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Dzięgelewska-Sokołowska Ż, Majewska A, Szopa I, Gajewska M. Chemerin Stimulates the Secretory Activity of BME-UV1 Bovine Mammary Epithelial Cells. Int J Mol Sci 2024; 25:4147. [PMID: 38673732 PMCID: PMC11050135 DOI: 10.3390/ijms25084147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2024] [Revised: 04/03/2024] [Accepted: 04/08/2024] [Indexed: 04/28/2024] Open
Abstract
Adipose tissue is an active endocrine gland, synthesizing and secreting multiple signaling molecules termed adipokines. Following the detection of adipokines and their receptors in the mammary tissue of various species, it is indicated that adipokines play a role in the development of the mammary gland. The aim of the present study was to determine the concentration-dependent influence of three adipokines, leptin, adiponectin, and chemerin, on the viability, apoptosis, and secretory activity of BME-UV1 bovine mammary epithelial cells. The study confirmed that BME-UV1 cells contain the leptin receptor (Ob-R) protein, and express transcripts of adiponectin (ADIPOR1 and ADIPOR2) and chemerin (CMLKR1 and GPR1) receptors. Regardless of the administered dose, none of the three tested adipokines had an effect on the viability of BME-UV1 cells, and the number of apoptotic cells remained unchanged. However, chemerin (100 ng/mL) stimulated BME-UV1 cells to synthesize and secrete αS1-casein, the major protein component of milk. These results indicate that chemerin may be a potent regulator of the bovine mammary epithelial cells' functional differentiation, contributing, along with the major systemic hormones and local growth factors, to the development of the bovine mammary gland.
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Affiliation(s)
| | | | | | - Małgorzata Gajewska
- Department of Physiological Sciences, Institute of Veterinary Medicine, Warsaw University of Life Sciences (SGGW), Nowoursynowska 159b, 02-776 Warsaw, Poland; (Ż.D.-S.); (A.M.); (I.S.)
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Luzardo-Ocampo I, Dena-Beltrán JL, Ruiz-Herrera X, Ocampo-Ruiz AL, Martínez de la Escalera G, Clapp C, Macotela Y. Obesity-derived alterations in the lactating mammary gland: Focus on prolactin. Mol Cell Endocrinol 2023; 559:111810. [PMID: 36374835 DOI: 10.1016/j.mce.2022.111810] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Revised: 10/18/2022] [Accepted: 10/21/2022] [Indexed: 11/07/2022]
Abstract
Obesity is a modern pandemic with negative consequences in women's reproductive health. Women with overweight and obesity can develop mammary gland alterations that unable exclusive breastfeeding. Obesity associates with a disturbed lactating mammary gland endocrine environment including a decreased action of the hormone prolactin (PRL), the master regulator of lactation. The PRL receptor and the action of PRL are reduced in the mammary gland of lactating rodents fed an obesogenic diet and are contributing factors to impaired lactation in obesity. Also, treatment with PRL improves milk yield in women with lactation insufficiency. This review focuses on the impact of diet-induced obesity in the lactating mammary gland and how obesity impairs the lactogenic action of PRL. Although obesity alters lactation performance in humans and rodents, the responsible mechanisms have been mainly addressed in rodents.
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Affiliation(s)
- Ivan Luzardo-Ocampo
- Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Campus UNAM-Juriquilla, 76230, Querétaro, Mexico
| | - José L Dena-Beltrán
- Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Campus UNAM-Juriquilla, 76230, Querétaro, Mexico
| | - Xarubet Ruiz-Herrera
- Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Campus UNAM-Juriquilla, 76230, Querétaro, Mexico
| | - Ana Luisa Ocampo-Ruiz
- Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Campus UNAM-Juriquilla, 76230, Querétaro, Mexico
| | - Gonzalo Martínez de la Escalera
- Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Campus UNAM-Juriquilla, 76230, Querétaro, Mexico
| | - Carmen Clapp
- Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Campus UNAM-Juriquilla, 76230, Querétaro, Mexico
| | - Yazmín Macotela
- Instituto de Neurobiología, Universidad Nacional Autónoma de México (UNAM), Campus UNAM-Juriquilla, 76230, Querétaro, Mexico.
