BRCC36 Deubiquitinates HMGCR to Regulate the Interplay Between Ferroptosis and Pyroptosis

Various forms of programmed cell death (PCD) exhibit distinct characteristics depending on their specific molecular mechanisms, and there are interactions among these different forms. Ferroptosis, which is related to autophagy and apoptosis, has an unknown potential interaction with pyroptosis. This study revealed a mutually antagonistic relationship between ferroptosis and pyroptosis, with 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) playing a key role in their interaction. It is found that HMGCR predominantly localized to mitochondria during ferroptosis but shifted to the endoplasmic reticulum following treatment with a pyroptosis inducer. Furthermore, this study demonstrated that BRCC36 (BRCA1/BRCA2-containing complex subunit 36) deubiquitinated HMGCR in a manner dependent on deubiquitinating enzyme (DUB) activity, and inhibited ferroptosis and promoted pyroptosis. Moreover, as an oncogene in hepatocellular carcinoma (HCC), BRCC36 promoted cancer cell proliferation, migration, invasion, and tumor growth. Thiolutin, an inhibitor of BRCC36, effectively suppressed the interaction between BRCC36 and HMGCR, leading to the inhibition of HCC growth. Therefore, targeting BRCC36 can offer a novel and promising therapeutic strategy for HCC treatment. In conclusion, these findings provide new theoretical evidence for further characterizing tumor heterogeneity and offer new molecular targets for the diagnosis and treatment of HCC.

β-Sitosterol Alleviates the Proliferation and Migration of Cystitis Glandularis-Associated Cells by Targeting HMGCR to Induce NLRP3-Dependent Pyroptosis

BACKGROUND

Cystitis glandularis (CG) is a proliferative lesion of the bladder mucosa, and the incidence rate of CG has increased year by year. Considering the potential function of β-sitosterol in CG, we aim to fathom its effect and mechanism of CG.

METHODS

Primary human cells isolated from CG patients and following transfection as needed, were treated with different concentrations of β-sitosterol. Cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and transwell assay was used to test the cell migration. Meanwhile, co-immunoprecipitation was employed to evaluate the interaction between 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) and NLR family pyrin domain containing 3 (NLRP3). Additionally, pyroptosis-associated proteins and HMGCR expressions were tested using western blot or quantitative real-time reverse transcription polymerase chain reaction.

RESULTS

β-sitosterol suppressed cell viability and migration, enhanced cell pyroptosis, and upregulated expressions of NLRP3, Cleaved Caspase-1, interleukin-1β (IL-1β), gasdermin D-N-terminal domain (GSDMD-N), and HMGCR in CG primary cells (p < 0.05). HMGCR silencing promoted cell viability and migration, inhibited cell pyroptosis, and downregulated expressions of NLRP3, Cleaved Caspase-1, IL-1β, and GSDMD-N in β-sitosterol-affected CG primary cells (p < 0.05). HMGCR interacted with NLRP3.

CONCLUSIONS

β-sitosterol alleviates the proliferation and migration of CG-associated cells by targeting HMGCR to induce NLRP3-dependent pyroptosis. These findings confirmed the therapeutic effect of β-sitosterol on treating CG.

Mechanisms of 3-Hydroxyl 3-Methylglutaryl CoA Reductase in Alzheimer's Disease

Alzheimer's disease (AD) is the most common neurodegenerative disease worldwide and has a high incidence in the elderly. Unfortunately, there is no effective therapy for AD owing to its complicated pathogenesis. However, the development of lipid-lowering anti-inflammatory drugs has heralded a new era in the treatment of Alzheimer's disease. Several studies in recent years have shown that lipid metabolic dysregulation and neuroinflammation are associated with the pathogenesis of AD. 3-Hydroxyl 3-methylglutaryl CoA reductase (HMGCR) is a rate-limiting enzyme in cholesterol synthesis that plays a key role in cholesterol metabolism. HMGCR inhibitors, known as statins, have changed from being solely lipid-lowering agents to neuroprotective compounds because of their effects on lipid levels and inflammation. In this review, we first summarize the main regulatory mechanism of HMGCR affecting cholesterol biosynthesis. We also discuss the pathogenesis of AD induced by HMGCR, including disordered lipid metabolism, oxidative stress, inflammation, microglial proliferation, and amyloid-β (Aβ) deposition. Subsequently, we explain the possibility of HMGCR as a potential target for AD treatment. Statins-based AD treatment is an ascent field and currently quite controversial; therefore, we also elaborate on the current application prospects and limitations of statins in AD treatment.

