<p>Obesity and nutrition-related non-communicable diseases continue to be major challenges that are increasing in severity worldwide. Science-centered carbohydrate dietary strategies may be a viable approach to help address such challenges. Recent reports from our laboratory indicate that certain carbohydrates with slow digestion profiles have the ability to trigger the gut-brain axis and reduce food intake and to slow gastric emptying and potentially affect appetite. Slow carbohydrate digestion may have other impacts on energy metabolism that have not been explored. In the current investigations, we sought to better understand the delayed gastric emptying profile of pearl millet-based foods as well as to understand how altering carbohydrate digestion rate impacts substrate utilization for energy.</p> <p>In the first study, the physical breakdown of pearl millet couscous particles in a simulated gastric environment (Human Gastric Simulator) was studied compared to wheat couscous matched in particle size, and select physicochemical properties of each type of couscous were characterized. Because we previously showed that pearl millet couscous had a marked delay in gastric emptying compared to white rice, boiled potatoes, and pasta in a human study in Mali, the objective of the first investigation was to test the hypothesis that pearl millet couscous was more resistant to breakdown in the stomach than wheat couscous and would take longer to empty. Our findings indicated that pearl millet couscous instead broke down into smaller, more numerous particles than wheat couscous. However, pearl millet had a slower starch hydrolysis property compared to wheat couscous per unit surface area. Pearl millet also had a smaller amylose chain length (839-963 DP) compared to wheat (1225-1563 DP), which may enable a denser packing of millet starch molecules that hinders hydrolysis. We also visually observed that the pearl millet particles formed a paste while breaking down that could reasonably generate viscosity in the stomach to potentially delay gastric emptying. </p> <p>Based off the findings from simulated gastric digestion, we next conducted a human study (<i>n</i>=14) in the U.S. to test the hypothesis that pearl millet-based foods (couscous – commercial and self-made, thick porridge) would reduce glycemic response, increase satiety, and delay gastric emptying compared to wheat couscous and white rice. We complemented this human study with additional <i>in vitro </i>work using an advanced gastrointestinal digestion system (TIMagc) to determine if the viscosity of pearl millet couscous particles as they were breaking down in the stomach was contributing to a decrease in gastric emptying. Our findings indicated that all the pearl millet-based foods and wheat couscous had lower overall glycemic response than white rice, but only the self-made millet couscous showed higher satiety through subjective appetitive response ratings. Surprisingly, there were no differences in gastric emptying among the foods. Additionally, the half-emptying times for these foods were all ~3 h, which is similar to the comparably low half-emptying times observed for white rice, boiled potatoes, and pasta in the previous Mali study. We now hypothesize that there may be diet-induced changes in gut-brain axis signaling when slowly digestible carbohydrates are consumed repeatedly over time, perhaps through modulating the number or sensitivity of small intestinal L-cells. We also found that millet couscous did not exhibit high viscosity in the TIMagc, suggesting that viscosity was not impacting its rate of gastric emptying. We conclude that at least some pearl millet-based foods possess a slow digestion property that may act to trigger the gut-brain axis or ileal brake to increase feelings of satiety or slow gastric emptying, but the discrepancy between U.S. and Malian populations requires further study. </p> <p>In the final investigation, we examined how altering carbohydrate digestion affected partitioning of carbohydrate versus fat for oxidation as well as the efficiency of switching oxidation between these two substrates (termed “metabolic flexibility”) in mice. Metabolic flexibility has been associated with good health related to decreased adipose tissue in the body and improved insulin sensitivity and may have implications on weight management. Carbohydrate digestion was adjusted by: (1) testing mice that lacked a complete set of enzymes by knocking out maltase-glucoamylase (Mgam; null) for moderating starch digestion versus testing wild-type mice; (2) using diets in these two groups of mice to moderate starch digestion that had different levels of resistant starch (53%, 35%, and 18%), had only raw corn starch or sucrose, or were high in fat; and (3) providing a supplement of fungal amyloglucosidase (AMG) to the mice treatment groups to increase starch digestion. Respiratory exchange ratio (RER) was measured through indirect calorimetry and mathematical modeling was used to characterize the diurnal shifts in RER (sine equation) as well as carbohydrate versus fat oxidation and metabolic flexibility (percent relative cumulative frequency [PRCF] with Weibull and Mixed Weibull Cumulative Distribution functions). Our results suggest that null mice lacking Mgam had somewhat increased metabolic