Inhibiting the fructose transporter GLUT5 boosts testosterone production in a murine mLTC-1 leydig cell line

Abstract

Over the past few decades, a significant change globally in sugar intake has coincided with a rising incidence of male infertility, which is now a major public health concern. Diets rich in fructose have been implicated in both male infertility and increased susceptibility to metabolic disorders, such as obesity, diabetes, and related heart problems. While fructose is known to be present in seminal fluid and crucial for sperm motility, the precise role of fructose in testicular function remains largely unknown.

GLUT5 is an exclusive fructose transporter essential for dietary fructose uptake in the intestine. It is also expressed mainly in germ and Leydig cells. We recently revealed that disrupting the Glut5 gene in male mice impairs spermatogenesis and steroidogenesis. However, its specific role within Leydig cells remains unexplored. Therefore, we investigated its role by inhibiting GLUT5 in a murine Leydig cell line (mLTC-1) using a specific inhibitor of GLUT5, MSNBA, combined with a multi-omics approach.

Exposing mLTC-1 cells to MSNBA reduced the intracellular fructose content, limited cell proliferation, and enhanced progesterone and androgens production (Δ4-androstenedione and testosterone). The latter was associated with the upregulation of two genes and proteins involved in steroidogenesis, such as Hsd3b and steroidogenic acute regulatory protein (StAR). GLUT5 inhibition in mLTC-1 cells also modified lipid and carbohydrate metabolism. Lipidomic analysis showed decreased cholesterol esters and a shift in the ratio of polyunsaturated fatty acids (PUFAs) to monounsaturated fatty acids (MUFAs). These lipid changes correlated with alterations in the expression of mRNA-encoding enzymes involved in lipogenesis, such as ELOVL6. Metabolomics analysis showed a reduction in most glycolysis metabolites, except for pyruvate and lactate. However, pyruvate could conserve its level by a production through an amino acid pathway using the higher branched-chain amino acid content. Nevertheless, the activity of mitochondria measured by seahorse was not altered. The transcriptomic analysis performed by BRB-seq approach revealed an upregulation of several androgen-sensitive genes, such as Akap5, Slc39a9, an androgen receptor or lactate dehydrogenase A (Ldha), which produces lactate, and downregulation of several genes associated with the insulin pathway such as Tsc2 or the hexokinase Hkdc1.

In conclusion, GLUT5 supported fructose intake in the murine Leydig cell line mLTC-1, leading to a reduction in cell proliferation. The consequences of inhibition of GLUT5 led to an increase in fatty acids cell content, a perturbation in glycolysis and amino-acid metabolism but an enhanced androgen production. Since androgens regulate spermatogenesis, hyperandrogenism induced by a lower fructose content in Leydig cells may be a primary cause leading to the disruption of sperm production and quality, as well as sexual behavior, as described in the GLUT5 KO mouse model.