Maternal IGFBP-4 Concentration Is Lower in Pregnant Than in Non-Pregnant Dairy Heifers at Day 18 of Pregnancy
Presentation Number: SUN-0644
Date of Presentation: June 22nd, 2014
Marie Meyerholz*1, Kirsten Mense1, Matthias Linden2, Hendrike Knaack1, Elisa Wirthgen3, Andreas Hoeflich4, Michael Steufmehl5, Olivier Sandra6, Christoph Richard6, Martina Hoedemaker1 and Marion Piechotta1
1University of Veterinary Medicine, Hannover, 2Leibniz University Hannover, Hannover, 3Ligandis GbR, 4Leibniz Institute for Farm Animal Biology, Dummerstorf, 5University of Veterinary Medicine, 6INRA - Centre de Jouy-en-Josas, Jouy-en-Josas, France
The somatotropic axis plays an important role for embryonic growth and development. However, less is known about the effect of early pregnancy (embryo signaling) on the maternal GH-IGF-system. The aim was to investigate endocrine endpoints of the somatotropic axis in pregnant vs. non-pregnant dairy heifers until d18 of pregnancy. Blood samples of Holstein Friesian heifers (n=30) were taken on d0 (day of ovulation, defined by ultrasonography) and days 7, 14, 16 and 18 in repeated consecutive pregnant (p) and non-pregnant (np) periods. Additionally, liver biopsies were taken on d18. Heifers received artificial insemination or embryo transfer and pregnancy was verified either on d18 (P4 >2.0 and successful recovery of a conceptus [n=12]) or retrospectively on d42 (detection of embryonic heart beat [n=21]). The cows were defined as non-pregnant on d18 if P4 was <2.0 and no conceptus was recovered (n=29). Out of 62 periods, 38 were selected to build 19 pairs (np-p or p-np) for analysis by ANOVA as repeated measurements. Concentrations of progesterone, estrogens, GH, IGF-I and IGF-II were measured by the use of validated immunoassays. The blood concentration of IGFBP-2 to -4 at d0, d14 and d18 was determined using a quantitative western ligand blot. Hepatic mRNA expression of GHR, IGF-I, IGF-II, IGFBP-2 to -4 was detected by qPCR. At d18 the IGF-I [ng/ml] serum concentration tended to be lower in pregnant compared to non-pregnant heifers (284.9±82.6 vs. 321.8±81.6; P=0.082). In both groups IGF-I decreased from d0 to d16 (P<0.001) and increased towards d18 in pregnant (P<0.05) and in non-pregnant (P<0.001) heifers. The IGF-II [ng/ml] concentrations between pregnant and non-pregnant were comparable and increased in both groups between d0 and d14 (P<0.05). At d18, the IGFBP-4 [µg/ml] blood concentration was lower in pregnant (0.44±0.26) compared to non-pregnant heifers (0.75±0.36) (P=0.012). In liver biopsies IGFBP-3 expression tended to be lower in pregnant compared to non-pregnant cows (P<0.1). The reduced maternal serum IGFBP-4 may be due to enhanced proteolytic activity and as IGFBP-4 can inhibit IGF-I action, these data propose, that it may also lead to increased free IGF-I levels, potentially useful for local action at the cellular level e.g. in the endometrium of pregnant individuals.
Nothing to Disclose: MM, KM, ML, HK, EW, AH, MS, OS, CR, MH, MP