Novel mechanism for plasma glucose-lowering action of metformin in streptozotocin-induced diabetic rats

Can exercise benefits be harnessed with drugs? A new way to combat neurodegenerative diseases by boosting neurogenesis

Adult hippocampal neurogenesis (AHN) is affected by multiple factors, such as enriched environment, exercise, ageing, and neurodegenerative disorders. Neurodegenerative disorders can impair AHN, leading to progressive neuronal loss and cognitive decline. Compelling evidence suggests that individuals engaged in regular exercise exhibit higher production of proteins that are essential for AHN and memory. Interestingly, specific molecules that mediate the effects of exercise have shown effectiveness in promoting AHN and cognition in different transgenic animal models. Despite these advancements, the precise mechanisms by which exercise mimetics induce AHN remain partially understood. Recently, some novel exercise molecules have been tested and the underlying mechanisms have been proposed, involving intercommunications between multiple organs such as muscle-brain crosstalk, liver-brain crosstalk, and gut-brain crosstalk. In this review, we will discuss the current evidence regarding the effects and potential mechanisms of exercise mimetics on AHN and cognition in various neurological disorders. Opportunities, challenges, and future directions in this research field are also discussed.

A combination of gliclazide and metformin attenuates obesity-induced polycystic ovary syndrome in female Wistar rats

Presently, it is known that the progression of obesity concomitantly leads to polycystic ovary syndrome and infertility. This study aimed to evaluate the potential effects of metformin (M; insulin secretagogues) and gliclazide (G; insulin sensitizer) alone and their combination at different doses to treat obesity-induced PCOS. High high-fat diet was given to all female Wistar rats for nine weeks to induce obesity except for the normal control group which received a normal chow diet. Estradiol valerate (0.8 mg/kg) was also given to all obese rats to induce polycystic ovarian syndrome. After the induction, M (100, 300 mg/kg) and G (5, 10 mg/kg) were given orally either individually or in combination for 28 days. The notable (p < 0.0001) reduction in body weight and blood glucose level was observed in treatment groups in contrast to disease control (DCG). The marked (p < 0.05-0.0001) decrease in hemocylated hemoglobin, serum insulin, cholesterol, triglycerides, and testosterone was observed in treated groups, notably in combination groups (M100+G10 mg/kg) in contrast to DCG. There was a considerable (p < 0.01-0.0001) increase in progesterone E2, estradiol, luteinizing, and follicle-stimulating hormones in treated groups as compared to DCG. Treatment with M and G treated groups also exhibited marked (p < 0.05-0.0001) increases in SOD, CAT, and GSH while decreased in NO and MDA levels in ovary tissue as evidenced by the histological study of the ovary. Treatment with M and G alone and in combination significantly (p < 0.0001) restored the serum IL-6, NrF2, and NF-κB levels as compared to DCG. The results inveterate that the M and G combination (M100+G10, and M300+G10) was useful in treating obesity-induced infertility due to antioxidant properties, hypolipidemic effects, and modulation of inflammatory markers.

A novel action of insulin sensitizing drug as a potential promotor of preovulatory follicles, ovulation rate and prolificacy in sheep

The effect of the insulin-sensitizing drug metformin on preovulatory follicle (POF) number, ovulation rate, fetal rate and prolificacy was studied in forty-six cyclic Malpura ewes. After estrus synchronization, the ewes were equally divided into two groups (n = 23). The treatment group (MET) received a daily oral dose of metformin at a rate of 500 mg/animal for approximately 12 weeks, spanning five estrous cycles, as against untreated control (CON). All the ewes were bred to proven rams at the end of treatment. Ovarian ultrasound scans were performed at each estrus and day 9 of each cycle to assess the number and diameter of POFs and corpora lutea (CL), respectively. A comprehensive assessment of circulating hormones including, estradiol, progesterone, androstenedione, and insulin as well as metabolic indicators such as glucose, and lipid profile parameters was performed. At the end of treatment on the day of estrus (E5D0), the treatment showed a stimulatory effect on follicular development with a 53.2% (P < 0.001) increase in the number of POFs. It also increased the ovulation rate by 67.4% (P < 0.01), with a higher proportion (χ2df1 = 10.7, P < 0.001) of ewes in the MET group having multiple ovulations compared to the CON group (82.6 vs. 30.4%). With 1.48 ± 0.12 prolificacy rate in MET ewes, the proportion of ewes giving birth to multiple lambs was 2.9-fold higher than in the CON group. Plasma estradiol, insulin, glucose, total cholesterol, and LDL-cholesterol concentrations were lower (P < 0.05) in the MET ewes than in the CON. The results of the present study indicate that metformin can increase the number of POF, ovulation rate, fetal rate and prolificacy in ewes, while reducing the plasma estradiol, insulin, glucose and cholesterol in MET ewes.

Exercise mimetics: a novel strategy to combat neuroinflammation and Alzheimer's disease

Neuroinflammation is a pathological hallmark of Alzheimer's disease (AD), characterized by the stimulation of resident immune cells of the brain and the penetration of peripheral immune cells. These inflammatory processes facilitate the deposition of amyloid-beta (Aβ) plaques and the abnormal hyperphosphorylation of tau protein. Managing neuroinflammation to restore immune homeostasis and decrease neuronal damage is a therapeutic approach for AD. One way to achieve this is through exercise, which can improve brain function and protect against neuroinflammation, oxidative stress, and synaptic dysfunction in AD models. The neuroprotective impact of exercise is regulated by various molecular factors that can be activated in the same way as exercise by the administration of their mimetics. Recent evidence has proven some exercise mimetics effective in alleviating neuroinflammation and AD, and, additionally, they are a helpful alternative option for patients who are unable to perform regular physical exercise to manage neurodegenerative disorders. This review focuses on the current state of knowledge on exercise mimetics, including their efficacy, regulatory mechanisms, progress, challenges, limitations, and future guidance for their application in AD therapy.

Metformin inhibits paclitaxel-induced mechanical allodynia by activating opioidergic pathways and reducing cytokines production in the dorsal root ganglia and thalamus

It has been shown that AMP-activated protein kinase (AMPK) is involved in the nociceptive processing. This observation has prompted us to investigate the effects of the AMPK activator metformin on the paclitaxel-induced mechanical allodynia, a well-established model of neuropathic pain. Mechanical allodynia was induced by four intraperitoneal (i.p) injections of paclitaxel (2 mg/kg.day) in mice. Metformin was administered per os (p.o.). Naltrexoneandglibenclamide were used to investigate mechanisms mediating metformin activity. Concentrations of cytokines in the dorsal root ganglia (DRG) and thalamus were determined. After a single p.o. administration, the two highest doses of metformin (500 and 1000 mg/kg) attenuated the mechanical allodynia. This response was attenuated by all doses of metformin (250, 500 and 1000 mg/kg) when two administrations, 2 h apart, were carried out. Naltrexone (5 and 10 mg/kg, i.p.), but not glibenclamide (20 and 40 mg/kg, p.o.), attenuated metformin activity. Concentrations of tumor necrosis factor (TNF)-α, interleukin (IL)-1β and CXCL-1 in the DRG were increased after administration of paclitaxel. Metformin (1000 mg/kg) reduced concentrations of TNF-α, IL-1β and CXCL-1 in the DRG. Concentration of IL-6, but not TNF-α, in the thalamus was increased after administration of paclitaxel. Metformin (1000 mg/kg) reduced concentration of IL-6 in the thalamus. In summary, metformin exhibits activity in the model of neuropathic pain induced by paclitaxel. This activity may be mediated by activation of opioidergic pathways and reduced production of TNF-α, IL-1β and CXCL-1 in the DRG and IL-6 in the thalamus.

The efficacy of using metformin and/or quercetin for amelioration of gamma-irradiation induced tongue toxicity in diabetic rats

BACKGROUND

Diabetes is a common disease that cancer patients may suffer from and may aggravate side effects of radiotherapy. This study aimed to detect whether metformin and/or quercetin will improve gamma-irradiation induced tongue toxicity in diabetic rats.

METHODS

35 male albino rats were divided into five groups; NOR no streptozotocin, no radiation and no treatment was given, DR rats were subjected to streptozotocin then gamma-irradiation, DRM rats were subjected to streptozotocin then gamma-irradiation then metformin, DRQ rats were subjected to streptozotocin then gamma-irradiation then quercetin, DRMQ rats were subjected to streptozotocin then gamma-irradiation then metformin and quercetin. Rats were euthanized 24 h after last treatment dose. Mean blood glucose level was recorded. Tongue specimens were stained with H&E and CD68. Histomorphometric analysis of length, diameter and taste buds of lingual papillae and epithelial, keratin and lamina propria thickness and CD68 positive cells were calculated.

