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Biomedical subjects

Daniel Tomé

Publications and source records attributed to Daniel Tomé.

At least 37 records · Page 2Linked to original sources

Acute third ventricular administration of leptin decreases protein and fat in self-selecting rats.

The peripheral administration of leptin reduces food intake (FI) body weight gain (BWG) and modifies food choice. The aim of this study was to examine the effect of acute cerebral injections of leptin on food selection in rats. Male rats were first adapted to the food choice paradigm (protein, carbohydrate, fat) for 3 weeks. They were then implanted with a cannula in the third ventricle. Leptin (leptin group=L) or saline (control group=C) injections were performed at either the beginning or the end of the night at 4-day intervals. FI was recorded continuously, 3 days before, during and then after injections. Rats were sacrificed 86 h after the second injection. After both injections, BWG and FI were reduced. The reduction in FI concerned only nocturnal intake, whatever the timing of the injection. When the injection was given at the beginning of the night, the reductions after a 1-h latency period were -45% and -27.5% during the first and second days, respectively. Following the second injection, the same effects were observed immediately (-16% and -41%, respectively). Only the fat and protein intakes were significantly reduced. This lower FI was due to a reduction in meal size and duration. The reduction resulted in a lower BWG and total white adipose tissue mass. At the time of sacrifice, 6 h after food deprivation, leptinemia and insulinemia were reduced in leptin-treated rats. Glycemia values were identical. It was thus demonstrated that central leptin was a satiation factor rather than a satiety factor.

Animal Feed↗

Peanut-lupine antibody cross-reactivity is not associated to cross-allergenicity in peanut-sensitized mouse strains.

BACKGROUND: Peanut hypersensitivity is one of the most common food allergies and one of the most common causes of death by food anaphylaxis in children and adults. Cross-reactivity of peanut-specific antibody (Ab) with other legumes is frequently demonstrated but it still remains to be demonstrated whether these responses could lead to clinical signs of cross-allergenicity. OBJECTIVE: We sought to evaluate peanut-specific serum IgE and IgG1 antibody (Ab) responses and anaphylactic reaction in mice strains and to assess both cross-reactivity and cross-allergenicity of peanut and lupine. METHODS: Four mice strains (i.e., C3H, BALB/c, CBA and SJL) were sensitized to peanut by intraperitoneal (ip) injection of crude peanut protein extract with alum. Other groups were given oral peanut extract without adjuvant. Peanut-specific antibodies (Abs) and anaphylactic responses to peanut challenge were examined. RESULTS: The C3H, CBA (H-2(k)) and BALB/c (H2-(d)) mice exhibited high levels of peanut-specific serum IgE, IgG1 Ab responses after the intra-peritoneal sensitization. Only the two strains of mice in the H-2(k) background developed anaphylactic symptoms upon intra-peritoneal challenge with crude peanut protein extract. While cross-reactivity of peanut and lupine was confirmed by ELISA, no clinical symptom of cross-allergenicity was seen after challenge with lupine. Mice that were given oral peanut showed only increase in peanut-specific IgG2a, but no IgE or IgG1 Abs and failed to develop anaphylactic reactions following injection of either peanut or lupine protein. CONCLUSION: These results show that mice of different genetic backgrounds can be sensitized to peanut by ip injection to develop anti-peanut Abs that cross react with lupine. In addition, cross-allergenicity may not directly correlate with the presence of cross-reactive Abs since no clinical symptoms of cross-allergenicity was seen after ip challenge with lupine.

Allergens↗

Oral and nasal sensitization promote distinct immune responses and lung reactivity in a mouse model of peanut allergy.

Despite structural and functional differences between the initial sites of contact with allergens in the gastrointestinal and nasal tracts, few animal models have examined the influence of the mucosal routes of sensitization on host reactivity to food or environmental antigens. We compared the oral and nasal routes of peanut sensitization for the development of a mouse model of allergy. Mice were sensitized by administration of peanut proteins in the presence of cholera toxin as adjuvant. Antibody and cytokine responses were characterized, as well as airway reactivity to nasal challenge with peanut or unrelated antigens. Oral sensitization promoted higher levels of IgE, but lower IgG responses, than nasal sensitization. Both orally and nasally sensitized mice experienced airway hyperreactivity on nasal peanut challenge. The peanut challenge also induced lung eosinophilia and type 2 helper T-cell-type cytokines in orally sensitized mice. In contrast, peanut challenge in nasally sensitized mice promoted neutrophilia and higher levels of lung MAC-1(+) I-A(b low) cells and inflammatory cytokines. In addition, nasal but not oral, sensitization promoted lung inflammatory responses to unrelated antigens. In summary, both oral and nasal peanut sensitization prime mice for airway hyperreactivity, but the initial mucosal route of sensitization influences the nature of lung inflammatory responses to peanut and unrelated allergens.

