Diet Switch Research Articles

Fat and Sucrose Intake Induces Obesity-Related Bone Metabolism Disturbances: Kinetic and Reversibility Studies in Growing and Adult Rats.

Metabolic and bone effects were investigated in growing (G, n = 45) and mature (M, n = 45) rats fed a high-fat/high-sucrose diet (HFS) isocaloric to the chow diet of controls (C, n = 30 per group). At week 19, a subset of 15 rats in each group (HFS or C, at both ages) was analyzed. Then one-half of the remaining 30 HFS rats in each groups continued HFS and one-half were shifted to C until week 27. Although no serum or bone marrow inflammation was seen, HFS increased visceral fat, serum leptin and insulin at week 19 and induced further alterations in lipid profile, serum adiponectin, and TGFβ1, TIMP1, MMP2, and MMP9, suggesting a prediabetic phenotype and cardiovascular dysfunction at week 27 more pronounced in M than G. These events were associated with dramatic reduction of osteoclastic and osteoid surfaces with accelerated mineralizing surfaces in both HFS age groups. Mineral metabolism and its major regulators were disturbed, leading to hyperphosphatemia and hypocalcemia. These changes were associated with bone alterations in the weight-bearing tibia, not in the non-weight-bearing vertebra. Indeed in fat rats, tibia trabecular bone accrual increased in G whereas loss of trabecular bone in M was alleviated. At diaphysis cortical porosity increased in G and even more in M at week 27. After the diet switch, metabolic and bone cellular disturbances fully reversed in G, but not in M. Trabecular benefit of the obese was preserved in both age groups and in M the age-related bone loss was even lighter after the diet switch than in prolonged HFS. At the diaphysis, cortical porosity normalized in G but not in M. Hypocalcemia in G and M was irreversible. Thus, the mild metabolic syndrome induced by isocaloric HFS is able to alter bone cellular activities and mineral metabolism, reinforce trabecular bone, and affect cortical bone porosity in an irreversible manner in older rats.

Resource requirements of parrots: nest site selectivity and dietary plasticity of Psittaciformes

Parrots (Order Psittaciformes) are secondary cavity-nesters that depend on existing cavities for nest sites, and consume plant resources of fruits, seeds, and flowers that are highly variable, but little is known of resource selectivity by parrots, or how they deal with variable environments. We reviewed published studies of nest-cavity use by parrots, and those evaluating parrot diet and their relationship with food resources. Most studies have been conducted within the last 20 years and these present data on resource use for only one-third of parrot species worldwide. However, basic information on resource requirements is lacking for the vast majority of Psittaciformes, particularly for species from the Asian region. Nesting studies have found that parrots use nest cavities in large trees, high above the ground, with large nest chambers, of 0.5–1 m deep, and entrance diameters related to body size of the parrot species. A few studies demonstrate that parrots select nest sites based on cavity characteristics, which may influence nest success, but a complete evaluation of adaptive nest site selection by Psittaciformes is lacking. Parrots have varied diets and may employ a combination of strategies of diet switching, habitat shifts, and movements to track food resources. This plasticity in diet and foraging strategy may influence the extent to which parrots can respond to anthropogenic pressures of global change. Parrots may also play an important functional role in forest ecosystems, yet little is currently known of plant–animal interactions of parrots, or the impact of parrot populations on forest dynamics. Based on our review of the literature, we suggest that to meet their resource requirements, parrots employ resource selection strategies of hierarchical nest site selection to increase the likelihood of nest success, and plasticity in diet and foraging strategy to track variable food resources. Future studies need to evaluate resource selection and the consequences of this for fitness in order to assess the potential impacts of global change on parrot populations, and to identify characteristics which make species vulnerable to human pressures.

Modelling and determination of metabolic pools by stable carbon isotopes in the avian duodenal mucosa and albumen.

