Effects of elevated plasma FFA and insulin on muscle glycogen usage during exercise

1977 ◽  
Vol 43 (4) ◽  
pp. 695-699 ◽  
Author(s):  
D. L. Costill ◽  
E. Coyle ◽  
G. Dalsky ◽  
W. Evans ◽  
W. Fink ◽  
...  
Keyword(s):  
Muscle Glycogen ◽  
Plasma Insulin ◽  
Control Experiment ◽  
Muscular Activity ◽  
Fold Increase ◽  
Elevated Plasma ◽  
Glycogen Depletion ◽  
Total Carbohydrate ◽  
Plasma Ffa ◽  
Glycogen Utilization

Seven men were studied during 30 min of treadmill exercise (approximately 70% VO2 max) to determine the effects of increased availability of plasma free fatty acids (FFA) and elevated plasma insulin on the utilization of muscle glycogen. This elevation of plasma FFA (1.01 mmol/1) with heparin (2,000 units) decreased the rate of muscle glycogen depletion by 40% as compared to the control experiment (FFA = 0.21 mmol/1). The ingestion of 75 g of glucose 45 min before exercise produced a 3.3-fold increase in plasma insulin and a 38% rise in plasma glucose at 0 min of exercise. Subsequent exercise increased muscle glycogen utilization and total carbohydrate (CHO) oxidation 17 and 13%, respectively, when compared to the control trial. This elevation of plasma insulin produced hypoglycemia (less than 3.5 mmol/1) in most subjects throughout the exercise. These data illustrate the regulatory influence of both plasma insulin and FFA on the rate of CHO usage during prolonged severe muscular activity.

Regulation of muscle glycogen phosphorylase activity during intense aerobic cycling with elevated FFA

1996 ◽  
Vol 270 (1) ◽  
pp. E116-E125 ◽  
Author(s):  
D. J. Dyck ◽  
S. J. Peters ◽  
P. S. Wendling ◽  
A. Chesley ◽  
E. Hultman ◽  
...  
Keyword(s):  
Muscle Glycogen ◽  
Glycogen Phosphorylase ◽  
O2 Consumption ◽  
Elevated Plasma ◽  
Phosphorylase Activity ◽  
Allosteric Regulator ◽  
Plasma Ffa ◽  
Glycogen Phosphorylase Activity ◽  
Muscle Biopsies ◽  
Allosteric Activator

This study examined muscle glycogenolysis and the regulation of glycogen phosphorylase (Phos) activity during 15 min of cycling at 85% of maximal O2 consumption (VO2max) in control and high free fatty acid (FFA; Intralipid-heparin) conditions in 11 subjects. Muscle biopsies were sampled at rest and 1, 5, and 15 min of exercise, and glycogen Phos transformation state (%Phos alpha), substrate (Pi, glycogen), and allosteric regulator (ADP, AMP, IMP) contents were measured. Infusion of intralipid elevated plasma FFA from 0.32 +/- 0.04 mM at rest to 1.00 +/- 0.04 mM just before exercise and 1.12 +/- 0.10 mM at 14 min of exercise. In the control trial, plasma FFA were 0.36 +/- 0.04 mM at rest and unchanged at the end of exercise (0.34 +/- 0.03 mM). Seven subjects used less muscle glycogen (46.7 +/- 7.6%, mean +/- SE) during the Intralipid trial, and four did not respond. In subjects who spared glycogen, glycogen Phos transformation into the active (alpha) form was unaffected by high FFA except for a nonsignificant reduction during the initial 5 min of exercise. Total AMP and IMP contents were not significantly different during exercise between trials, but total ADP was significantly lower with Intralipid only at 15 min. The calculated free ADP, AMP, and Pi contents were lower with Intralipid but not significantly different. However, when the present results were pooled with the data from a previous study using the same protocol [Dyck et al., Am. J. Physiol. 265 (Endocrinol, Metab. 28): E852-E859, 1993], the free ADP, AMP, and Pi contents of all subjects who spared glycogen (n = 13) were significantly lower at 15 min in the Intralipid trial. The findings suggest that the elevation of plasma FFA during intense cycling spares muscle glycogen by posttransformational regulation of Phos. This may be due to blunted increases in the contents of AMP, an allosteric activator of Phos alpha, and Pi, a substrate for Phos.

