Paul H. Lenz

γ-tocotrienol as a hypocholesterolemic and antioxidant agent in rats fed atherogenic diets

This study was designed to determine whether incorporation of γ-tocotrienol or α-tocopherol in an atherogenic diet would reduce the concentration of plasma cholesterol, triglycerides and fatty acid peroxides, and attenuate platelet aggregability in rats. For six weeks, male Wistar rats (n=90) were fed AIN76A semisynthetic test diets containing cholesterol (2% by weight), providing fat as partially hydrogenated soybean oil (20% by weight), menhaden oil (20%) or corn oil (2%). Feeding the ration with menhaden oil resulted in the highest concentrations of plasma cholesterol, low and very low density lipoprotein cholesterol, triglycerides, thiobarbituric acid reactive substances and fatty acid hydroperoxides. Consumption of the ration containing γ-tocotrienol (50 μ/kg) and α-tocopherol (500 mg/kg) for six weeks led to decreased plasma lipid concentrations. Plasma cholesterol, low and very low density lipoprotein cholesterol, and triglycerides each decreased significantly (P<0.001). Plasma thiobarbituric acid reactive substances decreased significantly (P<0.01), as did the fatty acid hydroperoxides (P<0.05), when the diet contained both chromanols. Supplementation with γ-tocotrienol resulted in similar, though quantitatively smaller, decrements in these plasma values. Plasma α-tocopherol concentrations were lowest in rats fed menhaden oil without either chromanol. Though plasma α-tocopherol did not rise with γ-tocotrienol supplementation at 50 mg/kg, γ-tocotrienol at 100 mg/kg of ration spared plasma α-tocopherol, which rose from 0.60±0.2 to 1.34±0.4 mg/dL (P<0.05). The highest concentration of α-tocopherol was measured in plasma of animals fed a ration supplemented with α-tocopherol at 500 mg/kg. In response to added collagen, the partially hydrogenated soybean oil diet without supplementary cholesterol led to reduced platelet aggregation as compared with the cholesterol-supplemented diet. However, γ-tocotrienol at a level of 50 mg/kg in the cholesterol-supplemented diet did not significantly reduce platelet aggregation. Platelets from animals fed the menhaden oil diet released less adenosine triphosphate than the ones from any other diet group. The data suggest that the combination of γ-tocotrienol and α-tocopherol, as present in palm oil distillates, deserves further evaluation as a potential hypolipemic agent in hyperlipemic humans at atherogenic risk.

Blood and liver lipids in torpid and aroused little brown bats, Myotis lucifugus

1. 1. Levels of serum and liver lipids were determined in torpid and aroused (4 hr post-torpor) Myotis lucifugus captured during hibernation. 2. 2. Serum cholesterol and triglyceride concentrations were not affected by arousal. 3. 3. The serum phospholipid concentration decreased 58 per cent and the serum free fatty acid concentration increased 266 per cent following arousal. 4. 4. Liver total lipid concentration decreased 68 per cent after arousal, but there was no change in liver weight. 5. 5. The decrease in the liver total lipid concentration was due to decreases in the cholesterol (87 per cent), triglyceride (73 per cent), phospholipid (54 per cent) and free fatty acid (90 per cent) concentrations.

Effect of dietary menhaden, Canola and partially hydrogenated soy oil supplemented with vitamin E upon plasma lipids and platelet aggregation.

Male Fisher rats were fed chow diets for two weeks after which they were divided into seven groups of ten rats each and fed 20% Canola, 20% menhaden, 20% partially hydrogenated soy oil (PHSO) or chow only, with or without 500 mg/Kg dietary vitamin E in chow containing 2% cholesterol for six weeks. Triglycerides were lower in the menhaden group and were essentially the same in the E supplemented groups as in their unsupplemented cohorts. Plasma cholesterol was higher in the Canola, and lower in the menhaden, groups, compared to the PHSO group. Cholesterol was the same in the E supplemented groups as in their unsupplemented cohorts. Plasma thiobarbituric acid reactant substances (TBARS) were higher in the menhaden group, compared to the chow group. Vitamin E supplementation lowered TBARS in the menhaden and PHSO groups, compared to the unsupplemented cohorts. Collagen induced platelet aggregation was lower in both Canola and menhaden groups, compared to the PHSO group. Vitamin E supplementation lowered collagen induced platelet aggregation only in the PHSO group. Thrombin induced platelet aggregation was lower in the Canola group, compared to the PHSO group. Vitamin E supplementation did not affect thrombin induced platelet aggregation compared to unsupplemented cohorts. Plasma vitamin E levels were lowest in the menhaden supplemented group compared to all other groups not receiving E, suggesting a greater requirement for E in this group. Finally, vitamin E supplementation raised the plasma E levels in all groups except the menhaden group when compared to unsupplemented cohorts.

The hypolipidemic effect of calcium-containing compounds and vitamin D2 in the rat

Two per cent dietary calcium carbonate alone (Group 1), in combination with vitamin D2 (Group 2) or oyster shell calcium with vitamin D2 (Group 3), was added to an atherogenic diet containing 20% fat and 2% cholesterol and fed to adult male Holtzman strain rats to evaluate the hypolipidemic effects of these supplements. A control group received the same diet, but the calcium was replaced by sand. After 21 days the serum cholesterol concentrations were lower by 35, 27 and 22%, respectively, in experimental groups 1, 2 and 3, compared to the controls. Serum triglyceride concentrations were lower by 10% in experimental groups 1, 2 and 3, compared to the controls. Serum triglyceride concentrations were lower by 10% in groups 1 and 2, and 17% in group 3. Concomitant with these decreases in serum lipids, there were increases in fecal 3-β-hydroxy-5-ene sterol, total glyceride and free fatty acid excretion. Serum calcium was elevated in the rats fed diets containing calcium when compared with the controls, whereas serum magnesium was depressed in thesy animals. Less calcium was excreted in the feces of rats fed calcium carbonate in combination with vitamin D than in those fed calcium carbonate. The results indicate a possible means of simultaneously treating both calcium deficiency and hyperlipidemia with a single agent.