Stable isotope analyses have helped in assessing dietary switches if the diet undergoes metabolic alteration (isotopic exchange). However, when considering the effects over time of switching from one diet to another, one can assess how quickly the new diet is incorporated into tissues via the isotopic renewal or incorporation rate, or turnover. Turnover is obtained using exponential curves that fit the original data, allowing the determination of practical order parameters such as the half-life (T) and the turnover constant (k). Researchers have found that metabolic incorporation can be fractionated. The resulting fractions, called metabolic pools, are identified using the linearization of the isotopic exchange model and its linear fit. This fractionation methodology is still not well defined. The objective of this study was to assess the behaviour of the metabolic renewal rate (turnover) in fractionated form, explain the theory, and apply it to data from the avian duodenal mucosa and albumen. We concluded that the duodenal mucosa has one metabolic pool, with a half-life of 1.23days, and that the albumen has two metabolic pools, with half-lives of 1.89 and 6.32days.

Abstract 542: The Effects of Soluble Epoxide Hydrolase Inhibition in Atherogenesis and Atherosclerotic Progression

Epoxyeicosatrienoic acids (EETs), metabolites of arachidonic acid (AA), are known to have anti-inflammatory effects and hydrolyzed by soluble epoxide hydrolase (sEH). We aimed to investigate the effect of sEH inhibition on atherosclerotic progression. LDLR-/- mice with or without sEH inhibitor and LDLR and sEH double knockout (DK) mice were fed with western diet for 6 weeks to induce arteriosclerosis, and then half of the mice switched to chow diet supplemented with sEH inhibitor for another 6 weeks. To further assess the role of sEH in atherosgenesis, we transplanted LDLR-/- or DK bone marrow into LDLR-/- recipients and also fed with 6 weeks western diet. The progression of atherosclerosis was evaluated and AA metabolites were analyzed by LC-MS/MS. The results revealed that sEH inhibition and gene knockout decreased western diet-induced high plasma LDL cholesterol level and the size of the atherosclerotic lesion in the aorta of the mice. Furthermore, mice with DK bone marrow transplantation developed less aortic lesion by less ly6chi monocyte infiltiation without diminished the cholesterol level in plasma. After diet switch, the cholesterol level dropped back to control level and the size of arotic lesion became smaller compared to the western diet group. When sEH inhibitor decreased sEH activity in the liver and increased EETs/DHETs ratio in the plasma, the plaque size seemed not being further reduced after diet switch. However, M2 type macrophage marker at protein and mRNA level was increased in the aortic lesions. In cultured macrophage, sEH inhibition and EETs supplements could increase the markers of M2 macrophage at mRNA level. Thus, sEH inhibition and depletion in macrophage attenuated atherosclerosis when fed with western diet. Although the role of the sEH inhibitor on atherosclerosis progression and plaque stability need to be further investigated. EETs levels and sEH activity may play a pivotal role in atherogenesis and monocyte/macrophage in filtration and differentiation.

Impact of weight loss on obese adipose tissue immune cell function (CAM1P.154)

Abstract Obesity induces inflammation in adipose tissue involving the recruitment and activation of macrophages, CD8+ and CD4+ T cells. These cells play a critical role in the development of insulin resistance seen with obesity. Weight loss can improve insulin resistance and health, but little is known concerning the effects of weight loss on immune activity in adipose tissue. Diet switch from a 60% high-fat diet to 13% normal-fat diet was used to induce weight loss in diet-induced obese C57Bl/6 mice. Adipose tissue fibrosis and macrophage accumulation was evaluated by histology. Leukocyte populations were analyzed by flow, including sorting and cytokine expression comparisons of adipose tissue macrophages before and after weight loss. Weight loss improved glucose tolerance and reduced serum insulin. However extensive adipose fibrosis developed after diet switch and was associated with macrophage accumulation. Analysis of macrophages after weight loss showed they retained a pro-inflammatory gene expression profile and had high surface marker expression of T cell co-stimulatory markers, similar to macrophages found in obese adipose tissue. These adipose macrophages were comprised of both old and newly recruited cells that continued to be activated after weight loss. The continued inflammatory activation of leukocytes after weight loss may help explain the variation seen in metabolic improvements and long-term weight management of patients in response to weight loss interventions.

