The protective effect of berberine on β-cell lipoapoptosis

Alkaloids as Promising Agents for the Management of Insulin Resistance: A Review

BACKGROUND

Insulin resistance is one of the main factors that lead to the development of type 2 diabetes mellitus (T2DM). The effect of alkaloids on insulin resistance has been extensively examined according to multiple scientific researches.

OBJECTIVE

In this work, we aimed to summarize the interesting results from preclinical and clinical studies that assessed the effects of natural alkaloids (berberine, nigelladine A, piperine, trigonelline, capsaicin, nuciferine, evodiamine, mahanine, and magnoflorine) on impaired insulin sensitivity and worsened insulin resistance, which play a pivotal role in the pathogenesis of type 2 diabetes.

METHODS

In the current review, PubMed, ScienceDirect, Springer, and Google Scholar databases were used. The inclusion criteria were based on the following keywords and phrases: insulin sensitivity, insulin resistance, alkaloids and insulin resistance, alkaloids and type 2 diabetes, mechanisms of action, and alkaloids.

RESULTS

The outcomes reported in this review demonstrated that the selected alkaloids increased insulin sensitivity and reduced insulin resistance in vitro and in vivo evidence, as well as in clinical trials, through improving insulin-signaling transduction mainly in hepatocytes, myocytes, and adipocytes, both at cellular and molecular levels. Insulin signaling components (InsR, IRS-1, PI3K, Akt, etc.), protein kinases and phosphatases, receptors, ion channels, cytokines, adipokines, and microRNAs, are influenced by alkaloids at transcriptional and translational levels, also in terms of function (activity and/or phosphorylation). Multiple perturbations associated with insulin resistance, such as ectopic lipid accumulation, inflammation, ER stress, oxidative stress, mitochondrial dysfunction, gut microbiota dysbiosis, and β-cell failure, are reversed after treatment with alkaloids. Furthermore, various indices and tests are employed to assess insulin resistance, including the Matsuda index, insulin sensitivity index (ISI), oral glucose tolerance test (OGTT), and insulin tolerance test (ITT), which are all enhanced by alkaloids. These improvements extend to fasting blood glucose, fasting insulin, and HbA1c levels as well. Additionally, the Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) and the Homeostasis Model Assessment of β-cell function (HOMA-β) are recognized as robust markers of insulin sensitivity and β-cell function, and it is noteworthy that alkaloids also lead to improvements in these two markers.

CONCLUSION

Based on the findings of the current review, alkaloids may serve as both preventive and curative agents for metabolic disorders, specifically type 2 diabetes. Nonetheless, there is an urgent need for additional clinical trials to explore the potential benefits of alkaloids in both healthy individuals and those with type 2 diabetes. Additionally, it is crucial to assess any possible side effects and interactions with antidiabetic drugs.

Berberine Potentiates Insulin Secretion and Prevents β-cell Dysfunction Through the miR-204/SIRT1 Signaling Pathway

Pancreatic β-cell dysfunction is a key link during the progression of type 2 diabetes (T2DM), and SIRT1 participates in the regulation of various physiological activities of islet β-cells. However, as a key link in signal transduction, it is not clear how SIRT1 is regulated. By TargetScan prediction, we found that miR-204, which is enriched in islets, has highly complementary binding sites with SIRT1. Therefore, we speculate that miR-204 may be the upstream regulatory target of SIRT1 in islets and thus participate in the occurrence of β-cell dysfunction. In this study, we explored the association between miR-204 and β-cell dysfunction, the therapeutic effects of berberine (BBR) on β-cell function and the possible mechanisms. We found that miR-204 increased and SIRT1 mRNA and protein levels decreased significantly in islets both in vivo and in vitro. MIN6 cells induced by palmitic acid exhibited increased apoptosis, and the accumulation of insulin and ATP in the supernatant decreased. Importantly, palmitic acid treatment combined with miR-204 silencing showed opposite changes. MiR-204 overexpression in MIN6 cells increased apoptosis and decreased insulin and ATP production and SIRT1 expression. SIRT1 overexpression reversed the damage to β-cells caused by miR-204. The BBR treatment effectively improved insulin synthesis, reduced miR-204 levels, and increased SIRT1 expression in islet tissue in diabetic mice. Overexpression of miR-204 reversed the protective effect of BBR on apoptosis and insulin secretion in MIN6 cells. Our study identifies a novel correlation between miR-204 and β-cell dysfunction in T2DM and shows that administration of BBR leads to remission of β-cell dysfunction by regulating the miR-204/SIRT1 pathway.

