Fibroblast growth factor 21 is expressed and secreted from skeletal muscle following electrical stimulation via extracellular ATP activation of the PI3K/Akt/mTOR signaling pathway

Optimal transcorneal electrical stimulation parameters for preserving photoreceptors in a mouse model of retinitis pigmentosa

JOURNAL/nrgr/04.03/01300535-202419110-00034/figure1/v/2024-03-08T184507Z/r/image-tiff Retinitis pigmentosa is a hereditary retinal disease that affects rod and cone photoreceptors, leading to progressive photoreceptor loss. Previous research supports the beneficial effect of electrical stimulation on photoreceptor survival. This study aims to identify the most effective electrical stimulation parameters and functional advantages of transcorneal electrical stimulation (tcES) in mice affected by inherited retinal degeneration. Additionally, the study seeked to analyze the electric field that reaches the retina in both eyes in mice and post-mortem humans. In this study, we recorded waveforms and voltages directed to the retina during transcorneal electrical stimulation in C57BL/6J mice using an intraocular needle probe with rectangular, sine, and ramp waveforms. To investigate the functional effects of electrical stimulation on photoreceptors, we used human retinal explant cultures and rhodopsin knockout (Rho-/-) mice, demonstrating progressive photoreceptor degeneration with age. Human retinal explants isolated from the donors' eyes were then subjected to electrical stimulation and cultured for 48 hours to simulate the neurodegenerative environment in vitro. Photoreceptor density was evaluated by rhodopsin immunolabeling. In vivo Rho-/- mice were subjected to two 5-day series of daily transcorneal electrical stimulation using rectangular and ramp waveforms. Retinal function and visual perception of mice were evaluated by electroretinography and optomotor response (OMR), respectively. Immunolabeling was used to assess the morphological and biochemical changes of the photoreceptor and bipolar cells in mouse retinas. Oscilloscope recordings indicated effective delivery of rectangular, sine, and ramp waveforms to the retina by transcorneal electrical stimulation, of which the ramp waveform required the lowest voltage. Evaluation of the total conductive resistance of the post-mortem human compared to the mouse eyes indicated higher cornea-to-retina resistance in human eyes. The temperature recordings during and after electrical stimulation indicated no significant temperature change in vivo and only a subtle temperature increase in vitro (~0.5-1.5°C). Electrical stimulation increased photoreceptor survival in human retinal explant cultures, particularly at the ramp waveform. Transcorneal electrical stimulation (rectangular + ramp) waveforms significantly improved the survival and function of S and M-cones and enhanced visual acuity based on the optomotor response results. Histology and immunolabeling demonstrated increased photoreceptor survival, improved outer nuclear layer thickness, and increased bipolar cell sprouting in Rho-/- mice. These results indicate that transcorneal electrical stimulation effectively delivers the electrical field to the retina, improves photoreceptor survival in both human and mouse retinas, and increases visual function in Rho-/- mice. Combined rectangular and ramp waveform stimulation can promote photoreceptor survival in a minimally invasive fashion.

HouShiHeiSan attenuates sarcopenia in middle cerebral artery occlusion (MCAO) rats

ETHNOPHARMACOLOGICAL RELEVANCE

Physical therapy is the main clinical treatment for limb symptoms after ischemic stroke, and there is a lack of reliable drug intervention programs. HouShiHeiSan (HS)comes from "Synopsis of the Golden Chamber", where it is recorded: "seauelae of wind stroke and heaviness of limbs", indicating this formulae is a promising opion for clinical practice.

AIM OF THE STUDY

The aim of this study is to explore the therapeutic effect of HS on sarcopenia after ischemic stroke (ISS) by using the middle cerebral artery occlusion (MCAO) rats.

