Overexpressed beta cell CART increases insulin secretion in mouse models of insulin resistance and diabetes

[Search for new immunohistochemical and circulating markers of insulinoma]

BACKGROUND

Insulinoma is a neuroendocrine tumor, the main manifestation of which is hypoglycemia. However, the symptoms of hypoglycemia can be non-specific for a long time, especially outside provocative conditions, and quite often the tumor manifests from a life-threatening condition - hypoglycemic coma. In this regard, timely laboratory diagnosis of insulinoma and determination of its aggressive course is one of the priorities in modern researches.

AIM

Search for new immunohistochemical (IHC) and circulating markers (CM) of insulinoma, including its aggressive course.

MATERIALS AND METHODS

The patients examined at the Endocrinology Research Centre in the period 2017-2022 and operated on for an insulin-producing tumor were included. Before surgery and 2-12 months after it, blood sampling was performed with the determination of targeted marker proteins. Some patients underwent an extended IHC examination of the tumor, surrounding tissue and islets of Langerhans with primary antibodies to target marker proteins with an assessment of the degree of their expression. To determine the aggressive course of the tumor, the degree of malignancy (Grade), the number of tumors and signs of recurrence were characterized.

RESULTS

Based on the analysis of literature and pathogenetic characteristics of insulinoma, the following candidates for targeted marker proteins were selected: cocaine and amphetamine-regulated transcript (CART), chromogranin B (CrB), neuroendocrine secretory protein 55 (NESP55), glucagon-like peptide 1 (GLP1), arylalkylamine-N-acetyltransferase (AA-NAT), melatonin, and, exclusively for IHC research, protein D52 (TPD52), as well as receptors for glucagon-like peptide-1 (rGLP1) and melatonin (MTNR1b). 41 patients were included in the study, of which 10 patients underwent an extended IHC study. In patients with both aggressive and non-aggressive insulinoma after surgical treatment, CM levels did not change significantly and in individual patients they could both increase and decrease, including those patients with the expression of the corresponding marker in tumor tissue. It was shown that CART was expressed only in the tumor (in 4/10 of cases), while MTNR1b and rGLP1 were expressed in the tumor (in 6/10 and 10/10, respectively) and the islets of Langerhans (in 5/9 and 9/9, respectively). The association of marker expression with the aggressiveness of the course of insulinoma has not been revealed.

CONCLUSION

The markers CART, MTNR1b and rGLP1 are of primary interest for further study in a larger sample of patients with insulinoma. Other markers (TPD52, XgB, NESP55, melatonin, AA-NAT) have not been shown to be associated with an insulin-producing tumor, therefore they are not promising for future researches. At the same time, it is necessary to continue research aimed at finding new both circulating and IHC markers in order to early diagnose the manifestation of the disease and its recurrence, and more accurately determine the malignant and proliferative potential of the tumor.

Evaluation of lncRNA Expression During the Differentiation of Mesenchymal Stem Cells to Insulin-Secreting Progenitors

Diabetes mellitus is a metabolic disease caused by a defect in insulin secretion, insulin function, or both that destroys pancreatic islet beta cells. There is ample evidence that long non-coding RNAs (lncRNAs) play a vital role in cell formation and differentiation. The present study aims to investigate the expression pattern of specific lncRNAs in mesenchymal stem cell (MSC) differentiation into insulin-producing beta cell (IPCs) progenitors for cell therapy purposes. MSCs were extracted from human umbilical cord Wharton jelly (hWJ-MSCs) using the explant method and cultured in two-dimensional (2D) and three-dimensional (3D) media on polylactic acid/Wax (PLA/Wax) nanofibrous scaffold using a three-step protocol containing CHIR99021 small molecules and Indolactam V. At the end of each differentiation step, immunocytochemistry and qRT-PCR were used to confirm the differentiation at the protein and RNA levels and the expression changes of six selective lncRNAs were evaluated by qRT-PCR. The results indicated that the expression of the selected lncRNAs was significantly altered during the differentiation process into beta progenitor cells, indicating their potential role in regulating the IPC differentiation process. More specifically, all of the desired lncRNAs demonstrated a significant increase during the beta cell differentiation, with HI-LNC71 and HI-LNA12 experiencing the highest expression in the produced Beta cell progenitors respectively (p<0.0001). These results can be valuable in tissue engineering and treatment studies by replacing beta precursor cells to control diabetic patients.

Expression and role of cocaine-amphetamine regulated transcript (CART) in the proliferation of biliary epithelium

Cholangiocytes, the epithelial cells that line the biliary tree, can proliferate under the stimulation of several factors through both autocrine and paracrine pathways. The cocaine-amphetamine-regulated-transcript (CART) peptide has several physiological functions, and it is widely expressed in several organs. CART increases the survival of hippocampal neurons by upregulating brain-derived neurotrophic factor (BDNF), whose expression has been correlated to the proliferation rate of cholangiocytes. In the present study, we aimed to evaluate the expression of CART and its role in modulating cholangiocyte proliferation in healthy and bile duct ligated (BDL) rats in vivo, as well as in cultured normal rat cholangiocytes (NRC) in vitro. Liver samples from both healthy and BDL (1 week) rats, were analyzed by immunohistochemistry and immunofluorescence for CART, CK19, TrkB and p75NTR BDNF receptors. PCNA staining was used to evaluate the proliferation of the cholangiocytes, whereas TUNEL assay was used to evaluate biliary apoptosis. NRC treated or not with CART were used to confirm the role of CART on cholangiocytes proliferation and the secretion of BDNF. Cholangiocytes proliferation, apoptosis, CART and TrkB expression were increased in BDL rats, compared to control rats. We found a higher expression of TrkB and p75NTR, which could be correlated with the proliferation rate of biliary tree during BDL. The in vitro study demonstrated increased BDNF secretion by NRC after treatment with CART compared with control cells. As previously reported, proliferating cholangiocytes acquire a neuroendocrine phenotype, modulated by several factors, including neurotrophins. Accordingly, CART may play a key role in the remodeling of biliary epithelium during cholestasis by modulating the secretion of BDNF.

