Altered Glucose Transport Research Articles

UCP1-dependent brown adipose activation accelerates cardiac metabolic remodeling and reduces initial hypertrophic and fibrotic responses to pathological stress.

Brown adipose tissue (BAT) is correlated to cardiovascular health in rodents and humans, but the physiological role of BAT in the initial cardiac remodeling at the onset of stress is unknown. Activation of BAT via 48 h cold (16°C) in mice following transverse aortic constriction (TAC) reduced cardiac gene expression for LCFA uptake and oxidation in male mice and accelerated the onset of cardiac metabolic remodeling, with an early isoform shift of carnitine palmitoyltransferase 1 (CPT1) toward increased CPT1a, reduced entry of long chain fatty acid (LCFA) into oxidative metabolism (0.59 ± 0.02 vs. 0.72 ± 0.02 in RT TAC hearts, p < .05) and increased carbohydrate oxidation with altered glucose transporter content. BAT activation with TAC reduced early hypertrophic expression of β-MHC by 61% versus RT-TAC and reduced pro-fibrotic TGF-β1 and COL3α1 expression. While cardiac natriuretic peptide expression was yet to increase at only 3 days TAC, Nppa and Nppb expression were elevated in Cold TAC versus RT TAC hearts 2.7- and 2.4-fold, respectively. Eliminating BAT thermogenic activation with UCP1 KO mice eliminated differences between Cold TAC and RT TAC hearts, confirming effects of BAT activation rather than autonomous cardiac responses to cold. Female responses to BAT activation were blunted, with limited UCP1 changes with cold, partly due to already activated BAT in females at RT compared to thermoneutrality. These data reveal a previously unknown physiological mechanism of UCP1-dependent BAT activation in attenuating early cardiac hypertrophic and profibrotic signaling and accelerating remodeled metabolic activity in the heart at the onset of cardiac stress.

Phenotypes of streptozotocin-induced gestational diabetes mellitus in mice.

Gestational diabetes mellitus (GDM) in human patients disrupts glucose metabolism post-pregnancy, affecting fetal development. Although obesity and genetic factors increase GDM risk, a lack of suitable models impedes a comprehensive understanding of its pathology. To address this, we administered streptozotocin (STZ, 75 mg/kg) to C57BL/6N mice for two days before pregnancy, establishing a convenient GDM model. Pregnant mice exposed to STZ (STZ-pregnant) were compared with STZ-injected virgin mice (STZ-virgin), citrate buffer-injected virgin mice (CB-virgin), and pregnant mice injected with citrate buffer (CB-pregnant). STZ-pregnant non-obese mice exhibited elevated blood glucose levels on gestational day 15.5 and impaired glucose tolerance. They also showed fewer normal fetuses compared to CB-pregnant mice. Additionally, STZ-pregnant mice had the highest plasma C-peptide levels, with decreased pancreatic islets or increased alpha cells compared to CB-pregnant mice. Kidneys isolated from STZ-pregnant mice did not display histological alterations or changes in gene expression for the principal glucose transporters (GLUT2 and SGLT2) and renal injury-associated markers. Notably, STZ-pregnant mice displayed decreased gene expression of insulin-receiving molecules (ISNR and IGFR1), indicating heightened insulin resistance. Liver histology in STZ-pregnant mice remained unchanged except for a pregnancy-related increase in lipid droplets within hepatocytes. Furthermore, the duodenum of STZ-pregnant mice exhibited increased gene expression of ligand-degradable IGFR2 and decreased expression of GLUT5 and GLUT12 (fructose and glucose transporters, respectively) compared to STZ-virgin mice. Thus, STZ-pregnant mice displayed GDM-like symptoms, including fetal abnormalities, while organs adapted to impaired glucose metabolism by altering glucose transport and insulin reception without histopathological changes. STZ-pregnant mice offer a novel model for studying mild onset non-obese GDM and species-specific differences in GDM features between humans and animals.

Ageing-Related Alterations in Renal Epithelial Glucose Transport.

