Mice deficient in Sfrp1 exhibit increased adiposity, dysregulated glucose metabolism, and enhanced macrophage infiltration

A positive correlation of serum SFRP1 levels with the risk of developing type 2 diabetes mellitus: a case-control study

OBJECTIVE

Secreted frizzled-related protein 1 (SFRP1) is an adipokine whose production is significantly altered in metabolic disorders. Considering the relationship between dysfunction of Wnt/β-catenin signaling and metabolic disorders as well as the inhibitory effects of SFRP1 on this signaling pathway, the present work aimed to investigate the correlation between serum SFRP1 levels and type 2 diabetes mellitus (T2DM) and its developing risk factors for the first time.

METHODS

This case-control study measured serum levels of SFRP1, tumor necrosis factor (TNF)-α, interleukin (IL)-6, adiponectin, and fasting insulin using enzyme-linked immunosorbent assay kits in 80 T2DM patients and 80 healthy individuals. Biochemical parameters were determined using the AutoAnalyzer instrument.

RESULTS

The T2DM group had higher levels of SFRP1 compared with the controls (146.8100 ± 43.61416 vs 81.9531 ± 32.78545 pg/mL; P < .001). There was a positive correlation between SFRP1 and insulin (r = 0.327, P = .003), TNF-α (r = 0.420, P < .001) as well as homeostatic model assessment for insulin resistance (r = 0.328, P = .003) in the T2DM group. In addition, 10-unit changes in SFRP1 levels showed the risk of T2DM in both the unadjusted (odds ratio [OR] [95% CI] = 1.564 [1.359-1.800]) and adjusted models accounting for age, gender, and body mass index (OR [95% CI] = 1.564 [1.361-1.799]; P < .001). A cut-off value of SFRP1 (105.83 pg/mL) was identified to distinguish between the T2DM patients and the healthy subjects, with sensitivity of 75.0% and specificity of 80.0%.

CONCLUSION

According to our research, there was a significant and positive link between the amount of SFRP1 and the likelihood of developing T2DM as well as the related factors like insulin resistance index and TNF-α. These results indicated that SFRP1 might have a potential role in the development of T2DM.

SFRP1 decreases WNT-Mediated M2 macrophage marker expression in breast tissue

The Wnt family of secreted proteins are involved in mammary gland development and tumorigenesis. It has recently been shown that Wnt ligands promote M2 macrophage polarization and so we sought to determine the effects of a Wnt signaling antagonist, Secreted Frizzled Related Protein 1 (SFRP1), on M2 marker expression. We measured a murine M2 marker (Arg1) in mice with a targeted deletion of Sfrp1 during different stages of mammary gland development including puberty, pregnancy, and lactation, as well as in response to obesity. Next, to determine whether Wnt signaling/antagonism affects human M2 markers (CD209 and CCL18), we treated a human patient derived explant (PDE) breast tissue sample with exogenous Wnt3a in the presence and absence of rSFRP1. Finally, we expanded our PDE study to 13 patients and performed bulk RNAseq analysis following the treatment described above. We found that in loss of Sfrp1 in the murine mammary gland increased Arg1 expression. Moreover, we showed that Wnt3a increases CD209 and CCL18 mRNA and protein expression in breast PDEs and that their expression is decreased in response to rSFRP1. Our RNAseq analysis unveiled novel genes that were affected by Wnt3a treatment and subsequently reversed when rSFRP1 was added. Validation of these data exhibited that chemokines involved in promoting macrophage polarization and cancer metastasis, including CCL11 and CCL26, were stimulated by Wnt3a signaling and their expression was abrogated by treatment with rSFRP1. Our data suggest that SFRP1 may be an important mediator that tempers Wnt signaling in the tumor microenvironment.

Impact of Altered Body Composition on Clinical and Oncological Outcomes in Intrahepatic Cholangiocarcinoma

Intrahepatic cholangiocarcinoma is a common primary liver tumor with limited treatment options and poor prognosis. Changes in body composition (BC) have been shown to affect the prognosis of various types of tumors. Therefore, our study aimed to investigate the correlation between BC and clinical and oncological outcomes in patients with iCCA. All patients with iCCA who had surgery from 2010 to 2022 at our institution were included. We used CT scans and 3D Slicer software to assess BC and conducted logistic regressions as well as Cox regressions and Kaplan-Meier analyses to investigate associations between BC and clinical variables with focus on postoperative complications and oncological outcomes. BC was frequently altered in iCCA (n = 162), with 53.1% of the patients showing obesity, 63.2% sarcopenia, 52.8% myosteatosis, 10.1% visceral obesity, and 15.3% sarcopenic obesity. The multivariate analysis showed no meaningful association between BC and perioperative complications. Myosteatosis was associated with reduced overall survival (OS) in iCCA patients (myosteatosis vs. non-myosteatosis, 7 vs. 18 months, p = 0.016 log rank). Further, the subgroup analysis revealed a notable effect in the subset of R0-resected patients (myosteatosis vs. non-myosteatosis, 18 vs. 32 months, p = 0.025) and patients with nodal metastases (myosteatosis vs. non-myosteatosis, 7 vs. 18 months, p = 0.016). While altered BC is not associated with perioperative outcomes in iCCA, myosteatosis emerges as a prognostic factor for reduced OS in the overall and sub-populations of resected patients.

Comparative Transcriptomic Profiles of Differentiated Adipocytes Provide Insights into Adipogenesis Mechanisms of Subcutaneous and Intramuscular Fat Tissues in Pigs

Subcutaneous fat thickness and intramuscular fat content are closely related to meat production and quality in the pig industry. Adipogenesis in adipocytes from subcutaneous and intramuscular fat tissues involves different genes and regulatory mechanisms. Analyzing the data of mRNA and miRNA transcriptomes during the differentiation of adipocytes from these two sources will help identify the different mechanisms of subcutaneous and intramuscular fat deposition. In this study, RNA sequencing technology was used to analyze the differential expression of genes and miRNAs in subcutaneous and intramuscular adipocytes at days 0, 2, 4, and 8 of differentiation. We mainly attributed the difference between fat depositions of the two types of adipocytes to variations in the expression patterns of related genes. Through combined weighted gene co-expression network analysis and K-MEANS, we identified 30 and 22 genes that mainly regulated the differentiation of subcutaneous adipocytes and intramuscular adipocytes, respectively. A total of 17 important candidate miRNAs were identified. This study provides valuable reference for the study of different mechanisms of adipogenesis among subcutaneous and intramuscular fat and contributes to improving pig breeding.

