Biomarkers in nutritional epidemiology: applications, needs and new horizons

Modern epidemiology suggests a potential interactive association between diet, lifestyle, genetics and the risk of many chronic diseases. As such, many epidemiologic studies attempt to consider assessment of dietary intake alongside genetic measures and other variables of interest. However, given the multi-factorial complexities of dietary exposures, all dietary intake assessment methods are associated with measurement errors which affect dietary estimates and may obscure disease risk associations. For this reason, dietary biomarkers measured in biological specimens are being increasingly used as additional or substitute estimates of dietary intake and nutrient status. Genetic variation may influence dietary intake and nutrient metabolism and may affect the utility of a dietary biomarker to properly reflect dietary exposures. Although there are many functional dietary biomarkers that, if utilized appropriately, can be very informative, a better understanding of the interactions between diet and genes as potentially determining factors in the validity, application and interpretation of dietary biomarkers is necessary. It is the aim of this review to highlight how some important biomarkers are being applied in nutrition epidemiology and to address some associated questions and limitations. This review also emphasizes the need to identify new dietary biomarkers and highlights the emerging field of nutritional metabonomics as an analytical method to assess metabolic profiles as measures of dietary exposures and indicators of dietary patterns, dietary changes or effectiveness of dietary interventions. The review will also touch upon new statistical methodologies for the combination of dietary questionnaire and biomarker data for disease risk assessment. It is clear that dietary biomarkers require much further research in order to be better applied and interpreted. Future priorities should be to integrate high quality dietary intake information, measurements of dietary biomarkers, metabolic profiles of specific dietary patterns, genetics and novel statistical methodology in order to provide important new insights into gene-diet-lifestyle-disease risk associations.     

Dietary cholesterol and atherosclerosis

The perceived relationship between dietary cholesterol, plasma cholesterol and atherosclerosis is based on three lines of evidence: animal feeding studies, epidemiological surveys, and clinical trials. Over the past quarter century studies investigating the relationship between dietary cholesterol and atherosclerosis have raised questions regarding the contribution of dietary cholesterol to heart disease risk and the validity of dietary cholesterol restrictions based on these lines of evidence. Animal feeding studies have shown that for most species large doses of cholesterol are necessary to induce hypercholesterolemia and atherosclerosis, while for other species even small cholesterol intakes induce hypercholesterolemia. The species-to-species variability in the plasma cholesterol response to dietary cholesterol, and the distinctly different plasma lipoprotein profiles of most animal models make extrapolation of the data from animal feeding studies to human health extremely complicated and difficult to interpret. Epidemiological surveys often report positive relationships between cholesterol intakes and cardiovascular disease based on simple regression analyses; however, when multiple regression analyses account for the colinearity of dietary cholesterol and saturated fat calories, there is a null relationship between dietary cholesterol and coronary heart disease morbidity and mortality. An additional complication of epidemiological survey data is that dietary patterns high in animal products are often low in grains, fruits and vegetables which can contribute to increased risk of atherosclerosis. Clinical feeding studies show that a 100 mg/day change in dietary cholesterol will on average change the plasma total cholesterol level by 2.2-2.5 mg/dl, with a 1.9 mg/dl change in low density lipoprotein (LDL) cholesterol and a 0.4 mg/dl change in high density lipoprotein (HDL) cholesterol. Data indicate that dietary cholesterol has little effect on the plasma LDL:HDL ratio. Analysis of the available epidemiological and clinical data indicates that for the general population, dietary cholesterol makes no significant contribution to atherosclerosis and risk of cardiovascular disease.     

Effects of dietary cholesterol and fatty acids on plasma cholesterol level and hepatic lipoprotein metabolism