RESULTS

Blood glucose level of DRMQ was significantly lower than DR, DRM and DRQ, whereas higher than NOR. Metformin or quercetin partially restored tongue structure, papillae length and diameter and tongue layers thickness. The ameliorative effect was superior when metformin and quercetin were used together. Diabetes and irradiation significantly increased number of CD68 positive macrophages in submucosa and muscles. Metformin or quercetin significantly reduced number of lingual macrophages with more noticeable effect for quercetin. Treatment with metformin and quercetin significantly decreased number of macrophages.

CONCLUSIONS

Combined use of metformin and quercetin might help mitigate the harmful effects of radiotherapy and diabetes on lingual tissues.

The healing bitterness of Gentiana lutea L., phytochemistry and biological activities: A systematic review

Over many years, natural products have been a source of healing agents and have exhibited beneficial uses for treating human diseases. The Gentiana genus is the biggest genus in the Gentianaceae, with over 400 species distributed mainly in alpine zones of temperate countries around the world. Plants in the Gentiana genus have historically been used to treat a wide range of diseases. Still, only in the last years has particular attention been paid to the biological activities of Gentiana lutea Linn., also known as yellow Gentian or bitterwort. Several in vitro/vivo investigations and human interventional trials have demonstrated the promising activity of G. lutea extracts against oxidative stress, microbial infections, inflammation, obesity, atherosclerosis, etc.. A systematic approach was performed using Pubmed and Scopus databases to update G. lutea chemistry and activity. Specifically, this systematic review synthesized the major specialized bitter metabolites and the biological activity data obtained from different cell lines, animal models, and human interventional trials. This review aims to the exaltation of G. lutea as a source of bioactive compounds that can prevent and treat several human illnesses.

Metformin modulates mitochondrial function and mitophagy in peripheral blood mononuclear cells from type 2 diabetic patients

Type 2 diabetes is a chronic metabolic disease that affects mitochondrial function. In this context, the rescue mechanisms of mitochondrial health, such as mitophagy and mitochondrial biogenesis, are of crucial importance. The gold standard for the treatment of type 2 diabetes is metformin, which has a beneficial impact on the mitochondrial metabolism. In this study, we set out to describe the effect of metformin treatment on mitochondrial function and mitophagy in peripheral blood mononuclear cells (PBMCs) from type 2 diabetic patients. We performed a preliminary cross-sectional observational study complying with CONSORT requirements, for which we recruited 242 subjects, divided into 101 healthy volunteers, 93 metformin-treated type 2 diabetic patients and 48 non-metformin-treated type 2 diabetic patients. Mitochondria from the type 2 diabetic patients not treated with metformin displayed more reactive oxygen species (ROS) than those from healthy or metformin-treated subjects. Protein expression of the electron transport chain (ETC) complexes was lower in PBMCs from type 2 diabetic patients without metformin treatment than in those from the other two groups. Mitophagy was altered in type 2 diabetic patients, evident in a decrease in the protein levels of PINK1 and Parkin in parallel to that of the mitochondrial biogenesis protein PGC1α, both of which effects were reversed by metformin. Analysis of AMPK phosphorylation revealed that its activation was decreased in the PBMCs of type 2 diabetic patients, an effect which was reversed, once again, by metformin. In addition, there was an increase in the serum levels of TNFα and IL-6 in type 2 diabetic patients and this was reversed with metformin treatment. These results demonstrate that metformin improves mitochondrial function, restores the levels of ETC complexes, and enhances AMPK activation and mitophagy, suggesting beneficial clinical implications in the treatment of type 2 diabetes.

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Metformin promoted electron transport chain expression on type 2 diabetic patients.

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Metformin restored mitophagy levels via PINK1 and PARKIN on type 2 diabetic patients.

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Mitochondrial biogenesis was enhanced by metformin on type 2 diabetic patients.

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Metformin restored AMPK activation on type 2 diabetic patients.

The effects of metformin monotherapy and combination of metformin and glibenclamide therapy on the expression of RAGE, Sirt1, and Nrf2 genes in peripheral blood mononuclear cells of type 2 diabetic patients

Purpose

Although metformin is the first-line treatment of type 2 diabetes mellitus (T2DM), a few studies have evaluated the benefits of monotherapies (metformin) versus combination therapy (metformin and glibenclamide) for treatment of T2DM patients. The present study aimed to evaluate the effect of monotherapy with metformin compared to combination therapy with metformin and glibenclamide on the expression of RAGE, Nrf 2, and Sirt1genes.

Methods

EightyT2DM patients and 40 healthy individuals participated in this case-control study. The patients in the treatment group were divided into two groups who received either metformin alone (n = 40) or metformin in combination with glibenclamide (n = 40). FBS, HbA1c, and fructosamine were measured. The expression of RAGE, Nrf 2, and Sirt 1 genes in PBMC of all subjects were assessed using real-time PCR.

Results

RAGE gene expression in both treatment groups was significantly lower than the control (P < 0.05). RAGE gene expression was significantly reduced in the combination of metformin and glibenclamide treated group compared to metformin group (P < 0.05). Additionally, the expression of Sirt 1 and Nrf 2 genes in both treatment groups was higher than that of the control group (P < 0.05). The expression of Sirt 1 and Nrf 2 genes in metformin and glibenclamide treated group were higher than the metformin group (P < 0.05).

Conclusion

Combination therapy (metformin and glibenclamide) showed stronger effect on repression of the RAGE gene and activation of Nrf 2 and Sirt 1 genes compared to monotherapy (metformin); therefore, it can be concluded that combination therapy may have more protective effects on the T2DM patients. No significant correlation was observed between HbA1c and RAGE, Sirt 1, and Nrf 2 genes expression.

Nutritional Contributions and Health Associations of Traditional Fermented Foods

The growing interest in the consumption and study of traditionally fermented food worldwide has led to the development of numerous scientific investigations that have focused on analyzing the microbial and nutritional composition and the health effects derived from the consumption of these foods. Traditionally fermented foods and beverages are a significant source of nutrients, including proteins, essential fatty acids, soluble fiber, minerals, vitamins, and some essential amino acids. Additionally, fermented foods have been considered functional due to their prebiotic content, and the presence of specific lactic acid bacterial strains (LAB), which have shown positive effects on the balance of the intestinal microbiota, providing a beneficial impact in the treatment of diseases. This review presents a bibliographic compilation of scientific studies assessing the effect of the nutritional content and LAB profile of traditional fermented foods on different conditions such as obesity, diabetes, and gastrointestinal disorders.

Potential Interaction of Fresh Garlic with Metformin during Ischemia-Reperfusion Induced Cardiac Injury in Diabetic Rats

Methods

The study was undertaken on both normoglycemic and alloxan (90 mg/kg) induced diabetic Sprague Dawley rats weighing 150–250 g. At the completion of the treatment phase (30 days for garlic, 250 mg/kg, oral; 10 days for MET, 70 mg/kg, oral), rats were anesthetized and mounted on the modified Langendorff's apparatus. IRI was produced by myocardial no-flow global ischemia. Developed tension (DT) and heart rate (HR) were recorded both before and after ischemia. The perfusate was collected to estimate the leakage of cardiac biomarkers (Creatine Kinase-MB: CK-MB and Lactate dehydrogenase: LDH). Hearts were removed from the setup and utilized to prepare heart tissue homogenate (HTH) and histological slides. The endogenous antioxidants, superoxide dismutase (SOD) and catalase (CAT), in addition to oxidative thiobarbituric acid substances (TBS), were estimated in HTH.

Results

The hemodynamic parameters, including percentage recovery in HR and DT, were found significantly higher in animals pretreated with garlic and MET in diabetic rats (DR). Both SOD and CAT enzyme activities increased significantly while TBS levels were reduced in the HTH of animals treated with garlic and MET. The cardiac markers CK-MB and LDH levels also increased in HTH with a corresponding decrease in the perfusate. The histopathological changes in the heart and pancreas demonstrated noticeable protection of the tissues due to pretreatment with garlic and MET. Taken together, these findings advocate that reactive oxygen species derived from hyperglycemia execute an important function in myocardial global IRI; the therapy of garlic homogenate was found to be effective in alleviating these toxic effects.

