Apolipoprotein A-I positively associated with diabetes in women independently of apolipoprotein E genotype and apolipoprotein B levels

Can biomarkers be used to improve diagnosis and prediction of metabolic syndrome in childhood cancer survivors? A systematic review

Childhood cancer survivors (CCS) are at increased risk to develop metabolic syndrome (MetS), diabetes, and cardiovascular disease. Common criteria underestimate adiposity and possibly underdiagnose MetS, particularly after abdominal radiotherapy. A systematic literature review and meta-analysis on the diagnostic and predictive value of nine newer MetS related biomarkers (adiponectin, leptin, uric acid, hsCRP, TNF-alpha, IL-1, IL-6, apolipoprotein B (apoB), and lipoprotein(a) [lp(a)]) in survivors and adult non-cancer survivors was performed by searching PubMed and Embase. Evidence was summarized with GRADE after risk of bias evaluation (QUADAS-2/QUIPS). Eligible studies on promising biomarkers were pooled. We identified 175 general population and five CCS studies. In the general population, valuable predictive biomarkers are uric acid, adiponectin, hsCRP and apoB (high level of evidence), and leptin (moderate level of evidence). Valuable diagnostic biomarkers are hsCRP, adiponectin, uric acid, and leptin (low, low, moderate, and high level of evidence, respectively). Meta-analysis showed OR for hyperuricemia of 2.94 (age-/sex-adjusted), OR per unit uric acid increase of 1.086 (unadjusted), and AUC for hsCRP of 0.71 (unadjusted). Uric acid, adiponectin, hsCRP, leptin, and apoB can be alternative biomarkers in the screening setting for MetS in survivors, to enhance early identification of those at high risk of subsequent complications.

Association of apolipoproteins A1 and B with type 2 diabetes and fasting blood glucose: a cross-sectional study

BACKGROUND

Apolipoprotein (Apo) may be associated with type 2 diabetes (T2D), however, little is known whether or not serum apolipoproteins are correlated with fasting blood glucose (FBG) and the prevalence of T2D in Chinese populations. In this study, we examined the association of serum ApoA1, ApoB, and the ratio of ApoB/ApoA1 (ApoB/A1 ratio) with T2D and FBG level, and compared apolipoprotein indicators in predicting T2D in Chinese adults.

METHODS

A total of 1027 subjects were enrolled in this cross-sectional study. The association of ApoA1, ApoB, and ApoB/A1 ratio with T2D prevalence was determined using logistic regression models. Multivariate-analysis of covariance (ANCOVA) was performed for comparisons of the mean difference in FBG level.

RESULTS

We found that ApoB and ApoB/A1 ratio were positively associated with T2D prevalence and FBG, while inverse association was noted between ApoA1 and T2D prevalence as well as FBG. Stratified analyses for sex, age, body mass index (BMI), smoking, and alcohol consumption showed no significant difference for the association of ApoA1, ApoB, and ApoB/A1 ratio with the prevalence of T2D among subgroups (all p-interactions> 0.05). Nonetheless, ApoA1 poorly performed in predicting T2D as it provided an AUC value of 0.310 that was significantly lower than those observed for ApoB (AUC value: 0.631) and ApoB/A1 ratio (AUC value: 0.685). Finally, path analyses indicated that the association between ApoB and T2D was mediated by BMI.

CONCLUSIONS

This study reveals the association of serum ApoA1, ApoB, and ApoB/A1 ratio with T2D and FBG in Chinese adults, suggesting that ApoB and ApoB/A1 ratio may be early indicators for predicting T2D. Prospective investigation in large cohort is needed.

Beyond the CNS: The many peripheral roles of APOE

Apolipoprotein E (APOE) is a multifunctional protein synthesized and secreted by multiple mammalian tissues. Although hepatocytes contribute about 75% of the peripheral pool, APOE can also be expressed in adipose tissue, the kidney, and the adrenal glands, among other tissues. High levels of APOE production also occur in the brain, where it is primarily synthesized by glia, and peripheral and brain APOE pools are thought to be distinct. In humans, APOE is polymorphic, with three major alleles (ε2, ε3, and ε4). These allelic forms dramatically alter APOE structure and function. Historically, the vast majority of research on APOE has centered on the important role it plays in modulating risk for cardiovascular disease and Alzheimer's disease. However, the established effects of this pleiotropic protein extend well beyond these two critical health challenges, with demonstrated roles across a wide spectrum of biological conditions, including adipose tissue function and obesity, metabolic syndrome and diabetes, fertility and longevity, and immune function. While the spectrum of biological systems in which APOE plays a role seems implausibly wide at first glance, there are some potential unifying mechanisms that could tie these seemingly disparate disorders together. In the current review, we aim to concisely summarize a wide breadth of APOE-associated pathologies and to analyze the influence of APOE in the development of several distinct disorders in order to provide insight into potential shared mechanisms implied in these various pathophysiological processes.

