Body iron stores and heme-iron intake in relation to risk of type 2 diabetes: a systematic review and meta-analysis

Relationship Between Hepatic Iron Concentration and Glycemic Metabolism, Prediabetes, and Type 2 Diabetes: A Systematic Review

CONTEXT

Emerging research has suggested a potential link between high iron levels, indicated by serum ferritin levels, and the development of type 2 diabetes (T2D). However, the role of hepatic iron concentration (HIC) on T2D development and progression is not well understood.

OBJECTIVES

This study aims to systematically review the literature on HIC and/or the degree of hepatic iron overload (HIO) in individuals with prediabetes and/or diagnosed T2D, and to analyze associations between HIC and markers of glucose metabolism.

DATA SOURCES

The databases Medline, PubMed, Embase, CINAHL, and Web of Knowledge were searched for studies published in English from 1999 to March 2024. This review followed the Preferred Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist.

DATA EXTRACTION

Data were extracted following the established eligibility criteria. Study characteristics and biomarkers related to prediabetes, T2D, and HIO were extracted. The risk of bias was analyzed using the Newcastle-Ottawa Scale. Data were stratified by the exposure and analyzed in subgroups according to the outcome. Data regarding the HIC values in controls, individuals with prediabetes, and individuals with T2D and the association estimates between HIC or HIO and markers of glycemic metabolism, prediabetes, or T2D were extracted.

DATA ANALYSIS

A total of 12 studies were identified, and data from 4110 individuals were analyzed. HIO was not consistently observed in prediabetic/T2D populations; however, elevated HIC was frequently observed in prediabetic and T2D individuals, and was associated with the disruption of certain glycemic markers in some cases.

CONCLUSION

The extent of iron overload, as indicated by hepatic iron load, varied among the prediabetic and T2D populations studied. Further research is needed to understand the distribution and regulation of iron in T2D pathology.

Adherence to the EAT-Lancet reference diet and risk of type 2 diabetes: results from the NutriNet-Santé cohort study

BACKGROUND

In 2019, the EAT-Lancet Commission proposed a planetary, healthy, and reference diet, designed to reduce the global health-environmental double burden of current dietary patterns. We aim to investigate the association between the EAT-Lancet reference diet and type 2 diabetes (T2D) risk.

METHODS

This observational and prospective web-based study was conducted using data from 88 964 adults participating to the French NutriNet-Santé cohort 2009-22 (78.8% female; mean (SD) baseline age of participants was 43.8 (14.5) years). Dietary intakes were assessed at least by three repeated 24 hour-dietary records (mean = 6.3 (2.8)). The endpoint was incident T2D. The main exposure was the EAT-Lancet diet index (ELD-I) modeled as a continuous variable and sex-specific quintiles (Qs). Hazard ratios (HRs) and confidence intervals (CIs) were assessed by Cox proportional hazards models adjusted for potential confounders. The body mass index (BMI) role as a potential mediating factor in the relationship was also investigated.

RESULTS

During follow-up (median = 8.79 years), 812 incident T2D cases occurred. The ELD-I ranged from -192 to 429 points with a median (interquartile range [IQR]) score of 42.8 (29.1) points. For each 25.7-point increase in ELD-I score (1SD), the risk of T2D is reduced by 11% (HR1SD: 0.89; 95% CI: 0.82-0.96; P = .003). The association studied was mediated up to 61% by BMI.

CONCLUSIONS

In this large cohort study, an increase in adherence to the EAT-Lancet reference diet was associated with a decreased risk of T2D beyond BMI. These results support previous findings and highlights the interest of the EAT-Lancet reference diet as a healthy and sustainable diet.

Iron Status Correlates Strongly to Insulin Resistance Among US Adults: A Nationwide Population-Based Study

CONTEXT

Evidence on the link between iron status markers and insulin resistance (IR) is limited.

OBJECTIVE

We aimed to explore the relationship between iron status and IR among US adults.

METHODS

This study involved 2993 participants from the National Health and Nutrition Examination Survey (NHANES) 2003-2006, 2017-2020. IR is characterized by a homeostatic model assessment (HOMA)-IR value of ≥2.5. Weighted linear and multivariable logistic regression analyses were used to examine the linear relationships between iron status and IR. Furthermore, restricted cubic splines (RCS) were used to identify the nonlinear dose-response associations. Stratified analyses by age, sex, body mass index, and physical activity were also performed. Last, a receiver operating characteristic (ROC) curve was used to evaluate the predictive value of iron status in IR.

RESULTS

In weighted linear analyses, serum iron (SI) exhibited a negative correlation with HOMA-IR (β -0.03, 95% CI -0.05, -0.01, P = .01). In weighted multivariate logistic analyses, iron intake and the serum transferrin receptor (sTfR) were positively correlated with IR (OR 1.02, 95% CI 1.00-1.04, P = .04; OR 1.07, 95% CI 1.02-1.13, P = .01). Also, SI and transferrin saturation (TSAT) were negatively correlated with IR (OR 0.96, 95% CI 0.94-0.98, P < .0001; OR 0.98, 95% CI 0.97-0.99, P < .001) after adjusting for confounding factors. RCS depicted a nonlinear dose-response relationship between sTfR and TSAT and IR. This correlation remained consistent across various population subgroups. The ROC curve showed that TSAT performed better than iron intake, SI and sTfR in ROC analyses for IR prediction.

CONCLUSION

All biomarkers demonstrated significantly lower risk of IR with increasing iron levels, which will contribute to a more comprehensive and in-depth understanding of the relationship between the 2 and provide a solid foundation for future exploration of the mechanisms underlying their relationship.

The complementary roles of iron and estrogen in menopausal differences in cardiometabolic outcomes

Biological hormonal changes are frequently cited as an explanatory factor of sex and menopause differences in cardiometabolic diseases (CMD) and its associated risk factors. However, iron metabolism which varies between sexes and among women of different reproductive stages could also play a role. Recent evidence suggest that iron may contribute to CMD risk by modulating oxidative stress pathways and inflammatory responses, offering insights into the mechanistic interplay between iron and CMD development. In the current review, we provide a critical appraisal of the existing evidence on sex and menopausal differences in CMD, discuss the pitfall of current estrogen hypothesis as sole explanation, and the emerging role of iron in CMD as complementary pathway. Prior to menopause, body iron stores are lower in females as compared to males, but the increase during and after menopause, is tandem with an increased CMD risk. Importantly, basic science experiments show that an increased iron status is related to the development of type 2 diabetes (T2D), and different cardiovascular diseases (CVD). While epidemiological studies have consistently reported associations between heme iron intake and some iron biomarkers such as ferritin and transferrin saturation with the risk of T2D, the evidence regarding their connection to CVD remains controversial. We delve into the factors contributing to this inconsistency, and the limitation of relying on observational evidence, as it does not necessarily imply causation. In conclusion, we provide recommendations for future studies on evaluating the potential role of iron in elucidating the sex and menopausal differences observed in CMD.

Impact of age, sex, and thyroid autoimmunity on the association between selenium intake and type 2 diabetes mellitus

BACKGROUND

The association between dietary selenium(Se) intake and type 2 diabetes mellitus (T2DM) remains controversial. The present study aimed to investigate this association using data from the National Health and Nutrition Examination Survey (NHANES) database for the years 2007-2012.

METHODS

Three thousand seventy three individuals aged 20 years and above were eligible for inclusion in this cross-sectional study. The average age of the participants was 50.74 years and the proportions of males and females were nearly equal (49.12% vs. 50.88%). The odds ratios (OR) of the association between dietary Se intake (log2-transformed) and T2DM were examined through the multivariate logistic regression model. Subgroup analyses were conducted based on age, sex, and thyroid autoimmunity to assess the potential impact of these variables on the relationship. Fitted smoothing curves and threshold effect analysis were conducted to describe the nonlinear relationship.

RESULTS

In the fully adjusted model, a significant positive association between Se intake and T2DM was observed (OR = 1.49, 95% CI: 1.16, 1.90, p = 0.0017). After stratifying the data by age, sex, and thyroid autoimmunity, a significant positive association between Se intake and T2DM was observed in individuals under 65 years of age, males, and those with negative thyroid autoimmunity. A two-segment linear regression model was analyzed for sex stratification, revealing a threshold effect in males with an inflection point of 90.51 μg, and an inverted U-shaped relationship in females with an inflection point of 109.90 μg, respectively.

