Anesthesia's Effects on Plasma Glucose and Insulin and Cardiac Hexokinase at Similar Hemodynamics and Without Major Surgical Stress in Fed Rats

The anterior chamber of the eye technology and its anatomical, optical, and immunological bases

The anterior chamber of the eye (ACE) is distinct in its anatomy, optics, and immunology. This guarantees that the eye perceives visual information in the context of physiology even when encountering adverse incidents like inflammation. In addition, this endows the ACE with the special nursery bed iris enriched in vasculatures and nerves. The ACE constitutes a confined space enclosing an oxygen/nutrient-rich, immune-privileged, and less stressful milieu as well as an optically transparent medium. Therefore, aside from visual perception, the ACE unexpectedly serves as an excellent transplantation site for different body parts and a unique platform for noninvasive, longitudinal, and intravital microimaging of different grafts. On the basis of these merits, the ACE technology has evolved from the prototypical through the conventional to the advanced version. Studies using this technology as a versatile biomedical research platform have led to a diverse range of basic knowledge and in-depth understanding of a variety of cells, tissues, and organs as well as artificial biomaterials, pharmaceuticals, and abiotic substances. Remarkably, the technology turns in vivo dynamic imaging of the morphological characteristics, organotypic features, developmental fates, and specific functions of intracameral grafts into reality under physiological and pathological conditions. Here we review the anatomical, optical, and immunological bases as well as technical details of the ACE technology. Moreover, we discuss major achievements obtained and potential prospective avenues for this technology.

Time course changes in insulin sensitivity during cardiac surgery: A retrospective study on intraoperative glycemic management using an artificial pancreas

INTRODUCTION

Glycemic control is essential for improving the prognosis of cardiac surgery, although precise recommendations have not yet been established. Under a constant blood glucose level, the insulin infusion rate correlates with insulin resistance during glycemic control using an artificial pancreas (AP). We conducted this retrospective study to elucidate changes in intraoperative insulin sensitivity as a first step to creating glycemic control guidelines.

METHODS

Fifty-five cardiac surgery patients at our hospital who underwent intraoperative glycemic control using an AP were enrolled. Twenty-three patients undergoing surgical procedures requiring cardiac arrest under hypothermic cardiopulmonary bypass (CPB) with minimum rectal temperatures lower than 32°C, 13 patients undergoing surgical procedures requiring cardiac arrest under hypothermic CPB with minimum rectal temperatures of 32°C, eight patients undergoing on-pump beating coronary artery bypass grafting and 11 patients undergoing off-pump coronary artery bypass were assigned to groups A, B, C and D, respectively. We analyzed the time course of changes in the data derived from glycemic control using the AP.

RESULTS

Significant time course changes were observed in groups A and B, but not in groups C and D. Insulin resistance was induced after the start of hypothermic CPB in groups A and B, and the induced change was not resolved by the rewarming procedure, remaining sustained until the end of surgery.

CONCLUSIONS

Hypothermia is the predominant factor of the induced insulin resistance during cardiac surgery. Thus, careful glycemic management during hypothermic CPB is important. Prospective clinical studies are required to confirm the findings of this study.

Preclinical Imaging of Cardiovascular Disesase

Noninvasive imaging techniques, such as SPECT, PET, CT, echocardiography, or MRI, have become essential in cardiovascular research. They allow for the evaluation of biological processes in vivo without the need for invasive procedures. Nuclear imaging methods, such as SPECT and PET, offer numerous advantages, including high sensitivity, reliable quantification, and the potential for serial imaging. Modern SPECT and PET imaging systems, equipped with CT and MRI components in order to get access to morphological information with high spatial resolution, are capable of imaging a wide range of established and innovative agents in both preclinical and clinical settings. This review highlights the utility of SPECT and PET imaging as powerful tools for translational research in cardiology. By incorporating these techniques into a well-defined workflow- similar to those used in clinical imaging- the concept of "bench to bedside" can be effectively implemented.

Impact of total intravenous anesthesia and total inhalation anesthesia as the anesthesia maintenance approaches on blood glucose level and postoperative complications in patients with type 2 diabetes mellitus: a double-blind, randomized controlled trial

BACKGROUND

Diabetes mellitus is a prevalent metabolic disease in the world. Previous studies have shown that anesthetics can affect perioperative blood glucose levels which related to adverse clinical outcomes. Few studies have explored the choice of general anesthetic protocol on perioperative glucose metabolism in diabetes patients. We aimed to compare total intravenous anesthesia (TIVA) with total inhalation anesthesia (TIHA) on blood glucose level and complications in type 2 diabetic patients undergoing general surgery.

METHODS

In this double-blind controlled trial, 116 type 2 diabetic patients scheduled for general surgery were randomly assigned to either the TIVA group or TIHA group (n = 56 and n = 60, respectively). The blood glucose level at different time points were measured and analyzed by the repeated-measures analysis of variance. The serum insulin and cortisol levels were measured and analyzed with t-test. The incidence of complications was followed up and analyzed with chi-square test or Fisher's exact test as appropriate. The risk factors for complications were analyzed using the logistic stepwise regression.

RESULTS

The blood glucose levels were higher in TIHA group than that in TIVA group at the time points of extubation, 1 and 2 h after the operation, 1 and 2 days after the operation, and were significantly higher at 1 day after the operation (10.4 ± 2.8 vs. 8.1 ± 2.1 mmol/L; P < 0.01). The postoperative insulin level was higher in TIVA group than that in TIHA group (8.9 ± 2.9 vs. 7.6 ± 2.4 IU/mL; P = 0.011). The postoperative cortisol level was higher in TIHA group than that in TIVA group (15.3 ± 4.8 vs. 12.2 ± 8.9 ug/dL ; P = 0.031). No significant difference regarding the incidence of complications between the two groups was found based on the current samples. Blood glucose level on postoperative day 1 was a risk factor for postoperative complications (OR: 1.779, 95%CI: 1.009 ~ 3.138).

CONCLUSIONS

TIVA has less impact on perioperative blood glucose level and a better inhibition of cortisol release in type 2 diabetic patients compared to TIHA. A future large trial may be conducted to find the difference of complications between the two groups.

TRIAL REGISTRATION

The protocol registered on the Chinese Clinical Trials Registry on 20/01/2020 (ChiCTR2000029247).

Correlation of theophylline levels in rat exhaled breath and lung tissue after its intravenous injection

It is important to know the drug level in the target tissue to determine its dose. Some methods rely on blood levels of a drug to estimate its concentration in the tissues, which can be inaccurate. We thought that drug levels in exhaled breath aerosol (EBA) to give a more accurate value of the level of a test drug in the lung. Rats were intravenously injected with the bronchodilator theophylline and exhaled breath was collected up to 10-20 min after administration. Immediately after breath collection, lung, liver, kidney, and blood were collected and the pharmacokinetics were examined using these samples. Awake free-moving rats were used to efficiently collect exhaled breath from rats with low tidal volume. The amount of exhaled breath of rats was estimated by the amount of exhaled water vapor, and the drug concentration in exhaled breath sample was expressed by the amount of water vapor as the denominator. By using the active sampling method in which the adsorbent is sucked by a pump, theophylline in rat exhaled breath could be measured accurately. When the correlation of theophylline concentration in each sample was examined, a high correlation (r²= 0.74) was found only in exhaled breath and lung tissue. EBA was considered better than blood in pharmacokinetic analysis of lung tissue.

Comparisons of α2-Adrenergic Agents, Medetomidine and Xylazine, with Pentobarbital for Anesthesia: Important Pitfalls in Diabetic and Nondiabetic Rats

Purpose: Anesthesia is necessary to conduct rodent electroretinograms (ERGs). We evaluated utility of the α2-agonist medetomidine versus xylazine for ERG studies in nondiabetic and diabetic rats. Pentobarbital was included as a comparator. Methods: Male Sprague-Dawley rats, with and without streptozotocin (STZ)-induced diabetes, were anesthetized with medetomidine (1 mg/kg), xylazine (10 mg/kg) (both with ketamine 75 mg/kg), or pentobarbital (70 mg/kg). The depth of anesthesia was assessed, and if adequate, scotopic ERGs were recorded. Blood glucose was monitored. Results: In nondiabetic rats, all three agents induced satisfactory anesthesia, but with differing durations: medetomidine > pentobarbital > xylazine. ERG responses were similar under medetomidine and xylazine, but relatively reduced under pentobarbital. Both α2-agonists (but not pentobarbital) elicited marked hyperglycemia (peak values 316.1 ± 42.6 and 300.3 ± 29.5 mg/dL, respectively), persisting for 12 h. In diabetic rats, elevated blood glucose concentrations were not affected by any of the agents, but the depth of anesthesia under medetomidine and xylazine was inadequate for ERG recording. Conclusions: In nondiabetic rats, medetomidine and xylazine elicited comparable effects on ERGs that differ from pentobarbital, but both perturbed glucose metabolism, potentially confounding experimental outcomes. In STZ-diabetic rats, neither α2-agent provided adequate anesthesia, while pentobarbital did so. Problems with α2-anesthetic agents, including medetomidine, must be recognized to ensure meaningful interpretation of experimental results.