Animals↗

Comparison of fat storage between Fischer 344 and obesity-resistant Lou/C rats fed different diets.

OBJECTIVE: We aimed to characterize further the Lou/C (LOU) and Fischer 344 (F344) rat strains for nutritional traits to validate their use as contrasting strains for molecular genetic studies. RESEARCH METHODS AND PROCEDURES: Five batches of LOU and F344 rats were used to measure caloric intake, weight gain, and body composition when fed a chow diet, a self-selection diet (together with the study of preferences for macronutrients), hypercaloric diets, and a chow diet in a cold environment. RESULTS: Despite a higher caloric intake when fed a chow diet, LOU rats showed a lower weight gain, final body weight, and percentage of fat tissue, together with a higher percentage of carcass weight, than F344 rats. When fed a self-selection diet, LOU males ingested less protein and more fat than F344 males, and the reverse was observed for females. In this condition, feed efficiency was reduced in LOU but increased in F344 rats compared with the chow diet. Diet-induced obesity was observed in F344 rats but not in LOU rats fed hypercaloric diets. In a cold environment, both LOU and F344 rats displayed an increased percentage of brown adipose tissue compared with control groups, together with a higher caloric intake. DISCUSSION: The study shows robust nutritional differences between the LOU rat, a lean strain with a low feed efficiency and resistant to diet-induced obesity, and the contrasting F344 rat strain. It also shows the interest in these strains for studying the genetic components of resistance to obesity.

Adipose Tissue↗

Postprandial metabolic utilization of wheat protein in humans.

BACKGROUND: The quality of cereal protein has been little studied in humans despite its quantitative importance in the diet, particularly in developing countries. OBJECTIVE: The objective of this study was to determine the nutritional value of wheat protein in humans as assessed by the measurement of their real ileal digestibility and postprandial retention. DESIGN: Healthy young adults (n = 14) were fitted with an intestinal tube to allow the collection of intestinal fluid in the duodenum or terminal ileum. Subjects received a mixed meal of 136 g wheat toast that contained 24.6 g uniformly and intrinsically [(15)N]-labeled wheat protein. Intestinal fluid, blood, and urine were collected for 8 h postprandially. RESULTS: The real ileal digestibility of dietary wheat nitrogen amounted to 90.3 +/- 4.3%. The cumulative amount of dietary nitrogen transferred to the deamination pools reached a plateau at 8 h of 24.7 +/- 6.8% of the amount ingested. The urinary excretion of dietary nitrogen in ammonia was high (0.8 +/- 0.3% of ingested dose). The incorporation of dietary nitrogen into serum protein reached 7.0 +/- 1.9% of the meal. Postprandial wheat protein retention was 66.1 +/- 5.8%. CONCLUSIONS: Our results show that wheat proteins had the same true ileal digestibility as did most of the plant proteins already studied in humans, but also that they had a lower postprandial nitrogen retention value. However, this low value was higher than that predicted from the calculation of indispensable amino acid scores, ie, 89% rather than 30-40% of the nutritional value of milk proteins.

Adult↗

Fos-positive neurons are increased in the nucleus of the solitary tract and decreased in the ventromedial hypothalamus and amygdala by a high-protein diet in rats.

