Compromised glycolysis contributes to foot process fusion of podocytes in diabetic kidney disease: Role of ornithine catabolism

Urinary podocyte markers in diabetic kidney disease

Podocytes are involved in maintaining kidney function and are a major focus of research on diabetic kidney disease (DKD). Urinary biomarkers derived from podocyte fragments and molecules have been proposed for the diagnosis and monitoring of DKD. Various methods have been used to detect intact podocytes and podocyte-derived microvesicles in urine, including centrifugation, visualization, and molecular quantification. Quantification of podocyte-specific protein targets and messenger RNA levels can be performed by Western blotting or enzyme-linked immunosorbent assay and quantitative polymerase chain reaction, respectively. At present, many of these techniques are expensive and labor-intensive, all limiting their widespread use in routine clinical tests. While the potential of urinary podocyte markers for monitoring and risk stratification of DKD has been explored, systematic studies and external validation are lacking in the current literature. Standardization and automation of laboratory methods should be a priority for future research, and the added value of these methods to routine clinical tests should be defined.

Baicalin ameliorates renal fibrosis by upregulating CPT1α-mediated fatty acid oxidation in diabetic kidney disease

BACKGROUND

Diabetic kidney disease (DKD) is a leading cause of end-stage renal disease (ESRD). The progression of DKD is often marked by heightened renal fibrosis due to hindered fatty acid oxidation within renal tubules. Baicalin (BA), a naturally derived compound, has exhibited the potential to mitigate the advancement of DKD. Delving deeper into the precise targets and mechanisms of BA's effect on DKD is crucial.

PURPOSE

This study sought to elucidate the specific mechanism through which BA moderates the progression of DKD.

METHODS

Renal tubular tissues from diabetic (db/db) and control (db/m) mice were subjected to mRNA sequencing to discern BA's influence on DKD. Immunohistochemical staining and Western blot were employed to assess the expression of CPT1α in DKD patients and db/db and db/m mice administered with either BA (50 mg/kg/day) or a vehicle for 12 weeks. In vitro, human proximal renal tubule cells (HK-2) were treated with 40 mM high glucose or 50 μM BA. The potential inhibitory mechanism of BA on renal fibrosis in DKD was evaluated using Oil Red O staining and oxygen consumption rate (OCR) measurements.

RESULTS

The results demonstrated that BA notably reduced lipid accumulation and renal fibrosis in db/db mice. Moreover, mRNA sequencing pinpointed a significant downregulation of CPT1α in DKD. In vitro assays revealed that both the overexpression of CPT1α and treatment with BA exerted similar influences on mitochondrial respiration, fatty acid oxidation, and renal fibrosis levels. Given the pronounced downregulation of CPT1α in DKD patients and its substantial correlation with clinical indicators, it was evident that CPT1α could serve as a therapeutic target for BA in addressing DKD.

CONCLUSION

Our findings demonstrated that BA potentially enhances FAO by augmenting the expression of CPT1α, subsequently diminishing renal fibrosis in DKD. As such, CPT1α emerges as a promising therapeutic target for DKD intervention.

Upregulation of FAM83F by c-Myc promotes cervical cancer growth and aerobic glycolysis via Wnt/β-catenin signaling activation

Cervical cancer (CC) seriously affects women's health. Therefore, elucidation of the exact mechanisms and identification of novel therapeutic targets are urgently needed. In this study, we identified FAM83F, which was highly expressed in CC cells and tissues, as a potential target. Our clinical data revealed that FAM83F protein expression was markedly elevated in CC tissues and was positively correlated with poor prognosis. Moreover, we observed that FAM83F knockdown significantly inhibited cell proliferation, induced apoptosis, and suppressed glycolysis in CC cells, while its overexpression displayed opposite effects. Mechanistically, FAM83F regulated CC cell growth and glycolysis by the modulation of Wnt/β-catenin pathway. The enhancing effects of FAM83F overexpression on CC cell proliferation and glycolysis could be impaired by the Wnt/β-catenin inhibitor XAV939. Moreover, we found that c-Myc bound to the FAM83F promoter and activated the transcription of FAM83F. Notably, knockdown of FAM83F impaired the enhancement of cell proliferation and glycolysis induced by ectopic c-Myc. Consistent with in vitro findings, results from a xenograft mouse model confirmed the promoting role of FAM83F. In summary, our study demonstrated that FAM83F promoted CC growth and glycolysis through regulating the Wnt/β-catenin pathway, suggesting that FAM83F may be a potential molecular target for CC treatment. Schematic summary of c-Myc-activated FAM83F transcription to promote cervical cancer growth and glycolysis by targeting the Wnt/β-catenin signal pathway.

LRH-1 activation alleviates diabetes-induced podocyte injury by promoting GLS2-mediated glutaminolysis

Alteration of metabolic phenotype in podocytes directly contributes to the development of albuminuria and renal injury in conditions of diabetic kidney disease (DKD). This study aimed to identify and evaluate liver receptor homologue-1 (LRH-1) as a possible therapeutic target that alleviates glutamine (Gln) metabolism disorders and mitigates podocyte injury in DKD. Metabolomic and transcriptomic analyses were performed to characterize amino acid metabolism changes in the glomeruli of diabetic mice. Next, Western blotting, immunohistochemistry assays, and immunofluorescence staining were used to detect the expression of different genes in vitro and in vivo. Furthermore, Gln and glutamate (Glu) content as well as ATP generation were examined. A decrease in LRH-1 and glutaminase 2 (GLS2) expression was detected in diabetic podocytes. Conversely, the administration of LRH-1 agonist (DLPC) upregulated the expression of GLS2 and promoted glutaminolysis, with an improvement in mitochondrial dysfunction and less apoptosis in podocytes compared to those in vehicle-treated db/db mice. Our study indicates the essential role of LRH-1 in governing the Gln metabolism of podocytes, targeting LRH-1 could restore podocytes from diabetes-induced disturbed glutaminolysis in mitochondria.