Secreted Frizzled Related Proteins in Cardiovascular and Metabolic Diseases

Abnormal gene expression and secreted protein levels are accompanied by extensive pathological changes. Secreted frizzled related protein (SFRP) family members are antagonistic inhibitors of the Wnt signaling pathway, and they were recently found to be involved in the pathogenesis of a variety of metabolic diseases, which has led to extensive interest in SFRPs. Previous reports highlighted the importance of SFRPs in lipid metabolism, obesity, type 2 diabetes mellitus and cardiovascular diseases. In this review, we provide a detailed introduction of SFRPs, including their structural characteristics, receptors, inhibitors, signaling pathways and metabolic disease impacts. In addition to summarizing the pathologies and potential molecular mechanisms associated with SFRPs, this review further suggests the potential future use of SFRPs as disease biomarkers therapeutic targets.

Brown Adipose Expansion and Remission of Glycemic Dysfunction in Obese SM/J Mice

We leverage the SM/J mouse to understand glycemic control in obesity. High-fat-fed SM/J mice initially develop poor glucose homeostasis relative to controls. Strikingly, their glycemic dysfunction resolves by 30 weeks of age despite persistent obesity. The mice dramatically expand their brown adipose depots as they resolve glycemic dysfunction. This occurs naturally and spontaneously on a high-fat diet, with no temperature or genetic manipulation. Removal of the brown adipose depot impairs insulin sensitivity, indicating that the expanded tissue is functioning as an insulin-stimulated glucose sink. We describe morphological, physiological, and transcriptomic changes that occur during the brown adipose expansion and remission of glycemic dysfunction, and focus on Sfrp1 (secreted frizzled-related protein 1) as a compelling candidate that may underlie this phenomenon. Understanding how the expanded brown adipose contributes to glycemic control in SM/J mice will open the door for innovative therapies aimed at improving metabolic complications in obesity.

Role of Secreted Frizzled-Related Protein 1 in Early Mammary Gland Tumorigenesis and Its Regulation in Breast Microenvironment

In mice, the lack of secreted frizzled-related protein 1 (SFRP1) is responsible for mammogenesis and hyperplasia, while, in bovines, its overexpression is associated with post-lactational mammary gland involution. Interestingly, there are no reports dealing with the role of SFRP1 in female involution. However, SFRP1 dysregulation is largely associated with human tumorigenesis in the literature. Indeed, the lack of SFRP1 is associated with both tumor development and patient prognosis. Considering the increased risk of breast tumor development associated with incomplete mammary gland involution, it is crucial to demystify the "grey zone" between physiological age-related involution and tumorigenesis. In this review, we explore the functions of SFRP1 involved in the breast involution processes to understand the perturbations driven by the disappearance of SFRP1 in mammary tissue. Moreover, we question the presence of recurrent microcalcifications identified by mammography. In bone metastases from prostate primary tumor, overexpression of SFRP1 results in an osteolytic response of the tumor cells. Hence, we explore the hypothesis of an osteoblastic differentiation of mammary cells induced by the lack of SFRP1 during lobular involution, resulting in a new accumulation of hydroxyapatite crystals in the breast tissue.

Effects of in ovo injection of vitamin C on heat shock protein and metabolic genes expression

Some studies have shown that the excessive metabolic heat production is the primary cause for dead chicken embryos during late embryonic development. Increasing heat shock protein (HSP) expression and adjusting metabolism are important ways to maintain body homeostasis under heat stress. This study was conducted to investigate the effects of in ovo injection (IOI) of vitamin C (VC) at embryonic age 11th day (E11) on HSP and metabolic genes expression. A total of 320 breeder eggs were randomly divided into normal saline and VC injection groups. We detected plasma VC content and rectal temperature at chick's age 1st day, and the mRNA levels of HSP and metabolic genes in embryonic livers at E14, 16 and 18, analysed the promoter methylation levels of differentially expressed genes and predicted transcription factors at the promoter regions. The results showed that IOI of VC significantly increased plasma VC content and decreased rectal temperature (P < 0.05). In ovo injection of VC significantly increased heat shock protein 60 (HSP60) and pyruvate dehydrogenase kinase 4 (PDK4) genes expression at E16 and PDK4 and secreted frizzled related protein 1 (SFRP1) at E18 (P < 0.05). At E16, IOI of VC significantly decreased the methylation levels of total CpG sites and -336 CpG site in HSP60 promoter and -1137 CpG site in PDK4 promoter (P < 0.05). Potential binding sites for nuclear factor-1 were found around -389 and -336 CpG sites in HSP60 promoter and potential binding site for specificity protein 1 was found around -1137 CpG site in PDK4 promoter. Our results suggested that IOI of VC increased HSP60, PDK4 and SFRP1 genes expression at E16 and 18, which may be associated with the demethylation in gene promoters. Whether IOI of VC could improve hatchability needs to be further verified by setting uninjection group.

Genome-Wide Association Study of Metabolic Syndrome Reveals Primary Genetic Variants at CETP Locus in Indians

Indians, a rapidly growing population, constitute vast genetic heterogeneity to that of Western population; however they have become a sedentary population in past decades due to rapid urbanization ensuing in the amplified prevalence of metabolic syndrome (MetS). We performed a genome-wide association study (GWAS) of MetS in 10,093 Indian individuals (6,617 MetS and 3,476 controls) of Indo-European origin, that belong to our previous biorepository of The Indian Diabetes Consortium (INDICO). The study was conducted in two stages-discovery phase (N = 2,158) and replication phase (N = 7,935). We discovered two variants within/near the CETP gene-rs1800775 and rs3816117-associated with MetS at genome-wide significance level during replication phase in Indians. Additional CETP loci rs7205804, rs1532624, rs3764261, rs247617, and rs173539 also cropped up as modest signals in Indians. Haplotype association analysis revealed GCCCAGC as the strongest haplotype within the CETP locus constituting all seven CETP signals. In combined analysis, we perceived a novel and functionally relevant sub-GWAS significant locus-rs16890462 in the vicinity of SFRP1 gene. Overlaying gene regulatory data from ENCODE database revealed that single nucleotide polymorphism (SNP) rs16890462 resides in repressive chromatin in human subcutaneous adipose tissue as characterized by the enrichment of H3K27me3 and CTCF marks (repressive gene marks) and diminished H3K36me3 marks (activation gene marks). The variant displayed active DNA methylation marks in adipose tissue, suggesting its likely regulatory activity. Further, the variant also disrupts a potential binding site of a key transcription factor, NRF2, which is known for involvement in obesity and metabolic syndrome.

