Possible role of type 1 and type 2 taste receptors on obesity-induced inflammation.

Obesity is characterized by chronic low-grade inflammation that could lead to other health complications, such as cardiovascular disease, diabetes, and various forms of cancer. Emerging evidence has shown that taste perception is altered during the development of obesity. Moreover, suppression of taste receptor or taste signaling molecules potentiate the inflammatory response, and the progression of inflammation attenuates the expression of taste receptors in vivo. Together, these findings suggest a possible interplay between taste signaling and inflammation. This review summarizes the interactions between type 1 (T1Rs) and type 2 taste receptors (T2Rs) and inflammation, as well as the impact of obesity on T1R- and T2R-mediated signaling. Furthermore, we evaluate the possible role that taste receptors play in regulating the inflammatory response during obesity as a therapeutic target to prevent the progression of comorbidities associated with obesity.

Combined Supplementation with Vitamin B-6 and Curcumin is Superior to Either Agent Alone in Suppressing Obesity-Promoted Colorectal Tumorigenesis in Mice.

BACKGROUND: Obesity increases the colorectal cancer risk, in part by elevating colonic proinflammatory cytokines. Curcumin (CUR) and supplemental vitamin B-6 each suppress colonic inflammation. OBJECTIVES: We examined whether the combination of CUR and vitamin B-6 amplifies each supplement's effects and thereby suppress obesity-promoted tumorigenesis. METHODS: Male Friend Virus B (FVB) mice (4-week-old; n = 110) received 6 weekly injections of azoxymethane beginning 1 week after arrival. Thereafter, they were randomized to receive a low-fat diet (10% energy from fat), a high-fat diet (HFD; 60% energy from fat), a HFD containing 0.2% CUR, a HFD containing supplemental vitamin B-6 (24 mg pyridoxine HCl/kg), or a HFD containing both CUR and supplemental vitamin B-6 (C + B) for 15 weeks. Colonic inflammation, assessed by fecal calprotectin, and tumor metrics were the primary endpoints. The anti-inflammatory efficacy of the combination was also determined in human colonic organoids. RESULTS: HFD-induced obesity produced a 2.6-fold increase in plasma IL-6 (P < 0.02), a 1.9-fold increase in fecal calprotectin (P < 0.05), and a 2.2-fold increase in tumor multiplicity (P < 0.05). Compared to the HFD group, the C + B combination, but not the individual agents, decreased fecal calprotectin (66%; P < 0.01) and reduced tumor multiplicity and the total tumor burden by 60%-80% (P < 0.03) in an additive fashion. The combination of C + B also significantly downregulated colonic phosphatidylinositol-4,5-bisphosphate 3-kinase, Wnt, and NF-κB signaling by 31%-47% (P < 0.05), effects largely absent with the single agents. Observations that may explain how the 2 agents work additively include a 2.8-fold increased colonic concentration of 3-hydroxyanthranillic acid (P < 0.05) and a 1.3-fold higher colonic concentration of the active coenzymatic form of vitamin B-6 (P < 0.05). In human colonic organoids, micromolar concentrations of CUR, vitamin B-6, and their combination suppressed secreted proinflammatory cytokines by 41%-93% (P < 0.03), demonstrating relevance to humans. CONCLUSIONS: In this mouse model, C + B is superior to either agent alone in preventing obesity-promoted colorectal carcinogenesis. Augmented suppression of procancerous signaling pathways may be the means by which this augmentation occurs.

Parabacteroides distasonis attenuates tumorigenesis, modulates inflammatory markers and promotes intestinal barrier integrity in azoxymethane-treated A/J mice.

