Carol H.Y. Fong

Circulating Adipocyte–Fatty Acid Binding Protein Levels Predict the Development of the Metabolic Syndrome A 5-Year Prospective Study

Background— Adipocyte-fatty acid binding protein (A-FABP), a major cytoplasmic protein in adipocytes, plays a central role in the development of diabetes and atherosclerotic cardiovascular disease in experimental animals. We have previously shown that A-FABP is present in the bloodstream and that its circulating levels correlate with metabolic risk factors in a cross-sectional study. In the present study, we further evaluated the prospective association of A-FABP with the metabolic syndrome (MetS) as defined by the updated National Cholesterol Education Program criteria. Methods and Results— In the present study, 495 nondiabetic adults from the population-based Hong Kong Cardiovascular Risk Factor Prevalence Study were prospectively followed up for 5 years. The relationship of serum A-FABP with the MetS and its components was investigated. At baseline, high A-FABP levels were associated with the MetS (odds ratio, 4.0; 95% CI, 1.5 to 10.4; highest versus lowest sex-specific tertile, adjusted for age, body mass index, the homeostasis model assessment index for insulin resistance, C-reactive protein, and adiponectin, P=0.005). On long-term follow-up, subjects with higher baseline A-FABP levels had progressively worse cardiometabolic risk profile and increasing risk of the MetS. Among 376 subjects without the MetS at baseline, 50 had developed it at 5 years. Apart from the homeostasis model assessment index for insulin resistance (P=0.001), baseline A-FABP was the only independent predictor of the development of the MetS during the 5-year follow-up (odds ratio, 4.7; 95% CI, 1.8 to 11.9; highest versus lowest sex-specific tertile, P=0.001, adjusted for the homeostasis model assessment index for insulin resistance and body mass index). A-FABP was predictive of the MetS even after adjustment for each of its individual components. Conclusions— Circulating A-FABP predicts the development of the MetS independently of adiposity and insulin resistance.

Hypoadiponectinemia as a Predictor for the Development of Hypertension. A 5-Year Prospective Study

Low circulating levels of adiponectin, an adipokine with insulin-sensitizing, antiatherogenic, and anti-inflammatory properties, are found in hypertensive patients. Adiponectin replenishment ameliorated hypertension in adiponectin-deficient mice or obese, hypertensive mice with hypoadiponectinemia, suggesting an etiologic role of adiponectin in hypertension. We aimed to determine, in this 5-year prospective study, whether hypoadiponectinemia could predict the development of hypertension in a nondiabetic Chinese cohort. A total of 577 subjects (249 men and 328 women) were recruited from the population-based Hong Kong Cardiovascular Risk Factor Prevalence Study and prospectively followed up for 5 years. The relationship of serum adiponectin with the development of hypertension (sitting blood pressure ≥140/90 mm Hg) was investigated in a nested case–control study consisting of 70 subjects who had developed hypertension on follow-up and 140 age- and sex-matched control subjects who were normotensive both at baseline and at year 5. At baseline, serum adiponectin level in the lowest sex-specific tertile was more likely to be associated with hypertension (P=0.003 versus the highest tertile, after adjusting for age, body mass index, fasting insulin, and high-sensitivity C-reactive protein). At year 5, baseline serum adiponectin was a significant independent predictor of incident hypertension in the nested case–control study (P=0.015; age adjusted), together with mean arterial pressure (P<0.001), high-sensitivity C-reactive protein (P=0.018), and body mass index (P=0.004). Normotensive subjects with baseline serum adiponectin levels in the lowest sex-specific tertile had an increased risk of becoming hypertensive (adjusted odds ratio: 2.76; 95% CIs: 1.06 to 7.16; P=0.037 versus highest tertile). Our data suggest that hypoadiponectinaemia may be involved in the pathogenesis of hypertension in humans.

