6.2±0.6 and 5.8±1.6 ng/ml per 30 min, respectively). However, systolic blood pressure at 12 weeks was higher in mice fed Na 2% (138±3 mm Hg) than those fed Na 0.01% and 0.1% (129±3 and 128±4 mmHg, respectively). In contrast, mice fed Na 0.01% (0.17±0.02 mm²) had larger atherosclerotic lesion areas in aortic roots than those fed Na 2% (0.09±0.01 mm²), whereas lesion areas in mice fed Na 0.1% (0.12±0.02 mm²) were intermediate between and not significantly different from those in Na 0.01% and Na 2% groups. In conclusion, while high dietary sodium intake led to higher systolic blood pressure, low dietary sodium intake augmented atherosclerosis in hypercholesterolemic mice.     

Anatomical dissociation of melanocortin receptor agonist effects on taste- and gut-sensitive feeding processes

Injections of the melanocortin 3/4 receptor (MCR) agonist melanotan II (MTII) to a variety of brain structures produces anorexia, suggesting distributed brain MCR control of food intake. We performed a detailed analysis of feeding behavior (licking microstructure analysis) after a range of MTII doses (0.005 nM to 1 nM) was targeted to the forebrain (third ventricle, 3V) or hindbrain (fourth ventricle, 4V) regions. MTII (0.1 nM and 1 nM) delivered to the 3V or 4V significantly reduced 0.8 M sucrose intake. The anorexia was mediated by reductions in the number of licking bursts in the meal, intrameal ingestion rate, and meal duration; these measures have been associated with postingestive feedback inhibition of feeding. Anorexia after 3V but not 4V MTII injection was also associated with a reduced rate of licking in the first minute (initial lick rate) and reduced mean duration of licking bursts; these measures have been associated with taste evaluation. MTII effects on taste evaluation were further explored: In experiment 2, 3V MTII (1 nM) significantly reduced intake of noncaloric 4 mM saccharin and 0.1 M and 1 M sucrose solutions, but not water. The anorexia was again associated with reduced number of licking bursts, ingestion rate, meal duration, initial lick rate, and mean burst duration. In experiments 3 and 4, brief access (20 s) licking responses for sweet sucrose (0.015 M to 0.25 M) and bitter quinine hydrochloride (0.01 mM to 1 mM) solutions were evaluated. Licking responses for sucrose were suppressed, whereas those for quinine solutions were increased after 3V MTII, but not after 4V MTII injections (0.1 nM and 1 nM). The results suggest that multiple brain MCR sites influence sensitivity to visceral feedback, whereas forebrain MCR stimulation is necessary to influence taste responsiveness, possibly through attenuation of the perceived intensity of taste stimuli.     

Hindbrain administration of NMDA receptor antagonist AP-5 increases food intake in the rat

Hindbrain administration of MK-801, a noncompetitive N-methyl-D-aspartate (NMDA) channel blocker, increases meal size, suggesting NMDA receptors in this location participate in control of food intake. However, dizocilpine (MK-801) reportedly antagonizes some non-NMDA ion channels. Therefore, to further assess hindbrain NMDA receptor participation in food intake control, we measured deprivation-induced intakes of 15% sucrose solution or rat chow after intraperitoneal injection of either saline vehicle or D(-)-2-amino-5-phosphonopentanoic acid (AP5), a competitive NMDA receptor antagonist, to the fourth ventricular, or nucleus of the solitary tract (NTS). Intraperitoneal injection of AP5 (0.05, 0.1, 1.0, 3.0, and 5.0 mg/kg) did not alter 30-min sucrose intake at any dose (10.7 +/- 0.4 ml, saline control) (11.0 +/- 0.8, 11.2 +/- 1.0, 11.2 +/- 1.0, 13.1 +/- 2.2, and 11.0 +/- 1.9 ml, AP5 doses, respectively). Fourth ventricular administration of both 0.2 mug (16.7 +/- 0.6 ml) and 0.4 mug (14.9 +/- 0.5 ml) but not 0.1 and 0.6 mug of AP5 significantly increased 60-min sucrose intake compared with saline (11.2 +/- 0.4 ml). Twenty-four hour chow intake also was increased compared with saline (AP5: 31.5 +/- 0.1 g vs. saline: 27.1 +/- 0.6 g). Furthermore, rats did not increase intake of 0.2% saccharin after fourth ventricular AP5 administration (AP5: 9.8 +/- 0.7 ml, vs. saline: 10.5 +/- 0.5 ml). Finally, NTS AP5 (20 ng/30 nl) significantly increased 30- (AP5: 17.2 +/- 0.7 ml vs. saline: 14.6 +/- 1.7 ml), and 60-min (AP5: 19.4 +/- 0.6 ml vs. saline: 15.5 +/- 1.4 ml) sucrose intake, as well as 24-h chow intake (AP5: 31.6 +/- 0.3 g vs. saline: 26.1 +/- 1.2 g). These results support the hypothesis that hindbrain NMDA receptors participate in control of food intake and suggest that this participation also may contribute to control of body weight over a 24-h period.     

