Wnt Pathway Inhibitor DKK1: A Potential Novel Biomarker for Adiposity

Emerging evidence indicates that ectopic skeletal muscle adiposity may be a risk factor for type 2 diabetes (T2D), especially in persons of African ancestry. <i>In vitro</i> studies suggest that a Wnt pathway inhibitor, Dickkopf-related protein 1 (DKK1), plays a role in adiposity regulation and could be a biomarker for adiposity in humans. The objective of this study was to test whether serum DKK1 levels relate to adiposity measures in a cohort from an African ancestry population at high risk for T2D. Fasting serum DKK1 was measured in a sample of 159 men of African ancestry aged ≥40 years (mean age ± SD, 63.5 ± 8.2 years; mean body mass index, 27.8 ± 4.5 kg/m²). Anthropometrics included total-body and trunk adiposity measured by dual-energy x-ray absorptiometry and lower-leg skeletal muscle density measured by CT [which reflects the intramuscular adiposity content (mg/cm³)]. Serum DKK1 was positively correlated with BMI (<i>r</i> = 0.20; <i>P</i> = 0.01), waist circumference (<i>r</i> = 0.15; <i>P</i> = 0.046), DXA total-body adiposity (<i>r</i> = 0.24; <i>P</i> = 0.003), and DXA trunk adiposity (<i>r</i> = 0.21; <i>P</i> = 0.009), independent of age and height. In addition, serum DKK1 was inversely correlated with skeletal muscle density (<i>r</i> = -0.25; <i>P</i> = 0.002), independent of age, BMI, and calf muscle area. No significant correlation was found between serum DKK1 and fasting serum glucose or insulin levels or insulin resistance estimated by homeostasis model assessment. These findings suggest that higher levels of serum DKK1 may be associated with greater overall, central, and ectopic skeletal muscle adiposity. Further studies are needed to unravel the potential role of DKK1 in the regulation of adiposity in humans.