Diabetes & Metabolism Journal

Articles in E-pub version are posted online ahead of regular printed publication.

Original Articles

Basic Research
Revealing VCAN as a Potential Common Diagnostic Biomarker of Renal Tubules and Glomerulus in Diabetic Kidney Disease Based on Machine Learning, Single-Cell Transcriptome Analysis and Mendelian Randomization: Li Jiang, Jie Jian, Xulin Sai, Xiai Wu; Received May 5, 2024 Accepted September 7, 2024 Published online January 24, 2025; DOI: https://doi.org/10.4093/dmj.2024.0233 [Epub ahead of print]

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Abstract PDF: Background
Diabetic kidney disease (DKD) is recognized as a significant complication of diabetes mellitus and categorized into glomerular DKDs and tubular DKDs, each governed by distinct pathological mechanisms and biomarkers.
Methods
Through the identification of common features observed in glomerular and tubular lesions in DKD, numerous differentially expressed gene were identified by the machine learning, single-cell transcriptome and mendelian randomization.
Results
The diagnostic markers versican (VCAN) was identified, offering supplementary options for clinical diagnosis. VCAN significantly highly expressed in glomerular parietal epithelial cell and proximal convoluted tubular cell. It was mainly involved in the up-regulation of immune genes and infiltration of immune cells like mast cell. Mendelian randomization analysis confirmed that serum VCAN protein levels were a risky factor for DKD, while there was no reverse association. It exhibited the good diagnostic potential for estimated glomerular filtration rate and proteinuria in DKD.
Conclusion
VCAN showed the prospects into DKD pathology and clinical indicator.

Basic Research
Ras Guanine Nucleotide-Releasing Protein-4 Inhibits Erythropoietin Production in Diabetic Mice with Kidney Disease by Degrading HIF2A: Junmei Wang, Shuai Huang, Li Zhang, Yixian He, Xian Shao, A-Shan-Jiang A-Ni-Wan, Yan Kong, Xuying Meng, Pei Yu, Saijun Zhou; Received July 18, 2024 Accepted September 7, 2024 Published online January 23, 2025; DOI: https://doi.org/10.4093/dmj.2024.0398 [Epub ahead of print]

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Abstract PDF: Background
In acute and chronic renal inflammatory diseases, the activation of inflammatory cells is involved in the defect of erythropoietin (EPO) production. Ras guanine nucleotide-releasing protein-4 (RasGRP4) promotes renal inflammatory injury in type 2 diabetes mellitus (T2DM). Our study aimed to investigate the role and mechanism of RasGRP4 in the production of renal EPO in diabetes.
Methods
The degree of tissue injury was observed by pathological staining. Inflammatory cell infiltration was analyzed by immunohistochemical staining. Serum EPO levels were detected by enzyme-linked immunosorbent assay, and EPO production and renal interstitial fibrosis were analyzed by immunofluorescence. Quantitative real-time polymerase chain reaction and Western blotting were used to detect the expression of key inflammatory factors and the activation of signaling pathways. In vitro, the interaction between peripheral blood mononuclear cells (PBMCs) and C3H10T1/2 cells was investigated via cell coculture experiments.
Results
RasGRP4 decreased the expression of hypoxia-inducible factor 2-alpha (HIF2A) via the ubiquitination–proteasome degradation pathway and promoted myofibroblastic transformation by activating critical inflammatory pathways, consequently reducing the production of EPO in T2DM mice.
Conclusion
RasGRP4 participates in the production of renal EPO in diabetic mice by affecting the secretion of proinflammatory cytokines in PBMCs, degrading HIF2A, and promoting the myofibroblastic transformation of C3H10T1/2 cells.