Berberine is an insulin secretagogue targeting the KCNH6 potassium channel

Coptis chinensis is an ancient Chinese herb treating diabetes in China for thousands of years. However, its underlying mechanism remains poorly understood. Here, we report the effects of its main active component, berberine (BBR), on stimulating insulin secretion. In mice with hyperglycemia induced by a high-fat diet, BBR significantly increases insulin secretion and reduced blood glucose levels. However, in mice with hyperglycemia induced by global or pancreatic islet β-cell-specific Kcnh6 knockout, BBR does not exert beneficial effects. BBR directly binds KCNH6 potassium channels, significantly accelerates channel closure, and subsequently reduces KCNH6 currents. Consequently, blocking KCNH6 currents prolongs high glucose-dependent cell membrane depolarization and increases insulin secretion. Finally, to assess the effect of BBR on insulin secretion in humans, a randomized, double-blind, placebo-controlled, two-period crossover, single-dose, phase 1 clinical trial (NCT03972215) including 15 healthy men receiving a 160-min hyperglycemic clamp experiment is performed. The pre-specified primary outcomes are assessment of the differences of serum insulin and C-peptide levels between BBR and placebo treatment groups during the hyperglycemic clamp study. BBR significantly promotes insulin secretion under hyperglycemic state comparing with placebo treatment, while does not affect basal insulin secretion in humans. All subjects tolerate BBR well, and we observe no side effects in the 14-day follow up period. In this study, we identify BBR as a glucose-dependent insulin secretagogue for treating diabetes without causing hypoglycemia that targets KCNH6 channels.

Berberine modulates deacetylation of PPARγ to promote adipose tissue remodeling and thermogenesis via AMPK/SIRT1 pathway

Pharmacological stimulation of adipose tissue remodeling and thermogenesis to increase energy expenditure is expected to be a viable therapeutic strategy for obesity. Berberine has been reported to have pharmacological activity in adipose tissue to anti-obesity, while the mechanism remains unclear. Here, we observed that berberine significantly reduced the body weight and insulin resistance of high-fat diet mice by promoting the distribution of brown adipose tissue and thermogenesis. We have further demonstrated that berberine activated energy metabolic sensing pathway AMPK/SIRT1 axis to increase the level of PPARγ deacetylation, which leads to promoting adipose tissue remodeling and increasing the expression of the thermogenic protein UCP-1. These findings suggest that berberine that enhances the AMPK/SIRT1 pathway can act as a selective PPARγ activator to promote adipose tissue remodeling and thermogenesis. This study proposes a new mechanism for the regulation of berberine in adipose tissue and offers a great prospect for berberine in obesity treatment

In silico network pharmacology and in vivo analysis of berberine-related mechanisms against type 2 diabetes mellitus and its complications

ETHNOPHARMACOLOGICAL RELEVANCE

Berberine (BBR), extracted from the traditional medicinal plant Coptis chinensis Franch., has been widely used for the treatment of type 2 diabetes mellitus (T2DM) and its complications.

AIM OF THE STUDY

To determine the potential pharmacological mechanisms underlying BBR therapeutic effect on T2DM and its complications by in silico network pharmacology and experimental in vivo validation.

MATERIALS AND METHODS

A predictive network depicting the relationship between BBR and T2DM was designed based on information collected from several databases, namely STITCH, CHEMBL, PharmMapper, TTD, Drugbank, and PharmGKB. Identified overlapping targets related to both BBR and T2DM were crossed with information on biological processes (BPs) and molecular/signaling pathways using the DAVID platform and Cytoscape software. Three candidate targets identified with the BBR-T2DM network (RXRA, KCNQ1 and NR3C1) were evaluated in the C57BL/6J mouse model of T2DM. The mice were treated with BBR or metformin for 10 weeks. Weight, fasting blood glucose (FBG), oral glucose tolerance, and expression levels of the three targets were evaluated.

