Influence of carbohydrate loading on fuel substrate turnover and oxidation during prolonged exercise

1993 ◽  
Vol 74 (4) ◽  
pp. 1921-1927 ◽  
Author(s):  
A. N. Bosch ◽  
S. C. Dennis ◽  
T. D. Noakes
Keyword(s):  
Blood Glucose ◽  
Muscle Glycogen ◽  
Glucose Oxidation ◽  
Prolonged Exercise ◽  
Glycogen Content ◽  
Glucose Turnover ◽  
Muscle Glycogen Content ◽  
Glycogen Utilization ◽  
Total Muscle ◽  
Glycogen Breakdown

This study compared liver glucose turnover, blood glucose oxidation, and muscle glycogen utilization in 15 male endurance-trained cyclists who rode for 180 min at 70% of maximal O2 consumption in either a carbohydrate-(CHO) loaded (CL) or a non-CHO-loaded (NL) state. Total CHO oxidation during exercise was similar in the CL and NL subjects (492 +/- 77 vs. 448 +/- 43 g, respectively), as were blood glucose oxidation (103 +/- 19 vs. 99 +/- 7 g, respectively) and liver glucose appearance (110 +/- 15 vs. 127 +/- 16 g, respectively). However, total muscle glycogen utilization was greater in CL than NL subjects (134 +/- 11 vs. 95 +/- 12 mmol/kg wet wt; P < 0.05), the former of which had higher muscle glycogen content at the start (194 +/- 4 vs. 124 +/- 7 mmol/kg wet wt; P < 0.05) and throughout the trial. Whereas high rates of muscle glycogen breakdown were maintained throughout the trial in CL subjects, rates of muscle glycogenolysis in NL subjects decreased to 26 mmol.kg wet wt-1.h-1 after 60 min of exercise (P < 0.05) when their muscle glycogen content had declined to 70 mmol/kg wet wt. Comparable rates of blood glucose and overall CHO oxidation in CL and NL subjects, despite a slowing of muscle glycogenolysis in the NL group, could be explained by an accelerated breakdown of glycogen in the nonworking muscles to redistribute CHO (lactate) to the working muscles for oxidation.(ABSTRACT TRUNCATED AT 250 WORDS)

Preexercise muscle glycogen content affects metabolism during exercise despite maintenance of hyperglycemia

1998 ◽  
Vol 274 (1) ◽  
pp. E83-E88 ◽  
Author(s):  
Sandra M. Weltan ◽  
Andrew N. Bosch ◽  
Steven C. Dennis ◽  
Timothy D. Noakes
Keyword(s):  
Muscle Glycogen ◽  
Glucose Oxidation ◽  
Glycogen Content ◽  
Respiratory Exchange Ratio ◽  
Glucose Infusion ◽  
Muscle Glycogen Content ◽  
Hyperglycemic Clamp ◽  
Upper Limit ◽  
Glycogen Utilization ◽  
Total Glucose

Trained cyclists with low muscle glycogen (LGH; n = 8) or normal glycogen (NGH; n = 5) exercised for 145 min at 70% of maximal oxygen uptake during a hyperglycemic clamp. Respiratory exchange ratio was higher in NGH than LGH, and free fatty acid concentrations were lower in NGH than LGH. Areas under the curve for insulin and lactate were lower in LGH than NGH. Total glucose infusion and total glucose oxidation were not different between NGH and LGH, and total glucose oxidation amounted to 65 and 66% of total glucose infusion in NGH and LGH, respectively. Rates of glucose oxidation rose during exercise, reaching peaks of 9.2 ± 1.7 and 8.3 ± 1.1 mmol/min in NGH and LGH, respectively. Muscle glycogen disappearance was greater in NGH than LGH. Thus 1) low muscle glycogen content does not cause increased glucose oxidation, even during hyperglycemia; instead there is an increase in fat oxidation, 2) there is an upper limit to the rate of glucose oxidation during exercise with hyperglycemia irrespective of muscle glycogen status, and 3) net muscle glycogen utilization is determined by muscle glycogen content at the start of exercise, even during hyperglycemia.

Influence of carbohydrate ingestion on fuel substrate turnover and oxidation during prolonged exercise

1994 ◽  
Vol 76 (6) ◽  
pp. 2364-2372 ◽  
Author(s):  
A. N. Bosch ◽  
S. C. Dennis ◽  
T. D. Noakes
Keyword(s):  
Blood Glucose ◽  
Muscle Glycogen ◽  
Glucose Oxidation ◽  
Prolonged Exercise ◽  
Fat Free Mass ◽  
O2 Uptake ◽  
Carbohydrate Ingestion ◽  
Glycogen Utilization

