Resistance of hepatic glycogen to depletion in obese Zucker rats

1991 ◽  
Vol 69 (6) ◽  
pp. 841-845 ◽  
Author(s):  
Harry Koubi ◽  
Claude Duchamp ◽  
Alain Géloën ◽  
Alain Fréminet ◽  
Yves Minaire
Keyword(s):  
Cold Exposure ◽  
Liver Glycogen ◽  
Zucker Rats ◽  
Hepatic Glycogen ◽  
Glycogen Store ◽  
Obese Rats ◽  
Fasting And Refeeding ◽  
Obese Zucker Rats ◽  
Ad Libitum ◽  
Glycogen Stores

Glycogen stores (liver and carcass) have been studied in lean and obese Zucker rats. The animals were submitted to one of three feeding conditions: ad libitum, a 48-h fast, or a 48-h fast and food ad libitum for 24 h, and to two environmental conditions, either thermoneutrality or an acute cold exposure (2 days at 4–7 °C). After a 2-day fast at 25 °C, the liver glycogen store was reduced by 45 times in the lean rats, while it was decreased by only 3 times in the obese rats. Under these conditions, the liver glycogen store was 45 times higher in the obese than in the lean rats. After 2 days in the cold, liver glycogen store was 4.4 times higher in obese rats than in lean rats. After a 2-day fast in the cold, the liver glycogen store in the obese rats was 30 times higher than in the lean rats. In comparison to fasting at thermoneutrality, fasting in the cold did not lead to a further reduction in hepatic glycogen in obese Zucker rats. The differences observed in the mobilization of the hepatic glycogen store between obese and lean rats have not been found in the mobilization of the carcass glycogen store. Drastic conditions, such as a 2-day fast in the cold, did not exhaust the glycogen store in obese Zucker rats. The present observations point out that obese Zucker rats cannot mobilize the entire hepatic glycogen store, as seen in lean control rats. The role of this abnormality in the high hyperlipogenesis that maintains the obese state is still to be evaluated.Key words: glycogen, fasting and refeeding, cold exposure, obesity, liver.

Substrate utilization during acute exercise in obese Zucker rats

1990 ◽  
Vol 69 (6) ◽  
pp. 1987-1991 ◽  
Author(s):  
C. E. Torgan ◽  
J. T. Brozinick ◽  
M. E. Willems ◽  
J. L. Ivy
Keyword(s):  
Acute Exercise ◽  
Respiratory Exchange Ratio ◽  
Liver Glycogen ◽  
Zucker Rats ◽  
Insulin Resistant ◽  
Sedentary Group ◽  
Obese Rats ◽  
Obese Zucker Rats ◽  
Glycogen Utilization ◽  
Total Muscle

The purpose of the present study was to compare the carbohydrate use of insulin-resistant obese Zucker rats with that of their lean littermates during steady-state exercise. Obese and lean rats were randomly assigned to a sedentary group or to a run group in which rats ran at 72-73% of their maximal O2 consumption, with the duration of exercise set to require an energy expenditure of 2.1-2.2 kcal. During the run the respiratory exchange ratio was significantly higher in the obese than in the lean rats [0.94 +/- 0.01 (SE) and 0.86 +/- 0.01, respectively], which indicate that the obese rats required 54% more carbohydrate than the lean rats. Total muscle glycogen utilization in the soleus, plantaris, and red and white gastrocnemius was not different between groups. Obese rats had total liver glycogen values five times greater than those of lean rats (833.38 +/- 101.4 and 152.8 +/- 37.5 mg, respectively) and utilized twice as much liver glycogen as their lean littermates (193.5 and 90.4 mg, respectively). The obese rats exhibited higher blood glucose and insulin concentrations than the lean rats during the run. These findings indicate that, despite their characteristic insulin resistance, the obese Zucker rats had a greater dependency on carbohydrate as a substrate during exercise than their lean littermates and that the major source of this carbohydrate was liver glycogen.

scholarly journals Chronic suppression of insulin by diazoxide alters the activities of key enzymes regulating hepatic gluconeogenesis in Zucker rats

