The small RNA miR-375 - a pancreatic islet abundant miRNA with multiple roles in endocrine beta cell function

MicroRNA 29 modulates β-cell mitochondrial metabolism and insulin secretion via underlying miR-29-OXPHOS complex pathways

AIM

MicroRNAs (miRNAs) regulate β-cell function, and β-cell mitochondria and insulin secretion are perturbed in diabetes. We aimed to identify key miRNAs regulating β-cell mitochondrial metabolism and novel β-cell miRNA-mitochondrial pathways.

METHODS

TargetScan (http://www.targetscan.org/) was used to predict if 16 miRNAs implicated in β-cell function target 27 cis-eGenes implicated in mitochondrial activity. The expression of candidate miRNAs and insulin secretion after 24 and 1 h pre-incubation in 2.8, 11.1- and 16.7-mM glucose was measured in clonal INS-1 832/13 β-cells. MiR-29 silenced INS-1 832/13 cells were assessed for insulin secretion (glucose, pyruvate, and K+), target cis-eGene expression (Ndufv3 and Ndufa10 components of mitochondrial complex I (CI)), OXPHOS (CI-V) protein expression, and mitochondrial OXPHOS respiration/activity. The expression of differentially expressed miR-29 miRNAs was evaluated in Goto-Kakizaki (GK) rat, db/db mouse and type 2 diabetic (T2D) human islets, as well as NMRI mouse islets cultured under glucolipotoxic conditions.

RESULTS

MiR-29, miR-15 and miR-124 were predicted to regulate ~20 cis-eGenes, while miR-29 alone was predicted to regulate ≥12 of these in rat and human species. MiR-29 expression and insulin secretion were reduced in INS-1 832/13 cells after 24 h in elevated glucose. MiR-29 knockdown increased all tested insulin secretory responses, Nudfv3, Ndufa10, complex I and II expression, and cellular mitochondrial OXPHOS. MiR-29 expression was reduced in db/db islets but increased in GK rat and T2D human islets.

CONCLUSION

We conclude miR-29 is a key miRNA in regulating β-cell mitochondrial metabolism and insulin secretion via underlying miR-29-OXPHOS complex pathways. Furthermore, we infer reduced miR-29 expression compensatorily enhances insulin secretion under glucotoxicity.

Targeting β-Cell Plasticity: A Promising Approach for Diabetes Treatment

The β-cells within the pancreas play a pivotal role in insulin production and secretion, responding to fluctuations in blood glucose levels. However, factors like obesity, dietary habits, and prolonged insulin resistance can compromise β-cell function, contributing to the development of Type 2 Diabetes (T2D). A critical aspect of this dysfunction involves β-cell dedifferentiation and transdifferentiation, wherein these cells lose their specialized characteristics and adopt different identities, notably transitioning towards progenitor or other pancreatic cell types like α-cells. This process significantly contributes to β-cell malfunction and the progression of T2D, often surpassing the impact of outright β-cell loss. Alterations in the expressions of specific genes and transcription factors unique to β-cells, along with epigenetic modifications and environmental factors such as inflammation, oxidative stress, and mitochondrial dysfunction, underpin the occurrence of β-cell dedifferentiation and the onset of T2D. Recent research underscores the potential therapeutic value for targeting β-cell dedifferentiation to manage T2D effectively. In this review, we aim to dissect the intricate mechanisms governing β-cell dedifferentiation and explore the therapeutic avenues stemming from these insights.

The role of noncoding RNAs in beta cell biology and tissue engineering

The loss or dysfunction of pancreatic β-cells, which are responsible for insulin secretion, constitutes the foundation of all forms of diabetes, a widely prevalent disease worldwide. The replacement of damaged β-cells with regenerated or transplanted cells derived from stem cells is a promising therapeutic strategy. However, inducing the differentiation of stem cells into fully functional glucose-responsive β-cells in vitro has proven to be challenging. Noncoding RNAs (ncRNAs) have emerged as critical regulatory factors governing the differentiation, identity, and function of β-cells. Furthermore, engineered hydrogel systems, biomaterials, and organ-like structures possess engineering characteristics that can provide a three-dimensional (3D) microenvironment that supports stem cell differentiation. This review summarizes the roles and contributions of ncRNAs in maintaining the differentiation, identity, and function of β-cells. And it focuses on regulating the levels of ncRNAs in stem cells to activate β-cell genetic programs for generating alternative β-cells and discusses how to manipulate ncRNA expression by combining hydrogel systems and other tissue engineering materials. Elucidating the patterns of ncRNA-mediated regulation in β-cell biology and utilizing this knowledge to control stem cell differentiation may offer promising therapeutic strategies for generating functional insulin-producing cells in diabetes cell replacement therapy and tissue engineering.

Beyond insulin: Unraveling the complex interplay of ER stress, oxidative damage, and CFTR modulation in CFRD

CF-related diabetes (CFRD) is a prevalent comorbidity in people with Cystic Fibrosis (CF), significantly impacting morbidity and mortality rates. This review article critically evaluates the current understanding of CFRD molecular mechanisms, including the role of CFTR protein, oxidative stress, unfolded protein response (UPR) and intracellular communication. CFRD manifests from a complex interplay between exocrine pancreatic damage and intrinsic endocrine dysfunction, further complicated by the deleterious effects of misfolded CFTR protein on insulin secretion and action. Studies indicate that ER stress and subsequent UPR activation play critical roles in both exocrine and endocrine pancreatic cell dysfunction, contributing to β-cell loss and insulin insufficiency. Additionally, oxidative stress and altered calcium flux, exacerbated by CFTR dysfunction, impair β-cell survival and function, highlighting the significance of antioxidant pathways in CFRD pathogenesis. Emerging evidence underscores the importance of exosomal microRNAs (miRNAs) in mediating inflammatory and stress responses, offering novel insights into CFRD's molecular landscape. Despite insulin therapy remaining the cornerstone of CFRD management, the variability in response to CFTR modulators underscores the need for personalized treatment approaches. The review advocates for further research into non-CFTR therapeutic targets, emphasizing the need to address the multifaceted pathophysiology of CFRD. Understanding the intricate mechanisms underlying CFRD will pave the way for innovative treatments, moving beyond insulin therapy to target the disease's root causes and improve the quality of life for individuals with CF.

Extracellular miRNAs in the serum and feces of mice exposed to high‑dose radiation

Exposure to high-dose radiation causes life-threatening intestinal damage. Histopathology is the most accurate method of judging the extent of intestinal damage following death. However, it is difficult to predict the extent of intestinal damage. The present study investigated extracellular microRNAs (miRNAs or miRs) in serum and feces using a radiation-induced intestinal injury mouse model. A peak of 25-200 nucleotide small RNAs was detected in mouse serum and feces by bioanalyzer, indicating the presence of miRNAs. Microarray analysis detected four miRNAs expressed in the small intestine and increased by >2-fold in serum and 19 in feces following 10 Gy radiation exposure. Increased miR-375-3p in both serum and feces suggests leakage due to radiation-induced intestinal injury and may be a candidate for high-dose radiation biomarkers.

