Genome maintenance and human longevity

Accumulation of DNA damage and mutations is considered an important causal factor in age-related diseases. Genetic defects in DNA repair cause premature onset and accelerated progression of age-related diseases and a shorter life span in humans and mice, providing strong evidence that genome maintenance is a bona fide longevity assurance pathway. However, the contribution of genome maintenance to human longevity itself remains to be established. Here, we review the results of human genetics studies, including genome wide association studies, and attempted to catalogue all genes involved in major DNA repair pathways that harbor variants associated with longevity. We hope to provide a comprehensive review to facilitate future endeavors aimed at uncovering the functional role of genome maintenance genes in human longevity.

Association of iron indices and type 2 diabetes: a meta-analysis of observational studies

The literature on the role of body iron status in the development of type 2 diabetes (T2D) in humans is inconsistent. We aimed to assess the association between iron indices and T2D by a meta-analysis of previously published studies. A systematic literature search was conducted in PubMed and EMBASE. Observational studies on the association of ferritin (when controlled for age and sex), transferrin saturation, soluble transferrin receptor and transferrin with T2D were included. Pooled association estimates were calculated using a random effects model. Forty-six eligible studies were identified. The pooled multivariable adjusted relative risks of T2D in the highest versus lowest quartile of ferritin levels were significantly elevated in both cross-sectional as well as prospective studies and after restriction to inflammation-adjusted studies [overall: 1.67 (95% CI 1.41-1.99)]. The mean difference indicated 43.54 ng/mL (95% CI 28.14-58.94) higher ferritin levels in type 2 diabetic individuals. The relative risk for a transferrin saturation ≥ 50% was 1.59 (95% CI 1.28-1.97), the mean difference was -1.92% [95% CI -2.99-(-0.85)]. Study-specific results of soluble transferrin receptor and transferrin levels were extremely heterogeneous. Ferritin and clinically elevated transferrin saturation were strongly associated with an increased risk of T2D, overall and in prospective studies. Ferritin was also significantly associated after multivariable adjustment including inflammation. Thus, the current evidence hints at a causal effect; however, publication bias and unmeasured confounding cannot be excluded.

Body iron stores in middle-aged North Indian patients with type 2 diabetes and obesity

Introduction:

Evidence from various epidemiological and clinical studies suggests that iron overload is proinflammatory and proatherosclerotic. Excess body iron has been positively associated with insulin resistance, type 2 diabetes and obesity.

Aim of the Study:

To study the relationship of body iron stores with type 2 diabetes and obesity in middle aged North Indian population.

Materials and Methods:

The participant population consisted of four groups of randomly selected participants (between 40 and 65 years of age and postmenopausal women); Group A: Normal individuals (controls), Group B: Obese nondiabetic individuals, Group C: Lean diabetic patients, Group D: Obese diabetic patients. Blood was examined for hematological, biochemical estimations, C-reactive protein, and serum ferritin (SF).

Observation and Results:

A total of 197 participants were enrolled. The mean SF levels (ng/ml) among males were: Group A (n = 18) 148.56 ± 119.90; Group B (n = 25) 129.11 ± 94.77; Group C (n = 27) 127.96 ± 109.65 and Group D (n = 22) 148.36 ± 104.94. The mean SF levels (ng/ml) among females were: Group A (n = 23) 67.44 ± 37.59; Group B (n = 25) 59.62 ± 43.56; Group C (n = 24) 77.97 ± 91.46 and Group D (n = 33) 66.46 ± 86.05. No statistical difference was found among the groups in both the sexes.

Conclusions:

Our observation is in sharp contrast to the earlier studies published from the West stressing that iron stores are increased in obesity and diabetes. We conclude that SF may not be a strong risk factor in the pathogenesis of obesity and diabetes in middle aged North Indians.

Association between total, processed, red and white meat consumption and all-cause, CVD and IHD mortality: a meta-analysis of cohort studies

An association between processed and red meat consumption and total mortality has been reported by epidemiological studies; however, there are many controversial reports regarding the association between meat consumption and CVD and IHD mortality. The present meta-analysis was carried out to summarise the evidence from prospective cohort studies on the association between consumption of meat (total, red, white and processed) and all-cause, CVD and IHD mortality. Cohort studies were identified by searching the PubMed and ISI Web of Knowledge databases. Risk estimates for the highest v. the lowest consumption category and dose-response meta-analysis were calculated using a random-effects model. Heterogeneity among the studies was also evaluated. A total of thirteen cohort studies were identified (1 674 272 individuals). Subjects in the highest category of processed meat consumption had 22 and 18 % higher risk of mortality from any cause and CVD, respectively. Red meat consumption was found to be associated with a 16 % higher risk of CVD mortality, while no association was found for total and white meat consumption. In the dose-response meta-analysis, an increase of 50 g/d in processed meat intake was found to be positively associated with all-cause and CVD mortality, while an increase of 100 g/d in red meat intake was found to be positively associated with CVD mortality. No significant associations were observed between consumption of any type of meat and IHD mortality. The results of the present meta-analysis indicate that processed meat consumption could increase the risk of mortality from any cause and CVD, while red meat consumption is positively but weakly associated with CVD mortality. These results should be interpreted with caution due to the high heterogeneity observed in most of the analyses as well as the possibility of residual confounding.

