RESUMO
BACKGROUND: l-Tryptophan reduces energy intake in healthy men. The underlying mechanisms, including appetite, plasma cholecystokinin (CCK), tryptophan (Trp), and the ratio of Trp to large neutral amino acids (Trp:LNAAs ratio), and whether responses differ in lean and obese individuals, are uncertain. OBJECTIVES: We evaluated the effects of intragastric Trp on energy intake (primary outcome) and their potential mechanisms, pre- and postmeal, in lean men and those with obesity. METHODS: Twelve lean men [mean ± SD age: 30 ± 3 y; BMI (in kg/m2): 23 ± 1] and 13 men with obesity (mean ± SD age: 31 ± 3 y; BMI: 33 ± 1) received, on 3 separate occasions, in double-blind, randomized order, 3 g ("Trp-3") or 1.5 g ("Trp-1.5") Trp, or control ("C"), intragastrically, 30 min before a buffet-meal. Energy intake from the buffet-meal, hunger, fullness, and plasma CCK and amino acid concentrations were measured in response to Trp alone and for 2 h postmeal. Data were analyzed using maximum likelihood mixed-effects models, with treatment, group, and treatment-by-group interaction as fixed effects. RESULTS: Trp alone increased plasma CCK, Trp, and the Trp:LNAAs ratio (all P < 0.001), with no difference between groups. Trp suppressed energy intake (P < 0.001), with no difference between groups (lean, C: 1085 ± 102 kcal, Trp-1.5: 1009 ± 92 kcal, Trp-3: 868 ± 104 kcal; obese, C: 1249 ± 98 kcal, Trp-1.5: 1217 ± 90 kcal, Trp-3: 1012 ± 100 kcal). Postmeal, fullness was greater after Trp-3 than after C and Trp-1.5 (all P < 0.05), and in men with obesity than in lean men (P < 0.05). Plasma Trp and the Trp:LNAAs ratio were greater after Trp-3 and Trp-1.5 than after C (all P < 0.001), and tended to be less in men with obesity than in the lean (P = 0.07) (Trp:LNAAs ratio: lean, C: 1.5 ± 0.2, Trp-1.5: 6.9 ± 0.7, Trp-3: 10.7 ± 1.4; obese, C: 1.4 ± 0.1, Trp-1.5: 4.6 ± 0.7, Trp-3: 7.8 ± 1.3). There were inverse correlations of energy intake with plasma Trp and the Trp:LNAAs ratio in both groups (lean, both r = -0.50, P < 0.01; obese, both r = -0.40, P < 0.05). CONCLUSIONS: Intragastric Trp has potent energy intake-suppressant effects, in both lean men and those with obesity, apparently related to the Trp:LNAAs ratio.
Assuntos
Apetite , Triptofano , Adulto , Colecistocinina , Método Duplo-Cego , Ingestão de Energia , Humanos , Masculino , ObesidadeRESUMO
The fatty acid, lauric acid (C12), and the amino acid, leucine (Leu) stimulate gut hormones, including CCK, associated with suppression of energy intake. In our recent study, intraduodenal infusion of a combination of C12 and l-tryptophan, at loads that individually did not affect energy intake, reduced energy intake substantially, associated with much greater stimulation of CCK. We have now investigated whether combined administration of C12 and Leu would enhance the intake-suppressant effects of each nutrient, when given at loads that each suppress energy intake individually. Sixteen healthy, lean males (age: 23 ± 2 yr) received, in randomized, double-blind fashion, 90-min intraduodenal infusions of control (saline), C12 (0.4 kcal/min), Leu (0.45 kcal/min), or C12+Leu (0.85 kcal/min). Antropyloroduodenal pressures were measured continuously and plasma CCK at 15-min intervals, and energy intake from a standardized buffet-meal, consumed immediately postinfusion, was quantified. All nutrient infusions stimulated plasma CCK compared with control (P < 0.05). Moreover, C12 and C12+Leu stimulated CCK compared with Leu (P < 0.05) (mean concentration, pmol/L; control: 2.3 ± 0.3, C12: 3.8 ± 0.3, Leu: 2.7 ± 0.3, and C12+Leu: 4.0 ± 0.4). C12+Leu, but not C12 or Leu, stimulated pyloric pressures (P < 0.05). C12+Leu and C12 reduced energy intake (P < 0.05), and there was a trend for Leu to reduce (P = 0.06) energy intake compared with control, with no differences between the three nutrient treatments (kcal; control: 1398 ± 84, C12: 1226 ± 80, Leu: 1260 ± 92, and C12+Leu: 1208 ± 83). In conclusion, combination of C12 and Leu, at the loads given, did not reduce energy intake beyond their individual effects, possibly because maximal effects had been evoked.
