Hypoglycemic effect of catalpol on high-fat diet/streptozotocin-induced diabetic mice by increasing skeletal muscle mitochondrial biogenesis

Mitochondrial quality control in human health and disease

Mitochondria, the most crucial energy-generating organelles in eukaryotic cells, play a pivotal role in regulating energy metabolism. However, their significance extends beyond this, as they are also indispensable in vital life processes such as cell proliferation, differentiation, immune responses, and redox balance. In response to various physiological signals or external stimuli, a sophisticated mitochondrial quality control (MQC) mechanism has evolved, encompassing key processes like mitochondrial biogenesis, mitochondrial dynamics, and mitophagy, which have garnered increasing attention from researchers to unveil their specific molecular mechanisms. In this review, we present a comprehensive summary of the primary mechanisms and functions of key regulators involved in major components of MQC. Furthermore, the critical physiological functions regulated by MQC and its diverse roles in the progression of various systemic diseases have been described in detail. We also discuss agonists or antagonists targeting MQC, aiming to explore potential therapeutic and research prospects by enhancing MQC to stabilize mitochondrial function.

The potential of therapeutic strategies targeting mitochondrial biogenesis for the treatment of insulin resistance and type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a persistent metabolic disorder marked by deficiencies in insulin secretion and/or function, affecting various tissues and organs and leading to numerous complications. Mitochondrial biogenesis, the process by which cells generate new mitochondria utilizing existing ones plays a crucial role in energy homeostasis, glucose metabolism, and lipid handling. Recent evidence suggests that promoting mitochondrial biogenesis can alleviate insulin resistance in the liver, adipose tissue, and skeletal muscle while improving pancreatic β-cell function. Moreover, enhanced mitochondrial biogenesis has been shown to ameliorate T2DM symptoms and may contribute to therapeutic effects for the treatment of diabetic nephropathy, cardiomyopathy, retinopathy, and neuropathy. This review summarizes the intricate connection between mitochondrial biogenesis and T2DM, highlighting the potential of novel therapeutic strategies targeting mitochondrial biogenesis for T2DM treatment and its associated complications. It also discusses several natural products that exhibit beneficial effects on T2DM by promoting mitochondrial biogenesis.

Rat Model of Type 2 Diabetes Mellitus Recapitulates Human Disease in the Anterior Segment of the Eye

Changes in the anterior segment of the eye due to type 2 diabetes mellitus (T2DM) are not well-characterized, in part due to the lack of a reliable animal model. This study evaluates changes in the anterior segment, including crystalline lens health, corneal endothelial cell density, aqueous humor metabolites, and ciliary body vasculature, in a rat model of T2DM compared with human eyes. Male Sprague-Dawley rats were fed a high-fat diet (45% fat) or normal diet, and rats fed the high-fat diet were injected with streptozotocin i.p. to generate a model of T2DM. Cataract formation and corneal endothelial cell density were assessed using microscopic analysis. Diabetes-related rat aqueous humor alterations were assessed using metabolomics screening. Transmission electron microscopy was used to assess qualitative ultrastructural changes ciliary process microvessels at the site of aqueous formation in the eyes of diabetic rats and humans. Eyes from the diabetic rats demonstrated cataracts, lower corneal endothelial cell densities, altered aqueous metabolites, and ciliary body ultrastructural changes, including vascular endothelial cell activation, pericyte degeneration, perivascular edema, and basement membrane reduplication. These findings recapitulated diabetic changes in human eyes. These results support the use of this model for studying ocular manifestations of T2DM and support a hypothesis postulating blood-aqueous barrier breakdown and vascular leakage at the ciliary body as a mechanism for diabetic anterior segment pathology.

Protective effect of Qingluotongbi formula against Tripterygium wilfordii induced liver injury in mice by improving fatty acid β-oxidation and mitochondrial biosynthesis

CONTEXT

Qingluotongbi formula (QLT) is a Chinese medicine compound consisting of Tripterygium wilfordii Hook. f. (Celastraceae, TW), Panax notoginseng (Burkill) F.H.Chen (Araliaceae, PN), Rehmannia glutinosa (Gaertn.) DC. (Orobanchaceae, RG), Sinomenium acutum (Thunb.) Rehder & E.H. Wilson (Menispermaceae, SA), and Bombyx mori L. (Bombycidae, BM).

OBJECTIVE

This study investigated the protective effect and possible mechanism of QLT against TW-induced liver injury in mice.

MATERIALS AND METHODS

To establish the model of TW-induced liver injury in mice, C57BL/6J mice were randomly divided into 4 groups: control group, low-dose TW group, middle-dose TW group, and high-dose TW group. To observe the effects of QLT and its individual ingredients against TW-induced liver injury, C57BL/6J mice were randomly divided into 7 groups: control group, TW group, QLT group, PN group, RG group, SA group, BM group.After administration for 7 days, C57BL/6J mice were tested for biochemical indicators and liver pathological changes. Then, we evaluated the mitochondrial function and analysed the gene and protein expression related to the peroxisome proliferator-activated receptor alpha (PPARα)/peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) pathway by quantitative real-time PCR (qRT-PCR) and Western blotting.

RESULTS

Compared with the control group (0.30 ± 0.35), TW significantly increased mice liver histological score (L, 0.95 ± 1.14; M, 1.25 ± 1.16; H, 4.00 ± 1.13). QLT and its ingredients significantly improved the pathology scores (CON, 0.63 ± 0.74; TW, 4.19 ± 1.53; QLT, 1.56 ± 0.62; PN, 1.94 ± 0.68; RG, 2.75 ± 1.39; SA, 4.13 ± 0.99; BM, 4.13 ± 0.99). Western blot and qRT-PCR analysis revealed that QLT and its ingredients reversed TW-induced suppression of PPARα/PGC1-α pathway.Discussion and conclusions: These findings provide valuable information for compound compatibility studies and TW clinical applications.

Protective effects of catalpol on cardio-cerebrovascular diseases: A comprehensive review

Catalpol, an iridoid glucoside isolated from Rehmannia glutinosa, has gained attention due to its potential use in treating cardio-cerebrovascular diseases (CVDs). This extensive review delves into recent studies on catalpol's protective properties in relation to various CVDs, such as atherosclerosis, myocardial ischemia, infarction, cardiac hypertrophy, and heart failure. The review also explores the compound's anti-oxidant, anti-inflammatory, and anti-apoptotic characteristics, emphasizing the role of vital signaling pathways, including PGC-1α/TERT, PI3K/Akt, AMPK, Nrf2/HO-1, estrogen receptor (ER), Nox4/NF-κB, and GRP78/PERK. The article discusses emerging findings on catalpol's ability to alleviate diabetic cardiovascular complications, thrombosis, and other cardiovascular-related conditions. Although clinical studies specifically addressing catalpol's impact on CVDs are scarce, the compound's established safety and well-tolerated nature suggest that it could be a valuable treatment alternative for CVD patients. Further investigation into catalpol and related iridoid derivatives may unveil new opportunities for devising natural and efficacious CVD therapies.

From Xiaoke to diabetes mellitus: a review of the research progress in traditional Chinese medicine for diabetes mellitus treatment

Diabetes mellitus (DM) is a chronic metabolic disorder characterized by hyperglycemia resulting from insulin secretion defects or insulin resistance. The global incidence of DM has been gradually increasing due to improvements in living standards and changes in dietary habits, making it a major non-communicable disease that poses a significant threat to human health and life. The pathogenesis of DM remains incompletely understood till now, and current pharmacotherapeutic interventions are largely inadequate, resulting in relapses and severe adverse reactions. Although DM is not explicitly mentioned in traditional Chinese medicine (TCM) theory and clinical practice, it is often classified as "Xiaoke" due to similarities in etiology, pathogenesis, and symptoms. With its overall regulation, multiple targets, and personalized medication approach, TCM treatment can effectively alleviate the clinical manifestations of DM and prevent or treat its complications. Furthermore, TCM exhibits desirable therapeutic effects with minimal side effects and a favorable safety profile. This paper provides a comprehensive comparison and contrast of Xiaoke and DM by examining the involvement of TCM in their etiology, pathogenesis, treatment guidelines, and other relevant aspects based on classical literature and research reports. The current TCM experimental research on the treatment of DM by lowering blood glucose levels also be generalized. This innovative focus not only illuminates the role of TCM in DM treatment, but also underscores the potential of TCM in DM management.

