The Expression of Insulin in the Central Nervous System: What Have We Learned So Far?

After being discovered over a century ago, insulin was long considered to be a hormone exclusively produced by the pancreas. Insulin presence was later discovered in the brain, which was originally accounted for by its transport across the blood-brain barrier. Considering that both insulin mRNA and insulin were detected in the central nervous system (CNS), it is now known that this hormone is also synthesized in several brain regions, including the hypothalamus, hippocampus, cerebral and cerebellar cortex, and olfactory bulb. Although many roles of insulin in the CNS have been described, it was initially unknown which of them could be attributed to brain-derived and which to pancreatic insulin or whether their actions in the brain overlap. However, more and more studies have been emerging lately, focusing solely on the roles of brain-derived insulin. The aim of this review was to present the latest findings on the roles of brain-derived insulin, including neuroprotection, control of growth hormone secretion, and regulation of appetite and neuronal glucose uptake. Lastly, the impairment of signaling initiated by brain-derived insulin was addressed in regard to memory decline in humans.

Obstructive Sleep Apnea and Cardiovascular Risk: The Role of Dyslipidemia, Inflammation, and Obesity.

Introduction: The present study aimed to establish the role of lipid abnormalities and inflammatory markers for developing cardiovascular risk, as well as to address the importance of obesity as a common comorbidity in patients with obstructive sleep apnea (OSA). Methods: The study was conducted as a prospective cohort study including 120 patients with newly diagnosed OSA between 2019 and 2020, at University Clinical Hospital Center "Bezanijska kosa", Belgrade, Serbia. The diagnosis was established by polysomnography. In all patients, sociodemographic data, respiratory, lipid, and inflammatory parameters were collected and complete echocardiographic study and 24-h blood pressure monitoring were performed. Results: The mean patient age was 55.7 ± 13.8 years. Study population was mostly male (70.0%) and obese (56.7%). At least 30 apneas or hypopneas per hour were present in 39.0% of patients. A strong positive correlation was found between OSA severity and BMI (r = 0.562, p < 0.001), both associated with lipid, inflammatory and respiratory parameters, and cardiovascular profile of patients with OSA (p < 0.05 for all). Echocardiographic study and 24-h blood pressure monitoring parameters were in turn correlated with lipid and inflammatory markers (p < 0.05 for all). Conclusion: The results of this study support the important role of dyslipidemia and inflammation, as well as coexistence of obesity in the pathogenesis of numerous conditions linked with an increased risk of cardiovascular morbidity and mortality in patients with OSA.

Correlation of Dyslipidemia and Inflammation With Obstructive Sleep Apnea Severity.

Introduction: Obstructive sleep apnea (OSA) is a serious condition linked with various metabolic disorders and associated with increased all-cause and cardiovascular mortality. Although the potential mechanisms of pathophysiological processes related to OSA are relatively well known, the data regarding the correlation between obstructive sleep apnea, dyslipidemia, and systemic inflammation are still inconclusive. Methods: The study was conducted as a retrospective cohort study including 328 patients with newly diagnosed obstructive sleep apnea during the period between April 2018, and May 2020, in University Clinical Hospital Center "Bezanijska kosa", Belgrade, Serbia. Polysomnography was performed in all patients according to the protocol. Numerous demographic, antropometric, laboratory, and clinical data were correlated to Apnea-Hypopnea Index (AHI) as a dependent variable, with a particular review on the relation between lipid abnormalities, inflammatory parameters, and obstructive sleep apnea severity. Multivariate logistic regression model was used to assess predictors of severe OSA (AHI ≥30 per hour). Results: A total of 328 patients were included in the study. The mean age of the patients was 54.0 ± 12.5 years and more than two-thirds were male (68.8%). The majority of the patients had an AHI of at least 30 events per hour. Patients with severe OSA were more frequently male, obese, hypertensive and hyperlipidemic, and had increased neck circumference (both male and female patients). One hundred and thirty-two patients had metabolic syndrome. Patients with severe OSA more frequently had metabolic syndrome and significantly higher levels of glucose, creatinine, uric acid, AST, ALT, CK, microalbumine/creatinine ratio, triglyceride, total cholesterol, HDL, total cholеsterol to HDL-C ratio, CRP, and ESR. In the multivariate linear regression model with AHI (≥30 per hour) as a dependent variable, of demographic and clinical data, triglycerides ≥1.7 mmol/L and CRP >5 mg/L were significantly associated with AHI≥30 per hour. Conclusion: The present study on 328 patients with newly diagnosed obstructive sleep apnea revealed significant relation of lipid abnormalities, inflammatory markers, and other clinically important data with obstructive sleep apnea severity. These results can lead to a better understanding of the underlying pathophysiological processes and open the door to a new world of potentially useful therapeutic modalities.

