Serum Values of Cholesterol Absorption and Synthesis Biomarkers in Japanese Healthy Subjects: The CACHE Study HEALTHY Analysis

AIM

Blood cholesterol absorption and synthesis biomarkers predict cardiovascular risk. This study aimed to determine the values of serum non-cholesterol sterol markers [lathosterol (Latho), campesterol (Campe), and sitosterol (Sito)] in healthy individuals and factors affecting these markers.

METHODS

The CACHE Consortium compiled clinical data, including serum Latho (cholesterol synthesis marker), and Campe and Sito (cholesterol absorption markers), by a gas chromatography method in 2944 individuals. Healthy subjects were selected by excluding those with prior cardiovascular disease, diabetes mellitus, hypertension, chronic kidney disease, familial hypercholesterolemia, sitosterolemia, current smokers, those with low (＜17 kg/m2) or high (≥ 30 kg/m2) body mass index (BMI), and those with treatment for dyslipidemia or hyperuricemia. Nonlinear regression stratified by sex was used to examine the associations of cholesterol metabolism markers with age, BMI, and serum lipid levels.

RESULTS

Of 479 individuals selected, 59.4% were female; the median age was 48 years in females and 50 years in males. The three markers showed positively skewed distributions, and sex differences were present. Age was associated positively with Latho, inversely with Campe, but not significantly with Sito. BMI was associated positively with Latho, but not significantly with Campe or Sito. High-density lipoprotein cholesterol (HDL-C) was positively associated with Campe and Sito, but not significantly with Latho. Non-HDL-C was positively associated with the three markers.

CONCLUSION

Our study results in the healthy subjects help to interpret the non-cholesterol sterol markers for cardiovascular risk assessment in patients with cardiovascular risk factors.

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.

Role of Cholesterol and its Biosynthetic Precursors on Membrane Organization and Dynamics: A Fluorescence Approach

Cholesterol is the most representative sterol present in membranes of higher eukaryotes, and is the end product of a long and multistep biosynthetic pathway. Lathosterol and zymosterol are biosynthetic precursors of cholesterol in Kandutsch-Russell and Bloch pathways, respectively. Lathosterol differs with cholesterol merely in the position of the double bond in the sterol ring, whereas zymosterol differs with cholesterol in position and number of double bonds. In this work, we have monitored the effect of cholesterol and its biosynthetic precursors (lathosterol and zymosterol) on membrane organization and dynamics in fluid and gel phase membranes. Toward this goal, we have utilized two fluorescent membrane probes, DPH and its cationic derivative TMA-DPH. Our results using these probes show that cholesterol and its biosynthetic precursors (lathosterol and zymosterol) exhibit similar trend in maintaining membrane organization and dynamics (as reported by fluorescence anisotropy and apparent rotational correlation time), in fluid phase POPC membranes. Notably, although lathosterol and zymosterol show similar trend in maintaining membrane organization and dynamics, the corresponding change for cholesterol is different in gel phase DPPC membranes. These results demonstrate that the position and number of double bonds in sterols is an important determinant in maintaining membrane physical properties. Our results assume significance since accumulation of precursors of cholesterol have been reported to be associated with severe pathological conditions.

Association of Kidney Function with Serum Levels of Cholesterol Absorption and Synthesis Markers: The CACHE Study CKD Analysis

AIM

Serum levels of cholesterol absorption and synthesis markers are known to be associated with cardiovascular risk. Individuals with reduced kidney function or chronic kidney disease (CKD) are at an increased risk for cardiovascular disease. Hence, we examined the relationship between estimated glomerular filtration rate (eGFR) and serum markers of cholesterol absorption and synthesis.

METHODS

The CACHE (Cholesterol Absorption and Cholesterol synthesis in High-risk patiEnts) Consortium, comprised of 13 research groups in Japan possessing data of lathosterol (Latho, synthesis marker) and campesterol (Campe, absorption marker) measured via gas chromatography, compiled the clinical data using the REDCap system. Among the 3597 records, data from 2944 individuals were utilized for five analyses including this CKD analysis.

