Diet-induced bacterial immunogens in the gastrointestinal tract of dairy cows: Impacts on immunity and metabolism

Dairy cows are often fed high grain diets to meet the energy demand for high milk production or simply due to a lack of forages at times. As a result, ruminal acidosis, especially subacute ruminal acidosis (SARA), occurs frequently in practical dairy production. When SARA occurs, bacterial endotoxin (or lipopolysaccharide, LPS) is released in the rumen and the large intestine in a large amount. Many other bacterial immunogens may also be released in the digestive tract following feeding dairy cows diets containing high proportions of grain. LPS can be translocated into the bloodstream across the epithelium of the digestive tract, especially the lower tract, due to possible alterations of permeability and injuries of the epithelial tissue. As a result, the concentration of blood LPS increases. Immune responses are subsequently caused by circulating LPS, and the systemic effects include increases in concentrations of neutrophils and the acute phase proteins such as serum amyloid-A (SAA), haptoglobin (Hp), LPS binding protein (LBP), and C-reactive protein (CRP) in blood. Entry of LPS into blood can also result in metabolic alterations. Blood glucose and nonesterified fatty acid concentrations are enhanced accompanying an increase of blood LPS after increasing the amount of grain in the diet, which adversely affects feed intake of dairy cows. As the proportions of grain in the diet increase, patterns of plasma β-hydoxybutyric acid, cholesterol, and minerals (Ca, Fe, and Zn) are also perturbed. The bacterial immunogens can also lead to reduced supply of nutrients for synthesis of milk components and depressed functions of the epithelial cells in the mammary gland. The immune responses and metabolic alterations caused by circulating bacterial immunogens will exert an effect on milk production. It has been demonstrated that increases in concentrations of ruminal LPS and plasma acute phase proteins (CRP, SAA, and LBP) are associated with declines in milk fat content, milk fat yield, 3.5% fat-corrected milk yield, as well as milk energy efficiency.     

Proteomic analysis of diet-induced hypercholesterolemic mice

We report here a proteomic analysis of differentially expressed liver proteins of both C57BL/6J (B6, atherosclerosis-susceptible strain) and C3H/HeJ mice (C3H, atherosclerosis-resistant strain), which were fed either control or a high-fat enriched atherogenic diet for eight weeks. We observed differential patterns of plasma lipids between the two strains when both were fed atherogenic diets. That is, although low density lipoprotein cholesterol level was highly elevated in both, the levels of total cholesterol and triglyceride in B6 mice were much lower than those in C3H mice when they were fed atherogenic diets. However, the high density lipoprotein cholesterol level was increased in the latter but decreased in the former. Histopathological observation revealed that more prominent lipid droplets were present in B6 mice than in C3H mice, when they were maintained on the atherogenic diets. Proteomic analysis of liver tissues of these two strains showed that a total of 30 proteins were significantly changed in the livers obtained from both strains after being fed the atherogenic diet. Of these, 14 protein spots including carbonic anhydrase III, senescence marker protein 30 and selenium binding protein 2 were differentially changed only in B6 mice, which was also confirmed in part by Western blotting. An additional 16 protein spots including glutathione S-transferase subclass, apolipoprotein E and chaperonin proteins were changed in both strains. We also identified 28 proteins that were differentially expressed in the livers of both B6 and C3H mice, regardless of diet feeding condition. Of these, 4 protein spots in B6 mice and 11 protein spots in C3H mice were up-regulated. Thirteen strain specific protein spots including antioxidant protein 2, apolipoprotein E and apolipoprotein A-I were also detected in different positions in two-dimensional electrophoresis. These results suggest a clear distinction in differential expression of oxidative stress proteins and lipid metabolism related proteins between the two strains in response to atherogenic diet feeding, which might account for their difference in susceptibility to atherogenesis.     