flexibility than wild-type mice despite exhibiting minimal to no effects on carbohydrate oxidation. Intriguingly, the raw corn starch diet increased fat oxidation and generally promoted metabolic flexibility, although it did not increase carbohydrate oxidation relative to the other carbohydrate-predominant diets. Increasing carbohydrate digestion through AMG supplementation increased carbohydrate oxidation, and generally prompted earlier shifts to carbohydrate oxidation than without AMG supplementation. These findings provide a basis for better understanding the metabolic consequences of altering carbohydrate digestion and establish novel tools that can be utilized in future investigations. Overall, we propose that moderating carbohydrate digestion provides the ideal combination of balancing carbohydrate and fat oxidation while promoting metabolic flexibility. </p> <p>In conclusion, a slow digestion property may enable some types of pearl millet to trigger the ileal brake and gut-brain axis feedback systems to decrease glycemic response and increase satiety. Moreover, consuming carbohydrates with slow digestion may optimize substrate utilization for energy by the body. In addition to triggering the ileal brake and gut-brain axis, modulating carbohydrate digestion to more effectively switch between carbohydrate and fat for oxidation may be beneficial for weight management and metabolic disease prevention.</p>

Raw seeds of sixteen common bean (Phaseolus vulgaris L.) cultivars were evaluated along two consecutive harvests (2001/2002 and 2002/2003) concerning their physicochemical characteristics, as well as the effect of cooking and storage conditions on starch and dietary fiber contents. Serum lipids and blood glucose levels were also evaluated in normolipidemic-normoglycemic rats witch were fed diets containing bean cultivars with different soluble fiber/total fiber ratios (SF/TF): Pérola diet (0.11), Diamante Negro diet (0.19) and Iraí diet (0.26); control group was fed a standard diet (with insoluble fiber). Except for dry matter, moisture, and total dietary fiber, cultivars kept their chemical characteristics between harvests. Regarding similarity among macronutrient levels (crude protein-CP, total dietary fiber, insoluble dietary fiber, soluble dietary fiber-SF, digestible starch-DS, and resistant starch-RS) seeds from harvests 2001/2002 and 2002/2003 were categorized into four different groups; the same was done for micronutrients (Fe, Zn, Mn, Cu, Ca, Mg, and P), and four groups were also identified. Guateian 6662 and Rio Tibagi were considered the cultivars with the best nutritional profile (highest levels of CP, SF, DS, Fe, and Zn). Storage under refrigerated or freezing conditions did not change fiber content of cooked beans, but decreased their DS content and increased RS content, mainly in seeds with low RS levels before cooking. Concerning biological response, rats fed bean diets experienced lower values for serum cholesterol (P<0.05) and lower glycemic indexes (P<0.05). It was also observed a similar weight gain among groups, however animals fed bean based diets showed lower fat retention (P<0.05). The effects of bean diets on experimental groups were more remarkable in animals fed Iraí diet (SF/TF: 0.26). / Foram analisadas as características físico-químicas de sementes cruas de dezesseis cultivares de feijão comum (Phaseolus vulgaris L.), ao longo de duas safras consecutivas (2001/2002 e 2002/2003), bem como os teores de amido e fibra alimentar nas sementes após cozimento e estocagem. Avaliaram-se, também, os lipídeos séricos e a glicose sanguínea de ratos normolipidêmicos e normoglicêmicos, alimentados com dietas contendo cultivares de feijão com diferentes relações fibra solúvel/fibra total (FS/FT): dieta Pérola (0,11), dieta Diamante Negro (0,19) e dieta Iraí (0,26); o grupo controle recebeu dieta padrão (com fibra insolúvel). Exceto pelos teores de matéria seca, umidade e fibra alimentar total, as cultivares estudadas mantiveram suas características físico-químicas constantes ao longo das safras. Conforme a similaridade nos teores de macronutrientes (proteína bruta-PB, fibra alimentar total, fibra alimentar insolúvel, fibra alimentar solúvel-FS, amido disponível-AD e amido resistente-AR) as sementes das safras 2001/2002 e 2002/2003 foram categorizadas em quatro grupos distintos; da mesma forma, em relação aos micronutrientes (Fe, Zn, Mn, Cu, Ca, Mg e P), quatro grupos puderam ser identificados. As cultivares Guateian 6662 e Rio Tibagi apresentaram o melhor perfil nutricional (maiores teores de PB, FS, AD, Fe e Zn). A armazenagem sob refrigeração e o congelamento não determinaram alterações nos teores de fibra dos grãos cozidos, mas redução do AD e aumento do AR, principalmente naqueles com AR mais baixo antes do cozimento. Em relação à resposta biológica, os ratos alimentados com dietas contendo feijão apresentaram valores para colesterol sérico e índice glicêmico menores que os do grupo controle (p<0,05). Foi observado, também, que apesar do ganho de peso dos animais ter sido semelhante entre os grupos, os ratos alimentados com as dietas contendo feijão apresentaram menor retenção de gordura corporal (p<0,05). Os efeitos das dietas sobre os animais experimentais foram mais expressivos no grupo alimentado com a dieta Iraí (FS/FT: 0,26).

