Effect of Dietary Restriction on the Response of α2-Macroglobulin During an Acute Phase Response

The effects of aseptic abscesses induced by subcutaneous injections of turpentine (5 mL/kg body weight) on the acute-phase protein response (α ₂-macroglobulin, α₂-M) and on the circulating albumin and total protein concentrations were assessed in young rats that were made malnourished by restricting dietary intake to an extent that either impaired growth (60% of normal intake) or caused weight loss (0% to 45% of normal intake). The measurements were obtained daily during a period of 4 days in malnourished rats that had lost about 25% body weight but had maintained a stable weight thereafter, or in rats that had lost about 12% body weight and were continuing to lose weight at various rates at the time of the turpentine injection. In animals that were injected while they maintained a stable weight after losing about 25% body weight, the α₂-M response was attenuated fourfold to eightfold compared with control animals (the area under the 4-day α₂-M curve in control rats was 23.3 ± 2.3 g/L/d). In the depleted animals that were injected while they were actively losing weight (∼12.5% weight loss), the attenuation of the α ₂-M response was related to the rate of weight loss or to the extent of dietary restriction (area under the 4-day α₂-M curve ranged from 5.7 ± 1.4 g/L/d in animals receiving 15% restricted diet to 15.6 ± 1.5 g/L/d in animals receiving the 45% restricted diet). The hypoalbuminemic response was similar in different groups, and the change in total protein concentration generally reflected the change in α₂-M response. The results suggest that dietary restriction can attenuate the acute-phase protein response and that the magnitude of this attenuation depends not only on the extent of depletion but also on the rate with which the depletion is occurring. (Journal of Parenteral and Enteral Nutrition 18: 510-515, 1994)