Influence of Sire Breed on the Interplay among Rumen Microbial Populations Inhabiting the Rumen Liquid of the Progeny in Beef Cattle

This study aimed to evaluate whether the host genetic background impact the ruminal microbial communities of the progeny of sires from three different breeds under different diets. Eighty five bacterial and twenty eight methanogen phylotypes from 49 individuals of diverging sire breed (Angus, ANG; Charolais, CHA; and Hybrid, HYB), fed high energy density (HE) and low energy density (LE) diets were determined and correlated with breed, rumen fermentation and phenotypic variables, using multivariate statistical approaches. When bacterial phylotypes were compared between diets, ANG offspring showed the lowest number of diet-associated phylotypes, whereas CHA and HYB progenies had seventeen and twenty-three diet-associated phylotypes, respectively. For the methanogen phylotypes, there were no sire breed-associated phylotypes; however, seven phylotypes were significantly different among breeds on either diet (P<0.05). Sire breed did not influence the metabolic variables measured when high energy diet was fed. A correlation matrix of all pairwise comparisons among frequencies of bacterial and methanogen phylotypes uncovered their relationships with sire breed. A cluster containing methanogen phylotypes M16 (Methanobrevibacter gottschalkii) and M20 (Methanobrevibacter smithii), and bacterial phylotype B62 (Robinsoniella sp.) in Angus offspring fed low energy diet reflected the metabolic interactions among microbial consortia. The clustering of the phylotype frequencies from the three breeds indicated that phylotypes detected in CHA and HYB progenies are more similar among them, compared to ANG animals. Our results revealed that the frequency of particular microbial phylotypes in the progeny of cattle may be influenced by the sire breed when different diets are fed and ultimately further impact host metabolic functions, such as feed efficiency.     

Factors influencing bacterial attachment to the ruminal epithelium in vitro

Some factors influencing bacterial attachment to the rumen epithelium were studied in vitro using mixed rumen bacteria (upper- or lower-layer bacteria formed at bacterial sediment by centrifugation), isolated from steers fed a roughage diet, and rumen epithelial cells collected from beef cattle given low-concentrate (50%; LC) and high-concentrate (90%; HC) diets. Optimal incubation conditions for bacterial attachment to rumen epithelial cells were 39 degrees C for 30 min. The bacteria isolated from the upper layer had a higher attaching activity to the LC epithelial cells than those of the lower layer. A higher degree of bacterial attachment was observed using the rumen epithelium from steers fed the LC diet rather than the HC diet (p<0.01). Ethylenediamine dihydroiodide (EDDI) added at 10 through 40 &mgr;g/ml increased bacterial attachment to the HC epithelial cells. Ammonia at 50 through 100 &mgr;g/ml positively affected bacterial attachment to both LC and HC epithelial cells. Bacterial attachment to the HC epithelial cells was enhanced (p<0.01) by the addition of a reducing agent (L-cysteine.HCl) but no increase was noted with LC cells. L- or D-lactate, volatile and unsaturated fatty acids markedly decreased bacterial attachment to rumen epithelial cells.     

White adipose tissue genome wide-expression profiling and adipocyte metabolic functions after soy protein consumption in rats

Obesity is associated with an increase in adipose tissue mass due to an imbalance between high dietary energy intake and low physical activity; however, the type of dietary protein may contribute to its development. The aim of the present work was to study the effect of soy protein versus casein on white adipose tissue genome profiling, and the metabolic functions of adipocytes in rats with diet-induced obesity. The results showed that rats fed a Soy Protein High-Fat (Soy HF) diet gained less weight and had lower serum leptin concentration than rats fed a Casein High-Fat (Cas HF) diet, despite similar energy intake. Histological studies indicated that rats fed the Soy HF diet had significantly smaller adipocytes than those fed the Cas HF diet, and this was associated with a lower triglyceride/DNA content. Fatty acid synthesis in isolated adipocytes was reduced by the amount of fat consumed but not by the type of protein ingested. Expression of genes of fatty acid oxidation increased in adipose tissue of rats fed Soy diets; microarray analysis revealed that Soy protein consumption modified the expression of 90 genes involved in metabolic functions and inflammatory response in adipose tissue. Network analysis showed that the expression of leptin was regulated by the type of dietary protein and it was identified as a central regulator of the expression of lipid metabolism genes in adipose tissue. Thus, soy maintains the size and metabolic functions of adipose tissue through biochemical adaptations, adipokine secretion, and global changes in gene expression.     