Conclusion

The combined therapy of MET and garlic provided synergistic cardioprotection, implying that garlic seems to possess promise in lowering toxic parameters by protecting diabetic induced myocardial injury.

Chemical and biological investigations of Limonium axillare reveal mechanistic evidence for its antidiabetic activity

Root and bark of Limonium axillare (Forssk) Kuntze are used as antidiabetic remedies in parts of East Africa, but this activity has never been fully investigated. To validate its ethnobotanical use, we compared the chemical and pharmacological profiles of the ethanolic extracts of L. axillare root (REE) and aerial parts (AEE). Administration of REE (500 mg kg-1) reduced streptozotocin-induced hyperglycemia by 44%, restored serum insulin levels, reestablished Glut2 and Glut4 expression and ameliorated pancreatic tissue damage in diabetic rats. In vitro studies revealed a strong radical scavenging effect, α-glucosidase, and α-amylase inhibition activity of REE at IC50 at 25.2, 44.8 and 89.1μg/mL, respectively. HPLC analysis identified ten phenolic compounds in REE with umbelliferone as the major constituents at 10 ± 0.081 mg/g of extract. Additionally, six compounds were isolated from REE including, β-sitosterol-3-palmitate, β-sitosterol, myricetin and gallic acids with two new tetrahydrofuran monoterpenes; 2-isopropyl- 3,4,4, trimethyl-tetrahydrofuran (3), and 2-isopropyl-4-methyl-tetrahydrofuran-3,4 dicarboxylic acid (4), the latter was revealed by molecular docking to be a good ligand to glycerol-3-phosphate dehydrogenase a key enzyme in glycolysis.

Morphine induces physiological, structural, and molecular benefits in the diabetic myocardium

The obesity epidemic has increased type II diabetes mellitus (T2DM) across developed countries. Cardiac T2DM risks include ischemic heart disease, heart failure with preserved ejection fraction, intolerance to ischemia-reperfusion (I-R) injury, and refractoriness to cardioprotection. While opioids are cardioprotective, T2DM causes opioid receptor signaling dysfunction. We tested the hypothesis that sustained opioid receptor stimulus may overcome diabetes mellitus-induced cardiac dysfunction via membrane/mitochondrial-dependent protection. In a murine T2DM model, we investigated effects of morphine on cardiac function, I-R tolerance, ultrastructure, subcellular cholesterol expression, mitochondrial protein abundance, and mitochondrial function. T2DM induced 25% weight gain, hyperglycemia, glucose intolerance, cardiac hypertrophy, moderate cardiac depression, exaggerated postischemic myocardial dysfunction, abnormalities in mitochondrial respiration, ultrastructure and Ca2+ -induced swelling, and cell death were all evident. Morphine administration for 5 days: (1) improved glucose homeostasis; (2) reversed cardiac depression; (3) enhanced I-R tolerance; (4) restored mitochondrial ultrastructure; (5) improved mitochondrial function; (6) upregulated Stat3 protein; and (7) preserved membrane cholesterol homeostasis. These data show that morphine treatment restores contractile function, ischemic tolerance, mitochondrial structure and function, and membrane dynamics in type II diabetic hearts. These findings suggest potential translational value for short-term, but high-dose morphine administration in diabetic patients undergoing or recovering from acute ischemic cardiovascular events.

Effect of the Surfactant and Liquid Lipid Type in the Physico-chemical Characteristics of Beeswax-based Nanostructured Lipid Carrier (NLC) of Metformin

BACKGROUND

Metformin (MF) is an antidiabetic drug that belongs to class III of the biopharmaceutical classification system (BCS) characterized by high solubility and low permeability.

OBJECTIVE

The study aimed to prepare metformin as nanostructured lipid carriers (MF-NLCs) to control the drug release and enhance its permeability through the biological membrane.

METHODS

2² full factorial design was used to make the design of MF-NLCs formulations. MFNLCs were prepared by hot-melt homogenization-ultra sonication technique using beeswax as solid lipid in the presence of liquid lipid (either capryol 90 or oleic acid) and surfactant (either poloxamer 188 or tween 80).

RESULTS

The entrapment efficiency (EE%) of MF-NLCs was ranged from 85.2±2.5 to 96.5±1.8%. The particle size was in the nanoscale (134.6±4.1 to 264.1±4.6 nm). The value of zeta potential has a negative value ranged from -25.6±1.1 to -39.4±0.9 mV. The PDI value was in the range of 0.253±0.01 to 0.496±0.02. The cumulative drug release was calculated for MF-NLCs and it was found that Q_12h ranged from 90.5±1.7% for MF-NLC1 to 99.3±2.8 for MF-NLC4. Infra-red (IR) spectroscopy and differential scanning calorimetry (DSC) studies revealed the compatibility of the drug with other ingredients. MF-NLC4 was found to be the optimized formulation with the best responses.

CONCLUSION

2² full factorial design succeed to obtain an optimized formulation which controls the drug release and increases the drug penetration.

A Review on Oxidative Stress, Diabetic Complications, and the Roles of Honey Polyphenols

Despite the availability of various antidiabetic drugs, diabetes mellitus (DM) remains one of the world's most prevalent chronic diseases and is a global burden. Hyperglycaemia, a characteristic of type 2 diabetes mellitus (T2DM), substantially leads to the generation of reactive oxygen species (ROS), triggering oxidative stress as well as numerous cellular and molecular modifications such as mitochondrial dysfunction affecting normal physiological functions in the body. In mitochondrial-mediated processes, oxidative pathways play an important role, although the responsible molecular mechanisms remain unclear. The impaired mitochondrial function is evidenced by insulin insensitivity in various cell types. In addition, the roles of master antioxidant pathway nuclear factor erythroid 2-related factor 2 (Nrf2)/Kelch-like ECH-associated protein 1 (Keap1)/antioxidant response elements (ARE) are being deciphered to explain various molecular pathways involved in diabetes. Dietary factors are known to influence diabetes, and many natural dietary factors have been studied to improve diabetes. Honey is primarily rich in carbohydrates and is also abundant in flavonoids and phenolic acids; thus, it is a promising therapeutic antioxidant for various disorders. Various research has indicated that honey has strong wound-healing properties and has antibacterial, anti-inflammatory, antifungal, and antiviral effects; thus, it is a promising antidiabetic agent. The potential antidiabetic mechanisms of honey were proposed based on its major constituents. This review focuses on the various prospects of using honey as an antidiabetic agent and the potential insights.

Protective effects of Artemisia judaica extract compared to metformin against hepatorenal injury in high-fat diet/streptozotocine-induced diabetic rats

Diabetes mellitus (DM) is one of the most dangerous incurable diseases that affects a large number of people worldwide. Artemisia species have various protective activities and are widely used for the control of diabetes in folkloric medicine. Therefore, the current study was designed to illustrate the protective effect of oral administration of Artemisia judaica extract (AjE) against hepatorenal damage in a high-fat diet/streptozotocin (HFD/STZ) rat model of hyperlipidemia and hyperglycemia. Animals were divided into five groups-control, AjE, HFD/STZ, HFD/STZ-AjE (300 mg/kg), and HFD/STZ-MET (100 mg/kg)-and treated daily for 28 days. The results revealed that STZ-injected rats showed marked hyperglycemia and hypoinsulinemia in addition to high levels of cholesterol, triglycerides, and low- and high-density lipoproteins compared to control rats. Significant elevations in hepatic (AST and ALT) and renal (urea, uric acid, and creatinine) function markers were observed in the serum of diabetic rats. Additionally, STZ injection caused remarkable elevations in lipid peroxidation and nitric oxide levels as well as suppression of antioxidant markers (superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, and glutathione). Marked elevations in TNF-α and Bax levels with a decline in Bcl-2 levels were detected after STZ injection. Furthermore, TGF-β1 expression levels were significantly upregulated in the liver and kidney tissues. Rats that received AjE or MET showed significant improvement in most of the aforementioned parameters, and the protective efficacy was higher for AjE than for MET. Histopathological screening confirmed the biochemical findings. Conclusively, our results illustrated the antihyperglycemic, antihyperlipidemic, antioxidant, anti-inflammatory, and antiapoptotic activities of AjE against hepatorenal injury in HFD/STZ-induced diabetes.

