scholarly journals Functional localization of glucose transporter 2 in rat liver.

1996 ◽  
Vol 44 (11) ◽  
pp. 1231-1236 ◽  
Author(s):  
A Ogawa ◽  
K Kurita ◽  
Y Ikezawa ◽  
M Igarashi ◽  
T Kuzumaki ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Rat Liver ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Glucose Transporter ◽  
Mrna Level ◽  
Functional Difference ◽  
Isolation Technique ◽  
Glucose Transporter 2 ◽  
Normal Rat ◽  
Basolateral Plasma Membrane

Heterogeneity of zonal hepatocytes is important to elicit specific liver function. We investigated the distribution of glucose transporter 2 (GLUT-2) in normal rat liver by immunostaining and Northern blot analysis. GLUT-2 stained by immunohistochemistry was distributed predominantly in the periportal hepatocytes and gradually thinned towards the perivenous zone. Ultrastructural immunostaining of GLUT-2 showed that it was localized on microvilli of the sinusoidal plasma membrane of hepatocytes but not on the basolateral plasma membrane. Consistent with the distribution of GLUT-2 protein, the level of GLUT-2 mRNA in periportal hepatocytes was 1.9-fold higher than in perivenous hepatocytes selectively isolated by the differential isolation technique. In addition, the mRNA level of phosphoenolpyruvate carboxykinase, one of the key enzymes of gluconeogenesis, was also twofold higher in the periportal hepatocytes. These results suggest that GLUT-2 contributes to the functional difference between periportal and perivenous hepatocytes in glucose metabolism of the liver.

scholarly journals Dietary Tryptophan Supplementation Alters Fat and Glucose Metabolism in a Low-Birthweight Piglet Model

Nutrients ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 2561
Author(s):  
Parniyan Goodarzi ◽  
Mohammad Habibi ◽  
Kennedy Roberts ◽  
Julia Sutton ◽  
Cedrick Ndhumba Shili ◽  
...  
Keyword(s):  
Feeding Behavior ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Low Birthweight ◽  
Glucose Transporter ◽  
Protein Abundance ◽  
Metabolic Complications ◽  
Glucose And Lipid Metabolism ◽  
Glucose Transporter 2 ◽  
Lower Protein ◽  
Type 3

Low birthweight (LBW) is associated with metabolic complications, such as glucose and lipid metabolism disturbances in early life. The objective of this study was to assess: (1) the effect of dietary tryptophan (Trp) on glucose and fat metabolism in an LBW piglet model, and (2) the role peripheral 5-hydroxytryptamine type 3 (5HT3) receptors in regulating the feeding behavior in LBW piglets fed with Trp-supplemented diets. Seven-day-old piglets were assigned to 4 treatments: normal birthweight-0%Trp (NBW-T0), LBW-0%Trp (LBW-T0), LBW-0.4%Trp (LBW-T0.4), and LBW-0.8%Trp (LBW-T0.8) for 3 weeks. Compared to LBW-T0, the blood glucose was decreased in LBW-T0.8 at 60 min following the meal test, and the triglycerides were lower in LBW-T0.4 and LBW-T0.8. Relative to LBW-T0, LBW-T0.8 had a lower transcript and protein abundance of hepatic glucose transporter-2, a higher mRNA abundance of glucokinase, and a lower transcript of phosphoenolpyruvate carboxykinase. LBW-T0.4 tended to have a lower protein abundance of sodium-glucose co-transporter 1 in the jejunum. In comparison with LBW-T0, LBW-T0.4 and LBW-T0.8 had a lower transcript of hepatic acetyl-CoA carboxylase, and LBW-T0.4 had a higher transcript of 3-hydroxyacyl-CoA dehydrogenase. Blocking 5-HT3 receptors with ondansetron reduced the feed intake in all groups, with a transient effect on LBW-T0, but more persistent effect on LBW-T0.8 and NBW-T0. In conclusion, Trp supplementation reduced the hepatic lipogenesis and gluconeogenesis, but increased the glycolysis in LBW piglets. Peripheral serotonin is likely involved in the regulation of feeding behavior, particularly in LBW piglets fed diets supplemented with a higher dose of Trp.

scholarly journals Albumin binding of unconjugated [3H]bilirubin and its uptake by rat liver basolateral plasma membrane vesicles

1996 ◽  
Vol 316 (3) ◽  
pp. 999-1004 ◽  
Author(s):  
Lorella PASCOLO ◽  
Savino DEL VECCHIO ◽  
Ronald K. KOEHLER ◽  
J. Enrique BAYON ◽  
Cecile C. WEBSTER ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Rat Liver ◽  
Basolateral Membrane ◽  
Membrane Vesicles ◽  
Plasma Membrane Vesicles ◽  
Experimental Conditions ◽  
Saturation Kinetics ◽  
Basolateral Plasma Membrane ◽  
Component C ◽  
Uptake Studies

