Acute effects of dietary glycemic index on antioxidant capacity in a nutrient-controlled feeding study

Bioguided Optimization of the Nutrition-Health, Antioxidant, and Immunomodulatory Properties of Manihot esculenta (Cassava) Flour Enriched with Cassava Leaves

Manihot esculenta (cassava) roots is a major food crop for its energy content. Leaves contain nutrients and demonstrate biological properties but remain undervalorized. In order to develop a bioguided optimization of cassava nutrition-health properties, we compared the phytochemistry and bioactive potential of cassava root flour extract (CF) with cassava flour extract enriched with 30% leaves powder (CFL). Cassava flour supplementation impact was explored on flour composition (starch, fiber, carotenoids, phenolic compounds), in vivo glycemic index, and bioactivity potential using macrophage cells. We assessed the impact of cassava flour supplementation on free radicals scavenging and cellular production of pro-inflammatory mediators. CFL showed higher levels of fiber, carotenoids, phenolic compounds, and lower glycemic index. Significantly higher bioactive properties (anti-inflammatory and antioxidant) were recorded, and inhibition of cytokines production has been demonstrated as a function of extract concentration. Overall, our results indicate that enrichment of cassava flour with leaves significantly enhances its nutrition-health and bioactive potential. This bioguided matrix recombination approach may be of interest to provide prophylactic and therapeutic dietary strategy to manage malnutrition and associated chronic non-communicable diseases characterized by low-grade inflammation and unbalanced redox status. It would also promote a more efficient use of available food resources.

Glycemic Index and Glycemic Load of Two Dishes Cooked with Alache (Anoda cristata) and Chaya (Cnidoscolus aconitifolius) Plants from the Traditional Mexican Diet

Correct nutrition is important for keeping good health; to attain that, the diet has to include vegetables such as quelites. The objective of this study was to determine the glycemic index (GI) and glycemic load (GL) of rice and a tamal prepared with and without two species of quelites: "alache" (Anoda cristata) and "chaya" (Cnidoscolus aconitifolius). The GI was measured in 10 healthy subjects, 7 women and 3 men, with the following mean metrics: age, 23 years old; body weight, 61.3 kg; height, 1.65 m; body mass index, 22.7 kg/m²; and basal glycemia, 77.4 mg/dL. Capillary blood samples were collected within 2 h after the meal. White rice (rice with no quelites) had a GI of 75.35 ± 15.6 and a GL of 36.17 ± 7.8; rice with alache had a GI of 33.74 ± 5.85 and a GL 33.74 ± 1.85. White tamal had a GI of 57.33 ± 10.23 and a GC of 26.65 ± 5.12; tamal with chaya had a GI of 46.73 ± 22.1 and a GL of 23.36 ± 11. The GI and GL values recorded for the combination of quelites with rice and tamal confirmed that quelites could be a good alternative for healthy diets.

The Impact of Foods, Nutrients, or Dietary Patterns on Telomere Length in Childhood and Adolescence: A Systematic Review

Environmental factors such as diet can affect telomere length (TL) dynamics. However, the role that children’s and adolescents’ diets play in maintaining TL is not well understood. Thus, we conducted a systematic review to examine the association between the intake of nutrients, foods, food groups, and/or dietary patterns and TL in childhood and adolescence. Following the PRISMA guidelines, we searched MEDLINE via PubMed, Embase, and Cochrane databases and additional registers and methods. The five selected studies were cross-sectional and conducted in children and adolescents aged 2 to 18 years. The main results suggest that a higher consumption of fish, nuts and seeds, fruits and vegetables, green leafy and cruciferous vegetables, olives, legumes, polyunsaturated fatty acids, and an antioxidant-rich diet might positively affect TL. On the contrary, a higher intake of dairy products, simple sugar, sugar-sweetened beverages, cereals, especially white bread, and a diet high in glycaemic load were factors associated with TL shortening. To our knowledge, this is the first systematic review examining the impact of dietary intake factors on TL in childhood and adolescence. Although limited, these results are consistent with previous studies in different adult populations. Further research is needed to ascertain potential nutritional determinants of TL in childhood and adolescence.

Legume Consumption and Cardiometabolic Health

Legumes are key components of several plant-based diets and are recognized as having a wide range of potential health benefits. Previous systematic reviews and meta-analyses have summarized the evidence regarding different cardiometabolic outcomes, such as cardiovascular disease (CVD) and type 2 diabetes (T2D), and legume consumption. However, those studies did not differentiate between nonsoy and soy legumes, which have different nutritional profiles. The aim of the present updated review, therefore, was to summarize and meta-analyze the published evidence regarding legume consumption (making a distinction between nonsoy and soy legumes) and cardiometabolic diseases. In addition, we reviewed randomized clinical trials assessing the effect of legume consumption on CVD risk factors in order to understand their associations. The results revealed a prospective, significant inverse association between total legume consumption and CVD and coronary heart disease risk, whereas a nonsignificant association was observed with T2D and stroke. In the stratified analysis by legume subtypes, only nonsoy legumes were associated with lower risk of T2D. Unfortunately, owing to the paucity of studies analyzing legumes and CVD, it was not possible to stratify the analysis for these outcomes. Because of the high degree of heterogeneity observed for most of the outcomes and the few studies included in some analyses, further prospective studies are warranted to determine the potential role of legume consumption on CVD and T2D.

Effects of low glycemic index diet on insulin resistance among obese adolescent with non-alcoholic fatty liver disease: a randomized controlled trial

BACKGROUND Obesity is strongly correlated with insulin resistance (IR) and nonalcoholic fatty liver disease (NAFLD). Some studies suggest that dietary intake with low glycemic index (GI) may prevent IR and reduce the incidences of NAFLD. This study was aimed to determine the effects of low GI diet on IR among obese adolescents with NAFLD. METHODS This study was a randomized controlled trial conducted in two JuniorHigh Schools in Semarang, Indonesia. The subjects were 12–14 years obese students with NAFLD, which divided into intervention and control groups according to schools using block random allocation. The intervention group received nutrition education and lunch diet (low energy, low GI, and low fat); meanwhile, the control group only received nutrition education for 12 weeks. The biochemical evaluation included fasting blood glucose (FBG) and insulin levels. IR was assessed using homeostatic model assessment-insulin resistance (HOMA-IR). RESULTS Thirty-two subjects were enrolled in this study, 16 of which were assigned to the intervention group and the other to the control group. After 12 weeks, the energy and carbohydrate intake reduced in the intervention group (p < 0.05), FBG remained unchanged, and HOMA-IR increased (4.9 [3.7]–7.2 [3.5]) compared to the control group (6.4 [4.9]–5.5 [2.8]) (p < 0.05). Meanwhile, within the control group, there were no significant differences in the energy and carbohydrate intake as well as biochemical variables. CONCLUSIONS Low GI modification diet alone may not reduce IR in the obeseadolescents with NAFLD.

Low glycaemic index diets as an intervention for obesity: a systematic review and meta-analysis

OBJECTIVES

Low glycaemic index (GI) diets may aid in weight loss by reducing postprandial blood glucose excursions, leading to more stable blood glucose concentrations and therefore a reduction in hunger. To test this hypothesis, we conducted a systematic review and meta-analysis of randomized controlled trials comparing low GI diets with other diet types.