Circulating palmitate uptake and oxidation are not altered by glycogen depletion in contracting skeletal muscle

1995 ◽  
Vol 78 (4) ◽  
pp. 1266-1272 ◽  
Author(s):  
L. P. Turcotte ◽  
P. Hespel ◽  
E. A. Richter
Keyword(s):  
Skeletal Muscle ◽  
Electrical Stimulation ◽  
Carbohydrate Metabolism ◽  
Muscle Glycogen ◽  
Glucose Utilization ◽  
Plasma Free Fatty Acid ◽  
Glycogen Depletion ◽  
Plasma Ffa ◽  
Ffa Metabolism ◽  
Palmitate Uptake

The extent to which muscle glycogen depletion affects plasma free fatty acid (FFA) metabolism in contracting skeletal muscle is not well characterized. To study this question, rats were glycogen depleted (GD) or supercompensated (SC) by swimming exercise and diet treatment 24 h before perfusion of their isolated hindquarters at rest and during electrically induced muscle contractions. After 20 min of equilibration with glucose (6 mM), palmitate (2,000 microM), and [1–14C]palmitate, palmitate uptake and oxidation were found to be similar between groups at rest and during electrical stimulation. Palmitate uptake increased by 55% during electrical stimulation and averaged 2.75 +/- 0.56 mumol.g-1.h-1. Resting palmitate oxidation averaged 0.14 +/- 0.03 mumol.g-1.h-1 and increased to 0.53 +/- 0.06 and 0.47 +/- 0.08 mumol.g-1.h-1 during electrical stimulation in GD and SC, respectively. Glucose uptake was significantly higher in GD than in SC at rest and during electrical stimulation and significantly increased in both groups during electrical stimulation to reach values of 11.8 +/- 1.2 and 7.6 +/- 1.4 mumol.g-1.h-1, respectively. Lactate release was lower in GD than in SC at rest and during electrical stimulation and was highest after 2 min of stimulation in both groups. Additional experiments at perfusate palmitate concentrations of 600–900 microM yielded similar results. These results show that, in contracting perfused skeletal muscle, muscle glycogen depletion increases glucose utilization but does not affect total plasma FFA oxidation, suggesting that regulation within pathways of carbohydrate metabolism takes precedence over regulation between pathways of lipid and carbohydrate metabolism.

scholarly journals Beetroot juice ingestion during prolonged moderate-intensity exercise attenuates progressive rise in O2 uptake

2018 ◽  
Vol 124 (5) ◽  
pp. 1254-1263 ◽  
Author(s):  
Rachel Tan ◽  
Lee J. Wylie ◽  
Christopher Thompson ◽  
Jamie R. Blackwell ◽  
Stephen J. Bailey ◽  
...  
Keyword(s):  
Muscle Glycogen ◽  
Exercise Bout ◽  
Moderate Intensity ◽  
Beetroot Juice ◽  
Elevated Plasma ◽  
Glycogen Depletion ◽  
Moderate Intensity Exercise ◽  
Double Blind ◽  
Plasma Nitrite ◽  
Over Time