Assuntos
Colecistocinina/sangue , Ingestão de Energia , Motilidade Gastrointestinal/efeitos dos fármacos , Ácidos Láuricos/farmacologia , Leucina/farmacologia , Adolescente , Adulto , Apetite/efeitos dos fármacos , Método Duplo-Cego , Ingestão de Alimentos/efeitos dos fármacos , Humanos , Ácidos Láuricos/administração & dosagem , Leucina/administração & dosagem , Masculino , Adulto JovemRESUMO
Background: Lysine is reported to lower the glycemic response to oral glucose in humans and, albeit at high loads, to slow gastric emptying of glucose and decrease food intake in rats.Objective: We investigated the effects of intragastrically administered lysine on early (15 min) and later (60 min) blood glucose and insulin responses to and gastric emptying of a mixed-nutrient drink, and effects on subsequent energy intake.Methods: Twelve healthy volunteers (7 men and 5 women; mean ± SEM age: 24 ± 2 y) received intragastric infusions (200 mL) containing 5 or 10 g l-lysine or a control solution within 2 min on 3 different occasions in randomized order. Fifteen minutes later, participants consumed a mixed-nutrient drink (300 mL, 400 kcal, and 56 g carbohydrates) within 1 min. For the next hour (t = 0-60 min), we collected blood samples every 15 min (to measure blood glucose, plasma insulin, and plasma glucagon) and breath samples every 5 min (to measure gastric emptying via a 13C-acetate breath test). We then quantified subjects' energy intake from a buffet-style meal (t = 60-90 min).Results: There were no differences between the 2 lysine treatments; hence, data were pooled for further analysis. Lysine did not affect blood glucose at 15 min or the blood glucose area under the curve from 0 to 60 min (AUC0-60min) but it decreased blood glucose at 60 min compared with the control solution (-9.1% ± 3.1%, P < 0.01). Similarly, the early insulin response and insulin AUC0-60min were not affected by lysine, but plasma insulin at 60 min was 20.9% ± 5.6% lower than after the control (P < 0.05). Plasma glucagon at both 15 min (20.7% ± 4.7%, P < 0.001) and 60 min (14.1% ± 5.4%, P < 0.05) and the glucagon AUC0-60min (P < 0.01) were greater after lysine than after the control. Lysine did not slow gastric emptying, and there was no effect on energy intake.Conclusion: In healthy adults, lysine slightly reduced the glycemic response to an oral mixed-macronutrient drink, an effect that was apparently independent of insulin or slowing of gastric emptying. This trial was registered at www.anzctr.orgau as 12614000837628.
Assuntos
Bebidas/análise , Glicemia/metabolismo , Carboidratos da Dieta/farmacologia , Esvaziamento Gástrico/efeitos dos fármacos , Insulina/sangue , Lisina/farmacologia , Adulto , Testes Respiratórios , Dióxido de Carbono , Carboidratos da Dieta/análise , Relação Dose-Resposta a Droga , Método Duplo-Cego , Ingestão de Alimentos , Feminino , Humanos , Lisina/administração & dosagem , Masculino , Adulto JovemRESUMO
Intraduodenal infusion of lipid or protein potently reduces subsequent energy intake. There is evidence that the underlying mechanisms differ significantly between the two nutrients. While intraduodenal lipid stimulates glucagon-like peptide-1 and CCK much more than protein, the release of insulin and glucagon is substantially greater in response to protein. Ghrelin and PYY are both involved in short-term regulation, while leptin is a long-term regulator, of energy balance; the acute effects of nutrients on leptin release are unclear. We investigated the comparative effects of intraduodenal lipid and protein on plasma ghrelin, PYY, and leptin concentrations. Thirteen lean, young men received 90-min intraduodenal infusions of protein (whey hydrolysate) or lipid (long-chain triglyceride emulsion) at a rate of 3 kcal/min, or saline control, on three separate days. Blood samples were collected at baseline and regularly during infusions. Both lipid and protein potently suppressed plasma ghrelin compared with control (both P < 0.001), with no difference between them. While both lipid and protein stimulated plasma PYY (P < 0.001), the effect of lipid was substantially greater than that of protein (P < 0.001). Neither intraduodenal lipid nor protein affected plasma leptin. In conclusion, intraduodenal lipid and protein have discrepant effects on the release of PYY, but not ghrelin. When considered with our previous findings, it appears that, with the exception of ghrelin, the energy intake-suppressant effects of lipid and protein are mediated by different mechanisms.