RESULTS

This study analyzed data from 2200 individuals including 522 hemodialysis patients; 42.3% were female, the median age was 58 years, and the median eGFR was 68.9 mL/min/1.73 m². Latho, Campe, and Campe/Latho ratio were significantly different when compared across CKD stages. When the associations of eGFR with these markers were assessed with multivariable nonlinear regression models, Latho, Campe, and Campe/Latho ratio showed positive, inverse, and inverse associations with eGFR. These associations were significantly modified by sex, the presence/absence of diabetes mellitus, and the presence/absence of statin use.

CONCLUSION

We showed that individuals with lower eGFR have lower cholesterol synthesis marker levels and higher cholesterol absorption marker levels in this large sample.

Relationship between Diabetes Mellitus and Serum Lathosterol and Campesterol Levels: The CACHE Study DM Analysis

AIM

Risk of cardiovascular disease is increased in patients with diabetes mellitus (DM). Cholesterol metabolism (hepatic synthesis and intestinal absorption) is known to be associated with cardiovascular risk. Next, we examined the association of DM with cholesterol absorption/synthesis.

METHODS

The CACHE Consortium, which is comprised of 13 research groups in Japan possessing data of lathosterol (Latho, synthesis marker) and campesterol (Campe, absorption marker) measured by gas chromatography, compiled the clinical data using the REDCap system. Among the 3597 records, data from 2944 individuals were used for several analyses including this study.

RESULTS

This study analyzed data from eligible 2182 individuals including 830 patients with DM; 42.2% were female, median age was 59 years, and median HbA1c of patients with DM was 7.0%. There was no difference in Latho between DM and non-DM individuals. Campe and Campe/Latho ratio were significantly lower in DM individuals than in non-DM individuals. When the associations of glycemic control markers with these markers were analyzed with multivariable-adjusted regression model using restricted cubic splines, Campe and Campe/Latho ratio showed inverse associations with glucose levels and HbA1c. However, Latho showed an inverted U-shaped association with plasma glucose, whereas Latho showed a U-shaped association with HbA1c. These associations remained even after excluding statin and/or ezetimibe users.

CONCLUSION

We demonstrated that DM and hyperglycemia were independent factors for lower cholesterol absorption marker levels regardless of statin/ezetimibe use.

Plasma lathosterol measures rates of cholesterol synthesis and efficiency of dietary phytosterols in reducing the plasma cholesterol concentration

OBJECTIVES

Because the plasma campesterol/cholesterol ratio does not differ between groups that absorb different amounts of cholesterol, the authors investigated whether the plasma Phytosterols (PS) relate to the body's cholesterol synthesis rate measured as non-cholesterol sterol precursors (lathosterol).

METHOD

The authors studied 38 non-obese volunteers (58±12 years; Low-Density Lipoprotein Cholesterol ‒ LDL-C ≥ 130 mg/dL) randomly assigned to consume 400 mL/day of soy milk (Control phase) or soy milk + PS (1.6 g/day) for four weeks in a double-blind, cross-over study. PS and lathosterol were measured in plasma by gas chromatography coupled to mass spectrophotometry.

RESULTS

PS treatment reduced plasma total cholesterol concentration (-5.5%, p < 0.001), LDL-C (-7.6%, p < 0.001), triglycerides (-13.6%, p < 0.0085), and apolipoprotein B (apo B) (-6.3%, p < 0.008), without changing high density lipoprotein cholesterol (HDL-C concentration), but plasma lathosterol, campesterol and sitosterol expressed per plasma cholesterol increased.