Nitrate-rich beetroot juice (BR) supplementation has been shown to increase biomarkers of nitric oxide availability with implications for the physiological responses to exercise. We hypothesized that BR supplementation before and during prolonged moderate-intensity exercise would maintain an elevated plasma nitrite concentration ([[Formula: see text]]), attenuate the expected progressive increase in V̇o2 over time, and improve performance in a subsequent time trial (TT). In a double-blind, randomized, crossover design, 12 men completed 2 h of moderate-intensity cycle exercise followed by a 100-kJ TT in three conditions: 1) BR before and 1 h into exercise (BR + BR); 2) BR before and placebo (PL) 1 h into exercise (BR + PL); and 3) PL before and 1 h into exercise (PL + PL). During the 2-h moderate-intensity exercise bout, plasma [[Formula: see text]] declined by ~17% in BR + PL but increased by ~8% in BR + BR such that, at 2 h, plasma [[Formula: see text]] was greater in BR + BR than both BR + PL and PL + PL ( P < 0.05). V̇o2 was not different among conditions over the first 90 min of exercise but was lower at 120 min in BR + BR (1.73 ± 0.24 l/min) compared with BR + PL (1.80 ± 0.21 l/min; P = 0.08) and PL + PL (1.83 ± 0.27 l/min; P < 0.01). The decline in muscle glycogen concentration over the 2-h exercise bout was attenuated in BR + BR (~28% decline) compared with BR + PL (~44% decline) and PL + PL (~44% decline; n = 9, P < 0.05). TT performance was not different among conditions ( P > 0.05). BR supplementation before and during prolonged moderate-intensity exercise attenuated the progressive rise in V̇o2 over time and appeared to reduce muscle glycogen depletion but did not enhance subsequent TT performance. NEW & NOTEWORTHY We show for the first time that ingestion of nitrate during exercise preserves elevated plasma [nitrite] and negates the progressive rise in O2 uptake during prolonged moderate-intensity exercise.

Effect of carbohydrate ingestion on metabolism during running and cycling

2001 ◽  
Vol 91 (5) ◽  
pp. 2125-2134 ◽  
Author(s):  
Melissa J. Arkinstall ◽  
Clinton R. Bruce ◽  
Vasilis Nikolopoulos ◽  
Andrew P. Garnham ◽  
John A. Hawley
Keyword(s):  
Body Mass ◽  
Plasma Glucose ◽  
Muscle Glycogen ◽  
Lactate Threshold ◽  
Glucose Oxidation ◽  
Dry Mass ◽  
Carbohydrate Oxidation ◽  
Total Carbohydrate ◽  
Carbohydrate Ingestion ◽  
Glycogen Utilization

The effects of carbohydrate or water ingestion on metabolism were investigated in seven male subjects during two running and two cycling trials lasting 60 min at individual lactate threshold using indirect calorimetry, U-14C-labeled tracer-derived measures of the rates of oxidation of plasma glucose, and direct determination of mixed muscle glycogen content from the vastus lateralis before and after exercise. Subjects ingested 8 ml/kg body mass of either a 6.4% carbohydrate-electrolyte solution (CHO) or water 10 min before exercise and an additional 2 ml/kg body mass of the same fluid after 20 and 40 min of exercise. Plasma glucose oxidation was greater with CHO than with water during both running (65 ± 20 vs. 42 ± 16 g/h; P < 0.01) and cycling (57 ± 16 vs. 35 ± 12 g/h; P < 0.01). Accordingly, the contribution from plasma glucose oxidation to total carbohydrate oxidation was greater during both running (33 ± 4 vs. 23 ± 3%; P < 0.01) and cycling (36 ± 5 vs. 22 ± 3%; P < 0.01) with CHO ingestion. However, muscle glycogen utilization was not reduced by the ingestion of CHO compared with water during either running (112 ± 32 vs. 141 ± 34 mmol/kg dry mass) or cycling (227 ± 36 vs. 216 ± 39 mmol/kg dry mass). We conclude that, compared with water, 1) the ingestion of carbohydrate during running and cycling enhanced the contribution of plasma glucose oxidation to total carbohydrate oxidation but 2) did not attenuate mixed muscle glycogen utilization during 1 h of continuous submaximal exercise at individual lactate threshold.

