The Role of PKM2 in Diabetic Microangiopathy

The PKM2 activator TEPP-46 suppresses cellular senescence in hydrogen peroxide-induced proximal tubular cells and kidney fibrosis in CD-1db/db mice

AIM/INTRODUCTION

Senescence is a key driver of age-related kidney dysfunction, including diabetic kidney disease. Oxidative stress activates cellular senescence, induces abnormal glycolysis, and is associated with pyruvate kinase muscle isoform 2 (PKM2) dysfunction; however, the mechanisms linking PK activation to cellular senescence have not been elucidated. We hypothesized that PKM2 activation by TEPP-46 could suppress oxidative stress-induced renal tubular cell injury and cellular senescence.

MATERIALS AND METHODS

To investigate the effects of PKM2 activation on oxidative stress-induced cellular senescence, we conducted β-galactosidase staining and western blot analysis on human primary renal tubular cells (pRPTECs) treated with hydrogen peroxide with or without TEPP-46. IL-6 levels and glycolytic flux were measured. Cell viability and apoptosis were assessed via the MTS assay and caspase 3 cleavage. For in vivo experiments, we utilized CD-1db/db mice, a fibrotic type 2 diabetes model, which exhibit kidney fibrosis. After 4 weeks of TEPP-46 intervention, kidney fibrosis and the expression of senescence markers were analyzed.

RESULTS

In pRPTECs, hydrogen peroxide increased the number of β-galactosidase-positive cells, the expression of senescence markers (p16, p21, p53), and p38 phosphorylation; co-incubation with TEPP-46 suppressed these alterations. Hydrogen peroxide reduced cell viability, induced apoptosis, mesenchymal alterations, and increased lactate production and IL-6 secretion; co-incubation with TEPP-46 or a p38 inhibitor mitigated these effects. In CD-1db/db mice, TEPP-46 intervention suppressed apoptosis, fibrosis, and tended to reduce the levels of senescence-associated molecules in the kidney.

CONCLUSIONS

PKM2 activation could be a molecular target for protection against senescence-associated organ damage, including diabetic kidney disease.

Diabetic microenvironment deteriorates the regenerative capacities of adipose mesenchymal stromal cells

BACKGROUND

Type 2 diabetes is an endocrine disorder characterized by compromised insulin sensitivity that eventually leads to overt disease. Adipose stem cells (ASCs) showed promising potency in improving type 2 diabetes and its complications through their immunomodulatory and differentiation capabilities. However, the hyperglycaemia of the diabetic microenvironment may exert a detrimental effect on the functionality of ASCs. Herein, we investigate ASC homeostasis and regenerative potential in the diabetic milieu.

METHODS

We conducted data collection and functional enrichment analysis to investigate the differential gene expression profile of MSCs in the diabetic microenvironment. Next, ASCs were cultured in a medium containing diabetic serum (DS) or normal non-diabetic serum (NS) for six days and one-month periods. Proteomic analysis was carried out, and ASCs were then evaluated for apoptosis, changes in the expression of surface markers and DNA repair genes, intracellular oxidative stress, and differentiation capacity. The crosstalk between the ASCs and the diabetic microenvironment was determined by the expression of pro and anti-inflammatory cytokines and cytokine receptors.

RESULTS

The enrichment of MSCs differentially expressed genes in diabetes points to an alteration in oxidative stress regulating pathways in MSCs. Next, proteomic analysis of ASCs in DS revealed differentially expressed proteins that are related to enhanced cellular apoptosis, DNA damage and oxidative stress, altered immunomodulatory and differentiation potential. Our experiments confirmed these data and showed that ASCs cultured in DS suffered apoptosis, intracellular oxidative stress, and defective DNA repair. Under diabetic conditions, ASCs also showed compromised osteogenic, adipogenic, and angiogenic differentiation capacities. Both pro- and anti-inflammatory cytokine expression were significantly altered by culture of ASCs in DS denoting defective immunomodulatory potential. Interestingly, ASCs showed induction of antioxidative stress genes and proteins such as SIRT1, TERF1, Clusterin and PKM2.

CONCLUSION

We propose that this deterioration in the regenerative function of ASCs is partially mediated by the induced oxidative stress and the diabetic inflammatory milieu. The induction of antioxidative stress factors in ASCs may indicate an adaptation mechanism to the increased oxidative stress in the diabetic microenvironment.

