Anuradha S. Pappu

Expanded-dose simvastatin is effective in homozygous familial hypercholesterolaemia

Patients with homozygous familial hypercholesterolaemia (HFH) have abnormalities in both low-density lipoprotein (LDL) receptor alleles, resulting in severe hypercholesterolaemia and premature coronary heart disease. Limited treatment options are available and the response to drug therapy has been poor. In the present paper, we have evaluated the efficacy and safety of simvastatin at doses beyond the current maximal dose of 40 mg/day in patients with HFH. After a 4 week placebo diet run-in period, 12 patients with well-characterized HFH were randomized to simvastatin 80 mg/day administered in three divided doses (n = 8; group 1) or 40 mg once daily (n = 4; group 2). After 9 weeks, the dose in group 1 was increased to 160 mg/day while the dose in group 2 was kept at 40 mg/day, but with the drug given in three divided doses and treatment continued for an additional 9 weeks. All 12 patients completed the study and there were no serious or unexpected adverse effects. LDL-cholesterol concentrations fell by 14% at the 40 mg/day dose, but were reduced further at the higher doses (25% at the 80 mg/day and by 31% at the 160 mg/day dosage, P < 0.0001). Excretion of urinary mevalonic acid, as an index of in vivo cholesterol biosynthesis, was reduced but did not correlate with reduction in LDL-cholesterol in the individual patients. The magnitude of response to therapy was not predicted by the LDL-receptor gene defect as patients with the same LDL-receptor mutations responded differently to the same dose of simvastatin therapy. The ability of expanded doses of simvastatin (80 or 160 mg/day) to reduce LDL-cholesterol levels in patients with HFH, even if receptor negative, suggests that at these doses, the drug reduces LDL production. Simvastatin therapy, at doses of 80 or 160 mg/day, should therefore be considered in all patients with HFH, either as an adjunct to apheresis, or as monotherapy for those patients who do not have access to apheresis or other such treatment modalities.

Smith-Lemli-Opitz syndrome.

Smith-Lemli-Opitz syndrome (SLOS) is an autosomal recessive, multiple congenital malformation and intellectual disability syndrome, with clinical characteristics that encompass a wide spectrum and great variability. Elucidation of the biochemical and genetic basis for SLOS, specifically understanding SLOS as a cholesterol deficiency syndrome caused by mutation in DHCR7, opened up enormous possibilities for therapeutic intervention. When cholesterol was discovered to be the activator of sonic hedgehog, cholesterol deficiency with inactivation of this developmental patterning gene was thought to be the cause of SLOS malformations, yet this explanation is overly simplistic. Despite these important research breakthroughs, there is no proven treatment for SLOS. Better animal models are needed to allow potential treatment testing and the study of disease pathophysiology, which is incompletely understood. Creation of human cellular models, especially models of brain cells, would be useful, and in vivo human studies are also essential. Biomarker development will be crucial in facilitating clinical trials in this rare condition, because the clinical phenotype can change over many years. Additional research in these and other areas is critical if we are to make headway towards ameliorating the effects of this devastating condition.

Dietary Cholesterol Feeding Suppresses Human Cholesterol Synthesis Measured by Deuterium Incorporation and Urinary Mevalonic Acid Levels

The objective of this study was to measure the response of cholesterol biosynthesis in subjects to three different amounts of dietary cholesterol: 50 (low), 350 (medium), and 650 (high) mg cholesterol per 2800 kcal. Individuals with low (n = 7), normal (n = 12), and elevated (n = 11) plasma cholesterol concentrations consumed in random order solid-food test diets (15%, 55%, and 30% of energy as protein, carbohydrate, and fat, respectively) at each dietary cholesterol level. The three diets were consumed for 4 weeks each, and each dietary phase was separated by a 4-week washout period. During the final week of each diet, 0.7 g D2O was given per kilogram of body water and deuterium incorporation into the erythrocyte cholesterol pool was measured for 24 hours. Urinary mevalonate levels were also determined in samples obtained during two consecutive 24-hour periods. Both techniques provided measurements of whole-body cholesterol biosynthesis. In all subjects the cholesterol synthesis rate as measured by deuterium incorporation was significantly lower (P < .05) after the transition from low- to medium- and low- to high-cholesterol diets. Urinary mevalonate excretion decreased after the change from the medium- to high- (P < .05) and low- to high- (P < .01) cholesterol diets. Although correspondence between the two methods was poor, they both indicated some suppression of cholesterol synthesis by dietary cholesterol. The response of cholesterogenesis to different amounts of dietary cholesterol was related to the rate of synthesis under depressed conditions of the low-cholesterol diet. These findings indicate modest downregulation of synthesis in response to dietary cholesterol in humans, independent of plasma cholesterol levels.