Using highly purified unconjugated [3H]bilirubin (UCB), we measured UCB binding to delipidated human serum albumin (HSA) and its uptake by basolateral rat liver plasma membrane vesicles, in both the absence and presence of an inside-positive membrane potential. Free UCB concentrations ([Bf]) were calculated from UCB–HSA affinity constants (K´f), determined by five cycles of ultrafiltration through a Centricon-10 device (Amicon) of the same solutions used in the uptake studies. At HSA concentrations from 12 to 380 μM, K´f (litre/mol) was inversely related to [HSA], irrespective of the [Bt]/[HSA] ratio. K´f was 2.066×106+(3.258×108/[HSA]). When 50 mM KCl was iso-osmotically substituted for sucrose, the K´f value was significantly lower {2.077×106+(1.099×108/[HSA])}. The transport occurred into an osmotic-sensitive space. Below saturation ([Bf] ⩽ 65 nM), both electroneutral and electrogenic components followed saturation kinetics with respect to [Bf], with Km values of 28±7 and 57±8 nM respectively (mean±S.D., n = 3, P < 0.001). The Vmax was greater for the electrogenic than for the electroneutral component (112±12 versus 45±4 pmol of UCB·mg-1 of protein·15 s-1, P < 0.001). Sulphobromophthalein trans-stimulated both electrogenic (61%) and electroneutral (72%) UCB uptake. These data indicate that: (a) as [HSA] increases, K´f decreases, thus increasing the concentration of free UCB. This may account for much of the enhanced hepatocytic uptake of organic anions observed with increasing [HSA]. (b) UCB is taken up at the basolateral membrane of the hepatocyte by two systems with Km values within the range of physiological free UCB levels in plasma. The electrogenic component shows a lower affinity and a higher capacity than the electroneutral component. (c) It is important to calculate the actual [Bf] using a K´f value determined under the same experimental conditions (medium and [HSA]) used for the uptake studies.

Taurocholate transport by basolateral plasma membrane vesicles isolated from developing rat liver

1985 ◽  
Vol 248 (6) ◽  
pp. G648-G654
Author(s):  
F. J. Suchy ◽  
S. M. Courchene ◽  
B. L. Blitzer
Keyword(s):  
Plasma Membrane ◽  
Rat Liver ◽  
Basolateral Membrane ◽  
Membrane Vesicles ◽  
Marker Enzyme ◽  
Marker Enzymes ◽  
Plasma Membrane Vesicles ◽  
Adult Rat ◽  
Basolateral Plasma Membrane ◽  
Taurocholate Transport

Taurocholate transport was characterized in basolateral plasma membrane vesicles prepared from the livers of 14-day-old Sprague-Dawley rats using a self-generating Percoll gradient method. Liver plasma membrane protein yield, intravesicular volume, and enrichments of various marker enzymes were similar to those obtained for vesicles from adult rat liver. The basolateral marker enzyme Na+-K+-ATPase was enriched 26-fold in the suckling rat basolateral membrane fraction while the bile canalicular marker enzymes alkaline phosphatase and Mg2+-ATPase were enriched only 3- and 5-fold, respectively. The activities of marker enzymes for endoplasmic reticulum, mitochondria, or lysosomes were not enriched compared with homogenate. In the presence of an inwardly directed 100 mM Na+ gradient, vesicle accumulation of taurocholate transiently reached a concentration 1.5- to 2-fold higher than that at equilibrium ("overshoot") in suckling and adult membrane vesicles, but the initial rate of taurocholate entry and peak intravesicular accumulation were markedly decreased in suckling compared with adult membrane vesicles. In the presence of an inwardly directed 100 mM K+ gradient, the rate of uptake was slower, and no overshoot occurred in either suckling or adult rat vesicles. The decreased rate of Na+-coupled taurocholate uptake by membrane vesicles from suckling rat liver could not be explained on the basis of more rapid dissipation of the transmembrane Na+ gradient. Kinetic studies demonstrated saturable, Na+-dependent taurocholate uptake for both suckling and adult vesicles. However, the Vmax for taurocholate uptake in suckling rat vesicles was less than half of the adult rate (2.46 +/- 0.13 vs. 5.25 +/- 0.22 nmol X mg prot-1 X min-1, respectively, P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals The Roles of Liver Inflammation and the Insulin Signaling Pathway in PM2.5 Instillation-Induced Insulin Resistance in Wistar Rats