METHODS

We included 101 studies involving 109 study arms and 8,527 participants. We meta-analysed the studies using a random-effects model and conducted subgroup analyses and meta-regression based on control diet, blood glucose control, baseline BMI and dietary GI.

RESULTS

Low GI diets resulted in small but significant improvements in body weight, BMI, LDL and total cholesterol overall, although no individual control diet was significantly different from low GI diets. Studies in people with normal blood glucose who achieved a difference in GI of 20 points or more resulted in a larger reduction in body weight (SMD = -0.26; 95% CIs [-0.43, -0.09]), and total cholesterol (SMD = -0.24; 95% CIs [-0.42, -0.05]) than studies that only achieved a smaller reduction in GI.

CONCLUSIONS

Low GI diets, especially diets achieving a substantial decrease in GI, were moderately effective in lowering body weight. However, efforts should be made to increase compliance with low GI diets, in order for them to be effective in people with overweight and obesity.

Relevance of the Glycemic Index and Glycemic Load for Body Weight, Diabetes, and Cardiovascular Disease

Despite initial enthusiasm, the relationship between glycemic index (GI) and glycemic response (GR) and disease prevention remains unclear. This review examines evidence from randomized, controlled trials and observational studies in humans for short-term (e.g., satiety) and long-term (e.g., weight, cardiovascular disease, and type 2 diabetes) health effects associated with different types of GI diets. A systematic PubMed search was conducted of studies published between 2006 and 2018 with key words glycemic index, glycemic load, diabetes, cardiovascular disease, body weight, satiety, and obesity. Criteria for inclusion for observational studies and randomized intervention studies were set. The search yielded 445 articles, of which 73 met inclusion criteria. Results suggest an equivocal relationship between GI/GR and disease outcome. The strongest intervention studies typically find little relationship among GI/GR and physiological measures of disease risk. Even for observational studies, the relationship between GI/GR and disease outcomes is limited. Thus, it is unlikely that the GI of a food or diet is linked to disease risk or health outcomes. Other measures of dietary quality, such as fiber or whole grains may be more likely to predict health outcomes. Interest in food patterns as predictors of health benefits may be more fruitful for research to inform dietary guidance.

An Academia-Industry Partnership for Planning and Executing a Community-Based Feeding Study

A research team from Boston Children's Hospital and Harvard Medical School conducted a community-based feeding study in collaboration with Framingham State University (FSU) and Sodexo, the food service contractor at FSU. The study was a randomized controlled trial, implemented on the FSU campus. For the final year of the study, a satellite feeding site was established at Assabet Valley Regional Technical High School. The purpose of the study was to assess the biological effects of different macronutrient diets. An academia-industry partnership was developed to overcome common challenges associated with hospital-based feeding studies. Benefits included the following: a study site outside of Boston (reducing inconvenience for participants), access to a large commercial kitchen and study-specific kiosk (promoting efficiency), collaboration with Sodexo chefs (ensuring palatability of meals), and opportunity to procure food from contracted vendors. The research (academia) and food service (industry) teams worked together to design, plan, and execute intervention protocols using an integrated approach. During execution, the research team was primarily responsible for overseeing treatment fidelity, whereas the food service team provided culinary expertise, with a strong focus on hospitality and food quality. The study was conducted in 3 cohorts between August 2014 and May 2017. Participants received all of their food for ∼30 wk, totaling >160,000 meals. For all 3 cohorts combined, 234 participants provided informed consent, 229 started a standard run-in weight-loss diet, 164 lost a mean ± SD 12% ± 2% of baseline body weight and were randomly assigned to different macronutrient diets for weight-loss maintenance, and 148 completed the study. During the final and largest cohort, as many as 114 participants received daily meals concurrently. The daily cost per participant for preparation and service of weighed meals and snacks was ∼$65. This academia-industry partnership provides a model for controlled feeding protocols in nutrition research, potentially with enhanced cost-effectiveness, practicality, and generalizability. This trial was registered at http://www.clinicaltrials.gov as NCT02068885.

Strategies to decrease oxidative stress biomarker levels in human medical conditions: A meta-analysis on 8-iso-prostaglandin F2α

The widespread detection of elevated oxidative stress levels in many medical conditions has led to numerous efforts to design interventions to reduce its effects. Efforts have been wide-ranging, from dietary changes to administration of antioxidants, supplements, e.g., omega-3-fatty acids, and many medications. However, there is still no systemic assessment of the efficacy of treatments for oxidative stress reduction across a variety of medical conditions. The goal of this meta-analysis is, by combining multiple studies, to quantitate the change in the levels of the popular oxidative stress biomarker 8-iso-prostaglandin F2α (8-iso-PGF2α) after a variety of treatment strategies in human populations. Nearly 350 unique publications with 180 distinct strategies were included in the analysis. For each strategy, the difference between pre- or placebo and post-treatment levels calculated using Hedges' g value of effect. In general, administration of antibiotics, antihyperlipidemic agents, or changes in lifestyle (g = - 0.63, - 0.54, and 0.56) had the largest effect. Administration of supplements, antioxidants, or changes in diet (g = - 0.09, - 0.28, - 0.12) had small quantitative effects. To fully interpret the effectiveness of these treatments, comparisons to the increase in g value for each medical condition is required. For example, antioxidants in populations with coronary artery disease (CAD) reduce the 8-iso-PGF2α levels by g = - 0.34 ± 0.1, which is quantitatively considered a small effect. However, CAD populations, in comparison to healthy populations, have an increase in 8-iso-PGF2α levels by g = 0.38 ± 0.04; therefore, the overall reduction of 8-iso-PGF2α levels is ≈ 90% by this treatment in this specific medical condition. In conclusion, 8-iso-PGF2α levels can be reduced not only by antioxidants but by many other strategies. Not all strategies are equally effective at reducing 8-iso-PGF2α levels. In addition, the effectiveness of any strategy can be assessed only in relation to the medical condition investigated.

The effect of dietary glycemic index and glycemic load on inflammatory biomarkers: a systematic review and meta-analysis of randomized clinical trials

Background

To our knowledge, there is no study available that summarizes earlier findings on the effect of dietary glycemic index (GI) and glycemic load (GL) on inflammatory biomarkers.

Objective

This systematic review and meta-analysis was conducted to systematically review the available clinical trials that examined the effects of low-GI (LGI) and low-GL (LGL) diets on several inflammatory biomarkers in adults.

Design

We searched for relevant articles published up to June 2017 through PubMed, Medline, SCOPUS, EMBASE, and Google Scholar with the use of relevant keywords. Clinical trials that examined the effect of dietary GI and GL on inflammation in adults were included.