RESULTS

A total of 31 targets of BBR that were also related to T2DM were identified, of which 14 had already been reported in previous studies. Furthermore, these 31 overlapping targets were enriched in 21 related BPs and 18 pathways involved in T2DM treatment. The identified BP-target-pathway network revealed the underlying mechanisms of BBR antidiabetic activity were mediated by core targets such as RXRA, KCNQ1, and NR3C1. In vivo experiments further confirmed that treatment with BBR significantly reduced weight and FBG and alleviated insulin resistance in T2DM mice. Moreover, BBR treatment promoted RXRA expression, whereas it reduced KCNQ1 and NR3C1 expression in the liver.

CONCLUSION

Using network pharmacology and a T2DM mouse model, this study revealed that BBR can effectively prevent T2DM symptoms through vital targets and multiple signaling pathways. Network pharmacology provides an efficient, time-saving approach for therapeutic research and the development of new drugs.

Berberine alleviates lipid metabolism disorders via inhibition of mitochondrial complex I in gut and liver

This study is to investigate the relationship between berberine (BBR) and mitochondrial complex I in lipid metabolism. BBR reversed high-fat diet-induced obesity, hepatic steatosis, hyperlipidemia and insulin resistance in mice. Fatty acid consumption, β-oxidation and lipogenesis were attenuated in liver after BBR treatment which may be through reduction in SCD1, FABP1, CD36 and CPT1A. BBR promoted fecal lipid excretion, which may result from the reduction in intestinal CD36 and SCD1. Moreover, BBR inhibited mitochondrial complex I-dependent oxygen consumption and ATP synthesis of liver and gut, but no impact on activities of complex II, III and IV. BBR ameliorated mitochondrial swelling, facilitated mitochondrial fusion, and reduced mtDNA and citrate synthase activity. BBR decreased the abundance and diversity of gut microbiome. However, no change in metabolism of recipient mice was observed after fecal microbiota transplantation from BBR treated mice. In primary hepatocytes, BBR and AMPK activator A769662 normalized oleic acid-induced lipid deposition. Although both the agents activated AMPK, BBR decreased oxygen consumption whereas A769662 increased it. Collectively, these findings indicated that BBR repressed complex I in gut and liver and consequently inhibited lipid metabolism which led to alleviation of obesity and fatty liver. This process was independent of intestinal bacteria.

The mitohormetic response as part of the cytoprotection mechanism of berberine : Berberine induces mitohormesis and mechanisms

It was well-known that Berberine, a major bioactive compound extracted from natural plants Coptis chinensis, has anti-diabetic effects for decades in china. Other types of pharmacological activities, such as anti-inflammatory, antimicrobial, hypolipidemic, and anti-cancer effects, have also been examined. At cellular level, these pharmacological activities were mostly an inhibitory effect. However, the cytoprotective effect of berberine was also observed in various types of cells, such as neurons, endothelial cells, fibroblasts, and β-cells. The paradoxical result may be closely associated with characteristics and distribution of berberine within cells, and they can be explained mechanically by mitohormesis, one particular form of hormesis. Here, we reviewed the mitohormetic response and assessed the berberine-induced effects and the possible signaling pathway involved. These findings may contribute to better clinical applications of berberine and indicate that some mitochondria-targeted conventional drugs should be considered carefully in clinical application.

Natural Alkaloids Intervening the Insulin Pathway: New Hopes for Anti-Diabetic Agents?

BACKGROUND

Accumulating experimental data supports the capacity of natural compounds to intervene in complicated molecular pathways underlying the pathogenesis of certain human morbidities. Among them, diabetes is now a world's epidemic associated with increased risk of death; thus, the detection of novel anti-diabetic agents and/or adjuvants is of vital importance. Alkaloids represent a diverse group of natural products with a range of therapeutic properties; during the last 20 years, published research on their anti-diabetic capacity has been tremendously increased.

PURPOSE

To discuss current concepts on the anti-diabetic impact of certain alkaloids, with special reference to their molecular targets throughout the insulin-signaling pathway.

METHODOLOGY

Upon in-depth search in the SCOPUS and PUBMED databases, the literature on alkaloids with insulin secretion/sensitization properties was critically reviewed.

RESULTS

In-vitro and in-vivo evidence supports the effect of berberine, trigonelline, piperine, oxymatrine, vindoneline, evodiamine and neferine on insulin-signaling and related cascades in beta-cells, myocytes, adipocytes, hepatocytes and other cells. Associated receptors, kinases, hormones and cytokines, are affected in terms of gene transcription, protein expression, activity and/or phosphorylation. Pathophysiological processes associated with insulin resistance, beta-cell failure, oxidative stress and inflammation, as well as clinical phenotype are also influenced.