MATERIALS AND METHODS

After 7 days of adaptive feeding Sprague-Dawley (SD) rats were randomly divided into sham and MCAO surgery groups. After MCAO operation, the agreement of the models was evaluated with a laser speckle instrument, and then, treatment groups were administered HS and related solvent. During the 7 days treatment period, the Zea-Longa score was used to assess the neural function, the treadmill for exercise capacity and traction instrument for grip strength. Besides, the physiological electrical signal system was used to record muscular electrical signals, while the muscle thickness was measured by ultrasound. After data acquisition on the 7th day after MCAO operation, the soleus muscle was dissected, and the indexes of length, weight of whole muscle tissue and cross-sectional area of muscular cells by H&E were recorded. Subsequently, mechanistic indicators were examined. MuRF1 and MAFbx expression was detected by immunohistochemistry (IHC). Furthermore, the expression level of more related indicators of muscular differentiation and cellular proterin balance, including mTOR, p-mTOR, AKT, p-AKT, p70s6k, p-p70s6, FOXO1, p-FOXO1, MyoD1, Myostatin, MuRF1 and MAFbx, were tested via Western blot.

RESULTS

HS improved motor performance and promoted muscle regeneration in MCAO rats. In terms of motor ability, HS mixed with alcohol significantly improved the neurological function damage, reduce the weight loss, increase the running distance per unit time and increase the grip strength. The postoperative muscle electrical signal intensity increased, and muscle thickness, weight, and length were maintained. The HS with alcohol group significantly maintained the cross-sectional size of muscle cells and reduced the number of MyoD1 and myostatin-positive cells in the muscle tissue. It simultaneously promoted the expression of p-mTOR, p-AKT, p-p70s6k, and MyoD1 to promote the synthesis of muscle proteins and inhibited the expression of p-FOXO1, myostatin, MAFbx, and MuRF1 to reduce muscle protein degradation.

CONCLUSION

HS can enhance muscle protein synthesis and decrease protein breakdown by activating the AKT/mTOR/FOXO1 pathway, thereby preserving muscle health and enhancing motor performance following stroke in rats.

High-intensity exercise alongside insulin alleviates muscle atrophy in type 1 diabetes mellitus concomitant with modulation of mitophagy-related proteins in skeletal muscle

Background: Diabetes patients' quality of life can be severely impacted by diabetic muscle atrophy.Aim: This study aimed to explore the impact of high-intensity exercise (HIE) alongside insulin treatment on muscle atrophy in a rat model of type 1 diabetes mellitus (T1DM).Methodology: Fifty rats were allocated into five groups; Group 1, control sedentary (CS), T1DM was elicited in the rest of the groups by giving them Streptozotocin (STZ) (60 mg/kg), where group 2 (DS) remained sedentary, while groups 3,4,5 were treated with insulin after induction of diabetes. Group 4 (DI+MIE) and 5 (DI+ HIE) underwent moderate and high-intensity exercise, respectively.Results: HIE for 14 days combined with insulin treatment significantly restored muscle strength and mass with a significant modification in the mitophagy-related proteins and fibroblast growth factor 21 (FGF 21) compared to other treated groups.Conclusion: This study concluded that there is a therapeutic role for HIE with insulin against T1DM-induced muscle atrophy.

