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Open access

LPS infusion suppresses serum FGF21 levels in healthy adult volunteers

Esben S Lauritzen, Nikolaj Rittig, Ermina Bach, Niels Møller, and Mette Bjerre

Context

During the inflammatory acute phase response, plasma glucose and serum triglycerides are increased in humans. Fibroblast growth factor (FGF) 21 has plasma glucose and lipid-reducing actions, but its role in the acute inflammatory response in human is unknown.

Objective

To investigate circulating levels of FGF21 after lipopolysaccharide (LPS) infusion.

Design

Two randomized, single-blinded, placebo-controlled crossover trials were used.

Setting

The studies were performed at a university hospital clinical research center.

Patients and interventions

Study 1 (LPS bolus): Eight young, healthy, lean males were investigated two times: (1) after isotonic saline injection and (2) after LPS injection (bolus of 1 ng/kg). Each study day lasted 4 h. Study 2 (continuous LPS infusion): Eight, healthy males were investigated two times: (1) during continuously isotonic saline infusion and (2) during continuous LPS infusion (0.06 ng/kg/h). Each study day lasted 4 h. Circulating FGF21 levels were quantified every second hour by an immunoassay.

Results

A LPS bolus resulted in a late suppression (t = 240 min) of serum FGF21 (P = 0.035). Continuous LPS infusion revealed no significant effects on FGF21 levels (P = 0.82).

Conclusions

Our studies show that a bolus of LPS results in decreased FGF21 levels 4 h from exposure.

Open access

Macrophage activation marker sCD163 correlates with accelerated lipolysis following LPS exposure: a human-randomised clinical trial

Nikolaj Rittig, Mads Svart, Niels Jessen, Niels Møller, Holger J Møller, and Henning Grønbæk

Background

Macrophage activation determined by levels of soluble sCD163 is associated with obesity, insulin resistance, diabetes mellitus type 2 (DM2) and non-alcoholic fatty liver disease (NAFLD). This suggests that macrophage activation is involved in the pathogenesis of conditions is characterised by adaptions in the lipid metabolism. Since sCD163 is shed to serum by inflammatory signals including lipopolysaccharides (LPS, endotoxin), we investigated sCD163 and correlations with lipid metabolism following LPS exposure.

Methods

Eight healthy male subjects were investigated on two separate occasions: (i) following an LPS exposure and (ii) following saline exposure. Each study day consisted of a four-hour non-insulin-stimulated period followed by a two-hour hyperinsulinemic euglycemic clamp period. A 3H-palmitate tracer was used to calculate the rate of appearance (Rapalmitate). Blood samples were consecutively obtained throughout each study day. Abdominal subcutaneous adipose tissue was obtained for western blotting.

Results

We observed a significant two-fold increase in plasma sCD163 levels following LPS exposure (P < 0.001), and sCD163 concentrations correlated positively with the plasma concentration of free fatty acids, Rapalmitate, lipid oxidation rates and phosphorylation of the hormone-sensitive lipase at serine 660 in adipose tissue (P < 0.05, all). Furthermore, sCD163 concentrations correlated positively with plasma concentrations of cortisol, glucagon, tumour necrosis factor (TNF)-α, interleukin (IL)-6 and IL-10 (P < 0.05, all).

Conclusion

We observed a strong correlation between sCD163 and stimulation of lipolysis and fat oxidation following LPS exposure. These findings support preexisting theory that inflammation and macrophage activation play a significant role in lipid metabolic adaptions under conditions such as obesity, DM2 and NAFLD.

Open access

Plasma levels of glucagon but not GLP-1 are elevated in response to inflammation in humans

Justyna Modrzynska, Christine F Klein, Kasper Iversen, Henning Bundgaard, Bolette Hartmann, Maike Moss, Nikolaj Rittig, Niels Moeller, Jens J Holst, and Nicolai J Wewer Albrechtsen

Objective: Glucagon and glucagon-like peptide-1 (GLP-1) originate from the common precursor, proglucagon, and their plasma concentrations have been reported to be increased during inflammatory conditions. Increased blood glucose levels are frequently observed in septic patients, and therefore we hypothesized that glucagon, but not GLP-1, is increased in individuals with inflammation.

Design: Prospective longitudinal cohort study.

Materials and Methods: We measured glucagon and GLP-1 in plasma sampled consecutively in three cohorts consisting of patients with infective endocarditis (n=16), urosepsis (n=28) and post-operative inflammation following percutaneous aortic valve implantation or thoracic endovascular aortic repair (n=5). Correlations between C-Reactive Protein (CRP), a marker of systemic inflammation, and glucagon and GLP-1 concentrations were investigated. Additionally, glucagon and GLP-1 concentrations were measured after a bolus infusion of lipopolysaccharide (LPS, 1ng/kg) in nine healthy young males.

Results: Glucagon and CRP were positively and significantly correlated (r=0.27; P=0.0003), whereas no significant association between GLP-1 and CRP was found (r=0.08, P=0.30). LPS infusion resulted in acute systemic inflammation reflected by increased temperature, pulse, tumor necrosis factor-α (TNFα), interleukin-6 (IL-6) and concomitantly increased concentrations of glucagon (P<0.05) but not GLP-1.

Conclusions :Systemic inflammation caused by bacterial infections or developed as a non-infected condition is associated with increased plasma concentration of glucagon, but not GLP-1. Hyperglucagonemia may contribute to the impaired glucose control in patients with systemic inflammatory diseases.