João R. Araújo

Chemopreventive effect of dietary polyphenols in colorectal cancer cell lines.

Colorectal cancer (CRC) is the second most fatal and the third most diagnosed type of cancer worldwide. Despite having multifactorial causes, most CRC cases are mainly determined by dietary factors. In recent years, a large number of studies have attributed a protective effect to polyphenols and foods containing these compounds (fruits and vegetables) against CRC. Indeed, polyphenols have been reported to interfere with cancer initiation, promotion, and progression, acting as chemopreventive agents. The aim of this review is to summarize the main chemopreventive properties of some polyphenols (quercetin, rutin, myricetin, chrysin, epigallocatechin-3-gallate, epicatechin, catechin, resveratrol, and xanthohumol) against CRC, observed in cell culture models. From the data reviewed in this article, it can be concluded that these compounds inhibit cell growth, by inducing cell cycle arrest and/or apoptosis; inhibit proliferation, angiogenesis, and/or metastasis; and exhibit anti-inflammatory and/or antioxidant effects. In turn, these effects involve multiple molecular and biochemical mechanisms of action, which are still not completely characterized. Thus, caution is mandatory when attempting to extrapolate the observations obtained in CRC cell line studies to humans.

Impact of Gestational Diabetes Mellitus in the Maternal-to-Fetal Transport of Nutrients

Gestational diabetes mellitus (GDM) is a metabolic disorder prevalent among pregnant women. This disease increases the risk of adverse perinatal outcomes and diseases in the offspring later in life. The human placenta, the main interface between the maternal and fetal blood circulations, is responsible for the maternal-to-fetal transfer of nutrients essential for fetal growth and development. In this context, the aim of this article is to review the latest advances in the placental transport of macro and micronutrients and how they are affected by GDM and its associated conditions, such as elevated levels of glucose, insulin, leptin, inflammation, and oxidative stress. Data analyzed in this article suggest that GDM and its associated conditions, particularly high levels of glucose, leptin, and oxidative stress, disturb placental nutrient transport and, consequently, fetal nutrient supply. As a consequence, this disturbance may contribute to the fetal and postnatal adverse health outcomes associated with GDM.

Folates and aging: Role in mild cognitive impairment, dementia and depression

In almost all tissues, including the brain, folates are required for one-carbon transfer reactions, which are essential for the synthesis of DNA and RNA nucleotides, the metabolism of amino acids and the occurrence of methylation reactions. The aim of this paper is to review the impact of folate status on the risk of development of neuropsychiatric disorders in older individuals. The prevalence of folate deficiency is high among individuals aged ≥ 65 years mainly due to reduced dietary intake and intestinal malabsorption. Population-based studies have demonstrated that a low folate status is associated with mild cognitive impairment, dementia (particularly Alzheimers disease) and depression in healthy and neuropsychiatric diseased older individuals. The proposed mechanisms underlying that association include hyperhomocysteinemia, lower methylation reactions and tetrahydrobiopterin levels, and excessive misincorporation of uracil into DNA. However, currently, there is no consistent evidence demonstrating that folic acid supplementation improves cognitive function or slows cognitive decline in healthy or cognitively impaired older individuals. In conclusion, folate deficiency seems to be an important contributor for the onset and progression of neuropsychiatric diseases in the geriatric population but additional studies are needed in order to increase the knowledge of this promising, but still largely unexplored, area of research.

Antipsychotics-induced metabolic alterations: focus on adipose tissue and molecular mechanisms.

The use of antipsychotic drugs for the treatment of mood disorders and psychosis has increased dramatically over the last decade. Despite its consumption being associated with beneficial neuropsychiatric effects in patients, atypical antipsychotics (which are the most frequently prescribed antipsychotics) use is accompanied by some secondary adverse metabolic effects such as weight gain, dyslipidemia and glucose intolerance. The molecular mechanisms underlying these adverse effects are not fully understood but have been suggested to involve a dysregulation of adipose tissue homeostasis. As such, the aim of this paper is to review and discuss the role of adipose tissue in the development of secondary adverse metabolic effects induced by atypical antipsychotics. Data analyzed in this article suggest that atypical antipsychotics may increase adipose tissue (particularly visceral adipose tissue) lipogenesis, differentiation/hyperplasia, pro-inflammatory mediator secretion and insulin resistance and decrease adipose tissue lipolysis. Consequently, patients receiving antipsychotic medication could be at risk of developing obesity, type 2 diabetes and cardiovascular disease. A better knowledge of the impact of these drugs on adipose tissue homeostasis may unveil strategies to develop novel antipsychotic drugs with less adverse metabolic effects and to develop adjuvant therapies (e.g. behavioral and nutritional therapies) to neuropsychiatric patients receiving antipsychotic medication.

