Effects of sustained swimming on hepatic glucose production of rainbow trout

1999 ◽  
Vol 202 (16) ◽  
pp. 2161-2166 ◽  
Author(s):  
D.S. Shanghavi ◽  
J.M. Weber
Keyword(s):  
Rainbow Trout ◽  
Glucose Utilization ◽  
Blood Glucose Concentration ◽  
Hepatic Glucose Production ◽  
Mammalian Species ◽  
Glucose Production ◽  
Glucose Kinetics ◽  
Fourfold Increase ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Hepatic Glucose

The rate of hepatic glucose production (R(a)glucose) was measured by continuous infusions of 6-[(3)H]glucose in live rainbow trout (Oncorhynchus mykiss) before, during and after swimming for 3 h at 1.5 body lengths s(−)(1) in a swim tunnel. Contrary to expectation, we found that sustained swimming causes a 33 % decline in the R(a),(glucose) of trout (from 7.6+/−2.1 to 5.1+/−1.3 (μ)mol kg(−)(1)min(−)(1), means +/− s.e.m., N=7), even though exercise of the same intensity elicits a two- to fourfold increase in all the mammalian species investigated to date. Measurements of catecholamine levels show that circulating [epinephrine] decreases by 30 % during exercise (from 4.7+/−0.3 to 3.3+/−0.4 nmol l(−)(1), N=8), suggesting that this hormone is partly responsible for controlling the decline in R(a)glucose. The inhibiting effect of swimming on hepatic glucose production persists for at least 1 h after the cessation of exercise. In addition, rainbow trout can maintain a steady blood glucose concentration throughout sustained exercise by closely matching hepatic glucose production with peripheral glucose utilization, even though this species is generally considered to be a poor glucoregulator. This study provides the first continuous measurements of glucose kinetics during the transition from rest to work in an ectotherm and it suggests that circulating glucose is not an important fuel for aerobic locomotion in trout.

Insulin action during fasting and refeeding in rat determined by euglycemic clamp

1985 ◽  
Vol 249 (5) ◽  
pp. E514-E518 ◽  
Author(s):  
L. Penicaud ◽  
J. Kande ◽  
J. Le Magnen ◽  
J. R. Girard
Keyword(s):  
Glucose Utilization ◽  
Blood Glucose Concentration ◽  
Hepatic Glucose Production ◽  
Glucose Production ◽  
Insulin Concentration ◽  
Hepatic Glucose ◽  
Glucose Clearance ◽  
Fasting And Refeeding ◽  
Fasted Rats

To further characterize the role of insulin in glucose metabolism during fasting and refeeding, euglycemic-hyperinsulinemic clamps were performed in control, 3 day-fasted, and 3 day-fasted then 3 day-refed rats. Glucose production and utilization were measured by using [3-3H]glucose. In control and refed rats, hepatic glucose production was totally suppressed at insulin concentration higher than 500 microU/ml; by contrast, during fasting, hepatic glucose production was not suppressed even at insulin concentration tenfold higher. Maximal increment of glucose utilization was lower in fasted than in control rats. Three days of refeeding restored almost entirely normal responses to insulin for glucose utilization. Blood glucose concentration was clamped at a different level in fasted and in control and refed rats; however, increment in glucose clearance in response to insulin was lower in fasted rats than in the two other groups. Thus fasting produces a state of insulin unresponsiveness both at the hepatic and peripheral levels, normal responsiveness being restored after 3 days of refeeding.

Regulation of glucose production in rainbow trout: role of epinephrine in vivo and in isolated hepatocytes

2000 ◽  
Vol 278 (4) ◽  
pp. R956-R963 ◽  
Author(s):  
Jean-Michel Weber ◽  
Deena S. Shanghavi
Keyword(s):  
Rainbow Trout ◽  
Hepatic Glucose Production ◽  
Glucose Production ◽  
Isolated Hepatocytes ◽  
Relative Increase ◽  
Dependent Manner ◽  
Rainbow Trout Oncorhynchus Mykiss

