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PubMedDate not supplied

A specific pattern of splicing for the horse alphaS1-Casein mRNA and partial genomic characterization of the relevant locus.

Mares' milk has a composition very different from that of cows' milk. It is much more similar to human milk, in particular in its casein fraction. This study reports on the sequence of a 994 bp amplified fragment corresponding to a horse alphaS1-Casein (alphaS1-Cn) cDNA and its comparison with its caprine, pig, rabbit and human counterparts. The alignment of these sequences revealed a specific pattern of splicing for this horse primary transcript. As in humans, exons 3', 6' and 13' are present whereas exons 5, 13 and 14 are absent in this equine mRNA sequence. BAC clones, screened from a horse BAC library, containing the alphaS1-Cn gene allowed the mapping of its locus by FISH on equine chromosome 3q22.2-q22.3 which is in agreement with the Zoo-FISH results. Genomic analysis of the alphaS1-Cn gene showed that the region from the second exon to the last exon is scattered within a nucleotide stretch nearly 15-kb in length which is quite similar in size to its ruminant and rabbit counterparts. The region between alphaS1- and beta-Cn genes, suspected to contain cis-acting elements involved in the expression of all clustered casein genes, is similar in size (ca 15-kb) to the caprine and mouse intergenic region.

Amino Acid Sequence↗
PubMedDate not supplied

Geographic distribution of haplotype diversity at the bovine casein locus.

The genetic diversity of the casein locus in cattle was studied on the basis of haplotype analysis. Consideration of recently described genetic variants of the casein genes which to date have not been the subject of diversity studies, allowed the identification of new haplotypes. Genotyping of 30 cattle breeds from four continents revealed a geographically associated distribution of haplotypes, mainly defined by frequencies of alleles at CSN1S1 and CSN3. The genetic diversity within taurine breeds in Europe was found to decrease significantly from the south to the north and from the east to the west. Such geographic patterns of cattle genetic variation at the casein locus may be a result of the domestication process of modern cattle as well as geographically differentiated natural or artificial selection. The comparison of African Bos taurus and Bos indicus breeds allowed the identification of several Bos indicus specific haplotypes (CSN1S1*C-CSN2*A2-CSN3*AI / CSN3*H) that are not found in pure taurine breeds. The occurrence of such haplotypes in southern European breeds also suggests that an introgression of indicine genes into taurine breeds could have contributed to the distribution of the genetic variation observed.

Animals↗
PubMed2005

Possible mechanisms behind the differential effects of soy protein and casein feedings on colon cancer biomarkers in the rat.

In the present studies, several hypotheses were tested to explain previously reported differential effects of soy and casein on colon cancer biomarkers like cell proliferation, fecal fat, fecal bile acid, alkaline phosphatase, and magnesium excretion in rats. In Study 1, the effect of methionine, a limiting amino acid in soy protein and an amino acid that is thought to have a marked effect on colonic cell proliferation, was tested. It was concluded that methionine up to 1% in the diet had no effect on cell proliferation, using the 3H-thymidine assay. The same study revealed that fecal alkaline phosphatase excretion is a good marker for colonic epithelial damage and fecal magnesium excretion is not. In Study 2, the hypothesis was tested that soy fractions enriched with isoflavones and saponins may increase fat excretion and so influence colonic cell proliferation in rats. It was indeed shown that soy protein isolate and an ethanolic extract from soy protein isolate slightly increased fecal fat excretion (up to 1.7-fold). However, fecal water bile acid and free fatty acid concentrations were decreased after feeding soy protein-based diets compared with casein, and no difference in fecal alkaline phosphatase excretion was observed. In Study 3, the lytic potential of soy saponins and the interaction between saponins and some lytic bile acids were tested in vitro. Data suggest a protective effect from soy saponins by reducing lytic activity of cholic acid. The overall conclusion is that soy protein compared with casein influences several colon cancer risk parameters, indicating a more protective rather than a stimulating effect on colon cancer risk.

Alkaline Phosphatase↗
PubMed1980

Calcium requirement for prolactin actions on ribonucleic acid and casein synthesis in mouse mammary gland explants.

