T.R. Wrenn

Efficiency of transfer of polyunsaturated fats into milk.

Polyunsaturated milk has been produced by feeding cows safflower oil enclosed in a casein coat protected with formaldehyde (SOC-F) or formaldehyde-treated soybean (SB) preparations. The efficiency of transfer of dietary 18∶2 ranged from 17 to 42% for various lots of SOC-F and was only 2–8% for SB (per cent transfer=18.2 in milk fat per dietary 18∶2×100). The 18∶2 content of the milk fat increased from basal levels of 2–3% of total fatty acids to 35% with certain SOC-F levels and 7% with SB. Major compensatory changes were noted in 14∶0 and 16∶0 fatty acids. Blood cholesterol, triglycerides and nonesterified fatty acids all increased markedly as cows were fed increasing amounts of SOC-F. There was no increase in cholesterol in the milk.

Vitamin e, cholesterol, and lipids during atherogenesis in rabbits.

Rabbits were fed diets including cholesterol and 10% butterfat to determine whether polyunsaturated butter (9% 18∶2) would be less atherogenic than normal saturated butter (3% 18∶2) when fed for 12 weeks. The cholesterol diets alone, 0.5% or 2%, produced aortic plaque development, and plasma cholesterol increased 20 times, lipids increased 10 times, and vitamin E increased 5 times. The inclusion of both fat and cholesterol in the diet produced a synergistic effect, doubling these values to 40 times for cholesterol, 20 times for lipids, and 10 times for vitamin E. The higher circulating levels of cholesterol caused increased tissue levels of cholesterol. With 2% cholesterol and fat, liver and aorta cholesterol increased 10 times, heart 4 times, and muscle cholesterol 2 times. The lower 0.5% dietary cholesterol load was successful in limiting the amount of tissue cholesterol increase. Liver, aorta, heart, and muscle levels of cholesterol were only about half the concentration attained when 2% cholesterol was fed. It was concluded that there were no differences in plasma or tissue cholesterol, vitamin E, or atherosclerosis attributable to the polyunsaturated nature of the diet. The 10% butterfat diets alone, whether saturated or unsaturated, did not induce aortic plaques and did not increase blood or tissue cholesterol, lipids, or vitamin E. Our results suggest that the lipid mobilizing effect is mediated by cholesterol, probably by conversion to bile acids and a stimulation in intestinal absorption.

Effects of feeding formaldehyde treated, full fat soybean flours on milk fat polyunsaturated fatty acids

Raw, commercial, and extrusion cooked full fat soy flours were treated with formaldehyde and then fed to dairy cows. This treatment protected the polyunsaturated fats of the soy from hydrogenation by microbial action in the cow’s rumen. With all of these materials, higher than usual amounts of polyunsaturated fats were incorporated into the milk. In a screening test limited to one cow, an advantage as measured by milk yield, fat yield, protein, solids-not-fat, and increased milk fat C18:2 was seen for the formaldehyde treated, full fat soy flour. The percentage of linoleic acid more than doubled in the milk fat of cows receiving the protected products. Only very slight quantities of formaldehyde (0.1–0.2 ppm) were found in the milk. The efficiency of transfer of the C18:2 from the feed to milk was ca. 37%. This represented a marked improvement over previous trials in which we fed expensive safflower oil-casein-formaldehyde supplements.

Reduction of blood and liver cholesterol in the rat by straight and branched chain alkyl amines