Modulation of Glucose Uptake in a Human Choriocarcinoma Cell Line (BeWo) by Dietary Bioactive Compounds and Drugs of Abuse

The aim of this work was to investigate the putative modulation of glucose uptake in trophoblast cells by several dietary compounds and by drugs of abuse. For this, the acute (26 min) and chronic (48 h) effect of these substances on the apical uptake of 3H-2-deoxy-D-glucose (3H-DG) by a human choriocarcinoma cell line (BeWo) was determined. 3H-DG apical uptake by BeWo cells was time dependent, displayed saturable kinetics (Vmax=1210+/-29 nmol mg protein(-1) 6 min(-1) and Km=13.4+/-0.5 mM) and was insulin-insensitive and cytochalasin B-sensitive (by up to 60%). Acutely, acetaldehyde (30-100 mM), resveratrol, xanthohumol, epigallocatechin-3-gallate (100 microM), chrysin and quercetin (10-100 microM) decreased 3H-DG apical uptake, whereas rutin, catechin (10-100 microM), epicatechin (100 microM) and ethanol (10 mM) increased it. Quercetin and xanthohumol seem to be non-competitive inhibitors of 3H-DG apical uptake, whereas both epigallocatechin-3-gallate and acetaldehyde decreased both the Km and Vmax values. Chronically, rutin and myricetin increased the apical uptake of 3H-DG both isolated (0.1-1 microM) and in combination (both at 1 microM), whereas theophylline (0.1-1 microM) and amphetamine, 3,4-methylenedioxymethamphetamine (0.25-1 microM) and Delta9-tetrahydrocannabinol (1 nM) decreased it. In conclusion, 3H-DG apical uptake by BeWo cells is differentially modulated by different compounds present in drinks and by drugs of abuse.

In Vitro Studies on the Inhibition of Colon Cancer by Butyrate and Polyphenolic Compounds

Our aim was to investigate the effect of several dietary polyphenols on uptake of 14C-butyrate (14C-BT) by Caco-2 cells and try to correlate this effect with the modulation of the anticarcinogenic effect of BT in these cells. Acutely, uptake of 14C-BT (10 μM) was decreased by resveratrol, quercetin, myricetin, and chrysin, and increased by xanthohumol, catechin, and epicatechin; and uptake of 14C-BT (20 mM) was reduced by resveratrol, quercetin, myricetin, chrysin, EGCG, and epicatechin. Resveratrol acts as a competitive inhibitor of 14C-BT uptake. Chronically, quercetin and EGCG increased uptake of 14C-BT (10 μM), whereas myricetin, rutin, chrysin, and xanthohumol decreased it. Moreover, catechin (1 μM), quercetin, myricetin, rutin, EGCG, and chrysin increased uptake of 14C-BT (20 mM), whereas catechin (0.1 μM) decreased it. EGCG, myricetin, and catechin decreased MCT1 mRNA expression, while chrysin increased it; quercetin, rutin, and xanthohumol had no effect. BT (5 mM; 48 h) markedly decreased cellular viability and proliferation and increased cell differentiation and apoptosis. In general, combination of polyphenolic compounds with BT did not significantly modify these changes. In conclusion, changes in uptake of BT induced by polyphenols do not correlate with changes on the effect of BT upon cell viability, cell proliferation, differentiation, and apoptosis.

Gestational diabetes mellitus decreases placental uptake of long-chain polyunsaturated fatty acids: involvement of long-chain acyl-CoA synthetase

The long-chain polyunsaturated fatty acids (LC-PUFAs) arachidonic (AA) and docosahexaenoic (DHA) acids are essential for fetal development. Gestational diabetes mellitus (GDM) is a pregnancy disorder associated with perinatal and lifelong risk complications for both the mother and the newborn. Our aim was to investigate the influence of GDM, and some of its associated conditions, upon the placental uptake of AA and DHA. Uptake of (14)C-AA and (14)C-DHA by human trophoblasts obtained from normal pregnancies (NTB cells) was mediated by both saturable (for lower substrate concentrations) and non-saturable (for higher substrate concentrations) mechanisms. Uptake of both fatty acids was inhibited by other LC-PUFAs and, markedly, by the long-chain acyl-CoA synthetase (ACSL) inhibitor, triacsin C. Human trophoblasts obtained from GDM pregnancies (DTB cells) showed a significantly lower (14)C-AA and (14)C-DHA accumulation, through a decrease in both the saturable and the non-saturable components of uptake, which was associated with a decrease in ACSL1 mRNA levels. Uptake of LC-PUFAs by NTB cells increased (by 20-25%) after short-term exposure to TNF-α ((14)C-AA and (14)C-DHA) and insulin ((14)C-DHA). In conclusion, GDM, distinctly from its associated conditions, markedly decreases placental uptake of LC-PUFAs, which probably contributes to the deleterious effects of this disease for the newborn.