Deciphering Cell Lineage Specification during Male Sex Determination with Single-Cell RNA Sequencing

The gonad is a unique biological system for studying cell-fate decisions. However, major questions remain regarding the identity of somatic progenitor cells and the transcriptional events driving cell differentiation. Using time-series single-cell RNA sequencing on XY mouse gonads during sex determination, we identified a single population of somatic progenitor cells prior to sex determination. A subset of these progenitors differentiates into Sertoli cells, a process characterized by a highly dynamic genetic program consisting of sequential waves of gene expression. Another subset of multipotent cells maintains their progenitor state but undergoes significant transcriptional changes restricting their competence toward a steroidogenic fate required for the differentiation of fetal Leydig cells. Our findings confirm the presence of a unique multipotent progenitor population in the gonadal primordium that gives rise to both supporting and interstitial lineages. These also provide the most granular analysis of the transcriptional events occurring during testicular cell-fate commitment.

Acute effects of active breaks during prolonged sitting on subcutaneous adipose tissue gene expression: an ancillary analysis of a randomised controlled trial

Active breaks in prolonged sitting has beneficial impacts on cardiometabolic risk biomarkers. The molecular mechanisms include regulation of skeletal muscle gene and protein expression controlling metabolic, inflammatory and cell development pathways. An active communication network exists between adipose and muscle tissue, but the effect of active breaks in prolonged sitting on adipose tissue have not been investigated. This study characterized the acute transcriptional events induced in adipose tissue by regular active breaks during prolonged sitting. We studied 8 overweight/obese adults participating in an acute randomized three-intervention crossover trial. Interventions were performed in the postprandial state and included: (i) prolonged uninterrupted sitting; or prolonged sitting interrupted with 2-minute bouts of (ii) light- or (iii) moderate-intensity treadmill walking every 20 minutes. Subcutaneous adipose tissue biopsies were obtained after each condition. Microarrays identified 36 differentially expressed genes between the three conditions (fold change ≥0.5 in either direction; p < 0.05). Pathway analysis indicated that breaking up of prolonged sitting led to differential regulation of adipose tissue metabolic networks and inflammatory pathways, increased insulin signaling, modulation of adipocyte cell cycle, and facilitated cross-talk between adipose tissue and other organs. This study provides preliminary insight into the adipose tissue regulatory systems that may contribute to the physiological effects of interrupting prolonged sitting.

Cellular Senescence, Neurological Function, and Redox State

SIGNIFICANCE

Cellular senescence, characterized by permanent cell cycle arrest, has been extensively studied in mitotic cells such as fibroblasts. However, senescent cells have also been observed in the brain. Even though it is recognized that cellular energetic metabolism and redox homeostasis are perturbed in the aged brain and neurodegenerative diseases (NDDs), it is still unknown which alterations in the overall physiology can stimulate cellular senescence induction and their relationship with the former events. Recent Advances: Recent findings have shown that during prolonged inflammatory and pathologic events, the blood-brain barrier could be compromised and immune cells might enter the brain; this fact along with the brain's high oxygen dependence might result in oxidative damage to macromolecules and therefore senescence induction. Thus, cellular senescence in different brain cell types is revised here.

CRITICAL ISSUES

Most information related to cellular senescence in the brain has been obtained from research in glial cells since it has been assumed that the senescent phenotype is a feature exclusive to mitotic cells. Nevertheless, neurons with senescence hallmarks have been observed in old mouse brains. Therefore, although this is a controversial topic in the field, here we summarize and integrate the observations from several studies and propose that neurons indeed senesce.

FUTURE DIRECTIONS

It is still unknown which alterations in the overall metabolism can stimulate senescence induction in the aged brain, what are the mechanisms and signaling pathways, and what is their relationship to NDD development. The understanding of these processes will expose new targets to intervene age-associated pathologies.-Antioxid. Redox Signal. 28, 1704-1723.

Identifying novel strategies for treating human hair loss disorders: Cyclosporine A suppresses the Wnt inhibitor, SFRP1, in the dermal papilla of human scalp hair follicles

Hair growth disorders often carry a major psychological burden. Therefore, more effective human hair growth–modulatory agents urgently need to be developed. Here, we used the hypertrichosis-inducing immunosuppressant, Cyclosporine A (CsA), as a lead compound to identify new hair growth–promoting molecular targets. Through microarray analysis we identified the Wnt inhibitor, secreted frizzled related protein 1 (SFRP1), as being down-regulated in the dermal papilla (DP) of CsA-treated human scalp hair follicles (HFs) ex vivo. Therefore, we further investigated the function of SFRP1 using a pharmacological approach and found that SFRP1 regulates intrafollicular canonical Wnt/β-catenin activity through inhibition of Wnt ligands in the human hair bulb. Conversely, inhibiting SFRP1 activity through the SFRP1 antagonist, WAY-316606, enhanced hair shaft production, hair shaft keratin expression, and inhibited spontaneous HF regression (catagen) ex vivo. Collectively, these data (a) identify Wnt signalling as a novel, non–immune-inhibitory CsA target; (b) introduce SFRP1 as a physiologically important regulator of canonical β-catenin activity in a human (mini-)organ; and (c) demonstrate WAY-316606 to be a promising new promoter of human hair growth. Since inhibiting SFRP1 only facilitates Wnt signalling through ligands that are already present, this ‘ligand-limited’ therapeutic strategy for promoting human hair growth may circumvent potential oncological risks associated with chronic Wnt over-activation.

Hair loss is a common disorder and can lead to psychological distress. Cyclosporine A, a fungal metabolite commonly used as an immunosuppressant, can potently induce hair growth in humans. However, it cannot be effectively used to restore hair growth because of its toxic profile. In this study, we used Cyclosporine A as a lead compound to identify novel therapeutic targets that can aid the development of new hair growth–promoting agents. Through microarray analysis, we found that the level of the secreted Wnt inhibitor, SFRP1, was significantly reduced by Cyclosporine A. This inspired us to design a new pharmacological approach that uses WAY-316606, a reportedly well-tolerated and specific antagonist of SFRP1, to prolong the growth phase of the hair cycle. We show that WAY-316606 enhances human hair growth ex vivo, suggesting that it is a more targeted hair growth promoter with the potential to treat human hair loss disorders.

