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Title: Pre-pregnancy fat free mass and associations to glucose metabolism before and during pregnancy

Author
item DIAZ FUENTES, EVA - University Arkansas For Medical Sciences (UAMS)
item BORSHEIM, ELISABET - Arkansas Children'S Nutrition Research Center (ACNC)
item SHANKAR, KARTIK - Arkansas Children'S Nutrition Research Center (ACNC)
item CLEVES, MARIO - University Arkansas For Medical Sciences (UAMS)
item ANDRES, ALINE - Arkansas Children'S Nutrition Research Center (ACNC)

Submitted to: Journal of Clinical Endocrinology and Metabolism
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/21/2018
Publication Date: 11/28/2018
Citation: Diaz Fuentes, E.C., Borsheim, E., Shankar, K., Cleves, M.A., Andres, A. 2018. Pre-pregnancy fat free mass and associations to glucose metabolism before and during pregnancy. Journal of Clinical Endocrinology and Metabolism. https://doi.org/10.1210/jc.2018-01381.
DOI: https://doi.org/10.1210/jc.2018-01381

Interpretive Summary: Fat free mass (FFM), largely composed of skeletal muscle, is usually associated with better health outcomes, in contrast to fat mass (FM) that when in excess is linked to several metabolic diseases. However, the association between FFM and health outcomes is confounded in obesity, since obese individuals have greater FFM content compared to normal weight people. Little is known about the relative importance of FFM and metabolic health during pregnancy. For instance, one may ask how changes or differences in body composition impact the body’s ability to control blood sugar by regulating the actions of the hormone insulin. To assess the potential contributions of gestational weight gain (GWG), FFM and FM compartments to insulin resistance during pregnancy, we recruited 43 sedentary women of all BMI categories (normal weight to obese) prior to gestation and measured their body composition using air displacement plethysmography. Participants returned to the Arkansas Children's Nutrition Center (ACNC) for blood draw at gestational weeks 8 and 30. In this group of sedentary women, FFM, FM and GWG were each correlated with insulin resistance during pregnancy. Our results suggest that regardless of skeletal muscle mass, poor skeletal muscle insulin sensitivity may be contributing to dysregulated glucose metabolism during pregnancy. Future studies assessing skeletal muscle health and evaluations of potential interventions to improve muscle insulin sensitivity during pregnancy are necessary.

Technical Abstract: Our aim was to quantify the individual contribution of pre- pregnancy (PP) fat-free mass (FFM), expressed as PP-FFM index [PP-FFMI=FFM (kg)/height (m2)], on markers of glucose homeostasis before and during pregnancy. Body composition was assessed in 43 women before pregnancy using air-displacement plethysmography. Blood was drawn at PP and gestation week 8 and 30. Relationships between body composition (independent) variables and glucose homeostasis (dependent) variables were assessed using adjusted correlations, and simple and multiple linear regression analyses. Results. At PP, FFMI was the strongest predictor of plasma insulin concentration (Pr2=18.3, p=0.005) and HOMA2-IR (Pr2=22, p=0.002). At gestation week 30, PP-FFMI and gestational weight gain were the strongest predictors of insulin concentration (PP-FFMI: Pr2=23, p=0.005; GWG: Pr2=14, p=0.032), HOMA2-IR (PP-FFMI: Pr2=22, p=0.006; GWG: Pr2=15, p=0.028), 1st phase insulin response (PP-FFMI: Pr2=16, p=0.025; GWG: Pr2=18, p=0.016), and 2nd phase insulin response (PP-FFMI: Pr2=16, p=0.024; GWG: Pr2=20, p=0.011). Also, PP % fat mass (PP-%FM) and PP-FFMI were the strongest predictors of the estimated metabolic clearance rate of glucose (PP-%FM: Pr2=28, p=0.002; PP-FFMI: Pr2=12, p=0.050). PP-FFMI was a predictor of markers of glucose homeostasis before and during pregnancy. Studies assessing the impact of skeletal muscle quality on metabolic regulation during pregnancy are warranted. Fat free mass (FFM), largely composed of skeletal muscle, is usually associated with better health outcomes, in contrast to fat mass (FM) that when in excess is linked to several metabolic diseases. However, the association between FFM and health outcomes is confounded in obesity, since obese individuals have greater FFM content compared to normal weight people. Little is known about the relative importance of FFM and metabolic health during pregnancy. For instance, one may ask how changes or differences in body composition impact the body's ability to control blood sugar by regulating the actions of the hormone insulin. To assess the potential contributions of gestational weight gain (GWG), FFM and FM compartments to insulin resistance during pregnancy, we recruited 43 sedentary women of all BMI categories (normal weight to obese) prior to gestation and measured their body composition using air displacement plethysmography. Participants returned to the Arkansas Children's Nutrition Center (ACNC) for blood draw at gestational weeks 8 and 30. In this group of sedentary women, FFM, FM and GWG were each correlated with insulin resistance during pregnancy. Our results suggest that regardless of skeletal muscle mass, poor skeletal muscle insulin sensitivity may be contributing to dysregulated glucose metabolism during pregnancy. Future studies assessing skeletal muscle health and evaluations of potential interventions to improve muscle insulin sensitivity during pregnancy are necessary.