Cholesterol absorption: influence of body weight and the role of plant sterols

Low-density lipoprotein cholesterol elevation, ketogenic diets, body mass index, and heterozygous ABCG5 genetic variation: Review, case report, and large population analysis

BACKGROUND

Low-body mass index (BMI) has been associated with marked low-density-lipoprotein-cholesterol (LDL-C) elevations in response to very-low-carbohydrate diets (VLCD).

METHODS

We report a case (51-year-old woman, BMI 18.5 kg/m2) whose LDL-C was >500 mg/dL on a VLCD diet. We characterized her plasma lipoproteins and noncholesterol-sterols (gas chromatography/mass spectrometry) and the DNA sequences of her genes affecting lipid metabolism. We also carried out a large population analysis (224,126 subjects, 54% female, mean age 54 years) examining interrelationships between BMI and serum lathosterol/total cholesterol and β-sitosterol/total cholesterol ratios.

RESULTS

In this case, her LDL-C concentration increased from 142 mg/dL to 555 mg/dL on a VLCD, and her plasma β-sitosterol level was very high at 12.8 mg/L. DNA analysis revealed a heterozygous pathogenic ABCG5 exon 9 variant (c.1323_1324+2del at position g.44051049 TACAC>T). With dietary cholesterol restriction and ezetimibe therapy, her LDL-C and β-sitosterol levels decreased by 75% and 46% to 139 mg/dL and 7.1 mg/L, respectively. In the population analysis, we noted a significant inverse correlation between BMI and the plasma β-sitosterol/total cholesterol ratio (r = -0.573, P < .00001). Those with a BMI <20 kg/m2 had mean β-sitosterol/total cholesterol values that were significantly higher (+63%, P < .00001) than values in obese women. The converse was true for the plasma lathosterol/total cholesterol ratio. Similar findings were noted in men.

CONCLUSIONS

Our data are consistent with the concepts that low BMI predisposes to increased plasma β-sitosterol/total cholesterol ratios and an increased serum LDL-C when on high cholesterol VLCD diets, and that this response may be markedly enhanced in subjects with pathogenic heterozygous ABCG5 variants.

Free cholesterol, cholesterol precursor and plant sterol levels in atherosclerotic plaques are independently associated with symptomatic advanced carotid artery stenosis

BACKGROUND AND AIMS

Circulating sterols result either from cholesterol (CH) synthesis or intestinal uptake. They are mainly esterified and can be oxygenated. Sterols accumulate in atherosclerotic plaques whereby their clinical impact is uncertain. Here, we determined associations between circulating and plaque sterol levels in patients with advanced carotid artery stenosis in respect to a prior ischemic event and statin treatment.

METHODS

Free and esterified CH, CH precursors and plant sterols as well as oxysterols were quantified by liquid chromatography-tandem mass spectrometry in 63 consecutive patients undergoing carotid endarterectomy.

RESULTS

CH, CH precursors, plant sterols and oxysterols accumulated in carotid artery plaques. Absolute circulating sterol levels were not predictive for their corresponding plaque levels. After normalisation to CH, plant sterol but not oxysterol levels correlated between plasma and plaques. Among the circulating sterols, oxysterols occurred proportionally less in plaques. Furthermore, CH and plant sterols were less esterified in plaques than in plasma. Patients who experienced a prior ischemic event (n = 29) and asymptomatic patients had, except for lanosterol, comparable circulating sterol levels. In contrast, the absolute plaque levels of free CH, CH precursors and plant sterols as well as oxysterols were increased in symptomatic compared to asymptomatic patients. These differences remained significant for free CH, precursors and 3 out of 4 analyzed plant sterols after adjustment to the most influencing covariates - statin treatment, type 2 diabetes and age.

CONCLUSIONS

Increased absolute plaque levels of free CH, precursors and plant sterols predict an ischemic event in patients with advanced carotid artery stenosis.

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.

