Abstract
Background: Fetuin-A and retinol-binding protein 4 (RBP4) are secreted as both hepatokine and adipokine. These are involved in insulin resistance, obesity-related dyslipidemia, and atherosclerosis. To date, correlations of circulating fetuin-A and RBP4 with lipoprotein subfractions as well as high-density lipoprotein (HDL)-linked proteins have not been entirely investigated in morbid obese and lean non-diabetic subjects. Methods: One-hundred obese non-diabetic patients (body mass index, BMI: 42.5 ± 8.1 kg/m2) along with 32 gender and age-matched normal weight controls (BMI: 24.5 ± 2.5 kg/m2) were enrolled in our study. Serum fetuin-A and RBP4 were measured by ELISA. Lipoprotein subfractions were distributed by Lipoprint gelelectrophoresis. Results: Serum fetuin-A and RBP4 were unexpectedly lower in obese patients (p < 0.01 and p < 0.01, respectively) compared to controls and correlated with each other (r = 0.37; p < 0.001). Fetuin-A had positive correlations with HDL-C (r = 0.22; p = 0.02), apolipoprotein AI (apoAI) (r = 0.33; p < 0.001), very-low density lipoprotein (VLDL) subfraction (r = 0.18; p = 0.05), and large HDL subfraction levels (r = 0.3; p = 0.001) but did not show correlation with carbohydrate parameters in all subjects. RBP4 correlated positively with HDL-C (r = 0.2; p = 0.025), apoAI (r = 0.23; p = 0.01), VLDL subfraction (r = 0.37; p < 0.001), intermediate HDL subfraction (r = 0.23; p = 0.01), and small HDL subfraction (r = 0.21; p = 0.02) concentrations, as well as C-peptide levels in overall participants. Backward stepwise multiple regression analysis showed that serum fetuin-A concentration is best predicted by RBP4 and large HDL subfraction. In model 2, VLDL subfraction was the independent predictor of serum RBP4 level. Conclusions: Our data may indicate a potential role of fetuin-A and RBP4 in impaired lipoprotein metabolism associated with obesity.
Highlights
high-density lipoprotein (HDL)-C and ApoAI concentrations were significantly lower in enrolled obese patients compared to controls
Carbohydrate parameters, fasting glucose, and hemoglobin A1C (HbA1C) levels were slightly elevated in obese patients compared to healthy, lean participants, but they still stayed in the normal range
Similar to another study [24], we described a positive correlation between fetuin-A and high-density lipoprotein cholesterol (HDL-C) levels; to our best knowledge, this is the first report about correlation between circulating fetuin-A and apolipoprotein AI (apoAI) as well as large HDL subfraction levels
Summary
Collectively termed as adipokines and hepatokines, respectively—have paracrine, endocrine, and systemic effects. The dysregulation of these adipo- and hepatokines (e.g., leptin, chemerin, plasminogen activator inhibitor-1, afamin, fetuin-A, retinol-binding protein 4 etc.) has been associated with central obesity and obesity-related co-morbidities including metabolic syndrome, type 2 diabetes, dyslipidemia, and enhanced atherogenesis. Fetuin-A and retinol-binding protein 4 (RBP4) are secreted as both hepatokine and adipokine. These are involved in insulin resistance, obesity-related dyslipidemia, and atherosclerosis. Correlations of circulating fetuin-A and RBP4 with lipoprotein subfractions as well as high-density lipoprotein (HDL)-linked proteins have not been entirely investigated in morbid obese and lean non-diabetic subjects.
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