scholarly journals Renal GLUT2 is Essential in Regulating Systemic Glucose Homeostasis by Glycosuria

2021 ◽  
Vol 5 (Supplement_1) ◽  
pp. A324-A324
Author(s):  
Leticia M de Souza Cordeiro ◽  
Nagavardhini Devisetty ◽  
David McDougal ◽  
Dorien J M Peters ◽  
Kavaljit H Chhabra
Keyword(s):  
Glucose Tolerance ◽  
Glucose Homeostasis ◽  
Serum Insulin ◽  
Urine Volume ◽  
Fold Increase ◽  
Normal Serum ◽  
Oral Glucose ◽  
Loss Of Function ◽  
Melanocortin System ◽  
Deficient Mice

Abstract Diabetes increases renal GLUT2 levels and consequently, worsens hyperglycemia by enhancing glucose reabsorption. We recently demonstrated that renal GLUT2 is a primary effector of the central melanocortin system in regulating glucose homeostasis. Therefore, we hypothesized that renal GLUT2 is essential for maintaining systemic glucose homeostasis by regulating glycosuria. To test the hypothesis, we generated kidney-specific inducible Glut2 knockout (KO) mice [Glut2LoxP/LoxP x KspCadCreERT2 (inducible by tamoxifen)]. These mice exhibited 90% reduction in Glut2 expression selectively in the kidneys, without affecting the expressions of other renal glucose transporters, such as Glut1, Sglt1, and Sglt2. To evaluate the physiological contribution of renal GLUT2 in systemic glucose homeostasis, we performed oral glucose tolerance tests (OGTT) in kidney-specific Glut2 KO mice and their control littermates (Ctrl). We observed that the kidney-specific GLUT2 deficient mice exhibited improved glucose tolerance compared to their Ctrls (AUC for OGTT, 41,950 ±2,014 vs. 52,165 ±1,686 mg/dL.min). To measure glycosuria in the kidney-specific Glut2 KO mice, we placed the mice in metabolic cages and collected 24h urine after acclimating the mice in the new cages. Indeed, the GLUT2 deficient mice had ~1,800-fold increase in urine glucose levels (53.5 ±11 vs. 0.03 ±0.005 mg/24h) and exhibited an increased urine volume (2.5 ±0.3 vs. 0.9 ±0.3 mL/24h) and water intake (7.6 ±0.7 vs. 4.9 ±0.7 mL/24h) compared to their Ctrl littermates. The improvement in glucose tolerance in the kidney-specific Glut2 KO mice was independent of the insulin signaling because we did not observe any changes in insulin tolerance tests (ITT) (AUC for ITT, 10,982 ±414 vs. 11,275 ±583 mg/dL.min) and serum insulin levels (1.07 ±0.14 vs. 1.05 ±0.13 ng/mL) between the groups. Importantly, the kidney-specific GLUT2 deficient mice had normal serum creatinine (0.42 ±0.02 vs. 0.41 ±0.03 mg/dL), free fatty acid (0.43 ±0.14 vs. 0.53±0.14 nmol/µL), β-hydroxybutyrate (0.29 ±0.01 vs. 0.27 ±0.02 mM) and glucagon (14 ±4 vs. 10 ±1 pg/mL) levels. Moreover, the kidney-specific Glut2 KO mice had normal glomerular area (4,190 ±119 vs. 4,219 ±186 µm2) as measured by kidney histology and normal glomerular filtration rate (153 ±9 vs. 173 ±10 [µL/min/b.w.]/100) compared with their Ctrl littermates, indicating the absence of any known renal injury. Altogether, we have developed a new mouse model in which we can knockout Glut2 selectively in the kidneys in adult mice. We show that loss-of-function of kidney-specific GLUT2 improves glucose tolerance due to elevated glycosuria without producing any known side effects. In conclusion, blocking kidney-specific GLUT2 has the potential to treat diabetes.

scholarly journals Blackthorn Flower Extract Impact on Glycaemic Homeostasis in Normoglycemic and Alloxan-Induced Hyperglycaemic C57BL/6 Mice

2021 ◽  
Vol 59 (3) ◽  
Author(s):  
Irena Crnić ◽  
Tajana Frančić ◽  
Petar Dragičević ◽  
Vedran Balta ◽  
Verica Dragović-Uzelac ◽  
...  
Keyword(s):  
Blood Glucose ◽  
Glucose Tolerance ◽  
Glucose Homeostasis ◽  
Serum Insulin ◽  
Sugar Content ◽  
Tolerance Test ◽  
Oral Glucose ◽  
Mice Model ◽  
Flower Extract ◽  
Prunus Spinosa