Electroacupuncture at Bilateral ST36 Acupoints: Inducing the Hypoglycemic Effect through Enhancing Insulin Signal Proteins in a Streptozotocin-Induced Rat Model during Isoflurane Anesthesia

In rats with 2-deoxy-2-(3-(methyl-3-nitrosoureido)-d-glucopyranose streptozotocin- (STZ-) induced insulin-dependent diabetes (IDDM), continuous 15 Hz electrical stimulation at bilateral ST36 acupoints for 30 and 60 minutes has been shown to prevent hyperglycemia. We hypothesized that the mechanism of action in STZ-induced IDDM rats is that electrical stimulation at bilateral ST36 acupoints is effective in improving insulin receptor substrate type 1 (IRS-1) and glucose transporter type 4 (GLUT4) protein expressions associated with counteracting both plasma glucose and free fatty acid (FFA) levels during isoflurane anesthesia. In this study, twenty-six healthy male Wistar rats, weighing 250–350 g and aged 8–10 weeks were tested. Rats in the experimental electroacupuncture (EA) group (n = 13) received 15 Hz electrical stimulation at bilateral ST 36 acupoints for 30 and 60 minutes. Rats in the control group (n = 13) were handled but not subjected to the stimulation treatment. In both IDDM and normal Wistar rats, we observed a negative change in plasma glucose levels when rats were given the EA treatment, but a positive change in plasma glucose without EA treatment relative to baseline. Within the IDDM group, a negative change in FFA levels was observed when rats were given the EA treatment, while a positive change in the FFA level was shown without the EA treatment. In the expressed protein signals, we found a significant elevation in both GLUT4 and IRS-1 proteins in the IDDM group treated by EA. Moreover, we found a significant mean difference between GLUT4 and IRS-1 protein expression levels relative to β-actin. Our findings suggested that EA at bilateral ST36 acupoints could serve as an effective strategy for lowering plasma glucose by decreasing free fatty acid levels and improving the expression of IRS-1 and GLUT4 proteins in a STZ-IDDM rat model during isoflurane anesthesia.

RNA editing of 5-HT2C R impairs insulin secretion of pancreatic beta cells via altered store-operated calcium entry

Recent studies emphasize the importance of 5-HT2C receptor (5-HT_2C R) signaling in the regulation of energy homeostasis. The 5-HT_2C R is the only G-protein-coupled receptor known to undergo post-transcriptional adenosine to inosine (A-to-I) editing by adenosine deaminase acting on RNA (ADAR). 5-HT_2C R has emerged as an important role in the modulation of pancreatic β cell functions. This study investigated mechanisms behind the effects of palmitic acid (PA) on insulin secretion in different overexpressed 5-HT_2C R edited isoforms in pancreatic MIN6 β cells. Results showed that the expressions of 5HT_2C R and ADAR2 were upregulated in the pancreatic islets of mice fed with high-fat diet (HFD) compared to control mice. PA treatment significantly induced the expressions of 5-HT_2C R and ADAR2 in pancreatic MIN6 β cells. PA treatment significantly induced the editing of 5-HT_2C R in pancreatic MIN6 β cells. There was no significant difference in cell viability between naïve cells and three overexpressed 5-HT_2C R edited isoforms in pancreatic MIN6 β cells. Overexpressed 5-HT_2C R edited isoforms showed reduced glucose-stimulated insulin secretion (GSIS) compared with green fluorescent protein (GFP) expressed cells. Moreover, 5-HT_2C R edited isoforms displayed reduced endoplasmic reticulum (ER) calcium release and store-operated calcium entry (SOCE) activation, probably through inhibition of stromal interaction molecule 1 trafficking under PA treatment. Altogether, our results show that PA-mediated editing of 5-HT_2C R modulates GSIS through alteration of ER calcium release and SOCE activation in pancreatic MIN6 β cells.

Cardioprotecive Properties of Known Agents in Rat Ischemia-Reperfusion Model Under Clinically Relevant Conditions: Only the NAD Precursor Nicotinamide Riboside Reduces Infarct Size in Presence of Fentanyl, Midazolam and Cangrelor, but Not Propofol

Background: Cardioprotective strategies against ischemia-reperfusion injury (IRI) that remain effective in the clinical arena need to be developed. Therefore, maintained efficacy of cardioprotective strategies in the presence of drugs routinely used clinically (e.g., opiates, benzodiazepines, P2Y₁₂ antagonist, propofol) need to be identified in preclinical models. Methods: Here, we examined the efficacy of promising cardioprotective compounds [fingolimod (Fingo), empagliflozin (Empa), melatonin (Mela) and nicotinamide riboside (NR)] administered i.v. as bolus before start ischemia. Infarct size as percentage of the area of risk (IS%) was determined following 25 min of left ascending coronary (LAD) ischemia and 2 h of reperfusion in a fentanyl-midazolam anesthetized IRI rat model. Plasma lactate dehydrogenase (LDH) activity at 30 min reperfusion was determined as secondary outcome parameter. Following pilot dose-response experiments of each compound (3 dosages, n = 4-6 animals per dosage), potential cardioprotective drugs at the optimal observed dosage were subsequently tested alone or in combination (n = 6-8 animals per group). The effective treatment was subsequently tested in the presence of a P2Y₁₂ antagonist (cangrelor; n = 6/7) or propofol aesthesia (n = 6 both groups). Results: Pilot studies suggested potential cardioprotective effects for 50 mg/kg NR (p = 0.005) and 500 μg/kg melatonin (p = 0.12), but not for Empa or Fingo. Protection was subsequently tested in a new series of experiments for solvents, NR, Mela and NR+Mela. Results demonstrated that only singular NR was able to reduce IS% (30 ± 14 vs. 60 ± 16%, P = 0.009 vs. control). Mela (63 ± 18%) and NR+Mela (47 ± 15%) were unable to significantly decrease IS%. NR still reduced IS in the presence of cangrelor (51 ± 18 vs. 71 ± 4%, P = 0.016 vs. control), but lost protection in the presence of propofol anesthesia (62 ± 16 vs. 60 ± 14%, P = 0.839 vs. control). LDH activity measurements supported all IS% results. Conclusion: This observational study suggests that NR is a promising cardioprotective agent to target cardiac ischemia-reperfusion injury in clinical conditions employing opioid agonists, benzodiazepines and platelet P2Y₁₂ inhibitors, but not propofol.

SGLT2 inhibition does not reduce glucose absorption during experimental peritoneal dialysis

INTRODUCTION

Unwanted glucose absorption during peritoneal dialysis (PD) remains a clinical challenge, especially in diabetic patients. Recent experimental data indicated that inhibitors of the sodium and glucose co-transporter (SGLT)-2 could act to reduce glucose uptake during PD, which raises the question of whether glucose absorption may also occur via intracellular or trans-cellular pathways.

METHODS

We performed PD in anesthetized Sprague-Dawley rats using a fill volume of 20 mL with either 1.5% glucose fluid or 4.25% glucose fluid for 120 min dwell time to evaluate the effects of SGLT2 inhibition by empagliflozin on peritoneal water and solute transport. To assess the diffusion capacity of glucose, we developed a modified equation to measure small solute diffusion capacity, taking convective- and free water transport into account.

RESULTS

SGLT2 inhibition markedly increased the urinary excretion of glucose and lowered plasma glucose after PD compared to sham groups. Glucose absorption for 1.5% glucose was 165 mg 95% CI (145-178) in sham animals and 157 mg 95% CI (137-172) for empagliflozin-treated animals. For 4.25% glucose, absorption of glucose was 474 mg 95% CI (425-494) and 472 mg 95% CI (420-506) for sham and empagliflozin groups, respectively. No significant changes in the transport of sodium or water across the peritoneal barrier could be detected.

CONCLUSION

We could not confirm recent findings that SGLT2 inhibition reduced glucose absorption and increased osmotic water transport during experimental PD.

Sodium-glucose cotransporter 2 inhibitors reduce myocardial infarct size in preclinical animal models of myocardial ischaemia-reperfusion injury: a meta-analysis

AIMS/HYPOTHESIS

Large cardiovascular outcome trials demonstrated that the cardioprotective effects of sodium-glucose cotransporter 2 (SGLT2) inhibitors might reach beyond glucose-lowering action. In this meta-analysis, we sought to evaluate the potential infarct size-modulating effect of SGLT2 inhibitors in preclinical studies.