Anti-HMGCR immune-mediated necrotising myopathy: Addressing the remaining issues

The discovery of autoantibodies directed against the 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) enzyme has defined a sub-set of immune-mediated necrotising myopathy (IMNM) which is strongly associated with exposure to statin medications. Although understanding of anti-HMGCR IMNM has grown considerably with the reporting of multiple cohorts in North America, Europe, Asia and Oceania, there remain many unanswered questions. The true incidence of anti-HMGCR IMNM is not known and heterogeneity of phenotype and treatment response within this autoantibody sub-group is being increasingly recognised. Statin-naïve adults and juvenile patients with anti-HMGCR potentially share characteristics distinct from statin-exposed patients, alluding to unique pathogenesis. Conflicting data exists on whether malignancies are associated with anti-HMGCR and further clarification is required to determine the degree of cancer screening required. Treatment approaches to anti-HMGCR IMNM are heterogeneous but generally highlight the efficacy of intravenous immunoglobulin. Even with multimodal immunosuppression, patients with anti-HMGCR remain prone to relapse, with younger patients generally manifesting more refractory disease. In this Review, we aim to summarise the current literature on anti-HMGCR and discuss the remaining issues.

Efgartigimod restores muscle function in a humanized mouse model of immune-mediated necrotizing myopathy

OBJECTIVE

Immune-mediated necrotizing myopathies (IMNMs) are severe forms of myositis often associated with pathogenic anti-3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) autoantibodies (aAbs). Efgartigimod is an engineered human IgG1 Fc fragment that antagonizes the neonatal Fc receptor (FcRn), thereby preventing recycling and promoting lysosomal degradation of IgG, including aAbs. We evaluated the therapeutic effects of IgG reduction by efgartigimod in a humanized murine model of IMNM.

METHODS

Disease was induced in C5-deficient (C5def) or Rag2-deficient (Rag2-/-) mice receiving co-injections of anti-HMGCR+ IgG from an IMNM patient and human complement. C5def mice were treated in a preventive setting with s.c. injections of efgartigimod and Rag2-/- mice in a curative setting after disease was induced by anti-HMGCR+ IgG injections. Anti-HMGCR aAbs levels were monitored in mouse serum and muscle tissue. Histological analysis was performed on muscle sections. Muscle force was assessed by grip test or measurement of gastrocnemius strength upon electrostimulation.

RESULTS

Administration of efgartigimod rapidly reduced total IgG levels, including the level of pathogenic anti-HMGCR aAbs, in both serum (P < 0.0001) and muscle (P < 0.001). In the preventive setting, efgartigimod prevented myofibre necrosis (P < 0.05), thus precluding loss of muscle strength (P < 0.05). In the therapeutic setting, efgartigimod prevented further necrosis and allowed muscle fibre regeneration (P < 0.05). Hence, muscle strength returned to normal (P < 0.01).

CONCLUSION

Efgartigimod reduces circulating IgG levels, including pathogenic anti-HMGCR+ IgG aAbs, in a humanized mouse model of IMNM, preventing further necrosis and allowing muscle fibre regeneration. These results support investigating the therapeutic efficacy of efgartigimod through a clinical trial in IMNM patients.

Clinical associations of patients with anti-3-hydroxy-3-methylglutaryl CoA reductase antibody-associated immune-mediated necrotising myopathy

BACKGROUND

Anti-3-hydroxy-3-methylglutaryl CoA reductase (HMGCR) antibodies are associated with a subtype of immune-mediated necrotising myopathy (IMNM).

AIMS

To determine clinical associations of anti-HMGCR antibodies for anti-HMGCR-associated IMNM (HMGCR-IMNM) among a cohort of patients in Western Australia and to determine whether serial HMGCR antibody levels parallel disease activity.

METHODS

Adult patients with positive anti-HMGCR antibodies detected by enzyme-linked immunosorbent assay between January 2015 and November 2019 were included. Symptoms, examination findings, imaging findings and blood test results were reviewed retrospectively using patient records and laboratory database results.

RESULTS

Among 26 patients with positive anti-HMGCR antibodies, 23 were diagnosed with HMGCR-IMNM representing a positive predictive value (PPV) of 88%. Myopathy was frequently severe at diagnosis with limb weakness graded as Medical Research Council score 3 or below in 78% of patients, bulbar muscle weakness in 39% and an average creatine kinase (CK) at diagnosis of 7986 U/L. The majority (83%) required at least two therapies to maintain remission, 48% had at least one flare of disease and 57% did not achieve CK normalisation. Correlation between CK and anti-HMGCR antibody level at diagnosis was low (r = 0.04). Anti-HMGCR antibodies fell with treatment in 10 of 12 patients, but remained persistently positive in 83% of patients.

CONCLUSIONS

The PPV of anti-HMGCR antibodies for HMGCR-IMNM in this Western Australian cohort is 88%. Patients typically present with proximal limb weakness, dysphagia and markedly elevated CK, and, despite multiagent immunosuppression, a significant number of patients have evidence of persistent biochemical myositis. Anti-HMGCR antibodies did not correlate with CK levels at diagnosis.