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Ruiz TFR, Taboga SR, Leonel ECR. Molecular mechanisms of mammary gland remodeling: A review of the homeostatic versus bisphenol a disrupted microenvironment. Reprod Toxicol 2021; 105:1-16. [PMID: 34343637 DOI: 10.1016/j.reprotox.2021.07.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Revised: 07/26/2021] [Accepted: 07/29/2021] [Indexed: 12/30/2022]
Abstract
Mammary gland (MG) undergoes critical points of structural changes throughout a woman's life. During the perinatal and pubertal stages, MG develops through growth and differentiation to establish a pre-mature feature. If pregnancy and lactation occur, the epithelial compartment branches and differentiates to create a specialized structure for milk secretion and nurturing of the newborn. However, the ultimate MG modification consists of a regression process aiming to reestablish the smaller and less energy demanding structure until another production cycle happens. The unraveling of these fascinating physiologic cycles has helped the scientific community elucidate aspects of molecular regulation of proliferative and apoptotic events and remodeling of the stromal compartment. However, greater understanding of the hormonal pathways involved in MG developmental stages led to concern that endocrine disruptors such as bisphenol A (BPA), may influence these specific development/involution stages, called "windows of susceptibility". Since it is used in the manufacture of polycarbonate plastics and epoxy resins, BPA is a ubiquitous chemical present in human everyday life, exerting an estrogenic effect. Thus, descriptions of its deleterious effects on the MG, especially in terms of serum hormone concentrations, hormonal receptor expression, molecular pathways, and epigenetic alterations, have been widely published. Therefore, allied to a didactic description of the main physiological mechanisms involved in different critical points of MG development, the current review provides a summary of key mechanisms by which the endocrine disruptor BPA impacts MG homeostasis at different windows of susceptibility, causing short- and long-term effects.
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Affiliation(s)
- Thalles Fernando Rocha Ruiz
- São Paulo State University (Unesp), Department of Biology, Institute of Biosciences, Humanities and Exact Sciences, São José Do Rio Preto, Brazil.
| | - Sebastião Roberto Taboga
- São Paulo State University (Unesp), Department of Biology, Institute of Biosciences, Humanities and Exact Sciences, São José Do Rio Preto, Brazil.
| | - Ellen Cristina Rivas Leonel
- São Paulo State University (Unesp), Department of Biology, Institute of Biosciences, Humanities and Exact Sciences, São José Do Rio Preto, Brazil; Federal University of Goiás (UFG), Department of Histology, Embryology and Cell Biology, Institute of Biological Sciences, Goiânia, Brazil.
