Effect of a prolonged low-dose lipopolysaccharide infusion on feed intake and metabolism in heifers.

Abstract

Prolonged infusions of bacterial lipopolysaccharides (LPS) are known to model gram-negative bacterial infections, but the basic mechanisms of the LPS effects on feed intake and metabolism and their potential interdependence are largely unknown. The aim of the present study was to distinguish and to better characterize the feeding suppressive and metabolic effects of LPS. Six heifers were infused intravenously for 100 min with either 1) LPS (2 microg/kg BW) with free access to feed, 2) saline with free access to feed, or 3) saline with feeding restricted to the amount of feed consumed after LPS infusion. Feed intake, body temperature, plasma concentrations of various metabolites and hormones, and the respiratory quotient and heat production were measured. The LPS reduced feed intake and induced pronounced changes in metabolic energy turnover and fat and carbohydrate metabolism that were largely independent of the concomitant feed intake reduction. Some of the metabolic changes were biphasic; the first phase resembled a stress response with increases in plasma glucose and cortisol, and the second phase reflected a beginning energy deficit with low plasma glucose and enhanced lipolysis. The coincidence of a short-term surge of plasma insulin with marked transient decreases in plasma FFA, glycerol, and beta-hydroxybutyrate as well as with the transition from hyper- to hypoglycemia indicates that insulin plays a role in some of the metabolic responses to LPS. The failure of LPS to clearly increase energy expenditure despite the increase in body temperature suggests that anaerobic mechanisms of heat production and, perhaps, a reduced peripheral blood flow contributed to the fever. Many of the initial metabolic responses occurred before and, therefore, independent of, an increase in circulating tumor necrosis factor-alpha.

High concentrate-induced subacute ruminal acidosis (SARA) increases plasma acute phase proteins (APPs) and cortisol in goats

“…The previous studies showed that cytokines secreted by immune cells can activate the hypothalamic-pituitary-adrenal axis (HPA) after dairy cows were subjected to LPS injection (Steiger et al, 1999;Waldron et al, 2003). The results from Karrow et al (2010) also showed that sheep injected with interleukine-6 stimulated cortisol and corticotrophin hormone secretion into the peripheral circulating system, indicating a cross-talk of immune system and the HPA axis.…”

Metabolic Endotoxemia Initiates Obesity and Insulin Resistance

“…As whole-body insulin resistance was not induced by the LPS infusion, our data showed the liver as a first target of LPS-induced insulin resistance. The role of LPS as a regulator of energy metabolism has been proposed previously (32,33). In most of the studies that described the anorectic and metabolic effects of LPS, endotoxemia was very elevated or given as single shot and witnessed a state of acute phase infection.…”

The effects of pathogen challenges on the performance of naïve and immune animals: the problem of prediction

“…Experiments with intravenously administered bacteria (Ruot et al, 2000;Papet et al, 2002), lipopolysaccharide, LPS, (Steiger et al, 1999), and local (nasal or oral) bacterial (Wannemacher et al, 1971;Powanda et al, 1972;Wannemacher et al, 1974), or, bacterial antigen challenges (Klasing et al, 1987;Arnold et al, 1989) have shown reductions in growth that were not accounted for by reduced VFI. Challenges with LPS, while not a 'true' bacterial challenge, stimulate a similar kind of response, but of smaller and shorter magnitude, to that of bacterial challenges.…”