The kidney plays a crucial role in glucose homeostasis by regulating glucose transport. We aimed to investigate the impact of alterations in glucose transport on glucose metabolism during ageing. Adult male Sprague Dawley rats were divided into five groups: 3-month, 6-month, and 12-month control groups, and 6- and 12-month groups receiving the hydrogen sulfide donor molecule GYY4137. The study found that, as age increased, daily urinary uric acid and protein levels increased in the 12-month group. Blood sugar level and HOMA-IR index increased in the 12-month group, and were partially improved by GYY4137. The kidney tissue showed mild glomerulosclerosis in the 12-month group, which was diminished by GYY4137. Gene expression analysis showed decreased sirtuin and increased p21 expression in the aging groups. Increased SGLT1 and SGLT2 expression was observed in the 12-month group, which was reversed by GYY4137. Both GLUT1 and GLUT2 expression was increased in the 6- and 12-month groups, and reversed by GYY4137 in the 12-month group. The study concluded that aging was associated with increased blood sugar levels and the HOMA-IR index, and the abundance of renal glucose transporters increased as aging progressed. GYY4137 effectively reversed aging-related alterations in glucose homeostasis and renal epithelial transporters.

12 Amino Acid Nutrition in Dairy Cattle: Beyond Milk Protein

Abstract The transition from gestation to lactation, also known as the transition period, is a critical time for dairy cows. This phase is typically defined as 3 weeks before parturition through 3 weeks after parturition. Peak disease incidence (shortly after parturition) corresponds with the time of greatest negative energy balance (NEB) and negative protein balance (NPB), the peak in blood concentrations of nonesterified fatty acids, and the greatest acceleration of milk yield. Decreased fertility in the face of increasing milk production may be attributable to greater severity of postpartum NEB and NPB resulting from inadequate transition management or increased disease rates. The depth and duration of NEB and NPB are highly related to dry matter intake. Formulating and delivering appropriate diets that limit total energy intake to requirements but also provide proper intakes of all other nutrients [including the indispensable amino acids (IAA) Met and Lys] before calving can help lessen the extent of NEB and NPB after calving. Supplementation of rumen-protected methionine (RPM) during the transition period improved uterine immune function through improved glandular morphology, increased neutrophil infiltration after calving, and discovery of neutrophil extracellular trap formation in bovine endometrial tissue. Its supplementation has been reported to reduce the incidence of health complications, better lactation performance, and more favorable biomarker and plasma AA profiles, common in cows with increased liver functionality index. Cows supplemented with rumen-protected lysine (RPL) had decreased liver oxidative stress (SOD1, superoxide dismutase 1) and acute phase response (SAA3, serum amyloid A3) and reduced gene expression of NFKB1 (nuclear factor kappa B1) leading to increased proinflammatory IL1B postpartum, likely indicating improved immune activation when cows consumed RPL, a necessary component of early postpartum health. Our group has reported that a prepartum supply of RPL altered uteroplacental metabolism and glucose transport. This was demonstrated through increased expression of uterine transcripts involved in energy metabolism (GLUT3, glucose transporter 3; PCK1, phosphoenolpyruvate carboxykinase 1) and placental metabolism (FGF2, fibroblast growth factor 2; FGF2R, fibroblast growth factor 2 receptor; and PGF, placental growth factor). We also have demonstrated that RPL prepartum increased the placental protein abundance of FGF2 and LRP1 (low-density lipoprotein receptor-related protein 1), indicating possible enhanced placental metabolic activity, probably linked to trophoblast proliferation and migration processes. Finally, calves from dams fed RPL prepartum had improved overall growth and intake than calves from dams not receiving RPL. In conclusion, providing RPM and RPL during the transition period impacts dairy cows' health, uterine environment, and offspring.

IDF21-0037 The association between cognitive functioning and SLC2A1 level in patients with newly diagnosed type 2 diabetes mellitus

