Insulin and Nutritional Insufficiency Regulate Growth Hormone Receptor and Growth Hormone Responsiveness of Liver and Adipose Tissue in Lactating Dairy Cows PDF Download
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Author: Robert Paul Rhoads Publisher: ISBN: 9780496620098 Category : Languages : en Pages : 193
Book Description
In transition dairy cows, plasma insulin-like growth factor (IGF)-I declines near parturition despite elevated growth hormone (GH). Furthermore, GH administration cannot restore plasma IGF-I suggesting impaired hepatic GH-dependent IGF-I production. In contrast, the metabolic effects of GH on adipose tissue are believed to persist. Objectives of this thesis were: (1) To determine the role of insulin in the regulation of hepatic IGF-I production during early lactation and (2) To examine the GH responsiveness of liver and adipose tissue during undernutrition. The first study showed that hepatic cyclophilin and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA abundance was regulated during the transition period, periods of hyperinsulinemia and poor nutrition. In the second study, a reduction in plasma insulin paralleled exactly the deteriorating energy balance during the periparturient period. To test the role of insulin, we performed hyperinsulinemic-euglycemic clamps in late pregnant and early lactating dairy cows. Hyperinsulinemia increased plasma IGF-I irrespective of physiological state. This effect was associated with increased abundance of hepatic IGF-I mRNA. Furthermore, insulin increased hepatic GH receptor (GHR) abundance by stimulating GHR1A mRNA. Finally, insulin increased the abundance of the GHR in adipose tissue without altering total GHR mRNA indicating that the regulation of GHR synthesis differs between tissues. In the third study, late lactating dairy cows were treated for 4 days with saline or bovine somatotropin (bST) when well-fed (120% of total requirements) or underfed (30% of maintenance requirements). Underfed cows approximated early lactating cows in their degree of negative energy balance, elevations in plasma GH and reductions in plasma IGF-I and insulin. Underfed cows had decreased GHR abundance in liver and adipose tissue without a reduction in GHR mRNA. In well-fed cows, both tissues responded in a robust manner to GH (parameters were plasma IGF-I concentration for liver, epinephrine-stimulated plasma NEFA for adipose tissue, and IGF-I mRNA for both tissues). In underfed cows, these responses were reduced in liver and lost completely in adipose tissue. In conclusion, an adequate level of insulin is needed for hepatic IGF-I production. Lower GHR abundance cannot completely account for reduced GH responsiveness of liver and adipose tissue in underfed cows.
Author: Robert Paul Rhoads Publisher: ISBN: 9780496620098 Category : Languages : en Pages : 193
Book Description
In transition dairy cows, plasma insulin-like growth factor (IGF)-I declines near parturition despite elevated growth hormone (GH). Furthermore, GH administration cannot restore plasma IGF-I suggesting impaired hepatic GH-dependent IGF-I production. In contrast, the metabolic effects of GH on adipose tissue are believed to persist. Objectives of this thesis were: (1) To determine the role of insulin in the regulation of hepatic IGF-I production during early lactation and (2) To examine the GH responsiveness of liver and adipose tissue during undernutrition. The first study showed that hepatic cyclophilin and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA abundance was regulated during the transition period, periods of hyperinsulinemia and poor nutrition. In the second study, a reduction in plasma insulin paralleled exactly the deteriorating energy balance during the periparturient period. To test the role of insulin, we performed hyperinsulinemic-euglycemic clamps in late pregnant and early lactating dairy cows. Hyperinsulinemia increased plasma IGF-I irrespective of physiological state. This effect was associated with increased abundance of hepatic IGF-I mRNA. Furthermore, insulin increased hepatic GH receptor (GHR) abundance by stimulating GHR1A mRNA. Finally, insulin increased the abundance of the GHR in adipose tissue without altering total GHR mRNA indicating that the regulation of GHR synthesis differs between tissues. In the third study, late lactating dairy cows were treated for 4 days with saline or bovine somatotropin (bST) when well-fed (120% of total requirements) or underfed (30% of maintenance requirements). Underfed cows approximated early lactating cows in their degree of negative energy balance, elevations in plasma GH and reductions in plasma IGF-I and insulin. Underfed cows had decreased GHR abundance in liver and adipose tissue without a reduction in GHR mRNA. In well-fed cows, both tissues responded in a robust manner to GH (parameters were plasma IGF-I concentration for liver, epinephrine-stimulated plasma NEFA for adipose tissue, and IGF-I mRNA for both tissues). In underfed cows, these responses were reduced in liver and lost completely in adipose tissue. In conclusion, an adequate level of insulin is needed for hepatic IGF-I production. Lower GHR abundance cannot completely account for reduced GH responsiveness of liver and adipose tissue in underfed cows.