Cardiovascular Risk/Epidemiology
Normalized Creatinine-to-Cystatin C Ratio and Risk of Cardiometabolic Multimorbidity in Middle-Aged and Older Adults: Insights from the China Health and Retirement Longitudinal Study: Honglin Sun, Zhenyu Wu, Guang Wang, Jia Liu; Received May 2, 2024 Accepted November 15, 2024 Published online January 20, 2025; DOI: https://doi.org/10.4093/dmj.2024.0100 [Epub ahead of print]

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Abstract PDF: Background
Normalized creatinine-to-cystatin C ratio (NCCR) was reported to approximate relative skeletal muscle mass and diabetes risk. However, the association between NCCR and cardiometabolic multimorbidity (CMM) remains elusive. This study aimed to explore their relationship in a large-scale prospective cohort.
Methods
This study included 5,849 middle-age and older participants from the China Health and Retirement Longitudinal Study (CHARLS) enrolled between 2011 and 2012. The baseline NCCR was determined as creatinine (mg/dL)/cystatin C (mg/L)×10/body mass (kg). CMM was defined as the simultaneous occurrence of two or more of the following conditions: heart disease, stroke, and type 2 diabetes mellitus. Logistic regression analysis and Cox regression analysis were employed to estimate the relationship between NCCR and CMM. The joint effect of body mass index and NCCR on the risk of CMM were further analyzed.
Results
During a median 4-year follow-up, 227 (3.9%) participants developed CMM. The risk of CMM was significantly decreased with per standard deviation increase of NCCR (odds ratio, 0.72; 95% confidence interval, 0.62 to 0.85) after adjustment for confounders (P<0.001). Further sex-specific analysis found significant negative associations between NCCR and CMM in female either without or with one CMM component at baseline, which was attenuated in males but remained statistically significant among those with one basal CMM component. Notably, non-obese individuals with high NCCR levels had the lowest CMM risk compared to obese counterparts with low NCCR levels in both genders.
Conclusion
High NCCR was independently associated with reduced risk of CMM in middle-aged and older adults in China, particularly females.

Drug/Regimen
Study Design and Protocol for a Randomized Controlled Trial of Enavogliflozin to Evaluate Cardiorenal Outcomes in Type 2 Diabetes (ENVELOP): Nam Hoon Kim, Soo Lim, In-Kyung Jeong, Eun-Jung Rhee, Jun Sung Moon, Ohk-Hyun Ryu, Hyuk-Sang Kwon, Jong Chul Won, Sang Soo Kim, Sang Yong Kim, Bon Jeong Ku, Heung Yong Jin, Sin Gon Kim, Bong-Soo Cha, on Behalf of Investigators of ENVELOP Study; Received May 9, 2024 Accepted August 14, 2024 Published online January 6, 2025; DOI: https://doi.org/10.4093/dmj.2024.0238 [Epub ahead of print]

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Abstract PDF Supplementary Material PubReader ePub: Background
The novel sodium-glucose cotransporter-2 (SGLT2) inhibitor enavogliflozin effectively lowers glycosylated hemoglobin levels and body weights without the increased risk of serious adverse events; however, the long-term clinical benefits of enavogliflozin in terms of cardiovascular and renal outcomes have not been investigated.
Methods
This study is an investigator-initiated, multicenter, randomized, pragmatic, open-label, active-controlled, non-inferiority trial. Eligible participants are adults (aged ≥19 years) with type 2 diabetes mellitus (T2DM) who have a history of, or are at risk of, cardiovascular disease. A total of 2,862 participants will be randomly assigned to receive either enavogliflozin or other SGLT2 inhibitors with proven cardiorenal benefits, such as dapagliflozin or empagliflozin. The primary endpoint is the time to the first occurrence of a composite of major adverse cardiovascular or renal events (Clinical Research Information Service registration number: KCT0009243).
Conclusion
This trial will determine whether enavogliflozin is non-inferior to dapagliflozin or empagliflozin in terms of cardiorenal outcomes in patients with T2DM and cardiovascular risk factors. This study will elucidate the role of enavogliflozin in preventing vascular complications in patients with T2DM.

