Hepatic expression of apolipoprotein A-I gene in rats is upregulated by monounsaturated fatty acid diet

Adding MUFA to a dietary portfolio of cholesterol-lowering foods reduces apoAI fractional catabolic rate in subjects with dyslipidaemia

The present randomised parallel study assessed the impact of adding MUFA to a dietary portfolio of cholesterol-lowering foods on the intravascular kinetics of apoAI- and apoB-containing lipoproteins in subjects with dyslipidaemia. A sample of sixteen men and postmenopausal women consumed a run-in stabilisation diet for 4 weeks. Subjects were then randomly assigned to an experimental dietary portfolio either high or low in MUFA for another 4 weeks. MUFA substituted 13·0 % of total energy from carbohydrate (CHO) in the high-MUFA dietary portfolio. Lipoprotein kinetics were assessed after the run-in and portfolio diets using a primed, constant infusion of [2H3]leucine and multicompartmental modelling. The high-MUFA dietary portfolio resulted in higher apoAI pool size (PS) compared with the low-MUFA dietary portfolio (15·9 % between-diet difference, P= 0·03). This difference appeared to be mainly attributable to a reduction in apoAI fractional catabolic rate (FCR) after the high-MUFA diet ( − 5·6 %, P= 0·02 v. pre-diet values), with no significant change in production rate. The high-MUFA dietary portfolio tended to reduce LDL apoB100 PS compared with the low-MUFA dietary portfolio ( − 28·5 % between-diet difference, P= 0·09), predominantly through an increase in LDL apoB100 FCR (23·2 % between-diet difference, P= 0·04). These data suggest that adding MUFA to a dietary portfolio of cholesterol-lowering foods provides the added advantage of raising HDL primarily through a reduction in HDL clearance rate. Replacing CHO with MUFA in a dietary portfolio may also lead to reductions in LDL apoB100 concentrations primarily by increasing LDL clearance rate, thus potentiating further the well-known cholesterol-lowering effect of this diet.

Nutritional Intervention Study with Argan Oil in Man: Effects on Lipids and Apolipoproteins

AIM

To evaluate whether the consumption of virgin argan oil (VAO) is associated with a change in serum lipids and reduces the risk of cardiovascular disease in healthy Moroccans.

METHODS

Sixty volunteers consumed butter (25 g/day) during 2 weeks (stabilization period) and were randomly divided into two groups: the treatment group received 25 g/day of VAO during 3 weeks (intervention period), and the control group received 25 g/day of extra virgin olive oil (EVO). Throughout the study, weight, blood pressure, and daily food intake were measured. Serum total cholesterol and low- and high-density lipoprotein cholesterol, triglycerides, and apolipoproteins A-I and B were measured at the end of each diet period.

RESULTS

Analysis of food intake showed that the daily diet is isocaloric for the butter regimen (2,537 +/- 244 kcal/day) as well as for the VAO and EVO regimens (2,561+/- 246 and 2,560 +/- 253 kcal/day, respectively). Analysis of the lipid intake showed a reduction in saturated fatty acids with VAO and EVO regimens (27 +/- 1.4 and 26.4 +/- 3.4%, respectively) as compared with the stabilization period (41.6 +/- 2.4%). The analysis of serum lipids showed a significant increase in high-density lipoprotein cholesterol and apolipoprotein A-I in both VAO group (8.4%, p = 0.012, and 5.2%, p = 0.027, respectively) and EVO group (17.3%, p = 0.001, and 5.9%, p = 0.036, respectively). However, low-density lipoprotein cholesterol and apolipoprotein B (13.8%, p = 0.037, and 7.8%, p = 0.039, respectively) decreased significantly only in EVO group as compared with the stabilization period, while triglycerides decreased significantly by 17.5% (p = 0.039) only in VAO group.

CONCLUSION

These results confirm the cholesterol-lowering effect of EVO and show for the first time the triglyceride-lowering effect of VAO in men.

