Rosmarinic Acid Mediates Mitochondrial Biogenesis in Insulin Resistant Skeletal Muscle Through Activation of AMPK

Plant-Based Diets and Phytochemicals in the Management of Diabetes Mellitus and Prevention of Its Complications: A Review

Diabetes mellitus (DM) is currently regarded as a global public health crisis for which lifelong treatment with conventional drugs presents limitations in terms of side effects, accessibility, and cost. Type 2 diabetes (T2DM), usually associated with obesity, is characterized by elevated blood glucose levels, hyperlipidemia, chronic inflammation, impaired β-cell function, and insulin resistance. If left untreated or when poorly controlled, DM increases the risk of vascular complications such as hypertension, nephropathy, neuropathy, and retinopathy, which can be severely debilitating or life-threatening. Plant-based foods represent a promising natural approach for the management of T2DM due to the vast array of phytochemicals they contain. Numerous epidemiological studies have highlighted the importance of a diet rich in plant-based foods (vegetables, fruits, spices, and condiments) in the prevention and management of DM. Unlike conventional medications, such natural products are widely accessible, affordable, and generally free from adverse effects. Integrating plant-derived foods into the daily diet not only helps control the hyperglycemia observed in DM but also supports weight management in obese individuals and has broad health benefits. In this review, we provide an overview of the pathogenesis and current therapeutic management of DM, with a particular focus on the promising potential of plant-based foods.

Combination of plant metabolites hinders starch digestion and glucose absorption while facilitating insulin sensitivity to diabetes

Introduction

Diabetes mellitus (DM) is a common endocrine disease resulting from interactions between genetic and environmental factors. Type II DM (T2DM) accounts for approximately 90% of all DM cases. Current medicines used in the treatment of DM have some adverse or undesirable effects on patients, necessitating the use of alternative medications.

Methods

To overcome the low bioavailability of plant metabolites, all entities were first screened through pharmacokinetic, network pharmacology, and molecular docking predictions. Experiments were further conducted on a combination of antidiabetic phytoactive molecules (rosmarinic acid, RA; luteolin, Lut; resveratrol, RS), along with in vitro evaluation (α-amylase inhibition assay) and diabetic mice tests (oral glucose tolerance test, OGTT; oral starch tolerance test, OSTT) for maximal responses to validate starch digestion and glucose absorption while facilitating insulin sensitivity.

Results

The results revealed that the combination of metabolites achieved all required criteria, including ADMET, drug likeness, and Lipinski rule. To determine the mechanisms underlying diabetic hyperglycemia and T2DM treatments, network pharmacology was used for regulatory network, PPI network, GO, and KEGG enrichment analyses. Furthermore, the combined metabolites showed adequate in silico predictions (α-amylase, α-glucosidase, and pancreatic lipase for improving starch digestion; SGLT-2, AMPK, glucokinase, aldose reductase, acetylcholinesterase, and acetylcholine M2 receptor for mediating glucose absorption; GLP-1R, DPP-IV, and PPAR-γ for regulating insulin sensitivity), in vitro α-amylase inhibition, and in vivo efficacy (OSTT versus acarbose; OGTT versus metformin and insulin) as nutraceuticals against T2DM.

Discussion

The results demonstrate that the combination of RA, Lut, and RS could be exploited for multitarget therapy as prospective antihyperglycemic phytopharmaceuticals that hinder starch digestion and glucose absorption while facilitating insulin sensitivity.

Thymus atlanticus: A Source of Nutrients with Numerous Health Benefits and Important Therapeutic Potential for Age-Related Diseases

Thymus atlanticus (Lamiaceae) is a plant endemic to the Mediterranean basin that is found in significant quantities in the arid regions of Morocco. Thymus atlanticus is used in traditional medicine to treat infectious and non-infectious diseases. It is also used for the isolation of essential oils and for the seasoning of many dishes in the Mediterranean diet. The major constituents of Thymus atlanticus are saponins, flavonoids, tannins, alkaloids, various simple and hydroxycinnamic phenolic compounds, and terpene compounds. Several of these compounds act on signaling pathways of oxidative stress, inflammation, and blood sugar, which are parameters often dysregulated during aging. Due to its physiochemical characteristics and biological activities, Thymus atlanticus could be used for the prevention and/or treatment of age-related diseases. These different aspects are treated in the present review, and we focused on phytochemistry and major age-related diseases: dyslipidemia, cardiovascular diseases, and type 2 diabetes.

Natural Drugs: A New Direction for the Prevention and Treatment of Diabetes

Insulin resistance, as a common pathological process of many metabolic diseases, including diabetes and obesity, has attracted much attention due to its relevant influencing factors. To date, studies have mainly focused on the shared mechanisms between mitochondrial stress and insulin resistance, and they are now being pursued as a very attractive therapeutic target due to their extensive involvement in many human clinical settings. In view of the complex pathogenesis of diabetes, natural drugs have become new players in diabetes prevention and treatment because of their wide targets and few side effects. In particular, plant phenolics have received attention because of their close relationship with oxidative stress. In this review, we briefly review the mechanisms by which mitochondrial stress leads to insulin resistance. Moreover, we list some cytokines and genes that have recently been found to play roles in mitochondrial stress and insulin resistance. Furthermore, we describe several natural drugs that are currently widely used and give a brief overview of their therapeutic mechanisms. Finally, we suggest possible ideas for future research related to the unique role that natural drugs play in the treatment of insulin resistance through the above targets.