The serum small non-coding RNA (SncRNA) landscape as a molecular biomarker of age associated muscle dysregulation and insulin resistance in older adults

Small noncoding RNAs (sncRNAs) are implicated in age-associated pathologies, including sarcopenia and insulin resistance (IR). As potential circulating biomarkers, most studies have focussed on microRNAs (miRNAs), one class of sncRNA. This study characterized the wider circulating sncRNA transcriptome of older individuals and associations with sarcopenia and IR. sncRNA expression including miRNAs, transfer RNAs (tRNAs), tRNA-associated fragments (tRFs), and piwi-interacting RNAs (piRNAs) was measured in serum from 21 healthy and 21 sarcopenic Hertfordshire Sarcopenia Study extension women matched for age (mean 78.9 years) and HOMA2-IR. Associations with age, sarcopenia and HOMA2-IR were examined and predicted gene targets and biological pathways characterized. Of the total sncRNA among healthy controls, piRNAs were most abundant (85.3%), followed by tRNAs (4.1%), miRNAs (2.7%), and tRFs (0.5%). Age was associated (FDR < 0.05) with 2 miRNAs, 58 tRNAs, and 14 tRFs, with chromatin organization, WNT signaling, and response to stress enriched among gene targets. Sarcopenia was nominally associated (p < .05) with 12 tRNAs, 3 tRFs, and 6 piRNAs, with target genes linked to cell proliferation and differentiation such as Notch Receptor 1 (NOTCH1), DISC1 scaffold protein (DISC1), and GLI family zinc finger-2 (GLI2). HOMA2-IR was nominally associated (p<0.05) with 6 miRNAs, 9 tRNAs, 1 tRF, and 19 piRNAs, linked with lysine degradation, circadian rhythm, and fatty acid biosynthesis pathways. These findings identify changes in circulating sncRNA expression in human serum associated with chronological age, sarcopenia, and IR. These may have clinical utility as circulating biomarkers of ageing and age-associated pathologies and provide novel targets for therapeutic intervention.

Dysregulated miRNA-375, IL-17, TGF-β, and Microminerals Are Associated with Calpain-10 SNP 19 in Diabetic Patients: Correlation with Diabetic Nephropathy Stages

Zinc (Zn) and copper (Cu) have been shown to have the potential to improve glucose metabolism through interactions with cytokines and signaling events with multiple genes. miRNA-375 and the Calpin-10 gene are potential genetic biomarkers for the early prediction of diabetic nephropathy (DN). 128 healthy controls and 129 type 2 diabetic (T2DM) participants were matched for age and sex. Three subgroups were identified from the T2DM group: 39 patients had microalbuminuria, 41 had macroalbuminuria, and 49 patients had renal problems. Circulating miR-375 expression levels were measured via qPCR. Calpain-10 SNP 19 (rs3842570) genotyping was assessed with allele-specific PCR in all the included participants. Spectrophotometry was used to measure the concentrations of serum copper, zinc, and magnesium, while ELISA was used to measure the levels of TGF-β and IL-17. There was significant up-regulation in the expression of miR-375 and serum levels of TGF-β, IL-17, Cu, and the Cu/Zn ratio, whereas, in contrast to the control group, the Zn and Mg levels were lower in the T2DM group. The DN groups had significantly lower miR-375, TGF-β, IL-17, Mg, and Zn levels compared with the T2DM without nephropathy group. Furthermore, between TGF-β, IL-17, and miRNA-375, there were notable correlations. Calpain-10 SNP 19 genotype 22 and allele 2 were linked to a higher incidence of T2DM and DN. Significant TGF-β, Cu, Cu/Zn ratio, HbAc1, and creatinine levels, but insignificant miRNA-375 levels, were associated with genotype 22 of Calpain-10 SNP 19. interactions between the Calpain-10 SNP 19 genotype 22 and IL-17, TGF-β, mineral levels, and miRNA-375 might contribute to the aetiology of DN and T2DM and may have clinical implications for diagnosis and management.

Beta-cell death and dysfunction drives hyperglycaemia in organ donors

BACKGROUND

Donor hyperglycaemia following brain death has been attributed to reversible insulin resistance. However, our islet and pancreas transplant data suggest that other mechanisms may be predominant. We aimed to determine the relationships between donor insulin use and markers of beta-cell death and beta-cell function in pancreas donors after brain death.

METHODS

In pancreas donors after brain death, we compared clinical and biochemical data in 'insulin-treated' and 'not insulin-treated donors' (IT vs. not-IT). We measured plasma glucose, C-peptide and levels of circulating unmethylated insulin gene promoter cell-free DNA (INS-cfDNA) and microRNA-375 (miR-375), as measures of beta-cell death. Relationships between markers of beta-cell death and islet isolation outcomes and post-transplant function were also evaluated.

RESULTS

Of 92 pancreas donors, 40 (43%) required insulin. Glycaemic control and beta-cell function were significantly poorer in IT donors versus not-IT donors [median (IQR) peak glucose: 8 (7-11) vs. 6 (6-8) mmol/L, p = .016; C-peptide: 3280 (3159-3386) vs. 3195 (2868-3386) pmol/L, p = .046]. IT donors had significantly higher levels of INS-cfDNA [35 (18-52) vs. 30 (8-51) copies/ml, p = .035] and miR-375 [1.050 (0.19-1.95) vs. 0.73 (0.32-1.10) copies/nl, p = .05]. Circulating donor miR-375 was highly predictive of recipient islet graft failure at 3 months [adjusted receiver operator curve (SE) = 0.813 (0.149)].

CONCLUSIONS

In pancreas donors, hyperglycaemia requiring IT is strongly associated with beta-cell death. This provides an explanation for the relationship of donor IT with post-transplant beta-cell dysfunction in transplant recipients.

The role of noncoding RNAs in pancreatic birth defects

Congenital defects in the pancreas can cause severe health issues such as pancreatic cancer and diabetes which require lifelong treatment. Regenerating healthy pancreatic cells to replace malfunctioning cells has been considered a promising cure for pancreatic diseases including birth defects. However, such therapies are currently unavailable in the clinic. The developmental gene regulatory network underlying pancreatic development must be reactivated for in vivo regeneration and recapitulated in vitro for cell replacement therapy. Thus, understanding the mechanisms driving pancreatic development will pave the way for regenerative therapies. Pancreatic progenitor cells are the precursors of all pancreatic cells which use epigenetic changes to control gene expression during differentiation to generate all of the distinct pancreatic cell types. Epigenetic changes involving DNA methylation and histone modifications can be controlled by noncoding RNAs (ncRNAs). Indeed, increasing evidence suggests that ncRNAs are indispensable for proper organogenesis. Here, we summarize recent insight into the role of ncRNAs in the epigenetic regulation of pancreatic development. We further discuss how disruptions in ncRNA biogenesis and expression lead to developmental defects and diseases. This review summarizes in vivo data from animal models and in vitro studies using stem cell differentiation as a model for pancreatic development.

A Review of micro RNAs changes in T2DM in animals and humans

Type 2 diabetes mellitus (T2DM) and its associated complications have become a crucial public health concern in the world. According to the literature, chronic inflammation and the progression of T2DM have a close relationship. Accumulated evidence suggests that inflammation enhances the insulin secretion lost by islets of Langerhans and the resistance of target tissues to insulin action, which are two critical features in T2DM development. Based on recently highlighted research that plasma concentration of inflammatory mediators such as tumor necrosis factor α and interleukin-6 are elevated in insulin-resistant and T2DM, and it raises novel question marks about the processes causing inflammation in both situations. Over the past few decades, microRNAs (miRNAs), a class of short, noncoding RNA molecules, have been discovered to be involved in the regulation of inflammation, insulin resistance, and T2DM pathology. These noncoding RNAs are specifically comprised of RNA-induced silencing complexes and regulate the expression of specific protein-coding genes through various mechanisms. There is extending evidence that describes the expression profile of a special class of miRNA molecules altered during T2DM development. These modifications can be observed as potential biomarkers for the diagnosis of T2DM and related diseases. In this review study, after reviewing the possible mechanisms involved in T2DM pathophysiology, we update recent information on the miRNA roles in T2DM, inflammation, and insulin resistance.

Ang II Controls the Expression of Mapkap1 by miR-375 and Affects the Function of Islet β Cells

BACKGROUND

The RAS system is involved in the regulation of islet function, but its regulation remains unclear.

OBJECTIVE

This study investigates the role of an islet-specific miR-375 in the effect of RAS system on islet β-cells.

METHODS

miR-375 mimics and inhibitors were transfected into insulin-secreting MIN6 cells in the presence or absence of RAS component.