Transition from a normal- (NP) to a high-protein (HP) diet induces a rapid depression in food intake and a progressive but incomplete return to the initial intake during the succeeding days. The aim of this study was to determine which CNS regions are involved in the HP diet-induced satiety in rats. Brains were collected from 3 groups of adult rats after habituation to an NP diet (21 d), during the transition phase to a HP diet (2 d), or after habituation to the HP diet (21 d). Fos expression was measured in several brain areas that are involved in the control of food intake (solitary tract nucleus, anterior piriform cortex, lateral hypothalamus, arcuate nucleus, posterior para ventricular nucleus, medio ventral hypothalamus, dorso medial hypothalamus, amygdala, and accumbens nucleus). Changes occurred in the majority of these regions during the transition period from the NP diet to the HP diet. After habituation to the HP diet, significant changes in Fos expression were restricted to an increase in the nucleus of the solitary tract and a decrease in the ventromedial hypothalamus and the cortex of the amygdala. Considering the functional characteristics of these areas, the present results suggest that the vagus nerve conveys the information relative to the quantity of protein ingested, that hypothalamic sites regulate food intake and may alter sympathetic nervous system activity, and that higher brain functions such as memory processing by the limbic system or food reward system are involved in the HP diet-induced satiety in rats.

Adaptation, Physiological↗

Intraperitoneal leptin modifies macronutrient choice in self-selecting rats.

This study aimed to evaluate the consequences on food intake and body weight (BW) of leptin administration in rats receiving a choice between the three macronutrients. Two studies were performed: during the first, rats received an acute intraperitoneal (IP) leptin administration (1 mg/kg) twice (at 8 and 14 weeks of age), at the beginning of the nocturnal cycle, while during the second, they received a chronic leptin infusion (osmotic minipump, 7 days). The total 24-h food intake after acute leptin injections was reduced by 14% and 17%, respectively. Body weight gain (BWG) after leptin injections was about half that seen on control days. Chronic leptin infusion reduced total intake, affecting mainly protein (P). Fat intake increased slightly since day 2 and became significant on the fourth day. After the leptin infusion, carbohydrate (CHO) eaters (>35% carbohydrate/total energy) significantly reduced the carbohydrate proportion in their total energy intake. There was no difference concerning macronutrient selection by fat eaters (Hfat). Leptin infusion reduced the number of mixed meals on the first day. In addition, the thermogenesis of brown adipose tissue (BAT) was higher in leptin than in control (C) rats. Consequently, leptin injections reduced food intake and BWG and increased thermogenesis, thus acting on the two terms of the energy balance. Moreover, leptin has different effects on macronutrient preferences, dependent upon age (tests 1 and 2) and the type (acute or chronic) of injection. High leptinemia level related to age or to minipump infusion lead to leptin resistance as found in old or obese subjects. It could explain our results.

Adipose Tissue, Brown↗

Postprandial intestinal and whole body nitrogen kinetics and distribution in piglets fed a single meal.

Our aim was to characterize the postprandial total and dietary N fluxes in the portal drained viscera (PDV) and whole body after administration of a single meal in young pigs. Seven 4-wk-old piglets, implanted with a portal flow probe and portal, arterial and venous catheters, received a primed constant [(18)O]urea intravenous infusion and were studied for 8 h after a bolus mixed meal ingestion (46 mmol N/kg body wt) intrinsically labeled with (15)N to trace dietary N fluxes. The real cecal digestibility of the formula was 94.3% (SD 1.8). PDV output of dietary N was found principally in the pool of circulating protein (51% of the measured dietary N PDV output), in the free alpha-amino N pool (44%), and to a lesser extent in ammonia (5%). Dietary N release in alpha-amino N and ammonia mainly occurred during the first 3 h. Total and exogenous postprandial urea productions were 5.8 and 2.0 mmol N/kg body wt, respectively. At the end of the postprandial period, losses of dietary N amounted to 10.3% of the dose: 5.7% through ileal losses and 4.6% by deamination and transfer to urea. Net postprandial retention of dietary N was 90.4% (SD 1.3), of which 20% was found in splanchnic zone (small intestine 10%, liver 5%, and plasma protein 3%) and 42% in peripheral zone (muscle 31%, skin 6%). In conclusion, our results show a high efficiency of dietary N utilization for muscular uptake and anabolic utilization. However, the results obtained point out the necessity to further explore the form of dietary N released into the portal blood.

Adaptation, Physiological↗

Bound ferulic acid from bran is more bioavailable than the free compound in rat.