CONCLUSIONS

The lathosterol-to-cholesterol plasma ratio predicted the plasma cholesterol response to PS feeding. The highest plasma lathosterol concentration during the control phase was associated with a lack of response of plasma cholesterol during the PS treatment period. Consequently, cholesterol synthesis in non-responders to dietary PS being elevated in the control phase indicates these cases resist to further synthesis rise, whereas responders to dietary PS, having in the control phase synthesis values lower than non-responders, expand synthesis on alimentary PS. Responders absorb more PS than non-responders, likely resulting from responders delivering into the intestinal lumen less endogenous cholesterol than non-responders do, thus facilitating greater intestinal absorption of PS shown as increased plasma PS concentration.

Anagliptin Monotherapy for Six Months in Patients With Type 2 Diabetes Mellitus and Hyper-Low-Density Lipoprotein Cholesterolemia Reduces Plasma Levels of Fasting Low-Density Lipoprotein Cholesterol and Lathosterol: A Single-Arm Intervention Trial

Background

Anagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, has been shown to decrease plasma low-density lipoprotein cholesterol (LDL-C) levels. The objective of our study was to elucidate the mechanisms responsible for the anagliptin-mediated improvements in high LDL-C levels (hyper-LDL cholesterolemia).

Methods

We prospectively examined the effects of anagliptin monotherapy on fasting plasma lathosterol, sitosterol, and campesterol levels in patients with type 2 diabetes mellitus and hyper-LDL cholesterolemia for 6 months. We examined 14 patients who did not use hypoglycemic or lipid-lowering drugs for 4 months before initiating the study. Plasma variables related to glucose and lipid metabolism were measured before and after 6 months of treatment and pre- and postprandially using the cookie-loading test.

Results

After treatment, anagliptin monotherapy (n = 14) significantly decreased fasting LDL-C (175.6 to 148.5 mg/dL, mean values before and after the treatment, respectively) and plasma lathosterol levels (3.56 to 2.49 mg/dL), whereas it did not lower fasting sitosterol or campesterol levels. Furthermore, fasting plasma lathosterol levels were negatively correlated with preprandial glucagon-like peptide-1 (GLP-1) levels after anagliptin treatment.

Conclusions

Anagliptin monotherapy may have a beneficial effect on lipid metabolism, which could be mediated by the inhibition of hepatic cholesterol synthesis rather than the inhibition of intestinal lipid transport.

Empagliflozin increases plasma levels of campesterol, a marker of cholesterol absorption, in patients with type 2 diabetes: Association with a slight increase in high-density lipoprotein cholesterol

BACKGROUND AND AIMS

Sodium/glucose cotransporter 2 (SGLT2) inhibitors decrease plasma triglyceride levels and slightly increase low-density lipoprotein (LDL-c) and high-density lipoprotein cholesterol (HDL-c). However, the mechanisms underlying such changes in the blood lipid profile remain to be determined. We investigated how empagliflozin affects plasma markers of cholesterol absorption and synthesis, and evaluated the relationship between changes in these markers and blood lipids in patients with type 2 diabetes.

METHODS AND RESULTS

In a randomized, active-controlled, open-label trial, 51 patients were randomly allocated in 2:1 ratio to receive empagliflozin 10 mg/day (n = 32) or standard therapy (n = 19) for 12 weeks. We measured plasma levels of lathosterol as a marker of cholesterol synthesis, and campesterol and sitosterol as markers of cholesterol absorption, at baseline and 12 weeks after treatment. In the empagliflozin group, serum HDL-c, but not LDL-c, significantly increased between baseline and 12 weeks (54.4 ± 16.3 vs. 58.8 ± 19.6 mg/dl; p = 0.0006), whereas in the standard therapy group, HDL-c and LDL-c remained unchanged. In the empagliflozin group, plasma campesterol also increased significantly (4.14 ± 1.88 vs. 4.90 ± 2.26 μg/ml, p = 0.0008), whereas no change in plasma campesterol or sitosterol was found in the control group. Although plasma lathosterol showed no change in the whole empagliflozin group, it decreased significantly in patients who were not taking statins. In statin non-users, plasma lathosterol decreased significantly after treatment with empagliflozin (2.71 ± 0.99 vs. 1.91 ± 0.99 μg/ml, p < 0.05). In the empagliflozin group, changes in plasma campesterol correlated positively with changes in HDL-c.

