Body temperature and heat production in suckling rat endotoxaemia: beneficial effects of glutamine

Abstract

Background/purpose: Sepsis is an important cause of neonatal mortality. The aim of the study was to investigate the metabolism of endotoxic neonatal rats and the potential beneficial effect of glutamine.

Methods: Suckling rats received intraperitoneal saline (control; C), endotoxin (300 microg/g LPS; E), saline+glutamine (2 mmol/g; CG), endotoxin+glutamine (EG), saline+leucine (2 mmol/g; CL) or endotoxin+leucine (EL). Sepsis score (0-8) and rectal temperature were monitored. Hypothermia was defined as rectal temperature less than 32 degrees C. Oxygen consumption (VO2, mL/kg/h), a determinant of heat production, was measured by indirect calorimetry. Data (mean +/- SEM) were compared by analysis of variance (ANOVA), paired t test or Fisher's Exact test.

Results: Endotoxic (E) rats had significantly lower VO2 than C rats from 90 minutes postinjection to the end of the experiment, 210 minutes (VO2 from 150 to 210 minutes: C 671 +/- 45; E 429 +/- 36, P <.0004; n = 8; paired t test). VO2 of CL or CG rats was elevated between 90 and 210 minutes compared with control, but significantly (P <.01) only in the L group (C 706 +/- 31; CG 871 +/- 63; CL 984 +/- 31; n = 7-9, ANOVA). VO2 was significantly higher (P <.05) in EG rats than E rats (E 460 +/- 29; EG 654 +/- 68; n = 9-10). In the EL group, VO2 was raised but was not significantly different from E (E 460 +/- 29; EL 637 +/- 52; n = 8-10). EG rats were significantly less hypothermic between 90 and 210 minutes (58 of 132 measurements) compared with E (95 of 147; P =.0007, Fisher's Exact test), whereas the EL group were similarly hypothermic (74 of 120) to E (P =.7). Sepsis score was significantly lower in the EG group than both E and EL groups (E 4.9 +/- 0.3; EG 3.6 +/- 0.3; EL 5.0 +/- 0.3; n = 40; P <.01; ANOVA).

Conclusions: Neonatal endotoxaemia lowers VO2, heat production, and body temperature. Glutamine and leucine both cause nutrient-induced thermogenesis in control animals and restore VO2 of endotoxic animals. Glutamine additionally increases rectal temperature, reduces incidence of hypothermia, and improves clinical signs of endotoxic rats. This suggests that glutamine may be beneficial for nutrition in neonatal sepsis.