Early soy exposure via maternal diet regulates rat mammary epithelial differentiation by paracrine signaling from stromal adipocytes

Infant Formula Feeding Changes the Proliferative Status in Piglet Neonatal Mammary Glands Independently of Estrogen Signaling

BACKGROUND

Soy infant formula contains isoflavones, which are able to bind to and activate estrogen receptor (ER) pathways. The mammary gland is sensitive to estrogens, raising concern that the use of soy formulas may promote premature development.

OBJECTIVE

We aimed to determine if soy formula feeding increases mammary gland proliferation and differentiation in comparison to other infant postnatal diets.

METHODS

White-Dutch Landrace piglets aged 2 d received either sow milk (Sow), or were provided milk formula (Milk), soy formula (Soy), milk formula supplemented with 17-beta-estradiol (2 mg/(kg·d); M + E2), or milk formula supplemented with genistein (84 mg/L of diet; M + G) until day 21. Mammary gland proliferation and differentiation was assessed by histology, and real-time RT-PCR confirmation of differentially expressed genes identified by microarray analysis.

RESULTS

Mammary terminal end bud numbers were 19-31% greater in the Milk, Soy, and M + G groups relative to the Sow and M + E2, P <0.05. Microarray analysis identified differentially expressed genes between each formula-fed group relative to the Sow (±1.7-fold, P <0.05). Real-time RT-PCR confirmed 2- to 4-fold increases in mRNA transcripts of genes involved in cell proliferation, insulin-like growth factor 1 (IGF1), fibroblast growth factor 10 (FGF10), and fibroblast growth factor 18 (FGF18), in all groups relative to the Sow, P <0.05. In contrast, genes involved in cell differentiation and ductal morphogenesis, angiotensin II receptor type 2 (AGTR2), microtubule associated protein 1b (MAP1B), and kinesin family member 26b (KIF26B), were significantly upregulated by 2-, 4-, and 13-fold, respectively, in the M + E2 group. Additionally, mRNA expression of ER-specific gene targets, progesterone receptor (PGR), was increased by 12-fold, and amphiregulin (AREG) and Ras-like estrogen regulated growth inhibitor (RERG) expression by 1.5-fold in the M + E2 group, P <0.05. In the soy and M + G groups, mRNA expressions of fatty acid synthesis genes were increased 2- to 4-fold.

CONCLUSIONS

Our data indicate soy formula feeding does not promote ER-signaling in the piglet mammary gland. Infant formula feeding (milk- or soy-based) may initiate proliferative pathways independently of estrogenic signaling.

Dietary daidzein, but not genistein, has a hypocholesterolemic effect in non-ovariectomized and ovariectomized female Sprague-Dawley rats on a cholesterol-free diet

We compared the effects of two major isoflavones, daidzein and genistein, on lipid metabolism in rats. Daidzein (150 mg/kg diet), genistein (150 mg/kg diet), daidzein and genistein (1:1, 300 mg/kg diet), or control diets were fed to 4 groups of 6-week-old ovariectomized (Ovx) and non-Ovx Sprague Dawley rats for 4 weeks. Dietary daidzein, but not genistein, reduced serum and hepatic total cholesterol levels significantly relative to that by the control group, regardless of whether the rats had undergone ovariectomy. Genistein did not exhibit any physiological effects on lipid levels, but did affect genes involved in cholesterol metabolism. These results indicate that daidzein and genistein may influence lipid regulation via differing modes of action.

The α' subunit of β-conglycinin and various glycinin subunits of soy are not required to modulate hepatic lipid metabolism in rats

PURPOSE

This study examined the effect of soy proteins with depletion of different subunits of the two major storage proteins, β-conglycinin and glycinin, on hepatic lipids and proteins involved in lipid metabolism in rats, since the bioactive component of soy responsible for lipid-lowering is unclear.

METHODS

Weanling Sprague Dawley rats were fed diets containing either 20% casein protein in the absence (casein) or presence (casein + ISF) of isoflavones or 20% alcohol-washed soy protein isolate (SPI) or 20% soy protein concentrates derived from a conventional (Haro) or 2 soybean lines lacking the α' subunit of β-conglycinin and the A1-3 (1TF) or A1-5 (1a) subunits of glycinin. After 8 weeks, the rats were necropsied and liver proteins and lipids were extracted and analysed.