2002 ◽  
pp. 871-879 ◽  
Author(s):  
R Alemzadeh ◽  
S Holshouser ◽  
P Massey ◽  
J Koontz
Keyword(s):  
Phosphoenolpyruvate Carboxykinase ◽  
Glucose Transporter ◽  
Glycogen Synthase ◽  
Zucker Rats ◽  
Hepatic Glycogen ◽  
Hepatic Gluconeogenesis ◽  
Key Enzymes ◽  
Glucose Transporter 2 ◽  
Obese Rats ◽  
Obese Zucker Rats

OBJECTIVES: Chronic attenuation of hyperinsulinemia by diazoxide (DZ), an inhibitor of glucose-mediated insulin secretion, improved insulin sensitivity and glucose tolerance and caused down-regulation of lipid metabolizing enzymes in adipose tissue and decreased the rate of weight gain in mildly hyperglycemic obese Zucker rats. Since the liver plays a central role in glucose homeostasis, we studied the effect of chronic insulin suppression on key insulin-sensitive enzymes regulating hepatic gluconeogenesis. METHODS: DZ (150 mg/kg per day) or vehicle (control) was administered to 7-week-old female obese and lean Zucker rats for a period of 4 weeks. RESULTS: DZ-treated animals showed lower fasting plasma insulin levels (P<0.001) than their controls. Plasma glucose levels were lower in DZ obese rats than in controls (P<0.001), without a significant change in DZ lean animals. DZ had no effect on glucose transporter 2 protein expression in either strain. DZ treatment resulted in lower hepatic glucokinase (P<0.001) and glucose-6-phosphatase (P<0.0001) and phosphoenolpyruvate carboxykinase (PEPCK) activities only in obese rats compared with controls (P<0.001). However, DZ-treated lean rats demonstrated higher PEPCK activity than controls (P<0.002). DZ-treated animals demonstrated enhanced hepatic glucose-6-phosphate content (P<0.01), glycogen synthase activity (P<0.0001) and glycogen content (P<0.02) compared with their controls despite increased hepatic glycogen phosphorylase a activity in these animals (P<0.02). CONCLUSIONS: Chronic suppression of hyperinsulinemia in obese Zucker rats by DZ decreased the activities of key enzymes regulating hepatic gluconeogenesis, implying that attenuation of the hyperinsulinemic state by DZ may be therapeutically beneficial.

scholarly journals The effects of corticosterone, cold exposure and overfeeding with sucrose on brown adipose tissue of obese Zucker rats (fa/fa)

1983 ◽  
Vol 214 (1) ◽  
pp. 215-223 ◽  
Author(s):  
S Holt ◽  
D A York ◽  
J T R Fitzsimons
Keyword(s):  
Adipose Tissue ◽  
Food Intake ◽  
Brown Adipose Tissue ◽  
Cold Exposure ◽  
Zucker Rats ◽  
Brown Adipose ◽  
Obese Rats ◽  
Brown Adipose Tissue Thermogenesis ◽  
Obese Zucker Rats ◽  
Normal Increase

GDP binding to brown-adipose-tissue mitochondria was decreased in obese Zucker rats. Adrenalectomy restored both GDP binding and serum tri-iodothyronine of obese rats to values observed in lean rats. The effects of adrenalectomy on GDP binding and serum tri-iodothyronine were reversed by corticosterone. Decreasing food intake had no effect on brown-adipose-tissue GDP binding in obese rats. Young (5-week-old) obese rats showed a normal increase in brown-adipose-tissue mitochondrial GDP binding after housing at 4 degrees C for 7 days, but this response was attenuated in 10-week-old obese rats. Overfeeding with sucrose increased brown-adipose-tissue thermogenesis in lean, but not in obese, rats. After adrenalectomy, overfeeding with sucrose enhanced brown-adipose-tissue mitochondrial GDP binding in obese rats.

scholarly journals High Na intake increases renal angiotensin II levels and reduces expression of the ACE2-AT2R-MasR axis in obese Zucker rats