Assuntos
Gorduras na Dieta/administração & dosagem , Proteínas Alimentares/administração & dosagem , Duodeno/efeitos dos fármacos , Grelina/sangue , Leptina/sangue , Proteínas do Leite/administração & dosagem , Peptídeo YY/sangue , Hidrolisados de Proteína/administração & dosagem , Triglicerídeos/administração & dosagem , Adolescente , Adulto , Estudos Cross-Over , Método Duplo-Cego , Duodeno/metabolismo , Ingestão de Alimentos , Metabolismo Energético , Voluntários Saudáveis , Humanos , Masculino , Período Pós-Prandial , Fatores de Tempo , Proteínas do Soro do Leite , Adulto JovemRESUMO
The peptide transporter PEPT1, expressed in the brush border membrane of enterocytes, mediates the uptake of di- and tripeptides from luminal protein digestion in the small intestine. PEPT1 was proposed not to be expressed in normal colonic mucosa but may become detectable in inflammatory states such as Crohn's disease or ulcerative colitis. We reassessed colonic expression of PEPT1 by performing a systematic analysis of PEPT1 mRNA and protein levels in healthy colonic tissues in mice, rats, and humans. Immunofluorescence analysis of different mouse strains (C57BL/6N, 129/Sv, BALB/c) demonstrated the presence of PEPT1 in the distal part of the colon but not in proximal colon. Rat and human intestines display a similar distribution of PEPT1 as found in mice. However, localization in human sigmoid colon revealed immunoreactivity present at low levels in apical membranes but substantial staining in distinct intracellular compartments. Functional activity of PEPT1 in colonic tissues from mice was assessed in everted sac preparations using [¹4C]Gly-Sar and found to be 5.7-fold higher in distal compared with proximal colon. In intestinal tissues from Pept1-/- mice, no [¹4C]Gly-Sar transport was detectable but feces samples revealed significantly higher water content than in wild-type mice, suggesting that PEPT1 contributes to colonic water absorption. In conclusion, our studies unequivocally demonstrate the presence of PEPT1 protein in healthy distal colonic epithelium in mice, rats, and humans and proved that the protein is functional and contributes to electrolyte and water handling in mice.
Assuntos
Colo/metabolismo , Regulação da Expressão Gênica/fisiologia , Simportadores/metabolismo , Água/metabolismo , Adulto , Animais , Fezes/química , Feminino , Vida Livre de Germes , Humanos , Absorção Intestinal , Masculino , Camundongos , Camundongos Endogâmicos , Camundongos Knockout , Camundongos Transgênicos , Pessoa de Meia-Idade , Transportador 1 de Peptídeos , Ratos , Ratos Wistar , Simportadores/genética , Água/químicaRESUMO
(1) Background: Whey protein lowers postprandial blood glucose in health and type 2 diabetes, by stimulating insulin and incretin hormone secretion and slowing gastric emptying. The branched-chain amino acids, leucine, isoleucine and valine, abundant in whey, may mediate the glucoregulatory effects of whey. We investigated the comparative effects of intragastric administration of leucine, isoleucine and valine on the plasma glucose, C-peptide and glucagon responses to and gastric emptying of a mixed-nutrient drink in healthy men. (2) Methods: 15 healthy men (27 ± 3 y) received, on four separate occasions, in double-blind, randomised fashion, either 10 g of leucine, 10 g of isoleucine, 10 g of valine or control, intragastrically, 30 min before a mixed-nutrient drink. Plasma glucose, C-peptide and glucagon concentrations were measured before, and for 2 h following, the drink. Gastric emptying of the drink was quantified using 13C-acetate breath-testing. (3) Results: Amino acids alone did not affect plasma glucose or C-peptide, while isoleucine and valine, but not leucine, stimulated glucagon (p < 0.05), compared with control. After the drink, isoleucine and leucine reduced peak plasma glucose compared with both control and valine (all p < 0.05). Neither amino acid affected early (t = 0-30 min) postprandial C-peptide or glucagon. While there was no effect on overall gastric emptying, plasma glucose at t = 30 min correlated with early gastric emptying (p < 0.05). (4) Conclusion: In healthy individuals, leucine and isoleucine lower postprandial blood glucose, at least in part by slowing gastric emptying, while valine does not appear to have an effect, possibly due to glucagon stimulation.
Assuntos
Aminoácidos de Cadeia Ramificada/farmacologia , Glicemia/metabolismo , Peptídeo C/sangue , Esvaziamento Gástrico/efeitos dos fármacos , Glucagon/sangue , Isoleucina/farmacologia , Leucina/farmacologia , Valina/farmacologia , Adulto , Diabetes Mellitus Tipo 2 , Método Duplo-Cego , Polipeptídeo Inibidor Gástrico/sangue , Humanos , Insulina , Masculino , Pessoa de Meia-Idade , Período Pós-Prandial/efeitos dos fármacos , Proteínas do Soro do Leite/farmacologia , Adulto JovemRESUMO
AIMS: In healthy individuals, intragastric administration of the branched-chain amino acids, leucine and isoleucine, diminishes the glycaemic response to a mixed-nutrient drink, apparently by stimulating insulin and slowing gastric emptying, respectively. This study aimed to evaluate the effects of leucine and isoleucine on postprandial glycaemia and gastric emptying in type-2 diabetes mellitus (T2D). METHODS: 14 males with T2D received, on 3 separate occasions, in double-blind, randomised fashion, either 10 g leucine, 10 g isoleucine or control, intragastrically 30 min before a mixed-nutrient drink (500 kcal; 74 g carbohydrates, 18 g protein, 15 g fat). Plasma glucose, insulin and glucagon were measured from 30 min pre- until 120 min post-drink. Gastric emptying of the drink was also measured. RESULTS: Leucine and isoleucine stimulated insulin, both before and after the drink (all P < 0.05; peak (mU/L): control: 70 ± 15; leucine: 88 ± 17; isoleucine: 74 ± 15). Isoleucine stimulated (P < 0.05), and leucine tended to stimulate (P = 0.078), glucagon before the drink, and isoleucine stimulated glucagon post-drink (P = 0.031; peak (pg/mL): control: 62 ± 5; leucine: 70 ± 9; isoleucine: 69 ± 6). Neither amino acid affected gastric emptying or plasma glucose (peak (mmol/L): control: 12.0 ± 0.5; leucine: 12.5 ± 0.7; isoleucine: 12.0 ± 0.6). CONCLUSIONS: In contrast to health, in T2D, leucine and isoleucine, administered intragastrically in a dose of 10 g, do not lower the glycaemic response to a mixed-nutrient drink. This finding argues against a role for 'preloads' of either leucine or isoleucine in the management of T2D.