METHODS

In this preregistered meta-analysis (PROSPERO: CRD42020189124), we included placebo-controlled, interventional studies of small and large animal models of myocardial ischaemia-reperfusion injury, testing the effect of SGLT2 inhibitor treatment on myocardial infarct size (percentage of area at risk or total area). Standardised mean differences (SMDs) were calculated and pooled using random-effects method. We evaluated heterogeneity by computing Τ² and I² values. Meta-regression was performed to explore prespecified subgroup differences according to experimental protocols and their contribution to heterogeneity was assessed (pseudo-R² values).

RESULTS

We identified ten eligible publications, reporting 16 independent controlled comparisons on a total of 224 animals. Treatment with SGLT2 inhibitor significantly reduced myocardial infarct size compared with placebo (SMD = -1.30 [95% CI -1.79, -0.81], p < 0.00001), referring to a 33% [95% CI 20%, 47%] difference. Heterogeneity was moderate (Τ² = 0.58, I² = 60%). SGLT2 inhibitors were only effective when administered to the intact organ system, but not to isolated hearts (p interaction <0.001, adjusted pseudo-R² = 47%). While acute administration significantly reduced infarct size, chronic treatment was superior (p interaction <0.001, adjusted pseudo-R² = 85%). The medications significantly reduced infarct size in both diabetic and non-diabetic animals, favouring the former (p interaction = 0.030, adjusted pseudo-R² = 12%). Treatment was equally effective in rats and mice, as well as in a porcine model. Individual study quality scores were not related to effect estimates (p = 0.33). The overall effect estimate remained large even after adjusting for severe forms of publication bias.

CONCLUSIONS/INTERPRETATION

The glucose-lowering SGLT2 inhibitors reduce myocardial infarct size in animal models independent of diabetes. Future in vivo studies should focus on clinical translation by exploring whether SGLT2 inhibitors limit infarct size in animals with relevant comorbidities, on top of loading doses of antiplatelet agents. Mechanistic studies should elucidate the potential relationship between the infarct size-lowering effect of SGLT2 inhibitors and the intact organ system.

Central actions of insulin during pregnancy and lactation

Pregnancy and lactation are highly metabolically demanding states. Maternal glucose is a key fuel source for the growth and development of the fetus, as well as for the production of milk during lactation. Hence, the maternal body undergoes major adaptations in the systems regulating glucose homeostasis to cope with the increased demand for glucose. As part of these changes, insulin levels are elevated during pregnancy and lower in lactation. The increased insulin secretion during pregnancy plays a vital role in the periphery; however, the potential effects of increased insulin action in the brain have not been widely investigated. In this review, we consider the impact of pregnancy on brain access and brain levels of insulin. Moreover, we explore the hypothesis that pregnancy is associated with site-specific central insulin resistance that is adaptive, allowing for the increases in peripheral insulin secretion without the consequences of increased central and peripheral insulin functions, such as to stimulate glucose uptake into maternal tissues or to inhibit food intake. Conversely, the loss of central insulin actions may impair other functions, such as insulin control of the autonomic nervous system. The potential role of low insulin in facilitating adaptive responses to lactation, such as hyperphagia and suppression of reproductive function, are also discussed. We end the review with a list of key research questions requiring resolution.

Evaluation of the effects of two anaesthetic protocols on oxidative status and DNA damage in red-eared sliders (Trachemys scripta elegans) undergoing endoscopic coeliotomy

The aim of this study was to assess how red-eared sliders (Trachemys scripta elegans) respond to anaesthesia itself and coelioscopy. For that purpose, the turtles were anaesthetised with ketamine-medetomidine or propofol, and the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST) and the level of malondialdehyde (MDA) were determined by spectrophotometry. The possible genotoxic effects of the anaesthetic agents were estimated by comet assay. A total of 24 turtles were included in this study. The animals were divided into four groups according to the anaesthetic protocol and according to whether endoscopy would be performed. Significantly decreased activities of CAT were found only in the propofol group and in turtles undergoing coelioscopy. Both anaesthetic protocols induced significantly increased MDA levels, while no differences were observed after the intervention. A significant increase in GST activity was detected in turtles after both anaesthetic protocols, but after coelioscopy significant changes in GST activity were found only in the propofol group. However, no differences in SOD activity and no DNA damages were detected in either group. These findings suggest that ketamine-medetomidine may be more suitable anaesthetic agents in red-eared sliders than propofol.

What Is an L-Cell and How Do We Study the Secretory Mechanisms of the L-Cell?

Synthetic glucagon-like peptide-1 (GLP-1) analogues are effective anti-obesity and anti-diabetes drugs. The beneficial actions of GLP-1 go far beyond insulin secretion and appetite, and include cardiovascular benefits and possibly also beneficial effects in neurodegenerative diseases. Considerable reserves of GLP-1 are stored in intestinal endocrine cells that potentially might be mobilized by pharmacological means to improve the body's metabolic state. In recognition of this, the interest in understanding basic L-cell physiology and the mechanisms controlling GLP-1 secretion, has increased considerably. With a view to home in on what an L-cell is, we here present an overview of available data on L-cell development, L-cell peptide expression profiles, peptide production and secretory patterns of L-cells from different parts of the gut. We conclude that L-cells differ markedly depending on their anatomical location, and that the traditional definition of L-cells as a homogeneous population of cells that only produce GLP-1, GLP-2, glicentin and oxyntomodulin is no longer tenable. We suggest to sub-classify L-cells based on their differential peptide contents as well as their differential expression of nutrient sensors, which ultimately determine the secretory responses to different stimuli. A second purpose of this review is to describe and discuss the most frequently used experimental models for functional L-cell studies, highlighting their benefits and limitations. We conclude that no experimental model is perfect and that a comprehensive understanding must be built on results from a combination of models.

Effects of intravenous and inhalation anesthesia on blood glucose and complications in patients with type 2 diabetes mellitus: study protocol for a randomized controlled trial

Background

Diabetes mellitus (DM) is a metabolic disorder syndrome caused by relative or absolute lack of insulin and varying degrees of insulin resistance. The type and regimen of anesthesia may affect perioperative hyperglycemia following major surgical stress. The effect of perioperative anesthetics on the blood glucose level of diabetic patients will play an essential role in the postoperative recovery of patients. However, there is no rigorously-designed randomized controlled trial to compare the effects of total intravenous anesthesia (TIVA) and total inhalation anesthesia (TIHA) on blood glucose and complications in type 2 diabetes. Hence, we design this clinical trial to compare the effects of TIVA and TIHA of hyperglycemia and clinical outcomes in type 2 diabetes undergoing surgery.

Methods

This is a randomized, double-blind, parallel controlled trial. One hundred twelve patients with type 2 DM who meet the qualification criteria will be randomly divided into two groups: TIVA group and TIHA group. The levels of serum insulin and cortisol will be measured before and after the operation, and the levels of blood glucose at different setting time will be monitored. All patients will be followed up by blinded evaluators at baseline and 1, 3, 7, and 30 days after the intervention. The follow-up included postoperative complications [such as myocardial infarction (MI), stroke, renal failure, anastomotic fistula, stress ulcer, incision infection, lung infection] and adverse events.

Discussion

The routinely used clinical anesthesia schemes are TIVA, TIHA and intravenous-inhalation combined anesthesia. We expect that the results of this trial will provide high-quality clinical evidence for the choice of anesthesia options for patients with type 2 DM.

Trial registration

Chinese Clinical Trial Registry: ChiCTR2000029247, registration date: 20 January 2020.

The Pharmacokinetics of Medetomidine Administered Subcutaneously during Isoflurane Anaesthesia in Sprague-Dawley Rats

Anaesthetic protocols involving the combined use of a sedative agent, medetomidine, and an anaesthetic agent, isoflurane, are increasingly being used in functional magnetic resonance imaging (fMRI) studies of the rodent brain. Despite the popularity of this combination, a standardised protocol for the combined use of medetomidine and isoflurane has not been established, resulting in inconsistencies in the reported use of these drugs. This study investigated the pharmacokinetic detail required to standardise the use of medetomidine and isoflurane in rat brain fMRI studies. Using mass spectrometry, serum concentrations of medetomidine were determined in Sprague-Dawley rats during medetomidine and isoflurane anaesthesia. The serum concentration of medetomidine for administration with 0.5% (vapouriser setting) isoflurane was found to be 14.4 ng/mL (±3.0 ng/mL). The data suggests that a steady state serum concentration of medetomidine when administered with 0.5% (vapouriser setting) isoflurane can be achieved with an initial subcutaneous (SC) dose of 0.12 mg/kg of medetomidine followed by a 0.08 mg/kg/h SC infusion of medetomidine. Consideration of these results for future studies will facilitate standardisation of medetomidine and isoflurane anaesthetic protocols during fMRI data acquisition.

