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Biomedical subjects

M Sugano

Publications and source records attributed to M Sugano.

At least 307 records · Page 17Linked to original sources
PubMed1978

Regulation by dietary fats of 3-hydroxy-3-methylglutaryl-Coenzyme A reductase in rat liver.

The effects of various dietary fats on the activity of 3-hydroxy-3-methylglutaryl-Coenzyme A (HMG-CoA) reductase in rat liver microsomes, the rate-limiting enzyme in cholesterogenesis, were examined. A series of experiments demonstrated the dependency of the HMG-CoA reductase activity on the nature of dietary fats. When saturated fats with chain length of 12 to 18 were the dietary sources and were fed at the 10% level for 19 days, feeding fats with shorter chain fatty acids caused a lower enzyme activity compared to those with longer chain fatty acids. The activity was also regulated by the degree of unsaturation of dietary fats; when safflower oil, camellia oil or tristearin were fed at the 10% level for 18 days, the higher the unsaturation, the lower the activity. When trimyristin or tripalmitin were fed at the 10% level for 14 days, addition of essential fatty acid, at the level of minimum daily requirement (1% was replaced by safflower oil), did not affect the enzyme activity. Through the rate of incorporation of mevalonate into cholesterol in the 12,500 x g supernatant fraction of the liver was also found to be influenced by the types of dietary fats, the extent of the response appeared much smaller than that of HMG-CoA reductase. No consistent correlation between the HMG-CoA reductase activity and the content of microsomal cholesterol or cholesteryl ester and the fatty acid composition of microsomal lipids was observed.

Animals↗
PubMed1978

Effect of different levels of dietary alpha-tocopherol and linoleate on plasma and liver lipids in rats.

The influences of dietary alpha-tocopherol, in combination with three different levels of linoleate (low, moderate or high levels), on the concentrations of plasma and liver lipids in rats were examined. Male Wister rats were fed diets ad libitum for 2 weeks. dl-alpha-Tocopheryl acetate was added to the diets in 0, 20 or 200 mg tocopherol/100 g diet. The following results were obtained. (1) Higher dietary levels of alpha-tocopherol tended to cause higher plasma lipid levels in proportion to the amounts added. This phenomenon is most remarkable in rats fed a diet containing cholesterol and low linoleate (0.8% of calorie). (2) The concentrations of plasma lipids were influenced significantly than those of liver lipids by the levels of alpha-tocopherol under the conditions of this experiment.

Animals↗
PubMed1978

Dietary cholesterol influences fasting serum free amino acids in rats fed diets containing different sugars.

Fasting serum aminograms were studied in rats fed a commercial stock diet or purified diets supplemented with or without 1% cholesterol and 0.25% sodium cholate. Sucrose, glucose or fructose served as a carbohydrate source for each purified diet. Accompanied by marked rises in serum cholesterol, the serum amino acid profile of rats fed glucose or fructose diets was modified significantly by dietary cholesterol. On feeding a glucose diet, dietary cholesterol caused decreases in Trp, Thr and Tyr and increase in Pro and Met. However, the concentration of total essential amino acids remained unchanged. Feeding a fructose diet resulted in a significant reduction of the amino acid level in comparison with that observed with glucose. This decrease was routinely compensated by the inclusion of cholesterol in the diet with the concentration of a number of amino acids being increased. Only Trp was decreased by this dietary manipulation. The serum aminogram of rats fed either a commercial stock diet or a sucrose diet was inconsiderably modified by dietary cholesterol. These data denote that dietary cholesterol influences the metabolic process of amino acids and that the response to cholesterol is modified by the carbohydrate source of the diet.

Amino Acids↗
PubMed1978

Effects of dietary fats on the activity of 3-hydroxy-3-methylglutaryl-CoA reductase and sterol synthesis in the liver of fasted-refed rats.

The time course of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase activity and lipogenesis and cholesterogenesis from 1-14C-acetate and 2-14C-mevalonate was examined in the liver of rats refed diets containing different fats at the 10% level after 48 hr fasting. Fasting caused a profound depression of the reductase activity and sterol and fatty acid synthesis. In rats refed for 30 hr, the activity of HMG-CoA reductase was restored to about one-half of the level observed in prefasting rats, irrespective of the type of dietary fats. When safflower oil and trilaurin were dietary fats, the activity remained this level until 78 hr, then declined, whereas with tristearin, activity progressively increased until 78 hr. On refeeding for 174 to 222hr, the reductase activity was significantly higher in the tristearin than in the trilaurin group. Similar patterns were demonstrated in cholesterogenesis either from acetate or mevalonate, though extents of activation after refeeding were markedly different in these precursors. Dietary fat dependent changes in the content of hepatic cholesterol and in the concentration of plasma cholesterol were also observed.

Animal Nutritional Physiological Phenomena↗
PubMed1977

Some physical properties of free and esterified cholesterol mixtures: studies on relative stability of cholesterol ester ratio in blood plasma.

