Berberine attenuates fructose-induced insulin resistance by stimulating the hepatic LKB1/AMPK/PGC1α pathway in mice

Abstract

Context: Berberine is an alkaloid that possesses various pharmacologic effects.Objective: To explore the mechanism of berberine to improve insulin sensitivity in fructose-fed mice.Materials and methods: Sixty male ICR mice were randomly divided into 6 groups (10 mice in each group): control, fructose, pioglitazone (10 mg/kg) and berberine (50, 100, and 200 mg/kg). Except for the control group, the mice received 20% fructose drinking for 10 weeks. Pioglitazone and berberine were orally administered once daily during the last 4 weeks. The insulin sensitivity was evaluated using an oral glucose tolerance test (OGTT). The serum levels of fasting glucose and insulin, blood lipids, and hormones were determined. The hepatic AMP and ATP contents were detected using high performance liquid chromatography (HPLC) analysis, and the protein expression was examined by immunoblotting.Results: Berberine significantly reversed the insulin resistance induced by fructose, including lowering fasting insulin levels (from 113.9 to 67.4) and area under the curve (AUC) during OGTT (from 1310 to 1073), decreasing serum leptin (from 0.28 to 0.13) and increasing serum adiponectin levels (from 1.50 to 2.80). Moreover, berberine enhanced the phosphorylation levels of protein kinase B (PKB/AKT; 2.27-fold) and glycogen synthase kinase-3β (GSK3β; 2.56-fold), and increased hepatic glycogen content (from 0.19 to 1.65). Furthermore, berberine upregulated the protein expression of peroxisome proliferator activated receptor gamma coactivator 1α (PGC1α; 2.61-fold), phospho-AMP-activated protein kinase (p-AMPK; 1.35-fold) and phospho-liver kinase B1 (p-LKB1; 1.41-fold), whereas it decreased the AMP/ATP ratio (from 4.25 to 1.82).Conclusion: The present study demonstrated the protective effects of berberine against insulin resistance induced by fructose. Our findings may provide an experimental basis for the application of berberine in the treatment of insulin resistance.

Keywords: Insulin sensitivity; alkaloid; metabolic homeostasis; signalling pathway.

Figure 1.

Effects of berberine on body weight, food intake, abdominal fat and liver organ index in fructose-fed mice. (A) Body weight; (B) food intake; (C) liver index; (D) abdominal fat index. Data were expressed as the mean ± S.E.M. (n = 10). #p < 0.05, ##p < 0.01 vs. control group. *p < 0.05, **p < 0.01, ***p < 0.001 vs. fructose group.

Figure 2.

Effects of berberine on insulin resistance in fructose-fed mice. (A) OGTT; (B) AUCOGTT; (C) fasting serum insulin; (D) fasting serum glucose. Data were expressed as the mean ± S.E.M. (n = 10). #p < 0.05, ##p < 0.01 vs. control group. *p < 0.05, **p < 0.01 vs. fructose group.

Figure 3.

The effects of berberine on hepatic TG and glycogen content in fructose-fed mice. (A) Hepatic TG content; (B) hepatic glycogen content; (C) the protein expression of PGC1? in liver; (D) The protein expression of GSK? in liver; (E) the protein expression of AKT in liver; (F) the immunoblot bands. Data were expressed as the mean ± S.E.M. (n = 10 for TG and glycogen; n = 6 for WB). #p < 0.05, ##p < 0.01 vs. control group. *p < 0.05, **p < 0.01, ***p < 0.001 vs. fructose group.

Figure 4.

The effects of berberine on hepatic AMPK signalling in fructose-fed mice. (A) The protein expression of AMPK; (B) the protein expression of CaMKKβ; (C) the protein expression of LKB1; (D) the immunoblot bands. Data were expressed as the mean ± S.E.M. (n = 6). #p < 0.05 vs. control group. *p < 0.05 vs. fructose group.

Figure 5.

The effects of berberine on hepatic AMP/ATP ratio in fructose-fed mice. Data were expressed as the mean ± S.E.M. (n = 10). #p < 0.05 vs. control group. *p < 0.05, **p < 0.01, ***p < 0.001 vs. fructose group.