The effects of dietary cholesterol and fatty acids on the plasma cholesterol level and rates of very low density lipoprotein (VLDL) cholesterol secretion and low density lipoprotein (LDL) transport through LDL receptors in the liver of the hamster were investigated. Increases of plasma VLDL- and LDL-cholesterol levels and VLDL-cholesterol secretion from hepatocytes were observed in animals fed a diet enriched with 0.1% cholesterol for 2 weeks in comparison with animals fed a control diet. The addition of dietary palmitic acid accelerated the effect of dietary cholesterol on plasma VLDL- and LDL-cholesterol levels and VLDL-cholesterol secretion from hepatocytes. Dietary linoleic acid accelerated the effect of dietary cholesterol on VLDL-cholesterol secretion from hepatocytes and diminished the effect on the plasma LDL-cholesterol level. Hepatic LDL receptor activity was considerably suppressed by a control diet containing 0.05% cholesterol and a further small suppression was induced by a diet enriched with 0.1% cholesterol with or without 5% palmitic acid. However, dietary linoleic acid diminished the effect of dietary cholesterol on the suppression of hepatic LDL receptor activity. These results suggest that dietary palmitic acid augments the effect of dietary cholesterol in elevating the plasma LDL-cholesterol level through acceleration of VLDL-cholesterol secretion from the liver, and that dietary linoleic acid diminishes the effect of dietary cholesterol in elevating the plasma LDL-cholesterol level by preventing the suppression of hepatic LDL receptor activity induced by cholesterol.     

Diet and cancer prevention: Dietary compounds,dietary MicroRNAs,and dietary exosomes

Cancer is one of main health public problems worldwide. Several factors are involved in beginning and development of cancer. Genetic and internal/external environmental factors can be as important agents that effect on emerging and development of several cancers. Diet and nutrition may be as one of important factors in prevention or treatment of various cancers. A large number studies indicated that suitable dietary patterns may help to cancer prevention or could inhibit development of tumor in cancer patients. Moreover, a large numbers studies indicated that a variety of dietary compounds such as curcumin, green tea, folat, selenium, and soy isoflavones show a wide range anti‐cancer properties. It has been showed that these compounds via targeting a sequence of cellular and molecular pathways could be used as suitable options for cancer chemoprevention and cancer therapy. Recently, dietary microRNAs and exosomes have been emerged as attractive players in cancer prevention and cancer therapy. These molecules could change behavior of cancer cells via targeting various cellular and molecular pathways involved in cancer pathogenesis. Hence, the utilization of dietary compounds which are associated with powerful molecules such as microRNAs and exosomes and put them in dietary patterns could contribute to prevention or treatment of various cancers. Here, we summarized various studies that assessed effect of dietary patterns on cancer prevention shortly. Moreover, we highlighted the utilization of dietary compounds, dietary microRNAs, and dietary exosomes and their cellular and molecular pathways in cancer chemoprevention.     

The influence of sulphur,molybdenum and cadmium exposure on the growth of goat,cattle and pig

A three factorial designed feeding experiment with common carp (Cyprinus carpio L.) was carried out in an intensive experimental rearing system. Fish (initial body weight 200 g) were fed on two different levels of dietary energy (16 and 18 MJ DE/kg DM), two different levels of protein (320 and 420 g CP/kg DM) and also two different feeding intensities (100% and 75% of the maximum intake). The experiment was terminated when fish reached a mean body weight of 1300 g.

Growth, feed utilization and nutrient composition of the whole body and fillet were observed. The highest growth was obtained when the fish were fed on the diet containing high dietary energy and high dietary protein with satiation feeding. High dietary energy, high dietary protein and restriction of feed intake improved feed conversion ratios. High dietary energy, low dietary protein and restrictive feeding increased energy utilization. Low dietary protein and restrictive feeding resulted in better protein utilization.

Fish fed with high dietary energy contained more fat and less protein in their carcasses. A lower fat content but higher protein and higher ash content in fish carcasses was shown when fish were fed with a diet high in protein and fed restrictively.     

Dietary fibre--definition, chemistry and analytical determination

Dietary fibre includes non-starch polysaccharides and lignin that are not digested or absorbed in the human small intestine. It contains a mixture of chemically complex polysaccharides. Lignin is a highly cross-linked complex polymer of phenylpropane units. The plant cell wall is the main source of dietary fibre and its structure is reviewed briefly. The structure of the main dietary fibre polysaccharides is then summarized. The demarcation between starch--the main digestible polysaccharide--and dietary fibre presents some problems due to more or less enzyme resistant starch fractions that occur naturally or are formed with processing. "Resistant starch" formed during baking passes through the small intestine in the rat and, probably, in man and is fermented in the colon. It should therefore also be regarded as dietary fibre. Methods for dietary fibre determination fall into two categories: gravimetric methods, weighing the dietary fibre after removal of other components; component analysis methods, determining monomeric composition of fibre polysaccharides (preferably by gas-liquid chromatography) supplemented with a gravimetric lignin determination and separate assay of uronic acid components (pectin). Recently developed enzymatic gravimetric methods are most convenient for the assay of total dietary fibre or water soluble and insoluble fibre separately, whereas component analysis is required for determining the dietary fibre composition.     

