Calmodulin dependent protein kinase II activation by exercise regulates saturated & unsaturated fatty acids and improves some metabolic syndrome markers

Self-Assembly Hypoxic and ROS Dual Response Nano Prodrug as a New Therapeutic Approach for Glaucoma Treatments

Glaucoma is an irreversible blinding eye disease characterized by retinal ganglion cell (RGC) death.Previous studies have demonstrated that protecting mitochondria and activating the CaMKII/CREB signaling pathway can effectively protect RGC and axon. However, currently treatments are often unsatisfactory, and the pathogenesis of glaucoma requires further elucidation. In this study, a ROS-responsive dual drug conjugate (OLN monomer) is first designed that simultaneously bonds nicotinamide and oleic acid. The conjugate self-assembled into nanoparticles (uhOLN-NPs) through the aggregation of multiple micelles and possesses ROS scavenging capability. Then, a polymer with a hypoxic response function is designed, which encapsulates uhOLN-NPs to form nanoparticles with hypoxic and ROS responses (HOLN-NPs). Under hypoxia in RGCs, the azo bond of HOLN-NPs breaks and releases uhOLN-NPs. Meanwhile, under high ROS conditions, the thioketone bond broke, leading to the dissociation of nano-prodrug. The released nicotinamide and oleic acid co-scavenge ROS and activate the CaMKII/CREB pathway, protecting mitochondria in RGCs. HOLN-NPs exhibit a significantly superior protective effect on R28 cells in glutamate models of glaucoma. The accumulation of HOLN-NPs in retinal RGCs lead to significant inhibition of RGC apoptosis and axonal damage in vivo. Notably, HOLN-NPs provide a new therapeutic approach for patients with neurodegenerative disease.

CaMKII activity and metabolic imbalance-related neurological diseases: Focus on vascular dysfunction, synaptic plasticity, amyloid beta accumulation, and lipid metabolism

Metabolic syndrome (MetS) is characterized by insulin resistance, hyperglycemia, excessive fat accumulation and dyslipidemia, and is known to be accompanied by neuropathological symptoms such as memory loss, anxiety, and depression. As the number of MetS patients is rapidly increasing globally, studies on the mechanisms of metabolic imbalance-related neuropathology are emerging as an important issue. Ca2+/calmodulin-dependent kinase II (CaMKII) is the main Ca2+ sensor and contributes to diverse intracellular signaling in peripheral organs and the central nervous system (CNS). CaMKII exerts diverse functions in cells, related to mechanisms such as RNA splicing, reactive oxygen species (ROS) generation, cytoskeleton, and protein-protein interactions. In the CNS, CaMKII regulates vascular function, neuronal circuits, neurotransmission, synaptic plasticity, amyloid beta toxicity, lipid metabolism, and mitochondrial function. Here, we review recent evidence for the role of CaMKII in neuropathologic issues associated with metabolic disorders.

The functions of Ca2+/calmodulin-dependent protein kinase II (CaMKII) in diabetes progression

The increase in blood glucose causes a myriad of pathways and molecular components to malfunction, leading to diabetes. Diabetes affects each organ differently by activating distinct pathways. It has an impact on the liver, pancreas, kidney (nephropathy), eyes (retinopathy), and nervous system (neuropathy). Understanding the effects of diabetes on each organ is the first step in developing a sustained treatment for the disease. Among the many cellular molecules impacted by diabetes is Ca²⁺/calmodulin-dependent protein kinase II (CaMKII), a complex Ca²⁺/calmodulin-activated serine/threonine-protein kinase. When intracellular [Ca²⁺] rises, it binds to calmodulin (CaM) to produce Ca²⁺/CaM, which activates CaMKIIs. This factor is involved in the pancreas, liver, heart, muscles, and various organs. Thus, Understanding CaMKII action in each organ is critical for gaining a complete picture of diabetic complications. Therefore, this review covers CaMKII's functions in many organs and how it affects and has been affected by diabetes.