Proteome profile of bovine ruminal epithelial tissue based on GeLC–MS/MS

The proteome of rumen epithelial tissue was analysed by SDS-PAGE coupled with LC–MS/MS. 813 non-redundant proteins were identified of which 7.4 % featured membrane-spanning domains and 15.4 % harboured a signal peptide. According to the gene ontology annotation, the most abundant proteins exhibited binding activities related to their molecular functions, were proteins of cellular components or belonged to various metabolic processes. A predominant group of canonical pathways in the rumen epithelial tissue was identified using the IPA software. The GeLC–MS/MS approach was used to characterise the entire protein expression repertoire in rumen tissue, providing a more detailed understanding of the important biological processes in the rumen.     

Differential expression of skeletal muscle proteins in high‐fat diet‐fed rats in response to capsaicin feeding

In this study, the effects of capsaicin on expression of skeletal muscle proteins in Sprague–Dawley rats fed with a high‐fat diet (HFD) were investigated. Rats were fed a HFD with or without capsaicin treatment for 8 wk. After HFD feeding, capsaicin‐treated rats weighed an average of 8% less than those of the HFD control group. Gastrocnemius muscle tissue from lean and obese rats with or without capsaicin treatment was arrayed using 2‐DE for detection of HFD‐associated markers. Proteomic analysis using 2‐DE demonstrated that 36 spots from a total of approximately 600 matched spots showed significantly different expression; 27 spots were identified as gastrocnemius muscle proteins that had been altered in response to capsaicin feeding, and 6 spots could not be identified by mass fingerprinting. Expression of various muscle proteins was determined by immunoblot analysis for the determination of molecular mechanisms, whereby capsaicin caused inhibition of adipogenesis. Immunoblot analysis revealed increased uncoupling protein 3 (UCP3) protein expression in HFD‐fed rats, whereas contents were reduced with capsaicin treatment. Compared with the HFD control group, capsaicin treatment increased phosphorylation of AMP‐activated protein kinase (AMPIC) CP3 and acetyl‐CoA carboxylase (ACC). To support this result, we also analyzed in vitro differential protein expression in L6 skeletal muscle cells. These data suggest that the AMPK‐ACC‐malonyl‐CoA metabolic signaling pathway is one of the targets of capsaicin action. To the best of our knowledge, this is the first proteomic study to report on analysis of diet‐induced alterations of protein expression that are essential for energy expenditure in rat muscle.     

Magnesium absorption as influenced by the rumen passage kinetics in lactating dairy cows fed modified levels of fibre and protein

The potassium sensitive magnesium absorption through the rumen wall may be influenced by additional dietary properties, such as diet type, forage type or forage to concentrate ratio. These properties are likely associated to rumen passage kinetics modified by dietary fibre content. The study aimed to assess the effects of rumen passage kinetics on apparent Mg absorption and retention in lactating dairy cows fed modified levels of fibre. Six lactating Red-Holstein and Holstein cows, including four fitted with ruminal cannulas were randomly assigned to a 3 × 3 cross-over design. The experimental diets consisted of early harvested low NDF (341 g NDF/kg DM) and late harvested high NDF (572 g NDF/kg DM) grass silage (80% DM) and of concentrates (20% of DM). As the low-fibre diet was excessive in protein, a third high-fibre diet was formulated to be balanced in digestible protein with the low-fibre diet to avoid any eventual confounding effects of NDF and protein excess. All diets were formulated to contain iso-Ca, -P, -Mg, -K and -Na. Passage kinetics of solid and liquid phase of rumen digesta were evaluated using ruminal marker disappearance profiles. Cows fed the low-fibre diet had compared to the other diets, an up to 40% lower solid and 26% lower liquid phase volume of rumen digesta and a 10% numerically higher fractional rumen liquid passage rate. Rumen pH lost 0.6 units and Mg concentration in the rumen liquid phase tripled when cows were fed the low-fibre diet. Faecal Mg excretion was up to 14% higher in cows fed the low-fibre diet and Mg absorbability was 12% compared to up to 19% in other diets. Urinary Mg excretion in cows fed the low-fibre diet was half of the ones in the other treatments, but Mg retention was not affected. Dietary protein excess neither affected rumen passage kinetics nor Mg absorption and retention. Absorption of Mg was correlated with rumen liquid volume which both decreased with decreasing daily NDF intake (NDFi, 11.8 ± 2.4 l/kg NDFi). Consequently, daily Mg absorption decreased by 1.32 ± 0.28 g/kg decreasing NDFi. To conclude, in addition to the known antagonistic effect of dietary K, the present data indicate that Mg absorption was dependent from NDFi which modified rumen liquid volume, but was independent of dietary protein excess likely associated to low NDF herbages.     