Research background. The use of plants and their extracts in treatments of chronic diseases is widely known in traditional medicine. The aim of this study is to determine the effects of 10-day consumption of Prunus spinosa L. flower extract on blood glucose, glycaemic load, serum α-amlyase and serum insulin, in normoglycaemic and hypergycaemic (alloxan) mice model. Experimental approach. Normoglycemic and hyperglycemic (alloxan treated, 150 mg/kg body mass) C57BL/6 mice were treated daily, during 10 days, with Prunus spinosa L. flower extract by gavage. The sugar content within extract was determined by HPLC analysis. In mice, blood and serum blood glucose level and OGTT-test were determined by blood glucometer. Serum insulin was determined by ELISA assay and α-amlyase by colourimetric assay. Results and conclusions. The Prunus spinosa L. flower extract increased glucose in normoglycaemic mice by 30 % after 1st and 5th day and by 17 % after 10th day of consumption in normoglycaemic mice. It is a consequence of released sugars because sugar analysis revealed 59.8 mg/L monosaccharides, mainly fructose (55.7 mg/L) and glucose (24.3 mg/L) within the extract. On the opposite, the extract consumption, reduced serum blood glucose in alloxan-induced hyperglycaemic mice by 29 % after 10 days of treatment. Oral glucose tolerance test also confirmed that that in the hyperglycaemic group treated with Prunus spinosa L. flower extract glucose homeostasis was improved and showed decrease in blood glucose, since the blood glucose over the period of 120 min, glucose homeostasis is faster achieved after treatment with shows that in Prunus spinosa L. flower extract. Serum insulin increased by 49 % and serum alpha amylase by 46 % after 10 days of treatment with Prunus spinosa L. flower extract in hyperglycaemic group. Thus, it can be concluded that Prunus spinosa L. flower extract improved glucose tolerance, enhanced insulin secretion and lowered serum α-amylase activity. Novelty and scientific contribution. The results examined for the first time the potential of Prunus spinosa L. flower extract in hyperglycaemia management.

scholarly journals MON-639 Melanocortin 4 Receptor Contributes to Glucose Homeostasis by Regulating Kidney Glucose Reabsorption via the Glucose Transporter GLUT2

2020 ◽  
Vol 4 (Supplement_1) ◽  
Author(s):  
Leticia M de Souza Cordeiro ◽  
Nagavardhini Devisetty ◽  
Kavaljit H Chhabra
Keyword(s):  
Insulin Resistance ◽  
Glucose Tolerance ◽  
Glucose Homeostasis ◽  
Molecular Mechanisms ◽  
Area Under The Curve ◽  
Glucose Transporters ◽  
Oral Glucose ◽  
Melanocortin 4 Receptor ◽  
Glucose Reabsorption ◽  
Deficient Mice

Abstract Melanocortin 4 receptor (MC4R) is essential for normal body weight and food intake. Deficiency of MC4R causes obesity in humans and mice. While the function of MC4R is well established in appetite regulation, its direct role in glucose homeostasis is unclear. Humans and mice with MC4R deficiency exhibit hyperinsulinemia and insulin resistance; however, they remain protected from fasting hyperglycemia/diabetes. To determine the role of MC4R in glucose homeostasis, we performed oral glucose and intra-peritoneal insulin tolerance tests (OGTT / ITT) in male and female Mc4r knockout (KO) and wild type (WT) mice. Remarkably, Mc4r KO mice exhibited improved glucose tolerance compared to WT mice (Area under the curve for OGTT, male: 29,125±2,028 vs. 38,493±1,161 mg/dL.min; female: 36,322±1,100 vs. 49,539±1,911 mg/dL.min, p<0.0001). The improvement in glucose tolerance was despite insulin resistance in Mc4r KO mice (Plasma insulin, male: 9.9±1.7 vs. 0.7±0.1 ng/mL, female: 6.2±2.0 vs. 1.1±0.3 ng/mL, p<0.05; Area under the curve for ITT, male: 13,174±1,073 vs. 8,132±255 mg/dL.min; female: 13,927±1,253 vs. 7,506±267 mg/dL.min, p<0.01). Based on our previous findings from POMC deficient mice, we hypothesized that the improved glucose tolerance in the Mc4r KO mice is due to their elevated glycosuria (excretion of glucose in urine). To test this hypothesis, we challenged Mc4r KO and WT mice with oral glucose (250 mg) and collected their 24h urine to evaluate glycosuria. Indeed, the KO mice demonstrated elevated glycosuria compared to their WT littermates (Urine glucose, male: 284±48 vs. 0.4±0.03 mg/24h, female: 63.4±14 vs. 1±0.6 mg/24h, p<0.002). To assess molecular mechanisms underlying elevated glycosuria in Mc4r KO mice, we measured the gene expression and levels of the kidney glucose transporters GLUT1, GLUT2, SGLT1 and SGLT2. Glut2 mRNA was reduced by ̴ 40% and the protein level was decreased by ̴ 20% in Mc4r KO mice compared to their WT littermates. The other glucose transporters remained unchanged. Altogether, our study demonstrates that MC4R contributes to glucose homeostasis by regulating kidney glucose reabsorption via GLUT2. These findings may explain why MC4R deficient mice or humans remain protected from diabetes despite their longstanding obesity and insulin resistance.