Corticoid release and gluconeogenesis following triglyceride ingestion in the rat

Following a 5.0 ml triglyceride (cottonseed oil) gavage, there was a 60% elevation in the blood glucose concentration by the seventh hour in naturally occurring hypertriglyceridemic rats of the Long Evans strain. Glycogenolysis from liver or gastrocnemius muscle glycogen did not seem to be the source of this glucose. A significant elevation in the plasma total amino acid concentration concomitant with a peak in the blood urea nitrogen concentration by the fifth hour after gavage implicated gluconeogenesis. A prolonged plasma total corticoid elevation from hours 1 1/2 through 3 post-ingestion, which did not occur in non-fed or mineral oil-fed cohorts, supported gluconeogenesis. The serum total protein concentration rose significantly and progressively to a peak by the eighth hour due to an elevation in the albumin concentration. These elevations in serum proteins appeared to support glucocorticoid mediated gluconeogenesis. Adrenalectomy appeared to negate triglyceride-induced elevation in serum free amino acids, urea nitrogen, total protein and albumin.

Serum chemistry of the small Indian mongoose, herpestes auropunctatus

1. 1. Thirty serum components were quantitatively determined in Herpestes auropunctatus and Rattus norvegicus. 2. 2. Serum cholesterol was higher in wild mongooses than laboratory rats (P < 0.01). 3. 3. The higher serum osmolality (P < 0.01) in mongooses compared to rats was partially due to higher sodium (P < 0.01) and urea nitrogen (P < 0.01) concentrations. Serum nonprotein nitrogen components (creatinine, urea nitrogen, and uric acid) were more than 100% higher in mongooses than rats (P < 0.01). These relatively high serum values may be due to the urine concentrating mechanism of the mongoose kidney. 4. 4. Serum total protein was greater in wild mongooses than laboratory rats (P < 0·05), due to a higher gamma globulin concentration (P < 0·01).

Plasma lipid and glucose levels in the adrenalectomized rat following triglyceride ingestion

Adrenalectomy did not significantly alter plasma cholesterol, triglycerides and phospholipids in fasted naturally hypertriglyceridemic rats. Oral administration of cottonseed oil resulted in elevations in plasma cholesterol and phospholipids within 2 hr. Adrenalectomy negated these elevations. Triglycerides rose to an equal extent in both groups at the same time. A secondary rise in plasma glucose was noted at about 7 hr in the control rats; this rise was also negated by adrenalectomy.

Effect of dietary canola and reference oils upon serum lipids and platelet aggregation.

To compare Canola a terrestrial (n-3) oil with fish oil (n-3) and common vegetable oil (n-6) in decreasing serum lipids and platelet aggregation, various oils were included in Chow-based diets and fed to rats in an eight-weeks feeding trial. The Chow diet contained 2% cholesterol along with either Canola, menhaden, safflower, or partially hydrogenated soy oil, or no oil addendum. The menhaden oil group was the only one to show a significant reduction in serum cholesterol and triglycerides and at the same time yielded the most uniform decrease in platelet aggregability. However, this same group was also the only one to show a decrease in serum tocopherol levels, suggesting that improving an atherogenic risk profile may require antioxidant supplementation. In these rat trials, Canola oil supplementation did not yield the same results measured during menhaden supplementation.

Lipid metabolism following triglyceride ingestion in intact and adrenalectomized rats

Although both adrenalectomized and intact Long Evans rats absorbed the same amount of fat over a 24 hr period, the livers of the intact rats accumulated triglyceride while the livers of the adrenalectomized rats failed to do so. Of the glycerides excreted in the feces, the adrenalectomized rat excreted a significantly higher proportion of triglycerides while the intact rats excreted primarily monoglycerides. Fecal excretion of bile acids and phospholipids was significantly lower in the adrenalectomized rats compared to intact rats. Thus adrenal hormones appear to influence intestinal lipolysis. Serum and liver phospholipids appeared to be significantly lower in response to a fat load in adrenalectomized rats compared to intact rats. The phospholipid content of the small intestinal wall was five-fold higher in the intact rats than in the adrenalectomized rats. The adrenal gland appears to control phospholipid synthesis during triglyceride assimilation.

The hypolipidemic effect of SU-13,437 in rats with natural endogenous hypertriglyceridemia.

The oral administration of 25 mg 2-methyl-2-[p-(1,2,3,4-tetrahydro-1-naphthyl)-phenoxy] propionic acid (SU-13,437) per kilogram body weight per day in two-month-old female rats with naturally occurring hypertriglyceridemia resulted in a 31% decrease (P<0.01) in the serum triglyceride concentration after 14 days of treatment, compared with littermate controls receiving diluent (Polyethylene glycol-300) only. Phospholipid, cholesterol, free fatty acid, glucose, red blood cell and white blood cell concentrations were similar in the blood of treated and control animals after 14 days of treatment. Liver total and relative weight was increased as a result of SU-13,437 treatment (P<0.01). The liver total lipid concentration per 10 gm liver decreased (P<0.05) due to a decrease in triglyceride (P<0.01), cholesterol (P<0.01), and free fatty acid (P<0.05) concentration following treatment. The relative liver glycogen concentration was elevated in treated rats at 7 (P<0.01) and 14 (P<0.05) days of treatment.