CONCLUSIONS

The present study found a positive relationship between Se intake and the prevalence of T2DM. This association is particularly significant in younger individuals, males, and those with negative thyroid autoimmunity. Our results should be validated in future large prospective studies in different populations.

Meat and meat products - a scoping review for Nordic Nutrition Recommendations 2023

Meat is not only a source of several nutrients but also a proposed risk factor for several non-communicable diseases. Here, we describe the totality of evidence for the role of meat intake for chronic disease outcomes, discuss potential mechanistic pathways, knowledge gaps, and limitations of the literature. Use of the scoping review is based on a de novo systematic review (SR) and meta-analysis on the association between poultry intake and cardiovascular disease (CVD) and type 2 diabetes (T2D), qualified SRs (as defined in the Nordic Nutrition Recommendations 2023 project) on meat intake and cancer by the World Cancer Research Fund (WCRF), the International Agency for Research on Cancer (IARC), and a systematic literature search of SRs and meta-analyses. The quality of the SRs was evaluated using a modified AMSTAR 2 tool, and the strength of evidence was evaluated based on a predefined criteria developed by the WCRF. The quality of the SRs was on average critically low. Our findings indicate that the evidence is too limited for conclusions for most of the chronic disease outcomes. However, findings from qualified SRs indicate strong evidence that processed meat increases the risk of colorectal cancer and probable evidence that red meat (unprocessed, processed, or both) increases the risk. The evidence suggests that both unprocessed red meat and processed meat (also including processed poultry meat) are probable risk factors for CVD mortality and stroke, and that total red meat and processed meat are risk factors for CHD. We found no sufficient evidence suggesting that unprocessed red meat, processed red meat, total red meat, or processed meat (including red and white meat) would be protective of any chronic disease. There was also no sufficient evidence to conclude on protective effect of poultry on any chronic diseases; effects on the risk of CVD, stroke, and T2D, to any direction, were regarded as unlikely.

Iron - a background article for the Nordic Nutrition Recommendations 2023

Iron absorption from foods is generally lower than that of most other nutrients and is highly variable depending on individual iron status and iron bioavailability in the meal. Several large population groups in the Nordic and Baltic countries are at risk of iron deficiency, including infants, young children, menstruating females, pregnant women as well as vegetarians. Iron deficiency leads to anemia, fatigue, and limited capacity for physical activity. Of particular concern is that iron deficiency anemia in young children is associated with impaired neurodevelopment. A comprehensive literature search has been performed and summarized. New factorial calculations have been performed considering iron losses, iron absorption and iron requirements in various population groups. Recent data on iron intakes and the prevalence of iron deficiency in the Nordic countries are presented. Average requirements and tentative recommended intakes are presented for 12 different population groups. Pregnant women and those with high menstrual blood losses should consume iron-rich food and undergo screening for iron deficiency. Infants should consume iron-rich complementary foods and cow's milk should be avoided as a drink before 12 months of age and limited to < 500 mL/day in toddlers. Vegetarians should consume a diet including wholegrains, legumes, seeds, and green vegetables together with iron absorption enhancers. There is no evidence that iron intake per se increases the risk of cancer or diabetes. Iron absorption from foods is generally lower than that of most other nutrients and can vary between <2 and 50% depending on individual iron status and iron bioavailability in the meal.

Study of the Relationship Between Insulin Resistance, Iron Status Markers, and Body Weight in a Sample of Egyptian Population

BACKGROUND

Iron plays a key role in the regulation of body iron homeostasis and is used as a clinical marker for iron deficiency (ID) and hemochromatosis. The idea that iron dysregulation may contribute to various metabolic diseases, such as obesity, insulin resistance, MetS, and T2DM, is a hot topic of discussion.

AIM

The aim of this study is to investigate the relationship insulin resistance, iron status markers, and body weight in a sample of Egyptian population.

METHODS

A case control study was conducted on 90 subjects with age ranging from 18 to 70 years old from a diabetes outpatient clinic, and they were divided to three groups: Group I, non-obese- non-diabetic as the control group; Group II, obese-non-diabetic; and Group III, obese-diabetic.

RESULTS

In our study, there was no statistically significant difference between the three studied groups regarding the different iron parameters. Similarly, we found that neither HOMA-IR nor body weight had a significant correlation with iron status markers. On the contrary, we detected significant positive correlations between the TIBC and the fasting blood glucose, between the serum iron and the LDL, between the TSAT and the systolic blood pressure, and between the HOMA-IR and hematocrit.

CONCLUSION

Our study demonstrated no direct statistical significant relationship between the different iron parameters, obesity, and insulin resistance, either in the diabetic or non-diabetic subjects. This may be due to the complex metabolic dysregulation and the small number of the sample for future investigations.

High-throughput proteomics uncovers exercise training and type 2 diabetes-induced changes in human white adipose tissue

White adipose tissue (WAT) is important for metabolic homeostasis. We established the differential proteomic signatures of WAT in glucose-tolerant lean and obese individuals and patients with type 2 diabetes (T2D) and the response to 8 weeks of high-intensity interval training (HIIT). Using a high-throughput and reproducible mass spectrometry-based proteomics pipeline, we identified 3773 proteins and found that most regulated proteins displayed progression in markers of dysfunctional WAT from lean to obese to T2D individuals and were highly associated with clinical measures such as insulin sensitivity and HbA1c. We propose that these distinct markers could serve as potential clinical biomarkers. HIIT induced only minor changes in the WAT proteome. This included an increase in WAT ferritin levels independent of obesity and T2D, and WAT ferritin levels were strongly correlated with individual insulin sensitivity. Together, we report a proteomic signature of WAT related to obesity and T2D and highlight an unrecognized role of human WAT iron metabolism in exercise training adaptations.

The association between serum ferritin and bilirubin with glycemic control among patients with type 2 diabetes mellitus

Previous evidence has shown an association between serum ferritin and bilirubin levels in the development of type 2 diabetes mellitus (T2DM) and glycemic control. However, the evidence is scarce in Saudi Arabia. In this study, we aimed to evaluate the association between serum ferritin and bilirubin levels with glycemic control in patients with T2DM. This was a cross-sectional study that involved 153 patients with T2DM recruited from outpatient diabetes clinics. Participants were categorized into two groups: well-controlled and uncontrolled T2DM, based on their glycemic status. We focused on comparing the iron profile and bilirubin levels between these two groups and examining the influence of antidiabetic medications on these parameters. A total of 153 patients with T2DM were included (58.2% women and 41.8% men). In both univariate and multivariate analyses, ferritin levels did not have a statistically significant association with glycemic control. However, patients with well-controlled T2DM had a significantly higher median level of total bilirubin and direct bilirubin than those with uncontrolled T2DM. Only direct bilirubin showed a statistically significant association with FBG less than 130 mg/dl and HbA1c level less than 7.0%. Ferritin level was not associated with glycemic control in patients with T2DM. On the other hand, direct bilirubin level was an independent predictor of better glycemic control. Monitoring direct bilirubin levels could aid in predicting glycemic control in T2DM and could be a potential target for developing antidiabetic medications.

Silibinin alleviates ferroptosis of rat islet β cell INS-1 induced by the treatment with palmitic acid and high glucose through enhancing PINK1/parkin-mediated mitophagy

Type 2 diabetes (T2DM) is induced by the abundance of glucose and lipids, which causes glucolipotoxicity to the pancreatic β-cells. Silibinin is a natural flavonoid possessing the regulatory activity on insulin production and therapeutic activity in diabetic mice; however, its effect on glucolipotoxicity is not fully explained. This in vitro study investigates the effects of silibinin on palmitic acid (PA) and high glucose (HG)-induced cell loss and ferroptosis of rat insulinoma INS-1 cells. In the cells treated with PA and HG, expressions of glucose transporter 4 (Glut4) and carnitine acyltransferase I (CPT1) for β-oxidation of fatty acids are reduced. Mitochondria are the metabolic organelles for glucose and fatty acids. The mitochondrial membrane potential (MMP) and ATP production were decreased, while the ROS level was elevated in the cells treated with PA and HG, indicating an induction of mitochondrial disorder. Cell loss was partially rescued by ferroptosis inhibition, suggesting an involvement of ferroptosis in the cells treated with PA and HG. More importantly, the increases in total iron, lipid ROS, MDA and COX-2, and the decrease in ferroptosis inhibitory molecules GSH, GPX4 and FSP1 appeared in the cells treated with PA and HG, confirming the occurrence of ferroptosis. Moreover, PINK1/parkin-mediated mitophagy, a vital process for selective elimination of damaged mitochondria, was blocked. Interestingly, silibinin rescued the mitochondria, restricted the ferroptosis and restored the mitophagy. By using the pharmacological stimulator and inhibitor of mitophagy, and si-RNA transfection to silence PINK1 expression, silibinin's protective effect against ferroptosis caused by PA and HG treatment was found to depend on mitophagy. Collectively, our current study reveals the new mechanisms for the protection of silibinin against the injury of INS-1 cells treated with PA and HG, elucidates the participation of ferroptosis in glucolipotoxicity, highlighting the involvement of mitophagy in defense against ferroptotic cell death.