The Chemopreventive Effect of the Dietary Compound Kaempferol on the MCF-7 Human Breast Cancer Cell Line Is Dependent on Inhibition of Glucose Cellular Uptake

Our aim was to investigate the effect of several dietary polyphenols on glucose uptake by breast cancer cells. Uptake of 3H-deoxy-D-glucose (3H-DG) by MCF-7 cells was time-dependent, saturable, and inhibited by cytochalasin B plus phloridzin. In the short-term (26 min), myricetin, chrysin, genistein, resveratrol, kaempferol, and xanthohumol (10–100 µM) inhibited 3H-DG uptake. Kaempferol was found to be the most potent inhibitor of 3H-DG uptake [IC50 of 4 µM (1.6–9.8)], behaving as a mixed-type inhibitor. In the long-term (24 h), kaempferol (30 µM) was also able to inhibit 3H-DG uptake, associated with a 40% decrease in GLUT1 mRNA levels. Interestingly enough, kaempferol (100 µM) revealed antiproliferative (sulforhodamine B and 3H-thymidine incorporation assays) and cytotoxic (extracellular lactate dehydrogenase activity determination) properties, which were mimicked by low extracellular (1 mM) glucose conditions and reversed by high extracellular (20 mM) glucose conditions. Finally, exposure of cells to kaempferol (30 µM) induced an increase in extracellular lactate levels over time (to 731 ± 32% of control after a 24 h exposure), due to inhibition of MCT1-mediated lactate cellular uptake. In conclusion, kaempferol potently inhibits glucose uptake by MCF-7 cells, apparently by decreasing GLUT1-mediated glucose uptake. The antiproliferative and cytotoxic effect of kaempferol in these cells appears to be dependent on this effect.

Characterization of Butyrate Uptake by Nontransformed Intestinal Epithelial Cell Lines

Butyrate (BT) is one of the main end products of anaerobic bacterial fermentation of dietary fiber within the human colon. Among its recognized effects, BT inhibits colon carcinogenesis. Our aim was to characterize uptake of BT by two nontransformed intestinal epithelial cell lines: rat small intestinal epithelial (IEC-6) and fetal human colonic epithelial (FHC) cells. Uptake of 14C-BT by IEC-6 cells was (1) time- and concentration-dependent; (2) pH-dependent; (3) Na+-, Cl−- and energy-dependent; (4) inhibited by BT structural analogues; (5) sensitive to monocarboxylate transporter 1 (MCT1) inhibitors; and (6) insensitive to DIDS and amiloride. IEC-6 cells express both MCT1 and Na+-coupled monocarboxylate transporter 1 (SMCT1) mRNA. We conclude that 14C-BT uptake by IEC-6 cells mainly involves MCT1, with a small contribution of SMCT1. Acute exposure to ethanol, acetaldehyde, indomethacin, resveratrol and quercetin reduced 14C-BT uptake. Chronic exposure to resveratrol and quercetin reduced 14C-BT uptake but had no effect on either MCT1 or SMCT1 mRNA levels. Uptake of 14C-BT by FHC cells was time- and concentration-dependent but pH-, Na+-, Cl−- and energy-independent and insensitive to BT structural analogues and MCT1 inhibitors. Although MCT1 (but not SMCT1) mRNA expression was found in FHC cells, the characteristics of 14C-BT uptake by FHC cells did not support either MCT1 or SMCT1 involvement. In conclusion, uptake characteristics of 14C-BT differ between IEC-6 and FHC cells. IEC-6 cells demonstrate MCT1- and SMCT1-mediated transport, while FHC cells do not.

Exposure to non-nutritive sweeteners during pregnancy and lactation: Impact in programming of metabolic diseases in the progeny later in life

The nutritional environment during embryonic, fetal and neonatal development plays a crucial role in the offsprings risk of developing diseases later in life. Although non-nutritive sweeteners (NNS) provide sweet taste without contributing to energy intake, animal studies showed that long-term consumption of NSS, particularly aspartame, starting during the perigestational period may predispose the offspring to develop obesity and metabolic syndrome later in life. In this paper, we review the impact of NNS exposure during the perigestational period on the long-term disease risk of the offspring, with a particular focus on metabolic diseases. Some mechanisms underlying NNS adverse metabolic effects have been proposed, such as an increase in intestinal glucose absorption, alterations in intestinal microbiota, induction of oxidative stress and a dysregulation of appetite and reward responses. The data reviewed herein suggest that NNS consumption by pregnant and lactating women should be looked with particular caution and requires further research.