RESULTS

Compared to control, in Ang II-treated MIN6 cells, miR-375 mimic transfection results in a decrement in cell viability and Akt-Ser levels (0.739±0.05 vs. 0.883±0.06 and 0.40±0.04 vs. 0.79±0.04, respectively), while the opposite occurred in miR-375 inhibitor-transfected cells (1.032±0.11 vs. 0.883±0.06 and 0.98±0.05 vs. 0.79±0.04, respectively, P<0.05). Mechanistically, transfection of miR- 375 mimics into Ang II-treated MIN6 cells significantly reduced the expression of Mapkap1 protein (0.97±0.15 vs. 0.63±0.06, P<0.05); while miR-375 inhibitor-transfected cells elevated Mapkap1 expression level (0.35±0.11 vs. 0.90±0.05, P<0.05), without changes in mRNA expression. Transfection of miR-375 specific inhibitors TSB-Mapkap1 could elevate Mapkap1 (1.62±0.02 vs. 0.68±0.01, P<0.05), while inhibition of Mapkap1 could significantly reduce the level of Akt-Ser473 phosphorylation (0.60±0.14 vs. 1.80±0.27, P<0.05).

CONCLUSION

The effects of Ang II on mouse islet β cells were mediated by miR-375 through miR- 375/Mapkap 1 axis. This targeted regulation may occur by affecting Akt phosphorylation of β cells. These results may provide new ideas and a scientific basis for further development of miRNA-targeted islet protection measures.

MicroRNAs in Type 2 Diabetes: Focus on MicroRNA Profiling in Islets of Langerhans

Differential expression of microRNAs (miRNAs) is observed in many diseases including type 2 diabetes (T2D). Insulin secretion from pancreatic beta cells is central for the regulation of blood glucose levels and failure to release enough insulin results in hyperglycemia and T2D. The importance in T2D pathogenesis of single miRNAs in beta cells has been described; however, to get the full picture, high-throughput miRNA sequencing is necessary. Here we describe a method using small RNA sequencing, from sample preparation to expression analysis using bioinformatic tools. In the end, a tutorial on differential expression analysis is presented in R using publicly available data.

Evaluation of serum miR-216a and miR-375 as biomarkers in dogs with acute pancreatitis

BACKGROUND

Serum microRNAs have emerged as biomarkers of various diseases. Overexpression of serum miR-216a and miR-375 occurs in dogs with experimentally induced acute pancreatitis (AP).

OBJECTIVES

To identify the possibility of using serum miR-216a and miR-375 as biomarkers for the diagnosis and evaluation of treatment response in dogs with naturally occurring AP.

ANIMALS

Twenty-one dogs with AP and 20 healthy dogs.

METHODS

Cross-sectional study. The relative expression of serum hsa-miR-216a-5p, cfa-miR-216a, and cfa-miR-375 were analyzed using reverse transcription and real-time PCR.

RESULTS

A significant difference in the serum expression of cfa-miR-375 was found between dogs with AP (median [interquartile range] 3.59 [1.55-24.52]-fold) and healthy dogs (0.81 [0.54-2.21]-fold, P < .001), and no significant differences were observed in hsa-miR-216a-5p and cfa-miR-216a (P > .05). The area under the receiver operating characteristic curve of serum cfa-miR-375 for differentiating between AP dogs and healthy dogs was 0.84 (95% confidence interval [CI]: 0.71-0.96). The expressions of hsa-miR-216a-5p and cfa-miR-375 were positively correlated with the concentrations of serum C-reactive protein (r_s  = .46, r_s  = .48, respectively), but not with the serum specific canine pancreatic lipase. The expression of cfa-miR-375 was significantly less after treatment in dogs with AP (P = .02).

CONCLUSIONS AND CLINICAL IMPORTANCE

Serum cfa-miR-375 could be a potential biomarker for the diagnosis and evaluation of treatment response of AP in dogs. In addition, miR-216a and miR-375 could be associated with inflammatory processes in dogs with AP.

Milk Exosomal microRNAs: Postnatal Promoters of β Cell Proliferation but Potential Inducers of β Cell De-Differentiation in Adult Life

Pancreatic β cell expansion and functional maturation during the birth-to-weaning period is driven by epigenetic programs primarily triggered by growth factors, hormones, and nutrients provided by human milk. As shown recently, exosomes derived from various origins interact with β cells. This review elucidates the potential role of milk-derived exosomes (MEX) and their microRNAs (miRs) on pancreatic β cell programming during the postnatal period of lactation as well as during continuous cow milk exposure of adult humans to bovine MEX. Mechanistic evidence suggests that MEX miRs stimulate mTORC1/c-MYC-dependent postnatal β cell proliferation and glycolysis, but attenuate β cell differentiation, mitochondrial function, and insulin synthesis and secretion. MEX miR content is negatively affected by maternal obesity, gestational diabetes, psychological stress, caesarean delivery, and is completely absent in infant formula. Weaning-related disappearance of MEX miRs may be the critical event switching β cells from proliferation to TGF-β/AMPK-mediated cell differentiation, whereas continued exposure of adult humans to bovine MEX miRs via intake of pasteurized cow milk may reverse β cell differentiation, promoting β cell de-differentiation. Whereas MEX miR signaling supports postnatal β cell proliferation (diabetes prevention), persistent bovine MEX exposure after the lactation period may de-differentiate β cells back to the postnatal phenotype (diabetes induction).

lncRNA TINCR Regulates Proliferation and Invasion of Hepatocellular Carcinoma Cells by Regulating the miR-375/ATG7 Axis

Purpose

The aim of this study was to examine the role of the long noncoding RNA (lncRNA) terminal differentiation-induced noncoding RNA (TINCR) on the proliferation, apoptosis, and invasion of liver cancer cells and its mechanism.

Methods

The expression of lncRNA TINCR in twenty cases of liver cancer tissues, matched liver cancer cell lines, and paracancerous tissues was analyzed by RT-PCR. CCK-8, clonogenic test, flow cytometry, and Transwell assay were used to measure the effect of lncRNA TINCR overexpression and knockdown on cell proliferation, apoptosis, and invasion. Luciferase reporter and Western blotting showed that lncRNA TINCR regulates the expression of ATG7 through miR-375, and the rescue experiment proved that lncRNA TINCR controls the invasion and proliferation of liver cancer cells via the miR-375/ATG7 signaling pathway. Furthermore, in vivo nude mouse assay demonstrated that overexpression of lncRNA TINCR inhibited liver cancer cell growth.

Results

The lncRNA TINCR was highly expressed in liver cancer tissues and cell lines. Liver cancer cells responded differently to knockdown of the lncRNA TINCR compared to overexpression in terms of proliferation, colony formation, and invasion. miR-375 negatively affected the expression of ATG7. The lncRNA TINCR bound to miR-375 and influenced its expression. Transfection of miR-375 mimics greatly inhibited the inhibitory effect of lncRNA TINCR knockdown on the invasion and proliferation, whereas transfection of miR-375 inhibitor considerably reverses this effect on liver cancer cells. Overexpressing lncRNA TINCR increased liver cancer cell proliferation in vivo.

Conclusion

By controlling the miR-375/ATG7 axis, the lncRNA TINCR impacts the proliferation and invasion of liver cancer cells. Therefore, the lncRNA TINCR/miR-375/ATG7 signaling axis could be a novel biological target for the diagnosis and therapy of liver cancer.

microRNAs in newborns with low birth weight: relation to birth size and body composition

BACKGROUND

Children with low birth weight (LBW) have a higher risk of developing endocrine-metabolic disorders later in life. Deregulation of specific microRNAs (miRNAs) could underscore the programming of adult pathologies. We analyzed the miRNA expression pattern in both umbilical cord serum samples from LBW and appropriate-for-gestational-age (AGA) newborns and maternal serum samples in the 3rd trimester of gestation, and delineated the relationships with fetal growth, body composition, and markers of metabolic risk.

METHODS

Serum samples of 12 selected mother-newborn pairs, including 6 LBW and 6 AGA newborns, were used for assessing miRNA profile by RNA-sequencing. The miRNAs with differential expression were validated in a larger cohort [49 maternal samples and 49 umbilical cord samples (24 LBW, 25 AGA)] by RT-qPCR. Anthropometric, endocrine-metabolic markers and body composition (by DXA) in infants were determined longitudinally over 12 months.