Inhibition of cholesterol synthesis by atorvastatin in homozygous familial hypercholesterolaemia.

Patients with homozygous familial hypercholesterolaemia (HoFH) have markedly elevated low density lipoprotein (LDL) cholesterol levels that are refractory to standard doses of lipid-lowering drug therapy. In the present study we evaluated the effect of atorvastatin on steady state concentrations of plasma lipids and mevalonic acid (MVA), as well as on 24-h urinary excretion of MVA in patients with well characterized HoFH. Thirty-five HoFH patients (18 males; 17 females) received 40 mg and then 80 mg atorvastatin/day. The dose of atorvastatin was increased further to 120 mg/day in 20 subjects and to 160 mg/day in 13 subjects who had not achieved LDL cholesterol goal, or in whom the dose of atorvastatin had not exceeded 2.5 mg/kg body wt per day. LDL cholesterol levels were reduced by 17% at the 40 mg/day and by 28% at the 80 mg/day dosage (P<0.01). Reduction in LDL cholesterol in the five receptor negative patients was similar to that achieved in the 30 patients with residual LDL receptor activity. Plasma MVA and 24-h urinary excretion of MVA, as markers of in vivo cholesterol synthesis, were elevated at baseline and decreased markedly with treatment. Urinary MVA excretion decreased by 57% at the 40 mg/day dose and by 63% at the 80 mg/day dosage (P<0. 01). There was a correlation between reduction in LDL cholesterol and reduction in urinary MVA excretion; those patients with the highest basal levels of MVA excretion and thus the highest rates of cholesterol synthesis having the greatest reduction in LDL cholesterol (r=0.38; P=0.02). Increasing the dose of atorvastatin to 120 and 160 mg/day did not result in any further reduction in LDL cholesterol or urinary MVA excretion suggesting a plateau effect with no further inhibition of cholesterol synthesis at doses of atorvastatin greater than 80 mg/day.

Correspondence between plasma mevalonic acid levels and deuterium uptake in measuring human cholesterol synthesis

Abstract. To assess the validity of two techniques capable of identifying immediate changes in human cholesterol production, plasma mevalonic acid levels and the rate of uptake of deuterium into plasma free cholesterol were compared in 5 healthy individuals over 48 h. The free‐living subjects self‐selected three meals per day prior to and during study. At t = 0, deuterium oxide was administered orally. Blood samples were collected before and every 4 h after dosing. Total cholesterol and mevalonic acid levels were determined in plasma at each timepoint. Deuterium enrichment changes in plasma free cholesterol, relative to plasma water content, were used to calculate free cholesterol fractional synthetic rates (FSR) at each timepoint. Total plasma cholesterol levels remained constant, whereas significant circadian rhythmicity was observed in both plasma mevalonic acid and deuterium uptake methods, with nadir and peak formation rates indicated at 14.00 to 16.00 h and about midnight, respectively. It is suggested that plasma mevalonic acid levels and free cholesterol deuterium uptake rate techniques are both suitable techniques for short‐term measurement of human cholesterol synthesis.