Trends of the Prevalence of Pre-gestational Diabetes in 2030 and 2050 in Belgrade Cohort.

The aim of this study was to analyze the trends in diabetes in pregnancy in Belgrade, Serbia for the period of the past decade and forecast the number of women with pre-gestational diabetes for the years 2030 and 2050. The study included the data on all pregnant women with diabetes from the registry of the deliveries in Belgrade, by the City Institute of Public Health of Belgrade, Serbia for the period between 2010 and 2020 and the published data on the deliveries on the territory of Belgrade. During the examined period the total number of live births in Belgrade was 196,987, and the prevalence of diabetes in pregnancy was 3.4%, with the total prevalence of pre-gestational diabetes of 0.7% and overall prevalence of GDM of 2.7%. The average age of women in our study was significantly lower in 2010 compared to 2020. The forecasted prevalence of pre-gestational diabetes among all pregnant women for 2030 is 2% and 4% for 2050 in our cohort. Our study showed that the prevalence of pre-gestational diabetes has increased both among all pregnant women and among women with diabetes in pregnancy in the past decade in Belgrade, Serbia and that it is expected to increase further in the next decades and to further double by 2050.

Maternal and Fetal Outcomes among Pregnant Women with Diabetes.

The aim of this study was to examine the differences in pregnancy complications, delivery characteristics, and neonatal outcomes between women with type 1 diabetes mellitus (T1DM), type 2 diabetes mellitus (T2DM), and gestational diabetes mellitus (GDM). This study included all pregnant women with diabetes in pregnancy in Belgrade, Serbia, between 2010 and 2020. The total sample consisted of 6737 patients. In total, 1318 (19.6%) patients had T1DM, 138 (2.0%) had T2DM, and 5281 patients (78.4%) had GDM. Multivariate logistic regression with the type of diabetes as an outcome variable showed that patients with T1DM had a lower likelihood of vaginal delivery (OR: 0.73, 95% CI: 0.64-0.83), gestational hypertension (OR: 0.47, 95% CI: 0.36-0.62), higher likelihood of chronic hypertension (OR: 1.88, 95% CI: 1.55-2.29),and a higher likelihood ofgestational age at delivery before 37 weeks (OR: 1.38, 95% CI: 1.18-1.63) compared to women with GDM. Multivariate logistic regression showed that patients with T2DM had a lower likelihood ofgestational hypertension compared to women with GDM (OR: 0.37, 95% CI: 0.15-0.92).Our results indicate that the highest percentage of diabetes in pregnancy is GDM, and the existence of differences in pregnancy complications, childbirth characteristics, and neonatal outcomes are predominantly between women with GDM and women with T1DM.

Food For Thought: Short-Term Fasting Upregulates Glucose Transporters in Neurons and Endothelial Cells, But Not in Astrocytes.

Our group previously reported that 6-h fasting increased both insulin II mRNA expression and insulin level in rat hypothalamus. Given that insulin effects on central glucose metabolism are insufficiently understood, we wanted to examine if the centrally produced insulin affects expression and/or regional distribution of glucose transporters, and glycogen stores in the hypothalamus during short-term fasting. In addition to determining the amount of total and activated insulin receptor, glucose transporters, and glycogen, we also studied distribution of insulin receptors and glucose transporters within the hypothalamus. We found that short-term fasting did not affect the astrocytic 45 kDa GLUT1 isoform, but it significantly increased the amount of endothelial 55 kDa GLUT1, and neuronal GLUT3 in the membrane fractions of hypothalamic proteins. The level of GLUT2 whose presence was detected in neurons, ependymocytes and tanycytes was also elevated. Unlike hepatic glycogen which was decreased, hypothalamic glycogen content was not changed after 6-h fasting. Our findings suggest that neurons may be given a priority over astrocytes in terms of glucose supply even during the initial phase of metabolic response to fasting. Namely, increase in glucose influx into the brain extracellular fluid and neurons by increasing the translocation of GLUT1, and GLUT3 in the cell membrane may represent the first line of defense in times of scarcity. The absence of co-localization of these membrane transporters with the activated insulin receptor suggests this process takes place in an insulin-independent manner.

Beneficial Effect of Virgin Coconut Oil on Alloxan-Induced Diabetes and Microbiota Composition in Rats.

