Initiation of metformin in early pregnancy results in fetal bioaccumulation, growth restriction, and renal dysmorphology in a primate model.

BACKGROUND: In recent years, pragmatic metformin use in pregnancy has stretched to include prediabetes mellitus, type 2 diabetes mellitus, gestational diabetes mellitus, and (most recently) preeclampsia. However, with its expanded use, concerns of unintended harm have been raised. OBJECTIVE: This study developed an experimental primate model and applied ultrahigh performance liquid chromatography coupled to triple-quadrupole mass spectrometry for direct quantitation of maternal and fetal tissue metformin levels with detailed fetal biometry and histopathology. STUDY DESIGN: Within 30 days of confirmed conception (defined as early pregnancy), 13 time-bred (timed-mated breeding) Rhesus dams with pregnancies designated for fetal necropsy were initiated on twice-daily human dose-equivalent 10 mg/kg metformin or vehicle control. Pregnant dams were maintained as pairs and fed either a control chow or 36% fat Western-style diet. Metformin or placebo vehicle control was delivered in various treats while the animals were separated via a slide. A cesarean delivery was performed at gestational day 145, and amniotic fluid and blood were collected, and the fetus and placenta were delivered. The fetus was immediately necropsied by trained primate center personnel. All fetal organs were dissected, measured, sectioned, and processed per clinical standards. Fluid and tissue metformin levels were assayed using validated ultrahigh performance liquid chromatography coupled to triple-quadrupole mass spectrometry in selected reaction monitoring against standard curves. RESULTS: Among 13 pregnancies at gestational day 145 with fetal necropsy, 1 dam and its fetal tissues had detectable metformin levels despite being allocated to the vehicle control group (>1 µmol metformin/kg maternal weight or fetal or placental tissue), whereas a second fetus allocated to the vehicle control group had severe fetal growth restriction (birthweight of 248.32 g [<1%]) and was suspected of having a fetal congenital condition. After excluding these 2 fetal pregnancies from further analyses, 11 fetuses from dams initiated on either vehicle control (n=4: 3 female and 1 male fetuses) or 10 mg/kg metformin (n=7: 5 female and 2 male fetuses) were available for analyses. Among dams initiated on metformin at gestational day 30 (regardless of maternal diet), significant bioaccumulation within the fetal kidney (0.78-6.06 µmol/kg; mean of 2.48 µmol/kg), liver (0.16-0.73 µmol/kg; mean of 0.38 µmol/kg), fetal gut (0.28-1.22 µmol/kg; mean of 0.70 µmol/kg), amniotic fluid (0.43-3.33 µmol/L; mean of 1.88 µmol/L), placenta (0.16-1.00 µmol/kg; mean of 0.50 µmol/kg), fetal serum (0.00-0.66 µmol/L; mean of 0.23 µmol/L), and fetal urine (4.10-174.10 µmol/L; mean of 38.5 µmol/L) was observed, with fetal levels near biomolar equivalent to maternal levels (maternal serum: 0.18-0.86 µmol/L [mean of 0.46 µmol/L]; maternal urine: 42.60-254.00 µmol/L [mean of 149.30 µmol/L]). Western-style diet feeding neither accelerated nor reduced metformin bioaccumulations in maternal or fetal serum, urine, amniotic fluid, placenta, or fetal tissues. In these 11 animals, fetal bioaccumulation of metformin was associated with less fetal skeletal muscle (57% lower cross-sectional area of gastrocnemius) and decreased liver, heart, and retroperitoneal fat masses (P<.05), collectively driving lower delivery weight (P<.0001) without changing the crown-rump length. Sagittal sections of fetal kidneys demonstrated delayed maturation, with disorganized glomerular generations and increased cortical thickness. This renal dysmorphology was not accompanied by structural or functional changes indicative of renal insufficiency. CONCLUSION: Our study demonstrates fetal bioaccumulation of metformin with associated fetal growth restriction and renal dysmorphology after maternal initiation of the drug within 30 days of conception in primates. Given these results and the prevalence of metformin use during pregnancy, additional investigation of any potential immediate and enduring effects of prenatal metformin use is warranted.

Lost in translation: Cesarean antibiotics and the infant microbiome.

In this issue of Cell Host & Microbe, Sinha et al. describe their randomized trial assessing whether antibiotics given for maternal benefit prior to Cesarean disrupted the infants' microbiomes. Despite pre-incision antibiotics reaching the neonate, there was no meaningful alteration to the infant microbiome-especially when compared with breastmilk feeding.

Maternal and early life exposures and their potential to influence development of the microbiome.

At the dawn of the twentieth century, the medical care of mothers and children was largely relegated to family members and informally trained birth attendants. As the industrial era progressed, early and key public health observations among women and children linked the persistence of adverse health outcomes to poverty and poor nutrition. In the time hence, numerous studies connecting genetics ("nature") to public health and epidemiologic data on the role of the environment ("nurture") have yielded insights into the importance of early life exposures in relation to the occurrence of common diseases, such as diabetes, allergic and atopic disease, cardiovascular disease, and obesity. As a result of these parallel efforts in science, medicine, and public health, the developing brain, immune system, and metabolic physiology are now recognized as being particularly vulnerable to poor nutrition and stressful environments from the start of pregnancy to 3 years of age. In particular, compelling evidence arising from a diverse array of studies across mammalian lineages suggest that modifications to our metagenome and/or microbiome occur following certain environmental exposures during pregnancy and lactation, which in turn render risk of childhood and adult diseases. In this review, we will consider the evidence suggesting that development of the offspring microbiome may be vulnerable to maternal exposures, including an analysis of the data regarding the presence or absence of a low-biomass intrauterine microbiome.

Phosphate vibrations probe local electric fields and hydration in biomolecules.

The role of electric fields in important biological processes such as binding and catalysis has been studied almost exclusively by computational methods. Experimental measurements of the local electric field in macromolecules are possible using suitably calibrated vibrational probes. Here we demonstrate that the vibrational transitions of phosphate groups are highly sensitive to an electric field and show how that sensitivity can be quantified, allowing electric field measurements to be made in phosphate-containing biological systems without chemical modification.

Turning the "Phage" on Malnutrition and Stunting.

Bacteriophages shape bacterial ecosystems, including community membership and their metabolic function. In this issue of Cell Host & Microbe, Mirzaei et al. (2020) identify harbored bacteriophages among a Proteobacteria-dominant community unique to toddlers with stunted growth from Bangladesh, and that confer the capacity to similarly tailor microbiota profiles in vitro.

Measurement tools and target symptoms/skills used to assess treatment response for individuals with autism spectrum disorder.

This study examined the measurement tools and target symptoms/skills used to assess treatment response during Autism Spectrum Disorder (ASD) intervention trials from 2001 through 2010. Data from 195 prospective trials were analyzed. There were 289 unique measurement tools, of which 61.6 % were used only once, and 20.8 % were investigator-designed. Only three tools were used in more than 2 % of the studies, and none were used in more than 7 % of studies. Studies investigated an average of 11.4 tool-symptom combinations per trial, with as many as 45 in one study. These results represent a lack of consistency in outcome measurements in ASD intervention trials. These findings highlight the need to set guidelines for appropriate outcome measurement in the ASD field.