Cholesterol and cataracts

Lanosterol regulates abnormal amyloid accumulation in LECs through the mediation of cholesterol pathway metabolism

Age-related cataract (ARC) is the predominant cause of global blindness, linked to the progressive aging of the lens, oxidative stress, perturbed calcium homeostasis, hydration irregularities, and modifications in crystallin proteins. Currently, surgical intervention remains the sole efficacious remedy, albeit carrying inherent risks of complications that may culminate in irreversible blindness. It is urgent to explore alternative, cost-effective, and uncomplicated treatment modalities for cataracts. Lanosterol has been widely reported to reverse cataracts, but the mechanism of action is not yet clear. In this study, we elucidated the mechanism through which lanosterol operates in the context of cataract reversal. Through the targeted suppression of sterol regulatory element-binding protein 2 (SREBP2) followed by lanosterol treatment, we observed the restoration of lipid metabolism disorders induced by SREBP2 knockdown in lens epithelial cells (LECs). Notably, lanosterol exhibited the ability to effectively counteract amyloid accumulation and cellular apoptosis triggered by lipid metabolism disorders. In summary, our findings suggest that lanosterol, a pivotal intermediate in lipid metabolism, may exert its therapeutic effects on cataracts by influencing lipid metabolism. This study shed light on the treatment and pharmaceutical development targeting Age-related Cataracts (ARC).

Role of Oxysterols in Ocular Degeneration Mechanisms and Involvement of P2X7 Receptor

Ocular degeneration, including cataracts, glaucoma, macular degeneration, and diabetic retinopathy, is a major public health challenge, as it affects the quality of life of millions of people worldwide and, in its advanced stages, leads to blindness. Ocular degeneration, although it can affect different parts of the eye, shares common characteristics such as oxysterols and the P2X7 receptor. Indeed, oxysterols, which are cholesterol derivatives, are associated with ocular degeneration pathogenesis and trigger inflammation and cell death pathways. Activation of the P2X7 receptor is also linked to ocular degeneration and triggers the same pathways. In age-related macular degeneration, these two key players have been associated, but further studies are needed to extrapolate this interrelationship to other ocular degenerations.

Lanosterol Synthase Prevents EMT During Lens Epithelial Fibrosis Via Regulating SREBP1

Purpose

Epithelial-mesenchymal transition (EMT) of lens epithelial cells (LECs) is a predominant pathological process underlying fibrotic cataracts. Here we investigated the role and mechanism of lanosterol synthase (LSS), a key rate-limiting enzyme in sterol biosynthesis, in EMT of LECs.

Methods

Human lens epithelial explants, primary rabbit LECs, and whole rat lenses were treated with TGFβ2. RNA-sequencing was conducted to explore genetic changes during fibrosis of human lens epithelial explants. Loss- and gain-of-function studies were performed in primary LECs to investigate roles and mechanisms of LSS, lanosterol and sterol regulatory element binding transcription protein 1 (SREBP1) in EMT. Rat lenses were applied to evaluate the potential effect of lanosterol on lens fibrosis. Expression of LSS, SREBP1, EMT-related regulators, and markers were analyzed by Western blot, qRT-PCR, or immunofluorescent staining.

Results

LSS and steroid biosynthesis were downregulated in TGFβ2-induced lens fibrosis. LSS inhibition directly triggered EMT by inducing Smad2/3 phosphorylation and nucleus translocation, an overexpression of LSS protected LECs from EMT by inhibiting Smad2/3 activation. Moreover, LSS inhibition decreased the expression of SREBP1, which regulated EMT via intervening TGFβ2/Smad2/3 transduction. Furthermore, lanosterol protected LECs from EMT caused by both TGFβ2 treatment and LSS inhibition via suppressing Smad2/3 activation and maintained lens transparency by preventing fibrotic plaques formation.

Conclusions

We first identified that LSS protected LECs from EMT and played an antifibrotic role to maintain lens transparency. Additionally, lanosterol and sterol biosynthesis regulation might be promising strategies for preventing and treating fibrotic cataracts.

Gene profiles and mutations in the development of cataracts in the ICR rat model of hereditary cataracts

Cataracts are opacifications of the lens that cause loss of visual acuity and ultimately of eyesight. Age-related cataract develops in most elderly people, but the mechanisms of cataract onset are incompletely understood. The Ihara Cataract Rat (ICR) is an animal model of hereditary cataracts showing cortical opacity that commonly develops prematurely. We identified putative mechanisms of cataract onset in the ICR rat model by measuring gene expression changes before and after cortical cataract development and conducting point mutation analysis. Genes differentially expressed between 4-week-old animals without cortical cataracts and 8-10-week-old animals with cortical cataracts were selected from microarray analysis. Three connections were identified by STRING analysis: (i) Epithelial-Mesenchymal Transition (EMT), including Col1a2, and Pik3r1. (ii) Lens homeostasis, including Aqp5, and Cpm. (iii) Lipid metabolism, including Scd1, Srebf1, and Pnpla3. Subsequently, mutation points were selected by comparing ICR rats with 12 different rats that do not develop cataracts. The apolipoprotein Apoc3 was mutated in ICR rats. Analyses of gene expression changes and point and mutations suggested that abnormalities in EMT or lipid metabolism could contribute to cataract development in ICR rats.

Challenges and Opportunities in P450 Research on the Eye

Of the 57 cytochrome P450 enzymes found in humans, at least 30 have ocular tissues as an expression site. Yet knowledge of the roles of these P450s in the eye is limited, in part because only very few P450 laboratories expanded their research interests to studies of the eye. Hence the goal of this review is to bring attention of the P450 community to the eye and encourage more ocular studies. This review is also intended to be educational for eye researchers and encourage their collaborations with P450 experts. The review starts with a description of the eye, a fascinating sensory organ, and is followed by sections on ocular P450 localizations, specifics of drug delivery to the eye, and individual P450s, which are grouped and presented based on their substrate preferences. In sections describing individual P450s, available eye-relevant information is summarized and concluded by the suggestions on the opportunities in ocular studies of the discussed enzymes. Potential challenges are addressed as well. The conclusion section outlines several practical suggestions on how to initiate eye-related research. SIGNIFICANCE STATEMENT: This review focuses on the cytochrome P450 enzymes in the eye to encourage their ocular investigations and collaborations between P450 and eye researchers.

Effect of alirocumab on cataracts in patients with acute coronary syndromes

BACKGROUND

Some data suggest that low levels of low-density lipoprotein cholesterol (LDL-C) are associated with risk of cataracts. Proprotein convertase subtilisin-kexin type 9 (PCSK9) inhibitors reduce LDL-C below levels achieved with statins alone. We determined whether the incidence of cataracts was influenced by treatment with the PCSK9 inhibitor alirocumab versus placebo, and whether that incidence was affected by achieved LDL-C levels.

METHODS

The ODYSSEY OUTCOMES trial (NCT01663402) compared alirocumab with placebo in 18,924 patients with recent acute coronary syndrome receiving high-intensity or maximum-tolerated statin. Incident cataracts were pre-specified events of interest. In multivariable analysis using propensity score-matching on characteristics including cataract risk factors, incident cataracts were compared in the alirocumab and placebo groups according to LDL-C levels achieved with alirocumab.

RESULTS

Over median follow-up of 2.8 years (interquartile range 2.3 - 3.4), the incidence of cataracts was similar with alirocumab (127/9462 [1.3%]) versus placebo (134/9462 [1.4%]); hazard ratio [HR] 0.94, 95% confidence interval [CI] 0.74 - 1.20). In patients treated with alirocumab with ≥ 2 LDL-C values < 25 mg/dL (0.65 mmol/L), the incidence of cataracts was 71/4305 (1.6%), versus 60/4305 (1.4%) in propensity score-matched patients from the placebo group (HR 1.10, CI 95% 0.78 - 1.55). In patients treated with alirocumab with ≥ 2 LDL-C values < 15 mg/dL (0.39 mmol/L), the incidence of cataracts was 13/782 (1.7%), versus 36/2346 (1.5%) in matched patients from the placebo group (HR 1.03, CI 95% 0.54 - 1.94).

CONCLUSION

Treatment with alirocumab versus placebo, added to statin, did not influence the incidence of cataracts, even when achieved LDL-C levels on alirocumab were very low. Longer follow-up studies might be necessary to exclude the long-term effects on the incidence or progression of cataracts.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT01663402 .

