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Osorio JS, Lohakare J, Bionaz M. Biosynthesis of milk fat, protein, and lactose: roles of transcriptional and posttranscriptional regulation. Physiol Genomics 2016; 48:231-56. [DOI: 10.1152/physiolgenomics.00016.2015] [Citation(s) in RCA: 113] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The demand for high-quality milk is increasing worldwide. The efficiency of milk synthesis can be improved by taking advantage of the accumulated knowledge of the transcriptional and posttranscriptional regulation of genes coding for proteins involved in the synthesis of fat, protein, and lactose in the mammary gland. Research in this area is relatively new, but data accumulated in the last 10 years provide a relatively clear picture. Milk fat synthesis appears to be regulated, at least in bovines, by an interactive network between SREBP1, PPARγ, and LXRα, with a potential role for other transcription factors, such as Spot14, ChREBP, and Sp1. Milk protein synthesis is highly regulated by insulin, amino acids, and amino acid transporters via transcriptional and posttranscriptional routes, with the insulin-mTOR pathway playing a central role. The transcriptional regulation of lactose synthesis is still poorly understood, but it is clear that glucose transporters play an important role. They can also cooperatively interact with amino acid transporters and the mTOR pathway. Recent data indicate the possibility of nutrigenomic interventions to increase milk fat synthesis by feeding long-chain fatty acids and milk protein synthesis by feeding amino acids. We propose a transcriptional network model to account for all available findings. This model encompasses a complex network of proteins that control milk synthesis with a cross talk between milk fat, protein, and lactose regulation, with mTOR functioning as a central hub.
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Affiliation(s)
| | - Jayant Lohakare
- Oregon State University, Corvallis, Oregon; and
- Kangwon National University, Chuncheon, South Korea
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Bentley PA, Wall EH, Dahl GE, McFadden TB. Responses of the mammary transcriptome of dairy cows to altered photoperiod during late gestation. Physiol Genomics 2015; 47:488-99. [PMID: 26175502 DOI: 10.1152/physiolgenomics.00112.2014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Accepted: 07/13/2015] [Indexed: 11/22/2022] Open
Abstract
Cows exposed to short day photoperiod (SD, 8L:16D) during the 60-day nonlactating period prior to parturition produce more milk in their subsequent lactation compared with cows exposed to long day photoperiod (LD, 16L:8D). Although this response is well established in dairy cows, the underlying mechanisms are not understood. We hypothesized that differential gene expression in cows exposed to SD or LD photoperiods during the dry period could be used to identify the functional basis for the subsequent increase in milk production during lactation. Pregnant, multiparous cows were maintained on an SD or LD photoperiod for 60 days prior to parturition. Mammary biopsies were obtained on days -24 and -9 relative to parturition and Affymetrix GeneChip Bovine Genome Arrays were used to quantify gene expression. Sixty-four genes were differentially expressed (P ≤ 0.05 and fold-change ≥ |1.5|) between SD and LD treatments. Many of these genes were associated with cell growth and proliferation, or immune function. Ingenuity Pathway Analysis predicted upstream regulators to include TNF, TGF-β1, interferon-γ, and several interleukins. In addition, expression of 125 genes was significantly different between day -24 and day -9; those genes were associated with milk component metabolism and immune function. The interaction of photoperiod and time affected 32 genes associated with insulin-like growth factor I signaling. Genes differentially expressed in response to photoperiod were associated with mammary development and immune function consistent with the enhancement of milk yield in the ensuing lactation. Our results provide insight into the mechanisms by which photoperiod affects the mammary gland and subsequently lactation.