Prevention and management of type 2 diabetes: dietary components and nutritional strategies

In the past couple of decades, evidence from prospective observational studies and clinical trials has converged to support the importance of individual nutrients, foods, and dietary patterns in the prevention and management of type 2 diabetes. The quality of dietary fats and carbohydrates consumed is more crucial than is the quantity of these macronutrients. Diets rich in wholegrains, fruits, vegetables, legumes, and nuts; moderate in alcohol consumption; and lower in refined grains, red or processed meats, and sugar-sweetened beverages have been shown to reduce the risk of diabetes and improve glycaemic control and blood lipids in patients with diabetes. With an emphasis on overall diet quality, several dietary patterns such as Mediterranean, low glycaemic index, moderately low carbohydrate, and vegetarian diets can be tailored to personal and cultural food preferences and appropriate calorie needs for weight control and diabetes prevention and management. Although much progress has been made in development and implementation of evidence-based nutrition recommendations in developed countries, concerted worldwide efforts and policies are warranted to alleviate regional disparities.

Effects of iron overload on chronic metabolic diseases

Iron can affect the clinical course of several chronic metabolic diseases such as type 2 diabetes, obesity, non-alcoholic fatty liver disease, and atherosclerosis. Iron overload can affect major tissues involved in glucose and lipid metabolism (pancreatic β cells, liver, muscle, and adipose tissue) and organs affected by chronic diabetic complications. Because iron is a potent pro-oxidant, fine-tuned control mechanisms have evolved to regulate entry, recycling, and loss of body iron. These mechanisms include the interplay of iron with transferrin, ferritin, insulin, and hepcidin, as well as with adipokines and proinflammatory molecules. An imbalance of these homoeostatic mechanisms results in systemic and parenchymal siderosis that contributes to organ damage (such as β-cell dysfunction, fibrosis in liver diseases, and atherosclerotic plaque growth and instability). Conversely, iron depletion can exert beneficial effects in patients with iron overload and even in healthy frequent blood donors. Regular assessment of iron balance should be recommended for patients with chronic metabolic diseases, and further research is needed to produce guidelines for the identification of patients who would benefit from iron depletion.

Effects of Dietary Supplementation with Agaricus sylvaticus Schaeffer on Glycemia and Cholesterol after Streptozotocin-Induced Diabetes in Rats

This study evaluated the effect of the Agaricus sylvaticus (sun mushroom) on biochemical tests of the plasma and on the morphology of the pancreas in an experimental model of type I diabetes mellitus (DM1) induced by streptozotocin. One gram of dry A. sylvaticus was homogenized and mixed with the chow. Male Wistar rats were allocated as follows: normoglycemic control that received commercial chow; normoglycemic control group that received chow with A. sylvaticus; diabetic group that received commercial chow; and diabetic group that received chow with A. sylvaticus. Weight, food, and water consumption were measured every two days. Blood glucose levels were measured twice a week. After 30 days, the animals were euthanized and blood was collected for the analysis of cholesterol, HDL, triglycerides, blood sugar, glutamic-pyruvic transaminase (GPT), alkaline phosphatase, iron, transferrin, and urea. The pancreas was processed for microscopic analysis. A. sylvaticus modulated the levels of cholesterol, HDL, triglycerides, blood sugar, GPT, alkaline phosphatase, iron, transferrin, and urea to levels similar to those found in the controls and led to compensatory hyperplasia of the islets of Langerhans. A. sylvaticus is potentially beneficial in the control of type 1 diabetes, and it may also prevent pancreas damage.

Ferritin levels and risk of metabolic syndrome: meta-analysis of observational studies

Background

Elevated ferritin levels have been associated with single cardiovascular risk factors but the relationship to the presence of metabolic syndrome is inconclusive.

The aim of this systematic review and meta-analysis of published observational studies was to estimate the association between serum ferritin levels and metabolic syndrome in adults.

Methods

The Pubmed, SCOPUS and the Cochrane Library databases were searched for epidemiological studies that assessed the association between ferritin levels and metabolic syndrome and were published before September 2013. There were no language restrictions. Two investigators independently selected eligible studies. Measures of association were pooled by using an inverse-variance weighted random-effects model. The heterogeneity among studies was examined using the I² index. Publication bias was evaluated using the funnel plot.

Results

Twelve cross-sectional, one case–control and two prospective studies met our inclusion criteria including data from a total of 56,053 participants. The pooled odds ratio (OR) for the metabolic syndrome comparing the highest and lowest category of ferritin levels was 1.73 (95% CI: 1.54, 1.95; I² = 75,4%). Subgroup analyses indicate that pooled OR was 1.92 (95% CI: 1.61, 2.30; I² = 78%) for studies adjusting for C-reactive protein (CRP), and 1.52 (95% CI:1. 36, 1.69; I² = 41%) for studies that did not adjust for CRP (P = 0.044). This finding was remarkably robust in the sensitivity analysis. We did not find publication bias.

Conclusions

The meta-analysis suggests that increased ferritin levels are independently and positively associated with the presence of the metabolic syndrome with an odds ratio higher than 1.73.

