Experimental evidence for curcumin and its analogs for management of diabetes mellitus and its associated complications

Advancements in curcumin-loaded PLGA nanoparticle delivery systems: progressive strategies in cancer therapy

Cancer is a leading cause of death worldwide, and imposes a substantial socioeconomic burden with little impact especially on aggressive types of cancer. Conventional therapies have many serious side effects including generalised systemic toxicity which limits their long-term use. Tumour resistance and recurrence is another main problem associated with conventional therapy. Purified or extracted natural products have been investigated as cost-effective cancer chemoprotective agents with the potential to reverse or delaying carcinogenesis. Curcumin (CUR) as a natural polyphenolic component, exhibits many pharmacological activities such as anti-cancer, anti-inflammatory, anti-microbial, activity against neurodegenerative diseases including Alzheimer, antidiabetic activities (type II diabetes), anticoagulant properties, wound healing effects in both preclinical and clinical studies. Despite these effective protective properties, CUR has several limitations, including poor aqueous solubility, low bioavailability, chemical instability, rapid metabolism and a short half-life time. To overcome the pharmaceutical problems associated with free CUR, novel nanomedicine strategies (including polymeric nanoparticles (NPs) such as poly (lactic-co-glycolic acid) (PLGA) NPs have been developed. These formulations have the potential to improve the therapeutic efficacy of curcuminoids. In this review, we comprehensively summarise and discuss recent in vitro and in vivo studies to explore the pharmaceutical significance and clinical benefits of PLGA-NPs delivery system to improve the efficacy of CUR in the treatment of cancer.

Compound SJ-12 attenuates streptozocin-induced diabetic cardiomyopathy by stabilizing SERCA2a

Heart failure (HF) is one of the major causes of death among diabetic patients. Although studies have shown that curcumin analog C66 can remarkably relieve diabetes-associated cardiovascular and kidney complications, the role of SJ-12, SJ-12, a novel curcumin analog, in diabetic cardiomyopathy and its molecular targets are unknown. 7-week-old male C57BL/6 mice were intraperitoneally injected with single streptozotocin (STZ) (160 mg/kg) to develop diabetic cardiomyopathy (DCM). The diabetic mice were then treated with SJ-12 via gavage for two months. Body weight, fast blood glucose, cardiac utrasonography, myocardial injury markers, pathological morphology of the heart, hypertrophic and fibrotic markers were assessed. The potential target of SJ-12 was evaluated via RNA-sequencing analysis. The O-GlcNAcylation levels of SP1 were detected via immunoprecipitation. SJ-12 effectively suppressed myocardial hypertrophy and fibrosis, thereby preventing heart dysfunction in mice with STZ-induced heart failure. RNA-sequencing analysis revealed that SJ-12 exerted its therapeutic effects through the modulation of the calcium signaling pathway. Furthermore, SJ-12 reduced the O-GlcNAcylation levels of SP1 by inhibiting O-linked N-acetylglucosamine transferase (OGT). Also, SJ-12 stabilized Sarcoplasmic/Endoplasmic Reticulum Calcium ATPase 2a (SERCA2a), a crucial regulator of calcium homeostasis, thus reducing hypertrophy and fibrosis in mouse hearts and cultured cardiomyocytes. However, the anti-fibrotic effects of SJ-12 were not detected in SERCA2a or OGT-silenced cardiomyocytes, indicating that SJ-12 can prevent DCM by targeting OGT-dependent O-GlcNAcylation of SP1.These findings indicate that SJ-12 can exert cardioprotective effects in STZ-induced mice by reducing the O-GlcNAcylation levels of SP1, thus stabilizing SERCA2a and reducing myocardial fibrosis and hypertrophy. Therefore, SJ-12 can be used for the treatment of diabetic cardiomyopathy.

Therapeutic Effects of Curcumin Derivatives against Obesity and Associated Metabolic Complications: A Review of In Vitro and In Vivo Studies

Obesity is a major cause of morbidity and mortality globally, increasing the risk for chronic diseases. Thus, the need to identify more effective anti-obesity agents has spurred significant interest in the health-promoting properties of natural compounds. Of these, curcumin, the most abundant and bioactive constituent of turmeric, possesses a variety of health benefits including anti-obesity effects. However, despite its anti-obesity potential, curcumin has demonstrated poor bioavailability, which limits its clinical applicability. Synthesizing curcumin derivatives, which are structurally modified analogs of curcumin, has been postulated to improve bioavailability while maintaining therapeutic efficacy. This review summarizes in vitro and in vivo studies that assessed the effects of curcumin derivatives against obesity and its associated metabolic complications. We identified eight synthetic curcumin derivatives that were shown to ameliorate obesity and metabolic dysfunction in diet-induced obese animal models, while five of these derivatives also attenuated obesity and associated metabolic complications in cell culture models. These curcumin derivatives modulated adipogenesis, lipid metabolism, insulin resistance, steatosis, lipotoxicity, inflammation, oxidative stress, endoplasmic reticulum stress, apoptosis, autophagy, fibrosis, and dyslipidemia to a greater extent than curcumin. In conclusion, the findings from this review show that compared to curcumin, synthetic curcumin derivatives present potential candidates for further development as therapeutic agents to modulate obesity and obesity-associated metabolic complications.

