Diabetic Muscle Research Articles

Abstract 4129523: MicroRNA-1282 Rescues Diabetic Limb Ischemia Via a SERF2-Protein Aggregation Pathway

Introduction: Patients with diabetes are at higher risk of chronic limb-threatening ischemia (CLTI), a severe form of peripheral artery disease (PAD) causing restricted blood flow to the lower limbs due, in part, to impaired angiogenesis. However, the role of microRNAs (miRNAs) in diabetic CLTI remains poorly understood. By integrating plasma miRNA sequencing data from PAD patients with diabetes with a diabetic CLTI mouse model, we have recently identified the conserved miRNA miR-1282 that is in cis-antisense orientation to SERF2, a gene associated with amyloid aggregation. Therefore, we hypothesize that miR-1282 orchestrates endothelial angiogenesis and proteostasis during diabetic CLTI. Methods: Using miR-1282 overexpression or SERF2 knockdown studies, we characterized mouse orthologs of human miR-1282 and SERF2 for angiogenesis, apoptosis, protein aggregation, and oxidative stress in diabetic mouse skeletal muscle endothelial cells (ECs). In vivo, miR-1282 mimics were delivered intramuscularly to assess their impact on blood flow recovery, angiogenesis, and protein aggregation. Mechanistic insights in ECs were gained via RNA-seq, predictive algorithms, and proteomic analyses. Results: miR-1282 inhibited the expression of its cis-antisense target SERF2 by 98%. miR-1282 is a hypoxia-induced endothelial-enriched miRNA, and its expression was inversely correlated with SERF2 expression. miR-1282 levels were markedly reduced after femoral artery ligation (FAL) in diabetic db/db mice. Overexpression of miR-1282 or SERF2 knockdown enhanced angiogenesis and reduced protein aggregation, apoptosis, and oxidative stress in both normal and hypoxic conditions in vitro. Delivery of miR-1282 mimics in db/db mice improved blood flow recovery by 108% and angiogenesis by 98%, and reduced protein aggregation by 48% and tissue necrosis. Coupling RNA-seq profiling and prediction algorithms of ECs upon miR-1282 overexpression or SERF2 knockdown revealed EREG, BAG5, CASP3, ARG1, and HSP90AA1 as potential downstream regulators. Pathway enrichment analysis implicated inhibition of endothelial apoptosis, ER stress, and protein stability among the most dysregulated processes. Conclusion: A novel mouse ortholog of human miR-1282 augments endothelial functions and diminishes protein aggregation in diabetic CLTI via suppression of its cis-antisense target SERF2. These findings uncover new potential therapeutic targets in treating diabetic CLTI.

Elevated glucose levels increase vascular calcification risk by disrupting extracellular pyrophosphate metabolism.

Vascular calcification is a major contributor to cardiovascular disease, especially diabetes, where it exacerbates morbidity and mortality. Although pyrophosphate is a recognized natural inhibitor of vascular calcification, there have been no prior studies examining its specific deficiency in diabetic conditions. This study is the first to analyze the direct link between elevated glucose levels and disruptions in extracellular pyrophosphate metabolism. Rat aortic smooth muscle cells, streptozotocin (STZ)-induced diabetic rats, and diabetic human aortic smooth muscle cells were used to assess the effects of elevated glucose levels on pyrophosphate metabolism and vascular calcification. The techniques used include extracellular pyrophosphate metabolism assays, thin-layer chromatography, phosphate-induced calcification assays, BrdU incorporation for DNA synthesis, aortic smooth muscle cell viability and proliferation assays, and quantitative PCR for enzyme expression analysis. Additionally, extracellular pyrophosphate metabolism was examined through the use of radiolabeled isotopes to track ATP and pyrophosphate transformations. Elevated glucose led to a significant reduction in extracellular pyrophosphate across all diabetic models. This metabolic disruption was marked by notable downregulation of both the expression and activity of ectonucleotide pyrophosphatase/phosphodiesterase 1, a key enzyme that converts ATP to pyrophosphate. We also observed an upregulation of ectonucleoside triphosphate diphosphohydrolase 1, which preferentially hydrolyzes ATP to inorganic phosphate rather than pyrophosphate. Moreover, tissue-nonspecific alkaline phosphatase activity was markedly elevated across all diabetic models. This shift in enzyme activity significantly reduced the pyrophosphate/phosphate ratio. In addition, we noted a marked downregulation of matrix Gla protein, another inhibitor of vascular calcification. The impaired pyrophosphate metabolism was further corroborated by calcification experiments across all three diabetic models, which demonstrated an increased propensity for vascular calcification. This study demonstrated that diabetes-induced high glucose disrupts extracellular pyrophosphate metabolism, compromising its protective role against vascular calcification. These findings identify pyrophosphate deficiency as a potential mechanism in diabetic vascular calcification, highlighting a new therapeutic target. Strategies aimed at restoring or enhancing pyrophosphate levels may offer significant potential in mitigating cardiovascular complications in diabetic patients, meriting further investigation.

