Chili Peppers, Curcumins, and Prebiotics in Gastrointestinal Health and Disease

To Explore the Putative Molecular Targets of Diabetic Nephropathy and their Inhibition Utilizing Potential Phytocompounds

BACKGROUND

This review critically addresses the putative molecular targets of Diabetic Nephropathy (DN) and screens effective phytocompounds that can be therapeutically beneficial, and highlights their mechanistic modalities of action.

INTRODUCTION

DN has become one of the most prevalent complications of clinical hyperglycemia, with individual-specific variations in the disease spectrum that leads to fatal consequences. Diverse etiologies involving oxidative and nitrosative stress, activation of polyol pathway, inflammasome formation, Extracellular Matrix (ECM) modifications, fibrosis, and change in dynamics of podocyte functional and mesangial cell proliferation adds up to the clinical complexity of DN. Current synthetic therapeutics lacks target-specific approach, and is associated with the development of inevitable residual toxicity and drug resistance. Phytocompounds provides a vast diversity of novel compounds that can become an alternative therapeutic approach to combat the DN.

METHODS

Relevant publications were searched and screened from research databases like GOOGLE SCHOLAR, PUBMED and SCISEARCH. Out of 4895 publications, the most relevant publications were selected and included in this article.

RESULT

This study critically reviews over 60 most promising phytochemical and provides with their molecular targets, that can be of pharmacological significance in context to current treatment and concomitant research in DN.

CONCLUSION

This review highlights those most promising phytocompounds that have the potential of becoming new safer naturally-sourced therapeutic candidates and demands further attention at clinical level.

Prebiotic effects of plant-derived (poly)phenols on host metabolism: Is there a role for short-chain fatty acids?

The gut microbiota has been extensively investigated during the last decade because of its effects on host neuroendocrine pathways and other processes. The imbalance between beneficial and pathogenic bacteria, known as dysbiosis, may be a determining predisposing factor for many noncommunicable chronic diseases, such as obesity, type 2 diabetes mellitus, metabolic syndrome, and Alzheimer's disease. On the other hand, interventions aiming to reestablish the balance between microbiota components have been suggested as potential preventive therapeutic strategies against these disorders. Among these interventions, dietary supplementation with (poly)phenols has been highlighted due to the modulatory effects exerted by those compounds on the gut microbiota. In addition, (poly)phenol consumption is associated with increased production of short-chain fatty acids (SCFAs), a set of microbial metabolites whose actions are ascribed to improving the abovementioned metabolic disorders. Thus, this review discusses the modulation of the gut microbiota by prebiotic (poly)phenols based on in vivo studies performed with isolated (poly)phenolic compounds, their interaction with the gut microbiota and the production of SCFAs in pursuit of the molecular mechanisms underlying the health effects of (poly)phenols on host metabolism.

Detection of indigenous gut bacteria related to red chilli pepper (Capsicum annuum) in murine caecum and human faecal cultures

BACKGROUND

Red chilli pepper (Capsicum annuum; RP) is a popular spice containing the active compound capsaicin. Indigenous gut bacteria and metabolism can affect host health. The functions of capsaicin, including the regulation of metabolic health and anti-oxidant properties, may be correlated with the gut microbiota.

METHODS

To identify indigenous gut bacteria that are responsive to RP, Institute of Cancer Research mice fed a diet with no fibre or with 5% (w/w) RP for 14 days. Additionally, human stool samples collected from four healthy volunteers were incubated without (control) or with 2% (w/v) RP at 37 °C for 24 h. Microbiota in murine caecal samples and human faecal cultures were analysed using 16S rRNA (V4) amplicon sequencing.

RESULTS

Compared with the microbiota in mice fed no-fibre diets, Lachnospiraceae spp.-, Muribaculaceae spp.-, and Phacaeicola vulgatus-like bacteria were defined as murine RP-responsive indigenous gut bacteria (RP-RIB). In the human faecal cultures, acetate and propionate levels were higher in RP cultures than in the control cultures. Subdoligranulum spp.-, Blautia spp.-, Faecalibacterium prausnitzii-, P. vulgatus-, and Prevotella copri-like bacteria were defined as human RP-RIB. Compared with control culture Fe-reducing power was increased in the culture with RP.