Metabolic Risk/Epidemiology
Kidney Gastrin/CCKBR Attenuates Type 2 Diabetes Mellitus by Inhibiting SGLT2-Mediated Glucose Reabsorption through Erk/NF-κB Signaling Pathway: Xue Zhang, Yuhan Zhang, Yang Shi, Dou Shi, Min Niu, Xue Liu, Xing Liu, Zhiwei Yang, Xianxian Wu; Received November 6, 2023 Accepted September 7, 2024 Published online December 24, 2024; DOI: https://doi.org/10.4093/dmj.2023.0397 [Epub ahead of print]

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Abstract PDF Supplementary Material PubReader ePub: Background
Both sodium-glucose cotransporters (SGLTs) and Na+/H+ exchangers (NHEs) rely on a favorable Na-electrochemical gradient. Gastrin, through the cholecystokinin B receptor (CCKBR), can induce natriuresis and diuresis by inhibiting renal NHEs activity. The present study aims to unveil the role of renal CCKBR in diabetes through SGLT2-mediated glucose reabsorption.
Methods
Renal tubule-specific Cckbr-knockout (Cckbr^CKO) mice and wild-type (WT) mice were utilized to investigate the effect of renal CCKBR on SGLT2 and systemic glucose homeostasis under normal diet, high-fat diet (HFD), and HFD with a subsequent injection of a low dose of streptozotocin. The regulation of SGLT2 expression by gastrin/CCKBR and the underlying mechanism was explored using human kidney (HK)-2 cells.
Results
CCKBR was downregulated in kidneys of diabetic mice. Compared with WT mice, Cckbr^CKO mice exhibited a greater susceptibility to obesity and diabetes when subjected to HFD. In vitro experiments using HK-2 cells revealed an upregulation of glucose transporters after incubation with high glucose, a response that was significantly attenuated following gastrin intervention. The glucose uptake from the culture medium of cells was altered accordingly. Moreover, gastrin administration effectively mitigated hyperglycemia in WT diabetic mice by inhibition of SGLT2 mediated glucose reabsorption, but this effect was compromised in the absence of CCKBR, as seen in Cckbr^CKO mice. Mechanistically, gastrin/CCKBR substantially reduced SGLT2 expression in HK-2 cells exposed to high glucose, via modulating Erk/nuclear factor-kappa B (NF-κB) pathway.
Conclusion
Our study underscores the crucial role of renal gastrin/CCKBR in SGLT2 regulation and glucose reabsorption, and renal gastrin/CCKBR can be a promising therapeutic target for diabetes.

Metabolic Risk/Epidemiology
Do Time-Dependent Repeated Measures of Anthropometric and Body Composition Indices Improve the Prediction of Incident Diabetes in the Cohort Study? Findings from a Community-Based Korean Genome and Epidemiology Study: Hye Ah Lee, Hyesook Park, Bomi Park; Received July 4, 2024 Accepted September 7, 2024 Published online November 15, 2024; DOI: https://doi.org/10.4093/dmj.2024.0357 [Epub ahead of print]

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Abstract PDF Supplementary Material PubReader ePub: Background
Cumulative evidence consistently shows that anthropometric and body composition measurements are strongly linked to the risk of incident diabetes, typically based on baseline measurements. This study aims to assess whether repeated measurements enhance the prediction of diabetes risk beyond baseline assessments alone.
Methods
We utilized data from a 16-year population-based follow-up cohort within the Korean Genome and Epidemiology Study, comprising 6,030 individuals aged 40 to 69 years at baseline. We included eight indices: a body shape index (ABSI), body adiposity index (BAI), waist circumference (WC), body mass index (BMI), waist-to-hip ratio (WHR), weight-adjusted skeletal muscle index (SMI), percent body fat, and fat-to-muscle ratio. The effect of these measurements for incident diabetes was estimated using Harrell’s C-indexes and hazard ratios with 95% confidence intervals, employing time-dependent Cox proportional hazard models.
Results
Over the 16-year follow-up, 939 new diabetes cases were identified (cumulative incidence, 15.6%). The median number of indicator measurements per participant was eight. The basic model, including 10 features (sex, age, education levels, physical activity, alcohol intake, current smoking, total energy intake, dietary diversity score, and log-transformed C-reactive protein levels, and quartiles of unweighted genetic risk score at baseline), yielded a Harrell’s C-index of 0.610. The highest C-index in repeated measurements was for WC (0.668) across the general population, weight-adjusted SMI in men, and WHR in women. However, except for ABSI and BAI, the diabetes predictive power of the other indicators was comparable. Additionally, repeated measurements of WC, BMI, and WHR in women were found to contribute to improved discrimination compared to baseline measurements, but not in men.
Conclusion
Utilizing repeated measurements of general and central adiposity to predict diabetes may be helpful in predicting hidden risks, especially in women.