RESULTS

The results showed that soy protein diets reduced lipid droplet accumulation and content in the liver compared to casein diets. The soy protein diets also decreased the level of hepatic mature SREBP-1 and FAS in males, with significant decreases in diets 1TF and 1a compared to the casein diets. The effect of the soy protein diets on female hepatic mature SREBP-1, FAS, and HMGCR was confounded since casein + ISF decreased these levels compared to casein alone perhaps muting the decrease by soy protein. A reduction in both phosphorylated and total STAT3 in female livers by ISF may account for the gender difference in mechanism in the regulation and protein expression of the lipid modulators.

CONCLUSIONS

Overall, soy protein deficient in the α' subunit of β-conglycinin and A1-5 subunits of glycinin maintain similar hypolipidemic function compared to the conventional soy protein. The exact bioactive component(s) warrant identification.

Vitamin D metabolism-related genetic variants, dietary protein intake and improvement of insulin resistance in a 2 year weight-loss trial: POUNDS Lost

AIMS/HYPOTHESIS

Vitamin D and related genetic variants are associated with obesity and insulin resistance. We aimed to examine whether vitamin D metabolism-related variants affect changes in body weight and insulin resistance in response to weight-loss diets varying in macronutrient content.

METHODS

Three vitamin D metabolism-related variants, DHCR7 rs12785878, CYP2R1 rs10741657 and GC rs2282679, were genotyped in 732 overweight/obese participants from a 2 year weight-loss trial (POUNDS Lost). We assessed genotype effects on changes in body weight, fasting levels of glucose and insulin, and HOMA-IR at 6 months (up to 656 participants) and 2 years (up to 596 participants) in response to low-protein vs high-protein diets, and low-fat vs high-fat diets.

RESULTS

We found significant interactions between DHCR7 rs12785878 and diets varying in protein, but not in fat, on changes in insulin and HOMA-IR at both 6 months (p for interaction <0.001) and 2 years (p for interaction ≤ 0.03). The T allele (vitamin-D-increasing allele) of DHCR7 rs12785878 was associated with greater decreases in insulin and HOMA-IR (p < 0.002) in response to high-protein diets, while there was no significant genotype effect on changes in these traits in the low-protein diet group. Generalised estimating equation analyses indicated significant genotype effects on trajectory of changes in insulin resistance over the 2 year intervention in response to high-protein diets (p < 0.001). We did not observe significant interaction between the other two variants and dietary protein or fat on changes in these traits.

CONCLUSIONS/INTERPRETATION

Our data suggest that individuals carrying the T allele of DHCR7 rs12785878 might benefit more in improvement of insulin resistance than noncarriers by consuming high-protein weight-loss diets.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00072995.

Polyphenols as Modulator of Oxidative Stress in Cancer Disease: New Therapeutic Strategies

Cancer onset and progression have been linked to oxidative stress by increasing DNA mutations or inducing DNA damage, genome instability, and cell proliferation and therefore antioxidant agents could interfere with carcinogenesis. It is well known that conventional radio-/chemotherapies influence tumour outcome through ROS modulation. Since these antitumour treatments have important side effects, the challenge is to develop new anticancer therapeutic strategies more effective and less toxic for patients. To this purpose, many natural polyphenols have emerged as very promising anticancer bioactive compounds. Beside their well-known antioxidant activities, several polyphenols target epigenetic processes involved in cancer development through the modulation of oxidative stress. An alternative strategy to the cytotoxic treatment is an approach leading to cytostasis through the induction of therapy-induced senescence. Many anticancer polyphenols cause cellular growth arrest through the induction of a ROS-dependent premature senescence and are considered promising antitumour therapeutic tools. Furthermore, one of the most innovative and interesting topics is the evaluation of efficacy of prooxidant therapies on cancer stem cells (CSCs). Several ROS inducers-polyphenols can impact CSCs metabolisms and self-renewal related pathways. Natural polyphenol roles, mainly in chemoprevention and cancer therapies, are described and discussed in the light of the current literature data.

Dose-dependent effects of isoflavone exposure during early lifetime on the rat mammary gland: Studies on estrogen sensitivity, isoflavone metabolism, and DNA methylation

SCOPE

Isoflavone (ISO) exposure during adolescence modulates 17β-estradiol (E2) sensitivity of the adult mammary gland. The present study investigated the dose dependency of these effects focusing on proliferation, estrogen receptor dependent and independent gene expression, as well as DNA methylation and ISO metabolism.