CONCLUSION

RP increases the amount of short-chain fatty acid-producing bacteria and beneficial gut bacteria in mouse and human faecal cultures. Overall, RP could have a positive effect on the host by altering the gut microbiota.

Plant-Derived (Poly)phenols and Their Metabolic Outcomes: The Pursuit of a Role for the Gut Microbiota

Plant-derived (poly)phenolic compounds have been undoubtedly shown to promote endocrine homeostasis through the improvement of diverse metabolic outcomes. Amongst diverse potential mechanisms, the prebiotic modulatory effects exerted by these compounds on the gut microbiota have supported their nutraceutical application in both experimental and clinical approaches. However, the comprehension of the microbiota modulatory patterns observed upon (poly)phenol-based dietary interventions is still in its infancy, which makes the standardization of the metabolic outcomes in response to a given (poly)phenol a herculean task. Thus, this narrative review sought to gather up-to-date information on the relationship among (poly)phenols intake, their modulatory effect on the gut microbiota diversity, and consequent metabolic outcomes as a supportive tool for the future design of experimental approaches and even clinical trials.

Capsaicin as an amphipathic modulator of NaV1.5 mechanosensitivity

SCN5A-encoded Na_V1.5 is a voltage-gated Na⁺ channel that drives the electrical excitability of cardiac myocytes and contributes to slow waves of the human gastrointestinal smooth muscle cells. Na_V1.5 is mechanosensitive: mechanical force modulates several facets of Na_V1.5’s voltage-gated function, and some Na_V1.5 channelopathies are associated with abnormal Na_V1.5 mechanosensitivity (MS). A class of membrane-active drugs, known as amphiphiles, therapeutically target Na_V1.5’s voltage-gated function and produce off-target effects including alteration of MS. Amphiphiles may provide a novel option for therapeutic modulation of Na_V1.5’s mechanosensitive operation. To more selectively target Na_V1.5 MS, we searched for a membrane-partitioning amphipathic agent that would inhibit MS with minimal closed-state inhibition of voltage-gated currents. Among the amphiphiles tested, we selected capsaicin for further study. We used two methods to assess the effects of capsaicin on Na_V1.5 MS: (1) membrane suction in cell-attached macroscopic patches and (2) fluid shear stress on whole cells. We tested the effect of capsaicin on Na_V1.5 MS by examining macro-patch and whole-cell Na⁺ current parameters with and without force. Capsaicin abolished the pressure- and shear-mediated peak current increase and acceleration; and the mechanosensitive shifts in the voltage-dependence of activation (shear) and inactivation (pressure and shear). Exploring the recovery from inactivation and use-dependent entry into inactivation, we found divergent stimulus-dependent effects that could potentiate or mitigate the effect of capsaicin, suggesting that mechanical stimuli may differentially modulate Na_V1.5 MS. We conclude that selective modulation of Na_V1.5 MS makes capsaicin a promising candidate for therapeutic interventions targeting MS.

Lactobacillus rhamnosus attenuates Thai chili extracts induced gut inflammation and dysbiosis despite capsaicin bactericidal effect against the probiotics, a possible toxicity of high dose capsaicin