Repression of the iron exporter ferroportin may contribute to hepatocyte iron overload in individuals with type 2 diabetes

OBJECTIVE

Hyperferremia and hyperferritinemia are observed in patients and disease models of type 2 diabetes mellitus (T2DM). Likewise, patients with genetic iron overload diseases develop diabetes, suggesting a tight link between iron metabolism and diabetes. The liver controls systemic iron homeostasis and is a central organ for T2DM. Here, we investigate how the control of iron metabolism in hepatocytes is affected by T2DM.

METHODS

Perls Prussian blue staining was applied to analyze iron distribution in liver biopsies of T2DM patients. To identify molecular mechanisms underlying hepatocyte iron accumulation we established cellular models of insulin resistance by treatment with palmitate and insulin.

RESULTS

We show that a subset of T2DM patients accumulates iron in hepatocytes, a finding mirrored in a hepatocyte model of insulin resistance. Iron accumulation can be explained by the repression of the iron exporter ferroportin upon palmitate and/or insulin treatment. While during palmitate treatment the activation of the iron regulatory hormone hepcidin may contribute to reducing ferroportin protein levels in a cell-autonomous manner, insulin treatment decreases ferroportin transcription via the PI3K/AKT and Ras/Raf/MEK/ERK signaling pathways.

CONCLUSION

Repression of ferroportin at the transcriptional and post-transcriptional level may contribute to iron accumulation in hepatocytes observed in a subset of patients with T2DM.

Evaluating renal iron overload in diabetes mellitus by blood oxygen level-dependent magnetic resonance imaging: a longitudinal experimental study

BACKGROUND

Iron overload plays a critical role in the pathogenesis of diabetic nephropathy. Non-invasive evaluation of renal iron overload in diabetes in the management and intervention of diabetic nephropathy is of great significance. This study aimed to explore the feasibility of blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) in evaluating renal iron overload in diabetes using a rabbit model.

METHODS

The rabbits were randomly divided into control, iron-overload (I), diabetes (D), and diabetes with iron-overload (DI) groups (each n = 19). The diabetes models were generated by injecting intravenous alloxan solution, and the iron-overload models were generated by injecting intramuscular iron-dextran. BOLD MRI was performed immediately (week 0) and at week 4, 8, and 12 following modeling. The differences in renal cortex (CR2*) and outer medulla R2* (MR2*) and the ratio of MR2*-CR2* (MCR) across the different time points were compared.

RESULTS

Iron was first deposited in glomeruli in the I group and in proximal tubular cells in renal cortex in the D group. In the DI group, there was iron deposition in both glomeruli and proximal tubular cells at week 4, and the accumulation increased subsequently. The degree of kidney injury and iron overload was more severe in the DI group than those in the I and D groups at week 12. At week 8 and 12, the CR2* and MR2* in the DI group were higher than those in the I and D groups (all P < 0.05). The MCR in the I, D, and DI groups decreased from week 0 to 4 (all P < 0.001), and that in the I group increased from week 8 to 12 (P = 0.034). CR2* and MR2* values displayed different trends from week 0-12. Dynamic MCR curves in the D and DI groups were different from that in the I group.

CONCLUSION

It presents interactions between diabetes and iron overload in kidney injury, and BOLD MRI can be used to evaluate renal iron overload in diabetes.

Genome-wide identification and expression analysis of mitogen-activated protein kinase (MAPK) genes in response to salinity stress in channel catfish (Ictalurus punctatus)

The mitogen-activated protein kinase (MAPK) gene family has been systematically described in several fish species, but less so in channel catfish (Ictalurus punctatus), which is an important global aquaculture species. In this study, 16 MAPK genes were identified in the channel catfish genome and classified into three subfamilies based on phylogenetic analysis, including six extracellular signal regulated kinase (ERK) genes, six p38-MAPK genes and four C-Jun N-terminal kinase (JNK) genes. All MAPK genes were distributed unevenly across 10 chromosomes, of which three (IpMAPK8, IpMAPK12 and IpMAPK14) underwent teleost-specific whole genome duplication during evolution. Gene expression profiles in channel catfish during salinity stress were analysed using transcriptome sequencing and qRT-PCR (quantitative reverse transcription PCR). Results from reads per kilobase million (RPKM) analysis showed IpMAPK13, IpMAPK14a and IpMAPK14b genes were differentially expressed when compared with other genes between treatment and control groups. Furthermore, three of these genes were validated by qRT-PCR, of which IpMAPK14a expression levels were significantly upregulated in treatment groups (high and low salinity) when compared with the control group, with the highest expression levels in the low salinity group (P < 0.05). Therefore, IpMAPK14a may have important response roles to salinity stress in channel catfish.

Red and processed meat intakes and cardiovascular disease and type 2 diabetes mellitus: An umbrella systematic review and assessment of causal relations using Bradford Hill's criteria

Observational research suggests higher red and processed meat intakes predict greater risks of developing or dying from cardiovascular diseases (CVD) and type 2 diabetes mellitus (T2DM), but this research limits causal inference. This systematic review of reviews utilizes both observational and experimental research findings to infer causality of these relations. Reviews from four databases were screened by two researchers. Reviews included unprocessed red meat (URM), processed meat (PM), or mixed URM + PM intake, and reported CVD or T2DM outcomes. Twenty-nine reviews were included, and causality was inferred using Bradford Hill's Criteria. Observational assessments of CVD outcomes and all meat types consistently reported weak associations while, T2DM outcomes and PM and Mixed URM + PM assessments consistently reported strong associations. Experimental assessments of Mixed URM + PM on CVD and T2DM risk factors were predominately not significant which lacked coherence with observational findings. For all meat types and outcomes, temporality and plausible mechanisms were established, but specificity and analogous relationships do not support causality. Evidence was insufficient for URM and T2DM. More experimental research is needed to strengthen these inferences. These results suggest that red and processed meat intakes are not likely causally related to CVD but there is potential for a causal relationship with T2DM.

Gastrointestinal and Liver Complications in Patients with Diabetes Mellitus-A Review of the Literature

The number of diabetes mellitus patients has increased over the last few years in developing countries, along with obesity and sedentary lifestyle. Besides macroangiopathy and microangiopathy, damage to the nerve fibers of the peripheral nervous system is the most common chronic complication of diabetes. Digestive complications in diabetic patients represent a consequence of diabetic autonomic neuropathy involving the gastrointestinal tract, but unfortunately not always evaluated by diabetologists. Aside from the complications encountered in the digestive tract, patients with diabetes mellitus are prone to developing liver diseases. This review will describe the prevalence of these complications, the modality of diagnosis, and therapeutical solutions in order to reduce the risk of progression of these complications in diabetic subjects.

Impaired pancreatic beta-cell function after a single dose of oral iron: a before-and-after (pre-post) study

INTRODUCTION

Although in vitro and animal studies have shown that iron loading in pancreatic beta-cells impaired insulin secretion, no human studies have documented the acute effects of oral iron on beta-cell insulin secretory capacity. In this study, we determined beta-cell insulin secretory capacity at baseline and after a single oral dose of iron (ferrous sulphate, 120 mg elemental iron) in healthy male individuals.

METHODS

Fifteen healthy male volunteers underwent an oral glucose tolerance test (OGTT) to document baseline glucose tolerance and insulin secretion kinetics (baseline OGTT). One week later, the same subjects underwent a second OGTT, two hours after an oral dose of ferrous sulfate (120 mg of elemental iron) (post-iron OGTT). Changes in disposition index, insulin secretion kinetics, glucose tolerance, insulin resistance, insulin clearance, and iron-related parameters in serum were determined.

RESULTS

Compared to baseline OGTT, the areas under the curve (AUC) for serum iron and transferrin saturation increased by 125% and 118% respectively, in the post-iron OGTT. The disposition index decreased by 20% (p=0.009) and the AUC for glucose concentrations increased by 5.7% (p<0.001) during the post-iron OGTT. The insulin secretion rate was marginally lower during the first hour (-3.5%, p=0.63), but became significantly higher during the second hour (22%, p=0.005) of the post-iron OGTT. Insulin resistance and insulin clearance rate were not affected by iron intake.

