Effects of Individual Essential Amino Acids on Growth Rates of Young Rats Fed a Low-Protein Diet.

To investigate the effects of individual essential amino acids (EAA) on growth and the underlying mechanisms, EAA individually supplemented a low-protein (LP) diet fed to young rats in the present study. Treatments were an LP diet that contained 6% crude protein (CP), a high-protein (HP) diet that contained 18% CP, and 10 LP diets supplemented with individual EAA to achieve an EAA supply equal to that of the HP diet. The CP concentration of the LP diet was ascertained from the results of the first experiment, which examined the effects of dietary CP concentrations on growth rates, with CP ranging from 2% to 26%. Weight gain was increased with the supplementation of His, Ile, Lys, Thr, or Trp as compared to the LP diet (p < 0.05). Feed intake was greater for the His-, Lys-, and Thr-supplemented treatments as compared to the LP group (p < 0.05). Protein utilization efficiency was lower for the HP group than other groups (p < 0.01). The supplementation of Leu, Lys, and Val led to reduced protein utilization efficiency (p < 0.05), but the supplementation of Thr and Trp led to greater efficiency than the LP group (p < 0.05). Compared to the LP group, plasma urea concentrations were elevated with individual EAA supplementation, with the exception of the Thr addition. The added EAA resulted in increased concentrations of the corresponding EAA in plasma, except for Arg and Phe supplementation. The supplementation of Arg, His, Leu, Lys, and Met individually stimulated mTORC1 pathway activity (p < 0.05), and all EAA resulted in the decreased expression of ATF4 (p < 0.05). In summary, the supplementation of His, Ile, Lys, Thr, or Trp to an LP diet improved the growth performance of young rats. Responses to His and Lys additions were related to the activated mTORC1 pathway and feed intake increases. The improved growth performance resulting from the addition of a single EAA is not solely attributed to the increased plasma availability of EAA. Rather, it may be the consequence of a confluence of factors encompassing signaling pathways, the availability of amino acids, and other associated elements. The additivity of these factors results in independent responses to several EAA with no order of limitation, as is universally encoded in growth models for all production animal species.

Responses in splanchnic and mammary amino acid metabolism to short-term graded removal of methionine in lactating goats.

Four multi-catheterized lactating goats were used in a 4 × 4 Latin square experiment to investigate the responses of amino acid metabolism in portal-drained viscera (PDV), liver, and mammary glands to short-term varying supplies of methionine (Met). During the last 45 h in each experimental period, goats were fasted for 12 h and then abomasally infused with an amino acid (AA) mixture plus glucose for 33 h. Treatments consisted of graded removal of Met from an infused AA mixture to achieve Met content in the infusate of 100% (complete), 60%, 30%, or 0% that in casein. Graded Met removal decreased the production of milk, milk protein, lactose, and fat linearly whilst also decreasing arterial Met concentration linearly (P < 0.05). Meanwhile, net PDV uptake and liver removal of Met decreased linearly (P < 0.05) due to decreased Met affinity of PDV and liver (P < 0.05). Net mammary uptake of Met (P > 0.1) was maintained as Met supply declined. This was achieved through increased mammary affinity (P < 0.05) and increased mammary blood flow (P < 0.05) totally offsetting the negative effect of decreased circulating Met concentration. Graded removal of Met from the infusate linearly decreased mammary uptake-to-milk output ratios of Met (P < 0.05) and tended to decrease essential amino acid (EAA) linearly (0.05 < P < 0.1). Treatments also linearly decreased circulating concentration of prolactin and linearly increased insulin concentration (P < 0.05). In conclusion, results of the present study indicated there were several mechanisms used to mitigate a Met deficiency, including reduced catabolism of Met in PDV, liver, and peripheral tissue (including mammary glands) and a linear increase in mammary blood flow. The observed decreases in milk protein production as Met supply decreased appear to be a result of regulatory events which may have been driven by decreased circulating prolactin, rather than as a result of decreased mammary Met uptake.

Effect of Maternal Gradient Nutritional Restriction during Pregnancy on Mammary Gland Development in Offspring.