The lens epithelium as a major determinant in the development, maintenance, and regeneration of the crystalline lens

The crystalline lens is a transparent and refractive biconvex structure formed by lens epithelial cells (LECs) and lens fibers. Lens opacity, also known as cataracts, is the leading cause of blindness in the world. LECs are the principal cells of lens throughout human life, exhibiting different physiological properties and functions. During the embryonic stage, LECs proliferate and differentiate into lens fibers, which form the crystalline lens. Genetics and environment are vital factors that influence normal lens development. During maturation, LECs help maintain lens homeostasis through material transport, synthesis and metabolism as well as mitosis and proliferation. If disturbed, this will result in loss of lens transparency. After cataract surgery, the repair potential of LECs is activated and the structure and transparency of the regenerative tissue depends on postoperative microenvironment. This review summarizes recent research advances on the role of LECs in lens development, homeostasis, and regeneration, with a particular focus on the role of cholesterol synthesis (eg., lanosterol synthase) in lens development and homeostasis maintenance, and how the regenerative potential of LECs can be harnessed to develop surgical strategies and improve the outcomes of cataract surgery (Fig. 1). These new insights suggest that LECs are a major determinant of the physiological and pathological state of the lens. Further studies on their molecular biology will offer possibility to explore new approaches for cataract prevention and treatment.

Association of Common and Rare Genetic Variation in the 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase Gene and Cataract Risk

Background Results from animal models and observational studies have raised concerns regarding the potential cataractogenic effects of statin treatment. We investigated whether common and rare genetic variants in HMGCR are associated with cataract risk, to gauge the likely long-term effects of statin treatment on lenticular opacities. Methods and Results We used genotyping data and exome sequencing data of unrelated European individuals in the UK Biobank to test the association between genetically proxied inhibition of HMGCR and cataract risk. First, we constructed an HMGCR genetic score consisting of 5 common variants weighted by their association with low-density lipoprotein cholesterol. Second, we analyzed exome sequencing data to identify carriers of predicted loss-of-function mutations in HMGCR. Common and rare variants in aggregate were then tested for association with cataract and cataract surgery. In an analysis of >402 000 individuals, a 38.7 mg/dL (1 mmol/L) reduction in low-density lipoprotein C by the HMGCR genetic score was associated with higher risk for cataract (odds ratio, 1.14 [95% CI, 1.00-1.39], P=0.045) and cataract surgery (odds ratio, 1.25 [95% CI, 1.06-1.48], P=0.009). Among 169 172 individuals with HMGCR sequencing data, we identified 32 participants (0.02%), who carried a rare HMGCR predicted loss-of-function variant. Compared with noncarriers, heterozygous carriers of HMGCR predicted loss-of-function had a higher risk of developing cataract (odds ratio, 4.54 [95% CI, 1.96-10.53], P=0.001) and cataract surgery (odds ratio, 5.27 [95% CI, 2.27-12.25], P=5.37×10-4). In exploratory analyses, we found no significant association between genetically proxied inhibition of PCSK9, NPC1L1, or circulating low-density lipoprotein cholesterol levels (P>0.05 for all) and cataract risk. Conclusions We found that genetically proxied inhibition of the HMGCR gene mimicking long-term statin treatment associated with higher risk of cataract. Clinical trials with longer follow-up are needed to confirm these findings.

Evaluation of lens opacity due to inhibition of cholesterol biosynthesis using rat lens explant cultures

Drug-induced lens opacity has the potential to cause blindness and is of concern in drug development. Inhibition of cholesterol biosynthesis is one of the causes of lens opacity. Lens opacity is only observed after chronic administration in in vivo nonclinical studies in drug development. Thus, to save resources (e.g., time and cost) and to reduce burden on animals, it is required to develop in vitro evaluation systems that can predict and avoid the risk of lens opacity earlier and easier. In this study, we investigated whether rat lens explant cultures could be useful for the evaluation of drug-induced lens opacity via inhibition of cholesterol biosynthesis. Nineteen drugs, including statins, allylamine, thiocarbamate, azole, and morpholine, which inhibit cholesterol biosynthesis, as well as a negative control (acetaminophen, rosiglitazone and troglitazone), were used. Rat lens explants were treated with drugs for 13 days at concentrations close to IC50 values or higher against cholesterol biosynthesis, and lens opacity (severity and region) was evaluated. In most cases, region-specific lens opacity limited in the equator to posterior pole, as observed in vivo was observed at IC50 values or higher concentrations. The severity of opacity was likely to be related to the inhibitory potency toward cholesterol biosynthesis, concentration of drugs distributed in the lens, or time of exposure. Furthermore, GSH levels were also involved in the deterioration of lens opacity. In conclusion, we demonstrated that rat lens explant cultures can be useful to assess the potential drug-induced lens opacity associated with inhibition of cholesterol biosynthesis and to elucidate the mechanisms of lens opacity.

Effect of hydrophilic and lipophilic statins on early onset cataract: A nationwide case-control study

BACKGROUND

Statin is biologically plausible in cataract development, but inconclusive associations between statin and cataract are presented in human studies. Given most early onset cataract (EOC) occurs in regions with high cholesterol composition, we therefore aimed to assess the association between statin and EOC.

METHODS

A population based case-control study was performed using the Taiwan National Health Insurance Research Database (NHIRD). The case involved patients aged 20-55 years with EOC. Controls were 1:1 matched by age, gender, year of index date, and propensity score estimated from comorbidities and comedications. Statin exposure, including intensity, properties and cumulative exposure one year before the index date were tracked. The odds ratios (ORs) of EOC associated with statin were estimated by conditional logistic regression.

RESULTS

A total of 4213 cases and 4213 controls were included. Statins were associated with EOC (OR = 3.257, 95% CI 2.519-4.211). The ORs of cataract was positively associated with cumulative exposure. Subgroup analysis indicated that the ORs of cataract were significant both in lipophilic (OR = 3.485, 95% CI 2.606-4.659) and hydrophilic (OR = 3.241, 95% CI 1.975-5.321) statin users.

CONCLUSIONS

Statins were associated with an increased risk of cataract in young populations.

Qki activates Srebp2-mediated cholesterol biosynthesis for maintenance of eye lens transparency

Defective cholesterol biosynthesis in eye lens cells is often associated with cataracts; however, how genes involved in cholesterol biosynthesis are regulated in lens cells remains unclear. Here, we show that Quaking (Qki) is required for the transcriptional activation of genes involved in cholesterol biosynthesis in the eye lens. At the transcriptome level, lens-specific Qki-deficient mice present downregulation of genes associated with the cholesterol biosynthesis pathway, resulting in a significant reduction of total cholesterol level in the eye lens. Mice with Qki depletion in lens epithelium display progressive accumulation of protein aggregates, eventually leading to cataracts. Notably, these defects are attenuated by topical sterol administration. Mechanistically, we demonstrate that Qki enhances cholesterol biosynthesis by recruiting Srebp2 and Pol II in the promoter regions of cholesterol biosynthesis genes. Supporting its function as a transcription co-activator, we show that Qki directly interacts with single-stranded DNA. In conclusion, we propose that Qki-Srebp2-mediated cholesterol biosynthesis is essential for maintaining the cholesterol level that protects lens from cataract development.

Drug-induced lenticular opacity and accumulation of cholesterol-related substances in the lens cortex of dogs

TP0446131, developed as an antidepressant agent, was found to cause lenticular opacity in a 13-week repeated-dose study in dogs. Histopathologically, the lenticular opacity was observed as a degeneration of the lens fibers, characterized by irregularity in the ordered arrangement of the fibers which is necessary to maintain the transparency of the lens, and was considered to manifest clinically as cataract. To evaluate the development mechanism of the lenticular opacity, the chemical constituents of the lens, which is known to be associated with the development of cataract, were examined. The results of liquid chromatography-tandem mass spectrometry analysis revealed an increase in the amplitudes of 3 unknown peaks in a dose- and time-dependent manner in the lens, with no remarkable changes in the other chemical components tested. In addition, the content of cholesterol, alterations of which have been reported to be associated with cataract, remained unchanged. The mass spectral data and chromatographic behavior of the 3 peaks indicated that these peaks corresponded to sterol-related substances, and that one of them was 7-dehydrocholesterol, a precursor of cholesterol biosynthesis. This finding suggested that TP0446131 exerts some effects on the cholesterol biosynthesis pathway, which could be involved in the development of the cataracts. Furthermore, increases in the levels of these sterol-related substances were also detected in the serum, and were, in fact, noted prior to the onset of the cataract, suggesting the possibility that these substances in the serum could be used as potential safety biomarkers for predicting the onset of cataract induced by TP0446131.