CONCLUSION

Empagliflozin increases serum campesterol, a marker of cholesterol absorption, in patients with type 2 diabetes. This increase may be associated with SGLT2 inhibitor-induced increases in HDL cholesterol.

Differences in lipid metabolism between anagliptin and sitagliptin in patients with type 2 diabetes on statin therapy: a secondary analysis of the REASON trial

Background

Anagliptin, a dipeptidyl peptidase-4 inhibitor, is reported to reduce the level of low-density lipoprotein cholesterol (LDL-C). The underlying mechanism of this effect and effect on lipid metabolism however remains uncertain.

Aim and methods

We therefore evaluate the effects of anagliptin on lipid metabolism-related markers compared with those of sitagliptin. The study was a secondary analysis using data obtained from the Randomized Evaluation of Anagliptin versus Sitagliptin On low-density lipoproteiN cholesterol in diabetes (REASON) trial. This trial in patients with type 2 diabetes at a high risk of cardiovascular events and on statin therapy showed that anagliptin reduced LDL-C levels to a greater extent than sitagliptin. Cholesterol absorption (campesterol and sitosterol) and synthesis (lathosterol) markers were measured at baseline and 52 weeks in the study cohort (n = 353).

Results

There was no significant difference in the changes of campesterol or sitosterol between the two treatment groups (p = 0.85 and 0.55, respectively). Lathosterol concentration was increased significantly at 52 weeks with sitagliptin treatment (baseline, 1.2 ± 0.7 μg/mL vs. 52 weeks, 1.4 ± 1.0 μg/mL, p = 0.02), whereas it did not change in the anagliptin group (baseline, 1.3 ± 0.8 μg/mL vs. 52 weeks, 1.3 ± 0.7 μg/mL, p = 0.99). The difference in absolute change between the two groups showed a borderline significance (p = 0.06).

Conclusion

These findings suggest that anagliptin reduces LDL-C level by suppressing excess cholesterol synthesis, even in combination with statin therapy.

Trial registration ClinicalTrials.gov number NCT02330406. https://clinicaltrials.gov/ct2/show/NCT02330406; registered January 5, 2015.

Serum non-cholesterol sterols and cholesterol metabolism in childhood and adolescence

BACKGROUND AND AIMS

The profile of cholesterol metabolism, i.e., high absorption vs. high synthesis, may have a role in the development of atherosclerosis, the early lesions of which can be present already in childhood. Since there is no information on cholesterol metabolism in children from birth to adolescence, we evaluated cholesterol metabolism in 0-15 year-old children and adolescents without dyslipidemia.

METHODS

The study population consisted of 96 children (39 girls, 57 boys) divided into age groups <1 (n = 14), 1-5 (n = 37), 6-10 (n = 24), and 11-15 (n = 21) years. Cholesterol metabolism was assessed by analysing serum non-cholesterol sterols, biomarkers of cholesterol synthesis and absorption, with gas-liquid chromatography.

RESULTS

Serum non-cholesterol sterol ratios to cholesterol did not differ between gender. Cholesterol precursors squalene, cholestenol, and desmosterol were higher in the <1 year than in the older age groups, whereas lathosterol was highest in the 11-15 year old. Plant sterols were low in the age group <1 year, after which they did not differ between the groups. Cholestanol was not age-dependent. From the age of 1 year, cholesterol homeostasis was intact. Cholesterol absorption prevailed cholesterol synthesis from 1 to 10 years of age (e.g., lathosterol/cholestanol ratio 0.35 ± 0.03 and 0.45 ± 0.05 in 1-5 and 6-10 vs. 0.66 ± 0.08 in 11-15 year-old (mean ± SE, p < 0.001).