Made available in DSpace on 2014-07-29T15:13:45Z (GMT). No. of bitstreams: 1 Tese parte1 Fabricia Rocha Chaves Miotto.pdf: 8322893 bytes, checksum: e402e3e9bcec9054d69df88cb3b48403 (MD5) Previous issue date: 2011-08-18 / This study aimed to evaluate intake, apparent digestibility of nutrients and nitrogen balance (NB) of diets containing babassu mesocarp bran (BMB) in replacement of elephant grass silage (0, 21, 38, 62 and 78%). Twenty sheep were placed in metabolism crates and allotted to a completely randomized design with four replicates. Were collected and recorded food intake and excretion of feces and urine. The intakes of dry matter (DM), organic matter (OM), crude protein (CP), ash, neutral detergent fibrous (NDF), acid detergent fibrous (ADF), hemicellulose and total carbohydrates were not affected by experimental diets. Change was observed in the intakes of non fibrous carbohydrates (NFC) and reduced intake of ether extract (EE) as % of live weight (%LW) and grams per unit of metabolic weight (g/UMW). The total digestible nutrients TDN intake had a quadratic response with maximum points at 37.3 and 37.9% of BMB when expressed in % LW and g/UMW, respectively. The apparent digestibilities of OM, NDF, ADF, CP and NFC reduced to the extent that the BMB has increased in the diets. The digestibility of DM, EE, and NFC had a quadratic response, where the maximum digestibility of DM was estimated at 10% BMB. TDN decreased 0.28% for each percentage point of inclusion in the diets of BMB. The BMB use reduces the fibrous fractions digestibility, but increases the NFC and TDN intake, indicating that this byproduct can be used as an energy source for ruminant diets. Note: Thesis w/seven chapters. Presented summary and abstract of the 2nd chapter / Objetivou-se avaliar consumo, digestibilidade aparente de nutrientes e balanço de nitrogênio (BN) de dietas contendo farelo de mesocarpo de babaçu (FMB) em substituição à silagem de capim elefante (0; 21; 38; 62 e 78%). Utilizaram-se 20 ovinos alojados em gaiolas metabólicas individuais e distribuídos em delineamento inteiramente casualisado com quatro repetições. Foram coletados e registrados o consumo de alimentos e excreções de fezes e urina. Os consumos de matéria seca (MS), matéria orgânica (MO), proteína brutua (PB), cinza, fibra em detergente neutro (FDN), fibra em detergente ácido (FDA), hemicelulose e carboidratos totais não foram influenciados pelas dietas experimentais. Foi observada alteração nos consumos de carboidratos não fibrosos (CNF) e redução nos consumos de extrato etéreo (EE) em % do PV e em gramas por unidade de tamanho metabólico (g/UTM). O consumo de nutrientes digestíveis totais (NDT) teve comportamento quadrático com pontos de máximo em 37,3 e 37,9% de FMB expressos em %PV e g/UTM, respectivamente. As digestibilidades aparentes da MO, FDN, FDA, PB e CNF reduziram na medida em que o FMB aumentou nas dietas. A digestibilidade da MS, EE e CNF tiveram comportamento quadrático, em que a máxima digestibilidade da MS foi estimada com 10% de FMB. O NDT reduziu 0,28% para cada ponto percentual de inclusão de FMB nas dietas. O uso do FMB reduz a digestibilidade de frações fibrosas, contudo aumenta o consumo de CNF e o consumo de NDT, o que indica que esse subproduto pode ser utilizado como fonte energética para dietas de ruminantes. OBS: Tese c/ sete capítulos. Apresentado resumo e abstract do 2° capítulo.