Background: Glucose is the main energy fuel of the brain tissue; the presence of glucose and its transport to the brain through the blood-brain barrier (BBB) and to individual brain cells plays a key role in normal physiological functioning and energy metabolism. SLC2A1 is the factor which plays an important role in the transport of glucose into the brain. Thus, it is important to understand the role of altered glucose transport in brain cells and its effect on the state of cognitive functioning in patients with newly diagnosed diabetes mellitus. Aim: The aim of our study was to examine the level of the gene encoding SLC2A1 and cognitive functioning in patients with newly diagnosed diabetes mellitus under the influence of metformin. Method: We enrolled 60 patients with newly diagnosed type 2 diabetes mellitus 17 males and 43 females (aged 60,9±1,40 years, HbA1c – 7,91±0,17%) (data are presented everywhere as mean±SEM). All patients received metformin SR as a starting glucose-lowering therapy. Real-time PCR analysis was performed for quantitative evaluation of gene of SLC2A1. The estimation of the SLC2A1 level was carried out at the beginning and 3 months after the treatment. Cognitive functioning was assessed using a standard neuropsychological battery of tests covering the domains of memory, executive functioning, and processing speed. Regression tests were performed adjusted for age, level education, sex. Results presents as B (95% CI). The statistical analysis was performed using SPSS-25. Results: We found correlations between SLC2A1 gene level and memory function (B=0.19(-0.00/0.39); p=0.05). We did not find the relationship between the level of SLC2A1 gene and executive functioning, and processing speed. We found a statistically significant increased levels of SLC2A1 gene after the treatment with metformin - 0.50±0.06 vs 1.11±0.22, respectively, p=0.01. Discussion: The changes of SLC2A1 gene can reflect the changes of glucose transport into the brain and can be partly corrected by treatment with metformin.

Establishment of long-term high-fat diet and low dose streptozotocin-induced experimental type-2 diabetes mellitus model of insulin resistance and evaluation of seed extracts of Syzygium cumini

Introduction: The principal mechanism responsible for reducing blood glucose is through insulin-stimulated glucose transport into skeletal muscle. The transporter protein that mediates this uptake is GLUT-4. A defect in this step is associated with reduced glucose utilization in muscle and adipose tissue, as observed in insulin-resistant type-2 diabetes mellitus (T2DM) patients. This study aimed to develop an experimental T2DM model and evaluate altered glucose transporter type 4 (GLUT-4) levels as a biomarker of insulin resistance. Antidiabetic activities of Syzygium cumini hydro-ethanolic seed extracts (SCE) were also evaluated. Methods: Adult male Wistar albino rats were fed a high-fat diet for 12 weeks and dosed intraperitoneally with streptozotocin (35 mg/kg). After treatment for 21 days, all investigations were done. The homeostasis model of assessment (HOMA) was used for the calculation of insulin resistance (HOMA-IR) and beta-cell function (HOMA-B) index. Diaphragm muscle and retroperitoneal fat were collected for real-time polymerase chain reaction (RT-PCR) studies. Results: A significant increase in fasting blood glucose, HOMA-IR, and serum lipids, and a decrease in serum insulin and HOMA-B were observed in the diabetic group, effects that reversed following pioglitazone and SCE treatment. The diabetic group showed a downregulation of GLUT-4 expression in skeletal muscle while an increase was observed in adipose tissue. Conclusion: A high-fat diet and low dose streptozotocin-induced experimental T2DM model of insulin resistance was developed to screen novel insulin sensitizers. Data generated demonstrated that altered GLUT-4 levels could be used as a biomarker of insulin resistance. Antidiabetic activity of S. cumini hydro-ethanolic seed extract was also confirmed in this study.

Blueberries and insulin protect microglial cells against high glucose-induced inflammation and restore GLUT-1

BACKGROUND: Growing evidence suggests that hyperglycemia could be harmful for cognitive function. That insulin (INS) has a neuro-modulatory role is supported by various findings, but its effect on microglia, the innate immune cells in the brain, is largely unknown. Blueberries have been shown to reduce neuro-inflammation. OBJECTIVE: We hypothesized that high glucose stimulated an inflammation in microglia and that BB and INS were able to reduce it and both might act through GLUT-1 transporter. METHODS: We examined the effects of low (5 mM), medium (25 mM), or high (50 mM) glucose, stimulated or not with lipopolysaccharide (LPS; 100 nM) with either BB extract (2 mg/ml) and/or INS, on inflammatory responses in a microglia cell line. Nitric oxide (NO) production and the expression levels of iNOS, TNF-α, NOX4 and glucose transporter protein-1 (GLUT1) were assessed. RESULTS: We observed that treatment with BB, similarly to INS treatments, reduced the high glucose concentration-induced response on oxidative stress and inflammation, and that this protective effect is more important with LPS added to glucose media. Interestingly, both BB and INS attenuated the LPS-induced inflammatory response on GLUT1. CONCLUSION: Increasing glucose concentration triggers inflammation by microglia. BB as well as INS protected microglia from high glucose levels, by reducing inflammation and altering glucose transport in microglia. These preliminary data compared for the first time BB to Insulin on microglia. Blueberries are promising dietary intervention to prevent diabetic neuropathy. Our preliminary results suggest a possible new mechanism involving GLUT-1 by which BB has insulin-like effects.