Author: Michelle Lynn Bode-Rhoads Publisher: ISBN: Category : Somatomedin Languages : en Pages : 376
Book Description
The components of the growth hormone (GH)/insulin-like growth factor (IGF) system play critical reproductive and metabolic roles in dairy cattle. In liver, GH receptor (GHR) and IGF-I are dynamically regulated by lactation and energy balance. Less is known about the regulation of GHR and IGF-I mRNA in reproductive tissues. The objective of these studies was to measure the expression of total GHR (tGHR), IGF-I and IGF binding protein (IGFBP) 2 mRNA in reproductive tissues during several stages of lactation and around the time of artificial insemination. Changes in gene expression were then evaluated for potential effects on fertility. The expression of tGHR, IGF-I and IGFBP-2 was measured in uterine, luteal, follicular and hepatic tissue three times during the early postpartum period. Expression of tGHR and IGFBP-2 mRNA in the reproductive tissues did not change during early lactation. Luteal and follicular expression of IGF-I changed in an inverse manner from the second sample collection to the third (luteal expression decreased and follicular expression increased). Further research is needed to elucidate the implications these changes have for fertility in dairy cattle. The expression of tGHR, IGF-I and IGFBP-2 was also measured in uterine and hepatic tissue at several stages of lactation around the time of insemination. Uterine tGHR mRNA, uterine IGF-I mRNA and plasma IGF-I concentrations increased at estrus. The timing of these changes suggests that uterine IGF-I does not directly affect early embryonic development, but may enhance the uterine environment for early embryonic development. The cows that became pregnant had higher liver tGHR and IGFBP-2 mRNA concentrations. The cows that became pregnant may have been metabolically distinct from the cows that did not become pregnant, resulting in different levels of hepatic gene expression and providing a reproductive advantage.
Author: Pierre Cronjé Publisher: CABI ISBN: 9780851997124 Category : Electronic books Languages : en Pages : 492
Book Description
The International Symposium on Ruminant Physiology (ISRP) is the premier forum for presentation and discussion of advances in knowledge of the physiology of ruminant animals. This book brings together edited versions of the keynote review papers presented at the symposium.