We aimed to investigate the effect of different levels of nutritional restriction on mammary gland development during the embryonic period by gradient nutritional restriction in pregnant female mice. We started the nutritional restriction of 60 female CD-1(ICR) mice from day 9 of gestation based on 100%, 90%, 80%, 70% and 60% of ad libitum intake. After delivery, the weight and body fat of the offspring and the mother were recorded (n = 12). Offspring mammary development and gene expression were explored by whole mount and qPCR. Mammary development patterns of in offspring were constructed using Sholl analysis, principal component analysis (PCA) and regression analysis. We found that: (1) Mild maternal nutritional restriction (90-70% of ad libitum intake) did not affect offspring weight, while body fat percentage was more sensitive to nutritional restriction (lower at 80% ad libitum feeding). (2) A precipitous drop in mammary development and altered developmental patterns occurred when nutritional restriction ranged from 80% to 70% of ad libitum intake. (3) Mild maternal nutritional restriction (90% of ad libitum intake) promoted mammary-development-related gene expression. In conclusion, our results suggest that mild maternal nutritional restriction during gestation contributes to increased embryonic mammary gland development. When maternal nutritional restriction reaches 70% of ad libitum intake, the mammary glands of the offspring show noticeable maldevelopment. Our results help provide a theoretical basis for the effect of maternal nutritional restriction during gestation on offspring mammary development and a reference for the amount of maternal nutritional restriction.

Comparison of growth performance and rumen metabolic pathways in sheep and goats under the same feeding pattern.

Diet and species are important factors affecting the rumen microbiota, with roughage stimulating rumen development and concentrate feeds being broken down by the decomposition of Ruminal flora to provide the organism with a large amount of energy. This study aimed to explore the effects of host and dietary factors on rumen flora composition and diversity, as well as on host metabolism. The study reports the research conducted on 5-month-old male Small-tail Han sheep and 5-month-old male Boer goat, each with an average weight of 33.87 ± 1.70 kg. Five animals of each species were divided into two groups, namely, the S group (Small-tail Han sheep) and the B group (Boer goat). The experiment was carried out in two various periods, namely, X and Y for groups S and B, respectively. The rations were fed with concentrate-to-roughage ratios of 3:7 and 5:5, respectively. Growth performance was measured by the weight increase index. The results showed that, under the same raising conditions, the ratio between body weight increases and the amount of feed was lower in the S group than in the B group, but the differences were not significant. According to the analysis of the apparent digestibility ratio of nutrition ingredients, the XS group had a significantly higher apparent digestibility ratio for acid detergent fiber than the XB group (p < 0.05). Even though the analysis of rumen fermentation parameters showed that the rumen pH has no significant differences between the XS and XB groups, it was significantly lower in the YS group than in the YB group. The XS group contained a significantly lower content of total volatile fatty acids than the XB group (p < 0.05). Analysis of the 16S rDNA sequencing results revealed that, compared to the B group, the S group was highly enriched with the following bacteria: Proteobacteria, γ-proteobacteria, Aeromonadales, and Succinivibrionaceae. Thus, the host species affected the abundance and diversity of rumen bacteria. Feed utilization efficiency of Small-tail Han sheep was higher than Boer goats, which might be specifically associated with Succinivibrionaceae. The results from this study show that animals belonging to the same family but different genera and species can differ in metabolic pathways even when they are provided with the same animal feed.

From natural environment to animal tissues: A review of microplastics(nanoplastics) translocation and hazards studies.

Microplastics (MPs) and nanoplastic (NPs) pollution is a global concern due to the massive use of plastic products. Although there have been many studies on the treatments of animals with MPs/NPs, there are few systematic summaries of MPs/NPs translocation and hazards in animals. This review comprehensively summarizes the pathways by which animals are exposed to MPs/NPs in the environment, in particular, to summarize in detail their translocation and hazards in vivo. Studies have shown that MPs/NPs enter the animals' body through water, food, breath and even skin, enter the blood circulation through the lungs and digestive tract, and eventually accumulate in various tissues. After a summary of the studies, we found a high correlation between the tissue accumulation of MPs/NPs and their particle size, with 4-20 µm MPs appearing to be more prone to accumulate in tissues. These MPs/NPs accumulated in animal tissues may be transferred to humans through the food chain. Thus, we summarized the studies on the accumulation of MPs/NPs in livestock and poultry products, showing that MPs/NPs in livestock and poultry products gradually increased with the complexity of processing and packaging processes. There are few reports related to direct contamination of livestock products by MPs/NPs, we hope that this review will bring together the growing body of evidence that MPs/NPs can directly harm human health through the food chain.