RESULTS

LBW newborns presented reduced circulating concentrations of miR-191-3p (P = 0.015). miR-191-3p levels reliably differentiated LBW from AGA individuals (ROC AUC = 0.76) and were positively associated with anthropometric and body composition measures at birth and weight Z-score at 12 months (P &lt; 0.05).

CONCLUSIONS

miR-191-3p was reliably different in LBW individuals, and could be a new player in the epigenetic mechanisms linking LBW and future endocrine-metabolic adverse outcomes.

IMPACT

Children with low birth weight (LBW) have a higher risk of developing endocrine-metabolic disorders. Deregulation of specific microRNAs (miRNAs) could underscore the programming of those pathologies. miR-191-3p is downregulated in serum of LBW newborns, and its concentrations associate positively with neonatal anthropometric measures, with lean mass and bone accretion at age 15 days and with weight Z-score at age 12 months. miR-191-3p was reliably different in individuals with LBW, and could be a new player in the epigenetic mechanisms connecting LBW and future endocrine-metabolic adverse outcomes.

Transgenic overexpression of microRNA-30d in pancreatic beta-cells progressively regulates beta-cell function and identity

Abnormal microRNA functions are closely associated with pancreatic β-cell loss and dysfunction in type 2 diabetes. Dysregulation of miR-30d has been reported in the individuals with diabetes. To study how miR-30d affects pancreatic β-cell functions, we generated two transgenic mouse lines that specifically overexpressed miR-30d in β-cells at distinct low and high levels. Transgenic overexpressed miR-30d systemically affected β-cell function. Elevated miR-30d at low-level (TgL, 2-fold) had mild effects on signaling pathways and displayed no significant changes to metabolic homeostasis. In contrast, transgenic mice with high-level of miR-30d expression (TgH, 12-fold) exhibited significant diet-induced hyperglycemia and β-cell dysfunction. In addition, loss of β-cell identity was invariably accompanied with increased insulin/glucagon-double positive bihormonal cells and excess plasma glucagon levels. The transcriptomic analysis revealed that miR-30d overexpression inhibited β-cell-enriched gene expression and induced α-cell-enriched gene expression. These findings implicate that an appropriate miR-30d level is essential in maintaining normal β-cell identity and function.

Purification of human iPSC-derived cells at large scale using microRNA switch and magnetic-activated cell sorting

For regenerative cell therapies using pluripotent stem cell (PSC)-derived cells, large quantities of purified cells are required. Magnetic-activated cell sorting (MACS) is a powerful approach to collect target antigen-positive cells; however, it remains a challenge to purify various cell types efficiently at large scale without using antibodies specific to the desired cell type. Here we develop a technology that combines microRNA (miRNA)-responsive mRNA switch (miR-switch) with MACS (miR-switch-MACS) to purify large amounts of PSC-derived cells rapidly and effectively. We designed miR-switches that detect specific miRNAs expressed in target cells and controlled the translation of a CD4-coding transgene as a selection marker for MACS. For the large-scale purification of induced PSC-derived cardiomyocytes (iPSC-CMs), we transferred miR-208a-CD4 switch-MACS and obtained purified iPSC-CMs efficiently. Moreover, miR-375-CD4 switch-MACS highly purified pancreatic insulin-producing cells and their progenitors expressing Chromogranin A. Overall, the miR-switch-MACS method can efficiently purify target PSC-derived cells for cell replacement therapy.

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MiR-208a-CD4 switch-MACS can purify a large amount of iPSC-CMs in a short time

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MiR-208a switch can purify iPSC-CMs in each subtype-specific protocol

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MiR-375-CD4 switch-MACS can be applied to pancreatic endocrine precursor cells

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MiR-switch-MACS method can be efficient for large-scale target cell purification

Human pancreatic islet miRNA-mRNA networks of altered miRNAs due to glycemic status

MicroRNAs (miRNAs) are short non-coding RNAs that regulate gene expression via mRNA targeting, playing important roles in the pancreatic islets. We aimed to identify molecular pathways and genomic regulatory regions associated with altered miRNA expression due to glycemic status, which could contribute to the development of type 2 diabetes (T2D). To this end, miRNAs were identified by a combination of differential miRNA expression and correlation analysis in human islet samples from donors with normal and elevated blood glucose levels. Analysis and clustering of highly correlated, experimentally validated gene targets of these miRNAs revealed two islet-specific clusters, which were associated with key aspects of islet functions and included a high number of T2D-related genes. Finally, cis-eQTLs and public GWAS data integration uncovered suggestive genomic signals of association with insulin secretion and T2D. The miRNA-driven network-based approach presented in this study contributes to a better understanding of impaired insulin secretion in T2D pathogenesis.

Extracellular miRNAs as mediators of obesity-associated disease

Extracellular miRNAs are found in a variety of body fluids and mediate intercellular and interorgan communication, thus regulating gene expression and cellular metabolism. These miRNAs are secreted either in small vesicles/exosomes (sEV) or bound to proteins such as Argonaute and high-density lipoprotein. Both exosomal and protein-bound circulating miRNAs are altered in obesity. Although all tissues can contribute to changes in circulating miRNAs, adipose tissue itself is an important source of these miRNAs, especially those in sEVs. These are derived from both adipocytes and macrophages and participate in crosstalk between these cells, as well as peripheral tissues, including liver, skeletal muscle and pancreas, whose function may be impaired in obesity. Changes in levels of circulating miRNAs have also been linked to the beneficial effects induced by weight loss interventions, including diet, exercise and bariatric surgery, further indicating a role for these miRNAs as mediators of disease pathogenesis. Here, we review the role of circulating miRNAs in the pathophysiology of obesity and explore their potential use as biomarkers and in therapy of obesity-associated metabolic syndrome.

Recent Advances in the Generation of β-Cells from Induced Pluripotent Stem Cells as a Potential Cure for Diabetes Mellitus

Diabetes mellitus (DM) is a group of metabolic disorders characterized by high blood glucose levels due to insufficient insulin secretion, insulin action, or both. The present-day solution to diabetes mellitus includes regular administration of insulin, which brings about many medical complications in diabetic patients. Although islet transplantation from cadaveric subjects was proposed to be a permanent cure, the increased risk of infections, the need for immunosuppressive drugs, and their unavailability had restricted its use. To overcome this, the generation of renewable and transplantable β-cells derived from autologous induced pluripotent stem cells (iPSCs) has gained enormous interest as a potential therapeutic strategy to treat diabetes mellitus permanently. To date, extensive research has been undertaken to derive transplantable insulin-producing β-cells (iβ-cells) from iPSCs in vitro by recapitulating the in vivo developmental process of the pancreas. This in vivo developmental process relies on transcription factors, signaling molecules, growth factors, and culture microenvironment. This review highlights the various factors facilitating the generation of mature β-cells from iPSCs. Moreover, this review also describes the generation of pancreatic progenitors and β-cells from diabetic patient-specific iPSCs, exploring the potential of the diabetes disease model and drug discovery. In addition, the applications of genome editing strategies have also been discussed to achieve patient-specific diabetes cell therapy. Last, we have discussed the current challenges and prospects of iPSC-derived β-cells to improve the relative efficacy of the available treatment of diabetes mellitus.