Because of a possible impact of capsaicin in the high concentrations on enterocyte injury (cytotoxicity) and bactericidal activity on probiotics, Lactobacillus rhamnosus L34 (L34) and Lactobacillus rhamnosus GG (LGG), the probiotics derived from Thai and Caucasian population, respectively, were tested in the chili-extract administered C57BL/6 mice and in vitro experiments. In comparison with placebo, 2 weeks administration of the extract from Thai chili in mice caused loose feces and induced intestinal permeability defect as indicated by FITC-dextran assay and the reduction in tight junction molecules (occludin and zona occludens-1) using fluorescent staining and gene expression by quantitative real-time polymerase chain reaction (qRT-PCR). Additionally, the chili extracts also induced the translocation of gut pathogen molecules; lipopolysaccharide (LPS) and (1→3)-β-d-glucan (BG) and fecal dysbiosis (microbiome analysis), including reduced Firmicutes, increased Bacteroides, and enhanced total Gram-negative bacteria in feces. Both L34 and LGG attenuated gut barrier defect (FITC-dextran, the fluorescent staining and gene expression of tight junction molecules) but not improved fecal consistency. Additionally, high concentrations of capsaicin (0.02-2 mM) damage enterocytes (Caco-2 and HT-29) as indicated by cell viability test, supernatant cytokine (IL-8), transepithelial electrical resistance (TEER) and transepithelial FITC-dextran (4.4 kDa) but were attenuated by Lactobacillus condition media (LCM) from both probiotic-strains. The 24 h incubation with 2 mM capsaicin (but not the lower concentrations) reduced the abundance of LGG (but not L34) implying a higher capsaicin tolerance of L34. However, Lactobacillus rhamnosus fecal abundance, using qRT-PCR, of L34 or LGG after 3, 7, and 20 days of the administration in the Thai healthy volunteers demonstrated the similarity between both strains. In conclusion, high dose chili extracts impaired gut permeability and induced gut dysbiosis but were attenuated by probiotics. Despite a better capsaicin tolerance of L34 compared with LGG in vitro, L34 abundance in feces was not different to LGG in the healthy volunteers. More studies on probiotics with a higher intake of chili in human are interesting.

Transient Receptor Potential Vanilloid Subtype 1: Potential Role in Infection, Susceptibility, Symptoms and Treatment of COVID-19

The battle against the new coronavirus that continues to kill millions of people will be still long. Novel strategies are demanded to control infection, mitigate symptoms and treatment of COVID-19. This is even more imperative given the long sequels that the disease has on the health of the infected. The discovery that S protein includes two ankyrin binding motifs (S-ARBMs) and that the transient receptor potential vanilloid subtype 1 (TRPV-1) cation channels contain these ankyrin repeat domains (TRPs-ARDs) suggest that TRPV-1, the most studied member of the TRPV channel family, can play a role in binding SARS-CoV-2. This hypothesis is strengthened by studies showing that other respiratory viruses bind the TRPV-1 on sensory nerves and epithelial cells in the airways. Furthermore, the pathophysiology in COVID-19 patients is similar to the effects generated by TRPV-1 stimulation. Lastly, treatment with agonists that down-regulate or inactivate TRPV-1 can have a beneficial action on impaired lung functions and clearance of infection. In this review, we explore the role of the TRPV-1 channel in the infection, susceptibility, pathogenesis, and treatment of COVID-19, with the aim of looking at novel strategies to control infection and mitigate symptoms, and trying to translate this knowledge into new preventive and therapeutic interventions.

Potential Interplay between Nrf2, TRPA1, and TRPV1 in Nutrients for the Control of COVID-19

In this article, we propose that differences in COVID-19 morbidity may be associated with transient receptor potential ankyrin 1 (TRPA1) and/or transient receptor potential vanilloid 1 (TRPV1) activation as well as desensitization. TRPA1 and TRPV1 induce inflammation and play a key role in the physiology of almost all organs. They may augment sensory or vagal nerve discharges to evoke pain and several symptoms of COVID-19, including cough, nasal obstruction, vomiting, diarrhea, and, at least partly, sudden and severe loss of smell and taste. TRPA1 can be activated by reactive oxygen species and may therefore be up-regulated in COVID-19. TRPA1 and TRPV1 channels can be activated by pungent compounds including many nuclear factor (erythroid-derived 2) (Nrf2)-interacting foods leading to channel desensitization. Interactions between Nrf2-associated nutrients and TRPA1/TRPV1 may be partly responsible for the severity of some of the COVID-19 symptoms. The regulation by Nrf2 of TRPA1/TRPV1 is still unclear, but suggested from very limited clinical evidence. In COVID-19, it is proposed that rapid desensitization of TRAP1/TRPV1 by some ingredients in foods could reduce symptom severity and provide new therapeutic strategies.

