Plasma Clusterin and Lipid Profile: A Link with Aging and Cardiovascular Diseases in a Population with a Consistent Number of Centenarians

Analysis of the aging-related biomarker in a nonhuman primate model using multilayer omics

BACKGROUND

Aging is a prominent risk factor for diverse diseases; therefore, an in-depth understanding of its physiological mechanisms is required. Nonhuman primates, which share the closest genetic relationship with humans, serve as an ideal model for exploring the complex aging process. However, the potential of the nonhuman primate animal model in the screening of human aging markers is still not fully exploited. Multiomics analysis of nonhuman primate peripheral blood offers a promising approach to evaluate new therapies and biomarkers. This study explores aging-related biomarker through multilayer omics, including transcriptomics (mRNA, lncRNA, and circRNA) and proteomics (serum and serum-derived exosomes) in rhesus monkeys (Macaca mulatta).

RESULTS

Our findings reveal that, unlike mRNAs and circRNAs, highly expressed lncRNAs are abundant during the key aging period and are associated with cancer pathways. Comparative analysis highlighted exosomal proteins contain more types of proteins than serum proteins, indicating that serum-derived exosomes primarily regulate aging through metabolic pathways. Finally, eight candidate aging biomarkers were identified, which may serve as blood-based indicators for detecting age-related brain changes.

CONCLUSIONS

Our results provide a comprehensive understanding of nonhuman primate blood transcriptomes and proteomes, offering novel insights into the aging mechanisms for preventing or treating age-related diseases.

Method to Assess the Intracellular Fate and Bioavailability of Clusterin Using Live Cell Confocal Microscopy Imaging

Clusterin, also known as apolipoprotein J, is an ATP-independent holdase chaperone protein. Clusterin is involved in various functions including protein quality control and lipid transport. Though clusterin is secreted upon stress, the intracellular fate of clusterin after a stress response is not well understood. The protocol described here utilizes clusterin tagged to fluorescent proteins like green fluorescent protein and red fluorescent protein to understand the intracellular fate of clusterin.

Strategies for consistent and automated quantification of HDL proteome using data-independent acquisition (DIA)

The introduction of mass spectrometry-based proteomics has revolutionized HDL field, with the description, characterization and implication of HDL-associated proteins in an array of pathologies. However, acquiring robust, reproducible data is still a challenge in the quantitative assessment of HDL proteome. Data-independent acquisition (DIA) is a mass spectrometry methodology that allows the acquisition of reproducible data, but data analysis remains a challenge in the field. Up to date, there is no consensus in how to process DIA-derived data for HDL proteomics. Here, we developed a pipeline aiming to standardize HDL proteome quantification. We optimized instrument parameters, and compared the performance of four freely available, user-friendly software tools (DIA-NN, EncyclopeDIA, MaxDIA and Skyline) in processing DIA data. Importantly, pooled samples were used as quality controls throughout our experimental setup. A carefully evaluation of precision, linearity, and detection limits, first using E. coli background for HDL proteomics, and second using HDL proteome and synthetic peptides, was undertaken. Finally, as a proof of concept, we employed our optimized and automated pipeline to quantify the proteome of HDL and apolipoprotein B (APOB)-containing lipoproteins. Our results show that determination of precision is key to confidently and consistently quantify HDL proteins. Taking this precaution, any of the available software tested here would be appropriate for quantification of HDL proteome, although their performance varied considerably.

Serum clusterin levels are not associated with chronic spontaneous urticaria regardless of serum lipids

BACKGROUND

Clusterin is related to immunity and inflammation via regulation of complement activation and bidirectional regulation of and by major proinflammatory cytokines. Clusterin levels have been the subject of a few researches both in patients with hyperlipidemia and those with chronic spontaneous urticaria (CSU) separately. The aims of this study were evaluate the levels of clusterin levels and serum lipids and the relationships between them in patients with CSU.

METHODS

Fifty patients with CSU and 30 healthy controls were enrolled into the study. The activity of urticaria of the patients was determined by urticaria activity score (UAS7). Serum clusterin, total cholesterol, HDL, LDL and triglyceride levels of the participants were measured and compared. The relationships between UAS, lipids and clusterin were examined.

RESULTS

There was no difference in clusterin levels between CSU patients and controls. Clusterin level was not related to activity of urticaria. Clusterin levels were not correlated with any of lipid parameters neither in CSU patients nor in controls.