BaoShenTongLuo formula protects against podocyte injury by regulating AMPK-mediated mitochondrial biogenesis in diabetic kidney disease

BACKGROUND

Mitochondrial dysfunction is considered to be an important contributor in podocyte injury under diabetic conditions. The BaoShenTongLuo (BSTL) formula has been shown to reduce podocyte damage and postpone the progression of diabetic kidney disease (DKD). The potential mechanisms underlying the effects of BSTL, however, have yet to be elucidated. In this study, we aimed to investigate whether the effects of BSTL are related to the regulation of mitochondrial biogenesis via the adenosine monophosphate-activated protein kinase (AMPK) pathway.

METHODS

High-Performance Liquid Chromatography Electrospray Ionization Mass Spectrometer (HPLC-ESI-MS) analysis was performed to investigate the characteristics of pure compounds in BSTL. db/db mice and mouse podocyte clone-5 (MPC5) cells were exposed to high glucose (HG) to induce DKD and podocyte damage. Body weight, random blood glucose, urinary albumin/creatinine ratio (UACR), indicators of renal function and renal histological lesions were measured. Markers of podocyte injury, mitochondrial morphology, mitochondrial deoxyribonucleic acid (mtDNA) content, mitochondrial respiratory chain complexes activities, reactive oxygen species (ROS) production, and mitochondrial membrane potential (MMP) levels were assessed. Protein expressions of AMPK, peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1α), transcription factor A (TFAM), mitochondrial fusion protein 2 (MFN2) and dynamin-related protein 1 (DRP1) were also detected. MPC5 cells were transfected with AMPKα small interfering RNA (AMPKα siRNA) to determine the underlying mechanisms of BSTL improvement of mitochondrial function under diabetic conditions.

RESULTS

In vivo, treatment with BSTL reduced the UACR levels, reversed the histopathological changes in renal tissues, and alleviated the podocyte injury observed in db/db mice. After BSTL treatment, the decreased mtDNA content and mitochondrial respiratory chain complex I, III, and IV activities were significantly improved, and these effects were accompanied by maintenance of the protein expression of p-AMPKαT172, PGC-1α, TFAM and MFN2. The in vitro experiments also showed that BSTL reduced podocyte apoptosis, suppressed excessive cellular ROS production, and reversed the decreased in MMP that were observed under HG conditions. More importantly, the effects of BSTL in enhancing mitochondrial biogenesis and reducing podocyte apoptosis were inhibited in AMPKα siRNA-treated podocytes.

CONCLUSION

BSTL plays a crucial role in protecting against podocyte injury by regulating the AMPK-mediated mitochondrial biogenesis in DKD.

Muscle Cell Insulin Resistance Is Attenuated by Rosmarinic Acid: Elucidating the Mechanisms Involved

Obesity and elevated blood free fatty acid (FFA) levels lead to impaired insulin action causing insulin resistance in skeletal muscle, and contributing to the development of type 2 diabetes mellitus (T2DM). Mechanistically, insulin resistance is associated with increased serine phosphorylation of the insulin receptor substrate (IRS) mediated by serine/threonine kinases including mTOR and p70S6K. Evidence demonstrated that activation of the energy sensor AMP-activated protein kinase (AMPK) may be an attractive target to counteract insulin resistance. We reported previously that rosemary extract (RE) and the RE polyphenol carnosic acid (CA) activated AMPK and counteracted the FFA-induced insulin resistance in muscle cells. The effect of rosmarinic acid (RA), another polyphenolic constituent of RE, on FFA-induced muscle insulin resistance has never been examined and is the focus of the current study. Muscle cell (L6) exposure to FFA palmitate resulted in increased serine phosphorylation of IRS-1 and reduced insulin-mediated (i) Akt activation, (ii) GLUT4 glucose transporter translocation, and (iii) glucose uptake. Notably, RA treatment abolished these effects, and restored the insulin-stimulated glucose uptake. Palmitate treatment increased the phosphorylation/activation of mTOR and p70S6K, kinases known to be involved in insulin resistance and RA significantly reduced these effects. RA increased the phosphorylation of AMPK, even in the presence of palmitate. Our data indicate that RA has the potential to counteract the palmitate-induced insulin resistance in muscle cells, and further studies are required to explore its antidiabetic properties.

Rosmarinic acid protects against lipopolysaccharide-induced cardiac dysfunction via activating Sirt1/PGC-1α pathway to alleviate mitochondrial impairment