CONCLUSIONS

Serum non-cholesterol sterols had different individual profiles by age in childhood and adolescence. From 1 to 10 years of age, cholesterol absorption prevailed cholesterol synthesis. This novel finding emphasizes the importance of dietary aspects related to cardiovascular risk even from early childhood.

Recovery of lipid metabolic alterations in hepatitis C patients after viral clearance: Incomplete restoration with accelerated ω-oxidation

BACKGROUND

How hepatitis C virus (HCV)-associated lipid metabolic alterations recover after sustained virological response (SVR) remains elusive.

OBJECTIVE

The aforementioned recovery pattern was investigated.

METHODS

In a prospective cohort study of 438 chronic hepatitis C (CHC) patients with SVR after anti-HCV therapy, 164 sex- and age-matched genotype I (G1) and G2 patients underwent paired-serum liquid chromatography-tandem mass spectrometry analyses before and 24 weeks after therapy. Subjects without CHC served as controls (n = 100).

RESULTS

CHC patients had lower baseline lipid levels than controls. Among CHC patients, pre-therapy total cholesterol levels were positively associated with HCV RNA levels; G1 patients had higher pre-therapy HCV RNA levels than G2 patients. Repeated measures analysis of variance of CHC patients showed that lathosterol, lanosterol, total hydroxysphingomyelin, and total phosphatidylcholines levels, and total dicarboxyacylcarnitine/total acylcarnitine (indicators of ω-oxidation) and pre-β-lipoprotein ratios elevated 24 weeks after therapy compared with the levels before therapy. Levels of total lysophosphatidylcholines and α- and β-lipoprotein ratios decreased. Subgroup analyses showed elevated 7-dehydrocholesterol and lanosterol levels, particularly in G2 and male patients, who had broader spectra of altered phosphatidylcholines and acylcarnitines than G1 and female patients, respectively. Compared with controls, CHC patients had higher post-therapy levels of total lysophosphatidylcholines and hydroxysphingomyelins and ratios of total dicarboxyacylcarnitines/total acylcarnitines but lower cholesterol levels.

CONCLUSIONS

At 24 weeks after therapy, accelerated cholesterol biosynthesis, hepatic lipid export, ω-oxidation, and decreased systemic inflammation were noted in CHC patients with SVR, with greater efficiency in G2 and male patients. Regardless, HCV-associated lipid metabolic alterations required >24 weeks for restoration or were incompletely reversible after SVR.

Attenuation of UVR-induced vitamin D3 synthesis in a mouse model deleted for keratinocyte lathosterol 5-desaturase

The lower risk of some internal cancers at lower latitudes has been linked to greater sun exposure and consequent higher levels of ultraviolet radiation (UVR)-produced vitamin D₃ (D₃). To separate the experimental effects of sunlight and of all forms of D₃, a mouse in which UVR does not produce D₃ would be useful. To this end we have generated mice carrying a modified allele of sterol C5-desaturase (Sc5d), the gene encoding the enzyme that converts lathosterol to 7-dehydrocholesterol (7-DHC), such that Sc5d expression can be inactivated using the Cre/lox site-specific recombination system. By crossing to mice with tissue-specific expression of Cre or CreER² (Cre/estrogen receptor), we generated two lines of transgenic mice. One line has constitutive keratinocyte-specific inactivation of Sc5d (Sc5d^k14KO). The other line (Sc5d^k14KOi) has tamoxifen-inducible keratinocyte-specific inactivation of Sc5d. Mice deleted for keratinocyte Sc5d lose the ability to increase circulating D₃ following UVR exposure of the skin. Thus, unlike in control mice, acute UVR exposure did not affect circulating D₃ level in inducible Sc5d^k14KOi mice. Keratinocyte-specific inactivation of Sc5d was proven by sterol measurement in hair - in control animals lathosterol and cholesta-7,24-dien-3β-ol, the target molecules of SC5D in the sterol biosynthetic pathways, together constituted a mean of 10% of total sterols; in the conditional knockout mice these sterols constituted a mean of 56% of total sterols. The constitutive knockout mice had an even greater increase, with lathosterol and cholesta-7,24-dien-3β-ol accounting for 80% of total sterols. In conclusion, the dominant presence of the 7-DHC precursors in hair of conditional animals and the lack of increased circulating D₃ following exposure to UVR reflect attenuated production of the D₃ photochemical precursor 7-DHC and, consequently, of D₃ itself. These animals provide a useful new tool for investigating the role of D₃ in UVR-induced physiological effects and, more broadly, for investigations of the cholesterol synthetic pathway in the skin and other targeted tissues.