Secreted frizzled-related protein 1 regulates the progression of neuropathic pain in mice following spinal nerve ligation

Previous studies have shown that the Wnt/β-catenin signaling pathway plays an important role in modulating neuropathic pain after sciatic nerve injury. In this study, we explored the role of secreted frizzled-related protein 1 (SFRP1), a Wnt antagonist, in neuropathic pain using a mouse model following spinal nerve ligation (SNL). We found SNL-induced SFRP1 downregulation in the spinal cord. Further, overexpression of SFRP1 via spinal injection into the spinal cord attenuated SNL-induced allodynia, hyperalgesia, and neuroinflammation. Consistently, in vitro assays also showed decreased expression of SFRP1 in spinal cord astrocytes after exposure to lipopolysaccharide (LPS). Overexpression of SFRP1 significantly alleviated the secretion of LPS-induced proinflammatory factors in spinal cord astrocytes. Furthermore, spinal injection of LPS-treated astrocytes induced allodynia and hyperalgesia, which were reversed by the overexpression of SFRP1 in these cells. Additionally, SNL increased Wnt3a and β-catenin levels and also induced an increase in nuclear expression of β-catenin; these effects were all attenuated by SFRP1. Finally, we found that downregulation of SFRP1, mainly through DNA methylation, is involved in the pathogenesis of neuropathic pain. Taken together, these results suggested that the SFRP1/Wnt3a/β-catenin signaling pathway might be a suitable therapeutic target for neuropathic pain.

Nonylphenol aggravates non-alcoholic fatty liver disease in high sucrose-high fat diet-treated rats

Exposure to environmental endocrine disruptors (EEDs) contributes to the pathogenesis of many metabolic disorders. Here, we have analyzed the effect of the EED-nonylphenol (NP) on the promotion of non-alcoholic fatty liver disease (NAFLD) in rats fed high sucrose-high fat diet (HSHFD). Fifty Sprague-Dawley rats were divided into five groups: controls fed a normal diet (C-ND); HSHFD-fed controls (C-HSHFD); and rats fed a HSHFD combined with NP at doses of 0.02 μg/kg/day (NP-L-HSHFD), 0.2 μg/kg/day (NP-M-HSHFD), and 2 μg/kg/day (NP-H-HSHFD). Subchronic exposure to NP coupled with HSHFD increased daily water and food intake (p < 0.05), hepatic echogenicity and oblique liver diameter (p < 0.05), and plasma levels of alanine aminotransferase, aspartate aminotransferase, total cholesterol, triglycerides, and low density lipoprotein cholesterol (p < 0.05). Combined exposure to NP and HSHFD induced macrovesicular steatosis with dilation and congestion of the central vein, liver inflammatory cell infiltration, and expression of genes regulating lipid metabolism, SREBP-1C, FAS, and Ucp2. These results demonstrate that NP aggravates NAFLD in HSHFD-treated rats by up-regulating lipogenic genes, and that HSHFD increases the toxic effects of NP. Thus subchronic NP exposure may lead to NAFLD, especially when combined with a high-sucrose/high-fat diet.

Recombinant SFRP5 protein significantly alleviated intrahepatic inflammation of nonalcoholic steatohepatitis

BACKGROUND

Secreted frizzled-related protein 5 (SFRP5) is an anti-inflammatory adipokine modulating metabolism dysfunction. This study aims to observe the effect of recombinant SFRP5 protein on nonalcoholic steatohepatitis (NASH).

METHODS

We set up a prokaryotic expression system and purified the recombinant SFRP5 protein. Recombinant SFRP5 protein was further identified by SDS-PAGE, western blot, high performance liquid chromatography (HPLC), protein mass spectrometry and in vitro Wnt5a-binding test. NASH mouse model was induced by methionine and choline deficient diet (MCDD) for 2 weeks. SFRP5 treatment group received intraperitoneal injection with a dosage of 10μg/kg SFRP5 twice a day for 2 weeks. Saline was used as control. Inflammation and fatty lesion score of liver tissue pathology and serum transaminase level were compared.

RESULTS

The purity of recombinant SFRP5 protein is 90% identified by HPLC. Its molecule size is 36,096.08 tested by mass spectrometry. Recombinant SFRP5 can specifically bind with Wnt5a which verifies its activity in vitro. The endotoxin level of this recombinant protein is 0.01EU/μg-0.1EU/μg and is suitable for animal experiment. SFRP5 can significantly improve liver inflammation (SFRP5 vs. control, 1.40 ± 0.70 vs. 2.00 ± 0.47, P < 0.05) as well as fatty lesion scores (SFRP5 vs. control, 1.40 ± 0.97 vs. 2.20 ± 0.63, P < 0.05), and lower ALT and AST levels. The mRNA expression of proinflammatory adipokines (IL-1β, IL-6, TNFα and MCP-1) in liver was down-regulated significantly after SFRP5 intervention. Immunohistochemistry and quantitative PCR revealed a dramatically down-regulation of F4/80 in liver after SFRP5 treatment.

CONCLUSIONS

Recombinant SFRP5 protein significantly alleviated NASH induced by MCDD.

Regulation of early growth response 2 expression by secreted frizzled related protein 1

BACKGROUND

Secreted frizzled-related protein 1 (SFRP1) expression is down-regulated in a multitude of cancers, including breast cancer. Loss of Sfrp1 also exacerbates weight gain as well as inflammation. Additionally, loss of SFRP1 enhances TGF-β signaling and the downstream MAPK pathway. TGF-β has been shown to increase the expression of Early Growth Response 2 (EGR2), a transcription factor implicated in immune function in a wide variety of cell types. The work described here was initiated to determine whether SFRP1 modulation affects TGF-β mediated EGR2 expression in mammary tissues as well as macrophage polarization.

METHODS

Real-time PCR analysis was performed to examine EGR2 expression in human and murine mammary epithelial cells and tissues in response to SFRP1 modulation. Chemical inhibition was employed to investigate the roles TGF-β and MAPK signaling play in the control of EGR2 expression in response to SFRP1 loss. Primary murine macrophages were isolated from Sfrp1^-/- mice and stimulated to become either M1 or M2 macrophages, treated with recombinant SFRP1, and real-time PCR was used to measure the expression of murine specific M1/M2 markers [Egr2 (M2) and Gpr18 (M1)]. Immunohistochemical analysis was used to measure the expression of human specific M1/M2 markers [CD163 (M2) and HLA-DRA (M2)] in response to rSFRP1 treatment in human mammary explant tissue.

