Are there differences in the biochemical profile of bilateral normal testes? A 3.0 T 1H‐MR spectroscopy study

Abstract

Bilateral normal testes asymmetry represents an interesting phenomenon. The aim was to assess possible differences in the biochemical profile of bilateral normal testes by 3.0 T proton magnetic resonance spectroscopy (1H‐MRS). Twenty‐one men were examined with scrotal 3.0 T MRI, including a single‐voxel point‐resolved spectroscopy sequence. MR spectra were obtained by placing a volume of interest in the middle of each normal testis. Normalised metabolite concentrations, defined as ratios of the calculated metabolite concentrations relative to creatine (Cr) concentration, were compared between bilateral normal testes using Mann–Whitney U test. 1H‐MRS allowed the detection of certain testicular metabolites, including total choline, Cr, myo‐inositol, Glx, total lipids and macromolecules resonating at 0.9, 1.3 and 2.0 ppm. Normal left testis had higher median normalised concentrations of Glx (p = .002) and lactate (p = .041) compared with the normal right testis. Differences in concentrations of Glx were attributed to differences in glutamate (p = .020). Normal testes asymmetry is confirmed in this study by differences in the biochemical testicular profile, as assessed by 3.0 T 1H‐MRS. Increase in levels of glutamate and lactate in normal left testis should be correlated with changes in metabolic pathways, specifically glycometabolism and amino acid metabolism.

Proton MR Spectroscopy in Assessing the Biochemical Milieu of Human Testes

“…13 Proton testicular spectra are acquired with a short TE (25-40 msec) single-voxel point-resolved spectroscopy sequence (PRESS). [19][20][21][22][25][26][27][28] A volume of interest (VOI) ranging from 10 × 10 × 10 mm 3 to 15 × 15 × 15 mm 3 is placed in the middle of normal testis, with care to include the majority of testicular parenchyma and to avoid adjacent structures and/or artifacts. T 2 -weighted imaging (T 2 WI) in the three orthogonal planes is used for VOI placement (Fig.…”

“…[20][21][22][23][24][25][26][27][28] Based on data from brain MRS and assuming that tCr remains relatively constant in the testis and, therefore, it can serve as an internal standard, normalized metabolite concentrations, defined as ratios of the calculated metabolite concentrations relative to Cr concentration were used for data interpretation. 20,21,27,28,30 However, possible tCr variability in normal and pathologic testes might justify the application of absolute MRS metabolite quantification in future studies. 25,26 Proton MRS of the testes is particularly challenging compared to the established MRS of the brain, breast, or prostate.…”

“…At 3.0T magnets, as spectra frequency separations improve, overlapping peaks of lipids and macromolecules resonating at 1.3 ppm and Lac become separated. 21 Lactate is a pivotal testicular metabolite, representing the main energy substrate for developing germ cells. [41][42][43][44] In addition, Lac has antiapoptotic effects on germ cells.…”

“…10-18 10-18 Data on the usefulness of proton MRS in assessing the biochemical milieu of human testes are still preliminary. [19][20][21][22][23][24][25][26][27][28] The proton MR spectra of normal testes have been described, showing age and bilateralism dependence. [19][20][21] Pathologic alterations in metabolic peaks have been reported in testes with impaired spermatogenesis and testicular mass lesions.…”

“…[19][20][21][22][23][24][25][26][27][28] The proton MR spectra of normal testes have been described, showing age and bilateralism dependence. [19][20][21] Pathologic alterations in metabolic peaks have been reported in testes with impaired spermatogenesis and testicular mass lesions. [22][23][24][25][26][27][28] The results of proton MRS are promising in testes with nonobstructive azoospermia (NOA), proving valuable noninvasive fingerprints of the complex process of spermatogenesis.…”