基于肠道菌群探讨高脂饮食在慢性便秘中的作用及机制

慢性便秘是一种患病率高、治疗困难的功能性肠道疾病。许多患者临床治疗效果差,生活质量显著降低。近年来的研究认为慢性便秘的发生发展与肠道菌群失调有关。饮食结构是影响肠道菌群组成的主要因素,已有研究发现高脂饮食可引起肠道菌群失调,进而导致慢性便秘的发生,但具体机制尚未完全阐明。本文从5-羟色胺、短链脂肪酸和慢性肠道炎症等几个方面综述高脂饮食通过影响肠道菌群引起慢性便秘的作用及机制,以期通过精准的饮食干预调节肠道菌群,达到预防和治疗慢性便秘的目的。

     

Effect of semolina-jaggery diet on survival and development of Drosophila melanogaster

Drosophila melanogaster is an ideal model organism for developmental studies. This study tests the potential of semolina-jaggery (SJ) diet as a new formulation for bulk rearing of flies. Semolina and jaggery are organic products obtained from wheat endosperm and cane sugar, respectively. Semolina is a rich source of carbohydrates and protein. Jaggery has a high content of dietary sugars. Moreover, preparation of semolina jaggery diet is cost-effective and easy. Thus, the current study aimed to compare survival and developmental parameters of flies fed the SJ diet to flies fed the standard cornmeal-sugar-yeast (CSY) diet. SJ diet enhanced survival of flies without affecting fecundity; male flies showed increased resistance to starvation. A higher number of flies emerged at F₂ and F₃ generation when fed the SJ diet than when fed the control CSY diet. SJ diet did not increase fly body weight and lipid percentage. Therefore, SJ diet can be used for bulk rearing of healthy flies at par with the standard cornmeal-sugar-yeast diet.     

Effect of semolina-jaggery diet on survival and development of Drosophila melanogaster

Drosophila melanogaster is an ideal model organism for developmental studies. This study tests the potential of semolina-jaggery (SJ) diet as a new formulation for bulk rearing of flies. Semolina and jaggery are organic products obtained from wheat endosperm and cane sugar, respectively. Semolina is a rich source of carbohydrates and protein. Jaggery has a high content of dietary sugars. Moreover, preparation of semolina jaggery diet is cost-effective and easy. Thus, the current study aimed to compare survival and developmental parameters of flies fed the SJ diet to flies fed the standard cornmeal-sugar-yeast (CSY) diet. SJ diet enhanced survival of flies without affecting fecundity; male flies showed increased resistance to starvation. A higher number of flies emerged at F₂ and F₃ generation when fed the SJ diet than when fed the control CSY diet. SJ diet did not increase fly body weight and lipid percentage. Therefore, SJ diet can be used for bulk rearing of healthy flies at par with the standard cornmeal-sugar-yeast diet.     

Low-protein diet enhances adiponectin secretion in rats

ABSTRACT

Previous studies including ours have shown that a low-protein diet up-regulates insulin signaling in the liver and muscle and induces fatty liver in rats. Adiponectin is known as an insulin-sensitizing adipocytokine. We, therefore, examined the effect of a low-protein diet on the adiponectin levels in rats. The low-protein diet significantly increased serum adiponectin level. However, mRNA and protein levels of adiponectin in white adipose tissue (WAT) were not changed by the low-protein diet. Since it is known that oligomerization is important to control serum adiponectin level, we examined the population of adiponectin oligomeric forms in WAT and found that low-protein diet did not change it. Despite these events, the amount of its secretion was significantly increased in the adipocytes isolated from WAT of low-protein diet-fed rats. These results indicate that a low-protein diet enhances adiponectin secretion, which is not due to the increased intracellular amount and oligomerization of adiponectin.     