Polyphenolic Compounds Activate SERCA1a and Attenuate Methylglyoxal- and Palmitate-Induced Impairment in Pancreatic INS-1E Beta Cells

Sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) is an important regulatory protein responsible for maintaining calcium homeostasis within cells. Impairment of SERCA associated with activity/expression decrease has been implicated in multiple chronic conditions, including cardiovascular diseases, diabetes, cancer, neurodegenerative diseases, and skeletal muscle pathologies. Natural polyphenols have been recognized to interact with several target proteins involving SERCA. To date, only a limited number of polyphenolic compounds or their derivatives have been described either to increase SERCA activity/expression directly or to affect Ca2+ signaling pathways. In this study, we tested polyphenols for their ability to activate SERCA1a in the absence or presence of methylglyoxal or palmitate and to impact insulin release in pancreatic beta cells. The protective effects of these compounds against methylglyoxal- or palmitate-induced injury were evaluated. Results indicate that 6-gingerol, resveratrol, and ellagic acid activate SERCA1a and protect against activity decrease induced by methylglyoxal and palmitate. Molecular docking analysis revealed the binding of these polyphenols to Glu439 in the SERCA1a P-domain, suggesting a critical role in the stimulation of enzyme activity. Ellagic acid was found to directly stimulate the activity of SERCA1a, marking the first instance of such an observation.

The Multifaceted Role of miR-23a in Cancer and Disease Progression

Abstract: MicroRNAs (miRNAs) are small, non-coding RNAs that play a crucial role in post-transcriptional gene regulation by modulating mRNA stability and translation. These evolutionarily conserved molecules undergo processing by ribonucleases Drosha and Dicer, ultimately joining the RNA-induced silencing complex to silence gene expression. Among them, miR-23a, located on chromosome 19, is significant for its roles in cell growth, differentiation, and various diseases, including cancer. Depending on the cancer type, miR-23a can function as both an oncogene and a tumour suppressor. While its overexpression often correlates with aggressive tumours, miR-23a holds promise as a biomarker for early cancer detection and a therapeutic target. Its diverse functions in cancer include promoting tumour growth and hindering immune responses, highlighting its potential for personalized medicine. Beyond cancer, miR-23a is involved in blood sugar regulation, insulin resistance, muscle atrophy, and other diseases. It modulates pathways in type 2 diabetes mellitus, muscle atrophy, leukemia, epilepsy, and osteoarthritis. This paper aims to comprehensively analyze the roles of miR-23a in cancer and other diseases, focusing on its regulatory mechanisms, target genes, and pathways. It also evaluates the potential of miR-23a as a biomarker and therapeutic target. Despite its significance, research gaps remain, particularly in understanding the interactions of miR-23a with other miRNAs and the detailed mechanisms underlying its role in various diseases. More research into miR-23a clustering and how it works with other miRNAs could help us learn more about it and find better ways to use it to diagnose and treat diseases.

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.

Effect of diabetes on microvascular morphology and permeability of rat skeletal muscle: in vivo imaging using two-photon laser scanning microscopy.

