Post-weaning diet affects faecal microbial composition but not selected adipose gene expression in the cat (Felis catus)

Abstract

The effects of pre- (i.e., gestation and during lactation) and post-weaning diet on the composition of faecal bacterial communities and adipose expression of key genes in the glucose and insulin pathways were investigated in the cat. Queens were maintained on a moderate protein:fat:carbohydrate kibbled ("Diet A"; 35:20:28% DM; n = 4) or high protein:fat:carbohydrate canned ("Diet B"; 45:37:2% DM; n = 3) diet throughout pregnancy and lactation. Offspring were weaned onto these diets in a nested design (n = 5 per treatment). Faecal samples were collected at wk 8 and 17 of age. DNA was isolated from faeces and bacterial 16S rRNA gene amplicons were analysed by pyrosequencing. RNA was extracted from blood (wk 18) and adipose tissue and ovarian/testicular tissues (wk 24) and gene expression levels determined using RT-qPCR. Differences (P<0.05) in composition of faecal bacteria were observed between pregnant queens fed Diet A or B. However, pre-weaning diet had little effect on faecal bacterial composition in weaned kittens. In contrast, post-weaning diet altered bacterial population profiles in the kittens. Increased (P<0.05) abundance of Firmicutes (77% vs 52% of total reads) and Actinobacteria (0.8% vs 0.2% of total reads), and decreased (P<0.05) abundance of Fusobacteria (1.6% vs 18.4% of total reads) were observed for kittens fed the Diet A compared to those fed Diet B post-weaning. Feeding Diet B pre-weaning increased (P<0.05) the expression levels of INRS, LEPT, PAI-1 and tended to increase GLUT1, while the expression levels of IRS-1 in blood increased in kittens fed Diet A pre-weaning. Post-weaning diet had no effect on expression levels of target genes. Correlations between the expression levels of genes involved in glucose and insulin pathways and faecal Bacteriodetes and Firmicutes phyla were identified. The reasons for why post-weaning diet affects microbial populations and not gene expression levels are of interest.

Figure 1. The effects of Diet A or Diet B on growth rates of kittens.

Data are reported as means ± SEM.

Figure 2. The effects of Diet A or Diet B on faecal microbial diversity in pregnant queens (Felis catus).

The rarefaction curves based on the Chao1 diversity index (at 97% sequence identity cut-off) indicate that faecal bacterial communities of cats fed Diet A (---; n =  3 cats) were less diverse than those of cats fed Diet B (–; n = 4 cats). Data are reported as means ± SEM.

Figure 3. The effects of pre- and post-weaning feeding of Diet A or Diet B on faecal microbial diversity in kittens (Felis catus).

The rarefaction curves based on the Chao1 diversity index (at 97% sequence identity cut-off) indicate that faecal bacterial communities of kittens fed Diet B (A-B and B-B; n = 10) were more diverse than those fed Diet A (A-A and B-A, n = 10). Pre-weaning diet did not have an effect on community diversity in the kitten. Data are reported as means ± SEM.

Figure 4. Principal Coordinate Analysis plot of weighted Unifrac phylogenetic distances showing the similarities between bacterial communities of queens fed Diet A or Diet B and their offspring fed Diet A (B-A or A-A) or Diet B (B-B or A-B) post-weaning.

Percentage of variation captured by each component indicated on axes.

Figure 5. Principal Coordinate Analysis plot of unweighted Unifrac phylogenetic distances showing the similarities between bacterial communities of queens fed Diet A or Diet B and their offspring fed Diet A (B-A or A-A) or Diet B (B-B or A-B) post-weaning.

Percentage of variation captured by each component indicated on axes.

Figure 6. Correlation heatmaps of faecal microbiota and gene expression in (A) blood, (B) adipose fat tissue, and (C) reproductive tissue.

Cell colour indicates strength and direction of correlation, with blue representing maximal negative correlation and red representing maximal positive correlation.