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Farmer C, Palin MF. Hyperprolactinemia using domperidone in prepubertal gilts: Effects on hormonal status, mammary development and mammary and pituitary gene expression. Domest Anim Endocrinol 2021; 76:106630. [PMID: 33979716 DOI: 10.1016/j.domaniend.2021.106630] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 03/30/2021] [Accepted: 04/04/2021] [Indexed: 01/24/2023]
Abstract
Objectives of this experiment were to determine if the domperidone protocol previously used for gestating gilts can also lead to hyperprolactinemia in growing gilts, and to assess the effects of such a protocol on hormonal status, mammary development and gene expression in mammary and pituitary tissue of gilts at puberty. The impact on future lactation performance was also determined. At 75 ± 3 kg body weight (BW), gilts were divided between: 1) controls (CTL), receiving daily intramuscular (IM) injections of canola oil (1.1 mL) for 29 d (n = 41), and 2) treated (DOMP), receiving daily IM injections with 0.5 mg/kg BW of the dopamine receptor antagonist domperidone for 29 d (n = 40). In addition to that daily injection, treated gilts also received twice daily IM injections with 0.5 mg/kg BW of domperidone over the first 3 d of treatment. Fifteen gilts per treatment were sacrificed at 210 ± 5 d of age to collect mammary glands (for compositional analysis and gene expression) and the anterior pituitary (for gene expression). Remaining gilts were bred and allowed to farrow. Blood was sampled at the onset of treatment and on days 14 and 30. Gilts that farrowed were also blood sampled on days 3 and 20 of lactation. Blood was assayed for prolactin (PRL), leptin, insulin-like growth factor 1 (IGF-1), urea, free fatty acids and glucose. Concentrations of PRL increased after 14 d and 30 d of treatment (P < 0.01) and were lesser on day 3 of lactation in DOMP than CTL gilts (P < 0.01). At puberty, there were tendencies (P < 0.10) for total parenchymal protein and DNA to be greater in DOMP than CTL gilts. Treatment did not affect mRNA abundance of PRL or the long form of the PRL receptor genes in the pituitary gland at puberty but expression level of the dopamine receptor D2 and PRL genes was much lower in pubertal than late-pregnant gilts (P < 0.001). Furthermore, many genes related with PRL had a much greater expression level in late pregnancy than at puberty. On day 20 of lactation, CTL sows had greater concentrations of urea than DOMP sows (P < 0.01). The growth rate of litters was not affected by treatment nor was milk composition (P > 0.10). Even though PRL concentrations were increased with treatment, the absence of effect on mammary development was either due to timing relative to developmental stage, whereby treatment was initiated when gilts were too young, or was because all PRL receptors may have been saturated thereby preventing biological action of additional PRL.
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Affiliation(s)
- C Farmer
- Agriculture and Agri-Food Canada, Sherbrooke R & D Centre, Sherbrooke, QC, J1M 0C8, Canada.
| | - M F Palin
- Agriculture and Agri-Food Canada, Sherbrooke R & D Centre, Sherbrooke, QC, J1M 0C8, Canada
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Duarte CRA, Farmer C, Palin MF. Body condition of late pregnant gilts affects the expression of selected adipokines and their receptors in mammary fat and backfat tissues. J Anim Sci 2019; 97:220-230. [PMID: 30321363 DOI: 10.1093/jas/sky391] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Accepted: 10/11/2018] [Indexed: 12/26/2022] Open
Abstract
The impact of body condition in late gestating gilts on gene expression of selected adipokines and their receptors in backfat and mammary fat tissues was studied. The presence of associations between mammary gland composition variables and the mRNA abundance of selected genes and serum concentrations of adiponectin and leptin was also investigated. A total of 45 gilts were selected at mating based on their backfat depth and were allocated to three groups: (1) low backfat (LBF; 12-15 mm; n = 14), (2) medium backfat (MBF; 17-19 mm; n = 15), and (3) high backfat (HBF; 22-26 mm; n = 16). Gilts were fed different amounts of a conventional diet to maintain differences in backfat depth throughout the gestation period. Blood samples were collected at day 109 of gestation to measure adiponectin and leptin serum concentrations. Gilts were slaughtered on day 110 of gestation, and mammary glands were collected to determine mammary composition. Mammary fat and backfat tissues were also sampled to measure the mRNA abundance of selected genes. In mammary fat tissue, there was an effect of body condition on the prolactin (PRL; P = 0.01), adiponutrin (PNPLA3; P < 0.10), and prolactin receptor long form (PRLR-LF; P < 0.10) genes. There was a greater PRL mRNA abundance in mammary fat tissue from HBF than LBF or MBF gilts (P < 0.05). The PNPLA3 mRNA abundance was lower in HBF than in MBF gilts (P < 0.05), and that of PRLR-LF was lower in LBF than in HBF gilts (P < 0.05). In backfat, body condition affected the mRNA abundance of leptin (P < 0.05) and PNPLA3 (P < 0.01), with the greatest expression levels being observed in HBF gilts for both genes. Association analyses suggest a detrimental effect of high circulating leptin concentrations on gilts mammary development, as reflected by the negative correlations between serum leptin and protein percent (r = -0.66, P < 0.01), and concentrations of DNA (r = -0.62, P < 0.01) and RNA (r = -0.60, P < 0.01) in mammary parenchyma. Current results show that body condition of gilts at the end of gestation can affect the expression of adipokines in mammary fat and backfat tissues, with a different regulation of transcript abundance being observed in these two fat depots. Results also suggest that circulating leptin is strongly associated with mammary gland composition of late pregnant gilts, whereas locally synthesized leptin from mammary fat tissue is not.