Association between APOE polymorphism and metabolic syndrome in Uyghur ethnic men

OBJECTIVES

This study aimed to examine the association between apolipoprotein E (APOE) polymorphism and metabolic syndrome (MetS) among Uyghur ethnic men in Xinjiang, China.

PARTICIPANTS

A total of 482 patients with MetS and 510 healthy sex-matched and age-matched controls were recruited from the Xinjiang Uyghur Autonomous Region of China. The participants were subjected to routine physical and blood biochemical tests, and APOE genotyping was performed.

RESULTS

The APOE ε3/3 was the predominant type, with a frequency of 71.8%, while ε2/2 was less common than ε4/4 in Uyghur males. The frequencies of the APOE2, E3 and E4 alleles in Uyghur males were 8.5%, 80.0% and 11.5%, respectively. However, the distribution of APOE genotypes was significantly different between the MetS and control groups (p<0.001). In the MetS group, the frequencies of the ε2 and ε4 alleles and the frequencies of the ε2/2, ε2/3 and ε2/4 genotypes were significantly lower than those of the control group. Those individuals without the ε2 and ε4 alleles had higher MetS prevalence than the other gene carriers, and the ORs of these individuals developing MetS were 1.5 and 1.27 compared to the gene carriers. Triglyceride, serum total cholesterol and low-density lipoprotein cholesterol levels were lower and serum high-density lipoprotein was higher in the ε2 carriers than the ε3 carriers, and the prevalence of MetS, central obesity, high blood pressure, hypercholesterolaemia and hypertriglyceridaemia was lower in the APOE2 group than in the APOE4 group. The risks of these individuals with ε4 allele carriers getting these changes were 1.327, 1.780, 1.888, 1.428 and 2.571 times greater than those of ε2 allele carriers.

CONCLUSIONS

APOE4 is associated with many individual components of MetS, whereas APOE2 was associated with a reduced risk of MetS at the univariate level in Uyghur ethnic men.

Abdominal obesity with hypertriglyceridaemia, lipoprotein(a) and apolipoprotein A-I determine marked cardiometabolic risk

BACKGROUND

Risks for coronary heart disease (CHD) and diabetes (T2DM) of the 'hypertriglyceridemic waist' phenotype (HtgW) warrant further investigation. We studied this issue and whether partial proinflammatory conversion of apolipoprotein (apo) A-I by lipoprotein(a) [Lp(a)] is a codeterminant.

MATERIALS AND METHODS

In a population-based prospective study, 1328 Turkish adults were analysed in four groups by the presence of abdominal obesity and elevated triglycerides (Htg).

RESULTS

LDL-cholesterol levels, significantly elevated in isolated Htg, were lower in HtgW, yet significantly higher apoB and complement C3 values existed in women with HtgW in whom also the lowest Lp(a) values prevailed. Lp(a) was linearly associated, more strongly in HtgW than in the remaining groups, with apoB and, in women inversely, with gamma-glutamyltransferase. Incident HtgW was predicted, not in men, but in women inversely by Lp(a) (OR 0.80 [95%CI 0.65; 0.97]), regardless of adjustment for relevant confounders. After adjustment for conventional risk factors, HtgW (OR 2.84) and high apoA-I/HDL-C ratio (OR 1.50) were significantly and additively associated with combined prevalent and incident CHD risk. High apoA-I and low HDL-cholesterol levels interacted therein in women. Type-2 diabetes was strongly predicted by HtgW, mediated in men by high apoA-I/HDL-C ratio.

CONCLUSION

HtgW is associated with excess inflammatory markers, is predicted in women paradoxically by lower circulating Lp(a) and is associated in both sexes with marked excess cardiometabolic risk to which high apoA-I/HDL-C ratio contributes additively. These findings are consistent in women with apoA-I being oxidized via aggregation to Lp(a).