DISCUSSION

Growing evidence suggests the ability of specific alkaloids to intervene in the insulin-signal transduction pathway, reverse molecular defects resulting in insulin resistance and glucose intolerance and improve disease complications, in-vitro and in-vivo. Future indepth molecular studies are expected to elucidate their exact mechanism of action, while large clinical trials are urgently needed to assess their potential as anti-diabetic agents.

The effects of Berberis vulgaris consumption on plasma levels of IGF-1, IGFBPs, PPAR-γ and the expression of angiogenic genes in women with benign breast disease: a randomized controlled clinical trial

BACKGROUND

The present study was designed to investigate the effects of Berberis vulgaris (BV) juice consumption on plasma levels of insulin-like growth factor (IGF-1), IGF-binding proteins (IGFBPs), and the expression of PPAR-γ, VEGF and HIF in women with benign breast disease.

METHODS

This parallel design randomized, double-blind controlled clinical trial was conducted on 85 eligible patients diagnosed with benign breast disease. They were assigned randomly into either BV juice group (n = 44, BV juice: 480 ml/day) or placebo group (n = 41, BV placebo juice: 480 ml/day) for 8 weeks intervention. Participants, caregivers and those who assessed laboratory analyses were blinded to the assignments. Plasma levels of biomarkers were measured at baseline and after 8 weeks by ELISA. Quantitative real-time PCR was used to measure the fold change in the expression of each interested gene.

RESULTS

The compliance of participants was 95.2% and 40 available subjects analyzed in each group at last. Relative treatment (RT) effects for BV juice caused 16% fall in IGF-1 concentration and 37% reduction in the ratio of IGF-1/1GFBP1. Absolute treatment effect expressed 111 ng/ml increased mean differences of IGFBP-3 between BV group and placebo. Plasma level of PPAR-γ increased in both groups but it was not significant. Fold changes in the expressions of PPAR-γ, VEGF and HIF showed down-regulation in the intervention group compared to placebos (P < 0.05).

CONCLUSIONS

The BV juice intervention over 8 weeks was accompanied by acceptable efficacy and decreased plasma IGF-1, and IGF-1/IGFBP-1 ratio partly could be assigned to enhanced IGFBP-1 level in women with BBD. The intervention caused reductions in the expression levels of PPAR, VEGF, and HIF which are remarkable genomic changes to potentially prevent breast tumorigenesis.

TRIAL REGISTRATION

IRCT2012110511335N2. Registered 10 July 2013 (retrospectively registered).

Berberine (BBR) Attenuated Palmitic Acid (PA)-Induced Lipotoxicity in Human HK-2 Cells by Promoting Peroxisome Proliferator-Activated Receptor α (PPAR-α)

BACKGROUND Berberine (BBR), a natural alkaloid isolated from Coptis chinensis, has frequently been reported as an antidiabetic reagent, partly due to its lipid-lowering activity. Evidence suggests that BBR ameliorates palmitate-induced lipid deposition and apoptosis in renal tubular epithelial cells (TECs), which tracks in tandem with the enhancement of peroxisome proliferator-activated receptor alpha (PPAR-alpha). The study aim was to investigate the roles of BBR in renal lipotoxicity in vitro, and investigate whether PPAR-alpha was the underlying mechanism. MATERIAL AND METHODS Human TECs (HK-2 cells) were injured with palmitic acid (PA), and then treated with BBR, BBR+PPAR-alpha inhibitor (GW6471), and PA+PPAR-alpha agonist (fenofibrate). Endoplasmic reticulum (ER) stress was assessed by measuring the expression of prospective evaluation of radial keratotomy (PERK), C/EBP-homologous protein (CHOP), and 78 kDa glucose-regulated protein (GRP78). Lipid metabolism was assessed by determining lipid anabolism-associated genes, including fatty acid synthase (FAS), acetyl-CoA carboxylase (ACC), and lipoprotein lipase (LPL), as well as lipid catabolism-associated gene, including carnitine palmitoyl transferase 1 (CPT1). Inflammatory response of HK-2 cells was evaluated by measuring interleukin (IL)-6 and tumor necrosis factor (TNF)-alpha. Cell apoptosis and protein levels of cleaved-caspase-3 were evaluated. RESULTS PA downregulated PPAR-alpha and induced server lipotoxicity in HK-2 cells by ER stress, increasing lipid deposition, and elevating inflammatory response of HK-2 cells accompanied with inducting cell apoptosis and cleaved-caspase-3, which were obviously reversed by additional treatment of BBR or PPAR-alpha agonist. However, the protective effect of BBR in PA-induced lipotoxicity in HK-2 cells was significantly ameliorated by PPAR-alpha inhibitor. CONCLUSIONS BBR attenuated PA-induced lipotoxicity via the PPAR-alpha pathway.

