Squalene and noncholesterol sterols in serum and lipoproteins of children with and without familial hypercholesterolemia

Association between Familial Hypercholesterolemia and Serum Levels of Cholesterol Synthesis and Absorption Markers: The CACHE Study FH Analysis

AIM

Serum levels of cholesterol absorption and synthesis markers are known to be associated with cardiovascular risk. Familial hypercholesterolemia (FH) is a well-known inherited disorder presenting elevated low-density lipoprotein cholesterol (LDL-C) and total cholesterol (TC) levels and premature coronary disease. In this study, we aim to examine the differences in terms of serum markers of cholesterol metabolism between FH and non-FH individuals and to examine their associations with serum lipid levels.

METHODS

In this study, we utilized data on serum markers of cholesterol metabolism, namely, lathosterol (Latho, synthesis marker), campesterol (Campe, absorption marker), and sitosterol (Sito, absorption marker) measured by gas chromatography of the CACHE consortium, which comprised of 13 research groups in Japan. Clinical data were compiled using REDCap system. Among the 2944 individuals in the CACHE population, we selected individuals without lipid-lowering medications and hemodialysis patients for this CACHE study FH analysis. Multivariable adjustment was performed to assess the associations.

RESULTS

In this study, we analyzed data from 51 FH patients and 1924 non-FH individuals. After adjustment for possible confounders, the FH group was shown to have significantly higher Campe and Sito concentrations and insignificantly higher Latho concentrations than the non-FH group. These marker concentrations showed nonlinear associations with TC in the FH group. Campe/Latho and Sito/Latho ratios were significantly higher in the FH group than in the non-FH group.

CONCLUSION

FH group had significantly elevated serum Campe and Sito concentrations and insignificantly elevated Latho concentrations; thus, intestinal cholesterol absorption relative to hepatic cholesterol synthesis was suggested to be elevated in patients with FH. Serum Latho, Campe, and Sito concentrations showed nonlinear associations with TC in the FH group.

Gas Chromatography and Flame-Ionization Detection of Non-Cholesterol Sterols as Indicators of Cholesterol Absorption and Synthesis in 158 Chinese Individuals with Normolipidemia, Hyperlipidemia, and Familial Hypercholesterolemia

Background

There are limited studies on the effects of cholesterol homeostasis in populations at high risk for cardiovascular disease. We aimed to use gas chromatography and flame-ionization detection (GC-FID) of non-cholesterol sterols as indicators of cholesterol absorption and synthesis. Sterol indicators of cholesterol absorption included campesterol, stigmasterol, and sitosterol. Sterol indicators of cholesterol synthesis included squalene, 7-lathosterol, and desmosterol.

Material/Methods

A total of 158 participants were enrolled in 3 groups: healthy control (n=64), hyperlipidemia (n=69), and familial hypercholesterolemia (FH, n=25). Age, sex, blood pressure, blood glucose, and lipoprotein were collected, and cholesterol absorption and synthesis markers were determined by GC-FID.

Results

All 6 cholesterol concentration indicators, except squalene, were significantly different among the 3 groups (all P<0.05); whereas in the ratio to cholesterol (%, sterols/cholesterol), only desmosterol and lathosterol were significantly different (P<0.05). Multifactorial regression analysis showed that triglycerides, total cholesterol, and desmosterol were independent risk factors affecting the development of hyperlipidemia (P<0.05). The efficacy of the ROC curve for the diagnosis of dyslipidemia was also higher for all 3 indices (Model 1, AUC=0.960). Model 1 was superior to Model 2 for the 6 indicators of cholesterol. For the FH and dyslipidemia groups, the 6-indicator model (Model 3) was shown to have a good diagnostic value (AUC=1.000).

Conclusions

The 6 sterol indicators of cholesterol absorption and synthesis had a dynamic course in all study participants. Desmosterol was an indicator of dyslipidemia. The combined use of the 6 sterol indicators differentiated between healthy individuals and patients with dyslipidemia and FH.