Lifestyle
Impact of Meal Frequency on Insulin Resistance in Middle-Aged and Older Adults: A Prospective Cohort Study: Ha-Eun Ryu, Jong Hee Lee, Byoungjin Park, Seok-Jae Heo, Yu-Jin Kwon; Received July 22, 2024 Accepted September 7, 2024 Published online November 13, 2024; DOI: https://doi.org/10.4093/dmj.2024.0407 [Epub ahead of print]

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Abstract PDF Supplementary Material PubReader ePub: Background
Insulin resistance (IR) is central to metabolic disorders and significantly influenced by diet. Studies on meal frequency (MF) and metabolic indicators have shown mixed results. This study explores the link between MF and IR in middle-aged and older adults.
Methods
This prospective cohort study included 4,570 adults aged 40 to 69 years from the Korean Genome and Epidemiologic Study. MF were divided into two groups based on whether they consumed three or more, or fewer than three, meals daily. IR was evaluated using the homeostasis model assessment of insulin resistance (HOMA-IR); participants were classified as IR if their HOMA-IR value was ≥2.5. Multiple Cox proportional hazard regression analyses were conducted to examine the association between MF and the incidence of IR.
Results
After adjusting for all variables, individuals in the MF ≥3 group showed a reduced incidence of IR compared to those in the MF <3 group (hazard ratio, 0.880; 95% confidence interval, 0.782 to 0.990). Additionally, subgroup analyses by sex, diabetes mellitus (DM), and body mass index (BMI) showed that this association persisted only in men, individuals without DM, and those with a BMI <25.
Conclusion
Our findings indicate that a higher MF among middle-aged and older adults is associated with a reduced incidence of IR. However, this association was maintained only in men, individuals without DM, and those without obesity.

Genetics
Exon Sequencing of HNF1β in Chinese Patients with Early-Onset Diabetes: Siqian Gong, Hong Lian, Yating Li, Xiaoling Cai, Wei Liu, Yingying Luo, Meng Li, Si-min Zhang, Rui Zhang, Lingli Zhou, Yu Zhu, Qian Ren, Xiuying Zhang, Jing Chen, Jing Wu, Xianghai Zhou, Xirui Wang, Xueyao Han, Linong Ji; Received March 20, 2024 Accepted July 24, 2024 Published online November 13, 2024; DOI: https://doi.org/10.4093/dmj.2024.0159 [Epub ahead of print]

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Abstract PDF Supplementary Material PubReader ePub: Background
Maturity-onset diabetes of the young (MODY) due to variants of hepatocyte nuclear factor 1-beta (HNF1β) (MODY5) has not been well studied in the Chinese population. This study aimed to estimate its prevalence and evaluate the application of a clinical screening method (Faguer score) in Chinese early-onset diabetes (EOD) patients.
Methods
Among 679 EOD patients clinically diagnosed with type 2 diabetes mellitus (age at diagnosis ≤40 years), the exons of HNF1β were sequenced. Functional impact of rare variants was evaluated using a dual-luciferase reporter system. Faguer scores ≥8 prompted multiplex ligation-dependent probe amplification (MLPA) for large deletions. Pathogenicity of HNF1β variants was assessed following the American College of Medical Genetics and Genomics (ACMG) guidelines.
Results
Two rare HNF1β missense mutations (E105K and G454R) were identified by sequencing in five patients, showing functional impact in vitro. Another patient was found to have a whole-gene deletion by MLPA in 22 patients with the Faguer score above 8. Following ACMG guidelines, six patients carrying pathogenic or likely pathogenic variant were diagnosed with MODY5. The estimated prevalence of MODY5 in Chinese EOD patients was approximately 0.9% or higher.
Conclusion
MODY5 is not uncommon in China. The Faguer score is helpful in deciding whether to perform MLPA analysis on patients with negative sequencing results.