Terminal investment strategies following infection are dependent on diet

When future reproductive potential is threatened, for example following infection, the terminal investment hypothesis predicts that individuals will respond by investing preferentially in current reproduction. Terminal investment involves reallocating resources to current reproductive effort, so it is likely to be influenced by the quantity and quality of resources acquired through diet. Dietary protein specifically has been shown to impact both immunity and reproduction in a range of organisms, but its impact on terminal investment is unclear. We challenged females from ten naturally derived fruit fly (Drosophila melanogaster) genotypes with the bacterial pathogen Pseudomonas aeruginosa. We then placed these on either a standard or isocaloric high‐protein diet, and measured multiple components of reproductive investment. As oogenesis requires protein, and flies increase egg production with protein intake, we hypothesized that terminal investment would be easier to observe if protein was not already limiting. Oral exposure to the pathogen triggered an increase in reproductive investment. However, whereas flies feeding on a high‐protein diet increased the number of eggs laid when exposed to P. aeruginosa, those fed the standard diet did not increase the number of eggs laid but increased egg‐to‐adult viability following infection. This suggests that the specific routes through which flies terminally invest are influenced by the protein content of the maternal diet. We discuss the importance of considering diet and natural routes of infection when measuring nonimmunological defences.     

Measuring rodent incisors from scats can increase accuracy of predator diet studies. An illustration based on island cats and rats

Non-invasive diet studies, which are a simple but important tool to understand trophic interactions inside ecosystems, need to be as detailed as possible. Determining the precise biomass of ingested prey is a key to obtaining not only a better understanding of the amount of food really ingested but also the predator-prey interactions. It is particularly relevant in the case of rodents, because they are often a predominant prey in carnivores' diet and can differ widely in biomass. This study demonstrates how an original and simple method for measuring rat incisors found in cat scats produces measurements which can be correlated with rat weight. This correlation, used in a field application, made it possible to: (i) calculate a more accurate biomass of rats in cat diets and thus obtain a better estimation of the proportion of rats compared to other prey in cat diets; (ii) show that cats preferentially ate smaller rats, indicating that the use of the mean weight of rodents sampled by trap-lines may induce a significant bias in the biomass calculation. Likewise, a correlation between rat lens weight and incisor measurements was found. Using this correlation, it should be possible to estimate the age of the rats eaten by cats and obtain a better understanding of the impact of predators on prey population dynamics. To cite this article: E. Bonnaud et al., C. R. Biologies 331 (2008).     

Feeding ecology has a stronger evolutionary influence on functional morphology than on body mass in mammals

Ecological specialization is a central driver of adaptive evolution. However, selective pressures may uniquely affect different ecomorphological traits (e.g., size and shape), complicating efforts to investigate the role of ecology in generating phenotypic diversity. Comparative studies can help remedy this issue by identifying specific relationships between ecologies and morphologies, thus elucidating functionally relevant traits. Jaw shape is a dietary correlate that offers considerable insight on mammalian evolution, but few studies have examined the influence of diet on jaw morphology across mammals. To this end, I apply phylogenetic comparative methods to mandibular measurements and dietary data for a diverse sample of mammals. Especially powerful predictors of diet are metrics that capture either the size of the angular process, which increases with greater herbivory, or the length of the posterior portion of the jaw, which decreases with greater herbivory. The size of the angular process likely reflects sizes of attached muscles that produce jaw movements needed to grind plant material. Further, I examine the impact of feeding ecology on body mass, an oft-used ecological surrogate in macroevolutionary studies. Although body mass commonly increases with evolutionary shifts to herbivory, it is outperformed by functional jaw morphology as a predictor of diet. Body mass is influenced by numerous factors beyond diet, and it may be evolutionarily labile relative to functional morphologies. This suggests that ecological diversification events may initially facilitate body mass diversification at smaller taxonomic and temporal scales, but sustained selective pressures will subsequently drive greater trait partitioning in functional morphologies.     

The effect of purified compared with nonpurified diet on bone changes induced by hindlimb suspension of female rats