Can non-cholesterol sterols indicate the presence of specific dysregulation of cholesterol metabolism in patients with colorectal cancer?

Colorectal cancer (CRC) is a highly prevalent malignancy. Previous studies suggested that cholesterol might play a signficant role in malignant transformation and proliferation. Non-cholesterol sterols (NCS), which are transported by serum lipoproteins alongside cholesterol, are regarded as cholesterol synthesis and absorption markers. Quantification of NCS in serum and HDL fraction (NCS_HDL), could provide a better insight into the cholesterol metabolism. The aim of this study was to examine the status of cholesterol synthesis and cholesterol absorption markers in serum and HDL fraction and explore their interrelation in CRC patients. Current study was designed as observational, case-control study. The study included 73 CRC patients and 95 healthy subjects. NCS and NCS_HDL concentrations were determined by HPLC-MS/MS. Based on NCS and NCS_HDL concentrations, different cholesterol homeostasis indices were calculated. Patients had significantly lower NCS (P<0.001) and NCS_HDL concentrations (P<0.001 for desmosterol_HDL; P<0.05 for lathosterol_HDL, P=0.001 for campesterol_HDL, P<0.001 for β-sitosterol_HDL). NCS_HDL/NCS (P<0.005 for desmosterol_HDL/desmosterol; P<0.05 for lathosterol_HDL/lathosterol; P<0.001 for both β-sitosterol_HDL/β-sitosterol and campesterol_HDL/campesterol) and synthesis to absorption ratio (CSI/CAI) (P<0.005) were increased in CRC patients. Additionally, low serum concentrations of desmosterol (P<0.001; OR=0.329; 95%CI (0.199-0.542)) and campesterol (P<0.001; OR=0.540; 95%CI (0.424-0.687)) were independent predictors of CRC presence. Our data suggest that cholesterol homeostasis in CRC is shifted towards increased synthesis. Relative abundance of NCS in HDL particles is increased, suggesting the possible overproduction of cholesterol precursors in peripheral tissues.

Plasma Non-cholesterol Sterols as Markers of Cholesterol Synthesis and Intestinal Absorption: A Critical Review

Plasma concentrations of phytosterols and non-cholesterol sterol precursors of cholesterol synthesis have been used as markers of intestinal cholesterol absorption and synthesis in inherited and secondary dyslipidemias and in population-based investigations to evaluate the risk for cardiovascular disease, respectively. The method aims at replacing initial research procedures such as the use of stable isotopes associated with fecal steroid balance, which are limited by the high cost and tedious procedures. However, we show in this review that numerous results obtained with serum sterol measurements are contradictory. In this regard, the following points are discussed: 1) how phytosterols relate to atherosclerosis considering that defects in biliary output or in the transport of phytosterols from the intestinal mucosa back into the intestinal lumen provide increased content of phytosterols and other sterols in plasma and tissues, thus not allowing to conclude that their presence in arteries and atheromas represents the etiology of atherosclerosis; 2) serum non-cholesterol sterols as markers of cholesterol synthesis and absorption, such as cholestanol, present discrepant results, rendering them often inadequate to identify cases of coronary artery disease as well as alterations in the whole body cholesterol metabolism; 3) such methods of measurement of cholesterol metabolism are confounded by factors like diabetes mellitus, body weight and other pathologies including considerable hereditary hyperlipidemias biological variabilities that influence the efficiency of synthesis and intestinal absorption of cholesterol.