Effect of a high-fat diet on the hepatic expression of nuclear receptors and their target genes: relevance to drug disposition

More than 1·4 billion individuals are overweight or obese worldwide. While complications often require therapeutic intervention, data regarding the impact of obesity on drug disposition are scarce. As the influence of diet-induced obesity on drug transport and metabolic pathways is currently unclear, the objective of the present study was to investigate the effect of high fat feeding for 13 weeks in female Sprague-Dawley rats on the hepatic expression of the nuclear receptors pregnane X receptor (PXR), constitutive androstane receptor (CAR), liver X receptor (LXR) and farnesoid X receptor (FXR) and several of their target genes. We hypothesised that high fat feeding would alter the gene expression of major hepatic transporters through a dysregulation of the expression of the nuclear receptors. The results demonstrated that, along with a significant increase in body fat and weight, a high-fat diet (HFD) induced a significant 2-fold increase in the expression of PXR as well as a 2-, 5- and 2·5-fold increase in the hepatic expression of the PXR target genes Abcc2, Abcb1a and Cyp3a2, respectively (P< 0·05). The expression levels of FXR were significantly increased in rats fed a HFD in addition to the increase in the expression levels of FXR target genes Abcb11 and Abcb4. The expression levels of both LXRα and LXRβ were slightly but significantly increased in rats fed a HFD, and the expression levels of their target genes Abca1 and Abcg5, but not Abcg8, were significantly increased. The expression of the nuclear receptor CAR was not significantly altered between the groups. This suggests that a HFD may induce changes in the hepatobiliary transport and metabolism of endogenous and exogenous compounds.

Berberine decreases cholesterol levels in rats through multiple mechanisms, including inhibition of cholesterol absorption

OBJECTIVE

The objective was to determine the mechanisms of action of berberine (BBR) on cholesterol homeostasis using in vivo and in vitro models.

METHODS

Male Sprague-Dawley rats were fed the AIN-93G diet (normal control) or modified AIN-93G diet containing 28% fat, 2% cholesterol and 0.5% cholic acid with treatment of 0 (atherogenic control), 50, 100, and 150 mg/kg·d of BBR, respectively by gavaging in water for 8 weeks. Cholesterol absorption rate was measured with the dual stable isotope ratio method, and plasma lipids were determined using the enzymatic methods. Gene and protein expressions of Acyl-coenzyme A:cholesterol acyltransferase-2 were analyzed in vivo and in vitro. Cholesterol micellarization, uptake and permeability were determined in vitro.

RESULTS

Rats on the atherogenic diet showed significantly hypercholesterolemic characteristics compared to normal control rats. Treatment with BBR in rats on the atherogenic diet reduced plasma total cholesterol and nonHDL cholesterol levels by 29%-33% and 31%-41%, respectively, with no significant differences being observed among the three doses. The fractional dietary cholesterol absorption rate was decreased by 40%-51%. Rats fed the atherogenic diet showed lower plasma triacylglycerol levels, and no changes were observed after the BBR treatment. BBR interfered with cholesterol micellarization, decreased cholesterol uptake by Caco-2 cells and permeability through Caco-2 monolayer. BBR also inhibited the gene and protein expressions of acyl-coenzyme A cholesterol acyltransferease-2 in the small intestine and Caco-2 cells.

CONCLUSION

BBR lowered blood cholesterol levels at least in part through inhibiting the intestinal absorption and further by interfering with intraluminal cholesterol micellarization and decreasing enterocyte cholesterol uptake and secretion.

Central role of SREBP-2 in the pathogenesis of osteoarthritis

Background

Recent studies have implied that osteoarthritis (OA) is a metabolic disease linked to deregulation of genes involved in lipid metabolism and cholesterol efflux. Sterol Regulatory Element Binding Proteins (SREBPs) are transcription factors regulating lipid metabolism with so far no association with OA. Our aim was to test the hypothesis that SREBP-2, a gene that plays a key role in cholesterol homeostasis, is crucially involved in OA pathogenesis and to identify possible mechanisms of action.