The actions of PRL on RNA and casein synthesis were tested in mouse mammary gland explants that were cultured with medium containing several concentrations of calcium ions. The PRL effects on both RNA and casein synthesis were the same when calcium concentrations between 0.3-11.3 mM were employed. In the absence of extracellular calcium ions, however, PRL had no action on RNA or casein synthesis, but a significant stimulation of ornithine decarboxylase activity by PRL was observed in the absence of calcium. Stimulatory actions of insulin, cGMP, and prostaglandin F2 alpha on RNA synthesis in the cultured explants were observed in the absence of calcium, but arachidonic acid had no effect under these conditions. It is concluded that specific actions of PRL in the mammary gland require the presence of extracellular calcium ions.

Animals↗
PubMed1990

Casein accumulation in mouse mammary epithelial cells after growth stimulated by different hormonal and nonhormonal agents.

Mammary epithelial cells obtained from virgin mice were cultured in collagen gel with linoleic acid-containing serum-free growth medium supplemented with hormonal (PRL and progesterone, epidermal growth factor, somatomedin-C) or nonhormonal (lithium ion, phosphatidic acid containing phospholipid liposomes) growth stimulating agents. The phenotypes of the resulting progeny cells were compared by examining the ultrastructure, immunohistochemical staining for luminal epithelial and myoepithelial cells and casein, and assessing the quantity of biochemically detectable alpha- and beta-casein. Although there are some differences in ultrastructure and immunostaining in the progeny cell populations induced by different growth-promoting agents, all the cultures were able to accumulate alpha- and beta-casein on subsequent stimulation by PRL and linoleic acid in the second phase of culture. Since, in vivo, luminal epithelial cells of the mammary gland are the only cell type capable of synthesizing milk products, these results indicate that all the different growth stimulants, hormonal and nonhormonal, result in the predominant proliferation of luminal-type epithelial cells. These results have important implications for studies of the mechanism of growth control in and transformation of mammary epithelial cells.

Animals↗
PubMed1976

Effects of prostaglandins on RNA and casein synthesis in mammary gland explants of mice.

Prostaglandins B2, E2, and F2alpha were found to stimulate RNA synthesis in mammary gland explants of mice in a prolactin-like manner. These effects were non-additive to maximally stimulatory concentrations of prolacin. Also, time-course studies showed that the effects of these prostaglandins only became apparent following at 2-4 hour lag period. The effects of these prostaglandins were not observed in explants which were not pretreated with insulin plus hydrocortisone, i.e., in tissues not responsive to prolactin Prostaglandins E1, A2, A1, B1, and F1alpha had no effects on the rate of RNA synthesis, but each of these prostaglandins abolished the responsivitiy of the explants to prolactin. Since DBcAMP, theophylline, and indomethacin were found previously to suppress the aciton of prolactin on RNA synthesis, the effects of these agents on the stimulatory effects of prostaglandins B2, E2, and F2alpha were tested. The incubation of explants with 5 mM DBcAMP or 5 mM thophylline abolished the effects of these prostaglandins on RNA synthesis. But incubation with indomethacin did not affect the responses to these prostaglandins. Prolactin-like effects of prostaglandins on casein synthesis were not observed. Prostaglandins E1, A2, A1, B2, F1alpha and indomethacin did, however, abolish the prolactin stimulation of casein synthesis. Furthermore, the preincubation of explants with prostaglandins B2, E2, F2alpha or arachidonic acid significantly shortened the time of onset of the prolactin stimulation of casein synthesis. The results are discussed with regard to a possible role of the prostaglandins as mediators for the actions of prolactin in the mammary gland.

Animals↗
PubMed1996

The role of prolactin and growth hormone in the regulation of casein gene expression and mammary cell survival: relationships to milk synthesis and secretion.