Luteolin Protects Against Obese Sarcopenia in Mice with High-Fat Diet-Induced Obesity by Ameliorating Inflammation and Protein Degradation in Muscles

SCOPE

Although sarcopenia is mainly caused by aging, sarcopenia due to obesity has become an emerging issue given the increase in obesity among people of various ages. There are studies on obesity or sarcopenia, our understanding of obesity-mediated sarcopenia is insufficient. Luteolin (LU) has exhibited antiobesity effects, but no studies have investigated the LU effects on antisarcopenia. This study therefore investigated the effects of LU on obese sarcopenia in mice with high-fat diet (HFD)-induced obesity.

METHODS AND RESULTS

To evaluate its inhibitory efficacy against obese sarcopenia, 5-week-old mice are fed an HFD supplemented with LU for 20 weeks. LU exerts suppressive effects on obesity, inflammation, and protein degradation in the HFD-fed obese mice. It also inhibits lipid infiltration into the muscle and decreases p38 activity and the mRNA expression of inflammatory factors, including TNF-α, Tlr2, Tlr4, MCP1, and MMP2, in the muscle. The suppression of muscle inflammation by LU leads to the inhibition of myostatin, FoxO, atrogin, and MuRF expression. These effects of LU affect inhibition of protein degradation and improvement of muscle function.

CONCLUSION

Here, it demonstrates that LU's antiobesity and antiinflammatory functionality affect inhibition of muscle protein degradation, and consequently, these interactions by LU exerts a protective effect against obese sarcopenia.

Impact of Ninjin’yoeito on frailty and short life in klotho-hypomorphic (kl/kl) mice

With the recent aging of society, the prevention of frailty has become an important issue because people desire both a long and healthy lifespan. Klotho-hypomorphic (kl/kl) mice are known to show phenotypes of premature aging. Ninjin’yoeito (NYT) is a traditional Japanese Kampo medicine used to treat patients with vulnerable constitution, fatigue or physical exhaustion caused by aging and illness. Recent studies have reported the potential efficacy of NYT against frailty. We therefore evaluated the effect of NYT on the gait function, activity, the histopathological status of organs and survival using kl/kl mice as a model of aging-related frailty. Two sets of 28-day-old male kl/kl mice were assigned to the vehicle (non-treated; NT), 3% or 5% NYT dietary groups. One set of groups (NT, n = 18; 3% NYT, n = 11; 5% NYT, n = 11) was subjected to the analysis of free walking, rotarod, and spontaneous activity tests at approximately 58 days old. Thereafter, we measured triceps surae muscles weight and myofiber cross-sectional area (CSA), and quantified its telomere content. In addition, we evaluated bone strength and performed histopathological examinations of organs. Survival was measured in the second set of groups (NT, 3% NYT and 5% NYT group, n = 8 each). In the walking test, several indicators such as gait velocity were improved in the NYT 3% group. Similar results were obtained for the latency to fall in the rotarod test and spontaneous motor activity. Triceps muscle mass, CSA and its telomere content were significantly improved in the NYT 3% group. Bone density, pulmonary alveolus destruction and testicular atrophy were also significantly improved in the NYT 3% group. Survival rate and body weight were both significantly improved in the NYT3% group compared with those in the NT group. Continuous administration of NYT from the early stage of aging improved not only gait performance, but also the survival in the aging-related frailty model. This effect may be associated with the improvements in aging-related organ changes such as muscle atrophy. Intervention with NYT against the progression of frailty may contribute to a longer, healthier life span among the elderly individuals.

Catalpol promotes mitochondrial biogenesis in chondrocytes

The chondrocyte mitochondrial dysfunction has been considered to be associated with the pathogenesis of joint diseases. Catalpol is an active traditional Chinese medicine ingredient named Di-Huang, which is used widely to treat different diseases. In this study, we found the addition of catalpol in chondrocytes induced the expression of crucial mitochondrial regulators, peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α), nuclear respiratory factor-1 (NRF1), and mitochondrial transcription factor A (TFAM). Catalpol promoted mitochondrial biogenesis, as revealed by the induction on the mitochondrial DNA/nuclear DNA (mtDNA/nDNA) and the expression of several mitochondrial genes including translocase of outer mitochondrial membrane 22 (Tomm22), translocase of outer mitochondrial membrane 70 (Tomm70), mitochondrial import inner membrane translocase subunit 50 (Timm50), NADH dehydrogenase [ubiquinone] iron-sulphur protein 3 (NDUFS3), adenosine triphosphate (ATP) synthase subunit D (ATP5d), and cytochrome B. Consequently, catalpol increased cytochrome c oxidase activity, the mitochondrial respiratory rate, and the extracellular ATP production, indicating that catalpol boosted mitochondrial function. Mechanistically, catalpol increased the activation of the cAMP-responsive element-binding protein (CREB), and the inhibition of CREB abolished catalpol-mediated promotion on mitochondrial biogenesis. In summary, this study demonstrated that catalpol has the potential to be used in the treatment of joint diseases.

Zi Shen Wan Fang regulates kynurenine metabolism to alleviate diabetes-associated cognitive impairment via activating the skeletal muscle PGC1α-PPARα signaling

BACKGROUND

Cognitive dysfunction is commonly observed in diabetic patients, yet, the underlying mechanisms are obscure and there are no approved drugs. Skeletal muscle is a key pathological organ in diabetes. Evidence is accumulating that skeletal muscle and brain communication are important for cognitive, and kynurenine (KYN) metabolism is one of the mediators.

PURPOSE

This study aims to elucidate the mechanism of diabetes-induced cognitive impairment (DCI) from the perspective of skeletal muscle and brain communication, and to explore the therapeutic effect of Zi Shen Wan Fang (ZSWF, a optimized prescription consists of Anemarrhenae Rhizoma (Anemarrhena asphodeloides Bge.), Phellodendri Chinensis Cortex (Phellodendron chinense Schneid.) and Cistanches Herba (Cistanche deserticola Y.C.Ma)), in order to provide new strategies for the prevention and treatment of DCI and preliminarily explore valuable drugs.

METHODS

DCI was induced by intraperitoneal injection of streptozotocin (STZ) combined with a high-fat diet and treated with different dosage ZSWF extract by oral gavage for 8 weeks, once a day. Cognitive and skeletal muscle function was assessed, synaptic plasticity and L-type amino acid transporter (LAT1) was measured. KYN and its metabolites as well as metabolic enzymes in the hippocampus, peripheral blood and skeletal muscle were measured. Peroxisome proliferator-activated receptor-γ co-activator-1α (PGC-1α) and peroxisome proliferator-activated receptor α (PPARα) were measured in skeletal muscle.

RESULTS

Compared with healthy mice, DCI mice not only showed decreased cognitive function and abnormal skeletal muscle function, but also showed imbalance of KYN metabolism in brain, circulating blood and skeletal muscle. Fortunately, ZSWF administration for 8 weeks notably attenuated the cognitive function, synaptic plasticity and skeletal muscle function in DCI mice. Besides, ZSWF significantly attenuated KYN metabolism in brain, circulation and skeletal muscle of DCI mice. Furthermore, ZSWF activated PGC1α-PPARα in skeletal muscle of DCI mice.