Sepsis-induced cardiomyopathy is a decisive factor that plays a critical role in the high mortality of septic patients in the critically ill. Mitochondrial dysfunction occurring during sepsis is a vital contributor to the pathogenesis of myocardial damage. Rosmarinic acid (RA), a natural poly-phenolic compound, has showed cardio-protective and mitochondrial protective effect. The present study was aimed to investigate the effect of RA on sepsis-induced cardiomyopathy. Adult mice were subjected to intraperitoneal injection of saline (control) or lipopolysaccharide (LPS, 5 mg/kg) to mimic sepsis-induced cardiomyopathy. Immediately after LPS challenge, vehicle or RA (100 mg/kg/day) was administrated via gavage. Cardiac function was examined with echocardiographic analyses 12 hours after LPS challenge and cumulative survival of mice was recorded for 8 days. Heart tissues were harvested 12 hours after LPS challenge to perform histological analyses and determine mitochondrial function. We found RA significantly improved cardiac function and survival of LPS-injected mice. Histologically, RA attenuated LPS-mediated cardiomyocyte damage, indicated by decreased cardiomyocyte apoptosis and improved myocardial swollen and disarrangement. Moreover, RA attenuated LPS-mediated myocardial mitochondrial dysfunction, indicated by improved mitochondrial ultrastructure, increased mitochondrial membrane potential (MMP), synthesis of adenosine triphosphate (ATP), markedly decreased reactive oxygen species (ROS) level and alleviated oxidative stress in heart tissues. RA treatment downregulated protein expression of Sirt1 and peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α), and Sirt1 inhibition blocked protective effect of RA on LPS-induced myocardial damage and mitochondrial dysfunction. Collectively, RA attenuates LPS-induced cardiac dysfunction via activating Sirt1/PGC-1α pathway to alleviate mitochondrial impairment. It may be a promising cardio-protective drug to be used for septic patients.

Photobiomodulation promotes repair following spinal cord injury by restoring neuronal mitochondrial bioenergetics via AMPK/PGC-1α/TFAM pathway

Background: Insufficient neuronal mitochondrial bioenergetics supply occurs after spinal cord injury (SCI), leading to neuronal apoptosis and impaired motor function. Previous reports have shown that photobiomodulation (PBM) could reduce neuronal apoptosis and promote functional recovery, but the underlying mechanism remains unclear. Therefore, we aimed to investigate whether PBM improved prognosis by promoting neuronal mitochondrial bioenergetics after SCI.

Methods: Sprague Dawley rats were randomly divided into four groups: a Sham group, an SCI group, an SCI + PBM group and an SCI + PBM + Compound C group. After SCI model was established, PBM and Compound C (an AMPK inhibitor) injection were carried out. The level of neuron apoptosis, the recovery of motor function and mitochondrial function were observed at different times (7, 14, and 28 days). The AMPK/PGC-1α/TFAM pathway was hypothesized to be a potential target through which PBM could affect neuronal mitochondrial bioenergetics. In vitro, ventral spinal cord 4.1 (VSC4.1) cells were irradiated with PBM and cotreated with Compound C after oxygen and glucose deprivation (OGD).

Results: PBM promoted the recovery of mitochondrial respiratory chain complex activity, increased ATP production, alleviated neuronal apoptosis and reversed motor dysfunction after SCI. The activation of the AMPK/PGC-1α/TFAM pathway after SCI were facilitated by PBM but inhibited by Compound C. Equally important, PBM could inhibit OGD-induced VSC4.1 cell apoptosis by increasing ATP production whereas these changes could be abolished by Compound C.

Conclusion: PBM activated AMPK/PGC-1α/TFAM pathway to restore mitochondrial bioenergetics and exerted neuroprotective effects after SCI.

Radiolabeling, biological distribution, docking and ADME studies of 99mTc-Ros as a promising natural tumor tracer

Rosmarinic acid (Ros) is one of phenolic metabolites with powerful potency as an anticancer agent, with different mechanisms to diminish the cancer cells. This current study represents radiolabeling of Ros with 99mTc using SnCl2 in pH4 for 15 min at 60 °C, The yield up to 92.2%. Biological evaluation in normal and cancer mice revealed the localization of the tracer in tumor tissue. Furthermore, docking and ADME (Absorption, Distribution, Metabolism, and Excretion) studies were performed, The resulted data clarifies the use of Ros as a promissing natural tracer.

The Antioxidant Activity of Thymus serpyllum Extract Protects against the Inflammatory State and Modulates Gut Dysbiosis in Diet-Induced Obesity in Mice

Nowadays, there is an increasing interest in alternative therapies in the treatment of metabolic syndrome that combine efficacy and safety profiles. Therefore, this study aimed to evaluate the effect of an extract of Thymus serpyllum, containing rosmarinic acid, on high-fat diet (HFD)-induced obesity mice, highlighting the impact of its antioxidant activity on the inflammatory status and gut dysbiosis. The extract was administered daily (50, 100 and 150 mg/kg) in HFD-fed mice. The treatment reduced body weight gain, glucose and lipid metabolic profiles. Moreover, the extract ameliorated the inflammatory status, with the c-Jun N-terminal kinases (JUNK) pathway being involved, and showed a significant antioxidant effect by the reduction of radical scavenging activity and the mitigation of lipid peroxidation. Moreover, the extract was able to modulate the altered gut microbiota, restoring microbial richness and diversity, and augmenting the counts of short-chain fatty acid producing bacteria, which have been associated with the maintenance of gut permeability and weight regulation. In conclusion, the antioxidant activity of Thymus serpyllum extract displayed a positive impact on obesity and its metabolic alterations, also reducing systemic inflammation. These effects may be mediated by modulation of the gut microbiota.

