Characterization of the functional and transcriptomic effects of pro-inflammatory cytokines on human EndoC-βH5 beta cells

Association of the apoptotic markers Apo1/Fas and cCK-18 and the adhesion molecule ICAM-1 with Type 1 diabetes mellitus in children and adolescents

BACKGROUND

Type 1 diabetes mellitus (T1DM) is characterized by immune and metabolic dysregulation. Apo1/Fas is implicated in maintaining homeostasis of the immune system. Cytokeratin-18 (cCK-18) is a predictive marker of liver disorders in T2DM. Intercellular adhesion molecule-1 (ICAM-1) is considered to increase susceptibility to diabetes mellitus. All three markers are associated with endothelial function, apoptosis and diabetes-related complications. The possible role of Apo1/Fas, cCK-18 and ICAM-1 was investigated in children and adolescents with T1DM.

METHOD

Forty-nine (49) children and adolescents with T1DM and 49 controls were included in the study. Somatometric measurements were obtained and the Body Mass Index (BMI) of the participants was calculated. Biochemical parameters were measured by standard laboratory methods and Apo1/Fas, cCK-18 and ICAM-1 were measured using appropriate ELISA kits. The statistical analysis was performed using the IBM SPSS Statistics 23 program.

RESULTS

Apo1/Fas (p = 0.001), cCK-18 (p < 0.001) and ICAM-1 (p < 0.001) were higher in patients with T1DM compared to the controls. Apo1Fas was negatively correlated with glucose (p = 0.042), uric acid (p = 0.026), creatinine (p = 0.022), total cholesterol (p = 0.023) and LDL (p = 0.005) in the controls. In children and adolescents with T1DM, Apo1/Fas was positively correlated with total cholesterol (p = 0.013) and LDL (p = 0.003). ICAM-1 was negatively correlated with creatinine (p = 0.019) in the controls, whereas in patients with T1DM it was negatively correlated with HbA1c (p = 0.05).

CONCLUSIONS

Apo1/Fas, cCK-18 and ICAM-1 may be useful as serological markers for immune and metabolic dysregulation in children and adolescents with T1DM. Also, Apo1/Fas may have a protective role against metabolic complications in healthy children.

Elevated Cathepsin S Serum Levels in New-Onset Type 1 Diabetes and Autoantibody-Positive Siblings

Accumulating data suggest a role for the lysosomal protease cathepsin S (CTSS) in type 1 diabetes. Circulating CTSS is increased in type 1 diabetes; however, whether CTSS has protective or deleterious effects is unclear. The study's objectives were to examine the biomarker potential of CTSS in new-onset type 1 diabetes, and to investigate the expression and secretion of CTSS in human islets and β-cells. The CTSS level was analyzed in serum from children with new-onset type 1 diabetes and autoantibody-positive and -negative siblings by ELISA. The expression and secretion of CTSS were evaluated in isolated human islets and EndoC-βH5 cells by real-time qPCR, immunoblotting, and ELISA. The CTSS serum level was elevated in children with new-onset type 1 diabetes and positively associated with autoantibody status in healthy siblings. Human islets and EndoC-βH5 cells demonstrated induction and secretion of CTSS after exposure to proinflammatory cytokines, a model system of islet inflammation. Analysis of publicly available single-cell RNA sequencing data on human islets showed that elevated CTSS expression was exclusive for the β-cells in donors with type 1 diabetes as compared with nondiabetic donors. These findings suggest a potential of CTSS as a diagnostic biomarker in type 1 diabetes.

ARTICLE HIGHLIGHTS

LGR4 is essential for maintaining β-cell homeostasis through suppression of RANK

Pancreatic β-cell stress contributes to diabetes progression. This study demonstrates that Leucine-rich repeat-containing G-protein-coupled-receptor-4 (LGR4) is critical for maintaining β-cell health and is modulated by stressors. In vitro , Lgr4 knockdown decreases proliferation and survival in rodent β-cells, while overexpression protects against cytokine-induced cell death in rodent and human β-cells. Mechanistically, LGR4 suppresses Receptor Activator of Nuclear Factor Kappa B (NFκB) (RANK) and its subsequent activation of NFκB to protect β-cells. β-cell-specific Lgr4 -conditional knockout (cko) mice exhibit normal glucose homeostasis but increased β-cell death in both sexes and decreased proliferation only in females. Male Lgr4 cko mice under stress display reduced β-cell proliferation and a further increase in β-cell death. Upon aging, both male and female Lgr4 cko mice display impaired β-cell homeostasis, however, only female mice are glucose intolerant with decreased plasma insulin. We show that LGR4 is required for maintaining β-cell health under basal and stress-induced conditions, through suppression of RANK.

