Foetal exposure to common environmental chemical bisphenol A (BPA) causes increased inflammation in fat tissues after birth, which can lead to obesity and metabolic syndrome, a new research has suggested.
BPA, found in plastic water bottles, older baby bottles and many other consumer products, is a known hormone disrupter with estrogen-like properties.
Study's lead author, Almudena Veiga-Lopez, DVM, PhD, a research investigator at the University of Michigan, Ann Arbor, said that the study, which examines the effects of BPA on sheep, improves the understanding of how prenatal BPA exposure regulates the inflammatory response in offspring in the tissues that are relevant to development of metabolic disease.
Veiga-Lopez said that sheep have similar body fat to that in humans, including visceral (deep belly) fat and subcutaneous fat, which is directly below the skin.
The researchers fed two groups of pregnant sheep corn oil, either with nothing added to it or with added BPA at a dose needed to achieve BPA levels similar to those seen in human cord blood in the umbilical cord blood of the sheep offspring.
Of the female offspring from the sheep, half from each group were overfed at approximately 6 weeks of age.
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All female offspring then were divided into four groups of nine to 12 animals each: (1) non-BPA-exposed controls that received a normal diet, (2) BPA-exposed offspring that received a normal diet, (3) overfed, obese controls and (4) overfed, obese BPA-exposed offspring.
At 15 months of age, sheep underwent a glucose tolerance test, to measure their insulin and blood sugar levels. Seven months later, the researchers collected samples of the animals' visceral and subcutaneous fat tissues to evaluate levels of two biological markers of inflammation.
These biomarkers were CD68, a marker for inflammatory cells, and adiponectin, a molecule with a known role in the development of metabolic syndrome. When the adiponectin level decreases or CD68 expression increases, inflammation is worse, according to Veiga-Lopez.
Adiponectin was decreased and CD68 expression was raised in the visceral fat of both obese groups, and CD68 expression also was raised in the subcutaneous fat in normal weight, BPA-exposed female offspring, Veiga-Lopez reported.
She said these results suggest that "prenatal BPA exposure and postnatal diet may interact to modulate inflammatory mechanisms in fat deposits."
Both obese groups had hyperinsulinemia, or high insulin levels, a precursor to insulin resistance, which is a prediabetic state, Veiga-Lopez reported.
She speculated that the hyperinsulinemia in obese offspring stems from changes that occurred in the two inflammatory markers in the visceral fat deposit.