Amorphous solid dispersion of Berberine mitigates apoptosis via iPLA2β/Cardiolipin/Opa1 pathway in db/db mice and in Palmitate-treated MIN6 β-cells

Aims: Berberine (BBR) improves beta-cell function in Type 2 diabetes (T2D) because of its anti-apoptotic activity, and our laboratory developed a new preparation named Huang-Gui Solid Dispersion (HGSD) to improve the oral bioavailability of BBR. However, the mechanism by which BBR inhibits beta-cell apoptosis is unclear. We hypothesized that the Group VIA Ca²⁺-Independent Phospholipase A₂ (iPLA₂β)/Cardiolipin(CL)/Opa1 signaling pathway could exert a protective role in T2D by regulating beta-cell apoptosis and that HGSD could inhibit β-cell apoptosis through iPLA₂β/CL/Opa1 upregulation.

Methods: We examined how iPLA₂β and BBR regulated apoptosis and insulin secretion through CL/Opa1 in vivo and in vitro. In in vitro studies, we developed Palmitate(PA)-induced apoptotic cell death model in mouse insulinoma cells (MIN6). iPLA₂β overexpression and silencing technology were used to examine how the iPLA₂β/CL/Opa1 interaction may play an important role in BBR treatment. In in vivo studies, db/db mice were used as a diabetic animal model. The pancreatic islet function and morphology, beta-cell apoptosis and mitochondrial injury were examined to explore the effects of HGSD. The expression of iPLA₂β/CL/Opa1 was measured to explore whether the signaling pathway was damaged in T2D and was involved in HGSD treatment.

Results: The overexpression of iPLA₂β and BBR treatment significantly attenuated Palmitate- induced mitochondrial injury and apoptotic death compared with Palmitate-treated MIN6 cell. In addition, iPLA₂β silencing could simultaneously partly abolish the anti-apoptotic effect of BBR and decrease CL/Opa1 signaling in MIN6 cells. Moreover, HGSD treatment significantly decreased beta-cell apoptosis and resulted in the upregulation of iPLA₂β/CL/Opa1 compared to those of the db/db mice.

Conclusion: The results indicated that the regulation of iPLA₂β/CL/Opa1 by HGSD may prevent beta-cell apoptosis and may improve islet beta-cell function in Type 2 diabetic mice and in palmitate-treated MIN6 cells.

Berberine attenuates hypoxia-induced pulmonary arterial hypertension via bone morphogenetic protein and transforming growth factor-β signaling

Hypoxia-induced excessive pulmonary artery smooth muscle cell (PASMC) proliferation plays an important role in the pathology of pulmonary arterial hypertension (PAH). Berberine (BBR) is reported as an effective antiproliferative properties applied in clinical. However, the effect of BBR on PAH remains unclear. In the present study, we elucidated the protective effects of BBR against abnormal PASMC proliferation and vascular remodeling in chronic hypoxia-induced hearts. Furthermore, the potential mechanisms of BBR were investigated. For this purpose, C57/BL6 mice were exposed to chronic hypoxia for 4 weeks to mimic severe PAH. Hemodynamic and pulmonary pathomorphology data showed that chronic hypoxia significantly increased the right ventricular systolic pressure (RVSP), the right ventricle/left ventricle plus septum RV/(LV + S) weight ratio, and the median width of pulmonary arterioles. BBR attenuated the elevations in RVSP and RV/(LV + S) and mitigated pulmonary vascular structure remodeling. BBR also suppressed the hypoxia-induced increases in the expression of proliferating cell nuclear antigen (PCNA) and of α-smooth muscle actin. Furthermore, administration of BBR significantly increased the expression of bone morphogenetic protein type II receptor (BMPR-II) and its downstream molecules P-smad1/5 and decreased the expression of transforming growth factor-β (TGF-β) and its downstream molecules P-smad2/3. Moreover, peroxisome proliferator-activated receptor γ expression was significantly decreased in the hypoxia group, and this decrease was reversed by BBR treatment. Our study demonstrated that the protective effect of BBR against hypoxia-induced PAH in a mouse model may be achieved through altered BMPR-II and TGF-β signaling.

