Composition of dietary fat source shapes gut microbiota architecture and alters host inflammatory mediators in mouse adipose tissue

Abstract

Background: Growing evidence shows that dietary factors can dramatically alter the gut microbiome in ways that contribute to metabolic disturbance and progression of obesity. In this regard, mesenteric adipose tissue has been implicated in mediating these processes through the elaboration of proinflammatory adipokines. In this study, we examined the relationship of these events by determining the effects of dietary fat content and source on gut microbiota, as well as the effects on adipokine profiles of mesenteric and peripheral adipocytes.

Methods: Adult male C57Bl/6 mice were fed milk fat-based, lard-based (saturated fatty acid sources), or safflower oil (polyunsaturated fatty acid)-based high-fat diets for 4 weeks. Body mass and food consumption were measured. Stool 16S ribosomal RNA (rRNA) was isolated and analyzed via terminal restriction fragment length polymorphism as well as variable V3-4 sequence tags via next-generation sequencing. Mesenteric and gonadal adipose samples were analyzed for both lipogenic and inflammatory mediators via quantitative real-time polymerase chain reaction.

Results: High-fat feedings caused more weight gain with concomitant increases in caloric consumption relative to low-fat diets. In addition, each of the high-fat diets induced dramatic and specific 16S rRNA phylogenic profiles that were associated with different inflammatory and lipogenic mediator profiles of mesenteric and gonadal fat depots.

Conclusions: Our findings support the notion that dietary fat composition can both reshape the gut microbiota and alter host adipose tissue inflammatory/lipogenic profiles. They also demonstrate the interdependency of dietary fat source, commensal gut microbiota, and inflammatory profile of mesenteric fat that can collectively affect the host metabolic state.

Keywords: fatty acids; lipids; nutrition; obesity.

Figure 1

Body weight and food consumption data. Values are means ± SEM (n = 3-4 per diet). Mice were fed either a high-fat (Milk-fat, Lard, or PUFA) or low-fat diet for four weeks. HF: High-fat. LF: Low-fat. PUFA: Polyunsaturated Fatty Acid, in the form of safflower oil.

Figure 1

Body weight and food consumption data. Values are means ± SEM (n = 3-4 per diet). Mice were fed either a high-fat (Milk-fat, Lard, or PUFA) or low-fat diet for four weeks. HF: High-fat. LF: Low-fat. PUFA: Polyunsaturated Fatty Acid, in the form of safflower oil.

Figure 2

Histological H&E stain of gonadal adipose tissue from mice fed high- or low-fat diet. Gonadal depots were excised, fixed in 4% formalin/PBS, and paraffin embedded. 5-micron sections were processed and are representative of n=3-4 per diet. Adipocyte areas were calculated using ImageJ software (described in Methods) quantifying 12 representative adipose cells in each section per diet group. No statistically significant difference was observed between mean adipocyte areas between each diet group (P>0.05).

Figure 2

Histological H&E stain of gonadal adipose tissue from mice fed high- or low-fat diet. Gonadal depots were excised, fixed in 4% formalin/PBS, and paraffin embedded. 5-micron sections were processed and are representative of n=3-4 per diet. Adipocyte areas were calculated using ImageJ software (described in Methods) quantifying 12 representative adipose cells in each section per diet group. No statistically significant difference was observed between mean adipocyte areas between each diet group (P>0.05).

Figure 3

Immunofluorescent stain of macrophage infiltration in gonadal adipose tissue. 5-micron sections were stained with immunofluorescent Mac2 antibody. Sections shown are representative of images taken from 3-4 biological replicates per group. Fluorescent intensity was quantified using ImageJ as described earlier. ***P < 0.001 vs. all dietary treatment groups.

Figure 3

Immunofluorescent stain of macrophage infiltration in gonadal adipose tissue. 5-micron sections were stained with immunofluorescent Mac2 antibody. Sections shown are representative of images taken from 3-4 biological replicates per group. Fluorescent intensity was quantified using ImageJ as described earlier. ***P < 0.001 vs. all dietary treatment groups.

Figure 4

Principle Component Analysis (PCA) plot of T-RFLP sets based on fecal microbiota before (initial, open shapes) and after (terminal, closed shapes) high- or low-fat diet.

Figure 5

Effects of diet on the gut microbial architecture. Relative abundances of different phyla in each respective diet group are shown.