Abstract 561: A Novel Integrin Modulating Arg-Gly-Asp(RGD)-Peptide-Coated Stent Reduces Neoatherosclerosis in a Rabbit Model

Objective: While drug-eluting stents have dramatically reduced restenosis, they are often associated with increased risk of late stent thrombosis and neointimal atherosclerosis (“neoatherosclerosis”). In-stent neoatherosclerosis represents a further accelerated and possibly more unstable manifestation of atherosclerotic progression in nascent neointimal tissue after stent implantation. We hypothesized that poor arterial re-endothelialization accompanied by leaky endothelial junctions is a primary mechanism contributing to neoatherosclerosis. In the present study, we tested the ability of a RGD-peptidomimetic-coating of bare metal stents to reduce the formation of in-stent neoatherosclerosis by promoting integrin-mediated adhesion of endothelial cells, and improving their functional integrity. Approach and Results: Established iliofemoral plaques were created in male New Zealand white rabbits (n=10) by balloon injury and feeding a high cholesterol (1.0%) diet for 5 wks, which was then switched to a low cholesterol diet (0.025%) for the remainder of the study. At 3 wks after diet switch, an RGD-coated stent was implanted together with a drug-eluting stent in the contralateral iliac artery, and animals were continued on the low cholesterol diet for 7 wks (serum cholesterol between 400-1,000 mg/dl). Endothelial permeability was assessed by FITC-dextran (250/500 kDa, approx. LDL radius) injected intravenously 1 h before termination. Oil red O and Filipin staining demonstrated neutral lipid and free cholesterol accumulation in the developing neointimal of stented arteries. En face confocal microscopy of the luminal surface following immunostaining against endothelial markers followed by scanning electron microscopy showed greater endothelial coverage of luminal surfaces for RGD-coated stents. Stents were further quantified by histomorphometric analysis for vascular healing, thrombus formation and inflammation. Conclusion: A rabbit neoatherosclerosis model was established to study the formation and progression of this novel disease manifestation. RGD-coated stents showed reduced formation of neoatherosclerosis in association with improved vessel healing and re-endothelialization compared to drug-eluting stents.

Population dynamics of thrushes and seasonal resource partition

We studied seasonal population dynamics in birds using four thrush species from the Yenisei middle taiga region as an example. Long-term data on bird route censuses, capture-mark-recapture, and nest observa- tions were incorporated in the analysis. Particularly, methodological problems that complicate a direct comparison between assessed numbers at different phases of the annual cycle are considered. The integrated analysis of the results allowed comparing changes in numbers, energy expenditure, age structure, migrating status, and density distribution of selected populations during the snowless period and relating them to seasonal changes in food resource abundance. Thrush population numbers within the breeding range, and their energy consumption in the Yenisei middle taiga proportionately reflect the seasonal change in abundance of food resources. The compliance between resource intake and carrying capacity of the environment is attained by: timing of arrival and departure regarding to the species' range of tolerance; change in numbers as a result of reproduction and mortality; change in numbers due to habitat changes and long-distance movements; increasing energetic expenditures during reproduction and molt; timing, intensity and replication of nesting attempts; timing of molt and proportion of molting individuals in a population; individual variations of the annual cycle. Reproductive growth of local bird populations is not fast enough to catch up with seasonal growth of ecosystems productivity. Superabundance of invertebrates at the peak of the season offers a temporal niche which, on the one hand, is suitable for species capable of diet switching, while, on the other hand, may be used by specialized consumers, namely tropical migrants for whom, at high resource level, a shortened breeding period suffices.