We have compared involution of the rat mammary gland, induced by litter removal, where milk accumulation occurs, with involution induced in the presence of the suckling young by combined PRL and GH deficiency. Both treatments induced involutionary processes involving apoptosis, as judged by DNA ladders and resulted in significant decreases in the DNA content of the gland. Surprisingly, the effects of hormone deprivation on protein output in milk were principally explained by the loss of secretory cells, as there were only modest decreases in casein messenger RNA (mRNA) expression and protein synthesis rates per U DNA in vitro. The association of casein mRNA with the polysome fraction was also unaffected by hormone deprivation, whereas involution induced by litter removal resulted in much greater decreases in steady state levels of casein mRNA and an increased association of the mRNAs with the monosome fraction. In PRL- and GH-deficient rats, PRL treatment could prevent all of these effects, GH was partially effective, whereas putative mediators of GH action, insulin-like growth factor I (IGF-I), IGF-II, and IGF-binding protein-3, were ineffective. This lack of effect of IGFs may be due to an inhibitory IGFBP, which we demonstrate to be present in increased amounts in the involuting mammary gland.

Animals↗
PubMed2001

Cooperative effects of STAT5 (signal transducer and activator of transcription 5) and C/EBPbeta (CCAAT/enhancer-binding protein-beta) on beta-casein gene transcription are mediated by the glucocorticoid receptor.

Beta-casein gene transcription is controlled primarily by a composite response element (CoRE) that integrates signaling from the lactogenic hormones, PRL, insulin, and hydrocortisone, in mammary epithelial cells. This CoRE contains binding sites for STAT5 (signal transducer and activator of transcription 5) and C/EBPbeta (CCAAT/enhancer-binding protein-beta) and several half-sites for glucocorticoid receptor (GR). To examine how interactions among these three transcription factors might regulate beta-casein gene transcription, a COS cell reconstitution system was employed. Cooperative transactivation was observed when all three factors were expressed, but unexpectedly was not seen between STAT5 and C/EBPbeta in the absence of full-length, transcriptionally active GR. Cooperativity required the amino-terminal transactivation domain of C/EBPbeta, and neither C/EBPalpha nor C/EBPdelta was able to substitute for C/EBPbeta when cotransfected with STAT5 and GR. Different GR determinants were needed for transcriptional cooperation between STAT5 and GR as compared with those required for all three transcription factors. These studies provide some new insights into the mechanisms responsible for high level, tissue-specific expression conferred by the beta-casein CoRE.

Animals↗
PubMed1995

Developmentally and hormonally regulated CCAAT/enhancer-binding protein isoforms influence beta-casein gene expression.

A highly conserved CCAAT/enhancer-binding protein (C/EBP)-binding site centered around -134 relative to the transcription start site in the rat beta-casein gene promoter is capable of interacting specifically with recombinant and mammary gland C/EBP proteins. Western blot analysis indicates that C/EBP levels change dramatically throughout mammary gland development. C/EBP alpha expression is barely detectable in mammary glands from virgin and pregnant animals but is expressed at high levels during lactation and at lower levels during involution. The expression of three C/EBP beta isoforms [the liver-enriched activating proteins (LAPs); and the liver-enriched inhibiting protein (LIP)] is elevated throughout pregnancy, with LIP expression increasing more than 100-fold. Thus, during pregnancy, a low LAP/LIP ratio (< 5) is maintained. C/EBP beta expression decreases at parturition, with LIP diminishing to levels observed in the virgin gland. Therefore, during lactation a more than 100-fold increase in the LAP/LIP ratio is observed. Treatment of the HC11 mammary epithelial cell line with hydrocortisone results in a 10- to 20-fold inhibition of LIP expression, with only minor changes in LAP levels. Therefore, glucocorticoids may impinge upon beta-casein gene expression by altering the ratio of the inhibitory to the activating isoforms of C/EBP beta. Several previously defined casein gene promoter regions capable of conferring hormone and extracellular matrix inducibility to reporter genes in mammary cells are suggested to be composite response elements, containing putative binding sites for the same set of hormonally and developmentally regulated factors: C/EBP, MGF/Stat5, and the glucocorticoid receptor.

Animals↗
PubMed2006

Distal regulation of alternative splicing by splicing enhancer in equine beta-casein intron 1.