Imbalance of the gut microbial community promotes inflammation and colorectal cancer (CRC). Previously, we demonstrated that freeze-dried Parabacteroides distasonis (Pd) suppressed obesity-driven colorectal tumorigenesis in mice. Here, we investigated if Pd could suppress the development of colon tumors in mice independent of obesity. Six-week-old male A/J mice were assigned to receive: (i) chow diet (CTR); (ii) chow with 0.04% wt/wt freeze-dried Pd (Pd-Early) or (iii) chow diet before switching to 0.04% Pd diet (Pd-Late). Mice remained on diet for 25 weeks with the switch for Pd-Late mice occurring after 19 weeks. All mice received 6 weekly injections of the colon carcinogen azoxymethane (AOM; 10 mg/kg I.P.) starting after 1 week on diet. Colon tumors were observed in 77, 55 and 40% in CTR, Pd-Early and Pd-Late mice, respectively (X2 = 0.047). Colonic expression of toll-like receptor 4, IL-4 and TNF-α was 40% (P < 0.01), 58% (P = 0.05) and 55% (P < 0.001) lower, respectively, in Pd-Early compared with CTR mice. Pd-Late mice displayed a 217% (P = 0.05) and 185% (P < 0.001) increase in colonic IL-10 and TGF-ß expression, respectively, compared with CTR mice and similar increases in protein abundances were detected (47-145%; P < 0.05). Pd-Early and Pd-Late mice both demonstrated increased colonic expression of the tight junction proteins Zonula occludens-1 (P < 0.001) and occludin (P < 0.001) at the transcript (2-3-fold; P < 0.01) and protein level (30-50%; P < 0.05) relative to CTR. Our results support a protective role for Pd in colonic tumorigenesis and maintenance of intestinal epithelial barrier in AOM-treated mice.

The Combination of Curcumin and Salsalate is Superior to Either Agent Alone in Suppressing Pro-Cancerous Molecular Pathways and Colorectal Tumorigenesis in Obese Mice.

SCOPE: High-fat diets (HFDs) and adiposity increase colorectal cancer risk, in part by elevating pro-inflammatory cytokines that activate pro-cancerous signaling pathways. Curcumin (CUR), a dietary polyphenol and salsalate (SAL), an non-steroidal anti-inflammatory drug (NSAID) lacking the gastrotoxicity of aspirin, each suppress inflammatory signaling, but via different cellular pathways. METHODS AND RESULTS: A/J mice (n = 110) are fed a low-fat diet (LFD, 10% kcal), a HFD (60% kcal), a HFD containing 0.4% CUR, a HFD containing 0.3% SAL, or a HFD containing both agents (CUR/SAL). All mice receive six injections of azoxymethane. Compared to LFD-fed mice, HFD-fed mice display elevated colonic cytokines, crypt cell proliferation, and increased tumorigenesis (p < 0.05). CUR/SAL significantly reduces colonic cytokines (p < 0.01), suppresses activation of the PI3K/Akt/mTOR/NF-κB/Wnt pathways (p < 0.01), activates AMPK (p < 0.01), attenuates abnormal proliferation of the colonic mucosa (p < 0.05), and reduces tumor multiplicity and burden (p < 0.05), in comparison to the HFD control. In contrast, CUR or SAL alone does not suppress abnormal crypt cell proliferation or tumor multiplicity, and is largely ineffective in modifying activation of these signaling pathways. CONCLUSION: These observations demonstrate the superiority of the CUR/SAL over the individual agents and provide a scientific basis for future translational studies in obese subjects and/or those habitually consuming HFDs.

Interleukin-1 Signaling Mediates Obesity-Promoted Elevations in Inflammatory Cytokines, Wnt Activation, and Epithelial Proliferation in the Mouse Colon.

Obesity is a prominent risk factor for colorectal cancer (CRC). One mechanism by which obesity promotes the development of CRC is by generating a chronic, low-grade state of colonic inflammation. Interleukin-1ß (IL-1ß), a proinflammatory cytokine often elevated in obesity, is known to activate several procarcinogenic signaling pathways that are implicated in colonic carcinogenesis. We therefore sought to define the role of IL-1ß in mediating some of the early biochemical and molecular events leading up to obesity-promoted CRC. Twenty-five wild-type (WT) C57BL/6J mice and 24 lacking a functional IL-1 receptor (IL1R-/-) were each randomized to either low-fat or high-fat diets, resulting in lean and obese mice. Compared to WT lean controls, WT obese mice displayed 30%-80% greater concentrations of IL-1ß and tumor necrosis factor-α (TNF-α) in the colonic mucosa (IL-1ß: P = 0.04; TNF-α: P < 0.05), activation of the Wnt signaling cascade [evidenced by a 2-fold increase in colonic crypt cells displaying intranuclear ß-catenin (P < 0.03)], and a significant expansion of the proliferation zone of the colonic crypt (P < 0.04). These obesity-induced alterations in colonic cytokines, Wnt signaling, and proliferation were absent in the obese IL1R-/- mice. In the absence of IL-1 signaling, obesity-induced elevations of colonic IL-1ß, TNF-α, Wnt activation, and enhanced epithelial proliferation no longer occur. These observations underscore the important mechanistic roles that IL-1 signaling appears to play in mediating the procancerous effects of obesity in the colon, thereby identifying a potential target for future strategies aimed at chemoprevention.

