(213) Association between Early Postpartum Appendicular Skeletal Muscle Mass Volume and Insulin Resistance during Pregnancy

Objective:
Reduced appendicular skeletal muscle (ASM) mass is linked to insulin resistance and a higher risk of type 2 diabetes, especially in non-obese women. However, the association between ASM volume and insulin dynamics during pregnancy is unclear. This study aimed to investigate if early postpartum ASM is associated with insulin resistance during pregnancy.

Study Design:
We conducted a prospective observational study on the association between postpartum trunk and ASM volume and low back pain in Japanese singleton pregnant women recruited at 35 weeks’ gestation. ASM was measured using the impedance method (Tanita MC780A-N) at four weeks postpartum. ASM/body mass index (BMI) was calculated as an ASM volume index. We included women who underwent an oral glucose tolerance test (OGTT) during pregnancy due to a positive gestational diabetes (GDM) screen. During the OGTT, HbA1c, fasting, and postprandial insulin levels were measured to calculate the homeostatic model assessment for insulin resistance (HOMA-IR) and the insulin sensitivity index (ISI). We examined the association between ASM/BMI and fasting glucose, HbA1c, and insulin sensitivity indices during pregnancy.

Results:
We included 226 women who underwent an OGTT at 25 weeks’ gestation. Postpartum ASM/BMI was significantly and negatively correlated with fasting glucose (r²=0.04, p=0.0042), HbA1c (r²=0.04, p=0.0045), and HOMA-IR (r²=0.20, p< 0.001), while positively correlated with ISI (r²=0.16, p< 0.0001). These correlations remained significant after controlling for age, gestational age at OGTT, and GDM status. ASM/BMI < 25th percentile was associated with >75th percentile HOMA-IR and < 25th percentile ISI, with adjusted odds ratios (95% confidence interval) of 6.27 (3.15-12.90) and 4.73 (2.40-6.57), respectively.

Conclusion:
This is the first report demonstrating that early postpartum ASM volume is associated with hyperglycemia and insulin resistance during pregnancy. Reduced ASM volume may contribute to gestational glucose intolerance.