Epidemiological associations between iron and cardiovascular disease and diabetes

Disruptions in iron homeostasis are linked to a broad spectrum of chronic conditions including cardiovascular, malignant, metabolic, and neurodegenerative disease. Evidence supporting this contention derives from a variety of analytical approaches, ranging from molecular to population-based studies. This review focuses on key epidemiological studies that assess the relationship between body iron status and chronic diseases, with particular emphasis on atherosclerosis ,metabolic syndrome and diabetes. Multiple surrogates have been used to measure body iron status, including serum ferritin, transferrin saturation, serum iron, and dietary iron intake. The lack of a uniform and standardized means of assessing body iron status has limited the precision of epidemiological associations. Intervention studies using depletion of iron to alter risk have been conducted. Genetic and molecular techniques have helped to explicate the biochemistry of iron metabolism at the molecular level. Plausible explanations for how iron contributes to the pathogenesis of these chronic diseases are beginning to be elucidated. Most evidence supports the hypothesis that excess iron contributes to chronic disease by fostering excess production of free radicals. Overall, epidemiological studies, reinforced by basic science experiments, provide a strong line of evidence supporting the association between iron and elevated risk of cardiovascular disease and diabetes. In this narrative review we attempt to condense the information from existing literature on this topic.

Insulin resistance modulates iron-related proteins in adipose tissue

OBJECTIVE Circulating markers of iron overload are associated with insulin resistance. Less is known about the impact of iron overload on adipose tissue (AT). We hypothesized that gene expression markers of iron metabolism in AT could be associated with insulin action. RESEARCH DESIGN AND METHODS The AT expression of ferroportin (SLC40A1), transferrin (TF), TF receptor (TFRC), ferritin (FT) heavy polypeptide 1 (FTH1), and FT light polypeptide (FTL) was analyzed cross-sectionally in three independent cohorts and also after weight loss-induced changes in insulin sensitivity (clamp M value) in an independent fourth cohort. RESULTS In human AT, TF mRNA and protein levels were decreased with obesity and insulin resistance in the three cohorts and were positively associated with adipogenic mRNAs and insulin action. Otherwise, FTL mRNA and protein and SLC40A1 transcripts were positively associated with BMI and negatively linked to adipogenic genes and insulin action. Bariatric surgery-induced weight loss led to increased TF and decreased TFRC, FTH1, FTL, and SLC40A1 in subcutaneous AT in parallel to improved insulin action. CONCLUSIONS These results suggest that iron overload impacts on AT in association with insulin resistance.

Heme, an essential nutrient from dietary proteins, critically impacts diverse physiological and pathological processes

Heme constitutes 95% of functional iron in the human body, as well as two-thirds of the average person’s iron intake in developed countries. Hence, a wide range of epidemiological studies have focused on examining the association of dietary heme intake, mainly from red meat, with the risks of common diseases. High heme intake is associated with increased risk of several cancers, including colorectal cancer, pancreatic cancer and lung cancer. Likewise, the evidence for increased risks of type-2 diabetes and coronary heart disease associated with high heme intake is compelling. Furthermore, recent comparative metabolic and molecular studies of lung cancer cells showed that cancer cells require increased intracellular heme biosynthesis and uptake to meet the increased demand for oxygen-utilizing hemoproteins. Increased levels of hemoproteins in turn lead to intensified oxygen consumption and cellular energy generation, thereby fueling cancer cell progression. Together, both epidemiological and molecular studies support the idea that heme positively impacts cancer progression. However, it is also worth noting that heme deficiency can cause serious diseases in humans, such as anemia, porphyrias, and Alzheimer’s disease. This review attempts to summarize the latest literature in understanding the role of dietary heme intake and heme function in diverse diseases.

IL-21 contributes to fatal inflammatory disease in the absence of Foxp3+ T regulatory cells

The cytokine IL-21 has been shown to influence immune responses through both costimulatory effects on effector T cells and opposing inhibitory effects on T regulatory cells (Tregs). To distinguish the effect of IL-21 on the immune system from that of its effect on Tregs, we analyzed the role of IL-21/IL-21R signaling in mice made genetically deficient in IL-2, which exhibit a deficit in IL-2-dependent Foxp3 regulatory T cells and suffer from a fatal multiorgan inflammatory disease. Our findings demonstrate that in the absence of IL-21/IL-21R signaling, Il2(-/-) mice retained a deficiency in Tregs yet exhibited a reduced and delayed inflammatory disease. The improved health of Il2(-/-)Il21r(-/-) mice was reflected in reduced pancreatitis and hemolytic anemia and this was associated with distinct changes in lymphocyte effector populations, including the reduced expansion of both T follicular helper cells and Th17 cells and a compensatory increase in IL-22 in the absence of IL-21R. IL-21/IL-21R interactions were also important for the expansion of effector and memory CD8(+) T cells, which were critical for the development of pancreatitis in Il2(-/-) mice. These findings demonstrate that IL-21 is a major target of immune system regulation.

Associations between red meat intake and biomarkers of inflammation and glucose metabolism in women

BACKGROUND

Greater red meat intake is associated with an increased type 2 diabetes and cardiovascular disease risk. However, the relation of red meat intake to biomarkers of inflammation and glucose metabolism has not been investigated thoroughly.

OBJECTIVE

We hypothesized that greater red meat intake would be associated with biomarkers of inflammation and glucose metabolism, which would be partly explained by body mass index (BMI).

DESIGN

We analyzed cross-sectional data from diabetes-free female participants in the Nurses' Health Study (n = 3690). Multiple linear regression was conducted to assess the associations of total, unprocessed, and processed red meat intakes (quartile categories) with plasma C-reactive protein (CRP), ferritin, adiponectin, fasting insulin, and hemoglobin A1c (Hb A1c).