Methodology/Principal Findings

We performed a genetic association analysis using a cohort of 1,410 Greek OA patients and healthy controls and found significant association between single nucleotide polymorphism (SNP) 1784G>C in SREBP-2 gene and OA development. Moreover, the above SNP was functionally active, as normal chondrocytes’ transfection with SREBP-2-G/C plasmid resulted in interleukin-1β and metalloproteinase-13 (MMP-13) upregulation. We also evaluated SREBP-2, its target gene 3-hydroxy-3-methylglutaryl-coenzymeA reductase (HMGCR), phospho-phosphoinositide3-kinase (PI3K), phospho-Akt, integrin-alphaV (ITGAV) and transforming growth factor-β (TGF-β) mRNA and protein expression levels in osteoarthritic and normal chondrocytes and found that they were all significantly elevated in OA chondrocytes. To test whether TGF-β alone can induce SREBP-2, we treated normal chondrocytes with TGF-β and found significant upregulation of SREBP-2, HMGCR, phospho-PI3K and MMP-13. We also showed that TGF-β activated aggrecan (ACAN) in chondrocytes only through Smad3, which interacts with SREBP-2. Finally, we examined the effect of an integrin inhibitor, cyclo-RGDFV peptide, on osteoarthritic chondrocytes, and found that it resulted in significant upregulation of ACAN and downregulation of SREBP-2, HMGCR, phospho-PI3K and MMP-13 expression levels.

Conclusions/Significance

We demonstrated, for the first time, the association of SREBP-2 with OA pathogenesis and provided evidence on the molecular mechanism involved. We suggest that TGF-β induces SREBP-2 pathway activation through ITGAV and PI3K playing a key role in OA and that integrin blockage may be a potential molecular target for OA treatment.

Effect of ezetimibe on remnant-like particle cholesterol in subjects with metabolic syndrome

OBJECTIVE

To investigate the influence of ezetimibe monotherapy on remnant-like particle cholesterol (RLP-C) in subjects with metabolic syndrome (MetS).

MATERIALS AND METHODS

Ezetimibe (10 mg/daily) was prescribed over a 12-week period for hypercholesterolemic subjects divided into groups with MetS (n = 28; male/female = 13/15; mean age 67 years) and without MetS (n = 22; male/female = 9/13; mean age 66 years). In the pre- and post-treatment phases, BMI, blood pressure and fasting blood levels of glucose, lipid panels and RLP-C were measured.

RESULTS

The group with MetS showed significantly higher RLP-C levels than the group without MetS [median level: 0.18 vs. 0.12 mmol/l (7.1 vs. 4.4 mg/dl), p < 0.01] in the pre-treatment phase. In the post-treatment phase, the low-density lipoprotein cholesterol levels were significantly reduced in both groups to a similar level (p < 0.001 in both), while there was a significantly greater reduction in RLP-C in the group with MetS than the group without MetS [median level: 0.12 vs. 0.11 mmol/l (4.8 vs. 4.1 mg/dl), p < 0.05]. This difference in RLP-C remained significant after adjusting for confounding factors.

CONCLUSION

Ezetimibe monotherapy may be associated with a greater reduction in RLP-C levels in subjects with MetS than in those without MetS.

Effects of a 2-y dietary weight-loss intervention on cholesterol metabolism in moderately obese men

BACKGROUND

Long-term dietary weight loss results in complex metabolic changes. However, its effect on cholesterol metabolism in obese subjects is still unclear.

OBJECTIVE

We assessed the effects of 2 y of weight loss achieved with various diet regimens on phytosterols (markers of intestinal cholesterol absorption), lanosterol (marker of de novo cholesterol synthesis), and changes in apolipoprotein concentrations.

DESIGN

We conducted the 2-y Dietary Intervention Randomized Controlled Trial (DIRECT-a study of low-fat, Mediterranean, and low-carbohydrate diets). We assessed circulating phytosterol and lanosterol concentrations and their ratios to cholesterol and apolipoproteins A-I and B-100 in 90 DIRECT participants at 0, 6, and 24 mo.

RESULTS

We observed a significant upregulation of the markers of cholesterol absorption (campesterol: +16.8%, P < 0.001) and a downregulation of the markers of cholesterol synthesis (lanosterol: -16.5%, P = 0.008) during the active weight-loss phase (first 6 mo, weight loss of 5%, 6%, and 10% in the 3 diet groups, respectively), followed by a rebound (campesterol: -6.2%, P = 0.045; lanosterol: +43.7%, P < 0.001) during the next 18 mo (weight gain of 1%, 1%, and 2% in the 3 diet groups, respectively). HDL cholesterol continuously increased during the study (17.0%, P < 0.001), whereas LDL cholesterol remained constant. At the end of the 24-mo follow-up period, campesterol (P < 0.001) and lanosterol (P = 0.016) amounts were significantly higher than baseline values. The concentration of apolipoprotein B-100 correlated with cholesterol metabolism (ρ = 0.299 and P = 0.020 for lanosterol; ρ = -0.105 and NS for campesterol), and the homeostasis model assessment of insulin resistance correlated with lanosterol (ρ = 0.09, P = 0.001).