Exploring the diverse role of pyruvate kinase M2 in cancer: Navigating beyond glycolysis and the Warburg effect

Pyruvate Kinase M2, a key enzyme in glycolysis, has garnered significant attention in cancer research due to its pivotal role in the metabolic reprogramming of cancer cells. Originally identified for its association with the Warburg effect, PKM2 has emerged as a multifaceted player in cancer biology. The functioning of PKM2 is intricately regulated at multiple levels, including controlling the gene expression via various transcription factors and non-coding RNAs, as well as adding post-translational modifications that confer distinct functions to the protein. Here, we explore the diverse functions of PKM2, encompassing newly emerging roles in non-glycolytic metabolic regulation, immunomodulation, inflammation, DNA repair and mRNA processing, beyond its canonical role in glycolysis. The ever-expanding list of its functions has recently grown to include roles in subcellular compartments such as the mitochondria and extracellular milieu as well, all of which make PKM2 an attractive drug target in the pursuit of therapeutics for cancer.

Low-level laser therapy alleviates periodontal age-related inflammation in diabetic mice via the GLUT1/mTOR pathway

Diabetes mellitus (DM) is a chronic age-related disease that was recently found as a secondary aging pattern regulated by the senescence associated secretory phenotype (SASP). The purpose of this study is to detect the potential efficacy and the specific mechanisms of low-level laser therapy (LLLT) healing of age-related inflammation (known as inflammaging) in diabetic periodontitis. Diabetic periodontitis (DP) mice were established by intraperitoneal streptozotocin (STZ) injection and oral P. gingivalis inoculation. Low-level laser irradiation (810 nm, 0.1 W, 398 mW/cm2, 4 J/cm2, 10 s) was applied locally around the periodontal lesions every 3 days for 2 consecutive weeks. Micro-CT and hematoxylin-eosin (HE) stain was analyzed for periodontal soft tissue and alveolar bone. Western blots, immunohistochemistry, and immunofluorescence staining were used to evaluate the protein expression changes on SASP and GLUT1/mTOR pathway. The expression of aging-related factors and SASP including tumor necrosis factor-α, interleukin (IL)-1β, and IL-6 were reduced in periodontal tissue of diabetic mice. The inhibitory effect of LLLT on GLUT1/mTOR pathway was observed by detecting the related factors mTOR, p-mTOR, GLUT1, and PKM2. COX, an intracytoplasmic photoreceptor, is a key component of the anti-inflammatory effects of LLLT. After LLLT treatment a significant increase in COX was observed in macrophages in the periodontal lesion. Our findings suggest that LLLT may regulate chronic low-grade inflammation by modulating the GLUT1/mTOR senescence-related pathway, thereby offering a potential treatment for diabetic periodontal diseases.

Inhibition of Pyruvate kinase M2 (PKM2) by shikonin attenuates isoproterenol-induced acute myocardial infarction via reduction in inflammation, hypoxia, apoptosis, and fibrosis

Myocardial infarction (MI) is a major cause of mortality and disability globally. MI results from acute or chronic myocardial ischemia characterized by an imbalance of oxygen demand and supply, leading to irreversible myocardial injury. Despite several significant efforts in the understanding of MI, the therapy of MI is not satisfactory due to its complicated pathophysiology. Recently, therapeutic potential of targeting pyruvate kinase M2 (PKM2) has been postulated in several cardiovascular diseases. PKM2 gene knockout and expression studies implicated the role of PKM2 in MI. However, the effects of pharmacological interventions targeting PKM2 have not been investigated in MI. Therefore, in the present study, effect of PKM2 inhibitor has been investigated in the MI along with elucidation of possible mechanism(s). MI in rats was induced by administrations of isoproterenol (ISO) at a dose of 100 mg/kg s.c. for two consecutives days at 24-h interval. At the same time, shikonin (PKM2 inhibitor) was administered at 2 and 4 mg/kg in ISO-induced MI rats. After the shikonin treatment, the ventricular functions were measured using a PV-loop system. Plasma MI injury markers, cardiac histology, and immunoblotting were performed to elucidate the molecular mechanism. Treatment of shikonin 2 and 4 mg/kg ameliorated cardiac injury, reduced infarct size, biochemical alterations, ventricular dysfunction, and cardiac fibrosis in ISO-induced MI. Expression of PKM2 in the ventricle was reduced while PKM1 expression increased in the shikonin treated group, indicating PKM2 inhibition restores PKM1 expression. In addition, PKM splicing protein (hnRNPA2B1 & PTBP1), HIF-1α, and caspase-3 expression were reduced after shikonin treatment. Our findings suggest that pharmacological inhibition of PKM2 with shikonin could be a potential therapeutic strategy to treat MI.