RESULTS

Greater total, unprocessed, and processed red meat intakes were associated with higher plasma CRP, ferritin, fasting insulin, and Hb A1c and lower adiponectin after adjustment for demographic information (P-trend ≤ 0.03 for all). Adiponectin was not associated with any type of red meat intake when further adjusted for medical and lifestyle factors. After adjustment for BMI, most of these associations with inflammatory and glucose metabolic biomarkers were substantially attenuated and no longer significant. BMI accounted for a statistically significant proportion of associations with CRP, Hb A1c, and fasting insulin (P-contribution ≤ 0.02 for all) but not with ferritin. Substituting a serving of total red meat intake with alternative protein food in a combination of poultry, fish, legumes, and nuts was associated with significantly lower CRP (β ± SE: -0.106 ± 0.043), ferritin (-0.212 ± 0.075), Hb A1c (-0.052 ± 0.015), and fasting insulin (-0.119 ± 0.036) (all P ≤ 0.02 for comparison of extreme quartiles for all).

CONCLUSIONS

Greater red meat intake is associated with unfavorable plasma concentrations of inflammatory and glucose metabolic biomarkers in diabetes-free women. BMI accounts for a significant proportion of the associations with these biomarkers, except for ferritin. Substituting red meat with another protein food is associated with a healthier biomarker profile of inflammatory and glucose metabolism.

Association between a gene variant near ataxia telangiectasia mutated and coronary artery disease in men

OBJECTIVE

Type 2 diabetes is accompanied by increased mortality from coronary artery disease (CAD), but the mechanisms linking these conditions remain elusive. Hence, treatment of hyperglycaemia alone is not sufficient to avoid CAD in diabetes. Alternative views suggest that metabolic and vascular diseases share unifying cellular defects that could serve as targets for novel therapeutic strategies. Recently, a variant [single-nucleotide polymorphism (SNP); rs11212617] near the gene for ataxia telangiectasia mutated (ATM) has been associated with glycaemic response to metformin.

MATERIALS AND METHODS

We determined rs11212617 in 240 male patients who underwent elective coronary angiography.

RESULTS

While the variant was not associated with glucose concentrations, the A allele was significantly associated with the presence of CAD (chi-square, p = 0.003), as well as with logarithmically transformed quantitative CAD indices [severe score (SS): 0.5 (0.4-0.6) vs 0.3 (0.2-0.5); extent score (ES): 2.63 (2.4-2.9) vs 1.94 (1.4-2.4), both p < 0.05, respectively]. Multivariate analysis revealed an independent association between the A allele with ES (β = 0.17, p < 0.01).

CONCLUSION

Our data suggest that ATM-dependent signalling might play a role in the development of atherosclerotic vascular disease, but larger studies are necessary to substantiate such a hypothesis.

Diabetes and hemochromatosis

The common form of hereditary hemochromatosis is an autosomal recessive disorder most prevalent in Caucasians that results in excessive iron storage. The clinical manifestations of hemochromatosis are protean. HFE genotype, which determines the degree of iron overload and duration of disease have profound effects on disease expression. The prevalence of diabetes in this population has likely been underestimated because of studies that include a broad range of ethnicities and associating diabetes with allele frequency in spite of the decreased risk of diabetes in heterozygotes compared with homozygotes. Loss of insulin secretory capacity is likely the primary defect contributing to development of diabetes with insulin resistance playing a secondary role. Phlebotomy can ameliorate the defects in insulin secretion if initiated early. Screening a select population of individuals with type 2 diabetes may identify patients with hemochromatosis early and substantially impact individual clinical outcomes.

Is oxidative stress induced by iron status associated with gestational diabetes mellitus?

Gestational diabetes mellitus (GDM) is a common pregnancy complication in high risk populations, and is associated with increased perinatal and long term outcomes for both mothers and newborns. Both its prevention and early management can be reinforced by identifying risks factors, particularly those factors influencing glucose metabolism. On the other hand, several epidemiological studies have shown an increased oxidative stress (OS) in pregnant women with GDM. Elevated OS was also reported in pregnant women supplemented with iron, which can generate OS and may also influence insulin resistance. This review summarizes the current state of knowledge, highlighting the potential relationship between OS induced by iron status and the development of GDM.

Current status of research on autoimmune pancreatitis

Autoimmune pancreatitis (AIP) is a form of chronic pancreatitis characterized clinically by frequent presentation with obstructive jaundice, histologically by lymphoplasmacytic infiltration with fibrosis, and therapeutically by a dramatic response to steroids. AIP have recently been classified into two subtypes, lymphoplasmacytic sclerosing pancreatitis (LPSP) and idiopathic duct centric pancreatitis (IDCP). The pathogenesis of AIP may involve genetic susceptibility, autoantibodies, molecular mimicry, imbalance of T-cell-mediated immune regulation, and gene mutation. In this article, we will systematically review typical and atypical clinical, imaging and histopathological features of AIP, with an emphasis placed on the advances in the diagnosis and treatment of this disease.

Heme iron intake and risk of new-onset diabetes in a Mediterranean population at high risk of cardiovascular disease: an observational cohort analysis

BACKGROUND

Several epidemiological studies have observed an increased risk of type 2 diabetes mellitus (T2DM) among subjects with a higher consumption of red and processed meat. Heme iron intake has been directly associated with a higher risk of T2DM in healthy adult Chinese and U.S populations. The objective of the present study was to evaluate the association between heme iron intake and the incidence of T2DM in a Mediterranean population at high cardiovascular risk.