Effect of serotonin on the cell viability of the bovine mammary alveolar cell-T (MAC-T) cell line.

5-Hydroxytryptamine (5-HT), a monoamine, as a local regulator in the mammary gland is a chemical signal produced by the mammary epithelium cell. In cows, studies have shown that 5-HT is associated with epithelial cell apoptosis during the degenerative phase of the mammary gland. However, studies in other tissues have shown that 5-HT can effectively promote cell viability. Whether 5-HT could have an effect on mammary cell viability in dairy cows is still unknown. The purpose of this study was to determine: (1) effect of 5-HT on the viability of bovine mammary epithelial cells and its related signaling pathways, (2) interaction between prolactin (PRL) and 5-HT on the cell viability. The bovine mammary alveolar cell-T (MAC-T) were cultured with different concentrations of 5-HT for 12, 24, 48 or 72 hours, and then were assayed using cell counting kit-8, polymerase chain reaction (PCR) and immunobloting. The results suggested that 20 µM 5-HT treatment for 12 or 24 h promote cell viability, which was mainly induced by the activation of 5-HT receptor (5-HTR) 1B and 4, because the increase caused by 5-HT vanished when 5-HTR 1B and 4 was blocked by SB224289 and SB204070. And protein expression of mammalian target of rapamycin (mTOR), eukaryotic translation elongation factor 2 (eEF2), janus kinase 2 (JAK2) and signal transducer and activator of transcription 5 (STAT5) were decreased after blocking 5-HT 1B and 4 receptors. When MAC-T cells were treated with 5-HT and PRL simultaneously for 24 h, both the cell viability and the level of mTOR protein were significantly higher than that cultured with 5-HT or PRL alone. In conclusion, our study suggested that 5-HT promotes the viability of MAC-T cells by 5-HTR 1B and/or 4. Furthermore, there is a reciprocal relationship between PRL and 5-HT.

Assessing Amino Acid Metabolism in Splanchnic Tissues and Mammary Glands to Short-Term Graded Removal of Lys From an Abomasal-Infused Amino Acid Mixture in Lactating Goats.

To investigate the responses of amino acid metabolism in portal-drained viscera (PDV), liver, and mammary glands (MGs) to a graded gradual decrease of post-ruminal Lys supply, four multi-catheterized lactating goats were used in a 4 × 4 Latin square experiment. Goats were fasted for 12 h and then received a 33-h abomasal infusion of an amino acid mixture and glucose. Treatments consisted of a graded decrease of Lys content in the infusate to 100 (complete), 60, 30, or 0% as in casein. Lys-removed infusions decreased the production of milk, milk protein, fat, and lactose linearly and also decreased arterial Lys concentrations linearly (p < 0.05). Net PDV uptake decreased linearly (p < 0.05) with decreasing PDV loss ratio (p < 0.05). Although liver removal of Lys decreased linearly (p < 0.05), the removal ratio relative to portal absorption changed small, which was about 10% in all four treatments. Reduced Lys supply resulted in a linear decrease in the utilization of Lys in the peripheral tissues (except mammary, p < 0.05) and the release of more Lys in MGs. Although net mammary uptake of Lys declined linearly (p < 0.05), lactating goats can partially offset the negative effect of decreased circulating Lys concentrations by increasing mammary affinity (p < 0.05) and increasing mammary blood flow (p < 0.05). Graded removal of Lys from the infusate linearly decreased mammary uptake-to-output ratios of Lys (p < 0.05) suggesting that mammary catabolism of Lys decreased. Meanwhile, the treatments linearly increased circulating concentrations of glucagon and linearly decreased prolactin (p < 0.05). In conclusion, the results of the present study indicated that there were several mechanisms used to mitigate a Lys deficiency, including reduced catabolism of Lys in PDV and peripheral tissues (including MGs) and linearly increased mammary blood flow and mammary affinity together with increased mammary uptake and U:O of branched-chain amino acids (BCAA). Given these changes, the decline in milk protein production could be attributed to the combined effect of mass action with Lys and hormonal status.

Metabolic profilings of rat INS-1 ß-cells under changing levels of essential amino acids.