Assuntos
Aminoácidos de Cadeia Ramificada/uso terapêutico , Glicemia/efeitos dos fármacos , Diabetes Mellitus Tipo 2/sangue , Esvaziamento Gástrico/efeitos dos fármacos , Isoleucina/uso terapêutico , Leucina/uso terapêutico , Período Pós-Prandial/efeitos dos fármacos , Adulto , Idoso , Aminoácidos de Cadeia Ramificada/farmacologia , Estudos Cross-Over , Suplementos Nutricionais , Método Duplo-Cego , Bebidas Energéticas , Humanos , Isoleucina/farmacologia , Leucina/farmacologia , Masculino , Pessoa de Meia-IdadeRESUMO
Circulating tryptophan/large neutral amino acids (tryptophan/LNAA) ratio, an indicator of brain serotonin levels, may be important in appetite regulation, together with gastrointestinal (gastric emptying, plasma cholecystokinin) mechanisms. We have compared effects of intragastric tryptophan ('Trp') on the plasma tryptophan/LNAA ratio in lean and obese men, and the associations of the tryptophan/LNAA ratio, gastric emptying and CCK concentrations with energy intake. Lean and obese male participants (n = 16 each) received 3 g Trp or volume-matched control intragastrically, 15 min before a mixed-nutrient drink (300 mL, 400 kcal) (t = 0 min) in randomised, double-blind fashion. Plasma amino acid (for calculation of the plasma tryptophan/LNAA ratio) and CCK concentrations were measured from t = -20-60 min. Gastric emptying was assessed from t = 0-60 min, and ad-libitum energy intake from a standardised buffet-style meal from t = 60-90 min. The increase in the plasma tryptophan/LNAA ratio was less in obese, than lean, participants (P < 0.05), and greater in lean participants who reduced their energy intake (by >0 kcal) after Trp compared with those who did not (by ≤0 kcal) (P < 0.05). Moreover, in participants who reduced their energy intake, the ratio was lower in obese, than in lean (P < 0.05). There was a trend for an inverse correlation between energy intake with the plasma tryptophan/LNAA ratio in lean (r = -0.4, P = 0.08), but not in obese, participants. There was no significant difference in gastric emptying or CCK between participants who reduced their energy intake and those who did not. In conclusion, the plasma tryptophan/LNAA ratio appears to be a determinant of the suppression of energy intake in response to tryptophan in normal-weight people, but not in those with obesity. The role of the plasma tryptophan/LNAA ratio to regulate energy intake, and potential changes in obesity, warrant evaluation in prospective studies.
Assuntos
Aminoácidos Neutros/sangue , Ingestão de Energia/efeitos dos fármacos , Obesidade/sangue , Triptofano/administração & dosagem , Triptofano/sangue , Adulto , Aminoácidos/sangue , Regulação do Apetite/efeitos dos fármacos , Índice de Massa Corporal , Colecistocinina/sangue , Método Duplo-Cego , Esvaziamento Gástrico/efeitos dos fármacos , Humanos , Peso Corporal Ideal , Infusões Parenterais , Masculino , Refeições/efeitos dos fármacos , Obesidade/tratamento farmacológicoRESUMO
Chronic isoleucine supplementation prevents diet-induced weight gain in rodents. Acute-isoleucine administration improves glucose tolerance in rodents and reduces postprandial glucose levels in humans. However, the effect of chronic-isoleucine supplementation on body weight and glucose tolerance in obesity is unknown. This study aimed to investigate the impact of chronic isoleucine on body weight gain and glucose tolerance in lean and high-fat-diet (HFD) induced-obese mice. Male C57BL/6-mice, fed a standard-laboratory-diet (SLD) or HFD for 12 weeks, were randomly allocated to: (1) Control: Drinking water; (2) Acute: Drinking water with a gavage of isoleucine (300 mg/kg) prior to the oral-glucose-tolerance-test (OGTT) or gastric-emptying-breath-test (GEBT); (3) Chronic: Drinking water with 1.5% isoleucine, for a further six weeks. At 16 weeks, an OGTT and GEBT was performed and at 17 weeks metabolic monitoring. In SLD- and HFD-mice, there was no difference in body weight, fat mass, and plasma lipid profiles between isoleucine treatment groups. Acute-isoleucine did not improve glucose tolerance in SLD- or HFD-mice. Chronic-isoleucine impaired glucose tolerance in SLD-mice. There was no difference in gastric emptying between any groups. Chronic-isoleucine did not alter energy intake, energy expenditure, or respiratory quotient in SLD- or HFD-mice. In conclusion, chronic isoleucine supplementation may not be an effective treatment for obesity or glucose intolerance.
