Cholestanol: A serum marker to guide LDL cholesterol-lowering therapy

Cholesterol-metabolism, plant sterols, and long-term cognitive decline in older people - Effects of sex and APOEe4

Neurodegenerative, vascular, and dementia diseases are linked to dysregulations in cholesterol metabolism. Dietary plant sterols, or phytosterols, may interfere to neurodegeneration and cognitive decline, and have cholesterol-lowering, anti-inflammatory, and antioxidant qualities. Here, we investigated the potential associations between circulating cholesterol precursors and metabolites, triglycerides, and phytosterols with cognitive decline in older people by performing multivariate analysis on 246 participants engaged in a population-based prospective study. In our analysis we considered the potential effect of sex and APOEe4. We reveal particular dysregulations of diet-derived phytosterols and endogenous cholesterol synthesis and metabolism, and their variations over time linked to cognitive decline in the general population. These results are significant to the development of interventions to avoid cognitive decline in older adults and suggest that levels of circulating sterols should be taken into account when evaluating risk.

Effects of an 8-week aerobic exercise program on plasma markers for cholesterol absorption and synthesis in older overweight and obese men

BACKGROUND

Increased physical activity is inversely related to the risk to develop cardiovascular disease (CVD). In a recent systematic review, it was reported that CVD patients had an increased cholesterol absorption and a decreased synthesis as compared with control participants. As increased physical activity levels reduce CVD risk, we hypothesized that exercise training will reduce cholesterol absorption and increase endogenous cholesterol synthesis in older overweight and obese men.

METHODS

A randomized, controlled, crossover trial was performed. Seventeen apparently healthy older overweight and obese men were randomized to start with an aerobic exercise or no-exercise control period for 8 weeks, separated by 12 weeks washout. Fasting serum total cholesterol (TC) and non-cholesterol sterol concentrations were measured at baseline, and after 4 and 8 weeks.

RESULTS

The aerobic exercise program did not affect serum TC concentrations. In addition, exercise did not affect TC-standardized serum concentrations of sitosterol and cholestanol that are markers for cholesterol absorption. However, a trend for reduced TC-standardized campesterol concentrations, which is another validated marker for cholesterol absorption, was observed as compared with control. Lathosterol concentrations, reflecting cholesterol synthesis, did not differ between both periods.

CONCLUSIONS

Aerobic exercise training for 8 weeks did not lower serum TC concentrations in older overweight and obese men, but a trend towards a decrease in the cholesterol absorption marker campesterol was found. The cholesterol synthesis marker lathosterol did not change.

TRIAL REGISTRATION

posted on www.clinicaltrials.gov as NCT03272061 on 7 September 2017.

Biomarkers of cholesterol homeostasis in a clinical laboratory database sample comprising 667,718 patients

BACKGROUND

Circulating noncholesterol sterols/stanols (NCS) are used in clinical lipidology as surrogate measures of cholesterol synthesis and absorption, where they can be valuable tools in assessing cholesterol metabolism and personalizing therapies in patients with dyslipidemia.

OBJECTIVES

To describe the distributions of plasma NCS concentrations and inter-NCS correlations in a large cohort of American patients constituting a clinical laboratory database, and to investigate the relationship between circulating NCS, age, sex, and apolipoprotein E (APOE) genotype.

METHODS

A total of 667,718 patient blood samples submitted for testing to Health Diagnostic Laboratory, Inc. (Richmond, VA) were analyzed for cholesterol absorption markers (sitosterol, campesterol, and cholestanol) and one cholesterol synthesis marker (desmosterol). NCS percentiles were determined, along with intermarker correlations (Pearson's R). Analysis of variance was used to assess the effect of age and sex on NCS level, and to evaluate the relationship between cholesterol synthesis/absorption status and APOE genotype in a subset of 336,866 patients.

RESULTS

Mean NCS concentrations were: sitosterol, 2.45 μg/mL; campesterol, 3.3 μg/mL; cholestanol, 2.92 μg/mL; and desmosterol 0.99 μg/mL. The correlations between each NCS and its ratio to total cholesterol ranged from 0.72 (cholestanol) to 0.94 (desmosterol). NCS levels were significantly affected by age and sex (P < .0001), and prevalence of cholesterol hyperabsorption was higher in APOE ε4 allele carriers compared with the other APOE genotypes.

CONCLUSIONS

We have described sample distributions of NCS biomarkers and characterized their relationship to age, sex, and APOE genotype. These data may facilitate research into altered cholesterol homeostasis and human disease, and help physicians optimize lipid-lowering therapies.

