Brain-Derived Neurotrophic Factor as a Potential Mediator of the Beneficial Effects of Myo-Inositol Supplementation during Suckling in the Offspring of Gestational-Calorie-Restricted Rats

Abstract

This study aims to investigate the potential mechanisms underlying the protective effects of myo-inositol (MI) supplementation during suckling against the detrimental effects of fetal energy restriction described in animal studies, particularly focusing on the potential connections with BDNF signaling. Oral physiological doses of MI or the vehicle were given daily to the offspring of control (CON) and 25%-calorie-restricted (CR) pregnant rats during suckling. The animals were weaned and then fed a standard diet until 5 months of age, when the diet was switched to a Western diet until 7 months of age. At 25 days and 7 months of age, the plasma BDNF levels and mRNA expression were analyzed in the hypothalamus and three adipose tissue depots. MI supplementation, especially in the context of gestational calorie restriction, promoted BDNF secretion and signaling at a juvenile age and in adulthood, which was more evident in the male offspring of the CR dams than in females. Moreover, the CR animals supplemented with MI exhibited a stimulated anorexigenic signaling pathway in the hypothalamus, along with improved peripheral glucose management and enhanced browning capacity. These findings suggest a novel connection between MI supplementation during suckling, BDNF signaling, and metabolic programming, providing insights into the mechanisms underlying the beneficial effects of MI during lactation.

Keywords: BDNF; adipose tissue; browning; glucose control; hypothalamus; insulin sensitivity; metabolic programming; perinatal.

Figure 1

Schematic representation of the experimental design. Abbreviations: controls (CON), calorie-restricted (CR), vehicle (V), myo-inositol (MI), day (d), months (m).

Figure 2

Plasma BDNF levels of male and female rats at 25 days, 5 months, and 7 months of age. Data are means ± SEM. Statistics: Three-way ANOVA was conducted to investigate the impacts of gestational calorie restriction (R), myo-inositol treatment (M), and/or sex (S). Within each sex, two-way ANOVA was used to assess the effects of R and/or M. Student’s t-test was used for individual group comparisons: *, different from their corresponding vehicle-supplemented group; #, different compared to their corresponding control group. Abbreviations: control (CON), gestational calorie-restricted (CR), vehicle (V), myo-inositol (MI).

Figure 3

Expression levels of Insr, Lepr, Bdnf, and Ntrk2 genes in the hypothalamus, retroperitoneal and inguinal white adipose tissue (rWAT and iWAT), and brown adipose tissue (BAT) of 25-day-old offspring from controls (CON) and calorie-restricted (CR) dams during gestation, treated with either vehicle (V) or myo-inositol (MI) during the lactation period. mRNA levels are expressed as a percentage of the value for the CON-V male rats. Data are mean ± SEM. Statistics: Three-way ANOVA was conducted to investigate the impacts of gestational calorie restriction (R), lactational myo-inositol treatment (M), and/or sex (S). Within each sex, two-way ANOVA was used to assess the effects of R and/or M. Student’s t-test was used for individual group comparisons: *, different from their corresponding vehicle-supplemented group; #, different compared to their corresponding control group.

Figure 4

Expression levels of hypothalamic energy control genes of 25-day-old and 7-month-old offspring from controls (CON) and calorie-restricted (CR) dams during gestation, treated with either vehicle (V) or myo-inositol (MI) during the lactation period. mRNA levels are expressed as a percentage of the value for the CON-V male rats. Data are mean ± SEM. Statistics: Three-way ANOVA was conducted to investigate the impacts of gestational calorie restriction (R), lactational myo-inositol treatment (M), and/or sex (S). Within each sex, two-way ANOVA was used to assess the effects R and/or M. Student’s t-test was used for individual group comparisons: *, different from their corresponding vehicle-supplemented group; #, different compared to their corresponding control group.

Figure 5

Expression levels of Bdnf and Ntrk2 genes in the hypothalamus, retroperitoneal and inguinal white adipose tissue (rWAT and iWAT), and brown adipose tissue (BAT) of 7-month-old offspring from controls (CON) and calorie-restricted (CR) dams during gestation, treated with either vehicle (V) or myo-inositol (MI) during the lactation period. mRNA levels are expressed as a percentage of the value for the CON-V male rats. Data are mean ± SEM. Statistics: Three-way ANOVA was conducted to investigate the impacts of gestational calorie restriction (R), lactational myo-inositol treatment (M), and/or sex (S). Within each sex, two-way ANOVA was used to assess the effects of R and/or M. Student’s t-test was used for individual group comparisons: *, different from their corresponding vehicle-supplemented group; #, different compared to their corresponding control group.

Figure 6

Expression levels of genes implicated in glucose uptake, browning, and thermogenesis in three adipose tissues (retroperitoneal and inguinal white adipose tissue (rWAT and iWAT, respectively) and brown adipose tissue (BAT)), as well as UCP1 protein levels in BAT, of 7-month-old offspring from controls (CON) and calorie-restricted (CR) dams during gestation, treated with either vehicle (V) or myo-inositol (MI) during the lactation period. Protein levels are expressed as a percentage of the value for the CON-V male rats. mRNA levels are expressed as a percentage of the value of the CON-V male animals. Data are mean ± SEM. Statistics: Three-way ANOVA was conducted to investigate the impacts of gestational calorie restriction (R), lactational myo-inositol treatment (M), and/or sex (S). Within each sex, two-way ANOVA was used to assess the effects of R and/or M. Student’s t-test was used for individual group comparisons: *, different from their corresponding vehicle-supplemented group; #, different compared to their corresponding control group. Representative bands from Western blot analysis of UCP1 and reference proteins (β-Actin and HSP90) for each animal group are displayed in Figure S3.

Figure 7

Protein levels of glucose transporter 4 (GLUT4) in the inguinal white adipose tissue of 7-month-old offspring from controls (CON) and calorie-restricted (CR) dams during gestation, treated with either vehicle (V) or myo-inositol (MI) during the lactation period. Data are mean ± SEM, expressed as the percentage for the CON-V animals for each sex. Statistics: Two-way ANOVA was used to assess the effects of calorie restriction (R) and/or myo-inositol supplementation (M). Student’s t-test was used for individual group comparisons: *, different from their corresponding vehicle-supplemented group; #, different compared to their corresponding control group. Representative bands from Western blot analysis of GLUT4 and reference proteins (β-Actin and/or HSP90) for each animal group are displayed in Supplementary Figure S3.