METHODS AND RESULTS

Female Wistar rats were lifelong exposed to an ISO-depleted diet or to diets enriched with a soy ISO extract (ISO-rich diet (IRD)) causing plasma concentrations as observed minimally (IRDlow) and maximally (IRDhigh) in Asian women. The extract was characterized by both phytochemical analysis and E-Screen. Rats were ovariectomized at postnatal day (PND) 80 and treated with E2 from PND94 to 97. In contrast to uterine response, body weight and visceral fat mass were affected by ISO. In the mammary gland, both E2-induced proliferation (proliferating cell nuclear antigen staining) and estrogen receptor activation (progesterone receptor staining) were significantly reduced by IRDhigh but not by IRDlow, which however attenuated Gdf15 mRNA expression. DNA methylation analysis revealed significant differences in the promoter regions of Aldhl1, Extl1, and WAP between IRDhigh and ISO-depleted diet.

CONCLUSION

Lifelong exposure to ISO results in dose-dependent differential effects on proliferation, gene expression, and DNA methylation in rat mammary glands. Yet, a decrease in estrogen responsiveness was only achieved by IRDhigh.

Genetic improvement of the microalga Phaeodactylum tricornutum for boosting neutral lipid accumulation

To obtain fast growing oil-rich microalgal strains has been urgently demanded for microalgal biofuel. Malic enzyme (ME), which is involved in pyruvate metabolism and carbon fixation, was first characterized in microalgae here. Overexpression of Phaeodactylum tricornutum ME (PtME) significantly enhanced the expression of PtME and its enzymatic activity in transgenic P. tricornutum. The total lipid content in transgenic cells markedly increased by 2.5-fold and reached a record 57.8% of dry cell weight with a similar growth rate to wild type, thus keeping a high biomass. The neutral lipid content was further increased by 31% under nitrogen-deprivation treatment, still 66% higher than that of wild type. Transgenic microalgae cells exhibited obvious morphological changes, as the cells were shorter and thicker and contained larger oil bodies. Immuno-electron microscopy targeted PtME to the mitochondrion. This study markedly increased the oil content in microalgae, suggesting a new route for developing ideal microalgal strains for industrial biodiesel production.

Maternal western style diet increases susceptibility to chemically-induced mammary carcinogenesis in female rats offspring

The present study investigated whether maternal exposure to western style diet (WD) increases susceptibility to mammary carcinogenesis induced by N-methyl-N-nitrosourea (MNU) in female offspring. Pregnant female Sprague-Dawley rats received WD diet or control diet from gestational day 12 until postnatal day (PND) 21. At PND 21, female offspring received a single dose of MNU (50 mg/kg body weight) and were fed chow diet until PND 110. Mammary gland structures were assessed on whole-mount preparations in the offspring at PND 21, and tumor morphology was examined at PND 110. Immunohistochemical analysis for cell proliferation (PCNA), apoptosis (cleaved caspase-3) and estrogen receptor alpha (ER-α) was performed in mammary terminal end buds (TEBs) at PND 21, and PCNA, ER-α, and p63 analysis in mammary tumors at PND 110. Maternal WD intake induced a significant increase in the number of TEBs (P = 0.024) and in PCNA labeling index (P < 0.020) in the mammary glands at PND 21. Tumor multiplicity, tumor weight, and PCNA labeling indexes were significantly higher in the WD offspring than that of the control offspring (P < 0.05). These findings indicate that maternal western style diet potentially enhanced the development of mammary tumors induced by MNU in female offspring, possibly by affecting the mammary gland differentiation.

