Liquid chromatography-mass spectrometry-based metabolomic analysis of livers from aged rats.

We used UPLC-Q-TOF MS to analyze hepatic metabolites of rats aged 6, 12, 18, and 24 months; the MS data were processed by partial least-squares discriminant analysis (PLS-DA) to investigate the discrimination among sample groups. Rats were significantly separated with increasing age, except those aged between 6 and 12 months. We identified only 25 of 120 metabolites contributing to the separation: lipid metabolites (glycerol-3-phosphate, linolenic acid, lysophosphatidylcholines [lysoPCs]), energy metabolism intermediates (betaine, carnitine, acylcarnitines, creatine, pantothenic acid), nucleic acid metabolites (inosine, xanthosine, uracil, hypoxanthine, xanthine), and tyrosine. Aging accumulated energy metabolism intermediates, hypoxanthine, xanthine, and 2 major lysoPCs (C18:0 and C22:6). The NAD level and NAD/NADH ratio decreased with age. It was indicated that aging might decrease energy production through ß-oxidation because of a decrease in NAD despite the accumulation of lipid energy metabolism intermediates. In addition to energy dysregulation, hypoxanthine and xanthine, which are elevated with age, might accumulate reactive oxygen species in the liver. These results strongly support two aging theories: those of energy dysregulation and free radicals. Additionally, we propose a metabolic pathway related to aging based on these hepatic metabolites. These metabolites and the proposed aging pathway could be used to understand aging and related diseases better, and increase the predictability of aging risk.

Predictive model of Staphylococcus aureus growth on egg products.

Egg products are widely consumed in Korea and continue to be associated with risks of Staphylococcus aureus-induced food poisoning. This prompted the development of predictive mathematical models to understand growth kinetics of S. aureus in egg products in order to improve the production of domestic food items. Egg products were inoculated with S. aureus and observe S. aureus growth. The growth kinetics of S. aureus was used to calculate lag-phase duration (LPD) and maximum specific growth rate (µmax) using Baranyi model as the primary growth model. The secondary models provided predicted values for the temperature changes and were created using the polynomial equation for LPD and a square root model for µmax. In addition, root mean square errors (RMSE) were analyzed to evaluate the suitability of the mathematical models. The developed models demonstrated 0.16-0.27 RMSE, suggesting that models properly represented the actual growth of S. aureus in egg products.

Metabolomic analysis of the effect of shade treatment on the nutritional and sensory qualities of green tea.

We analyzed metabolites from a 50% aqueous methanol extract of green teas treated with different shade periods (0, 15, 18, and 20 days) to investigate the effect of low light on their nutritional and sensory qualities. The shaded groups could be clearly distinguished from the control (0 day), and the 20 day group was separated from the 15 and 18 day groups. The shade treatment increased quercetin-galactosylrutinoside, kaempferol-glucosylrutinoside, epicatechin gallate, epigallocatechin gallate, tryptophan, phenylalanine, theanine, glutamine, glutamate, and caffeine levels but decreased quercetin-glucosylrutinoside, kaempferol-glucoside, gallocatechin, and epigallocatechin levels. Further studies on the nutritional benefits of these metabolites are needed. However, this result, along with the sensory evaluation and color measurement data, suggests that shade treatment improves the nutritional and sensory quality of green tea. Thus, we proposed a metabolomic pathway related to the effect of low light, which could elucidate the relationship between low light and tea quality.

LC-MS-based metabolomic analysis of serum and livers from red ginseng-fed rats.

Serum and liver metabolites in rats fed red ginseng (RG) were analyzed by ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry. The mass data were analyzed by partial least squares-discriminant analysis (PLS-DA) to discriminate between control and RG groups and identify metabolites contributing to this discrimination. The RG group was clearly separated from the control group on PLS-DA scores plot for serum samples, but not liver samples. The major metabolites contributing to the discrimination included lipid metabolites (lysophosphatidylcholine, acyl-carnitine, and sphingosine), isoleucine, nicotinamide, and corticosterone in the serum; the blood levels of all but isoleucine were reduced by RG administration. Not all metabolites were positively correlated with the health benefits of RG. However, the blood levels of lysophosphatidylcholine, which stimulate various diseases, and long-chain acylcarnitines and corticosterone, which activate the stress response, were reduced by RG, suggesting long-term RG might relieve stress and prevent physiological and biological problems.