Effect of Ezetimibe Monotherapy on Low-Density Lipoprotein Cholesterol and on Markers of Cholesterol Synthesis and Absorption in Japanese Patients With Hypercholesterolemia

Background

The aim of this study was to evaluate effect of ezetimibe monotherapy on serum low-density lipoprotein cholesterol (LDL-C) in Japanese patients and to investigate the association between changes of LDL-C and changes of markers for cholesterol synthesis and absorption.

Methods

Seventy-six hypercholesterolemic patients without statin therapy were enrolled and randomized to two groups, which were an ezetimibe group (group E, n = 44) and a control group without ezetimibe treatment that received diet therapy alone (group C, n = 32). The study period was 12 weeks. In group E, 10 mg of ezetimibe was administered daily after breakfast. Serum lipids were measured every 4 weeks, while lathosterol (a cholesterol synthesis marker) and campesterol and sitosterol (cholesterol absorption markers) were examined at baseline and at 12 weeks.

Results

A significant reduction of LDL-C was observed in group E at both 4 and 12 weeks (from 155 ± 3.9 to 128 ± 3.4 mg/dL and 132 ± 3.9 mg/dL, respectively, both P < 0.01), associated with an increase of high-density lipoprotein cholesterol (HDL-C)at 12 weeks (from 53 ± 1.3 to 55 ± 1.5 mg/dL, P < 0.05) and no change of triglycerides. In contrast, none of these lipids changed in group C. An increase of lathosterol and a decrease of campesterol and sitosterol were observed in group E, while none of these markers changed in group C. When group E was divided into two subgroups according to the reduction of LDL-C, which were a good response group (reduction ≥ 20 mg/dL, ΔLDL-C = -27.9 ± 1.3 mg/dL, n = 18) and a poor response group (reduction < 20 mg/dL, ΔLDL-C = -3.7 ± 2.5 mg/dL, n = 26), baseline levels of campesterol and sitosterol were higher in the good response group.

Conclusion

Ezetimibe monotherapy reduced LDL-C and increased HDL-C, with the reduction of LDL-C being greater in patients with higher levels of cholesterol absorption markers.

Early and brain region-specific decrease of de novo cholesterol biosynthesis in Huntington's disease: A cross-validation study in Q175 knock-in mice

Cholesterol precursors and cholesterol levels are reduced in brain regions of Huntington's disease (HD) mice. Here we quantified the rate of in vivo de novo cholesterol biosynthesis in the HD brain. Samples from different brain regions and blood of the heterozygous knock-in mouse model carrying 175 CAG repeats (Q175) at different phenotypic stages were processed independently by two research units to quantify cholesterol synthesis rate by ²H₂O labeling and measure the concentrations of lathosterol, cholesterol and its brain-specific cholesterol catabolite 24-hydroxy-cholesterol (24OHC) by isotope dilution mass spectrometry. The daily synthesis rate of cholesterol and the corresponding concentration of lathosterol were significantly reduced in the striatum of heterozygous Q175 mice early in the disease course. We also report that the decrease in lathosterol was inversely correlated with CAG-size at symptomatic stage, as observed in striatal samples from an allelic series of HD mice. There was also a significant correlation between the fractional synthesis rates of total cholesterol and 24OHC in brain of wild-type (WT) and Q175 mice, supporting the evidence that plasma 24OHC may reflect cholesterol synthesis in the adult brain. This comprehensive analysis demonstrates consistent cholesterol biosynthesis defects in HD mouse models and suggests that plasma 24OHC may serve as a biomarker of brain cholesterol metabolism.

