Disruption of the Hippocampal and Hypothalamic Blood-Brain Barrier in a Diet-Induced Obese Model of Type II Diabetes: Prevention and Treatment by the Mitochondrial Carbonic Anhydrase Inhibitor, Topiramate

Background: Type II diabetes is a vascular risk factor for cognitive impairment and increased risk of dementia. Disruption of the blood–retinal barrier (BRB) and blood–brain barrier (BBB) are hallmarks of subsequent retinal edema and central nervous system dysfunction. However, the mechanisms by which diet or metabolic syndrome induces dysfunction are not understood. A proposed mechanism is an increase in reactive oxygen species (ROS) and oxidative stress. Inhibition of mitochondrial carbonic anhydrase (mCA) decreases ROS and oxidative stress. In this study, topiramate, a mCA inhibitor, was examined for its ability to protect the BRB and BBB in diet-induced obese type II diabetic mice. Methods: BBB and BRB permeability were assessed using 14C-sucrose and 99mTc-albumin in CD-1 mice fed a low-fat (control) or a high-fat diet. Topiramate administration was compared to saline controls in both preventative and efficacy arms examining BRB and BBB disruption. Body weight and blood glucose were measured weekly and body composition was assessed using EchoMRI. Metabolic activity was measured using a comprehensive laboratory animal monitoring system. Brain tissues collected from the mice were assessed for changes in oxidative stress and tight junction proteins. Results: High-fat feeding caused increased entry of 14C-sucrose and 99mTc-albumin into the brains of diet-induced obese type II diabetic mice. Increased permeability to 14C-sucrose was observed in the hypothalamus and hippocampus, and attenuated by topiramate treatment, while increased permeability to 99mTc-albumin occurred in the whole brain and was also attenuated by topiramate. Treatment with topiramate decreased measures of oxidative stress and increased expression of the tight junction proteins ZO-1 and claudin-12. In the retina, we observed increased entry of 99mTc-albumin simultaneously with increased entry into the whole brain during the preventative arm. This occurred prior to increased entry to the retina for 14C-sucrose which occurred during the efficacy arm. Treatment with topiramate had no effect on the retina. Conclusions: Blood–brain barrier and blood–retinal barrier dysfunction were examined in a mouse model of diet-induced obese type II diabetes. These studies demonstrate that there are spatial and temporal differences in 14C-sucrose and 99mTc-albumin permeability in the brain and retina of diet-induced obese type II diabetic mice. Topiramate, a mitochondrial carbonic anhydrase inhibitor, is efficacious at both preventing and treating BBB disruption in this diet-induced obese type II diabetic mouse model

Lipopolysaccharide-induced blood-brain barrier disruption: roles of cyclooxygenase, oxidative stress, neuroinflammation, and elements of the neurovascular unit

Background: Disruption of the blood-brain barrier (BBB) occurs in many diseases and is often mediated by inflammatory and neuroimmune mechanisms. Inflammation is well established as a cause of BBB disruption, but many mechanistic questions remain. Methods: We used lipopolysaccharide (LPS) to induce inflammation and BBB disruption in mice. BBB disruption was measured using 14C-sucrose and radioactively labeled albumin. Brain cytokine responses were measured using multiplex technology and dependence on cyclooxygenase (COX) and oxidative stress determined by treatments with indomethacin and N-acetylcysteine. Astrocyte and microglia/macrophage responses were measured using brain immunohistochemistry. In vitro studies used Transwell cultures of primary brain endothelial cells co- or tri-cultured with astrocytes and pericytes to measure effects of LPS on transendothelial electrical resistance (TEER), cellular distribution of tight junction proteins, and permeability to 14C-sucrose and radioactive albumin. Results: In comparison to LPS-induced weight loss, the BBB was relatively resistant to LPS-induced disruption. Disruption occurred only with the highest dose of LPS and was most evident in the frontal cortex, thalamus, pons-medulla, and cerebellum with no disruption in the hypothalamus. The in vitro and in vivo patterns of LPS-induced disruption as measured with 14C-sucrose, radioactive albumin, and TEER suggested involvement of both paracellular and transcytotic pathways. Disruption as measured with albumin and 14C-sucrose, but not TEER, was blocked by indomethacin. N-acetylcysteine did not affect disruption. In vivo, the measures of neuroinflammation induced by LPS were mainly not reversed by indomethacin. In vitro, the effects on LPS and indomethacin were not altered when brain endothelial cells (BECs) were cultured with astrocytes or pericytes. Conclusions: The BBB is relatively resistant to LPS-induced disruption with some brain regions more vulnerable than others. LPS-induced disruption appears is to be dependent on COX but not on oxidative stress. Based on in vivo and in vitro measures of neuroinflammation, it appears that astrocytes, microglia/macrophages, and pericytes play little role in the LPS-mediated disruption of the BBB