Some physical properties of the mixtures composed of esterified and free cholesterol at various ratios were measured. Addition of a small proportion of free cholesterol, lowered slightly the melting point of the esterified cholesterol fraction from human plasma and it was kept nearly constant at this level by the addition of 30-40% of free cholesterol. Further addition of free cholesterol resulted in an abrupt rise in the melting point. The ranges of the stable plateau were clearly wider in esterified cholesterol with more polyunsaturated acids. The extent of inhibition of monolayer formation of free cholesterol with cholesterol palmitate was found to be greatest at a mixture ratio of 60-70%. In the case where cholesterol palmitate was added to an equimolar mixture of dipalmitoyl glycerophosphocholine and free cholesterol, a trimolecular mixed monolayer was formed above the mixing ratio, 7.5:2.5, of esterified and free cholesterol. The present studies clearly showed that there were distinct changes in some physical properties examined at the molar ratio of esterified cholesterol:free cholesterol of about 7:3.

Cholesterol↗
PubMed1977

A comparison of hypocholesterolemic activity of beta-sitosterol and beta-sitostanol in rats.

The hypocholesterolemic activity of beta-sitosterol and its hydrogenated product, beta-sitostanol (dihydrositosterol or stigmastanol) has been compared in young male rats. When cholesterol was included in the diet, sitostanol consistently exhibited significantly greater hypocholesterolemic activity than sitosterol. There were no apparent differences in the effects of the sterol and the stanol on the concentration of liver cholesterol and triglyceride. Increases in plasma triglyceride due to feeding sitosterol were not observed with sitostanol. Incorporation of dietary sitostanol into plasma, liver and other tissues was always negligible, and thus this stanol was almost completely recovered in feces, while there was considerable deposition of sitosterol (mean fecal recovery being 85% to 92%). The increase in fecal output of dietary cholesterol was significantly greater with the stanol than with sterol. There was no demonstrable negative effect on growth and weight of major visceral tissues in rats fed the sterol as well as the stanol. These observations together with those reported previously indicate that hydorgenation of phytosterols is a novel approach to enhance their hypocholesterolemic activities without influencing the relative safety of the initial sterols.

Adipose Tissue↗
PubMed1977

Growth and liver lipids of casein-fed rats incubated in the presence of glucose and lipid.

The effect of casein that has reacted with glucose and/or lipid on the growth and hepatic lipids of rats was studied. A mixture of casein-ethyl linoleate-glucose was kept at 50 degrees C and RH 80.4% for 14 days and defatted with ethyl ether and acetone. When the casein that had reacted with glucose and lipid was fed at at 10% dietary level for 14 days, the growth of rats was markedly depressed. Not only levels of hepatic lipids but also of plasma lipids were specifically modified. The accumulation of hepatic lipids was primarily due to the increase in triglyceride. When casein was reacted with glucose alone, similar but considerably lesser changes in the growth and liver lipid components were observed. These data indicate that casein characteristically deteriorates with glucose and/or lipid, but the effect of oxidation of the latter is very remarkable.

Animals↗
PubMed1975

Glycerolipid metabolism in cellular and subcellular fractions of fasted rat liver.

The effect of overnight fasting on glycerolipids of the rat liver organelles was studied. The concentration of microsomal phospholipids was markedly decreased by fasting, whereas that of mitochondria and whole liver increased significantly. The significant increase due to fasting in the activity of microsomal phosphorylcholine-glyceride transferase appeared to be responsible for the increased concentration of hepatic phospholipid. The incorporation by the liver slice of [1(-14)C] glycerol into PC3 in mitochondria was increased by fasting, while there was no difference in the microsomal fraction containing supernatant. The significant decrease in the relative proportions of oleic and linoleic acids and a significant increase in stearic and arachidonic acids in phosphatidylcholine were observed in the intact liver as well as its subcellular fractions. The possible relationship of these changes after fasting to the similarity in the incorporation pattern of [1(-14)C] glycerol into the molecular species of these glycerolipids was demonstrated.

Animals↗
PubMed1975

Nutritional regulation of lipid metabolism in rats. VII. Effect of overnight fasting on liver lipids of rats fed different levels of essential fatty acids.

Effect of dietary levels of essential fatty acid (EFA), 20% corn oil, 5% corn oil, 20% lard and no fat, on the overnight fasting-induced changes in the concentration and composition of liver lipids of rats was investigated. The increase due to fasting in triglyceride (TG) was not observed when the liver previously contained relatively large amounts of the glyceride. In contrast, phospholipid levels were similarly and significantly increased. Overnight fasting induced increases in percentage of linoleic acid in TG and arachidonic acid in TG and arachidonic acid in phosphatidylcholine, the extents of those being nearly paralleled with decreasing dietary levels of EFA. These changes are interpreted as a reflection of the compensatory action of the body.

Animals↗
PubMed1971

Phosphatidylcholine-cholesterol acyltransferase in the ultracentrifugal residual protein fraction of rat plasma.

1. The phosphatidylcholine-cholesterol acyltransferase of rat plasma was dissociated from the plasma lipoproteins by ultracentrifugation and shown to be present in the plasma residual-protein fraction of density >1.210. 2. The general properties of the acyltransferase were substantially unchanged in the residual fraction as judged from the effects of differences in the substrates and of overnight starvation on the formation of different cholesterol esters. 3. The enzyme from rats starved overnight, by comparison with the enzyme from fed rats, preferentially formed cholesteryl arachidonate at the expense of cholesteryl linoleate. 4. The results suggest that ultracentrifugal separation of the plasma residual fraction may be used as an initial step for the purification of the acyltransferase.

Acyltransferases↗