Parabacteroides distasonis attenuates toll-like receptor 4 signaling and Akt activation and blocks colon tumor formation in high-fat diet-fed azoxymethane-treated mice.

Gut dysbiosis may play an etiological role in colorectal tumorigenesis. We previously observed that the abundance of Parabacteroides distasonis (Pd) in stool was inversely associated with intestinal tumor burden and IL-1ß concentrations in mice. Here, we assessed the anti-inflammatory capacity of Pd membrane fraction (PdMb) in colon cancer cell lines. In addition, we tested whether Pd could suppress colon tumorigenesis in mice. Six-week-old male A/J mice were fed a low-fat (LF) diet, high-fat (HF) diet or HF+ whole freeze-dried Pd (HF + Pd, 0.04% wt/wt) for 24 weeks. After 1 week on diet, mice received 4 weekly injections of azoxymethane. PdMb robustly suppressed the production of pro-inflammatory cytokines and lowered the abundance of MyD88 and pAkt (ser473) induced by E. coli lipopolysaccharide in colon cancer cell lines. Moreover, PdMb induced apoptosis in colon cancer cell lines and blocked TLR4 activation in a reporter line. Colon tumors were observed in 0% of LF (0 of 19), 25% of HF (5 of 20) and 0% of HF + Pd mice (0 of 20) (p = 0.005). The latter group also displayed a lower abundance of MyD88 and pAkt (ser473) in colonic mucosa than HF mice. Taken together, these data suggest that Pd has anti-inflammatory and anti-cancer properties that are likely mediated by the suppression of TLR4 and Akt signaling, as well as promotion of apoptosis. Further work is needed to confirm these findings in additional models and fully elaborate the mechanism of action.

Curcumin and Salsalate Suppresses Colonic Inflammation and Procarcinogenic Signaling in High-Fat-Fed, Azoxymethane-Treated Mice.

High-fat diets (HFDs) and excess adiposity increase proinflammatory cytokines in the colon, altering gene expression in a manner that promotes the development of colorectal cancer (CRC). Thus, compounds that reduce this biochemical inflammation are potential chemopreventive agents. Curcumin (CUR), a dietary polyphenol, and salsalate (SAL), a non-steroidal anti-inflammatory drug, are both anti-inflammatories. We investigated the inhibitory effects of CUR with or without SAL on inflammatory cytokines and procarcinogenic signaling in azoxymethane (AOM)-treated A/J mice. A sub-tumorigenic AOM dose was chosen to produce a biochemical and molecular procarcinogenic colonic environment without tumors. Mice were fed either a HFD (60% of kilocalories) or low-fat diet (LFD) (10% of kilocalories). One HFD treatment group received 0.2% CUR in the diet; one received 0.2% CUR + 0.15% SAL; and one received 0.4% CUR + 0.3% SAL. The HFD mice developed 30% greater fat mass than the LFD mice (p < 0.05). The colonic concentrations of interleukin-1ß (IL-1ß) and interleukin-6 (IL-6) in the HFD mice were decreased by 50-69% by the high-dose combination regimen (p < 0.015). Only the combination regimens significantly suppressed phosphorylation of protein kinase B (Akt) and nuclear factor-κB (NF-κB) p65 (p < 0.044). The combination of CUR and SAL reduces the concentration of proinflammatory cytokines and diminishes activation of Akt and NF-κB more effectively than CUR alone, providing a scientific basis for examining whether this combination mitigates the risk of CRC in obese individuals.

Consumption of Dietary Resistant Starch Partially Corrected the Growth Pattern Despite Hyperglycemia and Compromised Kidney Function in Streptozotocin-Induced Diabetic Rats.

We previously demonstrated that feeding of dietary resistant starch (RS) prior to the induction of diabetes delayed the progression of diabetic nephropathy and maintained vitamin D balance in streptozotocin (STZ)-induced type 1 diabetic (T1D) rats. Here, we examined the impact of RS on kidney function and vitamin D homeostasis following STZ injection. Male Sprague-Dawley rats were administered STZ and fed a standard diet containing cornstarch or 20, 10, or 5% RS for 4 weeks. T1D rats fed 10 and 20% RS, but not 5% RS, gained more weight than cornstarch-fed rats. Yet, renal health and glucose metabolism were not improved by RS. Our data suggest that RS normalized growth patterns in T1D rats after diabetes induction in a dose-dependent manner despite having no effect on blood glucose and vitamin D balances. Future interventions should focus on the preventative strategies with RS in T1D.