Cholesterol metabolism in cardiac sarcoidosis

BACKGROUND AND AIMS

Patients with cardiac sarcoidosis (CS) suffer from myocardial inflammation, but atherosclerosis is not infrequent in these patients. However, the classical atherosclerotic risk factors, such as perturbed serum lipids and whole-body cholesterol metabolism, remain unravelled in CS.

METHODS

We assessed serum non-cholesterol sterols, biomarkers of whole-body cholesterol synthesis and cholesterol absorption efficiency, with gas-liquid chromatography in 39 patients with histologically verified CS and in an age-adjusted random population sample (n = 124).

RESULTS

CS was inactive or responding to treatment in all patients. Concentrations of serum, LDL, and HDL cholesterol and serum triglycerides were similar in CS patients and in control subjects. Cholesterol absorption markers were higher in CS patients than in controls (eg serum campesterol to cholesterol ratio in CS 246 ± 18 vs in controls 190 ± 8 10(2) x μmol/mmol of cholesterol, p = 0.001). Cholesterol synthesis markers were lower in CS patients than in controls (eg serum lathosterol to cholesterol ratio in CS 102 ± 8 vs in controls 195 ± 5 10(2) x μmol/mmol of cholesterol, p = 0.000). In CS patients, cholesterol absorption markers significantly correlated with plasma prohormone brain natriuretic peptide (proBNP), a marker of hemodynamic load.

CONCLUSION

High cholesterol absorption efficiency, which is suggested to be atherogenic, characterized the metabolic profile of cholesterol in CS patients. The association between cholesterol absorption efficiency and plasma proBNP concentration, which suggests a link between inflammation, cholesterol homeostasis, and hemodynamic load, warrants further studies in order to confirm this finding and to reveal the underlying mechanisms.

Serum sterol profiling reveals increased cholesterol biosynthesis in childhood obesity

Quantitative sterol profiling in obese children and their clinical implications have not been fully investigated. The aim of study was to evaluate the metabolic changes in serum cholesterol and its precursors and metabolites, and their associations with clinical characteristics of childhood obesity. A total of 253 children aged 6-14 years (72 obese, 39 overweight, and 72 normal controls; 147 girls and 106 boys) were recruited. Anthropometric indices, body composition, and fasting total lipid profiles were determined. Serum concentrations of 20 sterols, as their free fraction, were analyzed through gas chromatography-mass spectrometry-based metabolite profiling. There were no significant differences in total- and LDL-cholesterols between groups. Serum levels of the main cholesterol precursors, lanosterol (P<0.02) and lathosterol (P<0.0001), were significantly higher in obese children. In addition, they showed positive correlations with waist to hip ratio, body fat percent, and body fat mass. The metabolic ratios of lanosterol and lathosterol to cholesterol were also elevated (P<0.01 both), indicating the up-regulation of cholesterol biosynthesis with childhood obesity. In contrast, the absorption of plant sterols tended to show a compensatory decrease in obese children. Strong correlations between free cholesterol and total- and LDL-cholesterols were observed (r>0.760, P<0.001), while there was no correlation with HDL-cholesterols. The levels of total cholesteryl ester were closely associated with triglyceride (r=0.763, P<0.001). Quantitative results indicate that childhood obesity may increase cholesterol synthesis while maintaining overall cholesterol homeostasis.

Biological variation of β-sitosterol, campesterol, and lathosterol as cholesterol absorption and synthesis biomarkers

BACKGROUND

The analysis of blood for β-sitosterol and campesterol is the measures of cholesterol absorption while lathosterol is a measure of cholesterol synthesis.