Relationship between efficiency of nitrogen utilization and isotopic nitrogen fractionation in dairy cows: contribution of digestion v. metabolism?

Animal tissues are naturally ¹⁵N enriched relative to their diet and the extent of this difference (Δ¹⁵N_animal-diet) has been correlated to the efficiency of N assimilation in different species. The rationale is that transamination and deamination enzymes, involved in amino acid metabolism are likely to preferentially convert amino groups containing ¹⁴N over ¹⁵N. However, in ruminants the contribution of rumen bacterial metabolism relative to animal tissues metabolism to naturally enrich animal proteins in terms of ¹⁵N has been not assessed yet. The objective of this study was to assess the impact of rumen and digestion processes on the relationship between Δ¹⁵N_animal-diet and efficiency of N utilization for milk protein yield (milk N efficiency (MNE); milk N yield/N intake) as well as the relationship between the ¹⁵N natural abundance of rumen bacteria and the efficiency of N use at the rumen level. Solid- and liquid-associated rumen bacteria, duodenal digesta, feces and plasma proteins were obtained (n=16) from four lactating Holstein cows fed four different diets formulated at two metabolizable protein supplies (80% v. 110% of protein requirements) crossed by two different dietary energy source (diets rich in starch v. fiber). We measured the isotopic N fractionation between animal and diet (Δ¹⁵N_animal-diet) in these different body pools. The Δ¹⁵N_animal-diet was negatively correlated with MNE when measured in solid-associated rumen bacteria, duodenal digesta, feces and plasma proteins, with the strongest correlation found for the latter. However, our results showed a very weak ¹⁵N enrichment of duodenal digesta (Δ¹⁵N_{duodenal digesta-diet} mean value=0.42) compared with that observed in plasma proteins (Δ¹⁵N_{plasma protein-diet} mean value=2.41). These data support the idea that most of the isotopic N fractionation observed in ruminant proteins (Δ¹⁵N_{plasma protein-diet}) has a metabolic origin with very little direct impact of the overall digestion process on the existing relationship between Δ¹⁵N_{plasma protein-diet} and MNE. The ¹⁵N natural abundance of rumen bacteria was not related to either rumen N efficiency (microbial N/available N) or digestive N efficiency (metabolizable protein supply/CP intake), but showing a modest positive correlation with rumen ammonia concentration. When using diets not exceeding recommended protein levels, the contribution of rumen bacteria and digestion to the isotopic N fractionation between animal proteins and diet is low. In our conditions, most of the isotopic N fractionation (Δ¹⁵N_{plasma protein-diet}) could have a metabolic origin, but more studies are warranted to confirm this point with different diets and approaches.     

Response of rumen microbiota,and metabolic profiles of rumen fluid,liver and serum of goats to high-grain diets

Feeding ruminants a high-grain (HG) diet is a widely used strategy to improve milk yield and cost efficiency. However, it may cause certain metabolic disorders. At present, information about the effects of HG diets on the systemic metabolic profile of goats and the correlation of such diets with rumen bacteria is limited. In the present study, goats were randomly divided into two groups: one was fed the hay diet (hay; n = 5), while the other was fed HG diets (HG; n = 5). On day 50, samples of rumen contents, peripheral blood serum and liver tissues were collected to determine the metabolic profiles in the rumen fluid, liver and serum and the microbial composition in rumen. The results revealed that HG diets reduced (P < 0.05) the community richness and diversity of rumen microbiota, with an increase in the Chao 1 and Shannon index and a decrease in the Simpson index. HG diets also altered the composition of rumen microbiota, with 30 genera affected (P < 0.05). Data on the metabolome showed that the metabolites in the rumen fluid, liver and serum were affected (variable importance projection > 1, P <0.05) by dietary treatment, with 47, 10 and 27 metabolites identified as differentially metabolites. Pathway analysis showed that the common metabolites in the shared key pathway (aminoacyl-transfer RNA biosynthesis) in the rumen fluid, liver and serum were glycine, lysine and valine. These findings suggested that HG diets changed the composition of the rumen microbiota and metabolites in the rumen fluid, liver and serum, mainly involved in amino acid metabolism. Our findings provide new insights into the understanding of diet-related systemic metabolism and the effects of HG diets on the overall health of goats.     