Technology/Device
Efficacy and Safety of Automated Insulin Delivery Systems in Patients with Type 1 Diabetes Mellitus: A Systematic Review and Meta-Analysis: Wenqi Fan, Chao Deng, Ruoyao Xu, Zhenqi Liu, Richard David Leslie, Zhiguang Zhou, Xia Li; Received March 17, 2024 Accepted July 24, 2024 Published online November 13, 2024; DOI: https://doi.org/10.4093/dmj.2024.0130 [Epub ahead of print]

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Abstract PDF Supplementary Material PubReader ePub: Background
Automated insulin delivery (AID) systems studies are upsurging, half of which were published in the last 5 years. We aimed to evaluate the efficacy and safety of AID systems in patients with type 1 diabetes mellitus (T1DM).
Methods
We searched PubMed, Embase, Cochrane Library, Web of Science, and ClinicalTrials.gov until August 31, 2023. Randomized clinical trials that compared AID systems with other insulin-based treatments in patients with T1DM were considered eligible. Studies characteristics and glycemic metrics was extracted by three researchers independently.
Results
Sixty-five trials (3,623 patients) were included. The percentage of time in range (TIR) was 11.74% (95% confidence interval [CI], 9.37 to 14.12; P<0.001) higher with AID systems compared with control treatments. Patients on AID systems had more pronounced improvement of time below range when diabetes duration was more than 20 years (–1.80% vs. –0.86%, P=0.031) and baseline glycosylated hemoglobin lower than 7.5% (–1.93% vs. –0.87%, P=0.033). Dual-hormone full closed-loop systems revealed a greater improvement in TIR compared with hybrid closed-loop systems (–19.64% vs. –10.87%). Notably, glycemia risk index (GRI) (–3.74; 95% CI, –6.34 to –1.14; P<0.01) was also improved with AID therapy.
Conclusion
AID systems showed significant advantages compared to other insulin-based treatments in improving glucose control represented by TIR and GRI in patients with T1DM, with more favorable effect in euglycemia by dual-hormone full closedloop systems as well as less hypoglycemia for patients who are within target for glycemic control and have longer diabetes duration.

Basic Research
Rbbp6-Mediated Bmal1 Ubiquitination Inhibits YAP1 Signaling Pathway to Promote Ferroptosis in Diabetes-Induced Testicular Damage: Yuan Tian, Zhiqiang Zhu, Jun Qiao, Bei Liu, Yuehai Xiao; Received March 1, 2024 Accepted June 17, 2024 Published online November 6, 2024; DOI: https://doi.org/10.4093/dmj.2024.0099 [Epub ahead of print]