The rate of hepatic glucose production (Ra glucose) of rainbow trout ( Oncorhynchus mykiss) was measured in vivo by continuous infusion of [6-3H]glucose and in vitro on isolated hepatocytes to examine the role of epinephrine (Epi) in its regulation. By elevating Epi concentration and/or blocking β-adrenoreceptors with propranolol (Prop), our goals were to investigate the mechanism for Epi-induced hyperglycemia to determine the possible role played by basal Epi concentration in maintaining resting Ra glucose and to assess indirect effects of Epi in the intact animal. In vivo infusion of Epi caused hyperglycemia (3.75 ± 0.16 to 8.75 ± 0.54 mM) and a twofold increase in Ra glucose (6.57 ± 0.79 to 13.30 ± 1.78 μmol ⋅ kg− 1 ⋅ min− 1, n = 7), whereas Prop infusion decreased Ra from 7.65 ± 0.92 to 4.10 ± 0.56 μmol ⋅ kg− 1 ⋅ min− 1( n = 10). Isolated hepatocytes increased glucose production when treated with Epi, and this response was abolished in the presence of Prop. We conclude that Epi-induced trout hyperglycemia is entirely caused by an increase in Ra glucose, because the decrease in the rate of glucose disappearance normally seen in mammals does not occur in trout. Basal circulating levels of Epi are involved in maintaining resting Ra glucose. Epi stimulates in vitro glucose production in a dose-dependent manner, and its effects are mainly mediated by β-adrenoreceptors. Isolated trout hepatocytes produce glucose at one-half the basal rate measured in vivo, even when diet, temperature, and body size are standardized, and basal circulating Epi is responsible for part of this discrepancy. The relative increase in Ra glucose after Epi stimulation is similar in vivo and in vitro, suggesting that indirect in vivo effects of Epi, such as changes in hepatic blood flow or in other circulating hormones, do not play an important role in the regulation of glucose production in trout.

Hypoglycemia counterregulation in elderly humans: relationship to glucose levels

1994 ◽  
Vol 267 (4) ◽  
pp. E497-E506 ◽  
Author(s):  
F. J. Ortiz-Alonso ◽  
A. Galecki ◽  
W. H. Herman ◽  
M. J. Smith ◽  
J. A. Jacquez ◽  
...  
Keyword(s):  
Glucose Utilization ◽  
Hepatic Glucose Production ◽  
Severe Hypoglycemia ◽  
Glucose Production ◽  
Counterregulatory Hormones ◽  
Glucose Levels ◽  
Hepatic Glucose ◽  
Consistent Increase ◽  
Step Study ◽  
Elderly Humans

This study was designed to define the effect of human aging on hypoglycemia counterregulatory mechanisms. A hyperinsulinemic (2 mU.kg-1.min-1) glucose clamp procedure was used to control glucose and insulin levels during stepwise lowering of plasma glucose. Counterregulatory hormones, hepatic glucose production (HGP), glucose utilization, and symptoms of hypoglycemia were studied in 13 healthy young [age 24 +/- 1 (SE) yr] and 11 healthy old (age 65 +/- 1 yr) nondiabetic volunteers on two occasions: 1) at matched euglycemia and 70 and 60 mg/dl (study 1) and 2) at matched euglycemia and 60 and 50 mg/dl (study 2). The old had consistently lower epinephrine (P < 0.005), glucagon (P < 0.02), cortisol (P < 0.05), and pancreatic polypeptide (P < 0.02) responses at the 60-mg/dl glucose step in study 1. However, these differences were no longer detectable at the more severe hypoglycemic stimulus of 50 mg/dl in study 2. A consistent increase in HGP occurred in both groups only at the 50-mg/dl glucose step (study 2) and was not different between young and old. There were also no differences in symptom responses between young and old. In summary, we found that elderly individuals have a subtle impairment of the glucose counterregulatory response during moderate hypoglycemia, but this impairment is no longer detectable during more severe hypoglycemia.