Abstract P4-04-28: Weight loss reversed the carcinogenic effect of obesity on basal-like breast cancer

Abstract Epidemiologic studies demonstrate that obesity is associated with a subtype of breast cancer called basal-like breast cancer (BBC), which is fast proliferating and aggressive, with no targeted therapies. Using the C3(1)-TAg murine model of BBC, we have previously shown that obese adult mice displayed significantly decreased tumor latency compared to lean mice with induction of the oncogenic HGF/c-Met pathway. Reducing adiposity is predicted to lower incidence of BBC in human population studies. Thus, the objective of this study was to investigate how a diet-switch to reduce obesity affected BBC onset and early progression. C3(1)-TAg mice were placed on a control low fat diet (LFD) and remained lean, high-fat diet (HFD) to induce obesity, and a group made obese by HFD that were then switched to LFD to induce weight loss. Just two weeks after weight loss, mice in the diet switch group had weights and adiposity similar to lean mice. Weight loss caused a 51.4% decrease in adiposity (P<0.0001) compared to obese mice. Importantly, mice that lost weight displayed significantly delayed tumor latency (17 week) compared to obese mice on HFD (15 week), with no differences detected in tumor burden or growth. Therefore the obese microenvironment that promotes early tumor onset can be reprogrammed with weight loss and restoration of a lean phenotype. Ongoing studies are examining HGF/cMet expression by immunohistochemistry in normal mammary glands and tumors to determine the contribution of this obesity-responsive pathway. Metabolomics and RNAseq analysis will identify novel obesity-dependent pathways relevant to BBC. In conclusion, we demonstrated that loss of adiposity protected against early BBC onset. Further research will identify important biomarkers associated with obesity and weight loss that can be compared through conserved biology approaches. Citation Format: Yuanyuan Qin, Sneha Sundaram, Liyang Zhao, Luma Essaid, Kirk K McNaughton, Katharine M Bendt, David B Darr, Melissa A Troester, Liza Makowski. Weight loss reversed the carcinogenic effect of obesity on basal-like breast cancer [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P4-04-28.

Diet, Microbiota, and Microbial Metabolites in Rural Africans and African Americans

Epidemiological studies have provided strong evidence that sporadic colon cancer risk is driven by diet, with red meat and fat increasing, and fibre suppressing risk 1,2 and yet human dietary intervention studies with low fat, high fibre diets have yielded disappointing results 3. To investigate this controversy, we performed strictly controlled in‐house studies where the diets of high risk African Americans (high meat and fat, low fibre) and low risk rural Africans (low meat and fat, high fibre) were switched for two weeks, and at the same time interrogated the hypothesis that diet mediates cancer risk through its effects on microbiota metabolism. Diet switch induced significant reciprocal changes in mucosal biomarkers of inflammation and cancer risk, with reductions in African Americans and increases in Africans. That these changes were mediated by the microbiota was evidenced by similar reciprocal changes in its composition and function, exemplified by a loosening of the robust interaction structure geared to complex plant carbohydrate degradation and butyrate production in Africans, and a strengthening of intermicrobial connectivity in African Americans. Furthermore, phenotypic shifts in the metabolome revealed potential mechanisms responsible for the mucosa changes, with increased saccharolytic fermentation and anti‐neoplastic butyrate production and reduced microbial generation of pro‐carcinogenic secondary bile acids in Americans, and the reverse in Africans. In conclusion, our study reveals mechanisms responsible for the epidemiological association between western diets and high colon cancer risk, and indicates that halving fat intake and increasing fibre intake to approximately 50g/d (i.e. far greater changes than those achieved by past intervention studies) can be expected to have an immediate effect on cancer risk. Our findings also warn against the progressive westernization of the traditional African diet, where a reduction in butyrogenesis may permit the progression of chronic inflammation to neoplasia.