Modulation of reproductive dysfunctions associated with streptozocin-induced diabetes by Artemisia judaica extract in rats fed a high-fat diet

We investigated the palliative effect of Artemisia judaica extract (AjE) on testicular deterioration induced by DM in high-fat diet/streptozocin (HFD/STZ)-injected rats. Forty rats were allocated to the following five groups: control, AjE, HFD/STZ, HFD/STZ-AjE, and HFD/STZ-metformin. HFD/STZ-diabetic rats showed a marked decrease in testicular weight and male sex hormones. There was significant suppression of testicular antioxidant enzymes and glutathione content in HFD/STZ-diabetic rats. However, rats that had received the STZ injection and the high-fat diet displayed increased malondialdehyde content and nitric oxide levels as well as tumour necrosis factor-alpha. High levels of Bax and low levels of Bcl-2 were detected after the STZ injection. Obvious pathological alterations were found in the testicular tissue of the HFD/STZ-diabetic rats. Thus, the administration of AjE attenuated the biochemical, molecular, and histopathological changes in the testes of the diabetic rats. The obtained findings showed that AjE treatment attenuated the diabetes-induced reprotoxicity in male rats via its antioxidant, anti-inflammatory, and antiapoptotic properties.

Metformin Had Potential to Increase Endocan Levels in STZ-Induced Diabetic Mice

Background: Type 2 diabetes mellitus is a chronic metabolic disorder with prominent vascular injuries. In this condition, the levels of multiple pro- and anti-angiogenic factors have been shown to change. This study aimed to investigate the possible effect of metformin on pro-angiogenic factor, endocan levels, via the modulation of p-AMPK/AMPK axis in diabetic mice. Methods: Mice were randomly assigned to one of 4 groups (n=6): Control (normal saline) and the diabetic group was injected streptozotocin and two groups were given 50 and 100 mg/kg metformin orally, once daily for two weeks after diabetes induction. Endocan protein levels were detected in the liver and kidneys by ELISA and immunofluorescence analysis. Phosphorylation of AMPK was assessed using western blotting. Histological examination was performed to follow the metformin effect on Von Willebrand factor expression and diabetes-related pathologies. Results: ELISA assay showed an elevated levels of endocan in the renal and hepatic tissues of diabetic mice following treatment with metformin (p<0.05). Immunofluorescence and immunohistochemistry examination of kidneys showed that the increase of endocan protein coincided with the promotion of vWF factors in mice treated with metformin (p<0.05). We did not find endocan factor in hepatic tissue of diabetic mice pre- and post-treatment with metformin. Western blotting confirmed the phosphorylation of AMPK by metformin in kidneys (p<0.05), but these changes did not reach statistically significant levels in hepatic tissues (p>0.05). Conclusion: Metformin could change the endocan levels during diabetic condition possibly by the modulation of p-AMPK/AMPK axis.

Metformin/Donepezil combination modulates brain antioxidant status and hippocampal endoplasmic reticulum stress in type 2 diabetic rats

Purpose

Diabetes mellitus is associated with perturbations in brain biochemical parameters associated with dementia. This study aimed at comparing the effect of metformin and metformin/donepezil combination on oxidative stress, endoplasmic reticulum stress and inflammation in the brain of diabetic Wistar rats.

Methods

Diabetes was induced by single intraperitoneal injection of 40 mg/kg streptozotocin after administration of 10% fructose for 14 days. Animals were randomly assigned to four groups of five animals each. Group 1 was the normal control and received only distilled water. Groups 2 and 3 were diabetic rats treated with metformin/donepezil combination and metformin only respectively, while group 4 was diabetic control. Treatment lasted for 21 days after confirmation of diabetes. Activities of acetylcholinesterase (AchE), butyrylcholinesterase (BchE), superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase were evaluated in the brain of diabetic rats. Enzyme-linked immunosorbent assay was used to estimate brain levels of tumour necrosis factor-α (TNF-α), interleukin-6 (IL-6) malondialdehyde and glucose transporter-4 (GLUT4), while expression of endoplasmic reticulum stress markers - glucose regulated protein-78 (GRP78), activating transcription factor-4 (ATF4) and C/EBP homologous protein (CHOP) was determined using real-time PCR in the hippocampus of diabetic rats.

Results

Treatment with metformin/donepezil combination significantly reduced the activities of AchE, BchE as well as levels of malondialdehyde, TNF-α and IL-6, while the activities of SOD, GPx and catalase were significantly increased in the brain. Moreover, expression of ER stress markers was attenuated in the hippocampus.

Conclusion

Metformin/donepezil combination appeared more efficacious than metformin only and could be considered for managing diabetes-associated dementia.

Development of simultaneous determination of empagliflozin and metformin in human plasma using liquid chromatography-mass spectrometry and application to pharmacokinetics

A rapid and sensitive liquid chromatography-mass spectrometry method was developed, optimized, and validated for simultaneous quantification of empagliflozin and metformin in human plasma using empagliflozin D4and metformin D6 as an internal standard. Analytes and internal standard were extracted from plasma by optimized solid-phase extraction technique using Strata X polymeric reverse phase (30 mg-1cc) solid-phase extraction cartridges. The prepared samples were chromatographed on Orosil C18 column (150 × 4.6 mm, 3 µ). Separation was done by pumping isocratic mobile phase consisting of methanol and 10 mM ammonium trifluoroacetate (90:10, v/v) in positive ion mode at a flow rate of 0.8 mL/min. The API 3200 liquid chromatography-mass spectrometry system having turbo ion spray as an ion source coupled with Shimadzu Prominence ultrafast liquid chromatography system was operated under the selected reaction monitoring mode. Turbo ion spray ionization was used for mass transition of m/z 468.070/355.100 and m/z 130.072/71.200 for empagliflozin and metformin, respectively. A method was successfully validated for concentration range of 10.09-5013.46 ng/mL for both the analytes and according to the United States Food and Drugs Administration guidelines. The linearity was found to be in the range of 10.09-403.46 ng/mL for empagliflozin and 25.44-5013.46 ng/mL for metformin. The limit of quantification was found to be 10.09 ng/mL for empagliflozin and 25.44 ng/mL for metformin. Intra- and inter-day/between batch precision determination for empagliflozin and metformin, expressed as coefficient of variation were within the acceptance limits and ranged below 13.16%. A short run time of 3.3 min allows analysis of more than 400 plasma samples per day. The developed method was successfully applied to fasting pharmacokinetic study in healthy human volunteers. Results of incurred sample re-analysis were within the acceptance range of ±20% of original value, for 97.2% of samples reanalyzed for empagliflozin and 100% of samples reanalyzed for metformin.

Metabolic and Addiction Indices in Patients on Opioid Agonist Medication-Assisted Treatment: A Comparison of Buprenorphine and Methadone

Metabolic hormones stabilize brain reward and motivational circuits, whereas excessive opioid consumption counteracts this effect and may impair metabolic function. Here we addressed the role of metabolic processes in the course of the agonist medication-assisted treatment for opioid use disorder (OUD) with buprenorphine or methadone. Plasma lipids, hemoglobin A1C, body composition, the oral glucose tolerance test (oGTT) and the Sweet Taste Test (STT) were measured in buprenorphine- (n = 26) or methadone (n = 32)- treated subjects with OUD. On the whole, the subjects in both groups were overweight or obese and insulin resistant; they displayed similar oGTT and STT performance. As compared to methadone-treated subjects, those on buprenorphine had significantly lower rates of metabolic syndrome (MetS) along with better values of the high-density lipoproteins (HDL). Subjects with- vs. without MetS tended to have greater addiction severity. Correlative analyses revealed that more buprenorphine exposure duration was associated with better HDL and opioid craving values. In contrast, more methadone exposure duration was associated with worse triglycerides-, HDL-, blood pressure-, fasting glucose- and hemoglobin A1C values. Buprenorphine appears to produce beneficial HDL- and craving effects and, contrary to methadone, its role in the metabolic derangements is not obvious. Our data call for further research aimed at understanding the distinctive features of buprenorphine metabolic effects vis-à-vis those of methadone and their potential role in these drugs' unique therapeutic profiles.