Serum Adipocyte Fatty Acid–Binding Protein as a New Biomarker Predicting the Development of Type 2 Diabetes: A 10-year prospective study in a Chinese cohort

OBJECTIVE— Adipocyte fatty acid–binding protein (A-FABP) is abundantly expressed in adipocytes and plays a role in glucose homeostasis in experimental animals. We have previously shown that circulating A-FABP levels are associated with the metabolic syndrome, which confers an increased risk of type 2 diabetes. Here we investigated whether serum A-FABP levels could predict the development of diabetes in a 10-year prospective study. RESEARCH DESIGN AND METHODS— Baseline serum A-FABP levels were measured with an enzyme-linked immunosorbent assay in 544 nondiabetic subjects, recruited from the Hong Kong Cardiovascular Risk Factor Prevalence Study cohort, who were followed prospectively to assess the development of type 2 diabetes. The role of A-FABP in predicting the development of type 2 diabetes over 10 years was investigated using Cox regression analysis. RESULTS— At baseline, serum sex-adjusted A-FABP levels were higher in subjects with impaired glucose tolerance (IGT) or impaired fasting glucose (IFG) (P < 0.00001 versus normal glucose tolerance) and correlated positively with adverse cardiometabolic risk factors. Over 10 years, 96 subjects had developed type 2 diabetes. High baseline A-FABP was predictive of type 2 diabetes, independent of obesity, insulin resistance, or glycemic indexes (relative risk [RR] 2.25 [95% CI 1.40–3.65]; P = 0.001; above versus below sex-specific median). High A-FABP levels remained an independent predictor of type 2 diabetes in the high-risk IGT/IFG subgroup (adjusted RR 1.87 [1.12–3.15]; P = 0.018). CONCLUSIONS— Serum A-FABP was associated with glucose dysregulation and predicted the development of type 2 diabetes in a Chinese cohort.

Serum Fibroblast Growth Factor-21 Levels Are Associated With Carotid Atherosclerosis Independent of Established Cardiovascular Risk Factors

Objective—Serum levels of fibroblast growth factor-21 (FGF21), a metabolic hormone, have been shown to be elevated in subjects with adverse lipid profiles, obesity, metabolic syndrome, impaired glucose tolerance, type 2 diabetes mellitus, and hypertension. Recently, elevated serum FGF21 levels have also been reported in subjects with coronary heart disease or carotid artery plaques. However, whether serum FGF21 is independently associated with atherosclerotic diseases remains unclear. In this study, we examined the relationship between serum FGF21 levels and carotid intima-media thickness (IMT) in a large cohort of Southern Chinese subjects. Approach and Results—The cohort consisted of 670 subjects who underwent carotid IMT measurement. Serum FGF21 levels were measured with an ELISA kit. Serum FGF21 levels positively correlated with carotid IMT in women (r=0.32; P<0.001), but not in men (r=0.06; P=0.305). On multiple linear regression analysis, elevated serum FGF21 level in women was an independent risk factor for increased carotid IMT (P=0.039), together with age (P<0.001) and hypertension (P=0.011), in a model comprising also waist circumference, smoking history, serum creatinine, high sensitive C-reactive protein, dysglycemia, and dyslipidemia (adjusted R2=35.8%; P<0.001). Elevated serum FGF21 levels were also a significant independent risk factor of carotid IMT on multiple stepwise regression analysis (P=0.01). Conclusions—The present study is the first demonstration that elevated serum FGF21 levels are associated with carotid atherosclerosis in humans, independent of established risk factors including adverse lipid profiles and C-reactive protein. The role of FGF21 as a biomarker or therapeutic target of atherosclerotic diseases warrants further investigation.