Ferulic acid (FA) is reported as a good antioxidant absorbed by human or rat but only few data deal with the influence of the food matrix on its bioavailability and with its potential protection against cardiovascular diseases and cancer. Wheat bran is used as a source of ferulic acid, the compound being mainly bound to arabinoxylans of the plant cell walls. Pharmacokinetic profiles of FA and its metabolites are established in rats. Free and conjugated FA quickly appear in plasma, reach a plateau 1 h after intake and remain approximately constant at 1 microM up to 24 h. 2.3% of FA are eliminated in urine. Compared with results obtained after intake of free FA, the presence of FA-arabinoxylans bonds in the food matrix increases the occurrence time of FA in the organism and decreases the level of urinary excretion in 24 h. Nevertheless, sulfated FA is still the main plasmatic form. The antioxidant activity of plasmas of rats fed with a standard diet (containing no FA), pure ferulic acid (5.15 mg FA/kg bw) or bran (4.04 mg FA/kg bw) are measured in an ex vivo test using AAPH as free radical inducer. Plasmas of rats fed with bran show a better antioxidant activity than the control group and the pure FA supplemented group, increasing the resistance of erythrocytes to hemolysis by factors of 2 and 1.5, respectively. These results show the good bioavailability of FA from bran and its potential efficiency to protect organism against pathology involving radical steps of development.

Animals↗

A long-term high-protein diet markedly reduces adipose tissue without major side effects in Wistar male rats.

Although there is a considerable interest of high-protein, low-carbohydrate diets to manage weight control, their safety is still the subject of considerable debate. They are suspected to be detrimental to the renal and hepatic functions, calcium balance, and insulin sensitivity. However, the long-term effects of a high-protein diet on a broad range of parameters have not been investigated. We studied the effects of a high-protein diet in rats over a period of 6 mo. Forty-eight Wistar male rats received either a normal-protein (NP: 14% protein) or high-protein (HP: 50% protein) diet. Detailed body composition, plasma hormones and nutrients, liver and kidney histopathology, hepatic markers of oxidative stress and detoxification, and the calcium balance were investigated. No major alterations of the liver and kidneys were found in HP rats, whereas NP rats exhibited massive hepatic steatosis. The calcium balance was unchanged, and detoxification markers (GSH and GST) were enhanced moderately in the HP group. In contrast, HP rats showed a sharp reduction in white adipose tissue and lower basal concentrations of triglycerides, glucose, leptin, and insulin. Our study suggests that the long-term consumption of an HP diet in male rats has no deleterious effects and could prevent metabolic syndrome.

Adipose Tissue↗

Parenteral immunization to beta-lactoglobulin modifies the intestinal structure and mucosal electrical parameters in rabbit.

Systemic and local immune responses and the intestinal structure were examined in parenterally beta-Lg-sensitized rabbits. Immunization led to high IgG titers against beta-Lg. In a Ussing chamber, a sensitized ileum had a higher short-circuit current (Isc) and potential difference (PD) than a control following in vitro beta-Lg challenge. Histological study indicated that presence of the sensitizing antigen affected and considerably modified the structure of the intestinal mucosa in sensitized rabbits when compared to controls. These alterations were revealed by active atrophy and marked infiltration of the lymphocytes. These findings indicate that antigen exposure results in morphological changes and abnormalities affecting the transport of water and electrolytes. This study provides a clearer understanding of the physiopathological mechanisms of allergy to cow's milk protein.

Animals↗

Preabsorptive factors are not the main determinants of intake depression induced by a high-protein diet in the rat.

The factors involved in the depression of food intake produced by a high-protein diet are still poorly understood. The aim of this study was to assess the role of several preingestive or preabsorptive factors likely to influence food intake when rats were fed ad libitum. Food intake was measured after modifying the composition of the high-protein diet, i.e., the type of proteins, or carbohydrates. Moreover, correlations between high-protein diet intake and the quantity of fluid ingested or stomach volume were studied. By varying the carbohydrate composition (sucrose/cornstarch) and the protein source (soy or gluten or total milk protein) of high-protein diets, we modified the orosensory properties of these diets. However, no differences in food intake were observed between these groups of rats during the transition phase or after adaptation, except during the first day of soy- or gluten-based diets when the depression of food intake was intensified. The depression of high-protein diet intake was neither the consequence of any delay necessary to increase the fluid intake induced by eating a high-protein diet nor due to a marked increase in stomach volume, which might explain enhanced satiety and decreased food intake through the activation of vagal afferent fibers. Our experiments do not indicate a preponderant role for oropharyngeal or preabsorptive factors in the depression of food intake induced by a high-protein diet.