Temporal patterns of nutrition dependence in secondary sexual traits and their varying impacts on male mating success

Variation in the quantity of nutrients ingested over an individual's lifetime is likely to differentially affect distinct male secondary sexual traits and courtship signals, potentially providing females with information about a male's past and present foraging history. We hypothesize that female choice is thus influenced by a male's lifetime foraging history. To test this, we manipulated the quantity of nutrients (i.e. prey items) available to male wolf spiders, Schizocosa stridulans, using a fully crossed 2 × 2 design with low versus high prey quantity across juvenile and adult life stages, and assessed the impact of these diet treatments on male foreleg pigmentation, courtship rate and mating success. We found foreleg pigmentation to be dependent upon both juvenile and adult diet, with increased nutrition dependence of pigmented versus unpigmented leg segments. Despite this, the degree of foreleg pigmentation did not predict mating success. In contrast, courtship rate was not nutrient dependent, yet strongly predicted mating success. Finally, we found a significant interaction between juvenile diet, adult diet and courtship rate on mating success. Males that experienced a diet switch (low juvenile to high adult, LH; high juvenile to low adult, HL) exhibited no relationship between courtship rate and mating success, while those that experienced a consistent diet (LL; HH) showed increased mating success with increased courtship rates. Our results suggest that nutrition dependence of secondary sexual traits is not necessarily a predictor of their role in mating success and that female mate choice is the result of complex interactions between multiple male traits.

Introduced freshwater blenny influences the diet and body condition of the invasive dice snake in Lake Geneva

ABSTRACTNon‐indigenous species can have strong impacts on biodiversity by affecting trophic relationships in their new environments. The piscivorous dice snake (Natrix tessellata) has been introduced to Geneva Lake, western Switzerland, where the endangered viperine snake (Natrix maura) is native. Local, dramatic declines in the viperine snake population might be associated with the appearance of the dice snake through dietary overlap between these 2 species, which mainly feed on bullhead (Cottus gobio). In response to this decline, a control program for dice snake was implemented in 2007 to reduce numbers of this introduced snake. In 2010, a new species of fish, the freshwater blenny (Salaria fluviatilis), which shares the same habitat as the bullhead, was introduced into Lake Geneva and has since reached high densities. We determined the impact of freshwater blenny on diet composition and body condition of dice snakes. In addition, we tested for effects of the control program on the body condition of dice snakes and viperine snakes. We collected 294 dice snakes between 2007 and 2013. Based on morphology and a genetic marker (cytochrome b gene), we determined the fish species contained in these snakes’ stomachs. We found a drastic switch in dice snake diet following the arrival of freshwater blenny, as consumption of bullhead declined by 68% and was replaced by the blenny. In addition, the body condition of dice snakes increased significantly after the arrival of freshwater blenny. The body condition of both snake species was positively correlated with the number of dice snakes removed from the study area. This finding has important implications concerning the conservation of the endangered viperine snake, and suggests that the control program of dice snakes should be continued. © 2014 The Wildlife Society.

Regulation of nutrition-associated receptors in blood monocytes of normal weight and obese humans

Obesity, type 2 diabetes and associated metabolic diseases are characterized by low-grade systemic inflammation which involves interplay of nutrition and monocyte/macrophage functions. We suggested that some factors such as nutrient components, neuropeptides involved in the control of gastrointestinal functions, and gastrointestinal hormones might influence immune cell functions and in this way contribute to the disease pathogenesis. The aim of this study was to investigate the mRNA expression of twelve nutrition-associated receptors in peripheral blood mononuclear cells (PBMC), isolated monocytes and monocyte-derived macrophages and their regulation under the switching from the high-carbohydrate low-fat diet to the low-carbohydrate high-fat (LC/HFD) isocaloric diet in healthy humans. The mRNA expression of receptors for short chain fatty acids (GPR41, GPR43), bile acids (TGR5), incretins (GIPR, GLP1R), cholecystokinin (CCKAR), neuropeptides VIP and PACAP (VIPR1, VIPR2), and neurotensin (NTSR1) was detected in PBMC and monocytes, while GPR41, GPR43, GIPR, TGR5, and VIPR1 were found in macrophages. Correlations of the receptor expression in monocytes with a range of metabolic and inflammatory markers were found. In non-obese subjects, the dietary switch to LC/HFD induced the increase of GPR43 and VIPR1 expression in monocytes. No significant differences of receptor expression between normal weight and moderately obese subjects were found. Our study characterized for the first time the expression pattern of nutrition-associated receptors in human blood monocytes and its dietary-induced changes linking metabolic responses to nutrition with immune functions in health and metabolic diseases.