Results

Overall, 28 randomized controlled trials (RCTs) including 2961 participants (59% women, 41% men) were included in this meta-analysis. By combining findings from 14 studies on high-sensitivity C-reactive protein (hs-CRP) concentrations, we found no significant effect of LGI or LGL diets on serum hs-CRP concentrations compared with the control diet [weighted mean difference (WMD) for dietary GI: -0.05 mg/L (95% CI: -0.21, 0.10 mg/L); and WMD for dietary GL: 0.08 mg/L (95% CI: -0.26, 0.42 mg/L), respectively]. After combining effect sizes from 5 studies, we did not find significant changes in serum tumor necrosis factor α (TNF-α) concentrations comparing control diets with LGI (WMD: -0.18 mg/L; 95% CI: -0.43, 0.06 mg/L) or LGL (WMD: -0.20 mg/L; 95% CI: -0.33, 0.07 mg/L) diets. Significant changes were also not seen in leptin and interleukin 6 (IL-6) concentrations after the consumption of LGI or LGL diets.

Conclusions

We did not find any significant effect of dietary GI or GL on serum concentrations of inflammatory cytokines, including hs-CRP, leptin, IL-6, and TNF-α in adults. Additional RCTs-in particular, feeding trials-are required to shed light on this issue.

Oxidative stress increases the risk of pancreatic β cell damage in chronic renal hypertensive rats

Hypertension often occurs in conjunction with insulin resistance. The purpose of this study was to evaluate whether sustained renal hypertension increases the risk of diabetes mellitus in rats, and to define the underlying mechanisms. Two-kidney, one-clip hypertensive (2K1C) rats received captopril (50 mg/kg/day), α-lipoic acid (100 mg/kg/day), or vehicle treatment for 3 months after surgery. Blood pressure was measured by tail cuff plethysmography. Oral glucose tolerance test (OGTT), immunohistochemistry, and western blotting were performed. In addition, insulin secretion from islet cells was measured. OGTT yielded abnormal results, and the number of islet cells and the size of pancreatic β/α cells were decreased in 2K1C rats. Basal insulin levels were also reduced in the plasma. Insulin secretion from pancreatic islet cells in response to high glucose was also attenuated in 2K1C rats compared with sham rats. The levels of oxidative stress markers, including 8-hydroxydeoxyguanosine and NADPH oxidase-4, were increased in pancreatic tissue and pancreatic islets in 2K1C rats. The abnormalities observed in 2K1C rats were improved by captopril or α-lipoic acid treatment. These findings indicate that sustained renal hypertension may lead to pancreatic dysfunction, increasing oxidative stress in pancreatic islets.

Low glycemic index diet, exercise and vitamin D to reduce breast cancer recurrence (DEDiCa): design of a clinical trial

BACKGROUND

Mechanisms influencing breast cancer (BC) development and recurrence include hyperglycemia, hyperinsulinemia, high insulin-like growth factor-1, high circulating estrogen, inflammation and impaired cellular differentiation/apoptosis. A lifestyle program that targets all the above mechanisms may be warranted. Low glycemic index (GI) foods produce lower post-prandial glucose and insulin responses and have been associated with lower BC risk. Moderate physical activity post-diagnosis reduces BC recurrence and mortality, partly explained by reduced insulin and estrogen levels. Vitamin D increases cell differentiation/apoptosis and high serum vitamin D levels improve BC survival. Yet no trial has evaluated the combined effect of a low GI diet, moderate physical activity and vitamin D supplementation on BC recurrence in the context of a Mediterranean lifestyle setting.

METHODS

Women (30-74 yr) who had undergone surgery for primary histologically confirmed BC (stages I-III) within the previous 12 months, in cancer centres in Italy, will be randomized to follow, for a maximum of 33 months, either a high intensity treatment (HIT) composed of low GI diet + exercise + vitamin D (60 ng/mL serum concentration) or a lower intensity treatment (LITE) with general advice to follow a healthy diet and exercise pattern + vitamin D to avoid insufficiency. Both interventions are on a background of a Mediterranean diet. Considering a 20% recurrence rate within 3 years for BC cases and a predicted rate of 10% in the HIT group, with power of 80% and two-sided alpha of 0.05, the subject number required will be 506 (n = 253 in each arm). Clinic visits will be scheduled every 3 months. Dietary and exercise counselling and vitamin D supplements will be given at each clinic visit when blood samples, anthropometric measures and 7-day food records will be collected.

DISCUSSION

DEDiCa study aims to reduce BC recurrence in women with BC using a lifestyle approach with additional vitamin D and to investigate possible cardio-metabolic benefits as well as epigenetic modifications according to lifestyle changes. Given the supporting evidence and safety of the components of our intervention we believe it is feasible and urgent to test it in cancer patients.

TRIAL REGISTRATION

May 11, 2016; NCT02786875 .

EUDRACT NUMBER

2015-005147-14.

Wine grape pomace flour improves blood pressure, fasting glucose and protein damage in humans: a randomized controlled trial

BACKGROUND

The Mediterranean diet is a healthy diet with positive scientific evidence of preventing chronic diseases. Bioactive components support the healthy properties of the Mediterranean diet. Antioxidants and fiber, two components of the Mediterranean diet, are key functional nutrients for healthy eating and nutrition. Wine grape pomace is a rich source of these dietary constituents and may be beneficial for human health. Our hypothesis was that the intake of red wine grape pomace flour (WGPF) prepared from red wine grapes (Cabernet Sauvignon variety) reduced the metabolic syndrome in humans. To evaluate the effect of WGPF on components of metabolic syndrome we design a 16-week longitudinal intervention study. Thirty-eight males, 30-65 years of age, with at least one component of metabolic syndrome, were randomly assigned to either the intervention group (n = 25) or the control group (n = 13). At lunch, the intervention group was given 20 g of WGPF per day, which contained 10 g of dietary fiber, 822 mg of polyphenols and an antioxidant capacity of 7258 ORAC units. Both groups were asked to maintain their regular eating habits and lifestyles. Clinical evaluation, anthropometric measurements and biochemical blood analyses were done at the beginning and the end of the study.

RESULTS

WGPF intake significantly decreased systolic and diastolic blood pressure as well as fasting glucose levels. Plasma γ-tocopherol and δ-tocopherol increased and carbonyl group in plasma protein decreased in WGPT group, significantly. No significant effect was observed for waist circumference, HDL cholesterol, triglycerides, total antioxidant capacity and vitamin C in and between groups. The group-dependent magnitude of the differences between the baseline and final postprandial insulin values and γ-tocopherol concentrations was statistically significant.

CONCLUSIONS

The consumption of WGPF-rich in fiber and polyphenol antioxidants, as a food supplement in a regular diet improves blood pressure, glycaemia and postprandial insulin. In addition, increased antioxidant defenses and decreased oxidative protein damage indicating attenuation of oxidative stress. WGPF might be a useful food ingredient for health promotion and chronic disease prevention.

The relations between dietary antioxidant vitamins intake and oxidative stress in follicular fluid and ART outcomes

BACKGROUND

Oxidative stress (OS) in the follicular environment may affect on oocyte competence and antioxidant vitamins may modify its effects.

OBJECTIVE

This study was conducted to examine the effect of dietary intake of vitamin A, C and E on OS in follicular environment and assisted reproduction technology (ART) outcomes.