Cancer-associated fibroblasts promote tumor cell growth via miR-493-5p in intrahepatic cholangiocarcinoma

The association between tumor microenvironment (TME) and cancer-associated fibroblasts (CAFs) in intrahepatic cholangiocarcinoma (ICC) progression is poorly understood. This study aimed to reveal whether specific microRNAs (miRNAs) in extracellular vesicles (EVs) derived from CAFs were involved in ICC progression. Conditioned medium (CM) and EVs in the CM of CAFs and normal fibroblasts (NFs) derived from ICC specimens were used to investigate the effects on tumor cell lines. miRNA microarray assay was used to examine the miRNAs of EVs derived from CAFs and NFs in ICC, and the effects of miR-493-5p on tumor cell lines were examined. Additionally, databases were used to identify miR-493-5p targets, and the relationship between prognosis of ICC patients and cocaine- and amphetamine-regulated transcript propeptide (CARTPT), one of the targets of miR-493-5p, expression in ICC tissues was retrospectively analyzed. Compared with NF-derived CM and EVs, CAF-derived CM and EVs promoted cell lines in proliferation, scratch, migration, and invasion assays. miRNA microarray analysis revealed that miR-493-5p was significantly increased in CAF-derived EVs compared to NF-derived EVs. Tumor cell lines transfected with miR-493-5p were promoted in proliferation and scratch assays. Immunohistochemical staining was performed on 76 ICC specimens; both overall and recurrence-free survival rates were significantly worse in the CARTPT-negative group. Univariate and multivariate analyses showed that low CARTPT expression was an independent poor prognostic factor for overall and recurrence-free survival. Overall, our data suggest that CAFs in the ICC TME suppress CARTPT in tumor cells and promote tumor cells via miR-493-5p in EVs.

Differentially Expressed Genes and Molecular Susceptibility to Human Age-Related Diseases

Mainstream transcriptome profiling of susceptibility versus resistance to age-related diseases (ARDs) is focused on differentially expressed genes (DEGs) specific to gender, age, and pathogeneses. This approach fits in well with predictive, preventive, personalized, participatory medicine and helps understand how, why, when, and what ARDs one can develop depending on their genetic background. Within this mainstream paradigm, we wanted to find out whether the known ARD-linked DEGs available in PubMed can reveal a molecular marker that will serve the purpose in anyone's any tissue at any time. We sequenced the periaqueductal gray (PAG) transcriptome of tame versus aggressive rats, identified rat-behavior-related DEGs, and compared them with their known homologous animal ARD-linked DEGs. This analysis yielded statistically significant correlations between behavior-related and ARD-susceptibility-related fold changes (log₂ values) in the expression of these DEG homologs. We found principal components, PC1 and PC2, corresponding to the half-sum and the half-difference of these log₂ values, respectively. With the DEGs linked to ARD susceptibility and ARD resistance in humans used as controls, we verified these principal components. This yielded only one statistically significant common molecular marker for ARDs: an excess of Fcγ receptor IIb suppressing immune cell hyperactivation.

Recent Advances in the Treatment of Insulin Resistance Targeting Molecular and Metabolic Pathways: Fighting a Losing Battle?

Diabetes Mellitus (DM) is amongst the most notable causes of years of life lost worldwide and its prevalence increases perpetually. The disease is characterized as multisystemic dysfunctions attributed to hyperglycemia resulting directly from insulin resistance (IR), inadequate insulin secretion, or enormous glucagon secretion. Insulin is a highly anabolic peptide hormone that regulates blood glucose levels by hastening cellular glucose uptake as well as controlling carbohydrate, protein, and lipid metabolism. In the course of Type 2 Diabetes Mellitus (T2DM), which accounts for nearly 90% of all cases of diabetes, the insulin response is inadequate, and this condition is defined as Insulin Resistance. IR sequela include, but are not limited to, hyperglycemia, cardiovascular system impairment, chronic inflammation, disbalance in oxidative stress status, and metabolic syndrome occurrence. Despite the substantial progress in understanding the molecular and metabolic pathways accounting for injurious effects of IR towards multiple body organs, IR still is recognized as a ferocious enigma. The number of widely available therapeutic approaches is growing, however, the demand for precise, safe, and effective therapy is also increasing. A literature search was carried out using the MEDLINE/PubMed, Google Scholar, SCOPUS and Clinical Trials Registry databases with a combination of keywords and MeSH terms, and papers published from February 2021 to March 2022 were selected as recently published papers. This review paper aims to provide critical, concise, but comprehensive insights into the advances in the treatment of IR that were achieved in the last months.