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Affiliation(s)
- Cristiane R A Duarte
- Faculdade de Ciências Agrárias, Biológicas e da Saúde, Universidade do Estado de Mato Grosso, Tangará da Serra, MT, Brazil
| | - Chantal Farmer
- Agriculture and Agri-Food Canada, Sherbrooke R & D Centre, Sherbrooke, QC , Canada
| | - Marie-France Palin
- Agriculture and Agri-Food Canada, Sherbrooke R & D Centre, Sherbrooke, QC , Canada
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Sciascia QL, van der Linden DS, Sales FA, Wards NJ, Blair HT, Pacheco D, Oliver MH, McCoard SA. Parenteral administration of l-arginine to twin-bearing Romney ewes during late pregnancy is associated with reduced milk somatic cell count during early lactation. J Dairy Sci 2019; 102:3071-3081. [PMID: 30712927 DOI: 10.3168/jds.2018-15433] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Accepted: 11/30/2018] [Indexed: 11/19/2022]
Abstract
Maternal milk is the primary source of nutrition for suckling mammals, and its yield and composition are important determinants of survival during the early neonatal period. The objective of this study was to examine whether parenteral administration of l-Arg to twin-bearing ewes, during mid to late pregnancy, influenced prepartum maternal mammary gland development and subsequent lactation performance in the early postpartum period (14 d). At 80 d of pregnancy, multiparous Romney ewes were housed indoors in group pens, split into 2 cohorts, and fed a lucerne-based pellet diet, formulated to meet 100% of National Research Council-recommended requirements for twin-bearing pregnant ewes, once a day. Cohort 1 was administered l-Arg (72.7 mg/kg of live weight via i.v, 3 times a day) from d 100 of pregnancy until d 140. At d 140, ewes were euthanized and maternal mammary tissues were collected for analysis of the biochemical indices total DNA, RNA, protein, protein synthetic efficiency (protein:RNA), cell size (protein:DNA), transcriptional efficiency (RNA:DNA), and the abundance of mammalian target of rapamycin (mTOR) and mTORSer2448 protein. Cohort 2 was administered an identical l-Arg regimen as cohort 1, but from d 100 until parturition. Milk was collected over a 14-d period (d 1, 4, 7, 10, and 14) to assess milk yield and composition. In cohort 1, total mammary DNA (cell number) tended to be higher in l-Arg ewes, with no change in total mammary RNA or protein content, biochemical indices of protein synthetic efficiency, cell size or transcriptional efficiency, or mTOR protein abundance or phosphorylation. In cohort 2, milk composition analysis from l-Arg ewes showed lower (d 7-14) milk somatic cell counts, greater crude protein percentage from d 7 to 10 but lower at d 14, and altered absolute concentrations of some free AA (d 7 and 14) compared with controls. We propose that parenteral administration of l-Arg during late pregnancy is associated with increased mammary gland cellular content and decreased somatic cell counts during early lactation.