Association between cholesterol synthesis/absorption markers and effects of cholesterol lowering by atorvastatin among patients with high risk of coronary heart disease

No indices are currently available to facilitate clinicians to identify patients who need either statin monotherapy or statin-ezetimibe combined treatment. We aimed to investigate whether cholesterol synthesis and absorption markers can predict the cholesterol-lowering response to statin. Total 306 statin-naïve patients with high risk of coronary heart disease (CHD) were treated with atorvastatin 20 mg/day for 1 month. Cholesterol synthesis and absorption markers and LDL cholesterol (LDL-C) levels were measured before and after treatment. Atorvastatin decreased LDL-C by 36.8% (range: decrease of 74.5% to increase of 31.9%). Baseline cholesterol synthesis marker lathosterol and cholesterol absorption marker campesterol codetermined the effect of atorvastatin treatment. The effect of cholesterol lowering by atorvastatin was significantly associated with baseline lathosterol levels but modified bidirectionally by baseline campesterol levels. In patients with the highest baseline campesterol levels, atorvastatin treatment decreased cholesterol absorption by 46.1%, which enhanced the effect of LDL-C lowering. Atorvastatin treatment increased cholesterol absorption by 52.3% in those with the lowest baseline campesterol levels, which attenuated the effect of LDL-C reduction. Especially those with the highest lathosterol but the lowest campesterol levels at baseline had significantly less LDL-C reduction than those with the same baseline lathosterol levels but the highest campesterol levels (27.3% versus 42.4%, P = 0.002). These results suggest that combined patterns of cholesterol synthesis/absorption markers, rather than each single marker, are potential predictors of the LDL-C-lowering effects of atorvastatin in high-risk CHD patients.

Plasma plant sterols serve as poor markers of cholesterol absorption in man

The validation of the use of plasma plant sterols as a marker of cholesterol absorption is frail. Nevertheless, plant sterol concentrations are routinely used to describe treatment-induced changes in cholesterol absorption. Their use has also been advocated as a clinical tool to tailor cholesterol-lowering therapy. Prior to wider implementation, however, the validity of plant sterols as absorption markers needs solid evaluation. Therefore, we compared plasma plant sterol concentrations to gold-standard stable isotope-determined cholesterol absorption. Plasma campesterol/TC concentrations (camp/TC) were measured in a population of 175 mildly hypercholesterolemic individuals (age: 59.7 ± 5.6 years; BMI: 25.5 ± 2.9 kg/m(2); LDL-C: 4.01 ± 0.56 mmol/l). We compared cholesterol absorption according to the plasma dual-isotope method in subjects with the highest camp/TC concentrations (N = 41, camp/TC: 2.14 ± 0.68 μg/mg) and the lowest camp/TC concentrations (N = 39, camp/TC: 0.97 ± 0.22 μg/mg). Fractional cholesterol absorption did not differ between the groups (24 ± 12% versus 25 ± 16%, P = 0.60), nor was it associated with plasma camp/TC concentrations in the total population of 80 individuals (β = 0.13; P = 0.30, adjusted for BMI and plasma triglycerides). Our findings do not support a relation between plasma plant sterol concentrations and true cholesterol absorption and, therefore, do not favor the use of these sterols as markers of cholesterol absorption. This bears direct consequences for the interpretation of earlier studies, as well as for future studies targeting intestinal regulation of cholesterol metabolism.

Plasma noncholesterol sterols: current uses, potential and need for standardization

PURPOSE OF REVIEW

Noncholesterol sterols (NCSs) in plasma encompass endogenous cholesterol precursors and exogenous phytosterols and cholesterol metabolites, which are used as surrogate measures of cholesterol synthesis and cholesterol absorption, respectively. The ratios of cholesterol synthesis to cholesterol absorption surrogates are also utilized to assess the overall balance of cholesterol metabolism, with higher values representing more synthesis and lower values more absorption. The objective of this review is to focus on recent findings using plasma NCSs and their potential in customizing dietary and pharmacological hypolipidemic therapies.

RECENT FINDINGS

NCSs are often used to assess the impact of pharmacological and dietary interventions on cholesterol metabolism. Various forms of dyslipidemia have been characterized using NCSs, and NCSs may be a valuable tool in selecting appropriate treatment therapies. NCSs levels are affected by genetic, dietary and physiological factors and have been related to cardiovascular disease risk.