Reduction in plasma low-density lipoprotein cholesterol and urinary mevalonic acid by lovastatin in patients with heterozygous familial hypercholesterolemia

The effects of lovastatin, an inhibitor of 3-hydroxy-3-methyl glutaryl coenzyme A reductase (HMG CoA reductase), on 24-hour urinary excretion rates of mevalonic acid (an intermediate in cholesterol biosynthesis) and plasma low-density lipoprotein (LDL) cholesterol concentrations were evaluated in patients with heterozygous familial hypercholesterolemia (FH). The mean rates of urinary mevalonate excretion of 28 FH patients were initially higher (2.95 +/- 0.29 (+/- SEM) mumols/d) than in 17 control subjects (1.82 +/- 0.12 mumols/d). Patients with FH were treated with sequentially increasing doses of lovastatin (10, 20, 40, and 80 mg daily, taken as a twice daily dosage) for a period of 6 weeks on each dose. When compared to baseline, LDL cholesterol levels fell by 22%, 26%, 30%, and 35% respectively, on these different doses. The mean daily urinary mevalonate excretion decreased from baseline by 19% after 4 weeks on 10 mg daily of lovastatin, 35% on 20 mg, and 31% on 40 mg and 80 mg daily. Similar decreases in urinary mevalonate excretions were observed when patients with FH were treated directly with 40 mg (20 mg twice daily) or 80 mg (40 mg twice daily) mg of lovastatin daily. The magnitude of decrease in LDL cholesterol did not show any significant correlation with the changes in urinary excretion of mevalonic acid. Lovastatin therapy decreases rates of urinary mevalonate excretion (which has previously been shown to reflect rates of cholesterol synthesis) by up to 35% at doses of 20 to 80 mg/d; such a decrease seems unlikely to compromise other important cellular requirements for mevalonate.

Treatment of Pyruvate Carboxylase Deficiency With High Doses of Citrate and Aspartate

A patient with severe pyruvate carboxylase deficiency presented at age 11 weeks with metabolic decompensation after routine immunization. She was comatose, had severe lactic acidemia (22 mM) and ketosis, low aspartate and glutamate, elevated citrulline and proline, and mild hyperammonemia. Head magnetic resonance imaging showed subdural hematomas and mild generalized brain atrophy. Biotin-unresponsive pyruvate carboxylase deficiency was diagnosed. To provide oxaloacetate, she was treated with high-dose citrate (7.5 mol/kg(-1)/day(-1)), aspartate (10 mmol/kg(-1)/day(-1)), and continuous drip feeding. Lactate and ketones diminished dramatically, and plasma amino acids normalized, except for arginine, which required supplementation. In the cerebrospinal fluid (CSF), glutamine remained low and lysine elevated, showing the treatment had not normalized brain chemistry. Metabolic decompensations, triggered by infections or fasting, diminished after the first year. They were characterized by severe lactic and ketoacidosis, hypernatremia, and a tendency to hypoglycemia. At age 3(1/2) years she has profound mental retardation, spasticity, and grand mal and myoclonic seizures only partially controlled by anticonvulsants. The new treatment regimen has helped maintain metabolic control, but the neurological outcome is still poor.

The effects of simvastatin on plasma lipoproteins and cholesterol homeostasis in patients with heterozygous familial hypercholesterolaemia

We have examined the influence of simvastatin, a competitive inhibitor of 3‐hydroxy‐3‐methyl glutaryl coenzyme A reductase on plasma concentrations of lipids and lipoproteins, the rates of cholesterol biosynthesis and degradation of 125I‐labelled LDL by freshly isolated mononuclear leucocytes and the 24 h urinary excretion of mevalonic acid in patients with heterozygous familial hypercholesterolaemia. Patients were treated with progressively increasing doses of simvastatin (20, 40, and 80 mg day−1) taken in a twice‐daily dosage for a period of 6 weeks on each dose. Plasma concentrations of LDL cholesterol decreased by 36·6%, 45·6% and 47·1% respectively on the three doses. High‐affinity degradation of 125I‐LDL by freshly isolated mononuclear leucocytes increased significantly on the 20 mg day−1 dosage but no further increase was observed on doses of 40 and 80 mg of simvastatin per day. Rates of 2‐14C acetate incorporation into cholesterol by freshly isolated mononuclear leucocytes (obtained 12–15 h after the last dose of simvastatin) increased by 62%, 71% and 29% in cells isolated from patients on 20, 40, and 80 mg day−1 of simvastatin compared with values at baseline. In contrast, the 24 h excretion of mevalonic acid in the urine fell by 16·9%, 31·4% and 31·9% respectively on these three doses. Our results indicate that the potent hypocholesterolaemic effects of simvastatin are accompanied by increases in high‐affinity LDL receptor‐mediated degradation of LDL and a compensatory increase in cholesterol biosynthesis in freshly isolated mononuclear leucocytes but that rates of mevalonic acid excretion in the urine decrease.