2012 ◽  
Vol 303 (3) ◽  
pp. F412-F419 ◽  
Author(s):  
Preethi Samuel ◽  
Quaisar Ali ◽  
Rifat Sabuhi ◽  
Yonnie Wu ◽  
Tahir Hussain
Keyword(s):  
Sodium Intake ◽  
Zucker Rats ◽  
Kidney Cortex ◽  
Complex Nature ◽  
Ang Ii ◽  
Pronounced Increase ◽  
High Sodium ◽  
High Sodium Intake ◽  
Obese Rats ◽  
Obese Zucker Rats

High sodium intake is known to regulate the renal renin-angiotensin system (RAS) and is a risk factor for the pathogenesis of obesity-related hypertension. The complex nature of the RAS reveals that its various components may have opposing effects on natriuresis and blood pressure regulation. We hypothesized that high sodium intake differentially regulates and shifts a balance between opposing components of the renal RAS, namely, angiotensin-converting enzyme (ACE)-ANG II-type 1 ANG II receptor (AT1R) vs. AT2-ACE2-angiotensinogen (Ang) (1–7)-Mas receptor (MasR), in obesity. In the present study, we evaluated protein and/or mRNA expression of angiotensinogen, renin, AT1A/BR, ACE, AT2R, ACE2, and MasR in the kidney cortex following 2 wk of a 8% high-sodium (HS) diet in lean and obese Zucker rats. The expression data showed that the relative expression pattern of ACE and AT1BR increased, renin decreased, and ACE2, AT2R, and MasR remained unaltered in HS-fed lean rats. On the other hand, HS intake in obese rats caused an increase in the cortical expression of ACE, a decrease in ACE2, AT2R, and MasR, and no changes in renin and AT1R. The cortical levels of ANG II increased by threefold in obese rats on HS compared with obese rats on normal salt (NS), which was not different than in lean rats. The HS intake elevated mean arterial pressure in obese rats (27 mmHg) more than in lean rats (16 mmHg). This study suggests that HS intake causes a pronounced increase in ANG II levels and a reduction in the expression of the ACE2-AT2R-MasR axis in the kidney cortex of obese rats. We conclude that such changes may lead to the potentially unopposed function of AT1R, with its various cellular and physiological roles, including the contribution to the pathogenesis of obesity-related hypertension.

Temporal patterns of tissue glycogen, glucose, and glycogen phosphorylase activity prior to hibernation in freeze-tolerant chorus frogs, Pseudacris triseriata

2008 ◽  
Vol 86 (10) ◽  
pp. 1095-1100 ◽  
Author(s):  
Steve C. Dinsmore ◽  
David L. Swanson
Keyword(s):  
Glycogen Phosphorylase ◽  
Threshold Level ◽  
Liver Glycogen ◽  
Critical Threshold ◽  
Hepatic Glycogen ◽  
Phosphorylase Activity ◽  
Continuous Increase ◽  
Glycogen Accumulation ◽  
Chorus Frogs ◽  
Glycogen Stores

Freezing survival may differ among winters in chorus frogs ( Pseudacris triseriata (Wied-Neuwied, 1838)), and low freezing survival is associated with low hepatic glycogen stores. The pattern of prehibernation liver glycogen accumulation in chorus frogs is unknown. Frogs might accumulate hepatic glycogen stores until a threshold level sufficient for winter survival is attained, after which frogs enter hibernation (critical threshold hypothesis). According to this model, frogs active late in the season should only be those with low hepatic glycogen stores. Alternatively, hepatic glycogen levels might continue to increase throughout the fall as long as frogs remain active (continuous increase hypothesis). We tested these hypotheses by measuring liver and leg muscle glycogen, glucose, and glycogen phosphorylase activities in chorus frogs throughout the fall prehibernation period in southeastern South Dakota. Hepatic glycogen levels were significantly related to date and increased throughout the fall period, consistent with the continuous increase hypothesis. This suggests that hepatic glycogen levels do not serve as a cue for entrance into hibernation. Liver phosphorylase activity did not vary significantly with progression of the fall season and activity was lower than in winter, suggesting that the winter increment of phosphorylase activity requires some stimulus during hibernation (e.g., low temperatures).