This investigation evaluated the microvascular permeability and ultrastructure of skeletal muscle capillaries in the skeletal muscle of diabetic (DIA) rats using two-photon laser scanning microscopy (TPLSM) and transmission electron microscopy (TEM). Microvascular permeability was assessed in the tibialis anterior muscle of control (CON) and DIA (streptozocin) male Wistar rats (n = 20, 10-14 wk) by in vivo imaging using TPLSM after fluorescent dye intravenous infusion. Fluorescent dye leakage was quantified to determine microvascular permeability. The ultrastructure was imaged by TEM ex vivo to calculate the size and number of intercellular clefts between capillary endothelial cells and also intracellular vesicles. Compared with control, the volumetrically determined interstitial fluorescent dye leakage, the endothelial cell thickness, and the number of intercellular clefts per capillary perimeter were significantly higher, and the cleft width was significantly narrower in tibialis anterior (TA) of DIA (interstitial fluorescent dye leakage, 2.88 ± 1.40 vs. 10.95 ± 1.41 µm3 × min × 106; endothelial thickness, 0.28 ± 0.02 vs. 0.45 ± 0.03 µm; number of intercellular clefts per capillary perimeter, 6.3 ± 0.80 vs. 13.6 ± 1.7/100 µm; cleft width, 11.92 ± 0.95 vs. 8.40 ± 1.03 nm, CON vs. DIA, respectively, all P < 0.05). The size of intracellular vesicles in the vascular endothelium showed an increased proportion of large vesicles in the DIA group compared with the CON group (P < 0.05). Diabetes mellitus enhances the microvascular permeability of skeletal muscle microvessels due, in part, to a higher density and narrowing of the endothelial intercellular clefts, and larger intracellular vesicles.NEW & NOTEWORTHY Microvascular permeability in diabetic muscle was investigated using our original two-photon scanning laser microscopy method. Compared with controls, the leakage volume was increased in diabetic muscle, which was atrophic with smaller capillary diameter, endothelial cell thickening, and the appearance of more endothelial intercellular gaps or clefts, and large vesicles. Hyperpermeability was closely related to ultrafine structural changes of the capillary endothelial cell junctions.

Prevalence of Cardiomyopathy in Patients with Type 1 Diabetes Mellitus.

Background: Diabetic cardiac muscle disease or diabetic cardiomyopathy (DbCM) comprises a set of myocardial lesions that are not associated with coronary atherosclerosis or high blood pressure. It is characterized by fibrosis and hypertrophy, which ultimately results in heart failure. Diastolic dysfunction (DD) has been shown to be the first manifestation of diabetic cardiomyopathy. Currently, there are few studies on the prevalence of diabetic cardiomyopathy in adult patients diagnosed with type 1 diabetes mellitus (T1D). Methods: The study included 75 adult participants who underwent an echocardiogram. Data on their comorbidities were collected from their medical records and biochemical parameters were analyzed in blood and urine samples. Results: We found that the prevalence of DbCM in our T1D population was more than one-third (34%), which exceeded the prevalence reported in studies with adolescents and that reported in the population without diabetes. Also, we found that the probability of developing DD after 20 years of T1D diagnosis was 78%. Conclusions: Recommendations need to be issued in relation to diabetic cardiomyopathy to carry out secondary prevention in adult patients with T1D. More multicenter studies, which include a larger population, from different regions of the world need to be performed.

20(S)-ginsenoside Rg3 protects against diabetic muscle atrophy by promoting myoblastic differentiation and protecting mitochondrial function

BackgroundHigh glucose levels are a primary cause of diabetes-associated cellular dysfunction and tissue damage. Muscles are the key insulin target organ and therefore, have a high level of sensitivity to hyperglycemia. Our previous study revealed that 20(S)-ginsenoside Rg3 (S-Rg3) is a monomer with a good myogenic differentiation effect in ginsenoside. Furthermore, it can alleviate dexamethasone-induced muscle atrophy by protecting mitochondrial function. However, whether S-Rg3 is effective for diabetic-induced muscle atrophy has not been reported. PurposeThis study aimed to investigate the protective effect of S-Rg3 on diabetic-induced muscle atrophy. MethodsC2C12 myoblasts, Drosophila, and mice were used as model systems, and the protective effect of S-Rg3 on diabetes was evaluated by assessing the levels of glucose and lipids. Furthermore, H&E, toluidine blue, Giemsa, and immunofluorescence staining were performed to detect the effects of S-Rg3 on muscle atrophy and myogenic differentiation. Moreover, the effects of S-Rg3 on mitochondrial morphology and function were also evaluated by electron microscopy, flow cytometry, and Seahorse. In addition, the underlying pathways of S-Rg3 effects were detected by Western blot. The related inhibitors and gene mutations in Drosophila were used for validation. ResultsThe analysis of diabetic mice model fed with a high-fat diet (HFD) and high glucose (HG) revealed that in the injured C2C12 myoblasts, S-Rg3 treatment significantly reduced the levels of triglycerides and glucose. Furthermore, it promoted the differentiation of myoblasts and inhibited mitochondrial dysfunction. In the Drosophila HG and HFD diabetic model, S-Rg3 reduced triglyceride and trehalose levels, increased climbing distance values, promoted myoblasts differentiation, preserved mitochondrial function, and inhibited muscle atrophy. Mechanistically, the beneficial effects of S-Rg3 were at least partially associated with the phosphorylation of AMPK and FoxO3 together with the inhibition of Smad3 phosphorylation, this pathway was validated by the UAS-AMPKα-RNAi Drosophila model. ConclusionIn summary, this study revealed mechanistic insights into how S-Rg3 protects against diabetes-associated muscle atrophy in cells, Drosophila, and mice.