Effect and mechanism of HMG-CoA reductase inhibitor on the improvement of elderly essential hypertension-induced vascular endothelial function impairment based on the JAK/STAT pathway

OBJECTIVE

Our research was designed to figure out the influence and mechanism of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor on the improvement of elderly essential hypertension-induced vascular endothelial function impairment based on the JAK/STAT pathway.

METHODS

Eighty-six elderly patients with essential hypertension were randomized into a control group (oral Amlodipine Besylate Tablets) and an observation group (oral Amlodipine Besylate Tablets + HMG-CoA reductase inhibitor atorvastatin calcium). Patients in both groups were treated with the drug for 12 weeks. Blood pressure, serum levels of inflammatory factors, and vascular endothelial function indicators, and levels of blood lipids were measured. The modeled rats were treated with atorvastatin calcium and a JAK/STAT pathway inhibitor (AG490), and the levels of cardiac function-related indices, left ventricular mass index, lipid levels, serum inflammatory factors and vascular endothelial function-related indices were detected in each group.

RESULTS

HMG-CoA reductase inhibitor improved blood pressure levels, lipid levels, serum inflammatory factor levels and cardiac function in elderly patients with essential hypertension. Both HMG-CoA reductase inhibitor and AG490 improved blood pressure levels, lipid levels, serum inflammatory factor levels and cardiac function in SHR rats. Both HMG-CoA reductase inhibitor and AG490 decreased p-JAK2/JAK2 and p-STAT3/STAT3 expression levels.

CONCLUSION

Our study demonstrates that HMG-CoA reductase inhibitor improves elderly essential hypertension-induced vascular endothelial function impairment by blocking the JAK/STAT pathway.

Epidemiological and genetic features of anti-3‑hydroxy-3-methylglutaryl-CoA reductase necrotizing myopathy: Single-center experience and literature review

OBJECTIVE

To characterize the demographic, genetic, clinical, and serological features of patients with anti-3‑hydroxy-3-methylglutaryl-CoA reductase (HMGCR) immune-mediated necrotizing myopathy (IMNM) in a region of northern Spain.

METHODS

Study of all patients diagnosed with anti-HMGCR IMNM during a 5-year period at a reference hospital in northern Spain. Besides clinical and laboratory data, we analyzed the genetic influence of HLA genes and the rs4149056 (c.521T>C) single nucleotide polymorphism (SNP) in the SLCO1B1 gene.

RESULTS

8 patients (5 women, 3 men) with a mean ± SD age of 64.9 ± 7.3 years, fulfilled the criteria for anti-HMGCR IMNM. The incidence rate was 0.6 per 100.000 person-years and the prevalence 3 per 100.000 population. All patients had been exposed to statins. All of them had predominant lower limb proximal and symmetric muscle weakness that was severe in 2 and had elevated serum CK levels with a median [IQR] of 4488 [2538-9194] IU/L. Serum 25‑hydroxy vitamin D levels were decreased in all patients in whom it was determined. The 3 patients with a previous diagnosis of hypothyroidism had abnormal levels of TSH at the time of diagnosis. All patients experienced improvement with different schemes of immunosuppressive therapy. Noteworthy, 7 of 8 patients carried the HLA-DRB1*11 allele. The frequency of the rs4149056 C allele in the SLCO1B1 gene (12.5%) was similar to that of the general population.

CONCLUSION

In northern Spain, anti-HMGCR IMNM preferentially affects people over 50 years of age who are carriers of the HLA-DRB1*11 allele and take statins. Both low vitamin D levels and hypothyroidism may play a potential predisposing role in the development of this disease.

[Two cases of statin-induced immune-mediated necrotizing myopathy]

Statin-induced immune-mediated necrotizing myopathy (IMNM) is a rare subtype of idiopathic inflammatory myopathy (IIM) that distinct from other types of IIM and statin-induced muscle symptoms, regarding clinic, diagnosis and treatment. The condition, characterized by symmetrical proximal muscle weakness and significantly increased creatine kinase (CK) levels, is persistent after statin discontinuation. Muscle biopsy shows necrotic muscle fibers and regeneration fibers with minimal inflammatory infiltrates. Over the past decade, an autoantibody to hydroxymethylglutaryl coenzyme A reductase (HMGCR) has been identified for the diagnosis of statin-associated IMNM. Optimal treatment strategy is unclear, but aggressive immunosuppression has shown to be effective. This case report describes two patients with statin-induced IMNM. The patients present with proximal muscle weakness, elevated CK levels, and are subsequently positive for anti-HMGCR autoantibodies with necrosis in muscle biopsy.