The Role of miRNA in the Pathophysiology of Neuroendocrine Tumors

Neuroendocrine tumors (NETs) represent a tumor group that is both rare and heterogeneous. Prognosis is largely determined by the tumor grading and the site of the primary tumor and metastases. Despite intensive research efforts, only modest advances in diagnostic and therapeutic approaches have been achieved in recent years. For patients with non-respectable tumor stages, prognosis is poor. In this context, the development of novel diagnostic tools for early detection of NETs and prediction of tumor response to therapy as well as estimation of the overall prognosis would greatly improve the clinical management of NETs. However, identification of novel diagnostic molecules is hampered by an inadequate understanding of the pathophysiology of neuroendocrine malignancies. It has recently been demonstrated that microRNA (miRNA), a family of small RNA molecules with an established role in the pathophysiology of quite different cancer entities, may also play a role as a biomarker. Here, we summarize the available knowledge on the role of miRNAs in the development of NET and highlight their potential use as serum-based biomarkers in the context of this disease. We discuss important challenges currently preventing their use in clinical routine and give an outlook on future directions of miRNA research in NET.

miR-375 induces adipogenesis through targeting Erk1 in pancreatic duct cells under the influence of sodium palmitate

The goal of this study was to research long-term saturated fatty acid overexposure that can induce differentiation of pancreatic duct cells into adipocytes and also into β-cells. The important findings can be summarized as follows: (i) adipogenesis and early stage β-cell differentiation were stimulated in duct cells under lipotoxicity and glucolipotoxicity conditions, (ii) miR-375 expression was upregulated while its target Erk1 was downregulated and miR-375 inhibitor upregulated Erk1 while expression of adipogenesis markers was downregulated in duct cells under both conditions, (iii) apoptosis was induced in β and duct cells under both conditions, (iv) lipotoxicity induced proliferation of co-cultured β-cells. These findings suggest that long-term saturated fatty acid overexposure may cause intrapancreatic fat accumulation by inducing differentiation of duct cells into adipocytes and it may contributes to β-cell compensation by stimulating the early stage of β-cell differentiation in duct cells. In addition, miR-375 may have the potential to be a new target in the treatment of Type 2 diabetes, and NAFPD due to its role in the adipogenesis of duct cells.

Treatment of diabetic mice by microfluidic system-assisted transplantation of stem cells-derived insulin-producing cells transduced with miRNA

AIMS

Cell-based therapy is a promising approach for the treatment of type-1 diabetes mellitus. Identifying stem cells with differentiation potential to Insulin-producing cells (IPCs) and their application is an emerging issue. Different strategies have been used to support cell survival and their specific functions to control hyperglycemia conditions. Novel technologies using appropriate materials/fibers can improve cell transplantation.

MAIN METHODS

In the present study, IPCs were differentiated from adipose-derived stem cells transduced with miR-375 and anti-miR-7. The cells' survival rate was also improved using a microfluidic system before their in vivo transplantation.

KEY FINDINGS

After adopting a stable, functional condition of the IPCs, the cells were used for in vivo grafting to diabetic mice, which resulted in a substantial drop in blood glucose during four weeks of grafting compared to the control group (p < 0.0001). The pattern of blood glucose levels in the mice receiving fiber entrapped IPCs, was similar to that of non-diabetic mice. Blood insulin was elevated in diabetic mice which received a transplant of fiber-entrapped-IPCs carrying miR-375 and anti-miR-7 after five weeks of transplantation compared to the diabetic mice (p < 0.014).

SIGNIFICANCE

For the first time, this study showed that the two-component microfluidic system is useful for supporting the Collagen-Alginate fiber-entrapped IPCs and the miRNA-based cell therapy. Overall, our data show that the IPC encapsulation using a microfluidic system can support the cells in terms of morphology and biological function and their efficiency for controlling the hyperglycemia condition in diabetic mice.

The Role of MicroRNAs in the Induction of Pancreatic Differentiation

Stem cell-based therapy is one of the therapeutic options with promising results in the treatment of diabetes. Stem cells from various sources are expanded and induced to generate the cells capable of secreting insulin. These insulin-producing cells [IPCs] could be used as an alternative to islets in the treatment of patients with diabetes. Soluble growth factors, small molecules, geneencoding transcription factors, and microRNAs [miRNAs] are commonly used for the induction of stem cell differentiation. MiRNAs are small non-coding RNAs with 21-23 nucleotides that are involved in the regulation of gene expression by targeting multiple mRNA targets. Studies have shown the dynamic expression of miRNAs during pancreatic development and stem cell differentiation. MiR- 7 and miR-375 are the most abundant miRNAs in pancreatic islet cells and play key roles in pancreatic development as well as islet cell functions. Some studies have tried to use these small RNAs for the induction of pancreatic differentiation. This review focuses on the miRNAs used in the induction of stem cells into IPCs and discusses their functions in pancreatic β-cells.

The Predominant microRNAs in β-cell Clusters for Insulin Regulation and Diabetic Control

micro (mi)-RNAs are vital regulators of multiple processes including insulin signaling pathways and glucose metabolism. Pancreatic β-cells function is dependent on some miRNAs and their target mRNA, which together form a complex regulative network. Several miRNAs are known to be directly involved in β-cells functions such as insulin expression and secretion. These small RNAs may also play significant roles in the fate of β-cells such as proliferation, differentiation, survival and apoptosis. Among the miRNAs, miR-7, miR-9, miR-375, miR-130 and miR-124 are of particular interest due to being highly expressed in these cells. Under diabetic conditions, although no specific miRNA profile has been noticed, the expression of some miRNAs and their target mRNAs are altered by posttranscriptional mechanisms, exerting diverse signs in the pathobiology of various diabetic complications. The aim of this review article is to discuss miRNAs involved in the process of stem cells differentiation into β-cells, resulting in enhanced β-cell functions with respect to diabetic disorders. This paper will also look into the impact of miRNA expression patterns on in vitro proliferation and differentiation of β-cells. The efficacy of the computational genomics and biochemical analysis to link the changes in miRNA expression profiles of stem cell-derived β-cells to therapeutically relevant outputs will be discussed as well.

Exosomes from β-Cells Promote Differentiation of Induced Pluripotent Stem Cells into Insulin-Producing Cells Through microRNA-Dependent Mechanisms

OBJECTIVE

Exosomes have emerged as potential tools for the differentiation of induced pluripotent stem cells (iPSCs) into insulin-producing cells (IPCs). Exosomal microRNAs are receiving increasing attention in this process. Here, we aimed at investigating the role of exosomes derived from a murine pancreatic β-cell line and identifying signature exosomal miRNAs on iPSCs differentiation.

METHODS

Exosomes were isolated from MIN6 cells and identified with TEM, NTA and Western blot. PKH67 tracer and transwell assay were used to confirm exosome delivery into iPSCs. qRT-PCR was applied to detect key pancreatic transcription gene expression and exosome-derived miRNA expression. Insulin secretion was determined using FCM and immunofluorescence. The specific exosomal miRNAs were determined via RNA-interference of Ago2. The therapeutic effect of 21 day-exosome-induced IPCs was validated in T1D mice induced by STZ.

RESULTS

iPSCs cultured in medium containing exosomes showed sustained higher expression of MAFA, Insulin1, Insulin2, Isl1, Neuroud1, Nkx6.1 and NGN3 compared to control iPSCs. In FCM analysis, approximately 52.7% of the differentiated cells displayed insulin expression at the middle stage. Consistent with the gene expression data, immunofluorescence assays showed that Nkx6.1 and insulin expression in iPSCs were significantly upregulated. Intriguingly, the expression of pancreatic markers and insulin was significantly decreased in iPSCs cultured with siAgo2 exosomes. Transplantation of 21 day-induced IPCs intoT1D mice efficiently enhanced glucose tolerance and partially controlled hyperglycemia. The therapeutic effect was significantly attenuated in T1D mice that received iPSCs cultured with siAgo2 exosomes. Of the seven exosomal microRNAs selected for validation, miR-706, miR-709, miR-466c-5p, and miR-423-5p showed dynamic expression during 21 days in culture.

CONCLUSION

These data indicate that differentiation of exosome-induced iPSCs into functional cells is crucially dependent on the specific miRNAs encased within exosomes, whose functional analysis is likely to provide insight into novel regulatory mechanisms governing iPSCs differentiation into IPCs.

