Kazumi Kita

Influences of protein ingestion on glucagon-like peptide (GLP)-1-immunoreactive endocrine cells in the chicken ileum

Influences of a specific dietary nutrient on glucagon-like peptide (GLP)-1-containing cells in the chicken intestine are not yet clear. Significance of dietary protein level on GLP-1-containing cells in the chicken ileum was investigated. Chickens fed control or experimental diets of varying protein levels were examined using immunohistochemical and morphometrical techniques. We show that the protein ingestion had an impact on the activities of GLP-1-immunoreactive cells in the chicken ileum. Weight gains declined with decreasing dietary crude protein (CP) levels, but no significant differences were detected in the daily feed intake and villous height. GLP-1-immunoreactive cells with a round or oval shape were frequently observed in the lower CP level groups (4.5% and 0%). Frequencies of occurrence of GLP-1-immunoreactive cells were 41.1 ± 4.1, 38.5 ± 4, 34.8 ± 3.1 and 34.3 ± 3.7 (cells/mm(2) , mean ± SD) for dietary CP level of 18%, 9%, 4.5% and 0% groups, respectively and significant differences were recognized between the control and lower CP level groups (P<0.05). Multiple regression analysis indicated a significant correlation between the daily protein intake and frequencies of occurrence of GLP-1-immunoreactive cells. The protein ingestion is one of the signals that influence GLP-1-containing cells in the chicken small intestine.

Alleviation of body weight loss by dietary methionine is independent of insulin-like growth factor-I in protein-starved young chickens

It is well known that in protein-starved chickens, small amounts of amino acid supplement, especially methionine, reduces nitrogen excretion and thereby improves nitrogen balance. On the other hand, excess intake of methionine causes growth depression and the growth-depressive effect of excess methionine can be alleviated by consumption of dietary glycine. Insulin-like growth factor-I (IGF-I) is one of various growth-promoting factors relating to the efficiency of animal production and is known to be very sensitive to changes in nutritional status. In the present study, the interactive effect of glycine on nitrogen sparing effect of methionine in protein-starved chickens was examined. In addition, the relation of IGF-I and its specific binding protein to the nitrogen sparing effect of supplemented methionine was also investigated. Two-days refeeding of methionine supplemented to protein-free diet could promptly alleviate body weight loss in protein-starved chickens, and the alleviation of body weight loss by methionine was not improved by glycine supplements. Moreover, such acute alleviation of body weight loss by dietary methionine was independent of the change in plasma IGF-I concentration.

Fructosyl-Valine Orally Administrated to Chickens is Absorbed from Gastrointestinal Tract

Amadori products are non-enzymatically formed by binding carbonyl groups and amino groups. Glycated amino acids generated by reacting amino acid and glucose are also in a group of Amadori products of which the transport and metabolism have been investigated mainly in mammals but not in avians. In the present study, therefore, we examined whether dietary fructosyl-valine, which is one of the glycated amino acids, orally administrated to chickens can be incorporated into blood or not. Fructosyl-valine was orally administrated to the chicken and blood samples were collected at 0, 20, 40, 60, 120 and 180 min after administration. Plasma concentration of fructosyl-valine was measured by using LC/MS. The plasma concentration of fructosyl-valine was increased by passing time from 0 to 180 min after administration, and no change was observed in the control group. Conclusively, it was clarified that fructosyl-valine orally administrated to the chicken could be absorbed from gastrointestinal tract and incorporated into blood.

Tissue distribution of albumin-glucose advanced glycation end products administrated to chickens.

Glycation (Maillard reaction) starts from non-enzymatic amino-carbonyl reaction binding carbonyl group of reducing sugars to amino group of amino acids. The amino-carbonyl reaction leads to the formation of the stable Amadori product, which ultimately forms advanced glycation end products (AGE). Acceleration of glycation during hyperglycemia increases the production and accumulation of AGE, which is implicated in the gradual development of diabetic complications in diabetes mellitus. Avian species offers the great advantage of providing animal models for diabetology because high blood glucose concentration should accelerate to generate high concentration of AGE. In the present study, radioactive AGE was prepared from chicken serum albumin and (14)C-glucose. Radioactive AGE was administrated to examine the tissue distribution of AGE in chickens. Administration of radioactive AGE into the circulation of chickens revealed that AGE accumulated into specific tissues, liver, spleen and kidney, which have the function for clearing exogenous substances and endogenous metabolic waste products.