The purpose of this study was to compare the bone changes induced by unloading in rats fed different diets, because space flight studies use a semipurified diet, whereas space flight simulation studies typically use nonpurified diets. Female Sprague-Dawley rats were fed a purified American Institute of Nutrition (AIN) 93G diet or a standard nonpurified diet and kept ambulatory or subjected to unloading by hindlimb suspension (HLS) for 38 days. Bone mineral content (BMC), mechanical strength, and factors related to the diet that affect bone (i.e., urinary calcium excretion, estradiol, and corticosterone) were measured. Average food intakes (grams per day) differed for diets, but caloric intake (kilocalories per day) and the final body masses of treatment groups were similar. The HLS-induced decrease in femoral BMC was not statistically different for rats fed a nonpurified diet (-8.6%) compared with a purified AIN-93G diet (-11.4%). The HLS-induced decrease in femoral mechanical strength was not statistically different for rats fed a nonpurified diet (-24%) compared with a purified AIN-93G diet (-31%). However, bone lengths were decreased (P < 0.05) in rats fed a nonpurified diet compared with a purified diet. Plasma estradiol levels were lower (P < 0.05) in the HLS/AIN-93G group but similar in the HLS and ambulatory rats fed a nonpurified diet. Plasma estradiol was related to femoral BMC (r = 0.85, P < 0.01). Urinary calcium excretion was higher (P < 0.05) in rats fed a nonpurified diet than those fed a purified AIN-93G diet, which is consistent with the higher level of calcium in the nonpurified diet. Urinary corticosterone levels were higher (P < 0.05) in rats fed a nonpurified diet than rats fed the AIN-93G diet. Although the osteopenia induced by unloading was similar in both diet groups, there were differences in longitudinal bone growth, calcium excretion, plasma estradiol levels, and urinary corticosterone levels. Results indicate that the type of standard diet used is an important factor to consider when measuring bone end points.     

PPARalpha agonist induces the accumulation of ceramide in the heart of rats fed high-fat diet.

It was shown that high-fat feeding of mice with cardiac-specific overexpression of peroxisome proliferator-activated receptor (PPAR) alpha but not wild type animals leads to the accumulation of ceramide (an important mediator of lipotoxicity) in the heart [Finck et al. 2003 Proc Natl Acad Sci USA]. To investigate the mechanism of this phenomenon we examined the effects of PPARalpha activation on ceramide metabolism in the myocardium. Male Wistar rats were fed either a standard chow or a high-fat diet. Each group was divided into two subgroups: control and treated with selective PPARalpha activator - WY-14643. In the rats fed on the standard diet WY-14643 did not affect the myocardial content of sphingomyelin and ceramide but reduced the content of sphinganine and sphingosine. It also inhibited the activity of neutral sphingomyelinase and increased the activity of acid sphingomyelinase, whereas the activity of ceramidases and serine palmitoyltransferase (SPT) remained stable. High-fat diet itself did not affect the content of the examined sphingolipids. However, it reduced the activity of sphingomyelinases and ceramidases having no effect on the activity of SPT. Administration of WY-14643 to this group significantly increased the content of myocardial free palmitate, ceramide, sphingomyelin and the activity of SPT. Our results demonstrated that PPARalpha activation modulates myocardial ceramide metabolism and leads to the accumulation of ceramide in the heart of the high-fat fed rats due to its increased synthesis de novo.     

Early‐life exposure to high‐fat diet influences brain health in aging mice

Epidemiological studies have suggested a link between exposure to environmental factors early in life and susceptibility to neurodegenerative diseases in adulthood. In the short term, maternal diet is important for the growth and development of the fetus; however, it may also have long‐term effects on the health status of the offspring. Here, we investigate the effect that maternal high‐fat diet during gestation has on brain health of the offspring later in life. B6129SF2/J dams were fed a high‐fat diet during the 3 weeks’ gestation, then switched to standard chow diet after delivery. Offspring were always fed regular diet for the entire study and assessed in learning, memory, and brain pathology when 18 months old. Compared with offspring from control mothers, the ones from mothers exposed to high‐fat diet had significant better performance in learning and memory tests, which associated with an amelioration of synaptic integrity. Additionally, they had a significant reduction in total tau, a decrease in its pathological conformational changes and lower levels of caspase‐3‐cleaved isoforms. Our findings demonstrate that in utero exposure to high‐fat diet plays a protective role for offspring brain health later in life. They support the novel hypothesis that targeted dietary intervention specifically restricted to the gestation period could be implemented as preventative strategy for the age‐dependent decline in brain health.     