CONCLUSIONS

Findings of this study show that clusterin levels do not change due to CSU. Serum clusterin levels cannot be used as a diagnostic or a disease activity marker in CSU patients, regardless of the lipid profile.

Identification of Potential Targets Linked to the Cardiovascular/Alzheimer’s Axis through Bioinformatics Approaches

The identification of common targets in Alzheimer’s disease (AD) and cardiovascular disease (CVD) in recent years makes the study of the CVD/AD axis a research topic of great interest. Besides aging, other links between CVD and AD have been described, suggesting the existence of common molecular mechanisms. Our study aimed to identify common targets in the CVD/AD axis. For this purpose, genomic data from calcified and healthy femoral artery samples were used to identify differentially expressed genes (DEGs), which were used to generate a protein–protein interaction network, where a module related to AD was identified. This module was enriched with the functionally closest proteins and analyzed using different centrality algorithms to determine the main targets in the CVD/AD axis. Validation was performed by proteomic and data mining analyses. The proteins identified with an important role in both pathologies were apolipoprotein E and haptoglobin as DEGs, with a fold change about +2 and −2, in calcified femoral artery vs healthy artery, respectively, and clusterin and alpha-2-macroglobulin as close interactors that matched in our proteomic analysis. However, further studies are needed to elucidate the specific role of these proteins, and to evaluate its function as biomarkers or therapeutic targets.

Cholesterol and Alzheimer's Disease; From Risk Genes to Pathological Effects

While the central nervous system compromises 2% of our body weight, it harbors up to 25% of the body's cholesterol. Cholesterol levels in the brain are tightly regulated for physiological brain function, but mounting evidence indicates that excessive cholesterol accumulates in Alzheimer's disease (AD), where it may drive AD-associated pathological changes. This seems especially relevant for late-onset AD, as several of the major genetic risk factors are functionally associated with cholesterol metabolism. In this review we discuss the different systems that maintain brain cholesterol metabolism in the healthy brain, and how dysregulation of these processes can lead, or contribute to, Alzheimer's disease. We will also discuss how AD-risk genes might impact cholesterol metabolism and downstream AD pathology. Finally, we will address the major outstanding questions in the field and how recent technical advances in CRISPR/Cas9-gene editing and induced pluripotent stem cell (iPSC)-technology can aid to study these problems.

Clusterin serum levels are elevated in patients with early rheumatoid arthritis and predict disease activity and treatment response

Clusterin (CLU) is a molecular chaperone that participates in a variety of biological processes. Recent studies indicate its possible involvement in the development of bone erosions and autoimmunity. The aim of this study was to investigate its serum concentrations in patients with early rheumatoid arthritis (RA) and to explore their potential relationship with disease activity and treatment response. Serum levels of CLU were measured in 52 patients before and 3 months after the initiation of treatment and in 52 healthy individuals. CLU levels at baseline were significantly increased in patients with early RA compared with healthy subjects (p < 0.0001). After 3 months of treatment, the levels of CLU decreased and reached concentrations comparable to those in controls. Even though there was no relationship between CLU levels and disease activity at baseline, CLU levels positively correlated with disease activity at months 3, 6 and 12 after treatment initiation. Using ROC analysis, lower CLU baseline levels predicted achieving the therapeutic target of low disease activity and remission at months 3, 6 and 12. In summary, we found increased serum concentrations of clusterin in treatment-naïve patients with early rheumatoid arthritis, and we suggest clusterin as a predictive biomarker of disease activity and treatment response.

Sterol O-acyltransferase 2 chaperoned by apolipoprotein J facilitates hepatic lipid accumulation following viral and nutrient stresses

The risks of non-alcoholic fatty liver disease (NAFLD) include obese and non-obese stresses such as chronic hepatitis C virus (HCV) infection, but the regulatory determinants remain obscure. Apolipoprotein J (ApoJ) served as an ER-Golgi contact-site chaperone near lipid droplet (LD), facilitating HCV virion production. We hypothesized an interplay between hepatic ApoJ, cholesterol esterification and lipid deposit in response to NAFLD inducers. Exposures of HCV or free-fatty acids exhibited excess LDs along with increased ApoJ expression, whereas ApoJ silencing alleviated hepatic lipid accumulation. Both stresses could concomitantly disperse Golgi, induce closer ApoJ and sterol O-acyltransferase 2 (SOAT2) contacts via the N-terminal intrinsically disordered regions, and increase cholesteryl-ester. Furthermore, serum ApoJ correlated positively with cholesterol and low-density lipoprotein levels in normal glycaemic HCV patients, NAFLD patients and in mice with steatosis. Taken together, hepatic ApoJ might activate SOAT2 to supply cholesteryl-ester for lipid loads, thus providing a therapeutic target of stress-induced steatosis.

