Objective
Obesity and liver fat are associated with decreased levels of serum sex hormone binding globulin (SHBG). Laboratory studies suggest that hepatic de novo lipogenesis (DNL) is involved in the downregulation of SHBG synthesis. The aim of the present study was to address the role of DNL on serum SHBG in humans.
Design
A cross‐sectional study examining the association between DNL, measured by stable isotopes, and serum SHBG, stratified by sex.
Participants
Healthy men (n = 34) and women (n = 21) were combined from two cross‐sectional studies. Forty‐two per cent of participants had hepatic steatosis, and the majority were overweight (62%) or obese (27%).
Results
DNL was inversely associated with SHBG in women (β: −0.015, 95% CI: −0.030; 0.000), but not in men (β: 0.007, 95% CI: −0.005; 0.019) (p for interaction = .068). Adjustment for study population, age and body mass index did not materially change these results, although statistical significance was lost after adjustment for serum insulin.
Conclusions
An inverse association between DNL and SHBG may explain the decreased SHBG levels that are observed in obesity, at least in women.
Purpose
De novo lipogenesis has been inversely associated with serum sex hormone-binding globulin (SHBG) levels. However, the directionality of this association has remained uncertain. We, therefore, studied individuals with glycogen storage disease type 1a (GSD1a), who are characterized by a genetic defect in glucose-6-phosphatase resulting in increased rates of de novo lipogenesis, to assess the downstream effect on serum SHBG levels.
Methods
A case–control study comparing serum SHBG levels in patients with GSD1a (n = 10) and controls matched for age, sex, and BMI (n = 10). Intrahepatic lipid content and saturated fatty acid fraction were quantified by proton magnetic resonance spectroscopy.
Results
Serum SHBG levels were statistically significantly lower in patients with GSD1a compared to the controls (p = 0.041), while intrahepatic lipid content and intrahepatic saturated fatty acid fraction—a marker of de novo lipogenesis—were significantly higher in patients with GSD1a (p = 0.001 and p = 0.019, respectively). In addition, there was a statistically significant, inverse association of intrahepatic lipid content and saturated fatty acid fraction with serum SHBG levels in patients and controls combined (β: − 0.28, 95% CI: − 0.47;− 0.09 and β: − 0.02, 95% CI: − 0.04;− 0.01, respectively).
Conclusion
Patients with GSD1a, who are characterized by genetically determined higher rates of de novo lipogenesis, have lower serum SHBG levels than controls.
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