Mi-Ryung Kim

Tastes and structures of bitter peptide, asparagine-alanine-leucine-proline-glutamate, and its synthetic analogues.

Asn-Ala-Leu-Pro-Glu (NALPE) is a strong bitter peptide with a minimum response threshold (MRT) of 0.074 mM. To elucidate the relationship of spatial structure and bitterness on peptides, NALPE and its analogues, NALPW, NALPS, NALPL, NALPP, NALPD, and NALPR, were synthesized and sensorially evaluated. Structural analysis using computer simulation for each peptide revealed that the presence of a polar group and hydrophobic bitter amino acids, the composition of hydrophobic regions, the spatial orientation of the polar group and hydrophobic regions, and the proximity between polar groups and hydrophobic regions faced within the same plane space may be the major determinants for the taste type and intensity of peptide bitterness.

Oral Administration of a Hot Water Extract of the Softshell Turtle (Trionyx sinensis) Improves Exercise Performance

Freshwater softshell turtle (Trionyx sinensis) extract has been used traditionally as a tonic soup, and to recover from physical fatigue. To support these claims, the forelimb grip strength of mice was measured after feeding a soft-shell turtle extract for 7 days. The T. sinensis extract significantly increased the grip strength to 1.25±0.07 N (P<0.01), which is 16.8% higher than the force on day 0. After exercising, the blood glucose levels in extract-fed mice were 202% higher and urea levels were 73% lower, which were both significantly different than the levels observed after control treatment. Lactate dehydrogenase was significantly higher by 314%, and glutathione peroxidase increased by 165%. In addition, the obesity markers, serum triglyceride and cholesterol, decreased to 62% and 49%, respectively, after mice were fed the extract. These data show that the T. sinensis extract provided more energy for forelimb exercise, prevented protein catabolism and muscle fatigue, and decreased the oxidative stress caused by an exhaustive workout.

Anti-obesity effects of yellow catfish protein hydrolysate on mice fed a 45% kcal high-fat diet

Obesity contributes to the etiologies of a variety of comorbid conditions, such as type 2 diabetes, hypertension and cardiovascular disease. In the present study, the anti-obesity effects of yellow catfish protein hydrolysate (YPh) were observed in mice fed a 45% kcal high-fat diet (HFD) compared with those of mice treated with simvastatin. The HFD-fed control mice exhibited noticeable increase in body weight, and whole-body and abdominal fat densities, periovarian and abdominal wall-deposited fat pad weight, as well as in the levels of triglycerides (TG), blood total cholesterol (TC), low-density lipoprotein, alanine aminotransferase, aspartate aminotransferase, creatinine, blood urea nitrogen, and in the fecal TG and TC contents. However, they exhibited a decrease in serum high-density lipoprotein levels. In addition, an increase was detected in periovarian and dorsal abdominally deposited fat pad thickness, adipocyte hypertrophy, the number of steatohepatitis regions, hepatocyte hypertrophy and lipid droplet deposition-related renal tubular vacuolation degenerative lesions, along with increased hepatic lipid peroxidation and a deteriorated endogenous antioxidant defense system (glutathione, catalase and superoxide dismutase). However, all the above-mentioned obesity-related complications were dose-dependently and significantly inhibited after 84 days of thye consecutive oral administration of 125, 250 and 500 mg/kg YPh. In addition, YPh dose-dependently depleted the liver endogenous antioxidant defense system and inhibited hepatic lipid peroxidation. Overall, the effects of 250 mg/kg YPh on HFD-induced obesity and related complications were similar or more potent than those of 10 mg/kg simvastatin. These results indicate that YPh is a promising new potent medicinal ingredient for possible use in the treatment of obesity and related complications.

Pathogenic microorganisms, heavy metals, and antibiotic residues in seven Korean freshwater aquaculture species

This survey was performed to estimate the levels of pathogenic microorganisms, antibiotic residues, and heavy metals in seven Korean freshwater aquaculture species including Anguilla japonica, Cyprinus carpio nudus, Oncorhynchus mykiss, Pseudobagrus fulvidraco, Semisulcospira coreana, Silurus asotus, and Trionyxs sinensis. None of the ten foodborne pathogens tested in this study were found in any of the species collected from any of the aquaculture farms. Furthermore, no banned chemicals or antibiotic residues were found in any of the species collected from any of the aquaculture farms, except enrofloxacin, which was below guideline limits (0.1 mg/kg). Finally, no species had lead, cadmium, total arsenic, or total mercury concentrations above the Ministry of Food and Drug Safety (MSDF) guidelines (0.5, 0.5, 0.1, and 0.5 mg/kg, respectively). These results ensure the safety of freshwater aquaculture species and will be useful for developing consumption advisories of freshwater fishes.