RESULTS

Knockdown of SFRP1 expression increases the expression of EGR2 mRNA in human mammary epithelial cells and addition of rSFRP1 decreases the expression of EGR2 when added to explant mammary gland tissues. Chemical inhibition of both TGF-β and MAPK signaling in Sfrp1^-/- or knockdown mammary epithelial cells results in decreased expression of EGR2. Stimulated murine macrophages obtained from Sfrp1^-/- mice and treated with rSFRP1 exhibit a reduction in Egr2 expression and an increase in Gpr18 mRNA expression. Human mammary explant tissue treated with rSFRP1 decreases CD163 protein expression whereas there was no effect on the expression of HLA-DRA.

CONCLUSIONS

Loss of SFRP1 likely contributes to tumor progression by altering the expression of a critical transcription factor in both the epithelium and the immune system.

Reduced skeletal muscle secreted frizzled-related protein 3 is associated with inflammation and insulin resistance

OBJECTIVE

To investigate the role of secreted frizzled-related protein 3 (Sfrp3) in insulin sensitivity (ISi) and β-cell function in humans across a spectrum of glucose homeostasis.

METHODS

Subjects included those with normal glucose homeostasis (NGT; n = 18), prediabetes (PD; n = 11), or type 2 diabetes (T2D; n=12). Serum and skeletal muscle (SkM) Sfrp3 levels were measured by ELISA and qPCR, respectively, and insulin signaling pathway was assessed by Western blot. IS and β-cell function were assessed by indices derived from frequently sampled intravenous glucose tolerance test.

RESULTS

SkM Sfrp3 mRNA levels were significantly reduced in PD and T2D versus NGT. Similarly, serum Sfrp3 levels tended to be decreased in PD and T2D versus NGT. SkM Sfrp3 mRNA levels correlated negatively with circulating proinflammatory cytokines (IL-6, IFN-γ) and positively with IS. In vitro-differentiated myotubes from lean insulin-sensitive subjects treated with either lipopolysaccharide (LPS) or recombinant IL-6 demonstrated a dose-dependent reduction in Sfrp3 gene expression. Treatment of myotubes with recombinant Sfrp3 restored LPS- and IL-6-induced attenuation of insulin-stimulated Akt phosphorylation.

CONCLUSIONS

Inflammation-induced reduction in SkM Sfrp3 expression may contribute to insulin resistance, and this effect may be prevented by addition of exogenous Sfrp3. Thus, Sfrp3 may be a novel target for insulin sensitization.

High Dietary Selenium Intake Alters Lipid Metabolism and Protein Synthesis in Liver and Muscle of Pigs

BACKGROUND

Prolonged high intakes of dietary selenium have been shown to induce gestational diabetes in rats and hyperinsulinemia in pigs.

OBJECTIVE

Two experiments were conducted to explore metabolic and molecular mechanisms for the diabetogenic potential of high dietary selenium intakes in pigs.

METHODS

In Expt. 1, 16 Yorkshire-Landrace-Hampshire crossbred pigs (3 wk old, body weight = 7.5 ± 0.81 kg, 50% males and 50% females) were fed a corn-soybean meal basal diet supplemented with 0.3 or 1.0 mg Se/kg (as selenium-enriched yeast for 6 wk). In Expt. 2, 12 pigs of the same crossbreed (6 wk old, body weight = 16.0 ± 1.8 kg) were fed a similar basal diet supplemented with 0.3 or 3.0 mg Se/kg for 11 wk. Biochemical and gene and protein expression profiles of lipid and protein metabolism and selenoproteins in plasma, liver, muscle, and adipose tissues were analyzed.

RESULTS

In Expt. 1, the 1-mg-Se/kg diet did not affect body weight or plasma concentrations of glucose and nonesterified fatty acids. In Expt. 2, the 3-mg-Se/kg diet, compared with the 0.3-mg-Se/kg diet, increased (P < 0.05) concentrations of plasma insulin (0.2 compared with 0.4 ng/mL), liver and adipose lipids (41% to 2.4-fold), and liver and muscle protein (10-14%). In liver, the 3-mg-Se/kg diet upregulated (P < 0.05) the expression, activity, or both of key factors related to gluconeogenesis [phosphoenolpyruvate carboxykinase (PEPCK); 13%], lipogenesis [sterol regulatory element binding protein 1 (SREBP1), acetyl-coenzyme A carboxylase (ACC), and fatty acid synthase (FASN); 46-90%], protein synthesis [insulin receptor (INSR), P70 ribosomal protein S6 kinase (P70), and phosphorylated ribosomal protein S6 (P-S6); 88-105%], energy metabolism [AMP-activated protein kinase (AMPK); up to 2.8-fold], and selenoprotein glutathione peroxidase 3 (GPX3; 1.4-fold) and suppressed (P < 0.05) mRNA levels of lipolysis gene cytochrome P450, family 7, subfamily A, polypeptide 1 (CYP7A1; 88%) and selenoprotein gene selenoprotein W1 (SEPW1; 46%). In muscle, the 3-mg-Se/kg diet exerted no effect on the lipid profiles but enhanced (P < 0.05) expression of P-S6 and mammalian target of rapamycin (mTOR; 42-176%; protein synthesis); selenoprotein P (SELP; 40-fold); and tumor suppressor protein 53 (P53) and peroxisome proliferator-activated receptor γ (PPARG; 52-58%; lipogenesis) and suppressed (P < 0.05) expression of INSR (59%; insulin signaling); selenoprotein S (SELS); deiodinases, iodothyronine, type I (DIO1); and thioredoxin reductase 1 (TXNRD1; 50%; selenoproteins); and ACC1 and FASN (35-51%; lipogenesis).

CONCLUSION

Our research showed novel roles, to our best knowledge, and mechanisms of high selenium intakes in regulating the metabolism of protein, along with that of lipid, in a tissue-specific fashion in pigs.

MicroRNA-206 is differentially expressed in Brca1-deficient mice and regulates epithelial and stromal cell compartments of the mouse mammary gland

Depletion of Brca1 leads to defects in mouse mammary gland development and mammary tumors in humans and mice. To explore the role of microRNAs (miRNAs) in this process, we examined the mammary glands of MMTV-Cre Brca1^Co/Co mice for differential miRNA expression using a candidate approach. Several miRNAs were differentially expressed in mammary tissue at day 1 of lactation and in mammary epithelial cell lines in which Brca1 messenger RNA (mRNA) levels have been reduced. Functional studies revealed that several of these miRNAs regulate mammary epithelial cell function in vitro, including miR-206. Creation and analysis of MMTV-miR-206 transgenic mice showed no effect on lactational mammary development and no tumors, but indicates a role in mammary tissue remodeling in mature mice, potentially involving Igf-1 and Sfrp1. These results indicate the potential of miRNAs to mediate the consequences of Brca1 loss and suggest a novel function for miR-206.