Exploring stevioside binding affinity with various proteins and receptors actively involved in the signaling pathway and a future candidate for diabetic patients.

Introduction and Background: Diabetes is a chronic metabolic disease characterized by elevated blood glucose levels and is one of the main global health concerns. Synthetic sugar substrate has many side effects such as leukemia, bladder cancer, hepatotoxicity, breast cancer, headache, and brain toxicity. The WHO and FDA has recently banned some of the synthetic sugar alternatives due to their carcinogenic effects. Objective and Methodology: Therefore, the main objective of the current study was to investigate the safety and binding affinity of Stevioside with Glucose Transpoter-4 (GLUT-4), Akt, Insulin Receptor (IR) and Insulin Receptor Substrate-1 (IRS-1) to confirmed that Stevioside is one the potent natural sweetener/drug for diabetes. This study delves into the molecular interaction between Stevioside and key diabetic proteins: GLUT-4, Akt, IR and IRS-1. A precise molecular docking approach was used to simulate the binding affinity of Stevioside to these proteins. The pharmacokinetic properties of the molecule should be taken into consideration as important variables throughout the virtual screening process. Results: The result of active site analysis of GLUT-4, Akt, IR and IRS-1 showed a zone of 2158.359 Ǻ2, 579.259 Ǻ2, 762.651 Ǻ2, and 152.167 Ǻ2 and a volume of 2765.094 Ǻ³, 355.567 Ǻ³, 686.806 Ǻ³, and 116.874 Ǻ³, respectively. Docking analysis of the Stevioside compound showed the highest docking energy with scores of -9.9 with GLUT-4, -6.7 with Akt, -8.0 with IR and -8.8 with IRS-1. Studies indicated that it remains undigested by stomach acids and enzymes and is not absorbed in the upper small intestine. Further, tests revealed no hepatotoxicity, AMES toxicity, or skin sensitivity, making it a promising candidate for safe consumption as drug metabolism. Conclusion and Recommendations: Instead of other sugar alternatives, Stevioside will help diabetic patients with a lower chance of infections, lowered blood pressure/blood sugar, and increased glucose uptake in diabetic muscles. Stevioside is a natural sweetener, and the current study recommends its usage in various dietary products for diabetic patients.

New Glycotoxin Inhibitor from Sesuvium sesuvioides Mitigates Symptoms of Insulin Resistance and Diabetes by Suppressing AGE-RAGE Axis in Skeletal Muscle.

The current study intended to investigate the role of new natural compounds derived from the Sesuvium sesuvioides plant in mitigating symptoms of diabetes and insulin resistance in the diabetic mice model. Anti-advanced glycation activity, insulin, and adiponectin were quantified by enzyme-linked immunosorbent assay (ELISA). Glucose uptake was performed using enzymatic fluorescence assay, and glycogen synthesis was measured using PAS staining. Gene and protein expression was assessed using real time PCR (RT-PCR), and immunoblotting and fluorescent microscopy, respectively. The new flavonoid glycoside eupalitin 3-O-α-L-rhamnopyranosyl-(1→2)-β-D-glucopyranoside 1 isolated from S. sesuvioides exhibited anti-AGE activity by reducing human glycated albumin in liver cells. In a diabetic mouse model treated with compound 1, we observed improved glucose tolerance, increased adiponectin levels, and decreased insulin resistance. We also observed alleviated AGEs induced reduction in glucose uptake and restored glycogen synthesis in the compound 1-treated diabetic mice muscles. Exploring the molecular mechanism of action in skeletal muscle tissue of diabetic mice, we found that 1 reduced AGE-induced reactive oxygen species and the inflammatory gene in the muscle of diabetic mice. Additionally, 1 exhibited these effects by reducing the gene and protein expression of receptor for advanced glycation end products (RAGE) and inhibiting protein kinase C (PKC) delta activation. This further led us to demonstrate that compound 1 reduced serine phosphorylation of IRS-1, thereby restoring insulin sensitivity. We conclude that a new flavonoid glycoside from S. sesuvioides could be a therapeutic target for the treatment of symptoms of insulin resistance and diabetes.