The gut microbiota is composed of a diverse population of obligate and facultative anaerobic microorganisms which are shown to influence host metabolism and immune homeostasis. This study investigated the effects of virgin coconut oil on the weekly fasting glycaemia, daily food and water intake and weekly body mass gain over 16 weeks, as well as the changes in composition of gut microbiota in both non-diabetic and alloxan-induced diabetic rats. Although the intake of virgin coconut oil did not decrease the diabetes-induced hyperglycemia, it affected the secondary parameters, such as food and water intake and average body mass gain. Furthermore, its potential to positively affect the fecal microbiome was proved, since it significantly increased the abundance of probiotic bacteria, such as Lactobacillus, Allobaculum and Bifidobacterium species.

The Protective Effects of Probiotic Bacteria on Cadmium Toxicity in Rats.

One of the useful properties of probiotic bacteria is their capacity to bind different targets, thus eliminating them through feces. It is supposed that one of these targets could be cadmium, a widespread environmental toxicant that causes various disturbances in biological systems. This study examined the protective effects of probiotic supplementation against cadmium-induced toxicity in the rat. The experiment was conducted in the course of 5 weeks. Animals were divided into four groups: (1) controls, (2) probiotics treated, (3) cadmium treated, and (4) probiotics + cadmium treated. The cadmium concentration was measured in the blood, liver, kidney, and feces, as well as the blood alanine aminotransferase (ALT) and aspartate aminotransferase (AST) as biomarkers of the liver function. Histomorphological changes in the liver and kidney were also determined. Our results revealed that probiotics combined with cadmium increase this metal concentration in feces. As a result, blood, liver, and kidney Cd levels, as well as blood ALT and AST activities were lessened compared to the rat group treated with cadmium only. Besides, probiotics consumed simultaneously with cadmium attenuated histomorphological changes in the liver and kidney caused by cadmium. The rise in lactobacilli number in feces of rats treated simultaneously with cadmium and probiotics results in strong correlation with the increase of Cd concentration in their feces and the decrease of Cd concentration in their blood. We speculate that probiotics actively contribute to cadmium excretion through feces, probably, by its binding to their bacterial cell wall.

Nosocomial coagulase-negative staphylococci in Belgrade: between Scylla and Charybdis.

INTRODUCTION: Coagulase-negative staphylococci (CoNS) are increasingly resistant nosocomial pathogens. We aimed to analyze the prevalence of CoNS isolates in clinical settings, the evolution of antimicrobial resistance of CoNS, and antibiotic consumption in a hospital. METHODOLOGY: This retrospective cohort study was carried out at a tertiary healthcare facility over 17 months. Identification of isolated cultures and antibiotic susceptibility testing were performed using the Vitek2 system. Of 1,217 isolates, 209 were obtained from 193 patients who had symptoms of nosocomial infections. Data were analyzed by descriptive statistics. Antibiotic consumption in the hospital is expressed in defined daily doses/100 patient days. RESULTS: Sixty-one percent of patients were admitted to the internal medicine ward, while others were admitted to the surgical ward. Forty-four percent of Gram-positive isolates were from wound swabs, and 26% were from blood. The predominant Gram-positive bacteria were CoNS. Antibiotic resistance of CoNS was highest against beta-lactam antibiotics, macrolides, and tetracyclines. Tigecycline, linezolid, and vancomycin produced the highest activities against CoNS in in vitro conditions, and consumption of linezolid and tigecycline increased in the same period. CONCLUSION: There are just a few remaining therapeutic options for the treatment of CoNS according to our results; vancomycin, linezolid, and tigecycline might be considered as first-choice antibiotics, but such a hypothesis should be supported with a pharmacoeconomic analysis. Unfortunately, novel antimicrobial agents are still unavailable and/or too expensive in developing countries. However, inappropriate use of those antibiotics may lead to the rapid development of resistant strains in the near future.

Fasting induced cytoplasmic Fto expression in some neurons of rat hypothalamus.