Anesthesia with sevoflurane or isoflurane induces severe hypoglycemia in neonatal mice

Sevoflurane and isoflurane are among the most commonly used general anesthetics for children including infants, but their impact on metabolism, especially on blood glucose level, in children is not well understood. We investigated the impacts of anesthesia of neonatal (7–8 days old) and adult (2–3 months old) mice with the inhalational anesthetics 2.5% sevoflurane or 1.5% isoflurane, or the injectable anesthetics propofol (150 mg/kg) or avertin (375 mg/kg), for up to 6 hours. We found that sevoflurane and isoflurane induced severe hypoglycemia in neonatal mice and that this phenomenon was specific to the inhalational anesthetics because the injectable anesthetics propofol and avertin did not induce hypoglycemia. Surprisingly, the inhalational anesthesia induced hyperglycemia instead in adult mice. We also demonstrated that the inhalational anesthesia-induced hypoglycemia was a major cause of death for the neonatal mice receiving intranasal administration of saline prior to anesthesia. These studies revealed severe hypoglycemia in neonatal mice during anesthesia with sevoflurane or isoflurane. If this phenomenon also occurs in human, our findings would warrant closely monitoring blood glucose level and maintaining it in the normal range in infants receiving inhalational anesthesia.

Insulin-like growth factor-1 inhibits spreading depression-induced trigeminal calcitonin gene related peptide, oxidative stress & neuronal activation in rat

Migraineurs can show brain hyperexcitability and oxidative stress that may promote headache. Since hyperexcitability can enhance oxidative stress which promotes hyperexcitability, ending this feed-back loop may reduce migraine. Neocortical spreading depression, an animal model of migraine begins with hyperexcitability and triggers oxidative stress in the neocortical area involved and in the trigeminal system, which is important to pain pathway nociceptive activation in migraine. Additionally, oxidative stress causes increased trigeminal ganglion calcitonin gene-related peptide release and oxidative stress can reduce spreading depression threshold. Insulin-like growth factor-1 significantly protects against spreading depression in vitro by reducing oxidative stress and it is effective against spreading depression after intranasal delivery to animals. Here, we used adult male rats and extend this work to study the trigeminal system where insulin-like growth factor-1 receptors are highly expressed. Recurrent neocortical spreading depression significantly increased surrogate markers of trigeminal activation - immunostaining for trigeminal ganglion oxidative stress, calcitonin gene related peptide levels and c-fos in the trigeminocervical complex versus sham. These effects were significantly reduced by intranasal delivery of insulin-like growth factor-1 a day before recurrent neocortical spreading depression. Furthermore, intranasal treatment with insulin-like growth factor-1 significantly reduced naïve levels of trigeminal ganglion calcitonin gene related peptide versus sham with no impact on blood glucose levels. Intranasal delivery of insulin-like growth factor-1 not only mitigates neocortical spreading depression, a cause of migraine hyperexcitability modeled in animals, but also when neocortical spreading depression is triggered by supra-threshold stimuli, insulin-like growth factor-1 effectively reduces nociceptive activation in the trigeminal system.

Heat shock response to exercise in pancreatic islets of obese mice

Chronic obesity imposes an organismal state of low-grade inflammation because the physiological resolution of inflammation is progressively repressed giving rise to cellular senescence and its accompanying Senescence-Associated Secretory Phenotype (SASP), which avoids apoptosis but perpetuates the relay of inflammatory signals from adipose tissue toward the rest of the body. Conversely, resolution of inflammation depends on the integrity of heat shock response (HSR) pathway that leads to the expression of cytoprotective and anti-inflammatory protein chaperones of the 70 kDa family (HSP70). However, chronic exposure to the aforementioned injuring factors leads to SASP, which, in turn, suppresses the HSR. A main metabolic tissue severely jeopardized by obesity-related dysfunctions is the endocrine pancreas, particularly β-cells of the islets of Langerhans. Because exercise is a powerful inducer of HSR and predicted to alleviate negative health outcomes of obesity, we sought whether obesity influence HSP70 expression in pancreatic islets and other metabolic tissues (adipose tissue and skeletal muscle) of adult B6.129SF2/J mice fed on a high-fat diet (HFD) for 13 weeks since the weaning and whether acute exercise as well as moderate-intensity exercise training (8 weeks) could interfere with this scenario. We showed that acute exercise of moderate intensity protects pancreatic islets against cytokine-induced cell death. In addition, acute exercise challenge time-dependently increased islet HSP70 that peaked at 12 h post-exercise in both trained and untrained mice fed on a control diet, suggesting an adequate HSR to exercise training. Unexpectedly, however, neither exercise training nor acute exercise challenges were able to increase islet HSP70 contents in trained mice submitted to HFD, but only in untrained HFD animals. In parallel, HFD disrupted glycemic status which is accompanied by loss of muscular mass resembling sarcopenic obesity that could not be rescued by exercise training. These results suggest that exercise influences HSR in pancreatic islets but obesity undermines islet, muscle and adipose tissue HSR, which is associated with metabolic abnormalities observed in such tissues.

Body weight-dependent and independent improvement in lipid metabolism after Roux-en-Y gastric bypass in ApoE*3Leiden.CETP mice

BACKGROUND/OBJECTIVES

The incidence of obesity and metabolic syndrome (MetS) has rapidly increased worldwide. Roux-en-Y gastric bypass (RYGB) achieves long-term weight loss and improves MetS-associated comorbidities. Using a mouse model with a humanized lipoprotein metabolism, we elucidated whether improvements in lipid and glucose metabolism after RYGB surgery are body weight loss-dependent or not.

SUBJECTS/METHODS

Male ApoE*3Leiden.CETP (ApoE3L.CETP) mice fed Western type diet for 6 weeks underwent RYGB or Sham surgery. Sham groups were either fed ad libitum or were body weight-matched (BWm) to the RYGB mice to discriminate surgical effects from body weight loss-associated effects. Before and after surgery, plasma was collected to assess the metabolic profile, and glucose tolerance and insulin sensitivity were tested. Twenty days after surgery, mice were sacrificed, and liver was collected to assess metabolic, histological and global gene expression changes after surgery.

RESULTS

RYGB induced a marked reduction in body weight, which was also achieved by severe food restriction in BWm mice, and total fat mass compared to Sham ad libitum mice (Sham AL). Total cholesterol, non-high-density lipoprotein cholesterol (non-HDL-C) and ceramide were strongly reduced 20 days after surgery in RYGB compared to BWm mice. Glucose tolerance and insulin sensitivity improved 13 days after surgery similarly in RYGB and BWm mice. Liver histology confirmed lipid reduction in RYGB and BWm mice while the transcriptomics data indicated altered genes expression in lipid metabolism.

CONCLUSIONS

RYGB surgery improves glucose metabolism and greatly ameliorates lipid metabolism in part in a body weight-dependent manner. Given that ApoE3L.CETP mice were extensively studied to describe the MetS, and given that RYGB improved ceramide after surgery, our data confirmed the usefulness of ApoE3L.CETP mice after RYGB in deciphering the metabolic improvements to treat the MetS.

Effects of preoperative oral carbohydrate intake on catabolism, nutrition and adipocytokines during minor surgery: A randomized, prospective, controlled clinical phase II trial

BACKGROUND

We investigated the effects of preoperative oral carbohydrate loading on intraoperative catabolism, nutritional parameters, and adipocytokine levels during anesthesia.

METHODS

Study participants were randomized to two groups who were allowed to consume either no more than 250 mL of 18% oral carbohydrate solution (Arginaid Water: AW group) or no more than 500 mL of plain water (PW group) within the 2 hours before surgery, with no intraoperative glucose administration. Percentage changes from preoperative values of resting metabolic rate (RMR) and total body water (TBW), determined by bioelectrical impedance analysis (BIA), were compared. Blood levels of serum ketone bodies, free fatty acids (FFAs), insulin, 3-methyl histidine, blood glucose, retinol binding protein, adiponectin, and leptin were measured. BIA measurement and blood sampling were performed on entry to the operating room (M1) and 2 hours after the induction of anesthesia (M2). Chi squared test, Mann-Whitney U test, and Wilcoxon's test were used for comparisons of parameters. P values less than 0.05 constituted a significant difference.

