A metabolomic and pharmacokinetic study on the mechanism underlying the lipid-lowering effect of orally administered berberine

Abstract

Clinical and animal studies demonstrated that orally administered berberine had a distinct lipid-lowering effect. However, pharmacokinetic studies showed that berberine was poorly absorbed into the body so the levels of berberine in the blood and target tissues were far below the effective concentrations revealed. To probe the underlying mechanism, the effect of berberine on the biological system was studied on a high-fat-diet-induced hamster hyperlipidemia model. Our results showed that intragastrically-administered berberine was poorly absorbed into circulation and most berberine accumulated in gut content. Although the bioavailability of intragastrically administered berberine was much lower than that of intraperitoneally administered berberine, it had a stronger lipid-lowing effect, indicating that the gastrointestinal tract is a potential target for the hypolipidemic effect of berberine. A metabolomic study on both serum and gut content showed that orally administered berberine significantly regulated molecules involved in lipid metabolism, and increased the generation of bile acids in the hyperlipidemic model. DNA analysis revealed that the orally administered berberine modulated the gut microbiota, and berberine showed a significant inhibition of the 7α-dehydroxylation conversion of cholic acid to deoxycholic acid, indicating a decreased elimination of bile acids in the gut. However, in model hamsters, elevated bile acids failed to downregulate the expression and function of CYP7A1 in a negative feedback loop. It was suggested that the hypocholesterolemic effect of orally administered berberine involves modulating the turnover of bile acids and the farnesoid X receptor signal pathway.

Figure 1. Effect of berberine on serum lipid levels in hyperlipidemic hamsters

Total serum cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C) and low-density lipoprotein cholesterol (LDL-C) levels were determined after 2-week treatment of berberine (100 mg/kg/d, i.g.). C, Hamsters control; HF, Hamsters with high fatty diet; HFB, Hamsters with high fatty diet+BBR (100mg/kg, i.g.). Data are means ±SD (n = 5). Statistical significance relative to HF group, *p<0.05, * *P<0.01.

Figure 2. GC/TOF-MS analysis of the metabolites and cholic acid in serum from each group

C: Hamsters control; HF: high-fat diet group; HFB: HF treated with berberine. Values are mean ± SD (n = 5). Statistical significance was evaluated using one-way ANOVA.

Figure 3. The effect of berberine on metabolic pattern and synthesis of bile acids based on GC/MS analysis of the molecules in serum and gut content of hyperlipidemic hamsters treated with berberine

A, PLSDA plots based on serum data; B, PLSDA plots based on gut content data; C: OPLS S-plot between HF and HFB based on sera data; D, OPLS S-plot between HF and HFB based on data from gut content. C, treated with berberine; H, high-fat diet group; HB: HF treated with berberine.

Figure 4. The metabolic impact analysis based on GC/MS analysis of the molecules in serum and gut content of hyperlipidemic hamsters treated with berberine

A, Metabolic pathway analysis based on molecules in serum; B, Metabolic pathway analysis based on molecules in gut content ; C, Metabolite pathway enrichment based on serum metabolites; D, Metabolite pathway enrichment based on molecules in gut content.

Figure 5. Effect of berberine on CYP7A1 and CYP27A1 mRNA and protein levels

A, Effect of berberine on CYP7A1 mRNA expression in hamster liver(p>0.05). B, Effect of berberine on CYP27A1 mRNA expression in hamster liver(p>0.05). C, Real-time quantitative PCR analysis of CYP7A1 in HepG2 cells after 24 h of treatment with berberine (0 to 1 μg/mL). D, Real-time quantitative PCR analysis of CYP27A1 in HepG2 cells after 24 h of treatment with berberine (0 to 1 μg/mL). E, Western blot anslysis of CYP7A1 and CYP27A1 in HepG2 cells after 24 h of treatment with berberine (0 to 1 μg/mL). Levels of CYP7A1 and CYP27A1 RNA were normalized to those of β-actin in each sample.

Figure 6. Composition of gut microbiota in hamster gut content

A: Bacterial phylogenetic tree of hamster gut based on 16S rRNA gene sequences; B: Composition of the gut microbiome of hamster cecum (n = 5). C: normal group; HF: high-fat diet group; HFB: HF treated with berberine. All numeric results are means ± SD of triplicates, representative of three independent experiments. * P<0.05, * *P<0.01, relative to their controls, respectively. BBR, berberine.

Figure 7. Effect of berberine on the metabolism of cholic acid

A, Effect of berberine on the cholic acid 7α-dehydroxylation in Clostridium scindens. The 7α-dehydroxylation activities of human Clostridium scindens were determined as described in “Methods”. DCA, deoxycholic, allodeoxycholic, 3-dehydro-deoxycholic acid, 3-dehydro-allodeoxycholic acid. B, Effect of berberine on the metabolism of cholic acid in gut contents from HFD hamsters and the controls after incubation for 12 h with or without berberine. The percent decrease of cholic acid after in vitro incubation with fresh gut content, relative to the sterilized controls. C, Effect of berberine on the metabolism of cholic acid in gut contents from hamsters treated with or without berberine. BBR, berberine; HF, the HFD hamsters; C, the controls; HF+BBR, HFD hamsters treated with BBR (100 mg/kg); C+BBR, the controls treated with berberine(100 mg/kg). Values are mean ± SD of three independent experiments and analyzed using one-way ANOVA,* P<0.05, * *P<0.01, relative to their controls, respectively.