Turnover rate and oxidation of different free fatty acids in man during exercise

Havel, Richard J.; Carlson, Lars A.; Ekelund, Lars‐Göran; Holmgren, A.

doi:10.1152/jappl.1964.19.4.613

Cited by 184 publications

(62 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Palmitic (16 : 0), stearic (18 : 0), oleic (18 : 1) and linoleic (18 : 2) acids together represent approximately 80-90 % of the blood FA. The ratio between these FA, the muscle fractional uptake and the total net exchange are similar for these FA (Havel et al 1964;Hagenfeldt & Wahren, 1968, 1972Hagenfeldt, 1975) suggesting that they can all be used to represent blood FA.…”

Section: Source Of Fatty Acids For Skeletal Muscle Oxidationmentioning

confidence: 95%

“…Indeed, by the end of the 1930s the principal features of exercise metabolism were established (Christensen, 1932;Dill et al 1932;Bang, 1936;Böje, 1936). In the 1950-60s measurements of a-v difference and radioactive isotopes came into use (Zierler, 1961;Havel et al 1964Havel et al , 1967. During this period the taking of muscle biopsies had a renaissance when Bergström (1962) reintroduced the needle originally described by Duchenne in the middle of the 19th century.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Skeletal muscle substrate metabolism during exercise: methodological considerations

González‐Alonso

Sacchetti³

et al. 1999

Proc. Nutr. Soc.

View full text Add to dashboard Cite

fax +45 3545 7634, email cmrc@rh.dkThe aim of the present article is to evaluate critically the various methods employed in studies designed to quantify precisely skeletal muscle substrate utilization during exercise. In general, the pattern of substrate utilization during exercise can be described well from O 2 uptake measurements and the respiratory exchange ratio. However, if the aim is to quantify limb or muscle metabolism, invasive measurements have to be carried out, such as the determination of blood flow, arterio-venous (a-v) difference measurements for O 2 and relevant substrates, and biopsies of the active muscle. As many substrates and metabolites may be both taken up and released by muscle at rest and during exercise, isotopes can be used to determine uptake and/or release and also fractional uptake can be accounted for. Furthermore, the use of isotopes opens up further possibilities for the estimation of oxidation rates of various substrates. There are several methodological concerns to be aware of when studying the metabolic response to exercise in human subjects. These concerns include: (1) the muscle mass involved in the exercise is largely unknown (bicycle or treadmill). Moreover, whether the muscle sample obtained from a limb muscle and the substrate and metabolite concentrations are representative can be a problem; (2) the placement of the venous catheter can be critical, and it should be secured so that the blood sample represents blood from the active muscle with a minimum of contamination from other muscles and tissues; (3) the use of net limb glycerol release to estimate lipolysis is probably not valid (triacylglycerol utilization by muscle), since glycerol can be metabolized in skeletal muscle; (4) the precision of blood-borne substrate concentrations during exercise measured by a-v difference is hampered since they become very small due to the high blood flow. Recommendations are given in order to obtain more quantitative and conclusive data in studies investigating the regulatory mechanisms for substrate choice by muscle. Free fatty acids: Triacylglycerols: Exercise: Metabolic rate: Respiratory exchange ratioThrough the years, many approaches have been used to evaluate the contribution of carbohydrate and lipids to the increased energy requirements of skeletal muscle during exercise. Since both substrates are stored in the human body outside as well as within the muscle, another question is to what extent the intra-and extra-muscular substrate sources are utilized as a function of exercise intensity, work duration and substrate availability. Determination of the respiratory exchange ratio (RER) from the gas exchange in the lungs or the RQ from the arterial and venous concentration of blood gases can give quite a precise value for the relative contribution of carbohydrates and lipids at the whole-body level or over a limb. To determine the utilization of blood-borne substrates, i.e. the contribution of extramuscular sources, arterio-venous (a-v) differences for relevant substrates and me...

show abstract

Section: Source Of Fatty Acids For Skeletal Muscle Oxidationmentioning

confidence: 95%

mentioning

confidence: 99%

Skeletal muscle substrate metabolism during exercise: methodological considerations

González‐Alonso

Sacchetti³

et al. 1999

Proc. Nutr. Soc.