Increased beef consumption increases apolipoprotein A-I but not serum cholesterol of mildly hypercholesterolemic men with different levels of habitual beef intake

The objective of this research was to compare the effects of a lean beef enriched in oleic acid to a beef that is typical of the commercial beef consumed in the United States. Ten mildly hypercholesterolemic men, ages 34-58 years old, were selected from the Texas A&M University faculty and staff. Subjects were randomly assigned to one of two diets for a 6-week duration followed by a crossover after a 4-week habitual diet washout period. Diets were consumed daily for a 6-week study period. Participants substituted lean beef obtained from Wagyu bullocks or commercial beef for the meat typically consumed. Total cholesterol, apolipoproteins A-I and B, triacylglycerols, and low-density lipoprotein (LDL) and high-density lipoprotein (HDL) cholesterol were measured in serum samples collected weekly. Beef type had no effect on any measured variable. There were no significant differences between baseline HDL or LDL cholesterol concentrations after the consumption of the beef test diets. Apolipoprotein A-I, serum glucose, and uric acid concentrations were elevated by the additional dietary beef. Analysis of records of customary diets indicated that one group consumed 160 g of beef daily, whereas the other group consumed only 26 g of beef daily. Therefore, post hoc analyses tested the habitual beef intake x treatment time interaction. LDL cholesterol concentration was markedly higher in the group with low habitual beef intake (180 vs 144 mg/dl), and HDL cholesterol was slightly higher (44 vs 40 mg/dl; post-test values) than for the group with high habitual beef intake, but there were no habitual intake x time interactions for LDL or HDL cholesterol. Creatinine and blood urea nitrogen concentrations also were greater in the individuals habitually consuming less beef. This study had three important findings: i) a lean beef source enriched with oleic acid was no different from commercial beef in its effect on lipoprotein fractions; ii) neither previous level of beef intake nor baseline LDL cholesterol concentration influenced the serum cholesterol response to added dietary beef, which was negative; and iii) apolipoprotein A-I, but not HDL or LDL cholesterol, was sensitive to the additional dietary beef.

Dietary fat saturation affects apolipoprotein AII levels and HDL composition in postmenopausal women

Increased HDL-cholesterol levels have been associated with lower coronary heart disease (CHD) risk. However, HDL are heterogeneous lipoproteins, and particles enriched in apolipoprotein (Apo) AII have been associated with increased CHD risk. We examined the effect of dietary intervention on HDL composition in 14 postmenopausal women subjected to two consecutive diet periods, i.e., an oleic acid sunflower oil diet followed by a palmolein diet, each lasting 4 wk. The linoleic acid was kept at 4% total energy and the cholesterol intake at 400 mg/d. The palmolein diet increased serum total cholesterol (TC) (P < 0.001), phospholipids (P < 0.001), Apo AII (P < 0.001), HDL cholesterol (P < 0.05), HDL lipids (P < 0.05), HDL proteins (P < 0.01) and the HDL total mass (P < 0.05). The HDL cholesterol/Apo AI ratio was increased 22.0% (P < 0.05), whereas the HDL cholesterol/Apo AII and the Apo AI/Apo AII ratios were decreased 19.4% (P < 0.01) and 30.4%, (P < 0.001), respectively. When the effects of the dietary intervention were examined according to the cholesterolemia status (< or >6.2 mmol/L), the most significant changes (P < 0.001) were related to Apo AII levels. Moreover, a significant dietary oil by cholesterol level interaction was found for Apo AII and the HDL cholesterol/Apo AII ratio. In summary, a palmolein diet increased TC and HDL cholesterol compared with oleic acid sunflower oil diet; however, the increase in Apo AII but not in Apo AI suggests the impairment of reverse cholesterol transport and potentially an increase in CHD risk. This effect was more marked in women with serum TC > 6.2 mmol/L.

Effects of dietary fat amount and saturation on the regulation of hepatic mRNA and plasma apolipoprotein A-I in rats

The effects of the amount of dietary fat and saturation together with cholesterol both on hepatic apolipoprotein A-I gene mRNA levels and on plasma levels of this apolipoprotein were studied in male rats. To achieve these goals, seven groups of male Wistar rats were established: control group (n=5) consuming chow diet; cholesterol group (n=4) fed on a chow diet containing 0.1% (w/w) cholesterol; coco group (n=5) fed on a chow diet containing 0.1% (w/w) cholesterol and 40% coconut oil; corn group (n=5) fed on a chow diet containing 0.1% (w/w) cholesterol and 40% corn oil; and three olive groups consuming a chow diet containing 0.1% (w/w) cholesterol and percentages of 5 (n=5), 10 (n=4) and 40% (n=5), respectively, of olive oil. Animals were kept on these diets for 2 months and then sacrificed for lipoprotein, apolipoprotein and hepatic mRNA analysis. Dietary cholesterol by itself was hypercholesterolemic when compared to chow diet, an effect that was mainly due to an increase in LDL-cholesterol. Corn oil had a hypocholesterolemic action, whether compared to chow or to cholesterol diet, due to a reduction in HDL-cholesterol as well as LDL-cholesterol. HDL-cholesterol levels of 40% olive oil diet were lower than those corresponding to coconut oil and higher than those found in corn oil diet. When compared to control or cholesterol diets, plasma apoA-I concentration appeared significantly increased in coconut and 40% olive oil diets. Coconut oil or corn oil diets did not induce any significant change in apoA-I mRNA compared to control or cholesterol diets. Compared to cholesterol diet, 40 and 10% olive oil diets induced a significant increase in the expression of this message. A positive and significant (r=0.97, P<0.01) correlation between plasma apolipoprotein A-I concentration and its hepatic mRNA, was observed when the amount of dietary olive oil was 40% (w/w). A significant negative (r=-0.97, P<0.01) correlation was found in the corn oil group and no significant association was observed in the remaining groups. Based on the increased plasma levels in coconut oil and in high percentage olive oil diets, and the differences between these two diets for mRNA expression, it can be concluded that different fatty acid containing diets regulate apolipoprotein A-I through different mechanisms, and these mechanisms could be modulated by the fat intake.