Using n-alkanes to estimate diet composition of herbivores: a novel mathematical approach

N-alkanes are long-chain saturated hydrocarbons occurring in plant cuticles that can be used as chemical markers for estimating the diet composition of herbivores. An important constraint of using n-alkanes to estimate diet composition with currently employed mathematical procedures is that the number of markers must be equal or larger than the number of diet components. This is a considerable limitation when dealing with free-ranging herbivores feeding on complex plant communities. We present a novel approach for the estimation of diet composition using n-alkanes which applies equally to cases where the number of markers is lower, equal or greater than the number of plant species in the diet. The model uses linear programming to estimate the minimum and maximum proportions of each plant in the diet, and avoids the need for grouping species in order to reduce the number of estimated dietary components. We illustrate the model with two data sets of n-alkane content of plants and faeces obtained from a sheep grazing experiment conducted in Australia and a red deer study in Portugal. Our results are consistent with previous studies on those data sets and provide additional information on the proportions of individual species in the diet. Results show that sheep included in the diet high proportions of white clover (from 0.25 to 0.37), and relatively high proportions of grasses (e.g. brome from 0.14 to 0.26) but tended to avoid Lotus spp. (always less than 0.04 of the diet). For red deer we found high proportions of legumes (e.g. Trifolium angustifolium and Vicia sativa reaching maximum proportions of 0.42 and 0.30 of the diet, respectively) with grasses being less important and Cistus ladanifer, a browse, also having relevance (from 0.21 to 0.42 of the diet).     

Significance of diet type and diet quality for ecological diversity of African ungulates

1. We test two nutritional hypotheses for the ecological diversity of ungulates, the browser/grazer (diet type) and diet quality models, among free-ranging herbivores in a South African savanna, the Kruger National Park. Tests are based on assessment of relationships between diet type and diet quality with body mass and hypsodonty, two morphological features that have been associated with both elements. 2. We use stable carbon isotope ratios of faeces to reconstruct diet in terms of proportions of C(3) plants (browse) and C(4) plants (grass) consumed by different species in different seasons. These data are combined with proxies for diet quality (per cent nitrogen, neutral detergent fibre, acid detergent fibre, and acid detergent lignin) from faeces to track changes in diet quality. 3. Two statistical approaches are used in model selection, i.e. tests of significant correlations based on linear regression analyses, and an information-theory approach (Akaike's Information Criterion) providing insight into strength of evidence for models. 4. Results of both methods show that, contrary to many predictions, body mass and diet type are not related, but these data confirm predictions that diet quality decreases with increasing body size, especially during the dry season. Hypsodonty, as expected, varies with diet type, increasing with increased grass intake. 5. These findings support both a diet type and diet quality model, implying some degree of exclusivity. We propose that congruence between models may be achieved through addition of diet quality proxies not included here, because hypsodonty is more likely a reflection of the abrasive properties of consumed foods, i.e. related to food quality, rather than food type. This implies that adaptation to diets of varying quality, through changes in body size and dental features, has been the primary mechanism for diversification in ungulates. 6. Our interpretation contrasts with several recent studies advocating diet type as the primary factor, exemplifying that further reconciliation between the two models is needed. We discuss the implications of this study for future approaches to achieve a more cohesive understanding of the evolutionary outcomes of herbivore nutrition.     

Western gorilla diet: a synthesis from six sites

The objective of this paper is to collate information on western gorilla diet from six study sites throughout much of their current range, including preliminary information from two sites (Afi and Lossi), where studies of diet have begun only recently. Food lists were available from each site, derived from indirect signs of gorilla feeding (such as feces), with some observational data. Important staple, seasonal, and fallback foods have been identified, and a number of striking similarities across sites have been revealed based on a much larger data set than was previously available. It was confirmed that the western gorilla diet is always eclectic, including up to 230 items and 180 species. The greatest diversity is found among the fruit species eaten, fruit being included in western gorilla diets from all sites and throughout most or all of the year. Eight plant families provide important foods at five, or all six, sites, suggesting that it may be possible in the future to predict which habitats are the most suitable for gorillas. Gorillas exploit both rare and common forest species. Similarities and differences among sites can be explained superficially on the basis of geography and the past history of the forest. Gorilla density across sites appears to be most affected by the density of monocotyledonous bulk food plants, but its relationship to the density of important tree food species has yet to be tested.     