Implications of diet modification on sympathoinhibitory mechanisms and hypertension in obesity.

We have previously demonstrated that a number of rats fed a moderately high-fat diet (MHFD) become obese and hypertensive and had compromised sympathoinhibitory and vasodilator responses to the gut hormones cholecystokinin (CCK) and gastric leptin. This has implications for increased resistance in vascular beds that attract a large proportion of cardiac output after a meal and may be an important mechanism underlying the development of hypertension in obesity in which food consumption is greatly increased. The aim of this study was to determine whether swapping a MHFD for a low-fat diet (LFD) would induce weight loss in obese animals, reverse the signs of hypertension and restore sympathoinhibitory reflexes. Male Sprague-Dawley rats were placed on a LFD (controls; n = 8) or a MHFD (n = 24) for 11 weeks after which the latter displayed either an obesity-prone (OP) or obesity-resistant (OR) phenotype. All animals were fed a LFD for a further 6 weeks after which they were anaesthetised with isoflurane and artificially ventilated for evaluation of resting arterial pressure (AP) and renal sympathetic nerve responses to CCK (0.1-4 μg/kg) and leptin (15 μg/kg). Weight gain in OP animals remained higher than OR or controls following diet switch (P < 0.05 for both). Resting AP was not significantly different between OP (103 ± 4 mmHg), OR (102 ± 3 mmHg) or control (104 ± 3 mmHg) animals and sympathoinhibitory responses to CCK or leptin were not different between the groups (P > 0.05). These results demonstrate that diet modification can have beneficial effects on sympathetic function and restore normotension without the need for weight reduction.

Investigating diet and diet switching in green turtles (Chelonia mydas)

Understanding the dietary ecology of animals provides information about their habitat requirements, facilitating informed conservation. We used last-bite diet and stable isotope analysis to assess the diet of juvenile and adult green turtles (Chelonia mydas) at two different habitats located 10 km apart within Port Curtis, Queensland, Australia. Last-bite diet analysis indicated that turtles had distinctly different diets in these two habitats: in one the diet was dominated by red macroalgae and in the other the diet was dominated by seagrass. Only juveniles (n = 12) were caught in the habitat where red macroalgae dominated the diet, while both juveniles (n = 9) and adults (n = 38) were captured in the habitat where seagrass dominated the diet. In the seagrass habitat there was no difference in diet between juveniles and adults, and no difference in diet between adult males (n = 17) and females (n = 21). Because the red macroalgae and seagrass had distinctly different carbon stable isotope ratios, it was possible to detect a change in diet by comparing the carbon stable isotope ratio between serum and epidermal tissue sampled from the same turtle. In this region, a switch in diet would reflect a shift in foraging habitat. Such comparisons indicate that ~50% of turtles switched diet, and therefore changed foraging habitat between the time when blood serum and epidermis were formed. This implies that switching foraging habitat by green turtles within this region is a common occurrence, which is somewhat surprising because previously it was thought that foraging green turtles had high site fidelity with relatively small home ranges.