SS31 Confers Cerebral Protection by Reversing Mitochondrial Dysfunction in Early Brain Injury Following Subarachnoid Hemorrhage, via the Nrf2- and PGC-1α-Dependent Pathways

In early brain injury (EBI), oxidative stress occurs following subarachnoid hemorrhage (SAH), and mitochondria are intricately linked to this process. SS31, a mitochondria-targeting antioxidative peptide, has been demonstrated to be beneficial for multiple diseases because of its powerful antioxidant and neuroprotective properties. Although our previous study revealed that SS31 was involved in the powerful antioxidant effect following SAH, the underlying molecular mechanisms remained unclear. Thus, our study aimed to investigate the neuroprotective effects of SS31 by reversing mitochondrial dysfunction in EBI following SAH, via activating the Nrf2 signaling and PGC-1α pathways. Our findings confirmed that SS31 ameliorated SAH-triggered oxidative insult. SS31 administration decreased redundant reactive oxygen species, alleviated lipid peroxidation, and elevated the activities of antioxidant enzymes. Concomitant with the inhibited oxidative insult, SS31 dramatically attenuated neurological deficits, cerebral edema, neural apoptosis, and blood-brain barrier disruption following SAH. Moreover, SS31 remarkably promoted nuclear factor-erythroid 2 related factor 2 (Nrf2) nuclear shuttle and upregulated the expression levels of heme oxygenase-1 and NADPH: quinine oxidoreductase1. Additionally, SS31 enhanced the expression levels of PGC-1α and its target genes, and increased the mtDNA copy number, promoting mitochondrial function. However, PGC-1α-specific inhibitor SR-18292 pretreatment dramatically suppressed SS31-induced Nrf2 expression and PGC-1α activation. Furthermore, pretreatment with SR-18292 reversed the neuroprotective and antioxidant roles of SS31. These significant beneficial effects were associated with the activation of the Nrf2 signaling and PGC-1α pathways and were antagonized by SR-18292 administration. Our findings reveal that SS31 exhibits its neuroprotective activity by reversing mitochondrial dysfunction via activating the Nrf2 signaling pathway, which could be mediated through PGC-1α activation.

Myristic Acid Supplementation Aggravates High Fat Diet-Induced Adipose Inflammation and Systemic Insulin Resistance in Mice

Saturated fatty acids (SFAs) are considered to be detrimental to human health. One of the SFAs, myristic acid (MA), is known to exert a hypercholesterolemic effect in mice as well as humans. However, its effects on altering adipose tissue (AT) inflammation and systemic insulin resistance (IR) in obesity are still unclear. Here, we sought to determine the effects of a high fat (HF) diet supplemented with MA on obesity-associated metabolic disorders in mice. Wild-type C57BL/6 mice were fed a HF diet in the presence or absence of 3% MA for 12 weeks. Plasma lipids, plasma adipokines, AT inflammation, systemic IR, glucose homeostasis, and hepatic steatosis were assessed. The body weight and visceral adipose tissue (VAT) mass were significantly higher in mice receiving the HF+MA diet compared to HF diet-fed controls. Plasma total cholesterol levels were marginally increased in HF+MA-fed mice compared to controls. Fasting blood glucose was comparable between HF and HF+MA-fed mice. Interestingly, the plasma insulin and HOMA-IR index, a measure of insulin resistance, were significantly higher in HF+MA-fed mice compared to HF controls. Macrophage and inflammatory markers were significantly elevated in the AT and AT-derived stromal vascular cells upon MA feeding. Moreover, the level of circulating resistin, an adipokine promoting insulin resistance, was significantly higher in HF+MA-fed mice compared with HF controls. The insulin tolerance test revealed that the IR was higher in mice receiving the MA supplementation compared to HF controls. Moreover, the glucose tolerance test showed impairment in systemic glucose homeostasis in MA-fed mice. Analyses of liver samples showed a trend towards an increase in liver TG upon MA feeding. However, markers of oxidative stress and inflammation were reduced in the liver of mice fed an MA diet compared to controls. Taken together, our data suggest that chronic administration of MA in diet exacerbates obesity-associated insulin resistance and this effect is mediated in part, via increased AT inflammation and increased secretion of resistin.