CONCLUSIONS

Long-term weight loss is related to a characteristic response suggestive of altered cholesterol and apolipoprotein metabolism. Various diets have a similar effect on these effects. DIRECT is registered at clinicaltrials.gov as NCT00160108.

Plasma sterol evidence for decreased absorption and increased synthesis of cholesterol in insulin resistance and obesity

BACKGROUND

The rise in LDL with egg feeding in lean insulin-sensitive (LIS) participants is 2- and 3-fold greater than in lean insulin-resistant (LIR) and obese insulin-resistant (OIR) participants, respectively.

OBJECTIVE

We determined whether differences in cholesterol absorption, synthesis, or both could be responsible for these differences by measuring plasma sterols as indexes of cholesterol absorption and endogenous synthesis.

DESIGN

Plasma sterols were measured by gas chromatography-mass spectrometry in a random subset of 34 LIS, 37 LIR, and 37 OIR participants defined by the insulin sensitivity index (S(I)) and by BMI criteria selected from a parent group of 197 participants. Cholestanol and plant sterols provide a measure of cholesterol absorption, and lathosterol provides a measure of cholesterol synthesis.

RESULTS

The mean (±SD) ratio of plasma total absorption biomarker sterols to cholesterol was 4.48 ± 1.74 in LIS, 3.25 ± 1.06 in LIR, and 2.82 ± 1.08 in OIR participants. After adjustment for age and sex, the relations of the absorption sterol-cholesterol ratios were as follows: LIS > OIR (P < 0.001), LIS > LIR (P < 0.001), and LIR > OIR (P = 0.11). Lathosterol-cholesterol ratios were 0.71 ± 0.32 in the LIS participants, 0.95 ± 0.47 in the LIR participants, and 1.29 ± 0.55 in the OIR participants. After adjustment for age and sex, the relations of lathosterol-cholesterol ratios were as follows: LIS < OIR (P < 0.001), LIS < LIR (P = 0.03), and LIR < OIR (P = 0.002). Total sterol concentrations were positively associated with S(I) and negatively associated with obesity, whereas lathosterol correlations were the opposite.

CONCLUSIONS

Cholesterol absorption was highest in the LIS participants, whereas cholesterol synthesis was highest in the LIR and OIR participants. Therapeutic diets for hyperlipidemia should emphasize low-cholesterol diets in LIS persons and weight loss to improve S(I) and to decrease cholesterol overproduction in LIR and OIR persons.

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.

Effectiveness of thrice weekly ezetimibe

Ezetimibe is usually dosed daily, but its 22-hour elimination half-life permits significant cholesterol reduction with less frequent dosing. The aim of this study was to examine lipid changes in 33 patients treated with thrice-weekly ezetimibe for > or =1 month, who had pre- and postezetimibe lipid levels and no other concurrent changes in their lipid treatment. Ninety-four percent of the patients were treated with ezetimibe because they experienced myalgias, elevated transaminase levels, or gastrointestinal intolerance with higher doses of other lipid-lowering agents. Total cholesterol decreased by 15% (-36 +/- 28 mg/dl, p <0.001) and low-density lipoprotein cholesterol by 20% (-30 +/- 25 mg/dl, p <0.001) during 58 +/- 50 days of treatment. Most patients (85%) tolerated the treatment, and many (48%) achieved their low-density lipoprotein cholesterol goals. In conclusion, thrice-weekly ezetimibe decreases total and low-density lipoprotein cholesterol and is well tolerated. It is a viable treatment for patients intolerant of other lipid-lowering medications.