Non-Cholesterol Sterol Concentrations as Biomarkers for Cholesterol Absorption and Synthesis in Different Metabolic Disorders: A Systematic Review

Non-cholesterol sterols are validated biomarkers for intestinal cholesterol absorption and endogenous cholesterol synthesis. However, their use in metabolic disturbances has not been systematically explored. Therefore, we conducted a systematic review to provide an overview of non-cholesterol sterols as markers for cholesterol metabolism in different metabolic disorders. Potentially relevant studies were retrieved by a systematic search of three databases in July 2018 and ninety-four human studies were included. Cholesterol-standardized levels of campesterol, sitosterol and cholestanol were collected to reflect cholesterol absorption and those of lathosterol and desmosterol to reflect cholesterol synthesis. Their use as biomarkers was examined in the following metabolic disorders: overweight/obesity (n = 16), diabetes mellitus (n = 15), metabolic syndrome (n = 5), hyperlipidemia (n = 11), cardiovascular disease (n = 17), and diseases related to intestine (n = 16), liver (n = 22) or kidney (n = 2). In general, markers for cholesterol absorption and synthesis displayed reciprocal patterns, showing that cholesterol metabolism is tightly regulated by the interplay of intestinal absorption and endogenous synthesis. Distinctive patterns for cholesterol absorption or cholesterol synthesis could be identified, suggesting that metabolic disorders can be classified as 'cholesterol absorbers or cholesterol synthesizers'. Future studies should be performed to confirm or refute these findings and to examine whether this information can be used for targeted (dietary) interventions.

Desmosterol and DHCR24: unexpected new directions for a terminal step in cholesterol synthesis

3β-Hydroxysterol Δ(24)-reductase (DHCR24) catalyzes the conversion of desmosterol to cholesterol. This ultimate step of cholesterol biosynthesis appears to be remarkable in its diverse functions and the number of diseases it is implicated in from vascular disease to Hepatitis C virus (HCV) infection to cancer to Alzheimer's disease. This review summarizes the present knowledge on the DHCR24 gene, sterol Δ(24)-reductase protein and the regulation of both. In addition, the functions of desmosterol, DHCR24 and their roles in human diseases are discussed. It is apparent that DHCR24 exerts more complex effects than what would be expected based on the enzymatic activity of sterol Δ(24)-reduction alone, such as its influence in modulating oxidative stress. Increasing information about DHCR24 membrane association, processing, enzymatic regulation and interaction partners will provide further fundamental insights into DHCR24 and its many and varied biological roles.

Primary hyperlipidemias in children: effect of plant sterol supplementation on plasma lipids and markers of cholesterol synthesis and absorption

Plant sterols lower serum cholesterol concentration. Available data have confirmed the lipid-lowering efficacy in adults, while there is a relative dearth of data in children and almost exclusively restricted to subjects with familial hypercholesterolemia (FH). Aim of the present study was to evaluate the efficacy, tolerability and safety of plant sterol supplementation in children with different forms of primary hyperlipidemias. The effect of plant sterol consumption on plasma lipids was evaluated in 32 children with heterozygous FH, 13 children with Familial Combined Hyperlipidemia (FCH) and 13 children with Undefined Hypercholesterolemia (UH) in a 12-week open-label intervention study using plant sterol-enriched yoghurt. Plasma lipids and apolipoproteins were measured by routine methods. Markers of cholesterol synthesis (lathosterol) and absorption (campesterol and sitosterol) were measured by GC-MS. Tolerability and adherence to recommended regimen was very high. A significant reduction was observed in LDL-cholesterol in the three groups (10.7, 14.2 and 16.0% in FH, FCH and UH, respectively). Lathosterol concentrations were unchanged, reflecting a lack of increased synthesis of cholesterol. Of the two absorption markers, only sitosterol showed a slight but significant increase. Daily consumption of plant sterol dairy products favorably changes lipid profile by reducing LDL-cholesterol. To our knowledge, this is the first report of the use of plant sterols-enriched foods in treating children with primary hyperlipidemia such as FCH and UH, likely to be the most frequent form also in the young age in the western populations.

Cholesterol metabolism in pediatric short bowel syndrome after weaning off parenteral nutrition

BACKGROUND

Small intestine essentially regulates cholesterol homeostasis.