Elevated circulating adipocyte‐fatty acid binding protein levels predict incident cardiovascular events in a community‐based cohort: a 12‐year prospective study

Background Obesity is closely associated with various cardiovascular diseases (CVDs). Adipose tissue inflammation and perturbation of adipokine secretion may contribute to the pathogenesis of CVD. This study aimed to evaluate whether the 2 most abundant adipokines, adipocyte‐fatty acid binding protein (A‐FABP) and adiponectin, are independent risk factors predisposing to CVD. Method and Results We investigated prospectively the 12‐year development of CVD in relation to the baseline levels of A‐FABP and adiponectin in a population‐based community cohort comprising 1847 Chinese subjects recruited from the Hong Kong Cardiovascular Risk Factors Prevalence Study 2 (CRISPS 2) cohort without previous CVD. Baseline serum levels of A‐FABP, adiponectin, and C‐reactive protein (CRP), an established biomarker predictive of CVD, were measured. In all, 182 (9.9%) of the 1847 Chinese subjects developed CVD during a median follow‐up of 9.4 years. The CVD group had more traditional risk factors, higher baseline levels of A‐FABP and CRP (both P<0.001), but similar adiponectin levels (P=0.881) compared with the non‐CVD group. In Cox regression analysis including both biomarkers, the adjusted HR for A‐FABP and CRP for subjects above the optimal cutoff values were 1.57 (95% CI, 1.14 to 2.16; P=0.006) and 1.60 (95% CI, 1.12 to 2.27; P=0.01), respectively, after adjustment for traditional risk factors. The category‐free net reclassification index, but not the c‐statistic, showed improvement in predictive performance by the addition of A‐FABP to the traditional risk factor model (P=0.017). Conclusions Circulating A‐FABP level predicts the development of CVD after adjustment for traditional risk factors in a community‐based cohort. Its clinical use for CVD prediction warrants further validation.

Circulating Levels of Adipocyte and Epidermal Fatty Acid–Binding Proteins in Relation to Nephropathy Staging and Macrovascular Complications in Type 2 Diabetic Patients

OBJECTIVE—To investigate the relationships of serum adipocyte fatty acid–binding protein (A-FABP) and epidermal fatty acid–binding protein (E-FABP) with renal dysfunction and macrovascular complications in type 2 diabetic patients. RESEARCH DESIGN AND METHODS—The associations of serum A-FABP and E-FABP with markers of renal function, nephropathy staging, and macrovascular complications were examined in 237 type 2 diabetic patients. RESULTS—Serum A-FABP and E-FABP correlated significantly with serum creatinine, mean albumin excretion rate, and glomerular filtration rate (all P < 0.001) and were independently associated with diabetic nephropathy staging (P = 0.001 and P < 0.05, respectively). Circulating levels of both types of FABP were increased (P < 0.01) in subjects with macrovascular complications. Serum A-FABP was independently associated with macrovascular complications (odds ratio 2.92 [95% CI 1.42–6.01]; P = 0.004). CONCLUSIONS—Serum A-FABP and E-FABP might be novel serum biomarkers for evaluating the progression of nephropathy and its cardiovascular risk in type 2 diabetic patients.

Resistin gene polymorphisms and progression of glycaemia in southern Chinese: a 5-year prospective study

Objective  Human resistin gene (RETN) polymorphisms have been found to be associated with type 2 diabetes (T2DM), insulin resistance and/or obesity. We evaluated, in a 5‐year prospective study, whether RETN polymorphisms could predict the progression of glycaemia in southern Chinese.

Adiponectin Mediates the Suppressive Effect of Rosiglitazone on Plasminogen Activator Inhibitor-1 Production