Active role of amino acid metabolism in early diagnosis and treatment of diabetic kidney disease

Diabetic Kidney Disease (DKD) is one of the significant microvascular consequences of type 2 diabetes mellitus with a complex etiology and protracted course. In the early stages of DKD, the majority of patients experience an insidious onset and few overt clinical symptoms and indicators, but they are prone to develop end-stage renal disease in the later stage, which is life-threatening. The abnormal amino acid metabolism is tightly associated with the development of DKD, which involves several pathological processes such as oxidative stress, inflammatory response, and immune response and is also closely related to autophagy, mitochondrial dysfunction, and iron death. With a focus on taurine, branched-chain amino acids (BCAAs) and glutamine, we explored the biological effects of various amino acid mechanisms linked to DKD, the impact of amino acid metabolism in the early diagnosis of DKD, and the role of amino acid metabolism in treating DKD, to offer fresh objectives and guidelines for later early detection and DKD therapy.

The PI3K-Akt-mTOR pathway mediates renal pericyte-myofibroblast transition by enhancing glycolysis through HKII

BACKGROUND

Pericyte-myofibroblast transition (PMT) has been confirmed to contribute to renal fibrosis in several kidney diseases, and transforming growth factor-β1 (TGF-β1) is a well-known cytokine that drives PMT. However, the underlying mechanism has not been fully established, and little is known about the associated metabolic changes.

METHODS

Bioinformatics analysis was used to identify transcriptomic changes during PMT. PDGFRβ + pericytes were isolated using MACS, and an in vitro model of PMT was induced by 5 ng/ml TGF-β1. Metabolites were analyzed by ultraperformance liquid chromatography (UPLC) and tandem mass spectrometry (MS). 2-Deoxyglucose (2-DG) was used to inhibit glycolysis via its actions on hexokinase (HK). The hexokinase II (HKII) plasmid was transfected into pericytes for HKII overexpression. LY294002 or rapamycin was used to inhibit the PI3K-Akt-mTOR pathway for mechanistic exploration.

RESULTS

An increase in carbon metabolism during PMT was detected through bioinformatics and metabolomics analysis. We first detected increased levels of glycolysis and HKII expression in pericytes after stimulation with TGF-β1 for 48 h, accompanied by increased expression of α-SMA, vimentin and desmin. Transdifferentiation was blunted when pericytes were pretreated with 2-DG, an inhibitor of glycolysis. The phosphorylation levels of PI3K, Akt and mTOR were elevated during PMT, and after inhibition of the PI3K-Akt-mTOR pathway with LY294002 or rapamycin, glycolysis in the TGF-β1-treated pericytes was decreased. Moreover, PMT and HKII transcription and activity were blunted, but the plasmid-mediated overexpression of HKII rescued PMT inhibition.

CONCLUSIONS

The expression and activity of HKII as well as the level of glycolysis were increased during PMT. Moreover, the PI3K-Akt-mTOR pathway regulates PMT by increasing glycolysis through HKII regulation.

Single-cell transcriptomics: A new tool for studying diabetic kidney disease

The kidney is a complex organ comprising various functional partitions and special cell types that play important roles in maintaining homeostasis in the body. Diabetic kidney disease (DKD) is the leading cause of end-stage renal disease and is an independent risk factor for cardiovascular diseases. Owing to the complexity and heterogeneity of kidney structure and function, the mechanism of DKD development has not been fully elucidated. Single-cell sequencing, including transcriptomics, epigenetics, metabolomics, and proteomics etc., is a powerful technology that enables the analysis of specific cell types and states, specifically expressed genes or pathways, cell differentiation trajectories, intercellular communication, and regulation or co-expression of genes in various diseases. Compared with other omics, RNA sequencing is a more developed technique with higher utilization of tissues or samples. This article reviewed the application of single-cell transcriptomics in the field of DKD and highlighted the key signaling pathways in specific tissues or cell types involved in the occurrence and development of DKD. The comprehensive understanding of single-cell transcriptomics through single-cell RNA-seq and single-nucleus RNA-seq will provide us new insights into the pathogenesis and treatment strategy of various diseases including DKD.

NLRP3-mediated pyroptosis in diabetic nephropathy

Diabetic nephropathy (DN) is the main cause of end-stage renal disease (ESRD), which is characterized by a series of abnormal changes such as glomerulosclerosis, podocyte loss, renal tubular atrophy and excessive deposition of extracellular matrix. Simultaneously, the occurrence of inflammatory reaction can promote the aggravation of DN-induced kidney injury. The most important processes in the canonical inflammasome pathway are inflammasome activation and membrane pore formation mediated by gasdermin family. Converging studies shows that pyroptosis can occur in renal intrinsic cells and participate in the development of DN, and its activation mechanism involves a variety of signaling pathways. Meanwhile, the activation of the NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome can not only lead to the occurrence of inflammatory response, but also induce pyroptosis. In addition, a number of drugs targeting pyroptosis-associated proteins have been shown to have potential for treating DN. Consequently, the pathogenesis of pyroptosis and several possible activation pathways of NLRP3 inflammasome were reviewed, and the potential drugs used to treat pyroptosis in DN were summarized in this review. Although relevant studies are still not thorough and comprehensive, these findings still have certain reference value for the understanding, treatment and prognosis of DN.