AIMS

To evaluate cholesterol metabolism in short bowel syndrome (SBS).

METHODS

Cholesterol precursors (e.g., cholestenol, desmosterol and lathosterol) and plant sterols (campesterol and sitosterol), respective markers of cholesterol synthesis and absorption, were determined in SBS patients (n=12) an average of 31 months after weaning off parenteral nutrition and in age-matched controls (n=80).

RESULTS

Among patients, serum cholesterol precursor sterol to cholesterol ratios were 2-10 times higher (P<0.0001 for each). Those without any remaining ileum had 1.2-2.8 times higher precursor sterol to cholesterol ratios than those with an ileal remnant (P<0.05 for each). Serum cholesterol concentration, campesterol/cholesterol and campesterol/sitosterol were 34-39% lower (P<0.05 for each) in relation to controls. Bile acid absorption was markedly impaired (2.4 (0.2-3.2)%). Plant sterol ratios reflected the absolute length of remaining jejunum (r=0.625-0.663), and precursor sterol ratios inversely that of ileum (r=-0.589 to 0.750, P<0.05 for all).

CONCLUSION

After weaning off parenteral nutrition, patients with pediatric onset SBS continue to have marked intestinal malabsorption of bile acids and moderate cholesterol malabsorption resulting in decreased serum cholesterol despite a marked compensatory increase in cholesterol synthesis.

Plasma non-cholesterol sterols: a useful diagnostic tool in pediatric hypercholesterolemia

Current guidelines strongly recommend the identification of genetic forms of hypercholesterolemia (HC) during childhood.The usefulness of non-cholesterol sterols (NCS) in the diagnosis of genetic HC has not been fully explored. Plasma NCS were measured by gas chromatography/mass spectrometry (GC/MS) in 113 children with hypercholesterolemia affected by: autosomal dominant hypercholesterolemia (ADH), familial combined hyperlipidemia(FCHL), polygenic hypercholesterolemia (PHC), and in 79 controls to evaluate: i) plasma NCS profile in different genetic HC and ii) the usefulness of NCS for the diagnosis of HC beyond current clinical criteria. ADH was characterized by raised lathosterol/total cholesterol (TC) and reduced phytosterols/TC ratios, indicative of increased cholesterol synthesis. FCHL showed a slight increase of lathosterol/TC ratio, whereas PHC showed increased phytosterols/TC ratios, indicative of increased cholesterol absorption. In a post hoc discriminant analysis of patients with HC, lipid values correctly classified the 73% (14 of 19) of ADH, whereas the inclusion of plasma sterols allowed the correct identification of all 19 patients with ADH. FCHL was not differentiated from PHC (62 versus 69%).In conclusion, NCS measurement showed that cholesterol plasma levels are related to the cholesterol synthesis in ADH and to cholesterol absorption in PHC. NCS improve the detection of ADH in pediatric patients, whereas FCHL diagnosis is not improved.

Plasma plant sterol levels do not reflect cholesterol absorption in children with Smith-Lemli-Opitz syndrome

OBJECTIVE

To test the hypothesis that there is a correlation between the ratio of plant sterols to cholesterol in plasma and dietary cholesterol absorption in children with Smith-Lemli-Opitz syndrome (SLOS), a cholesterol synthesis disorder.

STUDY DESIGN

We obtained measurements of cholesterol absorption with a direct radioisotope cholesterol absorption method during 9 visits of children with SLOS. We measured plasma sterols in 22 children with SLOS and 16 control children, and we measured dietary intake of cholesterol and sitosterol (n=11 SLOS).

RESULTS

The correlations of 2 plasma plant sterol ratios (sitosterol/cholesterol and campesterol/cholesterol) with direct cholesterol absorption measurement were poor (R= -0.33 and R= -0.25, respectively), significantly lower than the published correlation in adults (R=0.73; P< .02).

