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Tissue density in the left caudate nucleus was significantly decreased in infants whose mothers had elevated pre-pregnancy body-mass indexes (BMI).

 Evidence Rating Level: 2 (Good)

Parental obesity, particularly maternal obesity prior to pregnancy, has been identified as a risk factor for offspring obesity by means of both heritable and environmental influences.

The mechanisms by which this is thought to take place are complex and varied, but alterations in functioning of neurotransmitter signalling are believed to contribute. This is particularly true of the caudate and lentiform nuclei. The striatum is implicated in reward pathways and hedonic eating, and preclinical studies have observed structural changes and differences in neural processing of both adolescents and adults who are overweight or obese. Diffusion tensor imaging (DTI) allows for the study of white matter and subcortical structures, and mean diffusivity (MD) is a measure derived from DTI images best used for assessing grey matter structures.

Decreased MD is a marker of high tissue density, and the current study hypothesized that pre-pregnancy BMI was positively associated with infant striatal MD.

Data collected on infants between 1 to 6 weeks from birth from the Finnbrain Birth Cohort Study was used. These infants were born to singleton pregnancies after gestational week 35 and did not demonstrate any perinatal complications. After all exclusion criteria were met, there were 116 mother-infant dyads whose MRI, obstetric data, and maternal demographics were collected. Sixteen of these dyads had mothers with gestational diabetes mellitus (GDM). The six striatal brain regions of interest included the right and left putamen, right and left globus pallidus, and right and left caudate nuclei.

There were no significant sex differences in mean MD values in these regions, but there was a positive association between pre-pregnancy BMI and mean MD only in the left caudate nucleus, regardless of maternal GDM status (p = .006, R2partial = .07).

These results correlate to previous studies which observed increased caudate nucleus activation in response to high sugar content food in adolescents with high-BMI parents.

Limitations to this study include the small number of dyads which included mothers with GDM, and a lack of control for paternal BMI values. Future studies should also control for other exposures in utero that may have contributed to these findings, and longitudinal studies should be implemented to assess for a programming effect.

However, these current findings suggest a positive association between maternal pre-pregnancy BMI and decreased tissue density in the left caudate nucleus, which could suggest a maturation effect.

Click to read the study in BMC Medicine

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