Statistical optimization of tetrahydrocurcumin loaded solid lipid nanoparticles using Box Behnken design in the management of streptozotocin-induced diabetes mellitus

In the past, curcumin was the go-to medication for diabetes, but recent studies have shown that tetrahydrocurcumin is more effective. The problem is that it's not very soluble in water or very bioavailable. So, our research aims to increase the bioavailability and anti-diabetic efficacy of tetrahydrocurcumin in streptozotocin-induced diabetic rats by synthesizing tetrahydrocurcumin-loaded solid lipid nanoparticles. Box Behnken Design was employed for the optimization of tetrahydrocurcumin-loaded solid lipid nanoparticles (THC-SLNs). The optimal formulation was determined by doing an ANOVA to examine the relationship between the independent variables (drug-to-lipid ratio, surfactant concentration, and co-surfactant concentration) and the dependent variables (particle size, percent entrapment efficiency, and PDI). Particle size, PDI, and entrapment efficiency all showed statistical significance based on F-values and p-values. The optimized batch was prepared using a drug-to-lipid ratio (1:4.16), 1.21% concentration of surfactant, and 0.4775% co-surfactant (observed with a particle size of 147.1 nm, 83.58 ± 0.838 % entrapment efficiency, and 0.265 PDI, and the values were found very close with the predicted ones. As the THC peak vanishes from the DSC thermogram of the improved formulation, this indicates that the drug has been transformed from its crystalline form into its amorphous state. TEM analysis of optimized formulation demonstrated mono-dispersed particles with an average particle size of 145 nm which are closely related to zetasizer's results. In-vitro release study of optimized formulation demonstrated burst release followed by sustained release up to 71.04% throughout 24 hrs. Increased bioavailability of the adjusted THC-SLN was found in an in vivo pharmacokinetics research with 9.47 folds higher AUC(0-t) compared to plain THC-suspension. Additionally, pharmacodynamic experiments of optimized formulation demonstrated a marked decrease in blood glucose level to 63.7% and increased body weight from 195.8 ± 7.223 to 231.2 ± 7.653 on the 28th day of the study and showed a better anti-diabetic effect than plain drug suspension. Results of stability studies revealed that formulation can be stored for longer periods at room temperature. Tetrahydrocurcumin can be effectively administered by SLN for the treatment of diabetes.

Novel N'-substituted benzylidene benzohydrazides linked to 1,2,3-triazoles: potent α-glucosidase inhibitors

Herein, various N'-substituted benzylidene benzohydrazide-1,2,3-triazoles were designed, synthesized, and screened for their inhibitory activity toward α-glucosidase. The structure of derivatives was confirmed using ¹H- and ¹³C-NMR, FTIR, Mass spectrometry, and elemental analysis. All derivatives exhibited good inhibition with IC₅₀ values in the range of 0.01 to 648.90 µM, compared with acarbose as the positive control (IC₅₀ = 752.10 µM). Among them, compounds 7a and 7h showed significant potency with IC₅₀ values of 0.02 and 0.01 µM, respectively. The kinetic study revealed that they are noncompetitive inhibitors toward α-glucosidase. Also, fluorescence quenching was used to investigate the interaction of three inhibitors 7a, 7d, and 7h, with α-glucosidase. Accordingly, the binding constants, the number of binding sites, and values of thermodynamic parameters were determined for the interaction of candidate compounds toward the enzyme. Finally, the in silico cavity detection plus molecular docking was performed to find the allosteric site and key interactions between synthesized compounds and the target enzyme.

Dual-stimuli responsive skin-core structural fibers with an in situ crosslinked alginate ester for hydrophobic drug delivery

To solve the problems of low bioavailability and low intestinal release efficiency of curcumin as a hydrophobic drug in the treatment of diabetes, a novel alginate ester/Antarctic krill protein/2-formylphenylboronic acid (AE/AKP/2-FPBA) skin-core structural fiber with pH and glucose stimulation responsiveness was prepared by an acid-catalyzed polyol in situ crosslinked phase separation method as a drug delivery system. The reaction mechanism and apparent morphology of the fiber were studied. The controlled release ability of the fiber in simulated liquids was evaluated. AE targeted the release of curcumin by pH stimulation; the release amount in the simulated colonic fluid reached 100%, while the release amount in the simulated digestive fluid was less than 12%. 2-FPBA controlled the release rate of curcumin by glucose stimulation, which increases with the increase of 2-FPBA content. Moreover, the cytotoxicity test confirmed that the skin-core structural fiber was non-toxic. These results suggest that skin-core structural fibers have great potential as curcumin delivery systems.

Quinazolinone-1,2,3-triazole-acetamide conjugates as potent α-glucosidase inhibitors: synthesis, enzyme inhibition, kinetic analysis, and molecular docking study

In this study, new hybrids of quinazolinone-1,2,3-triazole-acetamide were designed, synthesized, and screened for their α-glucosidase inhibitory activity. The results obtained from the in vitro screening indicated that all analogs exhibited significant inhibitory activity against α-glucosidase (IC50 values ranging from 4.8-140.2 μM) in comparison to acarbose (IC50 = 750.0 μM). The limited structure-activity relationships suggested the variation in the inhibitory activities of the compounds affected by different substitutions on the aryl moiety. The enzyme kinetic studies of the most potent compound 9c, revealed that it inhibited α-glucosidase in a competitive mode with a K i value of 4.8 μM. In addition, molecular docking studies investigated the structural perturbation and behavior of all derivatives inside the α-glucosidase active site. Next, molecular dynamic simulations of the most potent compound 9c, were performed to study the behavior of the 9c-complex during the time. The results showed that these compounds can be considered as potential antidiabetic agents.

Synthesis, in silico, in vitro and in vivo studies of novel natural-based arylidenes curcumin as potential glycohydrolase digestive enzymes inhibitors

Diabetes is one of the most common metabolic diseases in humans and the use of herbal medicines is of great clinical importance to inhibit carbohydrate-hydrolyzing enzymes and reduce blood glucose levels in diabetic patients. Inhibition of glycosidase activity is an effective way to treat and prevent diabetes. Therefore, in this study, curcumin-based benzaldehyde derivatives were synthesized and used as influential agents in the treatment of diabetes with inhibitory properties against two carbohydrate-hydrolyzing enzymes α-glucosidase (α-Glu) and α-amylase (α-Amy) as significant therapeutic targets for reducing postprandial hyperglycemia. Overall, the findings showed that due to the specific inhibitory activity against α-Glu in comparison with α-Amy, as well as more stability and antioxidant activity than curcumin, C5 and C8 derivatives are potentially important anti-diabetic drugs, not only to decrease glycemic index but also to limit the activity of the main production pathways of reactive oxygen species (ROS) in diabetic patients.Communicated by Ramaswamy H. Sarma.

