The Role of Lactate in Lipolysis and Catabolism in Humans

Lactate may have anti-lipolytic effects when plasma concentrations of lactate reach levels similar to those seen during high intensity exercise. This study aims to investigate how lactate concentrations similar to those achieved during high intensity exercise affects lipolysis in humans. In addition to this, to investigate how increased lactate concentrations affects glucose- and amino acid metabolism. 8 healthy males will be included. Study participants will undergo two separate investigation days that will be identical except for the interventions: 1. Intravenous sodium D/L-lactate 2. Intravenous sodium chloride. The study consists of a 3-hour basal period followed by a 3-hour hyperinsulinemic euglycemic clamp. During the study we will: * Estimate insulin sensitivity during the hyperinsulinemic euglycemic clamp (M value) * Use tracer kinetics to estimate lipid-, glucose and amino acid metabolism using \[9,10-3H\]-palmitate, \[3-3H\]-glucose, \[15N\]-phenylalanine, \[15N\]-tyrosine, \[2H4\]-tyrosine and \[13C\]-Urea. * Do muscle- and adipose tissue biopsies for analyses of signaling pathways involved in regulation of lipid-, glucose and amino acid metabolism. * Do blood samples of relevant hormones, metabolites and cytokines. * Use indirect calorimetry to estimate study participants' resting energy expenditure and respiratory quotient during the basal period. * Estimate cardiac ejection fraction by echocardiography and measure blood pressure during both the basal- and clamp period.