Feeding soy protein isolate and treatment with estradiol have different effects on mammary gland morphology and gene expression in weanling male and female rats

Isoflavones are phytochemical components of soy diets that bind weakly to estrogen receptors (ERs). To study potential estrogen-like actions of soy in the mammary gland during early development, we fed weanling male and female Sprague-Dawley rats a semipurified diet with casein as the sole protein source from postnatal day 21 to 33, the same diet substituting soy protein isolate (SPI) for casein, or the casein diet supplemented with estradiol (E2) at 10 μg/kg/day. In contrast to E2, the SPI diet induced no significant change in mammary morphology. In males, there were 34 genes for which expression was changed ≥2-fold in the SPI group vs. 509 changed significantly by E2, and 8 vs. 174 genes in females. Nearly half of SPI-responsive genes in males were also E2 responsive, including adipogenic genes. Serum insulin was found to be decreased by the SPI diet in males. SPI and E2 both downregulated the expression of ERα ( Esr1) in males and females, and ERβ ( Esr2) only in males. Chromatin immunoprecipitation revealed an increased binding of ERα to the promoter of the progesterone receptor ( Pgr) and Esr1 in both SPI- and E2-treated males compared with the casein group but differential recruitment of ERβ. ER promoter binding did not correlate with differences in Pgr mRNA expression. This suggests that SPI fails to recruit appropriate co-activators at E2-inducible genes. Our results indicate that SPI behaves like a selective estrogen receptor modulator rather than a weak estrogen in the developing mammary gland.

Early growth response protein-1 mediates lipotoxicity-associated placental inflammation: role in maternal obesity

Obesity is associated with low-grade chronic inflammation, which contributes to cellular dysfunction promoting metabolic disease. Obesity during pregnancy leads to a proinflammatory milieu in the placenta; however, the underlying causes for obesity-induced placental inflammation remain unclear. Here, we examine the mechanisms by which saturated fatty acids and inflammatory cytokines induce inflammation in placental trophoblasts. We conducted global transcriptomic profiling in BeWo cells following palmitate and/or TNFα treatment and gene/protein expression analyses of MAPK pathways and characterized downstream transcription factors directly regulating inflammatory cytokines. Microarray analysis revealed increased expression of genes regulating inflammation, stress response, and immediate early response in cytotrophoblasts in response to palmitic acid (PA), TNFα, or a combination of both (PA + TNFα). Both gene ontology and gene set enrichment analysis revealed MAPK and EGR-1 signaling to be upregulated in BeWo cells, which was confirmed via immunoblotting. Importantly, activation of JNK signaling was necessary for increased proinflammatory cytokine (IL-6, TNFα, and IL-8) and EGR1 mRNA. Consistent with the requirement of JNK signaling, ChIP analysis confirmed the recruitment of c-Jun and other MAPK-responsive immediate early factors on the EGR1 promoter. Moreover, recruitment of EGR-1 on cytokine promoters (IL-6, TNFα, and IL-8) and an impaired proinflammatory response following knockdown of EGR-1 suggested it as a central component of the mechanism facilitating inflammatory gene expression. Finally, akin to in vitro findings, term placenta from obese women also had both increased JNK and p38 signaling and greater EGR-1 protein relative to lean women. Our results demonstrate that lipotoxic insults induce inflammation in placental cells via activation of JNK/EGR-1 signaling.

Repression of mammary adipogenesis by genistein limits mammosphere formation of human MCF-7 cells

Mammary adipose tissue may contribute to breast cancer development and progression by altering neighboring epithelial cell behavior and phenotype through paracrine signaling. Dietary exposure to soy foods is associated with lower mammary tumor risk and reduced body weight and adiposity in humans and in rodent breast cancer models. Despite the suggested linkage between obesity and breast cancer, the local influence of bioactive dietary components on mammary adiposity for antitumor effects remains unknown. Herein, we report that post-weaning dietary exposure to soy protein isolate and its bioactive isoflavone genistein (GEN) lowered mammary adiposity and increased mammary tumor suppressor PTEN and E-cadherin expression in female mice, relative to control casein diet. To ascertain GEN's role in mammary adipose deposition that may affect underlying epithelial cell phenotype, we evaluated GEN's effects on SV40-immortalized mouse mammary stromal fibroblast-like (MSF) cells during differentiation into adipocytes. MSF cells cultured in a differentiation medium with 40 nM GEN showed reductions in mature adipocyte numbers, triglyceride accumulation, and Pparγ (Pparg) and fatty acid synthase transcript levels. GEN inhibition of adipose differentiation was accompanied by increased estrogen receptor β (Erβ (Esr2)) gene expression and was modestly recapitulated by ERβ-selective agonist 2,3-bis-(4-hydroxyphenyl)-propionitrile (DPN). Reduction of Erβ expression by siRNA targeting increased Pparγ transcript levels and stromal fibroblast differentiation into mature adipocytes; the latter was reversed by GEN but not by DPN. Conditioned medium from GEN-treated adipocytes diminished anchorage-independent mammosphere formation of human MCF-7 breast cancer cells. Our results suggest a mechanistic pathway to support direct regulation of mammary adiposity by GEN for breast cancer prevention.

