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Biomedical subjects

M Sugano

Publications and source records attributed to M Sugano.

At least 253 records · Page 14Linked to original sources
PubMed1986

Oxidation and esterification of geometrical and positional isomers of octadecenoic acids in perfused rat liver.

The metabolic fate of the geometrical isomers of 6-, 9-, and 11-octadecenoic acids was studied in isolated perfused rat livers. Although the ketogenicities of these monounsaturated fatty acids generally decreased as the double bond was moved away from the carboxyl group, a dependence on the geometrical difference was found only for 9-octadecenoate, the rate being significantly lower in the cis-isomer. Very low density lipoprotein lipid secretion was distinctly and specifically decreased when trans-9-octadecenoic acid was perfused, but no such difference was observed with other isomers. Various trans-isomers were actively incorporated into the hepatic lipids and secreted apparently at the expense of preexisting endogenous cis-octadecenoate. The trans-isomers were all incorporated exclusively at the 1-position of hepatic phosphatidylcholine. Concentrations of the cis-octadecenoate in the glycerolipids secreted and remaining in the liver were characteristically modified depending on the location of the ethylenic bond of the cis-octadecenoate. Thus, both the location of the double bond in the acyl-chain and the geometrical configuration specifically influence the rate of oxidation and esterification of octadecenoic acid in perfused rat liver.

Animals↗
PubMed1986

Hypocholesterolemic effect of gamma-linolenic acid as evening primrose oil in rats.

The hypocholesterolemic effect of polyunsaturated fatty acids was compared in male rats given high-cholesterol diets containing either evening primrose oil (EPO, linoleic plus gamma-linolenic), safflower oil (SFO, linoleic) or olive oil (OLO, low linoleic) at the 10% level. EPO with a phytosterol content of 1.47% was found to be more hypocholesterolemic than SFO (phytosterols 0.34%), and rats given EPO excreted more neutral (cholesterol and its metabolites) but not acidic steroids during the first 2 weeks of the feeding. Even when the phytosterol content of EPO and SFO was adjusted to be the same (0.67%), EPO was still more hypocholesterolemic than SFO but to a lesser extent, although fecal neutral steroid excretion was comparable in these two dietary fat regimens. The results indicate a significant hypocholesterolemic efficacy of gamma-linolenic acid.

Adipose Tissue↗
PubMed1986

Dietary manipulation of the disappearance of trans-octadecenoates in rat tissues.

The effects of dietary manipulations on the fate of trans-octadecenoates deposited in the tissues of rats were examined. Male rats were fed on a 15% fat diet containing trans-octadecenoic acids (46.6% of total fatty acids) for 35 days followed by various diets free of trans-fatty acids. After removal of trans-fatty acids from the diet, there were phased disappearances of trans-octadecenoates from the circulation; a rapid and broad reduction in one day and a slow and gradual reduction thereafter. The rate of the initial reduction in serum trans-octadecenoates was highest on a high fat (20%) diet in relation to low fat (1 or 5%) diets. However, the disappearance rate at the later stage was apparently the same among the various groups and trans-fatty acid contents in the serum declined to about 10% of the initial value in 2 weeks and thereafter. After 35 days, the concentration of trans-octadecenoates remaining in the adipose tissue was markedly lower in rats fed on a high protein (40%) diet. The effects of dietary fat type and cholesterol on the fate of serum trans-octadecenoates were virtually the same, but livers from rats fed on the cholesterol-free safflower oil diet contained more trans-fatty acids than those from rats fed on the corresponding olive oil diet. Thus, the amounts of trans-fatty acids stored in the tissues cannot be merely predicted from serum levels. It seems that both dietary fat and protein affect the metabolic rate of trans-octadecenoates in rats.

Adipose Tissue↗
PubMed1985

Secretion of apolipoproteins in the suckling rat. Absence of low-molecular-weight apolipoprotein B of hepatic origin.

Synthesis of apolipoprotein B in the intestine and liver in suckling rats whose duodena had been infused with [3H]lysine was estimated by measuring the radioactivity in the mesenteric lymph and blood serum. Apolipoprotein B synthesized in the suckling rat intestine was an exclusively low-molecular-weight form. In the serum d less than 1.21 g/ml fraction obtained from the lymph-diverted rats, apolipoprotein B of high molecular weight was only labeled with [3H]lysine in suckling rats, whereas both forms of apolipoprotein B were labeled in the adult rats. These results suggest developmental changes in hepatic apolipoprotein B synthesis and secretion.

Animal Population Groups↗
PubMed1985

Activities of liver mixed function oxidase system in rats fed trans fat.