CONCLUSIONS

These results indicate that abnormal PGC1α-PPARα signaling in skeletal muscle mediating KYN metabolism disorder is one of the pathological mechanisms of DCI, and ZSWF can reverse diabetes-induced cognitive impairment via activating skeletal muscle PGC1α-PPARα signaling to maintain KYN metabolism homeostasis.

Research progress on hydroxyl protection of iridoid glycosides

Iridoids, an important active ingredient, are widely distributed in varieties of Chinese herbal medicines and have varieties of pharmacological activities, such as anti-tumor, hypoglycemic, anti-inflammatory and so on, most of which exist in the form of glycosides in nature. However, its clinical application is limited by poor lipid solubility, low bioavailability and short half-life. It is necessary to optimize the structure of iridoids. It is hard to modify the hydroxyl groups at specific sites because iridoid glycosides are polyhydroxy compounds and very complex. In this paper, the words of ‘Iridoid glycosides’ and ‘Hydroxyl protection’ were used as the keywords, more than 200 articles from 1965 to 2021 were obtained from databases, such as CNKI, PubMed, Scifinder and so on. Finally, 60 articles were selected to summarize the hydroxyl protection of iridoid glycosides, which will provide a theoretical basis for their structural modification and stimulate their application potential in the field of drug research and development.

Comparative study on molecular mechanism of diabetic myopathy in two different types of streptozotocin-induced diabetic models

AIMS

Streptozotocin (STZ)-induced diabetic animal models have been widely used to study diabetic myopathy; however, non-specific cytotoxic effects of high-dose STZ have been discussed. The purpose of this study was to compare diabetic myopathy in a high-STZ model with another well-established STZ model with reduced cytotoxicity (high-fat diet (HFD) and low-dose STZ) and to identify mechanistic insights underlying diabetic myopathy in STZ models that can mimic perturbations observed in human patients with diabetic myopathy.

MAIN METHODS

Male C57BL6 mice were injected with a single high dose of STZ (180 mg/kg, High-STZ) or were given HFD plus low-dose STZ injection (STZ, 55 mg/kg/day, five consecutive days, HFD/STZ). We characterized diabetic myopathy by histological and immunochemical analyses and conducted gene expression analysis.

KEY FINDINGS

The high-STZ model showed a significant reduction in tibialis anterior myofiber size along with decreased satellite cell content and downregulation of inflammation response and collagen gene expression. Interestingly, blood corticosteroid levels were significantly increased in the high-STZ model, which was possibly related to lowered inflammation response-related gene expression. Further analyses using the HFD/STZ model showed downregulation of gene expression related to mitochondrial functions accompanied by a significant decrease in ATP levels in the muscles.

SIGNIFICANCE

The high-STZ model is suitable for studies regarding not only severe diabetic myopathy with excessive blood glucose but also negative impact of glucocorticoids on skeletal muscles. In contrast, the HFD/STZ model is characterized by higher immune responses and lower ATP production, which also reflects the pathologies observed in human diabetic patients.

Potential Natural Compounds for the Prevention and Treatment of Nonalcoholic Fatty Liver Disease: A Review on Molecular Mechanisms

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is a kind of metabolic stress-induced liver injury closely related to insulin resistance and genetic susceptibility, and there is no specific drug for its clinical treatment currently. In recent years, a large amount of literature has reported that many natural compounds extracted from traditional Chinese medicine (TCM) can improve NAFLD through various mechanisms. According to the latest reports, some emerging natural compounds have shown great potential to improve NAFLD but are seldom used clinically due to the lacking special research.

PURPOSE

This paper aims to summarize the molecular mechanisms of the potential natural compounds on improving NAFLD, thus providing a direction and basis for further research on the pathogenesis of NAFLD and the development of effective drugs for the prevention and treatment of NAFLD.

METHODS

By searching various online databases, such as Web of Science, SciFinder, PubMed, and CNKI, NAFLD and these natural compounds were used as the keywords for detailed literature retrieval.

RESULTS

The pathogenesis of NAFLD and the molecular mechanisms of the potential natural compounds on improving NAFLD have been reviewed.

CONCLUSION

Many natural compounds from traditional Chinese medicine have a good prospect in the treatment of NAFLD, which can serve as a direction for the development of anti-NAFLD drugs in the future.

Effects of Root Extract of Morinda officinalis in Mice with High-Fat-Diet/Streptozotocin-Induced Diabetes and C2C12 Myoblast Differentiation

Type 2 diabetes is the most common type of diabetes and causes a decline in muscle quality. In this study, we investigated the effects of the root extract of Morinda officinalis (MORE) on skeletal muscle damage in mice with high-fat-diet (HFD)/streptozotocin (STZ)-induced diabetes and the expression of myogenic and biogenesis regulatory proteins in C2C12 myoblast differentiation. An in vivo model comprised C57BL/6N mice fed HFD for 8 weeks, followed by a single injection of STZ at 120 mg/kg. MORE was administered at 100 and 200 mg/kg once daily (p.o.) for 4 weeks. The changes in body weight, calorie intake, and serum levels of glucose, insulin, total cholesterol (TCHO), HDL-cholesterol (HDL-C), LDL-cholesterol (LDL-C), aspartate transaminase (AST), and alanine aminotransferase (ALT) were investigated in diabetic mice. The histological changes in the gastrocnemius muscle were observed by H&E staining, and then the myofiber size was measured. The expression of the myogenic (MHC, myogenin, and MyoD) and biogenesis (PGC-1α, SIRT1, NRF1, and TFAM) regulatory proteins was examined in the muscle tissues and differentiated C2C12 myoblasts by Western blot, respectively. The administration of MORE at 200 mg/kg in mice with HFD/STZ-induced diabetes significantly reduced weight gains, calorie intake, insulin resistance, and serum levels of glucose, TCHO, LDL-C, AST, and ALT. MORE administration at 100 and 200 mg/kg significantly increased serum insulin and HDL-C levels in diabetic mice. In addition, MORE significantly increased the expression of MHC, myogenin, MyoD, PGC-1α, SIRT1, NRF1, and TFAM in muscle tissues as well as increased the myofiber size in diabetic mice. In C2C12 myoblast differentiation, MORE treatment at 0.5, 1, and 2 mg/mL significantly increased the expression of myogenic and biogenesis regulatory proteins in a dose-dependent manner. MORE improves diabetes symptoms in mice with HFD/STZ-induced diabetes by improving muscle function. This suggests that MORE could be used to prevent or treat diabetes along with muscle disorders.

Effect of genipin-1-β-d-gentiobioside on diabetic nephropathy in mice by activating AMP-activated protein kinase/silencing information regulator-related enzyme 1/ nuclear factor-κB pathway

OBJECTIVES

Genipin-1-β-d-gentiobioside (GG) is a kind of compound extracted from Gardenia jasminoides Ellis. The chemical structure of GG is similar to that of geniposide and has antidiabetic effects. We aimed to investigate the efficacy of GG on diabetic nephropathy (DN) in vivo and in vitro experiments and explore its potential mechanism.

METHODS

For high-fat diet/streptozotocin-induced DN mice used in our study, the general features of mice were analysed after GG treatment. Oxidative stress parameters and inflammatory factors were also measured by commercial kits. Kidney damage was assessed using hematoxylin and eosin (H&E), periodic acid-Schiff (PAS) and Masson staining, respectively. In vitro, podocyte injury was assessed by TUNEL and flow cytometric analyses. AMP-activated protein kinase/silencing information regulator related enzyme 1 (AMPK/SIRT1)/nuclear factor-κB (NF-κB) pathway-related proteins were detected by AMPK-siRNA intervention and western blotting.

KEY FINDINGS

Treatment of GG could increase cell survival and attenuated kidney damage. Despite the presence of inflammatory and oxidative stress, when GG retained the expression of AMPK/SIRT1, it could be observed that the downstream NLRP3 inflammatory-related proteins were inhibited.

CONCLUSIONS

Results showed that the protective efficacy of GG on DN works together with hypoglycemia and suppressing oxidative stress and inflammation, which at least partly involved in APMK/SIRT1/NF-κB-dependent pathway.