Berberine Protects Against Palmitate-Induced Apoptosis in Tubular Epithelial Cells by Promoting Fatty Acid Oxidation

BACKGROUND Increased lipid accumulation in renal tubular epithelial cells (TECs) contributes to their injury and dysfunction and progression of tubulointerstitial fibrosis. Berberine (BBR), a natural plant alkaloid isolated from traditional medicine herbs, is effective in lowing serum lipid, and has a protective effect on chronic kidney disease (CKD) with dyslipidemia, including diabetic nephropathy. The aim of this study was to investigate the effect of BBR on palmitate (PA)-induced lipid accumulation and apoptosis in TECs. MATERIAL AND METHODS Human kidney proximal tubular epithelial cell line (HK-2) cells were treated with PA, BBR, and/or palmitoyltransferase 1A (CPT1A) inhibitor Etomoxir. Intracellular lipid content was assessed by Oil Red O and Nile Red staining. Cell apoptosis rate was evaluated by flow cytometry assay. The expression of apoptosis-related protein cleaved-caspase3 and fatty acid oxidation (FAO)-regulating proteins, including CPT1A, peroxisome proliferator-activated receptor α (PPARα), and PPARγ co-activator-1α (PGC1α), was measured by Western blot analysis and immunofluorescence. RESULTS In the present study, PA treatment increased intracellular lipid deposition accompanied by elevated apoptosis in TECs compared with control group, whereas the protein expression of CPT1A, PPARα, and PGC1α, did not correspondingly increase in TECs. BBR significantly up-regulated the protein expression of CPT1A, PPARα, and PGC1α in TECs treated with or without PA, and reversed PA-induced intracellular lipid accumulation and apoptosis. Moreover, the CPT1A inhibitor Etomoxir counteracted the protective effect of BBR in TECs. CONCLUSIONS These in vitro findings suggest that PA can induce intracellular lipid accumulation and apoptosis in TECs, and the mechanism may be associated with inducing defective FAO, whereas BBR can protect TECs against PA-induced intracellular lipid accumulation and apoptosis by promoting FAO.

Berberine Improves Cognitive Deficiency and Muscular Dysfunction via Activation of the AMPK/SIRT1/PGC-1a Pathway in Skeletal Muscle from Naturally Aging Rats

OBJECTIVE

The manifestations of aging include cognitive deficits and muscular dysfunction, which are closely linked to impairment of mitochondrial biogenesis. Berberine, an isoquinoline alkaloid, presents multiple anti-diabetic pharmacological effects. Evidence has indicated that insulin resistance and cognitive impairment share the same pathogenesis, and berberine could reverse glucose metabolism abnormalities and muscle mitochondrial dysfunction induced by a high-fat diet. This study was used to investigate whether berberine could be used as an anti-aging drug to prevent cognitive deficits and muscular dysfunction in natural aging.

METHODS

Biochemical indicators and an intraperitoneal glucose tolerance test were tested in 5-month-old rats (5 mo group), 24-month-old rats (24 mo group) and 24-month-old rats that had undergone 6 months of berberine treatment (BBR group). A Morris water maze test was conducted to assess the cognitive ability of the rats. Insulin resistance in whole-body was evaluated by intraperitoneal glucose tolerance test (IPGTT). The morphology of the skeletal muscle tissue was observed by hematoxylin-eosin (HE) staining. The levels of total cholesterol, triglyceride, ATP and reactive oxygen species (ROS) were assessed with corresponding reagent kits. The protein expressions of GLUT4, AMPK, SIRT1 and PGC-1α in skeletal muscle were examined by Western blot.

RESULTS

The results showed that administration of berberine for 6 months significantly improved cognitive deficits and insulin resistance in naturally aging rats (p<0.01). Furthermore, berberine treatment helped normalize the disordered alignment and the decreased number of muscle fibers (p<0.01) in the skeletal muscle of 24 mo rats. Berberine decreased the levels of ROS in both the serum and the skeletal muscle of 24 mo rats (p<0.01). Berberine increased the protein expression of p-AMPK, SIRT1 and PGC-1α and increased the production of ATP in the skeletal muscle of aging rats (p<0.01).