CONCLUSION

The decrease in disposition index and glucose tolerance observed after the oral dose of iron points to an acute iron-induced impairment in pancreatic beta-cell insulin secretory capacity. This article is protected by copyright. All rights reserved.

Dietary iron modulates hepatic glucose homeostasis via regulating gluconeogenesis

Iron exerts significant influences on glucose metabolism. However, the regulatory mechanisms underlying disordered glucose response remains largely unclear. The aim of this study was to examine the impact of dietary iron on hepatic gluconeogenesis in mice and in rat liver-derived cells. High iron models of C57BL/6J mice were fed with 1.25 g Fe/kg diets for 9 weeks, and high-iron BRL-3A cell models were treated with 250 μmol/L FeSO₄ for 12 h and 24 h. Our data showed that higher iron intake resulted in higher hepatic iron without iron toxicity, and reduced body weight gain with no difference of food intakes. High dietary iron significantly increased 61% of hepatic glycogen deposition, but exhibited impairment in glucose responses in mice. Moreover, high dietary iron suppressed hepatic gluconeogenesis by repressing the expression of key gluconeogenic enzymes, phosphoenolpyruvate carboxykinase and glucose-6-phosphatase. Meanwhile, mice fed with higher iron diets exhibited both decreased AMP-activated protein kinase (AMPK) activity and peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) protein levels. Furthermore, in BRL-3A cells, iron treatment increased cellular glucose uptake, and altered gluconeogenesis rhythmically by regulating the activation of AMPK and expression of PGC-1α successively. This study demonstrated that dietary high iron was able to increase hepatic glycogen deposition by enhancement of glucose uptake, and suppress hepatic gluconeogenesis by regulation of AMPK and PGC-1α.

Paying the Iron Price: Liver Iron Homeostasis and Metabolic Disease

Iron is an essential metal element whose bioavailability is tightly regulated. Under normal conditions, systemic and cellular iron homeostases are synchronized for optimal function, based on the needs of each system. During metabolic dysfunction, this synchrony is lost, and markers of systemic iron homeostasis are no longer coupled to the iron status of key metabolic organs such as the liver and adipose tissue. The effects of dysmetabolic iron overload syndrome in the liver have been tied to hepatic insulin resistance, nonalcoholic fatty liver disease, and nonalcoholic steatohepatitis. While the existence of a relationship between iron dysregulation and metabolic dysfunction has long been acknowledged, identifying correlative relationships is complicated by the prognostic reliance on systemic measures of iron homeostasis. What is lacking and perhaps more informative is an understanding of how cellular iron homeostasis changes with metabolic dysfunction. This article explores bidirectional relationships between different proteins involved in iron homeostasis and metabolic dysfunction in the liver. © 2022 American Physiological Society. Compr Physiol 12:3641-3663, 2022.

Dietary iron intake and the risk of type 2 diabetes: a systematic review and dose-response meta-analysis of prospective cohort studies

PURPOSE

We aimed to assess the long-term association of total, heme, non-heme, and supplemental iron intake and risk of type 2 diabetes (T2D).

METHODS

PubMed, Scopus, and Web of Science were searched to October 2021. Two researchers extracted data in duplicate and rated the certainty in the estimates using the GRADE approach. Random-effects models were applied to estimate the relative risks (RRs) and 95% CIs. Dose-response associations were modeled by a one-stage weighted mixed-effects meta-analysis.

RESULTS

Eleven prospective cohort studies 323,788 participants and 28,837 incident cases of T2D were included. High versus low category meta-analysis indicated that higher heme iron intake was associated with a 20% higher risk of T2D (95% CI 1.07, 1.35; I² = 77%, n = 11; GRADE = moderate). Dose-response analysis indicated a positive monotonic association, wherein each 1 mg/day increment in heme iron intake was related to a 16% higher risk (95% CI 1.03, 1.30). No significant relationship was detected between dietary intakes of total, non-heme, and supplemental iron and risk of T2D (GRADE = very low).

CONCLUSIONS

In summary, higher heme iron intake was associated with a higher risk of T2D. Our results are in line with existing evidence indicating that adopting a Western-style dietary pattern, rich in dietary sources of heme iron, was associated with a higher risk of T2D.

REGISTRY AND REGISTRY NUMBER

The protocol of this systematic review was registered at PROSPERO (registration number: CRD42021226835).

Red and Processed Meat Intake in Relation to Non-Alcoholic Fatty Liver Disease Risk: Results from a Case-Control Study

Data on the association between dietary red meat intake and non-alcoholic fatty liver disease (NAFLD) are limited. We designed this case-control study to determine the association between red and processed meat consumption and risk of NAFLD in Iranian adults. A total of 999 eligible subjects, including 196 NAFLD patients and 803 non-NAFLD controls were recruited from hepatology clinics in Tehran, Iran. A reliable and validated food frequency questionnaire was used to evaluate the red and processed meat intakes. The analyzes performed showed that in an age- and gender-adjusted model, patients with the highest quartile of red meat intake had an approximately three-fold higher risk of NAFLD than those with the lowest quartile of intake (odds ratio [OR], 3.42; 95% confidence interval [CI], 2.16-5.43; p value < 0.001). Moreover, patients in the highest quartile of processed meat intake had a 3.28 times higher risk of NAFLD, compared to the lowest quartile(OR, 3.28; 95% CI, 1.97-5.46; p value < 0.001).Both these associations remained significant by implementing additional adjustments for body mass index, energy intake, dietary factors, diabetes, smoking, and physical activity (OR, 3.65; 95% CI, 1.85-7.18; p value < 0.001 and OR, 3.25; 95% CI, 1.57-6.73; p value = 0.002, respectively).Our findings indicate that both red and processed meat intakes are related to the increased odds of NAFLD; however, prospective studies are needed to confirm these results.

High serum iron markers are associated with periodontitis in post-menopausal women: A population-based study (NHANES III)

AIM

To investigate the association between increased serum markers of iron (ferritin and transferrin saturation) and the severity and extent of periodontitis in post-menopausal (PM) women.

MATERIALS AND METHODS

Data from 982 PM women participating in NHANES III were analysed. Exposures were high ferritin (≥300 μg/ml) and transferrin saturation (≥45%). The primary outcome was moderate/severe periodontitis defined according to Centers for Disease Control and Prevention and the American Academy of Periodontology. The extent of periodontitis was also assessed as outcome: proportion of sites affected by clinical attachment loss ≥4 mm and probing depth ≥4 mm. Crude and adjusted prevalence ratio (PR) and mean ratio (MR) were estimated using Poisson regression.

RESULTS

The prevalence of moderate/severe periodontitis was 27.56%. High ferritin was associated with moderate/severe periodontitis in the crude (PR 1.55, p = .018) and in the final adjusted model (PR 1.53, p = .008). High ferritin and transferrin saturation levels were associated with a higher proportion of sites with clinical attachment loss ≥4 mm (p < .05).

CONCLUSIONS

The increasing serum iron markers seem to contribute to periodontitis severity and extent in PM women.

Associations of Habitual Mineral Intake with New-Onset Prediabetes/Diabetes after Acute Pancreatitis

Associations between habitual dietary intake of minerals and glucose metabolism have been extensively studied in relation to metabolic disorders. However, similar research has yet to be conducted in individuals after acute pancreatitis (AP). The main aim was to investigate the associations between habitual intake of 13 minerals and glycaemic status: new-onset prediabetes/diabetes after AP (NODAP), pre-existing prediabetes/type 2 diabetes (T2DM), and normoglycaemia after AP (NAP). Associations between the dietary intake of minerals and markers of glucose metabolism (glycated haemoglobin and fasting plasma glucose) were also studied. The EPIC-Norfolk food frequency questionnaire was used in a cross-sectional fashion to determine the habitual intake of 13 dietary minerals. ANCOVA as well as multiple linear regression analyses were conducted and five statistical models were built to adjust for covariates. The study included 106 individuals after AP. In the NODAP group, intake of 4 minerals was significantly less when compared with the NAP group: iron (B = -0.076, p = 0.013), nitrogen (B = -0.066, p = 0.003), phosphorous (B = -0.046, p = 0.006), and zinc (B = -0.078, p = 0.001). Glycated haemoglobin was significantly associated with iodine intake (B = 17.763, p = 0.032) and manganese intake (B = -17.147, p = 0.003) in the NODAP group. Fasting plasma glucose was significantly associated with manganese intake (B = -2.436, p = 0.027) in the NODAP group. Habitual intake of minerals differs between individuals with NODAP, T2DM, and NAP. Prospective longitudinal studies and randomised controlled trials are now warranted to further investigate the associations between mineral intake and NODAP.