The effect of high-intensity interval training on type 2 diabetic muscle: A metabolomics-based study

BackgroundThis study aimed to investigate the effect of eight weeks of high-intensity interval training (HIIT) on muscle metabolism in rats with type 2 diabetes (T2D) using metabolomics approaches. Methods20 male Wistar rats at the age of 8 weeks-were assigned to four groups of five, each in the group randomly: control (CTL), type 2 diabetes (DB), HIIT (EX), and type 2 diabetes + HIIT (DBX). T2D was induced by two months of a high-fat diet plus a single dose of streptozotocin (35 mg/kg). Rats in the EX and DBX groups performed eight weeks of HIIT (running at 80–100 % of Vmax, 4–10 intervals). NMR spectroscopy was used to determine the changes in the muscle metabolome profile after training. ResultsChanges in metabolite abundance following exercise revealed distinct clustering in multivariate analysis. The essential metabolite changes between the DB and CTL groups were arginine metabolism, purine metabolism, phosphate pathway, amino sugar metabolism, glutathione metabolism, and aminoacyl-tRNA biosynthesis. However, Arginine biosynthesis, pyrimidine metabolism, aminoacyl-tRNA biosynthesis, and alanine, aspartate, and glutamate metabolism were altered between the DBX and DB groups. ConclusionThese results suggest that eight weeks of HIIT could reverse metabolic changes induced by T2D in rat muscles, contributing to reduced FBG and HOMA-IR levels.

Differential Mitochondrial Adaptation of the Slow and Fast Skeletal Muscles by Endurance Running Exercise in Streptozotocin-Induced Diabetic Mice.

The skeletal muscle is the main organ responsible for insulin action, and glucose disposal and metabolism. Endurance and/or resistance training raises the number of mitochondria in diabetic muscles. The details of these adaptations, including mitochondrial adaptations of the slow and fast muscles in diabetes, are unclear. This study aimed to determine whether exercise training in streptozotocin (STZ)-induced mice leads to differential adaptations in the slow and fast muscles, and improving glucose clearance. Eight-week-old mice were randomly distributed into normal control (CON), diabetes (DM), and diabetes and exercise (DM+Ex) groups. In the DM and DM+Ex groups, mice received a freshly prepared STZ (100 mg/kg) intraperitoneal injection on two consecutive days. Two weeks after the injection, the mice in the groups ran on a treadmill for 60 min at 20 m/min for a week and subsequently at 25 m/min for 5 weeks (5 days/week). The analyses indicated that running training at low speed (25 m/min) enhanced mitochondrial enzyme activity and expression of lactate and glucose transporters in the plantaris (low-oxidative) muscle that improved whole-body glucose metabolism in STZ-induced diabetic mice. There were no differences in glucose transporter expression levels in the soleus (high-oxidative) muscle. The endurance running exercise at 20-25 m/min was sufficient to induce mitochondrial adaptation in the low-oxidative muscles, but not in the high-oxidative muscles, of diabetic mice. In conclusion, the present study indicated that running training at 25 m/min improved glucose metabolism by increasing the mitochondrial enzyme activity and glucose transporter 4 and monocarboxylate transporter 4 protein contents in the low-oxidative muscles in STZ-induced diabetic mice.

Hypoglycemic Action of Glycocar on Insulin and Glucose Metabolism In Vivo

Background: Diabetes mellitus, particularly type 2, presents a growing global health challenge, with an estimated 700 million people expected to be affected by 2045. The disease is characterized by insulin resistance and impaired insulin secretion, necessitating effective treatments. This study aimed to explore the hypoglycemic mechanisms of Glykokar, a herbal formulation, in rats with alloxan-induced diabetes. The objective of this study was to investigate the hypoglycemic mechanisms of Glykokar, a herbal formulation. Methods: Eighteen rats with alloxan-induced diabetes were divided into groups receiving Glykokar at doses of 50 mg/kg or 100 mg/kg, and a control group receiving saline. The study measured the effects of Glykokar on C-peptide levels, glycogen content in liver and muscle, and the activity of hexokinase and phosphorylase enzymes over 7 and 14 days. Results: Results demonstrated that Glykokar significantly increased C-peptide levels, with the 100 mg/kg dose showing the greatest effect, enhancing C-peptide by 87.5% on day 14 compared to controls. Glycogen content in liver and muscle tissues was also elevated, particularly at the 100 mg/kg dose, which increased liver glycogen by 86% and muscle glycogen by 50%. Enzyme activity studies revealed that Glykokar reduced phosphorylase activity in diabetic muscle tissue and significantly boosted hexokinase and glucokinase activities, with the highest effects seen at the 100 mg/kg dose. Conclusion: The findings suggest that Glykokar’s hypoglycemic action is mediated through enhanced glucose metabolism in tissues, driven by increased enzymatic activity and glycogen storage. This study provides evidence for the potential of Glykokar as a therapeutic agent in managing hyperglycemia by improving glucose utilization and insulin secretion.

