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Hypolipidemic potential of squid homogenate irrespective of a relatively high content of cholesterol.

Nagata Y, Noguchi Y, Tamaru S, Kuwahara K, Okamoto A, Suruga K, Koba K, Tanaka K - Lipids Health Dis (2014)

Bottom Line: Hepatic level of mRNA of microsomal triglyceride transfer protein was significantly lower in the squid group.In the small intestine, the squid diet exhibited significantly lower gene expression of proteins involved in fatty acid transport and cholesterol absorption.These results imply that newly-developed squid homogenate has hypolipidemic potential primarily through decreased absorption of bile acids in the small intestine and suppressed lipogenesis in the liver.

View Article: PubMed Central - PubMed

Affiliation: Department of Nutrition, University of Nagasaki, 1-1-1 Manabino, Nagayo-cho, Nishisonogi-gun, Nagasaki 851-2195, Japan. y-nagata@sun.ac.jp.

ABSTRACT

Background: Our previous study has shown that regardless of a relatively high amount of cholesterol, squid homogenate lowers serum and hepatic cholesterol in animals. Since this work, we have developed a new method to inhibit autolysis of squid proteins with sodium citrate. This study aims to investigate how squid homogenate prepared with sodium citrate affects lipid metabolism in Sprague-Dawley rats at the molecular level.

Methods: We prepared squid homogenate with sodium citrate to inhibit autolysis of squid protein. In Experiment 1 (Exp. 1), rats were given a cholesterol-free control diet or a squid diet, with squid homogenate added at the level of 5% as dietary protein for 4 weeks. Blood, the liver and adipose tissue were taken after 6 hours fasting. Serum and hepatic lipids and activities of enzymes related to lipid metabolism were measured. In Experiment 2 (Exp. 2), the above-mentioned diets had cholesterol added at the level of 0.1% and given to rats. Lipid parameters, enzyme activities, and gene expression of proteins involved in lipid metabolism in the liver and the small intestine were determined. In addition, feces were collected for two days at the end of Exp. 2 to measure fecal excretion of steroids.

Results: In Exp.1, serum triglyceride and cholesterol were ~50% and ~20% lower, respectively, in the squid diet-fed rats than in the control diet-fed animals while hepatic cholesterol was ~290% higher in the squid diet-fed rats. When cholesterol was included into the diets (Exp. 2), serum lipids were significantly lower in the squid group while no difference of hepatic lipid was seen between two groups. Activities of hepatic lipogenic enzymes were significantly lower in rats on the squid diet while the enzyme responsible for fatty acid oxidation was not modified (Expt. 1 and 2). Hepatic level of mRNA of microsomal triglyceride transfer protein was significantly lower in the squid group. In the small intestine, the squid diet exhibited significantly lower gene expression of proteins involved in fatty acid transport and cholesterol absorption. Fecal secretion of acidic steroids, but not neutral steroids, was higher in rats fed the squid diet than in those fed the control diet.

Conclusion: These results imply that newly-developed squid homogenate has hypolipidemic potential primarily through decreased absorption of bile acids in the small intestine and suppressed lipogenesis in the liver.

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Related in: MedlinePlus

Effects of the diets on hepatic mRNA expression of lipid metabolism-related genes. Data are mean ± SE (n = 6-7). □: the control diet, ■: the squid diet. *: Significantly different from the control group at p <0.05.
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Fig1: Effects of the diets on hepatic mRNA expression of lipid metabolism-related genes. Data are mean ± SE (n = 6-7). □: the control diet, ■: the squid diet. *: Significantly different from the control group at p <0.05.