The Use of Bioactive Compounds in Hyperglycemia- and Amyloid Fibrils-Induced Toxicity in Type 2 Diabetes and Alzheimer’s Disease

It has become increasingly apparent that defective insulin signaling may increase the risk for developing Alzheimer’s disease (AD), influence neurodegeneration through promotion of amyloid formation or by increasing inflammatory responses to intraneuronal β-amyloid. Recent work has demonstrated that hyperglycemia is linked to cognitive decline, with elevated levels of glucose causing oxidative stress in vulnerable tissues such as the brain. The ability of β-amyloid peptide to form β-sheet-rich aggregates and induce apoptosis has made amyloid fibrils a leading target for the development of novel pharmacotherapies used in managing and treatment of neuropathological conditions such as AD-related cognitive decline. Additionally, deposits of β-sheets folded amylin, a glucose homeostasis regulator, are also present in diabetic patients. Thus, therapeutic compounds capable of reducing intracellular protein aggregation in models of neurodegenerative disorders may prove useful in ameliorating type 2 diabetes mellitus symptoms. Furthermore, both diabetes and neurodegenerative conditions, such as AD, are characterized by chronic inflammatory responses accompanied by the presence of dysregulated inflammatory biomarkers. This review presents current evidence describing the role of various small bioactive molecules known to ameliorate amyloidosis and subsequent effects in prevention and development of diabetes and AD. It also highlights the potential efficacy of peptide–drug conjugates capable of targeting intracellular targets.

Rosmarinic acid ameliorated cardiac dysfunction and mitochondrial injury in diabetic cardiomyopathy mice via activation of the SIRT1/PGC-1α pathway

Mitochondrial injury plays an essential role in the pathogenesis of diabetic cardiomyopathy (DCM). Previous studies demonstrated that rosmarinic acid (RA) treatment prevented high glucose-induced mitochondrial injury in vitro. However, whether RA can ameliorate cardiac function by preventing mitochondrial injury in DCM is unknown. The SIRT1/PGC-1α pathway has emerged as an important regulator of metabolic control and other mitochondrial functions. The present study was undertaken to determine the effects of RA on mitochondrial and cardiac function in DCM as well as the involvement of the SIRT1/PGC-1α pathway. Our results revealed that RA improved cardiac systolic and diastolic function and prevented mitochondrial injury in DCM, as shown by the reduced blood glucose and lipid levels, increased mitochondrial membrane potential levels, improved adenosine triphosphate synthesis, and inhibited apoptosis (P < 0.05). Moreover, RA upregulated the expression of SIRT1 and PGC-1α in DCM mice and high glucose-treated H9c2 cardiomyocytes (P < 0.05). Further mechanistic studies in H9c2 cardiomyocytes revealed that suppression of SIRT1 by Sh-SIRT1 counteracted the effects of RA on high glucose-induced abnormal metabolism of glucose and lipids, oxidative stress and apoptosis (P < 0.05). Taken together, these data indicate that RA prevented mitochondrial injury and cardiac dysfunction in DCM mice, and the SIRT1/PGC-1α pathway mediated the protective effects of RA.

Rosmarinic acid improves boar sperm quality, antioxidant capacity and energy metabolism at 17°C via AMPK activation

Boar sperm are susceptible to oxidative damage caused by reactive oxygen species (ROS) during storage. Adenosine monophosphate (AMP)-activated protein kinase (AMPK) is an important therapeutic target, because it is a cellular metabolism energy sensor and key signalling kinase in spermatozoa. We evaluated the effects of rosmarinic acid (RA), an antioxidant, on boar sperm during liquid storage to determine whether it protects boar sperm via AMPK activation. Boar ejaculates were diluted with Modena extender with different concentrations of RA and stored at 17°C for 9 days. Sperm quality parameters, antioxidant capacity, energy metabolism, AMPK phosphorylation and fertility were analysed. Compared with the control, 40 μmol/L significantly improved sperm motility, plasma membrane integrity and acrosome integrity (p < .05). The effective storage time of boar sperm was up to 9 days. On the third and seventh days, the sperm with RA exhibited increased total antioxidant capacity (T-AOC), superoxide dismutase (SOD) activity, adenosine triphosphate (ATP) content, mitochondrial membrane potential (ΔΨm) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) activity, whereas malondialdehyde (MDA) content was significantly decreased (p < .05). Western blot showed that RA, as well as AICAR (AMPK activator), promoted AMPK phosphorylation, whereas Compound C (AMPK inhibitor) inhibited this effect. The sperm-zona pellucida binding experiment showed that 40 μmol/L RA increased the number of sperm attached to the zona pellucida (p < .05). These findings suggest meaningful methods for improved preservation of boar sperm in vitro and provide new insights into the mechanism by which RA protects sperm cells from oxidative damage via AMPK activation.

Portulaca oleracea L. extract reduces hyperglycemia via PI3k/Akt and AMPK pathways in the skeletal muscles of C57BL/Ksj-db/db mice

HEADINGS ETHNOPHARMACOLOGICAL RELEVANCE

Portulaca oleracea L. is a succulent annual herb, which has various pharmacological effects including antidiabetic property. However, in vivo the reducing effect of P. oleracea on hyperglycemia and its mechanism of action have not been clarified in a mouse model of type 2 diabetes.

AIM OF THE STUDY

The effects of Portulaca oleracea L. extract (POE) on hyperglycemia were investigated in an animal model of type 2 diabetes.

MATERIALS AND METHODS

C57BL/Ksj-db/db mice were randomly divided into three groups: db/db-control group was fed a standard semi-synthetic diet (AIN-93 G), db/db-RG group was fed AIN-93 G supplemented with rosiglitazone (RG) (0.005%, w/w), and db/db-POE group was fed AIN-93 G supplemented with POE (0.4%, w/w) for 6 weeks. Diabetes-related physical and biochemical indicators and the phosphorylation of components of PI3k/Akt and AMPK pathways were measured.