Circulating levels of clusterin and complement factor H in patients with obstructive sleep apnea

Aim: Obstructive sleep apnea (OSA) activates the complement system; however, the levels of membrane attack complex (MAC) are unaltered suggesting regulatory mechanisms. Our aim was to investigate complement factor H (CFH) and clusterin, two important complement regulators in OSA. Materials & methods: We analyzed clusterin and CFH levels in plasma of 86 patients with OSA and 33 control subjects. Results: There was no difference in CFH levels between patients (1099.4/784.6-1570.5/μg/ml) and controls (1051.4/652.0-1615.1/μg/ml, p = 0.72). Clusterin levels were higher in patients with OSA (309.7/217.2-763.2/μg/ml vs 276.1/131.0-424.3/μg/ml, p = 0.048) with a trend for a positive correlation with disease severity (p = 0.073). Conclusion: Increase in clusterin levels may be protective in OSA by blocking the MAC formation.

Clusterin and Its Role in Insulin Resistance and the Cardiometabolic Syndrome

The cardiometabolic syndrome involves a clustering of metabolic and cardiovascular factors which increase the risk of patients developing both Type 2 Diabetes Mellitus and cardio/cerebrovascular disease. Although the mechanistic underpinnings of this link remain uncertain, key factors include insulin resistance, excess visceral adiposity, atherogenic dyslipidemia, and endothelial dysfunction. Of these, a state of resistance to insulin action in overweight/obese patients appears to be central to the pathophysiologic process. Given the increasing prevalence of obesity-related Type 2 Diabetes, coupled with the fact that cardiovascular disease is the number one cause of mortality in this patient population, a more thorough understanding of the cardiometabolic syndrome and potential options to mitigate its risk is imperative. Inherent in the pathogenesis of insulin resistance is an underlying state of chronic inflammation, at least partly in response to excess adiposity. Within obese adipose tissue, an immunomodulatory shift occurs, involving a preponderance of pro-inflammatory immune cells and cytokines/adipokines, along with antigen presentation by adipocytes. Therefore, various adipokines differentially expressed by obese adipocytes may have a significant effect on cardiometabolism. Clusterin is a molecular chaperone that is widely produced by many tissues throughout the body, but is also preferentially overexpressed by obese compared lean adipocytes and relates strongly to multiple components of the cardiometabolic syndrome. Herein, we summarize the known and potential roles of circulating and adipocyte-specific clusterin in cardiometabolism and discuss potential further investigations to determine if clusterin is a viable target to attenuate both metabolic and cardiovascular disease.

Complement in Neurologic Disease

Classic innate immune signaling pathways provide most of the immune response in the brain. This response activates many of the canonical signaling mechanisms identified in peripheral immune cells, despite their relative absence in this immune-privileged tissue. Studies over the past decade have strongly linked complement protein production and activation to age-related functional changes and neurodegeneration. The reactivation of the complement signaling pathway in aging and disease has opened new avenues for understanding brain aging and neurological disease pathogenesis and has implicated cell types such as astrocytes, microglia, endothelial cells, oligodendrocytes, neurons, and even peripheral immune cells in these processes. In this review, we aim to unravel the past decade of research related to complement activation and its numerous consequences in aging and neurological disease.

Combined Aerobic and Resistance Exercise Training Reduces Circulating Apolipoprotein J Levels and Improves Insulin Resistance in Postmenopausal Diabetic Women

BACKGROUND

Circulating apolipoprotein J (ApoJ) is closely associated with insulin resistance; however, the effect of exercise on circulating ApoJ levels and the association of ApoJ with metabolic indices remain unknown. Here, we investigated whether a combined exercise can alter the circulating ApoJ level, and whether these changes are associated with metabolic indices in patients with type 2 diabetes mellitus.

METHODS

Postmenopausal women with type 2 diabetes mellitus were randomly assigned into either an exercise (EXE, n=30) or control (CON, n=15) group. Participants in the EXE group were enrolled in a 12-week program consisting of a combination of aerobic and resistance exercises. At baseline, 4, 8, and 12 weeks, body composition and metabolic parameters including homeostatic model assessment of insulin resistance (HOMA-IR) and serum ApoJ levels were assessed.