Dietary supplement use among adolescent athletes in central Nebraska and their sources of information

The purpose of this study was to investigate the prevalence of dietary supplement use among adolescent athletes. The project was also directed at identifying the sources these student-athletes used for acquiring information about dietary supplements. One hundred thirty nine high school athletes (99 males; 34 females; mean age = 15.8 +/- 1.19 years) volunteered to participate in this study. A 16-question anonymous survey instrument examined use of dietary supplements, reasons for use, type of sport participation, and sources of information regarding dietary supplements. Of the participants in this study, 22.3% (N = 31) reported currently taking dietary supplements. There was no relationship found between dietary supplement use and age. There were a significantly higher number of males reporting current dietary supplement use. Of those who reported to be currently taking dietary supplements, sports performance (N = 25) was the most reported reason for use. There were no significant differences found in reported dietary supplement use between any of the sports. Of the participants, 38.1% (N = 53) listed their coach as their best source of information on dietary supplements. The results of this study offer the current literature some additional insight into trends in supplement use among high school student athletes. Practical implications suggest that it may be necessary to ensure coaches have sufficient knowledge about dietary supplements so that adolescent athletes are receiving accurate information.     

Response of liver and heart trace elements in rats to the interaction between dietary zinc and iron

An analysis of the interaction between dietary iron (Fe) and zinc (Zn) was performed by using data from Sprague-Dawley rats in a 5 x 4 fully crossed factorially arranged experiment. The concentrations of 9 trace elements from the liver and 10 from the heart were determined and subjected to diverse statistical analyses and were classified by their response to the interaction between dietary Fe and Zn. The interaction was studied by using analysis of variance (ANOVA), discriminant analysis, and logistic regression to determine the direction of interaction; that is, did dietary Fe affect dietary Zn or did dietary Zn affect dietary Fe? The use of discriminant analysis allowed for using multiple parameters (rather than a single parameter) to determine possible interactions between Fe and Zn. Thus, two main levels of interaction were studied: the separate response of each tissue mineral and the response of some grouped minerals. The responses studied were the effect of dietary Zn on tissue trace element parameters, the effect of dietary Fe on the parameters, the effect of dietary Zn on combined (grouped) parameters, and the effect of dietary Fe on combined parameters. As determined by ANOVA, only three individual trace elements--liver Fe, Cu, and Mo--were significantly affected by the interaction between Fe and Zn. However, a broader interaction between Fe and Zn is revealed when groups of, rather than single, trace elements arestudied. For example, an interaction between dietary Fe and Zn affects the weighted linear combination of heart Ca, Cu, K, Mg, Mn, P, and Zn. This article presents the hypothesis that grouped parameters may be useful as status indicators. The complete dataset can be found at http://www.gfhnrc.ars. usda.gov/fezn.     

Dietary Pattern and Its Association with the Prevalence of Obesity and Related Cardiometabolic Risk Factors among Chinese Children

Background

The association of dietary pattern with chronic diseases has been investigated widely in western countries. However, information is quite limited among children in China. Our study is aimed to identify the dietary patterns of Chinese children and examine their association with obesity and related cardiometabolic risk factors.

Methods

A total of 5267 children were selected using multistage random sampling from 30 primary schools of 5 provincial capital cities in China. Dietary intake was derived from 24 hour dietary recall for three consecutive days. Anthropometric measurements, glucose and lipid profiles were obtained. Factor analysis combined with cluster analysis was used for identifying major dietary patterns. The associations of dietary patterns with obesity and related cardiometabolic risk factors were examined by logistic regression analysis.

Results

Three mutually exclusive dietary patterns were identified, which were labeled as the healthy dietary pattern, the transitive dietary pattern, and the Western dietary pattern. Compared with children of the healthy dietary pattern, the multiple-adjusted odds ratios (95% confidence interval (CI)) of obesity were 1.11 (0.89–1.38) for children with the transitive dietary pattern and 1.80 (1.15–2.81) for children with the Western dietary pattern, which was 1.31 (95%CI 1.09–1.56) and 1.71 (95%CI: 1.13–2.56), respectively, for abdominal obesity. The Western dietary pattern was associated with significantly higher concentrations of low-density lipoprotein cholesterol (P<.001), triglycerides (P<.001), systolic blood pressure (P = 0.0435) and fasting glucose (P = 0.0082) and a lower concentration of high-density lipoprotein cholesterol (P = 0.0023), as compared with the healthy dietary pattern.