Hypothalamic Wnt Signalling and its Role in Energy Balance Regulation

Wnt signalling and its downstream effectors are well known for their roles in embryogenesis and tumourigenesis, including the regulation of cell proliferation, survival and differentiation. In the nervous system, Wnt signalling has been described mainly during embryonic development, although accumulating evidence suggests that it also plays a major role in adult brain morphogenesis and function. Studies have predominantly concentrated on memory formation in the hippocampus, although recent data indicate that Wnt signalling is also critical for neuroendocrine control of the developed hypothalamus, a brain centre that is key in energy balance regulation and whose dysfunction is implicated in metabolic disorders such as type 2 diabetes and obesity. Based on scattered findings that report the presence of Wnt molecules in the tanycytes and ependymal cells lining the third ventricle and arcuate nucleus neurones of the hypothalamus, their potential importance in key regions of food intake and body weight regulation has been investigated in recent studies. The present review brings together current knowledge on Wnt signalling in the hypothalamus of adult animals and discusses the evidence suggesting a key role for members of the Wnt signalling family in glucose and energy balance regulation in the hypothalamus in diet-induced and genetically obese (leptin deficient) mice. Aspects of Wnt signalling in seasonal (photoperiod sensitive) rodents are also highlighted, given the recent evidence indicating that the Wnt pathway in the hypothalamus is not only regulated by diet and leptin, but also by photoperiod in seasonal animals, which is connected to natural adaptive changes in food intake and body weight. Thus, Wnt signalling appears to be critical as a modulator for normal functioning of the physiological state in the healthy adult brain, and is also crucial for normal glucose and energy homeostasis where its dysregulation can lead to a range of metabolic disorders.

Gossypol ameliorates liver fibrosis in diabetic rats induced by high-fat diet and streptozocin

11β-hydroxysteroid dehydrogenase 1 (11β-HSD1) inhibitors have been shown to treat type 2 diabetes (T2D). Since gossypol is an 11β-HSD1 inhibitor, the objective of the present study was to treat T2D and T2D-related liver fibrosis in rat model using low-dose gossypol. T2D was induced by feeding with high fat diet plus injection of streptozocin (30mg/kg). Diabetic rats were treated with either vehicle control or racemic gossypol with a dose of 15mg/kg/day for 4weeks followed by 15mg/kg/week for additional 8weeks. Blood glucose, cholesterol, LDL, and triglycerides were measured. Messenger mRNA levels of glucocorticoid receptor (Nr3c1), phosphoenolpyruvate carboxykinase (Pck1), glucose-6-phosphatase (G6pc), collagen I (Col1a1), collagen III (Col3a1), fibronectin (Fn1), tissue inhibitor of metalloproteinase 1 (Timp1), and 2 (Timp2) were measured. T2D rats had higher serum glucose, cholesterol, LDL, and triglyceride levels compared to control. Liver Nr3c1, Col1a1, Col3a1, Fn1, Timp1, and Timp2 were increased in T2D rats. T2D liver showed significant fibrosis with the increases of α-smooth muscle actin and fibronectin. After gossypol treatment, serum glucose level was lowered by 64%. Liver fibrosis was significantly ameliorated. Nr3c1, Col1a1, Col3a1, Fn1, Timp1, Timp2, Pck1 as well as G6pc levels were significantly reduced. In conclusion, low dose gossypol is effective for the treatment of T2D and T2D-related fibrosis.

Therapeutic approach to target mesothelioma cancer cells using the Wnt antagonist, secreted frizzled-related protein 4: Metabolic state of cancer cells

Malignant mesothelioma (MM) is an aggressive cancer, characterized by rapid progression, along with late metastasis and poor patient prognosis. It is resistant to many forms of standard anti-cancer treatment. In this study, we determined the effect of secreted frizzled-related protein 4 (sFRP4), a Wnt pathway inhibitor, on cancer cell proliferation and metabolism using the JU77 mesothelioma cell line. Treatment with sFRP4 (250 pg/ml) resulted in a significant reduction of cell proliferation. The addition of the Wnt activator Wnt3a (250 pg/ml) or sFRP4 had no significant effect on ATP production and glucose utilisation in JU77 cells at both the 24 and 48 h time points examined. We also examined their effect on Akt and Glycogen synthase kinase-3 beta (GSK3β) phosphorylation, which are both important components of Wnt signalling and glucose metabolism. We found that protein phosphorylation of Akt and GSK3β varied over the 24h and 48 h time points, with constitutive phosphorylation of Akt at serine 473 (pAkt) decreasing to its most significant level when treated with Wnt3a+sFRP4 at the 24h time point. A significant reduction in the level of Cytochrome c oxidase was observed at the 48 h time point, when sFRP4 and Wnt3a were added in combination. We conclude that sFRP4 may function, in part, to reduce/alter cancer cell metabolism, which may lead to sensitisation of cancer cells to chemotherapeutics, or even cell death.

Loss of SFRP4 Alters Body Size, Food Intake, and Energy Expenditure in Diet-Induced Obese Male Mice

Secreted frizzled-related protein 4 (SFRP4) is an extracellular regulator of the wingless-type mouse mammary tumor virus integration site family (WNT) pathway. SFRP4 has been implicated in adipocyte dysfunction, obesity, insulin resistance, and impaired insulin secretion in patients with type 2 diabetes. However, the exact role of SFRP4 in regulating whole-body metabolism and glucose homeostasis is unknown. We show here that male Sfrp4(-/-) mice have increased spine length and gain more weight when fed a high-fat diet. The body composition and body mass per spine length of diet-induced obese Sfrp4(-/-) mice is similar to wild-type littermates, suggesting that the increase in body weight can be accounted for by their longer body size. The diet-induced obese Sfrp4(-/-) mice have reduced energy expenditure, food intake, and bone mineral density. Sfrp4(-/-) mice have normal glucose and insulin tolerance and β-cell mass. Diet-induced obese Sfrp4(-/-) and control mice show similar impairments of glucose tolerance and a 5-fold compensatory expansion of their β-cell mass. In summary, our data suggest that loss of SFRP4 alters body length and bone mineral density as well as energy expenditure and food intake. However, SFRP4 does not control glucose homeostasis and β-cell mass in mice.

