Effect of extracts from narezushi, a fermented mackerel product, on cholesterol metabolism in Wistar rats

Abstract

Narezushi extract was separated into peptide and nonpeptide fractions by ion-exchange column chromatography. The narezushi extract and fractions were administered to rats in a diet enriched with lipid and cholesterol for 30 days. In the narezushi extract and nonpeptide fraction groups, increases in triglyceride, total cholesterol, and low-density lipoprotein-cholesterol levels in the plasma and accumulation of total lipids and triglyceride in the liver were suppressed, while both lipid and cholesterol fecal excretion were increased. In the peptide fraction group, these effects were also observed, except for the suppressing effect on liver lipid accumulation. Narezushi extract administration tended to increase fecal bile acids and promoted the activity of cholesterol 7a-hydroxylase, the rate-limiting enzyme in the synthesis of bile acid from cholesterol in the liver. However, the activity of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the rate-limiting enzyme in the cholesterol synthesis system in the liver, decreased due to regulation by the feedback of lipid transportation from diet to the liver. These results suggest that both the increase in cholesterol and bile acid fecal excretion and the promotion of cholesterol 7a-hydroxylase activities are related to the hypocholesterolemic effects of narezushi extract. Amino acids and organic acids, which are abundantly contained in the nonpeptide fraction, seemed to have more intensive hypocholesterolemic effects than peptides existing in the peptide fraction.

Anticoagulating Effects of Water-Extractive Components from Heshiko and Narezushi, Japanese Fermented Aquatic Products

“…We already reported that the administration of the heshiko and narezushi extracts decreased systolic blood pressure and ACE activity in the aorta and plasma in the spontaneously hypertensive rat (26,27). Furthermore, the increases in plasma cholesterol and triacylglycerol levels in the rats fed the high-fat experimental diet were also suppressed by the administration of heshiko and narezushi extracts (28,29). In the rats administered heshiko and narezushi extracts, the PAI-1 activity of plasma decreased despite the difference in diet (data not shown).…”

“…These results indicate that the anticoagulating effect of the extracts from heshiko and narezushi is closely related to the acceleration of fi brinolysis via the increase of tPA activity and the decrease of PAI-1 activity. Antihypertensive and hypocholesterolemic effects of the extracts from heshiko and narezushi were likely to be attributable waterextractive components including peptides produced during processing (26)(27)(28)(29). Therefore, the water-extractive components including peptides produced by protein hydrolysis during processing also may enhance tPA activity through the inhibition of PAI-1 activity directly or through hypotensive and hypolipidemic effects.…”

“…We previously reported that extracts from heshiko and narezushi, traditional fermented aquatic products produced in the Wakasa Bay area of Japan, had hypotensive and hypocholesterolemic effects (26)(27)(28)(29) in animal experiments. Heshiko and narezushi were prepared by the aging of salted mackerel with rice bran or cooked rice, respectively, for several months at ambient temperature.…”

“…Heshiko and narezushi were prepared by the aging of salted mackerel with rice bran or cooked rice, respectively, for several months at ambient temperature. The physiological functions of heshiko and narezushi were attributable to the large amount of water-extractive components including free amino acids, peptides and organic acids produced during aging (28)(29)(30)(31). Inhibition of ACE activity and reduction of plasma triacylglycerol levels by the extracts from heshiko and narezushi suggests their potential to prevent thrombosis.…”

Inhibitory effect of water extractive components from heshiko and narezushi on plasma PAI-1 activity in rats

“…[15][16][17] Author already reported hypotensive and hypocholesterolemic effects as physiological functions of crude water-extractive components (extracts) from heshiko and narezushi. [18][19][20][21] Both heshiko and narezushi are Japanese traditional fermented products from salted mackerel, though there are some difference in their processing; the former is produced from salted mackerel by fermentation with rice-bran after salting raw mackerel with 20% weight of sodium chloride and the latter is done with boiled rice after salting raw mackerel with 5% weight of sodium chloride. Heshiko and narezushi commonly contain plenty of water-soluble components including peptides, and it was previously reported that the oral administration of heshiko and narezushi extracts delayed blood coagulation in rats in which the acceleration in fibrinolysis via increased tPA activity was involved.…”