Genetic Support of A Causal Relationship Between Iron Status and Type 2 Diabetes: A Mendelian Randomization Study

CONTEXT

Iron overload is a known risk factor for type 2 diabetes (T2D); however, iron overload and iron deficiency have both been associated with metabolic disorders in observational studies.

OBJECTIVE

Using mendelian randomization (MR), we assessed how genetically predicted systemic iron status affected T2D risk.

METHODS

A 2-sample MR analysis was used to obtain a causal estimate. We selected genetic variants strongly associated (P < 5 × 10-8) with 4 biomarkers of systemic iron status from a study involving 48 972 individuals performed by the Genetics of Iron Status consortium and applied these biomarkers to the T2D case-control study (74 124 cases and 824 006 controls) performed by the Diabetes Genetics Replication and Meta-analysis consortium. The simple median, weighted median, MR-Egger, MR analysis using mixture-model, weighted allele scores, and MR based on a Bayesian model averaging approaches were used for the sensitivity analysis.

RESULTS

Genetically instrumented serum iron (odds ratio [OR]: 1.07; 95% CI, 1.02-1.12), ferritin (OR: 1.19; 95% CI, 1.08-1.32), and transferrin saturation (OR: 1.06; 95% CI, 1.02-1.09) were positively associated with T2D. In contrast, genetically instrumented transferrin, a marker of reduced iron status, was inversely associated with T2D (OR: 0.91; 95% CI, 0.87-0.96).

CONCLUSION

Genetic evidence supports a causal link between increased systemic iron status and increased T2D risk. Further studies involving various ethnic backgrounds based on individual-level data and studies regarding the underlying mechanism are warranted for reducing the risk of T2D.

Leptin Receptor-Deficient db/db Mice Show Significant Heterogeneity in Response to High Non-heme Iron Diet

Recent studies have shown an association between iron homeostasis, obesity and diabetes. In this work, we investigated the differences in the metabolic status and inflammation in liver, pancreas and visceral adipose tissue of leptin receptor-deficient db/db mice dependent on high iron concentration diet. 3-month-old male BKS-Leprdb/db/JOrlRj (db/db) mice were divided into two groups, which were fed with different diets containing high iron (29 g/kg, n = 57) or standard iron (0.178 g/kg; n = 42) concentrations for 4 months. As anticipated, standard iron-fed db/db mice developed obesity and diabetes. However, high iron-fed mice exhibited a wide heterogeneity. By dividing into two subgroups at the diabetes level, non-diabetic subgroup 1 (<13.5 mmol/l, n = 30) significantly differed from diabetic subgroup two (>13.5 mmol/l, n = 27). Blood glucose concentration, HbA1c value, inflammation markers interleukin six and tumor necrosis factor α and heme oxygenase one in visceral adipose tissue were reduced in subgroup one compared to subgroup two. In contrast, body weight, C-peptide, serum insulin and serum iron concentrations, pancreatic islet and signal ratio as well as cholesterol, LDL and HDL levels were enhanced in subgroup one. While these significant differences require further studies and explanation, our results might also explain the often-contradictory results of the metabolic studies with db/db mice.

Iron intake and multiple health outcomes: Umbrella review

Iron is an essential trace element, while excess iron can lead to different levels of physical abnormalities or diseases. This umbrella review aimed to conduct a systematic evaluation of the possible relationships between iron intake and various health outcomes. We retrieved PubMed, Embase, Web of Science, Scopus, and the Cochrane Database of Systematic Reviews from inception through May 2021. A total of 34 meta-analyses with 46 unique health outcomes were identified. Heme iron intake was positively associated with nine outcomes, including colorectal cancer, type 2 diabetes mellitus, and cardiovascular disease mortality, while dietary total iron intake could decrease the risk of colorectal adenoma, esophageal cancer, coronary heart disease, and depression. Iron supplementation was a protective factor against eight outcomes. However, it was associated with decreased length and weight gain. The quality of evidence for most outcomes was "low" or "very low" with the remaining eleven as "high" or "moderate". All outcomes were categorized as class III, IV, or NS based on evidence classification. Although high iron intake has been identified to be significantly associated with a range of outcomes, firm universal conclusions about its beneficial or negative effects cannot be drawn given the low quality of evidence for most outcomes.

An Analysis of the Multifaceted Roles of Heme in the Pathogenesis of Cancer and Related Diseases

Heme is an essential prosthetic group in proteins and enzymes involved in oxygen utilization and metabolism. Heme also plays versatile and fascinating roles in regulating fundamental biological processes, ranging from aerobic respiration to drug metabolism. Increasing experimental and epidemiological data have shown that altered heme homeostasis accelerates the development and progression of common diseases, including various cancers, diabetes, vascular diseases, and Alzheimer's disease. The effects of heme on the pathogenesis of these diseases may be mediated via its action on various cellular signaling and regulatory proteins, as well as its function in cellular bioenergetics, specifically, oxidative phosphorylation (OXPHOS). Elevated heme levels in cancer cells intensify OXPHOS, leading to higher ATP generation and fueling tumorigenic functions. In contrast, lowered heme levels in neurons may reduce OXPHOS, leading to defects in bioenergetics and causing neurological deficits. Further, heme has been shown to modulate the activities of diverse cellular proteins influencing disease pathogenesis. These include BTB and CNC homology 1 (BACH1), tumor suppressor P53 protein, progesterone receptor membrane component 1 protein (PGRMC1), cystathionine-β-synthase (CBS), soluble guanylate cyclase (sGC), and nitric oxide synthases (NOS). This review provides an in-depth analysis of heme function in influencing diverse molecular and cellular processes germane to disease pathogenesis and the modes by which heme modulates the activities of cellular proteins involved in the development of cancer and other common diseases.

Unintended Consequences: Nutritional Impact and Potential Pitfalls of Switching from Animal- to Plant-Based Foods

Consumers are shifting towards plant-based diets, driven by both environmental and health reasons. This has led to the development of new plant-based meat alternatives (PBMAs) that are marketed as being sustainable and good for health. However, it remains unclear whether these novel PBMAs to replace animal foods carry the same established nutritional benefits as traditional plant-based diets based on pulses, legumes and vegetables. We modelled a reference omnivore diet using NHANES 2017–2018 data and compared it to diets that substituted animal products in the reference diet with either traditional or novel plant-based foods to create flexitarian, vegetarian and vegan diets matched for calories and macronutrients. With the exception of the traditional vegan diet, all diets with traditional plant-based substitutes met daily requirements for calcium, potassium, magnesium, phosphorus, zinc, iron and Vitamin B12 and were lower in saturated fat, sodium and sugar than the reference diet. Diets based on novel plant-based substitutes were below daily requirements for calcium, potassium, magnesium, zinc and Vitamin B12 and exceeded the reference diet for saturated fat, sodium and sugar. Much of the recent focus has been on protein quality and quantity, but our case study highlights the risk of unintentionally increasing undesirable nutrients while reducing the overall nutrient density of the diet when less healthy plant-based substitutes are selected. Opportunities exist for PBMA producers to enhance the nutrient profile and diversify the format of future plant-based foods that are marketed as healthy, sustainable alternatives to animal-based products.

