European Journal of Nutrition (v.48, #6)
Association of surrogate and direct measures of adiposity with risk of metabolic syndrome in rural Chinese women by Fengxiu Ouyang; Jonathan Necheles; Binyan Wang; Wei Ma; Zhiping Li; Xue Liu; Genfu Tang; Houxun Xing; Xiping Xu; Scott A. Venners; Wendy J. Brickman; Katherine Kaufer Christoffel; Donald Zimmerman; Xiaobin Wang (323-332).
Most studies linking obesity and metabolic syndrome (MS) have used body mass index (BMI) and waist circumference (WC) to measure obesity. While BMI is correlated with direct measures of total and central adiposity, it is influenced by lean body and bone mass. We hypothesize that direct measures of adiposity may help develop further insight into the link between obesity and MS, thus more accurately identifying individuals at high risk for MS.We examined how surrogate and direct measures of adiposity were associated with MS risk and if direct adiposity measures enhanced BMI and WC identification of MS risk.3,734 Chinese female twins aged 20–39 years were studied. Percent body fat (%BF) and proportion of trunk fat to total BF (%TF) were assessed by DEXA. Graphic plots and generalized estimating equations were used to examine the associations of adiposity measures with MS and its components. Concordance of adiposity measures and MS abnormalities between monozygotic (MZ) and dizygotic (DZ) twin pairs were compared.The prevalence of MS increased for high BMI (≥23 kg/m2), %BF (≥32), WC (≥80 cm), and (to a lesser degree) %TF (≥50). Below those thresholds, the prevalence of MS was low (0–5.3%). %TF was independently associated with higher risk of MS and its components even after adjusting for BMI and WC. As a result, among women with normal BMI and WC, high %TF was associated with 1.3–2.0-fold elevated risk of MS components. In contrast, women with high BMI but normal WC and %TF neither have significantly increased risk of MS, nor for any component other than high BP. MZ twins showed higher concordance for MS and its components than DZ twins.In this lean Chinese rural female sample, BMI ≥ 23 and WC ≥ 80 were associated with a markedly increased risk of MS, which was further enhanced by elevated %TF. Even in women with a normal BMI and WC, %TF was independently associated with MS and its components. Twin analysis findings suggest that adiposity measurements and MS risk are influenced by genetics.
Keywords: Body mass index; Waist circumference; Body composition; Metabolic syndrome; Chinese women; Twins
Glutamine attenuates nitric oxide synthase expression and mitochondria membrane potential decrease in interleukin-1β-activated rat hepatocytes by Jun Lu; Xin-ying Wang; Wen-hao Tang (333-339).
Mitochondrial dysfunction induced by nitric oxide (NO) overproduction is involved in the pathogenesis of organ failure during many severe diseases. Recently, several experiments have reported that glutamine (Gln) modifies inducible nitric oxide synthase (iNOS) gene expression which is thought to be responsible for its beneficial effects in critical illnesses.This study was designed to evaluate the effects of Gln on NO production, iNOS expression and mitochondria membrane potential (Δψm) variation in interleukin (IL)-1β-activated rat hepatocytes. The mechanical effects of nuclear factor kappaB (NF-κB) were also investigated.Primary cultured rat hepatocytes were isolated by an in situ collagenase perfusion method. The cultured hepatocytes were treated with IL-1β (1 nmol/l) alone or with Gln in concentrations ranging from 2 to 10 mmol/l for 24 h. The concentrations of alanine aminotransferase (ALT) and nitrite in the culture medium were detected by biochemical methods. The levels of iNOS protein and mRNA in the hepatocytes were analyzed by western blot and real-time RT-PCR. The Δψm of the hepatocytes was assessed with flow cytometry after incubating with fluorescent probe JC-1. Th binding activity of NF-κB in hepatocytes was investigated using electrophoretic mobility shift assay.IL-1β significantly enhanced iNOS protein and mRNA level in the cultured rat hepatocytes which consisted with the increased NO production and ALT releasing in the culture medium. These effects were inhibited by the treatment of glutamine in a dose-dependent manner. The Δψm of hepatocytes was markedly decreased after IL-1β stimulation which was significantly attenuated by Gln at 5 and 10 mmol/l. NF-κB activity was increased by IL-1β stimulation and this effect was augmented by Gln at 5 and 10 mol/l.These observations indicate that Gln has a capability to protect mitochondria function in hepatocytes under inflammatory stress. Although the molecular mechanism remains to be clarified, our findings suggest this effect may be related to down-regulation of iNOS gene expression through an NF-κB independent pathway.