Metformin and trimetazidine ameliorate diabetes-induced cognitive impediment in status epileptic rats

Patients with diabetes and epilepsy are more prone to cognitive impairment, dementia, and even Alzheimer's disease. Diabetes-induced inflammatory process is one of the main contributing factors; however, the impact on seizure is not clear. The current study is aimed to examine the role of metformin and trimetazidine in the reduction of neuronal damage caused by inflammatory mediators and apoptotic factors in diabetic epileptic rodent model. Diabetic epileptic rats received orally either metformin (100 mg/kg) or trimetazidine (10 mg/kg) for 3 weeks exhibited reduced cognitive function and ameliorated the disturbed brain neurotransmission. Besides, they improved both the inflammatory status and the histopathologic alterations. Administration of metformin or trimetazidine ameliorated the deterioration in cognitive function in Morris water maze (MWM) and reduced seizure score. Furthermore, brain neurotransmitters glutamate and γ-aminobutyric acid (GABA) were reverted back to their normal values. Both treatments reduced the rise in inflammatory cytokines interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α), apoptotic markers nuclear factor-κB (NF-κB) and caspase-3, and improved the pathological photomicrograph of the hippocampus of diabetic epileptic rats. Such effects were closely correlated to the observed increase in the adenosine triphosphate and adenosine diphosphate (ATP/ADP) ratio and reduction of death-associated protein (DAP) and mammalian target of rapamycin (mTOR). In conclusion, the current study shed light on the potential neuroprotective role of metformin and trimetazidine in the amelioration of cognitive function via hindering inflammatory processes in diabetic epileptic rats.

Promotion of Adropin Expression by Hyperglycemia Is Associated with STAT3 Activation in Diabetic Rats

BACKGROUND

Adropin is a secreted polypeptide that has been demonstrated to play an important role in energy homeostasis and lipid metabolism. Signal transducer and activator of transcription 3 (STAT3) may promote the transcription of target genes including adropin. In the current study, we investigated the effect of adropin on glucose metabolism in diabetic rats and the mechanism that governs this effect was subsequently assessed.

MATERIALS AND METHODS

Rats received a single injection of streptozotocin to induce type 1 diabetes. The diabetic rats were treated with insulin or phloridzin, another antidiabetic agent through inhibition of glucose reabsorption, for 7 days. Plasma glucose levels and adropin levels were measured. The interaction between STAT3 and adropin was evaluated using the human hepatoma HepG2 cell line. HepG2 cells were pretreated with the specific antagonist Stattic or with STAT3-specific siRNAs to knockout STAT3. Changes in energy homeostasis-associated gene expression were measured using real-time PCR. The protein expression levels of pSTAT3 and STAT3 were measured using Western blotting.

RESULTS

In diabetic rats, the serum concentrations of adropin were increased in the vehicle-treated group and decreased in the insulin- or phloridzin-treated group. In liver tissues, the Enho expression level and the activity of STAT3 also showed similar tendencies. After HepG2 cells were treated with medium containing high glucose, the ratio of p-STAT3 to STAT3, Enho mRNA levels and reactive oxygen species expression levels in HepG2 cells were significantly increased in conjunction with increased glucose levels. The effect was inhibited after pretreatment with Stattic or knockdown with STAT3-specific siRNAs.

CONCLUSION

STAT3 is involved in the genetic regulation of adropin, increasing the levels of circulating adropin and promoting Enho expression in the livers of diabetic rats.

Long-Term Moderate Exercise Combined with Metformin Treatment Induces an Hormetic Response That Prevents Strength and Muscle Mass Loss in Old Female Wistar Rats

Sarcopenia is a syndrome characterized by a progressive and generalized skeletal muscle mass and strength loss, as well as a poor physical performance, which as strongly been associated with aging. Sedentary lifestyle in the elderly contributes to this condition; however, physical activity improves health, reducing morbidity and mortality. Recent studies have shown that metformin (MTF) can also prevent muscle damage promoting muscular performance. To date, there is great controversy if MTF treatment combined with exercise training improves or nullifies the benefits provided by physical activity. This study is aimed at evaluating the effect of long-term moderate exercise combined with MTF treatment on body composition, strength, redox state, and survival rate during the life of female Wistar rats. In this study, rats performed moderate exercise during 20 of their 24 months of life and were treated with MTF for one year or for 6 months, i.e., from 12 to 24 months old and 18 to 24 months old. The body composition (percentage of fat, bone, and lean mass) was determined using a dual-energy X-ray absorption scanner (DXA), and grip strength was determined using a dynamometer. Likewise, medial and tibial nerve somatosensory evoked potentials were evaluated and the redox state was measured by HPLC, calculating the GSH/GSSG ratio in the gastrocnemius muscle. Our results suggest- that the MTF administration, both in the sedentary and the exercise groups, might activate a mechanism that is directly related to the induction of the hormetic response through the redox state modulation. MTF treatment does not eliminate the beneficial effects of exercise throughout life, and although MTF does not increase muscle mass, it increases longevity.

Efficacy of Ginger (Zingiber officinale) in Ameliorating Streptozotocin-Induced Diabetic Liver Injury in Rats: Histological and Biochemical Studies

Ginger (Zingiber officinale) was reported to have an antioxidant, antidiabetic effect. This study was done to investigate its therapeutic effect against functional and structural alteration in liver of diabetic rat (intraperitoneal streptozotocin (STZ) in a dose of 60 mg/kg/bw). Thirty adult male rats (three-months-old and 250 g weight) were sorted into five groups (N=6). G1 used as control, G2 was diabetic rats without any treatment, G3 was diabetic rats given oral ginger in a dose of 500 mg/kg/bw, G4 was diabetic rats treated with metformin (500 mg/kg/bw) while G5 received ginger orally. The experiment lasts for six weeks, animals were anesthetized by ether, body weight was recorded for all animals. Blood was collected for further analysis of lipid profile, liver enzymes and total antioxidant. Liver was dissected, weighted and samples were processed for histopathological study. The results showed significant decrease of glaucous level and liver enzymes in ginger treated rats. Total antioxidant was preserved. Ginger lowered blood glucose, level, regained body weight and liver index to near normal values. Diabetes induced degenerative changes and micro-vesicular lipid deposition in hepatocytes with moderate portal area fibrosis. Ultrastructure study confirmed such changes beside demonstrating increased lipid deposition in fat storing cells. Ginger was found to ameliorate those changes in treated animals. Results were matching metformin effects. In conclusion, Ginger as a natural safe Herbal medication can be used to support liver functions in diabetic status.

Mitochondrial dysfunction in type 2 diabetes mellitus: an organ-based analysis

Type 2 diabetes mellitus (T2DM) is a systemic disease characterized by hyperglycemia, hyperlipidemia, and organismic insulin resistance. This pathological shift in both circulating fuel levels and energy substrate utilization by central and peripheral tissues contributes to mitochondrial dysfunction across organ systems. The mitochondrion lies at the intersection of critical cellular pathways such as energy substrate metabolism, reactive oxygen species (ROS) generation, and apoptosis. It is the disequilibrium of these processes in T2DM that results in downstream deficits in vital functions, including hepatocyte metabolism, cardiac output, skeletal muscle contraction, β-cell insulin production, and neuronal health. Although mitochondria are known to be susceptible to a variety of genetic and environmental insults, the accumulation of mitochondrial DNA (mtDNA) mutations and mtDNA copy number depletion is helping to explain the prevalence of mitochondrial-related diseases such as T2DM. Recent work has uncovered novel mitochondrial biology implicated in disease progressions such as mtDNA heteroplasmy, noncoding RNA (ncRNA), epigenetic modification of the mitochondrial genome, and epitranscriptomic regulation of the mtDNA-encoded mitochondrial transcriptome. The goal of this review is to highlight mitochondrial dysfunction observed throughout major organ systems in the context of T2DM and to present new ideas for future research directions based on novel experimental and technological innovations in mitochondrial biology. Finally, the field of mitochondria-targeted therapeutics is discussed, with an emphasis on novel therapeutic strategies to restore mitochondrial homeostasis in the setting of T2DM.