Molecular and Biochemical Pathways of Catalpol in Alleviating Diabetes Mellitus and Its Complications

Catalpol isolated from Rehmannia glutinosa is a potent antioxidant and investigated against many disorders. This review appraises the key molecular pathways of catalpol against diabetes mellitus and its complications. Multiple search engines including Google Scholar, PubMed, and Science Direct were used to retrieve publications containing the keywords “Catalpol”, “Type 1 diabetes mellitus”, “Type 2 diabetes mellitus”, and “diabetic complications”. Catalpol promotes IRS-1/PI3K/AKT/GLUT2 activity and suppresses Phosphoenolpyruvate carboxykinase (PEPCK) and Glucose 6-phosphatase (G6Pase) expression in the liver. Catalpol induces myogenesis by increasing MyoD/MyoG/MHC expression and improves mitochondria function through the AMPK/PGC-1α/PPAR-γ and TFAM signaling in skeletal muscles. Catalpol downregulates the pro-inflammatory markers and upregulates the anti-inflammatory markers in adipose tissues. Catalpol exerts antioxidant properties through increasing superoxide dismutase (sod), catalase (cat), and glutathione peroxidase (gsh-px) activity in the pancreas and liver. Catalpol has been shown to have anti-oxidative, anti-inflammatory, anti-apoptosis, and anti-fibrosis properties that in turn bring beneficial effects in diabetic complications. Its nephroprotective effect is related to the modulation of the AGE/RAGE/NF-κB and TGF-β/smad2/3 pathways. Catalpol produces a neuroprotective effect by increasing the expression of protein Kinase-C (PKC) and Cav-1. Furthermore, catalpol exhibits a cardioprotective effect through the apelin/APJ and ROS/NF-κB/Neat1 pathway. Catalpol stimulates proliferation and differentiation of osteoblast cells in high glucose condition. Lastly, catalpol shows its potential in preventing neurodegeneration in the retina with NF-κB downregulation. Overall, catalpol exhibits numerous beneficial effects on diabetes mellitus and diabetic complications.

The effects of two iso-volume endurance training protocols on mitochondrial dysfunction in type 2 diabetic male mice

Purpose

Type 2diabetes(T2D) is one of the more common diseases in the world and has been widely spread. One of the suggested mechanisms in development of T2D, is mitochondrial dysfunction. The purpose of this study is to compare the effects of two endurance training protocols with low and moderate intensity on biogenesis and mitochondrial function, in Diabetic mice induced by high fat diet and Streptozotocin(STZ).

Methods

40 five week old mice divided to four groups including: health control (HC, n = 7), diabetic control (DC, n = 7), low endurance training (DLT, n = 7) and moderate endurance training (DMT, n = 7). DMT group ran at 5 m/min for an hour, 3 days a week on a treadmill, and DLT group ran at 3 m/min for an hour, 5 days a week on a treadmill for 8 weeks.

Results

The cytosolic content of PGC1α, Tfam and mitochondrial content of citrate synthase(Cs) and cytochrome c oxidase(Cox) in DC was significantly reduced compared to HC(P˂0.05). All of the parameters except for Cs in both DLT and DMT were increased compared to DC (P˂0.05), but there was no difference between them and the HC (P˃0.05). There was no difference in Cs enzyme between the DC and the DLT(P˃0.05), but it was significantly increased in the DMT(P˂0.05). There was a significantly difference between Cs enzyme in HC and DLT(P˂0.05), but there wasn't any significant difference between HC and DMT(P˃0.05).

Conclusions

The results showed that in same volume condition, both endurance training protocols improved the proteins involved in biogenesis and mitochondrial function in T2D mice and there was no significant difference between them.

Catalpol ameliorates psoriasis-like phenotypes via SIRT1 mediated suppression of NF-κB and MAPKs signaling pathways

Psoriasis is a chronic inflammatory skin disease that affects approximately 2% of worldwide population, and causing long-term troubles to the patients. Therefore, it is urgent to develop safe and effective therapeutic drugs. Catalpol is a natural iridoid glucoside, that has several remarkable pharmacological effects, however, whether catalpol can alleviated psoriasis has not been explored. The goal of the present work is to study the role of catalpol in psoriasis in vivo and in vitro. Imiquimod-induced psoriasis-like mice were applied with different concentrations of catalpol for 8 consecutive days. The severity degree of psoriasis was estimated and the skin pathological changes were detected by H&E staining. Also, TNF-α-stimulated keratinocytes were treated with different concentrations of catalpol, then the oxidative stress and inflammation factors, as well as the expression of SIRT1 and activation of NF-kB and MAPK pathways were measured. The results showed that catalpol reduced the erythema, scaling, ear thickness, and changed pathological phenotypes in the lesioned skin region in mice. Treatment with catalpol significantly suppressed the oxidative stress and inflammatory reactions in vivo and in vitro, as reflected by the decreased secretion or expression of oxidative stress indicators and proinflammatory factors. Furthermore, the SIRT1 was up-regulated and the NF-κB and MAPKs signaling pathways were suppressed by the treatment of catalpol in vivo and in vitro. In summary, our data suggested that catalpol may have a therapeutic property of psoriasis by ameliorating oxidative stress and inflammation partly through SIRT1 mediated suppression of NF-κB and MAPKs pathways.

Abbreviation: CAT: catalase; ELISA: enzyme-linked immunosorbent assay; GSH: glutathione; HRP: horseradish peroxidase; IMQ: imiquimod; JNK: c-Jun NH 2-terminal kinases; MAPKs: mitogen-activated protein kinases; MDA: malondialdehyde; NC: negative control group; NF-kB: nuclear factor kappa B; PASI: psoriasis area and severity index; PVDF: polyvinylidene difluoride membranes; qRT-PCR: quantitative real time polymerase chain reaction; ROS: reactive oxygen species; SDS-PAGE: sodium dodecyl sulfate-polyacrylamide gel; SIRT1: silent information regulator 1; SOD: Cu/Zn superoxide dismutase

Catalpol Ameliorates Insulin Sensitivity and Mitochondrial Respiration in Skeletal Muscle of Type-2 Diabetic Mice Through Insulin Signaling Pathway and AMPK/SIRT1/PGC-1α/PPAR-γ Activation

Catalpol was tested for various disorders including diabetes mellitus. Numerous molecular mechanisms have emerged supporting its biological effects but with little information towards its insulin sensitizing effect. In this study, we have investigated its effect on skeletal muscle mitochondrial respiration and insulin signaling pathway. Type-2 diabetes (T2DM) was induced in male C57BL/6 by a high fat diet (60% Kcal) and streptozotocin (50 mg/kg, i.p.). Diabetic mice were orally administered with catalpol (100 and 200 mg/kg), metformin (200 mg/kg), and saline for four weeks. Fasting blood glucose (FBG), HbA1c, plasma insulin, oral glucose tolerance test (OGTT), insulin tolerance test (ITT), oxygen consumption rate, gene (IRS-1, Akt, PI3k, AMPK, GLUT4, and PGC-1α) and protein (AMPK, GLUT4, and PPAR-γ) expression in muscle were measured. Catalpol (200 mg/kg) significantly (p < 0.05) reduced the FBG, HbA1C, HOMA_IR index, and AUC of OGTT whereas, improved the ITT slope. Gene (IRS-1, Akt, PI3k, GLUT4, AMPK, and PGC-1α) and protein (AMPK, p-AMPK, PPAR-γ and GLUT4) expressions, as well as augmented state-3 respiration, oxygen consumption rate, and citrate synthase activity in muscle was observed in catalpol treated mice. The antidiabetic activity of catalpol is credited with a marked improvement in insulin sensitivity and mitochondrial respiration through the insulin signaling pathway and AMPK/SIRT1/PGC-1α/PPAR-γ activation in the skeletal muscle of T2DM mice.