scholarly journals Plasma calcitonin gene-related peptide is increased prior to obesity, and sensory nerve desensitization by capsaicin improves oral glucose tolerance in obese Zucker rats

2005 ◽  
Vol 153 (6) ◽  
pp. 963-969 ◽  
Author(s):  
Dorte X Gram ◽  
Anker J Hansen ◽  
Michael Wilken ◽  
Torben Elm ◽  
Ove Svendsen ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Glucose Tolerance ◽  
Sensory Nerve ◽  
Zucker Rats ◽  
Oral Glucose ◽  
Oral Glucose Tolerance ◽  
Nerve Activity ◽  
Calcitonin Gene ◽  
Obese Rats ◽  
Obese Zucker Rats

Objective: It has earlier been demonstrated that capsaicin-induced desensitization improves insulin sensitivity in normal rats. However, whether increased capsaicin-sensitive nerve activity precedes the onset of insulin resistance in diet-induced obesity – and therefore might be involved in the pathophysiology – is not known. Further, it is of relevance to investigate whether capsaicin desensitization improves glycaemic control even in obese individuals and we therefore chose the obese Zucker rats to test this. Design and methods: Plasma levels of calcitonin gene-related peptide (CGRP; a marker of sensory nerve activity) was assessed in 8-week-old Zucker rats. To investigate whether capsaicin desensitization (100 mg/kg at 9 weeks of age) would also ameliorate glycaemia in this non-diabetic model, we assessed oral glucose tolerance at 7 weeks after capsaicin. Results: It was found that plasma CGRP levels were elevated in obese Zucker rats prior to the onset of obesity (16.1±3.4 pmol/l in pre-obese Zucker rats vs 6.9±1.1 pmol/l in lean littermates; P = 0.015) despite similar body weights. Furthermore, capsaicin desensitization reduced both fasting blood glucose (4.3±0.2 mmol/l vs 5.1±0.2 mmol/l in controls; P = 0.050) as well as the mean blood glucose level during an oral glucose tolerance test (OGTT) (6.8±0.3 mmol/l vs 8.6±0.5 mmol/l in control obese rats; P = 0.024) whereas the plasma insulin levels during the OGTT were unchanged. However this did not lead to an improvement in insulin resistance or to a reduction of tissue triglyceride accumulation in muscle or liver. Conclusion: We concluded that capsaicin-induced sensory nerve desensitization improves glucose tolerance in Zucker rats. Since, in this study, plasma CGRP levels, a marker of sensory nerve activity, were increased in the pre-obese rats, our data support the hypothesis that increased activity of sensory nerves precedes the development of obesity and insulin resistance in Zucker rats.

scholarly journals Adipose-tissue-specific increase in glyceraldehyde-3-phosphate dehydrogenase activity and mRNA amounts in suckling pre-obese Zucker rats. Effect of weaning

1988 ◽  
Vol 254 (2) ◽  
pp. 483-487 ◽  
Author(s):  
I Dugail ◽  
A Quignard-Boulange ◽  
R Bazin ◽  
X Le Liepvre ◽  
M Lavau
Keyword(s):  
Gene Expression ◽  
Adipose Tissue ◽  
Zucker Rats ◽  
Tissue Specific ◽  
Gapdh Gene ◽  
Gapdh Activity ◽  
Weanling Rats ◽  
Obese Rats ◽  
Specific Increase ◽  
Obese Zucker Rats

The regulation of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene expression was studied during the onset of obesity in the genetically obese (fa/fa) rat by determination of GAPDH activity and hybridizable mRNA amounts in adipose tissue and liver from suckling and weanling rats. GADPH activity remained low throughout the suckling period, and a burst of activity occurred after weaning in both lean and obese pups. As early as 7 days of age, adipose tissue from pre-obese rats displayed a significant increase in enzyme activity, whereas no difference could be detected in the liver. In both suckling (16 days of age) and weanling (30 days of age) obese rats a proportionate increase in GAPDH activity and mRNA amounts was observed in adipose tissue, but not in liver. It is concluded that the obese genotype influences GAPDH gene expression at a pretranslational level and in a tissue-specific manner. This phenomenon could partly contribute to the hyperactive fat accretion in the obese rat, since glycolysis is the major metabolic pathway for lipogenic substrates in adipose tissue.

