Effect of dietary cholesterol on low density lipoprotein-receptor, 3-hydroxy-3-methylglutaryl-CoA reductase, and low density lipoprotein receptor-related protein mRNA expression in healthy humans

The effect of simvastatin on gene expression of low-density lipoprotein receptor, sterol regulatory element-binding proteins, stearoyl-CoA desaturase 1 mRNA in rat hepatic tissues

The study aimed to assess the effect of simvastatin on gene expression of LDLR, SREBPs, and SCD1 in rat hepatic tissues fed with high-fat diets (HFD) and its association with some biochemical parameters. Thirty-two male Wister albino rats were divided into four equal groups (three test and one control groups). The biochemical parameters were determined by using spectrophotometer techniques and the Elisa method. Low-density lipoprotein receptor, sterol regulatory element-binding proteins, stearoyl-CoA desaturase1, Beta-actin were analysed by real-time quantitative polymerase chain reaction (RT-PCR) method. At the end of study, the livers of the rats were separated and changes of hepatic tissue were determined. LDLR, SREBP2, and SCD1 expression increased significantly when compared G1 versus G4 and G2 versus G4. The expression of LDLR, SREBP2, and SCD1 also increased significantly when compared G2 versus G3, G1versus G3 and G1 versus G3 and G2 versus G3. The serum level of cholesterol, triglyceride, glucose, LDL, and HDL increased significantly when compared G1 versus G3. LDL showed significantly decreased when compared G1 versus G2. Cholesterol, glucose and HDL and triglyceride levels were increased significantly when compared G1 versus G4 and G2. Treatment of rats with HFD and simvastatin 20 mg/kg, triglyceride and LDL were almost the same as a control group and LDLR expression increased 98% in liver tissue. Gene expressions may be up-regulated in liver tissue and they showed different effects on biochemical parameters.

Revisiting Human Cholesterol Synthesis and Absorption: The Reciprocity Paradigm and its Key Regulators

Hypercholesterolemia is a major risk factor for cardiovascular disease. Cholesterol homeostasis in the body is governed by the interplay between absorption, synthesis, and excretion or conversion of cholesterol into bile acids. A reciprocal relationship between cholesterol synthesis and absorption is known to regulate circulating cholesterol in response to dietary or therapeutic interventions. However, the degree to which these factors affect synthesis and absorption and the extent to which one vector shifts in response to the other are not thoroughly understood. Also, huge inter-individual variability exists in the manner in which the two systems act in response to any cholesterol-lowering treatment. Various factors are known to account for this variability and in light of recent experimental advances new players such as gene-gene interactions, gene-environmental effects, and gut microbiome hold immense potential in offering an explanation to the complex traits of inter-individual variability in human cholesterol metabolism. In this context, the objective of the present review is to provide an overview on cholesterol metabolism and discuss the role of potential factors such as genetics, epigenetics, epistasis, and gut microbiome, as well as other regulators in modulating cholesterol metabolism, especially emphasizing the reciprocal relationship between cholesterol synthesis and absorption. Furthermore, an evaluation of the implications of this push-pull mechanism on cholesterol-lowering strategies is presented.

Revisiting Human Cholesterol Synthesis and Absorption: The Reciprocity Paradigm and its Key Regulators

Hypercholesterolemia is a major risk factor for cardiovascular disease. Cholesterol homeostasis in the body is governed by the interplay between absorption, synthesis, and excretion or conversion of cholesterol into bile acids. A reciprocal relationship between cholesterol synthesis and absorption is known to regulate circulating cholesterol in response to dietary or therapeutic interventions. However, the degree to which these factors affect synthesis and absorption and the extent to which one vector shifts in response to the other are not thoroughly understood. Also, huge inter-individual variability exists in the manner in which the two systems act in response to any cholesterol-lowering treatment. Various factors are known to account for this variability and in light of recent experimental advances new players such as gene-gene interactions, gene-environmental effects, and gut microbiome hold immense potential in offering an explanation to the complex traits of inter-individual variability in human cholesterol metabolism. In this context, the objective of the present review is to provide an overview on cholesterol metabolism and discuss the role of potential factors such as genetics, epigenetics, epistasis, and gut microbiome, as well as other regulators in modulating cholesterol metabolism, especially emphasizing the reciprocal relationship between cholesterol synthesis and absorption. Furthermore, an evaluation of the implications of this push-pull mechanism on cholesterol-lowering strategies is presented.

