Gestational diabetes mellitus (GDM) is traditionally defined as glucose intolerance with first-time diagnosis during pregnancy (1). It develops in approximately 10% of pregnancies, making it one of the prevalent complications during gestation (2). Intrauterine exposure to GDM increases the risk of developing obesity in offspring (2). It is not yet clear which factors might drive these conditions later in life, but early neurodevelopmental processes appear sensitive to intrauterine hyperglycemia, hyperinsulinemia and neuroinflammation caused by maternal overnutrition, including hyperglycemia (3, 4). Furthermore, intrauterine exposure to GDM may lead to increased food intake, which is regulated by multiple brain regions (5).
The hippocampus is believed to influence food intake by integrating learned experience (food-related episodic memories, associations, incentive information) with interoceptive signals of nutritive state, as well as visual, gustatory, and olfactory cues (for review, see (6)). Animal models and behavioral studies in humans suggest that even a brief exposure to a diet rich in dietary fat and sugar can impair hippocampal-dependent learning and memory (7, 8). Furthermore, behavioral data in healthy humans showed that influencing meal memory may reduce or enhance later food intake. For example, recalling the most recent meal reduced subsequent food intake (9), while dividing attention during the meal increased later food intake (10). Furthermore, amnesic patients fail to interpret interoceptive signals (e.g., hunger and satiety) (11). Using fMRI, the hippocampus has been shown to be responsive to the ingestion of sugar, visual food cue exposure, and insulin administration in healthy adults (12, 13). Hippocampal dysfunctions may impair the ability to retrieve memories of meals, detect interoceptive signals, and lead to overeating (for reviews, see (14)). Significantly, data from animals and human suggests the development of the hippocampus is sensitive to GDM exposure (4, 15–17). In animals, intrauterine exposure to diabetes caused decreased neuronal density and reduced synaptic integrity in the hippocampus (4, 15, 16). GDM exposure was also associated with reduced thickness in the left hippocampus in children (17).
Neural food cue reactivity has been used in children to evaluate the neural basis of appetite control (18, 19). Children and adolescents with obesity exhibited higher neural responses to palatable food images in the reward-related regions, including the striatum, insula, amygdala, and hippocampus (20, 21). Waist circumference, rather than BMI, was associated with higher hippocampal activation during high caloric food cue exposure (22). Studies have demonstrated functional coupling between the hippocampus and multiple brain regions involved in reward processing (23, 24). Yet, evidence from resting-state fMRI studies suggests that the functional connectivity (FC) of the hippocampus to reward-related regions is altered by obesity in both children and adults (25–29). Specifically, children with obesity exhibited lower hippocampal FC to the orbitofrontal cortex and striatum (25, 26), while adults with obesity showed higher hippocampal FC to the striatum and lower to the anterior cingulate cortex, compared to individuals with normal weight (27–29). The discrepancy could be due to the developmental trajectory of the hippocampus (30). Unlike examining intrinsic networks during resting-state, task-based functional connectivity during a food cue task explores the brain's connectivity during exposure to food cues. During the presentation of appetizing food cues, evidence suggests that hippocampal FC to the orbitofrontal cortex, dorsomedial prefrontal cortex and dorsolateral prefrontal cortex increases with BMI in adults (31). Nevertheless, functional coupling of the hippocampus to other brain regions during exposure to visual food cues in GDM-exposed compared to unexposed children remains unexplored.
The current study investigates the relation between GDM exposure and FC of the hippocampus in children. We examined task-based FC of the bilateral hippocampus in children with and without GDM exposure using generalized psychophysiological interaction (gPPI) in response to visual food cues (high-calorie food minus non-food) in the BrainChild Cohort (5, 18). Prior studies (20, 21, 25–29, 31) indicate higher food-cue-induced neural reactivity of reward regions and alterations in hippocampal FC in children with obesity. Hence, we hypothesized that hippocampal FC is higher to reward-related regions during food cue presentation in children with GDM exposure when compared to children without exposure. Since prior evidence points to distinct effects of GDM on the left and right hippocampus (17) in children, we also investigated FC of the left and right hippocampus separately in an exploratory analysis.