Diagnostic Power of Circulatory Metabolic Biomarkers as Metabolic Syndrome Risk Predictors in Community-Dwelling Older Adults in Northwest of England (A Feasibility Study)

Background: Metabolic Syndrome (MetS) is a cluster of risk factors for diabetes and cardiovascular diseases with pathophysiology strongly linked to aging. A range of circulatory metabolic biomarkers such as inflammatory adipokines have been associated with MetS; however, the diagnostic power of these markers as MetS risk correlates in elderly has yet to be elucidated. This cross-sectional study investigated the diagnostic power of circulatory metabolic biomarkers as MetS risk correlates in older adults. Methods: Hundred community dwelling older adults (mean age: 68.7 years) were recruited in a study, where their blood pressure, body composition and Pulse Wave Velocity (PWV) were measured; and their fasting capillary and venous blood were collected. The components of the MetS; and the serum concentrations of Interleukin-6 (IL-6), Tumor Necrosis Factor-α (TNF-α), Plasminogen Activator Inhibitor-I (PAI-I), Leptin, Adiponectin, Resistin, Cystatin-C, C-Reactive Protein (CRP), insulin and ferritin were measured within the laboratory, and the HOMA1-IR and Atherogenic Index of Plasma (AIP) were calculated. Results: Apart from other markers which were related with some cardiometabolic (CM) risk, after Bonferroni correction insulin had significant association with all components of Mets and AIP. These associations also remained significant in multivariate regression. The multivariate odds ratio (OR with 95% confidence interval (CI)) showed a statistically significant association between IL-6 (OR: 1.32 (1.06–1.64)), TNF-α (OR: 1.37 (1.02–1.84)), Resistin (OR: 1.27 (1.04–1.54)) and CRP (OR: 1.29 (1.09–1.54)) with MetS risk; however, these associations were not found when the model was adjusted for age, dietary intake and adiposity. In unadjusted models, insulin was consistently statistically associated with at least two CM risk factors (OR: 1.33 (1.16–1.53)) and MetS risk (OR: 1.24 (1.12–1.37)) and in adjusted models it was found to be associated with at least two CM risk factors and MetS risk (OR: 1.87 (1.24–2.83) and OR: 1.25 (1.09–1.43)) respectively. Area under curve (AUC) for receiver operating characteristics (ROC) demonstrated a good discriminatory diagnostics power of insulin with AUC: 0.775 (0.683–0.866) and 0.785 by cross validation and bootstrapping samples for at least two CM risk factors and AUC: 0.773 (0.653–0.893) and 0.783 by cross validation and bootstrapping samples for MetS risk. This was superior to all other AUC reported from the ROC analysis of other biomarkers. Area under precision-recall curve for insulin was also superior to all other markers (0.839 and 0.586 for at least two CM risk factors and MetS, respectively). Conclusion: Fasting serum insulin concentration was statistically linked with MetS and its risk, and this link is stronger than all other biomarkers. Our ROC analysis confirmed the discriminatory diagnostic power of insulin as CM and MetS risk correlate in older adults.

Vegetarian Diet: An Overview through the Perspective of Quality of Life Domains

Vegetarianism has gained more visibility in recent years. Despite the well-described effects of a vegetarian diet on health, its influence on the quality of life of the individuals who follow it still needs to be properly investigated. Quality of life relates to a subjective perception of well-being and functionality, and encompasses four main life domains: physical, psychological, social, and environmental. The adoption of a vegetarian diet, despite being a dietary pattern, could potentially influence and be influenced by all of these domains, either positively or negatively. This review aims to present an overview of the background, conceptualization, features, and potential effects of vegetarianism in all quality of life domains. The choice of adopting a vegetarian diet could have positive outcomes, such as better physical health, positive feelings related to the adoption of a morally correct attitude, an increased sense of belonging (to a vegetarian community), and lower environmental impact. Other factors, however, could have a negative impact on the quality of life of those choosing to abstain from meats or other animal products, especially when they go beyond one's control. These include the environment, the social/cultural group in which a person is inserted, gender-based differences, economic aspects, and a limited access to a wide variety of plant-based foods. It is important to understand all the effects of adopting a vegetarian diet-beyond its nutritional aspects. Not only do studies in this area provide more consistent data, but they may also contribute to mitigating all factors that might prevent individuals from adopting a vegetarian diet, or that may have a negative impact on the quality of life of those who already follow it.

Electronic structure and reactivity of heme bound insulin

Insulin resistance as well as insulin deficiency are said to be principal to the development of type 2 diabetes mellitus (T2Dm). Heme has also been suggested to play an important role in the disease etiology since many of the heme deficiency symptoms constitute the common pathological features of T2Dm. Besides, iron overload, higher heme iron intake and transfusion requiring diseases are associated with a higher risk of T2Dm development. In this study the interaction between these two key components i.e. heme and insulin has been studied spectroscopically under different conditions which include the effect of excess peptide as well as increasing pH. The resultant heme-insulin complexes in their reduced state are found to produce very little partially reduced oxygen species (PROS) on getting oxidized by molecular oxygen. The interaction between insulin and previously reported T2Dm relevant heme-amylin complex were also examined using absorption and resonance Raman spectroscopy. The corresponding data suggest that insulin sequesters heme from heme-amylin to form the much less cytotoxic heme-insulin.

Diabesity negatively affects transferrin saturation and iron status. The DICARIVA study

AIMS

The relationship between iron status, obesity and type 2 diabetes mellitus (T2DM) has scarcely been tested. This study hypothesizes that patients with obesity and T2DM have altered iron metabolism.

METHODS

537 T2DM patients were selected from the cross-sectional DICARIVA study excluding patients with high-sensitivity-C-reactive-protein (hs-CRP) ≥  10 mg/L. Three groups according to body mass index (BMI) and waist perimeter (WP) were analysed: a) BMI < 30 kg/m², non-high WP (n = 105); b) BMI < 30 kg/m², high WP (n = 202); and c) diabesity, BMI ≥  30 kg/m², high WP (n = 230). Group differences on cardiometabolic and iron status markers were tested.

RESULTS

Women had significantly lower iron, ferritin, and transferrin saturation (TSAT) but higher transferrin and total iron binding capacity than men. Triglycerides/HDL-c ratio, as insulin-resistance (IR) marker, was higher in men while hs-CRP in women. TSAT was inversely related to BMI and hs-CRP. The diabesity group showed the highest hs-CRP (p < 0.001) and IR (p < 0.001) with the lowest TSAT (p = 0.003).

CONCLUSIONS

Low TSAT was highly prevalent in diabesity, mainly in women, suggesting that IR, inflammation, and abdominal adiposity alter iron transport and accumulation. The convenience of iron supplementation in diabesity patients with low TSAT should be urgently assessed, due the pro-oxidant effects of excess iron.

Interaction of ApoMyoglobin with Heme-hIAPP complex

Human Islet Amyloid Polypeptide (hIAPP) or amylin, can bind heme and the resultant complexes are prone to generate partially reduced oxygen species (PROS). The formation of PROS and the related oxidative stress highlight the importance of Heme-hIAPP in the onset and development of Type 2 Diabetes mellitus (T2Dm) in humans. In this study, the interaction of Heme-hIAPP with apomyoglobin (ApoMb) has been investigated using a combination of spectroscopic and electrophoresis techniques. Absorption, resonance Raman data and gel electrophoresis results confirm that ApoMb can uptake heme from Heme-hIAPP and constitute a six-coordinate high-spin ferric heme active site identical to that of myoglobin (Mb). The heme transfer reaction has two distinct kinetic steps. A possible mechanism of this reaction involves heme transfer to the apoprotein in the first step followed by a reorganisation of the protein chain to form the active site of native Mb. Increase in the pH of the reaction medium enhances the rate of the second step of heme transfer. This possibly corresponds to the deprotonation of a propionate side chain of the heme moiety at high pH which facilitates secondary interactions with the conserved distal Lys45 residue of horse heart Mb. Additionally, ApoMb sequesters ligand bound heme from Heme-hIAPP. After the heme transfer reaction, the amount of PROS formed by Heme-hIAPP complex diminishes significantly. This not only potentially diminishes heme-induced toxicity in the pancreatic β-cells but also produces Mb which has well-documented functions throughout the respiratory system and can thereby likely reduce the risks associated with T2Dm.

Iron Status is Associated with Mood, Cognition, and Functional Ability in Older Adults: A Cross-Sectional Study

Several conditions are risk factors for iron deficiency (ID), some of which are highly prevalent in older individuals. Despite the amount of evidence pointing for a role of ID in cognition, mood and physical functional ability, the research addressing these associations in older individuals is still scarce. In the present study, 162 older community-dwelling individuals (29.53% classified as ID) were enrolled in a cross-sectional analysis and characterized regarding cognition, mood, functional ability, general nutritional intake and iron status. Assessment of iron status was performed using several blood biomarkers. Storage and erythropoiesis dimensions were positively associated with memory, along with an interaction (moderator effect) between iron storage and nutritional status. A more depressed mood was negatively associated with (iron) transport, transport saturation and erythropoiesis dimensions, and functional tiredness was positively associated with the erythropoiesis dimension. These observations indicate that lower iron status is associated with depressive mood, functional tiredness and poorer memory ability, with the latter moderated by nutritional status. These findings suggest that using iron as a continuous variable may be useful in finding associations with iron homeostasis, eventually missed when iron levels are considered within the usual classification groups.