RESULTS

In the EXE group, ApoJ levels decreased 26.3% and 19.4%, relative to baseline, at 8 and 12 weeks, respectively. Between-group differences were significant at 8 and 12 weeks (P<0.05 and P<0.001, respectively). In the EXE group, 12 weeks of exercise resulted in significant decreases in body weight, percent body fat, and HOMA-IR indices. Concurrently, weight-adjusted appendicular skeletal muscle mass (ASM/wt) was increased in the EXE group compared with the CON group. Importantly, changes in the ApoJ level were significantly correlated with changes in ASM/wt.

CONCLUSION

Exercise training resulted in a significant decrease in the circulating ApoJ level, with changes in ApoJ associated with an improvement in some insulin resistance indices. These data suggest that circulating ApoJ may be a useful metabolic marker for assessing the effects of exercise on insulin resistance.

Comparative Proteomic Analysis of Serum from Pigs Experimentally Infected with Trichinella spiralis, Trichinella britovi, and Trichinella pseudospiralis

Although the available proteomic studies have made it possible to identify and characterize Trichinella stage-specific proteins reacting with infected host-specific antibodies, the vast majority of these studies do not provide any information about changes in the global proteomic serum profile of Trichinella-infested individuals. In view of the above, the present study aimed to examine the protein expression profile of serum obtained at 13 and 60 days postinfection (d.p.i.) from three groups of pigs experimentally infected with Trichinella spiralis, Trichinella britovi, and Trichinella pseudospiralis and from uninfected, control pigs by two-dimensional gel electrophoresis (2-DE) followed by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. The comparative proteomic analysis of the T. spiralis group vs. the control group revealed 5 differently expressed spots at both 13 and 60 d.p.i. Experimental infection with T. britovi induced significant expression changes in 3 protein spots at 13 d.p.i. and in 6 protein spots at 60 d.p.i. in comparison with the control group. Paired analyses between the group infected with T. pseudospiralis and the uninfected control group revealed 6 differently changed spots at 13 d.p.i. and 2 differently changed spots at 60 d.p.i. Among these 27 spots, 15 were successfully identified. Depending on the Trichinella species triggering the infection and the time point of serum collection, they were IgM heavy-chain constant region, antithrombin III-precursor, immunoglobulin gamma-chain, clusterin, homeobox protein Mohawk, apolipoprotein E precursor, serum amyloid P-component precursor, Ig lambda chains, complement C3 isoform X1, and apolipoprotein A-I. Our results demonstrate that various Trichinella species and different phases of the invasion produce a distinct, characteristic proteomic pattern in the serum of experimentally infected pigs.

A Cross-Sectional Study of Compositional and Functional Profiles of Gut Microbiota in Sardinian Centenarians

Sardinia, Italy, has a high prevalence of residents who live more than 100 years. The reasons for longevity in this isolated region are currently unknown. Gut microbiota may hold a clue. To explore the role gut microbiota may play in healthy aging and longevity, we used metagenomic sequencing to determine the compositional and functional differences in gut microbiota associated with populations of different ages in Sardinia. Our data revealed that the gut microbiota of both young and elderly Sardinians shared similar taxonomic and functional profiles. A different pattern was found in centenarians. Within the centenarian group, the gut microbiota was correlated with the functional independence measurement of the host. Centenarians had a higher diversity of core microbiota species and microbial genes than those in the young and elderly. We found that the gut microbiota in Sardinian centenarians displayed a rearranged taxonomic pattern compared with those of the young and elderly, featured by depletion of Faecalibacterium prausnitzii and Eubacterium rectale and enriched for Methanobrevibacter smithii and Bifidobacterium adolescentis Moreover, functional analysis revealed that the microbiota in centenarians had high capacity for central metabolism, especially glycolysis and fermentation to short-chain fatty acids (SCFAs), although the gut microbiota in centenarians was low in genes encoding enzymes involved in degradation of carbohydrates, including fibers and galactose.IMPORTANCE The gut microbiota has been proposed as a promising determinant for human health. Centenarians as a model for extreme aging may help us understand the correlation of gut microbiota with healthy aging and longevity. Here we confirmed that centenarians had microbiota elements usually associated with benefits to health. Our finding of a high capacity of glycolysis and related SCFA production represented a healthy microbiome and environment that is regarded as beneficial for host gut epithelium. The low abundance of genes encoding components of pathways involved in carbohydrate degradation was also found in the gut microbiota of Sardinian centenarians and is often associated with poor gut health. Overall, our study here represents an expansion of previous research investigating the age-related changes in gut microbiota. Furthermore, our study provides a new prospective for potential targets for gut microbiota intervention directed at limiting gut inflammation and pathology and enhancing a healthy gut barrier.