Abstract P184: Co-localization and Natriuretic Interdependence of Angiotensin AT2R and MasR in Obese Rat Kidney

Hypertension ◽  
2016 ◽  
Vol 68 (suppl_1) ◽  
Author(s):  
Sanket N Patel ◽  
Quaisar Ali ◽  
Ulrike Muscha Steckelings ◽  
Tahir Hussain
Keyword(s):  
Rat Kidney ◽  
Sulfhydryl Groups ◽  
Zucker Rats ◽  
Diabetic Rat ◽  
Physical Interaction ◽  
Potential Mechanism ◽  
Obese Rats ◽  
Obese Zucker Rats ◽  
Made In

The actions of angiotensin II type 2 receptor (AT 2 R) and receptor mas (MasR) are complex but show similar pro-natriuretic function; particularly AT 2 R expression and natriuretic function are enhanced in obese/diabetic rat kidney. In light of previous reports, we tested hypothesis that AT 2 R and MasR are interdependent to produce natriuresis in obese rats due to potential physical interaction. Infusion of AT 2 R agonist C21 (5 μg/kg/min) in obese Zucker rats (OZR) caused diuresis/natriuresis which were attenuated by simultaneous infusion of the AT 2 R antagonist PD123319 (50 μg/kg/min) or the MasR antagonist A-779 (50 μg/kg/min). Similarly, infusion of MasR agonist Ang-(1-7) (110 fmol/kg/min) in OZR caused diuresis/netriuresis, which were attenuated by simultaneous infusion of A-779 or PD123319. Dual labeling of AT 2 R and MasR in OZR kidney slices revealed four-fold co-localization of AT 2 R and MasR (9.83 vs. 2.50 dual labeled cells/1600 μm 2 ) compared with lean rats in which AT 2 R is not natriuretic. Moreover, the AT 2 R co-immunoprecipitates with MasR in cortical homogenate of OZR. Immunoblotting of AT 2 R and MasR with zero length oxidative (sulfhydryl groups) cross-linker cupric-phenanthroline in OZR cortical homogenate revealed a shift of AT 2 R (~62 kDa) and MasR (~54 kDa) bands upward with overlapping migration for their complexes (~160 kDa and 245 kDa) which were sensitive to the reducing β-mercaptoethanol. Similar observations were made in HK-2 cells, where glucose (25 mM) treatment enhanced the crosslinking. Collectively, the study reveals AT2R and MasR are co-localized and functionally interdependent in producing natriuretic response. Hyperglycemic oxidative stress affecting sulfhydryl groups present a potential mechanism of such physical interaction between these receptors. (Support: R01DK061578)

Effects of Epinephrine on Carbohydrate Metabolism in Underfed and ad Libitum-Fed Rats

1957 ◽  
Vol 190 (2) ◽  
pp. 239-242
Author(s):  
B. N. Spirtos ◽  
R. G. Stuelke ◽  
N. S. Halmi
Keyword(s):  
Carbohydrate Metabolism ◽  
Blood Sugar ◽  
Blood Lactate ◽  
Liver Glycogen ◽  
Hepatic Glycogen ◽  
Commercial Diet ◽  
Ad Libitum ◽  
Sugar Levels ◽  
Fasted Rats

Rats fed 10 gm of a commercial diet for 4–5 weeks and fasted for 24 hours showed less rise in liver glycogen and blood sugar levels in response to the injection of epinephrine than did ad libitum-fed-fasted rats. Gastrocnemius glycogen levels were found to be higher in underfed-fasted animals and fell to the same extent as in ad libitum fed-fasted animals when epinephrine was given. Blood lactate concentrations, however, rose less markedly in the underfed-fasted group. This may have been at least partly responsible for the diminished rise in hepatic glycogen and blood sugar.

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