SUMMARY

The expanded use of plasma NCSs is currently limited by the lack of standardized methodology. However, noncholesterol sterols are still a valuable research tool for the overall assessment of cholesterol metabolism and may have clinical potential in the personalization of diet and medicine.

Inhibition of intestinal cholesterol absorption might explain cholesterol-lowering effect of telmisartan

WHAT IS KNOWN AND OBJECTIVE

Telmisartan, an angiotensin II type 1 receptor blocker (ARB), acts as a partial agonist for peroxisome proliferator-activated receptor-γ, and thus improves abnormalities of glucose metabolism and hypertriglyceridaemia in addition to its documented blood pressure-lowering effects. Recently, it has been demonstrated that telmisartan also lowers the levels of total cholesterol and low-density lipoprotein (LDL) cholesterol levels. This study was designed to investigate the mechanism of cholesterol reduction.

METHODS

We measured serum levels of cholestanol, a cholesterol absorption marker, and lathosterol, a cholesterol synthesis marker, in 20 patients with both hypercholesterolaemia and hypertension. Ten patients were treated with telmisartan and the remaining 10 with fluvastatin.

RESULTS

After 3 months of treatment, total and LDL cholesterol levels decreased in the telmisartan group (P<0.01 for both total and LDL cholesterol levels) and the fluvastatin group (P<0.001 for both total and LDL cholesterol levels). The change in cholestanol level after 3 months of treatment was positively correlated with the levels of total (R=0.72, P<0.05) and LDL cholesterol (R=0.81, P<0.01) in the telmisartan group. The change in lathosterol level was positively correlated with the levels of total (R=0.88, P=0.001) and LDL cholesterol (R=0.89, P=0.001) in the fluvastatin group.

WHAT IS NEW AND CONCLUSIONS

Our results suggest that the cholesterol-lowering effect of telmisartan might be caused by inhibition of cholesterol absorption, whereas that of statins is by inhibition of cholesterol synthesis. If confirmed, co-treatment with the two agents may be useful for synergistically lowering cholesterol in hypertensive patients.

The C3435T polymorphism in ABCB1 influences atorvastatin efficacy and muscle symptoms in a high-risk vascular cohort

OBJECTIVE

The CC genotype of the C3435T polymorphism in ABCB1 is associated with increased P-glycoprotein expression, reduced low-density lipoprotein cholesterol (LDL-C) response to atorvastatin, and a reduced area-under-the-curve in pharmacokinetic studies. We sought to assess the relationship between 1) genotype and Atorvastatin efficacy, independently of variation in cholesterol metabolism and 2) genotype and myalgia.

METHODS

High-risk vascular patients were genotyped and treated with atorvastatin 80 mg for 6 weeks. The lipid panel and percent LDL-C reduction with atorvastatin were related to C3435T genotype. Genotypes and allele frequency were assessed in patients with and without myalgia.

RESULTS

A total of 117 patients were recruited and genotyped. Of these, 98 completed the study with adequate atorvastatin adherence, and 10 reported myalgia. T and C allele frequencies were 0.63 and 0.37, respectively. A 6-week course of atorvastatin (80 mg/day) reduced LDL-C by 58% ± 11% (mean ± SD). Patients with the CC genotype showed less LDL-C reduction with atorvastatin compared with the TT/TC genotype (53% vs 59%, respectively, P = .034), and this finding was independent of variation in cholesterol metabolism (P = .045 after correction for desmosterol and cholestanol/cholesterol ratio). The T allele was more frequent in patients with myalgia than those without (0.80 vs 0.62) and the C allele less frequent (0.20 vs 0.38, P = .043).

CONCLUSION

In patients treated with atorvastatin, the CC genotype at the C3435T polymorphism in ABCB1 is associated with reduced atorvastatin efficacy independently of cholesterol metabolism. The T allele is more frequent and the C allele less frequent in patients with myalgia.

Cholesterol absorption decreases after Roux-en-Y gastric bypass but not after gastric banding