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.

Regulation of rat liver apolipoprotein A-I, apolipoprotein A-II and acyl-coenzyme A oxidase gene expression by fibrates and dietary fatty acids

The regulation by fibrates and dietary fatty acids of the hepatic gene expression of apolipoproteins (apo) A-I and A-II, the major protein constituents of high-density lipoproteins, as well as of acyl-CoA oxidase, the rate-limiting enzyme of the peroxisomal beta-oxidation pathway, was studied in vivo in the rat and in vitro in primary cultures of rat hepatocytes. In primary hepatocytes, different fibrates decreased apo A-I and increased acyl-CoA oxidase mRNA levels, whereas apo A-II mRNA only decreased in level after treatment with fenofibric acid, but not after bezafibrate, gemfibrozil or Wy-14643 treatment. Treatment with fenofibric acid counteracted the increase in apo A-I mRNA levels observed after dexamethasone or all-trans retinoic acid treatment, whereas simultaneous addition of fenofibric acid together with all-trans retinoic acid or dexamethasone resulted in a superinduction of acyl-CoA oxidase mRNA. Addition of the n-3 polyunsaturated fatty acids (PUFAs), docosanohexaenoic acid and eicosanopentaenoic acid, or the fatty acid derivative alpha-bromopalmitate, decreased apo A-I and increased acyl-CoA oxidase mRNA in a dose-dependent and time-dependent manner, whereas apo A-II mRNA did not change significantly. Nuclear run-on experiments demonstrated that fenofibric acid and alpha-bromopalmitate decreased apo A-I and increased acyl-CoA oxidase gene expression at the transcriptional level. When rats were fed isocaloric diets enriched in saturated fat (hydrogenated coconut oil), n-6 PUFAs (safflower oil) or n-3 PUFAs (fish oil), a significant decrease in liver apo A-I and apo A-II mRNA levels was only observed after fish oil feeding. Compared to feeding low fat, liver acyl-CoA oxidase mRNA increased after fat feeding, but this effect was most pronounced (twofold) in rats fed fish oil. Results from these studies indicate that fish oil feeding reduces rat liver apo A-I and apo A-II gene expression, similar to results obtained after feeding fenofibrate. Fibrates and n-3 fatty acids (and the fatty acid derivative, alpha-bromopalmitate) down-regulate apo A-I and induce acyl-CoA oxidase gene expression through a direct transcriptional action on the hepatocyte. In contrast, only fenofibric acid, but not the other fibrates or fatty acids tested, decrease apo A-II gene expression in vitro.

Differential effect of dietary fat saturation and cholesterol on hepatic apolipoprotein gene expression in rats

The effects of dietary cholesterol and fat saturation on hepatic apolipoprotein A-I, A-II, A-IV, B, C-I, C-III, E and LDL receptor mRNA levels were studied in male rats. Animals were maintained for 2 months on a high fat diet (40% w/w) containing 0.1% cholesterol. Two groups of control animals received either chow diet or chow plus 0.1% cholesterol, while experimental groups received as their fat supplement coconut, corn or olive oil. Olive oil fed animals had higher levels of hepatic apo A-I than the control cholesterol group (1.6 +/- 0.3 vs. 0.8 +/- 0.2). Apo E mRNA levels were 50% and 72% higher in animals consuming the saturated (coconut) and unsaturated (corn and olive) fat diet than the control cholesterol group. Apo B and apo C-I mRNA levels were not affected by the experimental conditions. Apo A-IV mRNA increased between 66% and 127% in groups in which cholesterol was present. LDL receptor mRNA increased 2 times in the corn fed group compared with the control groups. These results indicate that the expression of genes coding for products involved in lipoprotein metabolism have a differential susceptibility to dietary fat saturation and cholesterol.