Assuntos
Glicemia/metabolismo , Suplementos Nutricionais , Isoleucina/administração & dosagem , Resultados Negativos , Fenômenos Fisiológicos da Nutrição/fisiologia , Obesidade/metabolismo , Obesidade/prevenção & controle , Magreza/metabolismo , Aumento de Peso/efeitos dos fármacos , Animais , Dieta Hiperlipídica/efeitos adversos , Intolerância à Glucose/dietoterapia , Intolerância à Glucose/prevenção & controle , Teste de Tolerância a Glucose , Humanos , Hiperglicemia/prevenção & controle , Isoleucina/farmacologia , Masculino , Camundongos Endogâmicos C57BLRESUMO
Whey protein is rich in the branched-chain amino acids, L-leucine, L-isoleucine and L-valine. Thus, branched-chain amino acids may, at least in part, mediate the effects of whey to reduce energy intake and/or blood glucose. Notably, 10 g of either L-leucine or L-isoleucine, administered intragastrically before a mixed-nutrient drink, lowered postprandial blood glucose, and intraduodenal infusion of L-leucine (at a rate of 0.45 kcal/min, total: 9.9 g) lowered fasting blood glucose and reduced energy intake from a subsequent meal. Whether L-valine affects energy intake, and the gastrointestinal functions involved in the regulation of energy intake, as well as blood glucose, in humans, is currently unknown. We investigated the effects of intraduodenally administered L-valine on antropyloroduodenal pressures, plasma cholecystokinin, blood glucose and energy intake. Twelve healthy lean men (age: 29 ± 2 years, BMI: 22.5 ± 0.7 kg/m²) were studied on 3 separate occasions in randomised, double-blind order. Antropyloroduodenal pressures, plasma cholecystokinin, blood glucose, appetite perceptions and gastrointestinal symptoms were measured during 90-min intraduodenal infusions of L-valine at 0.15 kcal/min (total: 3.3 g) or 0.45 kcal/min (total: 9.9 g), or 0.9% saline (control). Energy intake from a buffet-meal immediately after the infusions was quantified. L-valine did not affect antral, pyloric (mean number; control: 14 ± 5; L-Val-0.15: 21 ± 9; L-Val-0.45: 11 ± 4), or duodenal pressures, plasma cholecystokinin (mean concentration, pmol/L; control: 3.1 ± 0.3; L-Val-0.15: 3.2 ± 0.3; L-Val-0.45: 3.0 ± 0.3), blood glucose, appetite perceptions, symptoms or energy intake (kcal; control: 1040 ± 73; L-Val-0.15: 1040 ± 81; L-Val-0.45: 1056 ± 100), at either load (p > 0.05 for all). In conclusion, intraduodenal infusion of L-valine, at loads that are moderately (3.3 g) or substantially (9.9 g) above World Health Organization valine requirement recommendations, does not appear to have energy intake- or blood glucose-lowering effects.
Assuntos
Colecistocinina/sangue , Duodeno/efeitos dos fármacos , Ingestão de Energia/efeitos dos fármacos , Trato Gastrointestinal/fisiologia , Antro Pilórico/efeitos dos fármacos , Valina/administração & dosagem , Adulto , Apetite/efeitos dos fármacos , Austrália , Glicemia/análise , Índice de Massa Corporal , Dieta , Método Duplo-Cego , Duodeno/fisiologia , Jejum , Esvaziamento Gástrico/efeitos dos fármacos , Esvaziamento Gástrico/fisiologia , Motilidade Gastrointestinal/efeitos dos fármacos , Motilidade Gastrointestinal/fisiologia , Trato Gastrointestinal/efeitos dos fármacos , Humanos , Masculino , Pressão , Antro Pilórico/fisiologia , Inquéritos e QuestionáriosRESUMO
BACKGROUND: The fatty acid, lauric acid ('C12'), and the amino acid, L-tryptophan ('Trp'), modulate gastrointestinal functions including gut hormones and pyloric pressures, which are important for the regulation of energy intake, and both potently suppress energy intake. OBJECTIVE: We hypothesized that the intraduodenal administration of C12 and Trp, at loads that do not affect energy intake individually, when combined will reduce energy intake, which is associated with greater modulation of gut hormones and pyloric pressures. DESIGN: Sixteen healthy, lean males (age: 24 ± 1.5 y) received 90-min intraduodenal infusions of saline (control), C12 (0.3 kcal/min), Trp (0.1 kcal/min), or C12 + Trp (0.4 kcal/min), in a randomized, double-blind, cross-over study. Antropyloroduodenal pressures were measured continuously, and plasma cholecystokinin (CCK), ghrelin, and glucagon-like peptide-1 (GLP-1) concentrations, appetite perceptions, and gastrointestinal symptoms at 15-min intervals. Immediately after the infusions, energy intake from a standardized buffet meal was quantified. RESULTS: C12 + Trp markedly reduced energy intake (kcal; control: 1,232 ± 72, C12: 1,180 ± 82, Trp: 1,269 ± 73, C12 + Trp: 1,056 ± 106), stimulated plasma CCK (AUC(area under the curve)0-90 min, pmol/L*min; control: 21 ± 8; C12: 129 ± 15; Trp: 97 ± 16; C12 + Trp: 229 ± 22) and GLP-1 (AUC0-90 min, pmol/L*min; control: 102 ± 41; C12: 522 ± 102; Trp: 198 ± 63; C12 + Trp: 545 ± 138), and suppressed ghrelin (AUC0-90 min, pg/mL*min; control: -3,433 ± 2,647; C12: -11,825 ± 3,521; Trp: -8,417 ± 3,734; C12 + Trp: -18,188 ± 4,165) concentrations, but did not stimulate tonic, or phasic, pyloric pressures, compared with the control (all P < 0.05), or have adverse effects. C12 and Trp each stimulated CCK (P < 0.05), but to a lesser degree than C12 + Trp, and did not suppress energy intake or ghrelin. C12, but not Trp, stimulated GLP-1 (P < 0.05) and phasic pyloric pressures (P < 0.05), compared with the control. CONCLUSION: The combined intraduodenal administration of C12 and Trp, at loads that individually do not affect energy intake, substantially reduces energy intake, which is associated with a marked stimulation of CCK and suppression of ghrelin. The study was registered as a clinical trial at the Australian and New Zealand Clinical Trial Registry (www.anzctr.org.au,) as 12613000899741.