Keywords: Glutamine; Interleukin-1β; Nitric oxide; Mitochondria membrane potential; Rat hepatocytes
Tachyphylaxis effects on postprandial oxidative stress and mitochondrial-related gene expression in overweight subjects after a period of energy restriction by Ana B. Crujeiras; Dolores Parra; Estíbaliz Goyenechea; Itziar Abete; J. Alfredo Martínez (341-347).
Postprandially induced oxidative stress can cause damage to mitochondrial components and initiate cellular degradative processes; which are related to obesity comorbidities.This trial sought to determine whether weight loss induced by caloric restriction provides antioxidant protection to reduce the postprandial response of mitochondrial function and oxidative stress markers.A group of overweight/obese volunteers (n = 17; 39 ±7 years, 32.5 ± 4.8 kg/m2) followed an 8-week hypocaloric diet. Volunteers provided blood samples at fasting and 2-h after a test drink (CHO: 95% E, PROT: 5% E and containing antioxidants) and these were examined for postprandial oxidative stress responses, before and after the nutritional intervention. The expression of four mitochondrial-related genes, COX15, NDUFS2, MGST2 and TNF-alfa, was measured in peripheral blood mononuclear cells (PBMC) by quantitative RT-PCR. Lipid peroxidation and nitrosative stress biomarkers, total antioxidant capacity (AOP), uric acid and glutathione peroxidase were also determined.Before nutritional treatment, the test drink induced a postprandial increase in lipid peroxidation and nitrosative stress biomarkers with a concomitant increase in the AOP. The increase in postprandial oxidative stress biomarkers was accompanied by a decrease in PBMC COX15 mRNA levels. Interestingly, after the weight loss period (−5.8 ± 2.3%), the postprandial-induced changes were lower than at the beginning of the study and involved oxidative stress biomarkers and the COX15 and MGST2 transcripts. This finding suggests the occurrence of a tachyphylactic process.We demonstrate for the first time that the well-known effect of energy restriction on oxidative stress is accompanied by a tolerance mechanism on the postprandial oxidative stress response and mitochondrial function-related genes. Indeed, the COX15 and MGST2 gene expression assays in PBMC emerged as valuable nutrigenomic biomarkers of the oxidative response under energy-restriction conditions.
Keywords: Caloric restriction; Cytochrome c oxidase; COX15; Oxidative stress; Glutathione S-transferase; PBMC gene expression
Supplementation with cholecalciferol does not improve glycaemic control in diabetic subjects with normal serum 25-hydroxyvitamin D levels by Rolf Jorde; Yngve Figenschau (349-354).
Studies have suggested that vitamin D may be important for both insulin sensitivity and insulin secretion, and that supplementation with vitamin D may subsequently prevent development of type 2 diabetes.The objective of the current study was to test the hypothesis that supplementation with vitamin D would improve glycaemic control in subjects with type 2 diabetes.Thirty-six subjects with type 2 diabetes, treated with metformin and bed-time insulin, were randomised to supplementation with cholecalciferol (40,000 IU per week) versus placebo for 6 months. Thirty-two subjects participated throughout the entirety of the study. Fasting blood samples were drawn before and at the end of the 6 month study without the previous bed-time insulin injection. The insulin and metformin doses were not changed throughout the study.After 6 months, the fasting glucose, insulin, C-peptide, fructosamine, and HbA1c levels were not significantly different from baseline values. In addition, changes in these parameters (values at 6 months minus values at baseline) did not differ between the vitamin D and the placebo group.We were not able to demonstrate that vitamin D supplementation had a significant effect on glucose metabolism in subjects with type 2 diabetes but without vitamin D deficiency. Further studies are needed in larger groups of subjects with type 2 diabetes or impaired glucose tolerance, who also exhibit low serum 25-hydroxyvitamin D levels.
Keywords: Diabetes mellitus; Glucose; Placebo-controlled study; Vitamin D
Probiotic properties of Lactobacillus rhamnosus and Lactobacillus paracasei isolated from human faeces by Maria Cristina Verdenelli; Francesca Ghelfi; Stefania Silvi; Carla Orpianesi; Cinzia Cecchini; Alberto Cresci (355-363).