Water Consumption Increases Weight Loss During a Hypocaloric Diet Intervention in Middle‐aged and Older Adults

Water consumption acutely reduces meal energy intake (EI) among middle‐aged and older adults. Our objectives were to determine if premeal water consumption facilitates weight loss among overweight/obese middle‐aged and older adults, and to determine if the ability of premeal water consumption to reduce meal EI is sustained after a 12‐week period of increased water consumption. Adults (n = 48; 55–75 years, BMI 25–40 kg/m²) were assigned to one of two groups: (i) hypocaloric diet + 500 ml water prior to each daily meal (water group), or (ii) hypocaloric diet alone (nonwater group). At baseline and week 12, each participant underwent two ad libitum test meals: (i) no preload (NP), and (ii) 500 ml water preload (WP). Meal EI was assessed at each test meal and body weight was assessed weekly for 12 weeks. Weight loss was ～2 kg greater in the water group than in the nonwater group, and the water group (β = ?0.87, P < 0.001) showed a 44% greater decline in weight over the 12 weeks than the nonwater group (β = ?0.60, P < 0.001). Test meal EI was lower in the WP than NP condition at baseline, but not at week 12 (baseline: WP 498 ± 25 kcal, NP 541 ± 27 kcal, P = 0.009; 12‐week: WP 480 ± 25 kcal, NP 506 ± 25 kcal, P = 0.069). Thus, when combined with a hypocaloric diet, consuming 500 ml water prior to each main meal leads to greater weight loss than a hypocaloric diet alone in middle‐aged and older adults. This may be due in part to an acute reduction in meal EI following water ingestion.     

Effects of Oral and Gastric Stimulation on Appetite and Energy Intake

Appetite is regulated by many factors, including oro‐sensory and gastric signals. There are many studies on contributions of and possible interaction between sensory and gastric stimulation, but there are few studies in humans using simultaneous oral and gastric stimulation. We investigated the effect of simultaneous, but independently manipulated, oral and gastric stimulation on appetite ratings and energy intake. We hypothesized that compared with no stimulation, oral and gastric stimulation would equally and additively decrease appetite ratings and energy intake. Healthy men (n = 26, 21 ± 2 years, BMI 22 ± 3 kg/m²) participated in a randomized crossover trial with four experimental conditions and a control condition. Experimental conditions consisted of oral stimulation, with either 1 or 8 min modified sham feeding (MSF), and gastric stimulation, with either 100 or 800 ml intragastrically infused liquid (isocaloric, 99 kcal, 100 ml/min). The control condition consisted of no oral or gastric stimulation. Outcome measures were energy intake 30 min after the treatment and appetite ratings. Compared with the control condition, energy intake decreased significantly after the 8 min/100 ml (19% lower, P = 0.001) and 8 min/800 ml conditions (15% lower, P = 0.02), but not after the 1 min/100 ml (14% lower, P = 0.06) and 1 min/800 ml conditions (10% lower, P = 0.39). There was no interaction of oral and gastric stimulation on energy intake. Hunger and fullness differed across all conditions (P ≤ 0.01). In conclusion, duration of oral exposure was at least as important in decreasing energy intake as gastric filling volume. Oral and gastric stimulation did not additively decrease energy intake. Longer oro‐sensory stimulation, therefore, may be an important contributor to a lower energy intake.     