CONCLUSIONS

Berberine markedly ameliorates aging-related reductions in cognitive ability and muscular function, and the activation of the AMPK/SIRT1/PGC-1α pathway in skeletal muscle may be the underlying protective mechanism of berberine on muscular function.

The Preconditioning of Berberine Suppresses Hydrogen Peroxide-Induced Premature Senescence via Regulation of Sirtuin 1

With a long history of application in Chinese traditional medicine, berberine (BBR) was reported to exhibit healthspan-extending properties in some age-related diseases, such as type 2 diabetes and atherosclerosis. However, the antiaging mechanism of BBR is not completely clear. By means of hydrogen peroxide- (H₂O₂-) induced premature cellular senescence model, we found that a low-concentration preconditioning of BBR could resist premature senescence in human diploid fibroblasts (HDFs) measured by senescence-associated β-galactosidase (SA-β-gal), accompanied by a decrease in loss of mitochondrial membrane potential and production of intracellular reactive oxygen species (ROS). Moreover, the low-concentration preconditioning of BBR could make cells less susceptible to subsequent H₂O₂-induced cell cycle arrest and growth inhibition. Experimental results further showed that the low concentration of BBR could induce a slight increase of ROS and upregulate the expression level of sirtuin 1 (SIRT1), an important longevity regulator. H₂O₂-induced activation of checkpoint kinase 2 (Chk2) was significantly attenuated after the preconditioning of BBR. The present findings implied that the low-concentration preconditioning of BBR could have a mitohormetic effect against cellular senescence triggered by oxidative stress in some age-related diseases through the regulation of SIRT1.

Beneficial Effects of Berberine on Oxidized LDL-Induced Cytotoxicity to Human Retinal Müller Cells

Purpose

Limited mechanistic understanding of diabetic retinopathy (DR) has hindered therapeutic advances. Berberine, an isoquinolone alkaloid, has shown favorable effects on glucose and lipid metabolism in animal and human studies, but effects on DR are unknown. We previously demonstrated intraretinal extravasation and modification of LDL in human diabetes, and toxicity of modified LDL to human retinal Müller cells. We now explore pathogenic effects of modified LDL on Müller cells, and the efficacy of berberine in mitigating this cytotoxicity.

Methods

Confluent human Müller cells were exposed to in vitro–modified ‘highly oxidized, glycated (HOG-) LDL versus native-LDL (N-LDL; 200 mg protein/L) for 6 or 24 hours, with/without pretreatment with berberine (5 μM, 1 hour) and/or the adenosine monophosphate (AMP)-activated protein kinase (AMPK) inhibitor, Compound C (5 μM, 1 hour). Using techniques including Western blots, reactive oxygen species (ROS) detection assay, and quantitative real-time PCR, the following outcomes were assessed: cell viability (CCK-8 assay), autophagy (LC3, Beclin-1, ATG-5), apoptosis (cleaved caspase 3, cleaved poly-ADP ribose polymerase), oxidative stress (ROS, nuclear factor erythroid 2-related factor 2, glutathione peroxidase 1, NADPH oxidase 4), angiogenesis (VEGF, pigment epithelium-derived factor), inflammation (inducible nitric oxide synthase, intercellular adhesion molecule 1, IL-6, IL-8, TNF-α), and glial cell activation (glial fibrillary acidic protein).

Results

Native-LDL had no effect on cultured human Müller cells, but HOG-LDL exhibited marked toxicity, significantly decreasing viability and inducing autophagy, apoptosis, oxidative stress, expression of angiogenic factors, inflammation, and glial cell activation. Berberine attenuated all the effects of HOG-LDL (all P < 0.05), and its effects were mitigated by AMPK inhibition (P < 0.05).

Conclusions

Berberine inhibits modified LDL-induced Müller cell injury by activating the AMPK pathway, and merits further study as an agent for preventing and/or treating DR.

Pancreatic beta cell protection/regeneration with phytotherapy

Although currently available drugs are useful in controlling early onset complications of diabetes, serious late onset complications appear in a large number of patients. Considering the physiopathology of diabetes, preventing beta cell degeneration and stimulating the endogenous regeneration of islets will be essential approaches for the treatment of insulin-dependent diabetes mellitus. The current review focused on phytochemicals, the antidiabetic effect of which has been proved by pancreatic beta cell protection/regeneration. Among the hundreds of plants that have been investigated for diabetes, a small fraction has shown the regenerative property and was described in this paper. Processes of pancreatic beta cell degeneration and regeneration were described. Also, the proposed mechanisms for the protective/regenerative effects of such phytochemicals and their potential side effects were discussed.