MATERIALS AND METHODS

In this obsevationalprospective study, the intake levels of vitamin A, C, and E were matured by validated food frequency questionnaire and Malondialdehyde and the total antioxidant capacity (TAC) levels of follicular fluid (FF) in 219 women undergoing ART were assessed. The number of retrieved oocytes, percentages of metaphase II MII) stage oocytes, fertilization rate, and embryo quality were also determined.

RESULTS

No significant association was found between vitamins intake levels and OS biomarkers, but the mean of TAC level in FF among women who received vitamin C greater than 75 mg/d was higher than women with lower intakes (p<0.05). The ART parameters were not related to the vitamin E intake level, but the normal cleaved embryo rate was positively related to vitamin A (p<0.05) and vitamin C (p=0.02) intake levels. Also, the percentage of MII oocytes (p=0.02) and the fertilization rate (p<0.05) were related to the vitamin C intake level. The relation between the TAC level in FF and ART outcomes were not significant.

CONCLUSION

Current results indicated that high dietary intake of vitamin C would be followed by increasing the TAC level in FF and improving the oocyte competence, but this effect of vitamin C is not dependent of increasing of antioxidant defense in follicular environment.

[Oxidative stress hypothesis for Alzheimer's disease and its potential therapeutic implications]

Significantly increased levels of oxidized nucleic acids, proteins, and lipids have been described in the brains of subjects with Alzheimer disease (AD) and mild cognitive impairment (MCI) as well as young adults with Down syndrome, compared to age-matched controls. Therefore, it is speculated that oxidative stress (OS) and consequent cellular damage occur at an early-stage in the pathological cascade of AD. Until now, several antioxidants, mitochondrial protective agents, anti-inflammatory agents and metal chelators have been tested as possible OS-targeting therapeutics for AD. Although some of these agents have shown significant neuroprotective effects in cellular and animal models of AD, their efficacies in AD clinical trials have not been fully established. When limited efficacies of exogenous antioxidants in previous trials are taken into account, early-stage interventions aimed to activate endogenous antioxidants may be promising as OS-targeting therapeutic strategies for AD. A recent randomized controlled trial of dietary intervention for amnestic MCI is a good example of such an approach, where an OS-marker in cerebrospinal fluid is decreased and cognitive function is successfully improved by a diet with low-saturated fat and low-glycemic index. Indeed, transcriptional activators of endogenous antioxidants should be researched and tested in future clinical trials for AD.

Special Issue on "Analytical Methods for Oxidized Biomolecules and Antioxidants" The use of isoprostanoids as biomarkers of oxidative damage, and their role in human dietary intervention studies

Isoprostanoids are a group of non-enzymatic oxidized lipids from polyunsaturated fatty acids. They are commonly used as biomarkers for oxidative damage, to assess in vivo lipid peroxidation in diseases related to the vascular system and neurodegeneration. Currently, there is a mismatch with the outcome in the use of these biomarkers in intervention studies, particularly when testing the effect of antioxidants such as vitamins C and E, or zinc, or a cocktail of these, with other food components. Much of this is because the biomarkers, the method of measurement, and the duration of supplementation are unsuitable. In this review, we will highlight the formation of isoprostanoids from their respective fatty acids, and their application as biomarkers for oxidative damage in vivo, considering human dietary intervention studies evaluating plasma and urine, using mass spectrometry techniques.

Lifestyle-induced decrease in fat mass improves adiponectin secretion in obese adults

PURPOSE

Several studies have identified relationships between weight loss and adipokine levels; however, none have looked at the combined effect of aerobic exercise training with the consumption of a low- or a high-glycemic diet. We examined the effects of 12 wk of aerobic exercise combined with either a low-glycemic index diet (∼40 U) plus exercise (LoGIX) or a high-glycemic index diet (∼80 U) diet plus exercise (HiGIX) on plasma leptin and adiponectin (total and high molecular weight [HMW]) in 27 older obese adults (age = 65 ± 0.5 yr, body mass index = 34.5 ± 0.7 kg·m).

METHODS

Insulin sensitivity was calculated from an oral glucose tolerance test. Fasting HMW adiponectin and leptin were quantified from plasma samples obtained before the insulin sensitivity index obtained from the oral glucose tolerance test. Glucose and insulin measures were obtained before and every 30 min during the test. Dual-energy x-ray absorptiometry and computerized tomography were used to determine body composition and to quantify subcutaneous and visceral abdominal adiposity, respectively.

RESULTS

Fasting leptin was significantly decreased in both groups (LoGIX: preintervention = 33.8 ± 4.7, postintervention = 19.2 ± 4.5; HiGIX: preintervention = 27.9 ± 4.2, postintervention = 11.9 ± 2.2 ng·mL; P = 0.004), and HMW adiponectin was significantly increased (LoGIX: preintervention = 1606.9 ± 34.6, postintervention = 3502.3 ± 57; HiGIX: preintervention = 3704.8 ± 38.1, postintervention = 4284.3 ± 52.8 pg·mL; P = 0.003) after the 12-wk intervention. Total body fat was reduced after both interventions. Visceral fat mass was inversely correlated with HMW adiponectin, whereas subcutaneous fat correlated with leptin.

CONCLUSIONS

The data suggest that exercise training, independent of dietary glycemic index, favorably alters HMW adiponectin and leptin secretion and that a reduction in visceral fat mass is a key factor regulating HMW adiponectin in older obese persons.

Dietary total antioxidant capacity is associated with leukocyte telomere length in a children and adolescent population

BACKGROUND & AIMS

Oxidative stress and inflammation seem to be potential underlying mechanisms for telomere attrition. A lack of specific antioxidants is believed to increase free radical damage and a greater risk for telomere shortening. Our aim was to evaluate the relationship between diet and leukocyte telomere length in a cross-sectional study of children and adolescents. We hypothesized that dietary total antioxidant capacity would be positively associated with telomere length.

METHODS

Telomere length was measured by quantitative real-time polymerase chain reaction in 287 participants (55% males, 6-18 years), who were randomly selected from the GENOI study.

RESULTS

A positive correlation between dietary total antioxidant capacity and telomere length (r = 0.157, p = 0.007) was found after adjustment for age and energy intake. However, higher white bread consumption was associated with shorter telomeres (β = -0.204, p = 0.002) in fully-adjusted models. Interestingly, those individuals who had simultaneously higher dietary total antioxidant capacity and lower white bread consumption significantly presented the longest telomeres. Moreover, the multivariable-adjusted odds ratio for very short telomeres was 0.30 for dietary total antioxidant capacity (p = 0.023) and 1.37 for white bread (p = 0.025).

CONCLUSION

It was concluded that longer telomeres were associated with higher dietary total antioxidant capacity and lower white bread consumption in Spanish children and adolescents. These findings might open a new line of investigation about the potential role of an antioxidant diet in maintaining telomere length.