Acute Effects of Red Chili, a Natural Capsaicin Receptor Agonist, on Gastric Accommodation and Upper Gastrointestinal Symptoms in Healthy Volunteers and Gastroesophageal Reflux Disease Patients

The effects of chili on gastric accommodation (GA) in gastroesophageal reflux disease (GERD) patients have not been explored. Methods: In total, 15 healthy volunteers (HV) and 15 pH-positive non-erosive GERD (NERD) patients underwent single-photon emission computed tomography after ingesting 2 g of chili or placebo in capsules in a randomized double-blind crossover fashion with a one-week washout period. GA was the maximal postprandial gastric volume (GV) after 250 mL of Ensure^® minus the fasting GV. Upper gastrointestinal symptoms were evaluated by using a visual analog scale. Results: NERD patients but not HV had significantly greater GA after chili compared to a placebo (451 ± 89 vs. 375 ± 81 mL, p < 0.05). After chili, the postprandial GVs at 10, 20, and 30 min in NERD patients were significantly greater than HV (10 min, 600 ± 73 vs. 526 ± 70 mL; 20 min, 576 ± 81 vs. 492 ± 78 mL; 30 min, 532 ± 81 vs. 466 ± 86 mL, all p < 0.05). In NERD, chili was associated with significantly less satiety, more severe abdominal burning (p < 0.05), and a trend of more severe heartburn (p = 0.06) compared to the placebo. In HV, postprandial symptoms after chili and placebo ingestion were similar (p > 0.05). Conclusions: Chili enhanced GA in NERD patients but not in HV. This suggests that the modulation of GA in NERD is abnormal and likely involves transient receptor potential vanilloid 1 (TRPV1) sensitive pathways.

Efficacy of Curcuma longa in treatment of postprandial distress syndrome: An open-label randomized-controlled trial

Background: Proton pump inhibitors are effective for functional dyspepsia but ineffective in relieving postprandial distress syndrome. Curcuma longa might be effective for postprandial distress syndrome. The objective of this study was to compare the efficacy of Curcuma longa and simethicone for postprandial distress syndrome in an open-label randomized-controlled trial.

Methods: This trial was conducted between July 2018 and February 2019. In total, 78 patients were randomly assigned to receive 4 weeks of treatment with 750 or 1,500 mg oral Curcuma longa per day or 240 mg simethicone per day. The patients assessed their symptoms using the dyspepsia Global Overall Symptom scale at baseline, week 2, and week 4. After stopping medication for 2 weeks, the patients assessed recurrent symptoms and day of recurrence by themselves at the end of week 6.

Results: In total, 78 patients underwent randomization (27 in 750 mg Curcuma longa, 26 in 1500 mg Curcuma longa, and 25 in simethicone groups). After 2 weeks, there were no significant differences in all mean changes of symptoms scores (95%CI) of postprandial distress syndrome [-4.1 (-4.5, -2.6) vs -4.3 (-5.2, -3.3) vs -4.2 (-4.8, -3.5), P=0.954]. Over a period of 4 weeks, the reduction in mean scores was greater among participants receiving simethicone (although not statistically significant) compared with two intervention groups [-4.6 (-5.7, -3.6) vs -5.4 (-6.6, -4.1) vs -6.2 (-7.2, -5.2), P=0.122]. The rate of recurrence was significantly lower in simethicone than the two Curcuma longa groups (42.9 vs 45.5 vs 13.6%, P=0.047). There was no serious adverse event reported in all three groups.

Conclusions: Curcuma longa had a similar effect on treatment outcomes to simethicone after 2 and 4 weeks, but the recurrence rate of symptoms was significantly higher without serious adverse events.

Registration: Registered with the Thai Clinical Trials Registry on 31 January 2018; TCTR20180131001.