High serum clusterin levels are associated with premature coronary artery disease in a Chinese population

BACKGROUND

Clusterin plays an important role in the cardiovascular system, and serum levels of clusterin are higher in coronary artery disease patients. Here, we measured serum clusterin levels in premature coronary artery disease (PCAD) patients and explored the association of these levels with PCAD risk.

METHODS

Serum samples and general clinical information were obtained from 672 subjects including 364 PCAD subjects, 126 non-PCAD subjects, and 182 controls.

RESULTS

Serum clusterin levels were higher in PCAD patients than in controls, particularly in males with body mass index (BMI) < 25 kg/m² (P < 0.0001). Compared with the lowest tertile of clusterin, the odds ratio of PCAD in the highest tertile was higher in both a univariate and three adjustment models, and it was 3.146-fold higher in Model 3. This association was especially significant in subgroups with BMI < 25 kg/m² , total cholesterol < 5.7 mmol/L, high-density lipoprotein cholesterol ≥ 1.0 mmol/L, Urea < 7.14 mmol/L, and estimated glomerular filtration rate < 90 mL/min/1.73 m² . Serum clusterin may be a potential diagnostic biomarker for PCAD (sensitivity 60.7%, specificity 51.6%, area under the curve 0.595 [95% CI, 0.544-0.647], P < 0.0001), and a combination of clusterin with clinical variables in Model 3 resulted in improved diagnostic accuracy (sensitivity 86.3%, specificity 64.2%, area under the curve 0.829 [95% CI, 0.782-0.877], P < 0.0001).

CONCLUSIONS

Serum clusterin levels were increased in PCAD patients, especially for males with BMI < 25 kg/m² . Higher clusterin levels were independently associated with the presence of PCAD, particularly in subjects with normal BMI, lower total cholesterol, urea, estimated glomerular filtration rate, and higher high-density lipoprotein cholesterol. Clusterin might be a potential diagnostic biomarker for PCAD patients, especially in combination with clinical variables.

Mass spectrometry-based proteomics reveals the distinct nature of the skin proteomes of photoaged compared to intrinsically aged skin

OBJECTIVE

With increasing age, skin is subject to alterations in its organization, which impact on its function as well as having clinical consequences. Proteomics is a useful tool for non-targeted, semi-quantitative simultaneous investigation of high numbers of proteins. In the current study, we utilize proteomics to characterize and contrast age-associated differences in photoexposed and photoprotected skin, with a focus on the epidermis, dermal-epidermal junction and papillary dermis.

METHODS

Skin biopsies from buttock (photoprotected) and forearm (photoexposed) of healthy volunteers (aged 18-30 or ≥65 years) were transversely sectioned from the stratum corneum to a depth of 250 μm. Following SDS-PAGE, each sample lane was segmented prior to analysis by liquid chromatography-mass spectrometry/mass spectrometry. Pathway analysis was carried out using Ingenuity IPA.

RESULTS

Comparison of skin proteomes at buttock and forearm sites revealed differences in relative protein abundance. Ageing in skin on the photoexposed forearm resulted in 80% of the altered proteins being increased with age, in contrast to the photoprotected buttock where 74% of altered proteins with age were reduced. Functionally, age-altered proteins in the photoexposed forearm were associated with conferring structure, energy and metabolism. In the photoprotected buttock, proteins associated with gene expression, free-radical scavenging, protein synthesis and protein degradation were most frequently altered.

CONCLUSION

This study highlights the necessity of not considering photoageing as an accelerated intrinsic ageing, but as a distinct physiological process.

Clusterin Impairs Hepatic Insulin Sensitivity and Adipocyte Clusterin Associates With Cardiometabolic Risk

OBJECTIVE

Components of the adipose tissue (AT) extracellular matrix (ECM) are recently discovered contributors to obesity-related cardiometabolic disease. We identified increased adipocyte expression of ECM-related clusterin (apolipoprotein J) in obese versus lean women by microarray. Our objective was to determine 1) whether subcutaneous AT adipocyte (SAd) clusterin and serum clusterin are associated with insulin resistance (IR) and known markers of cardiometabolic risk and 2) how clusterin may contribute to increased risk.