Dietary cholesterol affects plasma lipid levels, the intravascular processing of lipoproteins and reverse cholesterol transport without increasing the risk for heart disease

The associations between dietary cholesterol and heart disease are highly controversial. While epidemiological studies and clinical interventions have shown the lack of correlation between cholesterol intake and cardiovascular disease (CVD) risk, there is still concern among health practitioners and the general population regarding dietary cholesterol. In this review, several clinical studies utilizing cholesterol challenges are analyzed in terms of changes that occur in lipoprotein metabolism resulting from excess consumption of cholesterol. Dietary cholesterol has been shown to increase both LDL and HDL in those individuals who respond to a cholesterol challenge without altering the LDL cholesterol/HDL cholesterol ratio, a key marker of CVD risk. Further, dietary cholesterol has been shown to increase only HDL with no changes in LDL with average cholesterol consumption and during weight loss interventions. Ingestion of cholesterol has also been shown to increase the size of both LDL and HDL particles with the associated implications of a less atherogenic LDL particle as well as more functional HDL in reverse cholesterol transport. Other changes observed in lipoprotein metabolism are a greater number of large LDL and decreases in small LDL subfractions. All this information put together points to specific roles of dietary cholesterol in substantially altering intravascular processing of lipoproteins as well as reverse cholesterol transport.

Gene expression of peripheral blood mononuclear cells as a tool in dietary intervention studies: What do we know so far?

Peripheral blood mononuclear cells (PBMCs) generally refer to monocytes and lymphocytes, representing cells of the innate and adaptive immune systems. PBMCs are a promising target tissue in the field of nutrigenomics because they seem to reflect the effects of dietary modifications at the level of gene expression. In this review, we describe and discuss the scientific literature concerning the use of gene expression at the mRNA level measured from PBMCs in dietary interventions studies conducted in humans. A search of literature was undertaken using PubMed (last assessed November 24, 2011) and 20 articles were selected for discussion. Currently, results from these studies showed that PBMCs seem to reflect liver environment and complement adipose tissue findings in transcriptomics. PBMC gene expression after dietary intervention studies can be used for studying the response of certain genes related to fatty acid and cholesterol metabolism, and to explore the response of dietary interventions in relation to inflammation. However, PBMC transcriptomics from dietary intervention studies have not resulted yet in clear confirmation of candidate genes related to disease risk. Use of microarray technology in larger well-designed dietary intervention studies is still needed for exploring PBMC potential in the field of nutrigenomics.

Dietary cholesterol: from physiology to cardiovascular risk

Dietary cholesterol comes exclusively from animal sources, thus it is naturally present in our diet and tissues. It is an important component of cell membranes and a precursor of bile acids, steroid hormones and vitamin D. Contrary to phytosterols (originated from plants), cholesterol is synthesised in the human body in order to maintain a stable pool when dietary intake is low. Given the necessity for cholesterol, very effective intestinal uptake mechanisms and enterohepatic bile acid and cholesterol reabsorption cycles exist; conversely, phytosterols are poorly absorbed and, indeed, rapidly excreted. Dietary cholesterol content does not significantly influence plasma cholesterol values, which are regulated by different genetic and nutritional factors that influence cholesterol absorption or synthesis. Some subjects are hyper-absorbers and others are hyper-responders, which implies new therapeutic issues. Epidemiological data do not support a link between dietary cholesterol and CVD. Recent biological data concerning the effect of dietary cholesterol on LDL receptor-related protein may explain the complexity of the effect of cholesterol on CVD risk.

Atorvastatin increases expression of low-density lipoprotein receptor mRNA in human circulating mononuclear cells

1. 3-Hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) inhibitors, or statins, are commonly used to lower plasma cholesterol levels. HMGCR and the low-density lipoprotein (LDL) receptor (LDLR) are of central importance to cholesterol homeostasis and yet there is a paucity of data on the effect of statins on the regulation of the LDLR and HMGCR in humans. 2. In the present study, we examined the effect of atorvastatin on the expression of HMGCR, LDLR and LDLR-related protein (LRP) mRNA in circulating mononuclear cells. Twelve human volunteers were treated with atorvastatin, 20 mg/day for 4 weeks. 3. Atorvastatin decreased plasma total and LDL-cholesterol by 29% (P < 0.0001) and 41% (P < 0.001), respectively, and increased LDLR mRNA abundance, in absolute terms, by 35% (P < 0.001) and 31% (P < 0.0001) and 37% (P = 0.01) relative to reference GAPDH and beta-actin mRNA, respectively. In contrast, atorvastatin had no significant effect on LRP or HMGCR mRNA levels. 4. The increase in LDLR mRNA in circulating mononuclear cells agrees with the few human studies conducted, as well as with in vitro and animal studies, whereas the unchanged HMGCR mRNA is consistent with the hepatic specificity of atorvastatin. The present study firmly documents an increase in LDLR mRNA levels in response to statin administration in normal humans.

