Similar carbohydrate but enhanced lactate utilization  during exercise after 9 wk of acclimatization to 5,620 m

Hall, Gerrit van; Calbet, José A. L.; Söndergaard, Hans Peter; Saltin, Bengt

doi:10.1152/ajpendo.00134.2001

Cited by 25 publications

(21 citation statements)

References 32 publications

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“…) was rather similar to the R a observed in active young subjects (17 Ϯ 2 mol ⅐ kg body mass Ϫ1 ⅐ min Ϫ1 ), and so was the relative contribution of leg lactate release to systemic lactate R a (34). This suggests that no difference exists between highly trained and active young individuals in whole body and skeletal muscle lactate appearance and clearance at rest.…”

supporting

confidence: 63%

“…During the 40 min of Continuous Arm ϩ Leg, the lactate R a was 184 Ϯ 17 mol ⅐ kg body mass Ϫ1 ⅐ min Ϫ1 . During bicycle exercise in active subjects, we have observed an arterial lactate concentration of 1.8 mmol/l at 46% V O 2 max , with a lactate R a of ϳ60 mol ⅐ kg body mass Ϫ1 ⅐ min Ϫ1 , and an arterial lactate concentration of ϳ6 mmol/l at 82% V O 2 max with a lactate R a of 160 mol ⅐ kg body mass Ϫ1 ⅐ min Ϫ1 (34). The latter lactate R a is thus even lower than during the 40 min of Continuous Arm ϩ Leg.…”

mentioning

confidence: 88%

“…From these studies it was concluded that skeletal muscles not only produce lactate, but they are also the major tissue for lactate removal from the circulation. Further studies with lactate isotopes have shown a simultaneous limb lactate uptake and release at rest and during exercise (15,16,34). This suggests a dynamic situation, with exchange of lactate as a carbohydrate source between fibers within the same muscle but also from one muscle group to another, whether actively contracting or not.…”

mentioning

confidence: 98%

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Leg and arm lactate and substrate kinetics during exercise

Hall

Jensen‐Urstad²,

Rosdahl

et al. 2003

American Journal of Physiology-Endocrinology and Metabolism

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152

132

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To study the role of muscle mass and muscle activity on lactate and energy kinetics during exercise, whole body and limb lactate, glucose, and fatty acid fluxes were determined in six elite cross-country skiers during roller-skiing for 40 min with the diagonal stride (Continuous Arm ϩ Leg) followed by 10 min of double poling and diagonal stride at 72-76% maximal O2 uptake. A high lactate appearance rate (Ra, 184 Ϯ 17 mol ⅐ kg Ϫ1 ⅐ min Ϫ1 ) but a low arterial lactate concentration (ϳ2.5 mmol/l) were observed during Continuous Arm ϩ Leg despite a substantial net lactate release by the arm of ϳ2.1 mmol/min, which was balanced by a similar net lactate uptake by the leg. Whole body and limb lactate oxidation during Continuous Arm ϩ Leg was ϳ45% at rest and ϳ95% of disappearance rate and limb lactate uptake, respectively. Limb lactate kinetics changed multiple times when exercise mode was changed. Whole body glucose and glycerol turnover was unchanged during the different skiing modes; however, limb net glucose uptake changed severalfold. In conclusion, the arterial lactate concentration can be maintained at a relatively low level despite high lactate Ra during exercise with a large muscle mass because of the large capacity of active skeletal muscle to take up lactate, which is tightly correlated with lactate delivery. The limb lactate uptake during exercise is oxidized at rates far above resting oxygen consumption, implying that lactate uptake and subsequent oxidation are also dependent on an elevated metabolic rate. The relative contribution of whole body and limb lactate oxidation is between 20 and 30% of total carbohydrate oxidation at rest and during exercise under the various conditions. Skeletal muscle can change its limb net glucose uptake severalfold within minutes, causing a redistribution of the available glucose because whole body glucose turnover was unchanged. lactate dehydrogenase; cross-country skiing; tracers AS EARLY AS 1907, Fletcher and Hopkins (11) not only provided definitive evidence of the relation between muscle activity and production of lactic acid in the amphibian skeletal muscle, but they also concluded that skeletal muscles possess the requisite chemical mechanisms for the removal of lactic acid once formed. Despite this early finding, lactate was long considered a metabolic end product, that is, lactate produced during muscle contraction and released into the circulation for subsequent uptake by the liver for recycling via gluconeogenesis. The importance of skeletal muscle in lactate clearance in humans became clear from experiments starting in the late 1950s. It was shown that, during exercise, lactate was taken up by nonactive skeletal muscles (1,7,12). Furthermore, when the arterial lactate concentration was also elevated, active skeletal muscles cleared lactate (12,26,30), and when two-legged cycle ergometer exercise was performed with one leg having a normal and the other a low glycogen content, the leg with the normal glycogen content released lactate, whereas lactate was taken up ...

