Extract of Cyclolepis genistoides D. Don (vernacular name Palo azul; Palo) are traditionally consumed in the Republic of Paraguay in South America for the treatment of diabetes and kidney disease, and is sold in Japan as dietary supplement. This study aimed to elucidate the mechanism of anti-diabetes activity of Palo, especially focused on insulin resistance. Palo promoted adipocytes differentiation and regulated adipokine profiles in 3T3-L1 adipocytes by modulation of PPARγ, a major regulator of adipose differentiation. Human adipocyte showed almost similar profile with 3T3-L1 against Palo treatment. Furthermore, Palo treatment (250 or 1000 mg/kg) was performed with C57BL/6J mice for 14 weeks, being fed high-fat-diet (HFD60) simultaneously. Palo 250 mg/kg exhibited a tendency to decrease subcutaneous adipose volume along with increase of PPARγ and its target, adiponectin mRNA expression. In addition, as the other insulin targeted cell, effect on muscle differentiation was examined. Palo increased differentiation of C2C12 mouse muscle myoblasts by increase of IGF-1, myogenin, and myosine heavy chain (MHC) as well as 5’-AMP-activated protein kinase (AMPK) activation. Palo subsequently promoted myotube formation under differentiation condition. From the above, it was clarified that Palo acts variously on the differentiation and maturation of both adipocytes and muscle cells, and from the viewpoint of the regulatory mechanism for adipocytes, PPARγ-inducing action was shown to be a mechanism that acts across species.
The number of patients with type 2 diabetes mellitus (T2DM) has rapidly increased, especially in East and Southeast Asia. In these areas, in general, people have especially vulnerable β-cells and insulin secretion deficiency and reduced β-cell mass are the primary cause of T2DM. Therefore, the alleviation of such β-cell dysfunction would provide therapeutic approaches to prevent the development of T2DM. Nobiletin, a polymethoxylated flavonoid found in citrus fruits, has been shown to improve obesity and insulin resistance in T2DM model mice. We focused on β-cells and investigated the effects of nobiletin on insulin secretion and β-cell apoptosis. In β-cell line INS-1, nobiletin increased glucose-induced insulin secretion (GSIS) in a concentration-dependent manner, which was inhibited by an Epac inhibitor. In addition, nobiletin at 10 μM inhibited thapsigargin-induced apoptosis, which was inhibited by a PKA inhibitor. Nobiletin also suppressed thapsigargin-induced increases in cleaved caspase-3 and phosphorylated JNK. Thus, nobiletin is suggested to promote GSIS and prevent ER stress-induced β-cell apoptosis, which are mediated via Epac and PKA-dependent pathways, respectively. In summary, nobiletin is suggested to exhibit insulinotropic and anti-apoptotic effects on β-cells, which are one of the causes of its anti-diabetic effect. Moreover, nobiletin seems to be able to alleviate the development of T2DM by protecting β-cells from apoptosis.
The peel of Citrus kawachiensis (Kawachi Bankan), a citrus species grown in Ehime, Japan, is abundant in auraptene. Auraptene, a coumarin compound, have been shown to exert anti-inflammatory effects in peripheral tissues, but it was still unclear of the effect in the brain. Hyperglycemia and brain ischemia induce inflammation and oxidative stress and cause massive damage in the brain; therefore, we examined the anti-inflammatory and other effects of the dried peel powder of C. kawachiensis and auraptene in a hyperglycemia and global cerebral ischemia models. The C. kawachiensis treatment inhibited astroglial activation in the hippocampus and the hyperphosphorylation of tau protein in hippocampal neurons, and also relieved the suppression of neurogenesis in the dentate gyrus of the hippocampus in the type 2 diabetic db/db mice. The C. kawachiensis treatment inhibited microglial and astroglial activation, and neuronal cell death in the hippocampus of transient global cerebral ischemia mice. It was suggested that the dried peel powder of C. kawachiensis exerts anti-inflammatory and neuroprotective effects in the brain. We attempted to demonstrate the effect of auraptene in the brains in streptozotocin-induced hyperglycemic mice and transient global cerebral ischemia mice. Auraptene administration showed the similar effects as the peel of C. kawachiensis in the hippocampus of these mice models. These results suggested that auraptene have potential effects as a neuroprotective agent in the peel of C. kawachiensis.
Sudachi (Citrus Sudachi) is a sour fruit and is a popular seasoning for Japanese dishes, Washoku. It can grow only in Tokushima and the surrounding areas for some reason, and therefore, Sudachi is a specialty of Tokushima prefecture in Japan. We usually use only its juice, and the size of the fruit is so small that a huge amount of pomace has been an industrial problem of the region. Therefore, we undertook exploratory studies of the Sudachi peel in terms of health promotion with making a kind of collaborative consortium for the study of acid citruses. Our recent activities on Sudachi research including the consortium were shared and discussed in the symposium, and the metabolic effects of Sudachi peel will be briefly introduced in the current manuscript.
