P. Barton Duell

HOMOCYST(E)INE : AN IMPORTANT RISK FACTOR FOR ATHEROSCLEROTIC VASCULAR DISEASE

Homocysteine is an intermediate compound formed during metabolism of methionine. The results of many recent studies have indicated that elevated plasma levels of homocyst(e)ine are associated with increased risk of coronary atherosclerosis, cerebrovascular disease, peripheral vascular disease, and thrombosis. The plasma level of homocyst(e)ine is dependent on genetically regulated levels of essential enzymes and the intake of folic acid, vitamin B6 (pyridoxine), and vitamin B12 (cobalamin). Impaired renal function, increased age, and pharmacologic agents (e.g. nitrous oxide, methotrexate) can contribute to increased levels of homocyst(e)ine. Plausible mechanisms by which homocyst(e)ine might contribute to atherogenesis include promotion of platelet activation and enhanced coagulability, increased smooth muscle cell proliferation, cytotoxicity, induction of endothelial dysfunction, and stimulation of LDL oxidation. Levels of homocysteine can be reduced with pharmacologic doses of folic acid, pyridoxine, vitamin B12, or betaine, but further research is required to determine the efficacy of this intervention in reducing morbidity and mortality associated with atherosclerotic vascular disease.

The relationship between maternal and neonatal umbilical cord plasma homocyst(e)ine suggests a potential role for maternal homocyst(e)ine in fetal metabolism

OBJECTIVE Data on fetal blood homocyst(e)ine concentrations are not available. We tested the hypothesis that homocyst(e)ine crosses the maternal/placental/fetal interphases and is sequestered by the fetus. STUDY DESIGN The concentration of homocyst(e)ine was determined at parturition in peripheral venous plasma from 35 nulliparous healthy pregnant women and umbilical arterial and venous plasma from their conceptus. RESULTS Findings demonstrated a descending concentration gradient of plasma homocyst(e)ine from maternal vein to umbilical vein and to umbilical artery; the decrease at each interphase approximated 1 micromol/L. The neonate weight and gestational age were inversely related to maternal homocyst(e)ine concentrations. CONCLUSION The umbilical vein to umbilical artery homocyst(e)ine decrement suggests that uptake of homocyst(e)ine occurs in the fetus. The likely incorporation of homocyst(e)ine into the fetal metabolic cycle may implicate maternal homocyst(e)ine as having a potential nutritional role in the fetus. Further studies are required to explain the role of homocyst(e)ine in fetal metabolism and development.

Rhabdomyolysis after taking atorvastatin with Gemfibrozil

The findings in this case indicate that atorvastatin, like other DL-3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, may increase the risk of myositis and rhabdomyolysis when used in combination with gemfibrozil.

Long-term efficacy and safety of mipomersen in patients with familial hypercholesterolaemia: 2-year interim results of an open-label extension

Abstract Aims To evaluate the efficacy and safety of extended dosing with mipomersen in patients with familial hypercholesterolaemia (HC) taking maximally tolerated lipid-lowering therapy. Methods and results A planned interim analysis of an ongoing, open-label extension trial in patients (n = 141) with familial HC receiving a subcutaneous injection of 200 mg mipomersen weekly plus maximally tolerated lipid-lowering therapy for up to 104 weeks. The mean changes in low-density lipoprotein cholesterol (LDL-C) from baseline to weeks 26 (n = 130), 52 (n = 111), 76 (n = 66), and 104 (n = 53) were −28, −27, −27, and −28%; and in apolipoprotein B −29, −28, −30, and −31%, respectively. Reductions in total cholesterol, non-high-density lipoprotein-cholesterol, and lipoprotein(a) were comparable with decreases in LDL-C and apolipoprotein B levels. Mean high-density lipoprotein cholesterol increased from baseline by 7 and 6% at weeks 26 and 52, respectively. The long-term safety profile of mipomersen was similar to that reported in the associated randomized placebo-controlled Phase 3 trials. Adverse events included injection site reactions and flu-like symptoms. There was an incremental increase in the median liver fat during the initial 6–12 months that appeared to diminish with continued mipomersen exposure beyond 1 year and returned towards baseline 24 weeks after last drug dose suggestive of adaptation. The median alanine aminotransferase level showed a similar trend over time. Conclusion Long-term treatment with mipomersen for up to 104 weeks provided sustained reductions in all atherosclerotic lipoproteins measured and a safety profile consistent with prior controlled trials in these high-risk patient populations. Clinicaltrials.gov NCT00694109.