Association between Habitual Dietary Iron Intake and Glucose Metabolism in Individuals after Acute Pancreatitis

Dietary intake of iron is known to be associated with impaired glucose metabolism. However, its involvement in derangements of glucose metabolism after acute pancreatitis (AP) is not completely understood. The aim was to investigate the association between dietary iron intake and markers of glucose metabolism in individuals after an attack of AP. Fasting blood samples were collected to analyse markers of glucose metabolism (fasting plasma glucose (FPG) and haemoglobin A1c (HbA1c)). The EPIC-Norfolk food frequency questionnaire was used to determine the habitual intake of dietary iron (total, haem, and non-haem). Multivariable linear regression analyses were conducted and six statistical models were built to adjust for covariates. A total of 109 individuals after AP were studied in a cross-sectional fashion. Total iron (β (95% confidence interval) = -0.19 (-0.35, -0.05); p = 0.01 in the most adjusted model) and non-haem iron (β (95% confidence interval) = -0.19 (-0.33, -0.04); p = 0.03 in the most adjusted model) were significantly associated with FPG, consistently in all adjusted model. Total iron and non-haem iron did not have consistent significant associations with HbA1c. Dietary haem iron intake was not associated with either FPG or HbA1c. Habitual intake of dietary iron is inversely associated with FPG in individuals after an attack of AP and may be involved in the pathogenesis of new-onset diabetes after pancreatitis. Prospective longitudinal studies are now warranted to unveil the specific mechanism underlying the involvement of dietary iron.

Iron metabolism and the exocrine pancreas

Although the pathophysiological mechanisms and consequences of gross derangements in iron metabolism are well known, little is known about the pathophysiological mechanisms underlying mild-to-moderate alterations in iron metabolism and their consequences. Growing evidence indicates that the exocrine pancreas has a bidirectional relationship with iron metabolism. Studies have shown alterations in circulating markers of iron metabolism, iron absorption, and intra-pancreatic iron deposition in pancreatitis. At the same time, exocrine pancreatic dysfunction has been shown in iron overload disorders. These observations reveal a compelling connection between the exocrine pancreas and iron metabolism, which are further elucidated by observations of therapeutic benefits of iron chelating agents and pancreatic enzyme replacement therapy. While the pancreas is not a major reservoir of iron in the body, better understanding of its relationship with iron metabolism may yield unexpected insights.

Maternal plant-based diet during gestation and pregnancy outcomes

PURPOSE

We aimed to explore the association of vegetarian-vegan diets and pregnancy outcomes.

METHODS

A retrospective, web-based study conducted in 2017. Women who delivered < 4 years prior to enrolment where eligible to participate. Participants were allocated to 3 groups based on their self-reported diet during pregnancy: omnivores, vegetarians or vegans. Outcomes of interest including birthweight centile, small for gestational age (SGA), large for gestational age (LGA), preterm birth (PTB), maternal excessive weight gain (EWG) and gestational diabetes (GDM) were compared between the groups.

RESULTS

Overall, 1419 women of which 234 vegans (16.5%), 133 vegetarian (9.4%) and 1052 omnivores (74.1%) were included in final analysis. Maternal vegan diet during pregnancy was associated with a lower birth weight centile as compared to omnivores (42.6 ± 25.9 vs. 52.5 ± 27.0 P < 0.001), a greater adjusted odds ratio (aOR) for SGA (aOR = 1.74; 95% CI 1.05, 2.86) but not with the risk of LGA (aOR = 0.55; 95% CI 0.30, 1.00). Further adjustment for BMI showed similar but nonsignificant associations for SGA and LGA as compared to the omnivore group. Vegan diet was associated with lower risk for maternal EWG (aOR = 0.61; 95% CI 0.44, 0.86) and modest nonsignificant association with GDM (aOR = 0.54 95% CI 0.28, 1.03) which was further attenuated by adjustment for pre-pregnancy BMI. Maternal diet group was not associated with the risk of PTB or low birth weight.

CONCLUSIONS

Maternal vegan diet is a protective factor from EWG but associated with a higher risk for SGA and lower birth weight centile. The association between vegan diet and fetal growth was mediated by maternal BMI.

Mediterranean Diet Effects on Type 2 Diabetes Prevention, Disease Progression, and Related Mechanisms. A Review

The search for a quality diet has grown over the past decade. Diet is considered one of the pillars for the prevention and progression of several diseases, among them: diabetes. Type 2 diabetes (T2D) is an epidemic of western countries that increases the vulnerability of other diseases, such as cardiovascular and cancer. T2D is associated with lifestyle and diet. The traditional Mediterranean diet has proven its benefits over several cardiovascular risk factors, and specifically on diabetes. This review compiles recent published evidence on the effects of the Mediterranean diet on the incidence and progression of type 2 diabetes (T2D) and its relation with several other cardiovascular healthy diets. We will also focus on how the Mediterranean diet could play a role in T2D-related mechanisms, such as anti-inflammatory or antioxidant compounds, glucagon-like peptide agonist compounds, and changes in gut microbiota. Each component of the Mediterranean diet could be involved in processes related to diabetes homeostasis, many of them sharing common physio-pathological pathways. The importance of this diet within the set of habits of a healthy lifestyle must be emphasized.

Iron metabolism and type 2 diabetes mellitus: A meta-analysis and systematic review

AIMS/INTRODUCTION

Iron metabolism can directly or indirectly affect the occurrence and development of type 2 diabetes. This meta-analysis and systematic review aimed to analyze the association between serum iron metabolism indicators and type 2 diabetes.

MATERIALS AND METHODS

The databases PubMed and Embase were searched for studies on the correlations between serum iron metabolism indicators (iron, ferritin, transferrin, hepcidin and soluble transferrin receptor) and type 2 diabetes since January 2006. Relevant data were extracted from the included studies, and meta-analysis was carried out.

RESULTS

A total of 12 case-control and cohort studies were analyzed. Of the 12 studies, 11 described the correlation between serum ferritin levels and type 2 diabetes. The median and high serum ferritin concentrations were significantly associated with the risks of type 2 diabetes (odds ratio [OR] 1.20, 95% confidence interval [CI] 1.08-1.33 and OR 1.43, 95% CI 1.29-1.59, respectively). However, the low concentration was not correlated with the risk of type 2 diabetes (OR 0.99, 95% CI 0.89-1.11). No significant association was observed between serum soluble transferrin receptor and type 2 diabetes, whereas the soluble transferrin receptor-to-ferritin ratio was significantly inversely related to the risk of type 2 diabetes in the median and high ratio subgroups (OR 0.71, 95% CI 0.51, 0.99 and OR 0.65, 95% CI 0.45-0.95).

CONCLUSIONS

The elevated serum ferritin was one of the risk factors for type 2 diabetes, and soluble transferrin receptor-to-ferritin ratio was inversely related to the risk of type 2 diabetes. A systematic review showed that serum transferrin and hepcidin might be directly or indirectly related to the development of diabetes.

Dietary Nonheme, Heme, and Total Iron Intake and the Risk of Diabetes in Adults: Results From the China Health and Nutrition Survey

OBJECTIVE

Excessive iron intake has been linked to diabetes risk. However, the evidence is inconsistent. This study examined the association between dietary heme and nonheme iron intake and diabetes risk in the Chinese population.

RESEARCH DESIGN AND METHODS

We included 17,026 adults (8,346 men and 8,680 women) who were part of the China Health and Nutrition Survey (1991-2015) prospective cohort. Dietary intake was measured by three consecutive 24-h dietary recalls combined with a household food inventory. Diabetes cases were identified through a questionnaire. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% CIs.

RESULTS

A total of 547 men and 577 women developed diabetes during 202,138 person-years of follow-up. For men, the adjusted HRs (95% CIs) for quintiles of nonheme iron intake were 1.00, 0.77 (0.58-1.02), 0.72 (0.54-0.97), 0.63 (0.46-0.85), and 0.87 (0.64-1.19) (P-nonlinearity = 0.0015). The corresponding HRs (95% CIs) for women were 1.00, 0.63 (0.48-0.84), 0.57 (0.43-0.76), 0.58 (0.43-0.77), and 0.67 (0.49-0.91) (P-nonlinearity < 0.0001). The dose-response curves for the association between nonheme iron and total iron intake and diabetes followed a reverse J shape in men and an L shape in women. No significant associations were observed between heme iron intake and diabetes risk.