Identification of differentially expressed proteins in ruminal epithelium in response to a concentrate-supplemented diet

Ruminal epithelium adapts to dietary change with well-coordinated alterations in metabolism, proliferation, and permeability. To further understand the molecular events controlling diet effects, the aim of this study was to evaluate protein expression patterns of ruminal epithelium in response to various feeding regimes. Sheep were fed with a concentrate-supplemented diet for up to 6 wk. The control group received hay only. Proteome analysis with differential in gel electrophoresis technology revealed that, after 2 days, 60 proteins were significantly modulated in ruminal epithelium in a comparison between hay-fed and concentrate-fed sheep (P < 0.05). Forty proteins were upregulated and 20 proteins were downregulated in response to concentrate diet. After 6 wk of this diet, only 14 proteins were differentially expressed. Among these, 11 proteins were upregulated and 3 downregulated. To identify proteins that were modulated by dietary change, two-dimensional electrophoresis was coupled with liquid chromatography electrospray ionization mass spectrometry. The differential expression of selected proteins, such as esterase D, annexin 5, peroxiredoxin 6, carbonic anhydrase I, and actin-related protein 3, was verified by immunoblotting and/or mRNA analysis. The identified proteins were mainly associated with functions related to cellular stress, metabolism, and differentiation. These results suggest new candidate proteins that may contribute to a better understanding of the signaling pathways and mechanisms that mediate rumen epithelial adaptation to high-concentrate diet.     

High-grain diets altered rumen fermentation and epithelial bacterial community and resulted in rumen epithelial injuries of goats

This study evaluated the effects of high-grain diets on the rumen fermentation, epithelial bacterial community, morphology of rumen epithelium, and local inflammation of goats during high-grain feeding. Twelve 8-month-old goats were randomly assigned to two different diets, a hay diet or a high-grain diet (65% grain, HG). At the end of 7 weeks of treatment, samples of rumen content and rumen epithelium were collected. Rumen pH was lower (P < 0.05), but the levels of volatile fatty acids and lipopolysaccharides were higher (P < 0.05) in the HG group than those in the hay group. The principal coordinate analysis indicated that HG diets altered the rumen epithelial bacterial community, with an increase in the proportion of genus Prevotella and a decrease in the relative abundance of the genera Shuttleworthia and Fibrobacteres. PICRUSt analysis suggested that the HG-fed group had a higher (P < 0.05) relative abundance of gene families related to energy metabolism; folding, sorting, and degradation; translation; metabolic diseases; and immune system. Furthermore, HG feeding resulted in the rumen epithelial injury and upregulated (P < 0.05) the gene expressions of IL-1β and IL-6, and the upregulations were closely related to the rumen pH, LPS level, and rumen epithelial bacteria abundance. In conclusion, our results indicated that the alterations in the rumen environment and epithelial bacterial community which were induced by HG feeding may result in the damage and local inflammation in the rumen epithelium, warranting further study of rumen microbial–host interactions in the HG feeding model.     

Comparison of high-protein diets and leucine supplementation in the prevention of metabolic syndrome and related disorders in mice

High-protein diets have been shown to promote weight loss, to improve glucose homeostasis and to increase energy expenditure and fat oxidation. We aimed to study whether leucine supplementation is able to mimic the alleviating effects of high-protein diets on metabolic syndrome parameters in mice fed high-fat diet.Male C57BL/6 mice were fed for 20 weeks with semisynthetic high-fat diets (20% w/w of fat) containing either an adequate (10% protein, AP) or high (50% protein, HP) amount of whey protein, or an AP diet supplemented with l-leucine corresponding to the leucine content of the HP diet (6% leucine, AP+L). Body weight and composition, energy expenditure, glucose tolerance, hepatic triacylglycerols (TG), plasma parameters as well as expression levels of mRNA and proteins in different tissues were measured. HP feeding resulted in decreased body weight, body fat and hepatic TG accumulation, as well as increased insulin sensitivity compared to AP. This was linked to an increased total and resting energy expenditure (REE), decreased feed energy efficiency, increased skeletal muscle (SM) protein synthesis, reduced hepatic lipogenesis and increased white fat lipolysis. Leucine supplementation had effects that were intermediate between HP and AP with regard to body composition, liver TG content, insulin sensitivity, REE and feed energy efficiency, and similar effects as HP on SM protein synthesis. However, neither HP nor AP+L showed an activation of the mammalian target of rapamycin pathway in SM. Leucine supplementation had no effect on liver lipogenesis and white fat lipolysis compared to AP. It is concluded that the essential amino acid leucine is able to mimic part but not all beneficial metabolic effects of HP diets.     