Mentions: To make the level of dietary cholesterol in the control diet equivalent to that in the squid diet, cholesterol was added to diets at the level of 0.1%. As shown in Table 4, no effect of the diets was seen on body weight gain, food intake, liver weight and adipose tissue weight. Serum levels of triglyceride, phospholipid and cholesterol were ~45%, ~35% and ~17% lower, respectively, in the squid group compared to the control group (Table 5). However, there was no significant difference in hepatic concentrations of triglyceride, cholesterol and phospholipid between two diets. The squid diet markedly affected hepatic lipogenic enzyme activities (Table 6); animals displayed significantly lower enzyme activities of fatty acid synthase (FAS) and PAP compared to the control diet. However, the diets did not change CPT activity. As shown in Table 7, fecal weight and fecal excretion of fatty acid were not influenced by the diets whereas fecal excretion of acidic steroids was significantly higher in the squid group than the control group with no change in neutral steroids. Figure 1 illustrates expression of genes involved in hepatic lipid metabolism. The expression of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoAR), essential for cholesterol synthesis, was non-significantly down-regulated by the squid diet (p =0.1) while that of CYP7A1, the rate-limiting enzyme in bile acid synthesis, was up-regulated (p =0.08). Although fecal excretion of bile acid, a ligand for farnesoid X receptor (FXR), was significantly enhanced by the squid diet, mRNA of hepatic FXR was not changed by the squid diet. Gene expression of enzyme responsible for fatty acid synthesis, FAS, was lower in the squid group than in the control group without a significant difference (p =0.17). The squid diet showed a significantly lower hepatic expression of microsomal triglyceride transfer protein (MTP), essential for very low density lipoprotein (VLDL) assembly/secretion (p <0.05). As shown in Figure 2, gene expression of jejunum Niemann- Pick C1-like 1 (NPC1L1), a critical mediator of intestinal dietary cholesterol absorption, was significantly lower in rats on the squid diet compared to those on the control diet (p <0.05), but the diets did not significantly alter acyl-coenzyme A:cholesterol acyltransferase 2 (ACAT2), the rate-limiting enzyme in intestinal cholesterol trafficking. In addition, mRNA of fatty acid translocase (CD 36), fatty acid transporter, in the jejunum was significantly lower in rats fed the squid diet compared to those fed the control diet (p <0.05). Gene expression of ileal bile acid binding protein (IBABP) (p =0.09), bile acid transporter, was lower in the squid group without a significant difference (Figure 2).Table 4


Hypolipidemic potential of squid homogenate irrespective of a relatively high content of cholesterol.

Nagata Y, Noguchi Y, Tamaru S, Kuwahara K, Okamoto A, Suruga K, Koba K, Tanaka K - Lipids Health Dis (2014)

Effects of the diets on hepatic mRNA expression of lipid metabolism-related genes. Data are mean ± SE (n = 6-7). □: the control diet, ■: the squid diet. *: Significantly different from the control group at p <0.05.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4232677&req=5

Fig1: Effects of the diets on hepatic mRNA expression of lipid metabolism-related genes. Data are mean ± SE (n = 6-7). □: the control diet, ■: the squid diet. *: Significantly different from the control group at p <0.05.
Mentions: To make the level of dietary cholesterol in the control diet equivalent to that in the squid diet, cholesterol was added to diets at the level of 0.1%. As shown in Table 4, no effect of the diets was seen on body weight gain, food intake, liver weight and adipose tissue weight. Serum levels of triglyceride, phospholipid and cholesterol were ~45%, ~35% and ~17% lower, respectively, in the squid group compared to the control group (Table 5). However, there was no significant difference in hepatic concentrations of triglyceride, cholesterol and phospholipid between two diets. The squid diet markedly affected hepatic lipogenic enzyme activities (Table 6); animals displayed significantly lower enzyme activities of fatty acid synthase (FAS) and PAP compared to the control diet. However, the diets did not change CPT activity. As shown in Table 7, fecal weight and fecal excretion of fatty acid were not influenced by the diets whereas fecal excretion of acidic steroids was significantly higher in the squid group than the control group with no change in neutral steroids. Figure 1 illustrates expression of genes involved in hepatic lipid metabolism. The expression of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMG-CoAR), essential for cholesterol synthesis, was non-significantly down-regulated by the squid diet (p =0.1) while that of CYP7A1, the rate-limiting enzyme in bile acid synthesis, was up-regulated (p =0.08). Although fecal excretion of bile acid, a ligand for farnesoid X receptor (FXR), was significantly enhanced by the squid diet, mRNA of hepatic FXR was not changed by the squid diet. Gene expression of enzyme responsible for fatty acid synthesis, FAS, was lower in the squid group than in the control group without a significant difference (p =0.17). The squid diet showed a significantly lower hepatic expression of microsomal triglyceride transfer protein (MTP), essential for very low density lipoprotein (VLDL) assembly/secretion (p <0.05). As shown in Figure 2, gene expression of jejunum Niemann- Pick C1-like 1 (NPC1L1), a critical mediator of intestinal dietary cholesterol absorption, was significantly lower in rats on the squid diet compared to those on the control diet (p <0.05), but the diets did not significantly alter acyl-coenzyme A:cholesterol acyltransferase 2 (ACAT2), the rate-limiting enzyme in intestinal cholesterol trafficking. In addition, mRNA of fatty acid translocase (CD 36), fatty acid transporter, in the jejunum was significantly lower in rats fed the squid diet compared to those fed the control diet (p <0.05). Gene expression of ileal bile acid binding protein (IBABP) (p =0.09), bile acid transporter, was lower in the squid group without a significant difference (Figure 2).Table 4