Rats were fed diets containing either camellia oil or partially hydrogenated corn oil as a source of cis or trans octadecenoate, respectively, in the presence of adequate linoleic acid. After 35 days of feeding the diets, activities of several hepatic drug metabolizing enzymes as well as the content of hepatic microsomal cytochrome P-450 were determined. Geometrical difference in the dietary fat did not affect the amount of microsomal protein nor the content of cytochrome P-450. Also, activities of NADPH cytochrome C reductase, aminopyrine N-demethylase and biphenyl hydroxylase were approximately the same between two groups of rats. Aniline hydroxylase was slightly elevated in the rats fed trans fat. It was concluded that the difference in the geometry of dietary fatty acids had little effect in modulating the hepatic mixed function oxidase system.

Animals↗
PubMed1985

Influence of dietary cis- and trans-fat on 1,2-dimethylhydrazine-induced colon tumors and fecal steroid excretion in Fischer 344 rats.

To investigate the effects of the difference in the geometry of dietary fatty acids on colon tumorigenesis, male rats were fed semipurified diets containing either partially hydrogenated corn oil (trans-monoene fat) or olive oil (cis-monoene fat) at the 10% level and received a single oral dosage of 1,2-dimethylhydrazine (DMH). The difference in the fatty acid composition of dietary fats was confined essentially to the geometrical isomerism of octadecenoate, and the linoleic acid content was made equivalent (2% of total energy). After about 15 mo of feeding, colon tumor incidence in DMH treated rats was nearly the same in both fat groups. Fecal neutral steroid excretion was higher, while the transformation of cholesterol to coprostanol was lower in rats given the trans-fat. There were no marked differences in the excretion and composition of fecal bile acids between two fat groups. Serum cholesterol and tocopherol levels of rats given trans-fat diets tended to be low. The results suggested that the trans-monoene behaves much like the cis-monoene in the incidence of DMH-induced colon tumors, although there were characteristic differences in metabolic events in the intestine.

1,2-Dimethylhydrazine↗
PubMed1985

Hypocholesterolemic effect of soybean protein in rats and mice after peptic digestion.

Analyses of gastrointestinal contents of rats fed soybean protein isolate and casein showed that soybean protein was readily digested in the stomach but migrated slowly in the small intestine. The soluble fraction of the stomach contents of rats fed soybean protein was separated by gel-filtration on Sephadex G25 into large and small molecular fractions, the latter was not found in rats fed casein. The formation of low-molecular-weight peptides was pH dependent, and analogous peptides were produced by pepsin in vitro not only from soybean protein but also from casein. In rats the peptic digest of soybean protein was found to be as hypocholesterolemic as intact soybean protein. Meanwhile, the cholesterol-lowering action of the large molecular fraction of the peptic digest tended to be greater than that of the small molecular fraction in mice. These observations suggest a significant role of peptic digestion in the cholesterol-lowering action of soybean protein.

Amino Acids↗
PubMed1985

Dietary fat dependence of intestinal 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity in rats.

The effects of dietary fats on intestinal 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity were studied in rats. Animals were fed experimental diets ad libitum for 7-13 d then killed in the morning for the determination of the reductase activity in an epithelial cell homogenate. When corn oil was the source of dietary fat, the specific activity of jejunal reductase depicted a biphasic pattern in response to dietary fat level with a peak activity when the diet contained 10% fat (by weight) whereas the specific activity of ileal reductase was independent of the fat level. Reductase activities were apparently independent of the degree of saturation of dietary fat (safflower oil, olive oil, lard and tallow) when each was fed as 10% of the diet. Both jejunal and ileal reductase activities were higher when trilaurin was fed than when other saturated fats (tricaprylin, trimyristin, tripalmitin and tristearin) were fed. The jejunum synthesized more cholesterol than the ileum. There was no significant correlation among the reductase activity, cholesterol content of the epithelial cells and the rate of fat absorption, suggesting a complex regulatory mechanism.

Animals↗
PubMed1985

Catabolism of newly formed triglyceride-rich lipoproteins and serum high density lipoproteins in rats fed soybean phospholipid and soybean oil.

Previous research has shown that serum cholesterol and apolipoprotein (apo) A-I were lower and serum apoB was higher in rats fed soybean phospholipid (PL) than in rats fed soybean oil. Secretion of cholesterol and apoA-I, but not apoB, from the liver and intestine was lower in rats fed soybean PL. In the present study catabolism of newly formed triglyceride (TG)-rich lipoproteins, from the liver and intestine, and of serum high density lipoproteins (HDL) were compared in rats fed soybean PL and in rats fed soybean oil. The following results were seen: Feeding of soybean PL was related to more TG and less cholesterol in intestinal lymph chylomicrons (CM) and hepatic very low density lipoproteins (VLDL) than was feeding of soybean oil. A lesser amount of the TG, labeled with [3H]oleate in CM and hepatic VLDL, was incorporated into the adipose tissue and muscle in vivo. The clearance of CM-TG from plasma was higher, but that of VLDL-TG and apoB labeled with [3H]lysine was lower. The catabolism of 125I-labeled HDL from the plasma was lower while hepatic uptake of 125I-labeled HDL, in vivo and in vitro, was higher. These results indicate that soybean PL modifies the catabolism of the respective serum lipoproteins. Therefore, we suggest that changes in both the catabolism and secretion of lipoproteins are responsible for the altered serum lipid and apolipoprotein patterns found in rats fed soybean PL.

