Plasma mevalonic acid exposure as a pharmacodynamic biomarker of fluvastatin/atorvastatin in healthy volunteers.

Fluvastatin and atorvastatin are inhibitors of hydroxy-methylglutaryl-CoA (HMG-CoA) reductase, the enzyme that converts HMG-CoA to mevalonic acid (MVA). The present study reports for the first time the analysis of mevalonolactone (MVL) in plasma samples by UPLC-MS/MS as well as the use of MVA, analyzed as MVL, as a pharmacodynamics parameter of fluvastatin in multiple oral doses (20, 40 or 80 mg/day for 7 days) and atorvastatin in a single oral dose (20, 40 or 80 mg) in healthy female volunteers. this study presents the use of MVL exposure as a pharmacodynamics biomarker of fluvastatin in multiple oral doses (20, 40 or 80 mg/day for 7 days) or atorvastatin in a single oral dose (20, 40 or 80 mg) in healthy volunteers (n = 30). The administration of multiple doses of fluvastatin (n = 15) does not alter the values (geometric mean and 95 % CI) of AUC0-24 h of MVL [72.00 (57.49-90.18) vs 65.57 (51.73-83.12) ng∙h/mL], but reduces AUC0-6 h [15.33 (11.85-19.83) vs 8.15 (6.18-10.75) ng∙h/mL] by approximately 47 %, whereas single oral dose administration of atorvastatin (n = 15) reduces both AUC0-24 h [75.79 (65.10-88.24) vs 32.88 (27.05-39.96) ng∙h/mL] and AUC0-6 h [17.07 (13.87-21.01) vs 7.01 (5.99-8.22) ng∙h/mL] values by approximately 57 % and 59 %, respectively. In conclusion, the data show that the plasma exposure of MVL represents a reliable pharmacodynamic parameter for PK-PD (pharmacokinetic-pharmacodynamic) studies of fluvastatin in multiple doses and atorvastatin in a single dose.

Mevalonate kinase deficiency associated with ataxia and retinitis pigmentosa in two brothers with MVK gene mutations.

PURPOSE: To report the clinical and molecular genetic findings in two brothers with retinitis pigmentosa (RP) and mevalonate kinase deficiency (MKD). METHODS: The brothers were examined clinically and with fundus autofluorescence, near-infrared autofluorescence, and spectral domain optical coherence tomography. Targeted resequencing was done with a custom designed gene panel containing 78 genes associated with RP. Mutations were confirmed by direct Sanger sequencing. RESULTS: Both brothers, aged 46 and 47 years, were found to carry compound heterozygous mutations in the MVK gene (c.59A>C, c.1000G>A) encoding mevalonate kinase. They presented with severe ataxia, pseudophakia due to early onset cataract, and progressed retinitis pigmentosa. In one brother with cystoid macular edema, treatment with dorzolamide was beneficial. Serum IgD levels were markedly increased in both brothers and mevalonic acid blood and urine levels were markedly increased in the one brother who could be examined. The disease severity differed between the brothers-one had more severe ataxia and less severe visual deficiency compared to the other. CONCLUSION: MKD can be associated with RP and early onset cataract. Most MKD patients developing RP carry the (p.Ala334Thr) mutation. Macular edema can be treated using local dorzolamide.

A Pilot Study of the Association of Markers of Cholesterol Synthesis with Disturbed Sleep in Smith-Lemli-Opitz Syndrome.

