PurposeAge-related macular degeneration (AMD) is a frequent, complex disorder in elderly of European ancestry. Risk profiles and treatment options have changed considerably over the years, which may have affected disease prevalence and outcome. We determined the prevalence of early and late AMD in Europe from 1990 to 2013 using the European Eye Epidemiology (E3) consortium, and made projections for the future.DesignMeta-analysis of prevalence data.ParticipantsA total of 42 080 individuals 40 years of age and older participating in 14 population-based cohorts from 10 countries in Europe.MethodsAMD was diagnosed based on fundus photographs using the Rotterdam Classification. Prevalence of early and late AMD was calculated using random-effects meta-analysis stratified for age, birth cohort, gender, geographic region, and time period of the study. Best-corrected visual acuity (BCVA) was compared between late AMD subtypes; geographic atrophy (GA) and choroidal neovascularization (CNV).Main Outcome MeasuresPrevalence of early and late AMD, BCVA, and number of AMD cases.ResultsPrevalence of early AMD increased from 3.5% (95% confidence interval [CI] 2.1%–5.0%) in those aged 55–59 years to 17.6% (95% CI 13.6%–21.5%) in those aged ≥85 years; for late AMD these figures were 0.1% (95% CI 0.04%–0.3%) and 9.8% (95% CI 6.3%–13.3%), respectively. We observed a decreasing prevalence of late AMD after 2006, which became most prominent after age 70. Prevalences were similar for gender across all age groups except for late AMD in the oldest age category, and a trend was found showing a higher prevalence of CNV in Northern Europe. After 2006, fewer eyes and fewer ≥80-year-old subjects with CNV were visually impaired (P = 0.016). Projections of AMD showed an almost doubling of affected persons despite a decreasing prevalence. By 2040, the number of individuals in Europe with early AMD will range between 14.9 and 21.5 million, and for late AMD between 3.9 and 4.8 million.ConclusionWe observed a decreasing prevalence of AMD and an improvement in visual acuity in CNV occuring over the past 2 decades in Europe. Healthier lifestyles and implementation of anti–vascular endothelial growth factor treatment are the most likely explanations. Nevertheless, the numbers of affected subjects will increase considerably in the next 2 decades. AMD continues to remain a significant public health problem among Europeans.

There is an urgency to find new treatment strategies that could prevent or delay the onset or progression of AMD. Different classes of lipids and lipoproteins metabolism genes have been associated with AMD in a multiple ways, but despite the ever-increasing knowledge base, we still do not understand fully how circulating lipids or local lipid metabolism contribute to AMD. It is essential to clarify whether dietary lipids, systemic or local lipoprotein metabolismtrafficking of lipids in the retina should be targeted in the disease. In this article, we critically evaluate what has been reported in the literature and identify new directions needed to bring about a significant advance in our understanding of the role for lipids in AMD. This may help to develop potential new treatment strategies through targeting the lipid homeostasis.

Biomarkers can help unravel mechanisms of disease and identify new targets for therapy. They can also be useful in clinical practice for monitoring disease progression, evaluation of treatment efficacy, and risk assessment in multifactorial diseases, such as age-related macular degeneration (AMD). AMD is a highly prevalent progressive retinal disorder for which multiple genetic and environmental risk factors have been described, but the exact etiology is not yet fully understood. Many compounds have been evaluated for their association with AMD. We performed an extensive literature review of all compounds measured in serum, plasma, vitreous, aqueous humor, and urine of AMD patients. Over 3600 articles were screened, resulting in more than 100 different compounds analyzed in AMD studies, involved in neovascularization, immunity, lipid metabolism, extracellular matrix, oxidative stress, diet, hormones, and comorbidities (such as kidney disease). For each compound, we provide a short description of its function and discuss the results of the studies in relation to its usefulness as AMD biomarker. In addition, biomarkers identified by hypothesis-free techniques, including metabolomics, proteomics, and epigenomics, are covered. In summary, compounds belonging to the oxidative stress pathway, the complement system, and lipid metabolism are the most promising biomarker candidates for AMD. We hope that this comprehensive survey of the literature on systemic and ocular fluid compounds as potential biomarkers in AMD will provide a stepping stone for future research and possible implementation in clinical practice.