Attempts to produce taste-aversion learning in rats exposed to 60-Hz electric fields

A measure of taste-aversion (TA) learning was used in three experiments to 1) determine whether exposure to intense 60-Hz electric fields can produce TA learning in male Sprague-Dawley rats, and 2) establish a dose-response function for the behavior in question. In Experiment 1, four groups of eight rats each were distributed into one of two exposures (69 ± 5 kV/m or 133 ± 10 kV/m) or into one of two sham-exposure groups. Conditioning trials paired 0.1% sodium saccharin in water with 3 h of exposure to a 60-Hz electric field. Following five conditioning trials, a 20-min, two-bottle preference test between water and saccharin-flavored water failed to reveal TA conditioning in exposed groups. In Experiment 2, four groups of eight rats each (34 ± 2 kV/m or 133 ± 10 kV/m and two sham-exposed groups) were treated as before. Electric-field exposure had no effect on TA learning. Experiment 3 tested for a possible synergy between a minimal dose (for TA learning) of cyclophosphamide (6 mg/kg) and 5 h of exposure to 133 ± 10 kV/m electric fields in a dark environment under conditions otherwise similar to those of Experiments 1 and 2. The results indicated no TA learning as reflected in the relative consumption of saccharin.     

Self-selection of Dietary Threonine in the Rat and the Effect of Taste Stimuli on its Selection

The possible regulation of dietary threonine intake and the effect of a palatable (sodium saccharin) or aversive (quinine sulfate) taste stimulus on the manner of threonine selection were investigated in rats using a self-selection feeding method. Weanling rats were offered the choice of two diets differing only in threonine content for 2 weeks. Both weight gain and food consumption in the rats offered the choice of diets were quite comparable to each other and were the same as those in rats fed one diet containing sufficient threonine. Threonine intake of the self-selecting rats ranged from 0.43 to 1.90% of the food consumed. The threonine concentrations in the plasma and brain of the self-selecting rats increased proportionally with the threonine intake. When rats were offered a choice of two diets containing various amounts of threonine with taste materials, i.e., sodium saccharin or quinine sulfate, neither the dietary threonine nor their growth were ever affected.

These results indicate clearly that rats have an ability to regulate threonine intake to meet their requirement for the l-amino acid, and the threonine selection is not influenced significantly by the dietary addition of palatable or aversive taste materials.     

Conditioned preference for sweet stimuli in OLETF rat: effects of food deprivation

The Otsuka Long-Evans Tokushima Fatty (OLETF) rat, an outbred strain of Long- Evans Tokushima Otsuka rat (LETO) that lacks CCK-1 receptor expression, is hyperphagic and develops obesity and type-2 diabetes. The present study sought to assess how OLETF rats alter intake, preference, and conditioned preference of palatable solutions after acute food deprivation. Our results show that after 24 h chow restriction, LETO rats increase both sucrose intake and two-bottle sucrose preference relative to their free-fed baseline, whereas OLETF rats do not increase sucrose intake (0.3 M or 1.0 M sucrose) or preference (1.0 M vs. 0.3 M sucrose) when they are food deprived. In contrast, OLETF rats exhibit a higher conditioned flavor preference when sucrose is used as unconditioned stimulus (US) relative to LETO rats, whether overnight food restricted (81% vs. 71% for OLETF and LETO rats, respectively) or free fed (82% vs. 54% for OLETF and LETO rats, respectively) during the test. When a noncaloric saccharin solution is used as US, OLETF rats show a higher preference for the saccharin-associated flavor relative to LETO rats when nondeprived (76% vs. 58% for OLETF and LETO rats, respectively); however, neither strain shows differential conditioned flavor preference for saccharin in the deprivation state during the test. These findings suggest that OLETF rats fail to integrate postabsorptive and orosensory effects of sucrose in a conditioning setting to influence intake. Thus, it appears that OLETF rats form preferences for sucrose based largely on orosensory and hedonic properties of the solution, rather than caloric value.     