METHODS

We assessed a subset of participants in the PREDIMED trial as an observational cohort, followed up for a maximum of eight years. We initially included 1073 non-diabetic subjects (57.1% women) aged 67.3 ± 6.0 years, at high cardiovascular risk. Diet was assessed at the study baseline using a validated, semi-quantitative food frequency questionnaire.

RESULTS

During the follow-up period 131 diabetics were newly diagnosed. The risk of developing T2DM was assessed using baseline heme iron intake and proportional hazard models, first unadjusted, then adjusted for energy, and finally adjusted for dietary, anthropometric, socio-demographic and lifestyle variables. Significant direct associations with the incidence of T2DM were found for heme iron (Hazard Ratio [HR] 1.30, 95% confidence interval [CI], 1.02 to 1.66). Secondarily, we have also observed that coffee (HR:0.93, 95% CI, 0.89 to 0.98) and alcoholic beverages (HR: 1.02, 95% CI, 1.01 to 1.04) were also found to reduce and increase the risk of T2DM, respectively.

CONCLUSION

High dietary intake of heme iron was associated with an increased risk of developing T2DM in a Mediterranean population at high cardiovascular risk.

TRIAL REGISTRATION

Identifier: ISRCTN35739639.

When less is more: novel mechanisms of iron conservation

Disorders of iron homeostasis are very common, yet the molecular mechanisms of iron regulation remain understudied. Over 20 years have passed since the first characterization of iron-regulatory proteins (IRP) as mediators of cellular iron-deficiency response in mammals through iron acquisition. However, little is known about other mechanisms necessary for adaptation to low-iron states. In this review, we present recent evidence that establishes the existence of a new iron-regulatory pathway aimed at iron conservation and optimization of iron use through suppression of nonessential iron-consuming processes. Moreover, we discuss the possible links between iron homeostasis and energy metabolism uncovered by studies of iron-deficiency response.

Elevated serum ferritin level is associated with the incident type 2 diabetes in healthy Korean men: a 4 year longitudinal study

Background

Elevated ferritin concentration has been implicated in the etiology of type 2 diabetes. Accumulating evidence, mostly from studies conducted on western populations, has demonstrated a strong association between the elevated ferritin concentrations and incident type 2 diabetes. In Asian populations, however, the longitudinal studies investigating the association of elevated serum ferritin levels and type 2 diabetes are lacking. In present study, we aimed to determine whether elevated serum ferritin levels are related to the incident type 2 diabetes in healthy Korean men.

Methodology/Principal Findings

This 4 year longitudinal observational study was conducted at the Asan Medical Center, Seoul, Republic of Korea. The study population consisted of 2,029 men without type 2 diabetes who underwent routine health examination in 2007 (baseline) and 2011 (follow-up). Baseline serum ferritin concentrations were measured by chemiluminescent two-site sandwich immunoassay. In multiple-adjusted model, the relative risk (RR) for incident type 2 diabetes was significantly higher in highest compared with the lowest ferritin quartile category, even after adjusting for confounding variables including homeostasis model assessment of insulin resistance (RR = 2.17, 95% confidence interval 1.27–3.72, P for trend = 0.013).

Conclusions/Significance

These results demonstrated that elevated level of serum ferritin at baseline was associated with incident type 2 diabetes in an Asian population.

Systematic review of clinical studies related to pork intake and metabolic syndrome or its components

Globally, both the incidence of type 2 diabetes and the consumption of meat, in particular pork meat, have increased, concurrently. Processed meats have been associated with an increased risk for diabetes in observational studies. Therefore, it is important to understand the possible mechanisms of this association and the impact of meats from different species. The goal of this systematic review was to assess experimental human studies of the impact of pork intake compared with other protein sources on early markers for the development of diabetes, ie, insulin resistance, glucose intolerance, and the components of the metabolic syndrome. A systematic review was conducted searching PubMed and EMBASE and using the Cochrane and PRISMA guidelines. Eight studies were eligible and critically reviewed. Five studies were based on a single meal or single day exposure to pork, as compared with other sources of protein. The glucose-insulin response following the pork meals did not differ compared with beef, shrimp, or mixed sources of proteins. However, compared with eggs, ham (processed meat) led to a larger insulin response in nonobese subjects. Compared with whey, ham led to a smaller insulin response and a larger glucose response. These findings suggest possible mechanisms for the association between processed meat and the development of diabetes. Nonprocessed pork meats were not compared with eggs or whey. The three longer interventions (11 days to 6 months) did not show a significant impact of pork on the components of the metabolic syndrome, with the exception of a possible benefit on waist circumference and high-density lipoprotein cholesterol (one study each with significant limitations). Most of the findings are weak and there is a lack of solid evidence. The literature on the topic is limited and important research gaps are identified. Considering recent trends and projections for diabetes and pork intake, this is an important global public health question that requires more attention in order to provide improved evidence-based dietary recommendations.