LDL-receptor mRNA expression in men is downregulated within an hour of an acute fat load and is influenced by genetic polymorphism

Little is known about the immediate effects of dietary fat on the expression of genes involved in cholesterol metabolism in humans. We investigated the effects of a high-fat meal on circulating mononuclear cell messenger RNA (mRNA) for the LDL receptor (LDLR), LDLR-related protein (LRP), and 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) over 10 h. Selection of 12 C and 7 T homozygotes for the LRP exon 22 C200T polymorphism for the study also enabled us to examine the influence of this polymorphism on postprandial mRNA expression and lipoproteins, of relevance because of LRP's role in postprandial lipoprotein metabolism and association of the polymorphism with coronary artery disease. We found a postprandial decrease in LDLR mRNA abundance relative to the reference beta-actin (BA) mRNA. The decreased LDLR/BA mRNA value was apparent at 1 h (P < 0.005) and decreased to 25% of baseline at 6 h (P < 0.005). The LRP/BA mRNA value was also lower at 6 h (16% decrease, P < 0.05). HMGCR mRNA expression was unchanged. C homozygotes for the C200T polymorphism had higher LDLR/BA values than T homozygotes (P = 0.01) and although plasma LDL cholesterol (LDL-C) concentrations decreased in the postprandial period (P < 0.002), the decrease was less in C than in T homozygotes (P < 0.05). This study constitutes the first observation, to our knowledge, of postprandial changes in LDLR and LRP mRNA expression. It documents immediate effects of a fatty meal on these mRNA as well as an LRP genotype effect on LDLR mRNA and LDL-C.

LDL Receptor–Related Protein and the Vascular Wall

LDL receptor–related protein 1 (LRP1) is highly expressed in the vascular wall and is mainly associated with macrophages and vascular smooth muscle cells (VSMCs). Overexpression of LRP1 in atherosclerotic lesions has been demonstrated in several animal models and human lesions. Clinical studies have suggested a relation between alterations in LRP1 expression and coronary heart disease. Indeed, it has been demonstrated that LRP1 gene expression is increased in blood mononuclear cells from patients with coronary obstruction and that the LRP1 mRNA-protein expression ratio is altered in coronary patients. Taken together, these results seem to suggest that LRP1 may be a pivotal receptor in the etiology of atherosclerosis. Our group has contributed to the elucidation of the physiopathologic role of LRP1 in the vascular wall by demonstrating that LRP1-mediated, matrix-retained LDL internalization could be crucial for VSMC–foam cell formation, that LRP1 is upregulated by lipid during human atherosclerotic lesion progression, and that LRP1-mediated aggregated LDL uptake causes the prothrombotic transformation of the vascular wall. Therefore, LRP1 seems to play a pathologic function during atherosclerotic lesion progression; however, LRP1 also seems to be essential for embryonic development and for the maintenance of vascular integrity. The protective effect of LRP1 in the vessel wall seems to be mainly due to its role in controlling certain signaling pathways. In this review, we will focus on the description of the main physiopathologic functions of LRP1 in the vascular wall.

Intracellular lipid accumulation, low-density lipoprotein receptor-related protein expression, and cell survival in vascular smooth muscle cells derived from normal and atherosclerotic human coronaries

BACKGROUND

Vascular smooth muscle cell (VSMC) regulation during atherosclerotic plaque progression is determinant for plaque stability.

AIMS

To study lipid accumulation, low-density lipoprotein receptor-related protein (LRP) expression, and cell survival in VSMCs isolated from nonatherosclerotic areas (normal VSMCs) and advanced atherosclerotic plaques (plaque-VSMCs) of human coronaries.

DESIGN

Normal or plaque-VSMCs were obtained from the intima by modification of the explant technique.