METHODS

The biological variability of β-sitosterol, campesterol, and lathosterol was measured using liquid-chromatography tandem mass spectrometry from a cohort of 25 apparently healthy subjects, where blood was taken once every weeks for 6 weeks. The analytical, intra-individual, and group inter-individual variations (CVA, CV(I), and CV(G), respectively) were calculated.

RESULTS

Using absolute values, the CVI for β-sitosterol, campesterol, and lathosterol was 11.8%, 11.8%, and 22.5%, respectively, and the CV(G) was 28.5%, 28.8%, and 52.0%, respectively. This produced reference change values of about 24-36% for declining values and 32-47% for increasing values. The index of individuality was between 0.41 and 0.58, indicating that population based reference values are of little use for these biomarkers. The number of points needed for a homeostatic setpoint was 5 samples for β-sitosterol and campesterol, and 19 samples for lathosterol. Similar findings were observed for values when normalized to total cholesterol. These results were higher than the biological variation for total, low density and high density cholesterol obtained from the literature. Results were essentially identical when sterol values were corrected to their respective total cholesterol concentration.

CONCLUSIONS

The establishment of the biological variation for these biomarkers enables their use in the interpretation of results from clinical trials and lipid lowering treatment of patients at risk for cardiovascular disease in clinical practice.

Disturbances in cholesterol, bile acid and glucose metabolism in peroxisomal 3-ketoacylCoA thiolase B deficient mice fed diets containing high or low fat contents

The peroxisomal 3-ketoacyl-CoA thiolase B (ThB) catalyzes the thiolytic cleavage of straight chain 3-ketoacyl-CoAs. Up to now, the ability of ThB to interfere with lipid metabolism was studied in mice fed a laboratory chow enriched or not with the synthetic agonist Wy14,643, a pharmacological activator of the nuclear hormone receptor PPARα. The aim of the present study was therefore to determine whether ThB could play a role in obesity and lipid metabolism when mice are chronically fed a synthetic High Fat Diet (HFD) or a Low Fat Diet (LFD) as a control diet. To investigate this possibility, wild-type (WT) mice and mice deficient for Thb (Thb(-/-)) were subjected to either a synthetic LFD or a HFD for 25 weeks, and their responses were compared. First, when fed a normal regulatory laboratory chow, Thb(-/-) mice displayed growth retardation as well as a severe reduction in the plasma level of Growth Hormone (GH) and Insulin Growth Factor-I (IGF-I), suggesting alterations in the GH/IGF-1 pathway. When fed the synthetic diets, the corrected energy intake to body mass was significantly higher in Thb(-/-) mice, yet those mice were protected from HFD-induced adiposity. Importantly, Thb(-/-) mice also suffered from hypoglycemia, exhibited reduction in liver glycogen stores and circulating insulin levels under the LFD and the HFD. Thb deficiency was also associated with higher levels of plasma HDL (High Density Lipoproteins) cholesterol and increased liver content of cholesterol under both the LFD and the HFD. As shown by the plasma lathosterol to cholesterol ratio, a surrogate marker for cholesterol biosynthesis, whole body cholesterol de novo synthesis was increased in Thb(-/-) mice. By comparing liver RNA from WT mice and Thb(-/-) mice using oligonucleotide microarray and RT-qPCR, a coordinated decrease in the expression of critical cholesterol synthesizing genes and an increased expression of genes involved in bile acid synthesis (Cyp7a1, Cyp17a1, Akr1d1) were observed in Thb(-/-) mice. In parallel, the elevation of the lathosterol to cholesterol ratio as well as the increased expression of cholesterol synthesizing genes were observed in the kidney of Thb(-/-) mice fed the LFD and the HFD. Overall, the data indicate that ThB is not fully interchangeable with the thiolase A isoform. The present study also reveals that modulating the expression of the peroxisomal ThB enzyme can largely reverberate not only throughout fatty acid metabolism but also cholesterol, bile acid and glucose metabolism.