Andrographolide restores glucose uptake in rat hippocampal neurons.

Cerebral glucose hypometabolism is a common pathophysiological characteristic of many neurodegenerative diseases. This metabolic dysfunction includes alterations in glucose transport from the blood into the neurons by the facilitative glucose transporters (GLUTs). Several studies suggest that metabolic disturbances precede clinical symptoms and correlate with disease progression. Some groups have started to explore the use of therapeutic strategies that target decreased cerebral glucose metabolism to promote its availability. We selected Andrographolide (Andro), a natural product obtained from Andrographis paniculate that has both anti-hyperglycemic and anti-diabetic effects. Although it was shown to promote glucose uptake in vivo, the underlying mechanisms remain unclear. Here, we evaluated the acute effects of Andro on glucose transport and metabolism using primary rat hippocampal neuronal cultures. Our results showed that Andro enhances neuronal glucose uptake and stimulates glucose metabolism by inducing GLUT3 and 4 expression in neurons, as well as by promoting glycolysis. We also observed that Andro-mediated effects depend on the activity of AMP-activated protein kinase (AMPK), one of the central regulators of glucose metabolism. Our studies open the possibility to use Andro as a drug to restore glucose levels in neurodegenerative diseases.

1762-P: Poor Sleep Quality Is Associated with Lower Absolute Cerebral Glucose Levels

Poor sleep quality has been associated with increased risk of metabolic syndrome and type 2 diabetes as well as acceleration of neurodegenerative diseases. In rodents, sleep restriction decreases glucose transport into the brain via downregulation of GLUT1, the primary glucose transporter at the blood-brain barrier. However, little is known about the association between sleep quality and glucose transport and metabolism in the human brain. In this exploratory analysis, we quantified cerebral glucose levels amongst individuals with good and poor sleep quality as defined by the widely used and well-validated Pittsburgh Sleep Quality Index (PSQI), which assesses 7 different components of sleep quality over a 1 month time period (PSQI≥5 = Poor sleep; PSQI&amp;lt;5 = Good sleep). Twelve healthy subjects completed the PSQI questionnaire. Eight (6F, age 27.6 ± 5.7, BMI 26.6 ± 8.2 kg/m2, HgbA1c 5.4 ± 0.2%) had good and 4 (2F, age 29.5± 2.4, BMI 27.8 ± 6.5 kg/m2, HgbA1c 5.2 ± 0.2%) had poor sleep. All subjects underwent 13C magnetic resonance spectroscopy brain scanning at 4 Tesla during a 2-hour hyperglycemic clamp (plasma glucose target ∼180 mg/dl) to measure absolute cerebral glucose levels as part of a larger study to investigate obesity and cerebral glucose metabolism. There were no differences in age, BMI, or HbA1c levels between groups with good and poor sleep. Individuals with good sleep had 63% higher absolute cerebral glucose levels at steady state compared to those with poor sleep (3.4 ± 0.7 mmol/L vs. 2.1 ± 0.9 mmol/L, p=.017). Higher PSQI scores correlated with lower absolute cerebral glucose levels (r= -0.725, p=0.008, PSQI for all subjects (mean±SD) = 4 ± 2). In this pilot and exploratory study, individuals with poor sleep quality have significantly lower absolute cerebral glucose levels, which suggests an association between poor sleep and altered cerebral glucose transport and/or metabolism. These findings may have wide-ranging implications for understanding the effects of sleep on brain function. Disclosure T.K. Stanley: None. F. Gunawan: None. N.S. Redeker: None. L. Jiang: None. A. Coppoli: None. D.L. Rothman: None. G.F. Mason: None. J. Hwang: Research Support; Self; General Electric. Funding American Diabetes Association (1-17-ICTS-013 to J.H.); National Institutes of Health (1R03DK121048)

Lactation Versus Formula Feeding: Insulin, Glucose, and Fatty Acid Metabolism During the Postpartum Period.