Statins for children with familial hypercholesterolemia

BACKGROUND

Familial hypercholesterolemia is one of the most common inherited metabolic diseases and is an autosomal dominant disorder meaning heterozygotes, or carriers, are affected. Those who are homozygous have severe disease. The average worldwide prevalence of heterozygous familial hypercholesterolemia is at least 1 in 500, although recent genetic epidemiological data from Denmark and next generation sequencing data suggest the frequency may be closer to 1 in 250. Diagnosis of familial hypercholesterolemia in children is based on elevated total cholesterol and low-density lipoprotein cholesterol levels or DNA-based analysis, or both. Coronary atherosclerosis has been detected in men with heterozygous familial hypercholesterolemia as young as 17 years old and in women with heterozygous familial hypercholesterolemia at 25 years old. Since the clinical complications of atherosclerosis occur prematurely, especially in men, lifelong treatment, started in childhood, is needed to reduce the risk of cardiovascular disease. In children with the disease, diet was the cornerstone of treatment but the addition of lipid-lowering medications has resulted in a significant improvement in treatment. Anion exchange resins, such as cholestyramine and colestipol, were found to be effective, but they are poorly tolerated. Since the 1990s studies carried out on children aged 6 to 17 years with heterozygous familial hypercholesterolemia have demonstrated significant reductions in their serum total and low-density lipoprotein cholesterol levels. While statins seem to be safe and well-tolerated in children, their long-term safety in this age group is not firmly established. This is an update of a previously published version of this Cochane Review.

OBJECTIVES

To assess the effectiveness and safety of statins in children with heterozygous familial hypercholesterolemia.

SEARCH METHODS

Relevant studies were identified from the Group's Inborn Errors and Metabolism Trials Register and Medline. Date of most recent search: 04 November 2019.

SELECTION CRITERIA

Randomized and controlled clinical studies including participants up to 18 years old, comparing a statin to placebo or to diet alone.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed studies for inclusion and extracted data.

MAIN RESULTS

We found 26 potentially eligible studies, of which we included nine randomized placebo-controlled studies (1177 participants). In general, the intervention and follow-up time was short (median 24 weeks; range from six weeks to two years). Statins reduced the mean low-density lipoprotein cholesterol concentration at all time points (high-quality evidence). There may be little or no difference in liver function (serum aspartate and alanine aminotransferase, as well as creatinine kinase concentrations) between treated and placebo groups at any time point (low-quality evidence). There may be little or no difference in myopathy (as measured in change in creatinine levels) (low-quality evidence) or clinical adverse events (moderate-quality evidence) with statins compared to placebo. One study on simvastatin showed that this may slightly improve flow-mediated dilatation of the brachial artery (low-quality evidence), and on pravastatin for two years may have induced a regression in carotid intima media thickness (low-quality evidence). No studies reported rhabdomyolysis (degeneration of skeletal muscle tissue) or death due to rhabdomyolysis, quality of life or compliance to study medication.

AUTHORS' CONCLUSIONS

Statin treatment is an effective lipid-lowering therapy in children with familial hypercholesterolemia. Few or no safety issues were identified. Statin treatment seems to be safe in the short term, but long-term safety remains unknown. Children treated with statins should be carefully monitored and followed up by their pediatricians and their care transferred to an adult lipidologist once they reach 18 years of age. Large long-term randomized controlled trials are needed to establish the long-term safety issues of statins.

Systemic medications and cortical cataract: the Singapore Epidemiology of Eye Diseases Study

BACKGROUND/AIMS

To evaluate the association between systemic medications and cortical cataract prevalence in an Asian population.

METHODS

The Singapore Epidemiology of Eye Diseases Study recruited 10 033 Chinese, Malay and Indian residents aged 40+ years living in Singapore. Information on medication use was collected at interview using questionnaires. The presence and severity of cortical cataract were assessed from lens photographs using the modified Wisconsin Cataract Grading System. Associations between medications and the presence of cortical cataract were assessed using logistic regression. Associations between medications and greater severity of cortical cataract (none, minimal, early and late) were assessed using ordinal logistic regression.

RESULTS

A total of 8965 participants were included, the mean age was 57.6 (SD=9.8) years, and 4555 (50.8%) were women. After adjusting for age, gender, ethnicity, body mass index, smoking status, socioeconomic status, hypertension, hyperlipidaemia, diabetes, duration of diabetes and cardiovascular disease, ACE inhibitors (OR=1.27; 95% CI 1.05 to 1.55), fibrates (OR=1.57; 95% CI 1.05 to 2.35), alpha-glucosidase inhibitors (AGIs) (OR=1.85; 95% CI 1.13 to 3.02) and insulin (OR=1.80; 95% CI 1.11 to 2.93) were significantly associated with the presence of cortical cataract. Further adjusting for concurrent medication use did not alter these associations. Consistently, the four medications were also associated with a greater severity level of cortical cataract.

CONCLUSION

ACE inhibitors, fibrates and AGIs were associated with increased prevalence of cortical cataract in this Asian population, independent of the presence of hypertension, hyperlipidaemia and diabetes, respectively. Whether they contribute to the risk of cortical cataract needs confirmation in longitudinal studies.

Why Is Very High Cholesterol Content Beneficial for the Eye Lens but Negative for Other Organs?

The plasma membranes of the human lens fiber cell are overloaded with cholesterol that not only saturates the phospholipid bilayer of these membranes but also leads to the formation of pure cholesterol bilayer domains. Cholesterol level increases with age, and for older persons, it exceeds the cholesterol solubility threshold, leading to the formation of cholesterol crystals. All these changes occur in the normal lens without too much compromise to lens transparency. If the cholesterol content in the cell membranes of other organs increases to extent where cholesterol crystals forma, a pathological condition begins. In arterial cells, minute cholesterol crystals activate inflammasomes, induce inflammation, and cause atherosclerosis development. In this review, we will indicate possible factors that distinguish between beneficial and negative cholesterol action, limiting cholesterol actions to those performed through cholesterol in cell membranes and by cholesterol crystals.

Statins in ophthalmology

Statins, 3-hydroxy-3-methyl-gutaryl coenzyme A reductase inhibitors, are a class of lipid-lowering drugs with anti-inflammatory, immunomodulatory, and vascular effects. Statins are increasingly being used in the treatment of a variety of medical conditions. We examine the actions of statins on the eye and its associated ophthalmic disorders. Statins can be synthetic or nonsynthetic, and their differentiating derivations may contribute to their varying cholesterol-lowering and pleiotropic effects. There is conflicting evidence on the ocular therapeutic and adverse effects of the statins. Statins may play a role in reducing the burden of dry eye, corneal ulcer scarring, thyroid-associated orbitopathy, glaucoma, uveitis and other associated ocular inflammatory states, cataract, proliferative vitreoretinopathy, diabetic retinopathy, macular degeneration, and choroidal melanoma. Topical preparations of statins can be formulated, thereby extending the range of ocular diseases that may be amenable to treatment. Statins have a relatively safe side effect profile, but rare and serious adverse reactions have been reported with their usage in ophthalmology, including myopathies and rhabdomyolysis with acute renal failure.

Statins and risk of cataracts: A systematic review and meta-analysis of observational studies

INTRODUCTION

Two previous meta-analyses evaluated the risk of cataracts associated with statins, but did not include relevant studies suggesting a cataractogenic effect.

AIMS

The aim of this systematic review and meta-analysis of observational studies is to evaluate such association considering the latest published evidence.

METHODS

A literature search was conducted to identify observational, comparative studies evaluating the risk of developing cataracts in patients treated with statins. A meta-analysis was performed to estimate odds ratios (ORs). Results were stratified according to the following studies' subgroups: design, methodological quality, method of diagnosis of cataract, patients' age, and median follow-up. Meta-regressions evaluated the influence of the following risk factors: smoking, hypertension, corticosteroids, selective serotonin reuptake inhibitors (SSRI), diabetes mellitus, and cardiovascular disease.

RESULTS

Twenty-one studies were included. Treatment with statins was associated with an increased risk of cataracts [OR: 1.11 (95% CI: 1.02-1.21); P = 0.017; I²  = 97.5%]. This risk remained statistically significant among case-controls, good methodological quality studies, studies with length of follow-up ≥5 years and those which outcome was cataract surgery. Between-studies heterogeneity was high among all risk estimates. Meta-regressions identified an inverse relationship between the risk of cataracts and the proportion of diabetic patients in the studies.

