Crocin-I Protects Against High-Fat Diet-Induced Obesity via Modulation of Gut Microbiota and Intestinal Inflammation in Mice

Abstract

Crocin-I can regulate physiological changes in the human body by altering inflammation and microbial composition. Gut microbiota are also involved in modulating the pathophysiology of obesity. However, crocin-I's effect on obesity and the mechanism underlying its effects on gut microbiota and inflammation remain poorly understood. Here, high-fat diet (HFD) -induced obese mice were administrated crocin-I (20 mg/kg/day) for 10 weeks using an oral gavage (HFD-C20 group). HFD-C20, HFD, and Normal chow (NC) groups were compared. The fat content, colon tissue inflammatory cytokine levels, gut microbiota, and short-chain fatty acids (SCFAs) levels were measured. We show that crocin-I reduced body weight and liver weight and improved glucose resistance in HFD-induced mice, and reduced the lipid accumulation in the liver. Strikingly, crocin-I alleviated intestinal microbial disorders and decreased the F/B ratio and the abundance of Proteobacteria in HFD-induced obese mice. Crocin-I also rescued the decrease in the levels of SCFAs and repaired altered intestinal barrier functioning and intestinal inflammation in HFD-induced obese mice. These findings indicate that crocin-I may inhibit obesity by modulating the composition of gut microbiota and intestinal inflammation.

Keywords: crocin-i; gut microbiota; inflammation; lipid metabolism; obesity.

FIGURE 1

Crocin-I alleviates growth phenotypes and biochemical index of HFD-induced obese mice. (A) Body weight; (B) food intake; (C) liver weight; (D) the ratio of liver/weight, (E) the ratio of kidney/weight, and (F) the ratio of epididymal fat/weight (n = 8); (G) lipid accumulation in WAT revealed by H&E staining. (H–J) The transcription levels of genes related to fatty acid synthesis in WAT. (K) Blood glucose value and (L) Area under the curve (AUC). n = 8 per group. Values represent mean ± SEM. *p < 0.05 and **p < 0.01, compared with control group; ^# p < 0.05 and ^## p < 0.01, compared with HFD group.

FIGURE 2

Crocin-I alleviates lipid accumulation in the liver induced by high-fat diet. (A) Lipid accumulation in liver tissue revealed by Oil Red O staining. (B) Levels of TG in the liver. (C) Levels of TC in the liver. (D) H&E staining of liver tissue. (E) mRNA expression of genes related to fatty acid synthesis. n = 8 per group. Values represent mean ± SEM. *p < 0.05 and **p < 0.01, compared with control group; ^# p < 0.05 compared with HFD group.

FIGURE 3

Crocin-I inhibited the low-grade inflammation and improved the intestinal barrier function in HFD mice. (A) H&E staining of the colon tissue. (B) The relative mRNA expression of inflammatory cytokines and (C) Tight junction proteins and mucin secretion in the colon tissue (n = 8). (D) The relative protein expression of. junction proteins and mucin secretion in the colon tissue (n = 3). (E) AB-PAS staining of the colon tissue. Values represent mean ± SEM. *p < 0.05 and **p < 0.01, compared with control group; ^# p < 0.05 and ^## p < 0.01, compared with HFD group.

FIGURE 4

Crocin-I altered the gut microbiota composition of HFD mice. Alpha-diversity (A) Shannon index and (B) Simpson index (n = 5). (C) The PCoA score plot of the metabolic profiling from the different groups. The green dots represent the control group, the blue dots represent the HFD group, and the purple dots represent the HFD-C20 group (n = 5). (D) Venn diagrams showing the numbers of unique and shared OTUs in the different groups. The numbers shown where circles overlap are the number of OTUs shared by groups. The numbers adjacent to the numbers of shared OTUs indicate the number of unique OTUs. (E) Ratio of Firmicutes/Bacteroidetes which is F/B. (F) Relative abundances of the cecal microbiota at the phylum level. (G) Community structure differences and cluster analysis heat map. (H) Abundances of KEGG pathways in the functional prediction between NC and HFD. (I) Abundances of KEGG pathways in the functional prediction between HFD and HFD-C20. Values represent mean ± SEM. *p < 0.05 and **p < 0.01, compared with control group; ^# p < 0.05 and ^## p < 0.01, compared with HFD group.

FIGURE 5

Crocin-I improved the SCFAs level in the feces of HFD mice. (A) Total SCFAs, (B) isobutyrate, (C) acetate, (D) butyrate, (E) isovalerate, (F) caproate, (G) propionate, and (H) valerate. n = 4 each group. Values represent mean ± SEM. *p < 0.05 and **p < 0.01, compared with control group; ^# p < 0.05 and ^## p < 0.01, compared with HFD group.