scholarly journals Effect of breakfast fat content on glucose tolerance and risk factors of atherosclerosis and thrombosis

1998 ◽  
Vol 80 (4) ◽  
pp. 323-331 ◽  
Author(s):  
David L. Frape ◽  
Norman R. Williams ◽  
Jayshri Rajput-Williams ◽  
B. W. Maitland ◽  
A. J. Scriven ◽  
...  
Keyword(s):  
Glucose Tolerance ◽  
Thrombus Formation ◽  
Serum Insulin ◽  
Lipid Fraction ◽  
Tolerance Test ◽  
Serum Glucose ◽  
Oral Glucose ◽  
Significant Treatment ◽  
Treatment Allocation ◽  
Insulin Responses

Twenty-four middle-aged healthy men were given a low-fat high-carbohydrate (5.5 g fat; L), or a moderately-fatty, (25.7 g fat; M) breakfast of similar energy contents for 28 d. Other meals were under less control. An oral glucose tolerance test (OGTT) was given at 09.00 hours on day 1 before treatment allocation and at 13.30 hours on day 29. There were no significant treatment differences in fasting serum values, either on day 1 or at the termination of treatments on day 29. The following was observed on day 29: (1) the M breakfast led to higher OGTT C-peptide responses and higher areas under the curves (AUC) of OGTT serum glucose and insulin responses compared with the OGTT responses to the L breakfast (P< 0.05); (2) treatment M failed to prevent OGTT glycosuria, eliminated with treatment L; (3) serum non-esterified fatty acid (NEFA) AUC was 59% lower with treatment L than with treatment M, between 09.00 and 13.20 hours (P<0.0001), and lower with treatment L than with treatment M during the OGTT (P= 0.005); (4) serum triacylglycerol (TAG) concentrations were similar for both treatments, especially during the morning, but their origins were different during the afternoon OGTT when the Svedberg flotation unit 20–400 lipid fraction was higher with treatment L than with treatment M (P= 0.016); plasma apolipoprotein B-48 level with treatment M was not significantly greater than that with treatment L (P= 0.086); (5) plasma tissue plasminogen-activator activity increased after breakfast with treatment L (P= 0.0008), but not with treatment M (P= 0.80). Waist:hip circumference was positively correlated with serum insulin and glucose AUC and with fasting LDL-cholesterol. Waist:hip circumference and serum TAG and insulin AUC were correlated with factors of thrombus formation; and the OGTT NEFA and glucose AUC were correlated. A small difference in fat intake at breakfast has a large influence on circulating diurnal NEFA concentration, which it is concluded influences adversely glucose tolerance up to 6 h later.

Chronic exercise increases insulin binding in muscles but not liver

1986 ◽  
Vol 251 (2) ◽  
pp. E196-E203
Author(s):  
A. Bonen ◽  
P. A. Clune ◽  
M. H. Tan
Keyword(s):  
Glucose Tolerance ◽  
Plasma Membranes ◽  
Serum Insulin ◽  
Exercise Bout ◽  
Insulin Binding ◽  
Tolerance Test ◽  
Time Of Day ◽  
Oral Glucose ◽  
Chronic Exercise ◽  
Binding Data