Influence of the mammary microenvironment on tumor progression: Identification of palmitoleic acid and osmotin as mediators of tumor cell growth

Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy and/or increased health problems. There are a number of factors that influence changes in body fat including diet, lifestyle, and genetics. Diet has been shown to be correlated to increased incidence of cancer and studies have shown that changes in fatty acid composition in diets are correlated with increased risk of a number of diseases including cancer. The main focus of these studies has been on understanding how diet, and dietary factors, influence tumor progression. In the first part of this study, a rat model was developed to study the effect of omega-3 or omega-6 polyunsaturated fatty acid rich diet on tumor development in prepubescent outbred female rats. Very few studies have evaluated the relationship between childhood diet and cancer, which is becoming increasingly important as childhood obesity is on the rise. Of the studies that have been completed, the focus has been on the effect of diet on tumor initiation and on the effect of in utero diet consumption on tumor development in offspring. Those studies have demonstrated that diets rich in omega-3 fatty acids are capable of inhibiting tumor initiation. Our work demonstrates that a diet rich in omega-3 fatty acids, given to a prepubescent rat from the time of weaning, has an adverse effect on tumor prevention. While the omega-3 group had increased tumor number, they had decreased tumor volume compared to the omega-6 group. Analysis of the fatty acid composition indicated that there was an increase in saturated fatty acid levels in the omega-3 fed group. Saturated fatty acids have been associated with an increase in breast cancer risk. Adipose tissue, the primary component of the tumor microenvironment, surrounds every organ in the human body. The tumor microenvironment has been shown to play a critical role in the growth and development of cancer. As obesity is associated with cancer incidence and diet influences obesity rates, understanding how diet changes the tumor microenvironment will provide insight into how obesity influences cancer incidence. Use of gas chromatography to analyze the fatty acid composition of mammary tissue has identified palmitoleic acid as a potential mediator of tumor cell growth. Follow up studies utilizing palmitoleic acid indicate that is in fact capable of promoting tumor cell growth and migration. Analysis of the mammary tissue from the omega fatty acid study indicate that palmitoleic acid levels were doubled in the omega-3 fed group compared to the omega-6 fed group. Analysis of mammary tissue from a previous animal study examining the effect of a western diet on tumor growth, indicated that the levels of palmitoleic acid were highest in the group containing the most aggressive types of tumors and the highest number of tumors. This provides the foundation for the development of palmitoleic acid as a potential cancer biomarker and potential molecular target for dietary intervention in cancer prevention. Contrary to the majority of adipocyte-secreted factors whose levels increase as adiposity increases and who promote tumorigenesis, adiponectin is an adipocyte-secreted factor whose levels decrease as adiposity increases and functions to inhibit tumorigenesis. Unfortunately, there are currently no known adiponectin-based therapies available to combat cancer. Osmotin, a plant protein identical in structure to adiponectin, has been identified as a potential alternative to an adiponectin-based therapy. The similarity in protein structure has allowed osmotin to initiate a similar physiological response in the cancer cell lines. Osmotin has been shown to inhibit tumor cell growth and induce apoptosis in the MCF-7 cell line. Further analysis indicates that osmotin inhibits cell cycle progression and decreases cyclinD1 activity. Osmotin was also shown to inhibit migration of MDA-MB-231 cells and U937 cells, a human macrophage cell line. Osmotin demonstrates a great deal of potential as a cancer therapeutic agent. It not only has antiproliferative properties, but has antimigratory properties which demonstrate its potential as an antimetastatic agent. There have been a number of advancements towards our understanding of how cancer works at the molecular level and a number of factors identified which initiate and promote cancer. Despite these advancements, there has been little progress in linking them to cancer preventions and treatments. Many studies have addressed the potential effects of diet on cancer incidence. Although a great deal of information has been gathered from these studies, there are still a lot of unknowns, thus providing a foundation for continued investigation into the role of diet and cancer