Glucagon-like peptide-1 is co-localized with neurotensin in the chicken ileum

Glucagon-like peptide (GLP)-1 and neurotensin (NT) are distributed throughout the chicken ileum. Here, we attempt to determine if GLP-1 and NT co-localize in the chicken ileum by using immunofluorescence, immunocytochemistry and in situ hybridization techniques. Three types of enteroendocrine cells, GLP-1+/NT+, GLP-1+/NT− and GLP-1−/NT+ cells, were detected in the mucosal epithelium by the double immunofluorescence method. The ratio of GLP-1+/NT+ cells at the crypts in the distal ileum was significantly higher than that in the proximal ileum. The ratios of the three cell types were similar along the crypt–villous axis in the proximal ileum but the percentage of GLP-1+/NT+ cells significantly decreased at the middle part of villi relative to crypts and the bottom part of villi in the distal ileum. Enteroendocrine cells that were immunoreactive to both GLP-1 and NT peptides and showed both proglucagon and NT precursor mRNA signals were found in the crypts of the distal ileum but not in the villous epithelium. The results from performing an immunocytochemical method with colloidal gold indicated that the GLP-1 content within GLP-1+/NT+ cell secretory granules decreased stepwise from the crypt to the middle part of the villus but the NT content in these granules increased in this direction. These findings reveal that the cells producing both GLP-1 and NT are mainly localized in the crypts of the chicken ileum but these endocrine cells specialize in NT-producing cells at the villous epithelium of the distal ileum.

Influence of long-term feeding of high-fat diet on quercetin and fat absorption from the small intestine in lymph duct-cannulated rats

ABSTRACT This study aimed to investigate the effect of dietary lipids and a long-term high-fat diet on lymphatic triglyceride and quercetin absorption in rats with a surgically implanted thoracic lymph cannula. Quercetin-3-O-β-glucoside reduced the lymphatic triglyceride output from the intestines; this reduction was prominent among rats fed a high-fat diet.

Half-life of Glycated Tryptophan in the Plasma of Chickens

Tryptophan, an essential amino acid, is enzymatically metabolized to two compounds, kynurenine and serotonin, and 95% of tryptophan is metabolized to kynurenine. As chickens have hyperglycemia and high temperature, tryptophan glycation occurs more easily in chickens than in mammals. Part of tryptophan is non-enzymatically converted to two types of glycated tryptophan, tryptophan-Amadori product and (1R, 3S)-1-(d-gluco-1, 2, 3, 4, 5-pentahydroxypentyl)-1,2,3,4-tetrahydro-β-carboline-3-carboxylic acid (PHP-THβC). Although these compounds are detected in the plasma of chickens, information on the half-life of PHP-THβC in the blood circulation is limited. Therefore, the present study aimed to measure the half-life of plasma PHP-THβC in chickens. PHP-THβC (114 nmol/0.2 mL/70 g body weight) was intravenously administered to chickens via the wing vein, and blood samples were collected at 0, 15, 30, 60, 180, 360, 720, and 1440 min after administration. Plasma concentrations of PHP-THβC were measured by liquid chromatography-mass spectrometry. Plasma PHP-THβC reached to a peak concentration of 16.1 βM at 30 min after administration, and then decreased rapidly to return to the physiological level (0 min) at 360 min after administration. The half-life of plasma PHP-THβC was calculated by non-linear regression analysis, and it was found to be 107 min. This study was the first to measure plasma half-life of glycated tryptophan.

