Natural Product Sciences 13(4) : 390-393 (2007)
390
Antidiabetic Effect of Auricularia auricula Mycelia in Streptozotocin-induced Diabetic Rats
Sung-Kyu Kim1,6, Un-Pyo Hong2, Jong-Soo Kim3, Cherl-Hyun Kim4, Ki-Woong Lee5, Sun-Eun Choi6, Kwan-Hee Park6, and Min-Won Lee6,*
1Nutra R&BT CO., LTD, Seoul 153-801, Korea
2MML Biotech CO., LTD, KangWon-do 200-160, Korea
3Natural R&BT CO., LTD, ChungNam 330-714, Korea
4Department of Animal Science & Resources, DanKook University, ChungNam 330-714, Korea
5Baby/Infant Foods Reserch Team, Namyang Dairy Products CO., LTD, ChungNam 314-914, Korea
6College of Pharmacy, Chung Ang University, Seoul 156-756 Korea
Abstract −Auricularia auricula (Heterobasidiae) called ‘tree ear’ or ‘ear mushroom’ was investigated to know its antidiabetic effect. Administration of dried powder of Auricularia auricula mycelia (AAM) (0.5 g/kg bw and 1.0 g/kg bw) caused a statistically significant reduction of plasma glucose (35% and 39%, respectively), total cholesterol (18% and 22%, respectively), triglyceride (12% and 13%, respectively), GOT (53% and 56%, respectively) GPT (26% and 37%, respectively), levels and the rate of liver weight against final total body weight (6% and 7%, respectively) compared with diabetic control group. These results support the antidiabetic effect of AAM.
Keywords −Auricularia auricula mycelia, Heterobasidiae, Antidiabetic effect, streptozotocin
Introduction
Diabetes mellitus is chronic metabolic disease with hyperglycemia and dyslipidemia. This disease is a major health problem which affects about 5% of the population (Jung, et al., 2007; Taylor, 1999). There has been a growing interest in alternative therapies and in the therapeutic use of natural products for diabetes (Kato and Miura, 1994; Kakuda, et al., 1996; Jung, et al., 2007).
Among the various natural products, mushrooms are being widely used as functional food for diabetes (Yang, et al., 2002). Auricularia auricula, which is parasitic on rotten trees in shady and damp zones (Han, et al., 1997) and commonly called ‘ear mushroom’ or ‘tree ear’
belongs to the Heterobasidiae familiy, have been broadly used for food supplement in East Asia. Its fruit body is a kind of edible black-brown mushroom with high contents of D-glucan, heteropolysaccharide (approximately 630 g/
kg in dried fruit body), lysine, leucine, Ca, P, Fe, carotene, vitamin B1, B2, nicotinic acid, lecithine, cephaline, sphingomyeline, ergosterol and 22,23-dihydroergosterol (Han, et al, 1997; Zhang, et al, 1995; Pisuena, et al.,
2003).
Auricularia auricula has been used in remedies for chronic diarrhea, dysentery, metrorrhagia, stomachache and toothache in Korean traditional medicine (Han, et al., 1997). Antidiabetic, antioxidant, anticoagulant, antitumor, immunological, anti-inflammatory and hepatotonic activities of this mushroom were reported (Acharya, et al., 2004;
Chang, et al., 1998; Fan, et al., 2006; Finkel and Holbrook, 2000; Kim, et al., 2004; Takeujchi, et al., 2004;
Yoon, et al., 2003). Recently, antidiabetic activities of several cultured mushroom mycelia were observed (Li, et al., 2006; Lo, et al., 2006; Yang, et al., 2006, Yang, et al., 2002; Zhang, et al., 2006). As part of our screening of antidiabetic natural products (Kwon, et al., 2001; Lee, et al, 2001), hypoglycemic and hypolipidemic effects of Auricularia auricula mycelia (AAM) which was produced by submerged culture was evaluated in streptozotocin- induced diabetic rats.
Experimental
Materials−The dried powders of liquid cultured AAM were procured from Nutra Biotech Co., Ltd., Korea. The drugs (500 and 1000 mg/kg b.w) were
*Author for correspondence
Fax: +82-2-822-9778; E-mail: mwlee@cau.ac.kr
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suspended in 1.0 ml distilled water and administered orally daily using an intragastric tube for two weeks.
Animals−Male Sprague Dawley (SD) rats (130 - 150 g each) were kept in the departmental animal house at 22 - 24oC, 12 h day: 12 h night cycle and relative air humidity 40 - 60% respectively for two weeks before the experiment. The animals were provided with rodent diet and water ad libitum and were divided into 4 groups of 10 rats each. The food and water were removed from cages 16 h before testing.
Experimental induction of diabetes−The animals were rendered diabetic by single intraperitoneal injection of freshly prepared STZ (Sigma, USA) 60 mg/kg b.w. in 0.1 M citrate buffer of pH 4.5 in a volume of 1 ml/kg bw Diabetes was confirmed in STZ rats by measuring the fasting blood glucose concentration after 48 h after the administration of STZ. The rats with blood glucose level more than 250 mg/dl were considered to be diabetic and included in the experiment.
Experimental design and treatment schedule−After induction of diabetes, the rats were divided into 4 groups.
Group I - Normal control rats, Group II - Diabetic control rats, Group III, IV - Dibetic rats treated with the drugs (0.5 and 1.0 g/kg bw).
