Effect of methanol/methylene chloride extract of Terminalia glaucescens

Results.

Body weight gain, food and water intakes, openfield test.

Body weight of all groups was not significantly different from normal control group before the
extract administration. From the 12^th days of treatment, NE200 and NE300 body weight gain

decreased progressively (Fig. 1). At the end of the treatment (Day30), as refer to control, significant decrease was observed in weight gain: -11% and -19% (P< 0.01) respectively in NE200 and in NE300.

Food and water intakes did not exhibit significant variation, but metabolic efficiency (ME) was significantly altered: -43 % and -69 % (P< 0.05) respectively in NE200 and NE300 (Table 1). The animal length, the Lee index and the heart weight decreased in dose dependant profile but not significantly. No weight variation of the liver, the kidney and the carcass was observed with any extract dose. The fat pad weight weights were reduced in dose dependant manner. Compared with vehicle the parametrial and the total fat mass were significantly reduced by the extract at 200 mg/kg and 300 mg/kg: respectively -45% (p<0.05) and -64% (P< 0.01) for the parametrial fat mass, -34 % (P< 0.05) and -48% (P< 0.0 1) for the total fat mass. The inguinal (ingWAT) and retroperitoneal (rWAT) fat mass lowering was significant (P< 0.05) with 300 mg/kg extract dose

In the openfield test no significant difference in behaviour (rearing, grooming and defecation) was noticed between control and extract treated mice. Motor activity apparently increased dose dependently (Table 2).

Plasma metabolites and leptin levels

No change was observed in blood glucose level. Compared to the control group, total cholesterol decreased significantly in all treated groups: -25%, -24%, -38% (P< 0.05) respectively for 100 mg/kg, 200 mg/kg and 300 mg/kg extract doses, while the extract apparently and dose dependently enhanced the HDL cholesterol and lowered the LDL cholesterol levels (Table 3). Triglyceridemia and NEFA decreased significantly (P< 0.05) at the doses 200 mg/kg and 300 mg/kg. Leptin level decreased in dose dependant manner, and the decrease was significant with 300 mg/kg extract dose (-28%, P< 0.05).

Glucose tolerance test

Increase in plasma glucose levels after glucose administration was lowered at 30, 60, 90 minutes in all mice treated with extract 200 mg/kg and 300 mg/kg bw (Fig 2). Compared with control group, the difference in plasma glucose level was significant (P< 0.05) with 300 mg/kg extract at 30 min (- 12%), 60 min (-15%) and 90 min (-11%).

Discussion

The study was carried out in the aim of assessing the effect of Terminalia glaucescens
(Combretaceae), plant used traditionally by corpulent persons against weight gain. A key

observation of the present work is that in adult male mice, methanol/methylene chloride leaves extract of T glaucescens in dose dependant manner decreased adipose tissue mass, body mass and all lipids parameters. The parametrial adipose tissue was significantly reduced, suggesting that the extract principally affects intra-abdominal adipose depots. The decrease in body mass may be correlated to the decrease of fat mass since organs weights (liver, heart and kidney) and carcass weight did not change markedly. Body mass and specially adipose tissue mass, result from the equilibrium between energy intake and energy expenditure⁸. The decrease in adipose tissue mass may results from either the decrease in food intake or increase in energy expenditure. Since the variation in food and water intakes in treated mice compared with control was not significant, the decrease in body mass could mainly result from the increase of energy expenditure. Locomotors activity which may be considered as a good index of energy expenditure was found notably changed during the open-field test in animals treated with extract, but the metabolic efficiency was affected by the 300 mg/kg extract, so the indirect calorimetry should be required to assess energy expenditure and to clarify this hypothesis. The preliminary phytochemical screening of T glaucescens extract revealed the presence of tannins, alkaloids, flavonoids and saponosides⁵. Flavonoids stimulate lipolysis in isolated rat adipocytes and decrease adipose deposition in mice9, 10. The presence of flavonoids and other compound in the extract might explain his effect on fat reduction.

Lipids parameters such as cholesterolemia, triglyceridemia and non esterified fatty acids (NEFA) were significantly reduced. These changes are coherent with the reduction in fat deposition. There is a risky relationship between serum lipids and cadiovascular disease11, ¹² . Thus, lowering the serum cholesterol, (LDL cholesterol) and triglycerides levels with the enhancing of HDL cholesterol level, is important for preventing high mortality life style-related cardiovascular diseases. T glaucescens can therefore be expected to help to prevent such disease and by this may explain the use of this plant in the treatment of diabetes and hypertension by tradipractitioner.

Elevated plasma free fatty acids (FFA) levels account for up to 50% of insulin resistance in obese patients with type 2 diabetes mellitus¹³. Hepatic lipid accumulation in diabetes has been linked to the development of hepatic insulin resistance¹⁴. T glaucescens extract by reducing plasma FFA will be benefit in obesity and type 2 diabetes cases, and may prevent cardiovascular diseases. It has been generally accepted that â-oxidation is increased in the liver of obese and diabetic patients¹⁵. The elevated FFA levels lead to excessive â-oxidation that eventually results in impaired glucose utilization in liver. Thus, a potential approach to decrease blood glucose levels in type 2 diabetic patients is to reduce excess â-oxidation. In this study the decrease of plasma FFA may result in the reduction of â-oxidation.

In genetic models of obesity in rodents leptin plays a major role as a controller of obesity,. a central role in the regulation of food intake, body weight and energy expenditure16, ¹⁷ . Plasma leptin level is positively correlated with fat mass, body weight and plasma insulin level¹⁸. The decrease in plasma leptin in this study is coherent with the reduction of body weight and fat mass.

The 300 mg/kg extract markedly lowered the level of plasma glucose in the glucose tolerant test and tended to decrease fasted plasma glucose, suggesting that the extract increases cellular sensitiveness to glucose. Flavonoids, triterpenoids, alkaloids and phenolics are know to be bioactive antidiabetic principles19, ²⁰. The effect of T glauscecens on glucose metabolism after glucose administration may be due to the presence of more than one antihyperglycaemic principles and their synergistic properties.

The present study has shown that T glaucescens extract improved blood lipids parameters, enhanced cellular glucose sensitiveness, and reduced the body fat mass and body weight gain. These properties might justify the usefulness of T glaucescens in obesity conditions.