RESULTS

Aggregated low-density lipoprotein (agLDL) (100 micro g mL(-1)) internalization induced higher intracellular cholesteryl ester (CE) accumulation in plaque-VSMC compared with normal VSMCs (89.28 +/- 6.1 vs. 60.34 +/- 4.1 micro g CE mg(-1) of protein; P < 0.05). This internalization was associated with LRP expression, as plaque-VSMCs show higher levels of LRP mRNA (6.06 +/- 0.55 vs. 3.87 +/- 0.28; P < 0.05) and LRP protein expression than normal VSMCs. However, plaque-VSMCs showed a lower proliferative response than normal VSMCs (6536 +/- 636 vs. 11151 +/- 815 c.p.m. [(3)H]thymidine; P < 0.05) and did not respond to platelet-derived growth factor BB (PDGF-BB) stimulus. In agreement, the Bcl(2)/BAX ratio was significantly lower in plaque-VSMCs compared with normal VSMCs (0.14 +/- 0.05 vs. 0.51 +/- 0.07; P < 0.05) and it was independent of lipid loading.

CONCLUSIONS

These results indicate that higher intracellular lipid deposition in plaque-VSMCs is related to higher LRP expression levels. However, LRP-mediated agLDL internalization is not directly related to the reduced survival of plaque-VSMCs.

Addition of inulin to a moderately high-carbohydrate diet reduces hepatic lipogenesis and plasma triacylglycerol concentrations in humans

BACKGROUND

A high-carbohydrate, low-fat diet is recommended for the prevention of atherosclerosis, because it reduces plasma cholesterol concentrations. However, such a diet can increase plasma triacylglycerol concentrations--an undesirable side effect. The addition of nondigestible carbohydrate could reduce the risk of elevated triacylglycerol concentrations.

OBJECTIVE

The objective was to determine whether the addition of a moderate dose of inulin to a moderately high-carbohydrate diet would decrease hepatic lipogenesis and plasma triacylglycerol concentrations and have a cholesterol-lowering action.

DESIGN

Eight healthy subjects were studied twice in a double-blind, randomized, placebo-controlled crossover study after consuming for 3 wk a moderately high-carbohydrate, low-fat diet (55% of total energy) plus an oral placebo or 10 g high-performance inulin/d. Hepatic lipogenesis and cholesterol synthesis (deuterated water method), plasma lipid concentrations, fatty acid synthase, acetyl-CoA carboxylase 1, and sterol responsive element binding protein 1c messenger RNA concentrations were measured in adipose tissue at the end of the 2 diet periods.

RESULTS

Plasma triacylglycerol concentrations and hepatic lipogenesis were lower after inulin than after placebo ingestion (P < 0.05), but cholesterol synthesis and plasma cholesterol concentrations were not significantly different between the 2 groups. None of the adipose tissue messenger RNA concentrations changed significantly after inulin ingestion.

CONCLUSIONS

The addition of high-performance inulin to a moderately high-carbohydrate, low-fat diet has a beneficial effect on plasma lipids by decreasing hepatic lipogenesis and plasma triacylglycerol concentrations. These results support the use of nondigestible carbohydrate for reducing risk factors for atherosclerosis.

Low-density lipoprotein upregulates low-density lipoprotein receptor-related protein expression in vascular smooth muscle cells: possible involvement of sterol regulatory element binding protein-2-dependent mechanism

BACKGROUND

Low-density lipoprotein (LDL) receptor-related protein (LRP) is highly expressed in vascular smooth muscle cells (VSMCs) of both normal and atherosclerotic lesions. However, little is known about LRP regulation in the vascular wall.

METHODS AND RESULTS

We analyzed the regulation of LRP expression in vitro in human VSMCs cultured with native LDL (nLDL) or aggregated LDL (agLDL) by semiquantitative reverse transcriptase-polymerase chain reaction, real-time polymerase chain reaction, and Western blot and in vivo during diet-induced hypercholesterolemia by in situ hybridization. LRP expression in human VSMCs is increased by nLDL and agLDL in a time- and dose-dependent manner. Maximal induction of LRP mRNA expression was observed after 24 hours of exposure to LDL. However, agLDL induced higher LRP mRNA expression (3.0-fold) than nLDL (1.76-fold). LRP mRNA upregulation was associated with an increase on LRP protein expression with the greatest induction by agLDL. VSMC-LRP upregulation induced by nLDL or agLDL was reduced by an inhibitor of sterol regulatory element binding protein (SREBP) catabolism (N-acetyl-leucyl-leucyl-norleucinal). In situ hybridization analysis indicates that there is a higher VSMC-LRP expression in hypercholesterolemic than in normocholesterolemic pig aortas.