The type 2 ryanodine receptor (RyR2) is a sarcoplasmic reticulum Ca2+ release channel that plays a central role in cardiac excitation-contraction coupling. Abnormal activity of the RyR2 is linked to abnormal Ca2+ signaling in cardiac cells, which often results in cardiac arrhythmias. For example, amino acid mutations in RyR2 have been reported to cause various types of arrhythmias, including catecholaminergic polymorphic ventricular tachycardia (CPVT), idiopathic ventricular fibrillation, and left ventricular non-compaction. At present, the total number of disease-associated RyR2 mutations exceeds 300. In addition, in chronic heart failure, modification of RyR2 by phosphorylation, oxidation or S-nitrosylation may cause abnormal channel activity. Arrhythmogenic mechanisms of these various disorders are not yet fully understood. We have recently established a method to quantitatively evaluate the effects of various arrhythmogenic mutations and modifications on RyR2 channels by using HEK293 expression system. We found that arrhythmogenic mutations in RyR2 are classified into two groups: gain-of-function and loss-of-function of the channel. Since they are indistinguishable in clinical diagnosis, our analysis is very useful for diagnosis and choice of treatment strategies for RyR2-linked arrhythmogenic diseases. This review describes the current advances and issues of research on RyR2 mutation-related arrhythmogenic disorders.
Pulmonary arterial hypertension (PAH) is a progressive and lethal disease of the pulmonary artery. The pathogenesis of PAH is mainly sustained vasoconstriction and vascular remodeling of the pulmonary artery. These pathogeneses cause progressive elevations in pulmonary vascular resistance and pulmonary arterial pressure in PAH patients. Elevated pulmonary arterial pressure leads to right heart failure and finally death. The vascular remodeling is caused by the enhanced proliferation and reduced apoptosis of pulmonary arterial smooth muscle cells (PASMCs). Excitable abnormality in the pulmonary artery of PAH patients is mostly mediated by an elevated cytosolic Ca2+ concentration. PASMCs express several Ca2+-permeable channels including voltage-dependent Ca2+ channels, store-operated Ca2+ (SOC) channels, and receptor-operated Ca2+ (ROC) channels. The activation and upregulation of these Ca2+ channels have been reported in PASMCs from PAH patients. Here, we analyzed pathophysiological functions of enhanced Ca2+ signaling mediated by SOC and ROC channels using PASMCs from idiopathic PAH patients and animal PAH models. Notch signal enhanced transient receptor potential canonical 6 (TRPC6) “SOC” channels via direct (non-genomic and stimulatory) and indirect (genomic and upregulating) effects in PAH. On the other hand, the activation of Ca2+-sensing receptors evoked Ca2+ influx through TRPC6 “ROC” channels in PAH. In addition, TRPC6 channel blocker and TRPC6 gene deletion inhibited the development of PAH. Specifically, TRPC6 channels potentially form both ROC and SOC channels in PASMCs, which are involved in the pathophysiological events in PAH. Therefore, targeting TRPC6 channels in PASMCs may help develop novel therapeutic approach for PAH.
Functional food material, polyamines are considered to be essential for growth factors in virtually all cells. The polyamines putrescine, spermidine and spermine are low molecular weight organic polycations, well known as mediators involved in cell homeostasis. The proposed functions of polyamines are the regulation of ion channels, nucleic acid packaging, signal transduction, cell proliferation, and differentiation, as well as gene expression. In skeletal muscle, regulation of polyamine levels is associated with muscle hypertrophy and atrophy, yet detailed studies are remained to be undergoing. Here, we studied how polyamines may affect the proliferation and/or differentiation of murine myoblast progenitor C2C12 cell line. Upon polyamine treatment of C2C12 cells during induction of myogenic differentiation, the number of myotubes significantly increased. Morphologically, polyamine-treated myotubes exhibited elongated cell body and contained larger amount of nuclei in the cell. On the other hand, the polyamine did not have influence on myoblasts proliferation. Furthermore, compensatory muscle hypertrophy of C57BL6 mice that underwent sciatic nerve transection of the left hindlimb was enhanced by administration of polyamines. Therefore, our study demonstrates that polyamines may play an important role in regulating myogenic differentiation rather than myoblasts proliferation.