Author: Behnam Saremi Publisher: Cuvillier Verlag ISBN: 3736944292 Category : Science Languages : en Pages : 170
Book Description
With the onset of lactation, dairy cows have to mobilize body reserves, mainly body fat, to cover the output of energy via milk. The homeorhetic metabolic adaptation to the needs of milk production is accomplished through the orchestrated action of hormones. In contrast to the “classical hormones” that knowingly control parturition, lactation and metabolism, the role and importance of messenger molecules originating from body fat (adipokines), of their receptors and also of nuclear receptors as key regulators of gene expression was only scarcely investigated in dairy cows. In particular, data on body fat were largely limited to subcutaneous (s.c.) fat from one location easily accessible via biopsy, whereas potentially heterogeneous reactions between different s.c. depots and also in different visceral (v.c.) fat were not yet comprehensively addressed. The aim of this dissertation was to characterize the mRNA expression of several adipokines and related factors that are involved in insulin sensitivity (IS) and in inflammation during the transition from pregnancy to lactation and during the subsequent lactation. In addition, dietary supplementation with either CLA vs. a control fat (supplementation period day 1 to day 105 or 182 of lactation) was tested for potential effects on the target mRNAs. The tissue in focus was adipose tissue (AT) with its different locations. Initially, suitable reference genes were identified as a methodological prerequisite for the studies. Using tissue samples obtained from both primiparous and pluriparous cows from animal experiments within a project cooperation, the time course of the mRNA abundance of 12 different target genes and 7 reference genes was characterized in s.c. fat and in liver from pluriparous cows and in three different s.c. and in three v.c. fat depots, in liver, skeletal muscle, and in mammary gland from primiparous cows. Two acute phase proteins, i.e. haptoglobin (Hp) and serum amyloid A3 (SAA3), were newly established as adipokines in cattle; both mRNAs yielded similar time course patterns with a peripartal peak. Treatment with CLA was mostly not affecting Hp and SAA3 mRNA expression; the decrease observed for Hp and SAA3 mRNA in 2 out of 6 fat depots tested indicates local anti-inflammatory effects of CLA. No CLA effect was observed for the Hp serum concentrations and for hepatic Hp mRNA. Indeed, we confirmed liver as the main site of Hp production. For the prioritization of nutrient uptake towards the mammary gland, IS in other peripheral organs is knowingly reduced. The mRNA expression of the target genes related with IS, i.e. adiponectin (ADIPOQ), leptin (LEP), their receptors (LEPR, LEPRB, ADIPOR1, ADIPOR2), of two nuclear receptor isoforms (PPARγ, PPARγ2) and of two pro-inflammatory cytokines (TNF-α, IL-6) in s.c.AT and in liver from pluriparous cows was mostly decreased from day 21 prepartum to day 21 postpartum in s.c.AT except TNF-α; in liver increases were observed for LEPRB and ADIPOR2, and decreasing abundance for all other hepatic target mRNAs except TNF-α and ADIPOR1 which remained constant in this time. In later lactation, prepartum values were reached again and were largely maintained until wk 36. The groups treated with CLA or control fat differed detachedly in mRNA abundance of PPARγ, LEPRB and TNF-α in liver and of PPARγ2 in s.c.AT; cows of the CLA group had also higher insulin concentrations and reduced systemic IS persisting after the end of CLA supplementation. In primiparous cows, changes with the duration of lactation were observed for most of the target mRNAs (except LEP) but not in all tissues investigated; time course and direction of change were partly divergent between the different tissues. CLA treatment for 105 days decreased the mRNA abundance of ADIPOQ, ADIPOR2, PPARγ2 and TNF-α in v.c.AT and in the mammary gland. The results of these studies provide a longitudinal characterization of the expression of genes that are particularly related to AT as a heterogeneous functional regulator in lactating dairy cows. The known effect of CLA inhibiting milk fat synthesis might at least be partly explained by the down-regulation of PPARγ2 in the mammary gland observed herein. The importance of the CLA induced effects on IS for animal health can presently not be finally assessed due to lack of validated reference values for IS in high yielding dairy cows.
Author: Isabel Varela-Nieto Publisher: Springer Science & Business Media ISBN: 0387262741 Category : Medical Languages : en Pages : 420
Book Description
Insulin-like growth factor (IGF)-I is a widely expressed growth factor with diverse effects on many tissues throughout development and in adult life. The purpose of this work is to provide detailed and updated information on the role of the growth hormone (GH)-IGF axis in fetal and postnatal development, as well as its physiological functions and implications in pathology.
Author: Robert Paul Rhoads
Author: Robert Paul Rhoads
Author: Robert Paul Rhoads
Author: Michelle Lynn Bode-Rhoads
Author: Ingrid Gause
Author: Mark A. McGuire
Author: Pierre Cronjé
Author: Behnam Saremi
Author: Isabel Varela-Nieto
Author: Jin Wook Kim
Author: William John Enright