Elevated plasma ferritin is associated with increased incidence of type 2 diabetes in middle-aged and elderly Chinese adults

Epidemiological studies suggest that elevated circulating ferritin is associated with heightened incident diabetes in mainly Western populations, although the results were not entirely consistent. We aimed to prospectively investigate the ferritin-diabetes association in an Asian population for the first time, to our knowledge, and also to examine this association with an updated meta-analysis. Our prospective study included 2198 community-living Chinese between 50 and 70 y of age in 2005. All individuals participated in a 6-y follow-up survey in 2011. Fasting plasma ferritin, high-sensitivity C-reactive protein (hsCRP), adiponectin, and γ-glutamyltransferase (GGT) were measured at baseline. A total of 538 incident diabetes cases were documented by self-reports and/or fasting glucose ≥7.0 mmol/L at the follow-up survey. After multiple adjustments, the RR of type 2 diabetes was 1.90 (95% CI: 1.37, 2.65) when comparing the highest with the lowest sex-specific ferritin quintile. The association remained significant after further controlling for BMI, hsCRP, adiponectin, and GGT. To update the evidence reported in previous meta-analyses, we searched all prospective studies evaluating the association between blood ferritin and incident diabetes on PubMed prior to October 24, 2012. Besides our prospective study, 9 additional studies were also included. The pooled RR was 1.60 (95% CI: 1.25, 2.04) when comparing the highest with the lowest category of ferritin with a moderate heterogeneity (I(2) = 49.0%; P = 0.03). A significant linear dose-response relationship was detected in this meta-analysis. Overall, our results indicate an independent and significant positive association between higher plasma ferritin, a marker of elevated body iron stores, and increased risk of developing type 2 diabetes in middle-aged and elderly Chinese adults, which is similar to Western populations.

rs189037, a functional variant in ATM gene promoter, is associated with idiopathic nonobstructive azoospermia

OBJECTIVE

To investigate the relationship between a functional variant rs189037(G>A) in ATM promoter and idiopathic nonobstructive azoospermia (INOA) in a Chinese population.

DESIGN

Case-control study.

SETTING

Medical academy and hospital.

PATIENT(S)

Two hundred twenty-nine INOA patients and 236 fertile male controls.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Genotyping was performed by polymerase chain reaction-based restriction fragment length polymorphism and subsequently confirmed by DNA sequencing. Odds ratio (ORs) and 95% confidence intervals (95% CIs) were calculated for the risk genotype and allele. Bioinformatic analysis was also performed to predict the biological function of rs189037(G>A).

RESULT(S)

The AA genotype and A allele at rs189037(G>A) locus were both associated with an increased risk of INOA, with OR 1.90 (95% CI 1.214-3.007) for AA and 1.41 (95% CI 1.112-1.775) for A allele. The heterozygous GA and GA+AA had no relationship with INOA risk, with OR 1.06 (95% CI 0.761-1.472) and 1.28 (95% CI 0.954-1.708), respectively. Meanwhile, stratification by genotype showed that INOA patients with AA had higher FSH level, lower total T level, and smaller testicular size than those patients with GG. Furthermore, bioinformatic analysis predicted that the rs189037(G>A) variant was located in a well-conserved region in ATM promoter and that the transition of allele G to allele A might lead to differential allelic expression of ATM gene via modifying of the DNA-binding ability of transcription factor E2F1.

CONCLUSION(S)

The genetic variant rs189037(G>A) in ATM gene promoter contributes to an increased risk of INOA in a Chinese population, possibly through affecting the DNA-binding ability of E2F1 and subsequent ATM expression.

Red meat, dietary heme iron, and risk of type 2 diabetes: the involvement of advanced lipoxidation endproducts

There is growing evidence of disordered iron homeostasis in the diabetic condition, with links proposed between dietary iron intakes and both the risk of disease and the risk of complications of advanced disease. In the United States, Britain, and Canada, the largest dietary contributors of iron are cereals and cereal products and meat and meat products. This review discusses the findings of cohort studies and meta-analyses of heme iron and red meat intakes and the risk of type 2 diabetes. These suggest that processed red meat is associated with increased risk, with high intakes of red meat possibly also associated with a small increased risk. Historically, humans have relied on large quantities of heme iron and red meat in their diets, and therefore it is paradoxical that iron from meat sources should be associated with the risk of type 2 diabetes. A reason for this association may be drawn from studies of dietary advanced glycation and lipoxidation endproducts present in processed food and the mechanisms by which insulin output by pancreatic islet cells might be influenced by the protein modifications present in processed red meat.

Processing of meats and cardiovascular risk: time to focus on preservatives

Dietary guidelines emphasize selecting lean (low-fat) meats to reduce saturated fat and cholesterol, but growing evidence suggests that health effects may relate to other ingredients, such as sodium, heme iron, or L-carnitine. Understanding how meats influence health, and on which nutrients this relationship depends, is essential to advise consumer choices, set guidelines, and inform food reformulations. A recent study published in BMC Medicine involving 448,568 participants in 10 European countries, provides important evidence in this regard. After multivariate adjustment, intake of unprocessed red meat was not significantly associated with total or cause-specific mortality; conversely, intake of processed meat was associated with a 30% higher rate of cardiovascular disease (CVD) (per 50 g/day, relative risk 1.30, 95% confidence interval 1.17 to 1.45) and also higher cancer mortality. These findings are consistent with our previous meta-analysis, based on smaller studies, showing strong associations of processed meats, but not unprocessed meats, with CVD. Preservatives are the notable difference; the calculated blood-pressure effects of sodium differences (around 400% higher in processed meats) explain most of the observed higher risk. Although unprocessed red meats seem to be relatively neutral for CVD, healthier choices are available, including fish, nuts, legumes, fruits, and vegetables. Public-health guidance should prioritize avoidance of processed meats, including the low-fat deli meats currently marketed as healthy choices, and the food industry should substantially reduce sodium and other preservatives in processed meats.See related research article here http://www.biomedcentral.com/1741-7015/11/63.