Diagnostic and predictive abilities of myokines in patients with heart failure

Myokines are defined as a heterogenic group of numerous cytokines, peptides and metabolic derivates, which are expressed, synthesized, produced, and released by skeletal myocytes and myocardial cells and exert either auto- and paracrine, or endocrine effects. Previous studies revealed that myokines play a pivotal role in mutual communications between skeletal muscles, myocardium and remote organs, such as brain, vasculature, bone, liver, pancreas, white adipose tissue, gut, and skin. Despite several myokines exert complete divorced biological effects mainly in regulation of skeletal muscle hypertrophy, residential cells differentiation, neovascularization/angiogenesis, vascular integrity, endothelial function, inflammation and apoptosis/necrosis, attenuating ischemia/hypoxia and tissue protection, tumor growth and malignance, for other occasions, their predominant effects affect energy homeostasis, glucose and lipid metabolism, adiposity, muscle training adaptation and food behavior. Last decade had been identified 250 more myokines, which have been investigating for many years further as either biomarkers or targets for heart failure management. However, only few myokines have been allocated to a promising tool for monitoring adverse cardiac remodeling, ischemia/hypoxia-related target-organ dysfunction, microvascular inflammation, sarcopenia/myopathy and prediction for poor clinical outcomes among patients with HF. This we concentrate on some most plausible myokines, such as myostatin, myonectin, brain-derived neurotrophic factor, muslin, fibroblast growth factor 21, irisin, leukemia inhibitory factor, developmental endothelial locus-1, interleukin-6, nerve growth factor and insulin-like growth factor-1, which are suggested to be useful biomarkers for HF development and progression.

Glucosamine Enhancement of Learning and Memory Functions by Promoting Fibroblast Growth Factor 21 Production

Fibroblast growth factor 21 (FGF21) plays a crucial role in metabolism and brain function. Glucosamine (GLN) has been recognized for its diverse beneficial effects. This study aimed to elucidate the modulation of FGF21 production by GLN and its impact on learning and memory functions. Using both in vivo and in vitro models, we investigated the effects of GLN on mice fed with a normal diet or high-fat diet and on mouse HT22 hippocampal cells, STHdhQ7/Q7 striatal cells, and rat primary cortical neurons challenged with GLN. Our results indicated that GLN promotes learning and memory functions in mice and upregulates FGF21 expression in the hippocampus, cortex, and striatum, as well as in HT22 cells, STHdhQ7/Q7 cells, and cortical neurons. In animals receiving GLN together with an FGF21 receptor FGFR1 inhibitor (PD173074), the GLN-enhanced learning and memory functions and induction of FGF21 production in the hippocampus were significantly attenuated. While exploring the underlying molecular mechanisms, the potential involvement of NF-κB, Akt, p38, JNK, PKA, and PPARα in HT22 and NF-κB, Akt, p38, and PPARα in STHdhQ7/Q7 were noted; GLN was able to mediate the activation of p65, Akt, p38, and CREB in HT22 and p65, Akt, and p38 in STHdhQ7/Q7 cells. Our accumulated findings suggest that GLN may increase learning and memory functions by inducing FGF21 production in the brain. This induction appears to be mediated, at least in part, through GLN's activation of the NF-κB, Akt, p38, and PKA/CREB pathways.

Potential role of Akt in the regulation of fibroblast growth factor 21 by berberine

Fibroblast growth factor 21 (FGF21) is expressed in several organs, including the liver, adipose tissue, and cardiovascular system, and plays an important role in cross-talk with other organs by binding to specific FGF receptors and their co-receptors. FGF21 represents a potential target for the treatment of obesity, type 2 diabetes mellitus, and non-alcoholic steatohepatitis (NASH). The production of FGF21 in skeletal muscle was recently suggested to be beneficial for metabolic health through its autocrine and paracrine effects. However, the regulatory mechanisms of FGF21 in skeletal muscle remain unclear. In the present study, we showed that berberine regulated FGF21 production in C2C12 myotubes in a dose-dependent manner. We also examined the effects of A-674563, a selective Akt1 inhibitor, on the berberine-mediated regulation of FGF21 expression in C2C12 myotubes. Berberine significantly increased the secretion of FGF21 in C2C12 myotubes, while A-674563 attenuated this effect. Moreover, a pre-treatment with A-674563 effectively suppressed berberine-induced increases in Bmal1 expression in C2C12 myotubes, indicating that the up-regulation of Bmal1 after the berberine treatment was dependent on Akt1. Additionally, berberine-induced increases in FGF21 secretion were significantly attenuated in C2C12 cells transfected with Bmal1 siRNA, indicating the contribution of the core clock transcription factor BMAL1 to Akt-regulated FGF21 in response to berberine. Collectively, these results indicate that berberine regulates the expression of FGF21 through the Akt1 pathway in C2C12 myotubes. Moreover, the core clock gene Bmal1 may participate in the control of the myokine FGF21. Berberine stimulated Akt1-dependent FGF21 expression in C2C12 myotubes. The up-regulation of FGF21 through the modulation of PI3K/AKT1/BMAL1 in response to berberine may be involved in the regulation of cellular function (such as Glut1 expression) by acting in an autocrine and/or paracrine manner in skeletal muscle.