Anti-diabetic functions of soy isoflavone genistein: mechanisms underlying its effects on pancreatic β-cell function

Type 2 diabetes is a result of chronic insulin resistance and loss of functional pancreatic β-cell mass. Strategies to preserve β-cell mass and a greater understanding of the mechanisms underlying β-cell turnover are needed to prevent and treat this devastating disease. Genistein, a naturally occurring soy isoflavone, is reported to have numerous health benefits attributed to multiple biological functions. Over the past 10 years, numerous studies have demonstrated that genistein has anti-diabetic effects, in particular, direct effects on β-cell proliferation, glucose-stimulated insulin secretion and protection against apoptosis, independent of its functions as an estrogen receptor agonist, antioxidant, or tyrosine kinase inhibitor. Effects are structure-specific and not common to all flavonoids. While there are limited data on the effects of genistein consumption in humans with diabetes, there are a plethora of animal and cell-culture studies that demonstrate a direct effect of genistein on β-cells at physiologically relevant concentrations (<10 μM). The effects appear to involve cAMP/PKA signaling and there are some studies that suggest an effect on epigenetic regulation of gene expression. This review focuses on the anti-diabetic effects of genistein in both in vitro and in vivo models and potential mechanisms underlying its direct effects on β-cells.

Cytosolic malic enzyme 1 (ME1) mediates high fat diet-induced adiposity, endocrine profile, and gastrointestinal tract proliferation-associated biomarkers in male mice

BACKGROUND

Obesity and associated hormonal disturbances are risk factors for colon cancer. Cytosolic Malic Enzyme (ME1) generates NADPH used for lipogenesis in gastrointestinal (GI), liver and adipose tissues. We have reported that inclusion of soy protein isolate (SPI) in the diet lowered body fat content and colon tumor incidence of rats fed AIN-93G diet, while others have demonstrated SPI inhibition of rat hepatic ME1 expression. The present study examined the individual and combined effects of dietary SPI and absence of ME1 on: 1) serum concentrations of hormones implicated in colon cancer development, 2) expression of lipogenic and proliferation-associated genes in the mouse colon and small intestine, and 3) liver and adipose expression of lipogenic and adipocytokine genes that may contribute to colon cancer predisposition.

METHODS

Weanling wild type (WT) and ME1 null (MOD-1) male mice were fed high-fat (HF), iso-caloric diets containing either casein (CAS) or SPI as sole protein source for 5 wks. Somatic growth, serum hormone and glucose levels, liver and adipose tissue weights, GI tissue parameters, and gene expression were evaluated.

RESULTS

The MOD-1 genotype and SPI-HF diet resulted in decreases in: body and retroperitoneal fat weights, serum insulin, serum leptin, leptin/adiponectin ratio, adipocyte size, colon mTOR and cyclin D1 mRNA abundance, and jejunum FASN mRNA abundance, when compared to WT mice fed CAS-HF. Regardless of diet, MOD-1 mice had reductions in liver weight, liver steatosis, and colon crypt depth, and increases in adipose tissue expression of IRS1 and IRS2, compared to WT mice. SPI-HF diet reduced ME1 gene expression only in retroperitoneal fat.

CONCLUSIONS

Data suggest that the pharmacological targeting of ME1 or the inclusion of soy protein in the diet may provide avenues to reduce obesity and its associated pro-tumorigenic endocrine environment and improve insulin sensitivity, potentially disrupting the obesity-colon cancer connection.

The maternal womb: a novel target for cancer prevention in the era of the obesity pandemic?

The dramatic rise in worldwide prevalence of obesity has necessitated the search for more efficacious antiobesity strategies to counter the increased cancer risks in overweight and obese individuals. The mechanistic pathways linking obesity status with adult chronic diseases such as cancer remain incompletely understood. A growing body of evidence suggests that novel approaches and interventional agents to disrupt the feed-forward cycle of maternal to offspring obesity transfer that is initiated in utero will be important for stemming both the obesity pandemic and the associated increase in cancer incidence. The convergence of multiple research areas including those encompassing the insulin and insulin-like growth factor systems, epigenetics, and stem cell biology is providing insights into the potential for cancer prevention in adult offspring previously exposed to the intrauterine environment of overweight/obese mothers. Here, we review the current state of this nascent research field, with a focus on three major cancers, namely breast, colorectal, and liver, and suggest some possible future directions to optimize its impact for the health of future generations.