Elevated Hepatic miR-22-3p Expression Impairs Gluconeogenesis by Silencing the Wnt-Responsive Transcription Factor Tcf7

Levels of miR-22-3p, a highly abundant hepatic microRNA, are abnormally increased in mouse models of insulin resistance and type 2 diabetes, yet its contribution to deregulated hepatic metabolism under diseased states is not well understood. Here, we unravel a novel link between elevated hepatic miR-22-3p expression and impaired gluconeogenesis in diabetic db/db mice via the regulation of Tcf7 (transcription factor 7). Our data demonstrate that miR-22-3p binds to the 3' untranslated region of TCF7 and downregulates it, and this microRNA-mediated regulation of TCF7 increases the expression of enzymes of the gluconeogenic pathway in HepG2 cells. Small interfering RNA-mediated knockdown of TCF7 in HepG2 cells also causes similar upregulation of gluconeogenic genes. Furthermore, in vivo silencing of miR-22-3p by antagomiR administration lowered random as well as fasting glucose levels in diabetic mice. miR-22-3p antagonism improved glucose tolerance and insulin sensitivity. Importantly, the hepatic Tcf7 levels were restored along with reduced hepatic glucose output, which was also reflected by the decreased expression of gluconeogenic genes. Our results support a critical role for miR-22-3p and its target, Tcf7, in the pathogenesis of diabetes by upregulating gluconeogenesis. Moreover, targeting the miR-22/Tcf7/Wnt axis might hold therapeutic potential for the treatment of altered hepatic physiology during insulin resistance and type 2 diabetes.

Impacts of Alternative Splicing Events on the Differentiation of Adipocytes

Alternative splicing was found to be a common phenomenon after the advent of whole transcriptome analyses or next generation sequencing. Over 90% of human genes were demonstrated to undergo at least one alternative splicing event. Alternative splicing is an effective mechanism to spatiotemporally expand protein diversity, which influences the cell fate and tissue development. The first focus of this review is to highlight recent studies, which demonstrated effects of alternative splicing on the differentiation of adipocytes. Moreover, use of evolving high-throughput approaches, such as transcriptome analyses (RNA sequencing), to profile adipogenic transcriptomes, is also addressed.

Sodium butyrate alleviates adipocyte inflammation by inhibiting NLRP3 pathway

Insulin resistance (IR) is a common feature of Type II diabetes, metabolic disorders, hypertension and other vascular diseases. Recent studies showed that obesity-induced inflammation may be critical for IR. To investigate the anti-inflammatory effect of sodium butyrate (NaB) on obesity-induced inflammation, the db/db mice were intraperitoneally injected with NaB for 6 weeks. Glucose control was evaluated by glucose tolerance test (GTT) and insulin tolerance test (ITT). Adipose tissue was harvested for gene expression analysis. 3T3-L1 adipocytes were treated with Tnf-α to mimic the inflammatory state and gene expression was detected by realtime PCR and Western blotting. Our results showed that NaB treatment improved glucose control in db/db mice as determined by GTT and ITT tests. Gene expression analysis showed that NaB inhibited cytokines and immunological markers including CD68, Interferon-γ and Mcp in adipose tissues in db/db mice. Moreover, NaB inhibited cytokine releasing in 3T3-L1 adipocytes treated with TNF-α. Further analysis of inflammation pathway showed that NLRP3 was activated in db/db mice, which was efficiently inhibited by NaB treatment. Our data suggest that inhibition of obesity-induced inflammation alleviates IR, and NaB might be a potential anti-inflammatory agent for obesity.

WISP1 is a novel adipokine linked to inflammation in obesity

WISP1 (Wnt1-inducible signaling pathway protein-1, also known as CCN4) is a member of the secreted extracellular matrix-associated proteins of the CCN family and a target gene of the Wingless-type (WNT) signaling pathway. Growing evidence links the WNT signaling pathway to the regulation of adipogenesis and low-grade inflammation in obesity. We aimed to validate WISP1 as a novel adipokine. Human adipocyte differentiation was associated with increased WISP1 expression and secretion. Stimulation of human macrophages with WISP1 led to a proinflammatory response. Circulating WISP1 and WISP1 subcutaneous adipose tissue expression were regulated by weight changes in humans and mice. WISP1 expression in visceral and subcutaneous fat tissue was associated with markers of insulin resistance and inflammation in glucose-tolerant subjects. In patients with nonalcoholic fatty liver disease, we found no correlation among disease activity score, liver fat content, and WISP1 expression. Insulin regulated WISP1 expression in adipocytes in vitro but had no acute effect on WISP1 gene expression in subcutaneous fat tissue in overweight subjects who had undergone hyperinsulinemic clamp experiments. The data suggest that WISP1 may play a role in linking obesity to inflammation and insulin resistance and could be a novel therapeutic target for obesity.

High-throughput screening of mouse gene knockouts identifies established and novel skeletal phenotypes

Screening gene function in vivo is a powerful approach to discover novel drug targets. We present high-throughput screening (HTS) data for 3 762 distinct global gene knockout (KO) mouse lines with viable adult homozygous mice generated using either gene-trap or homologous recombination technologies. Bone mass was determined from DEXA scans of male and female mice at 14 weeks of age and by microCT analyses of bones from male mice at 16 weeks of age. Wild-type (WT) cagemates/littermates were examined for each gene KO. Lethality was observed in an additional 850 KO lines. Since primary HTS are susceptible to false positive findings, additional cohorts of mice from KO lines with intriguing HTS bone data were examined. Aging, ovariectomy, histomorphometry and bone strength studies were performed and possible non-skeletal phenotypes were explored. Together, these screens identified multiple genes affecting bone mass: 23 previously reported genes (Calcr, Cebpb, Crtap, Dcstamp, Dkk1, Duoxa2, Enpp1, Fgf23, Kiss1/Kiss1r, Kl (Klotho), Lrp5, Mstn, Neo1, Npr2, Ostm1, Postn, Sfrp4, Slc30a5, Slc39a13, Sost, Sumf1, Src, Wnt10b), five novel genes extensively characterized (Cldn18, Fam20c, Lrrk1, Sgpl1, Wnt16), five novel genes with preliminary characterization (Agpat2, Rassf5, Slc10a7, Slc26a7, Slc30a10) and three novel undisclosed genes coding for potential osteoporosis drug targets.

WNT signaling: an emerging mediator of cancer cell metabolism?

WNT signaling was discovered in tumor models and has been recognized as a regulator of cancer development and progression for over 3 decades. Recent work has highlighted a critical role for WNT signaling in the metabolic homeostasis of mammals, where its misregulation has been heavily implicated in diabetes. While the majority of WNT metabolism research has focused on nontransformed tissues, the role of WNT in cancer metabolism remains underinvestigated. Cancer is also a metabolic disease where oncogenic signaling pathways regulate energy production and macromolecular synthesis to fuel rapidly proliferating tumors. This review highlights the emerging evidence for WNT signaling in the reprogramming of cancer cell metabolism and examines the role of these signaling pathways as mediators of tumor bioenergetics.