高通量测序技术在野生动物食性分析中的应用

食性研究是动物生态学颇受关注的一个重要内容,而食性分析方法由于受到技术和适用范围的限制,也在不断改进和更新。随着高通量测序技术的发展,该技术逐渐扩展到野生动物的食性分析,使食性分析的效率得到极大提升,并拓宽了食性分析的应用范围。尽管高通量测序应用于食性分析在数据量、灵敏度和分辨率方面的优势较为明显,但由于涉及到的步骤较多,受到的影响因素较为复杂,目前高通量测序应用于食性分析还属于研究比较薄弱的领域。概述了高通量测序技术应用于食性分析的基本流程,总结了该技术在食物组成分析、种内和种间食性关系、食物与栖息地、行为关系方面的研究动态,分析了PCR、污染和定量分析对该技术应用性的影响,提出了相应的解决对策和建议,并对其应用前景进行了展望。     

Platyrrhine incisors and diet

Despite the relatively large size of anthropoid incisors in relation to the remainder of the dental arcade, and their prominent role in the preprocessing of food prior to ingestion, comparatively little is known about the functional morphology of anthropoid incisor shape and crown curvature. The relationship between incisor allometry and diet is well documented for both platyrrhines and catarrhines; however, similar relationships between incisor shape and crown curvature have to date only been reported for living and fossil members of the superfamily Hominoidea. Given the limited taxonomic diversity among the extant members of that group, it is difficult to firmly establish the relative influence of phylogeny and dietary function in the governance of incisor crown curvature. Unlike hominoids, which are represented by only five living genera, extant platyrrhines are a more varied group that includes 16 ecologically diverse genera. In an effort to clarify the functional relationship between maxillary and mandibular incisor crown curvature and diet, this study uses high resolution polynomial curve fitting to quantify mesiodistal and cervicoincisal curvature for a taxonomically diverse platyrrhine sample (n = 133 individuals representing 18 taxa) with well documented dietary behavior. Results were consistent with prior analyses of hominoid incisor curvature and identify a significant and positive correlation between incisor crown curvature and diet such that increasing curvature is associated with a proportionate increase in frugivory. These results are independent confirmation of the results reported from a previous analysis of hominoid incisor curvature and provide new evidence to suggest that diet is the primary governing factor influencing anthropoid incisor curvature.     

The relationship between diet quality and basal metabolic rate in endotherms: insights from intraspecific analysis

In this article, we review intraspecific studies of basal metabolic rate (BMR) that address the correlation between diet quality and BMR. The "food-habit hypothesis" stands as one of the most striking and often-mentioned interspecific patterns to emerge from studies of endothermic energetics. Our main emphasis is the explicit empirical comparison of predictions derived from interspecific studies with data gathered from within-species studies in order to explore the mechanisms and functional significance of the putative adaptive responses encapsulated by the food-habit hypothesis. We suggest that, in addition to concentrating on the relationship among diet quality, internal morphology, and BMR, new studies should also attempt to unravel alternative mechanisms that shape the interaction between diet and BMR, such as enzymatic plasticity, and the use of energy-saving mechanisms, such as torpor. Another avenue for future study is the measurement of the effects of diet quality on other components of the energy budget, such as maximum thermogenic and sustainable metabolic rates. It is possible that the effects of diet quality operate on such components rather than directly on BMR, which might then push or pull along changes in these traits. Results from intraspecific studies suggest that the factors responsible for the association between diet and BMR at an ecological timescale might not be the same as those that promoted the evolution of this correlation. Further analyses should consider how much of a role the proximate and ultimate processes have played in the evolution of BMR.     