Relationship between phytosterol levels and components of the metabolic syndrome in the PROCAM study

BACKGROUND

Components of the metabolic syndrome such as hypertriglyceridemia, low high-density lipoprotein (HDL) cholesterol and obesity have been shown to be associated with increased cholesterol synthesis and reduced cholesterol absorption. In the present study, we measured the lathosterol/cholesterol ratio as an index of cholesterol synthesis and the ratios of cholestanol, campesterol and sitosterol to cholesterol as indices of cholesterol absorption, as well as components of the metabolic syndrome, in 324 men and 168 women from the PROCAM study, an epidemiological study in which raised sitosterol was previously associated with increased coronary risk. Our aim was to determine if the indices of cholesterol synthesis and absorption show a graded relationship with severity of metabolic syndrome.

RESULTS

No differences were seen between men and women with regard to the relationship of either the lathosterol/cholesterol or the sitosterol/cholesterol ratios and severity of metabolic syndrome. On multiple regression analysis in men and women together, body mass index showed a positive relationship with the lathosterol/cholesterol ratio (r=0.257, P<0.001) and a negative relationship with the sitosterol/cholesterol ratio (r=-0.221, P<0.001). HDL-cholesterol showed a negative relationship with the lathosterol/cholesterol ratio (r=-0.166, P=0.001). Triglycerides showed a negative relationship with the sitosterol/cholesterol ratio (r=0.141, P=0.005). Overall, these relationships were graded across quintiles of HDL cholesterol, body mass index and triglyceride and across an index of metabolic syndrome severity (number of components present). Only the cholestanol/cholesterol ratio showed a graded relationship with estimated overall coronary risk.

CONCLUSIONS

The metabolic syndrome is associated with increased cholesterol synthesis and reduced cholesterol absorption in a relationship that is graded across severity of the individual components of the syndrome and across an index of the severity of the metabolic syndrome as a whole.

Effect of ezetimibe in patients who cannot tolerate statins or cannot get to the low density lipoprotein cholesterol target despite taking a statin

BACKGROUND

Recent guidelines underline the need for high-risk patients to reach strict low density lipoprotein cholesterol (LDL-C) targets (1.8-2.6 mmol/L; 70-100 mg/dL), and specifically mention the possible use of combination therapy (e.g.statin + ezetimibe) to achieve these goals.

METHODS

A retrospective case-note audit was carried out to assess the response to administering ezetimibe in patients unable to tolerate statins (Group 1), or high dose of statins (Group 2) and patients who cannot achieve the LDL-C target (2.6 mmol/L; 100 mg/dL) despite taking a statin (Group 3).

RESULTS

Ezetimibe lowered LDL-C levels by 20-29% across the 3 patient groups after 2-3 months of treatment. High density lipoprotein cholesterol (HDL-C) levels tended to remain unchanged, although there was a consistent trend for a fall if baseline values were 'high'. However, the LDL-C/HDL-C ratio changed significantly and favourably in all groups. The fall in fasting triglyceride levels in all groups was greater (reaching 19-25%) when baseline levels were > or = 1.5 or 1.7 mmol/L (136-150 mg/dL). There were no marked abnormalities in liver function tests or creatine kinase activity. In Group 3 there was a significant trend for a fall in serum creatinine levels across the tertiles of baseline creatinine values. Limitations of the present study include the small sample size (especially in Groups 1 and 2), its short-term duration and the absence of event-based end-points. Therefore, the results are hypothesis-generating rather than conclusive.

CONCLUSIONS

When used alone or added to a statin, ezetimibe favourably altered the LDL-C/HDL-C ratio and lowered triglyceride levels. Ezetimibe was well tolerated in patients with statin intolerance and was associated with a 26% fall in LDL-C. An additional action may be some degree of improved renal function. Further studies are needed to confirm these findings.

