The aim of this study was to investigate the effect of a high‐fat (HF)/energy diet on the intestinal microbiota, the alkaline phosphatase (AP) activity, and related parameters of growth and obesity during the suckling and weaning periods in male Sprague‐Dawley rats. From birth, nutrition in suckling pups was manipulated by feeding rat dams either HF or a standard diet, and then after weaning, by exposure of experimental pups to the HF, and control rats to normal diet. On days 15, 20, 40 the numbers of 2 microbial groups, i.e., Bacteroides/Prevotella (BAC) and the Lactobacillus/Enterococcus (LAB) in the jejunum, were determined by fluorescent in situ hybridization technique, and the AP activity was assayed histochemically. During all investigated periods HF pups gained body fat more rapidly than control animals, but from weaning they displayed significantly stunted growth resulting in final body weight loss. Obesity in HF rats was also accompanied by higher LAB and lower numbers of BAC and with permanently higher AP activity. Correlation of these data showed significant negative correlation between LAB, AP, and weight gain and energy efficiency, and significant positive correlation of BAC and AP activity with body fat. These data support the concept that postnatal nutritional experience represents an important factor affecting the ontogeny of intestinal microbial communities and intestinal function. These acquired changes could be a component of regulatory mechanisms involved in adverse and/or positive consequences of HF diet for adiposity, body weight, and energy‐balance control in later life.

To investigate possible involvement of glucocorticoid receptor (GR) in mediating effects of maternal stress or therapeutically administered glucocorticoids on early embryo we analyzed the expression of GR subtypes in ovulated mouse oocytes and preimplantation embryos. RT-PCR analysis results showed that GRα and GRγ transcripts are relatively highly expressed in mouse oocytes, and both transcripts are present at lower amounts in preimplantation embryos. We also detected low expression of two other splice variants, GRβ and a transcript orthologous to the human GR-P subtype, mainly at the blastocyst stage. Using Western blot analysis, we detected several GR protein bands that differed in size between oocytes and preimplantation embryos. To compare the effects of corticosterone (a major endogenous glucocorticoid in rodents) and dexamethasone (a synthetic glucocorticoid) on early embryos, we cultured mouse preimplantation embryos in the presence of these glucocorticoids. Corticosterone showed a strong inhibitory effect on embryo development (starting from a 50 μM concentration), without a significant influence on apoptosis incidence. On the other hand, dexamethasone induced apoptosis in early embryo cells (starting from a 1.5 μM concentration), and its effect on embryo development was less detrimental than that found with the same dose of corticosterone. In summary, our results showed that different GR subtypes are expressed in ovulated mouse oocytes and preimplantation embryos and that the composition of GR subtypes changes during early embryo development. Moreover, we found significant differences in the effects of the two glucocorticoids on early embryo development, which might be associated with activation of different GR subtypes.