Metabolic adaptations during lactogenesis. Lactose synthesis in rabbit mammary tissue during pregnancy and lactation

Mellenberger, R. W.; Bauman, D. E.

doi:10.1042/bj1420659

Cited by 17 publications

(6 citation statements)

References 28 publications

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“…The LS content was higher in BMEC incubated with 10 and 20 mmol/L glucose than those incubated with 2.5 and 5 mmol/L glucose ( P< 0.05, Figure 3). Increased LS content was most closely correlated with increase of lactose biosynthesis [27], which was thought to be involved in the enhanced milk yield [28]. Based on current literature and our results, increasing glucose availability may stimulate lactose synthesis partly by altering the expression of B4GALT at transcriptional and post-transcriptional levels and then increase milk yield.…”

Section: Resultssupporting

confidence: 71%

Effects of Glucose Availability on Expression of the Key Genes Involved in Synthesis of Milk Fat, Lactose and Glucose Metabolism in Bovine Mammary Epithelial Cells

2013

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As the main precursor for lactose synthesis, large amounts of glucose are required by lactating dairy cows. Milk yield greatly depends on mammary lactose synthesis due to its osmoregulatory property for mammary uptake of water. Thus, glucose availability to the mammary gland could be a potential regulator of milk production. In the present study, the effect of glucose availability on expression of the key genes involved in synthesis of milk fat, lactose and glucose metabolism in vitro was investigated. Bovine mammary epithelial cells (BMEC) were treated for 12 h with various concentrations of glucose (2.5, 5, 10 or 20 mmol/L). The higher concentrations of glucose (10–20 mmol/L) did not affect the mRNA expression of acetyl-CoA carboxylase, diacyl glycerol acyl transferase, glycerol-3 phosphate acyl transferase and α-lactalbumin, whereas fatty acid synthase, sterol regulatory element binding protein-1 and beta-1, 4-galactosyl transferase mRNA expression increased at 10 mmol/L and then decreased at 20 mmol/L. The content of lactose synthase increased with increasing concentration of glucose, with addition of highest value at 20 mmol/L of glucose. Moreover, the increased glucose concentration stimulated the activities of pyruvate kinase and glucose-6-phosphate dehydrogenase, and elevated the energy status of the BMEC. Therefore, it was deduced that after increasing glucose availability, the extra absorbed glucose was partitioned to entering the synthesis of milk fat and lactose by the regulation of the mRNA expression of key genes, promoting glucose metabolism by glycolysis and pentose phosphate pathway as well as energy status. These results indicated that the sufficient availability of glucose in BMEC may promote glucose metabolism, and affect the synthesis of milk composition.

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Section: Resultssupporting

confidence: 71%

Effects of Glucose Availability on Expression of the Key Genes Involved in Synthesis of Milk Fat, Lactose and Glucose Metabolism in Bovine Mammary Epithelial Cells

2013

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“…In the rabbit, differentiated function, evidenced by an increase in the concentration of casein mRNA, appears between days 18 and 25 of pregnancy [22]. At the same time, the first increase in the rate of lactose biosynthesis is observed [23], and the rate and pattern of lipid synthesis changes to that characteristic of rabbit milk [24]. The decrease in prolactin receptor expression we observed after in vitro maintenance of cells obtained later than day 17 of pregnancy coincides, then, with this final stage of mammogenesis.…”

Section: Discussionmentioning

confidence: 99%

Prolactin receptor expression in monolayer cultures of rabbit mammary epithelial cells: Pre‐ and postpartum [¹²⁵I]‐prolactin binding activity