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Zhihua Zhang ◽  
Shujun Hu ◽  
Ping Fan ◽  
Ling Li ◽  
Shanshan Feng ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Rat Liver ◽  
Insulin Signaling ◽  
Glucose Transporter ◽  
Fasting Blood Glucose ◽  
Model Assessment ◽  
Glucose Transporter 2 ◽  
Systemic Insulin Resistance ◽  
Tnf Α ◽  
Phosphorylated Akt

To elucidate the mechanism of how the liver participates in PM2.5-caused insulin resistance. A novel Wistar rat model was developed in this study by instilling a suspension of lyophilized PM2.5 sample (2.5 mg/kg, 5 mg/kg, or 10 mg/kg) collected from the atmosphere. Systemic insulin resistance indicators, including serum fasting blood glucose (FBG), fasting insulin (FINS), Homeostatic Model Assessment for Insulin Resistance (HOMA-IR), and hemoglobin A1 (HbA1), were upregulated by the PM2.5 instillation. The area under the curve (AUCglu) calculated by intraperitoneal glucose tolerance testing (IPGTT) was also significantly greater in the PM2.5 instillation groups. Additionally, PM2.5 instillation was found to cause liver damage and inflammation. The serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), total bilirubin (TBIL), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) were significantly elevated by PM2.5 instillation. PM2.5 also triggered IL-6 and TNF-α transcription but inhibited mRNA synthesis and suppressed signaling activation of the insulin-phosphoinositide 3-kinase- (PI3K-) Akt-glucose transporter 2 (GLUT2) pathway in the rat liver by reducing the ratio of phosphorylated Akt to phosphorylated insulin receptor substrate 1 (IRS-1). Thus, PM2.5-induced inflammation activation and insulin signaling inhibition in the rat liver contribute to the development of systemic insulin resistance.

251 Dietary Tryptophan Supplementation Improves Fat and Glucose Metabolism in Low Birthweight Piglets

2021 ◽  
Vol 99 (Supplement_3) ◽  
pp. 129-130
Author(s):  
Parniyan Goodarzi ◽  
Mohammad Habibi ◽  
Kennedy Roberts ◽  
Julia Sutton ◽  
Cedrick N N Shili ◽  
...  
Keyword(s):  
Phosphoenolpyruvate Carboxykinase ◽  
Low Birthweight ◽  
Glucose Transporter ◽  
Growth Parameters ◽  
Fat Metabolism ◽  
Liver Fat ◽  
Protein Abundance ◽  
Metabolic Disturbances ◽  
Meal Test ◽  
Glucose Transporter 2

Abstract Low birthweight (LBW) is associated with complications such as insulin resistance, obesity and metabolic disturbances of glucose and fat metabolism in early life. Dietary tryptophan (Trp) has been shown to reduce liver fat and suppress hyperglycemia in different species. The objective of this study was to assess the effect of dietary Trp on growth and glucose and fat metabolism in LBW pigs. Piglets (7-days old) weighing &lt; 2 kg were considered as LBW while those weighting &gt; 2 kg were considered as normal birthweight (NBW) and randomly allocated to 4 milk-replacer based treatments (n = 7–8): 1) NBW-0% Trp (NBW-T0), 2) LBW-0% Trp (LBW-T0), 3) LBW-0.4% Trp (LBW-T0.4), and 4) LBW-0.8% Trp (LBW-T0.8) for 3 weeks. Growth parameters and body weight were measured biweekly. At week 3, blood and tissue samples were collected in overnight-fasted pigs after a meal test. The mRNA and protein abundance of key glucose and lipid metabolism markers were determined using qPCR and western blot, respectively. Univariate GLM with Dunnett’s post-hoc test (SPSS®) was used to analyze the data. Growth parameters did not change among groups. Plasma triglycerides concentration was lower in LBW-T0.4 and LBW-T0.8 compared to LBW-T0. Blood glucose was lower in LBW-T0.8 than LBW-T0 at 60 min following the meal test. LBW-T0.8 had a lower transcript and protein abundance of liver glucose transporter-2 relative to LBW-T0. Compared to LBW-T0, LBW-T0.8 had a higher mRNA abundance of glucokinase and tended to have a lower transcript of phosphoenolpyruvate carboxykinase in liver. Relative to LBW-T0, LBW-T0.4 tended to have a lower protein abundance of sodium-glucose co-transporter 1 in jejunum. Compared to LBW-T0, LBW-T0.4 and LBW-T0.8 had a lower transcript of liver acetyl-CoA carboxylase and LBW-T0.4 had a higher transcript of liver 3-hydroxyacyl-CoA dehydrogenase. In conclusion, Trp supplementation reduced the lipogenesis and gluconeogenesis, but increased the glycolysis in LBW piglets.

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