Differentiation of type 2 diabetes mellitus with different complications by proteomic analysis of plasma low abundance proteins

Exploring the interplay between adipokine-mediated celastrol target genes and T cells in diabetic nephropathy: a mendelian randomization-based causal inference

BACKGROUND

Diabetic nephropathy (DN) is influenced by dysregulated adipokines, which play a key role in inflammation, immune responses, and lipid metabolism. However, the precise molecular mechanisms linking adipokine dysregulation, immune cell infiltration, and metabolic reprogramming in DN remain poorly understood. Celastrol, a bioactive lipid regulator, has been shown to mitigate renal immune-inflammatory damage by inhibiting the PI3K/Akt/NF-κB signaling pathway. Yet, its specific impact on adipokine-mediated immune responses and lipid metabolism in DN is unclear. This study aims to elucidate the interplay between adipokine-mediated target genes in DN and investigate how celastrol modulates these interactions.

METHODS

Gene expression profiles of DN patients were obtained from GEO datasets (GSE30122 and GSE30528) and analyzed for differentially expressed genes (DEGs) using the limma package. Gene set variation analysis (GSVA) was conducted to assess lipid metabolism pathways, while Mendelian randomization (MR) and Pearson correlation evaluated the association between DEGs and adipokines. Immune cell infiltration was analyzed using the IOBR R package (MCP-counter and xCell methods), followed by MR analysis of DN-related immune responses. Celastrol target genes were identified using the SEA database.

RESULTS

A total of 70 intersecting DEGs were identified. GSVA revealed that brown and beige adipocyte differentiation pathways were downregulated, while adipocyte-related pathways were upregulated in DN (p < 0.05). MR analysis demonstrated that adiponectin was negatively associated with DN (OR = 0.77, P = 0.005), whereas leptin (OR = 1.92, P = 0.016) and resistin (OR = 1.43, P < 0.001) were positively associated. Three key genes, MAGI2, FGF9, and THBS2 were linked to DN risk and T cell infiltration. THBS2 was positively correlated with T cell infiltration (OR = 0.51, P = 6.7e-06), while FGF9 (OR = -0.8, P = 2.2e-16) and MAGI2 (OR = 0.75, P = 1.3e-13) were negatively correlated. 22 celastrol target genes, including MAGI2, FGF9, and THBS2, were identified.

CONCLUSION

Our findings reveal that celastrol modulates DN progression through adipokine-immune crosstalk, with FGF9, MAGI2, and THBS2 emerging as key regulatory genes. These insights provide new avenues for biomarker discovery and therapeutic implications in the development of DN.

Extracellular status of thrombospondin-2 in type 2 diabetes mellitus and utility as a biomarker in the determination of early diabetic kidney disease

OBJECTIVE

Thrombospondin-2 (TSP-2) is a multifunctional matricellular glycoprotein correlated with glucose homeostasis, insulin sensitivity, and estimated glomerular filtration rate. Investigation of the association of TSP-2 with type 2 diabetes mellitus (T2DM) and the potential diagnostic value of serum TSP-2 for detecting early diabetic kidney disease (DKD) is needed.

RESEARCH DESIGN AND METHODS

An enzyme-linked immunosorbent assay was used for detection serum TSP-2 levels in 494 Chinese T2DM subjects. The protein expression of TSP-2 in the kidney and other tissues were tested by western blotting.

RESULTS

Serum TSP-2 levels in T2DM subjects were significantly higher than in healthy individuals. Serum TSP-2 correlated positively with triglycerides, serum uric acid, creatinine, platelets, and urinary albumin-to-creatinine ratio (UACR), but negatively with estimated glomerular filtration rate, after adjusting for age, sex, and T2DM duration. Logistic regression analysis demonstrated an independent association between serum TSP-2 and early DKD. Furthermore, the high UACR identified at risk of early DKD increased significantly from 0.78 (95%CI 0.73-0.83) to 0.82 (95%CI 0.77-0.86, p < 0.001) when added to a clinical model consisting of TSP-2 and age. In db/db mice, serum TSP-2 levels were elevated. TSP-2 expression was markedly increased in the kidney tissue compared with that in db/m and m/m mice. Furthermore, serum TSP-2 expression correlated well with UACR in mice.