Role of CaMKII in the regulation of fatty acids and lipid metabolism

BACKGROUND & AIMS

Previous studies have reported the beneficial roles of the activation of calmodulin-dependent protein kinase (CaMK)II to many cellular functions associated with human health. This review aims at discussing its activation by exercise as well as its roles in the regulation of unsaturated, saturated, omega 3 fatty acids, and lipid metabolism.

METHODS

A wide literature search was conducted using online database such as 'PubMed', 'Google Scholar', 'Researcher', 'Scopus' and the website of World Health Organization (WHO) as well as Control Disease and Prevention (CDC). The criteria for the search were mainly lipid and fatty acid metabolism, diabetes, and metabolic syndrome (MetS). A total of ninety-seven articles were included in the review.

RESULTS

Calmodulin-dependent protein kinase activation by exercise is helpful in controlling membrane lipids related with type 2 diabetes and obesity. CaMKII regulates many health beneficial cellular functions in individuals who exercise compared with those who do not exercise. Regulation of lipid metabolism and fatty acids are crucial in the improvement of metabolic syndrome.

CONCLUSIONS

Approaches that involve CaMKII could be a new avenue for designing novel and effective therapeutic modalities in the treatment or better management of metabolic diseases such as type 2 diabetes and obesity.

The Regulation of Lipokines by Environmental Factors

Adipose tissue is a highly metabolically-active tissue that senses and secretes hormonal and lipid mediators that facilitate adaptations to metabolic tissues. In recent years, the role of lipokines, which are lipid species predominantly secreted from adipose tissue that act as hormonal regulators in many metabolic tissues, has been an important area of research for obesity and diabetes. Previous studies have identified that these secreted lipids, including palmitoleate, 12,13-diHOME, and fatty acid-hydroxy-fatty acids (FAHFA) species, are important regulators of metabolism. Moreover, environmental factors that directly affect the secretion of lipokines such as diet, exercise, and exposure to cold temperatures constitute attractive therapeutic strategies, but the mechanisms that regulate lipokine stimulation have not been thoroughly reviewed. In this study, we will discuss the chemical characteristics of lipokines that position them as attractive targets for chronic disease treatment and prevention and the emerging roles of lipokines as regulators of inter-tissue communication. We will define the target tissues of lipokines, and explore the ability of lipokines to prevent or delay the onset and development of chronic diseases. Comprehensive understanding of the lipokine synthesis and lipokine-driven regulation of metabolic outcomes is instrumental for developing novel preventative and therapeutic strategies that harness adipose tissue-derived lipokines.

Long-Term Impact of Neonatal Intake of Oleanolic Acid on the Expression of AMP-Activated Protein Kinase, Adiponectin and Inflammatory Cytokines in Rats Fed with a High Fructose Diet