CONCLUSIONS

The results point out an increased risk of cataract development with statins. However, since the magnitude of the effect is low and between-studies heterogeneity is high, the extent in which these results have impact on the benefit/risk ratio of statins is difficult to ascertain due to the uncertainty of the findings.

Detection of cholesterol bilayer domains in intact biological membranes: Methodology development and its application to studies of eye lens fiber cell plasma membranes

Four purported lipid domains are expected in plasma membranes of the eye lens fiber cells. Three of these domains, namely, bulk, boundary, and trapped lipids, have been detected. The cholesterol bilayer domain (CBD), which has been detected in lens lipid membranes prepared from the total lipids extracted from fiber cell plasma membranes, has not yet been detected in intact fiber cell plasma membranes. Here, a saturation-recovery electron paramagnetic resonance spin-labeling method has been developed that allows identification of CBDs in intact fiber cell plasma membranes of eye lenses. This method is based on saturation-recovery signal measurements of the cholesterol-analog spin label located in the lipid bilayer portion of intact fiber cell membranes as a function of the partial pressure of molecular oxygen with which the samples are equilibrated. The capabilities and limitations of this method are illustrated for intact cortical and nuclear fiber cell plasma membranes from porcine eye lenses where CBDs were detected in porcine nuclear intact membranes for which CBDs were also detected in lens lipid membranes. CBDs were not detected in porcine cortical intact and lens lipid membranes. CBDs were detected in intact membranes isolated from both cortical and nuclear fiber cells of lenses obtained from human donors. The cholesterol content in fiber cell membranes of these donors was always high enough to induce the formation of CBDs in cortical as well as nuclear lens lipid membranes. The results obtained for intact membranes, when combined with those obtained for lens lipid membranes, advance our understanding of the role of high cholesterol content and CBDs in lens biology, aging, and/or cataract formation.

Use of Lipid-Lowering Drugs and the Risk of Cataract: A Population-Based Nested Case-Control Study

Eye lens membrane cells require high cholesterol concentrations that might be counteracted by lipid-lowering drugs. Using a nationwide database, we conducted a nested case-control study to evaluate the risk of cataract development associated with the use of lipid-lowering drugs. Patients aged 45 years and over with first cataract surgery in 2014 (cases) and up to four controls matched on age, gender, diabetes, hypothyroidism, glucocorticoid use, cardiovascular risk, and area of residence were included in the study. Among the 2,811 cases and 11,106 matched controls included, analyses showed a significantly increased risk of cataract surgery for a cumulative exposure to fibrates exceeding 5 years (adjusted odds ratio (aOR) 1.58; 95% confidence interval (CI): 1.17-2.15), unlike cumulative exposure to statins, whatever the dose or duration of treatment (aORs from 1.00-1.08, none being significant). This study highlighted an increased risk of cataract surgery with prolonged use of fibrates but not of statins.

Clinical and pathophysiological evidence supporting the safety of extremely low LDL levels-The zero-LDL hypothesis

While the impact of very low concentrations of low-density lipoprotein cholesterol (LDL-C) on cardiovascular prevention is very reassuring, it is intriguing to know what effect these extremely low LDL-C concentrations have on lipid homoeostasis. The evidence supporting the safety of extremely low LDL levels comes from genetic studies and clinical drug trials. Individuals with lifelong low LDL levels due to mutations in genes associated with increased LDL-LDL receptor (LDLR) activity reveal no safety issues. Patients achieving extremely low LDL levels in the IMPROVE-IT and FOURIER, and the PROFICIO and ODYSSEY programs seem not to have an increased prevalence of adverse effects. The main concern regarding extremely low LDL-C plasma concentrations is the adequacy of the supply of cholesterol, and other molecules, to peripheral tissues. However, LDL proteomic and kinetic studies reaffirm that LDL is the final product of endogenous lipoprotein metabolism. Four of 5 LDL particles are cleared through the LDL-LDLR pathway in the liver. Given that mammalian cells have no enzymatic systems to degrade cholesterol, the LDL-LDLR pathway is the main mechanism for removal of cholesterol from the body. Our focus, therefore, is to review, from a physiological perspective, why such extremely low LDL-C concentrations do not appear to be detrimental. We suggest that extremely low LDL-C levels due to increased LDLR activity may be a surrogate of adequate LDL-LDLR pathway function.

Safety of Very Low Low-Density Lipoprotein Cholesterol Levels With Alirocumab: Pooled Data From Randomized Trials

BACKGROUND

Proprotein convertase subtilisin/kexin type 9 monoclonal antibodies can reduce low-density lipoprotein cholesterol (LDL-C) to very low levels when added to background lipid-lowering therapy.

OBJECTIVES

The safety of alirocumab was evaluated in patients with at least 2 consecutive LDL-C values <25 or <15 mg/dl in the ODYSSEY program, with follow-up as long as 104 weeks.

METHODS

Pooled data from 14 trials were analyzed (double-blind treatment 8 to 104 weeks; n = 3,340 alirocumab, n = 1,894 control [placebo or ezetimibe]; representing 4,029 [alirocumab] and 2,114 [control] double-blind patient-years' exposure).

RESULTS

In alirocumab-treated patients, 839 (25.1%) achieved 2 consecutive LDL-C values <25 mg/dl, and 314 (9.4%) achieved <15 mg/dl. Baseline LDL-C was lower (mean 100.3 vs. 134.3 mg/dl) in patients with LDL-C <25 versus ≥25 mg/dl. Similar rates of adverse events occurred in patients achieving LDL-C <25 and <15 mg/dl (72.7% and 71.7%, respectively), compared with 76.6% in those who did not achieve LDL-C <25 mg/dl. Neurological and neurocognitive events were similar among the 3 groups. In a propensity score analysis, the rate of cataracts was higher in patients with LDL-C <25 mg/dl (2.6%) versus ≥25 mg/dl (0.8%; hazard ratio: 3.40; 95% confidence interval: 1.58 to 7.35). However, no difference in cataract incidence was observed between pooled alirocumab and control groups.

CONCLUSIONS

LDL-C levels <25 or <15 mg/dl on alirocumab were not associated with an increase in overall treatment-emergent adverse event rates or neurocognitive events, although cataract incidence appeared to be increased in the group achieving LDL-C levels <25 mg/dl. (Pooled analyses of already reported trials; NCT01288443, NCT01288469, NCT01266876, NCT01812707, NCT01507831, NCT01617655, NCT01623115, NCT01709500, NCT01644175, NCT01644188, NCT01730040, NCT01730053, NCT01644474, and NCT01709513).

Statins for children with familial hypercholesterolemia

BACKGROUND

Familial hypercholesterolemia is one of the most common inherited metabolic diseases and is an autosomal dominant disorder meaning heterozygotes, or carriers, are affected. Those who are homozygous have severe disease. The average worldwide prevalence of heterozygous familial hypercholesterolemia is at least 1 in 500, although recent genetic epidemiological data from Denmark and next generation sequencing data suggest the frequency may be closer to 1 in 250. Diagnosis of familial hypercholesterolemia in children is based on elevated total cholesterol and low-density lipoprotein cholesterol levels or DNA-based analysis, or both. Coronary atherosclerosis has been detected in men with heterozygous familial hypercholesterolemia as young as 17 years old and in women with heterozygous familial hypercholesterolemia at 25 years old. Since the clinical complications of atherosclerosis occur prematurely, especially in men, lifelong treatment, started in childhood, is needed to reduce the risk of cardiovascular disease. In children with the disease, diet was the cornerstone of treatment but the addition of lipid-lowering medications has resulted in a significant improvement in treatment. Anion exchange resins, such as cholestyramine and colestipol, were found to be effective, but they are poorly tolerated. Since the 1990s studies carried out on children aged 6 to 17 years with heterozygous familial hypercholesterolemia have demonstrated significant reductions in their serum total and low-density lipoprotein cholesterol levels. While statins seem to be safe and well-tolerated in children, their long-term safety in this age group is not firmly established. This is an update of a previously published version of this Cochane Review.

OBJECTIVES

To assess the effectiveness and safety of statins in children with heterozygous familial hypercholesterolemia.

SEARCH METHODS

Relevant studies were identified from the Group's Inborn Errors and Metabolism Trials Register and Medline.Date of most recent search: 20 February 2017.