Milk production may involve a transient development of insulin resistance in nonmammary tissues to support redistribution of maternal macronutrients to match the requirements of the lactating mammary gland. In the current study, adipose and liver metabolic responses were measured in the fasting state and during a two-step (10 and 20 mU/m2/min) hyperinsulinemic-euglycemic clamp with stable isotopes, in 6-week postpartum women who were lactating (n = 12) or formula-feeding (n = 6) their infants and who were closely matched for baseline characteristics (e.g., parity, body composition, and intrahepatic lipid). When controlling for the low insulin concentrations of both groups, the lactating women exhibited a fasting rate of endogenous glucose production (EGP) that was 2.6-fold greater and a lipolysis rate that was 2.3-fold greater than the formula-feeding group. During the clamp, the groups exhibited similar suppression rates of EGP and lipolysis. In the lactating women only, higher prolactin concentrations were associated with greater suppression rates of lipolysis and lower intrahepatic lipid and plasma triacylglycerol concentrations. These data suggest that whole-body alterations in glucose transport may be organ specific and facilitate nutrient partitioning during lactation. Recapitulating a shift toward noninsulin-mediated glucose uptake could be an early postpartum strategy to enhance lactation success in women at risk for delayed onset of milk production.

HENT1 reverses chemoresistance by regulating glycolysis in pancreatic cancer.

Gemcitabine (GEM) chemotherapy, as the first-line regimen for pancreatic cancer, tends to induce drug resistance, which ultimately worsens the prognosis of patients with pancreatic cancer. Our previous study indicated a close correlation between pancreatic cancer progression and glucose metabolism, especially at the chemoresistant stage, highlighting the importance of the application of 18F-FDG PET dual-phase imaging in the early detection of pancreatic cancer. We speculate that glycolysis, participates in the development of chemoresistance in pancreatic cancer. In this article, we wanted to determine whether manipulating hENT1 expression in pancreatic cancer cells can reverse GEM chemoresistance and whether glucose transport and glycolysis are involved during this process. We found that hENT1 reversed GEM-induced drug resistance by inhibiting glycolysis and altering glucose transport mediated by HIF-1α in pancreatic cancer. Our findings also suggest that 18F-FDG PET dual-phase imaging after the 4th chemotherapy treatment can accurately identify drug-resistant pancreatic tumors and improve hENT1 reversal therapy. Our findings highlight that the dynamic observation of (retention index) RI changes from the beginning of treatment can also be helpful for evaluating the therapeutic effect.

Treatable Inherited Movement Disorders in Children: Spotlight on Clinical and Biochemical Features.

About 80% of monogenic metabolic diseases causing movement disorders (MDs) emerges during the first 2 decades of life, and a number of these conditions offers the opportunity of a disease-modifying treatment. The implementation of enlarged neonatal screening programs and the impressive rapid increase of the identification of new conditions are enhancing our potential to recognize and treat several diseases causing MDs, changing their outcome and phenotypic spectrum. A literature review of monogenic disorders causing MDs amenable to treatment was conducted focusing on early clinical signs and diagnostic biomarkers. A classification in 3 broad categories based on the therapeutic approach has been proposed. Some disorders result in irreversible neurotoxic lesions that can only be prevented if treated in a presymptomatic stage, and others present with a progressive neurological impairment that a timely diagnosis and treatment may reverse or improve. Some MDs are the result of the failure of intracellular energy supply or altered glucose transport. The treatment in these conditions includes vitamins or a metabolic shift from a carbohydrate to a fatty acid catabolism, respectively. Finally, a group of highly treatable MDs are the result of defects of neurotransmitter metabolism. In these disorders, the supplementation of precursors or mimetics of neurotransmitters can deeply change the disease natural history. To prevent serious and irreversible neurological impairment, the diagnostic work-up of MDs in children should consider a number of clinical red flags and biomarkers denoting specifically treatable diseases.

Cryptosporidium parvum alters glucose transport mechanisms in infected enterocytes.