Atypical presentation of anti-HMGCR myopathy

Immune-mediated necrotising myopathy is a subtype of idiopathic inflammatory myopathy characterised by muscle fibre necrosis without significant inflammatory infiltrate. Anti-3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCR) myopathy is seen in 6%-10% of idiopathic inflammatory myopathy and is diagnosed in the context of elevated serum creatine kinase levels, proximal muscle weakness and anti-HMGCR autoantibodies. We recently encountered a 61-year-old man with anti-HMGCR myopathy with an atypical skin manifestation, partially responsive to triple therapy with steroids, intravenous immunoglobulin (IVIG) and rituximab. To our knowledge, there have been only four reported cases of skin rash associated with anti-HMGCR myopathy. Our case demonstrates the importance of recognising atypical manifestations of anti-HMGCR myopathy. Early addition of IVIG and rituximab is also critical in patients not responding to steroid monotherapy. Delay in achieving remission leads to prolonged steroid use, lower likelihood of beginning physical therapy and overall worse clinical outcomes.

[Statins and oxidative stress]

Statins, as inhibitors of the first regulatory enzyme in cholesterol biosynthesis --HMG-CoA reductase--have a special impact in medical practice. Given their therapeutic efficacy, statins are believed to be the strongest class of agents in the treatment of cardiovascular disorders. Moreover, besides decreasing total cholesterol and C-LDL levels, numerous fundamental and clinical researches suggest that statins also have an antiinflammatory effect. Inflammation is closely related to the production of oxygen-derived reactive species (ROS). The antioxidant effects of statins associated with their ability to block the formation and/or action of ROS may add up their therapeutic efficacy. Within this context, the present paper presents data in literature related to the effect of statins on the expression and activity of NAD(P)H oxidase, activity of the enzymes involved in the antioxidative defence (SOD, GPx, catalase, paraoxonase), and their ability to act as free radical scavengers and oxidized-LDL inhibitors. By their antioxidant properties statins may decrease the atherogenic potential of lipoproteins.

Inflammatory biomarkers and statins

The concept of atherosclerosis as an inflammatory disorder has led to the exploration of new pathogeneses of this disease. In this regard, the levels of several inflammatory molecules are frequently increased in subjects at high risk of developing an acute coronary event. With a simple analysis we can characterize the circulating levels of a marker and its therapeutic modulation with various drugs. In this review we have analyzed different inflammatory markers currently used, such as C-reactive protein (CRP), CD40 ligand, adhesion molecules and chemokines, and their possible modulation by therapeutic intervention with 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors. Moreover, in the future, new technologies will allow us to discover new markers, or sets of them, that could indicate the direction to be taken in the prevention and treatment of cardiovascular diseases.

Esterified cholesterol accumulation induced by aggregated LDL uptake in human vascular smooth muscle cells is reduced by HMG-CoA reductase inhibitors

Vascular smooth muscle cell (VSMC) proliferation is a key event in the development of atherosclerotic lesions. VSMCs synthesize extracellular matrix, where low density lipoproteins (LDLs) are trapped and become aggregated (agLDL). The objective of this study was to investigate the cholesterol uptake and accumulation triggered by agLDL in comparison with native LDL (nLDL) on unstimulated and platelet-derived growth factor-stimulated human aortic VSMCs and the role of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors on these processes. Esterified cholesterol (EC) accumulation induced by agLDL in VSMCs was correlated with the degree of aggregation and concentration. The EC content of VSMCs treated with 100 microg/mL of agLDL (80% aggregated) increased approximately 70-fold over that in VSMCs incubated with the same concentration of nLDL. Whereas nLDL-derived EC was increased approximately twofold in platelet-derived growth factor-stimulated VSMCs, there was no effect of platelet-derived growth factor (10(-9) mol/L) on the uptake of agLDL. The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor simvastatin (5 micromol/L) reduced EC accumulation derived from agLDL uptake by 58% and 35% in platelet-derived growth factor-stimulated and unstimulated VSMCs, respectively. This inhibition was overcome by geranylgeraniol (10 micromol/L) and partially by farnesol (10 micromol/L). Fluorescence microscopy of the cellular internalization of agLDL labeled with the fluorochrome 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine demonstrated that simvastatin reduces EC accumulation derived from agLDL by inhibiting its endocytosis and that the effect is completely reversed by geranygeraniol. These results indicate that agLDLs are rapidly internalized by human VSMCs and that 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors modulate EC accumulation. These data suggest a possible mechanism by which statins could contribute to the passivation and stabilization of actively growing atherosclerotic lesions.

Cholesterol lowering with statin drugs, risk of stroke, and total mortality. An overview of randomized trials

OBJECTIVE

To examine whether cholesterol lowering with 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statin drugs) reduces the risks of stroke and total mortality.

DATA SOURCES

We conducted a computerized literature search from 1985 through 1995 to identify all published trials testing statin drugs. The Cholesterol and Recurrent Events (CARE) data were added after the report was published in October 1996. Our search was limited to English-language articles and included published overviews containing relevant individual trials.

TRIAL SELECTION

Criteria for inclusion of randomized trials in the overview were (1) statin drugs alone used to reduce lipid levels rather than multifactorial interventions including another type of cholesterol-lowering drug and (2) inclusion of data on deaths and/or strokes.