The complexity of cotranscriptional splicing is reflected in the coordinated interplay between various cis-elements and transacting factors. In this report, we demonstrated that a cis-element in intron 1 of the equine beta-casein gene (intronic splicing enhancer 1, ISE1) increases the inclusion of all weak exons in its pre-mRNA. The ISE1 also functioned on a hybrid transcript, which was transcribed from the alpha-globin promoter, where it increased the inclusion of the human fibronectin EDA exon and the beta-casein exon 5. The region of ISE1 necessary for its function included the same sequence as is found in some exonic splicing enhancers. Since the ISE1 influenced the splicing of the entire transcript from intron 1, we propose a model for the cotranscriptional splicing of beta-casein mRNA, where the 5' end of the growing transcript remains associated with the C-terminal domain of RNA polymerase II. Thus, the ISE1 remains in close proximity to the mRNA exit groove throughout transcription and influences all weak exons as soon as they are copied.

Alternative Splicing↗
PubMed1997

Reduction of renal transforming growth factor-beta activity without aggravation of growth retardation in nephritic rats by a methionine-threonine-supplemented low-casein diet.

The effects of a low-casein diet fortified with methionine and threonine on renal cortical and glomerular transforming growth factor (TGF)-beta activity were studied in rats with nephritis induced by anti-rat kidney glomerular basement membrane antiserum. Both normal and nephritic rats were fed experimental diets for 10 days. An injection of nephrotoxic serum increased urinary protein excretion and renal TGF-beta activity. A methionine-threonine-supplemented 8.5% casein diet, compared with a basal 20% casein diet, decreased these two measurements without aggravating growth retardation in nephritic rats. These results suggest that aggravation and alleviation of symptoms incident to anti-GBM nephritis are relevant to elevation and reduction of TGF-beta activity, respectively. The results also suggest that amino acid-balanced low-protein diets would have beneficial effects on glomerulonephritis without causing severe protein malnutrition.

Animals↗
PubMed1997

Comparison between dietary soybean protein and casein of the inhibiting effect on atherogenesis in the thoracic aorta of hypercholesterolemic (ExHC) rats treated with experimental hypervitamin D.

Atherosclerotic lesions of the thoracic aorta were induced in exogenously hypercholesterolemic (ExHC) rats by treating initially with hypervitamin D2 and subsequently feeding on hypercholesterolemic diets for 180 days. Dietary soybean protein, in comparison with casein, substantially decreased the degree of atherosclerotic lesions, which was evaluated by intimal thickening, although with a similar topographical distribution. The casein-fed rats tended to maintain a high concentration of serum cholesterol, particularly in triacylglycerol-rich lipoproteins. The concentrations of apo A-I and TBARS in the serum was comparable between the dietary protein groups. The data suggest that dietary soybean protein, compared to casein, produced lipoproteins which were less atherosclerotic by partitioning cholesterol in the triacylglycerol-poor lipoproteins.

Animals↗
PubMed1999

Stimulative effect of a casein hydrolysate on exocrine pancreatic secretion that is independent of luminal trypsin inhibitory activity in rats.

We have previously demonstrated that proteins could stimulate pancreatic secretion independently of luminal bile-pancreatic juice (BPJ) in a BPJ-diverted rat. To determine whether luminal protease-independent pancreatic secretion occurs in normal rats with BPJ returned to the upper small intestine, we investigated the pancreatic secretory response to intraduodenal instillation of a casein hydrolysate or the synthetic trypsin inhibitor, FOY 305, at concentrations which could almost equally inhibit hydrolysis of the synthetic substrate for trypsin with the luminal content. FOY 305 at 10 micrograms/ml and casein hydrolysate solutions at both 100 and 200 mg/ml similarly inhibited approx. 80% of the tryptic activity in the luminal contents of the proximal small intestine. Intraduodenal administration of casein hydrolysate solutions (100 and 200 mg/ml) significantly increased pancreatic secretion in a dose-dependent manner. However, intraduodenal administration of FOY 305 (10 micrograms/ml) was ineffective for stimulating pancreatic secretion. These results demonstrate that dietary protein enhances pancreatic secretion independently of the masking of luminal trypsin activity in rats.

Adolescent↗
PubMed2001

Arginine as an exacerbating factor for glomerulonephritis in rats fed a methionine-threonine-supplemented low casein diet.