Premenopausal black women have more risk factors for coronary heart disease than white women

Premenopausal black women have a 2- to 3-fold greater rate of coronary heart disease (CHD) than premenopausal white women. The purpose of this study was to provide greater insight into the reasons for this difference, which are currently unclear. We compared CHD risk factors in 99 black and 100 white, healthy premenopausal women, aged 18 to 45 years, and of relatively advantaged socioeconomic status. Compared with white women, black women had a higher body mass index (32.0 +/- 9.2 vs 29.0 +/- 9.4 kg/m2, p = 0.021), and higher systolic (124 +/- 17 vs 115 +/- 14 mm Hg, p <0.0001) and diastolic (79 +/- 14 vs 75 +/- 11 mm Hg, p = 0.048) blood pressures. The mean plasma lipoprotein(a) concentration was markedly higher in the black women (40.2 +/- 31.3 mg/dl) than in the white women (19.2 +/- 23.7 mg/dl, p <0.0001). The plasma total homocysteine level was also higher in the black women (8.80 +/- 3.38 vs 7.81 +/- 2.58 micromol/L, p = 0.013). The black women, however, had lower plasma triglyceride levels (0.91 +/- 0.46 vs 1.22 +/- 0.60 mmol/L, p <0.0001), and a trend toward higher high-density lipoprotein (HDL) cholesterol levels (1.37 +/- 0.34 vs 1.29 +/- 0.31 mmol/L, p = 0.064) than the white women. Plasma total and low-density lipoprotein (LDL) cholesterol levels were similar, despite a greater consumption of saturated fat and cholesterol by the black women. Rates of cigarette smoking and alcohol intake were low and similar between the races. In summary, premenopausal black women had a higher mean body mass index, blood pressure, lipoprotein(a), and plasma total homocysteine level, and a greater consumption of saturated fat and cholesterol than white women. These differences in coronary risk factors may place the black women in our study at increased risk for CHD compared with the white women.

Comparative hypolipidemic effects of lovastatin and simvastatin in patients with heterozygous familial hypercholesterolemia

We have compared the effects of lovastatin and simvastatin on plasma lipoproteins, fibrinogen and urinary mevalonic acid excretion in twenty-three patients with heterozygous familial hypercholesterolemia. After a baseline period patients were randomly assigned to receive lovastatin or simvastatin at doses of 10, 20 and 40 mg twice daily, for a period of 2 months each, and then, after a 4-week wash-out period, all patients received the alternate drug for a similar period of therapy. Both drugs were well-tolerated and no patients were withdrawn due to side effects. Lipid values returned to baseline after discontinuation of therapy and no carry-over effect was observed. Treatment with lovastatin resulted in decreases in LDL cholesterol concentrations from 274 mg/dl at baseline to 211, 192 and 178 mg/dl, respectively, on doses of 20, 40 and 80 mg/day. Treatment with simvastatin reduced concentrations of LDL cholesterol to 194, 168 and 156 mg/dl, respectively, on doses of 20, 40 and 80 mg/day. Concentrations of HDL cholesterol increased on both drugs, but no dose response relationship was apparent. Both drugs reduced the 24-h urinary excretion of mevalonic acid, an intermediate in cholesterol biosynthesis, but the magnitude of decrease was similar with lovastatin and simvastatin. Small, but statistically non-significant decreases in fibrinogen occurred with both drugs. Patients who showed the greatest hypolipidemic effect during treatment with lovastatin also showed an excellent therapeutic response to simvastatin and vice versa. We conclude that, on a milligram per milligram basis, simvastatin is twice as potent as lovastatin in the treatment of familial hypercholesterolemia and that with both drugs, reductions in LDL cholesterol concentrations are accompanied by decreases in the urinary excretion of mevalonic acid.