SELECTION CRITERIA

Randomized and controlled clinical studies including participants up to 18 years old, comparing a statin to placebo or to diet alone.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed studies for inclusion and extracted data.

MAIN RESULTS

We found 26 potentially eligible studies, of which we included nine randomized placebo-controlled studies (1177 participants). In general, the intervention and follow-up time was short (median 24 weeks; range from six weeks to two years). Statins reduced the mean low-density lipoprotein cholesterol concentration at all time points (moderate quality evidence). Serum aspartate and alanine aminotransferase, as well as creatinine kinase concentrations, did not differ between treated and placebo groups at any time point (low quality evidence). The risks of myopathy (low quality evidence) and clinical adverse events (moderate quality evidence) were very low and also similar in both groups. In one study simvastatin was shown to improve flow-mediated dilatation of the brachial artery (low quality evidence), and in another study treatment with pravastatin for two years induced a significant regression in carotid intima media thickness (low quality evidence).

AUTHORS' CONCLUSIONS

Statin treatment is an effective lipid-lowering therapy in children with familial hypercholesterolemia. No significant safety issues were identified. Statin treatment seems to be safe in the short term, but long-term safety remains unknown. Children treated with statins should be carefully monitored and followed up by their pediatricians and their care transferred to an adult lipidologist once they reach 18 years of age. Large long-term randomized controlled trials are needed to establish the long-term safety issues of statins.

Design strategies of oxidosqualene cyclase inhibitors: Targeting the sterol biosynthetic pathway

Targeting the sterol biosynthesis pathway has been explored for the development of new bioactive compounds. Among the enzymes of this pathway, oxidosqualene cyclase (OSC) which catalyzes lanosterol cyclization from 2,3-oxidosqualene has emerged as an attractive target. In this work, we reviewed the most promising OSC inhibitors from different organisms and their potential for the development of new antiparasitic, antifungal, hypocholesterolemic and anticancer drugs. Different strategies have been adopted for the discovery of new OSC inhibitors, such as structural modifications of the natural substrate or the reaction intermediates, the use of the enzyme's structural information to discover compounds with novel chemotypes, modifications of known inhibitors and the use of molecular modeling techniques such as docking and virtual screening to search for new inhibitors. This review brings new perspectives on structural insights of OSC from different organisms and reveals the broad structural diversity of OSC inhibitors which may help evidence lead compounds for further investigations with various therapeutic applications.

Association of angiotensin-converting enzyme, CYP46A1 genes polymorphism with senile cataract

Background:

Senile cataract is the most common type of cataract characterized by gradual progressive thickening of the lens of the eye. Previously, many studies investigated the association between genetic polymorphism and senile cataract. Angiotensin-converting enzyme (ACE) I/D polymorphism is the potential risk factor for many eye-related diseases such as retinopathy and glaucoma. CYP46A1 enzyme converts cholesterol to 24S-hydroxycholesterol; human lens' membranes contain the highest cholesterol content. Defects in enzymes of cholesterol metabolism can be associated with cataracts. Hence, the present study was carried out to investigate the association of ACE and CYP46A1 genes polymorphism with senile cataract cases and controls.

Materials and Methods:

ACE (rs 4646994) and CYP46A1 (rs 754203) genes polymorphism in cases and controls were evaluated by polymerase chain reaction and restriction fragment length polymorphism.

Results:

This study included 103 senile cataract cases (55 were males and 48 were females) and 102 controls (53 were males and 49 were females). Mean age of cases in this study was 52.02 ± 12.11 years while in control group 53.74 ± 11.87 years. Frequencies of ACE ID, DD, and II genotypes in senile cataract cases were 64.07%, 4.85%, and 31.06% and controls were 61.76%, 26.47%, and 11.76%, respectively. The CYP46A1 gene CT, CC, and TT genotype frequencies were 48.54%, 8.73%, and 42.71% in senile cataract cases and 28.43%, 3.92%, and 67.64% in healthy controls, respectively. ACE DD and II genotypes (P < 0.001,P = 0.0008) and CYP46A1 CT and TT genotypes (P = 0.003,P = 0.0003) were significantly associated with senile cataract cases compared to the controls.

Conclusion:

Findings of this study suggest that ACE and CYP46A1 genes polymorphism may be a predictive marker for early identification of population at risk of senile cataract. This potential role of ACE and CYP46A1 genes polymorphism as a marker of susceptibility to senile cataract needs further validation in studies involving larger number of patients from different regions.

The Toxicology of HMG—CoA Reductase Inhibitors: Prediction of Human Risk

The discovery that 3-hydroxy-3-methyglutaryl coenzyme A reductase was a rate-determining step in the biosynthesis of cholesterol led to the discovery of inhibitors of this enzyme. To support the development of these agents (statins) as potential hypocholesterolemic drugs, a variety of preclinical studies were conducted in several animal species. Not unexpectedly due to the central role played by mevalonic acid and its products including cholesterol in development and maintenance of cellular homeostasis, administration of high dosage levels of these agents led to the expression of a broad variety of adverse effects in many different tissues. Using the tools of toxicologic pathology and classical risk assessment, these varied toxicities were evaluated by many groups relative to the conditions of use in human therapy and a perspective was developed on potential human risk. These approaches of mechanism-based risk assessment predicted that most of the adverse effects observed in animals would not be seen under conditions of human use and supported the successful introduction of one of the most important classes of human medicines.

Statin use and risk of cataract: A nested case-control study within a healthcare database

BACKGROUND AND AIMS

We aimed to assess the association between exposure to statins and hospitalization for cataract.

METHODS

A population-based, nested case-control study was performed on a cohort of 134,441 patients from Lombardy (Italy), newly treated with statins between 2005 and 2007. Cases were patients hospitalized for cataract or lens extraction surgery after initial statin prescription until December 31, 2012. For each case patient, up to 5 controls were randomly selected from the cohort and matched by gender, age at cohort entry, and date of index prescription. Logistic regression was used to model the outcome risk associated with low (proportion of days covered, PDC 25-49%), intermediate (PDC 50-74%), and high (PDC ≥ 75%) adherence compared with very-low adherence (PDC < 25%).

RESULTS

1334 case patients were matched to 6601 controls. Mean age (SD) of cases and controls was about 70 years (9 years) and 51% of them were men. There was a slight but continuous trend toward an increased risk of cataract as adherence to statin therapy increased in the adjusted risk models, with a significant odds ratio of 1.19 (95% CI 1.01-1.40%) for PDC 50-74% and 1.20 (95% CI 1.02-1.40) for PDC ≥ 75% vs. PDC < 25%, respectively. There was no statistical evidence that the effect of statins on cataract risk differed according to statin potency at starting therapy.

CONCLUSIONS

Statin therapy was associated with a modestly increased risk of cataract surgery. Nevertheless, in view of the overwhelming benefit of statins for reduction of CV events, clinical practice for statins therapy does not need to change.

Organization of lipids in fiber-cell plasma membranes of the eye lens

The plasma membrane together with the cytoskeleton forms the only supramolecular structure of the matured fiber cell which accounts for mostly all fiber cell lipids. The purpose of this review is to inform researchers about the importance of the lipid bilayer portion of the lens fiber cell plasma membranes in the maintaining lens homeostasis, and thus protecting against cataract development.

Statin Use and Incident Cataract Surgery: A Case-Control Study

PURPOSE

To determine the association between statin use and incident cataract surgery.

METHODS

Using the resources of the Rochester Epidemiology Project, a retrospective population-based, case-control study was performed. Cases included 6024 county residents aged 50 years and older who had first-eye cataract surgery between 1 January 2004 and 31 December 2011. Controls included residents who had never had cataract surgery and were matched to cases by age, sex, and index date within 1 month of surgery. Statin medications continuously prescribed for at least 1 year before the surgery date (cases) or index date (controls) were examined. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using logistic regression models.

RESULTS

There were 2557 (42%) statin users among cases having cataract surgery compared to 2038 (34%) statin users among controls never having had cataract surgery (p < 0.0001). Incident cataract surgery was significantly associated with increased odds of statin use (OR 1.29, 95% CI 1.19-1.55) after adjusting for age, sex, diabetes, cardiovascular disease, cerebrovascular disease, peripheral vascular disease, renal disease, oral and inhaled steroid use, and selective serotonin reuptake inhibitor use. The association was consistent in both subgroups of women (OR 1.34, 95%CI 1.22-1.49) and men (OR 1.17, 95% CI 1.05-1.30).

CONCLUSIONS

Incident cataract surgery was associated with increased odds of statin use, and underscores the possibility that increasing statin use could be contributing to rising rates of cataract surgery.