CONCLUSIONS

Although the ratios of plant sterols to cholesterol in plasma has been used as a surrogate for cholesterol absorption in adults and children, these ratios may not accurately reflect cholesterol absorption in children with SLOS. These ratios should not be used as a surrogate for cholesterol absorption in children without further validation.

Cholesterol metabolism and non-cholesterol sterol distribution in lipoproteins of type 1 diabetes: The effect of improved glycemic control

In type 1 diabetes, the ratios to cholesterol of serum absorption markers, e.g., cholestanol, are elevated and those of synthesis markers, e.g., lathosterol, are reduced suggesting perturbed cholesterol metabolism. We studied 17 subjects with type 1 diabetes in poor glycemic control at baseline to assess whether improvement of glycemic control affects lathosterol and cholestanol ratios to cholesterol and their distribution in lipoproteins. Cholesterol and the non-cholesterol sterols were assayed directly from serum, and free and ester fractions after thin-layer chromatographic separation of lipoprotein sterols with gas-liquid chromatography. After the 2-6 months follow-up, the mean value of HbA1(c) decreased from 10.8% to 8.6% (p=0.001). Even though the concentrations of serum and lipoprotein cholesterol remained unchanged, the serum lathosterol to cholesterol ratio increased by 28% (p<0.05) and the lathosterol/cholestanol proportion by 23% (p<0.05). The ratios of total and esterified lathosterol to cholesterol in serum, chylomicrons and LDL, and free lathosterol to cholesterol in serum and IDL, were negatively associated with HbA1(c) at baseline and after follow-up, suggesting that the better glycemic control, the higher was cholesterol synthesis. The absorption markers were less consistently associated with HbA1(c). About half of the serum lathosterol and cholestanol was carried in LDL and one-fourth to one-fifth in HDL, but the lathosterol ratios were roughly similar in all lipoproteins. In contrast, cholestanol accumulated in chylomicrons and HDL. Glycemic control did not affect the distributions of lathosterol and cholestanol. In conclusion, improvement in glycemic control increased cholesterol synthesis, but had no effect on cholesterol absorption as measured by the serum or lipoprotein cholestanol to cholesterol ratio. From a clinical point of view, the better the glycemic control, the more antiatherogenic cholesterol metabolism may be in type 1 diabetes.

The distribution of squalene and non-cholesterol sterols in lipoproteins in type 2 diabetes

BACKGROUND

Lipoprotein distribution of non-cholesterol sterols was studied to evaluate in which lipoproteins they are carried in type 2 diabetes with body weight ranging from normal to overweight.

METHODS

Serum and lipoprotein squalene and non-cholesterol sterols were quantitated with gas-liquid chromatography in 33 diabetic subjects separated into normal (BMI < or = 25 kg/m2, n=10) and overweight (BMI > 25 kg/m2, n=23) groups.

RESULTS

Two-thirds of the non-cholesterol sterols were carried in LDL and one-fifth in HDL, whereas squalene was mainly in VLDL and LDL in both groups. In overweight versus normal weight subjects, the absorption marker concentrations and ratios to cholesterol in serum and lipoproteins were lower and those of synthesis higher. In both groups the synthesis and absorption markers were interrelated in all lipoproteins suggesting intact regulation of cholesterol metabolism. The absorption marker ratios to cholesterol were mostly carried in HDL (cholestanol) and IDL (campesterol and sitosterol), and synthesis markers in VLDL and IDL regardless of overweight. Synthesis marker ratios were underestimated in serum versus VLDL and IDL, and those of absorption markers in serum versus IDL and HDL (p<0.05 for all). Squalene was related to lathosterol in all lipoprotein fractions (e.g., in LDL r=+0.501, p<0.01) suggesting that in diabetes squalene, too, is an indicator of cholesterol synthesis.

CONCLUSIONS

The absorption sterols are carried in IDL and HDL, and the synthesis markers in VLDL and IDL regardless of weight. The lipoprotein squalene and non-cholesterol sterol ratios were under- or overestimated in serum, and whether their evaluation in lipoproteins versus in serum only gives better information on cholesterol metabolism should be investigated further also in normal population.