OBJECTIVE: Smith-Lemli-Opitz syndrome (SLOS) is a rare genetic disorder characterized by cholesterol synthesis impairment. A host of physical, developmental, and behavioral presentations are associated with SLOS, many of which have been related with disorder severity. Sleep disturbance is commonly reported in SLOS. This study is the first to examine the association between sleep disturbance and biomarkers of cholesterol synthesis defect. METHOD: Twenty youth with SLOS participated. Biomarkers of cholesterol synthesis were obtained, including plasma sterols (i.e., 7-dehydrocholesterol, 8-dehydrocholesterol, and cholesterol), mevalonic acid, and 24-S hydroxycholsterol. A ratio of plasma cholesterol precursors to cholesterol levels was used as a measure of biochemical severity. Parents reported their children's sleep problems using the Children's Sleep Habits Questionnaire. RESULTS: Most markers of cholesterol synthesis disruption were associated with overall sleep disturbance. Biochemical severity of SLOS was also associated with specific sleep problems (e.g., decreased sleep duration and increased sleep onset delay) and was identified as a significant predictor of these factors. CONCLUSION: This study is the first to demonstrate associative relationships between cholesterol levels and sleep disturbance in youth with SLOS. These results add to the current understanding of how cholesterol levels may contribute to the behavioral phenotype of SLOS. These findings may inform future studies related to the role cholesterol synthesis defects play in the behavioral phenotype of SLOS and, subsequently, modalities of intervention for behavioral symptoms.

An Ester of ß-Hydroxybutyrate Regulates Cholesterol Biosynthesis in Rats and a Cholesterol Biomarker in Humans.

In response to carbohydrate deprivation or prolonged fasting the ketone bodies, ß-hydroxybutyrate (ßHB) and acetoacetate (AcAc), are produced from the incomplete ß-oxidation of fatty acids in the liver. Neither ßHB nor AcAc are well utilized for synthesis of sterols or fatty acids in human or rat liver. To study the effects of ketones on cholesterol homeostasis a novel ßHB ester (KE) ((R)-3-hydroxybutyl (R)-3-hydroxybutyrate) was synthesized and given orally to rats and humans as a partial dietary carbohydrate replacement. Rats maintained on a diet containing 30-energy % as KE with a concomitant reduction in carbohydrate had lower plasma cholesterol and mevalonate (-40 and -27 %, respectively) and in the liver had lower levels of the mevalonate precursors acetoacetyl-CoA and HMG-CoA (-33 and -54 %) compared to controls. Whole liver and membrane LDL-R as well as SREBP-2 protein levels were higher (+24, +67, and +91 %, respectively). When formulated into a beverage for human consumption subjects consuming a KE drink (30-energy %) had elevated plasma ßHB which correlated with decreased mevalonate, a liver cholesterol synthesis biomarker. Partial replacement of dietary carbohydrate with KE induced ketosis and altered cholesterol homeostasis in rats. In healthy individuals an elevated plasma ßHB correlated with lower plasma mevalonate.

Synthesis of mevalonate- and fluorinated mevalonate prodrugs and their in vitro human plasma stability.

The mevalonate pathway is essential for the production of many important molecules in lipid biosynthesis. Inhibition of this pathway is the mechanism of statin cholesterol-lowering drugs, as well as the target of drugs to treat osteoporosis, to combat parasites, and to inhibit tumor cell growth. Unlike the human mevalonate pathway, the bacterial pathway appears to be regulated by diphosphomevalonate (DPM). Enzymes in the mevalonate pathway act to produce isopentenyl diphosphate, the product of the DPM decarboxylase reaction, utilize phosphorylated (charged) intermediates, which are poorly bioavailable. It has been shown that fluorinated DPMs (6-fluoro- and 6,6,6-trifluoro-5-diphosphomevalonate) are excellent inhibitors of the bacterial pathway; however, highly charged DPM and analogs are not bioavailable. To increase cellular permeability of mevalonate analogs, we have synthesized various prodrugs of mevalonate and 6-fluoro- and 6,6,6-trifluoromevalonate that can be enzymatically transformed to the corresponding DPM or fluorinated DPM analogs by esterases or amidases. To probe the required stabilities as potentially bioavailable prodrugs, we measured the half-lives of esters, amides, carbonates, acetals, and ketal promoieties of mevalonate and the fluorinated mevalonate analogs in human blood plasma. Stability studies showed that the prodrugs are converted to the mevalonates in human plasma with a wide range of half-lives. These studies provide stability data for a variety of prodrug options having varying stabilities and should be very useful in the design of appropriate prodrugs of mevalonate and fluorinated mevalonates.