RESULTS

Seventeen patients per group (34 patients total) were enrolled. RMR and TBW values did not differ between M1 and M2 measurements. Participants in the AW group had lower blood ketone body and FFA levels and higher insulin levels at M1. However, their ketone body and FFA levels rose and insulin levels fell after 2 hours, although ketone body and FFA levels in the AW group were still lower than those in the PW group. Although retinol binding protein, adiponectin, and leptin levels were not different in terms of preoperative oral carbohydrate loading, the levels of these substances in both groups were lower after 2 hours compared with levels on operating room entry.

CONCLUSIONS

Preoperative oral carbohydrate loading without intraoperative glucose administration appears to suppress catabolism for 2 hours after the start of surgery.

Total Intravenous Anesthesia in GLUT1 Deficiency Syndrome Patient: A Case Report

Patient: Female, 2

Final Diagnosis: GLUT1 deficiency syndrome

Symptoms: Mastoiditis

Medication: —

Clinical Procedure: General anesthesia

Specialty: Anesthesiology

Glucose and amino acid metabolism in mice depend mutually on glucagon and insulin receptor signaling

Glucagon and insulin are important regulators of blood glucose. The importance of insulin receptor signaling for alpha-cell secretion and of glucagon receptor signaling for beta-cell secretion is widely discussed and of clinical interest. Amino acids are powerful secretagogues for both hormones, and glucagon controls amino acid metabolism through ureagenesis. The role of insulin in amino acid metabolism is less clear. Female C57BL/6JRj mice received an insulin receptor antagonist (IRA) (S961; 30 nmol/kg), a glucagon receptor antagonist (GRA) (25-2648; 100 mg/kg), or both GRA and IRA (GRA + IRA) 3 h before intravenous administration of similar volumes of saline, glucose (0.5 g/kg), or amino acids (1 µmol/g) while anesthetized with isoflurane. IRA caused basal hyperglycemia, hyperinsulinemia, and hyperglucagonemia_. Unexpectedly, IRA lowered basal plasma concentrations of amino acids, whereas GRA increased amino acids, lowered glycemia, and increased glucagon but did not influence insulin concentrations. After administration of GRA + IRA, insulin secretion was significantly reduced compared with IRA administration alone. Blood glucose responses to a glucose and amino acid challenge were similar after vehicle and GRA + IRA administration but greater after IRA and lower after GRA. Anesthesia may have influenced the results, which otherwise strongly suggest that both hormones are essential for the maintenance of glucose homeostasis and that the secretion of both is regulated by powerful negative feedback mechanisms. In addition, insulin limits glucagon secretion, while endogenous glucagon stimulates insulin secretion, revealed during lack of insulin autocrine feedback. Finally, glucagon receptor signaling seems to be of greater importance for amino acid metabolism than insulin receptor signaling.

The effects of perinatal bisphenol A exposure on thyroid hormone homeostasis and glucose metabolism in the prefrontal cortex and hippocampus of rats

INTRODUCTION

Bisphenol A (BPA) is an endocrine disruptor widely used to manufacture consumer goods. Although the thyroid hormone (TH) disrupting potential of BPA has been thought to be responsible for the neuropsychiatric deficits in the animals that experienced perinatal BPA exposure, the TH availability change at the level of specific brain structures has not been subject to systematic investigation.

METHODS

In the present study the impacts of perinatal BPA exposure (0.1 mg/L in drinking water) spanning gestation and lactation on TH homeostasis in the prefrontal cortex (PFC) and hippocampus were assessed in male Sprague-Dawley rats at postnatal day 21 (PND21) and PND90. As TH regulates brain glucose metabolism at multiple levels，the effects of BPA treatment on glucose metabolism in the brain tissues were also assessed in adult rats.

RESULTS

The results showed heterogeneous changes in TH concentration induced by BPA between serum and brain tissues, additionally, in the BPA-treated pups, up-regulated expression of the TH transporter monocarboxylate 8 mRNA at PND21 and increased type 3 iodothyronine deiodinase mRNA expressions at PND21 and PND90 were observed. Meanwhile, decreased glucose metabolism was seen in the PFC and hippocampus, while deficits in locomotor activity, spatial memory and social behaviors occurred in BPA-treated groups.

CONCLUSION

These data support the concept that the developing brain possesses potent mechanisms to compensate for a small reduction in serum TH, such as serum hypothyrodism induced by BPA exposure, however, the long-term negative effect of BPA treatment on TH homeostasis and glucose metabolism may be attributable to neuropsychiatric deficits after mature.

The eye as a novel imaging site in diabetes research

Diabetes develops due to deficient functional β cell mass, insulin resistance, or both. Yet, various challenges in understanding the mechanisms underlying diabetes development in vivo remain to be overcome owing to the lack of appropriate intravital imaging technologies. To meet these challenges, we have exploited the anterior chamber of the eye (ACE) as a novel imaging site to understand diabetes basics and clinics in vivo. We have developed a technology platform transplanting pancreatic islets into the ACE where they later on can be imaged non-invasively for long time. It turns out that the ACE serves as an optimal imaging site and provides implanted islets with an oxygen-rich milieu and an immune-privileged niche where they undergo optimal engraftment, rich vascularization and dense innervation, preserve organotypic features and live with satisfactory viability and functionality. The ACE technology has led to a series of significant observations. It enables in vivo microscopy of islet cytoarchitecture, function and viability in the physiological context and intravital imaging of a variety of pathological events such as autoimmune insulitis, defects in β cell function and mass and insulin resistance during diabetes development in a real-time manner. Furthermore, application of the ACE technology in humanized mice and non-human primates verifies translational and clinical values of the technology. In this article, we describe the ACE technology in detail, review accumulated knowledge gained by means of the ACE technology and delineate prospective avenues for the ACE technology.

Functional and Morphological Characteristics of Pancreatic Islet Lesions Induced by Quinolone Antimicrobial Agent Gatifloxacin in Rats

We characterized pancreatic islet lesions induced by several quinolones using functional and morphological examinations of the pancreatic islets in male rats orally administered gatifloxacin, lomefloxacin, or levofloxacin at 300 mg/kg for 14 consecutive days. Consequently, in contrast to lomefloxacin or levofloxacin, gatifloxacin increased serum glucose and glycosylated albumin on day 14 and elevated serum glucose tended to decrease insulin in the intravenous glucose tolerance test. Microscopically, only gatifloxacin induced cytoplasmic vacuoles containing eosinophilic homogenous contents in islet cells. Immunohistochemical examination revealed that vacuolated islet cells were positively stained for insulin, demonstrating they were pancreatic β cells. Electron microscopy showed that the cytoplasmic vacuoles represented dilated cisterna of the rough endoplasmic reticulum filled with electron-lucent materials in pancreatic β cells. Moreover, insulin secretory granules were drastically decreased in vacuolated islet cells, suggesting impaired insulin synthesis and/or transport. This gatifloxacin-induced pancreatic toxicity in rats was considered to be associated with high pancreatic drug distribution. These results demonstrated that gatifloxacin provoked functional and morphological pancreatic β cell alteration associated with impaired insulin synthesis and/or transport, leading to hyperglycemia.

Euthanasia of laboratory mice: Are isoflurane and sevoflurane real alternatives to carbon dioxide?

In the European Union (EU) millions of laboratory mice are used and killed for experimental and other scientific purposes each year. Although controversially discussed, the use of carbon dioxide (CO₂) is still permitted for killing rodents according to the Directive 2010/63/EU. Within the scope of refinement, our aim was to investigate if isoflurane and sevoflurane are an appropriate alternative killing method to CO₂ in mice. Different concentrations of CO₂ (filling rates of 20%, 60%, 100%; CO₂ 20, 60, 100), isoflurane (Iso 2%, 5%) and sevoflurane (Sevo 4.8%, 8%) were compared in two mouse strains (NMRI, C57Bl/6J) using a broad spectrum of behavioral parameters, including the approach-avoidance test, and analyzing blood for stress parameters (glucose, adrenaline, noradrenaline). We focused in our study on the period from the beginning of the gas inlet to loss of consciousness, as during this period animals are able to perceive pain and distress. Our results show that only higher concentrations of CO₂ (CO₂ 60, 100) and isoflurane (5%) induced surgical tolerance within 300 s in both strains, with CO₂ 100 being the fastest acting inhalant anesthetic. The potency of halogenated ethers depended on the mouse strain, with C57Bl/6J being more susceptible than NMRI mice. Behavioral analysis revealed no specific signs of distress, e. g. stress-induced grooming, and pain, i. e. audible vocalizations, for all inhalant gases. However, adrenaline and noradrenaline plasma concentrations were increased, especially in NMRI mice exposed to CO₂ in high concentrations, whereas we did not observe such increase in animals exposed to isoflurane or sevoflurane. Escape latencies in the approach-avoidance test using C57Bl/6J mice did not differ between the three inhalant gases, however, some animals became recumbent during isoflurane and sevoflurane but not during CO₂ exposure. The rise in catecholamine concentrations suggests that CO₂ exposure might be linked to a higher stress response compared to isoflurane and sevoflurane exposure, although we did not observe a behavioral correlate for that. Follow-up studies investigating other fast-acting stress hormones and central anxiety circuits are needed to confirm our findings.