Conclusions

The Western dietary pattern characterized by red meat, eggs, refined grain and products, was positively associated with odds of obesity, the levels of plasma glucose, low-density lipoprotein cholesterol and triglycerides, and was inversely associated with the level of high-density lipoprotein cholesterol.     

Photocarcinogenesis and diet

Nearly 50 years ago the first reports appeared that cast suspicion on lipids, or peroxidative products thereof, as being involved in the expression of actinically induced cancer. Whereas numerous studies have implicated lipids as potentiators of specific chemical-induced carcinogenesis, only recently has the involvement of these dietary constituents in photocarcinogenesis been substantiated. It has now been demonstrated that both level of dietary lipid intake and degree of lipid saturation have pronounced effects on photoinduced skin cancer, with increasing levels of unsaturated fat intake enhancing cancer expression. The level of intake of these lipids is also manifested in the level of epidermal lipid peroxidation. Conversely, dietary antioxidants inhibit both lipid peroxidation and photocarcinogenesis, the degree of inhibition of the latter being roughly equivalent to the degree of cancer enhancement evoked by the respective level of dietary lipid. The apparent similarities of lipid effects on both chemical and photoinduced carcinogenesis suggest a common underlying role for these dietary constituents in the carcinogenic process. This role may involve free radical-mediated lipid peroxidative reactions. Regardless of the mechanism, it is obvious that both dietary lipid and antioxidants can modify the photocarcinogenic response of skin.     

重庆市市区中小学教师膳食食物摄入与营养知识知晓情况调查

目的:了解重庆市市区中小学教师膳食食物摄入与营养知识知晓情况,为指导该人群合理营养膳食提供依据。方法:以问卷形式对重庆市市区1345名中小学教师的膳食结构及营养知识知晓情况进行调查并对调查结果进行分析。结果:每天喝牛奶的占76%;经常摄入豆制品的占74%;经常摄入鱼类的占52%;每天摄入肉类的占50%;经常摄入蛋类的占78%;每天摄入蔬菜200 g的占55%;经常摄入粗粮的占73%。对自身膳食营养重视的占62%;回答了解或知道中国居民膳食指南占总人数的38%,其中男性占12%,女性占26%;回答了解或知道中国居民膳食宝塔的占37%,其中男性占10%,女性占27%。结论:该人群膳食食物摄入种类较多,食物来源丰富,但营养知识知晓情况较低,对自身健康关注的意识还有待提高。     

蔗糖诱发Sprague—Dawley雄性大鼠肥胖病高脂血症

用蔗糖作辅助铁水,饲养刚离乳的Sprague－Dawley雄性大鼠,180天后,53％大鼠肥胖成为饮食诱发肥胖型大鼠（DIO大鼠）,47％大鼠不肥胖成为饮食诱发肥胖抵抗型大鼠（DIO－R大鼠）且DIO和DIO－R大鼠均具高脂血症。说明25％蔗糖可诱发Sprague-Dawley雄性大鼠肥胖病高脂血症,但同样条件下为什么部分大鼠不肥胖还有待于进一步研究。另外,对DIO大鼠的肥胖机制作了初步探讨。     

Effect of quantity and quality of dietary protein on choline acetyltransferase and nerve growth factor, and their mRNAs in the cerebral cortex and hippocampus of rats

The brain protein synthesis is sensitive to the dietary protein; however, the role of dietary protein on biomarkers including choline acetyltransferase and nerve growth factor (NGF) for the function of cholinergic neurons remains unknown in young rats. The purpose of this study was to determine whether the quantity and quality of dietary protein affects the concentration of NGF and activity of choline acetyltransferase, and their mRNA levels in the brains of young rats. Experiments were carried out on five groups of young rats (4 weeks) given the diets containing 0, 5, 20% casein, 20% gluten or 20% gelatin for 10 days. The activity of choline acetyltransferase in the cerebral cortex and hippocampus declined gradually with a decrease in quantity and quality of dietary protein. The concentration of NGF in the cerebral cortex and the mRNA levels of choline acetyltransferase in the cerebral cortex and hippocampus did not differ among groups. However, the concentration and mRNA level of NGF in the hippocampus was significantly lower in rats fed with lower quantity of protein or lower quality of protein. In the hippocampus, the mRNA levels of NGF significantly correlated with the NGF concentration when the quantity (r = 0.704, P < 0.01) and quality (r = 0.682, P < 0.01) of dietary protein was manipulated. It was further found that a significant positive correlation existed between the NGF concentration and the activity of choline acetyltransferase in the hippocampus (dietary protein quantity, r = 0.632, P < 0.05; dietary protein quality, r = 0.623, P < 0.05). These results suggest that the ingestion of lower quantity and quality of dietary protein are likely to control the mRNA level and concentration of NGF, and cause a decline in the activity of choline acetyltransferase in the brains of young rats.     