Application of mass spectrometry enables the detection of metabolic differences between organisms with different nutritional settings. Divergence in the metabolic fingerprints of rat pancreatic INS-1 ß-cells were systematically captured with regard to ten individual essential amino acid (EAA) availability. A high-resolution tandem mass spectrometry system coupled to liquid chromatography produced a horizontal comparison of metabolic profilings of ß-cells with individual EAA elevated to 10 mmol/L by turn or removal individual EAA from the medium one by one. Quality control samples were injected at regular intervals throughout the analytical run to monitor and evaluate the stability of the system. The raw data of samples and reference compounds including study protocols have been deposited in the open metabolomics database MetaboLights to enable efficient reuse of the datasets, such as investigating the difference in metabolic process between diverse EAAs as well as screening and verifying potential metabolites affecting insulin secretion and ß-cell function.

Integration of transcriptomics and metabolomics provides metabolic and functional insights into reduced insulin secretion in MIN6 ß-cells exposed to deficient and excessive arginine.

Previous work demonstrated that arginine is one of the strongest insulin secretagogues. However, knowledge of the mechanisms linking chronic arginine metabolism with ß-cell function and insulin secretion is relatively limited. After preliminary selection of concentration according to the cell proliferation, the MIN6 pancreatic ß-cells were randomly assigned to culture in 0.04 mM (low-arginine, LA), 0.4 mM (standard-arginine, SA), or 8 mM arginine (high-arginine, HA) for 24 h. Following the treatment, a combination of transcriptomics and metabolomics, together with a series of molecular biological tests were performed to investigate the responses of ß-cells to varied arginine availability. Our results showed that HA treatment reduced the chronic insulin releases, and LA and HA treatments decreased the glucose-stimulated insulin secretions (GSIS) of ß-cells relative to the SA group (p < .05). Transcriptomics analysis indicated that LA administration significantly inhibited oxidative phosphorylation and ATP metabolic process but promoted DNA repair and mRNA processing in ß-cells, while HA administration affected ammonium ion metabolic process and mRNA export (p < .05). Both LA and HA regulated the expressions of genes involved in DNA replication, cell-cycle phase transition, and response to oxidative stress (p < .05). Protein-protein interaction and transcription factor analyses suggested that Trp53 and Nr4a2 genes may play key roles during arginine stimulation. On the contrary, metabolomics analysis demonstrated that the differentially expressed metabolites (DEM) of MIN6 ß-cells induced by LA were mainly enriched in glycerophospholipid metabolism, linoleic acid metabolism, and purine metabolism, while most DEMs between LA vs. SA comparison belonged to amino acid metabolism. When combined the three groups, co-expression analysis suggested that insulin secretions had strong associations with L-pyroglutamic acid, L-glutamate, and creatine concentrations, while intracellular insulin contents were mainly correlated to L-arginine, argininosuccinic acid, and phosphorylcholine. At last, integrated analysis of transcriptomics and metabolomics showed that glycerophospholipid metabolism, biosynthesis of unsaturated fatty acids, and amino acid metabolism were the most relevant pathways in ß-cells exposed to abnormal arginine supply. This descriptive bioinformatics analysis suggested that the disturbed carbohydrate, lipid, and amino acid metabolisms, as well as the increased apoptosis and elevated oxidative stress, contributed to the reduced insulin secretion and lower GSIS in ß-cells induced by LA or HA treatments, while some underlying mechanisms need to be further explored.

Regulation of mTORC1 by amino acids in mammalian cells: A general picture of recent advances.

The mechanistic target of rapamycin complex 1 (mTORC1) integrates various types of signal inputs, such as energy, growth factors, and amino acids to regulate cell growth and proliferation mainly through the 2 direct downstream targets, eukaryotic translation initiation factor 4E-binding protein 1 (4EBP1) and ribosomal protein S6 kinase 1 (S6K1). Most of the signal arms upstream of mTORC1 including energy status, stress signals, and growth factors converge on the tuberous sclerosis complex (TSC) - Ras homologue enriched in brain (Rheb) axis. Amino acids, however, are distinct from other signals and modulate mTORC1 using a unique pathway. In recent years, the transmission mechanism of amino acid signals upstream of mTORC1 has been gradually elucidated, and some sensors or signal transmission pathways for individual amino acids have also been discovered. With the help of these findings, we propose a general picture of recent advances, which demonstrates that various amino acids from lysosomes, cytoplasm, and Golgi are sensed by their respective sensors. These signals converge on mTORC1 and form a huge and complicated signal network with multiple synergies, antagonisms, and feedback mechanisms.

Interactions of amino acids and hormones regulate the balance between growth and milk protein synthesis in lactating rats fed diets differing in protein content.