Design, synthesis, spectroscopic characterizations, antidiabetic, in silico and kinetic evaluation of novel curcumin-fused aldohexoses

Curcumin (bis-α,β-unsaturated β-diketone) plays an important role in the prevention of numerous diseases, including diabetes. Curcumin, as an enzyme inhibitor, has ideal structural properties including hydrophobic nature, flexible backbone, and several available hydrogen bond (H-bond) donors and acceptors. In this study, curcumin-fused aldohexose derivatives 3(a-c) were synthesized and used as influential agents in the treatment of diabetes with inhibitory properties against two carbohydrate-hydrolyzing enzymes α-glucosidase (α-Gls) and α-amylase (α-Amy) which are known to be significant therapeutic targets for the reduction of postprandial hyperglycemia. These compounds were isolated, purified, and then spectrally characterized via FT-IR, Mass, ¹H, and ¹³C NMR, which strongly confirmed the targeted product's formation. Also, their inhibitory properties against α-Gls and α-Amy were evaluated spectroscopically. The Results indicated that all compounds strongly inhibited α-Amy and α-Gls by mixed and competitive mechanisms, respectively. The intrinsic fluorescence of α-Amy was quenched by the interaction with compounds 1 and 3b through a dynamic quenching mechanism, and the 1 and 3b/α-Amy complexes were spontaneously formed, mainly driven by the hydrophobic interaction and hydrogen bonding. Fourier transform infrared spectra (FT-IR) comprehensively verified that the binding of compounds 1 and 3b to α-Amy would change the conformation and microenvironment of α-Amy, thereby inhibiting the enzyme activity. Docking and molecular dynamics (MD) simulations showed that all compounds interacted with amino acid residues located in the active pocket site of the proteins. In vivo studies confirmed the plasma glucose diminution after the administration of compound 3b to Wistar rats. Accordingly, the results of the current work may prompt the scientific communities to investigate the possibility of compound 3b application in the clinic.

Tang-Ping-San Decoction Remodel Intestinal Flora and Barrier to Ameliorate Type 2 Diabetes Mellitus in Rodent Model

PURPOSE

Type 2 diabetes mellitus (T2DM) is a complex genetic disease associated with genetic and environmental factors. Previous studies have shown that changes in the gut microbiota may affect the development of host metabolic diseases and promote the progression of T2DM. Tang-ping-san (TPS) decoction can effectively treat T2DM. However, its specific mechanisms must be evaluated.

PATIENTS AND METHODS

In the present study, we established an animal model of T2DM using a high‑fat diet (HFD) with intraperitoneal injection streptozotocin injection.

RESULTS

The therapeutic effect of TPS decoction on T2DM in mice was initially evaluated. TPS decoction was found to improve hyperglycemia, hyperlipidemia, insulin resistance, and pathological liver, pancreatic, and colon changes. Moreover, it reduced the pro-inflammatory cytokine levels. Based on 16SrRNA sequencing, TPS decoction reduced the Firmicutes/Bacteroidetes ratio at the phylum level. At the genus level, it increased the relative abundances of Akkermansia, Muribaculaceae, and the Eubacterium coprostanoligenes group and decreased the relative abundance of Fusobacterium, Escherichia coli, Dubosiella, and Helicobacter.

CONCLUSION

TPS decoction improves T2DM and liver function and reduces the risk of hyperglycemia, hyperlipidemia, insulin resistance, pathological organ changes, and inflammatory reactions. The mechanism of TPS decoction in T2DM can be correlated with the reversal of gut microbiota dysfunction and repair of the intestinal mucosal barrier.

Pi-Dan-Jian-Qing Decoction Ameliorates Type 2 Diabetes Mellitus Through Regulating the Gut Microbiota and Serum Metabolism

Pi-Dan-Jian-Qing decoction (PDJQ) can been used in the treatment of type 2 diabetes mellitus (T2DM) in clinic. However, the protective mechanisms of PDJQ on T2DM remain unknown. Recent studies have shown that the changes in gut microbiota could affect the host metabolism and contribute to progression of T2DM. In this study, we first investigated the therapeutic effects of PDJQ on T2DM rats. 16S rRNA sequencing and untargeted metabolomics analyses were used to investigate the mechanisms of action of PDJQ in the treatment of T2DM. Our results showed that PDJQ treatment could improve the hyperglycemia, hyperlipidemia, insulin resistance (IR) and pathological changes of liver, pancreas, kidney, and colon in T2DM rats. PDJQ could also decrease the levels of pro-inflammatory cytokines and inhibit the oxidative stress. 16S rRNA sequencing showed that PDJQ could decrease the Firmicutes/Bacteroidetes (F to B) ratio at the phylum level. At the genus level, PDJQ could increase the relative abundances of Lactobacillus, Blautia, Bacteroides, Desulfovibrio and Akkermansia and decrease the relative abundance of Prevotella. Serum untargeted metabolomics analysis showed that PDJQ could regulate tryptophan metabolism, histidine metabolism, tricarboxylic acid (TCA) cycle, phenylalanine, tyrosine and tryptophan biosynthesis and tyrosine metabolism pathways. Correlation analysis indicated that the modulatory effects of PDJQ on the tryptophan metabolism, histidine metabolism and TCA cycle pathways were related to alterations in the abundance of Lactobacillus, Bacteroides and Akkermansia. In conclusion, our study revealed the various ameliorative effects of PDJQ on T2DM, including improving the liver and kidney functions and alleviating the hyperglycemia, hyperlipidemia, IR, pathological changes, oxidative stress and inflammatory response. The mechanisms of PDJQ on T2DM are likely linked to an improvement in the dysbiosis of gut microbiota and modulation of tryptophan metabolism, histamine metabolism, and the TCA cycle.

