l-Theanine promotes cultured human Sertoli cells proliferation and modulates glucose metabolism

Abstract

Purpose

l-Theanine is the major free amino acid present in tea (Camellia sinensis L.). The effects of several tea constituents on male reproduction have been investigated, but l-theanine has been overlooked. Sertoli cells (SCs) are essential for the physical and nutritional support of germ cells. In this study, we aimed to investigate the ability of l-theanine to modulate important mechanisms of human SCs (hSCs) metabolism, mitochondrial function and oxidative profile, which are essential to prevent or counteract spermatogenesis disruption in several health conditions.

Methods

We evaluated the effect of a dose of l-theanine attained by tea intake (5 μM) or a pharmacological dose (50 μM) on the metabolism (proton nuclear magnetic resonance and Western blot), mitochondrial functionality (protein expression of mitochondrial complexes and JC1 ratio) and oxidative profile (carbonyl levels, nitration and lipid peroxidation) of cultured hSCs.

Results

Exposure of hSCs to 50 µM of l-theanine increased cell proliferation and glucose consumption. In response to this metabolic adaptation, there was an increase in mitochondrial membrane potential, which may compromise the prooxidant–antioxidant balance. Still, no alterations were observed regarding the oxidative damages.

Conclusions

A pharmacological dose of l-theanine (50 µM) prompts an increase in hSCs proliferation and a higher glucose metabolization to sustain the pool of Krebs cycle intermediates, which are crucial for cellular bioenergetics and biosynthesis. This study suggests an interplay between glycolysis and glutaminolysis in the regulation of hSCs metabolism.

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Abbreviations

4-HNE:

4-Hydroxynonenal

AP:

Alkaline phosphatase

BBB:

Blood–brain barrier

BTB:

Blood–testis barrier

DNP:

2,4-Dinitrophenyl

EGCG:

Epigallocatechin gallate

FBS:

Fetal bovine serum

hSCs:

Human Sertoli cells

ITS:

Insulin–transferrin–sodium selenite

LDH:

Lactate dehydrogenase

MCT4:

Monocarboxylate transporter 4

NMR:

Nuclear magnetic resonance

PBS:

Phosphate-buffered saline

PVDF:

Polyvinylidene difluoride

ROS:

Reactive oxygen species

SCs:

Sertoli cells

SEM:

Standard error of the mean

SRB:

Sulforhodamine B

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Acknowledgements

This work was supported by “Fundação para a Ciência e a Tecnologia”—FCT to Tânia R. Dias (SFRH/BD/109284/2015); Raquel L. Bernardino (SFRH/BD/103105/2014); Marco G. Alves (IFCT2015); Pedro F. Oliveira (IFCT2015); CICS (UID/Multi/00709/2013), UMIB (PEst-OE/SAU/UI0215/2014) and REQUIMTE (UID/QUI/50006/2013). The work was co-funded by FEDER through the COMPETE/QREN, FSE/POPH (PTDC/BIM-MET/4712/2014 and PTDC/BBB-BQB/1368/2014), and POCI—COMPETE 2020 (POCI-01-0145-FEDER-007491) funds. The funding sources had no involvement in the study design; collection, analysis and interpretation of data; writing of the report; or in the decision to submit the article for publication.

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Authors

Contributions

TRD performed most of the experiments, analyzed the results and wrote the first draft of the manuscript. RLB helped in the cell cultures and data interpretation. MGA was responsible for the metabolic analysis and helped in data interpretation and discussion. JS and AB collected the testicular biopsies from the patients and obtained a written consent from each of them. MS, SC, BMS and PFO designed the study, helped with statistical analysis and revised the manuscript. The manuscript was written through the contributions of all authors. All authors have given approval to the final version of the manuscript.

Corresponding authors

Correspondence to Branca M. Silva or Pedro F. Oliveira.

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The authors declare that they have no conflict of interest.

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Dias, T.R., Bernardino, R.L., Alves, M.G. et al. l-Theanine promotes cultured human Sertoli cells proliferation and modulates glucose metabolism. Eur J Nutr 58, 2961–2970 (2019). https://doi.org/10.1007/s00394-019-01999-2

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Keywords

  • Cell metabolism
  • Glutamate
  • l-Theanine
  • Mitochondria
  • Antioxidant
  • Sertoli cell