Acute dermal and ocular irritation testing of rice bran supercritical CO2 extract (RB-SCE) and 0.5% RB-SCE essence product

This study was conducted to investigate the acute dermal and ocular irritation potential of rice bran supercritical CO2 extract (RB-SCE) and a 0.5% RB-SCE essence product in rabbits and guinea pigs. No abnormal clinical signs attributable to RB-SCE were detected. In the dermal irritation test, erythema, eschar, and edema formation was observed at 24 h of RB-SCE treatment, and the skin returned to normal after 72 h. The dermal primary irritation index (PII) of RB-SCE was 2.71; thus it was classified as a moderate irritant. In the ocular irritation test, there were no clinical signs related to the application of the RB-SCE; thus it was classified as a non-irritant according to the Draize scoring system. In a skin sensitivity test in rabbits, no abnormal clinical signs attributable to RB-SCE essence were observed and the PII was 0 because there was no evidence of erythema, eschar, or edema. In the guinea pig skin sensitivity test, no abnormal body weight changes or increased mortality was detected. Sensitization to the RB-SCE essence was 0%; thus it was classified as a very weak irritant.

Dermal toxicity study of rice bran supercritical CO2 extract in Sprague-Dawley rats

The present study was carried out to evaluate the dermal toxicity of topically administered rice bran supercritical CO2 extract (RB-SCE; 500, 1,000, and 2,000 mg/kg) in male and female rats when given as a single dose and a 4-week repeated dose. In all rats that underwent the single-dose toxicity test, there were no abnormal changes in clinical signs or body weight and no deaths or abnormal gross necropsy findings related to RB-SCE. Based on the above results, the LD50 is >2,000 mg/kg in both sexes. In all rats that underwent the 4-week repeated dermal toxicity test, there were no abnormal RB-SCEassociated changes with respect to external signs, urine and blood, or organs. The no-observed-adverse-effect level (NOAEL) of RB-SCE was thus considered to be 2,000 mg/kg/day for both sexes and the target organ. RB-SCE can be regarded as a very safe agent for topical dermal administration at a moderate dose.

Blood glycemia-modulating effects of melanian snail protein hydrolysates in mice with type II diabetes

Freshwater animal proteins have long been used as nutrient supplements. In this study, melanian snail (Semisulcospira libertina) protein hydrolysates (MPh) were found to exert anti-diabetic and protective effects against liver and kidney damage in mice with type II diabetes adapted to a 45% kcal high-fat diet (HFD). The hypoglycemic, hepatoprotective and nephroprotective effects of MPh were analyzed after 12 weeks of the continuous oral administration of MPh at 125, 250 and 500 mg/kg. Diabetic control mice exhibited an increase in body weight, and blood glucose and insulin levels, with a decrease in serum high-density lipoprotein (HDL) levels. In addition, an increase in the regions of steatohepatitis, hepatocyte hypertrophy, and lipid droplet deposit-related renal tubular vacuolation degenerative lesions were detected, with noticeable expansion and hyperplasia of the pancreatic islets, and an increase in glucagon- and insulin-producing cells, insulin/glucagon cell ratios in the endocrine pancreas and hepatic lipid peroxidation, as well as decreased zymogen contents. Furthermore, a deterioration of the endogenous antioxidant defense system was observed, with reduced glucose utilization related hepatic glucokinase (GK) activity and an increase in hepatic gluconeogenesis-related phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase (G6pase) activity. However, all of these diabetic complications were significantly inhibited by oral treatment with MPh in a dose-dependent manner. In addition, the marked dose-dependent inhibition of hepatic lipid peroxidation, the depletion of the liver endogenous antioxidant defense system, and changes in hepatic glucose-regulating enzyme activities were also observed. The results of this study suggest that MPh exerts potent anti-diabetic effects, along with the amelioration of related complications in mice with type II diabetes. The overall effects of MPh at a dose of 125 mg/kg on HFD-induced diabetes and related complications were similar or more potent than those of metformin (250 mg/kg).