Insulin-like growth factor-I (IGF-I), growth hormone (GH), and prolactin (PRL) play important roles in milk protein synthesis, and their plasma concentrations were reported to be affected by dietary protein intake. To investigate the relationship between circulating amino acid (AA) and concentrations of these hormones, 18 Wistar rats aged 14 wk were assigned to a low (LP; 9% protein), standard (SP; 21% protein), or high-protein (HP; 35% protein) diet from parturition through day 15 of lactation. Plasma, liver, pituitary gland, skeletal muscle, and mammary gland samples were collected at the end of treatment. Circulating and hepatic IGF-I concentrations increased linearly with elevated dietary protein concentrations (P < 0.0001). Rats receiving the HP diet had higher circulating GH (P < 0.01) and pituitary PRL concentrations (P < 0.0001) but lower pituitary GH concentration (P < 0.0001) relative to those in rats receiving the LP and SP diets. Pearson correlation test performed on composed data across treatments showed that several circulating AAs were correlated with circulating and tissue concentrations of IGF-I, GH, and PRL. Multiple linear regression analyses identified Leu, Gln, Ala, Gly, and Arg as the main AAs associated with hormone responses (R2 = 0.37 ~ 0.80; P < 0.05). Rats fed the LP and HP diets had greater Igf1 and Ghr gene expression in skeletal muscle than those fed the SP diets (P < 0.01). However, LP treatment decreased Prlr mRNA abundance in mammary glands as compared with the SP and HP treatments (P < 0.05). The HP diets increased AA transporter expression (P < 0.01) but decreased mammalian target of rapamycin (P < 0.05) and 70 kDa ribosomal protein S6 kinase 1 (P < 0.01) phosphorylation in mammary glands as compared with the LP and SP diets. The results of the present study suggested that several circulating AAs mediated the effects of dietary protein supply on concentrations of IGF-I, GH, and PRL, which in turn altered the metabolism status in peripheral tissues including the lactating mammary glands.

Identification of Whole-Genome Significant Single Nucleotide Polymorphisms in Candidate Genes Associated With Serum Biochemical Traits in Chinese Holstein Cattle.

A genome-wide association study (GWAS) was conducted on 23 serum biochemical traits in Chinese Holstein cattle. The experimental population consisted of 399 cattle, each genotyped by a commercial bovine 50K SNP chip, which had 49,663 SNPs. After data cleaning, 41,092 SNPs from 361 Holstein cattle were retained for GWAS. The phenotypes were measured values of serum measurements of these animals that were taken at 11 days after parturition. Two statistical models, a fixed-effect linear regression model (FLM) and a mixed-effect linear model (MLM), were used to estimate the association effects of SNPs. Genome-wide significant and suggestive thresholds were set up to be 1.22E-06 and 2.43E-06, respectively. In the Chinese Holstein population, FLM identified 81 genome-wide significant (0.05/41,092 = 1.22E-06) SNPs associated with 11 serum traits. Among these SNPs, five SNPs (BovineHD0100005950, ARS-BFGL-NGS-115158, BovineHD1500021175, BovineHD0800028900, and BTB-00442438) were also identified by the MLM to have genome-wide suggestive effects on CHE, DBIL, and LDL. Both statistical models pinpointed two SNPs that had significant effects on the Holstein population. The SNP BovineHD0800028900 (located near the gene LOC101903458 on chromosome 8) was identified to be significantly associated with serum high- and low-density lipoprotein (HDL and LDL), whereas BovineHD1500021175 (located in 73.4Mb on chromosome 15) was an SNP significantly associated with total bilirubin and direct bilirubin (TBIL and DBIL). Further analyses are needed to identify the causal mutations affecting serum traits and to investigate the correlation of effects for loci associated with fatty liver disease in dairy cattle.

High-production dairy cattle exhibit different rumen and fecal bacterial community and rumen metabolite profile than low-production cattle.