Data from: Songbird frequency selectivity and temporal resolution vary with sex and season

Many species of songbirds exhibit dramatic seasonal variation in song output. Recent evidence suggests that seasonal changes in auditory processing are coincident with seasonal variation in vocal output. Here we show for the first time that frequency selectivity and temporal resolution of the songbird auditory periphery change seasonally and in a sex-specific manner. Male and female house sparrows (Passer domesticus) did not differ in their frequency sensitivity during the non-breeding season, nor did they differ in their temporal resolution. In contrast, female house sparrows showed enhanced frequency selectivity during the breeding season which was matched by a concomitant reduction of temporal resolution. However, males failed to show seasonal plasticity in either of these auditory properties. We discuss potential mechanisms generating these seasonal patterns and the implications of sex-specific seasonal changes in auditory processing for vocal communication

House sparrow seasonal auditory filter and temporal resolution data

This is data collected on seasonal changes in house sparrow auditory filter shape and temporal resolution. The data was collected in Lafayette, Indiana from male and female house sparrows. Metadata in the spreadsheet provides information on column heading abbreviations. This spreadsheet was made in Microsoft Excel. Auditory filter shape and temporal resolution were determined from auditory evoked potentials (TDT platform) and custom scripts written for PRAAT and SAS 9.2. More details can be found in the associated text

Disruption of the hippocampal and hypothalamic blood–brain barrier in a diet-induced obese model of type II diabetes: prevention and treatment by the mitochondrial carbonic anhydrase inhibitor, topiramate

Abstract Background Type II diabetes is a vascular risk factor for cognitive impairment and increased risk of dementia. Disruption of the blood–retinal barrier (BRB) and blood–brain barrier (BBB) are hallmarks of subsequent retinal edema and central nervous system dysfunction. However, the mechanisms by which diet or metabolic syndrome induces dysfunction are not understood. A proposed mechanism is an increase in reactive oxygen species (ROS) and oxidative stress. Inhibition of mitochondrial carbonic anhydrase (mCA) decreases ROS and oxidative stress. In this study, topiramate, a mCA inhibitor, was examined for its ability to protect the BRB and BBB in diet-induced obese type II diabetic mice. Methods BBB and BRB permeability were assessed using 14C-sucrose and 99mTc-albumin in CD-1 mice fed a low-fat (control) or a high-fat diet. Topiramate administration was compared to saline controls in both preventative and efficacy arms examining BRB and BBB disruption. Body weight and blood glucose were measured weekly and body composition was assessed using EchoMRI. Metabolic activity was measured using a comprehensive laboratory animal monitoring system. Brain tissues collected from the mice were assessed for changes in oxidative stress and tight junction proteins. Results High-fat feeding caused increased entry of 14C-sucrose and 99mTc-albumin into the brains of diet-induced obese type II diabetic mice. Increased permeability to 14C-sucrose was observed in the hypothalamus and hippocampus, and attenuated by topiramate treatment, while increased permeability to 99mTc-albumin occurred in the whole brain and was also attenuated by topiramate. Treatment with topiramate decreased measures of oxidative stress and increased expression of the tight junction proteins ZO-1 and claudin-12. In the retina, we observed increased entry of 99mTc-albumin simultaneously with increased entry into the whole brain during the preventative arm. This occurred prior to increased entry to the retina for 14C-sucrose which occurred during the efficacy arm. Treatment with topiramate had no effect on the retina. Conclusions Blood–brain barrier and blood–retinal barrier dysfunction were examined in a mouse model of diet-induced obese type II diabetes. These studies demonstrate that there are spatial and temporal differences in 14C-sucrose and 99mTc-albumin permeability in the brain and retina of diet-induced obese type II diabetic mice. Topiramate, a mitochondrial carbonic anhydrase inhibitor, is efficacious at both preventing and treating BBB disruption in this diet-induced obese type II diabetic mouse model