An ultrasensitive enzymatic method for measuring mevalonic acid in serum.

We have developed a simple, precise, and ultrasensitive enzymatic method for measuring serum mevalonic acid (MVA) concentration, which is thought to be a good indicator of the in vivo cholesterol biosynthesis rate. This assay is based on an enzyme cycling reaction and makes use of HMG-CoA reductase (HMGR), thio-NAD, NADH, and CoA. MVA participates in the HMGR cycling reaction, and its level is measured based on the production of thio-NADH, which is determined from the change in absorbance at 405 nm. To achieve high specificity, we used mevalonate kinase (MVK) in addition to HMGR. Only substrates able to participate in both the HMGR cycling reaction and the MVK reaction are measured as MVA. The detection limit for MVA is 0.4 ng/ml (2.7 nmol/l), and the calibration curve for MVA is linear up to 44 ng/ml (300 nmol/l). Regression analysis with 40 serum samples showed the accuracy of quantifying MVA with this enzymatic assay to be comparable to that using LC-MS/MS (correlation: y = 0.83x + 0.24; r = 0.97). This procedure is simple, precise, and robust. It is also rapid and has a high throughput, making it potentially useful for clinical applications.

[Hyperimmunoglobulinemia D and periodic fever syndrome].

Hyperimmunogloblinemia D and periodic fever syndrome (HIDS) is inherited autoinflammatory syndrome caused by deficiency of the mevalonate kinase (MK), which is involved in metabolism of cholesterol. The disease is characterized as periodic fever from early infancy accompanied by elevated serum C-reactive protein. Since clinical symptoms such as abdominal symptom, skin rash, and arthritis are common to other autoinflammatory disease, the diagnosis of HIDS during clinical work is difficult for the physicians without suspicion of HIDS for infants suffering from fever of unknown origin. Moreover, serum IgD levels are not high during infancy conflicting to the name of the disease, which is often misunderstood in the clinicians. Thus, the diagnosis of HIDS in Japan is bothering, depending on the lack of correct recognition of the disease and on the lack of commercially available examination for the disease. It is important for clinicians, especially pediatricians to update current knowledge about HIDS and to learn the appropriate way to the definitive diagnosis of HIDS, because HIDS patients exist also in Japan and the specific therapies for HIDS would be developed in the near future.

Liquid chromatography-tandem mass spectrometry method for the measurement of serum mevalonic acid: a novel marker of hydroxymethylglutaryl coenzyme A reductase inhibition by statins.

BACKGROUND: Mevalonic acid (MVA) is synthesized at an early and rate-limiting step in the biosynthesis of cholesterol by the enzyme hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase, and is a useful measure of statin efficacy or treatment. A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the measurement of serum MVA has been developed. METHODS: Following the in vitro conversion of MVA to mevalonic acid lactone (MVAL) in the serum, MVAL and a deuterated internal standard were extracted using an online solid-phase extraction procedure. Chromatographic separation was achieved using a Luna PFP column (Phenomenex), with enhanced selectivity and improved resolution for polar compounds. A gradient system was used, with mobile phase comprising methanol and water (5 mmol/L ammonium formate buffer, pH 2.5). Analysis was performed using an API 5000 tandem mass spectrometer (Applied Biosystems) in positive electrospray ionization mode. RESULTS: The method showed excellent recoveries (98 ± 8%) and imprecision (intra-assay coefficient of variation of 2.2% [6.5 ng/mL] and 2.6% [10.5 ng/mL], and inter-assay coefficient of variation of 9% [10.5 ng/mL]). The assay provides a calibration range up to 50 ng/mL with a limit of detection at 0.1 ng/mL. CONCLUSION: A simple, rapid and analytically specific method has been developed for the measurement of serum MVA, in the form of MVAL. The high analytical sensitivity of the method allows for accurate quantitation of MVAL in serum samples, both at the endogenous levels found in healthy individuals and in statin-treated patients where normal levels are expected to be greatly reduced through the inhibition of HMG-CoA reductase.

