Finding of insulin sensitivity in newborn foals challenges existing concepts

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Findings suggest that the pancreas in newborn foals has a high insulin secretory capacity in order to favor energy conservation.
Findings suggest that the pancreas in newborn foals has a high insulin secretory capacity in order to favor energy conservation.

Foals are insulin sensitive in the first days of life, according to researchers, whose findings are at odds with previously published reports on the issue.

Researchers in the Ohio State University study sought to evaluate glucose and insulin dynamics in healthy newborn foals and compare the values to healthy horses.

Previously, researchers considered that newborn foals have impaired glucose tolerance because of delays in the pancreatic endocrine system maturing.

Few studies have investigated insulin sensitivity in newborn foals using dynamic testing methods, the study team noted.

In their research, they assessed insulin sensitivity by comparing the insulin-modified frequently sampled intravenous glucose tolerance test in 12 healthy Standardbred foals aged 24 to 60 hours old, and eight horses of various breeds aged 3 to 14 years.

“Our results challenge concepts presented in the literature stating that newborn foals are insulin resistant secondary to endocrine modifications that occur in the perinatal period,” Hannah Kinsella and her fellow researchers reported in the open-access journal PLOS ONE. “In fact, we showed that the neonatal foal is insulin sensitive in the first days of life,” they reported.

Newborn foals may also have mechanisms for maintaining normal concentrations of glucose in the blood in order to prevent low blood sugar during the postnatal period.

Their findings, they said, may indicate that evolutionary adaptations exist during the first days of life in order for foals to successfully transition to life beyond the uterus.

Discussing their findings, the researchers said neonatal foals undergo several physiologic changes at birth in order to survive the transition to life outside the womb.

“Many of the changes occurring during this transition, such as glucoregulation, are not present prior to birth but are required for survival.

“In this study, we showed that compared to horses, healthy neonatal foals are more insulin sensitive, with insulin having a higher capacity to promote glucose disposal and inhibit endogenous glucose production.

“This finding was unexpected, as neonatal foals have been considered to be physiologically insulin resistant as part of their delayed endocrine maturation and perinatal increases in cortisol concentrations.”

Their findings, they said, suggest that the endocrine pancreas in newborn foals has a high insulin secretory capacity in order to favor energy conservation.

“It is possible that foals adapted to produce insulin to preserve energy during the critical transition into extrauterine life, but also as a protective mechanism against insulin resistance.”

Baseline glucose concentrations in foals were found to be significantly higher than in horses. “The higher baseline glucose concentrations measured in the healthy foals of this study calls into question whether the goals for glycemic control in the equine neonate should be re-examined,” they said.

Critically ill newborn foals are prone to hypoglycemia, they noted, which can be secondary to factors including reduced milk intake and little glycogen storage after birth.

Based on this study, and previous studies performed by their laboratory, healthy equine newborns with no access to nursing do not develop low blood sugar until at least four hours of milk restriction.

“Published reference ranges for glucose in the neonatal foal are higher than those used for adults, and the results of this study further solidify that this should be taken into account in the clinical management of the neonatal foal.

“The question of whether the use of tight or liberal glycemic control is more beneficial in the treatment of the critically ill neonate continues to remain controversial, and additional investigation is warranted.”

The study team comprised Kinsella, Laura Hostnik, Hailey Snyder, Sarah Mazur, Ahmed Kamr, Teresa Burns and Ramiro Toribio, all with The Ohio State University; and John Mossbarger, with Midland Acres Inc in Bloomingburg, Ohio.

Kinsella HM, Hostnik LD, Snyder HA, Mazur SE, Kamr AM, Burns TA, et al. (2022) Comparison of insulin sensitivity between healthy neonatal foals and horses using minimal model analysis. PLoS ONE 17(1): e0262584. https://doi.org/10.1371/journal.pone.0262584

The study, published under a Creative Commons License, can be read here

 

 

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