• Journal of Nutrition and Health
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• v.29 no.7
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• pp.788-805
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• 1996

This study was performed to investigate effects of examination-stress and protein supplementation on nitrogen metabolism and blood protein levels of Korean college students. Experiment was conducted at the beginning of a academic term and during midterm examination. During midterm examination, subjects were classified into two groups randomly : protein supplemental group(male n=6, female n=10) and placebo group(male n=4, female n=9). Protein capsules(2g/day) above 10% of indispensible amino acids requirement estimates were given to supplemental group for 10 days. At the begining of the term, male students(n=12) ingested 223.15mgN/kg/d, excreted 20.7mgN/kg/d in feces, and excreted 94.31mgN/kg/d in urine. Their apparent protein protein digestibility was 90.72%, true N balance was +100.11mgN/kg/d, and the mean maintenance N requirement of mixed Korena diet calculated was 112.13mgN/kg/d. Female students(n=19) ingested 171.44mgN/kg/d, excreted 22.13mgN/kg/d in feces, and excreted 122.92mgN/kg/d in urine. Their apparent protein digestibility was 86.76%, true N blance was + 18.39mgN/kg/d, and the mean maintenance N requirement calculated was 135.31mgN/kg/d. Blood levels of serum total protein, albumin, and BUN were within normal range. During midterm examination, fecal and urinary N excretions of female subjects(n=19) were increased, especially urea N markedly, and urea N/creatinine N ratio was augumented significantly. Apparent protein digestibility of male subjects(n=10) was decreased. Examination-stress showed 8.05mgN/kg/d (7.2%) increase of mean maintenance N requirement in male and 8.55mgN/kg/d(6.3%) increase in female students in comparison with that of the beginning of the term. Serum total protein and albumin levels showed no significant change, but serum transferrin level of female were decreased significantly. During midterm examination, females supplemented with protein capsules(2g/d)had no significant increase in fecal and urinary N excretions.

• Journal of the Korean Society of Food Science and Nutrition
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• v.22 no.1
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• pp.8-14
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• 1993

In this study, the food intake, feces and urine of the seven high school girls were collected and the intake and excretion of protein and calcium were measured. The girls were 16 to 18 years old and the measurement continued for four weeks during which they maintained their normal living pattern and body weight. Each girl's daily intake and excretion of protein and calcium were measured and apparent digestibility and balance were also studied. The results are as follows ; Daily mean intake, feral loss and apparent digestibility of protein of each girl were 58.18$\pm$1.15g, 7.65$\pm$0.27g and 86.5$\pm$0.6%, respectively. The urinary loss of nitrogen was 7.39 $\pm$ 0.16g and showed the positive balance of 0.70$\pm$0.22g. Daily mean intake, fecal loss and apparent digestibility of calcium of each girl were 395.0$\pm$13.0mg, 233.6$\pm$15.9mg and 40.1$\pm$4.0%, respectively. The urinary luis of calcium was 145.7$\pm$7.6mg and showed the positive balance of 15.7$\pm$15.0mg.

• Journal of the Korean Society of Food Science and Nutrition
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• v.21 no.6
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• pp.639-647
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• 1992

In this study, the food intake, feces and urine of the seven high school boys were collected and the intake and excretion of protein and zinc were measured. The boys were 16~18 years old and the measurement continued for four weeks during which they maintained their normal living pattern and body weight. Each boy's daily intake and excretion of protein and zinc were measured and apparent digestibility and balance were also studied. The results are as follows. Daily mean intake, fecal loss and apparent digestibility of protein of each boy were $73.89{\pm}1.89g,\;10.86{\pm}0.37g$ and $84.9{\pm}0.5%,$ respectively. The urinary loss of nitrogen was $8.8{\pm}0.2g$ and showed the positive balance of $1.3{\pm}0.3g.$ Daily mean intake, fecal loss and apparent digestibility of zinc of each boy were $14.51{\pm}0.44mg,\;7.82{\pm}0.30mg$ and $43.6{\pm}2.9%,$ respectively. The urinary loss of zinc was $4.96{\pm}0.19mg$ and showed the positive balance of $1.72{\pm}0.58mg.$

• Nutrition Research and Practice
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• v.3 no.3
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• pp.200-207
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• 2009