CONCLUSIONS

TSP-2 is a novel glycoprotein associated with early DKD in patients with T2DM. The paradoxical increase of serum TSP-2 in T2DM individuals may be due to a compensatory response to chronic inflammatory and renal vascular endothelial growth, warranting further investigation.

Circulating thrombospondin-2 level for identifying individuals with rapidly declining kidney function trajectory in type 2 diabetes: a prospective study of the Hong Kong West Diabetes Registry

BACKGROUND

Thrombospondin-2 (TSP2) is a matricellular protein with tissue expression induced by hyperglycaemia. TSP2 has been implicated in non-diabetic renal injury in preclinical studies and high circulating levels were associated with worse kidney function in cross-sectional clinical studies. Therefore, we investigated the prospective associations of circulating TSP2 level with kidney function decline and the trajectories of estimated glomerular filtration rate (eGFR) in type 2 diabetes.

METHODS

Baseline serum TSP2 level was measured in 5471 patients with type 2 diabetes to evaluate its association with incident eGFR decline, defined as ≥ 40% sustained eGFR decline, using multivariable Cox regression analysis. Among participants with relatively preserved kidney function (Baseline eGFR ≥ 60 ml/min/1.73m2), joint latent class modelling was employed to identify three different eGFR trajectories. Their associations with baseline serum TSP2 was evaluated using multinomial logistic regression analysis. The predictive performance of serum TSP2 level was examined using time-dependent c-statistics and calibration statistics.

RESULTS

Over a median follow-up of 8.8 years, 1083 patients (19.8%) developed eGFR decline. Baseline serum TSP2 level was independently associated with incident eGFR decline (HR 1.21, 95%CI 1.07-1.37, P = 0.002). With internal validation, incorporating serum TSP2 to a model of clinical risk factors including albuminuria led to significant improvement in c-statistics from 83.9 to 84.4 (P < 0.001). Among patients with eGFR ≥ 60 ml/min/1.73m2, baseline serum TSP2 level was independently associated with a rapidly declining eGFR trajectory (HR 1.63, 95%CI 1.26-2.10, P < 0.001).

CONCLUSION

Serum TSP2 level was independently associated with incident eGFR decline, particularly a rapidly declining trajectory, in type 2 diabetes.

MicroRNA 1228 Mediates the Viability of High Glucose-Cultured Renal Tubule Cells through Targeting Thrombospondin 2 and PI3K/AKT Signaling Pathway

AIM

The present study aimed to elucidate the potential function of microRNA 1228 (miR-1228) on the high glucose (HG)-damaged human renal proximal tubule cells (HK-2) and the underlying mechanism.

METHODS

The datasets GSE47185 and GSE51674 were downloaded from the Gene Expression Omnibus database for mining differently expressed mRNAs and miRNAs, respectively. Bioinformatics online tools were applied to predict the binding sites between miR-1228 and thrombospondin 2 (THBS2), which was confirmed by dual-luciferase assay. Real-time quantitative polymerase chain reaction was used to detect the mRNA level of miR-1228/THBS2. Western blot was used to detect the protein level of THBS2 and the PI3K/AKT signaling pathway-associated markers. HK-2 cells were cultured in HG (30 mM) to mimic hyperglycemia. Cell counting kit 8 and flow cytometry assays were utilized to determine the cell proliferation and apoptosis.

RESULTS

The expression of THBS2 was significantly upregulated in diabetic nephropathy (DN) based on bioinformatics tools and identified as a direct target of miR-1228. miR-1228 was downregulated in DN and HG-damaged HK-2 cells. HG notably reduced HK-2 cell proliferation. This negative effect was attenuated by transfecting with an miR-1228 mimic and aggravated by transfecting with an miR-1228 inhibitor. However, under basal condition, there was no significant effect on the HK-2 cell proliferation among blank control, mimic, and inhibitor groups. Overexpression of THBS2 abolished the elevating effect of the miR-1228 mimic on the HG-damaged HK-2 cell proliferation, while restored the inhibitory effects of the miR-1228 mimic on the cell apoptosis. On the contrary, the suppressive effects on the proliferation and the enhancive effects on the apoptosis by silencing miR-1228 in HK-2 cells stimulated with HG can be weakened by recommendation of THBS2 small interference RNAs. Furthermore, we also found that HG significantly enhanced the phosphorylation levels of PI3K and AKT. In terms of overexpression and knockdown experiments, Western blot analysis further revealed that miR-1228 inhibited the activation of the PI3K/AKT signaling pathway in HG-damaged HK-2 cells by regulating THBS2.