EFFECTS OF SHRIMP (MACROBRACIUM ROSENBERGII)-DERIVED CHITOSAN ON PLASMA LIPID PROFILE AND LIVER LIPID PEROXIDE LEVELS IN NORMO- AND HYPERCHOLESTEROLAEMIC RATS

1. The effects of chitosan (CS) derived from the exoskeleton of the shrimp Macrobracium rosenbergii on bodyweight, plasma lipid profile, fatty acid composition, liver lipid peroxide (LPO) levels and plasma levels of glutamate pyruvate transaminase (GPT) were determined in normocholesterolaemic (NC) and hypercholesterolaemic (HC) Long Evans rats. 2. The NC rats were fed a diet containing 2% CS and the HC rats were fed a diet containing 2 and 4% CS for 8 weeks. Chitosan significantly reduced bodyweight gain only in HC + 4% CS rats compared with HC rats, but not in NC + 2% CS or HC + 2% CS rats. 3. Chitosan reduced plasma total cholesterol in the HC + 2% CS, HC + 4% CS and NC + 2% CS rats; however, low density lipoprotein-cholesterol decreased only in the first two groups. High-density lipoprotein-cholesterol (HDL-C) increased in the HC + 4% CS rats by 24% compared with the HC + 2% CS group and by 30% compared with HC rats; however, HDL-C did not increase in the NC + 2% CS group compared with NC rats. The level of plasma triglycerides decreased significantly only in HC + 2% CS rats compared with HC rats. 4. Chitosan significantly decreased plasma levels of arachidonic acid in the HC + 2% CS and HC + 4% CS groups, with a concurrent increase in the molar ratio of total unsaturated fatty acid (TUFA) to total saturated fatty acid (TSFA). 5. Moreover, CS increased liver LPO levels without affecting plasma levels of GPT. Liver LPO levels were positively correlated with the TUFA/TSFA molar ratio. 6. The present study suggests that dietary CS decreases the atherogenic lipid profiles of both NC and HC rats and reduces the bodyweight gain of HC rats.

The response of lipoproteins to dietary fat and cholesterol in lean and obese persons

Individuals differ in the response of their blood lipoproteins to cholesterol-lowering diets. One characteristic clearly associated with susceptibility to diet is leanness; many studies show that total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol concentrations respond more strongly to dietary fat and cholesterol in lean subjects than in obese subjects. This is unlikely to be due to differences in dietary compliance. A metabolic explanation is that obese people have a higher rate of total body cholesterol synthesis. The low-density lipoprotein receptors in their liver cells are partly suppressed by this large stream of endogenous cholesterol coming in from their enterohepatic circulation, and the amount added by dietary cholesterol relative to the endogenous pool would be less than in lean people. Whatever the mechanism, diets low in saturated fat and cholesterol are less effective in the obese. The most effective way for obese people to normalize their blood lipids is to lose weight, which is, unfortunately, hard to do in our society.

Non-low-density lipoprotein cholesterol-associated actions of ezetimibe: an overview

Ezetimibe, an intestinal cholesterol absorption inhibitor, lowers circulating low-density lipoprotein cholesterol (LDL-C) levels both when administered as monotherapy and in combination with other hypolipidaemic drugs, mostly statins. This review focuses on the effects of ezetimibe on non-LDL-C-associated variables. In most studies, ezetimibe effectively reduced triglyceride and increased high density lipoprotein cholesterol levels. The authors also consider the effect of ezetimibe on other variables such as C-reactive protein levels, insulin sensitivity and endothelial function. Ezetimibe is useful in patients with sitosterolaemia (a rare inherited disorder) as it significantly reduces plasma phytosterol concentrations. Ezetimibe fulfils two of the three essential characteristics of any drug (efficacy and safety). However, clinical studies are required to provide evidence of its ability to reduce vascular events.

The response of lipoproteins to dietary fat and cholesterol in lean and obese persons

Individuals differ in the response of their blood lipoproteins to cholesterol-lowering diets. One characteristic clearly associated with susceptibility to diet is leanness; many studies show that total cholesterol, low-density lipoprotein cholesterol, and high-density lipoprotein cholesterol concentrations respond more strongly to dietary fat and cholesterol in lean subjects than in obese subjects. This is unlikely to be due to differences in dietary compliance. A metabolic explanation is that obese people have a higher rate of total body cholesterol synthesis. The low-density lipoprotein receptors in their liver cells are partly suppressed by this large stream of endogenous cholesterol coming in from their enterohepatic circulation, and the amount added by dietary cholesterol relative to the endogenous pool would be less than in lean people. Whatever the mechanism, diets low in saturated fat and cholesterol are less effective in the obese. The most effective way for obese people to normalize their blood lipids is to lose weight, which is, unfortunately, hard to do in our society.