Blunting of cardioprotective actions of estrogen in female rodent heart linked to altered expression of cardiac tissue chymase and ACE2

Background:

Diastolic dysfunction develops in response to hypertension and estrogen (E2) loss and is a forerunner to heart failure (HF) in women. The cardiac renin–angiotensin system (RAS) contributes to diastolic dysfunction, but its role with respect to E2 and blood pressure remain unclear.

Methods:

We compared the effects of ovariectomy (OVX) or sham surgery on the cardiac RAS, left ventricular (LV) structure/function, and systemic/intracardiac pressures of spontaneously hypertensive rats (SHRs: n = 6 intact and 6 OVX) and age-matched Wistar-Kyoto (WKY: n = 5 intact and 4 OVX) controls.

Results:

WKY rats were more sensitive to OVX than SHRs with respect to worsening of diastolic function, as reflected by increases in Doppler-derived filling pressures (E/e′) and reductions in myocardial relaxation (e′). This pathobiologic response in WKY rats was directly linked to increases in cardiac gene expression and enzymatic activity of chymase and modest reductions in ACE2 activity. No overt changes in cardiac RAS genes or activities were observed in SHRs, but diastolic function was inversely related to ACE2 activity.

Conclusion:

Endogenous estrogens exert a more significant regulatory role upon biochemical components of the cardiac RAS of WKY versus SHRs, modulating the lusitropic and structural components of its normotensive phenotype.

Comparison of sevoflurane and propofol anesthesia on the incidence of hyperglycemia in patients with type 2 diabetes undergoing lung surgery

Background

The type and regimen of anesthesia may affect perioperative hyperglycemia following major surgical stress. This study compared the effects of sevoflurane and propofol on the incidence of hyperglycemia and clinical outcomes in diabetic patients undergoing lung surgery.

Methods

This retrospective study included 176 patients with type 2 diabetes mellitus who had undergone lung surgery. Blood glucose levels and clinical outcomes from the preoperative period to the first 2 post-operative days (PODs) were retrospectively examined in patients who received sevoflurane (group S, n= 87) and propofol (group P, n=89) for maintenance of general anesthesia. The primary endpoint was the incidence of persistent hyperglycemia (2 consecutive blood glucose levels >180 mg/dL [10.0 mmol/L]) during the perioperative period. The secondary composite endpoint was the incidence of major postoperative complications and 30-day mortality rate after surgery.

Results

Blood glucose levels similarly increased from the preoperative period to the second POD in both groups (p=0.857). Although blood glucose levels at 2 hours after surgery were significantly lower in group P than in group S (p=0.022; 95% confidence interval for mean difference, -27.154 to -2.090), there was no difference in the incidence of persistent hyperglycemia during the perioperative period (group S, 70%; group P, 69%; p=0.816). The composite of major postoperative complications and all-cause in-hospital and 30-day mortality rates were also comparable between the two groups.

Conclusion

Sevoflurane and propofol were associated with a comparable incidence of perioperative hyperglycemia and clinical outcomes in diabetic patients undergoing lung surgery.

Control of (pre)-analytical aspects in immunoassay measurements of metabolic hormones in rodents

The measurement of circulating hormones by immunoassay remains a cornerstone in preclinical endocrine research. For scientists conducting and interpreting immunoassay measurements of rodent samples, the paramount aim usually is to obtain reliable and meaningful measurement data in order to draw conclusions on biological processes. However, the biological variability between samples is not the only variable affecting the readout of an immunoassay measurement and a considerable amount of unwanted or unintended variability can be quickly introduced during the pre-analytical and analytical phase. This review aims to increase the awareness for the factors 'pre-analytical' and 'analytical' variability particularly in the context of immunoassay measurement of circulating metabolic hormones in rodent samples. In addition, guidance is provided how to gain control over these variables and how to avoid common pitfalls associated with sample collection, processing, storage and measurement. Furthermore, recommendations are given on how to perform a basic validation of novel single and multiplex immunoassays for the measurement of metabolic hormones in rodents. Finally, practical examples from immunoassay measurements of plasma insulin in mice address the factors 'sampling site and inhalation anesthesia' as frequent sources of introducing an unwanted variability during the pre-analytical phase. The knowledge about the influence of both types of variability on the immunoassay measurement of circulating hormones as well as strategies to control these variables are crucial, on the one hand, for planning and realization of metabolic rodent studies and, on the other hand, for the generation and interpretation of meaningful immunoassay data from rodent samples.

Assessing the influence of isoflurane anesthesia on cardiac metabolism using hyperpolarized [1-13 C]pyruvate

Isoflurane is a frequently used anesthetic in small-animal dissolution dynamic nuclear polarization-magnetic resonance imaging (DNP-MRI) studies. Although the literature suggests interactions with mitochondrial metabolism, the influence of the compound on cardiac metabolism has not been assessed systematically to date. In the present study, the impact of low versus high isoflurane concentration was examined in a crossover experiment in healthy rats. The results revealed that cardiac metabolism is modulated by isoflurane concentration, showing increased [1-¹³ C]lactate and reduced [¹³ C]bicarbonate production during high isoflurane relative to low isoflurane dose [average differences: +16% [1-¹³ C]lactate/total myocardial carbon, -22% [¹³ C]bicarbonate/total myocardial carbon; +51% [1-¹³ C]lactate/[¹³ C]bicarbonate]. These findings emphasize that reproducible anesthesia is important when studying cardiac metabolism. As the depth of anesthesia is difficult to control in an experimental animal setting, careful study design is required to exclude confounding factors.

A Mouse Model of Beta-Cell Dysfunction as Seen in Human Type 2 Diabetes

Loss of first-phase insulin release is an early pathogenic feature of type 2 diabetes (T2D). Various mouse models exist to study T2D; however, few recapitulate the early β-cell defects seen in humans. We sought to develop a nongenetic mouse model of T2D that exhibits reduced first-phase insulin secretion without a significant deficit in pancreatic insulin content. C57BL/6J mice were fed 10% or 60% fat diet for three weeks, followed by three consecutive, once-daily intraperitoneal injections of the β-cell toxin streptozotocin (STZ; 30, 50, or 75 mg/kg) or vehicle. Four weeks after injections, the first-phase insulin response to glucose was reduced in mice when high-fat diet was combined with 30, 50, or 75 mg/kg STZ. This was accompanied by diminished second-phase insulin release and elevated fed glucose levels. Further, body weight gain, pancreatic insulin content, and β-cell area were decreased in high fat-fed mice treated with 50 and 75 mg/kg STZ, but not 30 mg/kg STZ. Low fat-fed mice were relatively resistant to STZ, with the exception of reduced pancreatic insulin content and β-cell area. Together, these data demonstrate that in high fat-fed mice, three once-daily injections of 30 mg/kg STZ produces a model of β-cell failure without insulin deficiency that may be useful in studies investigating the etiology and progression of human T2D.

Biomimetic electrospun coatings increase the in vivo sensitivity of implantable glucose biosensors

In vivo tissue responses and functional efficacy of electrospun membranes based on polyurethane (PU) and gelatin (GE) as biomimetic coatings for implantable glucose biosensors was investigated in a rat subcutaneous implantation model. Three electrospun membranes with optimized fiber diameters, pore sizes, and permeability, both single PU and coaxial PU‐GE fibers and a solvent cast PU film were implanted in rats to evaluate tissue responses. For functional efficacy testing, four sensor variants coated with the above mentioned electrospun membranes as mass‐transport limiting and outermost biomimetic coatings were implanted in rats. The electrospun PU membranes had micron sized pores that were not permeable to host cells when implanted in the body. However, PU‐GE coaxial fiber membranes, having similar sized pores, were infiltrated with fibroblasts that deposited collagen in the membrane's pores. Such tissue response prevented the formation of dense fibrous capsule around the sensor coated with the PU‐GE coaxial fiber membranes, which helped improve the in vivo sensitivity for at least 3 weeks compared to the traditional sensors in rat subcutaneous tissue. Furthermore, the better in vitro sensor's sensitivity due to electrospun PU as the mass‐transport limiting membrane translated to better in vivo sensitivity. Thus, this study showed that electrospun membranes can play an important role in realizing long in vivo sensing lifetime of implantable glucose biosensors. © 2017 The Authors Journal of Biomedical Materials Research Part A Published by Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1072–1081, 2018.

