Production of a rapid hypercholesterolemia in young chick by feeding coconut oil from two different sources and fatty acid composition

Jejunal wall triglyceride concentration of morbidly obese persons is lower in those with type 2 diabetes mellitus

The overproduction of intestinal lipoproteins may contribute to the dyslipidemia found in diabetes. We studied the influence of diabetes on the fasting jejunal lipid content and its association with plasma lipids and the expression of genes involved in the synthesis and secretion of these lipoproteins. The study was undertaken in 27 morbidly obese persons, 12 of whom had type 2 diabetes mellitus (T2DM). The morbidly obese persons with diabetes had higher levels of chylomicron (CM) triglycerides (P < 0.001) and apolipoprotein (apo)B48 (P = 0.012). The jejunum samples obtained from the subjects with diabetes had a lower jejunal triglyceride content (P = 0.012) and angiopoietin-like protein 4 (ANGPTL4) mRNA expression (P = 0.043). However, the apoA-IV mRNA expression was significantly greater (P = 0.036). The jejunal triglyceride content correlated negatively with apoA-IV mRNA expression (r = -0.587, P = 0.027). The variables that explained the jejunal triglyceride content in a multiple linear regression model were the insulin resistance state and the apoA-IV mRNA expression. Our results show that the morbidly obese subjects with diabetes had lower jejunal lipid content and that this correlated negatively with apoA-IV mRNA expression. These findings show that the jejunum appears to play an active role in lipid homeostasis in the fasting state.

Modification of phospholipids fatty acid composition in reuber H35 hepatoma cells: Effect on HMG-CoA reductase activity

There is controversy about the effect of saturated and polyunsaturated fats on 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase, the main regulatory enzyme of cholesterogenic pathway. Results from dietary studies are difficult to interpret because diets normally contain a mixture of fatty acids. Therefore, we have used Reuber H35 hepatoma cells whose phospholipids were enriched in different individual fatty acids and have studied their effects on the cellular reductase activity. Lauric, myristic, eicosapentaenoic (EPA), and docosahexaenoic (DHA) acids were supplemented to the culture medium coupled to bovine serum albumin. The four fatty acids were incorporated into phospholipids from cells grown in media containing whole serum or lipoprotein-poor serum (LPPS). Reductase activity of cells cultivated in a medium with LPPS was three to four times higher than those cultivated in medium with whole serum. Saturated fatty acids increased reductase activity of cells grown in medium with whole serum, whereas n-3 polyunsaturated fatty acids (PUFA) decreased it. However, both saturated and polyunsaturated fatty acids increased reductase activity when serum lipoproteins were removed. In conclusion, this is one of the first reports demonstrating that saturated and n-3 PUFA only show differential effects on HMG-CoA reductase activity in the presence of lipoproteins.

Influence of fasting status on the effects of coconut oil on chick plasma and lipoprotein composition

For a better understanding of the hyperlipidemic function of saturated fat, we have studied the effects of diet supplementation with 10-20% coconut oil on the chick plasma and lipoprotein composition under postprandial and starvation conditions. A significant hypercholesterolemia was found in chicks fed the standard diet after 12 h of food deprivation. In these conditions, LDL-cholesterol also increased, whereas triglyceride levels were reduced in HDL, VLDL and chylomicron fractions. Coconut oil induced a significant hypercholesterolemia under both conditions, also increasing the plasma triglyceride content under postprandial conditions, but not after starvation. Coconut oil feeding increased all the chemical components of HDL, especially under postprandial conditions, but did not affect the HDL-triglycerides under food-deprivation conditions. Total cholesterol and triglyceride levels in LDL increased after coconut oil supplementation to the diet. Differences were more pronounced under postprandial conditions. Changes in VLDL and chylomicron composition were less evident.