This study examined effects of ingesting a 10% carbohydrate (CHO) drink (CI) or placebo (PI) at 500 ml/h on total (splanchnic) glucose appearance (endogenous+exogenous; Ra), blood glucose oxidation, and muscle glycogen utilization in 14 male endurance-trained cyclists who rode for 180 min at 70% of maximal O2 uptake after CHO loading [starting muscle glycogen 203 +/- 7 (SE) mmol/kg wet wt]. Total CHO oxidation was similar in CI and PI, but Ra increased significantly during the trial in both groups with CI reaching a plateau after 75 min. Ra was significantly greater in CI than in PI at the end of exercise. Blood glucose oxidation also increased significantly during the trial to a plateau in CI and was significantly higher in CI than in PI at the end of exercise. However, mean endogenous Ra was significantly lower in CI than in PI throughout exercise, as was oxidation of endogenous blood glucose, which remained almost constant in CI and reached 43 +/- 8 and 73 +/- 13 mumol.min-1.kg fat-free mass-1 in CI and PI, respectively, at the end of exercise. At 0.83 g/min of CHO ingestion, 0.77 +/- 0.03 g/min was oxidized. Muscle glycogen utilization was identical in both groups and was higher during the 1st h of exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

The Effects of Carbohydrate Loading on Muscle Glycogen Content and Cycling Performance

1995 ◽  
Vol 5 (1) ◽  
pp. 25-36 ◽  
Author(s):  
Laurie H.G. Rauch ◽  
Ian Rodger ◽  
Gary R. Wilson ◽  
Judy D. Belonje ◽  
Steven C. Dennis ◽  
...  
Keyword(s):  
Body Mass ◽  
Muscle Glycogen ◽  
Power Output ◽  
Glycogen Content ◽  
Potato Starch ◽  
Random Order ◽  
Cycling Performance ◽  
Muscle Glycogen Content ◽  
Glycogen Utilization ◽  
And Performance

This study compared the effects of supplementing the normal diets of 8 endurance-trained cyclists with additional carbohydrate (CHO), in the form of potato starch, for 3 days on muscle glycogen utilization and performance during a 3-hr cycle ride. On two occasions prior to the trial, the subjects ingested in random order either their normal CHO intake of 6.15 ± 0.23 g/kg body mass/day or a high-CHO diet of 10.52 ± 0.57 g/kg body mass/day. The trial consisted of 2 hr of cycling at ~75% ofwith five 60-s sprints at 100%at 20-min intervals, followed by a 60-min performance ride. Increasing CHO intake by 72 ± 9% for 3 days prior to the trial elevated preexercise muscle glycogen contents, improved power output, and extended the distance covered in 1 hr. Muscle glycogen contents were similar at the end of the 3-hr trial, indicating a greater utilization of glycogen when subjects were CHO loaded, which may have been responsible for their improved cycling performance.

scholarly journals Postmarathon paradox: insulin resistance in the face of glycogen depletion

1996 ◽  
Vol 270 (2) ◽  
pp. E336-E343 ◽  
Author(s):  
J. A. Tuominen ◽  
P. Ebeling ◽  
R. Bourey ◽  
L. Koranyi ◽  
A. Lamminen ◽  
...  
Keyword(s):  
Insulin Sensitivity ◽  
Lipid Oxidation ◽  
Muscle Glycogen ◽  
Glucose Oxidation ◽  
Glycogen Content ◽  
Glycogen Synthase ◽  
Glucose Disposal ◽  
Glycogen Depletion ◽  
Muscle Glycogen Content ◽  
Control Study

Acute physical exercise enhances insulin sensitivity in healthy subjects. We examined the effect of a 42-km marathon run on insulin sensitivity and lipid oxidation in 19 male runners. In the morning after the marathon run, basal serum free fatty acid concentration was 2.2-fold higher, muscle glycogen content 37% lower (P < 0.01), glycogen synthase fractional activity 56% greater (P < 0.01), and glucose oxidation reduced by 43% (P < 0.01), whereas lipid oxidation was increased by 55% (P < 0.02) compared with the control study. During euglycemic-hyperinsulinemic clamp, whole body glucose disposal was decreased by 12% (P < 0.01) because of a 36% lower glucose oxidation rate (P < 0.05), whereas the rate of lipid oxidation was 10-fold greater (P < 0.02) than in the control study. After the marathon, muscle glycogen content correlated positively with lipid oxidation (r = 0.60, P < 0.05) and maximal aerobic power (Vo2peak; r = 0.61, P < 0.05). Vo2peak correlated positively with basal lipid oxidation (r = 0.57, P < 0.05). In conclusion, 1) after the marathon run, probably because of increased lipid oxidation, the insulin-stimulated glucose disposal is decreased despite muscle glycogen depletion and the activation of glycogen synthase; 2) the contribution of lipid oxidation in energy expenditure is increased in proportion to physical fitness; 3) these adaptations of fuel homeostasis may contribute to the maintenance of physical performance after prolonged exercise.