Effect of metformin and flutamide on insulin, lipogenic and androgen-estrogen signaling, and cardiometabolic risk in a PCOS-prone metabolic syndrome rodent model

Polycystic ovary syndrome (PCOS) is highly associated with cardiometabolic risk and the metabolic syndrome (MetS), predisposing women to increased risk of developing type 2 diabetes and cardiovascular disease. Metformin is commonly used to treat insulin resistance-glucose intolerance, and flutamide, an androgen receptor (AR) antagonist, is used to target hyperandrogenemia and dyslipidemia. Currently, the physiological mechanism of action of these treatments on androgen, lipidogenic, and insulin signaling pathways remains unclear in PCOS. The aim of this study was to investigate the effects and mechanisms of action of metformin and flutamide on plasma lipid-apolipoprotein (Apo)B-lipoprotein and insulin-glucose metabolism, and endocrine-reproductive indices in a PCOS-prone MetS rodent model. PCOS-prone rodents were treated with metformin (300 mg/kg body wt), flutamide (30 mg/kg body wt), or metformin + flutamide combination treatment for 6 wk. Metformin was shown to improve fasting insulin and HOMA-IR, whereas flutamide and combination treatment were shown to reduce plasma triglycerides, ApoB48, and ApoB100, and this was associated with decreased intestinal secretion of ApoB48/triglyceride. Flutamide and metformin were shown to reduce plasma androgen indices and to improve ovarian primary and preovulatory follicle frequency. Metformin treatment increased hepatic estrogen receptor (ER)α, and metformin-flutamide decreased intestinal AR and increased ERα mRNA expression. Metformin-flutamide treatment upregulated hepatic and intestinal insulin signaling, including insulin receptor, MAPK1, and AKT2. In conclusion, cardiometabolic risk factors, in particular ApoB-hypertriglyceridemia, are independently modulated via the AR, and understanding the contribution of AR and insulin-signaling pathways further may facilitate the development of targeted interventions in high-risk women with PCOS and MetS.

Metformin inhibits visceral allodynia and increased gut permeability induced by stress in rats

BACKGROUND AND AIM

Metformin has been shown to have anti-cytokine property. Lipopolysaccharide (LPS)-induced or repeated water avoidance stress (WAS)-induced visceral allodynia and increased gut permeability were pro-inflammatory cytokine-dependent responses, which were considered to be animal models of irritable bowel syndrome (IBS). We hypothesized that metformin improves symptoms in the patients with IBS by attenuating these visceral changes and tested the hypothesis in rats.

METHODS

The threshold of the visceromotor response induced by colonic balloon distention was measured. Colonic permeability was determined in vivo by quantifying the absorbed Evans blue for 15 min spectrophotometrically.

RESULTS

Subcutaneously injected LPS (1 mg/kg) reduced the threshold of visceromotor response, and metformin (5-50 mg/kg for 3 days) intraperitoneally attenuated this response in a dose-dependent manner. Repeated WAS (1 h daily for 3 days) induced visceral allodynia, which was also blocked by metformin. The antinociceptive effect of metformin on the LPS-induced allodynia was reversed by compound C, an adenosine monophosphate-activated protein kinase inhibitor or N^G -nitro-L-arginine methyl ester, a nitric oxide synthesis inhibitor but not modified by naloxone. Additionally, it was blocked by sulpiride, a dopamine D2 receptor antagonist, but domperidone, a peripheral dopamine D2 receptor antagonist, did not alter it. Metformin also blocked the LPS-induced or repeated WAS-induced increased colonic permeability.

CONCLUSIONS

Metformin attenuated the visceral allodynia and increased gut permeability in animal IBS models. These actions may be evoked via activation of adenosine monophosphate-activated protein kinase, nitric oxide, and central dopamine D2 pathways. These results indicate the possibility that metformin can be useful for treating IBS.

Efficacy of a new delivery system based on solid lipid microparticles for the oral administration of the non-conventional antioxidant IAC on a diabetes mouse model

PURPOSE

We previously showed the positive effects of the new antioxidant molecule bis(1-hydroxy-2,2,6,6-tetramethyl-4-piperidinyl)-decandioate (IAC) in reducing basal hyperglycaemia and relieving glucose intolerance in a diabetes model. However, the chemical properties of IAC did not allow an efficient oral administration, thus representing the main failing of that study. Here, we tested the effect of a new oral delivery system based on solid lipid microparticles (SLMs) in a diabetes mouse model.

METHODS

The diabetes model was induced in C57B1/6J mice using streptozotocin and nicotinamide. Only the animals that overcame the glycaemic threshold of 180 mg/dL were enrolled in the study. Diabetic animals were then randomly assigned to 4 groups (n = 9) and treated once a day for 5 consecutive weeks with IAC (50, 100, and 150 mg/kg b.w.). The control group was composed of (n = 7) healthy mice that received only the vehicle. Glucose level was weekly monitored during the treatment period and up to 3 weeks after the suspension of the treatment. Glucose tolerance and insulin-resistance test were carried out.

RESULTS

Our results showed that SLMs maintained the IAC effect in reducing basal hyperglycaemia as well as improving the insulin sensitivity and glucose tolerance.

CONCLUSION

The present study confirms that SLMs are promising drug carriers, which allow the oral administration of IAC ensuring its therapeutic efficacy. The concrete possibility to administer IAC per os represents a significant breakthrough in the putative consideration of this multi-radical scavenger in the diabetes therapeutic approach.

Effect of Red Ginseng Extract on the Pharmacokinetics and Efficacy of Metformin in Streptozotocin-Induced Diabetic Rats

The purpose of this study was to investigate the effect of red ginseng extract on the pharmacokinetics (PK) and efficacy of metformin in streptozotocin-induced diabetic rats. The diabetes mellitus rat model was established by intraperitoneally administering multiple doses of streptozotocin (30 mg/kg, twice on day 1 and 8), and diabetic rats received metformin 50 mg/kg with or without single or multiple administration of Korean red ginseng extract (RGE, 2 g/kg/day, once or for 1 week). RGE administration did not affect the plasma concentration and renal excretion of metformin. Further, diabetic rats were administered metformin (50 mg/kg) and RGE (2 g/kg) alone or concomitantly for 5 weeks, and both regimens decreased the fasting blood glucose and glycated hemoglobin (Hb-A1c) levels. Furthermore, fasting blood glucose levels were reduced by metformin or RGE administered alone but recovered to the control level following co-administration, suggesting that the effect was additive. However, triglyceride and free fatty acid levels were not different with metformin and RGE treatment alone or in combination. Biochemical parameters such as alanine aminotransferase (ALT), aspartate aminotransferase (AST), triglycerides, total cholesterol, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol levels were not different among the three treatment groups. In conclusion, RGE and metformin showed an additive effect in glycemic control. However, the co-administration of RGE and metformin did not cause PK interactions or affect biochemical parameters including the free fatty acid, triglyceride, AST, ALT, or cholesterol levels.

Investigation of the pronounced erythropoietin-induced reduction in hyperglycemia in type 1-like diabetic rats

Erythropoietin (EPO) is known to stimulate erythropoiesis after binding with its specific receptor. In clinics, EPO is widely used in hemodialyzed patients with diabetes. However, changes in the expression of the erythropoietin receptor (EPOR) under diabetic conditions are still unclear. Therefore, we investigated EPOR expression both in vivo and in vitro. Streptozotocin-induced type 1-like diabetic rats (STZ rats) were used to evaluate the blood glucose-lowering effects of EPO. The expression and activity of the transducer and activator of transcription 3 (STAT3), the potential signaling molecule, was investigated in cultured rat skeletal myoblast (L6) cells incubated in high-glucose (HG) medium to mimic the in vivo changes. The EPO-induced reduction in hyperglycemia was more pronounced in diabetic rats. The increased EPOR expression in the soleus muscle of diabetic rats was reversed by the reduction in hyperglycemia. Glucose uptake was also increased in high-glucose (HG)-treated L6 cells. Western blotting results indicated that the EPO-induced hyperglycemic activity was enhanced mainly through an increase in EPOR expression. Increased EPOR expression was associated with the enhanced nuclear expression of STAT3 in HG-exposed L6 cells. In addition, treatment with siRNA specific to STAT3 reversed the increased expression of EPOR observed in these cells. Treatment with Stattic at a dose sufficient to inhibit STAT3 reduced the expression level of EPOR in STZ rats. In conclusion, the increased expression of EPOR by hyperglycemia is mainly associated with an augmented expression of nuclear STAT3, which was identified both in vivo and in vitro in the present study.