Effect of lncRNA WT1-AS regulating WT1 on oxidative stress injury and apoptosis of neurons in Alzheimer's disease via inhibition of the miR-375/SIX4 axis

Objective: To study the effect of lncRNA WT1-AS on oxidative stress injury (OSI) and apoptosis of neurons in Alzheimer's disease (AD) and its specific mechanisms related to the microRNA-375 (miR-375)/SIX4 axis and WT1 expression.

Results: After bioinformatic prediction, WT1-AS was found to be downregulated in Aβ_25-35treated SH-SY5Y cells, and WT1-AS overexpression inhibited WT1 expression. WT1 could target miR-375 to promote its expression. miR-375 bound to SIX4, and miR-375 overexpression inhibited SIX4 expression. WT1-AS inhibited OSI and apoptosis, while WT1 and miR-375 overexpression or SIX4 silencing reversed the WT1-AS effect on OSI and apoptosis. In vivo experiments revealed that WT1-AS improved learning/memory abilities and inhibited OSI and apoptosis in AD mice.

Conclusion: Overexpression of WT1-AS can inhibit the miR-375/SIX4 axis, OSI and neuronal apoptosis in AD by inhibiting WT1 expression.

Methods: Related lncRNAs were identified, and miR-375 downstream targets were predicted. WT1-AS, WT1, miR-375 and SIX4 expression was detected in a cell model induced by Aβ_25-35. The binding of WT1 with miR-375 and that of miR-375 with SIX4 were further confirmed. Adenosine triphosphate (ATP), reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and lactate dehydrogenase (LDH) activities, and apoptosis levels were tested after mitochondrial membrane potential observation. Learning/memory abilities and neuronal apoptosis were tested in a mouse model.

miR-27b Modulates Insulin Signaling in Hepatocytes by Regulating Insulin Receptor Expression

Insulin resistance (IR) is one of the key contributing factors in the development of type 2 diabetes mellitus (T2DM). However, the molecular mechanisms leading to IR are still unclear. The implication of microRNAs (miRNAs) in the pathophysiology of multiple cardiometabolic pathologies, including obesity, atherosclerotic heart failure and IR, has emerged as a major focus of interest in recent years. Indeed, upregulation of several miRNAs has been associated with obesity and IR. Among them, miR-27b is overexpressed in the liver in patients with obesity, but its role in IR has not yet been thoroughly explored. In this study, we investigated the role of miR-27b in regulating insulin signaling in hepatocytes, both in vitro and in vivo. Therefore, assessment of the impact of miR-27b on insulin resistance through the hepatic tissue is of special importance due to the high expression of miR-27b in the liver together with its known role in regulating lipid metabolism. Notably, we found that miR-27b controls post-transcriptional expression of numerous components of the insulin signaling pathway including the insulin receptor (INSR) and insulin receptor substrate 1 (IRS1) in human hepatoma cells. These results were further confirmed in vivo showing that overexpression and inhibition of hepatic miR-27 enhances and suppresses hepatic INSR expression and insulin sensitivity, respectively. This study identified a novel role for miR-27 in regulating insulin signaling, and this finding suggests that elevated miR-27 levels may contribute to early development of hepatic insulin resistance.

Therapeutic Potentials of MicroRNAs for Curing Diabetes Through Pancreatic β-Cell Regeneration or Replacement

MicroRNAs are a type of noncoding RNAs that regulates the expression of target genes at posttranscriptional level. MicroRNAs play essential roles in regulating the expression of different genes involved in pancreatic development, β-cell mass maintenance, and β-cell function. Alteration in the level of miRNAs involved in β-cell function leads to the diabetes. Being an epidemic, diabetes threatens the life of millions of patients posing a pressing demand for its urgent resolve. However, the currently available therapies are not substantial to cure the diabetic epidemic. Thus, researchers are trying to find new ways to replenish the β-cell mass in patients with diabetes. One promising approach is the in vivo regeneration of β-cell mass or increasing the efficiency of β-cell function. Another clinical strategy is the transplantation of in vitro developed β-like cells. Owing to their role in pancreatic β-cell development, maintenance, functioning and their involvement in diabetes, overexpression or attenuation of different miRNAs can cause β-cell regeneration in vivo or can direct the differentiation of various kinds of stem/progenitor cells to β-like cells in vitro. Here, we will summarize different strategies used by researchers to investigate the therapeutic potentials of miRNAs, with focus on miR-375, for curing diabetes through β-cell regeneration or replacement.

MicroRNA-375-mediated regulation of ILC2 cells through TSLP in allergic rhinitis

Background

Studies have shown that the number and function of type II innate lymphoid cells (ILC2) in peripheral blood of allergic rhinitis (AR) children increased significantly. This study aims to evaluate the role of miR-375 in the regulation of the differentiation and function of ILC2 through both in vivo and in vitro studies.

Methods

The expression of miR-375, thymic stromal lymphopoietin (TSLP) and the frequency of ILC2 were detected and compared between AR children and controls by real-time polymerase chain reaction (PCR), enzyme-linked immunosorbnent assay (ELISA) and flow cytometry, respectively. The miR-375 mimics or inhibitors were transfected into human nasal epithelial cells (HNECs), and the production of TSLP was detected by ELISA. HNECs and ILC2s were co-cultured to explore the role of miR-375 on ILC2s. AR mice models were established to prove the effect of miR-375 on ILC2s in vivo.

Results

The expression of TSLP, miR-375, and the frequency of ILC2 were significantly higher in AR compared with controls. We found that the TSLP expression by HNECs were significantly higher when transfected with miR-375 mimics than in those transfected with miR-control and miR-375 inhibitor. In the coculture system, HNECs transfected with miR-375 mimics promote the type II cytokines production by ILC2, and this effect was blocked by anti-TSLP. Our results also showed that the miR-375 inhibitors attenuate allergic symptoms and production of type II cytokines in AR mice.

Conclusions

Our findings suggest that miR-375-mediated regulation of ILC2 cells through TSLP, providing new potential treatment target for AR.

Directed differentiation into insulin-producing cells using microRNA manipulation

Our commentary is focused on three studies that used microRNA overexpression methods for directed differentiation of stem cells into insulin-producing cells. Islet transplantation is the only cell-based therapy used to treat type 1 diabetes mellitus. However, due to the scarcity of cadaveric donors and limited availability of good quality and quantity of islets for transplant, alternate sources of insulin-producing cells are being studied and used by researchers. This commentary provides an overview of distinct studies focused on manipulating microRNA expression to optimize differentiation of embryonic stem cells or induced pluripotent stem cells into insulin-producing cells. These studies have used different approaches to overexpress microRNAs that are highly abundant in human islets (such as miR-375 and miR-7) in their differentiation protocol to achieve better differentiation into functional islet beta (β)-cells.

MicroRNA-127 inhibits cell proliferation via targeting Kif3b in pancreatic β cells

MicroRNAs (miRNAs) have been implicated in β cells dysfunction. Previous studies indicated that miR-127 was specifically abundant in β cells and one of its target genes, Kif3b, promoted cell proliferation. However, the impact of the miR-127-Kif3b axis on β cells remains unknown. In this study, we revealed that miR-127 level was declined both in islets from the mice with a high-fat diet and in MIN6 cells with elevated glucose treatment. The elevated level of miR-127 attenuated β cell proliferation by repressing Kif3b expression without affecting apoptosis and cell cycle, and it dampened insulin secretion. Moreover, β cell-derived miR-127 could also affect the islet endothelial cell-line, MS1, in vitro via the transfer of extracellular vesicles (EVs). Treating MS1 cells with the EVs secreted by MIN6 cells exhibited a higher ability in cell migration and tube formation. However, this effect was abolished by the miR-127 inhibitor co-cultured with EVs-treated MS1 cells. Thus, we define that miR-127 is a crucial regulator of insulin secretion and cell proliferation in pancreatic β cells as well as a potential functional regulation factor in islet endothelial cells.

miR375-3p Distinguishes Low-Grade Neuroendocrine From Non-neuroendocrine Lung Tumors in FFPE Samples

Lung cancer is still one of the leading cause of death worldwide. The clinical variability of lung cancer is high and drives treatment decision. In this context, correct discrimination of pulmonary neuroendocrine tumors is still of critical relevance. The spectrum of neuroendocrine tumors is various, and each type has molecular and phenotypical differences. In order to advance in the discrimination of neuroendocrine from non-neuroendocrine lung tumors, we tested a series of 95 surgically resected and formalin-fixed paraffin embedded lung cancer tissues, and we analyzed the expression of miR205-5p and miR375-3p via TaqMan RT-qPCR. Via a robust mathematical approach, we excluded technical outliers increasing the data reproducibility. We found that miR375-3p levels are higher in low-grade neuroendocrine lung tumor samples compared to non-neuroendocrine lung tumors. However, miR375-3p is not able to distinguish among different types of neuroendocrine lung tumors. In this work, we provide a new molecular marker for distinguishing non-neuroendocrine from low-grade neuroendocrine lung tumors samples establishing an easy miRNA score to be used in clinical settings, enabling the pathologist to classify more accurately lung tumors biopsies, which may be ambiguously cataloged in routine examination.