DATA EXTRACTION

Data were extracted by 2 researchers, and only minor discrepancies, which were easily resolved by discussion, occurred. Principal investigators of the trials and their funding agencies were also contacted to secure any relevant data not included in the published reports.

DATA SYNTHESIS

A total of 16 individual trials including approximately 29 000 subjects treated and followed up an average of 3.3 years were included in the overview. The average reductions in total and low-density lipoprotein cholesterol achieved were large-22% and 30%, respectively. A total of 454 strokes (fatal plus nonfatal) and 1175 deaths occurred. Those assigned to statin drugs experienced significant reductions in risks of stroke of 29% (95% confidence interval [CI], 14%-41%) as well as total mortality of 22% (95% CI, 12%-31%), which was attributable to a significant reduction in cardiovascular disease (CVD) deaths of 28% (95% CI, 16%-37%). There was no evidence of any increased risk in non-CVD mortality (relative risk [RR], 0.93; 95% CI, 0.75-1.14). There was also no significant increase in risk of cancer (RR, 1.03; 95% CI, 0.90-1.17).

CONCLUSION

This overview of all published randomized trials of statin drugs demonstrates large reductions in cholesterol and clear evidence of benefit on stroke and total mortality. There was, as expected, a large and significant decrease in CVD mortality, but there was no significant evidence for any increases in either non-CVD deaths or cancer incidence.

Reductase inhibitor monotherapy and stroke prevention

BACKGROUND

Epidemiologic evidence and meta-analyses of data from early clinical trials suggest that lowering the levels of cholesterol does not reduce the events of stroke. These analyses have not included more recent clinical trials using reductase inhibitors.

OBJECTIVE

To conduct a meta-analysis of the effect of reducing cholesterol levels on stroke in all reported clinical trials of primary (n = 4) and secondary (n = 8) prevention of coronary heart disease that used reductase inhibitor monotherapy and provided information on incident stroke.

RESULTS

Analysis of combined data from primary and secondary prevention trials showed a highly statistically significant reduction of stroke associated with the use of reductase inhibitor monotherapy (27% reduction in stroke; P = .001). Analysis of secondary prevention trials alone disclosed a similar statistically significant effect (32% reduction in stroke; P = .001). A smaller nonsignificant reduction in stroke was noted in the primary prevention trials (15% reduction in stroke; P = .48).

CONCLUSIONS

Reductase inhibitors now in use for lowering cholesterol levels are more potent and have fewer side effects than the cholesterol-lowering agents previously available. They appear to reduce stroke, most notably in patients with prevalent coronary artery disease, which may be partly due to the effects of lowering the levels of cholesterol on the progression and plaque stability of extracranial carotid atherosclerosis or the marked reduction of incident coronary heart disease associated with treatment.

Genetic variant showing a positive interaction with beta-blocking agents with a beneficial influence on lipoprotein lipase activity, HDL cholesterol, and triglyceride levels in coronary artery disease patients. The Ser447-stop substitution in the lipoprotein lipase gene. REGRESS Study Group

BACKGROUND

Lipoprotein lipase (LPL) is the rate-limiting enzyme in the lipolysis of triglyceride-rich lipoproteins, and the gene coding for LPL is therefore a candidate gene in atherogenesis. We previously demonstrated that two amino acid substitutions in LPL, the Asn291-Ser and the Asp9-Asn, are associated with elevated triglycerides and lower HDL cholesterol and are present with greater frequency in coronary artery disease (CAD) patients than in normolipidemic control subjects. Conversely, a third frequent mutation in this gene, the Ser447-Stop, is reported by some investigators to underlie higher HDL cholesterol levels and would represent a beneficial genetic variant in lipoprotein metabolism. We therefore sought conclusive evidence for these allegations by investigating the effects of the LPL Ser447-Stop mutation on LPL and hepatic lipase (HL) activity, HDL cholesterol, and triglycerides in a large group of CAD patients (n = 820) with normal to mildly elevated total and LDL cholesterol levels.

METHODS AND RESULTS

Carriers of the Ser447-Stop allele (heterozygotes and homozygotes) had significantly higher postheparin LPL activity (P = .034), normal postheparin HL activity (P = .453), higher HDL cholesterol levels (P = .013), and lower triglyceride levels (P = .044) than noncarriers. The influence of the Ser447-Stop allele on LPL activity was pronounced in patients using beta-blockers (P = .042) and not significant in those not using them (P = .881), suggesting a gene-environment interaction between the Ser447-Stop mutation and beta-blockers.

CONCLUSIONS

We conclude that the LPL Ser447-Stop mutation has a significant positive effect on LPL activity and HDL cholesterol and triglyceride levels and that certain subgroups of CAD patients carrying the Ser447-Stop mutation will have less adverse metabolic effects when placed on beta-blockers. The LPL Ser447-Stop mutation therefore should have a protective effect against the development of atherosclerosis and subsequent CAD.

