Carnosine levels in the same individuals as measured by different modalities

Carnosine is an endogenous di-peptide (b-alanine -L- histidine) involved in maintaining tissue homeostasis. It is most abundant in skeletal muscle where its concentration has been determined in biopsy samples using tandem mass spectrometry (MS-MS). Carnosine levels can also be assessed in intact leg muscles by proton magnetic resonance spectroscopy (1H-MRS) or in blood and urine samples using mass spectrometry. Nevertheless, it remains uncertain how carnosine levels from these distinct compartments are correlated with each other when measured in the same individual. Furthermore, it is unclear which measurement modality might be most suitable for large-scale clinical studies. Hence, in 31 healthy volunteers, we assessed carnosine levels in skeletal muscle, via 1H-MRS, and in erythrocytes and urine by MS-MS. While muscle carnosine levels were higher in males, there was no sex-associated difference in urinary or erythrocyte levels. In a linear regression model adjusted for age, sex, race, ..., , , # Carnosine levels in the same individuals as measured by different modalities

[https://doi.org/10.5061/dryad.0rxwdbs6s](https://doi.org/10.5061/dryad.0rxwdbs6s)

Levels of endogenous carnosine as measured in the same individuals in urine and erythrocytes by mass spec and in skeletal muscle by MRS

## Description of the data and file structure

The data are in two Excel files listed by participant number.

In Excel file \"data_for_PLOS_ONE-1\", for each participant, we list:

1. C2/water levels as determined by MRS
2. C4/water levels as determined by MRS
3. RBS levels normalized to mg protein
4. Urinary levels normalized to mg creatinine

In Excel file \"Data_for_PLOS_ONE-2\", we list those MRS participants in whom we did repeat measures in a single voxel and repeat measures in the same voxel and values for these measures.

## Code/Software

No special code is needed to analyze the data.