P. Budowski

Lipid oxidation products and chick nutritional encephalopathy

Safflower oil and its distilled methyl esters were thermally oxidized and fed to young chicks in a vitamin E deficient diet. At a dietary level of 10%, the oxidized lipids caused more severe nutritional encephalopathy (NE) than the unoxidized methyl esters, indicating that factors other than dietary linoleic acid and vitamin E affect the development of NE. A polar lipid extract from oxidized methyl esters accelerated the induction of NE, as did the synthetic methyl esters of keto-octadecenoic and keto-octadecadienoic acids. Dicumarol exerted a protective action against NE. The possibility is discussed that conjugated keto-polyenoic fatty acids, provided by oxidized oils or formed endogenously in vitamin E deficiency, may play a role in causing NE.

Absorption of oleic and taurocholic acids from the intestine of the chick. Interactions and interference by proteins.

Abstract The interaction between fatty acids, bile acids and proteins in the intestinal lumen and its effect on the mucosal uptake of fatty acids and bile acids in chicks were studied in situ by means of ligated duodenal loops. The basal medium introduced into the loops contained oleic and taurocholic acids in bicarbonate buffer at pH 6.5, with trace amounts of [14C]oleic acid and [14C]-taurocholic acid, [3H]dextran serving as a nonabsorbable reference substance. Tests conducted with varying initial concentrations of oleic acid and taurocholic acid pointed to an optimal molar ratio of oleic acid to taurocholic acid at which the rates of mucosal uptake of both compounds were highest and numerically equal. Addition of casein, albumin or soy protein to the medium caused considerable inhibition of both oleic acid and taurocholic acid uptake. Taurocholic acid uptake alone, or that of the slightly water-soluble lauric acid alone, was similarly decreased by protein. Predigestion of the proteins with pepsin A (EC 3.4.23.1) or elastase (EC 3.4.21.11) eliminated the inhibitory effect on uptake of oleic acid and taurocholic acid. It was shown that casein is able to bind both oleic acid and taurocholic acid. Thus the presence of undigested protein in the upper small intestine of the chick may interfere with the mucosal uptake of lipids by a double action involving direct binding of fatty acids to the protein and disturbance of micellar solubilization of the lipids because of binding of bile acids.

Site of bile acid absorption in the rat

Bile acid absorption was measured in the small intestine of the rat using91Y as a nonabsorbed reference substance. Some 50% of the secreted bile acids were absorbed in the proximal half of the small intestine. In situ incubations of ligated intestinal segments into which tauro(14C-carbonyl)cholic acid was introduced confirmed the considerable uptake of bile acids in the jejunum. The in situ experiments indicated that serosal transport is the limiting stage of bile acid absorption in the jejunum but not in the ileum. Increasing bile acid concentrations in the in situ experiments did not affect the percentage disappearance of dose from the jejunum but reduced the percentage mucosal uptake in the ileum. It is concluded that, in the rat, the proximal small intestine is as important in the absorption of bile acids as the distal small intestine.

Intestinal absorption and plasma transport of lipids in chicks and rats

Labelled oleic acid was introduced into the duodenum of chicks in which the pancreatic-duodenal vein and brachial artery had been cannulated, and blood samples were withdrawn. Similar experiments were performed in rats which had not been venously cannulated. In rat plasma, over 92% of the label was found in the triglycerides, whereas in the chick 64% of the label was in the triglycerides and 27-31% in the free fatty acids. In the rat, over 85% of the lipid label circulating in the plasma was found in lipoproteins with hydrated density less than 1.006, whereas in the chick only 25% of the label was in this fraction and the majority of label was found with density greater than 1.063. It thus appears that both release and transport of fatty acids from the intestinal mucosa in chicks differs from the rat.

Response of lipogenic enzymes to overfeeding in liver and adipose tissue of light and heavy breeds of chicks

1. Chicks, 3-d-old, of a heavy breed (HB) and a light breed (LB) were overfed for 18 d. The activities of acetyl-CoA carboxylase ( EC 6.4.1.2; CBX), fatty acid synthetase (FAS), ATP citrate lyase ( EC 4.1.3.8; CCE), NADP-malate dehydrogenase (decarboxylating) ( EC 1.1.1.40; ME), 6-glucose-6-phosphate dehydrogenase ( EC 1.1.1.49; G6PDH) and phosphogluconate dehydrogenase ( EC 1.1.1.44; 6PGDH) were determined in abdominal adipose tissue (AT) and liver samples of overfed and ad lib. -fed chicks. Size and fat content of liver and adipose tissue were also determined in order to evaluate the extent of obesity. 2. On ad lib. -feeding HB chicks consumed more food, gained more weight and deposited more fat than the corresponding LB chicks. Their lipogenic enzymes were more active than in the LB chicks in both adipose tissue and liver. The increase in food consumption (%) that could be achieved by overfeeding was three times greater in the LB chicks than in the HB chicks. 3. Overfeeding increased the weight and fat content of liver and AT in both breeds. The specific activities of CBX, FAS, CCE and ME in liver and AT increased in the LB chicks only and the total activities of liver and AT enzymes increased much more in the LB chicks than in the HB chicks in which the increase was derived mainly from tissue enlargement. 4. The activity of the pentose cycle dehydrogenases was very low in liver, but in AT about one third of the NADPH generating capacity could be accounted for by these dehydrogenases. 5. The results show that lipogenic enzymes of chicks respond to an increased substrate flux. It is suggested that the enlarged liver, the higher participation of AT in lipogenesis and the uninterrupted supply of cropstored excess food enable the chick to accommodate the increased amounts of substrate with only moderate enzymic adaptation.