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Affiliation(s)
- P A Bentley
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada
| | - E H Wall
- Department of Animal Science, University of Vermont, Burlington, Vermont
| | - G E Dahl
- Department of Animal Sciences, University of Florida, Gainesville, Florida; and
| | - T B McFadden
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada; Department of Animal Science, University of Vermont, Burlington, Vermont; Division of Animal Sciences, University of Missouri, Columbia, Missouri
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Phyn C, Kay J, Rius A, Morgan S, Roach C, Grala T, Roche J. Temporary alterations to postpartum milking frequency affect whole-lactation milk production and the energy status of pasture-grazed dairy cows. J Dairy Sci 2014; 97:6850-68. [DOI: 10.3168/jds.2013-7836] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Accepted: 07/22/2014] [Indexed: 01/02/2023]
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Lemay DG, Hovey RC, Hartono SR, Hinde K, Smilowitz JT, Ventimiglia F, Schmidt KA, Lee JWS, Islas-Trejo A, Silva PI, Korf I, Medrano JF, Barry PA, German JB. Sequencing the transcriptome of milk production: milk trumps mammary tissue. BMC Genomics 2013; 14:872. [PMID: 24330573 PMCID: PMC3871720 DOI: 10.1186/1471-2164-14-872] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Accepted: 12/09/2013] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND Studies of normal human mammary gland development and function have mostly relied on cell culture, limited surgical specimens, and rodent models. Although RNA extracted from human milk has been used to assay the mammary transcriptome non-invasively, this assay has not been adequately validated in primates. Thus, the objectives of the current study were to assess the suitability of lactating rhesus macaques as a model for lactating humans and to determine whether RNA extracted from milk fractions is representative of RNA extracted from mammary tissue for the purpose of studying the transcriptome of milk-producing cells. RESULTS We confirmed that macaque milk contains cytoplasmic crescents and that ample high-quality RNA can be obtained for sequencing. Using RNA sequencing, RNA extracted from macaque milk fat and milk cell fractions more accurately represented RNA from mammary epithelial cells (cells that produce milk) than did RNA from whole mammary tissue. Mammary epithelium-specific transcripts were more abundant in macaque milk fat, whereas adipose or stroma-specific transcripts were more abundant in mammary tissue. Functional analyses confirmed the validity of milk as a source of RNA from milk-producing mammary epithelial cells. CONCLUSIONS RNA extracted from the milk fat during lactation accurately portrayed the RNA profile of milk-producing mammary epithelial cells in a non-human primate. However, this sample type clearly requires protocols that minimize RNA degradation. Overall, we validated the use of RNA extracted from human and macaque milk and provided evidence to support the use of lactating macaques as a model for human lactation.
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Affiliation(s)
- Danielle G Lemay
- Genome Center, University of California Davis, 451 Health Sciences Dr, Davis, CA 95616, USA
| | - Russell C Hovey
- Department of Animal Science, University of California Davis, One Shields Ave, Davis, CA 95616, USA
| | - Stella R Hartono
- Genome Center, University of California Davis, 451 Health Sciences Dr, Davis, CA 95616, USA
| | - Katie Hinde
- Department of Human Evolutionary Biology, Harvard University, Peabody Museum, 11 Divinity Avenue, Cambridge, MA 02138, USA
- California National Primate Research Center, University of California Davis, Road 98 and Hutchison Drive, Davis, CA, USA
| | - Jennifer T Smilowitz
- Department of Food Science and Technology, University of California Davis, One Shields Ave, Davis, CA 95616, USA
| | - Frank Ventimiglia
- California National Primate Research Center, University of California Davis, Road 98 and Hutchison Drive, Davis, CA, USA
| | - Kimberli A Schmidt
- Center for Comparative Medicine, University of California Davis, One Shields Ave, Davis, CA 95616, USA
| | - Joyce WS Lee
- California National Primate Research Center, University of California Davis, Road 98 and Hutchison Drive, Davis, CA, USA
| | - Alma Islas-Trejo
- Department of Animal Science, University of California Davis, One Shields Ave, Davis, CA 95616, USA
| | - Pedro Ivo Silva
- Genome Center, University of California Davis, 451 Health Sciences Dr, Davis, CA 95616, USA
| | - Ian Korf
- Genome Center, University of California Davis, 451 Health Sciences Dr, Davis, CA 95616, USA
| | - Juan F Medrano
- Department of Animal Science, University of California Davis, One Shields Ave, Davis, CA 95616, USA
| | - Peter A Barry
- Center for Comparative Medicine, University of California Davis, One Shields Ave, Davis, CA 95616, USA
| | - J Bruce German
- Department of Food Science and Technology, University of California Davis, One Shields Ave, Davis, CA 95616, USA