Hypoglycemic and antioxidant effects of five commercial turmeric (Curcuma longa) supplements

We evaluate the hypoglycemic and antioxidant effects of five commercial turmeric (Curcuma longa) supplements: (1) bulk samples, (2) turmeric root from India, (3) curcuma turmeric Pronat^® , (4) turmeric & black pepper Swanson^® , and (5) C3 complex^® turmeric curcumin. Glucose diffusion and enzymatic starch digestion assays, using α-amylase and α-glucosidase, were performed. The antioxidant activity of turmeric supplements was measured through lipid peroxidation inhibition and the scavenging radical assay. A starch dose of 102 mg/Kg of body weight (equivalent to 1 g/day in humans) was used to perform the oral starch tolerance test (OSTT) in Wistar male rats. All turmeric supplements decreased glucose diffusion and α-glucosidase enzyme activity, and inhibited lipid peroxidation. The rats that received bulk samples and CT showed significantly lower glucose levels than rats receiving acarbose and those of negative control group. Our results show that biological activities of turmeric supplements vary according to the commercial presentation. PRACTICAL APPLICATIONS: The study results suggest that the hypoglycemic and antioxidant effects of five commercial turmeric supplements vary among them. The information provided would be useful to physicians and individuals using these supplements.

Curcumin derivatives for Type 2 Diabetes management and prevention of complications

Type 2 diabetes Mellitus (T2DM) is characterized by chronically increased blood glucose levels, which is associated with impairment of the inflammatory and oxidative state and dyslipidaemia. Although it is considered a world heath concern and one of the most studied diseases, we are still pursuing an effective therapy for both the pathophysiological mechanisms and the complications. Curcumin, a natural compound found in the rhizome of Curcuma longa, is well known for its numerous biological activities, as demonstrated by several studies supporting that curcumin possesses hypoglycaemic, hypolipidemic, anti-inflammatory and antioxidant properties, among others. These effects have been explored to the attenuation of hyperglycaemia and progression of DM complications, being appointed as a potential therapeutic approach. Besides its strong intrinsic activity, the polyphenol has low bioavailability, compromising its therapeutic efficacy. In order to overcome this limitation, several chemical strategies have been applied to curcumin, such as drug delivery systems, chemical manipulation and the use of adjuvant therapies. Given the promising results obtained with curcumin derivative, in this review we discuss not only the therapeutic targets of curcumin, but also its most recently developed analogues and their efficacy in the management of T2DM pathophysiology and complications.

Synthesis of new curcumin derivatives as influential antidiabetic α-glucosidase and α-amylase inhibitors with anti-oxidant activity

In this study, a new class of curcumin derivatives was synthesized using a multicomponent reaction containing curcumin, aldehydes, and malononitrile. This new protocol afforded a novel class of 4H-pyran heterocycles incorporating curcumin moiety. The products were obtained in the presence of p-toluenesulfonic acid (PTSA) as a catalyst in ethanol solvent in good to excellent yields. The synthetic compounds indicated a notable inhibitory activity against α-glucosidase (α-Gls) and revealed a weak inhibitory property against α-amylase (α-Amy). Also, these synthetic compounds indicated significant antioxidant activity. The new curcumin derivatives were also discovered to display no significant effect against the growth of two bacterial microflora in the human intestine. A molecular docking study was done to realize the binding interaction of the synthetic curcumin derivatives with the α-Gls enzyme. The results of our study introduced new synthetic curcumin derivatives as potential antidiabetic drugs.

Recent advances in encapsulation of curcumin in nanoemulsions: A review of encapsulation technologies, bioaccessibility and applications

Curcumin is widely acknowledged for its beneficial activities. However, its application has remained challenging due to its low aqueous solubility, biochemical/structural degradation and poor bioavailability. For these reasons, many researches are aimed at overcoming these limitations using lipid-based nanosystems to encapsulate curcumin, especially nanoemulsions. This review highlights the theoretical aspects and recent advances of preparation technologies (phase inversion temperature, phase inversion composition, ultrasonication, high pressure homogenization and microfluidization) for encapsulation of curcumin in nanoemulsions. Additionally, the specific factors in designing nanoemulsions systems that affect the chemical stability and in vitro bioaccessibility of the encapsulated curcumin are discussed. Also, the importance of nanoemulsions in improving antioxidant, anti-inflammatory and anticancer activities of curcumin is underlined. Curcumin-loaded nanoemulsions preparation technologies have been proposed to provide efficient, systematic, and practical protocols for improved applications of curcumin. Additionally, key factors that influence curcumin delivery include the nature of emulsifier, the type and the amount of carrier oil and emulsifier-curcumin interactions. The pharmacological activities of curcumin including antioxidant, anti-inflammatory and anticancer activities can be improved by nanoemulsions.

Assessment and comparison of the antioxidant defense system in patients with type 2 diabetes, diabetic nephropathy and healthy people: A case-control study

INTRODUCTION

Findings of previous studies in the field of antioxidant defense system in patients with type 2 diabetes (T2DM), diabetic nephropathy (DM) are limited and conflicting. Therefore, we evaluated the antioxidant defense system status in type 2 diabetes patients, diabetic nephropathy and healthy subjects in Iranian population.

METHODS

This population-based case-control study was conducted in 2019 and included 30 individuals with T2DM and 30 patients with DN, as the case groups and 30 healthy subjects for the control group. Individuals entered to the study for case group were diagnosed as T2DM patients based on fast glucose blood tests (FGB) (≥126 mg/dL) and HbA₁ (≥6.5%). DN was defined based on these tests and macroalbuminuria (>300 mg/day). Serum was carefully separated and antioxidant defense system status was estimated. Dietary intakes were evaluated by using a food frequency questionnaire (FFQ).

RESULTS

Energy intake in control group was higher than case groups; BMI was higher in the DN group compared to the other groups. Significantly higher levels of MDA were observed in T2DM patients compared to control group in crude model (1.255 vs. 1.079 nmol/L; P = 0.006). The same results were shown after adjustment for potential confounders (1.256 vs. 1.085 nmol/L; P = 0.022). Total antioxidant capacity (TAC) was less in case groups compared with control group; level of catalase (CTL) and superoxide dismutase enzymes comparisons showed that DN patients had higher level than control group, but these associations were not significant.

