Alterations of the glutamatergic system in diabetes mellitus.

Diabetes mellitus (DM) is a chronic disease characterized by elevated blood glucose levels caused by a lack of insulin production (type 1 diabetes) or insulin resistance (type 2 diabetes). It is well known that DM is associated with cognitive deficits and metabolic and neurophysiological changes in the brain. Glutamate is the main excitatory neurotransmitter in the central nervous system that plays a key role in synaptic plasticity, learning, and memory processes. An increasing number of studies have suggested that abnormal activity of the glutamatergic system is implicated in the pathophysiology of DM. Dysfunction of glutamatergic neurotransmission in the central nervous system can provide an important neurobiological substrate for many disorders. Magnetic resonance spectroscopy (MRS) is a non-invasive technique that allows a better understanding of the central nervous system factors by measuring in vivo the concentrations of brain metabolites within the area of interest. Here, we briefly review the MRS studies that have examined glutamate levels in the brain of patients with DM. The present article also summarizes the available data on abnormalities in glutamatergic neurotransmission observed in different animal models of DM. In addition, the role of gut microbiota in the development of glutamatergic alterations in DM is addressed. We speculate that therapeutic strategies targeting the glutamatergic system may be beneficial in the treatment of central nervous system-related changes in diabetic patients.

Cushing's Syndrome: A Historic Review of the Treatment Strategies and Corresponding Outcomes in a Single Tertiary Center over the Past Half-Century.

Cushing's syndrome (CS) is associated with serious comorbidities and an increased mortality rate that could be reduced only if strict biochemical control is achieved. The aim of this study was to show the 50-year experience of a single tertiary center in the management of CS patients - the different treatment modalities used over the years and the corresponding outcomes. It was a retrospective study of a large cohort of patients from the Bulgarian CS database: 613 patients (374 with ACTH-dependent and 239 with ACTH-independent CS). Pituitary surgery was applied to 242 patients with Cushing's disease (CD) with initial remission rate of 74% of which 10% relapsed. Approximately 36% manifested with active disease during the long-term follow-up (26% with persistent disease, 10% relapses) most of which were subjected to a secondary treatment (13.6% to pituitary resurgery, 14% to pituitary radiotherapy, and 5.4% to bilateral adrenalectomy). A total of 294 CD patients received medical therapy with overall remission rates for the most commonly used drugs: dopamine agonists 20%, pasireotide 30%, and ketoconazole 63%. Significant improvement of results was achieved by combining drugs with different mechanisms of action. Regardless of the progress in the neurosurgery and radiotherapy techniques and new drugs discovery, the management of patients with CS remains a real challenge for physicians. Not only patients with adrenal carcinoma but also significant percentage of subjects with persistent and recurrent Cushing's disease often require a polymodal approach and the efforts of a multidisciplinary highly qualified, experienced, and motivated team in order to achieve a long-term remission.

MiRNA Signatures Related to Invasiveness and Recurrence in Patients With Non-Functioning Pituitary Neuroendocrine Tumors.

PURPOSE: This preliminary study aimed to analyze and identify differentially expressed miRNAs in Bulgarian patients with non-functioning pituitary neuroendocrine tumors (NFPitNET). The relationship between deregulated miRNAs and tumor invasiveness, recurrence, and size was determined. METHODS: Twenty patients with NFPitNET were selected and fresh pituitary tumor tissues were collected. RNA containing miRNAs were isolated using miRNAeasy mini kit and analyzed by quantitative real-time polymerase chain reaction (PCR) using LNA miRNA Cancer-Focus PCR Panel (Qiagen). RESULTS: Three miRNAs (miR-210-3p, miR-149-3p, and miR-29b-3p) were deregulated in invasive compared to non-invasive NFPitNETs. Differential expression of four-miRNA signatures - miRNA-17, miR-19, miR-106a, and miR-20, correlated with patient recurrence. CONCLUSION: This prospective pilot study selected a unique miRNA expression profile, that correlates with invasiveness and recurrence in non-functioning pituitary neuroendocrine tumors. Moreover, some of the selected miRNAs are reported for the first time in patients with this disease, shedding light on the molecular mechanisms involved in pituitary pathogenesis. The identified miRNAs demonstrate potential as biomarkers, deserving further investigation in a larger cohort to validate their clinical applicability.