The possibility of using microbes to maintain health, and to prevent or treat disease is a topic as old as microbiology. The research of novel probiotic strains is important in order to satisfy the increasing request of the market and to obtain functional products in which the probiotic cultures are more active and with better probiotic characteristics than those already present on the market.In this study, the probiotic potential of Lactobacillus strains isolated from Italian elderly human faeces was investigated.The Lactobacillus strains were identified and examined for resistance to gastric acidity and bile toxicity, adhesion to HT-29 cells, antimicrobial activities, antibiotic susceptibility and plasmid profile. Survival of the strains through human intestine was examined in a 3 months human feeding trial.Two strains, Lactobacillus rhamnosus IMC 501 and Lactobacillus paracasei IMC 502, tolerated well low pH and bile acids. In antimicrobial activity assays, both strains showed inhibitory properties towards selected potential harmful microorganisms, particularly against Candida albicans. The two selected strains expressed high in vitro adherence to HT-29 cells increasing this characteristic when they are used in combination and they were resistant to vamcomycin, colistin sulphate, gentamicin, oxolinic acid and kanamycin. Moreover, the two strains could be recovered from stools of volunteers after the feeding trials. Lactobacillus rhamnosus IMC 501 and L. paracasei IMC 502 present favourable strain-specific properties for their utilisation as probiotics in functional foods and the high adhesion ability of the L. rhamnosus IMC 501 and L. paracasei IMC 502 used in combination, confirmed by both in vitro and in vivo study, indicate that the two bacterial strains could be used as health-promoting bacteria.
Keywords: Lactobacillus rhamnosus ; Lactobacillus paracasei ; Probiotics; Adhesion; Probiotic combination; Human study
[6S]-5-Methyltetrahydrofolate enhances folate status in rats fed growing-up milk by Darío Pérez-Conesa; Juan Francisco Haro-Vicente; Fernando Romero Braquehais; Gaspar Ros (365-371).
To investigate the efficiency of [6S]-5-methyltetrahydrofolate or Metafolin® ([6S]-5-CH3-H4folate) on the recovery of folate status, we conducted a depletion–repletion rat model study using a growing-up milk as the folate carrier.The effect of [6S]-5-CH3-H4folate was compared to that of folic acid (PGA or Pte-Glu), by feeding two groups of folate-depleted rats a diet of fortified growing-up milk containing either 1,000 μg/l (2.2655 μmol/l) of Pte-Glu or 1,041.91 μg/l (2.2655 μmol/l) of [6S]-5-CH3-H4folate over a 4-week period. At the end of the study, the folate concentration in plasma, erythrocytes and liver was measured to establish the folate status of the animals. The folate content was determined in the plasma and erythrocytes by a time-resolved fluoroimmunoassay method and in the liver by a HPLC method.Plasma, erythrocyte and liver folate concentrations were significantly (P < 0.001) lower after a depletion period in rats fed the folate-deficient diet compared to rats fed a control diet. The folate form used significantly influenced the folate concentration in erythrocytes and liver, but not in plasma, after the rats’ body folate reserves were replenished by consuming the fortified growing-up milk. Thus, rats fed [6S]-5-CH3-H4folate-fortified growing-up milk showed significantly higher folate content in erythrocytes and liver (1,100.37 ng/ml and 4.22 μg/g, respectively), than did those fed Pte-Glu-fortified growing-up milk (827.71 ng/ml and 3.04 μg/g, respectively, in erythrocytes and liver).We conclude that the natural diastereomer [6S]-5-CH3-H4folate may adequately serve as an alternative to folic acid for the folate fortification of infant foods.
Keywords: [6S]-5-Methyltetrahydrofolate; Folic acid; TR-FIA assay; Growing-up milk; Weanling rats
Serum sterol responses to increasing plant sterol intake from natural foods in the Mediterranean diet by Verónica Escurriol; Montserrat Cofán; Mercè Serra; Mónica Bulló; Josep Basora; Jordi Salas-Salvadó; Dolores Corella; Itziar Zazpe; Miguel A. Martínez-González; Valentina Ruiz-Gutiérrez; Ramón Estruch; Emilio Ros (373-382).
