Gut microbiota are linked to increased susceptibility to hepatic steatosis in low-aerobic-capacity rats fed an acute high-fat diet

Abstract

Poor aerobic fitness is linked to nonalcoholic fatty liver disease and increased all-cause mortality. We previously found that rats with a low capacity for running (LCR) that were fed an acute high-fat diet (HFD; 45% kcal from fat) for 3 days resulted in positive energy balance and increased hepatic steatosis compared with rats that were highly aerobically fit with a high capacity for running (HCR). Here, we tested the hypothesis that poor physiological outcomes in LCR rats following acute HFD feeding are associated with alterations in cecal microbiota. LCR rats exhibited greater body weight, feeding efficiency, 3 days of body weight change, and liver triglycerides after acute HFD feeding compared with HCR rats. Furthermore, compared with HCR rats, LCR rats exhibited reduced expression of intestinal tight junction proteins. Cecal bacterial 16S rDNA revealed that LCR rats had reduced cecal Proteobacteria compared with HCR rats. Microbiota of HCR rats consisted of greater relative abundance of Desulfovibrionaceae and unassigned genera within this family, suggesting increased reduction of endogenous mucins and proteins. Although feeding rats an acute HFD led to reduced Firmicutes in both strains, short-chain fatty acid-producing Phascolarctobacterium was reduced in LCR rats. In addition, Ruminococcae and Ruminococcus were negatively correlated with energy intake in the LCR/HFD rats. Predicted metagenomic function suggested that LCR rats had a greater capacity to metabolize carbohydrate and energy compared with HCR rats. Overall, these data suggest that the populations and metabolic capacity of the microbiota in low-aerobically fit LCR rats may contribute to their susceptibility to acute HFD-induced hepatic steatosis and poor physiologic outcomes.

Keywords: NAFLD; aerobic fitness; microbiota; short-chain fatty acids.

Fig. 1.

Three-day (d) energy intake (A), 3-day body weight (BW) change (B), feeding efficiency (3-day weight gain/energy intake) (C), and final BW (D) in rats with low capacity for running (LCR) and high capacity for running (HCR) in response to being fed an acute, high-fat diet (HFD). Values are expressed as means ± SE. *Significant (P < 0.05) diet effect. †Significant (P < 0.05) strain effect. Means with different letters denote significant (P < 0.05) differences between treatments.

Fig. 2.

Liver triglycerides (TGs) (A), gene expression of IL-1β (B), Toll-like receptor-4 (TLR-4) (C), and free fatty acid receptor 2 (FFAR2) (D) in LCR and HCR rats in response to an acute HFD. Values are expressed as means ± SE. Means with different letters denote significant (P < 0.05) differences between treatments.

Fig. 3.

Markers of de novo lipogenesis, fatty acid transport, and mitochondrial biogenesis and content in LCR and HCR rats fed an acute HFD. Hepatic mRNA expression of sterol regulatory element-binding transcription factor 1 (SREBF1) (A), hepatic protein content of acetyl-coenzyme A carboxylase (ACC) (B), ACC Ser79 phosphorylation-specific (P-ACC) (C), ACC:P-ACC (D), fatty acid synthase (FAS) (E), CD36/fatty acid translocase (CD36) (F), peroxisome proliferator-activated receptor-α (PPARα) (G), peroxisome proliferator-activated receptor-gamma coactivator-1α (PGC-1α) (H), and cytochrome-c oxygenase 4 subunit 1 (COX4 subunit 1) (I) in LCR and HCR rats in response to an acute HFD. J: representative Western blots. Values are expressed as means ± SE. *Significant (P < 0.05) diet effect.

Fig. 4.

Beta diversity of cecal microbiota populations in LCR and HCR rats by plotted unweighted Unifrac distances as a principal coordinates analysis (PCoA) plot. Cecal microbiota of LCR rats are more similar to each other than to HCR rats (P < 0.05). LCR/Control (CON) (small dark circles), LCR/HFD (large dark circles), HCR/CON (small open circles), and HCR/HFD (large open circles).

Fig. 5.

Cecal phylum distribution for the LCR/CON (A), LCR/HFD (B), HCR/CON (C), and HCR/HFD (D) treatments. *Significant (P < 0.05) diet effect. †Significant (P < 0.05) strain effect.

Fig. 6.

Small intestinal gene expression of zonula occludens-1 (ZO-1) (A) and ZO-2 (B), TLR-4 (C), IL-1β (D), and free fatty acid receptor 2 (FFAR2) (E) in LCR and HCR rats in response to an acute HFD. Values are presented as means ± SE. Means with different letters denote significant (P < 0.05) differences between treatments.

Fig. 7.

Pearson's correlations in all rats between the Bacteroidetes to Firmicutes ratio and energy intake (A) and 3-day BW change (B); Ruminococcaceae and energy intake (C) and 3-day BW change (D); Ruminococcus and energy intake (E) and 3-day BW change (F); and the Bacteroidetes to Firmicutes ratio and liver TGs (G). Open circles, LCR/CON; closed circles, LCR/HFD, open squares, HCR/LFD; closed squares, HCR/HFD.

Fig. 8.

Pearson's correlations only in LCR/HFD between the Bacteroidetes to Firmicutes ratio and energy intake (A), the Bacteroidetes to Firmicutes ratio and 3-day BW change (B), Ruminococcaceae and energy intake (C), Ruminococcaceae and 3-day BW change (D), Ruminococcus and energy intake (E), and Ruminococcus and 3-day BW change (F). Closed circles, LCR/HFD; closed squares, HCR/HFD.

Fig. 9.

Pairwise comparisons by Welch's t-test of predicted metagenomic differences of microbiota between LCR/CON and HCR/CON (A), and LCR/CON and LCR/HFD (B). Values are presented as means ± SE. *Denotes a significant (P < 0.05) difference between treatment groups.