CONCLUSION

The findings illustrated that miR-1228 improved survivability and inhibited apoptosis in HK-2 cells stimulated with HG partly by restraining the activation of the PI3K/AKT signaling pathway.

Bioinformatics Analysis Reveals Crosstalk Among Platelets, Immune Cells, and the Glomerulus That May Play an Important Role in the Development of Diabetic Nephropathy

Diabetic nephropathy (DN) is the main cause of end stage renal disease (ESRD). Glomerulus damage is one of the primary pathological changes in DN. To reveal the gene expression alteration in the glomerulus involved in DN development, we screened the Gene Expression Omnibus (GEO) database up to December 2020. Eleven gene expression datasets about gene expression of the human DN glomerulus and its control were downloaded for further bioinformatics analysis. By using R language, all expression data were extracted and were further cross-platform normalized by Shambhala. Differentially expressed genes (DEGs) were identified by Student's t-test coupled with false discovery rate (FDR) (P < 0.05) and fold change (FC) ≥1.5. DEGs were further analyzed by the Database for Annotation, Visualization, and Integrated Discovery (DAVID) to enrich the Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway. We further constructed a protein-protein interaction (PPI) network of DEGs to identify the core genes. We used digital cytometry software CIBERSORTx to analyze the infiltration of immune cells in DN. A total of 578 genes were identified as DEGs in this study. Thirteen were identified as core genes, in which LYZ, LUM, and THBS2 were seldom linked with DN. Based on the result of GO, KEGG enrichment, and CIBERSORTx immune cells infiltration analysis, we hypothesize that positive feedback may form among the glomerulus, platelets, and immune cells. This vicious cycle may damage the glomerulus persistently even after the initial high glucose damage was removed. Studying the genes and pathway reported in this study may shed light on new knowledge of DN pathogenesis.

Hub Genes Associated with the Diagnosis of Diabetic Retinopathy

Purpose

This study aimed to identify genes that may be effective in diagnosing or treating diabetic retinopathy (DR), the most common complication of diabetes mellitus (DM).

Methods

Differentially expressed genes (DEGs) were identified between DR and DM in GSE146615 dataset. DEGs that were consistently up- or down-regulated under both standard glucose and high glucose conditions were identified as common genes and used to generate a protein-protein interaction network and modules. The module genes were assessed for the area under the receiver operating characteristic curve (AUC), leading to the identification of hub genes. Differentially methylated probes in GSE76169 were also compared with common DEGs to identify specific methylation markers of DR. Enrichment analysis was used to explore the biological characteristics. The Short Time-series Expression Miner algorithm was used to identify genes that were progressively dysregulated in the sequence: healthy controls < DM < DR.

Results

A total of 1917 common genes were identified for seven modules. The eight genes with AUC > 0.8 under high glucose and standard glucose conditions were considered as hub genes. The module genes were significantly enriched during vascular smooth muscle cell development and regulation of oxygen metabolism, while 92 methylation markers were involved in the similar terms. Among the progressively dysregulated genes, three intersection genes under both standard glucose and high glucose conditions were found to be module genes and were considered as key genes.

Conclusion

We identified eight potential DR-specific diagnostic and therapeutic genes, whose abnormal expression can cause oxidative stress, thus favoring the course of the disease.

Overview of genomics and post-genomics research on type 2 diabetes mellitus: Future perspectives and a framework for further studies

In this review, we briefly outlined salient features of pathophysiology and results of the genetic association studies hitherto conducted on type 2 diabetes. Primarily focusing on the current status of genomic research, we briefly discussed the limited progress made during the post-genomic era and tried to identify the limitations of the post-genomic research strategies. We suggested reanalysis of the existing genomic data through advanced statistical and computational methods and recommended integrated genomics-metabolomics approaches for future studies to facilitate understanding of the gene-environment interactions in the manifestation of the disease. We also propose a framework for research that may be apt for determining the effects of urbanization and changing lifestyles in the manifestation of complex genetic disorders like type 2 diabetes in the Indian populations and offset the confounding effects of both genetic and environmental factors in the natural way.