RESEARCH DESIGN AND METHODS

We validated increased clusterin expression in adipocytes from a separate group of 18 lean and 54 obese individuals. The relationship of clusterin gene expression and plasma clusterin with IR, cardiovascular biomarkers, and risk of cardiovascular disease (CVD) was then determined. Further investigations in human cultured cells and in aged LDLR-/- mice prone to development of obesity-associated complications were performed.

RESULTS

SAd clusterin correlated with IR, multiple CVD biomarkers, and CVD risk, independent of traditional risk factors. Circulating human clusterin exhibited similar associations. In human adipocytes, palmitate enhanced clusterin secretion, and in human hepatocytes, clusterin attenuated insulin signaling and APOA1 expression and stimulated hepatic gluconeogenesis. LRP2 (megalin), a clusterin receptor, highly expressed in liver, mediated these effects, which were inhibited by LRP2 siRNA. In response to Western diet feeding, an increase in adipocyte clusterin expression was associated with a progressive increase in liver fat, steatohepatitis, and fibrosis in aged LDLR-/- mice.

CONCLUSIONS

Adipocyte-derived clusterin is a novel ECM-related protein linking cardiometabolic disease and obesity through its actions in the liver.

Clusterin in Alzheimer's Disease: Mechanisms, Genetics, and Lessons From Other Pathologies

Clusterin (CLU) or APOJ is a multifunctional glycoprotein that has been implicated in several physiological and pathological states, including Alzheimer's disease (AD). With a prominent extracellular chaperone function, additional roles have been discussed for clusterin, including lipid transport and immune modulation, and it is involved in pathways common to several diseases such as cell death and survival, oxidative stress, and proteotoxic stress. Although clusterin is normally a secreted protein, it has also been found intracellularly under certain stress conditions. Multiple hypotheses have been proposed regarding the origin of intracellular clusterin, including specific biogenic processes leading to alternative transcripts and protein isoforms, but these lines of research are incomplete and contradictory. Current consensus is that intracellular clusterin is most likely to have exited the secretory pathway at some point or to have re-entered the cell after secretion. Clusterin's relationship with amyloid beta (Aβ) has been of great interest to the AD field, including clusterin's apparent role in altering Aβ aggregation and/or clearance. Additionally, clusterin has been more recently identified as a mediator of Aβ toxicity, as evidenced by the neuroprotective effect of CLU knockdown and knockout in rodent and human iPSC-derived neurons. CLU is also the third most significant genetic risk factor for late onset AD and several variants have been identified in CLU. Although the exact contribution of these variants to altered AD risk is unclear, some have been linked to altered CLU expression at both mRNA and protein levels, altered cognitive and memory function, and altered brain structure. The apparent complexity of clusterin's biogenesis, the lack of clarity over the origin of the intracellular clusterin species, and the number of pathophysiological functions attributed to clusterin have all contributed to the challenge of understanding the role of clusterin in AD pathophysiology. Here, we highlight clusterin's relevance to AD by discussing the evidence linking clusterin to AD, as well as drawing parallels on how the role of clusterin in other diseases and pathways may help us understand its biological function(s) in association with AD.

Circulating ApoJ is closely associated with insulin resistance in human subjects

OBJECTIVE

Insulin resistance is a major risk factor for type 2 diabetes. ApolipoproteinJ (ApoJ) has been implicated in altered pathophysiologic states including cardiovascular and Alzheimer's disease. However, the function of ApoJ in regulation of glucose homeostasis remains unclear. This study sought to determine whether serum ApoJ levels are associated with insulin resistance in human subjects and if they change after interventions that improve insulin sensitivity.

METHODS

Serum ApoJ levels and insulin resistance status were assessed in nondiabetic (ND) and type 2 diabetic (T2D) subjects. The impacts of rosiglitazone or metformin therapy on serum ApoJ levels and glucose disposal rate (GDR) during a hyperinsulinemic/euglycemic clamp were evaluated in a separate cohort of T2D subjects. Total ApoJ protein or that associated with the HDL and LDL fractions was measured by immunoblotting or ELISA.