Influence of Varying Dietary Protein Levels on Glycation of Albumin, Tryptophan and Valine in the Plasma of Chickens

Glycation is a chemical reaction in which reducing sugars bind non-enzymatically to compounds containing amino groups. Avian species like chickens are hyperglycemic animals and have high body temperature compared to mammalian species, which enables avian species to accelerate the glycation of proteins and amino acids with glucose. Although varying dietary crude protein (CP) levels alter plasma concentrations of proteins and amino acids, the influence of varying CP levels on the glycation of plasma proteins and amino acids has not been studied so far. In the present study, therefore, glycation of albumin, tryptophan and valine in the plasma of chickens fed diets with varying CP levels (0, 10, 20, 40 and 60%) was examined. At the end of the experimental period, blood samples were collected and plasma concentrations of glycoalbumin, glycated tryptophan (tryptophan-Amadori product and (1R, 3S) - 1 - (D - gluco - 1, 2, 3, 4, 5 - pentahydroxypentyl) - 1, 2, 3, 4 - tetrahydro - β - carboline - 3 - carboxylic acid (PHP-THβC)), and valine-Amadori product were measured. Although plasma albumin concentration was reduced along with the decrease in dietary CP levels from 20% to 0%, glycoalbumin in the plasma was increased under such dietary conditions. Similar increase in the ratios of tryptophan-Amadori product to tryptophan and valine-Amadori product to valine in the plasma of chickens fed a protein-free diet was observed. These results suggest that dietary protein deficiency might enhance the non-enzymatic glycation of plasma proteins and amino acids in chickens.

Incorporation of Glycated Tryptophan and Valine into Various Cells Derived from Chicken Embryos

Avian species including chickens are known to be hyperglycemic animals. Hyperglycemia promotes the glycation which at first forms Amadori products undergoing further complex reaction to form advanced glycation end products (AGEs). Our previous study revealed that AGEs derived from glucose and amino acids were predominantly incorporated into spleen, kidney and liver. However, it has not been elucidated whether Amadori products (glycated amino acids) can also be incorporated into cells or not. Therefore, in the present study, radioactive glycated-tryptophan and -valine were prepared and the incorporation of these glycated amino acids into various chicken embryonic cells was studied. Various embryonic cells prepared from muscle, liver, spleen and kidney of chicken embryos were incubated in Medium 199 supplemented with 14C-labeled glycated-tryptophan or -valine. After incubation, embryonic cells were well-rinsed and then the radioactivity incorporated into cells was measured. It was revealed that both glycated amino acids were incorporated into embryonic cells derived from muscle, liver, spleen and kidney. In muscular cells, the incorporation of glycated-tryptophan was higher than that of glycated-valine. On the other hand, in embryonic cells derived from liver and kidney, the amount of glycated-tryptophan incorporated into cells was almost the same to that of glycated-valine. In conclusion, it was supposed that both glycated-tryptophan and -valine could be incorporated into various cells derived from muscle, liver, spleen and kidney of chicken embryos and that the incorporation might have the organ specificity.

Influence of Trypsin-Digested Wheat Gluten Peptides with Different Molecular Size on Intestinal Absorption of Amino Acids in Chickens

Although a lot of food-derived peptides have been applied for medical use and therapeutic nutrition, the function of feed-derived peptides on nutritional physiology in chickens has not been clarified so far. Our previous study revealed that wheat gluten digested by trypsin could enhance the absorption of amino acids from small intestine. In the present study, we studied the influence of trypsin-digested wheat gluten peptides with different molecular weight (MW) on the intestinal absorption of amino acids in chickens. Wheat gluten was digested by trypsin and fractionated by using the ultrafiltration membrane. Wheat gluten peptides were divided into 3 fractions with different MW; MW more than 10,000, MW 3,000–10,000 and MW less than 3,000. Phosphate buffered saline and whole wheat gluten digesta were used as negative and positive controls, respectively. All of wheat gluten peptides were mixed with 2.5 M glucose-10 mM amino acid solution and administrated into the crop with a stomach tube. At 20 min after oral administration, blood samples were taken from mesenteric vein. Plasma amino acid concentration was determined using an automatic amino acid analyzer. The peptide fraction with MW more than 10,000 increased the intestinal absorption of phenylalanine and proline. The peptide fraction with MW 3,000–10,000 increased the intestinal absorption of proline. These results suggest that wheat gluten peptide with high MW might have the potency to enhance the absorption of aromatic amino acids from small intestine of young chickens.