Fat mass and obesity associated protein (Fto) is a nucleic acid demethylase, with a preference for thymine or uracil, according to the recent structural data. This fact suggests that methylated single-stranded RNA, rather than DNA, may be the primary Fto substrate. Fto is abundantly expressed in all hypothalamic sites governing feeding behavior. Considering that selective modulation of Fto levels in the hypothalamus can influence food intake, we set out to investigate the effect of 48 h fasting on the Fto expression in lateral hypothalamic area, paraventricular, ventromedial and arcuate nucleus, the regulatory centres of energy homeostasis. We have demonstrated that 48 h fasting causes not only an increase in the overall hypothalamic levels of both Fto mRNA and protein, but also alters Fto intracellular distribution. This switch happens in some neurons of paraventricular and ventromedial nucleus, as well as lateral hypothalamic area, resulting in the majority of the enzyme being localized outside the cell nuclei. Interestingly, the change in the Fto intracellular localization was not observed in neurons of arcuate nucleus, suggesting that fasting did not universally affect Fto in all of the hypothalmic sites involved in energy homeostasis regulation. Both Fto mRNA and catechol-O-methyltransferaze mRNA were upregulated in the identical time-dependent manner in fasting animals. This fact, combined with the knowledge of the Fto substrate preference, may provide further insight into monoamine metabolism in the state of disturbed energy homeostasis.

The effect of vasopressin 1b receptor (V1bR) blockade on HPA axis activity in rats exposed to acute heat stress.

Thermal stressors such as low and high ambient temperature elicit an abundance of neuroendocrine responses including activation of the hypothalamo-pituitary-adrenal (HPA) axis and arginine vasopressin (AVP) release. The exposure to heat is a particularly interesting model for studying AVP action because this kind of stressor represents not only an unpleasant experience but also a threat to osmotic homeostasis. As AVP has long been recognized as a hormone involved in the modulation of HPA axis activity, the aim of this study was to elucidate the role of AVP in acutely heat-exposed rats using Nelivaptan, a selective vasopressin 1b receptor (V1bR) antagonist. Rats were exposed to high ambient temperature (38°C) for 60 min. The circulating hormones were determined by ELISA or chemiluminescence, and intrapituitary adrenocorticotropic hormone (ACTH) and V1bR level were determined by western blot. The results obtained show that V1bR blockade negatively affected the increase in blood ACTH caused by heat exposure. This treatment alone, or in combination with Nelivaptan, decreased intrapituitary V1bR levels while circulating AVP concentration was increased under the same conditions. Furthermore, a strong correlation was observed between blood ACTH and corticosterone concentration. In conclusion, our results directly confirm the positive role of AVP in the regulation of ACTH secretion from the pituitary in animals exposed to heat. Moreover, the results suggest that AVP from the general circulation influences pituitary V1bR.

The effect of acute heat exposure on rat pituitary corticotroph activation: the role of vasopressin.

The increased ambient temperature affects the function of hypothalamic-pituitary-adrenal (HPA) axis. Since the correlation among vasopressin (VP), adrenocorticotropic hormone (ACTH) and corticosterone (CORT) responses to various stressors have been long recognized, the aim of this study was to reveal the aforementioned hormones production and morphology of the pituitary gland after exposure to acute heat. Rats were exposed to high ambient temperature (38 °C) for 20 or 60 minutes. The circulating hormones were determined by an ELISA test or chemiluminescence's method. The results obtained show the elevation in ACTH and CORT secretion depending on the duration of heat exposure. The VP concentration increased only after prolonged exposure to heat (60 min). The pituitary morphology was examined by routine and fluorescent immunohistochemistry as well as electron microscopy. Observed changes in the anterior and posterior pituitary well corresponded to circulating hormones, regarding the volume density of ACTH-immunopositive cells, percentage of ACTH immunopositive area v. total area and number of VP-immunopositive containing varicose fibers per total area. Acute heat exposure also induced changes in shapes of ACTH-immunopositive cells. Cells appeared stellate with numerous slender cytoplasmic processes and degranulated, which is the most obvious after 20 min. In addition, immunopositivity of endothelial and anterior pituitary cells for VP suggests its influence on ACTH secretion.

The effect of ascorbate supplementation on the activity of antioxidative enzymes in the rat hypothalamus and adrenals.

We investigated the effect of vitamin C on the oxidative status in the hypothalamus and adrenal glands of rats supplemented by its two doses over a four-week period. The results obtained have shown that vitamin C exerts effects which are tissue specific. In hypothalamus, it decreased the activity of copper zinc superoxide dismutase (CuZnSOD), the concentration of hydrogen peroxide (H2O2), as well as the activity of catalase and the level of lipid peroxidation, thus causing effects which are obviously antioxidative. On the other hand, the changes detected in adrenals indicate that vitamin C there performs some other, specific functions. They are followed by an increase in the activity of both CuZnSOD and MnSOD, as well as with the consequent rise of H2O2 content. However, these changes seem not to be of pro-oxidative nature since the level of lipid peroxidation in adrenals remains unchanged as compared to the controls.