The effect of lipids on taurocholate absorption from intestinal loops in the rat

The rates of uptake and serosal trans-fer of [14C]-labelled taurocholate (7.77 mM in bicarbonate buffer, pH 6.5) were determined in situ in ligated segments of rat intestine in the presence of lipids. Oleic acid, monoolein, lecithin, and lysolecithin enhanced taurocholate uptake and transfer in the jejunum, each lipid exhibiting and optimal concentration at which the bile acid fluxes were maximal. The maximal rates of bile acid uptake observed with the various lipids were close to four times the uptake rates found with the lipid-free taurocholate medium, whereas serosal transfer rates under optimal conditions were enhanced about six-fold. The optimal concentrations differed widely among the various lipids, being inversely related to the lipids’ polarity. Simultaneous measurement of taurocholate and [3H]-labelled oleic acid showed that under optimal conditions, when the molar concentration of oleic acid was about equal to that of the bile acid, the fatty aicd and bile acid also exhibited closely similar rates of absorption. At other fatty acid concentrations, the fractional rate of absorption of the bile acid was much lower than that of the fatty acid. The rates of uptake and serosal transfer of pure taurocholate by the ileum exceeded those of the jejunum by factors of about 7 and 15, respectively, but in the presence of lipids this difference in absorptive capacity for bile acid between the distal and proximal segment largely disappeared.

Cholesterol metabolism in the liver and intestine of the chick: Effect of dietary cholesterol, taurocholic acid and cholestyramine

The effect of feeding cholesterol, taurocholic acid, or cholestyramine to chicks on cholesterolgenesis from [1-14C] acetate in liver and intestine was determined in vitro using tissue slices, and in vivo by i.v. injection of [14C] acetate. The conversion of cholesterol to bile acids in liver in vivo was measured in the same treatments after i.v. injection of [3H] cholesterol. Hepatic cholesterogenesis in vitro and in vivo was depressed by dietary cholesterol and taurocholate and enhanced by cholestyramine. Intestinal cholesterogenesis in vivo was depressed only by taurocholate whereas ileal cholesterogenesis in vitro was reduced by dietary cholesterol. Conversion of cholesterol to bile acids was enhanced by dietary cholesterol and cholestyramine and depressed by taurocholate. Hepatic cholesterol metabolism in the chick appears to be regulated by mechanisms similar to those reported for other species.

Lipoxygenase and other enzymes of arachidonic acid metabolism in the brain of chicks affected by nutritional encephalomalacia

1. Prostaglandin endoperoxide synthetase (PES) and lipoxygenase (Lox) activities were compared in the cerebella and cerebra of vitamin E-sufficient young chicks and in chicks in which nutritional encephalomalacia (NE) was induced by a diet deficient in vitamin E. 2. Eicosanoid production patterns were qualitatively similar in the brains of both groups of chicks, but prostaglandin production was 50-60% less in cerebella of ataxic chicks, compared to control cerebella, while the opposite trend was observed in the cerebellar Lox pathway, as measured by radioimmunoassay of 15-HETE. 3. Cerebellar phospholipase A2 activity was twice that of the cerebrum but was not affected by NE. 4. Purification of Lox activity from the cerebellar homogenates produced a lower yield and enrichment when the starting material was taken from ataxic chicks, compared to the controls. 5. In addition there were qualitative differences in the purified fractions from both groups, as seen by pH optima and kinetics. 6. The results are consistent with the view that the cerebellum has less antioxidant protection than the cerebrum and that its higher phospholipase A2 activity and greater propensity to oxygenate arachidonic acid via the Lox pathway at the expense of the PES pathway may render this region of the brain particularly vulnerable to oxidative damage in NE.

The effect of phytosterols on the growth and sterol composition of Dermestes maculatus

Abstract Evidence is presented showing that several common plant sterols interfere with the growth-promoting action of cholesterol in the larvae of Dermestes maculatus when the latter are reared at 35% r.h. Phytosterols do not exhibit this effect when the larvae are grown at 65% r.h. There is, however, a pronounced interference by the plant sterols with the uptake of cholesterol, the cholesterol content of the larvae being reduced to about half its normal level. Campesterol occupies a unique place among the phytosterols tested, because of its ability to replace cholesterol with regard to growth and pupation. This property appears to be due to the ready uptake of campesterol by Dermestes , coupled with its partial conversion into cholesterol, and represents an interesting case of utilization of a typical phytosterol by a zoophagous insect.

Response of lipogenic enzymes and plasma lipids to starvation and refeeding in the adult Japanese quail (Coturnix coturnix japonica).

Adult male Japanese quail ( Coturnix coturnix japonica ) were starved for 48 or 60 h and then refed for either 24 or 48 h. Weight and lipid content of carcass and livers were determined, as was the lipid content of plasma. In addition, the activities of acetyl-CoA carboxylase ( EC 6.4.1.2; CBX), fatty acid synthetase (FAS), ATP citrate lyase ( EC 4.1.3.8; CCE) and malate dehydrogenase (decarboxylating) (NADP) ( EC 1.1.1.40; ME) were assayed in liver and in abdominal and neck adipose tissues (AAT and NAT, respectively). Body-weight and carcass lipids failed to return to normal in quail that had been starved for 48 h and refed during 24 h. When starving lasted 60 h, carcass lipids almost resumed the normal level only after 48 h of refeeding. All refeeding treatments caused a 2–3-fold increase in liver weight, with a parallel rise in fat content. In the livers of the refed quail the specific activities of all enzymes, except CBX, reached or slightly exceeded pre-starvation levels. Because of liver enlargement, the total activities of the lipogenic enzymes in the starved–refed quail exceeded pre-starvation levels. In the normally-fed quail the contribution of AAT and NAT to total lipogenesis was insignificant, and in the starved–refed birds it still remained very small compared to that of liver, despite the pronounced relative increase of lipogenic enzyme activities in these adipose tissues.