Paracrine-acting adiponectin promotes mammary epithelial differentiation and synergizes with genistein to enhance transcriptional response to estrogen receptor β signaling

Mammary stromal adipocytes constitute an active site for the synthesis of the adipokine, adiponectin (APN) that may influence the mammary epithelial microenvironment. The relationship between "local," mammary tissue-derived APN and breast cancer risk is poorly understood. Here, we identify a novel mechanism of APN-mediated signaling that influences mammary epithelial cell proliferation, differentiation, and apoptosis to modify breast cancer risk. We demonstrate that early dietary exposure to soy protein isolate induced mammary tissue APN production without corresponding effects on systemic APN levels. In estrogen receptor (ER)-negative MCF-10A cells, recombinant APN promoted lobuloalveolar differentiation by inhibiting oncogenic signal transducer and activator of transcription 3 activity. In ER-positive HC11 cells, recombinant APN increased ERβ expression, inhibited cell proliferation, and induced apoptosis. Using the estrogen-responsive 4X-estrogen response element promoter-reporter construct to assess ER transactivation and small interfering RNA targeting of ERα and ERβ, we show that APN synergized with the soy phytoestrogen genistein to promote ERβ signaling in the presence of estrogen (17β-estradiol) and ERβ-specific agonist 2,3-bis(4-hydroxyphenyl)-propionitrile and to oppose ERα signaling in the presence of the ERα-specific agonist 4,4',4'-(4-propyl-(1H)-pyrazole-1,3,5-triyl)trisphenol. The enhancement of ERβ signaling with APN + genistein cotreatments was associated with induction of apoptosis, increased expression of proapoptotic/prodifferentiation genes (Bad, p53, and Pten), and decreased antiapoptotic (Bcl2 and survivin) transcript levels. Our results suggest that mammary-derived APN can influence adjacent epithelial function by ER-dependent and ER-independent mechanisms that are consistent with reduction of breast cancer risk and suggest local APN induction by dietary factors as a targeted approach for promotion of breast health.

Genistein downregulates de novo lipid synthesis and impairs cell proliferation in human lung cancer cells

Cancer cells require high levels of lipid synthesis to produce structural, signaling and energetic lipids to support continuous replication. We and others have reported that constitutively increased lipogenesis, mainly by the tandem activation of acetyl-CoA carboxylase, fatty acid synthase and stearoyl-CoA desaturase-1 (SCD1), is critical to sustain the biological features of cancer cells, making this metabolic pathway a potential anticancer target for nutritional and pharmacological interventions. Isoflavones are biologically potent botanical compounds that possess clear antilipogenic and anticancer properties; however, the regulatory effects of these nutraceutical agents on lipid biosynthesis in cancer cells are still not well understood. Here we show that genistein, an isoflavone abundant in soybeans, decreased the levels of SCD1 protein in H460 human lung adenocarcinoma cells, consequently reducing the rate of biosynthesis of oleic acid as well as its presence in cancer cell lipids. Moreover, genistein promoted a marked reduction in de novo synthesis of major phospholipids, triacylglycerol and cholesterolesters. Finally, cancer cells treated with genistein displayed a dramatic reduction in cell proliferation as a result of a blockade in cell cycle progression through G(2)/M phases. As a whole, our data suggest that, by globally downregulating lipid biosynthesis, genistein suppresses cancer cell growth, emphasizing the relevance of this botanical compound as a potential therapeutic agent against lung cancer, a disease for which therapeutic choices remain limited.