Our aim was to simultaneously investigate the gut bacteria typical characteristic and conduct rumen metabolites profiling of high production dairy cows when compared to low-production dairy cows. The bacterial differences in rumen fluid and feces were identified by 16S rDNA gene sequencing. The metabolite differences were identified by metabolomics profiling with liquid chromatography mass spectrometry (LC-MS). The results indicated that the high-production dairy cows presented a lower rumen bacterial richness and species evenness when compared to low-production dairy cows. At the phylum level, the high-production cows increased the abundance of Proteobacteria and decreased the abundance of Bacteroidetes, SR1, Verrucomicrobia, Euryarchaeota, Planctomycetes, Synergistetes, and Chloroflexi significantly (p < 0.05). At the genus level, the rumen fluid of the high-production group was significantly enriched for Butyrivibrio, Lachnospira, and Dialister (p < 0.05). Meanwhile, rumen fluid of high-production group was depleted for Prevotella, Succiniclasticum, Ruminococcu, Coprococcus,YRC22, CF231, 02d06, Anaeroplasma, Selenomonas, and Ruminobacter significantly (p < 0.05). A total of 92 discriminant metabolites were identified between high-production cows and low-production cows. Compared to rumen fluid of low-production dairy cows, 10 differential metabolites were found up-regulated in rumen fluid of high-production dairy cows, including 6alpha-Fluoropregn-4-ene-3,20-dione, 3-Octaprenyl-4-hydroxybenzoate, disopyramide, compound III(S), 1,2-Dimyristyl-sn-glycerol, 7,10,13,16-Docosatetraenoic acid, ferrous lactate, 6-Deoxyerythronolide B, vitamin D2, L-Olivosyl-oleandolide. The remaining differential metabolites were found down-regulated obviously in high-production cows. Metabolic pathway analyses indicated that most increased abundances of rumen fluid metabolites of high-yield cows were related to metabolic pathways involving biosynthesis of unsaturated fatty acids, steroid biosynthesis, ubiquinone and other terpenoid-quinone biosynthesis. Most down-regulated metabolic pathways were relevant to nucleotide metabolism, energy metabolism, lipid metabolism and biosynthesis of some antibiotics.

Determination of microbiological characteristics in the digestive tract of different ruminant species.

Holstein dairy cows, Chinese Luxi Yellow cattle, Chinese Laoshan dairy goats, and Chinese Bohai Black cattle were selected for the study. The 16S rDNA sequencing technique was used to analyze the microflora in the digestive tract. The rumen flora in high milk-yield Holstein dairy cows showed significantly higher proportions of Treponema, Butyrivibrio, Coprococcus, Shuttleworthia, Lachnospira, and Selenomonas, compared with the rumen flora in Chinese Bohai Black cattle and Chinese Luxi Yellow cattle (p < 0.05). In addition, the abundances of Succiniclasticum, Ruminococcus, and Fibrobacter in the rumen fluid of high-yield dairy cows were significantly higher than those in rumen flora of dairy goats. Compared with ruminal flora in Chinese Luxi Yellow cattle, the rumen flora in high-yield dairy cattle showed significantly higher Prevotella. Compared with the rumen flora in Chinese Laoshan dairy goats, Chinese Bohai Black cattle, and Chinese Luxi Yellow cattle, the flora in high-yielding dairy cows showed significantly lower proportions of CF231, 02d06, Oscillospira, RFN20, Desulfovibrio, Methanobrevibacter, and SHD-231. In addition, compared with the rumen flora in dairy goats, the rumen flora in high-yielding dairy cattle displayed significantly lower proportion of Enterococcus. Compared with the rumen flora in Chinese Bohai Black cattle, the flora in high-yielding dairy cattle exhibited significantly lower Ruminococcus, YRC22, Pseudobutyrivibrio, L7A_E11, BF311, p-75-a5, and Dehalobacterium. Compared with the rumen flora in Chinese Luxi Yellow cattle, the flora in the high-yield dairy cows also displayed significantly lower proportions of Ruminococcus, YRC22, BF311, Paludibacter, and Dehalobacterium.

Plasma and Pancreas Islet Hormone Concentrations in Lactating Rats Are Associated with Dietary Protein Amounts.