1604-P: Lrrc2 Preserves Mitochondrial ATP Production in Diabetic Muscle and Promotes Adaptations to Exercise

1604-P: Lrrc2 Preserves Mitochondrial ATP Production in Diabetic Muscle and Promotes Adaptations to Exercise

Transcapillary PO2 Gradients in Contracting Muscles of Type I Diabetic Rats.

This study aimed to clarify the effect of Type I diabetes (DIA) on transcapillary PO2 gradients, which are oxygen-driving factors between the blood and the interstitium, in the contracting muscle of rats. Wistar male rats were divided into the diabetic (streptozocin i.p.) and sham groups. Microvascular and interstitial PO2 were measured in the extensor digitorum longus muscle during electrical stimulation-induced muscle contraction, using the phosphorescence quenching method. Transcapillary PO2 gradient, ΔPO2, was calculated as microvascular minus interstitial PO2. Resting microvascular PO2 was higher in the diabetic group than in the sham group (6.3 ± 1.7 vs. 4.7 ± 0.9 mmHg, p < 0.05) and remained for 180 s. Interstitial PO2 from rest to muscle contraction did not differ between the groups. The ΔPO2 was higher in the diabetic group than in the sham group at rest and during muscle contraction (4.03 ± 1.42 vs. 2.46 ± 0.90 mmHg at rest; 3.67 ± 1.51 vs. 2.22 ± 0.65 mmHg during muscle contraction, p < 0.05). Marked muscle atrophy was observed in the diabetic group. DIA increased microvascular and transcapillary PO2 gradients in the skeletal muscle. The enhanced PO2 gradients were maintained from rest to muscle contraction in diabetic muscle.

Abstract 3028: Diabetic Complication Ischemia Triggers Muscle Mass And Muscle Weight Loss By Reducing Mesenchymal Progenitor Cells Population Proliferation

Introduction: Mesenchymal progenitor cells (MPCs), such as myoblasts and fibroadipogenic progenitors (FAPs), and their communications with each other and with immune and vascular cells are responsible for muscle maintenance and regeneration. We hypothesize that in diabetes, loss of muscle mass after induction of hind limb ischemia is mediated by reduction in myoblast proliferation, thereby impairing muscle regeneration. Methods: Ischemic injury was induced in male diabetic (Akita) and littermate Wild Type (WT) mice via unilateral femoral artery ligation (FAL). Gastrocnemius muscle was collected at baseline, 3 and 7 days after surgery for single-cell RNA sequencing (scRNA seq). We identified the different cell populations in clusters, determined differentially-expressed genes, utilized Reactome Pathway Analysis and analyzed the cell cycle progression status and cell-cell interactions. Results: scRNA seq analysis of diabetic mice muscle, but not WT muscle, showed a reduction in MPCs, myoblasts and fibroadipogenic progenitors (FAPs) at 3 days post-FAL vs. baseline. FAPs were identified as two distinct subclusters; FAPs/Lum+ (associated with cell cycle regulation) and FAPs/Prg4+ (associated with extracellular matrix remodeling). We observed a lack of pathways involved in cell cycle progression in myoblasts at 3 days post- FAL in diabetic vs. WT muscle. At day 7 post-FAL, we observed an increased number of cell cycle pathways vs. day 3 post-FAL in diabetic muscle, implying a delayed response in the myoblasts. Cell cycle progression analysis revealed fewer diabetic myoblasts in S/G2M phase, with lower expression of proliferation markers (Mki67, Top2a, Mcm6 and Pcna), but no significant differences were observed in FAP/Lum+ cells. Cell-cell interaction analysis at day 3 post-FAL revealed fewer FAP-myoblast interactions in diabetic muscle, while interactions between either FAPs/myoblasts and myeloid cells were higher. Conclusion: These findings suggest that understanding the network of inter-cellular communications among MPCs, immune and vascular cells, and their roles in reduced myoblast proliferation after ischemia, is critical to identify new therapies to stimulate regeneration in diabetes and peripheral vascular disease.

