Jin-Joo Hue

Effects of Selenium on Colon Carcinogenesis Induced by Azoxymethane and Dextran Sodium Sulfate in Mouse Model with High-Iron Diet

Selenium (Se) is known to prevent several cancers while the relationship between high iron and the risk of colorectal cancer is controversial. To investigate the effects of Se in colon carcinogenesis, we subjected three different levels of Se and high-iron diet to a mouse model of colon cancer in which animals were treated with three azoxymethane (AOM) injections followed by dextran sodium sulfate (DSS) administration. There were five experimental groups including vehicle group [normal-Fe (NFe, 45 ppm)+medium-Se (MSe, 0.1 ppm)], positive control group (AOM/DSS+NFe+MSe), AOM/DSS+high-Fe (HFe, 450 ppm)+low-Se (LSe, 0.02 ppm), AOM/DSS+HFe+MSe, and AOM/DSS+HFe+high-Se (HSe, 0.5 ppm). The animals were fed on the three different Se diets for 24 weeks. The incidence of colon tumor in the high-Se diet group (AOM/DSS+HFe+HSe) showed 19.4% lower than positive control group, 5.9% lower than AOM/DSS+HFe+MSe diet group, and 11.1% lower than AOM/DSS+HFe+LSe group. The tumor multiplicity was significantly higher in the low-Se diet group (AOM/DSS+HFe+LSe) compare to all other AOM/DSS treated groups. In the high-Se diet group, the activity of hepatic GPx was comparable to that of positive control group, and significantly higher than those of low-Se or medium-Se diet groups. Expression level of hepatic GPx-1 showed similar results. Hepatic malondialdehyde (MDA) level (indicator of oxidative stress) in the low-Se diet group showed the highest compared to the other groups, and it was significantly higher than positive control group. In the high-Se diet group the level of MDA in the liver was significantly lower than all other AOM/DSS treated groups. High-Se diet group showed significantly lower proliferative index than low-Se and medium-Se groups. The apoptotic indices in low-Se group and medium-Se group were significantly lower than positive control group. However, apoptotic index of high-Se diet group was significantly higher than all other AOM/DSS treated groups. These findings suggest that dietary Se supplement may have protective effect against colon cancer by decreasing proliferation, increasing apoptosis of tumor cells, and reducing oxidative stress in mice with high iron diet.

Anti-obesity activity of diglyceride containing conjugated linoleic acid in C57BL/6J ob/ob mice

This study was to investigate the anti-obesity effects of diglyceride (DG)-conjugated linoleic acid (CLA) containing 22% CLA as fatty acids in C57BL/6J ob/ob male mice. There were four experimental groups including vehicle control, DG, CLA, and DG-CLA. The test solutions of 750 mg/kg dose were orally administered to the mice everyday for 5 weeks. CLA treatments significantly decreased mean body weight in the obese mice throughout the experimental period compared to the control (p < 0.01). All test solutions significantly decreased the levels of triglyceride, glucose and free fatty acids in the serum compared with control (p < 0.05). The levels of total cholesterol were also significantly reduced in DG and DG-CLA groups compared with the control group (p < 0.05). CLA significantly decreased weights of renal and epididymal fats compared with the control (p < 0.05). DG and DG-CLA also significantly decreased the epididymal fat weights compared with the control (p < 0.05). A remarkable decrease in the number of lipid droplets and fat globules was observed in the livers of mice treated with DG, CLA, and DG-CLA compared to control. Treatments of DG and CLA actually increased the expression of peroxisome proliferator-activated receptor gamma. These results suggest that DG-CLA containing 22% CLA have a respectable anti-obesity effect by controlling serum lipids and fat metabolism.

Effects of Diglyceride-Conjugated Linoleic Acid on Proliferation and Differentiation of 3T3-L1 Cells

Conjugated linoleic acid (CLA) has been recently reported to have an anti-obesity effect in animals and humans. The objective of this study was to investigate effects of diglyceride (DG)-CLA on proliferation and differentiation of 3T3-L1 preadipocytes. Cell proliferation was determined using WST-8 analysis and cell differentiation was determined by glycerol-3-phosphate dehydrogenase (GPDH) activity. Lipid accumulation in differentiating 3T3-L1 cells was determined by Oil red O staining. There were four experimental groups including vehicle control (DMSO), CLA, triglyceride (TG)-CLA, and DG-CLA. Treatments of CLA, TG-CLA, and DG-CLA at the concentrations of 10~1000 ㎍/㎖ reduced proliferation of preconfluent 3T3-L1 cells in a dose-dependent manner. Among them CLA was the most effective in the proliferation inhibition of preconfluent 3T3-L1 cells with increasing concentrations. Treatments of CLA and DG-CLA at the concentration of 100 ㎍/㎖ significantly inhibited differentiation of postconfluent 3T3-L1 cells as measured by GPDH activity (p＜0.05). In addition, treatments of CLA, TG-CLA, and DG-CLA effectively inhibited lipid accumulation during differentiation of 3T3-L1 cells. DG-CLA had the most inhibitory effect on the differentiation and lipid accumulation. These results suggest that the compounds including CLA have a respectable anti-obesity effect and that consumption of DG-CLA as a dietary oil may give a benefit for controlling overweight in humans.

Protective Effect of Carnosine Against Zn-Mediated Toxicity in Cortical Neuronal Cells

Zinc is an endogenous transition metal that can be synaptically released during neuronal activity. However, zinc may contribute to the neuropathology associated with a variety of conditions. Carnosine expressed in glial cells can modulate the effects of zinc on neuronal excitability as a zinc chelator. We hypothesize that carnosine may protect against neurotoxicity of zinc in cortical neuronal cells. The cortical neuronal cells from newborn rats were prepared and exposed to zinc chloride and/or carnosine at various concentrations. Zinc at the doses of 0 to 500 μM decreased neuronal cell viability in a dosedependent manner. Additionally, at the concentrations of 100 and 200 μM, it significantly decreased cell viability in an exposed time-dependent manner (p ＜ 0.05). Treatment with carnosine at the concentrations of 20 and 200 μM significantly increased neuronal cell proliferation by approximately 14% and 20%, respectively, compared to the control (p ＜ 0.05). At the concentrations of 100 and 200 μM zinc, 20 μM carnosine significantly increased the viability of neuronal cells by 18.3% and 12.1%, and 200 μM carnosine also increased it by 33.5% and 28.6%, respectively, compared to the normal control group (p ＜ 0.01). These results suggest that carnosine at a physiologically relevant level may protect against zinc-mediated toxicity in neuronal cells as an endogenous neuroprotective agent.