The validation of a simple LC/MS/MS method for determining the level of mevalonic acid in human plasma.

A simple plasma extraction method coupled with liquid chromatography-tandem mass spectrometry (LC/MS/MS) detection was developed and validated for the analysis of endogenous mevalonic acid (MVA), a biomarker indicative of the rate of cholesterol biosynthesis, in human plasma samples. The analyte was extracted from the plasma matrix using a straightforward liquid-liquid sample preparation procedure. The extract supernatants were evaporated, reconstituted in aqueous solvent and injected into the LC/MS/MS system without further processing. The chromatographic separation was achieved on a reverse-phase high-performance liquid chromatography column. The accuracy and precision of the method was determined over the concentration range 0.25-25 ng/mL MVA from human plasma extracts in three validation batch runs. Inter-assay precision (%CV) and accuracy (%RE) of the quality control samples were ≤7.00% (at lower limit quality control) and ≤6.10%, respectively. The sensitivity and throughput of this assay was significantly improved relative to previously published methods, resulting in smaller sample requirements and shorter analysis time. Assay results from a clinical study following the oral administration of an exploratory statin demonstrate that this procedure could potentially be used in the investigation of therapies associated with hypercholesterolemia.

Pharmacokinetic/pharmacodynamic modeling and simulation of rosuvastatin using an extension of the indirect response model by incorporating a circadian rhythm.

Pharmacokinetic/pharmacodynamic (PK/PD) modeling and simulation enable the prediction of the effect of a medication in various situations in clinical practice. The aims of this study were to predict the relationships between the effect of rosuvastatin and various factors such as poor compliance, and morning and evening dosages, as well as the change in the pharmacokinetics of rosuvastatin. We characterized the PK/PD model of plasma mevalonic acid (MVA) profiles after rosuvastatin administration and simulated the plasma MVA concentration in various dosage regimens. The plasma rosuvastatin and MVA concentrations reported by Martin et al. were used as the source of PK/PD modeling data. For each simulation, a summary parameter, the area under the plasma MVA concentration-time curves for 24 h in the steady state (AUEC(24)), was used to characterize the time course of each endpoint. To estimate the influence of PK parameters on rosuvastatin effects, the AUEC(24) reduction ratio of baseline levels was simulated from the 0.33-3.0-fold value of each PK parameter estimate. The AUEC(24) reduction ratio was 7.7% lower after morning administration than after evening administration. The changes in the PK parameters more prominently affected the AUEC(24) reduction ratio after morning administration than after evening administration. The simulated plasma MVA concentrations almost reached their baseline levels in the case of patients who forgot to take rosuvastatin. These results suggest that the parameters can be used to determine the effective rosuvastatin dosage regimen.

The effects of rosuvastatin on the serum cortisol, serum lipid, and serum mevalonic acid levels in the healthy Indian male population.

In this open-label, balanced, randomized, placebo-controlled, parallel study, healthy male volunteers were randomly divided into two groups. Each group received either a single oral dose of rosuvastatin 20 mg or placebo. Estimations were done at predose on day 1 of dosing (baseline) and 24 h postdose after days 7 and 14. Serum cortisol and serum lipid levels were estimated using enzyme-linked immunosorbent assay kits and serum mevalonic acid (MVA) levels were measured using validated liquid chromatography-tandem mass spectrometry method. Rosuvastatin produced a statistically significant (P < 0.05) decrease in total cholesterol, low-density lipoprotein cholesterol, very low-density lipoprotein cholesterol, and triglycerides. However, the increase in high-density lipoprotein cholesterol and decrease in cortisol and MVA were not statistically significant when compared to the placebo-treated group. The study showed that rosuvastatin at a dose of 20 mg/day for a period of 14 days was very potent as cholesterol-lowering agent, without any significant change in serum cortisol level in the healthy Indian male population.