Animals↗

Nutritional value of milk and meat products derived from cloning.

The development and use of milk and meat products derived from cloning depends on their safety and on the nutritional advantages they can confer to the products as perceived by consumers. The development of such products thus implies (i) to demonstrate their safety and security, (ii) to show that their nutritional value is equivalent to the traditional products, and (iii) to identify the conditions under which cloning could allow additional nutritional and health benefit in comparison to traditional products for the consumers. Both milk and meat products are a source of high quality protein as determined from their protein content and essential amino acid profile. Milk is a source of calcium, phosphorus, zinc, magnesium and vitamin B2 and B12. Meat is a source of iron, zinc and vitamin B12. An important issue regarding the nutritional quality of meat and milk is the level and quality of fat which usually present a high content in saturated fat and some modification of the fat fraction could improve the nutritional quality of the products. The role of the dietary proteins as potential allergens has to be taken into account and an important aspect regarding this question is to evaluate whether the cloning does not produce the appearance of novel allergenic structures. The presence of bio-activities associated to specific components of milk (lactoferrin, immunoglobulins, growth factors, anti-microbial components) also represents a promising development. Preliminary results obtained in rats fed cow's milk or meat-based diets prepared from control animals or from animals derived from cloning did not show any difference between control and cloning-derived products.

Animals↗

Acute ingestion of dietary proteins improves post-exercise liver glutathione in rats in a dose-dependent relationship with their cysteine content.

Dietary sulfur amino acids affect glutathione synthesis, but their acute effect under conditions of oxidative stress is unknown. We assessed the effect of the selective ingestion of alpha-lactalbumin, a cysteine-rich protein, on glutathione homeostasis before a single bout of exhaustive exercise. One hour before a 2-h run on a treadmill, untrained rats ingested a meal enriched with either milk protein (TMP), alpha-lactalbumin-enriched milk protein (alpha-LAC), glucose (GLUC) or milk protein plus 150 mg N-acetyl-L-cysteine, a pharmacologic cysteine donor (NAC). Glutathione status was monitored in the blood and measured postexercise in the liver and heart. A group of fed sedentary rats was used as a control (CON). Blood total glutathione levels declined over time in all test groups. Although postexercise heart glutathione did not differ among groups, postexercise liver glutathione was curvilinearly related to prior cysteine intake (R2=0.999, P<0.05). In alpha-LAC rats, liver glutathione was 60-80% higher than in GLUC or CON rats (P<0.05) and did not differ from that of NAC rats. Cysteine from dietary proteins exhibits a considerable, dose-dependent and acute stimulatory effect on liver glutathione during exercise but does not immediately benefit whole-body glutathione homeostasis, presumably because of an overlap between the postprandial and exercise-related states.

Acetylcysteine↗

Increasing the protein content in a carbohydrate-free diet enhances fat loss during 35% but not 75% energy restriction in rats.

The purpose of the present study was to test the influence of the amount of protein in a carbohydrate-free diet during a weight reducing program using severe (75%) or more moderate (35%) energy restriction in rats. In Expt. 1, 3 groups (n = 6) consumed ad libitum a high-carbohydrate, low-fat diet [P21C69L10 containing 21% of energy as protein (P21), 69% carbohydrate (C69) and 10% lipids (L10)], a high-carbohydrate, high-fat diet (P21C34L45), or a carbohydrate-free, high-fat, high-protein diet (P55L45). In Expt. 2, 7 groups (n = 7) were studied. For 20 d, groups 1-4 consumed ad libitum diets containing macronutrients at the proportions indicated in their designations [P14C56L30 (control diet), P30L70, P50L50, and P90L10]. Groups 5-7 were pair-fed the same diets at the level of the spontaneous intake of the P90L10 group on the previous day (35% energy restriction). In Expt. 3, 5 groups (n = 7) were fed 1 of the following diets for 20 d. Group 1 consumed the control diet (P14C56L30) ad libitum. Groups 2-5 were energy restricted to 25% of the daily energy intake of group 1 with diets varying in their protein and lipid concentrations (P14C56L30, P50L50, P70L30, and P90L10). A high-fat content in the diet devoid of carbohydrate did not increase energy intake and body adiposity and neither body weight nor body composition was significantly affected by the protein to lipid ratio when energy restriction was 75%; however, a protein content > 50% preserved lean body mass at the expense of fat mass when energy restriction was 35%. Our results show that the absence of carbohydrates from the diet induces a low energy intake and the preferential deposition of protein.

