Stable isotopic labelling is the most reliable and accurate method for quantitative proteomics and metabolomics. Proteomics studies on uniformly ¹⁵N-labelled rats have been previously reported using ¹⁵N-labelled algae as protein source for Stable Isotope Metabolic Labelling in Mammals (SILAM).[1]

Silantes provides

- SILAM Mouse Diets (diets vor other model organisms such as fly and worm are available on request),

- SILAM Mouse Tissues wet and

- SILAM Mouse Tissues lyophilized on request.

- New: 13C-SILAM Mouse diets are now available!

Silantes ¹⁵N-SILAM Diets for in-vivo labelling of mice

Silantes has developed a ¹⁵N-diet in cooperation with the group of Professor Chris Turck, Max-Planck-Institute of Psychiatry as a kit containing a ¹⁵N-labelled “heavy” diet (B) and unlabelled “light” diet (A).[2] It is an artificial feed using Harlan components and a hydrolysate of the bacteria Ralstonia eutropha as ¹⁵N-protein source. Feeding experiments showed that the mice accepted bacterial-based protein better than algae-based protein.

After the metabolic labelling (feeding) of the mice according to the scheme in figure 2 or figure 3, the mice are sacrificed. Differences in the protein patterns are determined in analogy to the established SILAC approach in cell culture (see literature for Silantes in vitro SILAC).

Silantes ¹³C-SILAM Diets for in-vivo labelling of mice

If the goal is to detect and relatively quantify a large number of metabolites in an untargeted manner, lower organisms can be fed or mammalian cells grown with a diet or media, respectively where ¹²C is replaced with the stable ¹³C isotope. The generated tissue or cellular material can then be used as isotope-labelled internal standard reference. This approach has been successfully established for microorganisms and was subsequently extended to plants and small animals.

Silantes has developed a diet to ¹³C-label mice with the aim of producing isotope-labelled material as reference for metabolomics studies.

Preliminary studies by us have shown that the partially ¹³C-labelled mouse reference material can be used for the relative quantification of amino acids in human plasma samples. We envision that this approach can be extended to the relative quantification of other small molecules of interest in metabolomics research.

We have developed 2 diets for metabolic ¹³C-labelling of mice:

1. Partially 13C-labelled SILAM mouse diet based on Ralstonia eutropha biomass with a ¹³C isotopic enrichment of > 20 atom %.
2. Uniformly 13C-labelled SILAM mouse diet based on Arthrospira maxima ("Spirulina") biomass with a ¹³C isotopic enrichment of > 98 atom %.

Metabolomics Study using the Partially ¹³C-labelled SILAM Mouse Diet

Get access to the study here

We have shown that amino acids in human plasma samples can be relatively quantified using reference material from mice fed for 14 days with the partially ¹³C-labelled diet.

Mouse amino acids from tissue and blood had up to 75% ¹³C enrichment levels
although the initial diet only had a ¹³C enrichment of ~20%.

Figure 1 shows the ¹³C enrichment of free amino acids in mouse plasma, heart tissue and plasma protein hydrolysates mapped on a simplified metabolic pathway. The overall average ¹³C enrichment was ~ 65%. Essential amino acids showed particularly high ¹³C isotope enrichment. This is due to the fact that essential amino acids cannot be produced by the organism itself and proteins from the partially ¹³C-enriched feed serve as the main protein source.

For the relative quantification of amino acids in human plasma samples, the partially ¹³C-labelled mouse reference material turned out to be a very valuable source. Since mice share many metabolic pathways with humans it is conceivable that our approach can be further extended to other small molecules of interest in human metabolomics research.

In addition, mouse ¹³C-labelled blood and tissue material can serve as valuable reference for metabolomics studies of mouse models, to verify biomarker candidates and aid in their identification