Background: Circulating amino acid (AA) and nitric oxide (NO) concentrations and hepatic gluconeogenesis are affected by previous protein intake. However, information about their relations and islet hormone responses is limited. Objective: This study investigated the associations between islet hormone concentrations with circulating AA and NO concentrations as well as with hepatic gluconeogenesis in lactating rats. Methods: At delivery, 18 Wistar rats aged 14 wk were assigned either to low-protein (LP; 9% protein), standard-protein (SP; 21% protein), or high-protein (HP; 35% protein) diets for 15 d in groups of 6 pups/dam. Circulating AA and NO concentrations, circulating and pancreas islet hormone concentrations, and the activities and gene expressions of hepatic phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6Pase) were measured at the end of treatment. Results: Circulating insulin and glucagon concentrations were greater in the HP than in the LP (25% and 17%, respectively) and SP (37% and 31%) diet groups, whereas compared with the SP group, pancreatic concentrations were lower in the LP (32% and 49%) and HP (34% and 46%) groups (P < 0.01). Hepatic PEPCK and G6Pase activities in the HP group were greater than those in the SP (15% and 15%) and LP (8% and 19%) groups (P < 0.05). In all groups, plasma NO concentrations were correlated negatively to circulating insulin (r = -0.77, P = 0.0003) and positively to pancreas insulin and glucagon concentrations and the insulin-to-glucagon ratio (r = 0.50-0.63; P < 0.05). Some circulating AAs correlated positively to circulating insulin and pancreas insulin and glucagon (r = 0.50-0.82, P < 0.05) but negatively to circulating glucagon (r = -0.53-0.68, P < 0.05). Conclusion: Variations in circulating AA and NO concentrations and hepatic gluconeogenic enzyme activities are likely intermediary responses involved in the effects of dietary protein amounts on the synthesis and secretion of islet hormones in lactating rats.

Effect of hay supplementation timing on rumen microbiota in suckling calves.

An animal feeding trial was conducted on 18 seven-day-old Holstein dairy bull calves weighing 42 ± 3 kg each. Calves were randomly assigned into three groups (n = 6 each). The dietary treatments were as follows: (1) milk and starter for the control group (MS), (2) supplementation of oat hay from week 2 on the basis of milk and starter (MSO2), and (3) supplementation of oat hay from week 6 on the basis of milk and starter (MSO6). All animals were fed starter and oat hay ad libitum. The major phyla in the different groups of rumen fluid included Firmicutes, Actinobacteria, Bacteroidetes, Proteobacteria, and Euryarchaeota. The major genera were identified, and major genera proportions in the three groups were as follows: Methanobrevibacter (Euryarchaeota), 2.1%, 1.7%, and 2.1%; Olsenella (Actinobacteria), 23.9%, 17.7%, and 12.8%; Prevotella (Bacteroidetes), 10.5%, 16.5%, and 19.2%; Dialister (Firmicutes), 3.3%, 4.1%, and 2.8%; Succiniclasticum (Firmicutes), 3.8%, 4.7%, and 9.2%; and Sharpea (Firmicutes), 0.4%, 2.5%, and 0.2%, respectively. There were no significant differences in the various phyla among the three groups (p > .05). The results showed that calves hay supplementation time did not affect the diversity of the rumen microbiota in the suckling calves. However, the hay supplementation altered the proportion of the various microbial populations, supplementation of oat hay from week 2 on the basis of milk and starter could improve calves rumen pH.

Support vector machine with hypergraph-based pairwise constraints.

Although support vector machine (SVM) has become a powerful tool for pattern classification and regression, a major disadvantage is it fails to exploit the underlying correlation between any pair of data points as much as possible. Inspired by the modified pairwise constraints trick, in this paper, we propose a novel classifier termed as support vector machine with hypergraph-based pairwise constraints to improve the performance of the classical SVM by introducing a new regularization term with hypergraph-based pairwise constraints (HPC). The new classifier is expected to not only learn the structural information of each point itself, but also acquire the prior distribution knowledge about each constrained pair by combining the discrimination metric and hypergraph learning together. Three major contributions of this paper can be summarized as follows: (1) acquiring the high-order relationships between different samples by hypergraph learning; (2) presenting a more reasonable discriminative regularization term by combining the discrimination metric and hypergraph learning; (3) improving the performance of the existing SVM classifier by introducing HPC regularization term. And the comprehensive experimental results on twenty-five datasets demonstrate the validity and advantage of our approach.

GABAergic inhibition through synergistic astrocytic neuronal interaction transiently decreases vasopressin neuronal activity during hypoosmotic challenge.

