Cloning of rabbit LCAT cDNA: increase in LCAT mRNA abundance in the liver of cholesterol-fed rabbits

Lecithin: cholesterol acyltransferase--from biochemistry to role in cardiovascular disease

PURPOSE OF REVIEW

We discuss the latest findings on the biochemistry of lecithin : cholesterol acyltransferase (LCAT), the effect of LCAT on atherosclerosis, clinical features of LCAT deficiency, and the impact of LCAT on cardiovascular disease from human studies.

RECENT FINDINGS

Although there has been much recent progress in the biochemistry of LCAT and its effect on high-density lipoprotein metabolism, its role in the pathogenesis of atherosclerosis is still not fully understood. Studies from various animal models have revealed a complex interaction between LCAT and atherosclerosis that may be modified by diet and by other proteins that modify lipoproteins. Furthermore, the ability of LCAT to lower apoB appears to be the best way to predict its effect on atherosclerosis in animal models. Recent studies on patients with LCAT deficiency have shown a modest but significant increase in incidence of cardiovascular disease consistent with a beneficial effect of LCAT on atherosclerosis. The role of LCAT in the general population, however, has not revealed a consistent association with cardiovascular disease.

SUMMARY

Recent research findings from animal and human studies have revealed a potential beneficial role of LCAT in reducing atherosclerosis but additional studies are necessary to better establish the linkage between LCAT and cardiovascular disease.

Apolipoprotein A-I and lecithin:cholesterol acyltransferase transfer induce cholesterol unloading in complex atherosclerotic lesions

Plasma levels of high-density lipoprotein (HDL) cholesterol and its major apolipoprotein (apo), apo A-I, are inversely correlated with the incidence of ischemic cardiovascular diseases. Reverse cholesterol transport is likely the main mechanism underlying the atheroprotective effects of HDL. Here, we investigated whether increased HDL cholesterol following hepatocyte-directed adenoviral rabbit apo A-I (AdrA-I) or rabbit lecithin-cholesterol acyltransferase (LCAT) (AdrLCAT) transfer may induce cholesterol unloading in complex atherosclerotic lesions in heterozygous low-density lipoprotein receptor-deficient rabbits fed a 0.15% cholesterol diet for 420 days before and for 120 days after transfer. HDL cholesterol levels increased 2.0-fold (P<0.001) and 1.9-fold (P<0.001) in the 120 days after transfer with AdrA-I and AdrLCAT, respectively, compared to levels just before transfer whereas non-HDL cholesterol remained unchanged. Increased HDL cholesterol following AdrA-I and AdrLCAT transfer resulted in a 31% (P<0.05) reduction of the intima/media ratio in comparison with the control progression group. Compared to the baseline group killed after 420 days of cholesterol diet, AdrA-I and AdrLCAT transfer reduced the percentage of Oil Red O area 1.6-fold (P<0.001) and 1.4-fold (P<0.001), respectively. In conclusion, increased HDL cholesterol after AdrA-I and AdrLCAT transfer inhibits progression of atherosclerosis and induces cholesterol unloading in complex lesions in rabbits.

Hypoglycemic and hypocholesterolemic potential of Persea americana leaf extracts

The effect of aqueous and methanolic leaf extracts of Persea americana on plasma glucose, total cholesterol, low-density lipoprotein cholesterol (LDL-CHOL), and high-density lipoprotein cholesterol (HDL-CHOL) in rats was investigated. Albino rats were fed a diet containing 20% groundnut oil, 0.5% cholesterol, and 0.25% cholic acid to induce hypercholesterolemia. They were then treated daily with aqueous or methanolic extract of P. americana leaf (10 mg/kg of body weight) for 8 weeks. There were no significant (P > .05) differences in the overall body weight gain of the hypercholesterolemic rats compared to normal control. Liver to body weight ratio, plasma glucose, total cholesterol (T-CHOL), and LDL-CHOL levels were significantly (P < .05) elevated in rats fed hypercholesterolemic diet compared to normal controls. The administration of aqueous and methanolic leaf extracts of P. americana induced reductions in plasma glucose (16% and 11%,respectively), T-CHOL (8% and 5%, respectively), and LDL-CHOL (19% and 20%, respectively) in the treated rats compared to the hypercholesterolemic controls. Also, plasma HDL-CHOL concentrations increased by 85% and 68%, respectively, in the aqueous and methanolic extract-treated rats compared to the hypercholesterolemic controls. These results suggest that aqueous and methanolic leaf extracts of P. americana lower plasma glucose and influence lipid metabolism in hypercholesterolemic rats with consequent lowering of T-CHOL and LDL-CHOL and a restoration of HDL-CHOL levels. This could represent a protective mechanism against the development of atherosclerosis.

Alterations in carbohydrate and lipid metabolism induced by a diet rich in coconut oil and cholesterol in a rat model

OBJECTIVE

The type of dietary fat as well as the amount of cholesterol occurring in the diet have been associated with several metabolic disorders. Thus, the aim of the present study was to investigate the influence of a hypercholesterolemic diet enriched with coconut oil and cholesterol on carbohydrate and lipid metabolism in a rat model.

METHODS

Twenty male Wistar rats weighing about 190 g were assigned to two dietary groups. One group received a semipurified control diet and the other was given a diet enriched in coconut oil (25% by weight) and cholesterol (1% by weight) for 26 days.

RESULTS

Our results indicated a significant increase in serum total cholesterol (+285%; p<0.001), low-density lipoproteins (+154%; p<0.01), liver cholesterol (+1509%; p<0.001), as well as a significant increase in liver weight (+46%; p<0.001) in those rats fed the hypercholesterolemia-inducing diet as compared to controls. Moreover, a significant decrease in serum high-density lipoproteins (-67%; p<0.001), triacylglycerols levels (-33%; p<0.05), and abdominal fat weight (-39%; p<0.01) were found. The observed alterations in serum lipid and lipoprotein profile resembled a situation of type IIa hyperlipidemia in humans. Measurement of several enzymes concerned with lipid utilization revealed a significant increase in 3-hydroxy-3-methylglutaryl-CoA reductase activity (+68%; p<0.01) in the liver of animals fed the hypercholesterolemic diet, while a significant reduction in plasma lecithin-cholesterol acyltransferase activity (-66%; p<0.001) was found. The situation of hypoglycemia (-18%; p<0.05) was accompanied by lower levels of serum insulin (-45%; p<0.01) and liver glycogen (-30%; p<0.05) in the hypercholesterolemic rats. Furthermore, glucose utilization was altered since lower glucose-6-Pase (-33%; p<0.05) and increased glucokinase (+212%; p<0.001) activities in the liver were found in the rat model of hypercholesterolemia.

CONCLUSION

These results provide new evidence that a diet-induced hypercholesterolemia in rats is associated with several adaptative changes in carbohydrate metabolism. These findings may be of importance not only considering the role of western diets on cholesterogenesis, but also in other metabolic disturbances involving lipid and carbohydrate metabolism.

Animal models: nutrition and lipoprotein metabolism

Despite limitations, animal models continue to provide insight into the etiology of atherosclerosis. Hamsters, guinea-pigs, and domesticated pigs are being used more frequently to address the biochemical bases for the effects of dietary lipids on cholesterol metabolism.