Management of hyperlipidemia in children with refractory nephrotic syndrome: the effect of statin therapy

The efficacy and safety of hydroxymethylglutaric coenzyme A reductase inhibitor (statins) in the treatment of hyperlipidemia were evaluated in 12 infants and children with steroid-resistant nephrotic syndrome followed prospectively for 1 to 5 years. All patients experienced a hypolipidemic response with a marked reduction in their total cholesterol (40%), low-density lipoprotein cholesterol (44%), and triglyceride levels (33%), but no appreciable change in high-density lipoprotein cholesterol. Statin therapy was well tolerated without clinical or laboratory adverse effects. In spite of a significant hypolipidemic response to statin therapy there were no changes observed in the degree of proteinuria, hypoalbuminemia, or in the rate of progression to chronic renal failure. Long-term controlled studies with statin therapy are needed to further document or negate their renoprotective role in refractory nephrotic syndrome.

Effect of fluvastatin on lipids and fibrinolysis in coronary artery disease

This randomized, double-blind, placebo-controlled study shows that 20-week fluvastatin treatment induces beneficial changes in the lipid panel and a shift in the fibrinolytic pathway toward activation through a decrease in tissue plasminogen activator antigen. Fluvastatin treatment causes no variation in lipoprotein(a) circulating levels.

Pleurotus fruiting bodies contain the inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase-lovastatin

In the fruiting bodies of the fungus Pleurotus ostreatus, also called the oyster mushroom, we found a competitive inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase-lovastatin. The appearance of the inhibitor during the development of fruiting bodies was followed and lovastatin determined in the vegetative mycelium, in the primordia, as well as in different parts of sporocarps of different sizes. Less lovastatin was found in stripes as compared to pili or in mature stages in the lamellae and basidiospores.

[Hypocholesterolemic statins. Evaluation and prospects]

Statins are a family of compounds which act on cells by inhibiting hydroxymethylglutaryl (HMG) CoA reductase, an enzyme that blocks the intracellular cholesterol synthesis and stimulates the formation and action of LDL receptors. Experience of 3 years after they were introduced in France and 10 years for studies of the first compound (lovastatin) has demonstrated that these drugs are potent hypercholesterolaemia-lowering agents, fairly well tolerated but possibly with some toxicity to muscles. In severe forms of pure hypercholesterolaemia they may be prescribed either alone or combined with biliary acid chelating resins. Their use in mild forms of hypercholesterolaemia will be justified when low-dose preparations are reimbursed by the French Social Security. In mixed hyperlipidaemia, statins are more effective than fibric acid derivatives on cholesterol but weaker on triglycerides. They provide an alternative to fibric acid derivatives when these fail, but they are not indicated in hypertriglyceridaemia. Studies are being carried out to demonstrate that statins have a preventive effect on cardiovascular diseases, in either clinical regression trials or atheromatous plaque regression studies.

Phenotypic heterogeneity in the syndromes of 3-methylglutaconic aciduria

Combined 3-methylglutaconic and 3-methylglutaric aciduria, one of the more common urinary organic acid abnormalities, has been observed in at least three clinical syndromes. We studied an additional seven patients with 3-methylglutaconic aciduria, four of whom were best categorized as having the type II syndrome, two as having an "unspecified" syndrome, and one who may have had a primary urea cycle defect. In cultured cells and autopsy tissues derived from patients with the type II and unspecified syndromes, we were unsuccessful in identifying a defect in the leucine degradative pathway distal to 3-methylcrotonyl-coenzyme A carboxylase and in the cholesterol biosynthetic pathway between 3-hydroxy-3-methylglutaryl-coenzyme A reductase and diphosphomevalonate decarboxylase. Further assessment of the cholesterol biosynthetic pathway in several patients with one of the two types of disease also provided no defined abnormality. The primary metabolic defects in the type II and unspecified syndromes remain undefined.

Purification and characterization of a protein inhibitor from rat liver that inhibits type 1 protein phosphatase when 3-hydroxy-3-methylglutaryl CoA reductase is the substrate

A protein inhibitor of HMG-CoA reductase phosphatase activity from rat liver was purified to homogeneity. The protein was purified 4,000-fold with an overall yield of 4%. The purified protein had a molecular mass of 31 kDa. This spontaneously active protein is thermostable and acid-resistant. The protein inhibitor is phosphorylated by glycogen synthase kinase-3 and cAMP-dependent protein kinase without change in its inhibitory activity. The inhibition caused by this inhibitor on phosphatases 1 and 2A is similar to that of inhibitor-2 from rabbit skeletal muscle using hydroxymethylglutaryl-CoA reductase as substrate. The regulation properties of this inhibitor towards phosphatase 1 together with another protein inhibitor of phosphatase 2A in cholesterol metabolism are discussed.

