Concomitant changes in progesterone catabolic enzymes, cytochrome P450 2C and 3A, with plasma insulin concentrations in ewes supplemented with sodium acetate or sodium propionate

Abstract

Progesterone is essential for maintaining pregnancy, and several authors have suggested that low peripheral concentrations of progesterone may be responsible for high rates of embryonic loss. The primary organ involved in the catabolism of progesterone is the liver, and cytochrome P450 2C and 3A sub-families account for a large proportion of this catabolism. Elucidating a mechanism to decrease progesterone catabolism, thereby increasing embryonic and uterine exposure to progesterone, seems a logical approach to ameliorate high rates of embryonic loss. The objectives of the current experiment were to determine the pattern of insulin secretion after supplementing feed with either sodium acetate or sodium propionate and to determine any association between the differential patterns of insulin secretion with the hepatic activity of cytochrome P450 2C and 3A and progesterone clearance. Sixteen ovariectomized ewes were fed 3 kg/day for 10 days of a diet consisting of 50% corn silage, 38% triticale haylage, 12% soybean meal and 600 ml of 3.5 M sodium acetate (energy control; n 5 8) or 2.0 M sodium propionate (gluconeogenic substrate; n 5 8). Equal portions of the ration (1 kg as-fed basis along with 200 ml of 3.5 M sodium acetate or 2.0 M sodium propionate) were offered three times daily at 0600, 1400 and 2200 h. Concentrations of insulin in plasma were determined immediately before feeding and at 15, 30, 60, 90, 120, 180, 240 and 300 min after feeding. Progesterone clearance from peripheral circulation (ng/ml per min) was measured by giving a 5 mg injection of progesterone into the left jugular vein and collecting blood via the right jugular vein at 0, 2, 4, 6, 8, 10, 15, 20 and 30 min afterwards. Liver biopsies were taken 1 h after feeding to determine cytochrome P450 2C and 3A activities. Insulin concentrations in ewes supplemented with sodium propionate were elevated at 15, 30 and 60 min after feeding compared to the sodium acetate group. Cytochrome P450 2C and 3A activities were decreased 1 h after feeding in the sodium propionate-treated ewes relative to sodium acetate. Insulin appears to down-regulate cytochrome P450 activity, which could be used to decrease the catabolism of progesterone during early gestation, thereby increasing peripheral concentrations of progesterone and, consequently, embryonic exposure to progesterone.

Diet-induced alterations in hepatic progesterone (P4) catabolic enzyme activity and P4 clearance rate in lactating dairy cows

“…5, 5, 6, 8, and 10 h post-feeding. P 4 concentrations; t is the time) as described by Lemley et al (2008a). The fractional rate constants of P 4 decay (k) were then used to calculate the half-life of P 4 using the equation: t 1/2 Zln(2)/k.…”

“…Insulin concentrations over the 10-h sampling period were determined using RIA (Lemley et al 2008a) with a sensitivity of 0 . 05 nM and intra-and inter-assay CV of 4 .…”

“…1 g/biopsy) were collected using a biopsy needle machined at the West Virginia University Physics Department (Morgantown, WV, USA) following the specifications of Swanson et al (2000). CYP2C and CYP3A activities were assessed on w200 mg of fresh liver sample following our previously published protocol (Lemley et al 2008a). Briefly, liver samples were submerged in phosphate buffer and homogenized using a Dounce homogenizer.…”

“…Similar to the in vitro data, Smith et al (2006) found a decrease in P 4 clearance in anestrous ewes orally gavaged with sodium propionate (gluconeogenic substrate) versus sodium acetate (energy control group). In a follow-up experiment, Lemley et al (2008a) found approximately a 50% decrease in both hepatic CYP2C and CYP3A activities at 1 h post-feeding in ovariectomized ewes supplemented with sodium propionate versus sodium acetate.…”

Reutilização de implantes de progesterona: do teste in vitro às taxas de concepção na IATF.

“…A biotransformação dos hormônios esteróides ocorre por hidroxilação no citocromo P450, mais especificamente as subfamílias CYP3A e CYP2C (YOU, 2004), e o processo está correlacionado negativamente às concentrações plasmáticas ou teciduais de insulina (BARNETT et al, 1990;SHIMOJO et al, 1993) Lemley et al, demonstraram que um aumento na concentração de insulina nos hepatócitos diminuiu a atividade enzímica, e uma queda de 50% nesta atividade ocorreu em experimento com ovelhas ovariectomizadas (LEMLEY et al, 2008). Dietas suplementadas com milho elevaram as concentrações de insulina em vacas leiteiras e a atividade da CYP3A e CYP2C foi diminuída pelo aumento da secreção de insulina (LEMLEY et al, 2010).…”