Unprocessed red and processed meats and risk of coronary artery disease and type 2 diabetes--an updated review of the evidence

Growing evidence suggests that effects of red meat consumption on coronary heart disease (CHD) and type 2 diabetes could vary depending on processing. We reviewed the evidence for effects of unprocessed (fresh/frozen) red and processed (using sodium/other preservatives) meat consumption on CHD and diabetes. In meta-analyses of prospective cohorts, higher risk of CHD is seen with processed meat consumption (RR per 50 g: 1.42, 95 %CI = 1.07-1.89), but a smaller increase or no risk is seen with unprocessed meat consumption. Differences in sodium content (~400 % higher in processed meat) appear to account for about two-thirds of this risk difference. In similar analyses, both unprocessed red and processed meat consumption are associated with incident diabetes, with higher risk per g of processed (RR per 50 g: 1.51, 95 %CI = 1.25-1.83) versus unprocessed (RR per 100 g: 1.19, 95 % CI = 1.04-1.37) meats. Contents of heme iron and dietary cholesterol may partly account for these associations. The overall findings suggest that neither unprocessed red nor processed meat consumption is beneficial for cardiometabolic health, and that clinical and public health guidance should especially prioritize reducing processed meat consumption.

Ferritin levels and risk of type 2 diabetes mellitus: an updated systematic review and meta-analysis of prospective evidence

BACKGROUND

Emerging evidence suggests that a strong link that exists between elevated baseline body iron stores and high risk of incident type 2 diabetes mellitus (T2DM) in general populations, but the precise magnitude of the associations remains uncertain.

METHODS

We conducted a systematic review and meta-analysis of published prospective studies evaluating the associations of baseline ferritin (a biomarker of body iron stores) levels with risk of T2DM in general populations. A subsidiary review of dietary heme iron status and T2DM risk associations was also conducted. Studies were identified in a literature search of PubMed, EMBASE, and Web of Science up to October 2012.

RESULTS

Of the 730 studies reviewed for eligibility, 12 published studies involving 185 462 participants and 11 079 incident T2DM events were included in the analyses. Nine studies assessed associations between ferritin levels and T2DM with heterogeneous findings (I(2)  = 58%, 12-80%, p = 0.014). The pooled fully adjusted relative risk (RR) with (95% confidence interval) for T2DM was 1.73 (1.35-2.22) in a comparison of extreme fifths of baseline ferritin levels. Three studies evaluated associations between dietary heme iron status and T2DM with a corresponding RR for T2DM of 1.28 (1.16-1.41). In dose-response analyses, the pooled RRs for an increment of 5 ng/mL in ferritin levels and 5 mg/day in dietary heme iron were, respectively, 1.01 (0.99-1.02) and 3.24 (2.05-5.10).

CONCLUSION

Elevated levels of ferritin may help identify individuals at high risk of T2DM. Further research is warranted to establish causality of these associations and to ascertain which patients are likely to benefit from lifestyle or therapeutic interventions.

Intakes of heme iron and zinc and colorectal cancer incidence: a meta-analysis of prospective studies

BACKGROUND

Epidemiologic findings concerning the associations between intakes of heme iron and zinc and colorectal cancer (CRC) incidence yielded conflicting results. We aimed to investigate the associations by performing a meta-analysis of prospective studies.

METHODS

We conducted a literature search on PubMed and EMBASE databases up to December 2012 to identify the prospective studies that investigated the relationships between heme iron or zinc intake and risk of CRC. We also reviewed the bibliographies of the retrieved articles to identify additional studies. We used a random-effects model to calculate the summary relative risks (RRs) with 95 % confidence intervals (CIs).

RESULTS

Eight studies on heme iron intake and six studies on zinc intake met the inclusion criteria. The summary RR of CRC for the highest versus the lowest intake was 1.14 (95 % CI = 1.04-1.24) for heme iron and 0.83 (95 % CI = 0.72-0.94) for zinc, respectively. The observed associations were not significantly modified by subsites within the colorectum, sex, geographic area, study duration, the number of cases, or the range of intakes. In the dose-response analyses, the summary RR of CRC was 1.11 (95 % CI = 1.03-1.18) for heme iron intake of 1 mg/day, and 0.86 (95 % CI = 0.78-0.96) for zinc intake of 5 mg/day, respectively. There was little evidence of publication bias.

CONCLUSION

This meta-analysis suggests a significant positive dose-response association of heme iron intake and a significant inverse dose-response association of zinc intake with risk of CRC.