Effect of carbohydrate ingestion on glucose kinetics during exercise in the heat

2001 ◽  
Vol 90 (2) ◽  
pp. 601-605 ◽  
Author(s):  
Damien J. Angus ◽  
Mark A. Febbraio ◽  
David Lasini ◽  
Mark Hargreaves
Keyword(s):  
Heart Rate ◽  
Relative Humidity ◽  
Respiratory Exchange Ratio ◽  
Glucose Solution ◽  
Hepatic Glucose Production ◽  
Glucose Production ◽  
Peak Oxygen Uptake ◽  
Glucose Kinetics ◽  
Carbohydrate Ingestion ◽  
Hepatic Glucose

Six endurance-trained men [peak oxygen uptake (V˙o 2) = 4.58 ± 0.50 (SE) l/min] completed 60 min of exercise at a workload requiring 68 ± 2% peak V˙o 2 in an environmental chamber maintained at 35°C (<50% relative humidity) on two occasions, separated by at least 1 wk. Subjects ingested either a 6% glucose solution containing 1 μCi [3-3H]glucose/g glucose (CHO trial) or a sweet placebo (Con trial) during the trials. Rates of hepatic glucose production [HGP = glucose rate of appearance (Ra) in Con trial] and glucose disappearance (Rd), were measured using a primed, continuous infusion of [6,6-2H]glucose, corrected for gut-derived glucose (gut Ra) in the CHO trial. No differences in heart rate, V˙o 2, respiratory exchange ratio, or rectal temperature were observed between trials. Plasma glucose concentrations were similar at rest but increased ( P < 0.05) to a greater extent in the CHO trial compared with the Con trial. This was due to the absorption of ingested glucose in the CHO trial, because gut Ra after 30 and 50 min (16 ± 5 μmol · kg−1 · min−1) was higher ( P < 0.05) compared with rest, whereas HGP during exercise was not different between trials. Glucose Rd was higher ( P < 0.05) in the CHO trial after 30 and 50 min (48.0 ± 6.3 vs 34.6 ± 3.8 μmol · kg−1 · min−1, CHO vs. Con, respectively). These results indicate that ingestion of carbohydrate, at a rate of ∼1.0 g/min, increases glucose Rd but does not blunt the rise in HGP during exercise in the heat.

Metformin improves peripheral but not hepatic insulin action in obese patients with type II diabetes

1989 ◽  
Vol 120 (3) ◽  
pp. 257-265 ◽  
Author(s):  
Ole Hother-Nielsen ◽  
Ole Schmitz ◽  
Per H. Andersen ◽  
Henning Beck-Nielsen ◽  
Oluf Pedersen
Keyword(s):  
Type Ii Diabetes ◽  
Insulin Action ◽  
Glucose Utilization ◽  
Hepatic Glucose Production ◽  
Glucose Production ◽  
Metformin Treatment ◽  
Obese Patients ◽  
Type Ii ◽  
Plasma Lactate ◽  
Hepatic Glucose

Abstract. Nine obese patients with Type II diabetes mellitus were examined in a double-blind cross-over study. Metformin 0.5 g trice daily or placebo were given for 4 weeks. At the end of each period fasting and day-time postprandial values of plasma glucose, insulin, C-peptide and lactate were determined, and in vivo insulin action was assessed using the euglycemic clamp in combination with [3-3H]glucose tracer technique. Metformin treatment significantly reduced mean day-time plasma glucose levels (10.2 ± 1.2 vs 11.4 ± 1.2 mmol/l, P< 0.01) without enhancing mean day-time plasma insulin (43 ± 4 vs 50 ± 7 mU/l, NS) or C-peptide levels (1.26 ± 0.12 vs 1.38 ± 0.18 nmol/l, NS). Fasting plasma lactate was unchanged (1.57 ± 0.16 vs 1.44 ± 0.11 mmol/l, NS), whereas mean day-time plasma lactate concentrations were slightly increased (1.78 ± 0.11 vs 1.38 ± 0.11 mmol/l, P< 0.01). The clamp study revealed that metformin treatment was associated with an enhanced insulin-mediated glucose utilization (370 ± 38 vs 313 ± 33 mg · m−2 · min−1, P< 0.01), whereas insulin-mediated suppression of hepatic glucose production was unchanged. Also basal glucose clearance was improved (61.0 ± 5.8 vs 50.6 ± 2.8 ml · n−2 · min−1,, P< 0.05), whereas basal hepatic glucose production was unchanged (81 ± 6 vs 77 ± 4 mg · m−2 · min−1, NS). Conclusions: 1) Metformin treatment in obese Type II diabetic patients reduces hyperglycemia without changing the insulin secretion. 2) The improved glycemic control during metformin treatment was associated with an enhanced insulin-mediated glucose utilization, presumably in skeletal muscle, whereas no effect could be demonstrated on hepatic glucose production.