Alirocumab in patients with heterozygous familial hypercholesterolaemia undergoing lipoprotein apheresis: the ODYSSEY ESCAPE trial

Aim To evaluate the effect of alirocumab on frequency of standard apheresis treatments [weekly or every 2 weeks (Q2W)] in heterozygous familial hypercholesterolaemia (HeFH). Methods and results ODYSSEY ESCAPE (NCT02326220) was a double-blind study in 62 HeFH patients undergoing regular weekly or Q2W lipoprotein apheresis. Patients were randomly assigned (2:1, respectively) to receive alirocumab 150 mg (n = 41) or placebo (n = 21) Q2W subcutaneously for 18 weeks. From day 1 to week 6, apheresis rate was fixed according to the patient’s established schedule; from weeks 7 to 18, apheresis rate was adjusted based on the patient’s low-density lipoprotein cholesterol (LDL-C) response in a blinded fashion. Apheresis was not performed when the LDL-C value was ≥30% lower than the baseline (pre-apheresis) value. The primary efficacy endpoint was the rate of apheresis treatments over 12 weeks (weeks 7–18), standardized to number of planned treatments. In the alirocumab group the least square (LS) mean ± SE (95% confidence interval [CI]) per cent change in pre-apheresis LDL-C from baseline at week 6 was −53.7 ± 2.3 (−58.2 to − 49.2) compared with 1.6 ± 3.1 (–4.7 to 7.9) in the placebo group. The primary efficacy endpoint showed statistically significant benefit in favour of alirocumab (Hodges–Lehmann median estimate of treatment difference: 0.75; 95% CI 0.67–0.83; P < 0.0001). Therefore, alirocumab-treated patients had a 0.75 (75%) additional reduction in the standardized rate of apheresis treatments vs. placebo-treated patients. During this period, 63.4% of patients on alirocumab avoided all and 92.7% avoided at least half of the apheresis treatments. Adverse event rates were similar (75.6% of patients on alirocumab vs. 76.2% on placebo). Conclusions Lipoprotein apheresis was discontinued in 63.4% of patients on alirocumab who were previously undergoing regular apheresis, and the rate was at least halved in 92.7% of patients. Alirocumab was generally safe and well tolerated.

Treatment Gaps in Adults with Heterozygous Familial Hypercholesterolemia in the United States: Data from the CASCADE-FH Registry

Background— Cardiovascular disease burden and treatment patterns among patients with familial hypercholesterolemia (FH) in the United States remain poorly described. In 2013, the FH Foundation launched the Cascade Screening for Awareness and Detection (CASCADE) of FH Registry to address this knowledge gap. Methods and Results— We conducted a cross-sectional analysis of 1295 adults with heterozygous FH enrolled in the CASCADE-FH Registry from 11 US lipid clinics. Median age at initiation of lipid-lowering therapy was 39 years, and median age at FH diagnosis was 47 years. Prevalent coronary heart disease was reported in 36% of patients, and 61% exhibited 1 or more modifiable risk factors. Median untreated low-density lipoprotein cholesterol (LDL-C) was 239 mg/dL. At enrollment, median LDL-C was 141 mg/dL; 42% of patients were taking high-intensity statin therapy and 45% received >1 LDL-lowering medication. Among FH patients receiving LDL-lowering medication(s), 25% achieved an LDL-C <100 mg/dL and 41% achieved a ≥50% LDL-C reduction. Factors associated with prevalent coronary heart disease included diabetes mellitus (adjusted odds ratio 1.74; 95% confidence interval 1.08–2.82) and hypertension (2.48; 1.92–3.21). Factors associated with a ≥50% LDL-C reduction from untreated levels included high-intensity statin use (7.33; 1.86–28.86) and use of >1 LDL-lowering medication (1.80; 1.34–2.41). Conclusions— FH patients in the CASCADE-FH Registry are diagnosed late in life and often do not achieve adequate LDL-C lowering, despite a high prevalence of coronary heart disease and risk factors. These findings highlight the need for earlier diagnosis of FH and initiation of lipid-lowering therapy, more consistent use of guideline-recommended LDL-lowering therapy, and comprehensive management of traditional coronary heart disease risk factors.