RESULTS

The blood glucose and the glycosylated hemoglobin levels (HbA1c) in db/db-POE group were significantly lower than those in db/db-control group. In db/db-POE group, The homeostatic index of insulin resistance (HOMA-IR) decreased significantly, whereas the quantitative insulin sensitivity check index (QUICKI) was higher than those in db/db-control group. POE significantly elicited the phosphorylation of IRS-1^Tyr612, Akt^Ser473, and AS160^Thr642, and the activation of PI3K in the skeletal muscle of mice. Additionally, POE significantly stimulated the phosphorylation of AMPK^Thr172, TBC1D1^Ser231, and ACC^Ser79 and elevated the expression of plasma membrane-glucose transporter type 4 (GLUT4).

CONCLUSIONS

These results indicate that POE reduces hyperglycemia by improving insulin resistance through the PI3k/Akt and AMPK pathways in the skeletal muscle of C57BL/Ksj-db/db mice.

Antidiabetic effect of Cordia morelosana, chemical and pharmacological studies

ETHNOPHARMACOLOGICAL IMPORTANCE

CORDIA MORELOSANA: Standley (Boraginaceae) is commonly used in folk medicine for the treatment of diarrhoea, kidney inflammation, diabetes, lung pain, bronchitis, asthma, hoarseness, cough and fever.

AIM

Current work was conducted to develop a bio-guided isolation of antidiabetic compounds from ethanolic extract of Cordia morelosana (EECm).

MATERIAL AND METHODS

The phytochemical bio-guided study was conducted by successive chromatographic techniques, and isolated compounds were characterized by 1D and 2D-NMR experiments. The in vivo antihyperglycemic and antidiabetic activities of EECm (100 mg/kg), and methyl rosmarinate (MR, 50 mg/kg) were determined on normoglycemic and diabetic murine models. Additionally, the in vitro activity was conducted to determine α-glucosidase inhibitory effect, and PPARs, GLUT4 and FATP expression on 3T3-L1 cells by RT-PCR. Acute and sub-chronic toxicological studies for EECm were conducted on rats, following the OECD guidelines (No. 420 and 407).

RESULTS

EECm promotes significant α-glucosidase inhibition (55.6%) at 1 mg/kg respect to the control. Also, EECm (100 mg/kg) showed significant antihyperglycemic effect on oral glucose tolerance test (OGTT), and in non-insulin dependent type 2 diabetes (NIDD) model, had antidiabetic activity (p < 0.001) compared to controls. The bio-guided isolation allowed to obtain four known compounds described as rosmarinic acid (RA), methyl rosmarinate (MR), nicotiflorine and 1-O-methyl-scyllo-inositol. On the other hand, MR showed significant antidiabetic and anthiyperglycemic activities (p < 0.05), and overexpression of PPARγ, PPARα, GLUT-4 and FATP than control. Docking studies were conducted with PPARγ and PPARα, showing interesting binding mode profile on those targets. Finally, EECm displayed a LD₅₀ > 2000 mg/kg and sub-chronic toxicological study reveals no toxic signs in animals tested compared to control.

CONCLUSION

EECm showed significant antihyperglycemic and antidiabetic actions being RA and MR the main antidiabetic metabolites.

Trelagliptin succinate: DPP-4 inhibitor to improve insulin resistance in adipocytes

Trelagliptin inhibits the enzyme dipeptidyl-4 (DPP-4) to treat type 2 diabetes and it may possess the potential to improve insulin resistance. However, the molecular mechanism is not known. In this study, the effect of trelagliptin succinate in improving insulin resistance was investigated. The differentiation system of 3T3-L1 mouse preadipocytes was used to determine the content of adipokines and the content of GLUT4 in the outer membrane. The expression of AKT, P-AKT, IRS-1 and P-IRS-1 in differentiated 3T3-L1 adipocytes was determined by western blotting. Our results demonstrated that trelagliptin succinate increased the expression of AKT, P-AKT, IRS-1 and P-IRS-1 in the PI-3K/AKT insulin signaling pathway. These events promote the trans-membrane function of GLUT4 and concomitant glucose intake in adipocytes. In addition, the secretion of free fatty acids and resistin were decreased. In conclusion, our study suggested that trelagliptin succinate improved insulin resistance in adipocytes via regulation of PI-3K/AKT/GLUT4 insulin signaling pathway.

Antidiabetic Effects and Mechanisms of Rosemary (Rosmarinus officinalis L.) and its Phenolic Components

Diabetes mellitus is a chronic endocrine disease result from absolute or relative insulin secretion deficiency, insulin resistance, or both, and has become a major and growing public healthy menace worldwide. Currently, clinical antidiabetic drugs still have some limitations in efficacy and safety such as gastrointestinal side effects, hypoglycemia, or weight gain. Rosmarinus officinalis is an aromatic evergreen shrub used as a food additive and medicine, which has been extensively used to treat hyperglycemia, atherosclerosis, hypertension, and diabetic wounds. A great deal of pharmacological research showed that rosemary extract and its phenolic constituents, especially carnosic acid, rosmarinic acid, and carnosol, could significantly improve diabetes mellitus by regulating glucose metabolism, lipid metabolism, anti-inflammation, and anti-oxidation, exhibiting extremely high research value. Therefore, this review summarizes the pharmacological effects and underlying mechanisms of rosemary extract and its primary phenolic constituents on diabetes and relative complications both in vitro and in vivo studies from 2000 to 2020, to provide some scientific evidence and research ideas for its clinical application.