Exercise training improves relaxation response and SOD-1 expression in aortic and mesenteric rings from high caloric diet-fed rats

Background

Obesity has been associated with a variety of disease such as type II diabetes mellitus, arterial hypertension and atherosclerosis. Evidences have shown that exercise training promotes beneficial effects on these disorders, but the underlying mechanisms are not fully understood. The aim of this study was to investigate whether physical preconditioning prevents the deleterious effect of high caloric diet in vascular reactivity of rat aortic and mesenteric rings.

Methods

Male Wistar rats were divided into sedentary (SD); trained (TR); sedentary diet (SDD) and trained diet (TRD) groups. Run training (RT) was performed in sessions of 60 min, 5 days/week for 12 weeks (70–80% VO_2max). Triglycerides, glucose, insulin and nitrite/nitrate concentrations (NO_x ^-) were measured. Concentration-response curves to acetylcholine (ACh) and sodium nitroprusside (SNP) were obtained. Expression of Cu/Zn superoxide dismutase (SOD-1) was assessed by Western blotting.

Results

High caloric diet increased triglycerides concentration (SDD: 216 ± 25 mg/dl) and exercise training restored to the baseline value (TRD: 89 ± 9 mg/dl). Physical preconditioning significantly reduced insulin levels in both groups (TR: 0.54 ± 0.1 and TRD: 1.24 ± 0.3 ng/ml) as compared to sedentary animals (SD: 0.87 ± 0.1 and SDD: 2.57 ± 0.3 ng/ml). On the other hand, glucose concentration was slightly increased by high caloric diet, and RT did not modify this parameter (SD: 126 ± 6; TR: 140 ± 8; SDD: 156 ± 8 and TRD 153 ± 9 mg/dl). Neither high caloric diet nor RT modified NO_x ^- levels (SD: 27 ± 4; TR: 28 ± 6; SDD: 27 ± 3 and TRD: 30 ± 2 μM). Functional assays showed that high caloric diet impaired the relaxing response to ACh in mesenteric (about 13%), but not in aortic rings. RT improved the relaxing responses to ACh either in aortic (28%, for TR and 16%, to TRD groups) or mesenteric rings (10%, for TR and 17%, to TRD groups) that was accompanied by up-regulation of SOD-1 expression and reduction in triglycerides levels.

Conclusion

The improvement in endothelial function by physical preconditioning in mesenteric and aortic arteries from high caloric fed-rats was directly related to an increase in NO bioavailability to the smooth muscle mostly due to SOD-1 up regulation.     

The Effect of Mannan Oligosaccharide Supplementation on Body Weight Gain and Fat Accrual in C57Bl/6J Mice

The prevalence of obesity in industrialized societies has become markedly elevated. In contrast, model organism research shows that reducing caloric intake below ad libitum levels provides many health and longevity benefits. Despite these benefits, few people are willing and able to reduce caloric intake over prolonged periods. Prior research suggests that mannooligosaccharide (MOS or mannan) supplementation can increase lifespan of some livestock and in rodents can reduce visceral fat without reducing caloric intake. Hence, we tested the effect of MOS supplementation as a possible calorie restriction (CR) mimetic (CRM) in mice. C57Bl/6J male mice were fed a high‐fat “western” type diet with or without 1% MOS (by weight) supplementation (n = 24/group) from 8 to 20 weeks of age. Animals were housed individually and provided 95% of ad libitum food intake throughout the study. Body weight was measured weekly and body composition (lean and fat mass) measured noninvasively every 3 weeks. Individual fat depot weights were acquired by dissection at study completion. Supplementation of a high‐fat diet with 1% MOS tended to reduce total food intake (mean ± s.d.; control (CON): 293.69 ± 10.53 g, MOS: 288.10 ± 11.82 g; P = 0.09) during the study. Moreover, MOS supplementation had no significant effect on final body weight (CON: 25.21 ± 2.31 g, MOS: 25.28 ± 1.49 g; P = 0.91), total fat (CON: 4.72 ± 0.90 g, MOS: 4.82 ± 0.83 g; P = 0.69), or visceral fat (CON: 1.048 ± 0.276 g, MOS: 1.004 ± 0.247 g; P = 0.57). Contrary to previous research, MOS supplementation had no discernable effect on body weight gain or composition during this 12‐week study, challenging the potential use of MOS as a CRM or body composition enhancer.     