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Abstract PDF Supplementary Material PubReader ePub: Background
Diabetes-induced testicular damage (DITD) is a common complication of diabetes. We investigated underlying mechanism of retinoblastoma-binding protein 6 (Rbbp6)-mediated brain and muscle ARNT-like 1 (Bmal1) ubiquitination in modulating ferroptosis in DITD.
Methods
Spermatogenic cell apoptosis and viability were measured by flow cytometry and cell counting kit 8 (CCK-8), respectively. The impact of Rbbp6 and Bmal1 on ferroptosis was assessed by determining expression of ferroptosis markers glutathione peroxidase 4 (GPX4) and solute carrier family 7 member 11 (SLC7A11), and levels of malondialdehyde (MDA), glutathione (GSH), iron, and lipid peroxidation. Co-immunoprecipitation was performed to determine the interaction between Rbbp6 and Bmal1, as well as the ubiquitination level of Bmal1. The expression levels of Rbbp6, Bmal1, Yes-associated protein 1 (YAP1), ferroptosis markers, and testicular steroidogenic enzymes were tested by Western blot.
Results
Bmal1 protein expression was significantly downregulated, while Rbbp6 was upregulated in DITD mouse model and high glucose (HG)-induced GC-1 spg cells. Overexpression of Bmal1 improved testicular injury in diabetic mice, reduced 4-hydroxynonenal (4-HNE), MDA, iron levels, and increased expression levels of GPX4, SLC7A11, GSH, as well as testicular steroidogenic enzymes. Rbbp6 decreased Bmal1 level through promoting its ubiquitination. Meanwhile, Rbbp6 knockdown inhibited the ferroptosis of HG-induced GC-1 spg cells, which were abolished by silencing Bmal1. In addition, knockdown of YAP1 or treatment with ferroptosis inducer erastin blocked the above effects caused by Bmal1 overexpression.
Conclusion
Rbbp6-mediated Bmal1 ubiquitination suppressed YAP1 pathway, promoting ferroptosis in DITD. This study highlighted Rbbp6/Bmal1/YAP1 axis as a potential therapeutic target for mitigating DITD.

Complications
To Determine the Risk-Based Screening Interval for Diabetic Retinopathy: Development and Validation of Risk Algorithm from a Retrospective Cohort Study: Jinxiao Lian, Ching So, Sarah Morag McGhee, Thuan-quoc Thach, Cindy Lo Kuen Lam, Colman Siu Cheung Fung, Alfred Siu Kei Kwong, Jonathan Cheuk Hung Chan; Received March 21, 2024 Accepted July 24, 2024 Published online October 31, 2024; DOI: https://doi.org/10.4093/dmj.2024.0142 [Epub ahead of print]

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Abstract PDF Supplementary Material PubReader ePub: Background
The optimal screening interval for diabetic retinopathy (DR) remains controversial. This study aimed to develop a risk algorithm to predict the individual risk of referable sight-threatening diabetic retinopathy (STDR) in a mainly Chinese population and to provide evidence for risk-based screening intervals.
Methods
The retrospective cohort data from 117,418 subjects who received systematic DR screening in Hong Kong between 2010 and 2016 were included to develop and validate the risk algorithm using a parametric survival model. The risk algorithm can be used to predict the individual risk of STDR within a specific time interval, or the time to reach a specific risk margin and thus to allocate a screening interval. The calibration performance was assessed by comparing the cumulative STDR events versus predicted risk over 2 years, and discrimination by using receiver operative characteristics (ROC) curve.
Results
Duration of diabetes, glycosylated hemoglobin, systolic blood pressure, presence of chronic kidney disease, diabetes medication, and age were included in the risk algorithm. The validation of prediction performance showed that there was no significant difference between predicted and observed STDR risks in males (5.6% vs. 5.1%, P=0.724) or females (4.8% vs. 4.6%, P=0.099). The area under the receiver operating characteristic curve was 0.80 (95% confidence interval [CI], 0.78 to 0.81) for males and 0.81 (95% CI, 0.79 to 0.83) for females.
Conclusion
The risk algorithm has good prediction performance for referable STDR. Using a risk-based screening interval allows us to allocate screening visits disproportionally more to those at higher risk, while reducing the frequency of screening of lower risk people.

