Mice of the 2 strains that consumed food ad libitum (AL) had a similar body mass at the age of 4 mo and consumed similar amounts of food throughout the experiment however, the body weight subsequently significantly increased (20%) in the C57BL/6 mice but did not increase significantly in the DBA/2 mice. We compared rates of resting oxygen consumption between C57BL/6 mice, whose life span is prolonged by ER, and the DBA/2 mice where it is not, at 6 and 23 mo of age, following 40% ER for 2 and 19 mo, respectively. In this study, our main objective was to determine whether energy restriction (ER) affects the rate of oxygen consumption of mice transiently or lastingly and whether metabolic rate plays a role in the ER-related extension of life span. We also demonstrate delineation in the response of insulin and IGF-1 to acute CR in mice. These strain-specific differences in glucose homeostatic parameters may underlie the reported unresponsiveness of DBA/2 mice to CR. DBA/2 mice were hyperinsulinaemic and insulin resistant compared to C57BL/6 mice. Acute CR had no effect on insulin levels, but lowered insulin sensitivity and decreased insulin-like growth factor-1 (IGF-1) levels in both strains. Glucose tolerance improved after 1 week of CR in C57BL/6 mice but improved only after 4 weeks in DBA/2 mice. Acute CR decreased fed blood glucose levels in both strains, decreased fasting blood glucose in C57BL/6 mice but increased fasting levels in DBA/2 mice. Resting metabolic rate (RMR) was unaltered by CR, following appropriate corrections for BM differences, although RMR was higher in DBA/2 compared to C57BL/6 mice.
Acute CR decreased body mass (BM) in both strains, with lean and fat mass decreasing in proportion to BM. To investigate potential differences underlying the CR response in male DBA/2 and C57BL/6 mice, we examined several metabolic parameters following acute (1-5 weeks) 30% CR. DBA/2 mice, unlike C57BL/6 mice, are reported to be unresponsive to CR. Significance of the StudyThe data provide a preliminary yet robust physiological background for targeting better field application of the technique.Ĭaloric restriction (CR) extends healthy lifespan in many organisms. This result depended upon the high compensation capacity for photosynthesis shown by vines in both treatments. Conclusionsĭefoliation above the bunch zone applied at lag-phase and postveraison (average 12☋rix) was effective in temporarily delaying technological ripeness without affecting colour and phenolics. While ripening was temporarily retarded in both DEF treatments, with sugar content being lower and titratable acidity higher, a week later both treatments had fully or partially recovered phenolic ripening was unaffected at either harvest date. The seasonal carbon/yield ratio did not differ between treatments because of the high capacity for photosynthetic compensation shown by the DEF treatments and quantified as about a 35% higher net CO2 gas exchange per unit of leaf area per day. Concurrently, single-leaf gas exchange was assessed, and at harvest yield components, grape composition and the leaf-to-fruit ratio were determined. Whole-canopy net CO2 gas exchange was monitored seasonally from 9 days before DEF-I to 35 days after DEF-II. Sangiovese grapevines were subjected to leaf removal treatments applied preveraison (DEF-I) and postveraison (DEF-II) by pulling out six to seven primary leaves and laterals, if any, above the bunch zone untouched vines served as the control. Our aim was to assess the physiological basis of late leaf removal applied above the bunch area as a tool for delaying ripening. Background and AimsGlobal warming is inducing a general earliness in the onset of grapevine phenological stages including ripening, a phenomenon that occurs often in the hottest seasons and which leads to unbalanced wines.