Restriction of energy intake, energy expenditure, and aging

Ramsey, Jon J.; Harper, Mary‐Ellen; Weindruch, Richard

doi:10.1016/s0891-5849(00)00417-2

Cited by 180 publications

(160 citation statements)

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“…In the present study, the mean body weight loss was 4% in food-restricted rats and 6% in 24-h fasted rats. Collectively, these results suggest that while food restriction results in a decrease in energy expenditure at the whole-body level [45], this adaptation is not always accompanied by a modification of resting energy state (PCr:ATP ratio) in skeletal muscle. Indeed, it appears that the PCr:ATP ratio is decreased when the food restrictionrelated weight loss is relatively high, i.e.…”

Section: Discussionmentioning

confidence: 84%

Dexamethasone impairs muscle energetics, studied by 31P NMR, in rats

Dumas

Biélicki²,

Renou³

et al. 2005

Diabetologia

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Aims/hypothesis: Glucocorticoid treatments are associated with increased whole-body oxygen consumption. We hypothesised that an impairment of muscle energy metabolism can participate in this increased energy expenditure. Methods: To investigate this possibility, we have studied muscle energetics of dexamethasone-treated rats (1.5 mg kg −1 day −1 for 6 days), in vivo by 31 P NMR spectroscopy. Results were compared with control and pair-fed (PF) rats before and after overnight fasting. Results: Dexamethasone treatment resulted in decreased phosphocreatine (PCr) concentration and PCr:ATP ratio, increased ADP concentration and higher PCr to γ-ATP flux but no change in β-ATP to β-ADP flux in gastrocnemius muscle. Neither 4 days of food restriction (PF rats) nor 24 h fasting affected high-energy phosphate metabolism. In dexamethasone-treated rats, there was an increase in plasma insulin and non-esterified fatty acid concentration. Conclusions/ interpretation: We conclude that dexamethasone treatment altered resting in vivo skeletal muscle energy metabolism, by decreasing oxidative phosphorylation, producing ATP at the expense of PCr.

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Section: Discussionmentioning

confidence: 84%

Dexamethasone impairs muscle energetics, studied by 31P NMR, in rats

Dumas

Biélicki²,

Renou³

et al. 2005

Diabetologia

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“…As pointed out by Ramsey et al (2000), in the context of responses of animals to caloric restriction, and more generally by Speakman et al (2002), the rate of living theory posits only that metabolic rate is related to the rate of ageing. A fair test of the theory is therefore only feasible if one modulates the rate of metabolism while holding other variables that might have an influence constant.…”

Section: Some Solutions and Some Additional Difficultiesmentioning

confidence: 99%

“…Finally, the fifth type of study includes taking environmental manipulations that extend lifespan (such as caloric restriction) and asking whether such manipulations have their effects because of a reduction in rates of energy metabolism. I will review the current situation regarding each of these types of study, except this latter area, the metabolic responses to caloric restriction, since this whole issue was the subject of a recent comprehensive review (Ramsey et al, 2000).…”

Section: Some Solutions and Some Additional Difficultiesmentioning

confidence: 99%

Body size, energy metabolism and lifespan

Speakman

2005

Journal of Experimental Biology

716

637

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Bigger animals live longer. The scaling exponent for the relationship between lifespan and body mass is between 0.15 and 0.3. Bigger animals also expend more energy, and the scaling exponent for the relationship of resting metabolic rate (RMR) to body mass lies somewhere between 0.66 and 0.8. Mass-specific RMR therefore scales with a corresponding exponent between -0.2 and -0.33. Because the exponents for mass-specific RMR are close to the exponents for lifespan, but have opposite signs, their product (the mass-specific expenditure of energy per lifespan) is independent of body mass (exponent between -0.08 and 0.08). This means that across species a gram of tissue on average expends about the same amount of energy before it dies regardless of whether that tissue is located in a shrew, a cow, an elephant or a whale. This fact led to the notion that ageing and lifespan are processes regulated by energy metabolism rates and that elevating metabolism will be associated with premature mortalitythe rate of living theory.The free-radical theory of ageing provides a potential mechanism that links metabolism to ageing phenomena, since oxygen free radicals are formed as a by-product of oxidative phosphorylation. Despite this potential synergy in these theoretical approaches, the free-radical theory has grown in stature while the rate of living theory has fallen into disrepute. This is primarily because comparisons made across classes (for example, between birds and mammals) do not conform to the expectations, and even within classes there is substantial interspecific variability in the mass-specific expenditure of energy per lifespan. Using interspecific data to test the rate of living hypothesis is, however, confused by several major problems. For example, appeals that the resultant lifetime expenditure of energy per gram of tissue is 'too variable' depend on the biological significance rather than the statistical significance of the variation observed. Moreover, maximum lifespan is not a good marker of ageing and RMR is not a good measure of total energy metabolism. Analysis of residual lifespan against residual RMR reveals no significant relationship. However, this is still based on RMR.A novel comparison using daily energy expenditure (DEE), rather than BMR, suggests that lifetime expenditure of energy per gram of tissue is NOT independent of body mass, and that tissue in smaller animals expends more energy before expiring than tissue in larger animals. Some of the residual variation in this relationship in mammals is explained by ambient temperature. In addition there is a significant negative relationship between residual lifespan and residual daily energy expenditure in mammals. A potentially much better model to explore the links of body size, metabolism and ageing is to examine the intraspecific links. These studies have generated some data that support the original rate of living theory and other data that conflict. In particular several studies have shown that manipulating animals to expend more or less energy ...

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“…Thus, to understand the effects of temperature on longevity it is important to take into consideration its relevance with respect to metabolic rate and the 'rate of living' theory. This theory, proposing that longevity and aging are inversely regulated by metabolic rates, ( [44,45]Reviewed in [46]) is supported by several kinds of evidence including the reduction of energy expenditure and increased energy efficiency in CR rodents, and challenged by others [47][48][49]. Results vary, also, depending on whether metabolism is measured as resting metabolic rate (at thermoneutral temperatures and in a post absorptive state) or as daily energy expenditure.…”

Section: Temperature and Energy Homeostasismentioning

confidence: 99%