Muscle Fiber Heterogeneity of Insulin Sensitivity in Syntaxin-4 Enriched Skeletal Muscle

Skeletal muscle insulin resistance (IR) is a primary cause for prediabetes, an intermediary condition of higher-than-normal blood glucose levels that left untreated progresses into type 2 diabetes (T2D). A number of contributing factors associated with skeletal muscle IR include aberrant mitochondrial function, elevated reactive oxygen species, inflammation, and reduction in oxidative slow-twitch type 1 skeletal muscle fibers. One leading candidate for reversing skeletal muscle IR is Syntaxin 4 (STX4), traditionally a cell surface transmembrane SNARE protein for GLUT4 vesicle exocytosis that our lab has recently discovered is also localized in the skeletal muscle outer mitochondrial membrane. Importantly, we previously demonstrated that doxycycline-induced skeletal muscle specific STX4 overexpression in obese, prediabetes male transgenic mice (skmSTX4-iOE) reversed IR and mitochondrial dysfunction associated with diabetes muscle. However, the precise mechanisms of how STX4 restores skeletal muscle insulin sensitivity remains to be determined. To test glucose uptake and insulin sensitivity we used the “gold standard” method of hyper-insulinemic-euglycemic clamp in chow-fed skmSTX4-iOE STX4 enriched mice against non-induced controls, we identified improved glucose clearance was only associated with increased insulin sensitivity in type 1 fiber rich soleus muscle. On the other hand, insulin tolerance test studies in doxycycline-induced skeletal muscle STX4 knockout (skmSTX4-iKO) male mice revealed the opposite phenotype, suggesting that STX4 activity in slow-twitch skeletal muscle may be a contributing factor for the reversal of IR. To determine the heterogeneity of STX4 activity between different skeletal muscle fibers, myogenic precursors and intercalating non-muscular tissue in skeletal muscle STX4 enriched skmSTX4-iOE mice, we aim to use our established single nuclear RNA-Sequencing platform (snRNA-Seq) to identify pathways in distinct fiber types associated with STX4 enrichment. Overall, our work aims to determine the functional requirements of STX4 in slow-and-fast twitch skeletal muscle fiber types and identify novel molecular pathways that may serve as useful targets for the reversal/protection against skeletal muscle IR in prediabetes and T2D. This study was supported by grants from the National Institutes of Health (DK067912, DK1129712 and DK102233) and City of Hope Shared Resources Pilot Grant. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Characteristics of Far-Infrared Ray Emitted from Functional Loess Bio-Balls and Its Effect on Improving Blood Flow.

XRD diffraction and IR absorption were investigated for raw loess powder and heat-treated loess powder. Raw loess retains its useful minerals, but loses their beneficial properties when calcined at 850 °C and 1050 °C. To utilize the useful minerals, loess balls were made using a low-temperature wet-drying method. The radiant energy and transmittance were measured for the loess balls. Far-infrared ray (FIR) emitted from loess bio-balls is selectively absorbed as higher vibrational energy by water molecules. FIR can raise the body's core temperature, thereby improving blood flow through the body's thermoregulatory mechanism. In an exploratory study with 40 participants, when the set temperature of the loess ball mat was increased from 25 °C to 50 °C, blood flow increased by 39.01%, from 37.48 mL/min to 52.11 mL/min, in the left middle finger; in addition, it increased by 39.62%, from 37.15 mL/min to 51.87 mL/min, in the right middle finger. The FIR emitted from loess balls can be widely applied, in various forms, to diseases related to blood flow, such as cold hands and feet, diabetic foot, muscle pain, and menstrual pain.

Diabetes in spotlight: current knowledge and perspectives of photobiomodulation utilization.

Diabetes is a global health concern characterized by chronic hyperglycemia resulting from insulinopenia and/or insulin resistance. The rising prevalence of diabetes and its associated complications (ulcers, periodontitis, healing of bone defect, neuropathy, retinopathy, cardiopathy and nephropathy) necessitate innovative therapeutic approaches. Photobiomodulation (PBM), involves exposing tissues and cells to low-energy light radiation, leading to biological effects, largely via mitochondrial activation. This review evaluates preclinical and clinical studies exploring the potential of PBM in diabetes and its complications, as well all clinical trials, both planned and completed, available on ClinicalTrials database. This review highlights the variability in PBM parameters across studies, hindering consensus on optimal protocols. Standardization of treatment parameters and rigorous clinical trials are needed to unlock PBM's full therapeutic potential. 87 clinical trials were identified that investigated PBM in diabetes mellitus (with 5,837 patients planned to be treated with PBM). Clinical trials assessing PBM effects on diabetic neuropathy revealed pain reduction and potential quality of life improvement. Studies focusing on wound healing indicated encouraging results, with PBM enhancing angiogenesis, fibroblast proliferation, and collagen density. PBM's impact on diabetic retinopathy remains inconclusive however, requiring further investigation. In glycemic control, PBM exhibits positive effects on metabolic parameters, including glucose tolerance and insulin resistance. Clinical studies have reported PBM-induced reductions in fasting and postprandial glycemia without an increased hypoglycemic risk. This impact of PBM may be related to its effects on the beta cells and islets in the pancreas. Notwithstanding challenges, PBM emerges as a promising adjunctive therapy for managing diabetic neuropathy, wound healing, and glycemic control. Further investigation into its impact on diabetic retinopathy and muscle recovery is warranted.

