Form of Supplemental Selenium Affects the Expression of mRNA Transcripts Encoding Selenoproteins, and Proteins Regulating Cholesterol Uptake, in the Corpus Luteum of Grazing Beef Cows

Abstract

Selenium (Se)-deficient soils necessitate supplementation of this mineral to the diet of forage-grazing cattle. Functionally, Se is incorporated into selenoproteins, some of which function as important antioxidants. We have previously shown that the source of supplemental Se; inorganic (sodium selenite or sodium selenate; ISe), organic (selenomethionine or selenocysteine; OSe) or 1:1 mix of ISe and OSe (MIX), provided to Angus-cross cows affects concentrations of progesterone (P4) during the early luteal phase of the estrous cycle. In this study, we sought to investigate (1) the effect of form of Se on the expression of mRNA encoding selenoproteins in the corpus luteum (CL), and (2) whether this previously reported MIX-induced increase in P4 is the result of increased luteal expression of key steroidogenic transcripts. Following a Se depletion and repletion regimen, 3-year-old, non-lactating, Angus- cross cows were supplemented with either ISe as the industry standard, or MIX for at least 90 days, with the CL then retrieved on Day 7 post-estrus. Half of each CL was used for analysis of targeted mRNA transcripts and the remainder was dissociated for culture with select agonists. The expression of three selenoprotein transcripts and one selenoprotein P receptor was increased (p < 0.05), with an additional five transcripts tending to be increased (p < 0.10), in cows supplemented with MIX versus ISe. In cultures of luteal cells, hCG-induced increases in P4 (p < 0.05) were observed in CL obtained from ISe-supplemented cows. The abundance of steroidogenic transcripts in the CL was not affected by the form of Se, however, the abundance of mRNA encoding 2 key transcripts regulating cholesterol availability (Ldlr and Hsl) was increased (p < 0.05) in MIX-supplemented cows. Overall, the form of Se provided to cows is reported to affect the expression of mRNA encoding several selenoproteins in the CL, and that the form of Se-induced effects on luteal production of P4 appears to be the result of changes in cholesterol availability rather than a direct effect on the expression of steroidogenic enzymes within the CL.

Pituitary and liver selenoprotein transcriptome profiles of grazing steers and their sensitivity to the form of selenium in vitamin-mineral mixes

“…Consequently, we accept the hypothesis that the pituitary and hepatic selenoprotein mRNA content of steers raised on MIX versus ISe forms of supplemental Se, and consumed MIX versus ISe forms of s u p p l e m e n t a l S e , wh i l e u n d e r go i n g s u m m e r -l o n g consumption of toxic endophyte-infected tall fescue, differed. When these findings are considered with our recent report that the mRNA content of GPX6, selenoprotein P, selenoR, and selenoV is increased in the corpus luteum (another high metabolic activity tissue) of MIX versus ISe replacement beef heifers (Carr et al, 2022), it seems reasonable to conclude that supplementation of cattle with different forms of Se affects the expressed selenoprotein transcriptome.…”

Transcriptomic Changes in Response to Form of Selenium on the Interferon-Tau Signaling Mechanism in the Caruncular Tissue of Beef Heifers at Maternal Recognition of Pregnancy

“…Using an extensively reported model [10,28,29,42,43], we studied the effects of supplemental form of Se as ISe (the industry standard) or a 1:1 mixture of ISe to OSe (MIX) on grazing beef cows and heifers and observed significant effects on the CL [10] and endometrium [34], which laid the premise for the present study. This experiment had two specific objectives.…”

“…Real-time PCR (qPCR) was used to quantify the relative abundance of mRNA in CAR samples for identified genes that differed according to the RNA-Seq analysis and to characterize mRNA transcript abundance of selenoproteins and related receptors in CAR at MRP using a technique that is routinely used in our laboratory [10,34,43]. Approximately 1 µg of RNA from each sample was reverse-transcribed into cDNA using SuperScript IV VILO Master Mix with ezDNAse Enzyme (Invitrogen by Thermo Fisher Scientific, Vilnius, Lithuania).…”

“…The physiological relevance of Se was initially identified as a necessary structural component of glutathione peroxidases (GPX; [7]), a group of selenoproteins with antioxidant activities that catalyze harmful hydrogen peroxide (H 2 O 2 ) into water (H 2 O [8]). Presently, there are 25 selenoprotein genes identified in humans [8] and pigs [9], and 25 selenoproteins that we routinely investigate in cattle [10,11]. Many selenoproteins, including selenoprotein H (SELENOH [12]), selenoprotein K (SELENOK [13]), selenoprotein M (SELENOM [14]), selenoprotein P (SELENOP [15]), selenoprotein R (SELENOR [16]), and selenoprotein W (SELENOW [17]), have been identified or proposed to have antioxidant capabilities.…”

Selenium in Bodily Homeostasis: Hypothalamus, Hormones, and Highways of Communication

“…Selenium supplementation was also found to affect progesterone levels of cows and sheep across different phases of estrus [ 284 , 285 ] and gestation [ 286 , 287 ]. Further investigation into relevant mRNA transcript levels in the corpus luteum uncovered no change in transcripts involved in progesterone synthesis, but yielded an increase in transcripts ( Ldlr and Hsl ) involved in the regulation of cholesterol availability [ 288 ]. This might suggest that selenium-induced effects on progesterone production in the corpus luteum are consequences of changes in cholesterol availability, rather than directly influencing progesterone synthesis.…”