Teaser

LGR4 receptor is critical for maintaining β-cell health under basal and stressed conditions, through suppression of RANK.

Mitochondrial bioenergetics, metabolism, and beyond in pancreatic β-cells and diabetes

In Type 1 and Type 2 diabetes, pancreatic β-cell survival and function are impaired. Additional etiologies of diabetes include dysfunction in insulin-sensing hepatic, muscle, and adipose tissues as well as immune cells. An important determinant of metabolic health across these various tissues is mitochondria function and structure. This review focuses on the role of mitochondria in diabetes pathogenesis, with a specific emphasis on pancreatic β-cells. These dynamic organelles are obligate for β-cell survival, function, replication, insulin production, and control over insulin release. Therefore, it is not surprising that mitochondria are severely defective in diabetic contexts. Mitochondrial dysfunction poses challenges to assess in cause-effect studies, prompting us to assemble and deliberate the evidence for mitochondria dysfunction as a cause or consequence of diabetes. Understanding the precise molecular mechanisms underlying mitochondrial dysfunction in diabetes and identifying therapeutic strategies to restore mitochondrial homeostasis and enhance β-cell function are active and expanding areas of research. In summary, this review examines the multidimensional role of mitochondria in diabetes, focusing on pancreatic β-cells and highlighting the significance of mitochondrial metabolism, bioenergetics, calcium, dynamics, and mitophagy in the pathophysiology of diabetes. We describe the effects of diabetes-related gluco/lipotoxic, oxidative and inflammation stress on β-cell mitochondria, as well as the role played by mitochondria on the pathologic outcomes of these stress paradigms. By examining these aspects, we provide updated insights and highlight areas where further research is required for a deeper molecular understanding of the role of mitochondria in β-cells and diabetes.

Renewable Human Cell Model for Type 1 Diabetes Research: EndoC-βH5/HUVEC Coculture Spheroids

In vitro drug screening for type 1 diabetes therapies has largely been conducted on human organ donor islets for proof of efficacy. While native islets are the ultimate target of these drugs (either in situ or for transplantation), significant benefit can be difficult to ascertain due to the highly heterogeneous nature of individual donors and the overall scarcity of human islets for research. We present an in vitro coculture model based on immortalized insulin-producing beta-cell lines with human endothelial cells in 3D spheroids that aims to recapitulate the islet morphology in an effort towards developing a standardized cell model for in vitro diabetes research. Human insulin-producing immortalized EndoC-βH5 cells are cocultured with human endothelial cells in varying ratios to evaluate 3D cell culture models for type 1 diabetes research. Insulin secretion, metabolic activity, live cell fluorescence staining, and gene expression assays were used to compare the viability and functionality of spheroids composed of 100% beta-cells, 1 : 1 beta-cell/endothelial, and 1 : 3 beta-cell/endothelial. Monoculture and βH5/HUVEC cocultures formed compact spheroids within 7 days, with average diameter ~140 μm. This pilot study indicated that stimulated insulin release from 0 to 20 mM glucose increased from ~8-fold for monoculture and 1 : 1 coculture spheroids to over 20-fold for 1 : 3 EndoC-βH5/HUVEC spheroids. Metabolic activity was also ~12% higher in the 1 : 3 EndoC-βH5/HUVEC group compared to other groups. Stimulating monoculture beta-cell spheroids with 20 mM glucose +1 μg/mL glycine-modified INGAP-P increased the insulin stimulation index ~2-fold compared to glucose alone. Considering their availability and consistent phenotype, EndoC-βH5-based spheroids present a useful 3D cell model for in vitro testing and drug screening applications.