Soltysiak

Fellows

1983

J of Cellular Biochemistry

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Expression of specific [125I]-prolactin-binding sites under culture conditions has been investigated for isolated mammary epithelial cells from virgin, pregnant, and lactating rabbits. Primary monolayer cultures were obtained by sequential enzymatic dispersion of mammary tissue followed by 48 hr incubation in a medium selective for epithelial cells. Scatchard analyses of binding data obtained from these cultures indicated a single class of receptor sites, the affinity constant of which (2.5 X 10(9) M-1) did not vary significantly during mammary development. The number of prolactin receptors, however, expressed by virgin and early pregnant epithelial cells was significantly increased over those from late pregnancy or lactation. Less differentiated cells also respond to growth in pregnant rabbit serum with an increase in specific [125I]-prolactin binding. The diminished receptor expression by cells obtained after 17 days of pregnancy coincides with the attainment of secretory capacity in the animal, and may reflect the influence of the low serum prolactin or high progesterone levels circulating during the last trimester in the rabbit, or be the cultural expression of secretory differentiation.

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“…This role for glycogen is most likely not limited to the mouse. Lactose synthase is active during pregnancy in the cow (Mellenberger et al, 1973) and rabbit (Mellenberger & Bauman, 1974), yet the rate of lactose synthesis at this time is far less than it is during lactation. Lactose production could be curtailed by glycogen synthesis in these animals as well.…”

Section: Discussionmentioning

confidence: 99%

Interrelationship of glycogen metabolism and lactose synthesis in mammary epithelial cells of mice

Emerman¹,

Bartley²,

Bissell³

1980

Biochemical Journal

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Glycogen metabolism in mammary epithelial cells was investigated (i) by studying the conversion of glucose into glycogen and other cellular products in these cells from virgin, pregnant and lactating mice and (ii) by assaying the enzymes directly involved with glycogen metabolism. We find that: (1) mammary epithelial cells synthesized glycogen at rates up to over 60% that of the whole gland; (2) the rate of this synthesis was modulated greatly during the reproductive cycle, reaching a peak in late pregnancy and decreasing rapidly at parturition, when abundant synthesis of lactose was initiated; (3) glycogen synthase and phosphorylase activities reflected this modulation in glycogen metabolism; (4) lactose synthesis reached a plateau during late pregnancy, even though lactose synthase is reported to increase in the mouse mammary gland at this time. We propose that glycogen synthesis restricts lactose synthesis during late pregnancy by competing successfully for the shared UDP-glucose pool. The physiological advantage of glycogen accumulation during late pregnancy is discussed.

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Metabolic adaptations during lactogenesis. Lactose synthesis in rabbit mammary tissue during pregnancy and lactation

Cited by 17 publications

References 28 publications

Effects of Glucose Availability on Expression of the Key Genes Involved in Synthesis of Milk Fat, Lactose and Glucose Metabolism in Bovine Mammary Epithelial Cells

Effects of Glucose Availability on Expression of the Key Genes Involved in Synthesis of Milk Fat, Lactose and Glucose Metabolism in Bovine Mammary Epithelial Cells

Prolactin receptor expression in monolayer cultures of rabbit mammary epithelial cells: Pre‐ and postpartum [¹²⁵I]‐prolactin binding activity

Interrelationship of glycogen metabolism and lactose synthesis in mammary epithelial cells of mice

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Metabolic adaptations during lactogenesis. Lactose synthesis in rabbit mammary tissue during pregnancy and lactation

Cited by 17 publications

References 28 publications

Effects of Glucose Availability on Expression of the Key Genes Involved in Synthesis of Milk Fat, Lactose and Glucose Metabolism in Bovine Mammary Epithelial Cells

Effects of Glucose Availability on Expression of the Key Genes Involved in Synthesis of Milk Fat, Lactose and Glucose Metabolism in Bovine Mammary Epithelial Cells

Prolactin receptor expression in monolayer cultures of rabbit mammary epithelial cells: Pre‐ and postpartum [125I]‐prolactin binding activity

Interrelationship of glycogen metabolism and lactose synthesis in mammary epithelial cells of mice

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Prolactin receptor expression in monolayer cultures of rabbit mammary epithelial cells: Pre‐ and postpartum [¹²⁵I]‐prolactin binding activity