Korean J Nutr.  2009 Dec;42(8):714-722.

Effect of Leucine Intake on Body Weight Reduction in Rats Fed High Fat Diet

• Park HJ
• Lee EJ
• Kim J
• Kim JY
• Kwon O
• Kim MK

Abstract

The principal objective of this study was to determine the effects of leucine on body weight reduction in high fat diet-induced overweight rats. To induce overweight, six-month-old male Sprague-Dawley rats (n = 80) were divided into 8 groups; one group of 10 rats was fed on a normal fat diet and the remaining 70 rats were fed on a high-fat diet (40% of energy as fat) for 14 weeks. Then, 10 rats fed on the normal fat diet and another 10 rats fed on the high fat diet were sacrificed to identify overweight induction. The remaining 60 rats were divided randomly into 6 groups according to body weight and fed on one of the diets with different dietary fat levels (9.6% or 40% of energy as fat) and leucine levels (0, 0.6 or 1.2 g/kg BW) for the following 5 weeks of experiments. The body weight loss in the Leu-administered groups (0.6 g, 1.2 g/kg BW) was significantly higher than those of Leu non-administered groups. The perirenal fat pad weights in the Leu-administered groups were significantly lower than those of the Leu non-administered groups. Of the hepatic enzymes, glucose-6-phosphate dehydrogenase (G6PDH) activities were reduced significantly in the Leu-administered groups than in the Leu non-administered groups. With the oral glucose tolerance test (OGTT), the incremental areas under the curve of the glucose response (IAUC) of the Leu-administered groups were significantly lower than those of the Leu non-administered groups. The fasting glucose concentration and HOMA-IR of the Leu-administered groups were significantly lower than those of the Leu non-administered groups. In conclusion, the results of this study suggest that one of the possible mechanisms of leucine in the observed body weight reduction might involve the inhibition of lipogenic enzyme activities such as glucose-6-phosphate dehydrogenase, rather than the activation of lipolysis enzymes. Additionally, leucine adminstration resulted in improved glucose metabolism.

Keyword

leucine; dietary fat level; body weight; hepatic enzyme activities; blood glucose

MeSH Terms

Adipose Tissue
Animals
Blood Glucose
Body Weight
Diet
Diet, High-Fat
Dietary Fats
Fasting
Glucose
Glucose Tolerance Test
Glucosephosphate Dehydrogenase
Humans
Leucine
Lipolysis
Male
Overweight
Rats
Rats, Sprague-Dawley
Weights and Measures
Blood Glucose
Dietary Fats
Glucose
Glucosephosphate Dehydrogenase
Leucine

Figure

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  Fig. 1 Perirenal fat pad (A) and epididymal fat pad (B) in rats fed diets with different levels of dietary fat and/or leucine (see Table 1 for group description). The high fat induced animals were orally administered Leucine as separate feeding for 5 weeks with control diet or continuous high fat diet. Values are expressed as mean ± SE shown by vertical bars. Values with different letters are significantly different at α = 0.05 level by one-way ANOVA.

• 

  Fig. 2 Activities of carnitine palmitoyl transferase (A), glucose-6-phosphate dehydrogenase (B), and malic enzyme (C) in rats fed diets with different levels of fat and/or leucine. Values are expressed as mean ± SE shown by vertical bars. Values with different letters are significantly different at α = 0.05 level by oneway ANOVA.

• 

  Fig. 3 Blood glucose concentrations during oral glucose tolerance test in rats fed diets with different levels of fat and/or leucine. The animals received orally administered glucose (1 g/kg bw) with or without leucin after overnight fasting for 12 h. Blood glucose levels were determined from tail blood samples at 0, 30, 60, 90, and 120 min and incremental blood glucose concentrations were integrated over a period of 2h (A: control diet with different leucine levels, B: high fat diet, C: incremental area under the curve of the glucose response). Values are expressed as mean ± SE shown by vertical bars. Values with different letters are significantly different at α = 0.05 level by one-way ANOVA.

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  Fig. 4 Effect of leucine with or without high fat diet for 5 weeks on biochemical parameters of blood glucose. Values are expressed as mean ± SE shown by vertical bars. Values with different letters are significantly different at α = 0.05 level by oneway ANOVA. A: Fasting blood glucose (A), B: plasma insulin, C: glucagon concentrations, D: insulin/glucagon ratio, E: HOMA-IR (Fasting plasma insulin (µU/mL) × fasting blood glucose (mmol/l)/22.5).

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