과일과 채소로부터 비만을 동반한 대사증후군 개선을 위한 기능성 식이소재 탐색 및 생리활성평가 - 체중조절 및 항산화효과를 중심으로 &#8211

Abstract

Obesity can be defined as a disorder of lipid metabolism and the process of obesity is regulated by enzymes involved in lipid metabolic pathway. Obesity is also characterized increases in the number and size of adipocyte differentiated from fibroblastic pre-adipocytes in adipose tissue. This imbalance is one of the major risk factors associated with a number of chronic diseases, thus it can induce additional metabolic syndromes like fatty liver, dyslipidemia, diabetes, hypertension and atherosclerosis. For the prevention or control of obesity and related syndrome, there are many different approaches available such as dietary control, exercise and medication. The drugs presently available, such as orlistat, sibutramine, and rimonabant, have modest clinical efficacy while antiobesity agents have been reported to have side effects including the possibility of a headache, stomach-ache, vomiting or a heart attack. On the other hand, various edible plants, such as fruits, vegetables or herbs, draw much attention because of their effectiveness, safety and availability. At present, there has been growing interest in exploiting the potential of foods, plants and naturally occurring materials for treating or preventing obesity and metabolic syndromes. The aim of this study was to collect the ethanol extracts of 26 fruits and vegetables purchased at local markets in Republic of Korea and to investigate lipase inhibitors resulting in suppression of triglyceride (TG) accumulation in 3T3-L1 cells. We also designed to examine the potential anti-diabetic and antioxidant effects of Korean fruits and vegetables extracts (ethanol fraction) against alloxan-induced oxidative stress in pancreatic β-cells, HIT-T15. We measured the anti-diabetic effect through 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) cell proliferation assay, lactate dehydrogenase (LDH) release assay, NAD+/NADH ratio, insulin secretion and the antioxidant enzyme activities. Furthermore, we investigated whether garlic stem (Allium sativum L.) extract (ASSE) and aged black garlic extract (AGE) have effects on the accumulation of body fat, and the lipid levels and antioxidant enzyme activity in the obese mice fed a high-fat diet. Among the results of the serial experiments, the strong lipase inhibitory activities were shown in the extracts of garlic (Allium sativum L.) stem, garlic (Allium sativum L.) bulb, kiwi (Apteryx australis) fruits, sweet persimmon (Diospyros kaki L.) fruits, apple (Malus Pumila) fruits, perilla (Perilla frutescens) leaves and Japanese apricot (Prunus mume) fruits, regardless of concentrations treated. Eight extracts including lead mustard (Brassica juncea var. integrilolia) leaves had no effect on lipase inhibition. During the differentiation of 3T3-L1 preadipocyte to mature adipocyte, the cells were treated with carrier or 7 extracts (1, 5 and 10 µ g/ml) which had high lipase inhibitory effects. We quantified lipid contents secreted by mature adipocytes and stained with Oil Red O. The cells treated with the kiwi (Apteryx australis) fruits and Japanese apricot (Prunus mume) fruits significantly decreased intracellular TG contents than the control. Alloxan significantly decreased cell viability, increased LDH leakage, and lowered NAD+/NADH ratio and insulin secretion in HIT-T15 cell. The HIT-T15 cells treated with alloxan showed also significant decreases in the activities of antioxidant enzymes such as, superoxide dismutase (SOD), glutathione S-transferase (GST), glutathione peroxidase (GPx) and glutathione reductase (GR). However, the extracts such as bog rhubarb (Petasites japonicas) leaves, garlic (Allium sativum L.) stem, Japanese apricot (Prunus mume) fruits and crown daisy (Chrysanthemum coronarium) leaves, significantly increased viability of alloxan-treated cells and lowered LDH leakage. Intracellular NAD+/NADH ratio and insulin secretion were also increased by the extracts, respectively. The HIT-T15 cells treated with alloxan showed significant decreases in the activities of antioxidant enzymes, while the fruits or vegetables extracts significantly elevated the levels of antioxidant enzymes. We have demonstrated for the first time that oral administration of ASSE promotes body weight loss and the decrease of WAT weight by suppressing the hypertrophy of WAT. Furthermore, it induced the reduction of TG, TC, LDL-C, VLDL-C and total lipid concentrations in the serum and the elevated ratio of HDL-C to TC near to the levels in normal mice. Interestingly, our results showed that the consumption of ASSE favorably affected the levels of serum adipokines, such as adiponectin and leptin, and homeostasis model assessment– insulin resistance (HOMA-IR) in obese mice fed a high-fat diet. The ASSE-consumed groups were shown significant reductions of lipid droplets and lipid parameters in hepatic tissue. Hepatic FAS contents and HMG-CoA reductase activity were significantly lowered in the administration of ASSE groups compared to the obese group. Hepatic antioxidant enzymes activities, includings SOD, GST, GPx and GR, were significantly higher in the ASSE groups than the obese group. In the indices of liver function and safety, ALT and AST of the ASSE-administered group fed normal diets were not significantly different compared to the normal control group. Six-week old male Sprague-Dawley rats were separately fed for 5 weeks with two kinds of diets; a normal diet (ND) or high-fat diet (HD). Then all rats fed ND and treated with carrier (normal and control), AGE (100, 250 and 500 mg/kg bw) or simvastatin (1 mg/kg bw) for further 5 weeks. The body and fat-pad weight, lipid parameter, antioxidant enzyme activity and lipid peroxidation in serum and hepatic tissue was investigated. AGE supplemented groups showed significantly lower body and adipose tissue weight compared to the control. AGE significantly improved lipid profile by decreasing serum TG and hepatic TC compared with control. AGE-treated groups were also observed significant increases glutathione (GSH)/oxidized GSH (GSSG) ratio in serum and hepatic tissue compared with control and near to the level of the positive control. Consumption of AGE significantly decreased serum lipid peroxidation level relative to the control. These findings showed that the local-produced fruits and vegetables extracts had lipase inhibitory activity and antioxidant enzyme activity. Based on these results, we suggest that the screened fruits and vegetables could be promising sources as the effective and safe lipase inhibitors for potent functional foods. We also suggest that the fruits and vegetables extracts have protective effects on the cytotoxicity and dysfunction of pancreatic β-cells against alloxan-induced oxidative stress through upregulation of antioxidant enzyme activities. In sequence, the interesting results show that the beneficial antiobesity and lipid-lowering effects of ASSE are mainly mediated by suppressing body fat accumulation, ameliorating hyperlipidemic status, modulating serum concentrations of adipokines and regulating hepatic antioxidant defense system in high-fat diet induced obese mice. Additionally, present study demonstrated that the administration of AGE exhibited antiobesity and hypolipidemic effect on high fat diet-induced obese rats may be due to reducing the body weight and improving the dyslipidemia via the promotion of body fat degration and alteration in lipid profiles and antioxidant defense system. Consequently, the results obtained from our study can provide some potential effects of ASSE or AGE supplements in the regulation of obesity, and the ASSE or AGE may be of value to develop an effective dietary supplement to treat and prevent obesity and its related metabolic disorders.