PCSK9 Association With Lipoprotein(a)

RATIONALE Lipoprotein(a) [Lp(a)] is a highly atherogenic low-density lipoprotein-like particle characterized by the presence of apoprotein(a) [apo(a)] bound to apolipoprotein B. Proprotein convertase subtilisin/kexin type 9 (PCSK9) selectively binds low-density lipoprotein; we hypothesized that it can also be associated with Lp(a) in plasma. OBJECTIVE Characterize the association of PCSK9 and Lp(a) in 39 subjects with high Lp(a) levels (range 39-320 mg/dL) and in transgenic mice expressing either human apo(a) only or human Lp(a) (via coexpression of human apo(a) and human apolipoprotein B). METHODS AND RESULTS We show that PCSK9 is physically associated with Lp(a) in vivo using 3 different approaches: (1) analysis of Lp(a) fractions isolated by ultracentrifugation; (2) immunoprecipitation of plasma using antibodies to PCSK9 and immunodetection of apo(a); (3) ELISA quantification of Lp(a)-associated PCSK9. Plasma PCSK9 levels correlated with Lp(a) levels, but not with the number of kringle IV-2 repeats. PCSK9 did not bind to apo(a) only, and the association of PCSK9 with Lp(a) was not affected by the loss of the apo(a) region responsible for binding oxidized phospholipids. Preferential association of PCSK9 with Lp(a) versus low-density lipoprotein (1.7-fold increase) was seen in subjects with high Lp(a) and normal low-density lipoprotein. Finally, Lp(a)-associated PCSK9 levels directly correlated with plasma Lp(a) levels but not with total plasma PCSK9 levels. CONCLUSIONS Our results show, for the first time, that plasma PCSK9 is found in association with Lp(a) particles in humans with high Lp(a) levels and in mice carrying human Lp(a). Lp(a)-bound PCSK9 may be pursued as a biomarker for cardiovascular risk.

Profiling sterols in cerebrotendinous xanthomatosis: Utility of Girard derivatization and high resolution exact mass LC―ESI-MSn analysis

In this study we profile free 3-oxo sterols present in plasma from patients affected with the neurodegenerative disorder of sterol and bile acid metabolism cerebrotendinous xanthomatosis (CTX), utilizing a combination of charge-tagging and LC-ESI-MS(n) performed with an LTQ-Orbitrap Discovery instrument. In addition, we profile sterols in plasma from 24-month-old cyp27A1 gene knockout mice lacking the enzyme defective in CTX. Charge-tagging was accomplished by reaction with cationic Girards P (GP) reagent 1-(carboxymethyl) pyridinium chloride hydrazide, an approach uniquely suited to studying the 3-oxo sterols that accumulate in CTX, as Girards reagent reacts with the sterol oxo moiety to form charged hydrazone derivatives. The ability to selectively generate GP-tagged 3-oxo-4-ene and 3-oxo-5(H) saturated plasma sterols enabled ESI-MS(n) analysis of these sterols in the presence of a large excess (3 orders of magnitude) of cholesterol. Often cholesterol detected in biological samples makes it challenging to quantify minor sterols, with cholesterol frequently removed prior to analysis. We derivatized plasma (10 μl) without SPE removal of cholesterol to ensure detection of all sterols present in plasma. We were able to measure 4-cholesten-3-one in plasma from untreated CTX patients (1207±302 ng/ml, mean±SD, n=4), as well as other intermediates in a proposed pathway to 5α-cholestanol. In addition, a number of bile acid precursors were identified in plasma using this technique. GP-tagged sterols were identified utilizing high resolution exact mass spectra (±5 ppm), as well as MS(2) ([M](+)→) spectra that possessed characteristic neutral loss of 79Da (pyridine) fragment ions, and MS(3) ([M](+)→[M-79](+)→) spectra that provided additional structurally informative fragment ions.