AMP-activated protein kinase (AMPK) is known to regulate both glucose and lipid metabolism, which play vital roles in the development of metabolic syndrome. One way of regulating AMPK is through hormonal activation using adiponectin. Patients diagnosed with type-2 diabetes (T2D) and obesity exhibit low adiponectin concentration levels in their blood. Moreover, studies have also shown that inflammatory processes play a significant role in the etiology of these metabolic diseases. In this study, the long-term effects of neonatal intake of oleanolic acid (OA) on the AMPK gene, genes associated with glucose transport and lipid metabolism, adiponectin levels, and inflammatory biomarkers in rats fed with a high fructose diet were investigated. Seven day old pups were randomly divided into five groups and treated as follows; 0.5% dimethylsulphoxide v/v in distilled water vehicle control (CON), oleanolic acid (OA, 60 mg/kg), high fructose diet (HF, 20% w/v), high fructose diet combined with oleanolic acid (HF+OA), and high fructose diet combined with metformin (HF+MET, 500 mg/kg). The treatments were administered once daily until day 14. The rats were then weaned at day 21 and fed standard rat chow and had ad libitum access to plain drinking water until day 112. The quantitative polymerase chain reaction (qPCR) was used to analyze the gene expressions of AMPK, Glut-4, Cpt-1, AdipoR1, AdipoR2, TNF-α, and IL-6 in the skeletal muscles. Bio-Plex Pro magnetic bead-based assay was used to measure plasma levels of inflammatory markers (TNF-α, IL-6, VEGF, and MCP-1) while ELISA kits were used to measure adiponectin concentration in blood plasma. The results obtained in this study showed that neonatal supplementation with OA significantly increased AMPK gene expression approximately ~4-fold in OA fed rats compared to those that were fed with HF alone. In addition, glut-4 gene expression was also significantly higher in the OA treatment group compared to all the other experimental groups except the CON group whereas Cpt-1 gene was more expressed when OA was administered alone. Together, these results indicated that OA can play a role in glucose and lipid metabolism gene regulation. Furthermore, the results showed that the OA group had ~1.5-fold increase in adiponectin concentration when comparedto the HF group. Moreover, HF increased levels of inflammatory cytokines, which was attenuated by neonatal administration of OA. Plasma concentration and gene expression in the skeletal muscle for TNF-α and IL-6 were significantly increased in rats that were treated with HF alone when compared to all the other groups. On the contrary, the high levels of TNF-α and IL-6 were reduced when OA was administered. These findings suggest that intake of oleanolic acid during the neonatal stage of development could be a potential strategic intervention for the long-term prevention of metabolic diseases such as T2D and obesity.

A Study on Neonatal Intake of Oleanolic Acid and Metformin in Rats (Rattus norvegicus) with Metabolic Dysfunction: Implications on Lipid Metabolism and Glucose Transport

Metabolic syndrome, a cluster of different disorders which include diabetes, obesity and cardiovascular diseases, is a global epidemic that is growing at an alarming rate. The origins of disease can be traced back to early developmental stages of life. This has increased mortalities and continues to reduce life expectancies of individuals across the globe. The aim of this study was to investigate the sub-acute and long term effects of neonatal oral administration of oleanolic acid and metformin on lipids (free fatty acids, FFAs) and genes associated with lipid metabolism and glucose transport using a neonatal rat experimental model. In the first study, seven days old pups were randomly grouped into control—distilled water (DW); oleanolic acid (60 mg/kg), metformin (500 mg/kg), high fructose diet (20% w/v, HF), oleanolic acid (OA) + high fructose diet (OA + HF), and Metformin + high fructose diet (MET + HF) groups. The pups were treated for 7 days, and then terminated on postnatal day (PD) 14. In the second study, rat pups were initially treated similarly to study 1 and weaned onto normal rat chow and plain drinking water on PD 21 till they reached adulthood (PD112). Tissue and blood samples were collected for further analyses. Measurement of the levels of free fatty acids (FFAs) was done using gas chromatography-mass spectrometry. Quantitative polymerase chain reaction (qPCR) was used to analyze the gene expression of glut-4, glut-5, fas, acc-1, nrf-1 and cpt-1 in the skeletal muscle. The results showed that HF accelerated accumulation of saturated FFAs within skeletal muscles. The HF fed neonatal rats had increased stearic acid, which was associated with decreased glucose, suppressed expression of glut-4, glut-5, nrf-1 and cpt-1 genes, and increased expression of acc-1 (p < 0.01) and fas. OA + HF and MET + HF treated groups had increased mono- and polyunsaturated FFAs; oleic, and octadecadienoic acids than the HF group. These unsaturated FFAs were associated with increased glut-4, glut-5 and nrf-1 (p < 0.01) and decreased acc-1 and fas (p < 0.05) in both OA + HF and MET + HF treated groups. Conclusions: The present study shows that neonatal oral administration of oleanolic acid and metformin potentially protects against the development of fructose-induced metabolic dysfunction in the rats in both short and long time periods.

