The present study aimed to evaluate the effects of paeoniflorin on insulin resistance and hepatic steatosis induced by fructose. Male Sprague-Dawley rats were fed 20% fructose drink for eight weeks. The insulin sensitivity, serum lipid profiles, and hepatic lipids contents were measured. The results showed that paeoniflorin significantly decreased serum insulin and glucagon levels, improved insulin sensitivity and serum lipids profiles, and alleviated hepatic steatosis in fructose-fed rats. Moreover, paeoniflorin enhanced the phosphorylation level of AMP-activated protein kinase (AMPK) and protein kinase B (PKB/AKT) and inhibited the phosphorylation of acetyl coenzyme A carboxylase (ACC)1 in liver. Paeoniflorin also increased the hepatic carnitine palmitoyltransferase (CPT)-1 mRNA and protein expression and decreased the mRNA expression of sterol regulatory element-binding protein (SREBP)1c, stearyl coenzyme A decarboxylase (SCD)-1 and fatty acid synthetase (FAS). Furthermore, we found that paeoniflorin significantly increased the heptatic protein expression of tumor suppressor serine/threonine kinase (LKB)1 but not Ca²⁺/CaM-dependent protein kinase kinase (CaMKK)β. These results suggest that the protective effects of paeoniflorin might be involved in the activation of LKB1/AMPK and insulin signaling, which resulted in the inhibition of lipogenesis, as well as the activation of β-oxidation and glycogenesis, thus ameliorated the insulin resistance and hepatic steatosis. The present study may provide evidence for the beneficial effects of paeoniflorin in the treatment of insulin resistance and non-alcoholic fatty liver.

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.

In traditional Chinese medicine, the role of the liver in depression is highly valued, and liver-relieving drugs, such as Sinisan, are often used to treat depression; however, the mechanism whereby these drugs work remains unclear. The present study aimed to reveal possible antidepressant mechanisms of Sinisan (SNS) by analyzing hepatic proteomics in chronic unpredictable mild stress (CUMS) mice. Using the CUMS mouse model of depression, the antidepressant effects of SNS were assessed by the sucrose preference test (SPT) and forced swimming test (FST). Hepatic differentially expressed proteins (DEPs) after SNS treatment were investigated by tandem mass tag (TMT) based quantitative proteomics analysis. Then, a bioinformatics analysis of DEPs was conducted through hierarchical clustering, Venn analysis, Gene Ontology (GO) annotation enrichment, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment. DEP genes were further validated by quantitative real-time polymerase chain reaction (qRT-PCR) analysis and western blotting. Behavioral results demonstrated that SNS significantly increased sucrose intake in SPT and shortened the immobility time in FST in model mice. Eighty-two DEPs were identified, including 37 upregulated and 45 downregulated proteins, between model and SNS groups. Enrichment analysis of GO annotations indicated that SNS primarily maintained cellular iron ion homeostasis by iron ion transportation and regulated expression of some extracellular structural proteins for oxidation-reduction processes. KEGG and Venn analysis showed that mineral absorption, steroid hormone biosynthesis and metabolism might be the principal pathways through which SNS acts on depression. Furthermore, several proteins involved in the biosynthesis and metabolism of steroid hormone pathways were significantly up/downregulated by SNS, including CYP2B19, CYP7B1 (validated by qRT-PCR) and HSD3b5 (validated by qRT-PCR and western blotting). Our results indicate that SNS plays important roles in antidepressant actions by restoring DEPs, resulting in the biosynthesis and metabolism of steroid hormones. The current results provide novel perspectives for revealing potential protein targets of SNS in depression.