The effect of magnesium and manganese uptake and accumulation on oxygen consumption and ammonia excretion in Porcellio spinicornis Say (Porcellionidae, Isopoda)

Mean concentrations of Mg and Mn in whole intermoult 7th growth-stage Porcellio spinicornis are positively correlated with dietary levels up to and including 1,000 ppm of these two trace metals. Lower tissue concentrations in isopods on 1,500 ppm diets are related to either a low food intake or a higher rate of metal excretion. Mean Mg concentration in whole isopods at the end of 7 days ranged from 27 388.26 +/- 598.56 micrograms/g dry tissue in the control to 69 122.08 +/- 31 682.98 micrograms/g dry tissue in the 1,000 ppm dietary group; in the 1,500 ppm dietary group, it amounted to 25 630.26 +/- 13 102.12 micrograms/g dry tissue. Mean Mn concentration varied from 85.53 +/- 11.23 micrograms/g dry tissue in the control to 229.05 +/- 32.33 micrograms/g dry tissue in 1,000 ppm dietary group; in the 1,500 ppm dietary group, it amounted to 199.57 +/- 18.99 micrograms/g dry tissue. Differences between the two sexes were significant at 5% level. Oxygen consumption was negatively and ammonia excretion was positively related to the dietary metal concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)     

Fatty acid composition of adipose tissue and blood in humans and its use as a biomarker of dietary intake

Accurate assessment of fat intake is essential to examine the relationships between diet and disease risk but the process of estimating individual intakes of fat quality by dietary assessment is difficult. Tissue and blood fatty acids, because they are mainly derived from the diet, have been used as biomarkers of dietary intake for a number of years. We review evidence from a wide variety of cross-sectional and intervention studies and summarise typical values for fatty acid composition in adipose tissue and blood lipids and changes that can be expected in response to varying dietary intake. Studies in which dietary intake was strictly controlled confirm that fatty acid biomarkers can complement dietary assessment methodologies and have the potential to be used more quantitatively. Factors affecting adipose tissue and blood lipid composition are discussed, such as the physical properties of triacylglycerol, total dietary fat intake and endogenous fatty acid synthesis. The relationship between plasma lipoprotein concentrations and total plasma fatty acid composition, and the use of fatty acid ratios as indices of enzyme activity are also addressed.     

Effect of dietary fatty acids on the body tissues of larval and juvenile cobia and their prey

Polyunsaturated fatty acids (PUFAs) have been used as biomarkers in pelagic ecosystems although previous studies have failed to quantify the timing of conservation of dietary PUFAs in pelagic fishes and invertebrates. Here we investigated the influence of diet upon the timing of conservation of PUFAs throughout multiple trophic exchanges in larval and juvenile cobia (Rachycentron canadum) and their prey. Cobia, rotifers (Brachionus plicatilis), and Artemia (A. franciscana) were fed laboratory processed or natural diets resembling prey and dietary modification of fatty acid signatures was quantified using two-source mixing models. Specimens were collected throughout the experiment to track dietary influences over time. Cobia larvae underwent significant dietary modification of PUFAs after 24 h and conserved > 90% of dietary PUFAs after an average of 6 days. Similar results were identified in juvenile cobia as significant dietary modification of PUFAs took place after 3 days and > 90% were conserved after an average of 12 days. In addition, no significant ontogenetic changes in PUFA signatures were identified in juvenile cobia throughout the 30-day experiment. PUFA signatures in prey items (rotifers and Artemia) underwent significant dietary modification in 24 h, with over 90% incorporation after 5-7 days. Results from this study support the premise that fatty acids are promising dietary indicators and may be useful for future studies examining trophic relationships in marine ecosystems and habitat use of marine fishes.     