Therapeutic Potential of Rosmarinic Acid: A Comprehensive Review

Naturally occurring food-derived active ingredients have received huge attention for their chemopreventive and chemotherapy capabilities in several diseases. Rosmarinic acid (RA) is a caffeic acid ester and a naturally-occurring phenolic compound in a number of plants belonging to the Lamiaceae family, such as Rosmarinus officinalis (rosemary) from which it was formerly isolated. RA intervenes in carcinogenesis through different ways, including in tumor cell proliferation, apoptosis, metastasis, and inflammation. On the other hand, it also exerts powerful antimicrobial, anti-inflammatory, antioxidant and even antidepressant, anti-aging effects. The present review aims to provide an overview on anticancer activities of RA and to deliberate its therapeutic potential against a wide variety of diseases. Given the current evidence, RA may be considered as part of the daily diet in the treatment of several diseases, with pre-determined doses avoiding cytotoxicity.

Rosmarinic acid improves hypertension and skeletal muscle glucose transport in angiotensin II-treated rats

BACKGROUND

Rosmarinic acid (RA) is a natural pure compound from herbs belonging to the Lamiaceae family, such as rosemary, sage, basil, and mint. The antioxidant, angiotensin-converting enzyme inhibitory, and vasodilatory effects of RA have been revealed. Angiotensin II (ANG II) is a potent agent that generates hypertension and oxidative stress. Hypertension and skeletal muscle insulin resistance are strongly related. The aim of this study was to evaluate the effects of acute and chronic RA treatment on blood pressure and skeletal muscle glucose transport in ANG II-induced hypertensive rats.

METHODS

Eight-week-old male Sprague Dawley rats were separated into SHAM and ANG II-infused (250 ng/kg/min) groups. ANG II rats were treated with or without acute or chronic RA at 10, 20, or 40 mg/kg. At the end of the experiment, body weight, liver and heart weights, oral glucose tolerance, skeletal muscle glucose transport activity, and signaling proteins were evaluated.

RESULTS

Both acute and chronic RA treatment decreased systolic, diastolic, and mean arterial blood pressure. Only acute RA at 40 mg/kg resulted in a reduction of fasting plasma glucose levels and an induction of skeletal muscle glucose transport activity. These effects might involve increased ERK activity in skeletal muscle. Meanwhile, chronic RA treatment with 10, 20, and 40 mg/kg prevented ANG II-induced hyperglycemia.

CONCLUSIONS

Both acute and chronic RA treatment attenuated ANG II-induced cardiometabolic abnormalities in rats. Therefore, RA would be an alternative strategy for improving skeletal muscle glucose transport and protecting against ANG II-induced hypertension and hyperglycemia.

Effect of Rosmarinic Acid on the Serum Parameters of Glucose and Lipid Metabolism and Oxidative Stress in Estrogen-Deficient Rats

Rosmarinic acid is found in medicinal and spice plants such as rosemary, lemon balm, and mint. The aim of the study was to investigate the effect of rosmarinic acid on parameters of glucose and lipid metabolism and parameters of oxidative stress in rats in the early phase of estrogen deficiency. The study was carried out on mature female Wistar rats divided into the following groups: sham-operated control rats, ovariectomized control rats, and ovariectomized rats treated orally with rosmarinic acid at a dose of 10 mg/kg or 50 mg/kg daily for 28 days. The concentration of sex hormones, parameters related to glucose and lipid metabolism as well as parameters of antioxidant abilities and oxidative damage were determined in the blood serum. In the ovariectomized control rats, the homeostasis model assessment of insulin resistance (HOMA-IR) index and cholesterol concentration increased, the superoxide dismutase activity increased, and the reduced glutathione concentration decreased. Administration of rosmarinic acid at both doses induced decreases in the fructosamine concentration and HOMA-IR, an increase in the concentration of reduced glutathione, and a decrease in the concentration of advanced oxidation protein products in ovariectomized rats. Moreover, rosmarinic acid at a dose of 50 mg/kg induced a decrease in the total cholesterol and triglyceride concentrations. The results indicate that rosmarinic acid may be useful in the prevention of metabolic disorders associated with estrogen deficiency, however further studies are necessary.

Antiobesity Effects of Purple Perilla (Perilla frutescens var. acuta) on Adipocyte Differentiation and Mice Fed a High-fat Diet

Purple perilla (PE) is a medicinal plant that has several health benefits. In this study, the antiobesity effect of PE was studied in 3T3-L1 preadipocytes and C57BL/6J mice fed high-fat diets. Triglyceride quantification and Oil Red O staining in matured adipocytes revealed that PE reduced lipid accumulation in differentiated adipocytes by downregulating adipogenic gene and upregulating lipolytic gene expressions. Mice were fed normal diet, high-fat diet and high-fat diet supplemented with different concentrations of PE. Treatment with PE significantly prevented body weight gain, improved serum lipids, hepatic lipids and reduced the epididymal fat. Furthermore, in the adipose tissue and liver, expression of genes related to lipolysis and fatty acid β-oxidation were upregulated in PE- treated mice. Thus, our results suggested that PE has antiobesity effects in rodents and can be effective in obesity management.

