Human milk imparts higher insulin concentration in infants born to women with type 2 diabetes mellitus

Abstract

Objective

Human milk (HM) insulin plays many roles for the infant, especially for the newborn. We hypothesized HM insulin in women with type 2 diabetes (T2DM) would be higher than BMI-matched women with either gestational diabetes (GDM) or normal glucose tolerance (NGT). In T2DM, we also assessed macronutrient composition and relationships between maternal glycemic control and HM insulin.

Study design

HM was characterized at 2-weeks postpartum among three BMI-matched groups: T2DM (n= 12), diet-controlled GDM (n= 12), and NGT (n= 12). In T2DM, additional fasting and postprandial HM samples were collected while wearing a continuous glucose monitor (CGM), as well as fasting and 90-minute postprandial samples after a standardized meal at 1–2 weeks postpartum.

Results

Fasting HM insulin was two times higher in T2DM compared to GDM and NGT (p < .001), which were not different from each other. Among T2DM, fasting (p < .001) and postprandial (p = .01) HM insulin levels were between 2 and 5× higher than plasma. Postprandial HM insulin (p = .03) and glucose (p < .001) were increased compared to fasting. Mean nocturnal glucose (p < .01) and maternal hemoglobin A1c (p < .01) positively associated with fasting HM insulin.

Conclusions

These data are the first to show HM insulin concentrations are doubled in T2DM compared to BMI-matched GDM and NGT. In HM of T2DM, insulin increases postprandially, may be concentrated relative to plasma, and is influenced by maternal glycemic control, with potential clinical implications that merit further study.

Keywords:

• Type 2 diabetes
• lactation
• human milk
• insulin
• gestational diabetes
• breastfeeding

Acknowledgements

The authors are grateful to all the women, infants, and their families for participating in the study. The authors acknowledge the support of Drs. Regina Reynolds, Laura Brown, Paul Rozance (Department of Pediatrics, University of Colorado), and Dr. Emily Su (Department of Obstetrics and Gynecology, University of Colorado). We also acknowledge Laurie Moss, Emily Dunn, and Jayne Martin Carli, PhD, for their invaluable study support.

Disclosure statement

The authors have no conflicts of interest to disclose.

Additional information

Funding

This work was supported by the Colorado Clinical & Translational Sciences Institute Child Maternal Health Pilot Program under UL1 TR000154, by the National Institutes of Health/National Center for Advancing Translational Sciences Colorado CTSA under Grants UL1 TR002535, T32-DK007658-28, NIH R01-DK101659 “Randomized Trial of Diet in GDM: Metabolic Consequences to Mother and Offspring” P.I. Teri L. Hernandez, F32-HD0978068, and T32-DK007658-21. This work was also supported by the Thrasher Research Fund Early Career Award and the University of Colorado Center for Women’s Health Research.