CONCLUSIONS

These results indicate that LRP expression in VSMCs is upregulated by intravascular and systemic LDL.

Mechanisms of the triglyceride- and cholesterol-lowering effect of fenofibrate in hyperlipidemic type 2 diabetic patients

In humans, the precise mechanisms of the hypolipidemic action of fenofibrate, a peroxisome proliferator-activated receptor-alpha agonist, remain unclear. To gain insight on these mechanisms, we measured plasma lipids levels, lipids synthesis (hepatic de novo lipogenesis and cholesterol synthesis), and mRNA concentrations in circulating mononuclear cells (RT-PCR) of hydroxymethylglutaryl (HMG)-CoA reductase, LDL receptor, LDL receptor- related protein (LRP), scavenger receptor class B type I (SR-BI), ABCAI, and liver X receptor (LXR)-alpha in 10 control subjects and 9 hyperlipidemic type 2 diabetic patients. Type 2 diabetic subjects were studied before and after 4 months of fenofibrate administration. Fenofibrate decreased plasma triglycerides (P < 0.01) and total cholesterol (P < 0.05) concentrations and slightly increased HDL cholesterol (P < 0.05). Hepatic lipogenesis, largely enhanced in diabetic subjects (16.1 +/- 2.1 vs. 7.5 +/- 1.6% in control subjects, P < 0.01), was decreased by fenofibrate (9.8 +/- 1.5%, P < 0.01). Fractional cholesterol synthesis was normal in diabetic subjects (3.5 +/- 0.4 vs. 3.3 +/- 0.5% in control subjects) and was unchanged by fenofibrate (3.5 +/- 0.5%). Absolute cholesterol synthesis was, however, increased in diabetic subjects before and after fenofibrate (P < 0.05 vs. control subjects). HMG-CoA reductase, LDL receptor, LRP, and SR-BI mRNA concentrations were not different in type 2 diabetic and control subjects and were unchanged by fenofibrate. LXR-alpha mRNA levels were increased (P < 0.05) by fenofibrate. ABCAI mRNA concentrations, which were decreased in diabetic subjects (P < 0.05) before fenofibrate, were increased (P < 0.05) by fenofibrate to values comparable to those of control subjects. The plasma triglyceride-lowering effect of fenofibrate is explained in part by a decrease in hepatic lipogenesis, the moderate fall in total plasma cholesterol is not explained by a reduction of whole-body cholesterol synthesis, and the increase in LXR-alpha and ABCAI mRNA levels suggests that fenofibrate stimulated reverse cholesterol transport.

Influence of dietary cholesterol on vitamin d metabolism in formula-fed preterm neonates

OBJECTIVES

Supplementation of preterm formulas with cholesterol could help to mimic the fat composition of human milk. However, this could possibly influence vitamin D 25-hydroxylation because this reaction is catalyzed in part by the mitochondrial cytochrome P-450, the enzyme responsible for the 27-hydroxylation of cholesterol. The purpose of this study was to verify whether the addition of cholesterol to preterm formulas could interfere with vitamin D metabolism in preterm neonates.

METHODS

In a prospective study, 30 preterm neonates were randomly assigned to a low (< 0.03 g/L), medium (0.15 g/L), or high (0.30 g/L) cholesterol-content preterm formula until theoretical term (i.e., 40 weeks post-conceptional age). Anthropometric data and serum hydroxy-vitamin D and 1,25 dihydroxy-vitamin D concentrations were measured at study entry and theoretical term. In a subgroup of 14 subjects, serum cholesterol and lymphocyte 3-hydroxy-3-methylglutaryl coenzyme A reductase mRNA were also assessed.

RESULTS

(median [25, 75 centiles]): At theoretical term, there were no significant differences in serum hydroxy-vitamin D concentrations among the three groups, even after adjustment for confounding variables (65 [50, 78] nmol/L, 79 [59, 86] nmol/L, and 67 [43, 103] nmol/L, respectively, = 0.65) or 1,25 dihydroxy-vitamin D ( = 0.88). Furthermore, there were no significant differences in 3-hydroxy-3-methylglutaryl coenzyme A reductase mRNA copy numbers.

CONCLUSIONS

In preterm neonates fed formulas with a cholesterol content similar to or higher than that of human milk, we did not observe deleterious effects on vitamin D metabolism. However, long-term effects of cholesterol supplementation require further studies.