Long-term regulation of sucrose intake by the female mosquito, Aedes taeniorhynchius

Newly emerged female Aedes taeniorhynchus were maintained in cups provided with potometers containing 5, 10, and 25% sucrose solutions. Mortality and the ab lib. intake of sucrose were recorded daily and groups were sampled at regular intervals for analysis of energy reserves.After a week of relatively substantial intake of sucrose at all three concentrations, a constancy in daily intake at much lower levels was observed during the next 4 weeks. The caloric intake was highest in the 25% sucrose solution group. There were no differences in mortality rates at these concentrations. Glycogen (0·7–1·0 cal/female) and triglycerides (3·5dash4 cal/female) reserves reached maximum levels after the first week and stabilized thereafter on all three concentrations. In this species the stabilization in intake of sucrose solution after the first week is correlated with the maximum accumulation of stored energy reserves as opposed to decreased activity or subtle changes associated with senescence.     

味觉刺激后瘦素及其受体表达的变化

目的 :研究经口腔味觉刺激后 ,大鼠血清瘦素水平和脑瘦素受体表达情况。方法 :给大鼠口腔味觉刺激 ,味觉刺激物包括 3mol/L蔗糖 ,5mmol/L糖精钠 ,0 .1mol/LNaCl,0 .0 1mol/LHCl,1mmol/L奎宁H2 SO4和 0 .1mol/L谷氨酸钠 ,采用大鼠瘦素放免试剂盒测定血清瘦素水平。应用免疫组织化学ABC法对大脑切片进行染色 ,一抗为特异性羊抗瘦素受体IgG。 结果 :与对照组 (以蒸馏水代替味觉刺激物 )相比 ,仅甜味组 (包括蔗糖和糖精钠 )血清瘦素水平升高 (P <0 .0 5 )。杏仁核、下丘脑、臂旁核和孤束核等与味觉和摄食明显相关的核团均存在瘦素受体免疫反应 (LR IR)阳性细胞 ,但是阳性细胞数目在味觉刺激组和对照组间无显著性差异。结论 :给大鼠甜味觉刺激后 ,血清瘦素水平升高。并且杏仁核这个在摄食的发动和引导中起重要作用的核团存在LR IR阳性细胞。这些结果提示瘦素可能通过调节味觉感受而影响摄食 ,有必要对瘦素在味觉感受方面的作用进一步研究     

Study of the effect of gymnemic acid on taste in hamster

Behavioral and electrophysiological experiments with 10 sweetenershave been made to test if gymnemic acid (GA) is able to blockthe response to sweet stimuli in single taste fibres of thechorda tympani proper nerve in hamsters. The hamster was chosenbecause earlier studies show that it is more sensitive to GAthan any other non-human species. Since GA has been shown toaffect the sweetness of many different substances, its effectswere studied on an array of sweeteners. To avoid, however, theinclusion of sweeteners unpalatable to the hamster, the hamsters'liking of this array was tested with two-bottle preference techniquefor –24 h. It was found that acesulfam-K, fructose, glucose,sucrose and xylitol were strongly liked, while the animals showedno preference for aspartame, D-tryptophane, sodium cyclamate,sodium saccharin and thaumatin over water. The summated nerveresponse of these stimuli was then recorded. It was found thatneither thaumatin nor aspartame elicited a response, while theother stimuli gave a good response. Finally, the sweetenerswhich were both preferred in the two-bottle tests and gave anerve response were used as taste stimuli in single fibre experimentstogether with sodium chloride, quinine hydrochloride, citricacid and saccharin. The single fibre recordings were made beforeand after application of 5 mg GA for 3 min on the tongue. Itwas found that GA did not cause any dramatic decrease or disappearanceof the responses to either the sweet or the non-sweet substances.The responses to the sweeteners, however, were more depressedthan those to the non-sweet stimuli.