Genetic and epidemiologic studies have shown that lipid genes and High Density Lipoproteins (HDL) are implicated in age-related macular degeneration (AMD). We studied circulating lipid levels in relation to AMD in a large European dataset, and investigated whether this relationship is driven by certain sub fractions. Design: (Pooled) analysis of cross-sectional data. Participants: 30,953 individuals aged 50+ participating in the E3 consortium; and 1530 individuals from the Rotterdam Study with lipid sub fraction data. Methods: In E3, AMD features were graded per eye on fundus photographs using the Rotterdam Classification. Routine blood lipid measurements were available from each participant. Data on genetics, medication and confounders such as body mass index, were obtained from a common database. In a subgroup of the Rotterdam Study, lipid sub fractions were identified by the Nightingale biomarker platform. Random-intercepts mixed-effects models incorporating confounders and study site as a random-effect were used to estimate the associations. Main Outcome Measures: early, late or any AMD, phenotypic features of early AMD, lipid measurements. Results: HDL was associated with an increased risk of AMD, corrected for potential confounders (Odds Ratio (OR) 1.21 per 1mmol/L increase (95% confidence interval[CI] 1.14-1.29); while triglycerides were associated with a decreased risk (OR 0.94 per 1mmol/L increase [95%CI 0.91-0.97]). Both were associated with drusen size, higher HDL raises the odds of larger drusen while higher triglycerides decreases the odds. LDL-cholesterol only reached statistical significance in the association with early AMD (p=0.045). Regarding lipid sub fractions: the concentration of extra-large HDL particles showed the most prominent association with AMD (OR 1.24 [95%CI 1.10-1.40]). The CETP risk variant (rs17231506) for AMD was in line with increased-HDL levels (p=7.7x10-7); but LIPC risk variants (rs2043085, rs2070895) were associated in an opposite way (p=1.0x10-6 and 1.6x10-4). Conclusions: Our study suggests that HDL-cholesterol is associated with increased risk of AMD and triglycerides negatively associated. Both show the strongest association with early AMD and drusen. Extra-large HDL sub fractions seem to be drivers in the relation with AMD, variants in lipid genes play a more ambiguous role in this association. Whether systemic lipids directly influence AMD or represent lipid metabolism in the retina remains a question to be answered.

It had been thought that complement factor D (FD) is activated at the site of synthesis, and only FD lacking a propeptide is present in blood. The serum of mannose-binding lectin–associated serine protease (MASP)-1/3(−/−) mice contains pro-FD and has markedly reduced alternative pathway activity. It was suggested that MASP-1 and MASP-3 directly activate pro-FD; however, other experiments contradicted this view. We decided to clarify the involvement of MASPs in pro-FD activation in normal, as opposed to deficient, human plasma and serum. Human pro-FD containing an APPRGR propeptide was produced in insect cells. We measured its activation kinetics using purified active MASP-1, MASP-2, MASP-3, as well as thrombin. We found all these enzymes to be efficient activators, whereas MASP proenzymes lacked such activity. Pro-FD cleavage in serum or plasma was quantified by a novel assay using fluorescently labeled pro-FD. Labeled pro-FD was processed with t1/2s of ∼3 and 5 h in serum and plasma, respectively, showing that proteolytic activity capable of activating pro-FD exists in blood even in the absence of active coagulation enzymes. Our previously developed selective MASP-1 and MASP-2 inhibitors did not reduce pro-FD activation at reasonable concentration. In contrast, at very high concentration, the MASP-2 inhibitor, which is also a poor MASP-3 inhibitor, slowed down the activation. When recombinant MASPs were added to plasma, only MASP-3 could reduce the half-life of pro-FD. Combining our quantitative data, MASP-1 and MASP-2 can be ruled out as direct pro-FD activators in resting blood; however, active MASP-3 is a very likely physiological activator.

OBJECTIVENonalcoholic fatty liver (NAFL) is thought to contribute to insulin resistance and its metabolic complications. However, some individuals with NAFL remain insulin sensitive. Mechanisms involved in the susceptibility to develop insulin resistance in humans with NAFL are largely unknown. We investigated circulating markers and mechanisms of a metabolically benign and malignant NAFL by applying a metabolomic approach.RESEARCH DESIGN AND METHODSA total of 265 metabolites were analyzed before and after a 9-month lifestyle intervention in plasma from 20 insulin-sensitive and 20 insulin-resistant subjects with NAFL. The relevant plasma metabolites were then tested for relationships with insulin sensitivity in 17 subjects without NAFL and in plasma from 29 subjects with liver tissue samples.RESULTSThe best separation of the insulin-sensitive from the insulin-resistant NAFL group was achieved by a metabolite pattern including the branched-chain amino acids leucine and isoleucine, ornithine, the acylcarnitines C3:0-, C16:0-, and C18:0-carnitine, and lysophosphatidylcholine (lyso-PC) C16:0 (area under the ROC curve, 0.77 [P = 0.00023] at baseline and 0.80 [P = 0.000019] at follow-up). Among the individual metabolites, predominantly higher levels of lyso-PC C16:0, both at baseline (P = 0.0039) and at follow-up (P = 0.001), were found in the insulin-sensitive compared with the insulin-resistant subjects. In the non-NAFL groups, no differences in lyso-PC C16:0 levels were found between the insulin-sensitive and insulin-resistant subjects, and these relationships were replicated in plasma from subjects with liver tissue samples.CONCLUSIONSFrom a plasma metabolomic pattern, particularly lyso-PCs are able to separate metabolically benign from malignant NAFL in humans and may highlight important pathways in the pathogenesis of fatty liver–induced insulin resistance.