Influence of muscle glycogen content on metabolic regulation

1998 ◽  
Vol 274 (1) ◽  
pp. E72-E82 ◽  
Author(s):  
Sandra M. Weltan ◽  
Andrew N. Bosch ◽  
Steven C. Dennis ◽  
Timothy D. Noakes
Keyword(s):  
Fatty Acids ◽  
Oxygen Uptake ◽  
Muscle Glycogen ◽  
Metabolic Regulation ◽  
Plasma Insulin ◽  
Glucose Oxidation ◽  
Glycogen Content ◽  
Respiratory Exchange Ratio ◽  
Normal Muscle ◽  
Muscle Glycogen Content

Euglycemia was maintained in 13 subjects with low muscle glycogen [low glycogen, euglycemic (LGE), n = 8; low glycogen, euglycemic, hyperinsulinemic (LGEI), n = 5] and 6 subjects with normal muscle glycogen (NGE), whereas hyperglycemia was maintained in 8 low muscle glycogen subjects (LGH). All subjects cycled for 145 min at 70% of maximal oxygen uptake during the infusions. Insulin was infused in LGEI at 0.2 mU ⋅ kg−1 ⋅ min−1. During exercise, respiratory exchange ratio (RER) was lower and norepinephrine higher in LGE than in NGE. In LGEI and LGH, RER at the start of exercise was the same as in LGE but did not decrease as in LGE. Free fatty acids (FFA) were higher and plasma insulin concentrations lower in LGE than NGE, LGEI, or LGH over the first 45 min of exercise. Rate of glucose infusion (Ri) and rate of glucose oxidation (Rox) were higher in LGH and LGEI than in NGE or LGE, and Ri matched Rox in all groups except LGH, in which Ri was greater than Rox. Muscle glycogen disappearance was greater in NGE than LGE, LGEI, or LGH, but the latter three groups did not differ. In conclusion, this study showed that low muscle glycogen content results in a decrease in RER, an increase in FFA, fat oxidation, and norepinephrine both at rest and during exercise, and does not affect Rox when euglycemia is maintained by infusion of glucose alone. Rox was increased only during insulin and hyperglycemia.

scholarly journals Apigenin: A methanol fraction component of Newbouldia laevis leaf, as a potential antidiabetic agent

2017 ◽  
Vol 6 (1) ◽  
pp. 38-44
Author(s):  
Chinyelu C. Osigwe ◽  
◽  
Peter A. Akah ◽  
Chukwuemeka S. Nworu ◽  
Festus B. C. Okoye ◽  
...  
Keyword(s):  
Diabetes Mellitus ◽  
Blood Glucose ◽  
Muscle Glycogen ◽  
Glycogen Content ◽  
Diabetic Rats ◽  
Antidiabetic Agent ◽  
Methanol Fraction ◽  
Antihyperglycemic Activity ◽  
Muscle Glycogen Content ◽  
Isolated Compound

The leaves of Newbouldia laevis is traditionally used to treat diabetes mellitus in southeast Nigeria. The apigenin isolated from the methanol fraction of dichloromethane/methanol (1:1) extract of the leaves was evaluated for antidiabetic and antihyperglycemic activity in alloxan-induced diabetic rats and on normal rats. Treatment of alloxan-diabetic rats with the compound (apigenin) significantly (p < 0.05) reduced blood glucose, and increased the liver and muscle glycogen content. The adrenaline-induced elevation of blood glucose of normal rats was significantly (p < 0.05) reduced by the isolated compound. These results suggest that apigenin may be the anti-diabetic principle in the leaves of Newbouldia laevis..

INSULIN SECRETAGOGUE POTENTIAL OF FERONIA ELEPHANTUM FRUIT EXTRACT IN STREPTOZOTOCIN INDUCED DIABETIC RATS

INDIAN DRUGS ◽  
2012 ◽  
Vol 49 (08) ◽  
pp. 45-50
Author(s):  
N. A Khatib ◽  
◽  
P. A Patil ◽  
P. Ismail
Keyword(s):  
Blood Glucose ◽  
Muscle Glycogen ◽  
Glycogen Content ◽  
Methanol Extract ◽  
Diabetic Rats ◽  
Fruit Extract ◽  
Insulin Secretagogue ◽  
Muscle Glycogen Content ◽  
Feronia Elephantum

Methanol extract of Feronia elephantum fruit at a dose of 400 mg/kg twice a day, was evaluated for its insulin secretagogue potential in streptozotocin (STZ) 50 mg/kg induced diabetic rats. Treatment showed significant (P<0.001) decrease in blood glucose and significant (P<0.001) increase in seruminsulin, hepatic, muscle glycogen content and restoration of disturbed dyslipidemia. Result obtained from the present study indicates that methanol extract of Feronia elephantum fruit has insulin secretagogue potential in STZ induced diabetic rats.

A major locus (RN) affecting muscle glycogen content is located on pig Chromosome 15

1996 ◽  
Vol 7 (1) ◽  
pp. 52-54 ◽  
Author(s):  
P. Mariani ◽  
K. Lundström ◽  
U. Gustafsson ◽  
A. -C. Enfält ◽  
R. K. Juneja ◽  
...  
Keyword(s):  
Muscle Glycogen ◽  
Glycogen Content ◽  
Chromosome 15 ◽  
Major Locus ◽  
Muscle Glycogen Content
Sign in / Sign up

Export Citation Format

Share Document