Secreted Frizzled-related protein 1 (Sfrp1) regulates the progression of renal fibrosis in a mouse model of obstructive nephropathy

Renal fibrosis is responsible for progressive renal diseases that cause chronic renal failure. Sfrp1 (secreted Frizzled-related protein 1) is highly expressed in kidney, although little is known about connection between the protein and renal diseases. Here, we focused on Sfrp1 to investigate its roles in renal fibrosis using a mouse model of unilateral ureteral obstruction (UUO). In wild-type mice, the expression of Sfrp1 protein was markedly increased after UUO. The kidneys from Sfrp1 knock-out mice showed significant increase in expression of myofibrobast markers, α-smooth muscle actin (αSMA). Sfrp1 deficiency also increased protein levels of the fibroblast genes, vimentin, and decreased those of the epithelial genes, E-cadherin, indicated that enhanced epithelial-to-mesenchymal transition. There was no difference in the levels of canonical Wnt signaling; rather, the levels of phosphorylated c-Jun and JNK were more increased in the Sfrp1(-/-) obstructed kidney. Moreover, the apoptotic cell population was significantly elevated in the obstructed kidneys from Sfrp1(-/-) mice following UUO but was slightly increased in those from wild-type mice. These results indicate that Sfrp1 is required for inhibition of renal damage through the non-canonical Wnt/PCP pathway.

Activation of noncanonical Wnt signaling through WNT5A in visceral adipose tissue of obese subjects is related to inflammation

CONTEXT

Wingless-type mouse mammary tumor virus integration site family (WNT)-5A is a glycoprotein involved in the regulation of the inflammatory response by activating the noncanonical Wnt signaling pathway. Secreted frizzled-related protein (SFRP)-5 acts as a decoy receptor that binds and sequesters WNT5A, preventing activation of frizzled receptors and attenuating the noncanonical Wnt signaling.

OBJECTIVE

The aim of the study was to evaluate the involvement of WNT5A and SFRP5 in obesity and obesity-related comorbidities as well as to explore their effect in visceral adipose tissue inflammation.

PATIENTS AND METHODS

Samples obtained from 90 subjects were used. Circulating and gene expression levels of WNT5A and SFRP5 were analyzed in different metabolic tissues. The effect of TNF-α and lipopolysaccharide on the transcript levels of WNT5A and SFRP5 in adipocytes was explored. We also investigated whether WNT5A itself can activate an inflammatory response.

RESULTS

Increased circulating levels of WNT5A in obese patients (P < .05) were decreased (P < .001) after gastric bypass. In this line, WNT5A mRNA in visceral adipose tissue was increased (P < .05) in obese patients with gene expression levels of SFRP5 being down-regulated (P < .05). WNT5A mRNA expression was significantly enhanced (P < .01) by lipopolysaccharide and TNF-α treatment, whereas no effects were found in SFRP5 gene expression levels. Furthermore, exogenous WNT5A induced (P < .05) IL-6, IL1B, MMP2, MMP9, and SSP1 mRNA expression in human adipocyte cultures.

CONCLUSIONS

Activation of noncanonical Wnt signaling through the up-regulation of WNT5A and down-regulation of SFRP5 may promote a proinflammatory state in visceral adipose tissue contributing to the development of obesity-associated comorbidities.

Is Alzheimer's disease related to metabolic syndrome? A Wnt signaling conundrum

Alzheimer's disease (AD) is the most common cause of dementia, affecting more than 36 million people worldwide. AD is characterized by a progressive loss of cognitive functions. For years, it has been thought that age is the main risk factor for AD. Recent studies suggest that life style factors, including nutritional behaviors, play a critical role in the onset of dementia. Evidence about the relationship between nutritional behavior and AD includes the role of conditions such as obesity, hypertension, dyslipidemia and elevated glucose levels. The coexistence of some of these cardio-metabolic risk factors is generally known as metabolic syndrome (MS). Some clinical studies support the role of MS in the onset of AD. However, the cross-talk between the molecular signaling implicated in these disorders is unknown. In the present review, we focus on the molecular correlates that support the relationship between MS and the onset of AD. We also discuss relevant issues such as the role of leptin, insulin and renin-angiotensin signaling in the brain and the possible role of Wnt signaling in both MS and AD. We discuss the evidence supporting the use of ob/ob mice, high-fructose diets, aortic coarctation-induced hypertension and Octodon degus, which spontaneously develops β-amyloid deposits and metabolic derangements, as suitable animal models to address the relationships between MS and AD. Finally, we examine emergent data supporting the role of Wnt signaling in the modulation of AD and MS, implicating this pathway as a therapeutic target in both conditions.

The effects of diet induced obesity on breast cancer associated pathways in mice deficient in SFRP1

Background

Secreted frizzled-related proteins (SFRPs) are a family of proteins that block the Wnt signaling pathway and loss of Sfrp1 expression is observed in breast cancer. The molecular mechanisms by which obesity contributes to breast tumorigenesis are not well defined, but involve increased inflammation. Mice deficient in Sfrp1 show enhanced mammary gland inflammation in response to diet induced obesity (DIO). Furthermore, mammary glands from Sfrp1^−/− mice exhibit increased Wnt signaling, decreased cell death responses, and excessive hyper branching. The work described here was initiated to investigate whether obesity exacerbates the aforementioned pathways, as they each play a key roles in the development of breast cancer.

Findings

Wnt signaling is significantly affected by DIO and Sfrp1^−/− loss as revealed by analysis of Myc mRNA expression and active β-catenin protein expression. Furthermore, Sfrp1^−/− mice fed a high fat diet (HFD) exhibit an increase in mammary cell proliferation. The death response is also impaired in the mammary gland of Sfrp1^−/− mice fed a normal diet (ND) as well as a HFD. In response to γ-irradiation, mammary glands from Sfrp1^−/− mice express significantly less Bax and Bbc3 mRNA, caspase-3 positive cells, and p53 protein. The expression of Wnt4 and Tnfs11 are critical for normal progesterone mediated mammary gland development and in response to obesity, Sfrp1^−/− mice express significantly more Wnt4 and Tnfs11 mRNA expression. Evaluation of progesterone receptor (PR) expression showed that DIO increases the number of PR positive cells.

Conclusions

Our data indicate that the expression of Sfrp1 is a critical factor required for maintaining appropriate cellular homeostasis in response to the onset of obesity.