Brain and optic system pathology in hypocholesterolemic dogs treated with a competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase

The cholesterol lowering compound lovastatin, a competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase (EC 1.1.1.34 HMG CoA reductase), was given in nine separate experiments to normocholesterolemic dogs at rates up to 180 times the maximum therapeutic dose in man (1 mg/kg/day). Mean serum total cholesterol concentrations were reduced as much as 88% below normal. Clinical evidence of neurotoxicity occurred in up to 37% of animals given 180 mg/kg/day lovastatin for 11 or more days, especially in one laboratory where the dosing regime resulted in higher concentrations of plasma drug levels. Dogs receiving 60 mg/kg/day or less never exhibited neurologic signs. The central nervous system (CNS) of affected dogs exhibited endothelial degeneration and hemorrhagic encephalopathy. Focal extravasation of horseradish peroxidase occurred frequently (6/8) in the retrolaminar optic nerve of asymptomatic or clinically affected dogs given 180 mg/kg/day lovastatin, with endothelial degeneration and discrete optic nerve degenerative lesions interpreted as ischemic. The association between the degree of hypocholesterolemia and occurrence of clinical signs was not exact. Total brain cholesterol was similar in treated and control dogs. Hypocholesterolemic dogs had proportionally lowered serum concentrations of alpha-tocopherol, but oral supplementation of this vitamin did not prevent the neurologic syndrome. Endothelial degeneration in the CNS and optic nerve may have reflected in vitro morphologic effects of HMG CoA reductase inhibitors due to extreme inhibition of nonsterol isoprene synthesis. Retinogeniculate axonal (Wallerian-like) degeneration occurred in greater than or equal to 12% of dogs given 60 mg/kg/day or more lovastatin, with central chromatolysis of occasional retinal ganglion cells. These neuroaxonal changes may have been secondary to vascular effects, but superimposed direct neurotoxic action at the high dosage levels of lovastatin could not be excluded. There was no evidence of drug induced adverse effects in the CNS of dogs given up to 30 mg/kg/day lovastatin for 2 years.

The regulation of 3-hydroxy-3-methylglutaryl-CoA reductase activity, cholesterol esterification and the expression of low-density lipoprotein receptors in cultured monocyte-derived macrophages

Human blood monocytes cultured in medium containing 20% whole serum showed the greatest activity of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase and [14C]acetate incorporation into non-saponifiable lipids around the 7th day after seeding, the period of greatest growth. Although there was enough low-density lipoprotein (LDL) in the medium to saturate the LDL receptors that were expressed by normal cells at that time, HMG-CoA reductase activity and acetate incorporation were as high in normal cells as in cells from familial-hypercholesterolaemic (FH) patients. Both the addition of extra LDL, which interacted with the cells by non-saturable processes, and receptor-mediated uptake of acetylated LDL significantly reduced reductase activity and increased incorporation of [14C]oleate into cholesteryl esters in normal cells and cells from FH patients ('FH cells'), and reduced the expression of LDL receptors in normal cells. Pre-incubation for 20h in lipoprotein-deficient medium apparently increased the number of LDL receptors expressed by normal cells but reduced the activity of HMG-CoA reductase in both normal and FH cells. During subsequent incubations the same rate of degradation of acetylated LDL and of non-saturable degradation of LDL by FH cells was associated with the same reduction in HMG-CoA reductase activity, although LDL produced a much smaller stimulation of oleate incorporation into cholesteryl esters. In normal cells pre-incubated without lipoproteins, receptor-mediated uptake of LDL could abolish reductase activity and the expression of LDL receptors. The results suggested that in these cells, receptor-mediated uptake of LDL might have a greater effect on reductase activity and LDL receptors than the equivalent uptake of acetylated LDL. It is proposed that endogenous synthesis is an important source of cholesterol for growth of normal cells, and that the site at which cholesterol is deposited in the cells may determine the nature and extent of the metabolic events that follow.

Difference in the ability of compactin and oxidized cholesterol, both known inhibitors of cholesterol biosynthesis, to suppress in vitro immune responses

Compactin, a fungal metabolite, is a well-characterized competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase, the enzyme which generally controls the rate of cholesterol biosynthesis in mammalian cells. Various products of cholesterol oxidation, e.g., 25-hydroperoxycholesterol and 25-hydroxycholesterol, also inhibit HMG CoA reductase but by an unknown mechanism which operates only in intact cells. In addition, oxidized cholesterol increases cholesterol esterification and suppresses the increase in low-density lipoprotein receptors which is the normal consequence of decreasing low-density lipoprotein supply. There are therefore, three ways in which the availability of nonesterified cholesterol to mammalian cells is decreased by oxidized cholesterol. It has been suggested that potent in vitro immunosuppression by compounds such as 25-hydroxycholesterol in the presence of cholesterol-containing fetal calf serum is a consequence of their ability to suppress cholesterol biosynthesis. This has been disputed in a previous paper (Humphries, G. M. K., and McConnell, H. M., J. Immunol., 122: 121-126, 1979) because mevalonate, the product of HMG CoA reductase activity, fails to abrogate the suppression. The present paper reports that compactin fails to suppress in vitro immune responses at concentrations known to inhibit HMG CoA reductase (either in the isolated or cellular form). This finding supports the previous conclusion that suppression of HMG CoA reductase activity is not sufficient to inhibit in vitro immune responses in the presence of an exogenous source of cholesterol.