Changes in bacterial diversity associated with epithelial tissue in the beef cow rumen during the transition to a high-grain diet

Our understanding of the ruminal epithelial tissue-associated bacterial (defined as epimural bacteria in this study) community is limited. In this study, we aimed to determine whether diet influences the diversity of the epimural bacterial community in the bovine rumen. Twenty-four beef heifers were randomly assigned to either a rapid grain adaptation (RGA) treatment (n = 18) in which the heifers were allowed to adapt from a diet containing 97% hay to a diet containing 8% hay over 29 days or to the control group (n = 6), which was fed 97% hay. Rumen papillae were collected when the heifers were fed 97%, 25%, and 8% hay diets. PCR-denaturing gradient gel electrophoresis (DGGE) and quantitative real-time PCR analysis were used to characterize rumen epimural bacterial diversity and to estimate the total epimural bacterial population (copy numbers of the 16S rRNA gene). The epimural bacterial diversity from RGA heifers changed (P = 0.01) in response to the rapid dietary transition, whereas it was not affected in control heifers. A total of 88 PCR-DGGE bands were detected, and 44 were identified from phyla including Firmicutes, Bacteroidetes, and Proteobacteria. The bacteria Treponema sp., Ruminobacter sp., and Lachnospiraceae sp. were detected only when heifers were fed 25% and 8% hay diets, suggesting the presence of these bacteria is the result of adaptation to the high-grain diets. In addition, the total estimated population of rumen epimural bacteria was positively correlated with molar proportions of acetate, isobutyrate, and isovalerate, suggesting that they may play a role in volatile fatty acid metabolism in the rumen.     

不同饲料饲养的近暗散白蚁工蚁肠道中差异蛋白分析

【目的】本研究旨在通过比较不同木质纤维素含量的饲料对近暗散白蚁Reticulitermesperilucifugus工蚁前中肠和后肠内容物蛋白的组成和表达差异,为揭示白蚁的营养消化吸收机理提供蛋白水平上的依据。【方法】用木质纤维素含量不同的3种饲料(松木、秸秆和滤纸)饲养近暗散白蚁工蚁,然后用双向电泳分析肠道不同部位的内容物蛋白,并对差异蛋白进行MALDI-TOF/MS测序及生物信息学分析。【结果】双向电泳结果发现,同一饲料饲养的近暗散白蚁工蚁前中肠可辨蛋白点数明显多于后肠;不同饲料饲喂的工蚁前中肠和后肠可辨蛋白点数依次是松木饲养的＞滤纸饲养的＞秸秆饲养的。通过对115个蛋白点的测序分析表明,不同饲料饲喂的工蚁前中肠和后肠中的主要差异蛋白为具有催化活性的蛋白质,包括与氨基酸代谢、丙酮酸代谢、碳代谢、氮代谢、TCA循环、糖酵解、糖异生和纤维素降解等相关的酶,以及参与细胞组成和信号传导的蛋白。【结论】木质纤维素含量不同的饲料饲养的近暗散白蚁工蚁肠道中的差异蛋白主要为具有催化活性的蛋白、细胞组成蛋白和信号传导蛋白,表明不同的饲料影响近暗散白蚁的肠道蛋白组成。这些结果为揭示白蚁对木质纤维素的降解机理提供了参考。     

Lipid-deprived diet perturbs O-glycosylation of secretory proteins in rat mammary epithelial cells

Nutrition modulates both production and composition of milk. Milk composition was studied in rats chronically fed a diet without additional lipids, and therefore eating only traces of the recommended supply of essential polyunsaturated fatty acid. Despite a large decrease in milk-protein synthesis, only protein composition, but not protein concentration, was found to change in the milk of rats following a lipid-deprived diet. Correlatively, we observed a substantial increase in the lactose concentration of milk. Analysis of milk proteins by two-dimensional electrophoresis demonstrated that the relative proportion of the various molecular forms of κ-casein, an O-glycosylated protein, was modified in the milk of rats receiving the lipid-deprived diet. In tissues, differences in the two-dimensional pattern of κ-casein between control and lipid-deprived rats were similar, if not identical. In contrast to κ-casein, the molecular forms of α-lactalbumin, an N-glycosylated protein, were not affected by the diet. These data provide evidence that O-glycosylation of milk proteins in the secretory pathway of mammary epithelial cells is modulated by the lipid content of experimental diets.     

