Impact of diet-induced maternal obesity and effects of high-fat diet on bowel functions in offsprings

Background and aim: The prevalence of body overweight or obesity has increased progressively over the past decades, and has reached epidemic proportions in many Western countries. Likewise, the prevalence of overweight and obesity in children has increased substantially, and obesity among women in their reproductive age represents a critical issue. Maternal obesity is known also to increase the risk of complications during pregnancy and to exert detrimental consequences on offsprings. This study investigated the impact of diet-induced maternal obesity on metabolic indexes, gastrointestinal transit, intestinal permeability and gut microbiota of offsprings receiving a diet with a standard or high fat content. Methods: C57BL/6J female mice (4-week old) were fed with standard diet (SD, 10% of energy from fat) or high-fat diet (HFD, 60% of energy from fat) for 8 weeks, to elicit obesity. Females were then mated with males fed with SD, and were exposed to SD or HFD throughout their pregnancy and lactation. At weaning (4 weeks of age), female and male pups were randomly assigned to SD or HFD for 8 weeks. In all groups, body weight was monitored once a week throughout the study. Blood samples were collected after 1 hour fasting, and metabolic parameters, such as glucose, triglycerides, cholesterol and insulin, were evaluated. Fecal pellet expulsion frequency was evaluated the day before sacrifice. Gastrointestinal transit was assessed 30 minutes after intragastric administration of non-absorbable fluorescein isothiocyanate labeled dextran (FITC-dextran 70 kDa). Intestinal permeability was assessed by plasma level assessment of low molecular weight (4 kDa) FITC-dextran, 4 hours its administration by oral gavage. Immunofluorescence staining for the neuronal marker HuC/D and the glial marker S100beta was examined by confocal microscopy in longitudinal muscle myenteric plexus preparations of ileum. The microbiota composition of offspring colonic fecal pellets was analyzed by 16rRNA amplicon sequencing. Results: Pups fed with HFD developed an increase in body weight gain, associated with increased metabolic indexes and changes in their microbiota, characterized by an increased abundance of Firmicutes and Proteobacteria and a reduction of Bacteroidetes, as compared to SD pups, irrespectively of the maternal diet. Female pups fed with HFD displayed a delay in gastrointestinal transit, which was more severe in pups born from obese mothers. Such a delay was confirmed by a concomitant reduction of stool expulsion frequency. Male pups born from SD mothers and fed with HFD displayed both a delay in gastrointestinal transit and a decrease in the frequency of fecal pellet expulsion. Notably, these alterations were more severe in male pups born HFD mothers and fed with SD. An increase in intestinal permeability was observed in offsprings born from SD mothers and fed with HFD, as compared to pups fed with SD. This alteration was enhanced further in pups born from obese mothers. In the myenteric plexus of both female and male pups fed with HFD, there was an increase in the immunoreactivity to S100beta. By contrast, S100beta immunopositivity was found to be reduced in male pups born from obese mothers and fed with SD, as compared to pups born from SD mothers. Staining for HuC/D was decreased in both female and male pups fed with HFD. Among the offsprings born from obese mothers, this change was more pronounced in pups fed with SD. Discussion and Conclusion: Body weight gain, alterations of metabolic parameters and changes in gut microbiota appear to occur mainly in offsprings with direct exposure to HFD. Conversely, maternal HFD consumption confers to the offsprings a higher susceptibility to develop bowel dysfunctions in terms of delayed intestinal transit and increased enteric permeability. Among the offsprings from obese mothers, the most detrimental impact was observed in male pups, as compared to females, particularly when fed with SD.