Cyclophilin D ablation is associated with increased end-ischemic mitochondrial hexokinase activity

Both the absence of cyclophilin D (CypD) and the presence of mitochondrial bound hexokinase II (mtHKII) protect the heart against ischemia/reperfusion (I/R) injury. It is unknown whether CypD determines the amount of mtHKII in the heart. We examined whether CypD affects mtHK in normoxic, ischemic and preconditioned isolated mouse hearts. Wild type (WT) and CypD-/- mouse hearts were perfused with glucose only and subjected to 25 min ischemia and reperfusion. At baseline, cytosolic and mtHK was similar between hearts. CypD ablation protected against I/R injury and increased ischemic preconditioning (IPC) effects, without affecting end-ischemic mtHK. When hearts were perfused with glucose, glutamine, pyruvate and lactate, the preparation was more stable and CypD ablation-resulted in more protection that was associated with increased mtHK activity, leaving little room for additional protection by IPC. In conclusion, in glucose only-perfused hearts, deletion of CypD is not associated with end-ischemic mitochondrial-HK binding. In contrast, in the physiologically more relevant multiple-substrate perfusion model, deletion of CypD is associated with an increased mtHK activity, possibly explaining the increased protection against I/R injury.

Crosstalk between cardiomyocyte-rich perivascular tissue and coronary arteries is reduced in the Zucker Diabetic Fatty rat model of type 2 diabetes mellitus

AIM

We tested the hypothesis that crosstalk between cardiomyocyte-rich perivascular tissue (PVT) and coronary arteries is altered in diabetes.

METHODS

We studied the vasoactive effects of PVT in arteries from the Zucker Diabetic Fatty (ZDF) rat model of type 2 diabetes, streptozotocin (STZ)-treated Wistar rats with type 1 diabetes, and corresponding - heterozygous Zucker Lean (ZL) or vehicle-treated Wistar - control rats. Vasocontractile and vasorelaxant functions of coronary septal arteries with and without PVT were investigated using wire myography.

RESULTS

After careful removal of PVT, vasoconstriction in response to serotonin and thromboxane analogue U46619 was similar in arteries from ZDF and ZL rats, whereas depolarization-induced vasoconstriction - caused by elevating extracellular [K⁺ ] - was reduced in arteries from ZDF compared to ZL rats. PVT inhibited serotonin-, U46619- and depolarization-induced vasoconstriction in arteries from ZL rats, but this anticontractile influence of PVT was attenuated in arteries from ZDF rats. Methacholine-induced vasorelaxation was smaller in arteries from ZDF than ZL rats both with and without PVT, and the antirelaxant influence of PVT was comparable between arteries from ZDF and ZL rats. We observed no differences in vasoconstriction, vasorelaxation or PVT-dependent vasoactive effects between arteries from STZ- and vehicle-treated Wistar rats.

CONCLUSION

Anticontractile influences of PVT are attenuated in coronary arteries from ZDF rats but unaffected in arteries from STZ-treated rats. Signs of endothelial dysfunction are evident in coronary septal arteries - with and without PVT - from ZDF rats but not STZ-treated rats. We propose that altered signalling between cardiomyocyte-rich PVT and coronary arteries can contribute to cardiovascular complications in type 2 diabetes mellitus.

Pharmacokinetics, toxicity, and cytochrome P450 modulatory activity of plumbagin

Background

The antimalarial activity of plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone), a naturally occurring naphthoquinone widely distributed in the Plumbaginaceae family has previously been demonstrated in vitro (good activity) and in vivo (weak activity). The aim of the study was to investigate the pharmacokinetic profile following a single oral dosing to explain inconsistency of results of the in vitro and in vivo antimalarial activities. In addition, toxicity profiles and potential of modulation of cytochrome P450 enzymes (CYP1A2 and CYP3A11) were also investigated.

Methods

The pharmacokinetics and toxicity of plumbagin were investigated in rats. The propensity of plumbagin to modulate the mRNA expression and activities of the two inducible forms of hepatic drug metabolizing enzyme cytochrome P450 (CYP450), i.e., CYP1A2 and CYP3A11, was investigated using microsomes prepared from mouse livers.

Results

Acute and subacute toxicity tests indicate low toxicity of plumbagin with maximum tolerated doses of 150 (single oral dose) and 25 (daily doses for 28 days) mg/kg body weight, respectively. The pharmacokinetic profile of plumbagin following a single oral dose of 100 mg/kg body weight suggests that delayed absorption and short residence time (median values of time to maximal concentration and elimination half-life = 9.63 and 5.0 h, respectively) in plasma. Plumbagin did not modulate mRNA expression and activities of CYP1A2 and CYP3A11.

Conclusions

Plumbagin was well tolerated following oral dose administration in rats. Pharmacokinetic property of this compound may be a limiting factor that explains the weak antimalarial activity of plumbagin observed in animal models. Potential metabolic interaction with co-administered drugs that are metabolized by CYP1A2 or CYP3A11 are unlikely.

Deficiency in the Heat Stress Response Could Underlie Susceptibility to Metabolic Disease

Heat treatment (HT) effectively prevents insulin resistance and glucose intolerance in rats fed a high-fat diet (HFD). The positive metabolic actions of heat shock protein 72 (HSP72), which include increased oxidative capacity and enhanced mitochondrial function, underlie the protective effects of HT. The purpose of this study was to test the ability of HSP72 induction to mitigate the effects of consumption of a short-term 3-day HFD in rats selectively bred to be low-capacity runners (LCRs) and high-capacity runners (HCRs)-selective breeding that results in disparate differences in intrinsic aerobic capacity. HCR and LCR rats were fed a chow or HFD for 3 days and received a single in vivo HT (41°C, for 20 min) or sham treatment (ST). Blood, skeletal muscles, liver, and adipose tissues were harvested 24 h after HT/ST. HT decreased blood glucose levels, adipocyte size, and triglyceride accumulation in liver and muscle and restored insulin sensitivity in glycolytic muscles from LCR rats. As expected, HCR rats were protected from the HFD. Importantly, HSP72 induction was decreased in LCR rats after only 3 days of eating the HFD. Deficiency in the highly conserved stress response mediated by HSPs could underlie susceptibility to metabolic disease with low aerobic capacity.

Use of anesthesia dramatically alters the oral glucose tolerance and insulin secretion in C57Bl/6 mice

Evaluation of the impact of anesthesia on oral glucose tolerance in mice. Anesthesia is often used when performing OGTT in mice to avoid the stress of gavage and blood sampling, although anesthesia may influence gastrointestinal motility, blood glucose, and plasma insulin dynamics. C57Bl/6 mice were anesthetized using the following commonly used regimens: (1) hypnorm/midazolam repetitive or single injection; (2) ketamine/xylazine; (3) isoflurane; (4) pentobarbital; and (5) A saline injected, nonanesthetized group. Oral glucose was administered at time 0 min and blood glucose measured in the time frame −15 to +150 min. Plasma insulin concentration was measured at time 0 and 20 min. All four anesthetic regimens resulted in impaired glucose tolerance compared to saline/no anesthesia. (1) hypnorm/midazolam increased insulin concentrations and caused an altered glucose tolerance; (2) ketamine/xylazine lowered insulin responses and resulted in severe hyperglycemia throughout the experiment; (3) isoflurane did not only alter the insulin secretion but also resulted in severe hyperglycemia; (4) pentobarbital resulted in both increased insulin secretion and impaired glucose tolerance. All four anesthetic regimens altered the oral glucose tolerance, and we conclude that anesthesia should not be used when performing metabolic studies in mice.

Effects of various types of anesthesia on hemodynamics, cardiac function, and glucose and lipid metabolism in rats

Anesthesia can affect respiratory, circulatory, and endocrine systems but is necessary for certain experimental procedures such as echocardiography and blood sampling in small animals. We have now investigated the effects of four types of anesthesia [pentobarbital sodium (PENT), ketamine-xylazine (K/X), and low- or high-dose isoflurane (ISO)] on hemodynamics, cardiac function, and glucose and lipid metabolism in Sprague-Dawley rats. Aortic pressure, heart rate, and echocardiographic parameters were measured at various time points up to 45 min after the induction of anesthesia, and blood was then collected for measurement of parameters of glucose and lipid metabolism. Systolic aortic pressure remained constant in the PENT group, whereas it showed a biphasic pattern in the K/X group and a gradual decline in the ISO groups. Marked bradycardia was observed in the K/X group. The serum glucose concentration was increased and the plasma insulin level was reduced in the K/X and ISO groups compared with the PENT group. The concentrations of free fatty acids and norepinephrine in plasma were increased in the K/X group. Despite the metabolic effects of K/X and ISO, our results suggest that the marked bradycardic effect of K-X renders this combination appropriate for measurement of Doppler-derived indexes of left ventricular diastolic function, whereas the relative ease with which the depth of anesthesia can be controlled with ISO makes it suitable for manipulations or data collection over long time periods. On the other hand, PENT may be best suited for experiments that focus on measurement of cardiac function by M-mode echocardiography and metabolic parameters.