High serum apolipoprotein E determines hypertriglyceridemic dyslipidemias, coronary disease and apoA-I dysfunctionality

The relevance of serum apolipoprotein E (apoE) levels to two hypertriglyceridemic dyslipidemias has not been clarified. We explored, in a cross-sectional (and short-term prospective) evaluation, the independent relationship of serum apoE to the atherogenic dyslipidemia, hypertriglyceridemia with elevated apoB (HtgB) and to apoA-I dysfunctionality, previously shown in Turkish adults to be independent of apoE genotype. Serum apoE concentrations were measured by immunonephelometry in 1,127 middle-aged adults. In multivariable regression analysis, apoE concentrations showed log-linear associations with apoB and apoA-I levels, waist circumference, independent of C-reactive protein (CRP), homeostatic model assessment (HOMA) index and other confounders. The likelihood of atherogenic dyslipidemia and of HtgB roughly tripled per 1-SD increment in apoE concentrations, additively to apoE genotype, HOMA, apoA-I, CRP concentrations and waist circumference; yet apoA-I, protective against atherogenic dyslipidemia, appeared to promote HtgB, a finding consistent with apoA-I dysfunctionality in this setting. Each 1-SD increment in the apoE level was moreover, associated in both genders with MetS (at OR 1.5), after adjustment for sex, age, apoB, apoA-I and CRP, or for apoE genotypes. Circulating apoE predicted in both genders age-adjusted prevalent and incident coronary heart disease (CHD), independent of apoE genotype and CRP (OR 1.32 [95 % CI 1.11; 1.58]). To conclude, in a general population prone to MetS, elevated apoE concentrations are strongly linked to HtgB and atherogenic dyslipidemia, irrespective of apoE genotype, are associated with MetS and CHD. Excess apoE reflects pro-inflammatory state and likely autoimmune activation.

Increased apoB/A-I ratio independently associated with Type 2 diabetes mellitus: cross-sectional study in a Korean population

AIMS

The aim of this study was to investigate whether increased apolipoprotein B/apolipoprotein A-I ratio is associated with Type 2 diabetes mellitus independent of other risk factors for Type 2 diabetes.

METHODS

A total of 70,063 subjects (41,391 men and 28,672 women; mean age 41.5 years) who visited the Health Screening Center at Kangbuk Samsung Hospital for a routine medical check-up between January 2009 and December 2009 were enrolled in this study.

RESULTS

The mean apolipoprotein B/apolipoprotein A-I ratio in the study subjects was 0.66 ± 0.18. The prevalence of Type 2 diabetes increased across the apolipoprotein B/apolipoprotein A-I ratio quartiles (1.0%, 1.6%, 2.9%, and 4.8% for the 1st through 4th quartiles, respectively, P < 0.001) and homeostasis model assessment-insulin resistance (HOMA2-IR) also showed an increasing tendency by quartile (P < 0.001). The apolipoprotein B/apolipoprotein A-I ratio was correlated with age, adiposity, blood pressure, HOMA2-IR value, fasting glucose levels, and other inflammatory marker, including high-sensitivity C-reactive protein, and lipoprotein (a) levels (all P < 0.001). In a multiple logistic regression model, the highest apolipoprotein B/apolipoprotein A-I ratio quartile was associated with Type 2 diabetes, even after controlling for other risk factors for diabetes, such as age, gender, BMI, systolic blood pressure, HOMA2-IR values, high-sensitivity C-reactive protein levels, family history of diabetes, presence of metabolic syndrome, and conventional lipid parameters (odds ratio 1.31; 95% confidence interval 1.17-1.46, P < 0.001).

CONCLUSIONS

The apolipoprotein B/apolipoprotein A-I ratio was found to be associated with Type 2 diabetes independent of other risk factors for diabetes and conventional lipid parameters.

Genetic variants and the metabolic syndrome: a systematic review

Several candidate gene studies on the metabolic syndrome (MetS) have been conducted. However, for most single nucleotide polymorphisms (SNPs) no systematic review on their association with MetS exists. A systematic electronic literature search was conducted until the 2nd of June 2010, using HuGE Navigator. English language articles were selected. Only genes of which at least one SNP-MetS association was studied in an accumulative total population ≥ 4000 subjects were included. Meta-analyses were conducted on SNPs with three or more studies available in a generally healthy population. In total 88 studies on 25 genes were reviewed. Additionally, for nine SNPs in seven genes (GNB3, PPARG, TCF7L2, APOA5, APOC3, APOE, CETP) a meta-analysis was conducted. The minor allele of rs9939609 (FTO), rs7903146 (TCF7L2), C56G (APOA5), T1131C (APOA5), C482T (APOC3), C455T (APOC3) and 174G>C (IL6) were more prevalent in subjects with MetS, whereas the minor allele of Taq-1B (CETP) was less prevalent in subjects with the MetS. After having systematically reviewed the most studied SNP-MetS associations, we found evidence for an association with the MetS for eight SNPs, mostly located in genes involved in lipid metabolism.