The parasite Cryptosporidium parvum Tyzzer 1912 destroys parts of the intestinal brush border membrane which is important for the uptake of nutrients like glucose. In this study, glucose transport mechanisms of the host cells (IPEC-J2 cells) infected by C. parvum were investigated. The mRNA expression levels of glucose transporters (GLUT) 1 and 2 and Na+-coupled glucose transporter (SGLT) 1 were compared in infected and uninfected cells over an infection time of 24-96 h by RT-qPCR. Furthermore, the protein expression of SGLT 1 and GLUT 2 was quantified in western blot studies. While the protein expression of SGLT 1 was not altered in infected cells, mRNA expression of SGLT 1 and GLUT 1 was significantly increased 24 h p. i. and decreased 96 h p. i. The mRNA expression of GLUT 2 was significantly decreased 24 h, 72 h, and 96 h p. i. and also correlated significantly with the infection dose at 72 h p. i. In contrast to that, the protein expression of GLUT 2 was significantly increased 48 h p. i., associated with a significantly higher intracellular glucose level in infected cells compared with control cells at that time point of infection. This points to an adaptation of the host cells' glucose uptake taking place in the acute phase of the infection. A better understanding of these molecular mechanisms following a C. parvum infection may probably lead to an improvement of therapy strategies in the future.

Maternal High-Fat Diet Consumption and Chronic Hyperandrogenemia Are Associated With Placental Dysfunction in Female Rhesus Macaques.

The risk of adverse perinatal outcomes with maternal polycystic ovary syndrome may differ among hyperandrogenic and nonhyperandrogenic phenotypes and is likely modulated by maternal obesity and diet. The relative contribution of maternal hyperandrogenism and nutritional status to placental dysfunction is unknown. Female rhesus macaques (N = 39) were assigned at puberty to one of four treatment groups: subcutaneous cholesterol implants and a standard chow diet (controls); testosterone (T) implants and a normal diet; cholesterol implants and a high-fat, Western-style diet (WSD); and testosterone implants in combination with a high-fat diet. After 3.5 years of treatment, contrast-enhanced and Doppler ultrasound analyses of placental blood flow were performed for a representative subset of animals from each treatment group during pregnancy, and placental architecture assessed with stereological analysis. Placental growth factors, cellular nutrient sensors, and angiogenic markers were measured with ELISA and Western blotting. WSD consumption was associated with a 30% increase in placental flux rate relative to that in animals receiving a normal diet. T and WSD treatments were each independently associated with increased villous volume, and T also was associated with an ∼ 40% decrease fetal capillary volume on stereological analysis. T treatment was associated with significantly increased mTOR and SOCS3 expression. WSD consumption was associated with decreased GLUT1 expression and microvillous membrane localization. Hyperandrogenemic and nonhyperandrogenemic phenotypes are associated with altered placental angiogenesis, nutrient sensing, and glucose transport. WSD and T appear to have distinct effects on vascular impedance and capillary angiogenesis.

Effects of Magnesium Deficiency on Mechanisms of Insulin Resistance in Type 2 Diabetes: Focusing on the Processes of Insulin Secretion and Signaling.

Magnesium (Mg2+) is an essential mineral for human health and plays an important role in the regulation of glucose homeostasis and insulin actions. Despite the widespread clinical evidences for the association of Mg2+ deficiency (MgD) and type 2 diabetes mellitus (T2D), molecular mechanisms by which Mg2+ contributes to insulin resistance (IR) are still under discussion. Mg2+ regulates electrical activity and insulin secretion in pancreatic beta-cells. Intracellular Mg2+ concentrations are critical for the phosphorylation of the insulin receptor and other downstream signal kinases of the target cells. Low Mg2+ levels result in a defective tyrosine kinase activity, post-receptor impairment in insulin action, altered cellular glucose transport, and decreased cellular glucose utilization, which promotes peripheral IR in T2D. MgD triggers chronic systemic inflammation that also potentiates IR. People with T2D may end up in a vicious circle in which MgD increases IR and IR causes MgD, that requires periodic monitoring of serum Mg2+ levels.

MiR-200a-5p augments cardiomyocyte hypertrophy induced by glucose metabolism disorder via the regulation of selenoproteins.

