Oral Presentation ESA-SRB-AOTA 2019

The relationship between maternal osteocalcin measurements and glucose metabolism in pregnancy (#256)

Angela McPhee 1 , Constance Yap 2 3 , Gideon Meyerowitz-Katz 4 5 , SA Paul Chubb 6 7 , Vita Birzniece 8 , Bu B Yeap 9 10 , N Wah Cheung 2 3 , Mark Mclean 1 11 , Sue Lynn Lau 1 2 3 11
  1. Department of Diabetes and Endocrinology, Blacktown Hospital, Sydney, NSW, Australia
  2. Diabetes and Endocrinology, Westmead Hospital, Sydney, NSW, Australia
  3. Faculty of Medicine, Western Clinical School, University of Sydney, Sydney, NSW, Australia
  4. Western Sydney Diabetes, Western Sydney Local Health District, Sydney, NSW, Australia
  5. University of Wollongong, Wollongong, NSW, Australia
  6. PathWest Laboratory Medicine, Fiona Stanley Hospital, Perth, WA, Australia
  7. School of Pathology and Laboratory Medicine, University of Western Australia, Perth, WA, Australia
  8. University of NSW, Kensington
  9. The Medical School, University of Western Australia, Perth, WA, Australia
  10. Department of Endocrinology and Diabetes, Fiona Stanley Hospital, Perth, WA, Australia
  11. School of Medicine, University of Western Sydney, Sydney, NSW, Australia

Introduction
Total osteocalcin (TOC) comprises of undercarboxylated (ucOC) and carboxylated (cOC) forms. In non-pregnant populations, low ucOC and cOC levels predict incident type 2 diabetes(1-4). Studies in pregnancy, however, demonstrate higher TOC in gestational diabetes (GDM) compared to controls(5, 6).

Aims/Methods
We evaluated the relationship between glucose and osteocalcin levels, using data from a prior randomised controlled trial of vitamin D supplementation in pregnancy. 209 women (gestational age <20 weeks) commenced vitamin D, 5000 or 400 IU daily, at a mean first visit gestation of 14.7 wks. 179 underwent OGTT at 26-28 weeks, 19 developed GDM. TOC, ucOC, proportion ucOC (%ucOC), P1NP and C-telopeptide (CTX) were measured in 205 stored serum samples collected at first visit and 174 samples at 26-28 weeks. We assessed correlation between baseline OC levels, glucose measures at OGTT, and bone turnover markers. Logistic regression evaluated baseline %ucOC as a predictor of subsequent GDM, adjusting for GDM risk factors.

Results
Table 1 lists baseline characteristics and biochemistry. %ucOC but not ucOC was correlated with 2-hr glucose (r=0.22, p=0.003).  Both ucOC and %ucOC correlated with BMI. ucOC positively correlated with CTX and P1NP (r=0.48, r=0.61 respectively, p<0.001), whereas %ucOC was negatively correlated with CTX and P1NP (r=-0.21, r =-0.34, p<0.01). OC levels did not change significantly between baseline and 26-28 weeks. The odds ratio (OR) for GDM for subjects with %ucOC values above the median (≥48.5% compared to <48.5%) was 4.07 (1.28-12.90, p=0.017).  Higher %ucOC remained significantly associated with GDM after adjusting for parity, BMI, ethnicity, family history of diabetes, maternal age, and 25OHvitD level at 26-28 weeks, OR 3.47 (1.02-11.81, p=0.046).

Conclusion
Higher %ucOC before 20 weeks’ gestation was associated with higher rates of GDM and higher 2-hr OGTT values. Data support a relationship between bone and glucose metabolism. Cause or direction of effect remains unknown.

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