Effects of acute behavioral stress and LPS-induced cytokine release on growth and energetics in mice

We examined the biological cost of a single episode of acute restraint stress on the growth and energetics of mice, and compared these effects with the effects of stress associated with LPS injection and the total cost of experiencing both stressors simultaneously. We monitored growth and energetics over a 24-h period in 31-day-old mice exposed to either 4 h of restraint stress (R), i.p. injection of 0.45 mg/g of lipopolysaccharide (L), or restraint plus L injection (RL). Compared to controls, either restraint or L significantly (p < 0.05) impaired growth, feed intake, and lean and fat energy deposition. The R and L treatments depressed (>100% lower than controls) body weight change. However, when applied in concert, the effect of restraint and LPS on growth, energy deposition, and feed intake did not summate. All stressors significantly increased circulating corticosterone (p < 0.05) at 1 and 4 h following the initiation of treatment, and there was no difference between the R, L, or RL treatments. Only L and RL increased (p < 0.05) circulating IL-1b at 1 and 4 h. LPS injection elevated (p < 0.05) IL-1b. Although a single episode of behavioral stress altered growth and energy partitioning, LPS-induced cytokine release inhibited energy deposition and growth to a greater extent than behavioral stress (p < 0.05), and no further suppression of energy deposition or growth occurred when the two stressors were combined over 24 h.