Correction: Paternal B Vitamin Intake Is a Determinant of Growth, Hepatic Lipid Metabolism and Intestinal Tumor Volume in Female Apc1638N Mouse Offspring.

[This corrects the article DOI: 10.1371/journal.pone.0151579.].

Paternal B Vitamin Intake Is a Determinant of Growth, Hepatic Lipid Metabolism and Intestinal Tumor Volume in Female Apc1638N Mouse Offspring.

BACKGROUND: The importance of maternal nutrition to offspring health and risk of disease is well established. Emerging evidence suggests paternal diet may affect offspring health as well. OBJECTIVE: In the current study we sought to determine whether modulating pre-conception paternal B vitamin intake alters intestinal tumor formation in offspring. Additionally, we sought to identify potential mechanisms for the observed weight differential among offspring by profiling hepatic gene expression and lipid content. METHODS: Male Apc1638N mice (prone to intestinal tumor formation) were fed diets containing replete (control, CTRL), mildly deficient (DEF), or supplemental (SUPP) quantities of vitamins B2, B6, B12, and folate for 8 weeks before mating with control-fed wild type females. Wild type offspring were euthanized at weaning and hepatic gene expression profiled. Apc1638N offspring were fed a replete diet and euthanized at 28 weeks of age to assess tumor burden. RESULTS: No differences in intestinal tumor incidence or burden were found between male Apc1638N offspring of different paternal diet groups. Although in female Apc1638N offspring there were no differences in tumor incidence or multiplicity, a stepwise increase in tumor volume with increasing paternal B vitamin intake was observed. Interestingly, female offspring of SUPP and DEF fathers had a significantly lower body weight than those of CTRL fed fathers. Moreover, hepatic trigylcerides and cholesterol were elevated 3-fold in adult female offspring of SUPP fathers. Weanling offspring of the same fathers displayed altered expression of several key lipid-metabolism genes. Hundreds of differentially methylated regions were identified in the paternal sperm in response to DEF and SUPP diets. Aside from a few genes including Igf2, there was a striking lack of overlap between these genes differentially methylated in sperm and differentially expressed in offspring. CONCLUSIONS: In this animal model, modulation of paternal B vitamin intake prior to mating alters offspring weight gain, lipid metabolism and tumor growth in a sex-specific fashion. These results highlight the need to better define how paternal nutrition affects the health of offspring.

Cytotoxic and antiangiogenic paclitaxel solubilized and permeation-enhanced by natural product nanoparticles.

Paclitaxel (PTX) is one of the most potent intravenous chemotherapeutic agents to date, yet an oral formulation has been problematic because of its low solubility and permeability. Using the recently discovered solubilizing properties of rubusoside (RUB), we investigated the unique PTX-RUB formulation. PTX was solubilized by RUB in water to levels of 1.6-6.3 mg/ml at 10-40% weight/volume. These nanomicellar PTX-RUB complexes were dried to a powder, which was subsequently reconstituted in physiologic solutions. After 2.5 h, 85-99% of PTX-RUB remained soluble in gastric fluid, whereas 79-96% remained soluble in intestinal fluid. The solubilization of PTX was mechanized by the formation of water-soluble spherical nanomicelles between PTX and RUB, with an average diameter of 6.6 nm. Compared with Taxol, PTX-RUB nanoparticles were nearly four times more permeable in Caco-2 cell monocultures. In a side-by-side comparison with dimethyl sulfoxide-solubilized PTX, PTX-RUB maintained the same level of cytotoxicity against three human cancer cell lines with IC50 values ranging from 4 to 20 nmol/l. In addition, tubule formation and migration of human umbilical vein endothelial cells were inhibited at levels as low as 5 nmol/l. These chemical and biological properties demonstrated by the PTX-RUB nanoparticles may improve oral bioavailability and enable further pharmacokinetic, toxicologic, and efficacy investigations.

Reformulation of etoposide with solubility-enhancing rubusoside.