High plasma homocyst(e)ine levels in elderly Japanese patients are associated with increased cardiovascular disease risk independently from markers of coagulation activation and endothelial cell damage

Elevated plasma homocyst(e)ine is a risk factor for cardiovascular disease (CVD) in many populations, but the relationship between homocyst(e)ine and CVD in Japanese subjects has been unclear. It has been hypothesized that the link between homocyst(e)ine and CVD may be mediated in part by activation of coagulation and endothelial cell injury in the elderly Japanese subjects. To further evaluate this hypothesis, the present cross-sectional study was designed to assess the relationships among plasma homocyst(e)ine concentrations, risk of CVD, and markers of coagulation (fibrinogen, FVII, F1+2, FVIIa and FXIIa) and endothelial cell damage (vWF and thrombomodulin) in 146 elderly Japanese subjects (79 healthy controls and 67 patients with CVD). The geometric mean (range) of plasma homocyst(e)ine concentrations was 10.2 (3.2--33) micromol/l in 79 Japanese healthy elderly subjects. As expected, healthy female and male elderly subjects had homocyst(e)ine levels that were 2.5 and 5.3 micromol/; higher, respectively, compared to healthy young control subjects (n=62). Healthy young and elderly men had homocyst(e)ine levels that were 1.7 and 4.5 micromol/l higher, respectively, compared to values in women. This higher plasma homocyst(e)ine levels in the elderly subjects were negatively correlated with levels of folic acid, albumin and total cholesterol, but were not significantly related to markers of coagulation or endothelial cell-damage. The results of multiple logistic regression analyses suggested that high homocyst(e)ine levels were independently related to CVD risk. In addition, levels of FVIIa, and F1+2 were significantly higher in elderly Japanese patients with CVD compared to elderly subjects without CVD, but were unrelated to plasma homocyst(e)ine concentrations. In summary, elevated plasma concentrations of homocyst(e)ine, FVIIa, and F1+2 were associated with increased risk of CVD in elderly male and female Japanese subjects, but the association between homocyst(e)ine and CVD was unrelated to abnormalities in markers of coagulation and endothelial cell damage in this population.

Differential effects of subcutaneous estrogen and progesterone on low-density lipoprotein size and susceptibility to oxidation in postmenopausal rhesus monkeys

OBJECTIVE To study the differential effects of subcutaneous E2 alone or in combination with P on the susceptibility of low-density lipoprotein (LDL) cholesterol to oxidation in naturally postmenopausal diet-controlled rhesus monkeys. DESIGN Prospective, longitudinal controlled study. SETTING Oregon Health Sciences University, Portland, Oregon, and Oregon Regional Primate Research Center, Beaverton, Oregon. PATIENT(S) Five naturally postmenopausal rhesus monkeys. INTERVENTION(S) Estradiol was administered subcutaneously for the first 4 weeks, followed by E2 plus P for 4 weeks, followed by a third 4-week washout period. MAIN OUTCOME MEASURE(S) Changes in plasma lipoprotein levels and oxidation of LDL and serum concentrations of E2 and P. RESULT(S) Levels of LDL cholesterol fell after 4 weeks of treatment with E2, compared with baseline. The lag time to half maximal light absorbancy after 4 weeks of E2 treatment was significantly increased compared with baseline. The maximal absorbance values and the slope of the propagation phase after 4 weeks of treatment with E2 were decreased compared with baseline. After 4 weeks of combined E2 and P treatment, all values were comparable to baseline. CONCLUSION(S) These results suggest that subcutaneous E2 therapy appears to enhance LDL resistance to oxidation and that this effect is attenuated by the addition of the P.