Diet in Irritable Bowel Syndrome (IBS): Interaction with Gut Microbiota and Gut Hormones

Diet plays an important role not only in the pathophysiology of irritable bowel syndrome (IBS), but also as a tool that improves symptoms and quality of life. The effects of diet seem to be a result of an interaction with the gut bacteria and the gut endocrine cells. The density of gut endocrine cells is low in IBS patients, and it is believed that this abnormality is the direct cause of the symptoms seen in IBS patients. The low density of gut endocrine cells is probably caused by a low number of stem cells and low differentiation progeny toward endocrine cells. A low fermentable oligo-, di-, monosaccharide, and polyol (FODMAP) diet and fecal microbiota transplantation (FMT) restore the gut endocrine cells to the level of healthy subjects. It has been suggested that our diet acts as a prebiotic that favors the growth of a certain types of bacteria. Diet also acts as a substrate for gut bacteria fermentation, which results in several by-products. These by-products might act on the stem cells in such a way that the gut stem cells decrease, and consequently, endocrine cell numbers decrease. Changing to a low-FODMAP diet or changing the gut bacteria through FMT improves IBS symptoms and restores the density of endocrine cells.

Curcumin Inhibits Chondrocyte Hypertrophy of Mesenchymal Stem Cells through IHH and Notch Signaling Pathways

Using tissue engineering technique to repair cartilage damage caused by osteoarthritis is a promising strategy. However, the regenerated tissue usually is fibrous cartilage, which has poor mechanical characteristics compared to hyaline cartilage. Chondrocyte hypertrophy plays an important role in this process. Thus, it is very important to find out a suitable way to maintain the phenotype of chondrocytes and inhibit chondrocyte hypertrophy. Curcumin deriving from turmeric was reported with anti-inflammatory and anti-tumor pharmacological effects. However, the role of curcumin in metabolism of chondrocytes, especially in the chondrocyte hypertrophy remains unclear. Mesenchymal stem cells (MSCs) are widely used in cartilage tissue engineering as seed cells. So we investigated the effect of curcumin on chondrogenesis and chondrocyte hypertrophy in MSCs through examination of cell viability, glycosaminoglycan synthesis and specific gene expression. We found curcumin had no effect on expression of chondrogenic markers including Sox9 and Col2a1 while hypertrophic markers including Runx2 and Col10a1 were down-regulated. Further exploration showed that curcumin inhibited chondrocyte hypertrophy through Indian hedgehog homolog (IHH) and Notch signalings. Our results indicated curcumin was a potential agent in modulating cartilage homeostasis and maintaining chondrocyte phenotype.

Mexican consensus on dyspepsia

Since the publication of the 2007 dyspepsia guidelines of the Asociación Mexicana de Gastroenterología, there have been significant advances in the knowledge of this disease. A systematic search of the literature in PubMed (01/2007 to 06/2016) was carried out to review and update the 2007 guidelines and to provide new evidence-based recommendations. All high-quality articles in Spanish and English were included. Statements were formulated and voted upon using the Delphi method. The level of evidence and strength of recommendation of each statement were established according to the GRADE system. Thirty-one statements were formulated, voted upon, and graded. New definition, classification, epidemiology, and pathophysiology data were provided and include the following information: Endoscopy should be carried out in cases of uninvestigated dyspepsia when there are alarm symptoms or no response to treatment. Gastric and duodenal biopsies can confirm Helicobacter pylori infection and rule out celiac disease, respectively. Establishing a strong doctor-patient relationship, as well as dietary and lifestyle changes, are useful initial measures. H2-blockers, proton-pump inhibitors, prokinetics, and antidepressants are effective pharmacologic therapies. H.pylori eradication may be effective in a subgroup of patients. There is no evidence that complementary and alternative therapies are beneficial, with the exception of Iberogast and rikkunshito, nor is there evidence on the usefulness of prebiotics, probiotics, or psychologic therapies. The new consensus statements on dyspepsia provide guidelines based on up-to-date evidence. A discussion, level of evidence, and strength of recommendation are presented for each statement.