Evidence for a role of insulin in the regulation of lipogenesis in lactating rat mammary gland. Measurements of lipogenesis in vivo and plasma hormone concentrations in response to starvation and refeeding.
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ABSTRACT:
SUBMITTER: Robinson AM
PROVIDER: S-EPMC1186235 | biostudies-other | 1978 Oct
REPOSITORIES: biostudies-other
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Project description:Starvation caused a marked increase in putrescine content in mammary gland of lactating rats, together with a marked decrease in activity of ornithine decarboxylase and appearance of measurable ornithine decarboxylase antizyme. 2. Refeeding for 5 h caused disappearance of free antizyme and ornithine decarboxylase activity returned to the value in fed animals. Putrescine concentration remained elevated. 3. There was no significant change in nucleic acid content of mammary gland from starved rats, but spermidine and spermine contents increased significantly. 4. Refeeding for 5 h returned the spermidine content of mammary glands to 'fed' values, and significantly decreased the content of spermine, although it did not reach control values. Thus changes in polyamine content of mammary gland in starved rats are clearly dissociated from changes in either RNA content or activities of polyamine-synthetic decarboxylases. 5. Starvation caused a fall in the content of spermidine in liver, with no change in spermine content. Refeeding for 5 h returned the spermidine content to 'fed' values.
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Project description:Temporal changes in circulating insulin concentrations were measured during re-feeding of 18 h-starved lactating rats. Insulin concentrations rose rapidly over the first 20 min of re-feeding with 5 g of chow diet, and then sharply declined between 20-30 min and remained low for the rest of the 90 min experimental period. Lipogenic activity in the mammary gland also exhibited a peak during re-feeding, but there was a clear time lag between the insulin response and the lipogenic response. Blood-flow measurements failed to show any major increase to the tissue during this activation of lipogenesis. Acute suppression of insulin secretion at 30 min (after the initial surge) abolished the switch-on of lipogenesis, suggesting that the insulin-sensitivity of the gland may be acutely enhanced over this period of re-feeding.
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Project description:Adrenal hormones, ACTH plasma concentrations and the ultrasonographic evaluation of the adrenal glands are considered complementary in clinical evaluations of the hypothalamic-pituitary-adrenal (HPA) axis function in several species. In dogs, age, size and weight have a significant effect on the ultrasonographic size of the adrenal glands. In neonatal foals, ultrasonographic evaluation and measurements of the adrenal glands have been demonstrated to be reliable; however, the effect of individual variables on ultrasonographic features has not been investigated, and the clinical usefulness of adrenal gland ultrasonography is still not known. The aims of this study were: (i) to provide and compare adrenal glands ultrasound measurements in healthy newborn Thoroughbred and Standardbred foals, and assess any effect of age, weight and sex on them; (ii) to assess and compare ACTH and steroid hormone concentrations in healthy neonatal foals of the two breeds. Venous blood samples and ultrasonographic images of the adrenal glands were collected from 10 healthy neonatal Thoroughbred and 10 healthy neonatal Standardbred foals. Ultrasonographic measurements of the adrenal glands were obtained and adrenocorticotropin (ACTH), cortisol, dehydroepiandrosterone (DHEA), progesterone (P4) and aldosterone plasma concentrations were assessed. The ACTH/cortisol, ACTH/progesterone, ACTH/aldosterone, ACTH/DHEA and cortisol/DHEA ratios were calculated. A significant positive correlation was found between the height of the right adrenal gland and the foal's weight; the width of the right and left adrenal gland and the medulla was significantly lower in Thoroughbreds than in Standardbreds. Cortisol and ACTH plasma concentrations were significantly higher and lower, respectively, in Thoroughbreds compared with Standardbreds. The cortisol/DHEA ratio was significantly higher in Thoroughbreds. This study provides reference ranges for neonatal Thoroughbred and Standardbred foals, and suggests the presence of breed-related differences in ultrasonographic adrenal gland measurements, plasmatic cortisol and ACTH concentrations. The higher cortisol/DHEA ratio detected in Thoroughbred foals could suggest a different response to environmental stimulation in the two breeds.