Made available in DSpace on 2016-08-17T17:11:05Z (GMT). No. of bitstreams: 1 DISSERTACAO_FLAVIO OLIVEIRA SOUZA.pdf: 1270083 bytes, checksum: 64eb72657a650bd6843728d330a5761e (MD5) Previous issue date: 2014-03-27 / The aim was to determine the methionine plus cystine with lysine ratio in diets for tambaqui (Colossoma macropomum) fingerlings. Six hundred tambaqui fingerlings of two distinct initial weights, 0.28 ± 0.08g and 0.94 ± 0.33g, were used in an experiment with randomised block design (criterion dependent upon initial average weight) composed of six treatments, five repetitions in two blocks and twenty fish per experimental unit. The treatments consisted of six experimental diets isolysinic digestible (1.45%), isoenergetic, isophosphorus and isocalcium containing different methionine plus cystine with digestible lysine ratio (50, 55, 60, 65, 70 and 75%). The fish were kept in 1,000 litre polyethylene tanks, equipped with individual aeration and water supplies, and were fed ad libitum in six daily meals for 45 days. Performance parameters, body composition, protein and body fat deposition and the efficiency nitrogen retention of the fishes were evaluated. The increase of the dietary digestible methionine plus cystine:lysine ratio in the diet affected the specific growth rate, feed:gain ratio, digestible methionine plus cystine intake and the body fat of the fishes. The effects were quadratic for the first two, with these variables improving up to methionine plus cystine:lysine ratio of 64.4% and 64.8%. The digestible methionine plus cystine intake increased and body fat decreased linearly with increase of methionine plus cystine:lysine ratio. The methionine plus cystine with lysine digestible ratio recommended in diets for tambaqui fingerlings is 64.8%, which corresponds the level of digestible methionine plus cystine of 0.94% (0.313% Mcal of ED). / Objetivou-se determinar a relação da metionina mais cistina com a lisina em rações para alevinos de tambaqui (Colossoma macropomum). Foram utilizados 600 alevinos de tambaqui de dois pesos iniciais distintos, 0,28 ± 0,08g e 0,94 ± 0,33g, em experimento com delineamento em blocos ao acaso (critério em função do peso médio inicial), composto por seis tratamentos, cinco repetições em dois blocos, e vinte peixes por unidade experimental. Os tratamentos consistiram de seis rações experimentais isolisínicas digestíveis (1,45%), isoenergéticas, isofosfóricas e isocálcicas, contendo diferentes relações de metionina mais cistina com a lisina digestível (50, 55, 60, 65, 70 e 75%). Os peixes foram mantidos em caixas de polietileno de 1.000 litros dotados de abastecimento de água e aeração individuais, e foram alimentados ad libitum em seis refeições diárias durante 45 dias. Avaliaram-se parâmetros de desempenho, composição corporal, deposição de proteína e gordura corporais e eficiência de retenção de nitrogênio dos peixes. O aumento da relação de metionina mais cistina:lisina digestível da dieta influenciaram na taxa de crescimento específico, na conversão alimentar, no consumo de metionina mais cistina digestíveis e no teor de gordura corporal dos peixes. Os efeitos foram quadráticos para as duas primeiras, melhorando essas variáveis até a relação metionina mais cistina:lisina digestível de 64,4% e 64,8%. O consumo de metionina mais cistina digestível aumentou e o teor de gordura corporal reduziu linearmente com a elevação da relação metionina mais cistina:lisina digestível. A relação metionina mais cistina com a lisina digestível recomendada nas rações para alevinos de tambaqui é de 64,8%, que corresponde ao nível de metionina mais cistina digestível de 0,94% (0,313% Mcal de ED).