CONCLUSIONS

We found that MDA levels were significantly higher in T2DM patients compared to control group. Level of TAC was less in case groups in comparison to controls. SOD and CTL levels were higher in DN compared to controls; these associations were not significant.

Therapeutic Applications of Curcumin Nanomedicine Formulations in Cardiovascular Diseases

Cardiovascular diseases (CVD) compromises a group of heart and blood vessels disorders with high impact on human health and wellbeing. Curcumin (CUR) have demonstrated beneficial effects on these group of diseases that represent a global burden with a prevalence that continues increasing progressively. Pre- and clinical studies have demonstrated the CUR effects in CVD through its anti-hypercholesterolemic and anti-atherosclerotic effects and its protective properties against cardiac ischemia and reperfusion. However, the CUR therapeutic limitation is its bioavailability. New CUR nanomedicine formulations are developed to solve this problem. The present article aims to discuss different studies and approaches looking into the promising role of nanotechnology-based drug delivery systems to deliver CUR and its derivatives in CVD treatment, with an emphasis on their formulation properties, experimental evidence, bioactivity, as well as challenges and opportunities in developing these systems.

Curcumin analog A13 alleviates oxidative stress by activating Nrf2/ARE pathway and ameliorates fibrosis in the myocardium of high-fat-diet and streptozotocin-induced diabetic rats

BACKGROUND

Diabetes mellitus is an important risk factor for cardiomyopathy. Increasing oxidative stress may be one of the main factors of diabetic cardiomyopathy. A13, a newly synthesized curcumin analog, was proved to be superior to curcumin in biological activity. However, little know about how A13 performed in diabetic models. In this study, we evaluated the ability of curcumin analog A13 to alleviate oxidative stress and ameliorate fibrosis in the myocardium, and explore the underlying mechanisms.

METHODS

Intraperitoneal injection of streptozotocin (30 mg/kg in 0.1 M sodium citrate buffer, pH 4.5) induced diabetes in high-fat fed rats. The rats were respectively treated with a daily dose of curcumin or A13 via intragastric intubation for 8 weeks. Myocardial tissue sections were stained with hematoxylin-eosin; oxidative stress was detected by biochemical assays; activation of the Nrf2/ARE pathway was detected by Western blot, immunohistochemical staining and RT-qPCR; myocardial fibrosis was identified by Western blot and Masson trichrome staining.

RESULTS

Treatment with curcumin analog A13 reduced the histological lesions of the myocardium in diabetic rats. Curcumin and A13 treatment decreased the malondialdehyde level and increased the activity of superoxide dismutase in the myocardium of diabetic rats. Molecular analysis and immunohistochemical staining demonstrated that dose of 20 mg/kg of A13 could activate the Nrf2/ARE pathway. Molecular analysis and Masson staining showed that curcumin analog A13 treatment significantly ameliorated fibrosis in myocardium of these diabetic rats.

CONCLUSION

Treatment with curcumin analog A13 protects the morphology of myocardium, restores the MDA levels and SOD activity, activates the Nrf2/ARE pathway and ameliorates myocardial fibrosis in diabetic rats. It may be a useful therapeutic agent for some aspects of diabetic cardiomyopathy.

A Systematic Review and Meta-analysis of Randomized Controlled Trials on the Effects of Turmeric and Curcuminoids on Blood Lipids in Adults with Metabolic Diseases

Dyslipidemia is a global health problem and a high risk factor for atherosclerosis, which can lead to serious cardiovascular disease (CVD). Existing studies have shown inconsistent effects of turmeric and curcuminoids on blood lipids in adults. We performed this systematic review and meta-analysis to evaluate the effects of turmeric and curcuminoids on blood triglycerides (TG), total cholesterol (TC), LDL cholesterol, and HDL cholesterol. We searched the English databases of the Web of Science, PubMed, Ovid (including EMBASE and MEDLINE), Scopus, and the Cochrane Library and 2 Chinese databases, Wanfang Data and China National Knowledge Infrastructure, for randomized controlled trials (RCTs) that studied the effects of turmeric and curcuminoids on blood TG, TC, LDL cholesterol, and HDL cholesterol in subjects with metabolic diseases. With random-effects models, separate meta-analyses were conducted by using inverse-variance. The results are presented as the mean difference with 95% CIs. Evidence from 12 RCTs for TG, 14 RCTs for TC, 13 RCTs for LDL cholesterol, and 16 RCTs for HDL cholesterol showed that turmeric and curcuminoids could lower blood TG by -19.1 mg/dL (95% CI: -31.7, -6.46 mg/dL; P = 0.003), TC by -11.4 mg/dL (95% CI: -17.1, -5.74 mg/dL; P < 0.0001), and LDL cholesterol by -9.83 mg/dL (95% CI: -15.9, -3.74 mg/dL; P = 0.002), and increase HDL cholesterol by 1.9 mg/dL (95% CI: 0.31, 3.49 mg/dL; P = 0.02). In conclusion, turmeric and curcuminoids can significantly modulate blood lipids in adults with metabolic diseases. However, these findings should be interpreted cautiously because of the significant heterogeneity between included studies (I2 > 50%). There is a need for further RCTs in future.