MicroRNA Networks in Pancreatic Islet Cells: Normal Function and Type 2 Diabetes

Impaired insulin secretion from the pancreatic β-cells is central in the pathogenesis of type 2 diabetes (T2D), and microRNAs (miRNAs) are fundamental regulatory factors in this process. Differential expression of miRNAs contributes to β-cell adaptation to compensate for increased insulin resistance, but deregulation of miRNA expression can also directly cause β-cell impairment during the development of T2D. miRNAs are small noncoding RNAs that posttranscriptionally reduce gene expression through translational inhibition or mRNA destabilization. The nature of miRNA targeting implies the presence of complex and large miRNA-mRNA regulatory networks in every cell, including the insulin-secreting β-cell. Here we exemplify one such network using our own data on differential miRNA expression in the islets of T2D Goto-Kakizaki rat model. Several biological processes are influenced by multiple miRNAs in the β-cell, but so far most studies have focused on dissecting the mechanism of action of individual miRNAs. In this Perspective we present key islet miRNA families involved in T2D pathogenesis including miR-200, miR-7, miR-184, miR-212/miR-132, and miR-130a/b/miR-152. Finally, we highlight four challenges and opportunities within islet miRNA research, ending with a discussion on how miRNAs can be utilized as therapeutic targets contributing to personalized T2D treatment strategies.

Multiomic Profiling Identifies cis-Regulatory Networks Underlying Human Pancreatic β Cell Identity and Function

EndoC-βH1 is emerging as a critical human β cell model to study the genetic and environmental etiologies of β cell (dys)function and diabetes. Comprehensive knowledge of its molecular landscape is lacking, yet required, for effective use of this model. Here, we report chromosomal (spectral karyotyping), genetic (genotyping), epigenomic (ChIP-seq and ATAC-seq), chromatin interaction (Hi-C and Pol2 ChIA-PET), and transcriptomic (RNA-seq and miRNA-seq) maps of EndoC-βH1. Analyses of these maps define known (e.g., PDX1 and ISL1) and putative (e.g., PCSK1 and mir-375) β cell-specific transcriptional cis-regulatory networks and identify allelic effects on cis-regulatory element use. Importantly, comparison with maps generated in primary human islets and/or β cells indicates preservation of chromatin looping but also highlights chromosomal aberrations and fetal genomic signatures in EndoC-βH1. Together, these maps, and a web application we created for their exploration, provide important tools for the design of experiments to probe and manipulate the genetic programs governing β cell identity and (dys)function in diabetes.

EndoC-βH1 is becoming an important cellular model to study genes and pathways governing human β cell identity and function, but its (epi)genomic similarity to primary human islets is unknown. Lawlor et al. complete and compare extensive EndoC and primary human islet multiomic maps to identify shared and distinct genomic circuitry.

A Comprehensive Molecular Characterization of the Pancreatic Neuroendocrine Tumor Cell Lines BON-1 and QGP-1

Experimental models of neuroendocrine tumor disease are scarce, with only a few existing neuroendocrine tumor cell lines of pancreatic origin (panNET). Their molecular characterization has so far focused on the neuroendocrine phenotype and cancer-related mutations, while a transcription-based assessment of their developmental origin and malignant potential is lacking. In this study, we performed immunoblotting and qPCR analysis of neuroendocrine, epithelial, developmental endocrine-related genes as well as next-generation sequencing (NGS) analysis of microRNAs (miRs) on three panNET cell lines, BON-1, QGP-1, and NT-3. All three lines displayed a neuroendocrine and epithelial phenotype; however, while insulinoma-derived NT-3 cells preferentially expressed markers of mature functional pancreatic β-cells (i.e., INS, MAFA), both BON-1 and QGP-1 displayed high expression of genes associated with immature or non-functional β/δ-cells genes (i.e., NEUROG3), or pancreatic endocrine progenitors (i.e., FOXA2). NGS-based identification of miRs in BON-1 and QGP-1 cells revealed the presence of all six members of the miR-17–92 cluster, which have been implicated in β-cell function and differentiation, but also have roles in cancer being both oncogenic or tumor suppressive. Notably, both BON-1 and QGP-1 cells expressed several miRs known to be negatively associated with epithelial–mesenchymal transition, invasion or metastasis. Moreover, both cell lines failed to exhibit migratory activity in vitro. Taken together, NT-3 cells resemble mature functional β-cells, while both BON-1 and QGP-1 are more similar to immature/non-functional pancreatic β/δ-cells or pancreatic endocrine progenitors. Based on the recent identification of three transcriptional subtypes in panNETs, NT-3 cells resemble the “islet/insulinoma tumors” (IT) subtype, while BON-1 and QGP-1 cells were tentatively classified as “metastasis-like/primary” (MLP). Our results provide a comprehensive characterization of three panNET cell lines and demonstrate their relevance as neuroendocrine tumor models.

Glucose stimulates microRNA-199 expression in murine pancreatic β-cells

MicroRNA 199 (miR-199) negatively impacts pancreatic β-cell function and its expression is highly increased in islets from diabetic mice as well as in plasma of diabetic patients. Here we investigated how miR-199 expression is regulated in β-cells by assessing expression of miR-199 precursors (primiR-199a1, primiR-199a2, and primiR-199b) and mature miR-199 (miR-199-3p and miR-199-5p) and promoter transcriptional activity assays in mouse islets and mouse insulinoma cells (MIN6) under different stimuli. We found that mouse islets equally express miR-199-3p and miR-199-5p. However, the primiRNA expression levels differed; although primiR-199a1 expression was about 30% greater than that of primiR-199a2, primiR-199b is barely detected in islets. We observed a 2-fold increase in primiR-199a1 and primiR-199a2 mRNA levels in mouse islets cultured in 10 mm glucose compared with 5.5 mm glucose. Similar responses to glucose were observed in MIN6 cells. Exposure to 30 mm KCl to induce membrane depolarization and calcium influx increased expression of primiR-199a2 but not of primiR-199a1 in MIN6 cells, indicating that calcium influx was involved. Transcriptional activity studies in MIN6 cells also revealed that primiR-199a2 promoter activity was enhanced by glucose and reduced by 2-deoxy-D-glucose-induced starvation. KCl and the potassium channel blocker tolbutamide also stimulated primiR-199a2 promoter activity. Calcium channel blockade by nifedipine reduced primiR-199a2 promoter activity in MIN6 cells, and diazoxide-mediated calcium influx inhibition blunted glucose up-regulation of miR-199-3p in islets. In conclusion, we uncover that glucose acutely up-regulates miR-199 family expression in β-cells. Glucose metabolism and calcium influx are involved in primiR-199a2 expression but not primiR-199a1 expression.

Nucleic acid-based theranostics in type 1 diabetes

Application of RNAi interference for type 1 diabetes (T1D) therapy bears tremendous potential. This review will discuss vehicles for oligonucleotide delivery, imaging modalities used for delivery monitoring, therapeutic targets, and different theranostic strategies that can be applied for T1D treatment.

