A novel diabetic foot ulcer diagnostic model: identification and analysis of genes related to glutamine metabolism and immune infiltration

BACKGROUND

Diabetic foot ulcer (DFU) is one of the most common and severe complications of diabetes, with vascular changes, neuropathy, and infections being the primary pathological mechanisms. Glutamine (Gln) metabolism has been found to play a crucial role in diabetes complications. This study aims to identify and validate potential Gln metabolism biomarkers associated with DFU through bioinformatics and machine learning analysis.

METHODS

We downloaded two microarray datasets related to DFU patients from the Gene Expression Omnibus (GEO) database, namely GSE134431, GSE68183, and GSE80178. From the GSE134431 dataset, we obtained differentially expressed Gln-metabolism related genes (deGlnMRGs) between DFU and normal controls. We analyzed the correlation between deGlnMRGs and immune cell infiltration status. We also explored the relationship between GlnMRGs molecular clusters and immune cell infiltration status. Notably, WGCNA to identify differentially expressed genes (DEGs) within specific clusters. Additionally, we conducted GSVA to annotate enriched genes. Subsequently, we constructed and screened the best machine learning model. Finally, we validated the predictions' accuracy using a nomogram, calibration curves, decision curve analysis (DCA), and the GSE134431, GSE68183, and GSE80178 dataset.

RESULTS

In both the DFU and normal control groups, we confirmed the presence of deGlnMRGs and an activated immune response. From the GSE134431 dataset, we obtained 20 deGlnMRGs, including CTPS1, NAGS, SLC7A11, GGT1, GCLM, RIMKLA, ARG2, ASL, ASNS, ASNSD1, PPAT, GLS2, GLUD1, MECP2, ASS1, PRODH, CTPS2, ALDH5A1, DGLUCY, and SLC25A12. Furthermore, two clusters were identified in DFU. Immune infiltration analysis indicated the presence of immune heterogeneity in these two clusters. Additionally, we established a Support Vector Machine (SVM) model based on 5 genes (R3HCC1, ZNF562, MFN1, DRAM1, and PTGDS), which exhibited excellent performance on the external validation datasetGSE134431, GSE68183, and GSE80178 (AUC = 0.929).

CONCLUSION

This study has identified five Gln metabolism genes associated with DFU, revealing potential novel biomarkers and therapeutic targets for DFU. Additionally, the infiltration of immune-inflammatory cells plays a crucial role in the progression of DFU.

Glutamine improves growth and intestinal health in juvenile hybrid groupers fed high-dose glycinin

Glutamine addition can improve immunity and intestinal development in fish. This study examined the protective roles of glutamine on growth suppression and enteritis induced by glycinin in juvenile hybrid groupers (female Epinephelus fuscoguttatus × male Epinephelus lanceolatus). The experiment set four isonitrogenous and isolipidic trial diets: a diet containing 10% glycinin (11S), 10% of 11S diet supplemented with 1% or 2% alanine-glutamine (1% or 2% Ala-Gln), and a diet containing neither 11S nor Ala-Gln (FM). A feeding trial was conducted in hybrid grouper for 8 weeks. Weight gain and specific growth rates in Groups 1% and 2% Ala-Gln were significantly higher than those of the 11S group but were similar to those of the FM group. The intestinal muscular layer thickness, plica height and width of the 2% Ala-Gln group were significantly higher than those of Group 11S. The enterocyte proliferation efficiency of the 11S group was significantly lower compared to other groups. Compared with the 11S group, Groups 1% and 2% Ala-Gln fish had increased intestinal lysozyme activities, complement 3 and immunoglobulin M as well as cathelicidin contents. The mRNA levels of tnf-α, il-1β, ifn-α, and hsp70 genes were more downregulated in Groups 1% and 2% Ala-Gln than in Group 11S. Compared with FM group, fish from the 11S group had significantly lower mRNA levels of myd88, ikkβ, and nf-κb p65 genes. These three values in the 2% Ala-Gln group were significantly lower than those in Group 11S but not significantly different from those of Group FM. The relative abundance of Vibrio in Group 11S was higher than that in Groups FM and 2% Ala-Gln. Intestinal glutamine, glutaminase, glutamic acid, α-ketoglutarate, malate dehydrogenase and ATP contents were higher in Groups 1% and 2% Ala-Gln than in Group 11S. These results suggest that glutamine is a useful feed additive to enhance growth and intestinal immunity, alleviate inflammation, and modulate gut microbiota in hybrid grouper fed high-dose glycinin.

Dysregulated Gln-Glu-α-ketoglutarate axis impairs maternal decidualization and increases the risk of recurrent spontaneous miscarriage

Recurrent spontaneous miscarriage (RSM) affects 1%-2% of fertile women worldwide and poses a risk of future pregnancy complications. Increasing evidence has indicated that defective endometrial stromal decidualization is a potential cause of RSM. Here, we perform liquid chromatography with mass spectrometry (LC-MS)-based metabolite profiling in human endometrial stromal cells (ESCs) and differentiated ESCs (DESCs) and find that accumulated α-ketoglutarate (αKG) derived from activated glutaminolysis contributes to maternal decidualization. Contrarily, ESCs obtained from patients with RSM show glutaminolysis blockade and aberrant decidualization. We further find that enhanced Gln-Glu-αKG flux decreases histone methylation and supports ATP production during decidualization. In vivo, feeding mice a Glu-free diet leads to a reduction of αKG, impaired decidualization, and an increase of fetal loss rate. Isotopic tracing approaches demonstrate Gln-dependent oxidative metabolism as a prevalent direction during decidualization. Our results demonstrate an essential prerequisite of Gln-Glu-αKG flux to regulate maternal decidualization, suggesting αKG supplementation as a putative strategy to rectify deficient decidualization in patients with RSM.