Service Group Stable Isotope Tracer and Nutrient Analytics

This service group deals with qualitative and quantitative analysis of metabolites and nutrients, either labelled with stable-isotopes (2H, 13C, 15N, 18O)- or unenriched, isolated from biological fluids (blood, saliva, urine, milk), tissues (e.g., liver, muscle) and excreta of e.g. cattle, pig, sheep, chicken and mice as well as feedstuffs.
This allows functional phenotyping of metabolic processes related to nutrition such as

  • Nutrient oxidation (e.g. glucose, amino acids),
  • Incorporation of nutrients into animal tissue or products (e.g. glucose into milk lactose),
  • Protein synthesis (whole body or selected tissue protein),
  • Nutrient fluxes (e.g. glucose, amino or fatty acids),
  • Gluconeogenesis (using D2O tracer),
  • Energy expenditure (by quantifying CO2-production with 13C bicarbonate or D218O tracers)

by dosing animals in vivo with stable-isotope labelled tracers and then follow-up on their fate in the body.

Chromatographic techniques

  • Gas-chromatography (GC)-flame ionisation detection (e.g. short-chain fatty acids, alcohols)
  • GC-mass spectrometry (e.g. long-chain fatty acids, glucose)
  • High performance liquid chromatography (HPLC) with fluorescence, diode array (UV-VIS) or refractive index detection  (e.g. amino acids, peptides, sugars / sugar alcohols, low molecula organic acids)
  • Thin layer chromatography (TLC, e.g. preparative isolation of lipid components)

Mass spectrometry-based stable isotope techniques

To analyse nutrients or metabolites chemically labelled with stable isotopes or at natural abundance (2H, 13C, 15N, 18O) to quantify nutrient and energy metabolism in vivo.

  • Elemental analysis–combustion-isotope ratio mass spectrometry (IRMS) to quantify 13C, 15N abundance in feedstuffs, tissues or biological fluids
  • Gas chromatography-combustion-IRMS to measure isotopic enrichment of individual substances (e.g. 13C natural abundance in fatty or amino acids)
  • Gas bench - Continuous Flow - IRMS to measure 13C or 18O abundance in breath gas-CO2 or 2H and 18O abundance in biological fluids (e.g. plasma, saliva, urine, milk)
  • Molecular mass spectrometry (GC-quadrupole-MS in electron impact (EI), positive (PCI) or negative (NCI) chemical ionisation mode) to identify or quantify the abundance of nutrients or metabolites (e.g. glucose, amino or keto acids) unenriched or labelled with stable isotopes in plasma or tissue

Clinical chemistry analytics

  • Measurement of enzyme and substrate concentrations in blood plasma or serum and urine by automated spectrophotometry (clinical chemistry benchtop analyser, ABX Pentra 400)
  • Metabolites: alanine amino transferase, albumin, aspartate amino transferase, gamma-glutamyl-transferase, lactate-dehydrogenase, beta-hydroxybutyrate, bilirubin, calcium, total cholesterol, HDL-cholesterol, LDL-cholesterol, glucose, glutamate-dehydrogenase, urea, uric acid, creatine-kinase, creatinine, lactate, non-esterified fatty acids, phosphor, total protein, triglycerides