The role of glycemic index and glycemic load in cardiovascular disease and its risk factors: a review of the recent literature

A number of meta-analyses of cohort studies have assessed the impact of glycemic load (GL) and glycemic index (GI) on cardiovascular outcomes. The picture that emerges is that for women, a significant association appears to exist between the consumption of high GL/GI diets and increased cardiovascular disease (CVD) risk. This association appears to be stronger in those with greater adiposity and possibly in those with diabetes, although these findings are not uniform. There is also an indication that raised CRP levels may be reduced, which has special implications for women whose CRP levels, as an emerging CVD risk factor, may be higher than men. For men, the situation is not as clear-cut. Although some studies show association, the meta-analyses have not demonstrated a significant direct association with CVD, despite current evidence that risk factors, including LDL-C, may be reduced on low-GI diets. Moreover, in a recent meta-analysis, increases in dietary GL have been associated with increased risk of diabetes, another CVD risk factor, in both men and women. Studies in men expressing relative risk of CVD in relation to GL and GI, with corresponding confidence intervals, are needed to provide the necessary power for future meta-analyses on this topic.

Obesity-related inflammation: implications for older adults

The combination of age-related increases in obesity and inflammation can lead to chronic disease, decreased strength, and physical disability. Lifestyle interventions that include moderate caloric restriction along with aerobic and resistance exercise have shown improvements in metabolic outcomes, strength, and physical function in obese older adults. Although few weight loss studies have addressed diet quality, evidence summarized in this review suggests that encouraging intake of antioxidant-rich fruits and vegetables, high-quality protein, low-glycemic index carbohydrates, and omega-3 fatty acids may further ameliorate obesity-related inflammation. Future controlled trials are indicated to examine the effects of incorporating these foods into multimodal weight loss interventions.

A randomized crossover study to assess the effect of an oat-rich diet on glycaemic control, plasma lipids and postprandial glycaemia, inflammation and oxidative stress in Type 2 diabetes

AIMS

In the UK, lifestyle intervention is first-line management in Type 2 diabetes. It is unclear what type of diet is most efficacious for improving glycaemic control. This study investigated the effects of an oat-enriched diet on glycaemic control, postprandial glycaemia, inflammation and oxidative stress compared with standard dietary advice.

METHODS

In a randomized crossover design, 27 volunteers with Type 2 diabetes, managed on diet and lifestyle only, were observed for two consecutive 8-week periods following either the oat-enriched diet or re-enforced standard dietary advice. Volunteers attended at baseline (habitual intake) and 8 and 16 weeks. Measurements included basic clinical measurements and fasted and postprandial (3-h) glucose and insulin in response to a healthy test meal. Markers of inflammation and oxidative stress, including high-sensitivity C-reactive protein, interleukin 6, interleukin 18, tumour necrosis factor-alpha, adiponectin, thiobarbituric acid reactive substances, oxygen radical antioxidant capacity, oxidized LDL and urinary isoprostanes, were also measured at fasting and in the postprandial period.

RESULTS

There were no diet-related effects on glycaemic control or glycaemic or insulinaemic responses to the test meal. Total cholesterol (5.1 ± 1.0 vs. 4.9 ± 0.8 mmol/l, P = 0.019) concentrations declined following the oat-enriched diet compared with standard dietary advice. There was a postprandial decline in adiponectin concentration (P = 0.009), but no effect of dietary intervention. None of the measures of oxidative stress or inflammation were altered by the oat-enriched diet compared with standard dietary advice.

CONCLUSION

The oat-enriched diet had a modest impact on lipid lowering, but did not impact on oxidative stress or inflammation in these volunteers with Type 2 diabetes.

Bioavailability of phenolics from an oleuropein-rich olive (Olea europaea) leaf extract and its acute effect on plasma antioxidant status: comparison between pre- and postmenopausal women

PURPOSE

Preclinical studies suggest a potential protective effect of oleuropein in osteoporosis, and one of the proposed mechanisms is the modulation of the oxidative stress. Oleuropein bioavailability and its effect on antioxidant status in pre- and postmenopausal women are unknown. The aim of the present study was to investigate the oral bioavailability of an olive leaf extract rich in oleuropein (40 %) and its effect on antioxidant status in postmenopausal women compared to premenopausal women.

METHODS

Premenopausal (n = 8) and postmenopausal women (n = 8) received 250 mg of olive leaf extract, blood samples (t = 0, 1, 2, 3, 4, 6, 8, 12, 16 and 24 h) were taken, and 24-h urine divided into five fractions was collected. Olive-leaf-extract-derived metabolites were analyzed in plasma and urine by HPLC-ESI-QTOF and UPLC-ESI-QqQ, and pharmacokinetics parameters were determined. Ferric reducing antioxidant ability and malondialdehyde levels were measured in plasma.

RESULTS

Plasma levels of hydroxytyrosol glucuronide, hydroxytyrosol sulfate, oleuropein aglycon glucuronide and oleuropein aglycon derivative 1 were higher in postmenopausal women. MDA levels were significantly decreased (32%) in postmenopausal women and inversely correlated with hydroxytyrosol sulfate levels. Postmenopausal women excreted less sulfated metabolites in urine than premenopausal women.

CONCLUSIONS

Our results suggest that postmenopausal women could be a target population for the intake of olive phenolics in order to prevent age-related and oxidative stress-related processes such as osteoporosis.

Effects of dietary glycemic index on brain regions related to reward and craving in men

BACKGROUND

Qualitative aspects of diet influence eating behavior, but the physiologic mechanisms for these calorie-independent effects remain speculative.

OBJECTIVE

We examined effects of the glycemic index (GI) on brain activity in the late postprandial period after a typical intermeal interval.

DESIGN

With the use of a randomized, blinded, crossover design, 12 overweight or obese men aged 18-35 y consumed high- and low-GI meals controlled for calories, macronutrients, and palatability on 2 occasions. The primary outcome was cerebral blood flow as a measure of resting brain activity, which was assessed by using arterial spin-labeling functional magnetic resonance imaging 4 h after test meals. We hypothesized that brain activity would be greater after the high-GI meal in prespecified regions involved in eating behavior, reward, and craving.

RESULTS

Incremental venous plasma glucose (2-h area under the curve) was 2.4-fold greater after the high- than the low-GI meal (P = 0.0001). Plasma glucose was lower (mean ± SE: 4.7 ± 0.14 compared with 5.3 ± 0.16 mmol/L; P = 0.005) and reported hunger was greater (P = 0.04) 4 h after the high- than the low-GI meal. At this time, the high-GI meal elicited greater brain activity centered in the right nucleus accumbens (a prespecified area; P = 0.0006 with adjustment for multiple comparisons) that spread to other areas of the right striatum and to the olfactory area.

CONCLUSIONS

Compared with an isocaloric low-GI meal, a high-GI meal decreased plasma glucose, increased hunger, and selectively stimulated brain regions associated with reward and craving in the late postprandial period, which is a time with special significance to eating behavior at the next meal. This trial was registered at clinicaltrials.gov as NCT01064778.

Long-term effects of low glycemic index/load vs. high glycemic index/load diets on parameters of obesity and obesity-associated risks: a systematic review and meta-analysis

AIM

The aim of the present meta-analysis was to investigate the long-term effects of glycemic index-related diets in the management of obesity with a special emphasis on the potential benefits of low glycemic index/load (GI/GL) in the prevention of obesity-associated risks.