Sarcopenia and frailty in aging, or cancer cachexia shows an abnormal decrease in skeletal muscle mass and muscle strength. However, the underlying mechanisms are not clear, and the promising drug seeds have not been discovered. The formation of skeletal muscle occurs not only during embryonic development but also in adulthood, and the muscle can be regenerated even if it is damaged by exercise overload or physical injury. Although p38MAPK is ubiquitous among tissues and transmits signal of inflammation and environmental stress into the nucleus, it has been revealed that this kinase is deeply involved in maintaining skeletal muscle homeostasis. Knowledge of p38MAPK accumulated so far suggests that it not only functions as an on-off switch for gene expression, but also it balances cell proliferation and differentiation of progenitor cells to properly respond to muscle damage and repair muscle according to its surrounding environmental cues. In addition, its role in cell fusion to induce myotube formation has been recently revealed. On the other hand, it has been pointed out that in aging and chronic inflammation, excessive enhancement of the p38MAPK activity may disrupt skeletal muscle homeostasis and lead to muscle pathology. Interestingly, animal models have shown that pharmacological manipulation of p38MAPK activity can re-activate aged muscle satellite cells, suggesting the possibility of plastically manipulating skeletal muscle aging. Furthermore, it has become possible to track the dynamics of intracellular signaling of skeletal muscle cells or muscle progenitor cells in time and space by using advanced imaging techniques. In this review, we focus on the functional roles and regulatory mechanism of p38MAPK in skeletal muscle and its relation to the pathology in the context of dysregulation of skeletal muscle formation and regeneration.
Given that safety (toxicity) liabilities in drug development still account for a large proportion of development discontinuations and market withdrawals, establishing an appropriate safety prediction and evaluation strategy is an important topic. In particular, discontinuation in the late stage of development following large investment has a significant impact. Accurate safety assessment in the early preclinical stage is therefore highly desirable. However, pre-GLP (exploratory) safety evaluation is not subject to regulatory guidelines, and structure and practices accordingly vary widely among companies. Against this background, it can be difficult for non-safety researchers to understand why a particular evaluation/assay system and study design have been selected and tested, and why these differ from those in other companies. This article introduces the background to and concept of a revised strategy for exploratory safety assessment at Astellas, and explains that exploratory safety assessment is not uniform but varies with strategy.
Romosozumab (EVENITY®) is a humanized monoclonal antibody designed to target sclerostin. Sclerostin is a glycoprotein that is secreted by osteocytes and that inhibits Wnt signaling in osteoblast lineage cells, leading to decreased bone formation by osteoblasts and increased bone resorption by osteoclasts. Romosozumab, by binding and inhibiting sclerostin, increases bone formation and decreases bone resorption. Romosozumab is known to mainly enable increase in modeling-based bone formation. In studies using ovariectomized (OVX) models of rats and cynomolgus monkeys, those administered romosozumab showed dose-dependently increased bone mass and strength. In addition, the bone-forming effect of romosozumab decreased after continued administration. In rats, romosozumab caused almost no focal osteoblast hyperplasia or benign or malignant bone tumors, presumably owing to the time-dependent decrease in the bone-forming effect. Clinical studies demonstrated inhibition of new vertebral fractures at 12 months of treatment, and increased bone mineral density at 6 months of treatment. With a dual effect on bone, increasing bone formation and decreasing bone resorption, romosozumab is expected to become a new treatment option, and was approved in January 2019 for the indication of “patients with osteoporosis at high risk for fracture”.
Parkinson’s disease is a neurodegenerative disorder characterized by the degenerative loss of dopaminergic neurons in the substantia nigra. Dopamine deficiency is thought to disrupt motor control of the basal ganglia and cause characteristic motor symptoms in Parkinson’s disease such as bradykinesia, akinesia, and tremor. Therefore, dopamine replacement therapy is widely used in the clinical setting. Safinamide is a novel, selective, and reversible inhibitor of monoamine oxidase B expected to increase dopamine levels in the brain and improve the symptoms of Parkinson’s disease. In addition, safinamide shows non-dopaminergic actions such as sodium channel blockade and inhibition of glutamate release. Preclinical studies have demonstrated that safinamide ameliorates “wearing off” symptoms after administration in rat and monkey models with selectively destroyed dopaminergic neurons. In the monkeys, safinamide concurrently inhibited levodopa-induced dyskinesia. These findings suggest that safinamide not only increases the dopaminergic effect of levodopa, but also reduces levodopa-induced adverse events via its non-dopaminergic effects. In clinical trials of patients with Parkinson’s disease with the “wearing off” phenomenon, safinamide has been found to prolong the “on time” and improve motor function as assessed by Unified Parkinson’s Disease Rating Scale Part III. In Japan, safinamide was approved in September 2019 as a levodopa combination drug for Parkinson’s disease with “wearing off” phenomenon. Safinamide is therefore expected to be a new treatment option for patients with Parkinson’s disease.