Meat consumption, diabetes, and its complications

Several prospective studies have reported that risk of type 2 diabetes (T2DM) is elevated in meat consumers, especially when processed meats are consumed. Elevated risks of coronary heart disease (CHD) and stroke in meat consumers have also been reported. In this overview, the evidence regarding meat consumption and the risk of diabetes, both type 1 diabetes (T1DM) and T2DM and their macro- and microvascular complications, is reviewed. For T2DM, we performed a new meta-analysis including publications up to October 2012. For T1DM, only a few studies have reported increased risks for meat consumers or for high intake of saturated fatty acids and nitrates and nitrites. For T2DM, CHD, and stroke, the evidence is strongest. Per 100 g of total meat, the pooled relative risk (RR) for T2DM is 1.15 (95 % CI 1.07-1.24), for (unprocessed) red meat 1.13 (95 % CI 1.03-1.23), and for poultry 1.04 (95 % CI 0.99-1.33); per 50 g of processed meat, the pooled RR is 1.32 (95 % CI 1.19-1.48). Hence, the strongest association regarding T2DM is observed for processed (red) meat. A similar observation has been made for CHD. For stroke, however, a recent meta-analysis shows moderately elevated risks for meat consumers, for processed as well as for fresh meats. For the microvascular complications of diabetes, few prospective data were available, but suggestions for elevated risks can be derived from findings on hyperglycemia and hypertension. The results are discussed in the light of the typical nutrients and other compounds present in meat--that is, saturated and trans fatty acids, dietary cholesterol, protein and amino acids, heme-iron, sodium, nitrites and nitrosamines, and advanced glycation end products. In light of these findings, a diet moderate to low in red meat, unprocessed and lean, and prepared at moderate temperatures is probably the best choice from the public health point of view.

WITHDRAWN: The effect of molecular design on the physical and biological properties of complementary self-assembling peptides

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Recombinant self-assembling peptides as biomaterials for tissue engineering

Synthetic nanostructures based on self-assembling systems that aim to mimic natural extracellular matrix are now being used as substrates in tissue engineering applications. Peptides are excellent starting materials for the self-assembly process as they can be readily synthesised both chemically and biologically. P₁₁-4 is an 11 amino acid peptide that undergoes triggered self-assembly to form a self-supporting hydrogel. It exists as unimers of random coil conformations in water above pH 7.5 but at low pH adopts an antiparallel β-sheet conformation. It also self-assembles under physiological conditions in a concentration-dependent manner. Here we describe an unimer P₁₁-4 production system and the use of a simple site-directed mutagenesis approach to generate a series of other P₁₁-family peptide expression vectors. We have developed an efficient purification strategy for these peptide biomaterials using a simple procedure involving chemical cleavage with cyanogen bromide then repeated filtration, lyophilisation and wash steps. We report peptide-fusion protein yields of ca. 4.64 g/L and we believe the highest reported recovery of a recombinant self-assembling peptide at 203 mg/L of pure recombinant P₁₁-4. This peptide forms a self-supporting hydrogel under physiological conditions with essentially identical physico-chemical properties to the chemically synthesised peptide. Critically it also displays excellent cytocompatibility when tested with primary human dermal fibroblasts. This study demonstrates that high levels of a series of recombinant self-assembling peptides can be purified using a simple process for applications as scaffolds in tissue engineering.

Self-assembling nanostructures to deliver angiogenic factors to pancreatic islets

Supramolecular self-assembly of nanoscale filaments offers a vehicle to signal cells within dense cell aggregates such as pancreatic islets. We previously developed a heparin-binding peptide amphiphile (HBPA) that self-assembles into nanofiber gels at concentrations of 1% by weight when mixed with heparin and activates heparin-binding, angiogenic growth factors. We report here on the use of these molecules at concentrations 100 times lower to drive delivery of the nanofibers into the dense islet interior. Using fluorescent markers, HBPA molecules, heparin, and FGF2 were shown to be present in and on the surface of murine islets. The intraislet nanofibers were found to be necessary to retain FGF2 within the islet for 48 h and to increase cell viability significantly for at least 7 days in culture. Furthermore, enhanced insulin secretion was observed with the nanofibers for 3 days in culture. Delivery of FGF2 and VEGF in conjunction with the HBPA/heparin nanofibers also induced a significant amount of islet endothelial cell sprouting from the islets into a peptide amphiphile 3-D matrix. We believe the infiltration of bioactive nanofibers in the interior of islets as an artificial ECM can improve cell viability and function in vitro and enhance their vascularization in the presence of growth factors such as FGF2 and VEGF. The approach described here may have significant impact on islet transplantation to treat type 1 diabetes.

Polymer nanofibrous structures: Fabrication, biofunctionalization, and cell interactions

Extracellular matrix fibers (ECM) such as collagen, elastin, and keratin provide biological and physical support for cell attachment, proliferation, migration, differentiation and ultimately cell fate. Therefore, ECM fibers are an important component in tissue and organ development and regeneration. Meanwhile, polymer nanofibers could play the same critical role in tissue regeneration process. Fibrous structures can be fabricated from a variety of materials and methods with diameters ranging throughout the size scale where cells can sense individual fibers (several nanometers to several microns). Polymer nanofiber scaffolds can be designed in a way that predictably modulates a variety of important cell behaviors towards a desired overall function. The nanofibrous topography itself, independent of the fiber material, has demonstrated the potential to modulate cell behaviors desirable in tissue engineering such as: unidirectional alignment; increased viability, attachment, and ECM production; guided migration; and controlled differentiation. The versatility of polymer nanofibers for functionalization with biomolecules opens the door to vast opportunities for the design of tissue engineering scaffolds with even greater control over cell incorporation and function. Despite the promise of polymer nanofibers as tissue engineering scaffolds there have been few clinically relevant successes because no single fabrication technique currently combines control over structural arrangement, material composition, and biofunctionalization, while maintaining reasonable cost and yield. Promising strategies are currently being investigated to allow for the fabrication of optimal polymer nanofiber tissue engineering scaffolds with the goal of treating damaged and degenerated tissues in a clinical setting.