Suppressed intestinal secondary bile acids in moxifloxacin-induced hyperglycemia: studies in normal and diabetic GK rats

Abstract

Objective: Moxifloxacin (MFLX) frequently induces dysglycemia when used in the treatment of infectious diseases, particularly in patients with diabetes. However, the mechanism through which MFLX affects host glucose metabolism remains unclear. This study aimed to investigate the possible mechanism underlying MFLX-induced hyperglycemia.

Methods: In this study, we investigated the short-term (3 days) and long-term (14 days) effects of MFLX on glucose metabolism in normal and type 2 diabetic GK rats. After oral administration of 40 mg/kg of MFLX, blood glucose, insulin, GLP-1, and fibroblast growth factor 15 (FGF15) levels in the blood of rats, as well as bile acids in both blood and feces, and gut microbiota, were examined. Liver and ileum tissues were promptly harvested for detecting the expression of hepatic 7α-hydroxylase (CYP7A1) and intestinal Takeda G-protein-coupled receptor 5 (TGR5) and farnesoid X receptor (FXR). In addition, we explored the effect of secondary bile acids (SBAs) on GLP-1 secretion in NCI-H716 cells, and observed the direct effect of MFLX on the expression of CYP7A1 in HepG2 cells and TGR5, FXR in NCI-H716 cells.

Results: It was demonstrated that MFLX induced hyperglycemia in diabetic rats, with a more pronounced reduction in serum insulin, GLP-1, and FGF15 levels than observed in normal rats. Gut microbiota associated with SBAs metabolism were significantly reduced, leading to decreased intestinal deoxycholic acid (DCA) and lithocholic acid (LCA). In vitro studies revealed that DCA and LCA (25 μM, 50 μM, and 100 μM) promoted GLP-1 secretion in a concentration-dependent manner in NCI-H716 cells. Meanwhile, we observed that the expression of intestinal TGR5 and FXR significantly downregulated, whereas CYP7A1 expression in liver was increased in GK rats after MFLX treatment. MFLX itself (0.1 μM, 1 μM, and 10 μM) did not directly altered TGR5 or FXR expressions in NCI-H716 cells, nor did it alter CYP7A1 expression in HepG2 cells, which indicated that the impact of MFLX on glucose metabolism was primarily induced by changes in bile acids metabolism resulting from alterations in the gut microbiota.

Conclusion: Our studies showed MFLX more likely to cause hyperglycemia when used in diabetic states and highlighted the critical role of gut microbiota-SBAs-TGR5/FXR pathway in MFLX-induced hyperglycemia.

Keywords: GLP-1; bile acid; gut microbiota; hyperglycemia; moxifloxacin.

FIGURE 1

The effect of MFLX on blood glucose, insulin, GLP-1 and FGF15 levels in normal and GK rats. (A, B) The body weight of rats after MFLX treatment for 3 days (A) and 14 days (B); (C, D) Changes in blood glucose, insulin, GLP-1, and FGF15 levels following MFLX administration for 3 days (C) and 14 days (D); (E, F) Oral glucose tolerance test (OGTT) results (E) and glucose-induced insulin levels (F) after 3 days of administration; (G, H) OGTT (G) and glucose-induced insulin levels (H) after 14 days of MFLX administration. Data represent n = 5 per group. Statistical significance was determined using a two-tailed Student’s t-test, with *p < 0.05 and **p < 0.01. All data are presented as the mean ± SD.

FIGURE 2

Dynamic change of BAs profile in serum and feces after MFLX treatment for 3 days. (A, B) Heatmaps showing 19 BAs in serum (A) and feces (B) after 3 days of MFLX treatment; (C, D) PBAs and SBAs in serum (C) and feces (D) following 3 days of MFLX treatment. Data are expressed as mean ± SD (n = 5). *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.

FIGURE 3

Dynamic change of BAs profile in serum and feces after MFLX treatment for 14 days. (A, B) Heatmaps showing 19 BAs in serum (A) and feces (B) after 14 days of MFLX treatment; (C, D) Levels of PBAs and SBAs in serum (C) and feces (D) after 14 days of MFLX treatment. Data are expressed as mean ± SD (n = 5). *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.

FIGURE 4

Alterations in intestinal unconjugated PBAs and SBAs levels. (A, B) Levels of CA and CDCA, DCA and LCA in feces after 3 days (A) and 14 days (B) of MFLX treatment; (C, D) Concentrations of DCA and LCA in feces after 3 days (C) and 14 days (D) of MFLX administration; (E, F) Levels of GLP-1 after 2-h incubation with DCA (E) and LCA (F) in NCI-H716 cells. All p-values were calculated using a two-tailed Student’s t-test, *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001. Data are presented as the mean ± SD.

FIGURE 5

MFLX-induced changes in gut microbiota. (A, B) Absolute abundance of the phylum Firmicute and Bacteroidetes in the intestine after 3 days (A) and 14 days (B) of MFLX treatment; (C, D) Correlation between fecal SBAs levels and bacterial genera identified from linear regression analysis. Legends indicate relative abundances and correlation values. Respectively. Data are presented as the mean ± SD, *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001.

FIGURE 6

Effect of MFLX on ileum FXR and TGR5. (A, B) Relative expression of TGR5 and FXR proteins in the ileum of rats after 3 days (A) and 14 days (B) of MFLX treatment; (C, D) Relative expression of TGR5 and FXR mRNAs in the ileum of rats after 3 days (C) and 14 days (D) of MFLX treatment; (E, F) Relative expression of TGR5 and FXR proteins (E) and mRNAs (F) in NCI-H716 cells following 24 h of MFLX treatment.

FIGURE 7

Effect of MFLX on hepatic metabolic enzymes. (A, B) Relative expression of CYP7A1, CYP8B1 and CYP27A1 in the liver of rats following 3 days (A) and 14 days (B) of MFLX treatment; (C) Relative expression of CYP7A1 proteins in HepG2 cells after 24 h of MFLX treatment.

FIGURE 8

The mechanism of moxifloxacin-induced hyperglycemia in this study.