Adipose Tissue↗

The mode of oral bovine lactoferrin administration influences mucosal and systemic immune responses in mice.

Food protein intake interacts with the immune system. In earlier nutritional and immunological studies, nutrients, particularly milk whey proteins, were generally administered in soluble form and by gavage. However, orogastric intubation does not represent a natural way of ingesting nutrients such as lactoferrin (Lf). We examined how different modes of oral administration of Lf could affect the regulatory effect of this molecule on intestinal and systemic immune responses. Groups of 10 female BALB/c mice were administered Lf daily for 6 wk. To address the influence of the oral modes of administration, mice were given Lf either in solution, by gastric intubation or in the drinking water, or as a powder, by buccal deposition or in the diet. Mucosal and systemic immune responses, including specific immunoglobulin (Ig) secretion, cell proliferation, and cytokine production, were analyzed and compared with those of naïve mice given water under the same conditions or positive control mice that were administered Lf by i.m. injection. The addition of Lf to the drinking water had no visible effect on the immune status. Gastric intubation, single buccal doses, and continuous doses of Lf in the diet stimulated transient systemic and intestinal antibody responses against Lf. All of these oral modes of Lf exposure biased mucosal and systemic T-cell responses toward Thelper (Th)2-types and elevated IgA production by mucosal cells. However, the less natural gastric intubation also promoted Th1-type responses as evidenced by serum IgG(2a) antibodies and the secretion of Th1 cytokine by mucosal and systemic T cells in vitro. Thus, one should carefully consider the oral mode of administration for understanding regulation of immune responses by food proteins such as Lf.

Administration, Oral↗

A very high 70%-protein diet does not induce conditioned taste aversion in rats.

This study was designed to assess the effects of transition and adaptation to a very high protein diet on behavioral food responses, energy intake, body weight gain, and body composition in rats. For this purpose, adult male Wistar rats were fed either a diet with 70% of energy as protein (P70 group) or a diet with 14% of energy as protein (P14 group) for 16 d. These two groups were compared with a P14 pair-fed (P14-pf) group. A behavioral satiety sequence was also examined. The P70 group ate 21% less than the P14 rats (P < 0.001) and gained less body weight (P < 0.01). The P70 group gained more carcass weight than either P14 or P14-pf rats (P < 0.05). Behavior and food intake data were affected in P70 rats on d 1 of eating the very high protein diet and then returned to baseline values as early as d 2 of consuming the P70 diet. Rats that adapted to the very high protein diet did not acquire a conditioned taste aversion but rather exhibited satiety and a normal behavioral satiety sequence.

Adipose Tissue↗

Intestinal lysine metabolism is driven by the enteral availability of dietary lysine in piglets fed a bolus meal.

Previous steady-state continuous-feeding studies have shown that the gut mucosa removes substantial amounts of both dietary and systemic amino acids. However, enteral nutrition is often given under non-steady-state conditions as a bolus meal, and this has been shown to influence systemic metabolism. Therefore, our aim was to quantify the relative metabolism of dietary and systemic lysine by the portal-drained viscera (PDV) under non-steady-state conditions after a single bolus meal. Five 28-day-old piglets implanted with arterial, venous, and portal catheters and with an ultrasonic portal flow probe were given an oral bolus feeding of a milk formula containing a trace quantity of intrinsically 15N-labeled soy protein and a continuous intravenous infusion of [U-13C]lysine for 8 h. Total lysine use by the PDV was maximal 1 h after the meal (891 micromol x kg(-1) x h(-1)) and was predominantly of dietary origin (89%), paralleling the enteral delivery of dietary lysine. Intestinal lysine use returned to a low level after 4 h postprandially and was derived exclusively from the arterial supply until 8 h. Cumulative systemic appearance of dietary lysine reached 44 and 80% of the ingested amount 4 and 8 h after the meal, respectively, whereas the PDV first-pass use of dietary lysine was 55 and 32% of the intake for these two periods, respectively. We conclude that the first-pass utilization rate of dietary lysine by the PDV is directly increased by the enteral lysine availability and that it is higher with a bolus than with continuous oral feeding.

Adaptation, Physiological↗