It has been postulated that the improved glucose tolerance provoked by chronic exercise is primarily attributable to increased insulin binding in skeletal muscle. Therefore, we investigated the effects of progressively increased training (6 wk) on insulin binding by five hindlimb skeletal muscles and in liver. In the trained animals serum insulin levels at rest were lower either in a fed (P less than 0.05) or fasted (P less than 0.05) state and after an oral glucose tolerance test (n = 8) (P less than 0.05). Twenty-four hours after the last exercise bout sections of the liver, soleus (S), plantaris (P), extensor digitorum longus (EDL), and red (RG) and white gastrocnemius (WG) muscles were pooled from four to six rats. From control animals, killed at the same time of day, muscles and liver were also obtained. Insulin binding to plasma membranes increased in S, P, and EDL (P less than 0.05) but not in WG (P = 0.07), RG (P greater than 0.1), or in liver (P greater than 0.1). There were insulin binding differences among muscles (P less than 0.05). Comparison of rank orders of insulin binding data with published glucose transport data for the same muscles revealed that these parameters do not correspond well. In conclusion, insulin binding to muscle is shown to be heterogeneous and training can increase insulin binding to selected muscles but not liver.

Effect of exercise training on glucose homeostasis in normal and insulin-deficient diabetic rats

1988 ◽  
Vol 65 (2) ◽  
pp. 844-851 ◽  
Author(s):  
L. J. Goodyear ◽  
M. F. Hirshman ◽  
S. M. Knutson ◽  
E. D. Horton ◽  
E. S. Horton
Keyword(s):  
Skeletal Muscle ◽  
Exercise Training ◽  
Glucose Tolerance ◽  
Glucose Uptake ◽  
Glucose Homeostasis ◽  
Plasma Glucose ◽  
Citrate Synthase ◽  
Diabetic Rats ◽  
Oral Glucose ◽  
Oral Glucose Tolerance

The effect of 8-wk of treadmill training on plasma glucose, insulin, and lipid concentrations, oral glucose tolerance, and glucose uptake in the perfused hindquarter of normal and streptozocin-treated, diabetic Sprague-Dawley rats was studied. Diabetic rats with initial plasma glucose concentrations of 200-450 mg/dl and control rats were divided into trained and sedentary subgroups. Training resulted in lower plasma free fatty acid concentrations and increased triceps muscle citrate synthase activity in both the control and diabetic rats; triglyceride concentrations were lowered by training only in the diabetic animals. Oral glucose tolerance and both basal and insulin-stimulated glucose uptake in hindquarter skeletal muscle were impaired in the diabetic rats, and plasma glucose concentrations (measured weekly) gradually increased during the experiment. Training did not improve the hyperglycemia, impaired glucose tolerance, or decreased skeletal muscle glucose uptake in the diabetic rats, nor did it alter these parameters in the normal control animals. In considering our results and those of previous studies in diabetic rats, we propose that exercise training may improve glucose homeostasis in animals with milder degrees of diabetes but fails to cause improvement in the more severely insulin-deficient, diabetic rat.

scholarly journals A Role for Intestinal Endocrine Cell-Expressed G Protein-Coupled Receptor 119 in Glycemic Control by Enhancing Glucagon-Like Peptide-1 and Glucose-Dependent Insulinotropic Peptide Release

Endocrinology ◽  
2008 ◽  
Vol 149 (5) ◽  
pp. 2038-2047 ◽  
Author(s):  
Zhi-Liang Chu ◽  
Chris Carroll ◽  
Jean Alfonso ◽  
Veronica Gutierrez ◽  
Hongmei He ◽  
...  
Keyword(s):  
Glucose Tolerance ◽  
Glucose Homeostasis ◽  
Oral Glucose ◽  
Hormone Release ◽  
Β Cells ◽  
Pancreatic Β Cells ◽  
Incretin Hormone ◽  
Glucagon Like Peptide ◽  
Insulinotropic Peptide ◽  
G Protein Coupled

We recently showed that activation of G protein-coupled receptor 119 (GPR119) (also termed glucose dependent insulinotropic receptor) improves glucose homeostasis via direct cAMP-mediated enhancement of glucose-dependent insulin release in pancreatic β-cells. Here we show that GPR119 also stimulates incretin hormone release and thus may regulate glucose homeostasis by this additional mechanism. GPR119 mRNA was found to be expressed at significant levels in intestinal subregions that produce glucose-dependent insulinotropic peptide and glucagon-like peptide (GLP)-1. Furthermore, in situ hybridization studies indicated that most GLP-1-producing cells coexpress GPR119 mRNA. In GLUTag cells, a well-established model of intestinal L-cell function, the potent GPR119 agonist AR231453 stimulated cAMP accumulation and GLP-1 release. When administered in mice, AR231453 increased active GLP-1 levels within 2 min after oral glucose delivery and substantially enhanced total glucose-dependent insulinotropic peptide levels. Blockade of GLP-1 receptor signaling with exendin(9–39) reduced the ability of AR231453 to improve glucose tolerance in mice. Conversely, combined administration of AR231453 and the DPP-4 inhibitor sitagliptin to wild-type mice significantly amplified both plasma GLP-1 levels and oral glucose tolerance, relative to either agent alone. In mice lacking GPR119, no such enhancement was seen. Thus, GPR119 regulates glucose tolerance by acting on intestinal endocrine cells as well as pancreatic β-cells. These data also suggest that combined stimulation of incretin hormone release and protection against incretin hormone degradation may be an effective antidiabetic strategy.