DATA SYNTHESIS

Electronic searches for randomized controlled trials (RCTs) comparing low glycemic index/load versus high glycemic index/load diets were performed in MEDLINE, EMBASE and the Cochrane Library. Outcome of interest markers included anthropometric data as well as biomarkers of CVD and glycemic control. Study specific weighted mean differences were pooled using a random effect model. 14 studies were included in the primary meta-analysis. Weighted mean differences in change of C-reactive protein [WMD: -0.43 mg/dl, (95% CI -0.78 to -0.09), p = 0.01], and fasting insulin [WMD: -5.16 pmol/L, (95% CI -8.45 to -1.88), p = 0.002] were significantly more pronounced in benefit of low GI/GL diets. However decrease in fat free mass [WMD: -1.04 kg (95% CI -1.73 to -0.35), p = 0.003] was significantly more pronounced following low GI/GL diets as well. No significant changes were observed for blood lipids, anthropometric measures, HbA1c and fasting glucose. Sensitivity analysis was performed for RCTs excluding subjects with type 2 diabetes. Decreases in C-reactive protein and fasting insulin remained statistically significant in the low GI/GL subgroups.

CONCLUSIONS

The present systematic review provides evidence for beneficial effects of long-term interventions administering a low glycemic index/load diet with respect to fasting insulin and pro-inflammatory markers such as C-reactive protein which might prove to be helpful in the primary prevention of obesity-associated diseases.

Protective effect of anti-oxidants on endothelial function in young Korean-Asians compared to Caucasians

Background

Previous studies show that Asians have an impaired blood flow response (BFR) to occlusion after a single high fat (HF) meal. The mechanism is believed to be the presence and susceptibility to high free radicals in their blood. The free radical concentration after a HF meal has not been examined in Asians. Further the BFR to heat after a single HF meal in Koreans has not been measured.

Material/Methods

This study evaluated postprandial endothelial function by measuring the BFR to vascular occlusion and local heat before and after a HF meal and the interventional effects of anti-oxidant vitamins on improving endothelial function in young Korean-Asians (K) compared to Caucasians (C) with these assessments. Ten C and ten K participated in the study (mean age 25.3±3.6 years old). BFR to vascular occlusion and local heat and oxidative stress were assessed after a single low fat (LF) and HF meal at 2 hours compared to baseline. After administration of vitamins (1000 mg of vitamin C, 800 IU of vitamin E, and 300 mg of Coenzyme Q-10) for 14 days, the same measurements were made.

Results

This study showed that the skin BFR to vascular occlusion and local heat following a HF meal significantly decreased and free radicals significantly increased at 2 hours compared to baseline in K (p<.001), but not in C. When vitamins were given, the BFR to vascular occlusion and local heat before and after HF meal were not significantly different in K and C.

Conclusions

These findings suggest that even a single HF meal can reduce endothelial response to stress through an oxidative stress mechanism but can be blocked by antioxidants, probably through scavenging free radicals in K. Since endothelial function improved even before a HF meal in K, endothelial damage from an Americanized diet may be reduced in K by antioxidants.

Nutrition and oxidative stress: a systematic review of human studies

Oxidative stress (OS) - defined as the imbalance between free radical production and antioxidant defences - is a condition associated with chronic-degenerative disease, such as cancer, metabolic and disease cardiovascular diseases (CVDs). Several studies have shown that diet and some of its components could influence the intensity of OS damage. The aim of this review was to critically examine some pieces of evidence from observational and intervention study in human beings to assess whether diet and its components can really modify OS in vivo. Furthermore, we tried to find out the possible mechanism behind this association. We considered all studies in MEDLINE which fitted with the following criteria: (1) adult subjects who were healthy or affected by metabolic disease and CVDs; (2) no food supplements, pillows, powder but only common foods and beverages and (3) OS assessment with well-known and validated in vivo biomarkers.

Associations of glycemic index and load with coronary heart disease events: a systematic review and meta-analysis of prospective cohorts

Background

Glycemic index (GI) and glycemic load (GL) have been associated with coronary heart disease (CHD) risk in some but not all cohort studies. We therefore assessed the association of GI and GL with CHD risk in prospective cohorts.

Methods and Results

We searched MEDLINE, EMBASE, and CINAHL (through April 5, 2012) and identified all prospective cohorts assessing associations of GI and GL with incidence of CHD. Meta-analysis of observational studies in epidemiology (MOOSE) methodologies were used. Relative measures of risk, comparing the group with the highest exposure (mean GI of cohorts=84.4 GI units, range 79.9 to 91; mean GL of cohorts=224.8, range 166 to 270) to the reference group (mean GI=72.3 GI units, range 68.1 to 77; mean GL=135.4, range 83 to 176), were pooled using random-effects models, expressed as relative risk (RR) with heterogeneity assessed by χ² and quantified by I². Subgroups included sex and duration of follow-up. Ten studies (n=240 936) were eligible. Pooled analyses showed an increase in CHD risk for the highest GI quantile compared with the lowest, with RR=1.11 (95% confidence interval [CI] 0.99 to 1.24) and for GL, RR=1.27 (95% CI 1.09 to 1.49), both with evidence of heterogeneity (I²>42%, P<0.07). Subgroup analyses revealed only a significant modification by sex, with the female cohorts showing significance for GI RR=1.26 (95% CI 1.12 to 1.41) and for GL RR=1.55 (95% CI 1.18 to 2.03).

Conclusions

High GI and GL diets were significantly associated with CHD events in women but not in men. Further studies are required to determine the relationship between GI and GL with CHD in men.

Characteristics of the spin-trapping reaction of a free radical derived from AAPH: further development of the ORAC-ESR assay

The characteristics of the spin-trapping reaction in the oxygen radical absorbance capacity (ORAC)-electron spin resonance (ESR) assay were examined, focusing on the kind of spin traps. 2,2-Azobis(2-amidinopropane) dihydrochloride (AAPH) was used as a free radical initiator. The spin adducts of the AAPH-derived free radical were assigned as those of the alkoxyl radical, RO· (R=H(2)N(HN)C-C(CH(3))(2)). Among the spin traps tested, 5,5-dimethyl-1-pyrroline N-oxide (DMPO), 5,5-dimethyl-4-phenyl-1-pyrroline N-oxide (4PDMPO), 5-(2,2-dimethyl-1,3-propoxycyclophosphoryl)-5-methyl-1-pyrroline N-oxide (CYPMPO), and 5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide (DEPMPO) were applicable to the ORAC-ESR assay. Optimal formation of spin-trapped radical adduct was observed with 1 mM AAPH, 10 mM spin trap, and 5 s UV irradiation. The calibration curve (the Stern-Volmer's plot) for each spin trap showed good linearity, and their slopes, k (SB)/k (ST), were estimated to be 87.7±2.3, 267±15, 228±9, and 213±16 for DMPO, 4PDMPO, CYPMPO, and DEPMPO, respectively. Though the k (SB)/k (ST) values for selected biosubstances varied with various spin traps, their ratios to Trolox (the relative ORAC values) were almost the same for all spin traps tested. The ORAC-ESR assay also had a very good reproducibility. The ORAC-ESR assay was conducted under stoichiometric experimental conditions. The present results demonstrate the superiority of the ORAC-ESR assay.