Assuntos
Colecistocinina/sangue , Ingestão de Energia/efeitos dos fármacos , Grelina/sangue , Peptídeo 1 Semelhante ao Glucagon/sangue , Ácidos Láuricos/farmacologia , Piloro/efeitos dos fármacos , Triptofano/farmacologia , Adulto , Apetite , Estudos Cross-Over , Método Duplo-Cego , Duodeno , Ingestão de Alimentos/efeitos dos fármacos , Ingestão de Alimentos/fisiologia , Ingestão de Energia/fisiologia , Hormônios Gastrointestinais/sangue , Humanos , Ácidos Láuricos/administração & dosagem , Masculino , Pressão , Valores de Referência , Triptofano/administração & dosagem , Adulto JovemRESUMO
Tryptophan stimulates plasma cholecystokinin and pyloric pressures, both of which slow gastric emptying. Gastric emptying regulates postprandial blood glucose. Tryptophan has been reported to decrease energy intake. We investigated the effects of intragastric tryptophan on the glycaemic response to, and gastric emptying of, a mixed-nutrient drink, and subsequent energy intake. Lean and obese participants (n = 16 each) received intragastric infusions of 1.5 g ("Trp-1.5g") or 3.0 g ("Trp-3.0g") tryptophan, or control, and 15 min later consumed a mixed-nutrient drink (56 g carbohydrates). Gastric emptying (13C-acetate breath-test), blood glucose, plasma C-peptide, glucagon, cholecystokinin and tryptophan concentrations were measured (t = 0-60 min). Energy intake was assessed between t = 60-90 min. In lean individuals, Trp-3.0g, but not Trp-1.5g, slowed gastric emptying, reduced C-peptideAUC and increased glucagonAUC (all P < 0.05), but did not significantly decrease the blood glucose response to the drink, stimulate cholecystokinin or reduce mean energy intake, compared with control. In obese individuals, Trp-3.0g, but not Trp-1.5g, tended to slow gastric emptying (P = 0.091), did not affect C-peptideAUC, increased glucagonAUC (P < 0.001) and lowered blood glucose at t = 30 min (P < 0.05), and did not affect cholecystokinin or mean energy intake. In obese individuals, intragastrically administered tryptophan may reduce postprandial blood glucose by slowing gastric emptying; the lack of effect on mean energy intake requires further investigation.
Assuntos
Depressores do Apetite/administração & dosagem , Bebidas , Glicemia/efeitos dos fármacos , Ingestão de Energia/efeitos dos fármacos , Alimentos Formulados , Obesidade/tratamento farmacológico , Triptofano/administração & dosagem , Administração Oral , Adulto , Depressores do Apetite/efeitos adversos , Bebidas/efeitos adversos , Biomarcadores/sangue , Glicemia/metabolismo , Peptídeo C/sangue , Colecistocinina/sangue , Método Duplo-Cego , Alimentos Formulados/efeitos adversos , Esvaziamento Gástrico/efeitos dos fármacos , Glucagon/sangue , Humanos , Masculino , Obesidade/sangue , Obesidade/diagnóstico , Obesidade/fisiopatologia , Período Pós-Prandial , Austrália do Sul , Fatores de Tempo , Resultado do Tratamento , Triptofano/efeitos adversosRESUMO
In contrast to the many studies of the effects of individual amino acids (AAs) on eating, no studies have compared the effects of different AAs on eating and underlying preabsorptive gastrointestinal mechanisms. To compare the effects of intraduodenal infusions of l-tryptophan (TRP), l-leucine (LEU), l-phenylalanine (PHE) and l-glutamine (GLN) on appetite, gastrointestinal hormone responses (including ghrelin, cholecystokinin (CCK), peptide YY (PYY) and glucagon-like peptide-1 [GLP-1]), glycemia (glucagon, insulin and glucose) and test meal size in healthy males, we retrospectively analyzed data from four published independent, randomized, double-blind, placebo-controlled studies of 90-min intraduodenal infusions of the individual AAs. The designs of the studies were identical, except the dose of TRP (0.15 kcal/min) was lower than that of the other AAs (0.45 kcal/min) because higher doses of this AA were not well tolerated. TRP and LEU decreased intake more than PHE (reductions relative to control, ~219 ± 68, ~170 ± 48 and ~12 ± 57 kcal, respectively), and TRP decreased intake more than GLN (~31 ± 82 kcal). These effects of TRP and LEU versus GLN, but not versus PHE, were paralleled by greater decreases in plasma ghrelin, and increases in CCK, concentrations. TRP increased PYY more than GLN or LEU, but not PHE. LEU increased PYY less than PHE. No significant differences were detected for GLP-1. PHE increased glucagon more than TRP or LEU, and increased insulin more than TRP. Under our experimental conditions, intraduodenal TRP and LEU were more satiating than PHE and GLN. The greater satiating efficacy of LEU versus PHE was significantly dissociated from the effects of these AAs on PYY, while the greater satiating potency of TRP versus PHE was significantly dissociated from the effects of these AAs on insulin and glucagon. In contrast, ghrelin and CCK, and potentially other mechanisms, including central sensing of individual AAs, appear to be stronger candidate mechanisms for the relative satiating effects obtained.