Ameliorative effects of l-carnitine on rats raised on a diet supplemented with lead acetate

Lead intoxication has been a major health hazard in humans. It affects people at all ages. Its toxicity is associated with various organs of the body and affects different metabolic pathways. Based on histological data, l-carnitine reduced the severity of tissue damage produced as a result of exposure of rats to lead acetate. The main objective of this study was to evaluate the underlying mechanism of protection offered by l-carnitine against lead acetate intoxication using male Sprague–Dawley rats.Forty male Sprague–Dawley rats were randomly divided into four groups with ten rats in each. The first group (G1) served as the control group and animals received standard diet only. The second group (G2) received lead acetate in their diet. The third group (G3) was the l-carnitine treated group and received the normal standard diet supplemented with l-carnitine. While the fourth group (G4) had a diet supplemented with both lead acetate and l-carnitine. At the end of each experiment, blood (serum and whole blood) were collected from each animal and analyzed for the following parameters: serum testosterone levels, serum nitric oxide and serum malondialdehyde. This is in addition to looking at the enzymatic activities of two important enzymes (superoxide dismutase and catalase) and on (glutathione reductase) which are indicative of the antioxidant activities in the whole blood. The results indicated that l-carnitine will counteract the undesirable effects of lead intoxication. It exerted its antioxidant potential by reducing the production of ROS and scavenging free radicals by maintaining and protecting the level of the of antioxidant enzymes SOD, CAT and glutathione peroxidase.Conclusion:l-Carnitine may play an important role in reversing the undesirable effects of lead intoxication. Future studies should be conducted to see whether such an effect is applicable in humans exposed to lead poising.     

Similarity and specialization of the larval versus adult diet of European butterflies and moths

Many herbivorous insects feed on plant tissues as larvae but use other resources as adults. Adult nectar feeding is an important component of the diet of many adult herbivores, but few studies have compared adult and larval feeding for broad groups of insects. We compiled a data set of larval host use and adult nectar sources for 995 butterfly and moth species (Lepidoptera) in central Europe. Using a phylogenetic generalized least squares approach, we found that those Lepidoptera that fed on a wide range of plant species as larvae were also nectar feeding on a wide range of plant species as adults. Lepidoptera that lack functional mouthparts as adults used more plant species as larval hosts, on average, than did Lepidoptera with adult mouthparts. We found that 54% of Lepidoptera include their larval host as a nectar source. By creating null models that described the similarity between larval and adult nectar sources, we furthermore showed that Lepidoptera nectar feed on their larval host more than would be expected if they fed at random on available nectar sources. Despite nutritional differences between plant tissue and nectar, we show that there are similarities between adult and larval feeding in Lepidoptera. This suggests that either behavioral or digestive constraints are retained throughout the life cycle of holometabolous herbivores, which affects host breadth and identity.     

Individual diet specialisation in sparrows is driven by phenotypic plasticity in traits related to trade‐offs in animal performance

Individual diet specialisation (IS) is frequent in many animal taxa and affects population and community dynamics. The niche variation hypothesis (NVH) predicts that broader population niches should exhibit greater IS than populations with narrower niches, and most studies that examine the ecological factors driving IS focus on intraspecific competition. We show that phenotypic plasticity of traits associated with functional trade‐offs is an important, but unrecognised mechanism that promotes and maintains IS. We measured nitrogen isotope (δ¹⁵N) and digestive enzyme plasticity in four populations of sparrows (Zonotrichia capensis) to explore the relationship between IS and digestive plasticity. Our results show that phenotypic plasticity associated with functional trade‐offs is related in a nonlinear fashion with the degree of IS and positively with population niche width. These findings are opposite to the NVH and suggest that among individual differences in diet can be maintained via acclimatisation and not necessarily require a genetic component.     

Optimal diet selection,frequency dependence and prey renewal

This paper extends existing models of frequency-dependent diet selection by considering the optimal diet selection of a predator feeding upon prey populations which can be depleted but are also capable of renewal (e.g. immigration, growth, or reproduction). This model and existing models which include prey depletion, predict partial-preference and a generic diet preference for the commonest prey types (apostatic selection). Unlike previous diet selection models, it is found that the optimal diet selection of an individual predator can be to favour the rarest prey type (anti-apostatic selection) when encounter rates are high, even if the individual prey do not differ in their nutritional value. Studies have demonstrated that predators generally show apostatic selection, even when all prey have the same nutritional value. Anti-apostatic selection has also been observed when prey are crowded, and therefore at high density, consistent with the idea of high encounter rates. This anti-apostatic diet selection has previously been proposed as evidence for the use of prey search images by a predator, or variation in individual prey preference. In this paper it is suggested that prey renewal is a further factor, often confounded in experiments, which could favour anti-apostatic selection.