Serum Lipoprotein(a) and High-Density Lipoprotein Cholesterol Associate with Diabetic Nephropathy: Evidence from Machine Learning Perspectives

Purpose

Diabetic nephropathy (DN) is a common complication of type 2 diabetes mellitus (T2DM) that significantly impacts the quality of life for affected patients. Dyslipidemia is a known risk factor for developing cardiovascular complications in T2DM patients. However, the association between serum lipoprotein(a) (Lp(a)) and high-density lipoprotein cholesterol (HDL-C) with DN requires further investigation.

Patients and Methods

For this cross-sectional study, we randomly selected T2DM patients with nephropathy (DN, n = 211) and T2DM patients without nephropathy (T2DM, n = 217) from a cohort of 142,611 patients based on predefined inclusion and exclusion criteria. We collected clinical data from the patients to identify potential risk factors for DN using binary logistic regression and machine learning. After obtaining the feature importance score of clinical indicators by building a random forest classifier, we examined the correlations between Lp(a), HDL-C and the top 10 indicators. Finally, we trained decision tree models with top 10 features using training data and evaluated their performance with independent testing data.

Results

Compared to the T2DM group, the DN group had significantly higher serum levels of Lp(a) (p < 0.001) and lower levels of HDL-C (p = 0.028). Lp(a) was identified as a risk factor for DN, while HDL-C was found to be protective. We identified the top 10 indicators that were associated with Lp(a) and/or HDL-C, including urinary albumin (uALB), uALB to creatinine ratio (uACR), cystatin C, creatinine, urinary ɑ1-microglobulin, estimated glomerular filtration rate (eGFR), urinary β2-microglobulin, urea nitrogen, superoxide dismutase and fibrinogen. The decision tree models trained using the top 10 features and with uALB at a cut-off value of 31.1 mg/L showed an average area under the receiver operating characteristic curve (AUC) of 0.874, with an AUC range of 0.870 to 0.890.

Conclusion

Our findings indicate that serum Lp(a) and HDL-C are associated with DN and we have provided a decision tree model with uALB as a predictor for DN.

A PKM2 inhibitor induces apoptosis and autophagy through JAK2 in human oral squamous cell carcinoma cells

The enzyme pyruvate kinase M2 (PKM2) is involved in glycolysis, which plays an important role in the regulation of tumor progression. In this study, we investigated the anti-tumor activity of N-(4-(3-(3-(methylamino)-3-oxopropyl)-5-(4'-(prop-2-yn-1-yloxy)-[1,1'-biphenyl]-4-yl)-1H-pyrazol-1-yl)phenyl)propiolamide (MTP), a PKM2 inhibitor, in oral squamous cell carcinoma (OSCC) cells. Our results showed that MTP inhibited cell growth with IC50 values of 0.59 μM and 0.78 μM in SCC2095 and HSC3 OSCC cells, respectively. MTP induced caspase-dependent apoptosis, which was associated with the modulation of PKM2 and oncogenic biomarkers epidermal growth factor receptor and β-catenin. In addition, MTP increased the generation of reactive oxygen species (ROS) and modulated the expression of autophagic gene products, including LC3B-II and p62. Western blotting showed that MTP inhibited Janus kinase 2 (JAK2) signaling, and JAK2 overexpression partially reversed MTP-mediated cytotoxicity. Taken together, these data indicate the potential use of MTP as a therapeutic agent for OSCC.

Pyruvate Kinase M2: A New Biomarker for the Early Detection of Diabetes-Induced Nephropathy

Diabetic nephropathy (DN) is a common complication of diabetes. DN progresses to end-stage renal disease, which has a high mortality rate. Current research is focused on identifying non-invasive potential biomarkers in the early stage of DN. We previously indicated that pyruvate kinase M2 (PKM2) is excreted in the urine of rats after cisplatin-induced acute kidney injury (AKI). However, it has not been reported whether PKM2 can be used as a biomarker to diagnose DN. Therefore, we try to compare whether the protein PKM2 can be detected in the urine samples from diabetic patients as shown in the results of DN models. In this study, high-fat diet (HFD)-induced Zucker diabetic fatty (ZDF) rats were used for DN phenotyping. After 19 weeks of receiving a HFD, the DN model's blood glucose, blood urea nitrogen, and serum creatinine levels were significantly increased; severe tubular and glomerular damages were also noted. The following protein-based biomarkers were increased in the urine of these models: kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), and PKM2. PKM2 had the earliest detection rate. In the urine samples of patients, PKM2 protein was highly detected in the urine of diabetic patients but was not excreted in the urine of normal subjects. Therefore, PKM2 was selected as the new biomarker for the early diagnosis of DN. Our results reflect current knowledge on the role of PKM2 in DN.