Effects of beta-carotene and vitamin A on progesterone production by cultured bovine granulosa cells

The Efficacy of β-Carotene in Cow Reproduction: A Review

β-carotene supplementation improves the reproductive performance of cattle. However, the research results on this topic have been inconsistent, and no clear conclusion has been reached. In previous reviews of this topic, the functional mechanism of β-carotene in reproduction remained unclear, but subsequent studies have shown that the antioxidant effects of β-carotene protect enzymes involved in ovarian sex steroid hormone production from the effects of oxygen radicals. This role consequently affects normal ovarian follicle dynamics, maintenance of luteal function, and the estrous cycle, and indirectly improves reproductive performance by preventing perinatal diseases and facilitating recovery from these diseases. Several factors must be considered in feeding management to determine whether β-carotene supplementation is effective for improving reproductive performance in cows. The same is true when the animal consumes a large amount of the antioxidant β-carotene due to lactation, aging, or season. Therefore, it is important to consider the balance between the supply and consumption of β-carotene and evaluate whether β-carotene supplementation has an effect on reproductive performance in cows.

High β ‐ carotene concentration in plasma enhances cyclic progesterone production in nonpregnant Japanese Black cows

β-Carotene is an essential nutrient in cattle reproduction. The objective of this study was to evaluate the effect of β-carotene supplementation on ovarian activities throughout the estrous cycle in nonpregnant Japanese Black cows. The estrous cycles of eight nonpregnant Japanese Black cows were synchronized using a double synch protocol, and the cows were divided into two groups. The cows in the β-carotene (BC) group received supplementation with 1000 mg/day β-carotene for 46 days including the synchronization period. The cows in the control (C) group did not receive β-carotene supplementation. The results showed that β-carotene supplementation at 1000 mg/day was sufficient to maintain a high plasma β-carotene concentration and increase the plasma retinol concentration and that β-carotene supplementation had no significant effects on the dominant follicle diameter, total number of estrus behaviors, or length of the estrous cycle. In contrast, the areas under the P₄ concentration curves in the BC group were higher than those obtained for the C group. In conclusion, a high plasma β-carotene concentration in Japanese Black cows promotes P₄ production in the luteal phase of the estrous cycle and total P₄ production throughout the estrous cycle without changing the length of the estrous cycle.

The antioxidant beta-carotene prevents covalent cross-linking between cholesterol side-chain cleavage cytochrome P450 and its electron donor, adrenodoxin, in bovine luteal cells

Steroid hormones are an important class of hormones synthesized from cholesterol by a number of endocrine organs; including ovaries, placenta, testes and adrenal glands. The first and rate-limiting step in steroidogenesis is the cleavage of the side-chain of the cholesterol molecule, catalysed by a cytochrome P450 enzyme, cholesterol side-chain cleavage enzyme. This enzyme, as with other P450 enzymes, produces oxygen radicals. Oxygen free radicals can cause deleterious effects such as cross-linking and aggregation of proteins. Cells can protect against such damage with the use of antioxidants. The corpus luteum, or 'yellow body', of the ovary is very steroidogenic and is exceedingly rich in the yellow antioxidant, beta-carotene. The corpus luteum produces the steroid hormone progesterone that is needed to support pregnancy. Here we have shown that by depleting, or conversely repleting, luteal cells of their beta-carotene content in vitro that P450 side-chain cleavage enzyme became covalently non-disulfide cross-linked to its electron donor, adrenodoxin, and hence inactivated. Bovine luteal cells were cultured in 10% fetal calf serum with or without additional treatments for up to 72 h. Under control conditions the cellular levels of beta-carotene and alpha-tocopherol fell by 50% within 24 h and remained low. P450 side-chain cleavage enzyme become non-disulfide covalently cross-linked to its electron donor, adrenodoxin, as determined by Western immunoblotting (N = 18). Aminoglutethamide inhibited this cross-linking. The addition of beta-carotene at levels found in bovine serum, but not alpha-tocopherol or ascorbic acid, inhibited the degree of the cross-linking.(ABSTRACT TRUNCATED AT 250 WORDS)