Selenium and selenoproteins are identified as potential determinants in pathological cellular hypertrophy. Cardiomyocytes hypertrophy is a compensatory form of heart disease characterized by increased size of cardiomyocytes. However, the link between cardiac hypertrophy and Se-specific microRNA (miRNA) remains to be characterized. In the current study, we established a miR-200a-5p mimic and an inhibitor cardiomyocytes model. Cardiomyocytes hypertrophy was induced in the miR-200a-5p mimic group. Hence, we detected the glucose level of cardiomyocytes to estimate the cellular glucose uptake. The effect of miR-200a-5p overexpression and the low expression on 25 selenoproteins mRNA levels was further explored using reverse transcription polymerase chain reaction. Overexpression of miR-200a-5p elevated glucose uptake and Txnrd2, 3 expression and reduced Sepp1, Seln, Selt, and Sep15 expression in cardiomyocytes. Contrary results were observed in cardiomyocytes with the knockdown of miR-200a-5p. We next assessed glucose metabolism-related genes in cardiomyocytes. The results showed that miR-200a-5p had a negative correlation with insulin-like growth factor gene-1, insulin-like growth factor binding protein (IGFBP)1, IGFBP2, IGFBP3, IGFBP4, and IGFBP5 and had a positive correlation with Akt, glucose transporter family (GLUT)2, GLUT3, and GLUT4. These results support the involvement of selenoproteins and glucose metabolism in the control of cardiomyocytes hypertrophy by Se-specific miRNA, suggesting that miR-200a-5p inhibited the expression of stress-related selenoproteins to alter glucose transport leading to glucose metabolism disorder, eventually inducing cardiomyocytes hypertrophy. Our finding highlights a pivotal role of Se-specific miRNA and selenoproteins in cardiac hypertrophy.

Insulin Deficiency Is a Major Contributor to Atrial Fibrillation

Diabetes has been identified as a major independent risk factor for atrial fibrillation (AF), the most common sustained cardiac arrhythmia. However, it is unknown whether glucose and insulin disturbances observed during diabetes directly affect the function of the atria, leading to AF. Thus, we hypothesized that insulin deficiency and impaired glucose transport provide a metabolic substrate for the development and maintenance of AF during diabetes. Transesophageal atrial pacing was used to induce AF in healthy, streptozotocin-induced type 1 diabetic and insulin-treated (via a subcutaneous pump) diabetic mice (n=4-11/group). Translocation of insulin-sensitive glucose transporters (GLUTs) was measured using a photolabeled biotinylation assay in the perfused heart. Atrial fibrosis and glycogen accumulation were measured using histological analyses. As expected, insulin-deficient diabetic mice displayed hyperglycemia (434 ± 50.9 mg/dl) while insulin-treated diabetic mice remained euglycemic (118.8 ± 3.3 mg/dl, p&amp;lt;0.05). At 8 weeks, diabetic mice displayed increased duration and frequency of AF episodes vs. age-matched controls (e.g., AF duration: 18.7 ± 6.2 s vs. 1.8 ± 1.1 s, respectively, p=0.032), whereas insulin-treated diabetic animals did not. In addition, the frequency of AF episodes was significantly correlated to blood glucose level (p=0.01). GLUT-4 and -8 translocation to the atrial cell surface was significantly downregulated in diabetic mice (by 67% and 79%, respectively; p≤0.001), and rescued by insulin treatment. We did not observe any fibrosis or glycogen accumulation in the atria of (treated and untreated) diabetic mice. We conclude that, in the absence of structural remodeling and atrial fibrosis, insulin and glucose disturbances were sufficient to induce AF during diabetes. Therefore, these data suggest that insulin deficiency during diabetes leads to alterations in glucose transport and energy production in the atria, which enhances its vulnerability to atrial fibrillation. Disclosure Z. Maria: None. A. Campolo: None. B.J. Scherlag: None. J.W. Ritchey: None. V. Lacombe: None.

Titanium dioxide nanoparticle exposure alters metabolic homeostasis in a cell culture model of the intestinal epithelium and Drosophila melanogaster

Nanosized titanium dioxide (TiO2) is a common additive in food and cosmetic products. The goal of this study was to investigate if TiO2 nanoparticles affect intestinal epithelial tissues, normal intestinal function, or metabolic homeostasis using in vitro and in vivo methods. An in vitro model of intestinal epithelial tissue was created by seeding co-cultures of Caco-2 and HT29-MTX cells on a Transwell permeable support. These experiments were repeated with monolayers that had been cultured with the beneficial commensal bacteria Lactobacillus rhamnosus GG (L. rhamnosus). Glucose uptake and transport in the presence of TiO2 nanoparticles was assessed using fluorescent glucose analog 2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose (2-NBDG). When the cell monolayers were exposed to physiologically relevant doses of TiO2, a statistically significant reduction in glucose transport was observed. These differences in glucose absorption were eliminated in the presence of beneficial bacteria. The decrease in glucose absorption was caused by damage to intestinal microvilli, which decreased the surface area available for absorption. Damage to microvilli was ameliorated in the presence of L. rhamnosus. Complimentary studies in Drosophila melanogaster showed that TiO2 ingestion resulted in decreased body size and glucose content. The results suggest that TiO2 nanoparticles alter glucose transport across the intestinal epithelium, and that TiO2 nanoparticle ingestion may have physiological consequences.