PRACTICAL APPLICATION

Purple perilla, rich in polyphenols such as rosmarinic acid, showed lipid lowering in adipocyte cells and prevented body weight gain in mice. Therefore we conclude that purple perilla may be a potential candidate for the development of functional foods or nutraceuticals in managing obesity in humans.

Rosmarinic Acid Activates AMPK to Inhibit Metastasis of Colorectal Cancer

Rosmarinic acid (RA) has been used as an anti-inflammatory, anti-diabetic, and anti-cancer agent. Although RA has also been shown to exert an anti-metastatic effect, the mechanism of this effect has not been reported to be associated with AMP-activated protein kinase (AMPK). The aim of this study was to elucidate whether RA could inhibit the metastatic properties of colorectal cancer (CRC) cells via the phosphorylation of AMPK. RA inhibited the proliferation of CRC cells through the induction of cell cycle arrest and apoptosis. In several metastatic phenotypes of CRC cells, RA regulated epithelial-mesenchymal transition (EMT) through the upregulation of an epithelial marker, E-cadherin, and the downregulation of the mesenchymal markers, N-cadherin, snail, twist, vimentin, and slug. Invasion and migration of CRC cells were inhibited and expressions of matrix metalloproteinase (MMP)-2 and MMP-9 were decreased by RA treatment. Adhesion and adhesion molecules such as ICAM-1 and integrin β1 expressions were also reduced by RA treatment. In particular, the effects of RA on EMT and MMPs expressions were due to the activation of AMPK. Moreover, RA inhibited lung metastasis of CRC cells by activating AMPK in mouse model. Collectively, these results proved that RA could be potential therapeutic agent against metastasis of CRC.

Rosmarinic acid attenuates cardiac fibrosis following long-term pressure overload via AMPKα/Smad3 signaling

Agonists of peroxisome proliferator-activated receptor gamma (PPAR-γ) can activate 5' AMP-activated protein kinase alpha (AMPKα) and exert cardioprotective effects. A previous study has demonstrated that rosmarinic acid (RA) can activate PPAR-γ, but its effect on cardiac remodeling remains largely unknown. Our study aimed to investigate the effect of RA on cardiac remodeling and to clarify the underlying mechanism. Mice were subjected to aortic banding to generate pressure overload induced cardiac remodeling and then were orally administered RA (100 mg/kg/day) for 7 weeks beginning 1 week after surgery. The morphological examination, echocardiography, and molecular markers were used to evaluate the effects of RA. To ascertain whether the beneficial effect of RA on cardiac fibrosis was mediated by AMPKα, AMPKα2 knockout mice were used. Neonatal rat cardiomyocytes and fibroblasts were separated and cultured to validate the protective effect of RA in vitro. RA-treated mice exhibited a similar hypertrophic response as mice without RA treatment, but had an attenuated fibrotic response and improved cardiac function after pressure overload. Activated AMPKα was essential for the anti-fibrotic effect of RA via inhibiting the phosphorylation and nuclear translocation of Smad3 in vivo and in vitro, and AMPKα deficiency abolished RA-mediated protective effects. Small interfering RNA against Ppar-γ (siPpar-γ) and GW9662, a specific antagonist of PPAR-γ, abolished RA-mediated AMPKα phosphorylation and alleviation of fibrotic response in vitro. RA attenuated cardiac fibrosis following long-term pressure overload via AMPKα/Smad3 signaling and PPAR-γ was required for the activation of AMPKα. RA might be a promising therapeutic agent against cardiac fibrosis.

Phenolic Substances from Ocimum Species Enhance Glucose-Stimulated Insulin Secretion and Modulate the Expression of Key Insulin Regulatory Genes in Mice Pancreatic Islets

Ocimum gratissimum and Ocimum basilicum are plants ethnopharmacologically used to treat diabetes mellitus, a life-threatening disease that affects millions of people worldwide. In order to further understand their antidiabetic potential, which has been previously demonstrated in animal models, we aimed to investigate the acute and chronic effects of major phenolic substances from both plants on insulin secretion and gene expression in pancreatic islets isolated from NMRI mice. Insulin secretion was measured after acute (1 h) and long-term (72 h) incubation of islets with one of four cinnamic acid derivatives (caftaric, caffeic, chicoric, and rosmarinic acids) or a C-glucosylated flavonoid (vicenin-2). All substances acutely enhanced glucose-stimulated insulin secretion (GSIS) from islets at concentrations from 10^-10 to 10^-6 M. They also increased GSIS after chronic incubation (10^-8 M). None of them increased insulin secretion in the presence of low glucose concentration. Furthermore, these substances markedly changed the gene expression profile of key insulin regulatory genes INS1, INS2, PDX1, INSR, IRS1, and proliferative genes as well as glucose transporter 2 (GLUT2), in treated islets. Thus, they may play an important role in diabetes treatment. This is the first report on the insulin-secretory activity of caftaric acid, rosmarinic acid, and vicenin-2.