Curcumin induces secretion of glucagon-like peptide-1 through an oxidation-dependent mechanism

Curcumin shows antiglycemic effects in animals. Curcumin is chemically unstable at physiological pH, and its oxidative degradation products were shown to contribute to its anti-inflammatory effects. Since the degradation products may also contribute to other effects, we analyzed their role in the antiglycemic activity of curcumin. We quantified curcumin-induced release of glucagon-like peptide 1 (GLP-1) from mouse STC-1 cells that represent enteroendocrine L-cells as a major source of this anti-diabetic hormone. Curcumin induced secretion of GLP-1 in a dose-dependent manner. Two chemically stable analogues of curcumin that do not readily undergo degradation, were less active while two unstable analogues were active secretagogues. Chromatographically isolated spiroepoxide, an unstable oxidative metabolite of curcumin with anti-inflammatory activity, also induced secretion of GLP-1. Stable compounds like the final oxidative metabolite bicyclopentadione, and the major plasma metabolite, curcumin-glucuronide, were inactive. GLP-1 secretion induced by curcumin and its oxidative degradation products was associated with activation of PKC, ERK, and CaM kinase II. Since activity largely correlated with instability of curcumin and the analogues, we tested the extent of covalent binding to proteins in STC-1 cells and found it occurred with similar affinity as N-ethylmaleimide, indicating covalent binding occurred with nucleophilic cysteine residues. These results suggest that oxidative metabolites of curcumin are involved in the antiglycemic effects of curcumin. Our findings support the hypothesis that curcumin functions as a pro-drug requiring oxidative activation to reveal its bioactive metabolites that act by binding to target proteins thereby causing a change in function.

Effects of Turmeric (Curcuma longa) Extract in streptozocin-induced diabetic model

Herbal remedies have been used for centuries to ameliorate complications of diabetes mellitus (DM). The aim of this study is to compare the effects of the oral curcumin supplement versus parenteral administration of turmeric extract on diabetic complications in a streptozocin (STZ) diabetic model. STZ DM rats received low and high doses turmeric extract intraperitoneally as well as oral curcumin. Curcumin and turmeric extracts significantly reduced blood glucose and creatinine levels, but not urea, and caused an increase in uric acid. Low dose improved liver enzymes, while higher dose and oral administration caused an increase in the ALT and AST. All groups showed an improvement in the serum cholesterol, while the triglycerides were not improved in the high and oral treatment. Histological evaluation showed islet cell protection. High-dose injection showed almost intact renal corpuscles as well as tubular structures with minimal degeneration. Treatment showed limited protection of Liver tissue. PRACTICAL APPLICATION: Curcumin has been heavily marketed as a protective agent. The current study shows some potential risk of curcumin use. Oral and injectable curcumin should be used with caution. Turmeric extract and oral curcumin supplement showed protective effects on pancreatic, and renal structure and function. Although both did show some improvement in liver function, higher doses caused disturbance in liver enzymes and did not show histological evidence of liver tissue protection.

The effect of curcumin supplementation on anthropometric indices, insulin resistance and oxidative stress in patients with type 2 diabetes: a randomized, double-blind clinical trial

BACKGROUND

Diabetes mellitus is a common metabolic disorders in human and affect a lot of people around the world. Curcumin is a component of turmeric and in many studies therapeutic effects such as anti-hypertensive, anti-hyperlipidemia, anti-hyperglycemia for this substance are shown.

AIM

The aim of this study was to investigate the effect of curcumin supplementation on anthropometric indices glycemic control and oxidative stress in overweight patients with type 2 diabetes.

MATERIALS AND METHODS

In this randomized, double-blind, placebo-controlled trial, 53 participants with type 2 diabetes were divided randomly into the experimental and control groups to receive either 1500 mg curcumin or placebo capsule three times in a day for 10 weeks.

RESULT

Supplementation with curcumin in type 2 diabetes compare to placebo causes a significant changes in mean weight (- 0.64 ± 0.22 vs. 0.19 ± 0.37 p < 0.05), body mass index (BMI) (0.3 ± 0.03 vs. 0.1 ± 0 p < 0.05), waist circumference (WC) (- 1.2 ± 0.4 vs. - 0.43 ± 0.11 p < 0.05) and fasting blood sugar (FBS) (- 7 ± 2 vs. 3 ± 0.2 p < 0.05) but did not show any difference for hemoglobin A1c (HbA1c), insulin, malondialdehyde (MDA), total antioxidant capacity (TAC), Homeostatic Model Assessment for Insulin Resistance (HOMA-IR) and pancreatic B cell function (HOMA-B) at end of study.

CONCLUSION

This study indicated that daily administration of 1500 mg curcumin has positive effects in reducing fasting blood glucose and weight in patients with type 2 diabetes.Trial registration NCT02529982. Registered 19 August 2015, http://www.clinicaltrial.gov.

A novel bioavailable hydrogenated curcuminoids formulation (CuroWhite™) improves symptoms and diagnostic indicators in rheumatoid arthritis patients - A randomized, double blind and placebo controlled study

Rheumatoid arthritis (RA) is an inflammatory disease that cause chronic pain, disability and joint destruction. The present placebo controlled randomized study aimed to evaluate the efficacy of a novel hydrogenated curcuminoid formulation-CuroWhite™, in rheumatoid arthritis (RA) patients. Twenty four RA patients were randomized in 1:1:1 ratio to receive 250 mg, 500 mg CuroWhite or placebo as one capsule a day, over a period of three months. Improvement in the ACR response, changes in disease activity assessed using the DAS 28 score, change in physical function assessed on change in ESR, CRP, RF values were evaluated before and after the study. Results suggested that patients who received CuroWhite both low and high doses reported statistically significant changes in their clinical symptoms towards end of the study when compared with placebo. There were significant changes in DAS28 (50–64%) VAS (63–72%) ESR (88–89%), CRP (31–45%) RF (80–84%) values and ACR response for CuroWhite groups in comparison with placebo. Thus, CuroWhite acts as the analgesic and anti-inflammatory product for management of RA by the reduction of the inflammatory action which was confirmed by improvement in ESR, CRP, VAS, RF, DAS-28 and ACR responses. CuroWhite was significantly effective against RA with highly safe without serious side effects and well tolerated.