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Affiliation(s)
- Quentin L Sciascia
- AgResearch Grasslands, Palmerston North 4442, New Zealand; Gravida, National Centre for Growth and Development, University of Auckland, Auckland 1023, New Zealand
| | - Danitsja S van der Linden
- AgResearch Grasslands, Palmerston North 4442, New Zealand; Gravida, National Centre for Growth and Development, University of Auckland, Auckland 1023, New Zealand
| | - Francisco A Sales
- AgResearch Grasslands, Palmerston North 4442, New Zealand; Gravida, National Centre for Growth and Development, University of Auckland, Auckland 1023, New Zealand
| | - Nina J Wards
- AgResearch Grasslands, Palmerston North 4442, New Zealand
| | - Hugh T Blair
- Gravida, National Centre for Growth and Development, University of Auckland, Auckland 1023, New Zealand; International Sheep Research Centre, Massey University, Palmerston North 4442, New Zealand
| | - David Pacheco
- AgResearch Grasslands, Palmerston North 4442, New Zealand
| | - Mark H Oliver
- Gravida, National Centre for Growth and Development, University of Auckland, Auckland 1023, New Zealand; Ngapouri Research Farm, Liggins Institute, University of Auckland, Auckland 3083, New Zealand
| | - Susan A McCoard
- AgResearch Grasslands, Palmerston North 4442, New Zealand; Gravida, National Centre for Growth and Development, University of Auckland, Auckland 1023, New Zealand.
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Palin MF, Farmer C, Duarte CRA. TRIENNIAL LACTATION SYMPOSIUM/BOLFA: Adipokines affect mammary growth and function in farm animals. J Anim Sci 2018; 95:5689-5700. [PMID: 29293788 DOI: 10.2527/jas2017.1777] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The essential role of mammary fat pads in mammary growth and morphogenesis was the first indication that biologically active molecules, secreted from adipocytes or other stromal cells, could regulate endocrine cues for growth and function of the mammary gland. The presence of leptin and adiponectin receptors in mammary tissues suggested that locally produced or circulating adipokines could affect mammary growth and function. Herein, we present the current knowledge on the role of adipokines in mammary cell proliferation and differentiation and in lactogenesis and galactopoiesis in farm animals. We also address the role of milk adipokines in the neonate. Accumulating evidence suggests that adipokines could act as metabolic sensors, regulating mammary growth and function in periods of metabolic adaptations such as late pregnancy and early lactation. Indeed, different experiments reported that adiponectin and leptin expression varies according to physiological stages and nutritional status of the animal. The current review also demonstrates that adipokines, such as leptin and adiponectin, are important regulators of the action of lactogenic hormones in the mammary gland. Findings also suggest important roles for adipokines in growth and intestinal maturation of the neonate.
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Odle AK, Allensworth-James M, Haney A, Akhter N, Syed M, Childs GV. Adipocyte Versus Somatotrope Leptin: Regulation of Metabolic Functions in the Mouse. Endocrinology 2016; 157:1443-56. [PMID: 26859333 PMCID: PMC4816722 DOI: 10.1210/en.2015-1811] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Leptin regulates food intake and energy expenditure (EE) and is produced in adipocytes, the pituitary, and several other tissues. Animals that are leptin or leptin receptor deficient have major metabolic complications, including obesity. This study tests the hypothesis that the pituitary somatotrope may contribute a source of leptin that maintains some of these metabolic functions. We created 2 different tissue-specific leptin knockout animals: a Somatotrope-Lep-null model and an Adipocyte-Lep-null model. Metabolic analysis of both models, along with a global deletion model, was performed. The Somatotrope-Lep-null animals had fewer somatotropes, and females had a 76% decrease in serum prolactin. During the dark (feeding) phase, females had a 35% increase in ambulation coupled with a 4% increase in EE. Mutants showed no change in food intake or weight gain and EE was unchanged in males. During the light (sleep) phase, Somatotrope-Lep-null mutant males had lower EE and females continued to have higher EE. The respiratory quotients (RQs) of mutants and littermate controls were decreased in males and increased in females; all were within the range that indicates predominant carbohydrate burning. The massively obese Adipocyte-Lep-null animals, however, had significant increases in food intake, sleep, and increased EE, with decreased activity. Changes in RQ were sexually dimorphic, with female mutants having higher RQ and males having decreased RQ. We conclude that both adipocyte and somatotrope leptin contribute to the metabolic homeostasis of the mouse, and that extraadipocyte sources of leptin cannot overcome the major metabolic challenges seen in these animals.