Adaptive defense of pests and switching predation can improve biological control by multiple natural enemies

AbstractOne of the most important questions in biological control is whether multiple natural enemies can provide greater suppression of agricultural pests than a single best enemy. Intraguild predation (IGP) among natural enemies has often been invoked to explain failure of biological control by multiple enemies, and classical theoretical studies on IGP have supported this view. However, empirical studies are inconclusive and have yielded both positive and negative results. We extend classical models by considering anti‐predator behavior of pests and diet switching of omnivorous natural enemies, and examine their effects on pest control. We assume that the pest can adaptively allocate effort toward the specific defense against each predator, and that the omnivorous natural enemy can consume disproportionately more of the relatively abundant prey (switching predation) by type III functional responses to prey items. The model predicts that adaptive defense augments pests but favors introduction of multiple natural enemies for controlling pests if IGP is weak. In contrast, switching predation does not make pest control by multiple natural enemies advantageous as in classical studies, in the absence of adaptive defense. However, switching predation reduces the necessity of defense by the pest against the omnivore and offsets the effect of adaptive defense. Thus, it makes the introduction of multiple natural enemies advantageous for pest control when the pest employs adaptive defense even if IGP is strong. These results suggest that types and combinations of behavior of prey and predators may greatly affect qualitative outcomes of biological control by multiple natural enemies.

Diet‐switching by omnivorous freshwater shrimp diminishes differences in nutrient recycling rates and body stoichiometry across a food quality gradient

Summary In tropical streams, omnivorous shrimp may be important nutrient recyclers, because they have a lower body P demand than fish. However, little is known about the controls on nutrient recycling by freshwater shrimp. Across a series of lowland tropical streams that range in dissolved P, we describe: (i) shrimp body stoichiometry in relation to stream P level; (ii) rates of P excretion by shrimp; (iii) shrimp trophic level using natural stable isotope values (δ15N); and (iv) the importance of shrimp as nutrient recyclers. Shrimp body elemental composition varied across the study streams, with higher shrimp %C and %N in low‐P streams. P content of shrimp did not change despite large differences in P content of their likely food resources. Also, shrimp P recycling rates did not increase in high‐P streams with P‐enriched food resources. Stable isotope results combined with change in body nutrient content (%N and %C) suggest that shrimp show different diet choices over the P gradient, feeding at a higher trophic level in low‐P streams. This dietary shift may partially compensate for the lower P content in a given food resource in the low‐P streams. However, P recycling rates were more variable than predicted based on diet choice and stream P level, suggesting that other physiological or behavioural mechanisms are involved. In comparison to fish species in these same study sites, shrimp species recycle P at lower rates per unit body mass than the majority of fish species, despite their lower body P content. Diet switching may be an important strategy for omnivorous shrimp in correcting the stoichiometric imbalance between food resource and consumer biomass.

Abstract SS01-01: The microbiome and colon cancer risk

Abstract Geographical and migration epidemiological studies, backed up by experimental studies, have produced overwhelming evidence that diet drives colon cancer risk, with high intakes of meat and fat increasing risk, and high consumption rates of fiber rich foods, such as grains, fruits and vegetables, reducing risk. To test our hypothesis that cancer risk is determined by the effect the diet has on the composition and function of the microbiota to produce metabolites that either promote mucosal health or are inflammatory and neoplastic, we have conducted studies in populations of high and low risk, namely African Americans who have the highest risk in the USA, and rural Africans, who rarely get the disease, and confirmed that high meat and fat intakes in Americans were associated with increased mucosal proliferation rates – a biomarker of cancer risk, while high fiber African diets were associated with low proliferation rates. We have demonstrated that dietary switch between these two populations produces reciprocal changes in the microbiome, metabolome, and mucosal biomarkers of risk within 2 weeks, leading to the conclusion that modification of the diets of westernized populations to contain high fiber (&amp;gt;45g/d) foods, such as grains and beans, together with lower intakes of animal fats, can be expected to immediately reduce cancer risk in African Americans. Citation Format: Stephen J. O'Keefe. The microbiome and colon cancer risk. [abstract]. In: Proceedings of the Sixth AACR Conference: The Science of Cancer Health Disparities; Dec 6–9, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2014;23(11 Suppl):Abstract nr SS01-01. doi:10.1158/1538-7755.DISP13-SS01-01

Torta de mamona não destoxificada na indução da muda forçada em poedeiras comerciais