Plasma and hepatic cholesterol and hepatic HMG CoA reductase levels in rats fed fluid or powdered skim milk

The effects of skim milk powder (SMP) and fluid skim milk (FSM) on plasma cholesterol (CH) and hepatic liquid concentrations, and 3-hydroxy-3-methyl-glutaryl coenzyme A (HMG CoA) reductase activity of rats of different ages were compared. Groups of young (23 days old) and older (45 days old) rats were fed a casein -based diet and provided tap water; the casein-based diet and FSM as fluid source; or tap water and the casein diet into which SMP (25% by wt.) had been isocalorically incorporated. Plasma CH concentrations were determined at 0, 1.5, 3 and 5 wk, hepatic total lipid, triglyceride and CH at 5 wk. Half of each group were killed at wk 3 and the other half at wk 5 for determinations of HMG CoA reductase activity. Both FSM and SMP decreased plasma CH levels at 1.5 and 3 wk of feeding in the young rats; plasma CH concentrations of the older rats were not altered by either FSM or SMP. Both milk derivatives increased HMG CoA reductase activity at wk 3 and wk 5 in both ages of rat, whereas hepatic lipid levels were unchanged. In these experiments the effects of feeding FSM of SMP along with a casein-based diet were comparable and included an increase in HMB CoA reductase activity, no change in hepatic lipid levels, and a decrease in plasma CH; the latter response depended on the initial age of the rat.

pH properties and chemical mechanism of action of 3-hydroxy-3-methylglutaryl coenzyme A reductase

The pH variation of the kinetic parameters V and V/K for the oxidation of mevaldate by NADP+ in the presence of CoA (reverse reaction) and for the reduction of mevaldate by NADPH in the presence or absence of CoA (forward reaction) for the reactions catalyzed by 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase was examined. In the reverse reaction a group, X, on the enzyme with a pK of 7.9 must be unprotonated for NADP+ binding and catalysis. The presence of NADP+ shifts this pK to a value below 6. The V/K profile for mevaldate shows that deprotonation of a group, Y, with a pK of 6.7 decreased the reaction rate by a factor of 27. In the forward reaction, the pK of the X group was about 6.9 except when CoA and mevaldate were both present, in which case it was shifted to 7.8. CoA decreased the Kms for mevaldate about 10-fold without changing the Vmax at the optimum protonation state. The catalytic group, X, was identified as a cationic acid, probably histidine. A catalytic mechanism is proposed in which the protonated form of histidine induces hydride transfer from the A side of NADPH by donating a proton to the carbonyl of HMG-CoA or to the aldehyde form of mevaldate. The role of the Y group, which from its pK of 6.7 and the chemistry involved may be a carboxyl group, is presumably to catalyze conversion of mevaldate thiohemiacetal formed in the reduction of HMG-CoA to CoA and the free aldehyde form of mevaldate. Mevaldate was shown by 1H NMR to contain 44% hydrate in D2O and 39% in H2O. When an enzymatic method was used, it was also determined that only one stereoisomer of mevaldate is used by HMG-CoA reductase.

Inhibition of 3-hydroxy-3-methylglutaryl coenzyme A reductase activity in Morris hepatoma 7800 after intravenous injection of mevalonic acid

The effect of i.v. injection of mevalonate on the activity of microsomal 3-hydroxy-3-methylglutaryl Coenzyme A reductase was studied in livers from non-tumor-bearing rats and in host liver and hepatomas from rats bearing transplantable Morris hepatoma 7800. We confirmed that a single bolus injection of 100 mg of mevalonate in non-tumor-bearing male rats caused a 90% inhibition of hepatic 3-hydroxy-3-methylglutaryl Coenzyme A reductase activity within 2 hr. In two experiments mevalonate injection caused a 50 to 60% reduction in enzyme activity of hepatomas but no significant decline in the enzyme activity in host livers. Thirty in after injection of [14C]mevalonate in a similarly sized bolus, the ratio of specific activities of cholesterol in liver:hepatoma:kidney:blood was 13:5.6:0.5:1. Thus, both the liver and hepatoma efficiently utilized mevalonate for the synthesis of cholesterol. The precise cause of the inhibition of enzyme activity in the liver of non-tumor-bearing rats and in the transplantable hepatomas is not clear from this study. However, on the basis of other published reports, we suggest that it resulted from the accumulation of endogenous cholesterol in microsomal membrane. The activity of cholesterol 7 alpha-hydroxylase, the rate-controlling enzyme for bile acid synthesis, was also studied in the hepatoma, but, in general, it did not differ from that in the host liver or control liver.