Bottom Line: Hepatic level of mRNA of microsomal triglyceride transfer protein was significantly lower in the squid group.In the small intestine, the squid diet exhibited significantly lower gene expression of proteins involved in fatty acid transport and cholesterol absorption.These results imply that newly-developed squid homogenate has hypolipidemic potential primarily through decreased absorption of bile acids in the small intestine and suppressed lipogenesis in the liver.

View Article: PubMed Central - PubMed

Affiliation: Department of Nutrition, University of Nagasaki, 1-1-1 Manabino, Nagayo-cho, Nishisonogi-gun, Nagasaki 851-2195, Japan. y-nagata@sun.ac.jp.

ABSTRACT

Background: Our previous study has shown that regardless of a relatively high amount of cholesterol, squid homogenate lowers serum and hepatic cholesterol in animals. Since this work, we have developed a new method to inhibit autolysis of squid proteins with sodium citrate. This study aims to investigate how squid homogenate prepared with sodium citrate affects lipid metabolism in Sprague-Dawley rats at the molecular level.

Methods: We prepared squid homogenate with sodium citrate to inhibit autolysis of squid protein. In Experiment 1 (Exp. 1), rats were given a cholesterol-free control diet or a squid diet, with squid homogenate added at the level of 5% as dietary protein for 4 weeks. Blood, the liver and adipose tissue were taken after 6 hours fasting. Serum and hepatic lipids and activities of enzymes related to lipid metabolism were measured. In Experiment 2 (Exp. 2), the above-mentioned diets had cholesterol added at the level of 0.1% and given to rats. Lipid parameters, enzyme activities, and gene expression of proteins involved in lipid metabolism in the liver and the small intestine were determined. In addition, feces were collected for two days at the end of Exp. 2 to measure fecal excretion of steroids.

Results: In Exp.1, serum triglyceride and cholesterol were ~50% and ~20% lower, respectively, in the squid diet-fed rats than in the control diet-fed animals while hepatic cholesterol was ~290% higher in the squid diet-fed rats. When cholesterol was included into the diets (Exp. 2), serum lipids were significantly lower in the squid group while no difference of hepatic lipid was seen between two groups. Activities of hepatic lipogenic enzymes were significantly lower in rats on the squid diet while the enzyme responsible for fatty acid oxidation was not modified (Expt. 1 and 2). Hepatic level of mRNA of microsomal triglyceride transfer protein was significantly lower in the squid group. In the small intestine, the squid diet exhibited significantly lower gene expression of proteins involved in fatty acid transport and cholesterol absorption. Fecal secretion of acidic steroids, but not neutral steroids, was higher in rats fed the squid diet than in those fed the control diet.

Conclusion: These results imply that newly-developed squid homogenate has hypolipidemic potential primarily through decreased absorption of bile acids in the small intestine and suppressed lipogenesis in the liver.

Show MeSH
Related in: MedlinePlus