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Project description:Arteriovenous differences of amino acids across the mammary glands of lactating rats are diminished when the rats are starved for 24 h. When 24 h-starved rats were refed for 2 1/2 h, the arteriovenous differences of amino acids returned to values similar to those found in well-fed rats. In order to find a possible explanation for these rapid changes, we tested the effect of ketone bodies on amino acid uptake by the gland. At 5 min after injection of acetoacetate to fed rats, when the total concentration of ketone bodies in blood was similar to that found in starvation, the uptake of amino acids by the mammary gland was similar to that found after starvation, i.e. lower than in fed rats. However, 30 min after administration of acetoacetate, when the arterial concentration of ketone bodies had returned to values similar to those in fed rats, the arteriovenous differences of amino acids were similar to those found in fed rats. We conclude that the changes in blood ketone bodies may be responsible, at least in part, for the changes in amino acid uptake that occur in starvation and in the starvation--refeeding transition.
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Project description:Lactating rats were starved for 48 h and refed a high-carbohydrate diet for a further 48 h. Starvation stops milk secretion, which resumes shortly after refeeding. Three lipogenic enzymes, fatty acid synthase, glucose 6-phosphate dehydrogenase (EC 1.1.1.49) and 'malic' enzyme (EC 1.1.1.40) all decrease in the mammary gland during starvation and are restored to the pre-starvation levels 48 h after refeeding. The same enzymes in liver also decrease during starvation, but increase to values significantly higher than those for the normal fed rats after refeeding the high-carbohydrate diet. For the fatty acid synthase these values were four times the pre-starvation values. Serum insulin and prolactin concentrations also increased upon refeeding the high-carbohydrate diet.
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Project description:Citrullination is a post-translational modification (PTM) in which positively charged peptidyl-arginine is converted into neutral peptidyl-citrulline by peptidylarginine deiminase (PAD or PADI) enzymes. The full protein citrullinome in many tissues is unknown. Herein, we used mass spectrometry and identified 107 citrullinated proteins in the lactation day 9 (L9) mouse mammary gland including histone H2A, α-tubulin, and β-casein. Given the importance of prolactin to lactation, we next tested if it stimulates PAD-catalyzed citrullination using mouse mammary epithelial CID-9 cells. Stimulation of CID-9 cells with 5 µg/mL prolactin for 10 min induced a 2-fold increase in histone H2A citrullination and a 4.5-fold increase in α-tubulin citrullination. We next investigated if prolactin-induced citrullination regulates the expression of lactation genes β-casein (Csn2) and butyrophilin (Btn1a1). Prolactin treatment for 12 h increased β-casein and butyrophilin mRNA expression; however, this increase was significantly inhibited by the pan-PAD inhibitor, BB-Cl-amidine (BB-ClA). We also examined the effect of tubulin citrullination on the overall polymerization rate of microtubules. Our results show that citrullinated tubulin had a higher maximum overall polymerization rate. Our work suggests that protein citrullination is an important PTM that regulates gene expression and microtubule dynamics in mammary epithelial cells.
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Project description:BACKGROUND:Nutrition affects milk composition thus influencing its nutritional properties. Nutrition also modifies the expression of mammary genes, whose regulation is not fully understood. MicroRNAs (miRNA) are small non coding RNA which are important post-transcriptional regulators of gene expression by targeting messenger RNAs. Our goal was to characterize miRNA whose expression is regulated by nutrition in the lactating goat mammary gland, which may provide clues to deciphering regulations of the biosynthesis and secretion of milk components. METHODOLOGY/PRINCIPAL FINDINGS:Using high-throughput sequencing technology, miRNomes of the lactating mammary gland were established from lactating goats fed ad libitum or deprived of food for 48 h affecting milk production and composition. High throughput miRNA sequencing revealed 30 miRNA with an expression potentially modulated by food deprivation; 16 were down-regulated and 14 were up-regulated. Diana-microT predictive tools suggested a potential role for several nutriregulated miRNA in lipid metabolism. Among the putative targets, 19 were previously identified as differently expressed genes (DEG). The functions of these 19 DEG revealed, notably, their involvement in tissue remodelling. CONCLUSION/SIGNIFICANCE:In conclusion, this study offers the first evidence of nutriregulated miRNA in the ruminant mammary gland. Characterization of these 30 miRNA could contribute to a clearer understanding of gene regulation in the mammary gland in response to nutrition.