The activities of a branched chain and several straight chain amines (C12 to C18 chain length), and the azasteroid 25-aza-5α-cholestane were compared with those of 20,25-diazacholesterol dihydrochloride, which is a potent hypocholesterolemic agent in the rat. These amines and azasteroids inhibit the Δ24-sterol reductase system in the tobacco hornworm,Manduca sexta (L.), and also block the conversion of C28 and C29 plant sterols to cholesterol, with a resulting accumulation of desmosterol. The effects of these compounds in the rat were determined on body weight gain, cholesterol, desmosterol, and lipid composition of blood, feces, liver, and epididymal fat pad weight. The two azasteroids and the branched chain amine, N,N-dimethyl-3, 7,11-trimethyldodecanamine, had the greatest effect, reducing total plasma lipids and plasma sterols to approximately 40–50% of the levels in control rats and produced a concomitant increase in plasma and liver desmosterol. The branched chain dodecanamine caused a reduction in both feed consumption and body weight gain. The branched and straight chain dodecanamines also severely reduced epididymal fat pad weight. Our results demonstrate that the simple azasteroid, 25-aza-5α-cholestane, is a more potent inhibitor of cholesterol biosynthesis than the diazasterol and that the Δ24-sterol reductase system in a mammal can be inhibited by simple, nonsteroidal, acyclic amines.

Effect of triundecanoin upon lipid metabolism in the cow.

The effect of feeding an odd-numbered carbon triglyceride, triundecanoin, upon lactation in the cow was studied. This fat appeared to be subject to considerable degradation in the rumen. There was no indication, however, that it yielded any increase in relative propionate concentration. A large amount of the odd-numbered carbon triglyceride was rejected by the animals, with a general decrease in feed consumption and consequent reduced milk yield. Fat production was unchanged. Some undecanoate passed into the milk but only at a low rate. There was a large difference in animal response. Feeding triundecanoin protected from rumen degradation led to a much greater transfer of undecanoate to the milk, prevented a significant decline in feed consumption and milk yield, but did not affect the milk composition appreciably. Smaller increases were observed in the amounts of other odd-numbered carbon fatty acids in the milk.

Stimulation of lipid absorption in young rats by cholesterol: Early time changes and effects on pentobarbital sleeping time

Four groups of young male and female rats were fed a chow diet (0), chow plus 10% corn oil (F), chow plus 1% cholesterol (C), or chow plus 1% cholesterol plus 10% corn oil (CF) for 1, 2, 4 and 8 days. After 2 dats, male F, C and CF rats exhibited a shorter anesthesia period (−20 to −30%) when given pentobarbital. By 4 days, male F and C rats had pentobarbital sleeping times (PB-ST) 20% less than 0 rats. These effects were additive and CF rats had 40% shorter PB-ST. Reduction of PB-ST by cholesterol and corn oil was similar but slightly less in female rats. Liver lipid content doubled in 4 days in CF rats, and liver cholesterol was 4 times that of 0 rats. These changes and the increases in metabolism of barbiturate suggested changes in liver microsomal enzyme activities. Serum glutamic oxaloacetic and glutamic pyruvic transaminase, two enzymes reflective of liver damage, did not increase after 8 days on C, F or CF diets. Our results suggest that consumption of an animal sterol and a high lipid diet by laboratory rats, normally consuming a diet low in fat (3–4%), increases the ability of the animal to detoxify a barbiturate. Storage of absorbed dietary cholesterol in the liver may represent a major mechanism for maintaining extra hepatic cholesterol homeostasis.

Necessity of vitamin B12 for growth of rats fed on an odd- or even-carbon-number fat.

1. The effect of vitamin B12 on growth was studied in young male and female rats fed on diets sufficient (+B12) or deficient (-B12) in vitamin B12 containing 30% of the dietary energy as fat, either maize oil (CO) or triundecanoin (TUD). 2. Vitamin B12 deficiency severely depressed growth. After 6 weeks the weight gain of CO(-B12) rats was only 72% of that of CO(+B12) rats and the gain of TUD(-B12) rats was only 47% of TUD(+B12) rats. 3. After fasting 24 or 96 h TUD-fed rats, both +B12 and -B12, had greater glycogen reserves and higher plasma glucose levels than CO-fed rats. 4. It is concluded that vitamin B12 is required for the metabolism and utilization of both an odd-carbon-number medium-chain fat, TUD, and an even-C-number long-chain fat, CO, during growth in rats.