Effects of berberine and cinnamic acid on palmitic acid-induced intracellular triglyceride accumulation in NIT-1 pancreatic β cells

OBJECTIVE

To investigate the effects of berberine (BBR) and cinnamic acid (CA), the main active components in Jiaotai Pill (, JTP), on palmitic acid (PA)-induced intracellular triglyceride (TG) accumulation in NIT-1 pancreatic β cells.

METHODS

Cells were incubated in culture medium containing PA (0.25 mmol/L) for 24 h. Then treatments with BBR (10 μmol/L), CA (100 μmol/L) and the combination of BBR and CA (BBR+CA) were performed respectively. Intracellular lipid accumulation was assessed by Oil Red O staining and TG content was measured by colorimetric assay. The expression of adenosine monophosphate-activated protein kinase (AMPK) protein and its downstream lipogenic and fatty acid oxidation genes, including fatty acid synthase (FAS), acetyl-coA carboxylase (ACC), phosphorylation acetyl-coA carboxylase (pACC), carnitine acyl transferase 1 (CPT-1) and sterol regulating element binding protein 1c (SREBP-1c) were determined by Western blot or real time polymerase chain reaction.

RESULTS

PA induced an obvious lipid accumulation and a significant increase in intracellular TG content in NIT-1 cells. PA also induced a remarkable decrease in AMPK protein expression and its downstream targets such as pACC and CPT-1. Meanwhile, AMPK downstream lipogenic genes including SREBP-1c mRNA, FAS and ACC protein expressions were increased. Treatments with BBR and BBR+CA, superior to CA, significantly reversed the above genes changes in NIT-1 pancreatic β cells. However, the synergistic effect of BBR and CA on intracellular TG content was not observed in the present study.

CONCLUSION

It can be concluded that in vitro, BBR and BBR+CA could inhibit PA-induced lipid accumulation by decreasing lipogenesis and increasing lipid oxidation in NIT-1 pancreatic β cells.

AMPK activation--protean potential for boosting healthspan

AMP-activated kinase (AMPK) is activated when the cellular (AMP+ADP)/ATP ratio rises; it therefore serves as a detector of cellular "fuel deficiency." AMPK activation is suspected to mediate some of the health-protective effects of long-term calorie restriction. Several drugs and nutraceuticals which slightly and safely impede the efficiency of mitochondrial ATP generation-most notably metformin and berberine-can be employed as clinical AMPK activators and, hence, may have potential as calorie restriction mimetics for extending healthspan. Indeed, current evidence indicates that AMPK activators may reduce risk for atherosclerosis, heart attack, and stroke; help to prevent ventricular hypertrophy and manage congestive failure; ameliorate metabolic syndrome, reduce risk for type 2 diabetes, and aid glycemic control in diabetics; reduce risk for weight gain; decrease risk for a number of common cancers while improving prognosis in cancer therapy; decrease risk for dementia and possibly other neurodegenerative disorders; help to preserve the proper structure of bone and cartilage; and possibly aid in the prevention and control of autoimmunity. While metformin and berberine appear to have the greatest utility as clinical AMPK activators-as reflected by their efficacy in diabetes management-regular ingestion of vinegar, as well as moderate alcohol consumption, may also achieve a modest degree of health-protective AMPK activation. The activation of AMPK achievable with any of these measures may be potentiated by clinical doses of the drug salicylate, which can bind to AMPK and activate it allosterically.

GPR40: a therapeutic target for mediating insulin secretion (review)

G-protein-coupled receptor 40 (GPR40), known as free fatty acid receptor 1, is mainly expressed in pancreatic β-cells and activated by medium- and long-chain fatty acids. Increasing evidence indicates that the activation of GPR40 in cells causes insulin secretion, and GPR40 has become an attractive therapeutic target for type 2 diabetes. Recently, certain novel GPR40 agonists have been identified that regulate glucose-stimulated insulin secretion, leading to the development of new drugs for the treatment of type 2 diabetes. In this review, we focus on progress in the physiological role of GPR40 and potential drugs targeting GPR40 over the past decade.