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supporting

confidence: 63%

mentioning

confidence: 88%

mentioning

confidence: 98%

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Leg and arm lactate and substrate kinetics during exercise

Hall

Jensen‐Urstad²,

Rosdahl

et al. 2003

American Journal of Physiology-Endocrinology and Metabolism

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152

132

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“…For a long time, lactate was thought to be a metabolic end product of glycolysis. Recently, however, lactate was shown to be incorporated into skeletal muscles and was utilized during skeletal muscle contraction and/or exercise (23)(24)(25). In the present study, we found that the pressure stimulus reduced lactate release.…”

Section: Discussionsupporting

confidence: 46%

Exposure to pressure stimulus enhances succinate dehydrogenase activity in L6 myoblasts

Morita¹,

Iizuka²,

Okita³

et al. 2004

American Journal of Physiology-Endocrinology and Metabolism

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.-Contraction of skeletal muscle generates pressure stimuli to intramuscular tissues. However, the effects of pressure stimuli, other than those created by electricity or nerve impulse, on physiological and biochemical responses in skeletal muscles are unknown. The purpose of this study is to examine the effects of a pure pressure stimulus on metabolic responses in a skeletal muscle cell line. Atmospheric pressure was applied to L6 myoblasts using an original apparatus. Succinate dehydrogenase (SDH) activity was evaluated by colorimetric assay using tetrazolium monosodium salt. The amounts of 2-deoxy-[ 3 H]glucose uptake and lactate release were measured. SDH activity was 2.6-to 2.9-fold higher in pressurized L6 cells than in nonpressurized L6 cells (P Ͻ 0.01), and 2-deoxy-[ 3 H]glucose uptake was 2.2-fold higher (P Ͻ 0.001). In addition, the amount of released lactate decreased from 6.8 to 3.7 mol/dish when pressure was applied (P Ͻ 0.001). In contrast, the intracellular lactate contents of the pressurized cells were higher than those of nonpressurized cells (P Ͻ 0.01). However, the total amount of released lactate and intracellular lactate was lower in the pressurized cells than in nonpressurized cells. These findings demonstrate that a pure pressure stimulus enhances aerobic metabolism in L6 skeletal muscle cells and raise the possibility that elevated intramuscular pressure during muscle activity may be an important factor in stimulating oxidative metabolic responses in skeletal muscles. mechanical pressure; aerobic metabolism; lactate; glucose uptake WHEN A MUSCLE CONTRACTS, it not only receives electrical stimulation but is also subjected to mechanical forces. The mechanical forces to skeletal muscles are classified into two components: stretching and intramuscular pressure. The former stimulus is developed during elongation of muscle length by external-strain force. On the other hand, intramuscular pressure is generated by contraction (i.e., force production) of the pressure-applied muscle itself, independent of alterations in muscle length (1). The effects of stretching stimuli on metabolism, intracellular signal events, and gene expression in skeletal muscle tissues or cells have been shown (3,6,9,15,16). In those studies, passive stretching (i.e., unrelated to innervation) caused glucose uptake in isolated muscles and cultured muscle cells (6,9,16). On the basis of those reports, it appears that skeletal muscle is sensitive to mechanical forces independent of electrical stimuli and humoral factors.With regard to intramuscular pressure, Ballard et al.(1) demonstrated that the intramuscular pressures at concentric contraction during walking and running were ϳ180 and 270 mmHg, respectively. However, very little is known about the effects of a pressure stimulus as a component of mechanical forces during contraction on the physiological and biochemical responses of skeletal muscles. On the basis of the intensity of the intramuscular pressure reported by Ballard et al. and the fact that a pressure stimulus i...