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Affiliation(s)
- Angela Katherine Odle
- Department of Neurobiology and Developmental Sciences, College of Medicine, Center for Translational Neurosciences, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205
| | - Melody Allensworth-James
- Department of Neurobiology and Developmental Sciences, College of Medicine, Center for Translational Neurosciences, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205
| | - Anessa Haney
- Department of Neurobiology and Developmental Sciences, College of Medicine, Center for Translational Neurosciences, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205
| | - Noor Akhter
- Department of Neurobiology and Developmental Sciences, College of Medicine, Center for Translational Neurosciences, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205
| | - Mohsin Syed
- Department of Neurobiology and Developmental Sciences, College of Medicine, Center for Translational Neurosciences, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205
| | - Gwen V Childs
- Department of Neurobiology and Developmental Sciences, College of Medicine, Center for Translational Neurosciences, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205
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Bionaz M, Loor JJ. Gene networks driving bovine mammary protein synthesis during the lactation cycle. Bioinform Biol Insights 2011; 5:83-98. [PMID: 21698073 PMCID: PMC3118679 DOI: 10.4137/bbi.s7003] [Citation(s) in RCA: 217] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
A crucial role for both insulin and mTOR in the regulation of milk protein synthesis is emerging. Bovine mammary biopsies harvested during late-pregnancy through end of subsequent lactation were used to evaluate via quantitative PCR the expression of 44 genes involved in pathways of insulin, mTOR, AMPK, and Jak2-Stat5 signalling and also glucose and amino acid (AA) transporters. We observed an increased expression during lactation of ELF5, AA and glucose transporters, insulin signaling pathway components, MAPK14, FRAP1, EIF4EBP2, GSK3A and TSC1 among mTOR signaling-related genes. Among ribosomal components RPL22 was down-regulated. The overall data support a central role of AA and glucose transporters and insulin signaling through mTOR for the regulation of protein synthesis in bovine mammary gland. Furthermore, the existence of translational competition favoring the translation of milk protein transcripts was inferred from the combined dataset.
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Affiliation(s)
- Massimo Bionaz
- Mammalian NutriPhysio Genomics, Department of Animal Sciences, University of Illinois, Urbana, IL 61801, USA
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Abstract
Leptin is an autocrine and paracrine factor which affects the development and function of mammary gland. The purpose of this study was to investigate the presence and regulatory effect of leptin in Chinese Guan Zhong dairy goat mammary gland from the virgin state to involution. The protein expression and localization of leptin and its long form receptor (OB-Rb) were detected by western blot and a confocal laser scanning microscope. Explants were cultured to detect the impacts of leptin on mammary gland, western blot was used to research leptin signal transduction pathway in pregnancy, lactation and involution. Leptin and amounts of OB-Rb protein were high throughout the virgin stage and at the beginning of pregnancy, lower at mid-pregnancy and throughout lactation, then higher at involution. Immunofluorescence performed with the anti-leptin and anti-leptin receptor antibody showed labelling located in adipose, epithelial cells, or extracellular matrix at different stages. The localization of leptin and OB-Rb revealed that leptin induced the expression of OB-Rb specifically and controlled the development and physiological function of the mammary gland by binding to OB-Rb. Leptin stimulated the proliferation and differentiation of ductal epithelial cells in pregnancy by JAK-MAPK signal pathway, enhanced the amount of β-casein in cultured lactating mammary gland by JAK-STAT5 signal pathway, made the mammary duct disappear and induced apoptosis of mammary epithelial cells and mammary gland restitution by JAK-STAT3 signal pathway in involution. Overall, this study demonstrated the importance and complexity of leptin and OB-Rb during mammary gland development and provides a valuable resource for future research in this area.
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