Detection of Glycemic Abnormalities in Young Adult Patients with Beta Thalassemia Major Using Continuous Glucose Monitoring System (CGMS) and Oral Glucose Tolerance Test (OGTT)

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 2158-2158
Author(s):  
Mohamed A. Yassin ◽  
Ahmed M Elawa ◽  
Ashraf T Soliman
Keyword(s):  
Glucose Tolerance ◽  
Oral Glucose Tolerance Test ◽  
Glucose Tolerance Test ◽  
Cell Function ◽  
Serum Insulin ◽  
Tolerance Test ◽  
Oral Glucose ◽  
Oral Glucose Tolerance ◽  
Β Cell ◽  
Β Cell Function

Abstract Abstract 2158 Introduction: Both insulin deficiency and insulin resistance are reported in patients with β thalassemia major (BTM). The use of continuous blood glucose monitoring system (CGMS) among the different methods for early detection of glycaemic abnormalities has not been studied thoroughly in these patients. Aims: The aims of this study were: 1. to detect glycaemic abnormalities, if any, in young adults with BTM using fasting blood glucose (FBG), oral glucose tolerance test (OGTT), 72-h continuous glucose concentration by CGMS system, and serum insulin and C-peptide concentrations 2. To compare the results of these two methods in detecting glycaemic abnormalities in these patients and 3. To calculate homeostatic model assessment (HOMA), and the quantitative insulin sensitivity check index (QUICKI) in these patients. In order to evaluate whether glycaemic abnormalities are due to insulin deficiency and/or resistance. Materials and methods: Randomly selected young adults (n = 14) with BTM were the subjects of this study. All patients were investigated using a standard oral glucose tolerance test (OGTT) (using 75 gram of glucose) and 72-h continuous glucose concentration by CGM system (Medtronic system). Fasting serum insulin and C-peptide concentrations were measured and HOMA-B, HOMA-IR were calculated accordingly. Results: Using OGTT, 5 patients had impaired fasting glucose (IFG) (Fasting BG from 5.6 to 6.9 mmol/L). Two of them had impaired glucose tolerance IGT (BG from 7.8 and < 11.1 mmol/L) and one had BG = 16.2 mmol/L after 2-hrs (diabetic). Using CGMS in addition to the glucose data measured by glucometer (3–5 times/ day), 6 patients had IFG. The maximum (postprandial) BG recorded exceeded 11.1 mmol/L in 4 patients (28.5%) (Diabetics) and was > 7.8 but < 11.1 mmol/L in 8 patients (57%) (IGT). The mean values of HOMA and QUICKI in patients with BTM were < 2.6 (1.6± 0.8) and > 0.33 (0.36±0.03) respectively ruling out significant insulin resistance in these adolescents. There was a significant negative correlation between the β-cell function (B %) on the one hand and the fasting and the 2-h BG (r= −0.6, and − 0.48, P< 0.01 respectively) on the other hand. Serum insulin concentrations were not correlated with fasting BG or ferritin levels. The average and maximum BG levels recorded by CGMS were significantly correlated with the fasting BG (r= 0.69 and 0.6 respectively with P < 0.01) and with the BG at 2-hour after oral glucose intake (r= 0.87and 0.86 respectively with P < 0.01). Ferritin concentrations were positively correlated with the fasting BG and the 2-h BG levels in the OGTT (r= 0.69, 0.43 respectively, P < 0.001) as well as with the average and the maximum BG recorded by CGM (r =0.75, and 0.64 respectively with P < 0.01). Ferritin concentrations were negatively correlated with the β-cell function (r= −0.41, P< 0.01). Conclusion: CGMS has proved to be superior to OGTT for the diagnosis of glycaemic abnormalities in young adult patients with BTM. In our patients, defective β-cell function rather than insulin resistance appeared to be the cause for these abnormalities. The significant correlations between serum ferritin concentrations and the beta cell functions suggested the importance of adequate chelation to prevent β-cell dysfunction Disclosures: No relevant conflicts of interest to declare.

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