The role of dietary supplementation with plant sterols and stanols in the prevention of cardiovascular disease

Several studies have shown that increased levels of low-density lipoprotein (LDL) cholesterol predict cardiovascular events. The Adult Treatment Panel II (ATP II) introduced the principle of therapeutic lifestyle changes, including plant sterols/stanols for the management of LDL cholesterol. Plant sterols and stanols in fat matrices effectively lower LDL cholesterol levels in hypercholesterolemic, diabetic, and healthy human volunteers. Recent studies also show that sterols (2 g/d) lower LDL cholesterol even when incorporated in nonfat matrices. In addition, they may reduce biomarkers of oxidative stress and inflammation. Plant sterols and stanols exert their hypocholesterolemic effects possibly by interfering with the uptake of both dietary and biliary cholesterol from the intestinal tract. Present evidence is accumulating to promote their use for lowering LDL cholesterol levels, as a first line of therapy (as well as adjunctive therapy) in patients on statin therapy.

Plasma Concentrations of Plant Sterols: Physiology and Relationship with Coronary Heart Disease

Recently, it has been questioned whether elevated levels of circulating plant sterols increase the risk of coronary heart disease (CHD). To date, no definitive conclusions regarding such a relationship have been reached, nor have there been any studies summarizing the factors that contribute to the observed elevations in plant sterol concentrations in plasma. Thus, the purpose of this review is to systematically compare the plant sterol levels of subjects from the general population and to describe factors that contribute to the variations observed. The question of whether elevated plasma concentrations of plant sterols are associated with an increased risk of CHD was also assessed. Results indicate that the key factors accounting for variations in circulating plant sterol concentrations include: apolipoprotein E phenotypes, ATP-binding cassette transporter polymorphisms, use of statin drugs, presence of metabolic syndrome, dietary intake of plant sterols, gender, and analytical techniques used in the measurement of plant sterols in the plasma. An analysis of the studies examining the relationship between circulating levels of plant sterols and CHD risk in non-sitosterolemic populations revealed no clear associations. Furthermore, it was shown that the above-mentioned factors play an important role in determining the levels of plant sterols in plasma. Since these factors may act as potential confounders, they must be controlled for before more solid conclusions can be reached.

Serum noncholesterol sterols in children with heterozygous familial hypercholesterolemia undergoing pravastatin therapy

OBJECTIVE

To assess causes for insufficient cholesterol-lowering response to pravastatin and plant stanol esters in children with heterozygous familial hypercholesterolemia (HeFH).

STUDY DESIGN

Nine of 16 children with HeFH who had not reached normocholesterolemia (< or =194 mg/dL [< or =5 mmol/L]) by 1 year after treatment (40 mg pravastatin and plant stanol ester) were called nonresponders. The 7 remaining children were responders. Serum noncholesterol sterol ratios (10(2) x mmol/mol of cholesterol), surrogate estimates of cholesterol absorption (cholestanol, campesterol, sitosterol) and synthesis (desmosterol and lathosterol), were studied at study baseline (on plant stanol esters) and during combination therapy with pravastatin and plant stanol esters.

RESULTS

Pravastatin decreased the serum levels of cholesterol and cholesterol synthesis markers, and increased the ratios of cholesterol absorption markers. Compared with the responders, the nonresponders had higher study baseline (on plant stanol esters) serum cholesterol concentrations (299 +/- 39 vs 251 +/- 35 mg/dL [7.7 +/- 1.0 vs 6.5 +/- 0.9 mmol/L]; P <.001) and higher respective ratios of campesterol (371 +/- 99 vs 277 +/- 67 10(2) x mmol/mol of cholesterol; P = .049) and sitosterol (176 +/- 37 vs 126 +/- 24 10(2) x mmol/mol of cholesterol; P = .008). The higher the ratio of cholestanol at study baseline, the smaller the 1-year percent reduction in cholesterol (r = .556; P = .025).