Differential changes in the fatty acid composition of the main lipid classes of chick plasma induced by dietary coconut oil

For a better understanding of the hyperlipidemic function of saturated fat, we have studied the comparative effects of diet supplementation with 10 and 20% coconut oil on the main lipid classes of chick plasma. Changes in fatty acid composition of free fatty acid and triglyceride fractions were parallel to that of the experimental diet. Thus, the increase in the percentages of 12:0 and 14:0 acids may contribute to the hypercholesterolemic effects of coconut oil feeding. Plasma phospholipids incorporated low levels of 12:0 and 14:0 acids whereas 18:0, the main saturated fatty acid of this fraction, also increased after coconut oil feeding. The percentage of 20:4 n-6 was higher in plasma phospholipids than in the other fractions and was significantly decreased by our dietary manipulations. Likewise, minor increases were found in the percentages of 12:0 and 14:0 acids in plasma cholesterol esters. However, the percentage of 18:2 acid significantly increased after coconut oil feeding. Our results show a relationship between fatty acid composition of diets and those of plasma free fatty acid and triglyceride fractions, whereas phospholipids and cholesterol esters are less sensitive to dietary changes.

Changes in plasma lipid composition induced by coconut oil. Effects of dipyridamole

The comparative effects of 10-20% coconut oil feeding on fatty acid composition of the main lipid classes of chick plasma have been studied with and without simultaneous treatment with dipyridamole in order to clarify the hypolipidemic role of this drug. Coconut oil drastically increased the percentages of lauric and myristic acids in free fatty acid and triacylglycerol fractions, whereas these changes were less pronounced in phospholipids and cholesterol esters. The percentage of arachidonic acid was higher in plasma phospholipids than in the other fractions and was significantly decreased by coconut oil feeding. Linoleic acid, the main fatty acid of cholesterol esters, was drastically increased by coconut oil feeding. Changes induced by the simultaneous administration of dipyridamole were more pronounced in the phospholipids and cholesterol esters than in the other fractions. The fall observed in linoleic acid levels after dipyridamole treatment may be of interest for a lower production of its derived eicosanoids, especially in plasma phospholipids and cholesterol esters.

Dipyridamole prevents the coconut oil-induced hypercholesterolemia. A study on lipid plasma and lipoprotein composition

For a better understanding of the hypolipidemic function of dipyridamole, we have studied the comparative effects of diet supplementation with 10% coconut oil with and without dipyridamole on the lipid plasma and lipoprotein composition in chicks. This study was performed under postprandial and food-deprivation (12h) conditions. Coconut oil induced a clear hypercholesterolemia under both feeding conditions. Simultaneous administration of dipyridamole maintained total and esterified cholesterol at levels similar to those observed in control animals sacrificed under postprandial conditions. Under these conditions, our results also show that dipyridamole significantly reduced cholesterol levels in all the chick plasma lipoproteins that were increased by coconut oil administration. Nevertheless, it should be emphasised that the levels of total cholesterol found in intermediate- and very-low-density lipoproteins were lower than in control. All chemical components of these fractions were significantly decreased by dipyridamole. The effects were not significant in chicks deprived of food. In conclusion, our results show that the hypercholesterolemia induced by coconut oil was prevented by dipyridamole. To our knowledge, this is one of the first reports on the antihypercholesterolemic effects of dipyridamole.

Dipyridamole reduces cholesterol and triglyceride levels in plasma and lipoproteins from young chicks fed a saturated fat-enriched diet

We have studied the value of dipyridamole for the prevention of hypercholesterolemia caused by saturated fat. This study shows that supplementation of 10-20% coconut oil to the diet induced a significant hypercholesterolemia under postprandial conditions. Simultaneous administration of dipyridamole and 10% coconut oil for 2 weeks maintained plasma cholesterol and triglycerides at levels similar to control, counteracting the increase induced by coconut oil. Dipyridamole significantly reduced cholesterol levels in all the chick plasma lipoproteins that were increased by coconut oil administration. However, it should be emphasized that cholesterol and other chemical components were more drastically reduced by dipyridamole in intermediate- and very-low-density lipoproteins than in other lipoprotein fractions.