Metabolic Risk/Epidemiology
Comparison of SPISE and METS-IR and Other Markers to Predict Insulin Resistance and Elevated Liver Transaminases in Children and Adolescents: Kyungchul Song, Eunju Lee, Hye Sun Lee, Hana Lee, Ji-Won Lee, Hyun Wook Chae, Yu-Jin Kwon; Received June 7, 2024 Accepted August 2, 2024 Published online October 29, 2024; DOI: https://doi.org/10.4093/dmj.2024.0302 [Epub ahead of print]

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Abstract PDF Supplementary Material PubReader ePub: Background
Studies on predictive markers of insulin resistance (IR) and elevated liver transaminases in children and adolescents are limited. We evaluated the predictive capabilities of the single-point insulin sensitivity estimator (SPISE) index, metabolic score for insulin resistance (METS-IR), homeostasis model assessment of insulin resistance (HOMA-IR), the triglyceride (TG)/ high-density lipoprotein cholesterol (HDL-C) ratio, and the triglyceride-glucose index (TyG) for IR and alanine aminotransferase (ALT) elevation in this population.
Methods
Data from 1,593 participants aged 10 to 18 years were analyzed using a nationwide survey. Logistic regression analysis was performed with IR and ALT elevation as dependent variables. Receiver operating characteristic (ROC) curves were generated to assess predictive capability. Proportions of IR and ALT elevation were compared after dividing participants based on parameter cutoff points.
Results
All parameters were significantly associated with IR and ALT elevation, even after adjusting for age and sex, and predicted IR and ALT elevation in ROC curves (all P<0.001). The areas under the ROC curve of SPISE and METS-IR were higher than those of TyG and TG/HDL-C for predicting IR and were higher than those of HOMA-IR, TyG, and TG/HDL-C for predicting ALT elevation. The proportions of individuals with IR and ALT elevation were higher among those with METS-IR, TyG, and TG/ HDL-C values higher than the cutoff points, whereas they were lower among those with SPISE higher than the cutoff point.
Conclusion
SPISE and METS-IR are superior to TG/HDL-C and TyG in predicting IR and ALT elevation. Thus, this study identified valuable predictive markers for young individuals.

Basic Research
NG2-Glia Cause Diabetic Blood-Brain Barrier Disruption by Secreting MMP-9: Xiaolong Li, Yan Cai, Zhu Zhong, Maolin Li, Dong Huang, Zhifei Qiao, Hongli Zhou, Zuo Zhang, Jiyin Zhou; Received September 25, 2023 Accepted February 22, 2024 Published online July 23, 2024; DOI: https://doi.org/10.4093/dmj.2023.0342 [Epub ahead of print]

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Abstract PDF PubReader ePub: Background
Disorders of the blood-brain barrier (BBB) arising from diabetes mellitus are closely related to diabetic encephalopathy. Previous research has suggested that neuron-glia antigen 2 (NG2)-glia plays a key role in maintaining the integrity of the BBB. However, the mechanism by which NG2-glia regulates the diabetic BBB remains unclear.
Methods
Type 2 diabetes mellitus (T2DM) db/db mice and db/m mice were used. Evans-Blue BBB permeability tests and transmission electron microscopy techniques were applied. Tight junction proteins were assessed by immunofluorescence and transmission electron microscopy. NG2-glia number and signaling pathways were evaluated by immunofluorescence. Detection of matrix metalloproteinase-9 (MMP-9) in serum was performed using enzyme-linked immunosorbent assay (ELISA).
Results
In T2DM db/db mice, BBB permeability in the hippocampus significantly increased from 16 weeks of age, and the structure of tight junction proteins changed. The number of NG2-glia in the hippocampus of db/db mice increased around microvessels from 12 weeks of age. Concurrently, the expression of MMP-9 increased in the hippocampus with no change in serum. Sixteen- week-old db/db mice showed activation of the Wnt/β-catenin signaling in hippocampal NG2-glia. Treatment with XAV-939 improved structural and functional changes in the hippocampal BBB and reduced MMP-9 secretion by hippocampal NG2-glia in db/db mice. It was also found that the upregulation of β-catenin protein in NG2-glia in the hippocampus of 16-week-old db/db mice was significantly alleviated by treatment with XAV-939.
Conclusion
The results indicate that NG2-glia can lead to structural and functional disruption of the diabetic BBB by activating Wnt/β-catenin signaling, upregulating MMP-9, and degrading tight junction proteins.

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