Ursolic acid activates the TGR5 receptor to enhance GLP-1 secretion in type 1-like diabetic rats

Endogenous Takeda G-protein-coupled receptor 5 (TGR5), G-protein-coupled bile acid receptor 1 (GPBAR1), regulates glucose metabolism. In animals, TGR5 activation by a chemical agonist may increase incretin secretion and reduce the blood sugar level. Recently, betulinic acid has been suggested to activate TGR5. Ursolic acid is a well-known pentacyclic triterpenoid that is similar to betulinic acid. It is of special interest to determine the potential effect of ursolic acid on TGR5. Therefore, we transfected cultured Chinese hamster ovary (CHO-K1) cells with the TGR5 gene. The functions of the transfected cells were confirmed via glucose uptake using a fluorescent indicator. Moreover, NCI-H716 cells that secreted incretin were also investigated, and the glucagon-like peptide (GLP-1) levels were quantified using ELISA kits. In addition, streptozotocin (STZ)-induced type 1-like diabetic rats were used to identify the effect of ursolic acid in vivo. Ursolic acid concentration dependently increased glucose uptake in CHO-K1 cells expressing TGR5. In NCI-H716 cells, ursolic acid induced a concentration-dependent elevation in GLP-1 secretion, which was inhibited by triamterene at the effective concentrations to block TGR5. Ursolic acid also increased the plasma GLP-1 level via TGR5 activation, which was further characterized in vivo with type 1-like diabetic rats. Moreover, ursolic acid is more effective than betulinic acid in reduction of hyperglycemia and increase of GLP-1 secretion. Therefore, we demonstrated that ursolic acid can activate TGR5, enhancing GLP-1 secretion in vitro and in vivo. Therefore, ursolic acid is suitable for use in TGR5 activation.

Synthetic and phytocompounds based dipeptidyl peptidase-IV (DPP-IV) inhibitors for therapeutics of diabetes

Currently antidiabetic therapeutic strategies are mainly based on synthetic hypoglycemic agent. Antidiabetic drugs are associated with significant adverse effects of hypoglycemia, dysfunction of insulin and weight gain. Nowadays, the novel Dipeptidyl peptidase-IV (DPP-IV) inhibitors unique approach for the management of diabetes has been considered to be safe, as DPP-IV inhibitors reduce blood glucose level by monitoring hyperglycemia including positive effects on body weight as it remains neutral, improves glycated hemoglobin levels and do not induce hypoglycemia. Inhibitors help to protect degradation of Glucagon-like peptide-1 (GLP-1) and gastric inhibitory peptide (GIP), gut hormones which helps to suppresses postprandial glucagon release, delay gastric emptying and regulate satiety. Therefore, the innovation of DPP-IV inhibitor based drugs regulates activity of incretin hormones such as GLP-1 and GIP. Commercially available DPP-IV inhibitors are chemically synthesized with good therapeutic value. However, the durability and long-term safety of DPP-IV inhibitors remains to be established. On the other hand, phytocompounds-based DPP-IV inhibitors are alternative and safe to use as compared to synthetic. Numerous novel antidiabetic compounds and group of compounds emerging in clinical development are through DPP-IV inhibition. This review summarized recent progress made on DPP-IV inhibitors from both synthetic as well as from natural sources.

Glycyrrhizic acid increases glucagon like peptide-1 secretion via TGR5 activation in type 1-like diabetic rats

Glycyrrhizic acid (GA) is belonged to triterpenoid saponin that is contained in the root of licorice and is known to affect metabolic regulation. Recently, glucagon like peptide-1 (GLP-1) has widely been applied in diabetes therapeutics. However, the role of GLP-1 in GA-induced anti-diabetic effects is still unknown. Therefore, we are interested in understanding the association of GLP-1 with GA-induced effects. In type 1-like diabetic rats induced by streptozotocin (STZ-treated rats), GA increased the level of plasma GLP-1, which was blocked by triamterene at a dose sufficient to inhibit Takeda G-protein-coupled receptor 5 (TGR5). The direct effect of GA on TGR5 has been identified using the cultured Chinese hamster ovary cells (CHO-K1 cells) transfected TGR5 gene. Moreover, in intestinal NCI-H716 cells that secreted GLP-1, GA promoted GLP-1 secretion with a marked elevation of calcium levels. However, both effects of GA were reduced by ablation of TGR5 with siRNA in NCI-H716 cells. Therefore, we demonstrated that GA can enhance GLP-1 secretion through TGR5 activation.

METABOLIC EFFECTS OF TULBAGHIA VIOLACEA HARV. IN A DIABETIC MODEL

Background:

Diabetes mellitus (DM) is a cluster of metabolic diseases with chronic hyperglycemia as a defining feature, associated with long-term organ damage and dysfunction. In this study we examined the effect of Tulbaghia violacea rhizome methanolic extract on blood glucose and lipids in normal and streptozotocin-induced diabetic rats.

Materials and Methods:

Male Wistar rats (250-300g) were injected intraperitoneally (i.p.) with streptozotocin (60mg/kg body weight) to induce diabetes; or provided with distilled water for the control (CON) (3 ml/kg/b.w.) animals and treatment with TVL (60mg/kg.b.w). The rats were divided into 5 groups of 6 animals per group as follows: Non-diabetic control (NDC)-received distilled water (3ml/kg.b.w), Non-diabetic TVL (ND+TVL)-received TVL (60mh/kg b.w), Diabetic control (DC)-received distilled water (3ml/kg.b.w), Diabetic experimental (D+TVL)-received TVL (60mg/kg.b.w), Diabetic experimental (D+M)-received Metformin (250 mg/kg.b.w). All doses were administered daily via oral gavage.

Results:

TVL-treated animals showed reduced blood glucose, increased plasma insulin, reduced plasma TG, TC, VLDL and increased HDL. Furthermore we found decreased thiobarbituric acid reactive substances (TBARS) and increased superoxide dismutase (SOD) activity and nitric oxide significantly. Regarding renal parameters we found increased blood urea nitrogen (BUN), and improved renal morphology in TVL-treated animals.

Conclusion:

Tulbaghia violacea has a hypoglycaemic effect which could due to its effects on multiple pathways of the hyperglycemic process. Further work is needed to identify the mechanism of its antidiabetic effect.

Ginsenoside Rh2 Improves Cardiac Fibrosis via PPARδ-STAT3 Signaling in Type 1-Like Diabetic Rats

Ginsenoside Rh2 (Rh2) is an active principal ingredient contained in ginseng (Panax ginseng Meyer), a medicinal herb used to enhance health worldwide. The present study is designed to investigate the effect of Rh2 on myocardial fibrosis in diabetic rats. In a streptozotocin-induced model of type-1 diabetic rats (STZ-diabetic rats), the increased fasting blood glucose levels and heart weight/body weight (HW/BW) ratio were substantially alleviated by Rh2. Moreover, Rh2 improved cardiac performance in STZ-diabetic rats. Histological results from Masson staining showed that Rh2 attenuated cardiac fibrosis in STZ-diabetic rats. The effects of Rh2 were reversed by GSK0660 at a dose sufficient to inhibit peroxisome proliferator-activated receptor δ (PPARδ) in STZ-diabetic rats. The role of PPARδ was subsequently investigated in vitro. Rh2 restored the decreased PPARδ expression level in high glucose-cultured cardiomyocytes. Moreover, increased protein levels of fibrotic signals, including signal transducer and activator of transcription 3 (STAT3), connective tissue growth factor (CCN2) and fibronectin, were reduced by Rh2 in high glucose-cultured cardiomyocytes. These effects of Rh2 were reversed by GSK0660 or siRNA specific for PPARδ Taken together, PPARδ activation may inhibit STAT3 activation to reduce CCN2 and fibronectin expression in diabetic rats with cardiac fibrosis. Moreover, Rh2 improves cardiac function and fibrosis by increasing PPARδ signaling. Therefore, Rh2 is suitable to develop as an alternative remedy for cardiac fibrosis.

Metformin ameliorates insulitis in STZ-induced diabetic mice

Background & Aims

Metformin is currently the most widely used first-line hypoglycemic agent for diabetes mellitus. Besides glucose-lowering action, there is increasingly interest in the potential anti-inflammatory action of this drug. In the present study, we investigated the actions of metformin on experimental insulitis using STZ-induced diabetic mice.

Methods

Mice with acute diabetes induced by STZ were administered metformin by gavage. Changes of blood glucose and body weight, and the daily amount of food and water intake were measured. Pancreatic tissues were collected for histologic analyses. Pathological assessment and immunohistochemistry analysis were used to determine the effect of metformin on insulitis. Inflammatory cytokines in the pancreas and insulin levels were measured through ELISA analysis.