The differences in cholesterol metabolism after the 2 most common forms of obesity surgery, Roux-en-Y gastric bypass (RYGB) and gastric banding (GB), have not been well characterized. In this study, effects of RYGB and GB on cholesterol absorption and synthesis were investigated. To this aim, 1-year follow-up of cholesterol metabolism in 2 nonrandomized cohorts undergoing either RYGB (n = 29; age, 45.2 +/- 7.7 years; body mass index [BMI], 46.0 +/- 6.1 kg/m(2)) or GB (n = 26; age, 45.9 +/- 8.6 years; BMI, 50.1 +/- 7.7 kg/m(2)) was performed in a university hospital center specializing in the treatment of morbid obesity. Serum markers of cholesterol synthesis (cholestenol, desmosterol, and lathosterol) and cholesterol absorption (campesterol, sitosterol, avenasterol, and cholestanol) were measured preoperatively and at follow-up and expressed as ratios to cholesterol. As expected based on observed weight loss (25% after RYGB and 17% after GB, P < .001 between groups), both operations decreased serum levels of cholesterol synthesis markers by 12% to 28% (all Ps < .001). A decrease in cholesterol absorption markers was only observed after RYGB (-26% for sitosterol) and not after GB (+16%, P = 2 x 10(-6) for difference between the groups). The difference in sitosterol ratio between the groups remained significant after adjustment for age, BMI, fasting insulin levels, and nutritional status (P = 2 x 10(-4)), indicating a specific effect related to RYGB. We conclude that decrease in cholesterol absorption is a novel beneficial effect of RYGB. Together with an improved control of blood glucose, this may contribute to a better cardiovascular risk profile after RYGB.

Lipid-lowering effects of ezetimibe for hypercholesterolemic patients with and without type 2 diabetes mellitus

To date, there are very few clinical reports that have compared the effects of ezetimibe on lipid parameters between hypercholesterolemic patients with and without type 2 diabetes mellitus (T2DM). In this study, we recruited patients for hypercholesterolemic groups with T2DM (n = 42; men/women = 24/18; HbA1c = 6.7 ± 5.4%) and without T2DM (n = 21; men/women = 7/14; HbA1c = 5.3 ± 0.4%). Patients were prescribed ezetimibe at a dose of 10 mg/daily for the course of the 12-week study. At baseline and after 12 weeks of treatment, several lipid parameters, including serum low-density-lipoprotein cholesterol (LDL-C), non-high-density-lipoprotein cholesterol (non-HDL-C), high-sensitivity C-reactive protein (hs-CRP), and cholesterol synthesis/absorption-related markers, were measured. Compared with those at the baseline, the levels of LDL-C, non-HDL-C, campesterol, and sitosterol were significantly reduced after 12 weeks of ezetimibe treatment in both groups. After adjusting for confounding factors, such as age, gender, smoking, and BMI, the levels of LDL-C and non-HDL-C displayed significantly greater reductions in the patients with T2DM (-25.1 ± 13.6% in LDL-C, -20.5 ± 11.2% in non-HDL-C) than those without T2DM (-20.5 ± 7.8% in LDL-C, P < 0.05; -17.4 ± 7.6% in non-HDL-C, P < 0.05). The reduction of the level of cholestanol was significantly and positively correlated with those of LDL-C and non-HDL-C in the patients with T2DM. Taken together, these findings indicate that ezetimibe could reduce the levels of atherogenic lipoproteins to a greater extent in hypercholesterolemic patients with T2DM than in those without T2DM.

Baseline cholesterol absorption and the response to ezetimibe/simvastatin therapy: a post-hoc analysis of the ENHANCE trial

Subjects with increased cholesterol absorption might benefit more from statin therapy combined with a cholesterol absorption inhibitor. We assessed whether baseline cholesterol absorption markers were associated with response to ezetimibe/simvastatin therapy, in terms of LDL-cholesterol (LDL-C) lowering and cholesterol absorption inhibition, in patients with familial hypercholesterolemia (FH). In a posthoc analysis of the two-year ENHANCE trial, we assessed baseline cholesterol-adjusted campesterol (campesterol/TC) and sitosterol/TC ratios in 591 FH patients. Associations with LDL-C changes and changes in cholesterol absorption markers were evaluated by multiple regression analysis. No association was observed between baseline markers of cholesterol absorption and the extent of LDL-C response to ezetimibe/simvastatin therapy (beta = 0.020, P = 0.587 for campesterol/TC and beta<0.001, P = 0.992 for sitosterol/TC). Ezetimibe/simvastatin treatment reduced campesterol levels by 68% and sitosterol levels by 62%; reductions were most pronounced in subjects with the highest cholesterol absorption markers at baseline, the so-called high absorbers (P < 0.001). Baseline cholesterol absorption status does not determine LDL-C lowering response to ezetimibe/simvastatin therapy in FH, despite more pronounced cholesterol absorption inhibition in high absorbers. Hence, these data do not support the use of baseline absorption markers as a tool to determine optimal cholesterol lowering strategy in FH patients. However, due to the exploratory nature of any posthoc analysis, these results warrant further prospective evaluation in different populations.