Increase of serum cholesterol levels by heat-moisture-treated high-amylose cornstarch in rats fed a high-cholesterol diet.

The effects of four cornstarches containing various contents of resistant starch on serum and liver cholesterol levels in rats fed a high-cholesterol diet were investigated. Male Sprague Dawley rats (aged 4 weeks) were divided into four groups (n = 7) and fed high-cholesterol diets containing 15% of cornstarch (CS), heat-moisture-treated CS (HCS), high-amylose CS (HA), or heat-moisture-treated HA (HHA) for 21 days. The results showed that the serum and hepatic level of total cholesterol, LDL-cholesterol, and triglyceride in rats of the HHA group and their arteriosclerosis index were significantly higher, suggesting that HHA increases the risk of arteriosclerosis under a high-cholesterol dietary condition. No significant between-group differences were noted in the levels of plasma mevalonic acid and hepatic HMG-CoA reductase mRNA, whereas fecal cholesterol excretion was significantly higher in the HHA group, indicating that the elevation of the serum and liver cholesterol levels was not due to the promotion of liver cholesterol synthesis and cholesterol absorption in the intestine.

Time-of-intake (morning versus evening) of extended-release fluvastatin in hyperlipemic patients is without influence on the pharmacodynamics (mevalonic acid excretion) and pharmacokinetics.

OBJECTIVE: Statins inhibit the rate-limiting step in cholesterol biosynthesis, the conversion of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) to mevalonate by HMG-CoA reductase. Statins are usually taken in the evening as the HMG-CoA reductase activity is high during the night. This recommendation might not apply if statins are given as extended-release (ER) formulations. The present study investigated the influence of time of intake of fluvastatin 80 mg ER on cholesterol biosynthesis. Main objectives were to measure the change in 24-hour urinary mevalonic acid excretion, to determine plasma concentrations of mevalonic acid and fluvastatin and to monitor triglycerides, total cholesterol, HDL-cholesterol and LDL-cholesterol. METHODS: This was a randomized, 2-period crossover study in 26 hypercholesterolemic patients who received a single daily dose of fluvastatin both in the morning and in the evening. RESULTS: At baseline, the amount of mevalonic acid was 204.9 +/- 68.1 microg/g creatinine. After a single dose of fluvastatin mean urine values of mevalonate were significantly reduced to 129.8 +/- 66.2 micro/g (evening) and to 118.7 +/-34.3 microg/g (morning; n.s. between groups), thus representing a reduction of about 39%. Compared to baseline, plasma mevalonate concentrations were decreased by fluvastatin resulting in similar 24-hour profiles after the morning and the evening dosage. The pharmacokinetics of fluvastatin were similar in both periods of the study, with higher plasma concentrations for several hours following the evening dosage. CONCLUSION: This study demonstrates that fluvastatin ER is equally effective in inhibiting cholesterol biosynthesis when given once daily in the morning and once daily in the evening.

Validation of the LC-MS/MS method for the quantification of mevalonic acid in human plasma and determination of the matrix effect.

A simple, specific, and sufficiently sensitive liquid chromatography-tandem mass spectrometry (negative-ion electrospray ionization) methodology to determine mevalonic acid (MVA) in human plasma is described, and its application to the analysis of rat plasma MVA levels after rosuvastatin administration is demonstrated. The method was validated over the linearity range of 0.5-50.0 ng/ml (r(2) > 0.99) using deuterated MVA as an internal standard. The lower limit of quantification was 0.5 ng/ml. The assay procedure involved the isolation of MVA from plasma samples using solid-phase extraction. Chromatographic separation was achieved on a HyPurity Advance column with a mobile phase consisting of ammonium formate buffer (10 mM, pH 8.0) and acetonitrile (70:30, v/v). Excellent precision and accuracy were observed. MVA and deuterated mevalonolactone were stable in water and plasma under different storage and processing conditions. The recovery observed was low, which was attributable to a significant matrix effect. A significant decrease (30-40%; P < 0.05) was observed in rat plasma MVA levels after rosuvastatin administration.