Key pathway and gene alterations in the gastric mucosa associated with obesity and obesity-related diabetes

BACKGROUND AND OBJECTIVE

The stomach plays an important role in obesity and obesity-related diabetes; yet, little is known about key pathways in the gastric mucosa associated with obesity and diabetes.

METHODS

We performed gene microarray and real time-polymerase chain reaction (RT-PCR) on gut mucosa samples from control subjects (CON), patients with simple obesity (OB), and patients with obesity and comorbid diabetes (OD) (n = 3 per group). Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses were used to predict the functional significance of differentially expressed genes.

RESULTS

In total, 262 genes were upregulated and 265 genes were downregulated in the OB group whereas 1756 genes were upregulated and 1053 genes were downregulated in the OD group compared with the CON group. Of these, 23 were co-regulated in both comparisons. Seven differentially expressed genes were validated by RT-PCR (NRIP3, L1CAM, TPO, P2RY1, OR8A1, ADAMTS19, and ASIC3). A functional analysis revealed that genes differentially expressed between the OB or OD and CON groups played crucial roles in metabolic, T cell, and G-protein coupled receptor biological processes, and primarily participated in the PI3K-Akt and AGE-RAGE signaling pathways.

CONCLUSIONS

Obesity and obesity-related diabetes are associated with important gene expression and pathway alterations in the stomach.

Differential proteome analysis of diabetes mellitus type 2 and its pathophysiological complications

The prevalence of Diabetes Mellitus Type 2 (DM 2) is increasing every passing year due to some global changes in lifestyles of people. The exact underlying mechanisms of the progression of this disease are not yet known. However recent advances in the combined omics more particularly in proteomics and genomics have opened a gateway towards the understanding of predetermined genetic factors, progression, complications and treatment of this disease. Here we shall review the recent advances in proteomics that have led to an early and better diagnostic approaches in controlling DM 2 more importantly the comparison of structural and functional protein biomarkers that are modified in the diseased state. By applying these advanced and promising proteomic strategies with bioinformatics applications and bio-statistical tools the prevalence of DM 2 and its associated disorders i-e nephropathy and retinopathy are expected to be controlled.

Identification of novel biomarkers to monitor β-cell function and enable early detection of type 2 diabetes risk

A decline in β-cell function is a prerequisite for the development of type 2 diabetes, yet the level of β-cell function in individuals at risk of the condition is rarely measured. This is due, in part, to the fact that current methods for assessing β-cell function are inaccurate, prone to error, labor-intensive, or affected by glucose-lowering therapy. The aim of the current study was to identify novel circulating biomarkers to monitor β-cell function and to identify individuals at high risk of developing β-cell dysfunction. In a nested case-control study from the Relationship between Insulin Sensitivity and Cardiovascular disease (RISC) cohort (n = 1157), proteomics and miRNA profiling were performed on fasting plasma samples from 43 individuals who progressed to impaired glucose tolerance (IGT) and 43 controls who maintained normal glucose tolerance (NGT) over three years. Groups were matched at baseline for age, gender, body mass index (BMI), insulin sensitivity (euglycemic clamp) and β-cell glucose sensitivity (mathematical modeling). Proteomic profiling was performed using the SomaLogic platform (Colorado, USA); miRNA expression was performed using a modified RT-PCR protocol (Regulus Therapeutics, California, USA). Results showed differentially expressed proteins and miRNAs including some with known links to type 2 diabetes, such as adiponectin, but also novel biomarkers and pathways. In cross sectional analysis at year 3, the top differentially expressed biomarkers in people with IGT/ reduced β-cell glucose sensitivity were adiponectin, alpha1-antitrypsin (known to regulate adiponectin levels), endocan, miR-181a, miR-342, and miR-323. At baseline, adiponectin, cathepsin D and NCAM.L1 (proteins expressed by pancreatic β-cells) were significantly lower in those that progressed to IGT. Many of the novel prognostic biomarker candidates were within the epithelial-mesenchymal transition (EMT) pathway: for example, Noggin, DLL4 and miR-181a. Further validation studies are required in additional clinical cohorts and in patients with type 2 diabetes, but these results identify novel pathways and biomarkers that may have utility in monitoring β-cell function and/ or predicting future decline, allowing more targeted efforts to prevent and intercept type 2 diabetes.