| Conjugated linoleic acid (CLA) refers to a group of polyunsaturated fatty acids that exist as positional and geometric isomers of linoleic acid (LA; 18:2). CLA possess many physiologic properties including reduce obesity and antiatherosclerosis, anticarcinogenesis, improve immune function, antidiabetogenesis and growth. Researchs have shown: CLA can reduce obesity through multi-ways and multi-factors. Research on the function of has suggested an important role in appetite regulation and energy metabolism. It is clear that the changes of food intake occur by hypothalamic neuropeptides. By Intracerebroventricular administration of CLA compared with non-conjugated LA, we observed the change of weight, appetite, blood lipid, leptin, NPY,AgRP,POMC mRNA expression in brain and CPT-1 mRNA expression in liver. Our experiment was conducted to extend these observations to hypothalamus and other regions within the central nervous system so that the mechanism of the actions of CLA might be more easily elucidated. Accordingly, and it is also beneficial for us to prevent and cure adiposity by using foods rich in CLA or CLA supplement. MethodsFor the experiment, normal Sprague-Dawley rats were divided into three groups (CLA, LA, NS group) and received ICV injections of either 150 nmol CLA, or LA as non-conjugated control, or normal saline. After the rats were anesthetized, a stainless steel ICV cannula was implanted 0.95 mm anterior to the lambdoidal suture, 1.4 mm lateral to the midline, and 3.3 mm from the skull surface. We collected the blood sample at 2, 4, 8, 12, 24 hours and triglycerides, total cholesterol, HDL cholesterol concentrations in the plasma were measured using kits. The rats were dissected in 48 hours and adipose tissues (subcutaneous, mesenteric, retroperitoneal, epididymal) were removed, blotted dry, and immediately weighed. To study the effects of exogenous CLA administration for 14 days on the expression of hypothalamic neuropeptides, we quantified the expression of NPY, AgRP and POMC mRNA by reverse transcriptase–polymerase chain reaction (RT-PCR).Results1. The effect of intracerebroventricular administration of CLA on weight and appetite. (1) The change of animal weight. After ICV administration, body weight was markedly reduced in CLA rats after 2 weeks of treatment. (2) The change of feeding behavior. ICV conjugated linoleic acid resulted in a 6-8 days marked inhibition on food intake, respectively. As control, the inhibition effect of linoleic acid is for 2-4 days. The administration of Normal Saline did not cause any change. (3) ICV CLA suppressed NPY mRNA expression by ~60% compared with before treatment, suppressed AgRP expression by ~75% as compared with before treatment and hypothalamic POMC expression was not altered following ICV CLA treatment.2. The effect of intracerebroventricular administration of CLA on lipid metabolism. (1) The change of fat distribution. The fat/body weight, subcutaneous and retro-peritoneal adipose tissue decreased in 48 hours. (2) The change of blood lipid. The plasma triglycerides increased and total cholesterol decreased at 2 hour and HDL concentration increased at 4 hour. (3) The lack of adipose stores was mirrored in the reduced liver triacylglycerol content of CLA-treated rats (no significant difference with control). The CPT-1 mRNA expression increased.Conclusions1. The body weight and food intake is decreased by ICV CLA;2. The inhibition of appetite by CLA is conducted by decreasing gene expression of NPY and AgRP;3. CLA can affect lipid metabolism through central nervous system (CNS), which may be related with the beneficial effect on weight-loss;4. The effect on lipid metabolism is related with increased CPT-1 expression;5. The effect of CNS on food intake and energy metabolism is very complicated and fatty acid makes an important role. CLA can affect CNS by multi-ways which need further investigation. |
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