CONCLUSIONS

Pravastatin treatment increases the markers of cholesterol absorption and decreases those of cholesterol synthesis in HeFH during simultaneous inhibition of cholesterol absorption. Combined inhibition of cholesterol absorption and synthesis may not normalize serum lipids in those patients with the highest cholesterol levels, especially if signs of enhanced cholesterol absorption are detectable.

Cholesterol Absorption and Synthesis in Pediatric Kidney, Liver, and Heart Transplant Recipients

BACKGROUND

Hypercholesterolemia after organ transplantation is common. Previously, we observed higher serum total cholesterol (TC) concentrations in our pediatric kidney than liver or heart transplant recipients. To find an explanation to the observed difference, our kidney recipients' cholesterol synthesis and absorption efficiency was compared to those of liver and heart recipients.

METHODS

Serum noncholesterol sterol ratios (10 x mmol to the mol of TC, surrogate estimates of hepatic cholesterol synthesis and intestinal absorption) were studied in 50 pediatric kidney, 25 liver and 12 heart transplant recipients without diabetes or cholestasis, and in 29 controls.

RESULTS

The kidney recipients had lower Delta-cholesterol (P=0.031), similar lathosterol and higher desmosterol ratios (markers of cholesterol synthesis) (P=0.020), and similar campesterol and sitosterol ratios (markers of cholesterol absorption) when compared to the controls. The liver recipients had lower campesterol ratios than the kidney recipients and controls (P=0.002). Glomerular filtration rates were not associated with the ratios of noncholesterol sterols. Multivariate analysis showed markers of cholesterol synthesis to be lower and absorption to be higher in the kidney than the liver or the heart transplant recipients. Weight-adjusted dosages of immunosuppressive agents were associated with some ratios of noncholesterol sterols and cholestanol though these varied between the transplant recipient groups.

CONCLUSIONS

Serum TC concentration in kidney recipients was not significantly associated with absorption efficiency or synthesis of cholesterol, though kidney transplantation was associated with low synthesis and high absorption efficiency of cholesterol. Immunosuppressive therapy with cyclosporine and methylprednisolone may modulate absorption efficiency and synthesis of cholesterol.

Effect of statins on noncholesterol sterol levels: implications for use of plant stanols and sterols

Normal serum contains small amounts of noncholesterol sterols, including those reflecting cholesterol absorption and those that are markers of cholesterol synthesis. Absorption marker sterols include serum plant sterols, whereas cholesterol precursor sterols correlate with whole-body synthesis of cholesterol. Thus, serum noncholesterol sterols, and especially their ratios to cholesterol, can be used to evaluate the major features of cholesterol metabolism (ie, synthesis and absorption). Statin treatment reduces serum cholesterol precursors but increases serum plant sterols severalfold, especially in subjects with high-absorption marker sterol levels indicative of efficient cholesterol and sterol absorption in general. Statin therapy is most effective in subjects with high serum cholesterol precursor levels. In subjects with high-absorption sterol markers, dietary cholesterol absorption inhibition (eg, with plant stanol and sterol ester margarine) needs to be combined with a statin to achieve effective serum cholesterol reduction. However, whereas dietary plant stanol esters reduce statin-induced elevations of serum plant sterol levels, serum plant sterol levels remain elevated during dietary plant sterol ester consumption. The clinical implication of high serum plant sterol levels is under active investigation.

Non-cholesterol sterols in serum, lipoproteins, and red cells in statin-treated FH subjects off and on plant stanol and sterol ester spreads

BACKGROUND

Serum plant sterol levels are increased by consumption of statins and dietary plant sterols, and decreased by dietary plant stanols, but little is known about combination therapy of statin and plant sterols.