Fibroblast Growth Factor 21: A Fascinating Perspective on the Regulation of Muscle Metabolism

Fibroblast growth factor 21 (FGF21) plays a vital role in normal eukaryotic organism development and homeostatic metabolism under the influence of internal and external factors such as endogenous hormone changes and exogenous stimuli. Over the last few decades, comprehensive studies have revealed the key role of FGF21 in regulating many fundamental metabolic pathways, including the muscle stress response, insulin signaling transmission, and muscle development. By coordinating these metabolic pathways, FGF21 is thought to contribute to acclimating to a stressful environment and the subsequent recovery of cell and tissue homeostasis. With the emphasis on FGF21, we extensively reviewed the research findings on the production and regulation of FGF21 and its role in muscle metabolism. We also emphasize how the FGF21 metabolic networks mediate mitochondrial dysfunction, glycogen consumption, and myogenic development and investigate prospective directions for the functional exploitation of FGF21 and its downstream effectors, such as the mammalian target of rapamycin (mTOR).

The pan-liver network theory: From traditional chinese medicine to western medicine

In traditional Chinese medicine (TCM), the liver is the "general organ" that is responsible for governing/maintaining the free flow of qi over the entire body and storing blood. According to the classic five elements theory, zang-xiang theory, yin-yang theory, meridians and collaterals theory, and the five-viscera correlation theory, the liver has essential relationships with many extrahepatic organs or tissues, such as the mother-child relationships between the liver and the heart, and the yin-yang and exterior-interior relationships between the liver and the gallbladder. The influences of the liver to the extrahepatic organs or tissues have been well-established when treating the extrahepatic diseases from the perspective of modulating the liver by using the ancient classic prescriptions of TCM and the acupuncture and moxibustion. In modern medicine, as the largest solid organ in the human body, the liver has the typical functions of filtration and storage of blood; metabolism of carbohydrates, fats, proteins, hormones, and foreign chemicals; formation of bile; storage of vitamins and iron; and formation of coagulation factors. The liver also has essential endocrine function, and acts as an immunological organ due to containing the resident immune cells. In the perspective of modern human anatomy, physiology, and pathophysiology, the liver has the organ interactions with the extrahepatic organs or tissues, for example, the gut, pancreas, adipose, skeletal muscle, heart, lung, kidney, brain, spleen, eyes, skin, bone, and sexual organs, through the circulation (including hemodynamics, redox signals, hepatokines, metabolites, and the translocation of microbiota or its products, such as endotoxins), the neural signals, or other forms of pathogenic factors, under normal or diseases status. The organ interactions centered on the liver not only influence the homeostasis of these indicated organs or tissues, but also contribute to the pathogenesis of cardiometabolic diseases (including obesity, type 2 diabetes mellitus, metabolic [dysfunction]-associated fatty liver diseases, and cardio-cerebrovascular diseases), pulmonary diseases, hyperuricemia and gout, chronic kidney disease, and male and female sexual dysfunction. Therefore, based on TCM and modern medicine, the liver has the bidirectional interaction with the extrahepatic organ or tissue, and this established bidirectional interaction system may further interact with another one or more extrahepatic organs/tissues, thus depicting a complex "pan-hepatic network" model. The pan-hepatic network acts as one of the essential mechanisms of homeostasis and the pathogenesis of diseases.