Assuntos
Aminoácidos/farmacologia , Depressores do Apetite/farmacologia , Ingestão de Alimentos/efeitos dos fármacos , Hormônios Gastrointestinais/sangue , Adolescente , Adulto , Aminoácidos/administração & dosagem , Apetite/efeitos dos fármacos , Depressores do Apetite/administração & dosagem , Glicemia/metabolismo , Colecistocinina/sangue , Método Duplo-Cego , Ingestão de Energia/efeitos dos fármacos , Grelina/sangue , Peptídeo 1 Semelhante ao Glucagon/sangue , Hormônios/sangue , Humanos , Masculino , Pessoa de Meia-Idade , Peptídeo YY/sangue , Ensaios Clínicos Controlados Aleatórios como Assunto , Adulto JovemRESUMO
BACKGROUND: The branched-chain amino acids leucine and isoleucine lower blood glucose after oral glucose ingestion, and the intraduodenal infusion of leucine decreases energy intake in healthy, lean men. OBJECTIVE: We investigated the effects of the intragastric administration of leucine and isoleucine on the gastric emptying of, and blood glucose responses to, a physiologic mixed-macronutrient drink and subsequent energy intake. DESIGN: In 2 separate studies, 12 healthy, lean subjects received on 3 separate occasions an intragastric infusion of 5 g leucine (leucine-5g) or an intragastric infusion of 10 g leucine (leucine-10g), an intragastric infusion of 5 g isoleucine (isoleucine-5g) or an intragastric infusion of 10 g isoleucine (isoleucine-10g), or a control. Fifteen minutes later, subjects consumed a mixed-nutrient drink (400 kcal, 56 g carbohydrates, 15 g protein, and 12 g fat), and gastric emptying (13C-acetate breath test) and blood glucose, plasma insulin, C-peptide, glucagon, glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP), and cholecystokinin (leucine study only) were measured for 60 min. Immediately afterward, energy intake from a cold, buffet-style meal was assessed. RESULTS: Compared with the control, leucine-10g decreased the blood glucose area under the curve (AUC) (P < 0.05) and tended to reduce peak blood glucose (P = 0.07), whereas effects of leucine-5g were NS. Leucine-10g, but not leucine-5g, increased plasma insulin and C-peptide AUCs (P < 0.01 for both), but neither dose affected glucagon, GLP-1, GIP, cholecystokinin, gastric emptying, or energy intake. Compared with the control, isoleucine-10g reduced the blood glucose AUC and peak blood glucose (P < 0.01), whereas effects of isoleucine-5g were NS. Neither load affected insulin, C-peptide, glucagon, GLP-1, or GIP. Isoleucine-10g, but not isoleucine-5g, slowed gastric emptying (P < 0.05), but gastric emptying was not correlated with the blood glucose AUC. Isoleucine did not affect energy intake. CONCLUSIONS: In healthy subjects, both leucine and isoleucine reduced blood glucose in response to a mixed-nutrient drink but did not affect subsequent energy intake. The mechanisms underlying glucose lowering appear to differ; leucine stimulated insulin, whereas isoleucine acted insulin independently. These trials were registered at www.anzctr.org.au as 12613000899741 and 12614000837628.