Results

Metformin significantly reduced blood glucose levels and improved aberrant water intake behavior in experimental diabetic mice. No significant differences were observed in terms of body weight and food intake behavior in metformin-treated animals. In the STZ-induced model of diabetes, we found the appearance of pronounced insulitis. However, metformin administration reduced the severity of insulitis assessed by blind pathological scoring. In addition, metformin treatment improved insulin levels in experimental diabetic mice. ELISA assay revealed decreased levels of inflammatory response marker IL-1β and TNF-α in the pancreatic tissues following metformin treatment.

Conclusion

Metformin attenuated insulitis in the STZ-induced mice model of diabetes. This islet-protective effect might be partly correlated with the anti-inflammatory action of metformin.

Exercise in a Pill: The Latest on Exercise-Mimetics

There is increasing evidence that an active lifestyle benefits both body and brain. However, not everyone may be able to exercise due to disease, injury or aging-related frailty. Identification of cellular targets activated by physical activity may lead to the development of new compounds that can, to some extent, mimic systemic and central effects of exercise. This review will focus on factors relevant to energy metabolism in muscle, such as the 5’ adenosine monophosphate-activated protein kinase (AMPK) - sirtuin (SIRT1) - Peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) pathway, and the molecules affecting it. In particular, putative exercise-mimetics such as AICAR, metformin, and GW501516 will be discussed. Moreover, plant-derived polyphenols such as resveratrol and (-)epicatechin, with exercise-like effects on the body and brain will be evaluated.

Effects of metformin on hyperglycemia in an experimental model of tacrolimus- and sirolimus-induced diabetic rats

BACKGROUND/AIMS

Metformin (MET) is a first-line drug for type 2 diabetes mellitus (DM); its effect on new-onset diabetes after transplantation caused by immunosuppressant therapy is unclear. We compared the effects of MET on DM caused by tacrolimus (TAC) or sirolimus (SRL).

METHODS

DM was induced by injection of TAC (1.5 mg/kg) or SRL (0.3 mg/kg) for 2 weeks in rats, and MET (200 mg/kg) was injected for 2 more weeks. The effects of MET on DM caused by TAC or SRL were evaluated using an intraperitoneal glucose tolerance test (IPGTT) and by measuring plasma insulin concentration, islet size, and glucose-stimulated insulin secretion (GSIS). The effects of MET on the expression of adenosine monophosphate-activated protein kinase (AMPK), a pharmacological target of MET, were compared between TAC- and SRL-treated islets.

RESULTS

IPGTT showed that both TAC and SRL induced hyperglycemia and reduced plasma insulin concentration compared with vehicle. These changes were reversed by addition of MET to SRL but not to TAC. Pancreatic islet cell size was decreased by TAC but not by SRL, but addition of MET did not affect pancreatic islet cell size in either group. MET significantly increased GSIS in SRL- but not in TAC-treated rats. AMPK expression was not affected by TAC but was significantly decreased in SRL-treated islets. Addition of MET restored AMPK expression in SRL-treated islets but not in TAC-treated islets.

CONCLUSIONS

MET has different effects on hyperglycemia caused by TAC and SRL. The discrepancy between these drugs is related to their different mechanisms causing DM.

Cryptotanshinone Inhibits STAT3 Signaling to Alleviate Cardiac Fibrosis in Type 1-like Diabetic Rats

Cryptotanshinone is an active principal ingredient isolated from Salvia miltiorrhiza (Danshen), a medicinal plant used in China to treat cardiac disorders. The objective of this study was to investigate the effect of cryptotanshinone on myocardial fibrosis in diabetic rats. In streptozotocin-induced type 1 diabetic model hyperglycemic rats (STZ-treated rats), fasting blood glucose levels and heart weight/body weight ratio were markedly increased but both were not modified by cryptotanshinone. Additionally, cardiac performance in catheterized STZ-treated rats was improved. The histological results from Masson staining showed that cryptotanshinone attenuated cardiac fibrosis in STZ-treated rats. Moreover, both the mRNA and protein levels of the signal transducer and activator of transcription 3 (STAT3), matrix metalloproteinase-9, and connective tissue growth factor were reduced by cryptotanshinone in high glucose-cultured cardiomyocytes, similar to the reductions observed in the hearts of STZ-treated rats. In conclusion, while STAT3 regulates matrix metalloproteinase-9 and connective tissue growth factor expression in diabetic rats with cardiac fibrosis, cryptotanshinone inhibited fibrosis to improve cardiac function by suppressing the STAT3 pathway. Cryptotanshinone is suitable as an alternative remedy for therapy of cardiac fibrosis. Copyright © 2017 John Wiley & Sons, Ltd.

Telmisartan improves cardiac fibrosis in diabetes through peroxisome proliferator activated receptor δ (PPARδ): from bedside to bench

BACKGROUND

Despite the known risk of diabetes-induced cardiac fibrosis, less is known about whether diabetes causes an altered cardiac phenotype independent of coronary atherosclerosis. Peroxisome proliferator-activated receptor δ (PPARδ), a versatile regulator of metabolic homeostasis, may be a potential therapeutic target. Herein we investigated the effectiveness of telmisartan, a unique angiotensin receptor blocker that increases PPARδ expression, in improving left ventricular remodeling in diabetic humans and rats.

METHODS

In this longitudinal, prospective study, we enrolled 15 diabetic patients receiving telmisartan (20 mg/day) for 12 weeks. After treatment, strain was measured and compared with the baseline value. Using streptozotocin to induce type 1 diabetes rat model, we measured PPARδ expression and downstream targets.

RESULTS

After treatment with telmisartan, both longitudinal and circumferential strains improved in diabetic patients. Compared with that of controls, the diabetic rat heart developed significant fibrosis, which markedly decreased after treatment with telmisartan (30 mg/kg/day, orally) for 7 days. After incubation with 30 mM glucose, rat cardiomyocytes showed a significant down-regulation of PPARδ. Interestingly, the increased expression of fibrosis-associated proteins, including signal transducer and activator of transcription 3 (STAT3) was attenuated by the co-incubation of GW0742, a PPARδ agonist. By knockdown or inhibition of STAT3, the hyperglycemia related high expression of fibrosis associated targets was reversed. Independent from the hyperglycemic incubation, STAT3 over-expression led to similar results. Conversely, in the presence of GSK0660, a PPARδ inhibitor, the protective effects of telmisartan were diminished.

CONCLUSION

Telmisartan improved the hyperglycemia-induced cardiac fibrosis through the PPARδ/STAT3 pathway. Graphical abstract Summary of the mechanism of telmisartan's effect on the suppression of hyperglycemia-induced cardiac fibrosis through PPARδ instead of the AMPK pathway. PPARδ peroxisome proliferator-activated receptor δ, STAT3 signal transducer and activator of transcription 3, CTGF connective tissue growth factor, MMP9 matrix metallopeptidase 9.

Anti-inflammatory effect of AMPK signaling pathway in rat model of diabetic neuropathy

Diabetic neuropathy (DN) is characterized as Hyperglycemia activates thdisturbed nerve conduction and progressive chronic pain. Inflammatory mediators, particularly cytokines, have a determinant role in the pathogenesis of neuropathic pain. The activity of adenosine monophosphate protein kinase (AMPK), an energy charge sensor with neuroprotective properties, is decreased in diabetes. It has been reported that activation of AMPK reduces the systemic inflammation through inhibition of cytokines. In this study, we aimed to investigate the probable protective effects of AMPK on DN in a rat of diabetes. DN was induced by injection of streptozotocin (65 mg/kg, i.p.). Motor nerve conduction velocities (MNCV) of the sciatic nerve, as an electrophysiological marker for peripheral nerve damage, were measured. Plasma levels of IL-6, TNF-α, CRP were assessed as relevant markers for inflammatory response. Also, the expression of phosphorylated AMPK (p-AMPK) and non-phosphorylated (non-p-AMPK) was evaluated by western blotting in the dorsal root ganglia. Histopathological assessment was performed to determine the extent of nerve damage in sciatic nerve. Our findings showed that activation of AMPK by metformin (300 mg/kg) significantly increased the MNCV and reduced the levels of inflammatory cytokines. In addition, we showed that administration of metformin increased the expression of p-AMPK as well as decline in the level of non p-AMPK. Our results demonstrated that co-administration of dorsomorphin with metformin reversed the beneficial effects of metformin. In conclusion, the results of this study demonstrated that the activation of AMPK signaling pathway in diabetic neuropathy might be associated with the anti-inflammatory response.