Suppression of Avian Hepatic Lipid Metabolism by Solvent Extracts of Garlic: Impact on Serum Lipids

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Abstract
The effects of garlic on lipid metabolism were examined in White Leghorn pullets that had been fed for 4 weeks either a control diet based on corn and soybean meal or an experimental diet containing either 3.8% garlic paste, a solvent extract (petroleum ether, methanol and water in sequence) of garlic paste, the residue or commercial garlic oil. Significant decreases in hepatic 3-hydroxy-3-methylglutaryl-CoA reductase (79–83%), cholesterol 7α-hydroxylase (43–51%), fatty acid synthetase (17–29%) and in representative pentose-phosphate pathway (23–39%) activities accompanied the feeding of the petroleum ether-, methanol- and water-soluble fractions of garlic. Garlic paste and oil also suppressed these activities. Significant decreases in serum lipids occurred in response to the feeding of these garlic fractions: serum total cholesterol by 20–25%, low density lipoprotein cholesterol by 28–41% and triglycerides by 10–26%; but high density lipoprotein cholesterol failed to respond to these treatments. The residue remaining after solvent fractionation had little influence on these parameters. These findings were substantiated by a second study in which pullets of a commercial broiler line were fed the garlic fractions. The results confirm that garlic oil and odorous components of garlic lower cholesterol levels. An odorless water-soluble component of garlic also has this effect. The mechanism of the hypocholesterolemic action is at the level of the suppression of cholesterol biosynthesis.