A low-glycemic index diet and exercise intervention reduces TNF(alpha) in isolated mononuclear cells of older, obese adults

Low-glycemic index diets and exercise independently improve glucose tolerance and reduce diabetes risk. However, the combined effect of a low-glycemic index diet and exercise on inflammation and glucose metabolism is not known. Therefore, we randomized 28 insulin-resistant adults (age: 66 ± 1 y; BMI: 34.2 ± 0.7 kg · m(-2)) to a 12-wk, low (LGI = 40) or high- (HGI = 80) glycemic index diet plus aerobic exercise (5 d · wk(-1), 60 min · d(-1), 80-85% heart rate(max)) intervention. All food and fluids were provided during the study. Inflammation was assessed from cytokine (TNFα and IL-6) secretion using peripheral blood mononuclear cells (MNC) stimulated overnight with LPS. Glycemic response was determined following ingestion of a 75-g glucose solution. Fasting blood samples were collected for additional cytokine [TNFα, IL-6, and monocyte chemoattractant protein 1 (MCP-1)] analysis. Both interventions decreased BMI (P < 0.001), fasting plasma glucose (P = 0.01), and insulin (P = 0.02). The glycemic response was reduced only in the LGI group (P = 0.04). Plasma and MNC-derived TNFα secretion were reduced in the LGI group (P = 0.02) but increased in the HGI group (P = 0.02). Secretion of IL-6 from MNC and plasma IL-6 and MCP-1 concentrations were reduced in the LGI group. The change in MNC-derived TNFα (r = 0.43; P = 0.04) and plasma MCP-1 (r = 0.44; P = 0.04) correlated with decreases in the glycemic response. These data highlight the importance of diet composition in the treatment and prevention of inflammation and hyperglycemia. A low-glycemic index diet has antiinflammatory and antidiabetogenic effects when combined with exercise in older, obese prediabetics.

Glycemic index and glycemic load and their association with C-reactive protein and incident type 2 diabetes

Objective. To investigate whether the Glycemic Index (GI) or Glycemic Load (GL) of a diet is associated with C-reactive Protein (CRP) and risk of type 2 diabetes in a prospective study. Materials and Methods. Our analysis included 4,366 participants who did not have diabetes at baseline. During follow-up 456 diabetes cases were confirmed. Dietary GI and GL were derived from a food-frequency questionnaire and its association with CRP was examined cross-sectionally using linear regression models. The association of GI and GL with diabetes incidence was examined using Cox proportional hazard models. Results. GL, but not GI, was associated with lnCRP at baseline (b_GL = 0.11 per 50 units; P = .01). When comparing the highest to the lowest tertile of GI with respect to diabetes incidence, a Relative Risk (RR) of 0.95 [95%CI 0.75, 1.21] was found after adjustment for lifestyle and nutritional factors. For GL the RR for diabetes incidence was 1.00 [95%CI 0.74, 1.36]. Additional adjustment for CRP did not change RRs. Conclusion. Since GI was not associated with CRP and risk of type 2 diabetes, it is unlikely that a high GI diet induces the previously shown positive association between CRP and risk of type 2 diabetes by increasing CRP concentrations.

Dietary hyperglycemia, glycemic index and metabolic retinal diseases

The glycemic index (GI) indicates how fast blood glucose is raised after consuming a carbohydrate-containing food. Human metabolic studies indicate that GI is related to patho-physiological responses after meals. Compared with a low-GI meal, a high-GI meal is characterized with hyperglycemia during the early postprandial stage (0-2h) and a compensatory hyperlipidemia associated with counter-regulatory hormone responses during late postprandial stage (4-6h). Over the past three decades, several human health disorders have been related to GI. The strongest relationship suggests that consuming low-GI foods prevents diabetic complications. Diabetic retinopathy (DR) is a complication of diabetes. In this aspect, GI appears to be useful as a practical guideline to help diabetic people choose foods. Abundant epidemiological evidence also indicates positive associations between GI and risk for type 2 diabetes, cardiovascular disease, and more recently, age-related macular degeneration (AMD) in people without diabetes. Although data from randomized controlled intervention trials are scanty, these observations are strongly supported by evolving molecular mechanisms which explain the pathogenesis of hyperglycemia. This wide range of evidence implies that dietary hyperglycemia is etiologically related to human aging and diseases, including DR and AMD. In this context, these diseases can be considered as metabolic retinal diseases. Molecular theories that explain hyperglycemic pathogenesis involve a mitochondria-associated pathway and four glycolysis-associated pathways, including advanced glycation end products formation, protein kinase C activation, polyol pathway, and hexosamine pathway. While the four glycolysis-associated pathways appear to be universal for both normoxic and hypoxic conditions, the mitochondria-associated mechanism appears to be most relevant to the hyperglycemic, normoxic pathogenesis. For diseases that affect tissues with highly active metabolism and that frequently face challenge from low oxygen tension, such as retina in which metabolism is determined by both glucose and oxygen homeostases, these theories appear to be insufficient. Several lines of evidence indicate that the retina is particularly vulnerable when hypoxia coincides with hyperglycemia. We propose a novel hyperglycemic, hypoxia-inducible factor (HIF) pathway, to complement the current theories regarding hyperglycemic pathogenesis. HIF is a transcription complex that responds to decrease oxygen in the cellular environment. In addition to playing a significant role in the regulation of glucose metabolism, under hyperglycemia HIF has been shown to increase the expression of HIF-inducible genes, such as vascular endothelial growth factor (VEGF) leading to angiogenesis. To this extent, we suggest that HIF can also be described as a hyperglycemia-inducible factor. In summary, while management of dietary GI appears to be an effective intervention for the prevention of metabolic diseases, specifically AMD and DR, more interventional data is needed to evaluate the efficacy of GI management. There is an urgent need to develop reliable biomarkers of exposure, surrogate endpoints, as well as susceptibility for GI. These insights would also be helpful in deciphering the detailed hyperglycemia-related biochemical mechanisms for the development of new therapeutic agents.

A low-glycemic index diet combined with exercise reduces insulin resistance, postprandial hyperinsulinemia, and glucose-dependent insulinotropic polypeptide responses in obese, prediabetic humans

BACKGROUND

The optimal lifestyle intervention that reverses diabetes risk factors is not known.

OBJECTIVE

We examined the effect of a low-glycemic index (GI) diet and exercise intervention on glucose metabolism and insulin secretion in obese, prediabetic individuals.

DESIGN

Twenty-two participants [mean ± SEM age: 66 ± 1 y; body mass index (in kg/m(2)): 34.4 ± 0.8] underwent a 12-wk exercise-training intervention (1 h/d for 5 d/wk at ≈ 85% of maximum heart rate) while randomly assigned to receive either a low-GI diet (LoGIX; 40 ± 0.3 units) or a high-GI diet (HiGIX; 80 ± 0.6 units). Body composition (measured by using dual-energy X-ray absorptiometry and computed tomography), insulin sensitivity (measured with a hyperinsulinemic euglycemic clamp with [6,6-(2)H(2)]-glucose), and oral glucose-induced insulin and incretin hormone secretion were examined.