Food Components in Health Promotion and Disease Prevention

The current obesity epidemic with its deleterious effects on public health and the increase in the prevalence of non-communicable diseases in our aging society have dramatically increased public awareness of nutrition-related health issues. On one hand, food components, such as fat, sugar, flavors, and spices, are major determinants of the hedonic value of food, and the constant and almost ubiquitous availability of good-tasting food in our affluent societies promotes overeating and weight gain. On the other hand, several food components, including flavoring compounds and the active ingredients of many plants, such as spices and herbs (e.g., polyphenols and capsaicinoids) or thylakoids, supposedly can decrease food intake and affect gastrointestinal function and metabolism. These substances may act as antioxidants, may stimulate the release of incretins and, hence, insulin, and may improve insulin sensitivity or decrease plasma levels of lipids. Such beneficial effects are often difficult to demonstrate in epidemiological studies because they may occur only at supraphysiological doses and/or when the purified compounds are administered, but they can be present under certain circumstances. This review discusses the putative mechanisms of the health-promoting and disease-preventing effects of some food components and their potential physiological relevance, primarily with respect to counteracting obesity and type 2 diabetes.

"mTOR Signaling Pathway": A Potential Target of Curcumin in the Treatment of Spinal Cord Injury

The purpose of this review is to discuss the possibility of the treatment of spinal cord injury (SCI) with curcumin via regulating the mTOR signaling pathway, which may provide another strong support for curcumin to be a promising medicine applied to the treatment of SCI. Curcumin is termed as a multifunctional targeting therapy drug that regulates the mTOR signaling pathway in the treatment of numerous diseases. Previous research has already revealed that mTOR signaling pathway plays a vital role in prognosis, which involves the axon regeneration and autophagy. This review discusses a potential mechanism that curcumin suppresses the activation of this pathway and ameliorates the microenvironment of axons regeneration which would provide a new way that induces autophagy appropriately.

Curcumin Improves Palmitate-Induced Insulin Resistance in Human Umbilical Vein Endothelial Cells by Maintaining Proteostasis in Endoplasmic Reticulum

Dysfunction of proteasome and autophagy will result in disturbance of endoplasmic reticulum (ER) proteostasis, and thus lead to long-term and chronic ER stress and subsequent unfolded protein response (UPR), which is implicated in the occurrence and development of insulin resistance. Curcumin exerts beneficial metabolic effects in in vitro cells and in vivo animal models of diabetes and diabetic complications including cardiovascular diseases, due to its powerful anti-oxidative and anti-inflammatory properties. However, its impacts on insulin resistance of endothelial cells and its underlying mechanism(s) remain ill-defined. Herein, we tested the hypothesis that curcumin action in ER protein quality control was related to improvement of insulin resistance in human umbilical vein endothelial cells (HUVECs) cultured with saturated fatty acid palmitate. We found that palmitate treatment induced insulin resistance of HUVECs and activated both the ubiquitin-proteasome system (UPS) and autophagy. Palmitate-stimulated activation of the UPS and autophagy was attenuated by pharmacological inhibition of ER stress. In addition, curcumin supplementation mitigated palmitate-induced insulin resistance, inhibited the UPS, and activated autophagy. Furthermore, curcumin administration suppressed palmitate-induced protein aggregation and ER stress. Genetic inhibition of autophagy by silencing autophagy protein 5 (Atg5) completely restored total protein ubiquitination and protein aggregation in HUVECs treated with combined curcumin and palmitate. Atg5-knockdown also abolished the beneficial effects of curcumin on palmitate-induced ER stress, JNK/IRS-1 pathway as well as insulin signaling. Our results reveal that curcumin-activated autophagy could maintain proteostasis in ER leading to attenuation of ER stress and subsequent inhibition of JNK/IRS-1 pathway and improvement of insulin resistance.

Curcuma longa L. extract improves the cortical neural connectivity during the aging process

Turmeric or Curcuma is a natural product that has anti-inflammatory, antioxidant and anti-apoptotic pharmacological properties. It can be used in the control of the aging process that involves oxidative stress, inflammation, and apoptosis. Aging is a physiological process that affects higher cortical and cognitive functions with a reduction in learning and memory, limited judgment and deficits in emotional control and social behavior. Moreover, aging is a major risk factor for the appearance of several disorders such as cerebrovascular disease, diabetes mellitus, and hypertension. At the brain level, the aging process alters the synaptic intercommunication by a reduction in the dendritic arbor as well as the number of the dendritic spine in the pyramidal neurons of the prefrontal cortex, hippocampus and basolateral amygdala, consequently reducing the size of these regions. The present review discusses the synaptic changes caused by the aging process and the neuroprotective role the Curcuma has through its anti-inflammatory, antioxidant and anti-apoptotic actions

Nanoencapsulation, an efficient and promising approach to maximize wound healing efficacy of curcumin: A review of new trends and state-of-the-art

Wound healing is a multifarious and vibrant process of replacing devitalized and damaged cellular structures, leading to restoration of the skin's barrier function, re-establishment of tissue integrity, and maintenance of the internal homeostasis. Curcumin (CUR) and its analogs have gained widespread recognition due to their remarkable anti-inflammatory, anti-infective, anticancer, immunomodulatory, antioxidant, and wound healing activities. However, their pharmaceutical significance is limited due to inherent hydrophobic nature, poor water solubility, low bioavailability, chemical instability, rapid metabolism and short half-life. Owing to their pharmaceutical limitations, newer strategies have been attempted in recent years aiming to mitigate problems related to the effective delivery of curcumanoids and to improve their wound healing potential. These advanced strategies include nanovesicles, polymeric micelles, conventional liposomes and hyalurosomes, nanocomposite hydrogels, electrospun nanofibers, nanohybrid scaffolds, nanoconjugates, nanostructured lipid carriers (NLCs), nanoemulsion, nanodispersion, and polymeric nanoparticles (NPs). The superior wound healing activities achieved after nanoencapsulation of the CUR are attributed to its target-specific delivery, longer retention at the target site, avoiding premature degradation of the encapsulated cargo and the therapeutic superiority of the advanced delivery systems over the conventional delivery. We have critically reviewed the literature and summarize the convincing evidence which explore the pharmaceutical significance and therapeutic feasibility of the advanced delivery systems in improving wound healing activities of the CUR and its analogs.