Study on the inhibitive effect of Catalpol on diabetic nephropathy

AIMS

Catalpol (Cat) can ameliorate oxide stress and inflammation caused by diabetic nephropathy (DN), but the molecular mechanisms are unclear. This study was designed to investigate the anti-diabetic effects of Cat and its potential mechanism.

MAIN METHODS

We constructed high-fat diet/streptozotocin (HFD/STZ)-induced DN mice and high glucose (HG)-induced podocyte model. The hypoglycemic effect of Cat was analyzed by general features of DN mice. Kidney function was detected via ELISA assay and Western blotting. Renal histopathology analysis was conducted via hematoxylin and eosin (H&E), Masson and periodic acid-silver metheramine (PASM) staining. Cellular viability was measured by TUNEL assay. In order to further study the potential mechanisms of Cat, various proteins in AMPK/SIRT1/NF-κB pathway were detected in DN mice and podocytes with siRNA-AMPK intervention using Western blotting, respectively.

KEY FINDINGS

We found hyperglycemia, renal structural and function abnormalities, and increased renal inflammation in DN mice. However, Cat effectively attenuated kidney damage caused by inflammation and increased AMPK, p-AMPK and SIRT1 levels. After AMPK-siRNA transfected into HG-induced podocyte model, AMPK, p-AMPK and SIRT1 levels were obviously decreased, while Cat reversed these chandes. The levels of p-NF-κB, ASC, Cleaved IL-1β, NLRP3, Cleaved caspase1 and GSDMD-N significantly decreased by Cat treatment both in DN mice and podocyte model, which indicated that Cat could activate AMPK/SIRT1/NF-κB pathway.

SIGNIFICANCE

Cat could effectively inhibit oxide stress and inflammation accompanied with pyroptosis and its mechanism might be related to AMPK/SIRT1/NF-κB pathway, indicating that Cat possessed potential value in the treatment of DN.

The hypoglycemic mechanism of catalpol involves increased AMPK-mediated mitochondrial biogenesis

Mitochondria serve as sensors of energy regulation and glucose levels, which are impaired by diabetes progression. Catalpol is an iridoid glycoside that exerts a hypoglycemic effect by improving mitochondrial function, but the underlying mechanism has not been fully elucidated. In the current study we explored the effects of catalpol on mitochondrial function in db/db mice and C2C12 myotubes in vitro. After oral administration of catalpol (200 mg·kg⁻¹·d⁻¹) for 8 weeks, db/db mice exhibited a decreased fasting blood glucose level and restored mitochondrial function in skeletal muscle. Catalpol increased mitochondrial biogenesis, evidenced by significant elevations in the number of mitochondria, mitochondrial DNA levels, and the expression of three genes associated with mitochondrial biogenesis: peroxisome proliferator-activated receptor gammaco-activator 1 (PGC-1α), mitochondrial transcription factor A (TFAM) and nuclear respiratory factor 1 (NRF1). In C2C12 myotubes, catalpol significantly increased glucose uptake and ATP production. These effects depended on activation of AMP-activated protein kinase (AMPK)-mediated mitochondrial biogenesis. Thus, catalpol improves skeletal muscle mitochondrial function by activating AMPK-mediated mitochondrial biogenesis. These findings may guide the development of a new therapeutic approach for type 2 diabetes.

Comparison of male reproductive parameters in mice with type 1 and type 2 diabetes

OBJECTIVE

The differences between type 1 and type 2 diabetes mellitus (T1DM and T2DM) in terms of their adverse effects on male reproductive parameters have never been elucidated. This study aimed to distinguish between the effects of the DM types in mice treated with multiple low doses of streptozotocin (STZ) to mimic human T1DM and coadministered a high-fat diet (HFD) to mimic human T2DM.

METHODS

The T1DM mice were intraperitoneally injected with STZ (40 mg/kg body weight) for 5 days. The T2DM mice received an HFD for 14 days prior to STZ injection (85 mg/kg body weight), followed by continuous feeding of an HFD. Male reproductive parameters were evaluated.

RESULTS

The reproductive organs of the DM mice weighed significantly less than those of controls, and the seminal vesicles plus prostates of the T1DM mice weighed less than those of the T2DM mice. Increased sperm abnormalities and incomplete DNA packaging were observed in the DM groups. Sperm concentration and the proportion of normal sperm were significantly lower in the T1DM group. The seminiferous histopathology of DM mice was classified into seven types. The penises of the DM mice were smaller than those of the controls; however, tunica albuginea thickness and the amount of penile collagen fibers were increased in these mice. Round germ cells were abundant in the epididymal lumens of the mice with DM.

CONCLUSION

T1DM adversely affected reproductive parameters to a greater extent than T2DM.

Targeting of miR-96-5p by catalpol ameliorates oxidative stress and hepatic steatosis in LDLr-/- mice via p66shc/cytochrome C cascade

Hepatic steatosis and oxidative stress are considered to be the sequential steps in the development of non-alcoholic fatty liver disease (NAFLD). We previously found that catalpol, an iridoid glucoside extracted from the root of Romania glutinosa L, protected against diabetes-induced hepatic oxidative stress. Here, we found that the increased expression of p66shc was observed in NAFLD models and catalpol could inhibit p66shc expression to ameliorate NAFLD effectively. However, the underlying mechanisms remained unknown. The aim of the present study was to investigate the p66shc-targeting miRNAs in regulating oxidative stress and hepatic steatosis, also the mechanisms of catalpol inhibiting NAFLD. We found that the effects of catalpol inhibiting hepatic oxidative stress and steasis are dependent on inhibiting P66Shc expression. In addition, miR-96-5p was able to suppress p66shc/cytochrome C cascade via targeting p66shc mRNA 3’UTR, and catalpol could lead to suppression of NAFLD via upregulating miR-96-5p level. Thus, catalpol was effective in ameliorating NAFLD, and miR-96-5p/p66shc/cytochrome C cascade might be a potential target.

Multiple Biological Effects of an Iridoid Glucoside, Catalpol and Its Underlying Molecular Mechanisms

Catalpol, an iridoid glucoside, is widely distributed in many plant families and is primarily obtained from the root of Rehmanniaglutinosa Libosch. Rehmanniaglutinosa is a plant very commonly used in Chinese and Korean traditional medicine for various disorders, including diabetes mellitus, neuronal disorders, and inflammation. Catalpol has been studied extensively for its biological properties both in vitro and in vivo. This review aims to appraise the biological effects of catalpol and their underlying mechanisms. An extensive literature search was conducted using the keyword "Catalpol" in the public domains of Google scholar, PubMed, and Scifinder. Catalpol exhibits anti-diabetic, cardiovascular protective, neuroprotective, anticancer, hepatoprotective, anti-inflammatory, and anti-oxidant effects in experimental studies. Anti-inflammatory and antioxidant properties are mostly related for its biological effect. However, some specific mechanisms are also elucidated. Elevated serotonin and BDNF level by catalpol significantly protect against depression and neurodegeneration. Catalpol demonstrated an increased mitochondrial biogenesis and activation of PI3K/Akt pathway for insulin sensitizing effect. Further, its cardiovascular protective effect was linked to PI3K/Akt, apelin/APJ and Jak-Stat pathway. Catalpol produced a significant reduction in cell proliferation and an increase in apoptosis in different cancer conditions. Overall, catalpol demonstrated multiple biological effects due to its numerous mechanisms including anti-inflammatory and antioxidant effects.