RESULTS

Both groups lost equal amounts of body weight (-8.8 ± 0.9%) and adiposity and showed similar improvements in peripheral tissue (+76.2 ± 14.9%) and hepatic insulin sensitivity (+27.1 ± 7.1%) (all P < 0.05). However, oral glucose-induced insulin secretion was reduced only in the LoGIX group (6.59 ± 0.86 nmol in the prestudy compared with 4.70 ± 0.67 nmol in the poststudy, P < 0.05), which was a change related to the suppressed postprandial response of glucose-dependent insulinotropic polypeptide. When corrected for changes in β cell glucose exposure, changes in insulin secretion were attenuated in the LoGIX group but became significantly elevated in the HiGIX group.

CONCLUSIONS

Although lifestyle-induced weight loss improves insulin resistance in prediabetic individuals, postprandial hyperinsulinemia is reduced only when a low-GI diet is consumed. In contrast, a high-GI diet impairs pancreatic β cell and intestinal K cell function despite significant weight loss. These findings highlight the important role of the gut in mediating the effects of a low-GI diet on type 2 diabetes risk reduction.

Dietary strategies for the prevention & treatment of metabolic syndrome

Obesity and the metabolic syndrome are epidemic health problems that are the root of many of the chronic diseases in our society. The increase in obesity in western societies can be largely attributed to changes in diet associated with modern civilization. Dietary strategies to reduce postprandial glucose and triglyceride spikes, and to increase the intake of dietary antioxidants, potassium, and omega-3 fatty acids will be helpful for improving health and reducing metabolic syndrome and obesity.

Carbohydrate nutrition and inflammatory disease mortality in older adults

BACKGROUND

Several studies suggest that carbohydrate nutrition is related to oxidative stress and inflammatory markers.

OBJECTIVE

We examined whether dietary glycemic index (GI), dietary fiber, and carbohydrate-containing food groups were associated with the mortality attributable to noncardiovascular, noncancer inflammatory disease in an older Australian cohort.

DESIGN

Analysis included 1490 postmenopausal women and 1245 men aged ge 49 y at baseline (1992-1994) from a population-based cohort who completed a validated food-frequency questionnaire. Cox proportional hazards ratios were calculated both for death from diseases in which inflammation or oxidative stress was a predominant contributor and for cardiovascular mortality.

RESULTS

Over a 13-y period, 84 women and 86 men died of inflammatory diseases. Women in the highest GI tertile had a 2.9-fold increased risk of inflammatory death compared with women in the lowest GI tertile [multivariate hazard ratio in energy-adjusted tertile 3 (tertile 1 as reference): 2.89; 95% CI: 1.52, 5.51; P for trend: 0.0006, adjusted for age, smoking, diabetes, and alcohol and fiber consumption]. Increasing intakes of foods high in refined sugars or refined starches (P = 0.04) and decreasing intakes of bread and cereals (P = 0.008) or vegetables other than potatoes (P = 0.007) also independently predicted a greater risk, with subjects' GI partly explaining these associations. In men, only an increased consumption of fruit fiber (P = 0.005) and fruit (P = 0.04) conferred an independent decrease in risk of inflammatory death. No associations were observed with cardiovascular mortality.

CONCLUSION

These data provide new epidemiologic evidence of a potentially important link between GI and inflammatory disease mortality among older women.

Consumption of a high glycemic index diet increases abdominal adiposity but does not influence adipose tissue pro-oxidant and antioxidant gene expression in C57BL/6 mice

The hypothesis of this study is that consumption of a high glycemic index (GI) starch will increase adiposity, increase expression of the pro-oxidant enzyme (nicotinamide adenine dinucleotide phosphate [NADPH] oxidase), and decrease expression of the antioxidant enzymes (catalase, glutathione peroxidase [GPx], and superoxide dismutase [SOD]) in adipose tissue of mice. C57BL/6 mice (n = 5-8/group) were fed a diet containing either high-GI starch (100% amylopectin) or low-GI starch (60% amylose/40% amylopectin) under low-fat (LF) or high-fat (HF) conditions for 16 weeks. Meal tolerance tests (MTTs) indicated that the postprandial blood glucose response over 120 minutes for the high-GI mice under LF and HF conditions was significantly greater than for mice fed low-GI diets. This result was not due to increased food consumption by the high-GI mice during the MTT. Although there was no difference in body weight between mice fed high-GI or low-GI starch, LF high-GI mice had significantly greater adiposity compared to LF low-GI mice. High-fat mice had a significant increase in NADPH oxidase expression compared to LF mice, but there was no significant effect of starch on NADPH oxidase expression. High-fat diet significantly decreased the expression of GPx and catalase, but there was no significant effect of starch on GPx and catalase expression. There was no difference in SOD expression among any of the diet groups. In conclusion, high GI diets increase adiposity under LF conditions but do not influence pro-oxidant or antioxidant enzyme gene expression in adipose tissue of C57BL/6 mice.

Randomized trial on the effects of a 7-d low-glycemic diet and exercise intervention on insulin resistance in older obese humans

BACKGROUND

The optimal combination of diet and exercise that produces the greatest reversal of obesity-related insulin resistance is unknown.

OBJECTIVES

We examined the effects of a combined 7-d low-glycemic index (low-GI) diet and exercise training intervention on insulin sensitivity in older obese humans.

DESIGN

Participants [n = 32; mean (+/-SEM) age: 66 +/- 1 y; body mass index (in kg/m(2)): 33.8 +/- 0.7] were randomly assigned to a parallel, double-blind, controlled-feeding trial and underwent supervised aerobic exercise (EX; 60 min/d at 80-85% maximum heart rate) in combination with either a low-GI (LoGI + EX: 41.1 +/- 0.4) or a high-GI (HiGI + EX: 80.9 +/- 0.6) diet. All meals were provided and were isocaloric to individual energy requirements. Insulin sensitivity and hepatic glucose production were assessed with a 40-mU x m(-2) x min(-1) hyperinsulinemic euglycemic clamp combined with a [6,6-(2)H(2)]-glucose infusion.

RESULTS

After the intervention, small decreases were observed in body weight (-1.6 +/- 0.2 kg; P < 0.0001) and fat mass (-1.7 +/- 0.9%; P = 0.004) in both groups. Maximal aerobic capacity ( O(2)max) also improved slightly (0.06 +/- 0.02 L/min; P = 0.004). Resting systolic blood pressure, fasting glucose, insulin, triglycerides, and cholesterol all decreased after the study (all P < 0.05). Larger changes in systolic blood pressure and O(2max) were seen in the LoGI + EX group. Insulin-stimulated glucose disposal (P < 0.001), insulin suppression of hepatic glucose production (P = 0.004), and postabsorptive fat oxidation (P = 0.03) improved equally in both groups after the intervention.

CONCLUSIONS

These findings suggest that the metabolic improvements after short-term exercise training in older obese individuals are dependent on increased physical activity and are not influenced by a low-GI diet. However, a low-GI diet has added benefit in alleviating hypertension, thus reducing the risk of diabetic and vascular complications.