Curcumin directly inhibits the transport activity of GLUT1

Curcumin, a major ingredient in turmeric, has a long history of medicinal applications in a wide array of maladies including treatment for diabetes and cancer. Seemingly counterintuitive to the documented hypoglycemic effects of curcumin, however, a recent report indicates that curcumin directly inhibits glucose uptake in adipocytes. The major glucose transporter in adipocytes is GLUT4. Therefore, this study investigates the effects of curcumin in cell lines where the major transporter is GLUT1. We report that curcumin has an immediate inhibitory effect on basal glucose uptake in L929 fibroblast cells with a maximum inhibition of 80% achieved at 75 μM curcumin. Curcumin also blocks activation of glucose uptake by azide, glucose deprivation, hydroxylamine, or phenylarsine oxide. Inhibition does not increase with exposure time and the inhibitory effects reverse within an hour. Inhibition does not appear to involve a reaction between curcumin and the thiol side chain of a cysteine residue since neither prior treatment of cells with iodoacetamide nor curcumin with cysteine alters curcumin's inhibitory effects. Curcumin is a mixed inhibitor reducing the Vmax of 2DG transport by about half with little effect on the Km. The inhibitory effects of curcumin are not additive to the effects of cytochalasin B and 75 μM curcumin actually reduces specific cytochalasin B binding by 80%. Taken together, the data suggest that curcumin binds directly to GLUT1 at a site that overlaps with the cytochalasin B binding site and thereby inhibits glucose transport. A direct inhibition of GLUT proteins in intestinal epithelial cells would likely reduce absorption of dietary glucose and contribute to a hypoglycemic effect of curcumin. Also, inhibition of GLUT1 activity might compromise cancer cells that overexpress GLUT1 and be another possible mechanism for the documented anticancer effects of curcumin.

Antidiabetic efficacy of citronellol, a citrus monoterpene by ameliorating the hepatic key enzymes of carbohydrate metabolism in streptozotocin-induced diabetic rats

Diabetes mellitus is a clinically complex disease characterized by chronic hyperglycemia with metabolic disturbances. During diabetes, endogenous hepatic glucose production is increased as a result of impaired activities of the key enzymes of carbohydrate metabolism. The purpose of the present study was to evaluate the antidiabetic efficacy of citronellol, a citrus monoterpene in streptozotocin (STZ)-induced diabetic rats. Diabetes mellitus was induced by a single intraperitoneal injection of STZ (40 mg/kg b.w). STZ induced diabetic rats received citronellol orally at the doses of 25, 50, and 100 mg/kg b.w for 30 days. In this study the levels of plasma glucose, insulin, hemoglobin (Hb), glycated hemoglobin (HbA1C), glycogen, and the activities of carbohydrate metabolic enzymes, liver and kidney markers were evaluated. Oral administration of citronellol (50 mg/kg) for 30 days dose dependently improved the levels of insulin, Hb and hepatic glycogen with significant decrease in glucose and HbA1C levels. The altered activities of carbohydrate metabolic enzymes, hepatic and kidney markers were restored to near normal. Citronellol supplement was found to be effective in preserving the normal histological appearance of hepatic cells and insulin-positive β-cells in STZ-rats. Our results suggest that administration of citronellol attenuates the hyperglycemia in the STZ-induced diabetic rats by ameliorating the key carbohydrate metabolic enzymes and could be developed as a functional and nutraceutical ingredient in combating diabetes mellitus.

Exploring the use of nanocarrier systems to deliver the magical molecule; Curcumin and its derivatives

Curcumin and its derivatives; curcuminoids have been proven as potential remedies in different diseases. However, their delivery carries several challenges owing to their poor aqueous solubility, photodegradation, chemical instability, poor bioavailability and rapid metabolism. This review explores and criticizes the numerous attempts that were adopted through the years to entrap/encapsulate this valuable drug in nanocarriers aiming to reach its most appropriate and successful delivery system.

Recent developments in curcumin and curcumin based polymeric materials for biomedical applications: A review

Turmeric (Curcuma longa) is a popular Indian spice that has been used for centuries in herbal medicines for the treatment of a variety of ailments such as rheumatism, diabetic ulcers, anorexia, cough and sinusitis. Curcumin (diferuloylmethane) is the main curcuminoid present in turmeric and responsible for its yellow color. Curcumin has been shown to possess significant anti-inflammatory, anti-oxidant, anti-carcinogenic, anti-mutagenic, anticoagulant and anti-infective effects. This review summarizes and discusses recently published papers on the key biomedical applications of curcumin based materials. The highlighted studies in the review provide evidence of the ability of curcumin to show the significant vitro antioxidant, diabetic complication, antimicrobial, neuroprotective, anti-cancer activities and detection of hypochlorous acid, wound healing, treatment of major depression, healing of paracentesis, and treatment of carcinoma and optical detection of pyrrole properties. Hydrophobic nature of this polyphenolic compound along with its rapid metabolism, physicochemical and biological instability contribute to its poor bioavailability. To redress these problems several approaches have been proposed like encapsulation of curcumin in liposomes and polymeric micelles, inclusion complex formation with cyclodextrin, formation of polymer-curcumin conjugates, etc.

Natural Nrf2 activators in diabetes

Prediabetes and diabetes are rising worldwide. Control of blood glucose is crucial to prevent or delay diabetic complications that frequently result in increased morbidity and mortality. Most strategies include medical treatment and changes in lifestyle and diet. Some nutraceutical compounds have been recognized as adjuvants in diabetes control. Many of them can activate the nuclear factor (erythroid-derived 2)-like 2 (Nrf2), which has been recognized as a master regulator of the antioxidant response. Recent studies have described the role of Nrf2 in obesity, metabolic syndrome, nephropathy, retinopathy and neuropathy, where its activation prevents the development of diabetes and its complications. It has been demonstrated that natural compounds derived from plants, vegetables, fungi and micronutrients (such as curcumin, sulforaphane, resveratrol and vitamin D among others) can activate Nrf2 and, thus, promote antioxidant pathways to mitigate oxidative stress and hyperglycemic damage. The role of some natural Nrf2 activators and its effect in diabetes is discussed.