Phytosterols in natural foods are thought to inhibit cholesterol absorption. The Mediterranean diet is rich in phytosterol-containing plant foods.To assess whether increasing phytosterol intake from natural foods was associated with a cholesterol-lowering effect in a substudy of a randomized trial of nutritional intervention with Mediterranean diets for primary cardiovascular prevention (PREDIMED study).One hundred and six high cardiovascular risk subjects assigned to two Mediterranean diets supplemented with virgin olive oil (VOO) or nuts, which are phytosterol-rich foods, or advice on a low-fat diet. Outcomes were 1-year changes in nutrient intake and serum levels of lipids and non-cholesterol sterols.Average phytosterol intake increased by 76, 158 and 15 mg/day in participants assigned VOO, nuts and low-fat diets, respectively. Compared to participants in the low-fat diet group, changes in outcome variables were observed only in those in the Mediterranean diet with nuts group, with increases in intake of fibre, polyunsaturated fatty acids and phytosterols (P < 0.020, all) and significant (P < 0.05) reductions of LDL-cholesterol (0.27 mmol/l or 8.3%) and the LDL/HDL-cholesterol ratio (0.29 mmol/l or 11.5%). Variations in saturated fat, cholesterol or fibre intake were unrelated to LDL-cholesterol changes. In the whole group, changes in serum sitosterol-to-cholesterol, which reflect those of dietary phytosterol intake and absorption, correlated inversely to LDL-cholesterol changes (r = −0.256; P = 0.008). In multivariate analyses, baseline LDL-cholesterol, increases in serum sitosterol ratios and statin use were independently associated with LDL-cholesterol reductions.Small amounts of phytosterols in natural foods appear to be bioactive in cholesterol lowering.
Keywords: Phytosterols; Mediterranean diet; Nuts; Olive oil; Cholesterol
Association between GPx1 Pro198Leu polymorphism, GPx1 activity and plasma selenium concentration in humans by E. Jablonska; J. Gromadzinska; E. Reszka; W. Wasowicz; W. Sobala; N. Szeszenia-Dabrowska; P. Boffetta (383-386).
Glutathione peroxidase 1 (GPx1) is an antioxidant selenoenzyme that protects the cells against reactive oxygen species. Its activity depends on the concentration of selenium (Se) which is present in the active centre of the enzyme. The genetic polymorphism of GPx1 encoding gene (GPx1) associated with the proline (Pro) to leucine (Leu) change at codon 198 is supposed to be functional. An in vitro study performed on human breast carcinoma cell line showed that GPx1Leu allele was associated with a lower responsiveness of the enzyme to Se added to the culture medium. Some authors observed a decrease in GPx1 activity associated with GPx1 Leu allele in humans; however, there were no findings on how GPx1 activity changes with Se concentration in individuals with different GPx1 genotypes.To assess whether GPx1 activity that depends on the Se status may be influenced by GPx1 polymorphism through studying this relationship in the blood of healthy individuals.The association between the Se status, GPx1 activity and GPx1 genotype was assessed in 405 individuals of Polish origin. GPx1 activity in red blood cells was measured by the spectrophotometric method by Paglia and Valentine, using t-butylhydroperoxide as the substrate. Plasma Se concentration was measured using graphite furnace atomic absorption spectrometry. GPx1 Pro198Leu polymorphism was determined with the Molecular Beacon Real-Time PCR assay.In the subjects examined, the mean plasma Se concentration was 54.4 ± 14.2 mcg/L. The mean GPx1 activity was 15.1 ± 4.7 U/g Hb. No difference regarding both the parameters was found between individuals with different GPx1 genotype. However, the association between GPx1 activity and Se concentration, analyzed separately for each genotype group, was not the same. The correlation coefficients amounted to r = 0.44 (p < 0.001) for Pro/Pro, r = 0.35 (p < 0.001) for Pro/Leu and r = 0.25 (p = 0.45) for Leu/Leu group, which indicates that the correlation strength was as follows: Pro/Pro > Pro/Leu > Leu/Leu. Notably, statistically significant difference in this relationship (analyzed as difference between correlation coefficients for linear trends) was found between genotypes Pro/Pro and Leu/Leu (p = 0.034).The findings of the present study provide evidence for the hypothesis based on in vitro studies which assumes that GPx1 Pro198Leu polymorphism has a functional significance for the human organism and that this functionality is associated with a different response of GPx1 activity to Se. They also point to the importance of the genetic background in the assessment of the Se status with the use of selenoprotein biomarkers such as GPx1 activity.
Keywords: Glutathione peroxidase; Selenium; Genetic polymorphism; Humans