Transplantation of a mammary stromal cell line into a mammary fat pad: development of the site-specific in vivo analysis system for mammary stromal cells

The interaction between mammary epithelial and stromal tissue is considered to be important in breast tissue development. In this study, we developed a transplantation procedure for the mammary stromal fibroblastic cell line (MSF) to examine its life in vivo. First we established MSF cells which stably expressed lacZ (lacZ/MSF) and had characteristics of mammary stromal cells. The lacZ/MSF cells were then transplanted into a cleared mammary fat pad of syngenic mice with and without mammary primary epithelial organoids. Whole mount X-gal and carmine staining of the transplants revealed that a number of undifferentiated lacZ/MSF cells survived around the mammary epithelial tissue when transplanted with organoids. These results indicate that transplantation of MSF cells into mammary fat pad was accomplished by co-transplantation with primary mammary organoids. Finally, we discuss the application of transplantation procedure for in vivo studies of the mammary stromal tissue development and stromal-epithelial interactions.

Bidirectional signaling of mammary epithelium and stroma: implications for breast cancer--preventive actions of dietary factors

The mammary gland is composed of two major cellular compartments: a highly dynamic epithelium that undergoes cycles of proliferation, differentiation and apoptosis in response to local and endocrine signals and the underlying stroma comprised of fibroblasts, endothelial cells and adipocytes, which collectively form the mammary fat pad. Breast cancer originates from subversions of normal growth regulatory pathways in mammary epithelial cells due to genetic mutations and epigenetic modifications in tumor suppressors, oncogenes and DNA repair genes. Diet is considered a highly modifiable determinant of breast cancer risk; thus, considerable efforts are focused on understanding how certain dietary factors may promote resistance of mammary epithelial cells to growth dysregulation. The recent indications that stromal cells contribute to the maintenance of the mammary epithelial 'niche' and the increasing appreciation for adipose tissue as an endocrine organ with a complex secretome have led to the novel paradigm that the mammary stromal compartment is itself a relevant target of bioactive dietary factors. In this review, we address the potential influence of dietary factors on mammary epithelial-stromal bidirectional signaling to provide mechanistic insights into how dietary factors may promote early mammary epithelial differentiation to decrease adult breast cancer risk.

PTEN and p53 cross-regulation induced by soy isoflavone genistein promotes mammary epithelial cell cycle arrest and lobuloalveolar differentiation

The tumor suppressors phosphatase and tensin homologue deleted on chromosome ten (PTEN) and p53 are closely related to the pathogenesis of breast cancer, yet pathway-specific mechanisms underlying their participation in mediating the protective actions of dietary bioactive components on breast cancer risk are poorly understood. We recently showed that dietary exposure to the soy isoflavone genistein (GEN) induced PTEN expression in mammary epithelial cells in vivo and in vitro, consistent with the breast cancer preventive effects of soy food consumption. Here, we evaluated PTEN and p53 functional interactions in the nuclear compartment of mammary epithelial cells as a mechanism for mammary tumor protection by GEN. Using the non-tumorigenic human mammary epithelial cells MCF10-A, we demonstrate that GEN increased PTEN expression and nuclear localization. We show that increased nuclear PTEN levels initiated an autoregulatory loop involving PTEN-dependent increases in p53 nuclear localization, PTEN-p53 physical association, PTEN-p53 co-recruitment to the PTEN promoter region and p53 transactivation of PTEN promoter activity. The PTEN-p53 cross talk induced by GEN resulted in increased cell cycle arrest; decreased pro-proliferative cyclin D1 and pleiotrophin gene expression and the early formation of mammary acini, indicative of GEN promotion of lobuloalveolar differentiation. Our findings provide support to GEN-induced PTEN as both a target and regulator of p53 action and offer a mechanistic basis for PTEN pathway activation to underlie the antitumor properties of dietary factors, with important implications for reducing breast cancer risk.