Chronic Hippocampal Expression of Notch Intracellular Domain Induces Vascular Thickening, Reduces Glucose Availability, and Exacerbates Spatial Memory Deficits in a Rat Model of Early Alzheimer.

The specific roles of Notch in progressive adulthood neurodegenerative disorders have begun to be unraveled in recent years. A number of independent studies have shown significant increases of Notch expression in brains from patients at later stages of sporadic Alzheimer's disease (AD). However, the impact of Notch canonical signaling activation in the pathophysiology of AD is still elusive. To further investigate this issue, 2-month-old wild-type (WT) and hemizygous McGill-R-Thy1-APP rats (Tg(+/-)) were injected in CA1 with lentiviral particles (LVP) expressing the transcriptionally active fragment of Notch, known as Notch Intracellular Domain (NICD), (LVP-NICD), or control lentivirus particles (LVP-C). The Tg(+/-) rat model captures presymptomatic aspects of the AD pathology, including intraneuronal amyloid beta (Aβ) accumulation and early cognitive deficits. Seven months after LVP administration, Morris water maze test was performed, and brains isolated for biochemical and histological analysis. Our results showed a learning impairment and a worsening of spatial memory in LVP-NICD- as compared to LVP-C-injected Tg(+/-) rats. In addition, immuno histochemistry, ELISA multiplex, Western blot, RT-qPCR, and 1H-NMR spectrometry of cerebrospinal fluid (CSF) indicated that chronic expression of NICD promoted hippocampal vessel thickening with accumulation of Aβ in brain microvasculature, alteration of blood-brain barrier (BBB) permeability, and a decrease of CSF glucose levels. These findings suggest that, in the presence of early Aβ pathology, expression of NICD may contribute to the development of microvascular abnormalities, altering glucose transport at the BBB with impact on early decline of spatial learning and memory.

Prior treatment with the AMPK activator AICAR induces subsequently enhanced glucose uptake in isolated skeletal muscles from 24-month-old rats.

5' AMP-activated protein kinase (AMPK) activation may be part of the exercise-induced process that enhances insulin sensitivity. Independent of exercise, acute prior treatment of skeletal muscles isolated from young rats with a pharmacological AMPK activator, 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside (AICAR), causes subsequently improved insulin-stimulated glucose uptake (GU). However, efficacy of a single prior AICAR exposure on insulin-stimulated GU in muscles from old animals has not been studied. The purpose of this study was to determine whether brief, prior exposure to AICAR (3.5 h before GU assessment) leads to subsequently increased GU in insulin-stimulated skeletal muscles from old rats. Epitrochlearis muscles from 24-month-old male rats were isolated and initially incubated ±AICAR (60 min), followed by incubation without AICAR (3 h), then incubation ±insulin (50 min). Muscles were assessed for GU (via 3-O-methyl-[3H]-glucose accumulation) and site-specific phosphorylation of key proteins involved in enhanced GU, including AMPK, Akt, and Akt substrate of 160 kDa (AS160), via Western blotting. Prior ex vivo AICAR treatment resulted in greater GU by insulin-stimulated muscles from 24-month-old rats. Prior AICAR treatment also resulted in greater phosphorylation of AMPK (T172) and AS160 (S588, T642, and S704). Glucose transporter type 4 (GLUT4) protein abundance was unaffected by prior AICAR and/or insulin treatment. These findings demonstrate that skeletal muscles from older rats are susceptible to enhanced insulin-stimulated GU after brief activation of AMPK by prior AICAR. Consistent with earlier research using muscles from young rodents, increased phosphorylation of AS160 is implicated in this effect, which was not attributable to altered GLUT4 glucose transporter protein abundance.