Etoposide (ETO), a widely used anti-cancer drug, is constrained by its low aqueous solubility and by side effects from both the drug and its solubilizing excipients. In this study, a recently discovered natural solubilizer rubusoside (RUB) was used to achieve the solubilization of ETO. Dynamic light scattering and freeze-fracture transmission electron microscopy studies showed that ETO and RUB formed ETO-RUB nanoparticles (∼6 nm in diameter). The powder of ETO-RUB nanoparticles was completely reconstitutable in water and remained stable in this solution at 25 and 37°C for at least 24h. Under other physiologic conditions, ETO solution was clear and free of precipitation at 25°C, but underwent various structural transformations. In PBS and simulated intestinal fluid, RUB-solubilized ETO underwent epimerization and equilibrated to cis-ETO. In simulated gastric fluid, RUB-solubilized ETO degraded to 4'-demethylepipodophyllotoxin-beta-d-glucoside and 4'-demethylepipodophyllotoxin. Higher temperatures favored epimerization or degradation. Furthermore, a side-by-side comparison with DMSO-solubilized ETO confirmed that the RUB-solubilized ETO showed no significant differences in cytotoxicity in colon, breast and prostate cancer cell lines. RUB effectively solubilized and stabilized etoposide, which sets the stage for further toxicology, bioavailability, and efficacy investigations.

Paclitaxel-induced apoptosis is blocked by camptothecin in human breast and pancreatic cancer cells.

The combination of paclitaxel (PTX) and topoisomerase I inhibitors such as camptothecin (CPT) constitutes a therapeutic strategy based on anticipated synergism. However, previous in vitro studies have generated contradictory findings for this strategy. The interaction between these drugs can be synergistic or antagonistic, depending on the cell type examined. To gain additional insight into this promising yet controversial strategy, we investigated the interaction between PTX and CPT in three different cell lines (PANC-1, MDA-MB-231 and HL-60) and explored possible underlying mechanisms of synergy or antagonism. Using a novel solubilizing natural compound, rubusoside, water-insoluble PTX and CPT were solubilized to enable the comparison of the effects of single drugs and their combination on cell viability. Intracellular drug concentrations were quantified to examine the effect of CPT on cellular uptake and accumulation of PTX. Flow cytometry and quantitative real-time PCR gene array analyses were used to explore the mechanisms behind the interaction between PTX and CPT. Our studies confirmed that rubusoside-solubilized PTX or CPT maintained cytotoxicity, causing significant reductions in cell viability. However, the efficacy of the combination of PTX and CPT produced varied results based on the cell line tested. CPT antagonistically reduced the cytotoxic activity of PTX in PANC-1 and MDA-MB-231 cells. The effect of CPT on the cytotoxicity of PTX was less pronounced in HL-60 cells, showing neither synergy nor antagonism. Analysis of apoptosis by flow cytometry revealed that upon co-treatment with CPT, apoptosis induced by PTX was attenuated in PANC-1 and MDA-MB-231 cells. In agreement with our cytotoxicity findings, no synergistic or antagonistic effects on apoptosis were observed in HL-60 cells. The antagonism in PANC-1 and MDA-MB-231 cells was not a result of reduced PTX uptake and accumulation because the amount of intracellular PTX was not altered upon co-treatment with CPT. Moreover, higher expression of anti-apoptosis-related transcripts (BCL2L10, CFLAR, HIP1 and TRADD) in PANC-1 cells was observed upon combination treatment over PTX treatment alone. Although exact underlying mechanisms are unknown, the suspected CPT-dependent reduction of intracellular PTX accumulation was ruled out. The findings of antagonism and increased anti-apoptotic gene transcription serve as a precaution to the design of combination drug strategies where a synergistic interaction may not exist.

A novel solubility-enhanced curcumin formulation showing stability and maintenance of anticancer activity.

Curcumin (CUR) is an active food compound, but its insolubility and instability in water contributes to low bioavailability. In this study, the solubility of CUR was enhanced by utilizing the solubilizing properties of rubusoside (RUB). The solubility of CUR in water increased linearly from 61 µg/mL to 2.318 mg/mL in the presence of RUB ranging from 1% to 10% (w/v). Dynamic light scattering and transmission electron microscopy studies found that CUR and RUB formed CUR-RUB nanoparticle (∼8 nm) complexes. The RUB-solubilized CUR was stable in physiological conditions and did not precipitate when diluted or degrade when spray-dried to a completely reconstitutable powder. Furthermore, cell viability assays demonstrated the efficacy of RUB-solubilized CUR against human colon, breast, and pancreatic cancer cell lines. The development of this new solubilized, stable, and biologically active CUR formulation lays the foundation for future bioavailability improvement.