Effect of Randomized Lipid Lowering With Simvastatin and Ezetimibe on Cataract Development (from the Simvastatin and Ezetimibe in Aortic Stenosis Study)

Recent American College of Cardiology/American Heart Association guidelines on statin initiation on the basis of total atherosclerotic cardiovascular disease risk argue that the preventive effect of statins on cardiovascular events outweigh the side effects, although this is controversial. Studies indicate a possible effect of statin therapy on reducing risk of lens opacities. However, the results are conflicting. The Simvastatin and Ezetimibe in Aortic Stenosis study (NCT00092677) enrolled 1,873 patients with asymptomatic aortic stenosis and no history of diabetes, coronary heart disease, or other serious co-morbidities were randomized (1:1) to double-blind 40 mg simvastatin plus 10 mg ezetimibe versus placebo. The primary end point in this substudy was incident cataract. Univariate and multivariate Cox models were used to analyze: (1) if the active treatment reduced the risk of the primary end point and (2) if time-varying low-density lipoproteins (LDL) cholesterol lowering (annually assessed) was associated with less incident cataract per se. During an average follow-up of 4.3 years, 65 patients (3.5%) developed cataract. Mean age at baseline was 68 years and 39% were women. In Cox multivariate analysis adjusted for age, gender, prednisolone treatment, smoking, baseline LDL cholesterol and high sensitivity C-reactive protein; simvastatin plus ezetimibe versus placebo was associated with 44% lower risk of cataract development (hazard ratio 0.56, 95% confidence interval 0.33 to 0.96, p = 0.034). In a parallel analysis substituting time-varying LDL-cholesterol with randomized treatment, lower intreatment LDL-cholesterol was in itself associated with lower risk of incident cataract (hazard ratio 0.78 per 1 mmol/ml lower total cholesterol, 95% confidence interval 0.64 to 0.93, p = 0.008). In conclusion, randomized treatment with simvastatin plus ezetimibe was associated with a 44% lower risk of incident cataract development. This effect should perhaps be considered in the risk-benefit ratio of statin treatment.

Novel splice-affecting variants in CYP27A1 gene in two Chilean patients with Cerebrotendinous Xanthomatosis

Cerebrotendinous Xanthomatosis (CTX), a rare lipid storage disorder, is caused by recessive loss-of-function mutations of the 27-sterol hydroxylase (CYP27A1), producing an alteration of the synthesis of bile acids, with an accumulation of cholestanol. Clinical characteristics include juvenile cataracts, diarrhea, tendon xanthomas, cognitive impairment and other neurological manifestations. Early diagnosis is critical, because treatment with chenodeoxycholic acid may prevent neurological damage. We studied the CYP27A1 gene in two Chilean CTX patients by sequencing its nine exons, exon-intron boundaries, and cDNA from peripheral blood mononuclear cells. Patient 1 is a compound heterozygote for the novel substitution c.256-1G > T that causes exon 2 skipping, leading to a premature stop codon in exon 3, and for the previously-known pathogenic mutation c.1183C > T (p.Arg395Cys). Patient 2 is homozygous for the novel mutation c.1185-1G > A that causes exon 7 skipping and the generation of a premature stop codon in exon 8, leading to the loss of the crucial adrenoxin binding domain of CYP27A1.

Statin use and risk for cataract: a nested case-control study of 2 populations in Canada and the United States

BACKGROUND

In current literature the association between statin use and cataracts is inconsistent and controversial. We sought to further examine the effect of statin use on the risk of cataract and need for surgical intervention in 2 North American populations.

METHODS

This retrospective nested case-control study derived data from the British Columbia (BC) Ministry of Health databases from 2000-2007 and the IMS LifeLink database from 2001-2011 to form 2 patient cohorts. The BC cohort was comprised of female and male patients; 162,501 patients were matched with 650,004 control subjects. The IMS LifeLink cohort was comprised of male patients aged 40-85 years; 45,065 patients were matched with 450,650 control subjects. Patients with statin use for > 1 year before the initial ophthalmology visit were identified. Diagnosis and surgical management of cataract were followed. Conditional logistic regression models were used to analyze data.

RESULTS

For the BC cohort, the crude rate ratio (RR) for use of any statin was 1.30, and the adjusted RR was 1.27 (95% confidence interval, 1.24-1.30). The adjusted RRs for each individual statin were all statistically significant. For the IMS LifeLink cohort, the crude RR for use of any statin was 1.13, and the adjusted RR was 1.07 (95% confidence interval, 1.04-1.10).

CONCLUSIONS

This study demonstrates that statin use is significantly associated with cataract requiring surgical intervention. This relationship was consistent in both North American cohorts. Further assessment of this relationship is recommended, especially because of increased statin use and the importance of acceptable vision in old age when cardiovascular disease is common.

Ophthalmic diseases and disorders in free-ranging rhesus macaque (Macaca mulatta) of Shivalik hill area of Himachal Pradesh, Northern India

BACKGROUND

The studies on ophthalmic diseases and disorders in a population of rhesus macaques, in particular with free-ranging macaques, are limited mainly by the difficulty in capturing animals and obtaining samples.

METHODS

From October 2011 to 2013, prevalence of various ophthalmic affections was recorded and analyzed on the basis of sex, age-group, and disease condition both in urban and peri-urban free-ranging rhesus macaques (Macaca mulatta) from various locations in Shivalik hill areas of Himachal Pradesh in northern India, as a part of clinical health examination.

RESULTS AND CONCLUSION

Ophthalmic diseases were more prevalent in macaques captured from urban settings than those from peri-urban, and difference between two groups was statistically significant (P < 0.01). Further classification of ophthalmic diseases revealed that traumatic injuries, corneal opacity, and cataract were significantly higher in urban than those in peri-urban macaque (P < 0.01). Similarly, the ophthalmic disorders among different age-groups were also found statistically significant (P < 0.01). The effect of sex on ophthalmic disorders was not found significant. Overviewing these results, disturbances in environment, close proximity to humans, and increasing age may lead to ophthalmic occurrences in these free-range macaques.

Properties of membranes derived from the total lipids extracted from clear and cataractous lenses of 61-70-year-old human donors

Human lens-lipid membranes prepared from the total lipids extracted from clear and cataractous lens cortexes and nuclei of 61-70-year-old donors by use of a rapid solvent-exchange method were investigated. The measured cholesterol-to-phospholipid (Chol/PL) molar ratio in these membranes was 1.8 and 4.4 for cortex and nucleus of clear lenses, respectively, and 1.14 and 1.45 for cataractous lenses. Properties and organization of the lipid bilayer were investigated by use of electron paramagnetic resonance spin-labeling methods. Formation of Chol crystals was confirmed by use of differential scanning calorimetry. Pure cholesterol bilayer domains (CBDs) were formed in all the membranes investigated. It was shown that in clear lens membranes of the nucleus, Chol exists in three different environments: (1) dispersed in phospholipid bilayers (PCDs), (2) in CBDs, and (3) in Chol crystals. In clear lens membranes of the cortex, and in cortical and nuclear cataractous lens membranes, Chol crystals were not detected, because of the lower Chol content. Profiles of membrane properties (alkyl-chain order, fluidity, oxygen transport, and hydrophobicity) across the PCD were very similar for clear and cataractous membranes. Profiles of the oxygen transport parameter across the CBD were, however, different for cortical clear and cataractous membranes-the amount and size of CBDs was less in cataractous membranes. These results suggest that high Chol content, formation of CBDs, and formation of Chol crystals should not be regarded as major predispositions for the development of age-related cataracts.

Involvement of oxysterols in age-related diseases and ageing processes

Ageing is accompanied by increasing vulnerability to major pathologies (atherosclerosis, Alzheimer's disease, age-related macular degeneration, cataract, and osteoporosis) which can have similar underlying pathoetiologies. All of these diseases involve oxidative stress, inflammation and/or cell death processes, which are triggered by cholesterol oxide derivatives, also named oxysterols. These oxidized lipids result either from spontaneous and/or enzymatic oxidation of cholesterol on the steroid nucleus or on the side chain. The ability of oxysterols to induce severe dysfunctions in organelles (especially mitochondria) plays key roles in RedOx homeostasis, inflammatory status, lipid metabolism, and in the control of cell death induction, which may at least in part contribute to explain the potential participation of these molecules in ageing processes and in age related diseases. As no efficient treatments are currently available for most of these diseases, which are predicted to become more prevalent due to the increasing life expectancy and average age, a better knowledge of the biological activities of the different oxysterols is of interest, and constitutes an important step toward identification of pharmacological targets for the development of new therapeutic strategies.