View full text Add to dashboard Cite

show abstract

“…In order to determine N IMCL , the number of protons per IMCL-CH 2 , it is necessary to estimate the chemical composition of IMCL. As a starting point, triacylglycerol compositions published by several authors (7,(86)(87)(88)(89) can be used (Table 2). In addition, the chemical shifts of fatty acid chains can be found in the literature (5) (Table 3) if repetition times of 1.5 s and longer are used for the determination of IMCL and the unsuppressed water signal for the calibration is acquired in an extra spectrum with very few acquisitions and very long TRs (>6 s).…”

Section: Calibration By the Water Signalmentioning

confidence: 99%

Role of proton MR for the study of muscle lipid metabolism

et al. 2006

View full text Add to dashboard Cite

1 H-MR spectroscopy (MRS) of intramyocellular lipids (IMCL) became particularly important when it was recognized that IMCL levels are related to insulin sensitivity. While this relation is rather complex and depends on the training status of the subjects, various other influences such as exercise and diet also influence IMCL concentrations. This may open insight into many metabolic interactions; however, it also requires careful planning of studies in order to control all these confounding influences. This review summarizes various historical, methodological, and practical aspects of 1 H-MR spectroscopy (MRS) of muscular lipids. That includes a differentiation of bulk magnetic susceptibility effects and residual dipolar coupling that can both be observed in MRS of skeletal muscle, yet affecting different metabolites in a specific way. Fitting of the intra-(IMCL) and extramyocellular (EMCL) signals with complex line shapes and the transformation into absolute concentrations is discussed. Since the determination of IMCL in muscle groups with oblique fiber orientation or in obese subjects is still difficult, potential improvement with high-resolution spectroscopic imaging or at higher field strength is considered. Fat selective imaging is presented as a possible alternative to MRS and the potential of multinuclear MRS is discussed. 1 H-MRS of muscle lipids allows non-invasive and repeated studies of muscle metabolism that lead to highly relevant findings in clinics and patho-physiology.

show abstract

“…This is manifested by impaired glucose disposal and increased plasma NEFA concentrations. Plasma NEFA concentrations are largely determined by effective adipose tissue lipolysis, as assessed by measurements of NEFA release [6], but are also regulated by NEFA clearance [7,8]. Lipolysis is abnormally increased under both basal [3] and insulin-suppressed conditions [3,9] in upper body obesity and type 2 diabetes [4,5].…”

Section: Introductionmentioning

confidence: 99%

Pioglitazone increases non-esterified fatty acid clearance in upper body obesity

Shadid

Jensen

2005

Diabetologia

View full text Add to dashboard Cite

Aims/hypothesis: Plasma NEFA concentrations are largely determined by adipose tissue lipolysis. Insulin suppression of lipolysis is commonly impaired with insulin resistance and improves with thiazolidinedione treatment of type 2 diabetes. The present studies were designed to assess the effects of thiazolidinedione on NEFA (oleate) metabolism that are independent of improved glycaemic control. Materials and methods: We measured plasma oleate concentration and flux ([ H 2 ] glucose) and substrate oxidation (indirect calorimetry) before and after pioglitazone (30 mg/day for ∼20 weeks) in 20 non-diabetic adults with upper body obesity. To assess the effects of improved insulin sensitivity per se we performed the same measurements in a matched group of volunteers treated with diet/exercise. Half of the two groups underwent these measurements during a hyperinsulinaemic-euglycaemic clamp, and the other half had their measurements taken during a (control) saline infusion before and after the intervention. Results: Both interventions increased insulinstimulated glucose disposal and reduced plasma oleate concentrations during the insulin clamp. After diet/exercise, oleate flux decreased (p=0.03) during the insulin clamp and oleate clearance remained unchanged (p=0.55), whereas in the pioglitazone group, oleate flux during the clamp was unchanged (p=0.97) and oleate clearance increased (p=0.003). Oleate clearance in the saline control condition was increased in the pioglitazone group compared with the diet/exercise group (p=0.02).Conclusions/ interpretation: In insulin-resistant, non-diabetic adults, pioglitazone increases NEFA clearance during physiological hyperinsulinaemia, whereas improved insulin sensitivity achieved by diet/exercise does not alter NEFA clearance but enhances insulin suppression of NEFA release. This action of pioglitazone may contribute to improved glucose metabolism in type 2 diabetes.

show abstract

Turnover rate and oxidation of different free fatty acids in man during exercise

Cited by 184 publications

References 0 publications

Skeletal muscle substrate metabolism during exercise: methodological considerations

Skeletal muscle substrate metabolism during exercise: methodological considerations

Role of proton MR for the study of muscle lipid metabolism

Pioglitazone increases non-esterified fatty acid clearance in upper body obesity

Contact Info

Product

Resources

About