Avaliou-se o uso de dietas com diferentes porcentagens de torta de mamona não destoxificada (TM) na indução da muda forçada, sendo utilizadas 120 poedeiras Lohman LSL de 81 semanas, distribuídas ao acaso em quatro tratamentos, com cinco repetições de seis aves. Um dos tratamentos consistiu na indução da muda pelo método do jejum por 11 dias, e os demais no uso de dietas de muda, compostas pela mistura de dieta de postura e TM nas quantidades de 20, 30 e 40%, por até 21 dias ou até quando as aves atingissem 23% de perda do peso. Diferenças significativas foram observadas nos eritrócitos, no hematócrito, na concentração média de hemoglobina globular, na proteína total do plasma, nos leucócitos e na alanina aminotransferase, medidos durante a indução da muda, bem como no desempenho das aves após a muda, no que diz respeito ao consumo de ração, à porcentagem de postura, ao peso do ovo, à massa do ovo e à conversão alimentar. A qualidade dos ovos não variou estatisticamente entre os métodos avaliados. A utilização da dieta de muda forçada contendo 40% de TM promoveu resultados semelhantes aos obtidos com o método do jejum, tanto para consumo de ração, porcentagem de postura, peso do ovo, massa do ovo, e conversão alimentar, como inerentes à qualidade dos ovos, quanto para densidade específica, unidade Haugh, porcentagens de gema, casca e albúmen. No entanto, menores alterações nos valores de eritrócitos, hematócrito e alanina aminotransferase foram observadas nesse método supracitado. O uso da dieta de muda contendo 40% de TM mostrou-se uma alternativa viável ao uso do método do jejum.

Dietary switch reveals fast coordinated gene expression changes in Drosophila melanogaster.

Dietary restriction (DR) reduces age-specific mortality and increases lifespan in many organisms. DR elicits a large number of physiological changes, however many are undoubtedly not related to longevity. Whole-genome gene expression studies have typically revealed hundreds to thousands of differentially expressed genes in response to DR, and a key open question is which subset of genes mediates longevity. Here we performed transcriptional profiling of fruit flies in a closely spaced time series immediately following a switch to the DR regime and identified four patterns of transcriptional dynamics. Most informatively we find 144 genes rapidly switched to the same level observed in the DR cohort and are hence strong candidates as proximal mediators of reduced mortality upon DR. This class was enriched for genes involved in carbohydrate and fatty acid metabolism. Folate biosynthesis was the only pathway enriched for gene up- regulated upon DR. Four among the down-regulated genes are involved in key regulatory steps within the pentose phosphate pathway, which has been previously associated with lifespan extension in Drosophila. Combined analysis of dietary switch with whole-genome time-course profiling can identify transcriptional responses that are closely associated with and perhaps causal to longevity assurance conferred by dietary restriction.

Transcriptional response to dietary restriction in Drosophila melanogaster

Dietary restriction (DR) extends lifespan in a wide variety of organisms. Although several genes and pathways associated with this longevity response have been identified, the specific mechanism through which DR extends lifespan is not fully understood. We have recently developed a novel methodology to screen for transcriptional changes in response to acutely imposed DR upon adult Drosophila melanogaster and identified groups of genes that switch their transcriptional patterns from a normal diet pattern to a restricted diet pattern, or ‘switching genes’. In this current report we extend our transcriptional data analysis with gene set enrichment analysis to generate a pathway-centered perspective. The pattern of temporal behavior in response to the diet switch is strikingly similar within and across pathways associated with mRNA processing and protein translation. Furthermore, most genes within these pathways display an initial spike in activity within 6–8h from the diet switch, followed by a coordinated, partial down-regulation after 24h. We propose this represents a stereotypical response to DR, which ultimately leads to a mild but widespread inhibition of transcriptional and translational activity. Inhibition of the protein synthesis pathway has been observed in DR in other studies and has been shown to extend lifespan in several model organisms.