The influence of obesity on folate status, DNA methylation and cancer-related gene expression in normal breast tissues from premenopausal women.

Epidemiological studies have established obesity as a critical risk factor for postmenopausal breast cancer (post-BC), whereas a reverse association holds prior to menopause. A significant scientific gap exists in understanding the mechanism(s) underpinning this epidemiological phenomenon, particularly the reverse association between obesity and premenopausal breast cancer (pre-BC). This study aimed to understand how folate metabolism and DNA methylation inform the association between obesity and pre-BC. Fifty normal breast tissue samples were collected from premenopausal women who underwent reduction mammoplasty. We modified the Lactobacillus Casei microbiological folate assay and measured folate levels in our breast tissue samples. The DNA methylation of LINE-1, a biomarker of genome-wide methylation, and the expression of a panel of breast cancer-related genes was measured by pyrosequencing and real-time PCR. We found that a high BMI is associated with an increase of folate levels in mammary tissue, with an increase of 2.65 ng/g of folate per every 5-unit increase of BMI (p < 0.05). LINE-1 DNA methylation was significantly associated with BMI (p < 0.05), and marginally associated with folate concentration (p = 0.087). A high expression of SFRP1 was observed in subjects with high BMI or high folate status (p < 0.05). This study demonstrated that, in premenopausal women, obesity is associated with increased mammary folate status, genome-wide DNA methylation and SFRP1 gene expression. Our findings indicated that the improved folate and epigenetic status represents a novel mechanism responsible for the reverse association between obesity and pre-BC.

Genetic ablation of tumor necrosis factor-alpha attenuates the promoted colonic Wnt signaling in high fat diet-induced obese mice.

Obesity is an established risk factor for colorectal cancer, but the mechanisms responsible for this relationship are not adequately delineated. Using a TNF-α-/- mouse model, the present study aimed to test the causal role of TNF-α in mediating the promotion of tumorigenic Wnt signaling by high-fat diet-induced obesity. A 2×2 factorial study was performed with wild-type and TNF-α-/- mice on a 60 kcal% high-fat diet or a 10 kcal% low-fat diet. The inflammatory cytokine profile and genes within the Wnt signaling pathway were measured by electrochemiluminescence assay, real-time PCR, Western blotting or immunohistochemistry. The high-fat diet increased body weights in both wild-type and TNF-α-/- animals (P<.05), but males were more sensitive to high-fat diet-induced weight gain and increases of colonic TNF-α than females (P<.05). Genetic ablation of TNF-α suppressed the obesity-promoted elevation of Wnt signaling, as indicated by decreased levels of phospho-GSK3ß and active ß-catenin, two key components within the Wnt pathway (P<.05). The transcriptional expression of several Wnt signaling targets (C-myc, Cyclin D1 and Axin 2) and cell proliferation, as indicated by Ki-67 staining, were attenuated by the deletion of TNF-α in the high-fat-fed TNF-α-/- animals comparing with the wild-type animals (P<.05). Our data collectively showed that the genetic deletion of TNF-α attenuated the tumorigenic Wnt signaling, which was otherwise elevated by high-fat diet-induced obesity, and demonstrated a causal role of TNF-α in mediating obesity-associated Wnt signaling, which indicates a potential mechanism of inflammation-driven Wnt signaling for obesity-associated colorectal carcinogenesis.

The Prevention of a High Dose of Vitamin D or Its Combination with Sulforaphane on Intestinal Inflammation and Tumorigenesis in Apc1638N Mice Fed a High-Fat Diet.

SCOPE: The previous study shows that obesity-promoted inflammation is responsible for the activation of the intestinal tumorigenic Wnt-signaling. The present study aims to test a dietary strategy, dietary supplementation with a high dose of vitamin D (VD) or its combination with sulforaphane (SFN) to inhibit intestinal inflammation and obesity-associated tumorigenesis. METHODS AND RESULTS: Apc1638N mice are randomly divided into four groups: LF, a low-fat diet (10 kcal% fat) with 200 IU VD; HF, a high-fat diet (60 kcal% fat) with 200 IU VD; HFD, a high-fat diet with 5000 IU VD; and HFDS, a high-fat diet plus 5000 IU VD and 0.23 g SFN per ≈4000 kcal. VD administration decreased tumor incidence and size, and the co-administration with SFN (HFDS) magnified the effects. Inflammation and Wnt-signaling are suppressed by VD. The addition of SFN decreased the activity of histone deacetylase (HDAC) and increased autophagy. CONCLUSION: The administration of VD, at 5000 IU level, exerts an anti-inflammatory property and leads to suppressed intestinal Wnt-signaling and tumorigenesis in obese mice. The molecular function of SFN on a high dose of VD supplementation, although displayed on the inhibition of HDAC and the activation of autophagy, needs further investigation.