Adipose Tissue↗
PubMed1985

Effects of cycloartenol on absorption and serum levels of cholesterol in rats.

The possibility that cycloartenol magnifies the hypocholesterolemic effect of beta-sitosterol was studied in two strains of rats fed on cholesterol-enriched (0.5%) diets. Cycloartenol was added to diets containing 1.0% or 0.5% beta-sitosterol at the 0.05% level and to diet free of plant sterol at the 0.5% level. In one experiment, diets included sodium cholate (0.125%). Due to the potent hypocholesterolemic efficacy of beta-sitosterol under the present dietary regimens, no clear additional effect (so-called synergistic effect) of cycloartenol was observed. However, in the experiment using Wistar rats, the decrease in serum apo A-I due to feeding cholesterol was ameliorated more effectively in combination with beta-sitosterol than with beta-sitosterol alone. The hepatic deposition of cholesterol was mitigated by dietary beta-sitosterol, and further, although slightly, by a combination of beta-sitosterol and cycloartenol, except in the experiment with diets containing sodium cholate. Fecal excretion of neutral and acidic steroids was not meaningly magnified by cycloartenol. Cycloartenol itself was not as effective as beta-sitosterol in mitigating lipid disorders due to dietary cholesterol. The rate of appearance of cholesterol in the thoracic duct lymph was not interfered with further by a combination of beta-sitosterol and cycloartenol compared to beta-sitosterol alone. This trimethylsterol was absorbed at a rate approximately 4-fold higher than that of beta-sitosterol, though much lower compared to cholesterol. These results suggest a preference for cycloartenol in cholesterol dynamics. However, cycloartenol seems unlikely to influence cholesterol absorption in the small intestine.

Animals↗
PubMed1984

Oxidation and esterification of cis- and trans-isomers of octadecenoic and octadecadienoic acids in isolated rat liver.

The metabolism of 9-octadecenoic and 9,12-octadecadienoic acids with different geometrical configurations was compared in isolated perfused rat liver. More ketone bodies were produced when the trans-isomers were infused. In contrast, only the cis-isomer augmented the triacylglycerol secretion almost entirely as very-low-density lipoprotein (VLDL). Although these responses were independent of the difference in the degree of unsaturation in both the cis- and trans-isomers, the trans-monoenic acid compared to the trans-dienic acid was incorporated more readily into perfusate and hepatic lipids. Quantitative information was obtained with radioactive tracer experiments. The hepatic uptakes of 9-[10-14C]octadecenoic acids were comparable in the cis- and trans-isomers. The trans-octadecenoic acid compared to the cis counterpart was oxidized more readily and incorporated more into liver phospholipid but less into perfusate and liver triacylglycerol. These reciprocal responses counterbalanced each other. The lower rates of triacylglycerol synthesis and secretion in the liver perfused with the trans-octadecenoic acid was confirmed using [2- 3H]glycerol as a tracer. The marked difference in the channelling of cis- and trans-fatty acids in the pathways of oxidation and esterification seems to modify the VLDL secretion in perfused rat liver. Present observations indicate a considerable difference in the fate of unsaturated fatty acids with different configurations. trans-Fatty acids are expected to be an efficient energy source in animal tissues and may not be hyperlipidemic.

Animals↗
PubMed1984

Effects of different levels of dietary trans-octadecenoate on steroid metabolism in rats.

Rats were fed semipurified diets containing olive oil or partially hydrogenated corn oil at the 5 or 20% level for ca. 30 days. These fat diets contained the same amount of octadecenoate but differed in the geometry with respect to each fat level. Contents of t-18:1 were 26% and 41% of total fatty acids, respectively. The linoleic acid content was also made equivalent (3.8 energy %). After feeding on cholesterol-free diets, rats on trans fat, compared to those on cis fat, showed: (a) no changes in serum cholesterol and apolipoprotein levels, (b) no effects on the bile flow and concentrations of biliary cholesterol or bile acids, (c) a trend toward increased fecal excretion of neutral and acidic steroids, (d) a lesser extent of transformation of cholesterol to coprostanol in the gut, and (e) no changes in the composition of biliary and fecal bile acids. Observations (c) and (d) were more marked with a high trans fat regimen. These observations, except for serum apolipoproteins and fecal steroid excretion, were practically reproducible even when rats were fed cholesterol-enriched diets.