Catalpol Ameliorates Podocyte Injury by Stabilizing Cytoskeleton and Enhancing Autophagy in Diabetic Nephropathy

Catalpol, an iridoid glycoside extracted from Rehmannia glutinosa, has been found to ameliorate diabetic nephropathy (DN), but the mechanism has not been clarified. Podocyte injury play a key role in the pathogenesis of DN. This study mainly investigated the protective effect and potential mechanism of catalpol on podocyte injury of DN in vivo and in vitro. The results indicated that the pathological features of DN in mice were markedly ameliorated after treatment with catalpol. Moreover, podocyte foot process effacement, and down-regulation of nephrin and synaptopodin expression in DN mice were also significantly improved after treatment with catalpol. In vitro, catalpol rescued disrupted cytoskeleton and increased migration ratio in podocytes induced by high glucose, the effect might be attributable to the inhibition of RhoA and Cdc42 activities but not Rac1. Furthermore, the impaired podocyte autophagy in DN mice was significantly enhanced after catalpol treatment. And catalpol also enhanced autophagy and lysosome biogenesis in cultured podocytes under high glucose condition. In addition, we found that catalpol could inhibit mTOR activity and promote TFEB nuclear translocation in vivo and in vitro experiments. Our study demonstrated that catalpol could ameliorate podocyte injury in DN, and the protective effect of catalpol might be attributed to the stabilization of podocyte cytoskeleton and the improvement of impaired podocyte autophagy.

Catalpol induces autophagy and attenuates liver steatosis in ob/ob and high-fat diet-induced obese mice

Impaired autophagy has been implicated in the pathogenesis of nonalcoholic fatty liver disease. Catalpol (CAT), a bioactive compound from Rehmannia (Di Huang) glutinosa, is known to ameliorate insulin resistance and the histological NAFLD spectrum in obese mice. Here, we investigated the effects of CAT on hepatic steatosis and autophagy in ob/ob and high-fat diet-induced obese mice, as well as in hepatocytes. In ob/ob mice, CAT reduced liver weight, liver triglyceride and cholesterol content, and hepatic lipogenic enzyme levels and increased fatty acid oxidase levels. In addition, CAT administration increased LC3-II levels and decreased SQSTM1/P62 levels in ob/ob mice. Similar effects on hepatic steatosis and autophagy were observed in high-fat diet-induced mice after administration of CAT. Additionally, we found that CAT stimulated AMPK and increased nuclear translocation of transcription factor EB (TFEB) in obese mice and hepatocytes. Inhibition of AMPK completely blocked the effects of CAT on TFEB nuclear localization, hepatic autophagy, and liver steatosis. These findings revealed that diminished AMPK/TFEB-dependent autophagy is involved in the pathogenesis of liver steatosis in obesity, and that CAT might be a novel therapeutic candidate for treatment of this condition.

Sugar-Lowering Drugs for Type 2 Diabetes Mellitus and Metabolic Syndrome-Review of Classical and New Compounds: Part-I

Diabetes mellitus (DM) is a metabolic disorder characterized by chronic hyperglycemia together with disturbances in the metabolism of carbohydrates, proteins and fat, which in general results from an insulin availability and need imbalance. In a great number of patients, marketed anti-glycemic agents have shown poor effectiveness in maintaining a long-term glycemic control, thus being associated with severe adverse effects and leading to an emerging interest in natural compounds (e.g., essential oils and other secondary plant metabolites, namely, flavonoid-rich compounds) as a novel approach for prevention, management and/or treatment of either non-insulin-dependent diabetes mellitus (T2DM, type 2 DM) and/or Metabolic Syndrome (MS). In this review, some of these promising glucose-lowering agents will be comprehensively discussed.

Expression of testicular phosphorylated proteins in types 1 and 2 diabetes mellitus in mice: An experimental study

Background

Types 1 and 2 diabetes mellitus (DM) are known to be the cause of sub/infertility. However, the comparisons of potential markers in spermatogenesis and steroidogenesis in DM males have never been elucidated.

Objective

This study aimed to examine the expressions of tyrosine-phosphorylated and steroidogenic acute regulatory (StAR) proteins in testis of DM mice.

Materials and Methods

Fifty-six male C57BL/6 mice were divided into four groups (n░=░14/ each): control of MLD-STZ (multiple low doses of streptozotocin), MLD-STZ, control of HFD-STZ (high-fat diet with STZ), and HFD-STZ. MLD-STZ mice (type 1 DM) were intraperitoneally (i.p.) injected with STZ at 40░mg/kg BW for five days. HFD-STZ mice (type 2 DM) received an HFD for 14 days and i.p.-induced by STZ at 85░mg/kg BW and fed with HFD. At the end of the experiment (days 36 and 72), the expressions of phosphorylated proteins and StAR were examined.

Results

Tyrosine phosphorylated proteins were localized in late spermatids, luminal fluid, and Leydig cells. The intensities of phosphorylated 110, 85, 72, 60, and 55░kDas were lower in the 36 day-DM mice. Although such intensities were present in both groups, only 85░kDa in the MLD-STZ mice was higher in HFD mice at 72 days. StAR expressions in both groups were decreased than that of the controls.

Conclusion

Decreased expressions of StAR and tyrosine-phosphorylated proteins may be directly involved in low testosterone levels and impaired spermatogenesis. These findings support the notion that both DM types play a role in male infertility.

Catalpol in Diabetes and its Complications: A Review of Pharmacology, Pharmacokinetics, and Safety

This review aimed to provide a general view of catalpol in protection against diabetes and diabetic complications, as well as its pharmacokinetics and safety concerns. The following databases were consulted with the retrieval of more than 100 publications through June 2019: PubMed, Chinese National Knowledge Infrastructure, WanFang Data, and web of science. Catalpol exerts an anti-diabetic effect in different animal models with an oral dosage ranging from 2.5 to 200 mg/kg in rats and 10 to 200 mg/kg in mice. Besides, catalpol may prevent the development of diabetic complications in kidney, heart, central nervous system, and bone. The underlying mechanism may be associated with an inhibition of inflammation, oxidative stress, and apoptosis through modulation of various cellular signaling, such as AMPK/PI3K/Akt, PPAR/ACC, JNK/NF-κB, and AGE/RAGE/NOX4 signaling pathways, as well as PKCγ and Cav-1 expression. The pharmacokinetic profile reveals that catalpol could pass the blood-brain barrier and has a potential to be orally administrated. Taken together, catalpol is a well-tolerated natural compound with promising pharmacological actions in protection against diabetes and diabetic complications via multi-targets, offering a novel scaffold for the development of anti-diabetic drug candidate. Further prospective and well-designed clinical trials will shed light on the potential of clinical usage of catalpol.

Juvenile murine models of prediabetes and type 2 diabetes develop neuropathy

Peripheral neuropathy (neuropathy) is a common complication of obesity and type 2 diabetes in children and adolescents. To model this complication in mice, 5-week-old male C57BL/6J mice were fed a high-fat diet to induce diet-induced obesity (DIO), a model of prediabetes, and a cohort of these animals was injected with low-dose streptozotocin (STZ) at 12 weeks of age to induce hyperglycemia and type 2 diabetes. Neuropathy assessments at 16, 24 and 36 weeks demonstrated that DIO and DIO-STZ mice displayed decreased motor and sensory nerve conduction velocities as early as 16 weeks, hypoalgesia by 24 weeks and cutaneous nerve fiber loss by 36 weeks, relative to control mice fed a standard diet. Interestingly, neuropathy severity was similar in DIO and DIO-STZ mice at all time points despite significantly higher fasting glucose levels in the DIO-STZ mice. These mouse models provide critical tools to better understand the underlying pathogenesis of prediabetic and diabetic neuropathy from youth to adulthood, and support the idea that hyperglycemia alone does not drive early neuropathy.

This article has an associated First Person interview with the first author of the paper.

Summary: The mouse models described in this paper provide critical tools to better understand the underlying pathogenesis of prediabetic and diabetic neuropathy from youth to adulthood.