Methods for the Determination of Rates of Glucose and Fatty Acid Oxidation in the Isolated Working Rat Heart

The mammalian heart is a major consumer of ATP and requires a constant supply of energy substrates for contraction. Not surprisingly, alterations of myocardial metabolism have been linked to the development of contractile dysfunction and heart failure. Therefore, unraveling the link between metabolism and contraction should shed light on some of the mechanisms governing cardiac adaptation or maladaptation in disease states. The isolated working rat heart preparation can be used to follow, simultaneously and in real time, cardiac contractile function and flux of energy providing substrates into oxidative metabolic pathways. The present protocol aims to provide a detailed description of the methods used in the preparation and utilization of buffers for the quantitative measurement of the rates of oxidation for glucose and fatty acids, the main energy providing substrates of the heart. The methods used for sample analysis and data interpretation are also discussed. In brief, the technique is based on the supply of ¹⁴C- radiolabeled glucose and a ³H- radiolabeled long-chain fatty acid to an ex vivo beating heart via normothermic crystalloid perfusion. ¹⁴CO2 and ³H2O, end byproducts of the enzymatic reactions involved in the utilization of these energy providing substrates, are then quantitatively recovered from the coronary effluent. With knowledge of the specific activity of the radiolabeled substrates used, it is then possible to individually quantitate the flux of glucose and fatty acid in the oxidation pathways. Contractile function of the isolated heart can be determined in parallel with the appropriate recording equipment and directly correlated to metabolic flux values. The technique is extremely useful to study the metabolism/contraction relationship in response to various stress conditions such as alterations in pre and after load and ischemia, a drug or a circulating factor, or following the alteration in the expression of a gene product.

Cafeteria diet induce changes in blood flow that are more related with heat dissipation than energy accretion

Background. A “cafeteria” diet is a self-selected high-fat diet, providing an excess of energy, which can induce obesity. Excess of lipids in the diet hampers glucose utilization eliciting insulin resistance, which, further limits amino acid oxidation for energy.

Methods. Male Wistar rats were exposed for a month to “cafeteria” diet. Rats were cannulated and fluorescent microspheres were used to determine blood flow.

Results. Exposure to the cafeteria diet did not change cardiac output, but there was a marked shift in organ irrigation. Skin blood flow decreased to compensate increases in lungs and heart. Blood flow through adipose tissue tended to increase in relation to controls, but was considerably increased in brown adipose tissue (on a weight basis).

Discussion. The results suggest that the cafeteria diet-induced changes were related to heat transfer and disposal.

A high fat diet alters metabolic and bioenergetic function in the brain: A magnetic resonance spectroscopy study

Diet-induced obesity and associated metabolic effects can lead to neurological dysfunction and increase the risk of developing Alzheimer's disease (AD) and Parkinson's disease (PD). Despite these risks, the effects of a high-fat diet on the central nervous system are not well understood. To better understand the mechanisms underlying the effects of high fat consumption on brain regions affected by AD and PD, we used proton magnetic resonance spectroscopy ((1)H-MRS) to measure neurochemicals in the hippocampus and striatum of rats fed a high fat diet vs. normal low fat chow. We detected lower concentrations of total creatine (tCr) and a lower glutamate-to-glutamine ratio in the hippocampus of high fat rats. Additional effects observed in the hippocampus of high fat rats included higher N-acetylaspartylglutamic acid (NAAG), and lower myo-inositol (mIns) and serine (Ser) concentrations. Post-mortem tissue analyses revealed lower phosphorylated AMP-activated protein kinase (pAMPK) in the striatum but not in the hippocampus of high fat rats. Hippocampal pAMPK levels correlated significantly with tCr, aspartate (Asp), phosphoethanolamine (PE), and taurine (Tau), indicating beneficial effects of AMPK activation on brain metabolic and energetic function, membrane turnover, and edema. A negative correlation between pAMPK and glucose (Glc) indicates a detrimental effect of brain Glc on cellular energy response. Overall, these changes indicate alterations in neurotransmission and in metabolic and bioenergetic function in the hippocampus and in the striatum of rats fed a high fat diet.

Influence of two anesthetic techniques on blood sugar level in head injury patients: A comparative study

BACKGROUND

Head injury presents a major worldwide social, economic, and health problem. Hyperglycemia is a significant indicator of the severity of injury and predictor of outcome, which can easily be prevented. There has been a long-standing controversy regarding the use of inhalational or intravenous (i.v.) anesthetic agents for surgery of head injury cases and impact of these agents on blood sugar level.

AIMS AND OBJECTIVES

The aim of this study is to find out anesthetic drugs and technique having minimal or no effect on the blood sugar, and Glasgow Coma Scale (GCS) of patients with a head injury by comparing two types of anesthetic techniques in surgery of head injury patients.

MATERIALS AND METHODS

This was a prospective, randomized, and comparative study, conducted on 60 adult head injury patients. The patients were divided into two groups of 30 each. Group I patients received induction with sevoflurane and then had O2 + air + sevoflurane for maintenance with controlled ventilation. Group II patients received induction with i.v. propofol and then had O2 + air + propofol for maintenance with controlled ventilation. Injection fentanyl was used in both the groups at the time of induction and in intermittent boluses in maintenance. In observation, blood sugar level and mean arterial pressure were assessed at different time periods perioperatively in both groups while GCS was analyzed pre- and post-operatively.

STATISTICAL ANALYSIS

Statistical analysis was performed by Microsoft Excel 2010 using t-test for comparison between the two groups and Z-test for comparison of proportions.

RESULTS AND CONCLUSION

Blood sugar level was found significantly higher in patients of sevoflurane group at 30 min after induction, at the end of surgery, and 1 h after the end of anesthesia than propofol group patients. This increase of blood sugar level did not have any significant alteration in the GCS profile of the patients in sevoflurane group as compared to propofol group patients. Nausea and vomiting were found more in sevoflurane group while hypotension and bradycardia were found more with propofol group.

Erythropoietin diminishes isoflurane-induced apoptosis in rat frontal cortex

BACKGROUND

During the brain growth spurt, anesthetic drugs can cause cellular and behavioral changes in the developing brain. The aim of this study was to determine the neuroprotective effect of erythropoietin after isoflurane anesthesia in rat pups.

METHODS

A total of 42, 7-day-old Wistar rats were divided into three groups. Control group (GC; n = 14): Rats breathed 100% oxygen for 6 h; Isoflurane group (GI; n = 14): Rats were exposed to 1.5% isoflurane in 100% oxygen for 6 h; Isoflurane + erythropoietin group (GIE; n = 14): 1000 IU·kg(-1) (intraperitoneal; IP) Erythropoietin was administered after isoflurane anesthesia. Each group was divided into two groups for pathology and learning and memory tests. Silver, caspase-3, and fluoro-jade C staining were used for detecting apoptotic cells in frontal cortex, striatum, hippocampus, thalamus, and amygdala. Morris water maze was used to evaluate learning and memory.

RESULTS

There was a significant increase in apoptotic cell count after isoflurane anesthesia in the frontal cortex when compared with control group (29.0 ± 9.27 vs 3.28 ± 0.75 [P = 0.002], 20.85 ± 10.94 vs 2.0 ± 0.81 [P = 0.002] and 24.57 ± 10.4 vs 5.14 ± 0.69 [P = 0.024] with silver, caspase-3, and fluoro-jade C staining, respectively). The apoptotic cell count in the frontal cortex was significantly higher in GIE than GC with caspase-3 staining (9.14 ± 3.13 vs 2.0 ± 0.81, P = 0.002). The apoptotic cell count in GIE was significantly reduced in the frontal cortex when compared with GI (4.0 ± 0.81 vs 29.0 ± 9.27 [P = 0.002], 9.14 ± 3.13 vs 20.85 ± 10.94 [P = 0.04] and 4.0 ± 1.63 vs 24.57 ± 10.4 [P = 0.012] with silver, caspase-3, and fluoro-jade C staining, respectively).

CONCLUSIONS

A total of 1000 IU·kg(-1) IP erythropoietin diminished isoflurane-induced neuroapoptosis. Further experimental studies have to be planned to reveal the optimal dose and timing of erythropoietin before adaptation to clinical practice.