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Project description:BackgroundThe mammary gland is a dynamic organ that undergoes important physiological changes during reproductive cycles. Until now, data regarding the characterisation of miRNA in the mammary gland have been scarce and mainly focused on their abnormal expression in breast cancer. Our goal was to characterise the microRNA (miRNA) involved in mechanisms regulating the mammary function, with particular focus on the lactation stage.Methodology/principal findingsUsing high-throughput sequencing technology, the exhaustive repertoires of miRNA expressed (miRNome) in mouse and bovine mammary glands during established lactation were identified, characterized and compared. Furthermore, in order to obtain more information on miRNA loading in the RNA-induced silencing complex (RISC), the miRNome was compared with that obtained from RNA associated with the AGO2 protein (AGO2-miRNome) in mouse lactating mammary gland. This study enabled the identification of 164 and 167 miRNA in mouse and bovine, respectively. Among the 30 miRNA most highly expressed in each species, 24 were common to both species and six of them were preferentially highly expressed in lactating than non-lactating mammary gland. The potential functional roles of these 24 miRNA were deduced using DIANA-miRPath software, based on miRNA/mRNA interactions. Moreover, seven putative novel miRNA were identified. Using DAVID analysis, it was concluded that the predicted targets of two of these putative novel miRNA are involved in mammary gland morphogenesis.Conclusion/significanceOur study provides an overview of the characteristics of lactating mouse and bovine mammary gland miRNA expression profiles. Moreover, species-conserved miRNA involved in this fundamental biological function were identified. These miRNomes will now be used as references for further studies during which the impact of animal breeding on the miRNA expression will be analysed.
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Project description:RNA-Seq enables the generation of extensive transcriptome information providing the capability to characterize transcripts (including alternative isoforms and polymorphism), to quantify expression and to identify differential regulation in a single experiment. Our aim in this study was to take advantage of using RNA-Seq high-throughput technology to provide a comprehensive transcriptome profiling of the sheep lactating mammary gland. Eight ewes of two dairy sheep breeds with differences in milk production traits were used in this experiment (four Churra and four Assaf ewes). Milk samples from these animals were collected on days 10, 50, 120 and 150 after lambing to cover the various physiological stages of the mammary gland across the complete lactation. RNA samples were extracted from milk somatic cells. The RNA-Seq dataset was generated using an Illumina HiSeq 2000 sequencer. The information reported here will be useful to understand the biology of lactation in sheep, providing also an opportunity to characterize their different patterns on milk production aptitude.
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Project description:BackgroundInsulin like growth factors (IGFs) and their binding proteins (IGFBPs) are secreted peptides that play major roles in regulating the normal development and maturation of mammary gland. While Igfbp7 has been shown to decrease breast tumor growth, its role in regulating the normal mammary gland development has not been studied. To this end, we generated Igfbp7-null mice and examined the development and maturation of mammary glands in the virgin, pregnant and lactating animals.ResultsWe report here that loss of Igfbp7 significantly retards mammary gland development in the virgin animals. More significantly, the pregnant Igfpb7-null glands contained fewer alveolar structures and that during lactation these glands exhibit the morphological changes that are associated with involution. The transcriptome profile of the Igfbp7-null glands on the lactation day 3 revealed a distinct involution-related gene signature compared to the lactating WT glands. Interestingly, we found that the lactating Igfbp7-null glands exhibit increased expression of Stat3 and enhanced activation of (phosphorylated) Stat3, combined with decreased expression of Stat5 suggesting that the absence of Igfbp7 accelerates the onset of involution. We also found that in absence of Igfpb7, the lactating glands contain increased Igfbp5 protein along with decreased expression of IGF-1 Receptor and Akt activation. Finally, we show that during the normal course of involution, Igfbp7 expression is significantly decreased in the mammary gland.ConclusionOur data suggest that loss of Igfbp7 induces precocious involution possibly through diminished cell survival signals. Our findings identify Igfbp7 as major regulator of involution in the mammary gland.
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