Roux-en-Y-Bariatric Surgery Reduces Markers of Metabolic Syndrome in Morbidly Obese Patients

Background

Obesity is closely linked to increased markers of metabolic syndrome and development of diabetes. Roux-en-Y bariatric surgery reduces hyperinsulinemia and improves insulin sensitivity and hence benefits morbidly obese patients.

Aim

To determine changes in markers of metabolic syndrome, pancreatic function, and hepatic insulin sensitivity in patients before and 1 year after undergoing Roux-en-Y gastric bypass surgery.

Methods

We enrolled 43 consecutive patients in a single center. Markers for metabolic syndrome included proinsulin, insulin, C-peptide, liver enzymes, and serum levels of selected microRNAs hsa-miR-122, hsa-miR-130, hsa-miR-132, and hsa-miR-375.

Results

After surgery, all patients showed a significant 37% drop of body mass index (p < 0.001). Furthermore, proinsulin (59% reduction, p < 0.001), insulin (76% reduction, p < 0.001), and C-peptide (56% reduction, p < 0.001) were all reduced 1 year after surgery. Using the hepatic insulin clearance score, we determined a significant increase in hepatic insulin clearance after surgery (76% increase, p < 0.001). Especially diabetic patients showed a marked 2.1-fold increase after surgery. Hepatic enzymes ALT (35% reduction, p = 0.002) and γGT (48% reduction, p < 0.001) were significantly reduced in all patients with similar improvement in diabetic and non-diabetic patients. miRNAs hsa-miR-122, hsa-miR-130, and hsa-miR-132 were all significantly reduced whereas hsa-miR-375 was increased after gastric bypass surgery (p < 0.001 for all miRNAs).

Conclusion

Both liver and pancreatic stress parameters were reduced significantly 1 year after Roux-en-Y gastric bypass surgery suggesting an overall amelioration of the metabolic syndrome in all patients regardless of previous health status.

Injured pancreatic β cells enhance the release of miR-375-3p into the extracellular space

miR-375-3p is a highly expressed microRNA in pancreatic β cells. We have previously reported that when mice were exposed to 7 Gy X-ray irradiation, miR-375-3p was increased in the serum and there was cytotoxicity in pancreatic β cells. However, it was unknown whether miR-375-3p is then released from injured pancreatic β cells to the extracellular space. The present study investigated the effect of ionizing radiation and streptozotocin (STZ) treatment on the expression of extracellular miR-375-3p into culture supernatants using the rat pancreatic β cell line RIN-5F. Cell growth was reduced, and cell death was increased at 24 h following exposure to 7 Gy irradiation as well as 24 h following treatment with 30 mM STZ compared with the control. Expression levels of miR-375-3p were significantly increased 24 h after 30 mM STZ treatment, yet this was only observed at 48 h following exposure to 7 Gy compared with the control. This suggests that the mechanism of cell death in RIN-5F is different between 7 Gy irradiation and 30 mM STZ treatment. The results of the present study suggest that injured pancreatic β cells enhance the release of miR-375-3p from cells into extracellular space.

Beta cell secretion of miR-375 to HDL is inversely associated with insulin secretion

Extracellular microRNAs (miRNAs) are a new class of biomarkers for cellular phenotypes and disease, and are bioactive signals within intercellular communication networks. Previously, we reported that miRNAs are secreted from macrophage to high-density lipoproteins (HDL) and delivered to recipient cells to regulate gene expression. Despite the potential importance of HDL-miRNAs, regulation of HDL-miRNA export from cells has not been fully studied. Here, we report that pancreatic islets and beta cells abundantly export miR-375-3p to HDL and this process is inhibited by cellular mechanisms that promote insulin secretion. Small RNA sequencing and PCR approaches were used to quantify beta cell miRNA export to HDL. Strikingly, high glucose conditions were found to inhibit HDL-miR-375-3p export, which was dependent on extracellular calcium. Likewise, stimulation of cAMP was found to repress HDL-miR-375-3p export. Furthermore, we found that beta cell ATP-sensitive potassium channel (K_ATP) channels are required for HDL-miRNA export as chemical inhibition (tolbutamide) and global genetic knockout (Abcc8^−/−) approaches inhibited HDL-miR-375-3p export. This process is not likely associated with cholesterol flux, as gain-of-function and loss-of-function studies for cholesterol transporters failed to alter HDL-miR-375-3p export. In conclusion, results support that pancreatic beta cells export miR-375-3p to HDL and this process is inversely regulated to insulin secretion.

MicroRNA-296-5p promotes healing of diabetic wound by targeting sodium-glucose transporter 2 (SGLT2)

BACKGROUND

Diabetic wounds are refractory and very difficult to heal. We aimed to use miRNA to identify novel and specific molecular markers for diabetes mellitus (DM) diagnosis and treatment.

METHODS

The expression level of miR-296-5p was determined in tissue samples of 12 DM patients. The effect of miR-296-5p on proliferation of β-cells was examined using Cell Counting Kit-8 (CCK-8) and colony formation assay. The effect of miR-296-5p on cell cycle progression was analysed using flow cytometry. The target gene was verified using luciferase reporter assay. A rat diabetes model was used to assess the effect of miR-296-5p in vivo.

RESULTS

Overexpression of miR-296-5p suppressed cell proliferation, arrested cell cycle progression, and increased the healing rate of diabetic wounds both in vivo and in vitro. TargetScan analysis results showed that miR-296-5p is a direct regulator of SGLT2.

CONCLUSIONS

miR-296-5p can increase the healing rate of diabetic wounds and may be an effective molecular tool in DM diagnosis and therapy.

In Vivo Silencing of MicroRNA-132 Reduces Blood Glucose and Improves Insulin Secretion

Dysfunctional insulin secretion is a hallmark of type 2 diabetes (T2D). Interestingly, several islet microRNAs (miRNAs) are upregulated in T2D, including miR-132. We aimed to investigate whether in vivo treatment with antagomir-132 lowers expression of miR-132 in islets thereby improving insulin secretion and lowering blood glucose. Mice injected with antagomir-132 for 24 h, had reduced expression of miR-132 expression in islets, decreased blood glucose, and increased insulin secretion. In isolated human islets treated with antagomir-132, insulin secretion from four of six donors increased. Target prediction coupled with analysis of miRNA-messenger RNA expression in human islets revealed DESI2, ARIH1, SLC25A28, DIAPH1, and FOXA1 to be targets of miR-132 that are conserved in both species. Increased expression of these targets was validated in mouse islets after antagomir-132 treatment. In conclusion, we identified a post-transcriptional role for miR-132 in insulin secretion, and demonstrated that systemic antagomir-132 treatment in mice can be used to improve insulin secretion and reduce blood glucose in vivo. Our study is a first step towards utilizing antagomirs as therapeutic agents to modulate islet miRNA levels to improve beta cell function.

Insight into miRNAs related with glucometabolic disorder

A microRNA (miRNA) is a single-stranded, small and non-coding RNA molecule that contains 20-25 nucleotides. More than 2000 miRNAs have been identified in human genes since the first miRNA was discovered in Caenorhabditis elegans in the early 1990s. miRNAs play a crucial role in various biological processes by regulating gene expression through post-transcriptional mechanisms. The alterations of their levels are associated with various diseases, such as glucometabolic disorder and lipid metabolism disorder. In recent years, miRNAs have been proved to be involved in regulating the functions of pancreatic β-cells, insulin resistance and other biological behaviors related to glucometabolic disorder and the pathogenesis of diabetes mellitus (DM). This review summarized specific miRNAs, including miRNA-375 (miR-375), miRNA-155 (miR-155), miRNA-21 (miR-21), miRNA-33 (miR-33), the let-7 family and some other miRNAs related to glucometabolic regulation, introduced the obstacles and challenges in miRNA therapy, and discussed the prospect of new treatment methods for glucometabolic disorder.