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Wall EH, Bond JP, McFadden TB. Milk yield responses to changes in milking frequency during early lactation are associated with coordinated and persistent changes in mammary gene expression. BMC Genomics 2013; 14:296. [PMID: 23638659 PMCID: PMC3658990 DOI: 10.1186/1471-2164-14-296] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Accepted: 04/20/2013] [Indexed: 11/24/2022] Open
Abstract
Background The lactating mammary gland responds to changes in milking frequency by modulating milk production. This response is locally regulated and, in dairy cows, the udder is particularly sensitive during early lactation. Relative to cows milked twice-daily throughout lactation, those milked four-times-daily for just the first 3 weeks of lactation produce more milk throughout that lactation. We hypothesized that the milk yield response would be associated with increased mammary cell turnover and changes in gene expression during frequent milking and persisting thereafter. Cows were assigned to unilateral frequent milking (UFM; left udder halves milked twice-daily; right udder halves milked four-times daily) on days 1 to 21 of lactation, followed by twice-daily milking for the remainder of lactation. Relative to udder halves milked twice-daily, those milked four-times produced more milk during UFM; the difference in milk yield declined acutely upon cessation of UFM after day 21, but remained significantly elevated thereafter. We obtained mammary biopsies from both udder halves on days 21, 23, and 40 of lactation. Results Mammary cell proliferation and apoptosis were not affected by milking frequency. We identified 75 genes that were differentially expressed between paired udder halves on day 21 but exhibited a reversal of differential expression on day 23. Among those genes, we identified four clusters characterized by similar temporal patterns of differential expression. Two clusters (11 genes) were positively correlated with changes in milk yield and were differentially expressed on day 21 of lactation only, indicating involvement in the initial milk yield response. Two other clusters (64 genes) were negatively correlated with changes in milk yield. Twenty-nine of the 75 genes were also differentially expressed on day 40 of lactation. Conclusions Changes in milking frequency during early lactation did not alter mammary cell population dynamics, but were associated with coordinated changes in mammary expression of at least 75 genes. Twenty-nine of those genes were differentially expressed 19 days after cessation of treatment, implicating them in the persistent milk yield response. We conclude that we have identified a novel transcriptional signature that may mediate the adaptive response to changes in milking frequency.
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Wall EH, McFadden TB. Triennial Lactation Symposium: A local affair: How the mammary gland adapts to changes in milking frequency. J Anim Sci 2011; 90:1695-707. [PMID: 22205668 DOI: 10.2527/jas.2011-4790] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Regular removal of milk from the mammary gland is critical to maintaining milk secretion. Early studies in rodents demonstrated that changes in milking frequency influenced mammary blood flow, as well as mammary cell number and activity. Later studies in ruminants confirmed those observations and that the response was regulated locally within the mammary gland. In addition, it was discovered that increased milking frequency (IMF) during early lactation stimulated an increase in milk production that partially persisted through late lactation, indicating long-term effects on mammary function. The local mechanisms regulating the mammary response to IMF are poorly understood, although several have been proposed. To gain insight into the mechanisms underlying the mammary response to IMF, and to identify genes associated with the response, we used a functional genomics approach and conducted experiments on dairy cows exposed to unilateral frequent milking [UFM; twice daily milking (2X) of the left udder half and 4-times daily milking (4X) of the right udder half]. Across multiple experiments, we were unable to detect an effect of UFM on mammary cell proliferation or apoptosis. We have, however, identified distinct transcriptional signatures associated with the mammary response to milk removal and to UFM during early lactation. Sequential sampling of mammary tissue revealed that when UFM was imposed during early lactation, at least 2 sets of genes were coordinately regulated with changes in differential milk production of 4X vs. 2X udder halves. Moreover, some genes were persistently differentially expressed in 4X vs. 2X udder halves after UFM and were associated with the persistent increase in milk yield. We conclude that a coordinated transcriptional response is associated with the increase in milk yield elicited by IMF during early lactation and that the 2 sets of differentially expressed genes may be a marker for the autocrine up-regulation of milk production. Moreover, we propose that we have identified a novel form of imprinting associated with persistent alteration of mammary function, which we term "lactational imprinting."
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Affiliation(s)
- E H Wall
- Department of Medicine,University of Vermont, Burlinglon 05405, USA
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