This study examined the effects of com gluten (CG) and its hydrolysate consumptions on weight reduction in rats fed a high-fat diet. Eight-month-old male Sprague-Dawley rats (n=40) were fed a high-fat diet (40% calorie as fat) for 4 weeks. They were then randomly divided into four groups and fed the isocaloric diets with different protein sources for 8 weeks. The protein sources were casein (control group), intact CG (CG group), CG hydrolysate A (CGHA group, 30% of protein as peptides and 70% as free amino acids) and CG hydrolysate P (CGHP group, 93% of protein as peptides and 7% as free amino acids). Body weight gain, adipose tissue weights, nitrogen balance, absorptions of energy, protein and fat, lipid profiles in plasma, liver and feces and hepatic activities of camitine palmitoyl transferase (CPT), fatty acid synthase (FAS), malic enzyme (ME) and glucose-6-phosphate dehydrogenase (G6PDH) were assessed. The CGHA diet had the highest amount of BCAAs, especially leucine, and most of them existed as free amino acid forms. The CGHA group showed significant weight reduction and negative nitrogen balance. Protein absorption and apparent protein digestibility in the CGHA group were significantly lower than those in other groups. Adipose tissue weights were the lowest in the CGHA group. Activity of CPT tended to be higher in the CGHA group than in other groups and those of FAS, ME and G6PDH were significantly lower in the CGHA group than in other groups. In conclusion, the CGHA diet which had relatively high amounts of free amino acids and BCAAs, especially leucine, had a weight reduction effect by lowering adipose tissue weight and the activities of FAS, ME and G6PDH in experimental animals, but it seemed to be a negative result induced by lowering protein absorption, increasing urinary nitrogen excretion and protein catabolism.

• Food Science of Animal Resources
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• v.43 no.3
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• pp.512-530
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• 2023

The present study evaluated the effects of fermented whey protein using kimchi lactic acid bacteria Lactobacillus casei DK211 on skeletal muscle mass, muscle strength, and physical performance in healthy middle-aged males performing regular resistance exercises. Effective protein supplementation and regular exercise are two important factors for improving muscle health. Therefore, in this study, the effects of consuming fermented whey protein twice a day were investigated and compared with that of non-fermented supplementation. Forty-eight males (average age 44.8) were randomly assigned to two groups: Fermented whey protein supplementation (FWPS) and non-fermented whey protein concentration supplementation (WPCS) groups. Each group ingested 37 g of FWPS or WPCS twice a day for eight weeks. Body composition, muscle strength, and physical performance were assessed pre- and post-intervention. Independent t-tests or chi-square tests for the categorical variables were performed for analyzing the observations. FWPS was effective in promoting the physical performance in dynamic balance measurement and muscle health, indicated through the increment in grip strength (left), upper arm circumference, and flat leg circumference from the baseline. However, similar improvements were not observed in the WPCS group. These results imply that whey protein fermented by L. casei DK211 is an effective protein supplement for enhancing muscle health in males performing regular resistance exercises.

• Journal of Nutrition and Health
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• v.21 no.2
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• pp.99-112
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• 1988

This study was performed to investigate the effects of dietary protein and calcium levels on calcium metabolism in eight healthy Korean adult females. The 2-day metabolic study consisted of a 2 day adaptation period and three 6-day experimental periods. Three experimental diets were low protein low calcium(LPLCa : protein 44g, Ca 422mg), higher protein low calcium(HPLCa : protein 85g, Ca 365mg), and high protein high calcium (HPHCa : protein 84g, Ca 727mg). The apparent calcium absorption was likely to be affected by the calcium intake rather than by the protein intake. Average calcium absorption rate was about 23-29% of calcium intake. The calcium balance was -21.44mg for LPCa, -25.02mg for HPLCa, and -3.22mg for HPHCa. Avergae urinary calcium excretion was 127.7mg for LPLCa, 108.6mg for HPLCa, and 215.4mg for HPHCa. Urinary calcium excretion was more closely related to the changes of calcium intake rather than of protein intake. These results seemed to be due to the interactions between the high phosphours contained in the high protein diet and the little discrepancy of protein intake levels.

• Korean Journal of Poultry Science
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• v.38 no.1
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• pp.37-43
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• 2011

The effect of cecal ligation on the utilization of dietary [15N]urea in chickens fed 5 % protein diet plus urea were investigated. Nitrogen balance and utilization tended (P<0.01) to increase by cecal ligation. Total uric acid excretion was significantly decrease by (P<0.01) cecal ligation in chickens from origin of diet and urea (P<0.01). Excretion of ammonia was increased in chickens from origin of diet, where as it decreased in chickens an urea diet (P<0.01). Amount of urea nitrogen excretion from origin of urea was significantly decrease (P<0.01) by cecal ligation, but cecal ligated chicken fed 5% protein diet with urea showed 51.6% urea utilization. Result obtained in present study indicates that ceca is having beneficial role for urea utilization in chicken fed protein deficient diets, but ceca do not always positive role for nitrogen utilization.