Mitochondrial dysfunction and inhibition of myoblast differentiation in mice with high-fat-diet-induced pre-diabetes

Pre-diabetes is characterized by impaired glucose tolerance (IGT) and/or impaired fasting glucose. Impairment of skeletal muscle function is closely associated with the progression of diabetes. However, the entire pathological characteristics and mechanisms of pre-diabetes in skeletal muscle remain fully unknown. Here, we established a mouse model of pre-diabetes, in which 6-week-old male C57BL6/J mice were fed either normal diet or high-fat diet (HFD) for 8 or 16 weeks. Both non-fasting and fasting glucose levels and the results of glucose and insulin tolerance tests showed that mice fed an 8-week HFD developed pre-diabetes with IGT; whereas mice fed a 16-week HFD presented with impaired fasting glucose and impaired glucose tolerance (IFG-IGT). Mice at both stages of pre-diabetes displayed decreased numbers of mitochondria in skeletal muscle. Moreover, IFG-IGT mice exhibited decreased mitochondrial membrane potential and ATP production in skeletal muscle and muscle degeneration characterized by a shift in muscle fibers from predominantly oxidative type I to glycolytic type II. Western blotting and histological analysis confirmed that myoblast differentiation was only inhibited in IFG-IGT mice. For primary skeletal muscle satellite cells, inhibition of differentiation was observed in palmitic acid-induced insulin resistance model. Moreover, enhanced myoblast differentiation increased glucose uptake and insulin sensitivity. These findings indicate that pre-diabetes result in mitochondrial dysfunction and inhibition of myoblast differentiation in skeletal muscle. Therefore, interventions that enhance myoblast differentiation may improve insulin resistance of diabetes at the earlier stage.

RhoA/ROCK-2 Pathway Inhibition and Tight Junction Protein Upregulation by Catalpol Suppresses Lipopolysaccaride-Induced Disruption of Blood-Brain Barrier Permeability

Lipopolysaccaride (LPS) directly or indirectly injures brain microvascular endothelial cells (BMECs) and damages the intercellular tight junction that gives rise to altered blood-brain barrier (BBB) permeability. Catalpol plays a protective role in LPS-induced injury, but whether catalpol protects against LPS-caused damage of BBB permeability and the underlying mechanism remain to be delineated. Prophylactic protection with catalpol (5 mg/kg, i.v.) consecutively for three days reversed the LPS-induced damage of BBB by decreased Evans Blue (EB) leakage and restored tight junctions in C57 mice. Besides, catalpol co-administrated with LPS increased BMECs survival, decreased their endothelin-1, TNF-Α and IL-6 secretion, improved transmembrane electrical resistance in a time-dependent manner, and in addition increased the fluorescein sodium permeability coefficient of BMECs. Also, transmission electron microscopy showed catalpol protective effects on tight junctions. Fluorescence staining displayed that catalpol reversed the rearrangement of the cytoskeleton protein F-actin and upregulated the tight junction protein of claudin-5 and ZO-1, which have been further demonstrated by the mRNA and protein expression levels of ZO-1, ZO-2, ZO-3, claudin-5, and occludin. Moreover, catalpol concurrently downregulated the mRNA and protein levels of RhoA, and ROCK2, the critical proteins in the RhoA/ROCK2 signaling pathway. This study thus indicated that catalpol, via inhibition of the RhoA/ROCK2 signaling pathway, reverses the disaggregation of cytoskeleton actin in BMECs and prevents down-regulation of junctional proteins, such as claudin-5, occludin, and ZO-1, and decreases endothelin-1 and inflammatory cytokine secretion, eventually alleviating the increase in LPS-induced BBB permeability.

A new hypoglycemic mechanism of catalpol revealed by enhancing MyoD/MyoG-mediated myogenesis

AIMS

Enhancing myogenesis has been identified as a possible target to improve insulin sensitivity and protect against metabolic diseases. Catalpol, an iridoid glycoside, has been shown to exert a hypoglycaemic effect by improvement of insulin sensitivity; however, the underlying mechanism remains unknown. In this study, we tested whether catalpol has the potential to improve insulin sensitivity by augmenting myogenesis.

MAIN METHODS

We examined the hypoglycaemic mechanism of catalpol in db/db mice and C2C12 cells. db/db mice were treated with catalpol (200 mg/kg) for 8 consecutive weeks. Serum analysis, skeletal muscle performance and histology, and gene and protein expression were performed. In vitro glucose uptake, gene and protein expression were determined, and small interfering RNA was used to identify the underlying hypoglycaemic mechanism of catalpol.

KEY FINDINGS

In this study, we tested whether catalpol has the potential to improve skeletal insulin sensitivity by augmenting myogenesis, in which we found that, catalpol treatment in db/db mice lowered blood glucose and improved insulin sensitivity via activation of phosphatidylinositol‑3‑Kinase (PI3K)/protein kinase B (AKT) pathway. Moreover, catalpol-treated mice exhibited enhanced myogenesis, as evidenced by increased myogenic differentiation (MyoD), myogenin (MyoG) and myosin heavy chain (MHC) expressions. The in vitro experimental results showed that both catalpol and metformin enhanced glucose uptake via activation of PI3K/AKT pathway. However, unlike metformin, the PI3K/AKT pathway activation by catalpol was dependent on enhanced MyoD/MyoG-mediated myogenesis.

SIGNIFICANCE

Improvement of insulin sensitivity by enhancing MyoD/MyoG-mediated myogenesis may constitute a new therapeutic approach for treating type 2 diabetes.

Activating the PGC-1α/TERT Pathway by Catalpol Ameliorates Atherosclerosis via Modulating ROS Production, DNA Damage, and Telomere Function: Implications on Mitochondria and Telomere Link

Catalpol, an iridoid glucoside, has been found present in large quantities in the root of Rehmannia glutinosa L. and showed a strong antioxidant capacity in the previous study. In the present work, the protective effect of catalpol against AS via inhibiting oxidative stress, DNA damage, and telomere shortening was found in LDLr^-/- mice. This study also shows that activation of the peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α)/telomerase reverse transcriptase (TERT) pathway, which is the new link between mitochondria and telomere, was involved in the protective effects of catalpol. Further, by using PGC-1α or TERT siRNA in oxLDL-treated macrophages, it is proved that catalpol reduced oxidative stress, telomere function, and related DNA damage at least partly through activating the PGC-1α/TERT pathway. Moreover, dual luciferase activity assay-validated catalpol directly enhanced PGC-1α promoter activity. In conclusion, our study revealed that the PGC-1α/TERT pathway might be a possible therapeutic target in AS and catalpol has highly favorable characteristics for the treatment of AS via modulating this pathway.

Catalpol attenuates oxidative stress and promotes autophagy in TNF-α-exposed HAECs by up-regulating AMPK

Catalpol attenuates oxidative stress and promotes autophagy in TNF-α-exposed HAECs through up-regulating AMPK.

Catalpol alleviates ovalbumin-induced asthma in mice: Reduced eosinophil infiltration in the lung

BACKGROUND

Radix Rehmanniae Preparata is a traditional Chinese herbal medicine used to treat asthma, and catalpol is one of the main active ingredients in this herb. In the present study, the effects of catalpol on asthma and the underlying mechanism were explored.

METHODS

Mice with ovalbumin (OVA)-induced asthma were given 5 or 10mg/kg catalpol from Day 15 to Day 28 (intraperitoneal injection). Histopathologic changes were detected by Hematoxylin and Eosin staining and Periodic Acid Schiff staining. The levels of IgE, interleukin (IL)-4, IL-5 and eotaxin were measured by ELISA. The numbers of lymphocytes, monocytes, basophils and eosinophils in the bronchoalveolar lavage fluid were determined by Wright-Giemsa staining. The expression and distribution of eotaxin and C-C chemokine receptor 3 (CCR3) were detected by immunohistochemistry and immunofluorescence. The expression of interleukin-5 receptor α (IL-5Rα) was detected by Western blot assay.