Animals↗
PubMed1984

Biliary steroid excretion in rats fed soybean protein and casein or their amino acid mixtures.

Male Wistar rats were fed 1% fat, cholesterol-free semipurified diets containing soybean protein isolate and casein or amino acid mixtures simulating these proteins for 28-30 days. The animals then underwent surgery for biliary diversion, and bile was collected for 2 hours. The rate of bile flow was not influenced by the type of dietary protein. The concentration and output of biliary cholesterol in rats fed soybean protein were significantly higher than in those fed casein, while biliary bile acid excretion was comparable. The group given the soy protein-type amino acid mixture also tended to excrete more biliary cholesterol relative to the casein-type amino acid mixture, although the difference was not significant, while biliary bile acid output was comparable. When 5% fat diets containing 0.5% cholesterol were given to rats, concentrations of both biliary cholesterol and bile acid were elevated significantly on a vegetable protein diet. In these experiments, there was a significant negative correlation between serum cholesterol and biliary cholesterol levels. Stimulation of the biliary excretion of cholesterol seems at least relevant to the cholesterol-lowering action of soybean protein.

Amino Acids↗
PubMed1984

Dietary protein-dependent modification of serum cholesterol level in rats. Significance of the arginine/lysine ratio.

Male rats were fed for 4 weeks cholesterol-free diets containing proteins from different sources, milk, fish, egg yolk, soybean, rice and peanut. The antihypercholesterolemic effect of vegetable proteins compared to animal proteins was certified. There was a negative correlation (gamma = -0.74) between the serum cholesterol level and the arginine/lysine ratio of dietary protein, suggesting a role of this ratio in determining the serum cholesterol level. In general, the fasting level of circulating insulin was lower whereas that of glucagon was higher on feeding vegetable proteins, thus resulting in a fall of the insulin/glucagon ratio. Changes in the hormonal status may be relevant to the protein effect.

Amino Acids↗
PubMed1984

Effect of dietary fat on lipid secretion and ketone body production in rat liver.

Perfused livers from rats fed different fats were used to examine the effect of dietary fat on the rat of hepatic lipoprotein synthesis and fatty acid metabolism. Dietary fats (10% level) used were safflower oil (18:2), camellia oil (18:1) and tristearin (18:0). The results were compared with those obtained from rats fed on a low-fat diet (1% safflower oil). When no oleate substrate was infused, triglyceride secretion rates were approximately the same among the different fat groups. Infusion of the fatty acid substrate increased the secretion of triglyceride to a similar extent in 10% fat groups while the magnitude of increase was more pronounced in the low-fat group. The magnitude of increases in ketone body production due to fatty acid supply was dependent either on the amount or the type of fat; the smallest on a low-fat diet and the greatest on a camellia oil diet. Rates of secretion cholesterol and phospholipid were modified by neither the amount nor the type of fat used. It was suggested that dietary fat may alter the rate of fatty acid catabolism without modifying lipoprotein synthesis. Safflower oil distinctly modified the fatty acid profile of triglyceride secreted. Polyunsaturated fat may exert its potent hypocholesterolemic effect through the modification of the composition of lipoprotein secreted.

Animals↗
PubMed1984

The distribution of 3-hydroxy-3-methylglutaryl coenzyme A reductase in the small intestine of rats fed raw or gelatinized starch as a carbohydrate source.

The effect of gelatinization of dietary starch (wheat, corn and potato) on the distribution of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase along the small intestine of rats was studied in villus and crypt cell populations isolated by graduated scraping. Gelatinized starch preferentially stimulated jejunal reductase activity in both villus and crypt cells and consequently retained the ileojejunal gradient for the reductase activity which is characteristic for rats fed on a sucrose- or glucose-enriched semi-purified diet. The distribution of the reductase in rats fed the raw starches, however, depended on the degree of gelatinization of the preparations; raw wheat starch maintained the ileojejunal gradient, whereas the corn or potato starch eliminated the gradient, and with the latter in particular, the reductase activity tended to be higher in the ileum than in the jejunum. The digestibility of dietary starches seems to be closely related to the intertissue distribution of the intestinal HMG-CoA reductase activity.

Animals↗
PubMed1984

Reversible inactivation-reactivation of 3-hydroxy-3-methylglutaryl coenzyme A reductase of rat intestine.

3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase in the ileum of rats was inactivated by Mg2+-ATP and reversibly reactivated by cytoplasmic activator from the liver. The mevalonate kinase reaction was presumably not involved in this inactivation. Studies of nucleotide specificity for the inactivation revealed that ATP was most effective in the reaction among the nucleotides tested. In contrast to the hepatic microsomal HMG-CoA reductase, more than one-half of intestinal reductase existed in an active form. These observations indicated the presence of phosphorylation-dephosphorylation mechanism for modulation of intestinal HMG-CoA reductase.

Adenosine Triphosphate↗