Influence of cold exposure on plasma triglyceride clearance in humans

Vallerand, A. L.; Jacobs, Ira

doi:10.1016/0026-0495(90)90097-v

Cited by 31 publications

(19 citation statements)

References 26 publications

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“…Cold stress is a powerful stimulus for sympathetic nervous system (SNS) activation in man, as reflected in the increased concentration of noradrenaline (Johnson, Hayward, Jacobs, Collis, Eckerson & Williams, 1977). In the present study, the -7-fold increase in this catecholamine reflected the strong adrenergic drive for vasoconstriction in the body shell, and is equivalent to (Vallerand et al 1988;Vallerand & Jacobs, 1990), or greater (MacNaughton et al 1990Vallerand, Jacobs & Kavanagh, 1989) than, the values quoted in earlier cold air exposure studies. Consistent with the majority of previous cold stress studies (including cold water immersion), the present study found no cold-induced increase in adrenaline concentration.…”

Section: Physiological Responses To Moderate Cold Stresssupporting

confidence: 44%

Physiological responses to moderate cold stress in man and the influence of prior prolonged exhaustive exercise

Weller¹,

Greenhaff²,

Macdonald³

1998

Experimental Physiology

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SUMMARYA study was undertaken in man to investigate whether during moderate cold stress, the proportion of carbohydrate (CHO) oxidized is increased, and whether prior prolonged exhaustive exercise compromises thermoregulation. Eight euglycaemic men were cooled by a liquid-conditioned suit (1) after an overnight fast (Con) and (2) -2 h after an exercise protocol in which CHO availability was substantially lowered (Post-Ex). The cooling stimulus lasted 90 min (Cooling) and was preceded by a 30 min thermo-neutral baseline phase (Base). In Con, aural temperature (Taural) and the rate of CHO oxidized (CHO..) were not altered from the values at Base during Cooling, whereas the following were increased: the rate of heat production (Hprod, 1.9-fold), thigh electromyographical activity (EMG, -2.5-fold), and the rate of fat oxidized (FAT0., -1.7-fold). In Post-Ex, Taural did not decrease from the value at Base during Cooling, and compared with Con, EMG, CHOOX and the rate of heat loss were not different, whereas Iprod (P 6 0.01), FATOX (P S 0-01) and mean skin temperature (P 6 0.01) were higher, and Taura1 was lower (P 6 0.05). It is concluded that during moderate cold stress, shivering thermogenesis is supported by an increase in the oxidation of fat, and despite an alteration in the initial thermoregulatory responses to Cooling -2 h after exhaustive exercise, thermoregulation was not impaired.

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Section: Physiological Responses To Moderate Cold Stresssupporting

confidence: 44%

Physiological responses to moderate cold stress in man and the influence of prior prolonged exhaustive exercise

Weller¹,

Greenhaff²,

Macdonald³

1998

Experimental Physiology

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“…In contrast to these animal studies, little is known about fuel metabolism in humans. Although it has been reported in humans that cold exposure increased basal levels of plasma FFA, glycerol, catecholamines and that it decreases plasma glucose and insulin (for a review see 14,17), these changes did not reveal any information with respect to substrate utilization. Using the well-known indirect calorimetry and nonprotein respiratory exchange ratio technique, we have recently demonstrated that the cold-induced increase in heat production (fasting semi-nude subjects at rest for 2 h at 10 °C, 1 ms'wind) was associated with a 58% and 63% increase in carbohydrate and lipid oxidation, respectively, and an un- Sl91 -S193, 1992. Recent advances on the influence of cold exposure on energy metabolism in animals and humans are summarized.…”

Section: Human Experimentsmentioning

confidence: 87%

Energy Metabolism During Cold Exposure

Vallerand¹,

Jacobs²

1992

Int J Sports Med

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Recent advances on the influence of cold exposure on energy metabolism in animals and humans are summarized. Although the cold-induced enhancements in carbohydrate metabolism have been the focus of numerous studies, it was only recently that pieces of evidence from animal studies have suggested that cold exposure exerts an insulin-like effect on peripheral tissue glucose uptake, which appears to proceed primarily via insulin-independent pathways. Interestingly, this phenomenon was observed in insulin-sensitive tissues of warm- a well as cold-adapted rats. Whereas previous human studies have concentrated on the cold-induced changes in basal levels of hormones and metabolic substrates, recent work from our laboratory has demonstrated that exposure to cold at rest shifts substrate utilization from mainly lipids at thermal neutrality to carbohydrates, representing the main fuel for shivering thermogenesis. Further investigation has revealed that the marked increment in carbohydrate oxidation in cold-exposed humans is derived from a greater utilization of both circulating glucose and intramuscular glycogen. With respect to lipid metabolism, recent studies have shown that the cold-induced increase in lipid oxidation in man is fuelled primarily by the fatty acids released from white adipose tissue triglycerides (TG) and possibly intramuscular TG, not plasma TG. One practical application of this work on energy metabolism in the cold resides in the pharmacological approach to improve cold tolerance, where pharmacological agents that alter energy metabolism and substrate utilization could be used to enhance cold thermogenesis and produce warmer body temperatures.

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“…Until very recently, the exact thermogenic role of lipids had not been clearly established. Many studies concluded that CHO were the preferred fuel (Vallerand & Jacobs 1989, 1990, Vallerand et al. 1989, 1995, 1999, MacNaughton et al.…”

Section: Earlier Work On Fuel Metabolism and Missing Linksmentioning

confidence: 99%

Fuel selection in shivering humans

Weber

Haman

2005

Acta Physiologica Scandinavica

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Heat exchange has been thoroughly studied in cold-exposed humans, but the metabolic substrates used for thermogenesis have received less attention. This review deals with oxidative fuel selection in shivering humans. Lipids provide most of the heat during low-intensity shivering, whereas carbohydrates become dominant under more extreme cold conditions. The contribution from plasma glucose always remains minor, but muscle glycogen plays an important role during intense shivering. Whether the size of muscle glycogen stores influences endurance in the cold remains to be demonstrated. The fuel selection patterns of shivering and exercise are different, but the mechanisms underlying this difference have not been investigated. The simultaneous measurement of metabolic substrate oxidation and muscle fibre recruitment has allowed to characterize two different mechanisms of fuel selection in shivering humans: the recruitment of different pathways within the same fibres and of different fuel-specific fibres within the same muscles. This suggests that muscle fibre composition of each individual may affect survival. Future research promises to provide a combination of theoretical advances on fundamental principles of fuel selection and applied strategies to manipulate fibre composition (through training) or fuel metabolism (through diet) to prolong human survival in cold environments.

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Influence of cold exposure on plasma triglyceride clearance in humans

Cited by 31 publications

References 26 publications

Physiological responses to moderate cold stress in man and the influence of prior prolonged exhaustive exercise

Physiological responses to moderate cold stress in man and the influence of prior prolonged exhaustive exercise

Energy Metabolism During Cold Exposure

Fuel selection in shivering humans

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