Dose selection and effect of Oolong tea on the expression of β3-adrenergic receptor gene for weight reducing

Baoqing MO; Ronghua CHEN; Xirong GUO

ABSTRACT

BACKGROUND:

Obesity is an important problem concerned domestically and internationally. How to control the body mass and to reduce the weight without any effect on normal food intake is the focus for study.

OBJECTIVE:

To probe into the weight-reducing effect of Oolong tea and its effect on the mRNA level of β3-adrenergic receptor(β3-AR).

DESIGN:

Completely randomized grouping, controlled trial

SETTING:

Department of Nutrition and Food Hygiene, College of Public Health, Nanjing Medical University; Institute of Pediatric Medicine, Nanjing Medical University.MATERIALS This experiment was conducted in the laboratory of Nanjing Medical University from September 2003 to February 2004. The obese rat models were made with the diet of high energy and high fat in male rats weighing about 80 g. Thirty-two male obese rats were selected.And Oolong tea extract was prepared, whose concentration was equivalent to 0.24 g of tea.

INTERVENTIONS:

Thirty-two male obese rats were divided randomly in-to 4 groups obese control group, low, middle and high dose of oolong tea groups. There were 8 rats in each group. The rats in the control group were fed by gavage with distilled water every day. The other rats in low, middle or high dose of Oolong tea groups were fed by gavage with 0.4 g/kg, 1.2 g/kg, and 2.4 g/kg of Oolong tea respectively. They were all fed with diet of high energy and high fat. Each rat was raised in separate cage. The room temperature for the rats remained about 22 ℃ with the humidity of 55%. The rats were free access to water, but the diet was fed twice a day at a fixed amount. If it was finished, no more diet would be added. Thirty days later, body mass, maximal diameter of adipocytes were measured, and β3-ARmRNA levels in adipose tissues were measured.MAIN OUTCOME

MEASURES:

Body mass, increased body mass,the weight of adipose tissues in retroperitoneal, peri-epididymal and interscapular regions and the maximal diameter of adipocytes were measured,β3- AR mRNA levels in the adipose tissues above were measured with the method of RT-PCR.

RESULTS:

According to intention-to-treat analysis, thirty-two male rats entered result analysis. [1]Body mass Increased weight of rats in 1.2 g/kg and 2.4 g/kg Oolong tea groups were significantly lower than that in the rats of control group and rats in 0.4 g/kg Oolong tea group (58.4±46.7,68.1±30.4,125.7±34.4,96.3±26.2,P ＜ 0.01), but the amount of total diet consumption was similar in each group (P ＞ 0.05). [2]Lipid coefficient in retroperitoneal and peri-epididymal regions of rats in 1.2 g/kg and 2.4 g/kg Oolong tea groups was lower than that in the rats of control group and rats in 0.4 g/kg Oolong tea group,(1.57±0.53,2.14±0.90 to 2.71±0.49,2.50±0.53, 1.14±0.38,1.43±0.53 to2.00±0.00,1.88±0.35), but there was no significant difference among groups of the ratio in inter-scapular regions (P ＞0.05). [3]The maximal diameter of adipocytes The maximal diameter in retroperitoneal, periepididymal and inter-scapular regions of the rats in 0.4 g/kg, 1.2 g/kg and 2.4 g/kg Oolong tea groups was significantly lower than that in the rats of control group[(113±24), (86±29), (90±23), (120±30)μm;(94±20), (80±18), (64±17), (111±21)μm; (24±11), (21 ±11), (22±10),(27±11)μm,P ＜ 0.05]. [4]β3-AR mRNA levels in adipose tissuesThe β3-AR mRNA levels in retroperitoneal, peri-epididymal and interscapular regions of the rats in 1.2 g/kg and 2.4 g/kg Oolong tea groups were significantly higher than those in rats of control group and rats with0.4 g/kg of Oolong tea (0.72±0.11,0.64±0.112,0.40±0.08,0.34±0.10 for retroperitoneal region, 1.06±0.21,1.02±0.24,0.42±0.15,0.43±0.11 for epididymal region, 1.01±0.42,0.70±0.17,0.42±0.10,0.49±0.16 for interscapular region, P ＜ 0.01).

CONCLUSION:

Oolong tea was of weight～reducing effect,which may be related to its effect to increase β3-AR mRNA level The middle dose (1.2 g/kg) may be optimal.These results may be helpful to the theory of weight reducing with tea and the selection ofoptimal dose.