Objective—The purpose of this study was to examine the effects of PPAR-&ggr; agonist rosiglitazone, relative to sulfonylureas, on circulating levels of adiponectin and the prothrombotic factor, plasminogen activator inhibitor (PAI)-1, in type 2 diabetic patients, and to investigate, in animal models, whether the antithrombotic action of rosiglitazone was mediated through adiponectin. Methods and Results—Our clinical study (n=64) showed that after 24-week add-on therapy, the rosiglitazone group had a greater mean reduction in plasma PAI-1 levels (25%, versus 12% in sulfonylurea group, P=0.002). Stepwise multiple linear regression analysis identified the reduction in plasma fasting glucose and the rise in adiponectin levels to be independently associated with the reduction in PAI-I concentration in the rosiglitazone-treated patients. Rosiglitazone (20 mg/kg/d) reduced adipose tissue PAI-1 mRNA expression and its plasma levels in wild-type C57 mice with diet-induced obesity (P<0.001), but this suppressive effect was attenuated in adiponectin knockout mice. Adenovirus-mediated overexpression of adiponectin led to a significant suppression of adipose tissue PAI-1 expression and its circulating concentrations in db/db diabetic mice. Our in vitro study demonstrated that recombinant adiponectin directly inhibited PAI-1 production in 3T3-L1 adipocytes. Conclusions—The antithrombotic effect of rosiglitazone is mediated, at least in part, through the suppressive effect of adiponectin on PAI-1 production.

Exome-wide association analysis reveals novel coding sequence variants associated with lipid traits in Chinese

Blood lipids are important risk factors for coronary artery disease (CAD). Here we perform an exome-wide association study by genotyping 12,685 Chinese, using a custom Illumina HumanExome BeadChip, to identify additional loci influencing lipid levels. Single-variant association analysis on 65,671 single nucleotide polymorphisms reveals 19 loci associated with lipids at exome-wide significance (P<2.69 × 10−7), including three Asian-specific coding variants in known genes (CETP p.Asp459Gly, PCSK9 p.Arg93Cys and LDLR p.Arg257Trp). Furthermore, missense variants at two novel loci—PNPLA3 p.Ile148Met and PKD1L3 p.Thr429Ser—also influence levels of triglycerides and low-density lipoprotein cholesterol, respectively. Another novel gene, TEAD2, is found to be associated with high-density lipoprotein cholesterol through gene-based association analysis. Most of these newly identified coding variants show suggestive association (P<0.05) with CAD. These findings demonstrate that exome-wide genotyping on samples of non-European ancestry can identify additional population-specific possible causal variants, shedding light on novel lipid biology and CAD.

Combined Use of Serum Adiponectin and Tumor Necrosis Factor-Alpha Receptor 2 Levels Was Comparable to 2-Hour Post-Load Glucose in Diabetes Prediction

Background Adipose tissue inflammation and dysregulated adipokine secretion are implicated in obesity-related insulin resistance and type 2 diabetes. We evaluated the use of serum adiponectin, an anti-inflammatory adipokine, and several proinflammatory adipokines, as biomarkers of diabetes risk and whether they add to traditional risk factors in diabetes prediction. Methods We studied 1300 non-diabetic subjects from the prospective Hong Kong Cardiovascular Risk Factor Prevalence Study (CRISPS). Serum adiponectin, tumor necrosis factor-alpha receptor 2 (TNF-α R2), interleukin-6 (IL-6), adipocyte–fatty acid binding protein (A-FABP) and high-sensitivity C-reactive protein (hsCRP) were measured in baseline samples. Results Seventy-six participants developed diabetes over 5.3 years (median). All five biomarkers significantly improved the log-likelihood of diabetes in a clinical diabetes prediction (CDP) model including age, sex, family history of diabetes, smoking, physical activity, hypertension, waist circumference, fasting glucose and dyslipidaemia. In ROC curve analysis, “adiponectin + TNF-α R2” improved the area under ROC curve (AUC) of the CDP model from 0.802 to 0.830 (P = 0.03), rendering its performance comparable to the “CDP + 2-hour post-OGTT glucose” model (AUC  = 0.852, P = 0.30). A biomarker risk score, derived from the number of biomarkers predictive of diabetes (low adiponectin, high TNF-α R2), had similar performance when added to the CDP model (AUC  = 0.829 [95% CI: 0.808–0.849]). Conclusions The combined use of serum adiponectin and TNF-α R2 as biomarkers provided added value over traditional risk factors for diabetes prediction in Chinese and could be considered as an alternative to the OGTT.