Host genetic factors affecting the gut microbiome play an important role
in obesity, yet limited attention has been paid on the host genetic
factors linked to physical fitness in modifying the microbiome. This
study determined whether sibling-matched pairs of rats selectively bred
for high (HCR) and low (LCR) aerobic capacity differ in their microbiome
age-dependently and which taxa associate with differential in
metabolism. Several taxa in young adult rats (hereafter young) linked to
inherited aerobic capacity, while in older adult (hereafter old) rats
most of the differences between the lines associated with body weight.
Despite the absence of weight differential between LCR and HCR when
young, the LCR microbiome contained more Actinobacteria,
Veillonellaceae, Coriobacteriaceae, Phascolarctobacterium, and Ruminococcus;
taxa previously linked to obesity. This raises the question whether the
microbiome contributes to the later development of obesity in LCR.
Age-related differences were detected in almost all taxa in both rat
lines. The young HCR measured higher for serum glycerol and free
fatty-acids and lower for cholesterol, HDL, LDL, and triglycerides than
LCR. The old HCR differed from the old LCR by lower LDL. Several
metabolites, including LDL, are associated age and genetic
background-dependently with the microbiome, which might explain the
metabolic differences between the lines. While old lines did not differ
in visceral adipose tissue gene expression, the young HCR expressed more
inflammatory genes than LCR, and several taxa including Proteobacteria
associated with these genes. In conclusion, intrinsic aerobic capacity
governs the microbiome, which may influence body weight, metabolism, and
gene expression.