Frequent Carbohydrate Ingestion Reduces Muscle Glycogen Depletion and Postpones Fatigue Relative to a Single Bolus

2020 ◽  
Vol 30 (3) ◽  
pp. 203-209
Author(s):  
Campbell Menzies ◽  
Michael Wood ◽  
Joel Thomas ◽  
Aaron Hengist ◽  
Jean-Philippe Walhin ◽  
...  
Keyword(s):  
Confidence Interval ◽  
Muscle Glycogen ◽  
Metabolic Response ◽  
Treadmill Running ◽  
Utilization Rate ◽  
Glycogen Depletion ◽  
Carbohydrate Ingestion ◽  
Single Bolus ◽  
Significant Difference ◽  
Glycogen Utilization

The timing of carbohydrate ingestion and how this influences net muscle glycogen utilization and fatigue has only been investigated in prolonged cycling. Past findings may not translate to running because each exercise mode is distinct both in the metabolic response to carbohydrate ingestion and in the practicalities of carbohydrate ingestion. To this end, a randomized, cross-over design was employed to contrast ingestion of the same sucrose dose either at frequent intervals (15 × 5 g every 5 min) or at a late bolus (1 × 75 g after 75 min) during prolonged treadmill running to exhaustion in six well-trained runners ( 61 ± 4 ml·kg−1·min−1). The muscle glycogen utilization rate was lower in every participant over the first 75 min of running (Δ 0.51 mmol·kg dm−1·min−1; 95% confidence interval [−0.02, 1.04] mmol·kg dm−1·min−1) and, subsequently, all were able to run for longer when carbohydrate had been ingested frequently from the start of exercise compared with when carbohydrate was ingested as a single bolus toward the end of exercise (105.6 ± 3.0 vs. 96.4 ± 5.0 min, respectively; Δ 9.3 min, 95% confidence interval [2.8, 15.8] min). A moderate positive correlation was apparent between the magnitude of glycogen sparing over the first 75 min and the improvement in running capacity (r = .58), with no significant difference in muscle glycogen concentrations at the point of exhaustion. This study indicates that failure to ingest carbohydrates from the outset of prolonged running increases reliance on limited endogenous muscle glycogen stores—the ergolytic effects of which cannot be rectified by subsequent carbohydrate ingestion late in exercise.

Insulin does not influence muscle glycogenolysis in adrenodemedullated exercising rats

1987 ◽  
Vol 253 (4) ◽  
pp. R535-R540
Author(s):  
H. T. Yang ◽  
K. I. Carlson ◽  
W. W. Winder
Keyword(s):  
Fatty Acid ◽  
Blood Glucose ◽  
Free Fatty Acid ◽  
Plasma Insulin ◽  
Insulin Infusion ◽  
Plasma Free Fatty Acid ◽  
The Other ◽  
Elevated Plasma ◽  
Glycogen Utilization ◽  
Blood Glucose Concentrations

Previous reports have indicated that adrenodemedullated (ADM) rats exhibit an impairment in muscle glycogenolysis and elevated plasma insulin during exercise. This study was designed to determine whether the impaired muscle glycogenolysis in ADM rats is due to absence of epinephrine or to the inappropriately elevated plasma insulin. Fasted ADM rats were infused with saline, with epinephrine (0.045 micrograms . 100 g-1 . min-1), or with epinephrine + insulin (1.6, 3.3, 6.6, and 8.3 ng . 100 g-1 . min-1) during a 30-min run on the treadmill (21 m/min, 10% grade). Soleus muscle glycogen decreased from 5.1 +/- 0.2 mg/g in resting ADM rats to 4.0 +/- 0.2, 0.8 +/- 0.1, and 0.8 +/- 0.1 mg/g in the exercising saline-, epinephrine-, and epinephrine + insulin (8.3 ng . 100 g-1 . min-1)-infused rats, respectively. Glycogen utilization in gastrocnemius and red and white quadriceps muscles during exercise was likewise unaffected by insulin infusion. Blood glucose concentrations were 3.75 +/- 0.08, 2.65 +/- 0.14, 3.93 +/- 0.20, and 2.03 +/- 0.09 mM in the same groups at the end of exercise. Blood lactate was 50% lower and the blood 3-hydroxybutyrate and plasma free fatty acid concentrations were significantly higher in the ADM + saline rats than the other exercising rats. We conclude that inappropriately elevated plasma insulin does not impair epinephrine-stimulated muscle glycogenolysis in fasted ADM rats during exercise.

