Oxidative Stress and Mitochondrial Functions in the Intestinal Caco-2/15 Cell Line

Although mitochondrial dysfunction and oxidative stress are central mechanisms in various pathological conditions, they have not been extensively studied in the gastrointestinal tract, which is known to be constantly exposed to luminal oxidants from ingested foods. Key among these is the simultaneous consumption of iron salts and ascorbic acid, which can cause oxidative damage to biomolecules.The objective of the present work was to evaluate how iron-ascorbate (FE/ASC)-mediated lipid peroxidation affects mitochondrion functioning in Caco-2/15 cells. Our results show that treatment of Caco-2/15 cells with FE/ASC (0.2 mM/2 mM) (1) increased malondialdehyde levels assessed by HPLC; (2) reduced ATP production noted by luminescence assay; (3) provoked dysregulation of mitochondrial calcium homeostasis as evidenced by confocal fluorescence microscopy; (4) upregulated the protein expression of cytochrome C and apoptotic inducing factor, indicating exaggerated apoptosis; (5) affected mitochondrial respiratory chain complexes I, II, III and IV; (6) elicited mtDNA lesions as illustrated by the raised levels of 8-OHdG; (7) lowered DNA glycosylase, one of the first lines of defense against 8-OHdG mutagenicity; and (8) altered the gene expression and protein mass of mitochondrial transcription factors (mtTFA, mtTFB1, mtTFB2) without any effects on RNA Polymerase. The presence of the powerful antioxidant BHT (50 microM) prevented the occurrence of oxidative stress and most of the mitochondrial abnormalities.Collectively, our findings indicate that acute exposure of Caco-2/15 cells to FE/ASC-catalyzed peroxidation produces harmful effects on mitochondrial functions and DNA integrity, which are abrogated by the powerful exogenous BHT antioxidant. Functional derangements of mitochondria may have implications in oxidative stress-related disorders such as inflammatory bowel diseases

Hepatocyte Nuclear Factor 4 Alpha Polymorphisms and the Metabolic Syndrome in French-Canadian Youth

<div><p>Objectives</p><p>Hepatocyte nuclear factor 4 alpha (HNF4α) is a transcription factor involved in the regulation of serum glucose and lipid levels. Several <i>HNF4A</i> gene variants have been associated with the risk of developing type 2 diabetes mellitus. However, no study has yet explored its association with insulin resistance and the cardiometabolic risk in children. We aimed to investigate the relationship between <i>HNF4A</i> genetic variants and the presence of metabolic syndrome (MetS) and metabolic parameters in a pediatric population.</p><p>Design and Methods</p><p>Our study included 1,749 French-Canadians aged 9, 13 and 16 years and evaluated 24 <i>HNF4A</i> polymorphisms that were previously identified by sequencing.</p><p>Results</p><p>Analyses revealed that, after correction for multiple testing, one SNP (rs736824; <i>P</i><0.022) and two haplotypes (P1 promoter haplotype rs6130608-rs2425637; <i>P</i><0.032 and intronic haplotype rs736824-rs745975-rs3212183; <i>P</i><0.025) were associated with the risk of MetS. Additionally, a significant association was found between rs3212172 and apolipoprotein B levels (coefficient: -0.14 ± 0.05; <i>P</i><0.022). These polymorphisms are located in <i>HNF4A</i> P1 promoter or in intronic regions.</p><p>Conclusions</p><p>Our study demonstrates that HNF4α genetic variants are associated with the MetS and metabolic parameters in French Canadian children and adolescents. This study, the first exploring the relation between <i>HNF4A</i> genetic variants and MetS and metabolic variables in a pediatric cohort, suggests that HNF4α could represent an early marker for the risk of developing type 2 diabetes mellitus.</p></div

Association between rs3212172 and metabolic variables.

<p>A negative coefficient suggests decreasing value of the marker for every additional copy of the SNP. The linear mixed model was adjusted for age, gender and body mass index. Apo B, apolipoprotein B; LDL-C, low-density lipoprotein-cholesterol; TC, total cholesterol.</p><p>Association between rs3212172 and metabolic variables.</p

Association between HNF4α haplotypes and metabolic syndrome.

<p>*Adjusted value based on permutation methods.</p><p>Association between HNF4α haplotypes and metabolic syndrome.</p

Two major haplotype blocks found in the <i>HNF4A</i> gene.

<p>Linkage disequilibrium plot in the <i>HNF4A</i> region is displayed. Haplotype analysis was carried out on the 9 SNPs for which the single SNP allelic association was significant or close to significant using HAPLOVIEW Software version 3.11.</p

Schematic illustration of the <i>HNF4A</i> SNPs found associated with metabolic syndrome or metabolic parameters.

<p>Relative position of SNPs within the <i>HNF4A</i> locus. ^aSNP associated with the metabolic syndrome; ^bhaplotype associated with metabolic syndrome; ^cSNP associated with apo B levels.</p