METHODS

We measured plant sterols in serum, lipoproteins, and red cells in subjects with familial hypercholesterolemia (FH) (n=18) treated with variable doses of statins off and on plant stanol (STA) and sterol ester (STE) spreads.

RESULTS

STA and STE spreads lowered LDL cholesterol approximately 15%. Plant sterols were decreased in serum, lipoproteins, and red cells by approximately 25% with STA and increased from 37% to 80% with STE, especially with high statin doses. The changes in serum were related to those in red cells. The baseline levels of serum plant sterols were negatively (r-range -0.639 to -0.935) and positively (r-range 0.526 to 0.598) correlated with the respective changes evoked by the STA and STE spreads.

CONCLUSIONS

STE reduces LDL cholesterol, but increases serum, lipoprotein, and red cell plant sterol levels in statin-treated FH subjects, while all the respective values are decreased with STA. Recent predictions that elevated serum plant sterols pose an increased coronary risk suggest that increases of serum plant sterol levels should be avoided, especially in atherosclerosis-prone individuals, such as subjects with FH.

Effects of dietary cholesterol on plasma lipoproteins in Smith-Lemli-Opitz syndrome

Smith-Lemli-Opitz syndrome is a condition of impaired cholesterol synthesis that is caused by mutations in DHCR7 encoding 7-dehydrocholesterol-Delta7 reductase. Birth defects and mental retardation are characteristic. Deficient plasma and tissue cholesterol and excess cholesterol precursors 7 and 8 dehydrocholesterol (7DHC and 8DHC) contribute to the pathogenesis. Cholesterol is transported to tissues via lipoproteins. We measured the effect of dietary cholesterol (egg yolk) on plasma lipoproteins to evaluate this potential treatment. We used the enzymatic method to measure total sterols in lipoproteins (n=12) and plasma (n=16). In addition, we analyzed individual plasma sterols by a gas chromatographic method. Samples were evaluated after 3 wk of a cholesterol-free diet and after 6-19 mo of dietary cholesterol. We also analyzed the distribution of sterols in lipoproteins and the apolipoprotein E genotype. Dietary cholesterol significantly increased the total sterols in plasma (2.22 +/- 0.13 to 3.10 +/- 0.22; mean +/- SEM; p < 0.002), in LDL (0.98 +/- 0.13 to 1.52 +/- 0.17 mM), and in HDL (0.72 +/- 0.04 to 0.92 +/- 0.07). Plasma cholesterol increased (1.78 +/- 0.16 to 2.67 +/- 0.25 mM; p < 0.007) and plasma 7DHC decreased in 10 children, but the mean decrease was not significant. The distribution of individual sterols in each lipoprotein fraction was similar to the distribution in plasma. The baseline cholesterol and the response to dietary cholesterol was the same in children with 3/3 and 3/4 apolipoprotein E genotypes. Dietary cholesterol increased total sterols in plasma, LDL, and HDL in children with Smith-Lemli-Opitz syndrome. These favorable increases in the lipoproteins are potentially therapeutic for this condition.

Guidelines for the diagnosis and management of heterozygous familial hypercholesterolemia

Familial hypercholesterolemia (FH) is a genetic disorder of lipoprotein metabolism characterized by very high plasma concentrations of low density lipoprotein cholesterol (LDLc), tendon xanthomas and increased risk of premature coronary heart disease (CHD). FH is a public health problem throughout the world. There are 10,000,000 people with FH worldwide, mainly heterozygotes, and approximately 85% of males and 50% of females with FH will suffer a coronary event before 65 years old if appropriate preventive efforts are not implemented. Early identification of persons with FH and their relatives, and the early start of treatment are essential issues in the prevention of premature cardiovascular disease (CVD) and death in this population. However, guidelines for the general population formally exclude FH from their diagnostic and treatment recommendations. These guidelines have been elaborated by a group of international experts with the intention to answer the main questions about heterozygous FH (heFH) subjects that physicians worldwide face in the diagnosis and management of these patients.