Photoperiod effects on corticosterone and seasonal clocks in cafeteria-induced obese fischer 344 rats are influenced by gut microbiota

Abstract

Seasonal rhythms are gaining attention given their impact on metabolic disorders development such as obesity gut microbiota is emerging as a key factor in mediating this link. However, the underlying mechanisms are still poorly understood. In this regard, corticosterone may play a role as it has been shown to be affected by gut bacteria and seasonal rhythms, and has been linked to obesity. Thus, this study aimed to investigate if seasonal rhythms effects on corticosterone are influenced by gut microbiota in obese rats and whether this may be related to seasonal and clock genes expression in the pituitary gland and colon. Fischer 344 male rats fed with cafeteria diet (CAF) were housed under different photoperiods for 9 weeks and treated with an antibiotic cocktail (ABX) in drinking water during the last 4 weeks. Rats fed with standard chow and CAF-fed rats without ABX were included as controls. ABX altered gut microbiota, corticosterone levels and seasonal clock expression in the pituitary depending on photoperiod conditions. These results suggest a link between gut bacteria, seasonal rhythms and corticosterone and a novel nutrigenomic target for obesity.

Keywords: Chga; Eya3; Antibiotic; Seasonal rhythms; Western diet.

Fig. 1

CAF, ABX and photoperiod effects on fecal microbiota composition. (a–c) α-diversity index calculate by observed operational taxonomic unit (a); abundance-based coverage estimators (ACE) (b); and Fisher (c); * and # indicate diet and ABX effect respectively analyzed by U-Mann Whitney test (*p < 0.05; **p ≤ 0.01; ***p ≤ 0.001; ##p ≤ 0.001); ab letters indicate photoperiod effect, analyzed by Kruskal–Wallis test followed by Bonferroni correction for multiple comparisons (p < 0.016) (d): β-diversity based on Bray–Curtis distances and visualized by a non-metric multidimensional scaling (NMDS)2D plot (PERMANOVA, p < 0.001); (e): Stacked bar plots showing the relative abundance of each taxa at phylum level; (f) Stacked bar plots showing the relative abundance of each taxa at genera level. Adapted from Arreaza-Gil et al..

Fig. 2

Corticosterone serum levels and GR expression in pituitary gland and colon. (a) Corticosterone serum levels in STD, CAF and CAF treated with ABX rats housed under three different photoperiods (L6, L12 and L18). (b) Relative GR expression (Nr3c1) in pituitary gland; (c) Relative gene expression of the GR (Nr3c1) in colon tissue; Data were analyzed by two-way ANOVA followed by pairwise comparison Sidak post hoc test: *indicates CAF effect (*p < 0.05; **p ≤ 0.01), #indicates ABX effect (#p < 0.05) and ab letters indicate photoperiod effect in each experimental group; Data are plotted as the mean ± SEM (n = 7–8). L6: 6 h light/18 h darkness, L12: 12 h light/12 h darkness, L18: 18 h light/6 h darkness, STD: standard chow diet, CAF: cafeteria diet, ABX: antibiotic cocktail (0.5 g/l ampicillin, 0.250 g/l vancomycin and 0.125 g/l imipenem). Nr3c1: nuclear receptor subfamily 3, group C, member 1.

Fig. 3

Seasonal genes expression in the pituitary gland. (a) Relative expression of Eya3 and (b) Chga in STD, CAF and CAF treated with ABX rats housed under different photoperiods (L6, L12 and L18). Data were analyzed by two-way ANOVA followed by pairwise comparison Sidak post hoc test: *indicates diet effect (***p ≤ 0.001) and ab letters indicate photoperiod effect. Data are plotted as the mean ± SEM (n = 7–8). L6: 6 h light/18 h darkness, L12: 12 h light/12 h darkness, L18: 18 h light/6 h darkness, STD: standard chow diet, CAF: cafeteria diet, ABX: antibiotic cocktail (0.5 g/l ampicillin, 0.250 g/l vancomycin and 0.125 g/l imipenem).

Fig. 4

Clock genes expression in pituitary gland. Data were analyzed by two-way ANOVA followed by pairwise comparison Sidak post hoc test: *indicates diet effect (***p ≤ 0.05), and ab letters indicate photoperiod effect in each photoperiod effect. Data are plotted as the mean ± SEM (n = 7–8). L6: 6 h light/18 h darkness, L12: 12 h light/12 h darkness, L18: 18 h light/6 h darkness, STD: standard chow diet; CAF: cafeteria diet, ABX: antibiotic cocktail.

Fig. 5

Clock genes expression in colon. Data were analyzed by two-way ANOVA followed by pairwise comparison Sidak post hoc test; *indicates diet effect (*p < 0.05), and ab letters indicate photoperiod effect in each experimental group; Data are plotted as the mean ± SEM (n = 7–8). L6: 6 h light/18 h darkness, L12: 12 h light/12 h darkness; L18: 18 h light/6 h darkness, STD: standard chow diet, CAF: cafeteria diet, ABX: antibiotic cocktail.

Fig. 6

Experimental design. 13-week-old male F344 rats were pair-housed under three different photoperiods (6, 12 or 18 h of light per day) for 9 weeks. In each photoperiod, rats were fed a STD or CAF diet. During the last 4 weeks, a group of CAF-fed rats were treated with an antibiotic cocktail (ABX) in drinking water (ampicillin: 0.5 g/l, vancomycin: 0.25 g/l, imipenem: 0.125 g/l). All rats were sacrificed at the same time point (3 h after the light was turned on, i.e., ZT3). F344: fischer 344 rats, OGTT: oral glucose tolerance test, L6: 6 h light/18 h darkness, L12: 12 h light/12 h darkness, L18: 18 h light/6 h darkness, STD: standard chow diet, CAF: cafeteria diet.