Deeper Dives Into Associations, Potential Mechanisms
The EPOCH prospective cohort study with which Dr. Hockett was involved gave her a front-seat view of the transgenerational adverse effects of in utero exposure to hyperglycemia. The study recruited ethnically diverse maternal/child dyads from the Kaiser Permanente of Colorado perinatal database from 1992 to 2002 and assessed 418 offspring at two points — a mean age of 10.5 years and 16.5 years — for fasting blood glucose, adiposity, and diet and physical activity. The second visit also involved an oral glucose tolerance test.
The 77 offspring who had been exposed in utero to GDM had a homeostatic model assessment of insulin resistance (HOMA-IR) that was 18% higher, a 19% lower Matsuda index, and a 9% greater HOMA of β-cell function (HOMA-β) than the 341 offspring whose mothers did not have diabetes. Each 5-kg/m2 increase in prepregnancy body mass index predicted increased insulin resistance, but there was no combined effect of both maternal obesity and diabetes in utero.
Exposed offspring had a higher BMI and increased adiposity, but when BMI was controlled for in the analysis of metabolic outcomes, maternal diabetes was still associated with 12% higher HOMA-IR and a 17% lower Matsuda index. “So [the metabolic outcomes] are a direct effect of maternal diabetes,” Dr. Hockett said at the DPSG meeting, noting the fetal overnutrition hypothesis in which maternal glucose, but not maternal insulin, freely passes through the placenta, promoting growth and adiposity in the fetus.
[The EPOCH results on metabolic outcomes and offspring adiposity were published in 2017 and 2019, respectively (Diabet Med. 2017;34:1392-9; Diabetologia. 2019;62:2017-24). In 2020, EPOCH researchers reported sex-specific effects on cardiovascular outcomes, with GDM exposure associated with higher total and LDL cholesterol in girls and higher systolic blood pressure in boys (Pediatr Obes. 2020;15[5]:e12611).]
Now, a new longitudinal cohort study underway in Phoenix, is taking a deeper dive, trying to pinpoint what exactly influences childhood obesity and metabolic risk by following Hispanic and American Indian maternal/child dyads from pregnancy until 18 years postpartum. Researchers are looking not only at associations between maternal risk factors (pregnancy BMI, gestational weight gain, and diabetes in pregnancy) and offspring BMI, adiposity, and growth patterns, but also how various factors during pregnancy — clinical, genetic, lifestyle, biochemical — ”may mediate the associations,” said lead investigator Madhumita Sinha, MD.
“We need a better understanding at the molecular level of the biological processes that lead to obesity in children and that cause metabolic dysfunction,” said Dr. Sinha, who heads the Diabetes Epidemiology and Clinical Research Section of the of the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) branch in Phoenix.
The populations being enrolled in the ETCHED study (for Early Tracking of Childhood Health Determinants) are at especially high risk of childhood obesity and metabolic dysfunction. Research conducted decades ago by the NIDDK in Phoenix showed that approximately 50% of Pima Indian children from diabetic pregnancies develop type 2 diabetes by age 25 (N Engl J Med. 1983;308:242-5). Years later, to tease out possible genetic factors, researchers compared siblings born before and after their mother was found to have type 2 diabetes, and found significantly higher rates of diabetes in those born after the mother’s diagnosis, affirming the role of in utero toxicity (Diabetes 2000;49:2208-11).
In the new study, the researchers will look at adipokines and inflammatory biomarkers in the mothers and offspring in addition to traditional anthropometric and glycemic measures. They’ll analyze placental tissue, breast milk, and the gut microbiome longitudinally, and they’ll lean heavily on genomics/epigenomics, proteomics, and metabolomics. “There’s potential,” Dr. Sinha said, “to develop a more accurate predictive and prognostic model of childhood obesity.”
The researchers also will study the role of family, socioeconomics, and environmental factors in influencing child growth patterns and they’ll look at neurodevelopment in infancy and childhood. As of October 2023, almost 80 pregnant women, most with obesity and almost one-third with type 2 diabetes, had enrolled in the study. Over the next several years, the study aims to enroll 750 dyads.