Phosphopeptide mapping identified a major autophosphorylation site, phospho (p)Thr-219, between the tandem C1 domains of the regulatory fragment in protein kinase C (PKC)h. Confirmation of this identification was derived using (p)Thr-219 antisera that reacted with endogenous PKCh in primary CD3 þ T cells after stimulation with phorbol ester, anti-CD3 or vanadate. The T219A mutation abrogated the capacity of PKCh to mediate NF-jB, NF-AT and interleukin-2 promoter transactivation, and reduced PKCh's ability in Jurkat T cells to phosphorylate endogenous cellular substrates. In particular, the T219A mutation impaired crosstalk of PKCh with Akt/PKBa in NF-jB activation. Yet, this novel (p)Thr-219 site did not affect catalytic activity or second-messenger lipid-binding activity in vitro. Instead, the T219A mutation prevented proper recruitment of PKCh in activated T cells. The PKChT219A mutant defects were largely rescued by addition of a myristoylation signal to force its proper membrane localization. We conclude that autophosphorylation of PKCh at Thr-219 plays an important role in the correct targeting and cellular function of PKCh upon antigen receptor ligation.

G-protein-coupled receptor kinases (GRKs) are important regulators of G-protein-coupled receptor function. Two members of this family L, GRK2 and GRK5 L, have been shown to be substrates for protein kinase C (PKC).Whereas PKC-mediated phosphorylation results in inhibition of GRK5, it increases the activity of GRK2 toward its substrates probably through increased affinity for receptor-containing membranes. We show here that this increase in activity may be caused by relieving a tonic inhibition of GRK2 by calmodulin. In vitro, GRK2 was preferentially phosphorylated by PKC isoforms ␣, ␥, and ␦. Two-dimensional peptide mapping of PKC␣-phosphorylated GRK2 showed a single site of phosphorylation, which was identified as serine 29 by HPLC-MS. A S29A mutant of GRK2 was not phosphorylated by PKC in vitro and showed no phorbol ester-stimulated phosphorylation when transfected into human embryonic kidney (HEK)293 cells. Serine 29 is located in the calmodulinbinding region of GRK2, and binding of calmodulin to GRK2 results in inhibition of kinase activity. This inhibition was almost completely abolished in vitro when GRK2 was phosphorylated by PKC. These data suggest that calmodulin may be an inhibitor of GRK2 whose effects can be abolished with PKC-mediated phosphorylation of GRK2. Signaling via G-protein-coupled receptors (GPCRs)1 is subject to a variety of regulatory processes. One of the key regulatory mechanisms is the control of receptor function by Gprotein-coupled receptor kinases (GRKs). These kinases phosphorylate the agonist-bound state of GPCRs, and this phosphorylation is often the initial step in homologous receptor desensitization, the loss of receptor responsiveness upon repeated or prolonged receptor stimulation (1, 2). To date, six members of the GRK family are known (3, 4). Of these, GRK2 (previously called ␤-adrenergic receptor kinase-1) as well as GRK3, GRK5, and GRK6 are widely expressed throughout the mammalian body whereas GRK1 (also known as rhodopsin kinase) and GRK4 have been found only in specific tissues.All GRKs have a similar molecular architecture. A central catalytic domain is flanked by an N-and C-terminal domain. The function of the latter is to provide a membrane anchor, which seems to be essential for receptor phosphorylation (5). The C terminus of GRK1 is farnesylated, whereas GRK2 and GRK3 possess a pleckstrin homology domain implicated in phosphatidylinositol bisphosphate and G-protein ␤␥-subunit binding. GRK4 and GRK6 are palmitoylated, and GRK5 binds phospholipids through a poorly defined polybasic domain (3, 4). The function of the N terminus is less clear. It has been shown for GRK1 that antibodies against an epitope in the N terminus prevent phosphorylation of light-activated rhodopsin but not of a peptide substrate (6). However, the epitope against which the antibodies were directed is poorly conserved in the GRK family. Recent results have indicated that the N terminus of GRK2 and GRK3 contains an RGS (regulator of G-protein signaling) domain that specifically binds to and act...