RESULTS

Catalpol inhibited OVA-induced inflammation and IgE secretion in the lung. OVA-induced type 2 inflammation was suppressed by catalpol as evidenced by decreased levels of IL-4 and IL-5. Moreover, catalpol inhibited the aberrant eosinophil infiltration in the lungs, and also suppressed OVA-induced elevation of eosinophil chemokine eotaxin and its receptor CCR3. In addition, IL-5Rα expression in the bone marrow cells derived from catalpol-treated asthmatic mice was lower than that from the untreated asthmatic mice.

CONCLUSION

Our study demonstrated that catalpol attenuated OVA-induced asthma and inhibit the infiltration of inflammatory cells, especially eosinophils, into the lung. This study suggests that catalpol may become a promising drug for the treatment of asthma.

Diabetic Osteoporosis: A Review of Its Traditional Chinese Medicinal Use and Clinical and Preclinical Research

Aim. The incidence of diabetic osteoporosis (DOP) is increasing due to lack of effective management over the past few decades. This review aims to summarize traditional Chinese medicine (TCM) suitability in the pathogenesis and clinical and preclinical management of DOP. Methods. Literature sources used were from Medline (Pubmed), CNKI (China Knowledge Resource Integrated Database), and CSTJ (China Science and Technology Journal Database) online databases. For the consultation, keywords such as diabetic osteoporosis (DOP), TCM, clinical study, animal experiment, toxicity, and research progress were used in various combinations. Around 100 research papers and reviews were visited. Results. Liver-spleen-kidney insufficiency may result in development of DOP. 18 clinical trials are identified to use TCM compound prescriptions for management of patients with DOP. TCM herbs and their active ingredients are effective in preventing the development of DOP in streptozotocin (STZ) and alloxan as well as STZ combined with ovariectomy insulted rats. Among them, most frequently used TCM herbs in clinical trials are Radix Astragali, Radix et Rhizoma Salviae Miltiorrhizae, Radix Rehmanniae Preparata, and Herba Epimedii. Some of TCM herbs also exhibit toxicities in clinical and preclinical research. Conclusions. TCM herbs may act as the novel sources of anti-DOP drugs by improving bone and glucolipid metabolisms. However, the pathogenesis of DOP and the material base of TCM herbs still merit further study.

Anti-diabetic activities of catalpol in db/db mice

The objective was to investigate the hypoglycemic action of catalpol in spontaneous diabetes db/db mice. 40 db/db mice were randomly divided into fi ve groups: model control gourp; db/db plus catalpol 40, 80, 120 mg/kg body wt. groups and db/db plus metformin 250 mg/kg group. Age-matched db/m mice were selected as normal control group. The mice were administered with corresponding drugs or solvent by gavage for 4 weeks. The oral glucose tolerance test was carried out at the end of 3(rd) week. After 4 weeks of treatment, the concentrations of fasting blood glucose (FBG), glycated serum protein (GSP), insulin (INS), triglyceride (TG), total cholesterol (TC) and adiponection (APN) in serum were detected. The protein expressions of phosphorylation-AMPKα1/2 in liver, phosphorylation-AMPKα1/2 and glucose transporter-4 (GLUT-4) in skeletal muscle and adipose tissues were detected by western blot. Real time RT-PCR was used to detect the mRNA expressions of acetyl-CoA carboxylase (ACC) and Hydroxymethyl glutaric acid acyl CoA reductase (HMGCR) in liver. Our results showed that catalpol could significantly improve the insulin resistance, decrease the serum concentrations of INS, GSP, TG, and TC. The concentrations of APN in serum, the protein expression of phosphorylation-AMPKα1/2 in liver, phosphorylation-AMPKα1/2 and GLUT-4 in peripheral tissue were increased. Catalpol could also down regulate the mRNA expressions of ACC and HMGCR in liver. In conclusion, catalpol ameliorates diabetes in db/db mice. It has benefi t eff ects against lipid/glucose metabolism disorder and insulin resistance. The mechanism may be related to up-regulating the expression of phosphorylation-AMPKα1/2.

Catalpol preserves neural function and attenuates the pathology of Alzheimer's disease in mice

Alzheimer's disease (AD) is the most common form of dementia and there currently are no effective treatment strategies available. Catalpol is an iridoid glucoside, and large quantities can be isolated from the genus Rehmannia (Orobanchaceae). The present study assessed whether catalpol had any protective effects against Alzheimer's disease using a murine model. Reactive oxygen species (ROS)-associated enzymes as well as soluble Aβ40 and Aβ42 were detected using kits. Thioflavin‑S staining was performed to detect senile plaques and reverse-transcription quantitative polymerase chain reaction was used to assess iroquois homeobox protein 3 (IRX3) and obesity‑associated genes, while western blot analysis was used for β‑secretase 1 (BACE1), insulin‑degrading enzyme (IDE) and neprilysin (NEP) detection. The Morris water maze was used to detect the learning ability and spatial memory. The results revealed that catalpol was able to reduce the oxidative stress in the cerebral cortex by regulating the activities and concentration of ROS‑associated enzymes superoxide dismutase, glutathione peroxidase and catalase, however not malondialdehyde. Catalpol was also identified to be able to reduce the levels of soluble Aβ40 and Aβ42 in the cerebral cortex and thus inhibit the formation of senile plaques. These effects were observed to be regulated by IDE, however not by BACE1 or NEP. It is suggested that catalpol is not capable of directly regulating the expression of IRX3 and obesity‑associated genes. Subsequent to the treatment with catalpol, impairments in learning and memory were also observed to be relieved using the Morris water maze test. The results of the present study indicate that catalpol may be a potential drug for the treatment of neurodegenerative diseases such as AD.

Mitochondrial fusion/fission process involved in the improvement of catalpol on high glucose-induced hepatic mitochondrial dysfunction

Catalpol, an iridoid glycoside, has been shown to exert hypoglycemic effect by rescuing mitochondrial function, but the detailed mechanism remains unclear yet. In this study, the effect and mechanism of catalpol on the hepatic mitochondria under diabetic conditions were further examined. Oral administration of catalpol significantly reduced the blood glucose, triglyceride, and cholesterol levels in high-fat diet- and streptozotocin-induced diabetic mice. Additionally, catalpol attenuated the decrease in liver mitochondrial ATP content resulting from diabetes. Furthermore, the number of mitochondria possessing a long size was increased in catalpol-treated mice. Interestingly, the catalpol-induced recovery of mitochondrial function was associated with decreased fission protein 1 and dynamin-related protein 1 expression as well as increased mitofusin 1 expression in the liver. In HepG2 cells, catalpol alleviated the decrease of ATP content and mitochondrial membrane potential, and the increase of reactive oxygen species formation induced by high glucose. MitoTracker Green stain shows that the tubular feature of mitochondria was maintained when cells were treated with catalpol. Catalpol also decreased fission protein 1 and dynamin-related protein 1 expression and increased mitofusin 1 expression in HepG2 cells. The present results suggest that catalpol can ameliorate hepatic mitochondrial dysfunction under a diabetic state, and this may be related to its regulation of mitochondrial fusion and fission events.

Comparative pharmacokinetics of catalpol and acteoside in normal and chronic kidney disease rats after oral administration of Rehmannia glutinosa extract

In this study, a sensitive and robust ultra-performance liquid chromatography-mass spectrometry method with multiple-reaction monitoring mode was developed, validated, and applied to determine pharmacokinetics of catalpol and acteoside in normal and doxorubicin-induced chronic kidney disease rats after oral administration of Rehmannia glutinosa extract. The lower limits of quantification for catalpol and acteoside in rat plasma were 2.62 and 0.61 ng/mL, with a signal-to-noise ratio of ≥10. Precision and accuracy studies showed that catalpol and acteoside plasma concentrations were within the 10% range in all studies. The extraction recoveries of catalpol and acteoside were both >68.24% and the matrix effects ranged from 96.59 to 101.62%. The method was successfully applied to the pharmacokinetic study of catalpol and acteoside after oral administration of RG extract to normal and model rats, respectively. This study might further support the traditional use of RG to treat kidney diseases clinically.