RESULTS

Fasting serum ApoJ levels were greatly elevated in T2D subjects (ND vs T2D; 100±8.3 vs. 150.6±8.5AU, P<0.0001). Circulating ApoJ levels strongly correlated with fasting glucose, fasting insulin, HOMA-IR, and BMI. ApoJ levels were significantly and independently associated with HOMA-IR, even after adjustment for age, sex, and BMI. Rosiglitazone treatment in T2D subjects resulted in a reduction in serum ApoJ levels (before vs. after treatment; 100±13.9 vs. 77±15.2AU, P=0.015), whereas metformin had no effect on ApoJ levels. The change in ApoJ levels during treatment was inversely associated with the change in GDR. Interestingly, ApoJ content in the LDL fraction was inversely associated with HOMA-IR.

CONCLUSION

Serum ApoJ levels are closely correlated with the magnitude of insulin resistance regardless of obesity, and decrease along with improvement of insulin resistance in response only to rosiglitazone in type 2 diabetes.

The clinical significance of plasma clusterin and Aβ in the longitudinal follow-up of patients with Alzheimer's disease

Background

Clusterin and beta-amyloid (Aβ) are involved in the pathogenesis of Alzheimer’s disease (AD). The clinical significance of plasma clusterin and Aβ in AD progression remains controversial.

Methods

We recruited 322 patients with AD and 88 controls between August 2012 and June 2013. All participants were evaluated at baseline with a clinical assessment, Mini-Mental State Examination (MMSE), and Clinical Dementia Rating (CDR) scales. Patients with AD were evaluated annually with the MMSE and Neuropsychiatric Inventory (NPI) scale during the 2-year follow-up period. The levels of plasma clusterin, Aβ1–40, and Aβ1–42 at baseline were analyzed to study the longitudinal changes in the patient scores on the MMSE and NPI during the follow-up period.

Results

Patients in the highest tertile of plasma clusterin levels showed significantly lower MMSE scores than those in the lowest tertile (p = 0.04). After adjustment for multiple covariates using the generalized estimating equation analysis, there was a significant decrease in the MMSE scores over the 2-year follow-up period among AD patients in the highest tertile of plasma clusterin levels compared with those in the lowest tertile (−2.09, 95% confidence interval (CI) = −3.67 to −0.51, p = 0.01). In apolipoprotein E (ApoE)4-positive AD patients, baseline measurements of the ratio of plasma Aβ1–42/Aβ1–40 in the highest tertile predicted an increase in NPI agitation/aggression scores over the 2-year follow-up period (6.06, 95% CI = 1.20–10.62, p = 0.02).

Conclusions

Plasma clusterin could serve as a biomarker for the severity of cognitive decline. Plasma Aβ in ApoE4-positive AD could predict long-term agitation/aggression symptoms.

Plasma apolipoproteins and physical and cognitive health in very old individuals

Apolipoproteins play a crucial role in lipid metabolism with implications in cardiovascular disease, obesity, diabetes, Alzheimer's disease, and longevity. We quantified 7 apolipoproteins in plasma in 1067 individuals aged 56-105 using immunoassays and explored relationships with APOE polymorphism ε2/3/4, vascular health, frailty, and cognition. ApoA1, ApoA2, ApoB, ApoC3, ApoE, ApoH, and ApoJ decreased from mid-life, although ApoE and ApoJ had U-shaped trends. Centenarians had the highest ApoE levels and the lowest frequency of APOE ε4 allele relative to younger groups. Apolipoprotein levels trended lower in APOE ε4 homozygotes and heterozygotes compared with noncarriers, with ApoE and ApoJ being significantly lower. Levels of all apolipoproteins except ApoH were higher in females. Sex- and age-related differences were apparent in the association of apolipoproteins with cognitive performance, as only women had significant negative associations of ApoB, ApoE, ApoH, and ApoJ in mid-life, whereas associations at older age were nonsignificant or positive. Our findings suggest levels of some apolipoproteins, especially ApoE, are associated with lifespan and cognitive function in exceptionally long-lived individuals.

Associations of lipid profiles with insulin resistance and β cell function in adults with normal glucose tolerance and different categories of impaired glucose regulation

Aims

To investigate the associations of dyslipidemia with insulin resistance and β cell function in individuals with normal glucose tolerance (NGT) and different categories of impaired glucose regulation (IGR).

Methods

544 subjects (365 with dyslipidemia and/or IGR and 179 with normal lipid and glucose tolerance) were enrolled in the study. All subjects underwent oral glucose tolerance test (OGTT). HOMA-IR was used to evaluate insulin sensitivity. Disposition index (DI) was used to evaluate β cell function. Multiple linear regression analysis was performed to assess correlations among lipid profiles, insulin resistance and β cell function.