Dietary fiber and lifestyle influence serum lipids in free living adult men

OBJECTIVE

The aim of this study was to determine the effect of dietary fiber consumption and lifestyle on serum lipids in adult men with non-restricted diet and physical activity.

METHODS

Two groups of 19 men were classified as high (48 g/day) and low fiber groups (27 g/day). Anthropometry, food frequency, daily weighed intakes and physical activity were done for a seven-day period. Fasting blood was collected and serum was analyzed for triglycerides, total cholesterol and lipoprotein cholesterol fractions.

RESULTS

Crude correlation coefficients showed that total cholesterol was negatively associated with physical activity, total dietary fiber and P/S ratio (r = 0.52; p < 0.001. r = -0.44; p < 0.01, r = 0.51, p < 0.001). LDL-C was also correlated negatively with total dietary fiber and P/S ratio (r = -0.34, p < 0.03; r = -0.53, p < 0.01). It was also positively associated with dietary cholesterol and body weight (r = 0.34, p < 0.03; r = 0.31, p < 0.05). Serum triglycerides had an inverse association with total dietary fiber and physical activity (r = -0.30: p < 0.05; r = -0.45, p < 0.004). After controlling for energy intake, total fat, saturated fat, dietary cholesterol, physical activity and body mass index, LDL-C/HDL-C, and TC/HDL-C, remained significantly associated with dietary fiber (r = 0.34; p < 0.05 and r = -0.38; p < 0.02, respectively).

CONCLUSIONS

This study provides evidence in free living men that there is an association between dietary fiber intake and favorable lipid status and that lifestyle defined by socioeconomic status, physical activity and the quality of the dietary fat intake can play an important role. Public health nutrition advice and policy should continue to emphasize the importance of these factors.

Effects of isoenergetic high-carbohydrate compared with high-fat diets on human cholesterol synthesis and expression of key regulatory genes of cholesterol metabolism

BACKGROUND

High-carbohydrate diets improve plasma cholesterol concentrations but increase triacylglycerol concentrations; the latter effect increases the risk of cardiovascular disease (CVD). Triacylglycerol concentrations increase only during very-high-carbohydrate diets consisting mainly of simple sugars.

OBJECTIVE

We compared the CVD risk profile, cholesterol metabolism, and glucose tolerance of 7 healthy subjects during 2 isoenergetic diets: a high-fat, low-carbohydrate diet (HF diet) and a moderately high-carbohydrate, low-fat diet (HC diet).

DESIGN

In a randomized crossover study, we measured the effects of the HF diet [40% carbohydrate and 45% fat (15% saturated, 15% monounsaturated, and 15% polyunsaturated)] and HC diet [55% carbohydrate (mainly complex) and 30% fat (10% saturated, 10% monounsaturated, and 10% polyunsaturated)] (3 wk each) on plasma lipid concentrations, oral glucose tolerance, cholesterol synthesis rate, and the messenger RNA (mRNA) concentrations of beta-hydroxy-beta-methylglutaryl coenzyme A (HMG-CoA) reductase, the LDL receptor, and the LDL-receptor-related protein (LRP).

RESULTS

Compared with the HF diet, the HC diet lowered total, LDL, and HDL cholesterol (P < 0.05 for all) without modifying the ratio of LDL to HDL cholesterol; triacylglycerol concentrations were unchanged. Lower cholesterol concentrations occurred despite a higher cholesterol synthesis rate (P < 0.05) and higher HMG-CoA reductase mRNA concentrations (P < 0.05). LDL receptor mRNA concentrations were unchanged, LRP mRNA concentrations were lower (P < 0.01), and oral glucose tolerance was better (P < 0.05) with the HC diet.

CONCLUSION

The beneficial effects of the HC diet on glucose tolerance and plasma cholesterol concentrations without increases in triacylglycerol show that this diet had favorable effects on both insulin sensitivity and the plasma lipid profile.

In-vivo and in-vitro nutrient-gene interactions

Association studies of gene variants and response to dietary challenges represent one way of investigating gene-nutrient interactions. Several studies reported in the present review concentrate on evaluating variation at the apolipoprotein AI-CIII-AIV and apolipoprotein E gene loci, as well as the fatty acid binding protein gene. In addition, the effect of nutrients can be directly evaluated at the level of gene expression, and reports of in-vitro studies of control of fatty acid and triglycerides synthesis are discussed in the present review.