Having it all: historical energy intakes do not generate the anticipated trade-offs in fecundity.
An axiom of life-history theory, and fundamental to our understanding of ageing, is that animals must trade-off their allocation of resources since energy and nutrients are limited. Therefore, animals cannot "have it all"--combine high rates of fecundity with extended lifespans. The idea of life-history trade-offs was recently challenged by the discovery that ageing may be governed by a small subset of molecular processes independent of fitness. We tested the "trade-off" and "having it all" theories by examining the fecundities of C57BL/6J mice placed onto four different dietary treatments that generated caloric intakes from -21 to +8.6% of controls. We predicted body fat would be deposited in relation to caloric intake. Excessive body fat is known to cause co-morbidities that shorten lifespan, while caloric restriction enhances somatic protection and increases longevity. The trade-off model predicts that increased fat would be tolerated because reproductive gain offsets shortened longevity, while animals on a restricted intake would sacrifice reproduction for lifespan extension. The responses of body fat to treatments followed our expectations, however, there was a negative relationship between reproductive performance (fecundity, litter mass) and historical intake/body fat. Our dietary restricted animals had lower protein oxidative damage and appeared able to combine life-history traits in a manner contrary to traditional expectations by having increased fecundity with the potential to have extended lifespans.
Johnston
S L
SL
Division of Energy Balance and Obesity, Rowett Research Institute, Greenburn Road, Bucksburn, Aberdeen AB21 9SB, UK.
Grune
T
T
Bell
L M
LM
Murray
S J
SJ
Souter
D M
DM
Erwin
S S
SS
Yearsley
J M
JM
Gordon
I J
IJ
Illius
A W
AW
Kyriazakis
I
I
Speakman
J R
JR
D000818:Animals; D001835:Body Weight; D002149:Energy Intake / Q000502:physiology*; D005260:Female; D005298:Fertility / Q000502:physiology*; D008099:Liver / Q000737:chemistry; D008136:Longevity / Q000502:physiology*; D051379:Mice; D018482:Muscle, Skeletal / Q000737:chemistry; D050050:Protein Carbonylation