Codonopsis lanceolata Water Extract Increases Hepatic Insulin Sensitivity in Rats with Experimentally-Induced Type 2 Diabetes

We examined the mechanisms and efficacy of Codonopsis lanceolata water extract (CLW) for treating type 2 diabetic (T2DM) symptoms. Partial pancreatectomized (Px) rats, a non-obese T2DM model, were provided high fat diets containing cellulose (control), 0.3% (CLW-L) or 1% CLW (CLW-H) for eight weeks. The positive control group was provided with rosiglitazone (20 mg/kg bw/day). The control group had lower epididymal fat masses than the CLW and the positive control groups, possibly due to urinary glucose loss, although CPT-1 and SIRT-1 expression was higher in the CLW group. CLW-H significantly reduced serum glucose levels and urinary glucose loss compared to the untreated control. The improvement of glucose utilization was associated with a higher fat mass in the CLW-H and positive control groups. Glucose-stimulated insulin secretion was higher in the untreated control than other groups and CLW tightly regulated insulin secretion as much as the positive control, and it was much tighter than the untreated control. Glucose infusion rates were higher during the hyperinsulinemic euglycemic clamp in the CLW and positive controls than the untreated control, and liver glucose outputs were lower during basal and hyperinsulinemic conditions in the CLW and positive control groups than the untreated control group. The increased hepatic insulin sensitivity was associated with enhanced insulin signaling in CLW (pAkt➔pGSK-1β). In conclusion, CLW consumption effectively alleviated diabetic symptoms by improving insulin sensitivity, potentiating hepatic insulin signaling and tightly regulating the insulin secretion capacity in non-obese T2DM rats.

Rosmarinic Acid, a Rosemary Extract Polyphenol, Increases Skeletal Muscle Cell Glucose Uptake and Activates AMPK

Skeletal muscle is a major insulin-target tissue and plays an important role in glucose homeostasis. Impaired insulin action in muscles leads to insulin resistance and type 2 diabetes mellitus. 5' AMP-activated kinase (AMPK) is an energy sensor, its activation increases glucose uptake in skeletal muscle and AMPK activators have been viewed as a targeted approach in combating insulin resistance. We previously reported AMPK activation and increased muscle glucose uptake by rosemary extract (RE). In the present study, we examined the effects and the mechanism of action of rosmarinic acid (RA), a major RE constituent, in L6 rat muscle cells. RA (5.0 µM) increased glucose uptake (186 ± 4.17% of control, p < 0.001) to levels comparable to maximum insulin (204 ± 10.73% of control, p < 0.001) and metformin (202 ± 14.37% of control, p < 0.001). Akt phosphorylation was not affected by RA, while AMPK phosphorylation was increased. The RA-stimulated glucose uptake was inhibited by the AMPK inhibitor compound C and was not affected by wortmannin, an inhibitor of phosphoinositide 3-kinase (PI3K). The current study shows an effect of RA to increase muscle glucose uptake and AMPK phosphorylation. RA deserves further study as it shows potential to be used as an agent to regulate glucose homeostasis.

Flavonoid-Rich Extract of Paulownia fortunei Flowers Attenuates Diet-Induced Hyperlipidemia, Hepatic Steatosis and Insulin Resistance in Obesity Mice by AMPK Pathway

The flavonoid-rich extract from Paulownia fortunei flowers (EPF) has been reported to prevent obesity and other lipid metabolism disease. However, the mechanism of its protective effects is not yet clear. The objective of this study was to investigate molecular factors involved in the hypoglycemic and hypolipidemic effects of EPF in obese mice fed a high-fat diet (HFD). Male h ICR (Institute of Cancer Research) mice were fed a HFD containing or not containing the EPF (50 or 100 mg/kg) for eight weeks. EPF reduced body weight gain, lipid accumulation in livers and levels of lipid, glucose and insulin in plasma as well as reduced insulin resistance as compared with the HFD group. EPF significantly decreased serum aminotransferase activity of the HFD group. We observed that EPF administration significantly increased the level of AMP-activated kinase (AMPK) phosphorylation and prevented fat deposits in livers and HepG2 cells, but these effects were blocked by compound C (an AMPK inhibitor). The protective effects of EPF were probably associated with the decrease in HMGCR, SREBP-1c and FAS expressions and the increase in CPT1 and phosphor-IRS-1 expressions. Our results suggest that EPF might be a potential natural candidate for the treatment and/or prevention of overweight and hepatic and metabolic-related alterations induced by HFD.

Mitophagy Transcriptome: Mechanistic Insights into Polyphenol-Mediated Mitophagy

Mitochondria are important bioenergetic and signalling hubs critical for myriad cellular functions and homeostasis. Dysfunction in mitochondria is a central theme in aging and diseases. Mitophagy, a process whereby damaged mitochondria are selectively removed by autophagy, plays a key homeostatic role in mitochondrial quality control. Upregulation of mitophagy has shown to mitigate superfluous mitochondrial accumulation and toxicity to safeguard mitochondrial fitness. Hence, mitophagy is a viable target to promote longevity and prevent age-related pathologies. Current challenge in modulating mitophagy for cellular protection involves identification of physiological ways to activate the pathway. Till date, mitochondrial stress and toxins remain the most potent inducers of mitophagy. Polyphenols have recently been demonstrated to protect mitochondrial health by facilitating mitophagy, thus suggesting the exciting prospect of augmenting mitophagy through dietary intake. In this review, we will first discuss the different surveillance mechanisms responsible for the removal of damaged mitochondrial components, followed by highlighting the transcriptional regulatory mechanisms of mitophagy. Finally, we will review the functional connection between polyphenols and mitophagy and provide insight into the underlying mechanisms that potentially govern polyphenol-induced mitophagy.