Aldose Reductase B1 in Pig Seminal Plasma: Identification, Localization in Reproductive Tissues, and Relationship With Quality and Sperm Preservation.

Yentel Mateo-Otero,Estel Viñolas-Vergés,Marc Yeste,Jordi Roca,Isabel Barranco,Jordi Ribas-Maynou,Marc Llavanera

doi:10.3389/fcell.2021.683199

Abstract

Aldose reductase B1 (AKR1B1), a NADPH-dependent enzyme that belongs to the aldo-keto reductase protein superfamily, has been reported to be involved in both male and female reproductive physiology. The objectives of this study were: (1) to evaluate the concentration of SP-AKR1B1 in pig ejaculate fractions; (2) to describe the immunohistochemical localization of AKR1B1 alongside the boar genital tract; (3) to evaluate the relationship between SP-AKR1B1 and sperm quality/functionality parameters. Ejaculates from seven boars (one ejaculate per boar) were collected in separate portions [the first 10 mL of the sperm rich fraction (SRF-P1), the rest of the SRF (SRF-P2), and the post-SRF (PSRF)], and the concentration of SP-AKR1B1 was assessed using an enzyme-linked immunosorbent assay (ELISA). Immunohistochemistry and immunoblotting targeting was conducted in the reproductive tissues of these boars. Additionally, the entire ejaculates of 14 boars (one ejaculate per boar) were collected and split into three separate aliquots for: (i) SP-AKR1B1 quantification; (ii) assessment of sperm concentration and morphology; and (iii) evaluation of sperm quality and functionality parameters upon ejaculate collection (0 h) and after 72 h of liquid storage at 17°C. Concentration of AKR1B1 in the SP of SRF-P1 (458.2 ± 116.33 ng/mL) was lower (P < 0.05) than that of SRF-P2 (1105.0 ± 229.80 ng/mL) and PSRF (1342.4 ± 260.18 ng/mL). Monomeric and dimeric AKR1B1 forms were expressed alongside the reproductive tissues, except in the bulbourethral glands. No relationship between SP-AKR1B1 and sperm quality/functionality parameters was observed either at 0 h or after 72 h of storage at 17°C. In conclusion, AKR1B1 is expressed in the reproductive organs of boars (except bulbourethral glands) and a higher concentration is found in the PSRF suggesting that seminal vesicles would be the main secretory source. However, this enzyme does not appear to be related to sperm quality/functionality or to the sperm ability to withstand liquid storage at 17°C.

Highlights

The immunoblotting assay revealed the presence of AKR1B1 along the entire male reproductive tissues except for bulbourethral glands (Figure 2)
Two specific bands were detected: (i) a 36 kDa band was found in testis, epididymal caput and corpus, and seminal vesicles; and (ii) a ∼80 kDa band was identified in testis, cauda, caput and corpus of epididymis, seminal vesicles, and prostate
The two bands were not seen when membranes were incubated with AKR1B1 blocking peptide, revealing that they were specific for AKR1B1

Summary

Introduction

Aldose reductase B1 (AKR1B1 or ALR2), a NADPH-dependent enzyme that belongs to the aldo-keto reductase protein superfamily (Bohren et al, 1989; Hyndman et al, 2003), has been reported to play an essential role in both male and female reproductive systems in humans (Bresson et al, 2011), cattle (Frenette et al, 2004; Girouard et al, 2009), rats (Kobayashi et al, 2002), sheep (Yang et al, 2019), and pigs (Steinhauser et al, 2016; Pérez-Patiño et al, 2018) This enzyme is known to be involved in the polyol pathway for fructose production, in the conversion of glucose into sorbitol (Kobayashi et al, 2002). Reinforcing the belief that this protein plays a major role in reproduction, an in-depth proteomic analysis of pig seminal plasma (SP) revealed that AKR1B1 is positively related to in vivo fertility outcomes (Pérez-Patiño et al, 2018)

Objectives

Methods

Results

Conclusion