First-trimester enzymatic and molecular prenatal diagnosis of mevalonic aciduria.

Prenatal diagnosis was offered to a family at risk of mevalonic aciduria. A chorionic villus sample was obtained and both mevalonate kinase activity and mutation analysis were done. An affected fetus was diagnosed.

Liquid chromatography/tandem mass spectrometry methods for quantitation of mevalonic acid in human plasma and urine: method validation, demonstration of using a surrogate analyte, and demonstration of unacceptable matrix effect in spite of use of a stable isotope analog internal standard.

Selective, accurate, and reproducible liquid chromatography/tandem mass spectrometry (LC/MS/MS) methods were developed and validated for the determination of mevalonic acid, an intermediate in the biosynthesis of cholesterol and therefore a useful biomarker in the development of cholesterol lowering drugs, in human plasma and urine. A hepta-deuterated analog of mevalonic acid was used as the internal standard. For both methods, calibration standards were prepared in water, instead of human plasma and urine, due to unacceptably high levels of endogenous mevalonic acid. The lower quality control (QC) samples were prepared in water while the higher QC samples were prepared in the biological matrices. For the isolation/purification of mevalonic acid from the plasma and urine matrices, the samples were first acidified to convert the acid analyte into its lactone form. For the plasma samples, the lactone analyte was retained on and then eluted off a polymeric solid-phase extraction (SPE) sorbent. For the urine method, the sample containing the lactone analyte was passed through a C-18 SPE column, which did not retain the analyte, with the subsequent analyte retention on and then elution off a polymeric SPE sorbent. Chromatographic separation was achieved isocratically on a polar-endcapped C-18 analytical column with a water/methanol mobile phase containing 0.5 mM formic acid. Detection was by negative-ion electrospray tandem mass spectrometry. The standard curve range was 0.500-20.0 ng/mL for the plasma method and 25.0-1,000 ng/mL for the urine method. Excellent accuracy and precision were obtained for both methods at all concentration levels tested. It was interesting to note that for certain batches of urine, when a larger sample volume was used for analysis, a high degree of matrix effect was observed which resulted not only in the attenuation of the absolute response, but also in a change of analyte/internal standard response ratio. This demonstrated that, under certain conditions, the use of a stable isotope analog internal standard does not, contrary to conventional thinking, guarantee the constancy of the analyte/internal response ratio, which is a prerequisite for a rugged bioanalytical method. On the other hand, under conditions where the sample matrix does not have such a deleterious effect, we have found that a stable isotope analog could serve as a surrogate (substitute) analyte. Thus, we have shown that using calibration standards prepared by spiking plasma with tri-deuterated or tetra-deuterated mevalonic acid, instead of mevalonic acid itself (the analyte), plasma QC samples that contain mevalonic acid can be successfully analyzed for the accurate and precise quantitation of mevalonic acid. The use of a surrogate analyte provides the opportunity to gauge the daily performance of the method for the low concentration levels prepared in the biological matrix, which otherwise is not achievable because of the endogenous concentrations of the analyte in the biological matrices.

Treatment with atorvastatin alters the ratio of interleukin-12/interleukin-10 gene expression [corrected].