Hypolipidemic and antioxidant effects of curcumin and capsaicin in high-fat-fed rats

The beneficial hypolipidemic and antioxidant influences of the dietary spice compounds curcumin and capsaicin were evaluated. Curcumin, capsaicin, or their combination were included in the diet of high-(30%)-fat-fed rats for 8 weeks. Dietary high-fat-induced hypertriglyceridemia was countered by dietary curcumin, capsaicin, or their combination by 12%-20%. Curcumin, capsaicin, and their combination also produced a slight decrease in serum total cholesterol in these animals. Serum alpha-tocopherol content was increased by dietary curcumin, capsaicin, and their combination in high-fat-fed rats. Serum total thiol content in high-fat-fed animals and serum ascorbic acid in normal animals was elevated by the combination of curcumin and capsaicin. Hepatic glutathione was increased by curcumin, capsaicin, or their combination in normal animals. Hepatic glutathione and alpha-tocopherol were increased, whereas lipid peroxide level was reduced by dietary curcumin and combination of curcumin and capsaicin in high-fat-fed animals. Serum glutathione peroxidase and glutathione transferase in high-fat-fed rats were generally higher as a result of dietary curcumin, capsaicin, and the combination of curcumin and capsaicin. Hepatic glutathione reductase and glutathione peroxidase were significantly elevated by dietary spice principles in high-fat-fed animals. The additive effect of the 2 bioactive compounds was generally not evident with respect to hypolipidemic or antioxidant potential. However, the effectiveness of the combination was higher in a few instances.     

Origin of hepatic triglyceride fatty acids: quantitative estimation of the relative contributions of linoleic acid by diet and adipose tissue in normal and ethanol-fed rats

The present study demonstrates that the rat liver obtains most of its triglyceride fatty acids from dietary sources. The dietary and adipose tissue contributions of linoleic acid for hepatic triglyceride esterification were shown to be 50.42 and 13.85 micro moles, respectively, during a 4-day period. When ethanol provided 40% of the caloric intake, fatty liver developed and hepatic triglyceride content increased threefold. Under these conditions, the dietary and adipose tissue contributions of linoleic acid were estimated at 192.85 and 10.73 micro moles, respectively. This increase in dietary fatty acid utilization was sufficient to account for the entire increase in esterified hepatic linoleic acid. Any explanation of these observations must include the high dietary fatty acid utilization in both control and ethanol-treated animals. One possibility is that most dietary lipids first enter a rapidly turning over pool in adipose tissue from which most hepatic triglyceride fatty acids are derived. Another is that dietary fatty acids, incorporated into chylomicrons, are stored separately and used preferentially by the liver as compared with lipids derived from adipose tissue and bound to albumin. The pros and cons of these possibilities are discussed.     

Biogeochemical and craniometric investigation of dietary ecology, niche separation, and taxonomy of Plio-Pleistocene cercopithecoids from the Makapansgat Limeworks

Three sympatric fossil cercopithecoid genera (Cercopithecoides, Parapapio, and Theropithecus) occur in Members 3 and 4 at the Makapansgat Limeworks hominin locality, South Africa, and their presence in a single ecosystem suggest a certain degree of ecological and/or dietary differentiation between taxa. Here, we explore the extent of dietary niche separation amongst these taxa using stable isotope (13C/12C, 18O/16O) and trace-element (Sr, Ba, Ca) analyses of fossil tooth enamel. In particular we searched for evidence of subtle niche separation between the more closely related, morphologically similar taxa of the genus Parapapio, as uncertainties exist around their taxonomy and taxonomic identification. Given these uncertainties, craniometric analyses were also performed to ground the dietary interpretations in a morphological context. The results found no clear taxonomic signal in the craniometric data for the Parapapio sample, and further indicate that this sample was no more variable morphologically than a single, geographically circumscribed, extant chacma baboon sample. In contrast, two overlapping dietary ecologies were found within this same Makapansgat Parapapio sample. Additionally, two widely differing dietary ecologies were found within the Cercopithecoides williamsi sample, while results for Theropithecus darti indicate a predominantly C4 diet. Hence, although biogeochemical dietary indicators point towards distinct dietary ecologies within and between fossil genera at Makapansgat, within the genus Parapapio disjunctions exist between the dietary categories and the taxonomic assignment of specimens.     

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

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