Ghrelin transport across the blood–brain barrier can occur independently of the growth hormone secretagogue receptor

Objective: The blood–brain barrier (BBB) regulates the entry of substrates and peptides into the brain. Ghrelin is mainly produced in the stomach but exerts its actions in the central nervous system (CNS) by crossing the BBB. Once present in the CNS, ghrelin can act in the hypothalamus to regulate food intake, in the hippocampus to regulate neurogenesis, and in the olfactory bulb to regulate food-seeking behavior. The goal of this study was to determine whether the primary signaling receptor for ghrelin, the growth hormone secretagogue receptor (GHSR), mediates the transport of ghrelin from blood to brain. Methods: We utilized the sensitive and quantitative multiple-time regression analysis technique to determine the transport rate of mouse and human acyl ghrelin (AG) and desacyl ghrelin (DAG) in wildtype and Ghsr null mice. We also measured the regional distribution of these ghrelin peptides throughout the brain. Lastly, we characterized the transport characteristics of human DAG by measuring the stability in serum and brain, saturability of transport, and the complete transfer across the brain endothelial cell. Results: We found the transport rate across the BBB of both forms of ghrelin, AG, and DAG, were not affected by the loss of GHSR. We did find differences in the transport rate between the two isoforms, with DAG being faster than AG; this was dependent on the species of ghrelin, human being faster than mouse. Lastly, based on the ubiquitous properties of ghrelin throughout the CNS, we looked at regional distribution of ghrelin uptake and found the highest levels of uptake in the olfactory bulb. Conclusions: The data presented here suggest that ghrelin transport can occur independently of the GHSR, and ghrelin uptake varies regionally throughout the brain. These findings better our understanding of the gut-brain communication and may lead to new understandings of ghrelin physiology. Keywords: Ghrelin, Blood–brain barrier, Growth hormone secretagogue receptor, Pharmacokinetic

Passage through the ocular barriers and beneficial effects in retinal ischemia of topical application of PACAP1-38 in rodents

The neuropeptide pituitary adenylate cyclase activating polypeptide (PACAP) has two active forms, PACAP1-27 and PACAP1-38. Among the well-established actions are PACAP's neurotrophic and neuroprotective effects, which have also been proven in models of different retinopathies. The route of delivery is usually intravitreal in studies proving PACAP's retinoprotective effects. Recently, we have shown that PACAP1-27 delivered as eye drops in benzalkonium-chloride was able to cross the ocular barriers and exert retinoprotection in ischemia. Since PACAP1-38 is the dominant form of the naturally occurring PACAP, our aim was to investigate whether the longer form is also able to cross the barriers and exert protective effects in permanent bilateral common carotid artery occlusion (BCCAO), a model of retinal hypoperfusion. Our results show that radioactive PACAP1-38 eye drops could effectively pass through the ocular barriers to reach the retina. Routine histological analysis and immunohistochemical evaluation of the Muller glial cells revealed that PACAP1-38 exerted retinoprotective effects. PACAP1-38 attenuated the damage caused by hypoperfusion, apparent in almost all retinal layers, and it decreased the glial cell overactivation. Overall, our results confirm that PACAP1-38 given in the form of eye drops is a novel protective therapeutic approach to treat retinal diseases