We previously demonstrated that a methionine-threonine-supplemented low (8.5%) casein diet (8.5CMT) reduced symptoms such as proteinuria in nephritic rats without severe protein malnutrition. In this study, we examined whether or not L-arginine supplementation to 8.5CMT would exacerbate proteinuria and other symptoms in nephritic rats. Male Wistar rats with glomerulonephritis induced by a single intravenous injection of nephrotoxic serum were fed either a 20% casein diet (control), 8.5% casein diet, 8.5CMT, or L-arginine-supplemented 8.5CMT (8.5CMTA) for 16 days. The 8.5CMTA, as compared with the 8.5CMT, aggravated proteinuria and glomerulonephritis. Administration of L-N(G)-nitroarginine methyl ester, an inhibitor of nitric oxide synthase, to 8.5CMTA-fed nephritic rats by drinking water for 14 days canceled the adverse effect of L-arginine on proteinuria and histopathological damage in glomeruli. These results suggest that the supplementation of L-arginine makes exacerbation via nitric oxide production in glomerulonephritis.

Animals↗
PubMed2002

Differential effects of dietary casein and soybean protein isolate on lipopolysaccharide-induced hepatitis in D-galactosamine-sensitized rats.

Effects of dietary protein type on lipopolysaccharide (LPS)-induced hepatitis, as assessed by plasma alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities, were investigated in D-galactosamine (GalN)-sensitized rats. The plasma ALT and AST activities in rats fed on 25% soybean protein isolate (SPI) diet were significantly suppressed to about 1/4 and 1/5 of the values in rats fed on 25% casein diet, respectively, 8 h after the injection of LPS + GalN. Although hepatic ALT and AST activities of normal rats were also lower in the SPI group than in the casein group, this could not explain the differences in plasma enzyme activities between the two groups. The hepatic glutathione concentration of normal rats was lower in the SPI group than in the casein group, but it was reversed in rats injected with drugs. The results suggest that SPI can protect animals from LPS + GalN-induced hepatitis, and that the hepatic glutathione level may participate in the effects of SPI.

Alanine Transaminase↗
PubMed2004

Neurite outgrowth-stimulating peptide derived from bovine kappa-casein.

We found a novel peptide that stimulates neurite outgrowth in Neuro-2a mouse neuroblastoma cells, from the pepsin-pancreatin digest of bovine kappa-casein. The amino acid sequence of this peptide is Phe-Leu-Pro-Tyr-Pro-Tyr (FLPYPY), corresponding to peptidic sequence 76-81 of bovine kappa-casein. The neurite outgrowth-stimulating activity of FLPYPY was seen over 10(-9) M. On the other hand, FLPYP and FLPYPYY, which corresponded to sequences 76-80 and 76-82 of bovine kappa-casein respectively, were ineffective.

Amino Acid Sequence↗
PubMed1988

Chemical characterization of a caseinophosphopeptide isolated from in vivo digests of a casein diet.

The in vivo formation of phosphopeptides derived from bovine casein was proved in small intestinal chyme of minipigs after ingestion of a diet containing casein. The main phosphopeptide was identified as a fragment of alpha s1-casein (f 66-74): SerP-SerP-SerP-Glu-Glu-Ile-Val-Pro-Asn. It is discussed, that caseinophosphopeptides are likely to promote the intestinal absorption of calcium and trace elements.

Amino Acids↗
PubMed2005

Pressure-induced dissociation of casein micelles: size distribution and effect of temperature.

Pressure-induced dissociation of a turbid solution of casein micelles was studied in situ in static and dynamic light scattering experiments. We show that at high pressure casein micelles decompose into small fragments comparable in size to casein monomers. At intermediate pressure we observe particles measuring 15 to 20 nm in diameter. The stability against pressure dissociation increased with temperature, suggesting enhanced hydrophobic contacts. The pressure transition curves are biphasic, compatible with a temperature (but not pressure)-dependent conformational equilibrium of two micelle species. Our thermodynamic model predicts an increase in structural entropy with temperature.

Caseins↗