• Animal Bioscience
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• v.35 no.1
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• pp.22-28
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• 2022

Objective: Endoplasmic reticulum (ER) stress engages the unfolded protein response (UPR) that serves as an important mechanism for modulating hepatic fatty acid oxidation and lipogenesis. Chronic fasting in mice induced the UPR activation to regulate lipid metabolism. However, there is no direct evidence of whether negative energy balance (NEB) induces ER stress in the liver of cows. This study aimed to elucidate the relationship between the NEB attributed to feed deprivation and ER stress in bovine hepatocytes. Methods: Blood samples and liver biopsy tissues were collected from 6 non-lactating cows before and after their starvation for 48 h. The blood non-esterified fatty acids (NEFA), β-hydroxybutyric acid (BHBA) and glucose level were analyzed. Real-time quantitative polymerase chain reaction and Western blotting were used to explore the regulation of genes associated with UPR and lipid metabolism. Results: The starvation increased the plasma BHBA and NEFA levels and decreased the glucose level. Additionally, the starvation caused significant increases in the mRNA expression level of spliced X-box binding protein 1 (XBP1s) and the protein level of phosphorylated inositol-requiring kinase 1 alpha (p-IRE1α; an upstream protein of XBP1) in the liver. The mRNA expression levels of peroxisome proliferator-activated receptor alpha and its target fatty acid oxidation- and ketogenesis-related genes were significantly upregulated by the starvation-mediated NEB. Furthermore, we found that the mRNA expression levels of lipogenic genes were not significantly changed after starvation. Conclusion: These findings suggest that in the initial stage of NEB in dairy cows, the liver coordinates an adaptive response by activating the IRE1 arm of the UPR to enhance ketogenesis, thereby avoiding a fatty liver status.

• Journal of Animal Science and Technology
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• v.49 no.5
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• pp.633-638
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• 2007

This study was conducted to determine the protein requirement level in growing Jindo dog through nitrogen balance experiment. Twelve female dogs aged 18～20 weeks old were allotted one of 3 dietary treatments containing 21, 23 and 25% of crude protein. Average daily gain of dogs fed experimental diets containing 21, 23 and 25% of crude protein were 65.42, 79.58 and 99.17g/d, respectively, and there was a significant difference between 21 and 25% of crude protein treatments(p<0.05). Retained nitrogen were calculated 0.74, 0.96 and 1.31g/kgBW.75/d for dogs fed diets containing 21, 23 and 25% of crude protein, respectively, and were significantly higher(p<0.05) in dogs fed 25% of crude protein diet then those of other dogs. A quadratic regression equation was calculated between nitrogen intake(x) and nitrogen retention(y); y=-2.519x2+12.79x-14.79, and it was found a significantly(p<0.05) higher regression coefficient of 0.782. From the above equation, it was estimated maintenance requirement of crude protein for growing Jindo dog is 11.25g/kg BW.75/d.

• Journal of Animal Science and Technology
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• v.44 no.5
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• pp.573-584
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• 2002

Milk urea nitrogen (MUN) and Milk protein (MP) are being used as indicators of the protein-energy balance and for actual farm feeding practices. The purpose of this study was to investigate the MUN and MP concentrations of individual cows and bulk tank milk to evaluate the dietary protein-energy balance from lactating Holstein cows. Mean MUN and MP concentrations in the milk samples obtained from 132,636 cows of 4,856 herd during Jan. 1999 to Dec. 2001 were 16.2 5.2mg/dl and 3.30 0.35%, respectively. The highest values were found during summer and lowest valued during winter in MUN. But, the average contents of MP were the highest during winter and the lowest during summer. In order to evaluate protein-energy balance for feeding, we set the level of recommended MP range of 2.90${\sim}$3.29% in early lactation considering a negative energy balance. The recommended level of MP in mid-lactation and late lactation were set as 3.10${\sim}$3.49%, and 3.30${\sim}$3.69%, respectively. Recommended MUN range of 12${\sim}$18 mg/dl was determined through the whole lactation period. Individual cows milk were analyzed by the 9 types based on this levels of MP and MUN in this study. Among the total cows investigated, 26.8%, 25.8%, and 22.2% have shown the recommended criteria of MP and MUN values, respectively. Also, of total herds surveyed, 11.6% had MUN values lower than 12.0 mg/dl and 32.9% had values higher than 18.0 mg/dl and 44.5% of total herd have not met with the recommended criteria of MP values in bulk tank milk. In case of MP, out of the total herd surveyed, 26.0% had MP values lower than 3.10% and 24.0% had values higher than 3.30% and 50.0% had MP values outside the recommended interval (3.1${\sim}$3.3%). This study has indicates that many dairy farms are under improper feeding management practice of the dietary protein-energy balance.