Regulation of blood glucose concentration: response of liver to glucose administration

1961 ◽  
Vol 201 (1) ◽  
pp. 41-46 ◽  
Author(s):  
Bernard R. Landau ◽  
Jack R. Leonards ◽  
Frank M. Barry
Keyword(s):  
Blood Glucose ◽  
Glucose Concentration ◽  
Blood Glucose Concentration ◽  
Dominant Role ◽  
Hepatic Glucose Production ◽  
High Protein Diet ◽  
Glucose Production ◽  
Hepatic Veins ◽  
Hepatic Glucose ◽  
Glucose Output

Hepatic glucose output has been determined during the infusion of glucose in gradually increasing quantities into unanesthetized dogs with cannulas inserted in their aortas, hepatic veins and portal veins. Profound changes in hepatic response to the infusions were consequent to differences in the composition of the diets ingested by the dogs in the days prior to these experiments. Infusion of glucose into dogs maintained on a high protein diet resulted in a rise in blood glucose concentration, with a cessation of net hepatic glucose production only at hyperglycemic levels. In contrast, in carbohydrate-fed dogs the blood glucose concentration increased very little on glucose infusion, and there was a net uptake of glucose by the liver. Under these conditions the liver appears to play a dominant role in the regulation of the constancy of the blood glucose concentration, and the regulating mechanism appears to be particularly sensitive to small changes in glucose concentration.

Influence of prior exercise and liver glycogen content on the sensitivity of the liver to glucagon

2002 ◽  
Vol 92 (1) ◽  
pp. 188-194 ◽  
Author(s):  
Victoria Matas Bonjorn ◽  
Martin G. Latour ◽  
Patrice Bélanger ◽  
Jean-Marc Lavoie
Keyword(s):  
Glucose Utilization ◽  
Glycogen Content ◽  
Hepatic Glucose Production ◽  
Glucose Production ◽  
Liver Glycogen ◽  
Hepatic Glycogen ◽  
Prior Exercise ◽  
Hepatic Glucose ◽  
Increased Sensitivity ◽  
Glucagon And Insulin

The purpose of the present study was to test the hypothesis that a prior period of exercise is associated with an increase in hepatic glucagon sensitivity. Hepatic glucose production (HGP) was measured in four groups of anesthetized rats infused with glucagon (2 μg · kg−1 · min−1 iv) over a period of 60 min. Among these groups, two were normally fed and, therefore, had a normal level of liver glycogen (NG). One of these two groups was killed at rest (NG-Re) and the other after a period of exercise (NG-Ex; 60 min of running, 15–26 m/min, 0% grade). The two other groups of rats had a high hepatic glycogen level (HG), which had been increased by a fast-refed diet, and were also killed either at rest (HG-Re) or after exercise (HG-Ex). Plasma glucagon and insulin levels were increased similarly in all four conditions. Glucagon-induced hyperglycemia was higher ( P < 0.01) in the HG-Re group than in all other groups. HGP in the HG-Re group was not, however, on the whole more elevated than in the NG-Re group. Exercised rats (NG-Ex and HG-Ex) had higher hyperglycemia, HGP, and glucose utilization than rested rats in the first 10 min of the glucagon infusion. HG-Ex group had the highest HGP throughout the 60-min experiment. It is concluded that hyperglucagonemia-induced HGP is stimulated by a prior period of exercise, suggesting an increased sensitivity of the liver to glucagon during exercise.

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