Assuntos
Bebidas , Glicemia/metabolismo , Isoleucina/administração & dosagem , Leucina/administração & dosagem , Adulto , Índice de Massa Corporal , Peptídeo C/sangue , Colecistocinina/sangue , Estudos Cross-Over , Carboidratos da Dieta/administração & dosagem , Gorduras na Dieta/administração & dosagem , Proteínas Alimentares/administração & dosagem , Ingestão de Energia , Feminino , Esvaziamento Gástrico , Polipeptídeo Inibidor Gástrico/sangue , Glucagon/sangue , Peptídeo 1 Semelhante ao Glucagon/sangue , Voluntários Saudáveis , Humanos , Insulina/sangue , Isoleucina/sangue , Leucina/sangue , Masculino , Adulto JovemRESUMO
BACKGROUND: Branched-chain amino acids (BCAAs), particularly leucine, act as nutrient signals regulating protein synthesis and degradation as well as glucose metabolism. In addition, leucine has been demonstrated in animal experiments to modulate eating and energy homeostasis. OBJECTIVE: We aimed to characterize the effects of physiologic and supraphysiologic loads of intraduodenal leucine on eating, gut hormone and motor functions, and blood glucose in humans. DESIGN: Twelve lean men were studied on 3 occasions in a randomized, double-blind order. Antropyloroduodenal motility, plasma ghrelin, cholecystokinin, glucagon-like peptide 1, peptide YY, insulin, glucagon, blood glucose, appetite perceptions, and gastrointestinal symptoms were measured during 90-min intraduodenal infusions of leucine at 0.15 kcal/min (total 3.3 g, 13.5 kcal), 0.45 kcal/min (total 9.9 g, 40.5 kcal), or saline (control). Ad libitum eating from a buffet lunch was quantified immediately after the infusions. RESULTS: Leucine at 0.45 kcal/min inhibited eating (energy intake by â¼13%, P < 0.05), increased plasma cholecystokinin, slightly reduced blood glucose and increased plasma insulin, and decreased antral pressures (all P < 0.05). Leucine at 0.15 kcal/min had no effect on food intake, blood glucose, or antral pressures but also slightly increased plasma cholecystokinin (P < 0.05). Neither dose affected plasma ghrelin, glucagon, glucagon-like peptide 1 and peptide YY, or pyloric and duodenal pressures. Plasma leucine concentrations were related to the dose of intraduodenal leucine, with substantial increases during both 0.15 and 0.45 kcal/min. CONCLUSIONS: The effects of intraduodenal infusions of free leucine on eating are probably not primarily mediated by changes in gut motor and hormone functions, with perhaps the exception of cholecystokinin. Instead, increased plasma leucine concentrations may be a potential signal mediating the eating-inhibitory effect of leucine. The study was registered as a clinical trial with the Australia and New Zealand Clinical Trial Registry (www.anzctr.org.au) as ACTRN12613000899741.
Assuntos
Glicemia/metabolismo , Ingestão de Alimentos/efeitos dos fármacos , Hormônios Gastrointestinais/sangue , Motilidade Gastrointestinal/efeitos dos fármacos , Leucina/administração & dosagem , Adolescente , Adulto , Apetite/efeitos dos fármacos , Índice de Massa Corporal , Colecistocinina/sangue , Relação Dose-Resposta a Droga , Método Duplo-Cego , Duodeno/efeitos dos fármacos , Duodeno/metabolismo , Ingestão de Energia , Grelina/sangue , Glucagon/sangue , Peptídeo 1 Semelhante ao Glucagon/sangue , Humanos , Insulina/sangue , Leucina/sangue , Masculino , Peptídeo YY/sangue , Adulto JovemRESUMO
BACKGROUND: PEPT1 was proposed to be expressed only in inflamed colonic tissues in which it could contribute to inflammatory bowel disease (IBD) development by transporting bacterial peptides, such as muramyl dipeptide (MDP), that activate intracellular pattern recognition receptors, such as the nucleotide-binding and oligomerization domain 2. To better define the pathological relevance of this transporter, we analyzed PEPT1 expression during intestinal inflammation and studied the susceptibility of Pept1-deficient (Pept1) mice to experimental colitis. METHODS: Wild-type and Pept1 mice were treated with dextran sulfate sodium and 2,4,6-trinitrobenzene sulfonic acid to induce colitis, and MDP-induced cytokine expression was studied in colonic tissue cultures. PEPT1 expression was characterized in mouse models of Crohn's disease-like ileitis (Tnf) or colitis (Il-10, Il-10XTlr2) and endoscopic tissue samples from descending colon of patients with IBD (n = 11) and controls (n = 17). Moreover, the prevalence of the PEPT1 single-nucleotide polymorphism rs2297322 was tested in German patients with IBD (n = 458) and controls (n = 452). RESULTS: PEPT1 expression was consistently reduced under condition of acute or chronic experimental inflammation. Wild-type and Pept1 mice revealed comparable susceptibility to dextran sulfate sodium-induced and 2,4,6-trinitrobenzene sulfonic acid-induced colitis, and MDP-induced cytokine expression was PEPT1-independent. PEPT1 expression levels were also decreased in descending colon of patients with IBD during acute inflammation, but the rs2297322 single-nucleotide polymorphism was not associated with IBD susceptibility in the German cohort. CONCLUSIONS: PEPT1 expression is reduced during intestinal inflammation and PEPT1 is neither required for MDP-induced immune response nor is the PEPT1 rs2297322 single-nucleotide polymorphism associated with IBD susceptibility in our German cohort. These data strongly argue against a primary role of PEPT1 in the initiation or progression of IBD.