A High-Fat High-Sucrose Diet Rapidly Alters Muscle Integrity, Inflammation and Gut Microbiota in Male Rats

Abstract

The chronic low-level inflammation associated with obesity is known to deleteriously affect muscle composition. However, the manner in which obesity leads to muscle loss has not been explored in detail or in an integrated manner following a short-term metabolic challenge. In this paper, we evaluated the relationships between compromised muscle integrity, diet, systemic inflammatory mediators, adipose tissue, and gut microbiota in male Sprague-Dawley rats. We show that intramuscular fat, fibrosis, and the number of pro-inflammatory cells increased by 3-days and was sustained across 28-days of high-fat high-sugar feeding compared to control-diet animals. To understand systemic contributors to muscle damage, dynamic changes in gut microbiota and serum inflammatory markers were evaluated. Data from this study links metabolic challenge to persistent compromise in muscle integrity after just 3-days, a finding associated with altered gut microbiota and systemic inflammatory changes. These data contribute to our understanding of early consequences of metabolic challenge on multiple host systems, which are important to understand as obesity treatment options are developed. Therefore, intervention within this early period of metabolic challenge may be critical to mitigate these sustained alterations in muscle integrity.

Figure 1. Short-term high-fat high-sucrose metabolic challenge induces alterations in body composition and body mass.

(A) Body fat increases at 7-days on a high-fat high-sucrose (HFS) metabolic challenge, and is sustained over 28-days of feeding compared to chow-fed controls. (B) Body mass, however, doesn’t increase significantly until 14-days on HFS metabolic challenge compared to chow-fed control animals. Raw data are shown, *indicates p ≤ 0.05 compared to chow-fed controls.

Figure 2. Myosin heavy chain (MHC) distribution in vastus lateralis muscles of chow-fed control rats and rats fed a high-fat high-sucrose diet for 28-days.

Figure 3. Histological assessments of VL muscle demonstrate rapid changes in muscle integrity with short-term high-fat high-sucrose metabolic challenge.

(A) Oil Red O Stainining for intramuscular lipid in vastus lateralis (VL) muscle sections taken at 100x magnification. (B) Raw average values for Oil Red O Staining for each animal, where 20–50 images were evaluated for a mid-belly cross-section. By 3-days of HFS feeding, animals demonstrated increased and sustained intramuscular lipid staining compared to chow-fed control animals. *indicates p ≤ 0.05 compared to chow-fed controls. (C) Picrosirius red staining for collagen in VL muscle sections, imaged at 100x magnification.(D) Raw average values for Picrosirius red staining for each animal, where 20–50 images were evaluated for a mid-belly cross-section. By 3-days of HFS feeding, animals demonstrated increased and sustained collagen staining compared to chow-fed control animals. *indicates p ≤ 0.05 compared to chow-fed controls. (E) Immunohistochemistry staining for CD68+ cells in VL muscle sections, imaged at 200x magnification.(D) Raw average values for CD68+ staining for each animal, where 8–10 images were randomly selected and evaluated for a given mid-belly cross-section. By 3-days of HFS feeding, animals demonstrated increased and sustained CD68+ staining compared to chow-fed control animals. *indicates p ≤ 0.05 compared to chow-fed controls.

Figure 4. Fluctuations in serum inflammatory mediators with high-fat high-sucrose metabolic challenge suggest dynamic systemic perturbations and restoration of homeostasis.

(A) Serum TNF-α was increased at 3-days in HFS animals, and then transiently increased again at 14-days on HFS compared to chow-fed control animals. (B) Serum leptin demonstrated a trend toward increases at 3-days, and 28-days compared to chow-fed controls. (C) IL-6 was increased at 3-days, 7-days, and 28-days in HFS animals compared to chow-fed control animals. (D) MCP-1 was increased at 14-days on HFS compared to chow-fed controls. ^‡indicates p < 0.10 vs chow-fed control; *indicates p ≤ 0.05; data are demonstrated as fold-change compared to chow-fed control and shown as mean ± SE.

Figure 5. Dynamic alterations in the relative abundance of gut microbial profiles were observed with short term high-fat high-sucrose metabolic challenge.

*indicates p ≤ 0.05 compared to chow-fed control diet animals, data are shown as mean ± SE.

Figure 6. Principal component analysis of the gut microbial relative abundance data reveals tighter clustering of samples with prolonged exposure to high-fat high-sucrose diet.

Results are plotted according to the first two principle components, which explain 50.6% (PC1) and 19.2% (PC2) of the variation in gut microbial composition between samples. The clustering of samples within each group is represented by their respective 95% confidence interval ellipse.