Muscle glycogen utilization during prolonged strenuous exercise when fed carbohydrate

1986 ◽  
Vol 61 (1) ◽  
pp. 165-172 ◽  
Author(s):  
E. F. Coyle ◽  
A. R. Coggan ◽  
M. K. Hemmert ◽  
J. L. Ivy
Keyword(s):  
Plasma Glucose ◽  
Muscle Glycogen ◽  
Average Rate ◽  
Water Solution ◽  
Vastus Lateralis ◽  
Carbohydrate Oxidation ◽  
Strenuous Exercise ◽  
Vastus Lateralis Muscle ◽  
Glycogen Depletion ◽  
Glycogen Utilization

The purpose of this study was to determine whether the postponement of fatigue in subjects fed carbohydrate during prolonged strenuous exercise is associated with a slowing of muscle glycogen depletion. Seven endurance-trained cyclists exercised at 71 +/- 1% of maximal O2 consumption (VO2max), to fatigue, while ingesting a flavored water solution (i.e., placebo) during one trial and while ingesting a glucose polymer solution (i.e., 2.0 g/kg at 20 min and 0.4 g/kg every 20 min thereafter) during another trial. Fatigue during the placebo trial occurred after 3.02 +/- 0.19 h of exercise and was preceded by a decline (P less than 0.01) in plasma glucose to 2.5 +/- 0.5 mM and by a decline in the respiratory exchange ratio (i.e., R; from 0.85 to 0.80; P less than 0.05). Glycogen within the vastus lateralis muscle declined at an average rate of 51.5 +/- 5.4 mmol glucosyl units (GU) X kg-1 X h-1 during the first 2 h of exercise and at a slower rate (P less than 0.01) of 23.0 +/- 14.3 mmol GU X kg-1 X h-1 during the third and final hour. When fed carbohydrate, which maintained plasma glucose concentration (4.2–5.2 mM), the subjects exercised for an additional hour before fatiguing (4.02 +/- 0.33 h; P less than 0.01) and maintained their initial R (i.e., 0.86) and rate of carbohydrate oxidation throughout exercise. The pattern of muscle glycogen utilization, however, was not different during the first 3 h of exercise with the placebo or the carbohydrate feedings. The additional hour of exercise performed when fed carbohydrate was accomplished with little reliance on muscle glycogen (i.e., 5 mmol GU X kg-1 X h-1; NS) and without compromising carbohydrate oxidation. We conclude that when they are fed carbohydrate, highly trained endurance athletes are capable of oxidizing carbohydrate at relatively high rates from sources other than muscle glycogen during the latter stages of prolonged strenuous exercise and that this postpones fatigue.

Glucose infusion attenuates endogenous glucose production and enhances glucose use of horses during exercise

2000 ◽  
Vol 88 (5) ◽  
pp. 1765-1776 ◽  
Author(s):  
Raymond J. Geor ◽  
Kenneth W. Hinchcliff ◽  
Richard A. Sams
Keyword(s):  
Muscle Glycogen ◽  
Hepatic Glucose Production ◽  
Isotonic Saline ◽  
Glucose Production ◽  
Endogenous Glucose Production ◽  
Carbohydrate Oxidation ◽  
Glucose Infusion ◽  
Total Carbohydrate ◽  
Glycogen Utilization ◽  
Glucose Availability