Maternal overweight programs insulin and adiponectin signaling in the offspring

Gestational exposure to maternal overweight (OW) influences the risk of obesity in adult life. Male offspring from OW dams gain greater body weight and fat mass and develop insulin resistance when fed high-fat diets (45% fat). In this report, we identify molecular targets of maternal OW-induced programming at postnatal d 21 before challenge with the high-fat diet. We conducted global transcriptome profiling, gene/protein expression analyses, and characterization of downstream signaling of insulin and adiponectin pathways in conjunction with endocrine and biochemical characterization. Offspring born to OW dams displayed increased serum insulin, leptin, and resistin levels (P < 0.05) at postnatal d 21 preceding changes in body composition. A lipogenic transcriptome signature in the liver, before development of obesity, was evident in OW-dam offspring. A coordinated locus of 20 sterol regulatory element-binding protein-1-regulated target genes was induced by maternal OW. Increased nuclear levels of sterol regulatory element-binding protein-1 and recruitment to the fatty acid synthase promoter were confirmed via ELISA and chromatin immunoprecipitation analyses, respectively. Higher fatty acid synthase and acetyl coenzyme A carboxylase protein and pAKT (Thr(308)) and phospho-insulin receptor-beta were confirmed via immunoblotting. Maternal OW also attenuated AMP kinase/peroxisome proliferator-activated receptor-alpha signaling in the offspring liver, including transcriptional down-regulation of several peroxisome proliferator-activated receptor-alpha-regulated genes. Hepatic mRNA and circulating fibroblast growth factor-21 levels were significantly lower in OW-dam offspring. Furthermore, serum levels of high-molecular-weight adiponectin (P < 0.05) were decreased in OW-dam offspring. Phosphorylation of hepatic AMP-kinase (Thr(172)) was significantly decreased in OW-dam offspring, along with lower AdipoR1 mRNA. Our results strongly suggest that gestational exposure to maternal obesity programs multiple aspects of energy-balance regulation in the offspring.

In utero and lactational exposure to blueberry via maternal diet promotes mammary epithelial differentiation in prepubescent female rats

Early developmental events influence the fine tuning of later susceptibility to adult diseases. Diet is a determinant of breast cancer risk, and our previous studies showed that diet-mediated changes in transcriptional programs promote early mammary gland differentiation. Although consumption of fruits is considered to elicit multiple health benefits, little is known on whether associated bioactive components modify the early differentiation program in developing mammary glands. Here, we evaluated the hypothesis that early exposure (in utero and lactational) to blueberry through maternal diet enhances mammary epithelial differentiation in female offspring. Pregnant Sprague-Dawley rats beginning at gestation day 4 were fed American Institute of Nutrition-based diets containing casein and whole blueberry powders added to casein at 2.5%, 5.0%, and 10% weight/weight. Female pups at weaning were evaluated for growth and mammary tissue parameters. Blueberry at 5% dose increased body and adipose fat weights, relative to the other diets. Mammary branch density and terminal end bud size were highest for the 5% blueberry group, whereas terminal end bud numbers were not affected by all diets. Mammary ductal epithelial cells of the 5% blueberry group had lower nuclear phosphorylated histone 3 and higher nuclear tumor suppressor phosphatase and tensin homolog deleted in chromosome 10 (PTEN) levels than the casein group. Although sera of both diet groups had similar antioxidant capacity, 5% blueberry sera elicited higher nuclear PTEN accumulation in human MCF-10A mammary epithelial cells. Our studies identify developing mammary glands as early targets of blueberry-associated bioactive components, possibly through systemic effects on epithelial PTEN signaling.

Carbohydrate-responsive gene expression in the adipose tissue of rats

Although obesity is often associated with high-fat diets, it can develop from a variety of meal patterns. Excessive intake of simple carbohydrates is one consistent eating behavior leading to obesity. However, the impact of overconsumption of diets with high carbohydrate to fat ratios (C/F) on body composition and global adipose tissue gene expression remains unclear. We used total enteral nutrition to evaluate the effects of caloric intake and C/F on body weight gain and development of obesity. Female Sprague Dawley rats were fed diets with either low C/F or high C/F (HC) (reflecting a 19.5-fold increase in C/F) at two levels of caloric intake: 187 or 220 kcal/kg(3/4) x d (15% excess) for 4 wk. At the end of the study period, rats fed HC diets had about 20% higher body weight at either caloric intake compared with rats fed low C/F diets (P < 0.05). Body composition (assessed by nuclear magnetic resonance, computerized tomography, and adipose tissue weights) revealed higher percent fat mass (P < 0.05) in HC rats. Obesity was associated with increased serum resistin, leptin, fasting hyperinsulinemia, and insulin resistance after an oral glucose challenge (P < 0.05). Microarray analyses of adipose tissues revealed HC diets led to changes in 270 and 464 transcripts at 187 and 220 kcal/kg(3/4) x d intakes. Genes regulating glucose transport, glycolysis, fatty acid and triglyceride biosynthesis, desaturation and elongation, adipogenesis, and adipokines were affected by HC diets. These results suggest that C/F and interactions with excessive caloric intake per se may regulate body composition and play important roles in the development of obesity and metabolic syndrome.