MCC950 Ameliorates Diabetic Muscle Atrophy in Mice by Inhibition of Pyroptosis and Its Synergistic Effect with Aerobic Exercise.

Diabetic muscle atrophy is an inflammation-related complication of type-2 diabetes mellitus (T2DM). Even though regular exercise prevents further deterioration of atrophic status, there is no effective mediator available for treatment and the underlying cellular mechanisms are less explored. In this study, we investigated the therapeutic potential of MCC950, a specific, small-molecule inhibitor of NLRP3, to treat pyroptosis and diabetic muscle atrophy in mice. Furthermore, we used MCC950 to intervene in the protective effects of aerobic exercise against muscle atrophy in diabetic mice. Blood and gastrocnemius muscle (GAS) samples were collected after 12 weeks of intervention and the atrophic state was assessed. We initially corroborated a diabetic muscle atrophy phenotype in db/db mice (D) by comparison with control m/m mice (W) by examining parameters such as fasting blood glucose (D vs. W: 24.47 ± 0.45 mmol L-1 vs. 4.26 ± 0.6 mmol L-1, p < 0.05), grip strength (D vs. W: 166.87 ± 15.19 g vs. 191.76 ± 14.13 g, p < 0.05), exercise time (D vs. W: 1082.38 ± 104.67 s vs. 1716 ± 168.55 s, p < 0.05) and exercise speed to exhaustion (D vs. W: 24.25 ± 2.12 m min-1 vs. 34.75 ± 2.66 m min-1, p < 0.05), GAS wet weight (D vs. W: 0.07 ± 0.01 g vs. 0.13 ± 0.01 g, p < 0.05), the ratio of GAS wet weight to body weight (D vs. W: 0.18 ± 0.01% vs. 0.54 ± 0.02%, p < 0.05), and muscle fiber cross-sectional area (FCSA) (D vs. W: 1875 ± 368.19 µm2 vs. 2747.83 ± 406.44 µm2, p < 0.05). We found that both MCC950 (10 mg kg-1) treatment and exercise improved the atrophic parameters that had deteriorated in the db/db mice, inhibited serum inflammatory markers and significantly attenuated pyroptosis in atrophic GAS. In addition, a combined MCC950 treatment with exercise (DEI) exhibited a further improvement in glucose uptake capacity and muscle performance. This combined treatment also improved the FCSA of GAS muscle indicated by Laminin immunofluorescence compared to the group with the inhibitor treatment alone (DI) (DEI vs. DI: 2597 ± 310.97 vs. 1974.67 ± 326.15 µm2, p < 0.05) or exercise only (DE) (DEI vs. DE: 2597 ± 310.97 vs. 2006.33 ± 263.468 µm2, p < 0.05). Intriguingly, the combination of MCC950 treatment and exercise significantly reduced NLRP3-mediated inflammatory factors such as cleaved-Caspase-1, GSDMD-N and prevented apoptosis and pyroptosis in atrophic GAS. These findings for the first time demonstrate that targeting NLRP3-mediated pyroptosis with MCC950 improves diabetic muscle homeostasis and muscle function. We also report that inhibiting pyroptosis by MCC950 can enhance the beneficial effects of aerobic exercise on diabetic muscle atrophy. Since T2DM and muscle atrophy are age-related diseases, the young mice used in the current study do not seem to fully reflect the characteristics of diabetic muscle atrophy. Considering the fragile nature of db/db mice and for the complete implementation of the exercise intervention, we used relatively young db/db mice and the atrophic state in the mice was thoroughly confirmed. Taken together, the current study comprehensively investigated the therapeutic effect of NLRP3-mediated pyroptosis inhibited by MCC950 on diabetic muscle mass, strength and exercise performance, as well as the synergistic effects of MCC950 and exercise intervention, therefore providing a novel strategy for the treatment of the disease.