BACKGROUND: Statins have been shown to have pleiotropic effects extending beyond their ability to lower cholesterol. MATERIAL AND METHODS: Seventeen patients with heterozygous familial hypercholesterolaemia participated in a single-blind placebo controlled study. The patients underwent three treatment regimens: placebo (4 weeks), atorvastatin 10 mg day(-1) (4 weeks) and atorvastatin 40 mg day(-1) (12 weeks). Following each treatment period, serum lipids and plasma mevalonic acid were measured, mononuclear leukocytes were isolated and total RNA was prepared. The content of mRNA for IL-12p35 and IL-10 was assayed, blinded, by real-time quantitative polymerase chain reactions. RESULTS: Treatment of the subjects with atorvastatin decreased the abundance of IL-12p35 mRNA in mononuclear cells, but did not alter that of IL-10, so that the ratio of the IL-12p35 to IL-10 mRNA content was significantly reduced (P < 0.0026). The IL-12p35/IL-10 ratio correlated significantly with plasma mevalonic acid concentrations but not with serum LDL concentrations. CONCLUSIONS: This study provides evidence that atorvastatin exerts an immunomodulatory effect in vivo, characterized by a decrease in the ratio of IL-12 mRNA to IL-10 mRNA in leukocytes. The immunomodulatory effect of statins, in addition to their cholesterol-lowering properties, may contribute to the rapid cardiovascular benefit observed during treatment with statins and reduced the rate of rejection in patients with solid organ transplantation.

Temperature dependence of mutant mevalonate kinase activity as a pathogenic factor in hyper-IgD and periodic fever syndrome.

Hyper-IgD and periodic fever syndrome (HIDS) and mevalonic aciduria are autosomal recessive disorders characterized by recurrent episodes of fever and generalized inflammation. Both syndromes are caused by specific mutations in the gene encoding mevalonate kinase (MK), resulting in a depressed enzymatic activity mainly due to reduced protein levels. We studied the effect of temperature on the activity of wild-type and several mutant MKs in fibroblasts. All fibroblast cell lines from HIDS patients and harbouring the common V377I MVK allele displayed substantially higher MK activities at 30 degrees C as compared to 37 degrees C. As shown by temperature inactivation experiments this resulted in a protein nearly as stable as in control cell lines, indicating that primarily the maturation of the protein is affected. Accordingly, when HIDS cell lines were cultured at 39 degrees C, MK activity decreased further. This triggered a compensatory increase in 3-hydroxy-3-methylglutaryl-CoA reductase activity, indicating that MK becomes progressively rate-limiting. A similar phenomenon occurs in vivo. MK activity in peripheral blood mononuclear cells drops 2-8-fold when HIDS patients experience febrile attacks. Our results suggest that minor elevations in temperature can set off a chain of events with MK becoming progressively rate-limiting, leading to a temporary deficiency of isoprenoid end-products, which induces inflammation and fever.

Effects of pravastatin sodium on mevalonate metabolism in common marmosets.

In experimental animals and humans, the concentration of serum mevalonate (MVA), a direct product of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, is considered to reflect the activity of whole-body sterol synthesis. The relationship between the concentration of serum MVA and the activity of sterol synthesis in tissues, however, has not been fully clarified. In the present study, we examined MVA metabolism by using pravastatin, a liver-selective inhibitor of HMG-CoA reductase, and common marmosets, a good model animal for studying lipid metabolism. In the time course study, the maximal reduction in the concentration of serum MVA was observed 2 h after a single oral administration of 30 mg/kg pravastatin to common marmosets. We, therefore, examined the relationship between the concentrations of serum and hepatic MVA, and sterol synthesis in some tissues at this time point. Sterol synthesis was determined ex vivo in tissue slices by measuring the incorporation of [14C]acetate into digitonin-precipitable [14C]sterols. Pravastatin at 0.03-30 mg/kg reduced dose-dependently the activity of hepatic sterol synthesis, whereas no significant reduction of sterol synthesis was observed in other tissues such as intestine, kidney, testis and spleen, even with the highest dose (30 mg/kg). The liver-specific inhibition of sterol synthesis caused parallel reductions in the concentrations of both serum and liver MVA. In addition, there were good correlations between the concentration of either serum or hepatic MVA and the activity of hepatic sterol synthesis. These data indicate that the major origin of serum MVA is the liver, and that the concentration of serum MVA reflects the concentration of hepatic MVA and the activity of hepatic sterol synthesis 2 h after a single oral administration of pravastatin in common marmosets.