The neuropeptide vasopressin is crucial to mammalian osmotic regulation. Local hypoosmotic challenge transiently decreases and then increases vasopressin secretion. To investigate mechanisms underlying this transient response, we examined the effects of hypoosmotic challenge on the electrical activity of rat hypothalamic supraoptic nucleus (SON) vasopressin neurons using patch-clamp recordings. We found that 5 min exposure of hypothalamic slices to hypoosmotic solution transiently increased inhibitory postsynaptic current (IPSC) frequency and reduced the firing rate of vasopressin neurons. Recovery occurred by 10 min of exposure, even though the osmolality remained low. The γ-aminobutyric acid (GABA)A receptor blocker, gabazine, blocked the IPSCs and the hypoosmotic suppression of firing. The gliotoxin l-aminoadipic acid blocked the increase in IPSC frequency at 5 min and the recovery of firing at 10 min, indicating astrocytic involvement in hypoosmotic modulation of vasopressin neuronal activity. Moreover, ß-alanine, an osmolyte of astrocytes and GABA transporter (GAT) inhibitor, blocked the increase in IPSC frequency at 5 min of hypoosmotic challenge. Confocal microscopy of immunostained SON sections revealed that astrocytes and magnocellular neurons both showed positive staining of vesicular GATs (VGAT). Hypoosmotic stimulation in vivo reduced the number of VGAT-expressing neurons, and increased co-localisation and molecular association of VGAT with glial fibrillary acidic protein that increased significantly by 10 min. By 30 min, neuronal VGAT labelling was partially restored, and astrocytic VGAT was relocated to the ventral portion while it decreased in the somatic zone of the SON. Thus, synergistic astrocytic and neuronal GABAergic inhibition could ensure that vasopressin neuron firing is only transiently suppressed under hypoosmotic conditions.

Hyposmolality differentially and spatiotemporally modulates levels of glutamine synthetase and serine racemase in rat supraoptic nucleus.

Prolonged hyposmotic challenge (HOC) has a dual effect on vasopressin (VP) secretion [Yagil and Sladek (1990) Am J Physiol 258(2 Pt 2):R492-R500]. We describe an electrophysiological correlate of this phenomenon, whereby in vitro HOC transiently reduced the firing activity of VP neurons within the supraoptic nucleus of brain slices, which was followed by a rebound increase of their activity; this was paralleled by changes in the level of proteins relevant to astroglia-neuronal interactions. Hence, in vitro HOC transiently (at 5 min) increased the level of astrocyte-specific glial fibrillary acidic protein (GFAP), which then declined to control or base level (at 20 min); this was blocked by the gliotoxin L-aminoadipic acid, but not by tetanus toxin, which was used to inhibit neurotransmission. Similarly, in vivo HOC led to changes in GFAP level, which after an early increase (10 min) returned to normal (30 min). Immunoassays revealed that neuronal, but not astrocytic, expression of serine racemase (SR) was increased at the late stage of HOC in vivo, whereas at an early stage there was a transient increase in level of the astrocyte-specific glutamine synthetase (GS). Furthermore, there was an increased molecular association between GFAP and GS at 10 min, whereas SR increased its association with the neuronal nuclear antigen NeuN at 30 min. These results suggest that the dual effect of HOC on VP neuronal secretion/activity could be related to metabolic/signaling changes in astrocytes (glutamate-glutamine conversion) and neurons (D-serine synthesis/ammonia production), which may account for the rebound in VP neuronal activity, presumably by promoting the activation of neuronal glutamate receptors.

SNAP-25 in hippocampal CA3 region is required for long-term memory formation.

SNAP-25 is a synaptosomal protein of 25 kDa, a key component of synaptic vesicle-docking/fusion machinery, and plays a critical role in exocytosis and neurotransmitter release. We previously reported that SNAP-25 in the hippocampal CA1 region is involved in consolidation of contextual fear memory and water-maze spatial memory (Hou et al. European J Neuroscience, 20: 1593-1603, 2004). SNAP-25 is expressed not only in the CA1 region, but also in the CA3 region, and the SNAP-25 mRNA level in the CA3 region is higher than in the CA1 region. Here, we provide evidence that SNAP-25 in the CA3 region is also involved in learning/memory. Intra-CA3 infusion of SNAP-25 antisense oligonucleotide impaired both long-term contextual fear memory and water-maze spatial memory, with short-term memory intact. Furthermore, the SNAP-25 antisense oligonucleotide suppressed the long-term potentiation (LTP) of field excitatory post-synaptic potential (fEPSP) in the mossy-fiber pathway (DG-CA3 pathway), with no effect on paired-pulse facilitation of the fEPSP. These results are consistent with the notion that SNAP-25 in the hippocampal CA3 region is required for long-term memory formation.