Nutr Res Pract.  2010 Dec;4(6):462-469.

Effect of dietary protamine on lipid metabolism in rats

• Hosomi R
• Fukunaga K
• Arai H
• Kanda S
• Nishiyama
• Yoshida M

Abstract

Protamine has been widely used as a pharmaceutical product and natural food preservative. However, few studies have been conducted to assess the beneficial function of dietary protamine. This study examined the effects of dietary salmon protamine on serum and liver lipid levels and the expression levels of genes encoding proteins involved in lipid homeostasis in the liver of rats. Groups of male Wistar rats were fed AIN93G diet containing 2% or 5% protamine. After 4 weeks of feeding these diets, markedly decreased serum and liver cholesterol (CHOL) and triacylglycerol levels were noted. Increased activity of liver carnitine palmitoyltransferase-2 and acyl-CoA oxidase, which are key enzymes of fatty acid beta-oxidation in the mitochondria and peroxisomes, was found in rats fed on protamine. Furthermore, rats fed protamine showed enhanced fecal excretion of CHOL and bile acid and increased liver mRNA expression levels of ATP-binding cassette (ABC) G5 and ABCG8, which form heterodimers and play a major role in the secretion of CHOL into bile. The decrease in triacylglycerol levels in protamine-fed rats was due to the enhancement of liver beta-oxidation. Furthermore, rats fed protamine exhibited decreased CHOL levels through the suppression of CHOL and bile acid absorption and the enhancement of CHOL secretion into bile. These results suggest that dietary protamine has beneficial effects that may aid in the prevention of lifestyle-related diseases such as hyperlipidemia and atherosclerosis.

Keyword

Protamine; lipid metabolism; beta-oxidation; cholesterol; triacylglycerol

MeSH Terms

Absorption
Acyl-CoA Oxidase
Animals
Atherosclerosis
Bile
Carnitine
Cholesterol
Diet
Homeostasis
Humans
Hyperlipidemias
Lipid Metabolism
Liver
Male
Mitochondria
Peroxisomes
Proteins
Rats
Rats, Wistar
RNA, Messenger
Salmon
Triglycerides
Acyl-CoA Oxidase
Carnitine
Cholesterol
Proteins
RNA, Messenger
Triglycerides

Figure

• 

  Fig. 1 The expression levels of enzymes related to cholesterol metabolism in the liver of Wistar rat fed diets of the control (□), ProtL (▒), and ProtH (■) diets. Data are means ± SD (n = 7). Relative values are presented as the ratio of each mRNA to GAPDH mRNA. Values not sharing a common letter are significantly different at P < 0.05. Data were analyzed by Tukey-Kramer test. The expression levels of enzymes related to cholesterol metabolism were analyzed by the real-time quantitative polymerase chain reaction method. CYP7A1, cholesterol 7α-hydroxylase; HMGR, 3-hydroxy-3methylglutaryl-CoA reductase; LDL-R, low density lipoprotein receptor; SR-B1, scavenger receptor class B type 1; ABCA1, ATP-binding cassette A1; ABCG5, ATP-binding cassette G5; ABCG8, ATP-binding cassette G8; GAPDH, glyceraldehyde-3-phosphate dehydrogenase

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