Biochemical Assay−After 2 weeks of treatments, the rats were fasted overnight, blood samples were collected from inferior vena cava. Blood glucose level was detected by using a portable blood glucose meter (Roche Diagnostis GmbH, Germany). Also, each plasma for the measurement of biochemical factors was obtained immediately by centrifuging blood samples. Using these samples, total cholesterol, triglyceride, glucose, GOT and GPT were determined by using commercial kits (Asan Pharma- ceutical, Korea) and measured by UV spectrometer (Mecasys Co., Ltd., Korea) at suitable wavelength. After each liver was removed and weighed, the rate of liver weight against final total body weight was calculated.
Statistical Analysis−All data were expressed mean ± S.D. Values were analyzed by one-way analysis of variance (ANOVA) followed by Ducan’s multiple range test (DMRT) using SPSS software package and considered to be significantly different when the p value was less than 0.05.
Result and Discussion
Induction of diabetes in the experimental rats was confirmed by high plasma glucose level in diabetic control group (299.97±18.11 mg/dl) compared with normal group (140.21±11.41 mg/ml). Oral administration
of 0.5 and 1.0 g/kg bw AAM reduced plasma glucose level (35% and 39%, respectively) compared with diabetic control group significantly (P< 0.05). (Table 2.) It has been reported that STZ treatment inhibited insulin secretion by the selective destruction of the beta-cells of the pancreatic langerhans islets (Mendola, et al., 1989;
Takasu, et al., 1991). The reduction of plasma glucose level in the AAM administered group means that AAM could repair the damage of the beta-cells and promote insulin synthesis (Gray and Flatt; 1998).
The low insulin level increases the concentrations of total cholesterol, triglyceride and the rate of liver weight against final total body weight because of lipolysis in the adipose tissues, movement of free fatty acids into the liver from the adipose tissues and secretion of very low-density lipoprotein (VLDL) into the plasma from the liver through inhibition of endothelial lipoprotein lipase (LPL) (Bierman, 1992; Garg and Grundy, 1990). Total cholesterol and triglyceride were increased in diabetic control group (158.80±14.22 mg/dl and 203.73±18.70 mg/dl) compared with normal group (99.25±9.50 mg/dl and 139.96±15.76 mg/dl) and oral administration of 0.5 and 1.0 g/kg bw AAM reduced total cholesterol level (18% and 22%, respectively) and triglyceride level (12%
and 13%, respectively) compared with diabetic control group significantly (P< 0.05) (Table 2.). The rate of liver weight against final total body weight was increased in diabetic control group (3.95±0.31 g/100 g bw) compared with normal group (3.28±0.25 g/100 g bw) and oral administration of 0.5 and 1.0 g/kg bw AAM decreased the rate of liver weight against final total body weight compared with diabetic control group (6% and 7%, respectively) (Table 1.). These results indicate that the promoted insulin production might influence above diabetic indices through inducing LPL.
Table 1. Total body and liver weights of normal, diabetic control and sample administered groups (S1 and S2)
Groups Liver weight (g) Total body weight (g) Rate (g/100g bw) N 9.67 ± 0.69 294.76 ± 11.21 3.28 ± 0.25 D 6.97 ± 0.92 176.60 ± 9.51 3.95 ± 0.31 S1 7.70 ± 0.82 208.89 ± 10.21 3.69 ± 0.21 S2 6.75 ± 0.73 184.47 ± 10.15 3.66 ± 0.26 N : Normal control
D : Diabetic control
S1: STZ-induced diabetic rats + 0.5 g/kg bw AAM administered group.
S2: STZ-induced diabetic rats + 1.0 g/kg bw AAM administered group.
Values are expressed as mean ± S.D (n≥7)
392 Natural Product Sciences
The GOT and GPT levels were elevated in diabetic control group (101.81±5.82 Kamen/ml and 80.38±6.43 Kamen/ml) compared with normal group (26.76±2.33 Kamen/ml, 26.96±2.13 Kamen/ml) and oral adminis- tration 0.5 and 1.0 g/kg bw AAM also reduced GOT (53% and 55%, respectively) and GPT (26% and 37%, respectively) levels compared with diabetic control group significantly (P< 0.05) (Table 2.).
Finally, the reductions of plasma glucose level and the lowering of plasma lipid level such as total cholesterol and triglyceride and lowering of elevated GOT, GPT levels in STZ-induced diabetic rats suggest that AAM might be developed as safe antidiabetic natural functional food ingredient.
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Table 2. Plasma glucose, total cholesterol, triglyceride, GOT and GPT levels in normal, diabetic control and sample administered groups (S1 and S2)
Groups Glucose
(mg/dl) Total cholesterol
(mg/dl) Triglyceride
(mg/ml) GOT
(Kamen/ml) GPT
(Kamen/ml) N 140.21 ± 11.41 a 99.25 ± 9.49 a 139.96 ± 15.76 a 26.76 ± 2.33 a 26.96 ± 2.13 a D 299.97 ± 18.11 b 158.81 ± 14.22 b 203.73 ± 18.70 b 101.81 ± 5.82 b 80.38 ± 6.43 b S1 193.61 ± 15.85 c 130.33 ± 19.45 c 177.73 ± 16.95 c 47.39 ± 4.02 c 58.91 ± 3.62 c S2 182.54 ± 15.45 c 122.88 ± 18.01 c 175.37 ± 21.39 c 44.83 ± 8.30 c 50.14 ± 3.60 c,d N : Normal control
D : Diabetic control
S1 : STZ-induced diabetic rats + 0.5 g/kg bw AAM administered group.
S2 : STZ-induced diabetic rats + 1.0 g/kg bw AAM administered group.
Values are expressed as mean ± S.D (n≥7)
Values bearing different superscripts in the same column are significantly different (P< 0.05).
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(Accepted December 5, 2007)