Results

Among subjects with NGT, those with dyslipidemia had higher level of HOMA-IR but lower level of DI. While among subjects with different categories of IGR, those with dyslipidemia and CGI had significantly decreased DI. No obvious differences of insulin resistance or β cell function were found in IFG or IGT subjects with or without dyslipidemia. TG and HDL-C were correlated with HOMA-IR (β = 0.79, p <0.001; β = -0.38, p = 0.027, respectively, compared with subjects in the low level groups). Moreover, TG and TC were negatively correlated with DI (β = -2.17, p = 0.013; β = -2.01, p = 0.034 respectively, compared with subjects in the low level groups) after adjusting for confounding parameters.

Conclusions

Dyslipidemia induces insulin resistance and impaired β cell response to insulin resistance in individuals with NGT. Furthermore, dyslipidemia diminishes β cell function in subjects with CGI. TG and HDL-C were correlated with insulin resistance, and TG, TC were negatively correlated with β cell response to insulin resistance in non-diabetic individuals.

Blocking beta 2-adrenergic receptor inhibits dendrite ramification in a mouse model of Alzheimer's disease

Dendrite ramification affects synaptic strength and plays a crucial role in memory. Previous studies revealed a correlation between beta 2-adrenergic receptor dysfunction and Alzheimer's disease (AD), although the mechanism involved is still poorly understood. The current study investigated the potential effect of the selective β₂-adrenergic receptor antagonist, ICI 118551 (ICI), on Aβ deposits and AD-related cognitive impairment. Morris water maze test results demonstrated that the performance of AD-transgenic (TG) mice treated with ICI (AD-TG/ICI) was significantly poorer compared with NaCl-treated AD-TG mice (AD-TG/NaCl), suggesting that β₂-adrenergic receptor blockage by ICI might reduce the learning and memory abilities of mice. Golgi staining and immunohistochemical staining revealed that blockage of the β₂-adrenergic receptor by ICI treatment decreased the number of dendritic branches, and ICI treatment in AD-TG mice decreased the expression of hippocampal synaptophysin and synapsin 1. Western blot assay results showed that the blockage of β₂-adrenergic receptor increased amyloid-β accumulation by downregulating hippocampal α-secretase activity and increasing the phosphorylation of amyloid precursor protein. These findings suggest that blocking the β₂-adrenergic receptor inhibits dendrite ramification of hippocampal neurons in a mouse model of AD.

Apolipoprotein J: A New Predictor and Therapeutic Target in Cardiovascular Disease?

Objective:

To review the functional mechanism of apolipoprotein J (apoJ) in the process of atherosclerosis and the feasibility of apoJ as a therapeutic endpoint.

Data Sources:

Relevant articles published in English from 1983 to present were selected from PubMed. The terms of “atherosclerosis, apolipoprotein J, clusterin (CLU), oxidative stress, and inflammation” were used for searching.

Study Selection:

Articles studying the role of apoJ with atherosclerosis and restenosis after injury were reviewed. Articles focusing on the intrinsic determinants of atherosclerosis were selected. The exclusion criteria of articles were that the studies on immunologic vasculitis.

Results:

ApoJ, involved in numerous physiological process important for lipid transportation and vascular smooth muscle cell differentiation, including apoptotic cell death, cell-cycle regulation, cell adhesion, tissue remodeling, immune system regulation, and oxidative stress, plays a role in the development of clinical atherosclerosis. In the process of relieving atherosclerosis, apoJ can promote cholesterol and phospholipid export from macrophage-foam cells, and exhibit cytoprotective and anti-inflammatory actions by interacting with lots of known inflammatory proteins which may predict the onset of clinical cardiovascular events and may actually play a causal role in mediating atherosclerotic disease such as C-reactive protein, paraoxonase, and leptin. As known as CLU, apoJ has been identified to play central roles in the process of vascular smooth cells migration, adhesion, and proliferation, which can contribute significantly to restenosis after vascular injury.

Conclusions:

Intense effort and substantial progress have been made to identify the apoJ that relieves atherosclerosis and vascular restenosis after percutaneous coronary intervention. More work is needed to elucidate the exact mechanisms of and the interrelationship between the actions of apoJ and to successfully achieve regression of atherosclerosis by regarding it as a therapeutic endpoint.