We examined the effects of increased glucose availability on glucose kinetics and substrate utilization in horses during exercise. Six conditioned horses ran on a treadmill for 90 min at 34 ± 1% of maximum oxygen uptake. In one trial [glucose (Glu)], glucose was infused at a mean rate of 34.9 ± 1.1 μmol ⋅ kg−1 ⋅ min−1, whereas in the other trial [control (Con)] an equivalent volume of isotonic saline was infused. Plasma glucose increased during exercise in Glu (90 min: 8.3 ± 1.7 mM) but was largely unchanged in Con (90 min: 5.1 ± 0.4 mM). In Con, hepatic glucose production (HGP) increased during exercise, reaching a peak of 38.6 ± 2.7 μmol ⋅ kg−1 ⋅ min−1after 90 min. Glucose infusion partially suppressed ( P < 0.05) the rise in HGP (peak value 25.8 ± 3.3 μmol ⋅ kg−1 ⋅ min−1). In Con, glucose rate of disappearance (Rd) rose to a peak of 40.4 ± 2.9 μmol ⋅ kg−1 ⋅ min−1after 90 min; in Glu, augmented glucose utilization was reflected by values for glucose Rd that were twofold higher ( P< 0.001) than in Con between 30 and 90 min. Total carbohydrate oxidation was higher ( P < 0.05) in Glu (187.5 ± 8.5 μmol ⋅ kg−1 ⋅ min−1) than in Con (159.2 ± 7.3 μmol ⋅ kg−1 ⋅min−1), but muscle glycogen utilization was similar between trials. We conclude that an increase in glucose availability in horses during low-intensity exercise 1) only partially suppresses HGP, 2) attenuates the decrease in carbohydrate oxidation during such exercise, but 3) does not affect muscle glycogen utilization.

scholarly journals Oxidative fuel selection and shivering thermogenesis during a 12- and 24-h cold-survival simulation

2016 ◽  
Vol 120 (6) ◽  
pp. 640-648 ◽  
Author(s):  
François Haman ◽  
Olivier L. Mantha ◽  
Stephen S. Cheung ◽  
Michel B. DuCharme ◽  
Michael Taber ◽  
...  
Keyword(s):  
Cold Exposure ◽  
Muscle Glycogen ◽  
Whole Body ◽  
Muscle Recruitment ◽  
Glycogen Depletion ◽  
Total Carbohydrate ◽  
Fuel Selection ◽  
Isotopic Methods ◽  
Shivering Thermogenesis

Because the majority of cold exposure studies are constrained to short-term durations of several hours, the long-term metabolic demands of cold exposure, such as during survival situations, remain largely unknown. The present study provides the first estimates of thermogenic rate, oxidative fuel selection, and muscle recruitment during a 24-h cold-survival simulation. Using combined indirect calorimetry and electrophysiological and isotopic methods, changes in muscle glycogen, total carbohydrate, lipid, protein oxidation, muscle recruitment, and whole body thermogenic rate were determined in underfed and noncold-acclimatized men during a simulated accidental exposure to 7.5°C for 12 to 24 h. In noncold-acclimatized healthy men, cold exposure induced a decrease of ∼0.8°C in core temperature and a decrease of ∼6.1°C in mean skin temperature (range, 5.4-6.9°C). Results showed that total heat production increased by approximately 1.3- to 1.5-fold in the cold and remained constant throughout cold exposure. Interestingly, this constant rise in Ḣprod and shivering intensity was accompanied by a large modification in fuel selection that occurred between 6 and 12 h; total carbohydrate oxidation decreased by 2.4-fold, and lipid oxidation doubled progressively from baseline to 24 h. Clearly, such changes in fuel selection dramatically reduces the utilization of limited muscle glycogen reserves, thus extending the predicted time to muscle glycogen depletion to as much as 15 days rather than the previous estimates of approximately 30–40 h. Further research is needed to determine whether this would also be the case under different nutritional and/or colder conditions.

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