Potential protein markers for nutritional health effects on colorectal cancer in the mouse as revealed by proteomics analysis

It is suggested that colorectal cancer might be prevented by changes in diet, and vegetable consumption has been demonstrated to have a protective effect. Until now, little is known about the effects of vegetable consumption at the proteome level. Therefore, the effect of increased vegetable intake on the protein expression in the colonic mucosa of healthy mice was studied. Aim was to identify the proteins that are differentially expressed by increased vegetable consumption and to discriminate their possible role in the protection against colorectal cancer. Mice were fed four different vegetable diets, which was followed by analysis of total cellular protein from colonic mucosal cells by a combination of 2-DE and MS. We found 30 proteins that were differentially expressed in one or more diets as compared to the control diet. Six could be identified by MALDI-TOF MS: myosin regulatory light chain 2, carbonic anhydrase I, high-mobility group protein 1, pancreatitis-associated protein 3, glyceraldehyde-3-phosphate dehydrogenase and ATP synthase oligomycin sensitivity conferral protein. Alterations in the levels of these proteins agree with a role in the protection against colon cancer. We conclude that these proteins are suitable markers for the health effect of food on cancer. The observed altered protein levels therefore provide support for the protective effects of vegetables against colorectal cancer.     

Altered Brown Adipose Tissue and Na,K Pump Activities During Diet-Induced Obesity and Weight Loss in Rats

Brown adipose tissue (BAT) thermogenesis is an uncoupled ATPase-independent thermogenic mechanism. Ion transport by the Na,K pump is an ATPase- dependent thermogenic mechanism. Both have been proposed as mechanisms of altered energy expenditure during states of dietary energy surfeit and deficit. Our aim was to study these mechanisms during diet-induced obesity and weight loss. Over 36 weeks rats were fed lard- or tallow-based diets (63% energy as fat), or a control diet (12% energy as fat). During periods of restriction rats were fed 50% of the energy intake of controls in the form of a control diet. Several components of thermogenic response increased in rats eating high fat diets and decreased following dietary restriction. BAT activation occurred, particularly with a lard-based diet, as indicated by increased GDP binding and uncoupling protein (UCP) content. Na,K pump activity in thymocytes increased with the feeding of both high fat diets at some time points. Plasma T₃ level increased in rats eating the lard-based diet and decreased with dietary restriction regardless of previous diet. Resting metabolic rate (RMR) of the animals was unchanged despite increases in these thermogenic components and was decreased in all groups following dietary restriction. Our results indicate a lack of any major role for activated BAT thermogenesis in mitigating the extent of the obesity induced by the high fat diets. The reasons for the differences in response to the two different sources of saturated fat, lard, and tallow, are not clear.     

Development of a diet for long-term raising of F344 rats--relationship between dietary digestible crude protein content and digestible energy content.

Mice and rats are frequently subjected to long-term raising in studies of aging. These animals are usually given growing or breeding diets from a young age. This raising method causes diseases such as chronic nephropathy with proteinuria due to nutritional excess. Consequently, a long-term raising study on male F344/DuCrj rats using nine sorts of diets differing in crude protein (CP; 12, 28, 44%) and digestible energy (DE; 2.8, 3.7, 4.5 kcal/g) contents was carried out. It was found that feed consumption was regulated by DE, not digestible crude protein (DCP) intake. Body weight was controlled within low energy areas, and was not influenced by feed or DCP intake. The liver and kidney weight at 105 weeks of age increased in response to an increase in the level of CP in the diet. Chronic nephropathy was severe in rats fed high protein diets and moderate levels of protein with moderate to high energy diets. Fatty liver and bile duct hyperplasia were found in rats fed a high protein and high energy diet. Few pathological findings of kidney and liver were found in the low protein and low energy diet group. The reduction of disorders attributable to excess energy or inappropriate diet suggests that low protein and low energy diets are most suitable for long-term raising in this strain of rat.