脳卒中易発性高血圧自然発症ラット(SHRSP)の高脂肪・高コレステロール食による飼育 : リポおよびアポ蛋白の動態に及ぼす食塩水併用投与の影響

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Recently, food intake in Japan has been characterized by an increase in fat intake, especially animal-fat intake and the maintenance of excess salt (sodium chloride) intake. It is generally accepted that the increase in fat intake is closely related to atherosclerosis, and excess salt intake is a high risk factor for the development of hypertension and cerebrovascular lesions. So far, in almost all reports, the increase in fat intake and excess salt intake have been studied independently, and there have been few reports on the combined effects of these two factors. Taking the above things into consideration, it would seem to be very interesting to investigate the effect of excess salt intake on lipid metabolism. In this paper, we studied the effects of excess salt intake on lipoprotein and apolipoprotein metabolisms, using stroke-prone spontaneously hypertensive rats (SHRSP) and normotensive Kyo: Wistar rats (WKY) as model animals. The results obtained were as follows: A significant increase in the concentration of serum total cholesterol (TC) was observed in SHRSP and WKY, when the rats were given a regular diet (CE-2, Clea Japan Inc.) and 1% sodium chloride solution (1% NaCl) as drinking water for 4 weeks. This was accompanied by a tendency toward increases in the concentrations of serum apolipoproteins in both strains. These results suggest that excess salt intake could accelerate the production of serum total lipoproteins in SHRSP and WKY, when the rats are fed a regular diet. Next, 1% NaCl and a high-fat and high-cholesterol diet (HFC diet) were simultaneously given to SHRSP and WKY for 6 weeks. The effects of simultaneous administration on lipoprotein and apolipoprotein metabolisms were compared with those of HFC feeding. One percent NaCl did not markedly affect hypercholesterolemia in WKY, while it induced more marked hypercholesterolemia in SHRSP that was associated with extreme elevations of serum TC and the atherogenic index (A.I.). This deleterious effect of 1% NaCl in SHRSP was due to drastic elevations of cholesterol contents in the very low density lipoprotein (VLDL), intermediate density lipoprotein (IDL) and low density lipoprotein (LDL) fractions. This was also associated with marked increases in apo B contents in the VLDL, IDL and LDL fractions and significant increases in apo E contents in the VLDL and IDL fractions. These results indicate that 1% NaCl induced much larger increases in serum atherogenic β-lipoproteins in SHRSP. In other words, hypertension of SHRSP may promote the deleterious effect of 1% NaCl on lipoprotein metabolism. In the high density lipoprotein (HDL) fraction of SHRSP, the effect of 1% NaCl was not so marked, although a significant decrease in apo A-IV content was observed. In the lipoprotein-free fraction of SHRSP, apo A-I, apo A-IV and apo E contents were markedly elevated by 1% NaCl administration, but the mechanism was not clear and is now under investigation. It is also very important to keep in mind that renal disorders such as renal failure or nephrotic syndrome possibly caused by 1% NaCl administration and/or hypertension occasionally have secondary effects on lipoprotein and apolipoprotein metabolisms.
日本衛生学会の論文

脳卒中易発性高血圧自然発症ラット(SHRSP)の高脂肪・高コレステロール食による飼育 : リポおよびアポ蛋白の動態に及ぼす食塩水併用投与の影響

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