Statin treatment, new-onset diabetes, and other adverse effects: a systematic review

Statin treatment prevents cardiovascular diseases probably beyond their lipid-lowering effect. Increasing evidence suggests that statins might increase the risk of new-onset diabetes; however, diabetes is known to increase the risk of cardiovascular diseases. The majority of the literature suggests an increased risk of new-onset diabetes in patients treated with statins in a number of different settings and that the risk appears greatest among the more potent statins. Furthermore, a dose-response curve has been shown between statin treatment and the development of diabetes. Possible mechanisms include muscle insulin resistance, lower expression of GLUT-4 in adipocytes impairing glucose tolerance and suppression of glucose-induced elevation of intracellular Ca(2+) level. However, other side effects have been reported such as increased risk of myotoxicity, increased liver enzymes, cataracts, mood disorders, dementias, hemorrhagic stroke and peripheral neuropathy, which should maybe be added to the increased risk of new-onset diabetes, when considering the risk- benefit ratio of statin treatment.

Statins for children with familial hypercholesterolemia

BACKGROUND

Familial hypercholesterolemia is one of the most common inherited metabolic diseases; the average worldwide prevalence of heterozygous familial hypercholesterolemia is at least 1 in 500. Diagnosis of familial hypercholesterolemia in children is based on highly elevated low-density lipoprotein (LDL) cholesterol level or DNA-based analysis, or both. Coronary atherosclerosis has been detected in men with heterozygous familial hypercholesterolemia as young as 17 years old and in women with heterozygous familial hypercholesterolemia at 25 years old. Since the clinical complications of atherosclerosis occur prematurely, especially in men, lifelong hypolipidemic measures, started in childhood, are needed to reduce the risk of cardiovascular disease. In children with familial hypercholesterolemia, diet is as yet the cornerstone of treatment. Anion exchange resins, such as cholestyramine and colestipol, have also been found to be effective, but are poorly tolerated. Since the 1990s statin studies have been carried out among children with familial hypercholesterolemia (aged 7 to 17 years). Statins greatly reduced their serum LDL cholesterol levels. Even though statins seem to be safe and well-tolerated in children, their long-term safety in this age group is not firmly established.

OBJECTIVES

To assess the effectiveness and safety of statins in children with familial hypercholesterolemia.

SEARCH METHODS

Relevant studies were identified from the Group's Inborn Errors and Metabolism Trials Register and Medline.Date of most recent search: 14 October 2013.

SELECTION CRITERIA

Randomized and controlled clinical studies including participants up to 18 years old, comparing a statin to placebo or to diet alone.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed studies for inclusion and extracted data.

MAIN RESULTS

We found 21 potentially eligible studies, of which we included eight randomized placebo-controlled studies (1074 participants). In general, the intervention and follow-up time was short (median 24 weeks; range from six weeks to two years). Statins reduced the mean LDL cholesterol concentration at all time points. Serum aspartate and alanine aminotransferase, as well as creatinine kinase concentrations, did not differ between treated and placebo groups at any time point. The risks of myopathy and clinical adverse events were very low and also similar in both groups. In one study simvastatin was shown to improve flow-mediated dilatation of the brachial artery, and in another study treatment with pravastatin for two years induced a significant regression in carotid intima media thickness.

AUTHORS' CONCLUSIONS

Statin treatment is an efficient lipid-lowering therapy in children with familial hypercholesterolemia. No significant safety issues were identified. Statin treatment seems to be safe in the short term, but long-term safety is unknown. Children treated with statins should be carefully monitored and followed up by their pediatricians or physicians into adulthood. Large long-term randomized controlled trials are needed to establish the long-term safety issues of statins.

Statin use and cataract surgery: a nationwide retrospective cohort study in elderly ethnic Chinese patients

BACKGROUND

Since a report of lenticular opacities in dogs treated with high dosages of statins, the debate on the relationship between statin therapy and cataracts has not reached a conclusion.

OBJECTIVE

The aim of this study was to evaluate the association between statin therapy and the risk of cataract surgery in an elderly ethnic Chinese population using time-dependent analysis to minimize immortal time bias.

METHODS

A retrospective cohort study using the Longitudinal Health Insurance Database 2005 randomly sampled from the National Health Insurance Research Database, Taiwan, was conducted. A total of 50,165 adults aged between 65 and 90 years in 1998 without records of statin therapy or diagnosis of cataracts between July 1997 and December 1997 were included in the analysis. The first record of lens extraction within the follow-up period (1998-2009) was set as the study endpoint. A propensity score was derived using a logistic regression model to model the receipt of statin therapy as a function of the baseline characteristics for every subject. We used the time-dependent Cox regression model to test the relative hazard of undergoing cataract surgery between statin users and non-users, while use of statins was treated as a time-dependent variable, controlling for baseline age and individual propensity score.

RESULTS

Of the 50,165 enrolled subjects, 17,670 individuals with an incident lens extraction were identified during a median follow-up of 10.7 years. The incidence of cataract surgery was 49.7/1,000 person-years in the statin-using period compared with 38.5/1,000 person-years in the statin-non-using period. The adjusted hazard ratio of cataract surgery was 1.20 (95 % CI 1.14-1.27; P < 0.001) in statin users compared with statin non-users.

CONCLUSION

Statin therapy was associated with a modestly increased risk of cataract surgery. We suggest regular checks for lens opacity in statin users.

Novel splice-affecting variants in CYP27A1 gene in two Chilean patients with Cerebrotendinous Xanthomatosis

Cerebrotendinous Xanthomatosis (CTX), a rare lipid storage disorder, is caused by recessive loss-of-function mutations of the 27-sterol hydroxylase (CYP27A1), producing an alteration of the synthesis of bile acids, with an accumulation of cholestanol. Clinical characteristics include juvenile cataracts, diarrhea, tendon xanthomas, cognitive impairment and other neurological manifestations. Early diagnosis is critical, because treatment with chenodeoxycholic acid may prevent neurological damage. We studied the CYP27A1 gene in two Chilean CTX patients by sequencing its nine exons, exon-intron boundaries, and cDNA from peripheral blood mononuclear cells. Patient 1 is a compound heterozygote for the novel substitution c.256-1G > T that causes exon 2 skipping, leading to a premature stop codon in exon 3, and for the previously-known pathogenic mutation c.1183C > T (p.Arg395Cys). Patient 2 is homozygous for the novel mutation c.1185-1G > A that causes exon 7 skipping and the generation of a premature stop codon in exon 8, leading to the loss of the crucial adrenoxin binding domain of CYP27A1.

Etiopathogenesis of cataract: an appraisal

Natural eye lens is a crystalline substance to produce a clear passage for light. Cataract is opacity within the clear lens of the eye and is the dominant cause of socio-medical problem i.e., blindness worldwide. The only available treatment of cataract is surgery. However, insufficient surgical facilities in poor and developing countries and post-operative complications inspire researchers to find out other modes of treatment for cataract. In this review, an attempt has been made to appraise various etiological factors of cataract to make their perception clear to build up counterpart treatment. Present study is an assortment of various available literatures and electronic information in view of cataract etiopathogenesis. Various risk factors have been identified in development of cataracts. They can be classified in to genetic factors, ageing (systemic diseases, nutritional and trace metals deficiencies, smoking, oxidative stress etc.), traumatic, complicated (inflammatory and degenerative diseases of eye), metabolic (diabetes, galactosemia etc.), toxic substances including drugs abuses, alcohol etc., radiation (ultraviolet, electromagnetic waves etc.) are implicated as significant risk factors in the development of cataract.