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“…However, empirical evidence in support of this hypothesis is based almost exclusively on studies of humans. Acclimation to hypoxia has been shown to increase carbohydrate utilization in some studies of human lowlanders and in some nonhuman animals (11,12,46,47), but not in others (48,49). In contrast, both Sherpas and Andean Quechuas show evidence for enhanced cardiac glucose uptake at the tissue level (50), and in Sherpas, the decreased ratio of phosphocreatine to ATP in cardiac myocytes suggests a greater reliance on glucose for ATP production (51).…”

Section: Discussionmentioning

confidence: 99%

Regulatory changes contribute to the adaptive enhancement of thermogenic capacity in high-altitude deer mice

Cheviron

Bachman

Connaty

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

168

226

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In response to hypoxic stress, many animals compensate for a reduced cellular O 2 supply by suppressing total metabolism, thereby reducing O 2 demand. For small endotherms that are native to high-altitude environments, this is not always a viable strategy, as the capacity for sustained aerobic thermogenesis is critical for survival during periods of prolonged cold stress. For example, survivorship studies of deer mice (Peromyscus maniculatus) have demonstrated that thermogenic capacity is under strong directional selection at high altitude. Here, we integrate measures of whole-organism thermogenic performance with measures of metabolic enzyme activities and genomic transcriptional profiles to examine the mechanistic underpinnings of adaptive variation in this complex trait in deer mice that are native to different elevations. We demonstrate that highland deer mice have an enhanced thermogenic capacity under hypoxia compared with lowland conspecifics and a closely related lowland species, Peromyscus leucopus. Our findings suggest that the enhanced thermogenic performance of highland deer mice is largely attributable to an increased capacity to oxidize lipids as a primary metabolic fuel source. This enhanced capacity for aerobic thermogenesis is associated with elevated activities of muscle metabolic enzymes that influence flux through fatty-acid oxidation and oxidative phosphorylation pathways in high-altitude deer mice and by concomitant changes in the expression of genes in these same pathways. Contrary to predictions derived from studies of humans at high altitude, our results suggest that selection to sustain prolonged thermogenesis under hypoxia promotes a shift in metabolic fuel use in favor of lipids over carbohydrates.functional genomics | RNA-seq | thermoregulation | transcriptomics D uring cold stress, homeothermic endotherms maintain a constant body temperature by increasing metabolic heat production. In small endotherms like mice that have high thermoregulatory demands, thermogenic capacity influences survival in cold environments and therefore has a clear connection to Darwinian fitness (1, 2). Indeed, thermogenic capacity in freeranging deer mice (Peromyscus maniculatus) is subject to strong directional selection at high altitude (3).Sustaining maximal thermogenic capacities during prolonged periods of cold stress requires a high rate of O 2 flux through oxidative pathways, and this requirement presents a unique challenge for endothermic animals that live under conditions of chronic O 2 deprivation at high altitude. The reduced partial pressure of O 2 (PO 2 ) at high altitude imposes well-documented constraints on aerobic metabolism (4-8), thereby exacerbating the increased thermoregulatory demands faced by endothermic animals that are native to cold, alpine environments.In rodents, aerobic thermogenesis is accomplished through both shivering and nonshivering mechanisms, and in deer mice, shivering accounts for roughly 35-50% of total thermogenic capacity (9). As with other forms of strenuous exerci...

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Similar carbohydrate but enhanced lactate utilization during exercise after 9 wk of acclimatization to 5,620 m

Cited by 25 publications

References 32 publications

Leg and arm lactate and substrate kinetics during exercise

Leg and arm lactate and substrate kinetics during exercise

Exposure to pressure stimulus enhances succinate dehydrogenase activity in L6 myoblasts

Regulatory changes contribute to the adaptive enhancement of thermogenic capacity in high-altitude deer mice

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