Hypocholesterolemic activity of dipyridamole: effects on chick plasma and lipoprotein composition and arachidonic acid levels

We have studied the effects of dipyridamole treatment on chick plasma and lipoprotein composition in postprandial and fasting (12 h) conditions. Plasma cholesterol levels were higher in fasted than in fed chicks, whereas triglycerides declined during starvation. Dipyridamole treatment reduced plasma cholesterol content, mainly of the free cholesterol fraction. In postprandial conditions, total cholesterol content of high and low density lipoproteins decreased in a similar proportion to that observed in plasma. However, cholesterol and other chemical constituents of intermediate and very low density lipoproteins were more drastically reduced by dipyridamole than in plasma. Total amounts of these lipoprotein fractions were also reduced about 50%. The effects of dipyridamole in fasted animals were not significant. To our knowledge, this is one of the first reports about the response of lipoprotein cholesterol to dipyridamole treatment. A strong decrease was also found in the arachidonic acid content of plasma phospholipids and cholesterol esters fractions.

Coconut oil induces short-term changes in lipid composition and enzyme activity of chick hepatic mitochondria

We studied the short-term effects of a 20% coconut oil supplementation to the chick diet on lipid composition of liver and hepatic mitochondria, and changes that occurred in mitochondrial-associated enzymes as a result of this diet. No significant differences were observed in the lipid contents of liver when young chicks were fed the experimental diet, whereas hepatic mitochondria rapidly changed in response to this diet. Total cholesterol significantly increased in mitochondria at 24 hours of coconut oil diet feeding and decreased when dietary treatment was prolonged for 5 to 14 days. Changes in total mitochondrial phospholipids showed an inverse profile. A significant decrease in phosphatidylethanolamine and an increase in sphingomyelin were found at 24 hours. The cholesterol/phospholipid molar ratio significantly and rapidly (24 hours) increased in mitochondria from treated animals. Cytochrome oxidase activity drastically increased after 24 hours of experimental diet feeding and lowered to the control values when dietary manipulation was prolonged for 5 to 14 days. ATPase activity showed an inverse profile. Changes in cytochrome oxidase activity were parallel to changes in the cholesterol/phospholipid molar ratio, whereas changes in ATPase activity showed an inverse correlation with changes in this molar ratio. To our knowledge, this is one of the first reports on the very rapid response (24 hours) of mitochondrial lipid composition and function to saturated fat feeding.

Differential effects of dietary fat on chick plasma and liver composition and HMG-CoA reductase activity

The comparative effects of diet supplementation with 10% saturated fat rich in 12:0 and 14:0 fatty acids (coconut oil), without and with 1% added cholesterol, and with 10% unsaturated fat rich in n-3 polyunsaturated fatty acids (menhaden oil) on cholesterol metabolism in neonatal chicks were examined to clarify the different mechanisms of their hyper- and hypolipidemic action. Supplementation of coconut oil produced a significant hypercholesterolemia after 7 days of treatment, with a similar increase in the amount of both free and esterified cholesterol. Supplementation of coconut oil plus cholesterol produced a higher increase of plasma cholesterol levels (approximately two to three times higher than those found with standard diet). However, supplementation of menhaden oil induced a significant decrease in total cholesterol after only 2 weeks of treatment. Levels of plasma triglycerides did not change by coconut oil addition to the diet, but a significant increase was observed after coconut oil plus cholesterol feeding. Menhaden oil produced a transient decrease in plasma triglycerides. Hepatic 3-hydroxy-3-methylglutaryl-CoA reductase activity did not change with coconut oil treatment. However, both coconut oil plus cholesterol and menhaden oil supplemented diets drastically decreased reductase activity after 1 week of dietary manipulation. These results show that different nutrients with the same inhibitory effect on reductase activity produced opposite effects on plasma cholesterol content, suggesting the existence of important differences in the regulatory mechanisms implied in cholesterol biosynthesis and its accumulation in plasma.