Characterization of the ordered phase formed by sphingomyelin analogues and cholesterol binary mixtures

The influences of structural alterations of sphingomyelin (SM) on its interactions with cholesterol (chol) and on ordered phase formation were examined by density measurements and surface pressure vs. molecular area isotherm measurements. In addition, we quantitatively characterized the ordered phase formed in each SM and chol binary mixture on the basis of the molecular compressional modulus of SM ( Cmol−1). Density measurements demonstrated that the ordered phase formation in threo-SM (tSM)/chol and dihydrosphingomyelin (DHSM)/chol binary bilayers shows similar chol concentration-dependency to that of natural erythro-SM (eSM)/chol bilayers; the ordered phase formation was completed in the presence of 25 mol% chol. In contrast, SM bearing a triple bond in the place of a double bond (tripleSM) required a greater concentration of chol to completely transform the bilayer into the ordered phase (at 40 mol% chol). Surface pressure vs. molecular area isotherms showed that the DHSM molecule ( Cmol−1 = 290 mN/m) is more rigid than eSM ( Cmol−1 = 240 mN/m) above 30 mol% chol (in the ordered phase), although these values are similar (140–150 mN/m) in the absence of chol (liquid condensed phase). Most likely, the DHSM/chol mixture forms a more ordered membrane than the eSM/chol mixture does. Moreover, in the absence of chol, the rigidity of the tripleSM molecule ( Cmol−1 = 250 mN/m) is significantly higher as compared with that of the eSM molecule ( Cmol−1 = 150 mN/m), which is probably due to the presence of a triple bond.

The controversy of a wider statin utilization: why?

INTRODUCTION

Several medical journals published viewpoints and counter-viewpoints supporting or opposing a wider utilization of statins for primary prevention. The objective of this article is not to weigh in the benefits versus risks of statin use, but to discuss various aspects of this controversy.

AREAS COVERED

This review discusses the challenges in examining the pleotropic effects/adverse events of statins. It also discusses the pitfalls in assessment of adverse events in randomized controlled trials and observational studies.

EXPERT OPINION

The challenges in solving this controversy include that the pleotropic effect of statins results in an extremely wide spectrum of reported benefits or adverse events, the reported harms/benefits are contradictory, there is basic research ground supporting both sides of the controversy, it is difficult to separate if adverse events are due to statins or due to lower cholesterol, and that there is a lack of standardized definition of statin-associated adverse events and their methods of ascertainment. Both randomized controlled trials and observational studies have pitfalls and caveats in assessment of adverse events. Understanding the points of debate is of paramount significance to enable clinicians to individualize patient care.

Age-related cataract is associated with type 2 diabetes and statin use

PURPOSE

Diabetes has been shown to be a risk factor for age-related (AR) cataract. As statins (HMG-CoA reductase inhibitors) are now commonly prescribed for patients with type 2 diabetes, their impact on AR cataract prevalence should be considered. This study determines associations between AR cataract, type 2 diabetes, and reported statin use in a large optometric clinic population.

METHODS

In all, 6397 patient files (ages <1-93 years) were reviewed. Overall prevalence of statin use was calculated for patients with type 2 diabetes (n = 452) and without diabetes (n = 5884). Multivariable logistic regression analysis for AR cataract was performed controlling for patient sex, smoking, high blood pressure, type 2 diabetes, and statin use.

RESULTS

The prevalence of statin use (in patients aged >38 years) was 56% for those with type 2 diabetes and 16% for those without diabetes. Type 2 diabetes was significantly associated with nuclear sclerosis (OR = 1.62, 1.14-2.29) and cortical cataract (OR = 1.37, 1.02-1.83). Statin use was associated with nuclear sclerosis (OR = 1.48, 1.09-2.00) and posterior subcapsular cataract (OR = 1.48, 1.07-2.04). The 50% probability of cataract in statin users occurred at age 51.7 and 54.9 years in patients with type 2 diabetes and without diabetes, respectively. In non-statin users, it was significantly later at age 55.1 and 57.3 years for patients with type 2 diabetes and without diabetes, respectively (p < 0.001).

CONCLUSIONS

In this population, statin use was substantially higher in patients with type 2 diabetes and was associated with AR cataracts. Further long-term study is warranted to recommend monitoring of crystalline lenses in patients with type 2 diabetes benefiting from statins.

Functions of cholesterol and the cholesterol bilayer domain specific to the fiber-cell plasma membrane of the eye lens

The most unique feature of the eye lens fiber-cell plasma membrane is its extremely high cholesterol content. Cholesterol saturates the bulk phospholipid bilayer and induces formation of immiscible cholesterol bilayer domains (CBDs) within the membrane. Our results (based on EPR spin-labeling experiments with lens-lipid membranes), along with a literature search, have allowed us to identify the significant functions of cholesterol specific to the fiber-cell plasma membrane, which are manifest through cholesterol-membrane interactions. The crucial role is played by the CBD. The presence of the CBD ensures that the surrounding phospholipid bilayer is saturated with cholesterol. The saturating cholesterol content in fiber-cell membranes keeps the bulk physical properties of lens-lipid membranes consistent and independent of changes in phospholipid composition. Thus, the CBD helps to maintain lens-membrane homeostasis when the membrane phospholipid composition changes significantly. The CBD raises the barrier for oxygen transport across the fiber-cell membrane, which should help to maintain a low oxygen concentration in the lens interior. It is hypothesized that the appearance of the CBD in the fiber-cell membrane is controlled by the phospholipid composition of the membrane. Saturation with cholesterol smoothes the phospholipid-bilayer surface, which should decrease light scattering and help to maintain lens transparency. Other functions of cholesterol include formation of hydrophobic and rigidity barriers across the bulk phospholipid-cholesterol domain and formation of hydrophobic channels in the central region of the membrane for transport of small, nonpolar molecules parallel to the membrane surface. In this review, we provide data supporting these hypotheses.

The use of rat lens explant cultures to study the mechanism of drug-induced cataractogenesis

Lens explant cultures were used to assess the mechanism of drug-induced cataractogenic potential of NVS001, a peroxisome proliferator-activated receptor delta (PPARδ) agonist, which resulted in cataract in all treated animals during a 13-week rat study. Ciglitazone, a PPARγ agonist and cataractogenic compound, was used as a positive control to validate this model. Rat lenses were extracted and cultured in medium supplemented with antibiotics for 24-h preincubation pretreatment. Lenses showing no signs of damage at the end of the preincubation pretreatment period were randomized into five experimental groups, (1) untreated control, (2) 0.1% dimethyl sulphoxide control, (3) 10μM NVS001, (4) 10μM ciglitazone, and (5) 10μM acetaminophen (negative control). Lenses were treated every 24 h after preincubation pretreatment for up to 48 h. Samples for viability, histology, and gene expression profiling were collected at 4, 24, and 48 h. There was a time-dependent increase in opacity, which correlated to a decrease in viability measured by adenosine triphosphate levels in NVS001 and ciglitazone-treated lenses compared with controls. NVS001 and ciglitazone had comparable cataractogenic effects after 48 h with histology showing rupture of the lens capsule, lens fiber degeneration, cortical lens vacuolation, and lens epithelial degeneration. Furthermore, no changes were seen when lenses were treated with acetaminophen. Gene expression analysis supported oxidative and osmotic stress, along with decreases in membrane and epithelial cell integrity as key factors in NVS001-induced cataracts. This study suggests that in vitro lens cultures can be used to assess cataractogenic potential of PPAR agonists and to study/understand the underlying molecular mechanism of cataractogenesis in rat.

A spontaneous mutation in Srebf2 leads to cataracts and persistent skin wounds in the lens opacity 13 (lop13) mouse

Lens opacity 13 (lop13) is a spontaneous, autosomal recessive mouse mutant that exhibits nuclear cataracts. Histological analysis revealed swollen lens fiber cells and the presence of bladder cells within the lens cortex, as well as morgagnian globules and liquefied material at the lens posterior. At 3 months of age, in addition to cataracts, lop13 mice also develop persistent skin wounds. Linkage analysis assigned the lop13 locus to a 1.1-Mb region on mouse Chr 15, encompassing 19 candidate genes. Sequence analysis identified a C3112T mutation in exon 18 of Sterol Regulatory Element Binding-Transcription Factor 2 (Srebf2) resulting in the R1038C substitution of a highly conserved arginine within the Srebf2 regulatory domain. Srebf2 belongs to a family of membrane-bound basic helix-loop-helix leucine zipper transcription factors that control the expression of genes involved in the biosynthesis and uptake of cholesterol and fatty acids. The lack of complementation observed in Srebf2 ( lop13/GT ) compound heterozygotes carrying the Srebf2 gene trapped allele (Srebf2 ( GT )) provides genetic evidence that the identified C3112T substitution in Srebf2 is responsible for the lop13 phenotype. Gas chromatography analysis identified lower levels of cholesterol in the lop13 brain, liver, and lens when compared to wild-type mice. These findings suggest that lop13 is a hypomorphic mutation in Srebf2. As such, the lop13 mouse presents an invaluable in vivo model for studying the contribution of Srebf2 and cholesterol to maintaining the homeostasis of the lens and skin.