Role of exercise-induced calmodulin protein kinase (CaMK)II activation in the regulation of omega-6 fatty acids and lipid metabolism genes in rat skeletal muscle

Activation of calmodulin dependent protein kinase (CaMK)II by exercise is beneficial in controlling membrane lipids associated with type 2 diabetes and obesity. Regulation of lipid metabolism is crucial in the improvement of type 2 diabetes and obesity associated symptoms. The role of CaMKII in membrane associated lipid metabolism was the focus of this study. Five to six weeks old male Wistar rats were used in this study. GC×GC-TOFMS technique was used to determine the levels of polyunsaturated fatty acids (linoleic acid, arachidonic acid and 11,14-eicosadienoic acid). Carnitine palmitoyltransferase (Cpt-1) and acetyl-CoA carboxylase (Acc-1) genes expression were assessed using quantitative real time PCR (qPCR). From the results, CaMKII activation by exercise increased the levels of arachidonic acid and 11,14-eicosadienoic acid while a decrease in the level of linolenic acid was observed in the skeletal muscle. The results indicated that exercise-induced CaMKII activation increased CPT-1 expression and decreased ACC-1 expression in rat skeletal muscle. All the observed increases with activation of CaMKII by exercise were aborted when KN93, an inhibitor of CaMKII was injected in exercising rats. This study demonstrated that CaMKII activation by exercise regulated lipid metabolism. This study suggests that CaMKII can be a vital target of therapeutic approach in the management of diseases such as type 2 diabetes and obesity that have increased to epidemic proportions recently.

Exercise increases hyper-acetylation of histones on the Cis-element of NRF-1 binding to the Mef2a promoter: Implications on type 2 diabetes

Exercise brings changes on the chromatin ensuing the upregulation of many genes that confer protection from type 2 diabetes. In type-2 diabetes, critical genes are down-regulated such as those involved in glucose transport (GLUT4, MEF2A) and also oxidative phosphorylation (NRF-1 and its target genes). Recent reports have shown that NRF-1 not only regulate mitochondrial oxidative genes but also controls MEF2A, the main transcription factor for glucose transporter, GLUT4. Such dual control of the two pathways by NRF-1 place it as critical gene in the design of therapeutic modalities much needed to cure or better manage type 2 diabetes. Although it is known that NRF-1 controls these dual pathways (glucose transport and oxidative phosphorylation), the actual molecular mechanisms involved surrounding this regulation remains elusive. NRF-1 itself is regulated through posttranslational modifications (acetylation, methylation and phosphorylation) resulting in enhanced binding to its target genes. This study is therefore aimed at assessing whether CaMKII, a kinase activated by exercise brings about hyper-acetylation of histones in the vicinity of NRF-1 target gene, Mef2a. Five to six weeks old male Wistar rats were used in this study. Chromatin immunoprecipitation (ChIP) assay was used to investigate the extent through which NRF-1 is bound to the Mef2a gene and if this was associated with hyper-acetylation of histones in the region of NRF-1 binding site of the Mef2a gene. Quantitative real time PCR (qPCR) was used to determine the gene expression of MEF2A and NRF-1. Results from this study indicated that exercise-induced CaMKII activation increased hyper-acetylation of histones in the region of NRF-1 binding site on vicinity of Mef2a gene and this was associated with the increased binding of NRF-1 to Mef2a gene. Exercise also increased the expression of NRF-1 and MEF2A genes. Administration of CaMKII inhibitor (KN93) prior to exercise attenuated the observed exercise-induced increase of NRF-1 and MEF2A expressions. In conclusion, this study demonstrated for the first time in our knowledge one mechanism through which NRF-1 regulates MEF2A, pathway critical in glucose transport.