CONCLUSIONS

Total iron and nonheme iron intake was associated with diabetes risk, following a reverse J-shaped curve in men and an L-shaped curve in women. Sufficient intake of nonheme or total iron might be protective against diabetes, while excessive iron intake might increase the risk of diabetes among men.

Food groups and the likelihood of non-alcoholic fatty liver disease: a systematic review and meta-analysis

Dietary habits have been implicated in the development and severity of non-alcoholic fatty liver disease (NAFLD). Several epidemiological studies attempted to assess the relationship between food groups and the likelihood of NAFLD, but these results were conflicting. The present meta-analysis was conducted to assess the association between food groups and the likelihood of NAFLD. Published literature was retrieved and screened from MEDLINE, Embase and Web of Science. Out of 7892 retrieved articles, twenty-four observational studies (fifteen cross-sectional studies and nine case–control studies) met our eligibility criteria and were finally included in this systematic review and meta-analysis. Consumption of both red meat and soft drinks contributed to a positive association with NAFLD. Inversely, nut consumption was negatively associated with NAFLD. There were no significant influences on the likelihood of NAFLD about consuming whole grains, refined grains, fish, fruits, vegetables, eggs, dairy products and legumes. This meta-analysis suggests that individuals who consumed more red meat and soft drinks may have a significantly increased likelihood of NAFLD, whereas higher nut intake may be negatively associated with NAFLD. Further prospective studies are required to assess the association between food patterns and NAFLD.

Sex-Specific Association of Circulating Ferritin Level and Risk of Type 2 Diabetes: A Dose-Response Meta-Analysis of Prospective Studies

CONTEXT

Although the role of iron in the development of type 2 diabetes (T2D) has long been a concern, prospective studies directly linking body iron stores to T2D risk in a sex-dependent context have been inconsistent.

OBJECTIVE

A systematic meta-analysis was conducted to explore the sex-specific association of circulating ferritin with T2D risk.

DATA SOURCES

We searched PubMed, Web of Science, and EMBASE databases to identify available prospective studies through 1 August 2018.

RESULTS

Fifteen prospective studies comprising 77,352 participants and 18,404 patients with T2D, aged 20 to 80 years, and with ∼3 to 17 years of follow-up were identified. For each 100-μg/L increment in ferritin levels of overall participants, T2D risk increased by 22% (RR, 1.22; 95% CI, 1.14 to 1.31). Of note, major heterogeneities by sex were identified, with increased ferritin level having an apparently greater effect on T2D risk in women (RR, 1.53; 95% CI, 1.29 to 1.82) than in men (RR, 1.21; 95% CI, 1.15 to 1.27) after exclusion of a study with high heterogeneity (41,512 men and 6974 women for sex-specific analyses; P = 0.020 for sex difference). Further nonlinear analysis between circulating ferritin and T2D risk also showed sex-dimorphic association in that the T2D risk of women was twice as strong in magnitude as that of men at the same ferritin level.

CONCLUSIONS

Greater circulating ferritin levels were independently associated with increased T2D risk, which appeared stronger among women than men. Our findings provide prospective evidence for further testing of the utility of ferritin levels in predicting T2D risk in a sex-specific manner.

Association of changes in red meat consumption with total and cause specific mortality among US women and men: two prospective cohort studies

OBJECTIVE

To evaluate the association of changes in red meat consumption with total and cause specific mortality in women and men.

DESIGN

Two prospective cohort studies with repeated measures of diet and lifestyle factors.

SETTING

Nurses' Health Study and the Health Professionals Follow-up Study, United States.

PARTICIPANTS

53 553 women and 27 916 men without cardiovascular disease or cancer at baseline.

MAIN OUTCOME MEASURE

Death confirmed by state vital statistics records, the national death index, or reported by families and the postal system.

RESULTS

14 019 deaths occurred during 1.2 million person years of follow-up. Increases in red meat consumption over eight years were associated with a higher mortality risk in the subsequent eight years among women and men (both P for trend<0.05, P for heterogeneity=0.97). An increase in total red meat consumption of at least half a serving per day was associated with a 10% higher mortality risk (pooled hazard ratio 1.10, 95% confidence interval 1.04 to 1.17). For processed and unprocessed red meat consumption, an increase of at least half a serving per day was associated with a 13% higher mortality risk (1.13, 1.04 to 1.23) and a 9% higher mortality risk (1.09, 1.02 to 1.17), respectively. A decrease in consumption of processed or unprocessed red meat of at least half a serving per day was not associated with mortality risk. The association between increased red meat consumption and mortality risk was consistent across subgroups defined by age, physical activity, dietary quality, smoking status, or alcohol consumption.

CONCLUSION

Increases in red meat consumption, especially processed meat, were associated with higher overall mortality rates.

Knowledge of diabetes and its determinants: a cross-sectional study among adults in a Japanese community

OBJECTIVE

To assess general knowledge of diabetes and its determinants among adult men and women in a Japanese community.

SETTING

A cross-sectional study with the residential registry in Gifu City. Blood tests were conducted to measure fasting blood glucose levels and the levels after 2 hours of a 75-gram oral glucose load. Participants' previous diagnosis of diabetes and demographic status were identified from a questionnaire. A validated food frequency questionnaire was also administered. To assess the association between good knowledge of diabetes and the level of each factor, a logistic regression was utilised with adjustments for age, education and parental history of diabetes.

PARTICIPANTS

A total of 1019 men and women aged 40-78 years.

PRIMARY OUTCOME MEASURE

The Diabetes Knowledge Questionnaire was administered. Participants with ≥75% of answers correct were defined as having a good knowledge of diabetes.

RESULTS

Previous diagnosis of diabetes was significantly associated with good knowledge of diabetes (OR=2.36; 95% CI 1.19 to 4.68). Among individuals with no previous diagnosis of diabetes, age ≥60 years (OR=0.55; 95% CI 0.36 to 0.86, p value for trend=0.02) and education <12 years (OR=0.54; 95% CI 0.30 to 0.97) were significantly associated with low knowledge of diabetes. The highest tertile intakes of green-yellow vegetables (OR=1.77; 95% CI 1.07 to 2.91, p value for trend=0.03) and seafood (OR=1.76; 95% CI 1.04 to 2.95, p value for trend=0.03) were associated with high knowledge of diabetes.

CONCLUSIONS

Some diabetes risk factors were implied to determine the general knowledge of diabetes. Conducting further studies of knowledge in various populations is warranted.

Is Grassfed Meat and Dairy Better for Human and Environmental Health?

The health of livestock, humans, and environments is tied to plant diversity-and associated phytochemical richness-across landscapes. Health is enhanced when livestock forage on phytochemically rich landscapes, is reduced when livestock forage on simple mixture or monoculture pastures or consume high-grain rations in feedlots, and is greatly reduced for people who eat highly processed diets. Circumstantial evidence supports the hypothesis that phytochemical richness of herbivore diets enhances biochemical richness of meat and dairy, which is linked with human and environmental health. Among many roles they play in health, phytochemicals in herbivore diets protect meat and dairy from protein oxidation and lipid peroxidation that cause low-grade systemic inflammation implicated in heart disease and cancer in humans. Yet, epidemiological and ecological studies critical of red meat consumption do not discriminate among meats from livestock fed high-grain rations as opposed to livestock foraging on landscapes of increasing phytochemical richness. The global shift away from phytochemically and biochemically rich wholesome foods to highly processed diets enabled 2.1 billion people to become overweight or obese and increased the incidence of type II diabetes, heart disease, and cancer. Unimpeded, these trends will add to a projected substantial increase in greenhouse gas emissions (GHGE) from producing food and clearing land by 2050. While agriculture contributes one quarter of GHGE, livestock can play a sizable role in climate mitigation. Of 80 ways to alleviate climate change, regenerative agriculture-managed grazing, silvopasture, tree intercropping, conservation agriculture, and farmland restoration-jointly rank number one as ways to sequester GHG. Mitigating the impacts of people in the Anthropocene can be enabled through diet to improve human and environmental health, but that will require profound changes in society. People will have to learn we are members of nature's communities. What we do to them, we do to ourselves. Only by nurturing them can we nurture ourselves.

Mineral Nutrition and the Risk of Chronic Diseases: A Mendelian Randomization Study

We applied Mendelian randomization analyses to investigate the potential causality between blood minerals (calcium, magnesium, iron, copper, and zinc) and osteoporosis (OP), gout, rheumatoid arthritis (RA), type 2 diabetes (T2D), Alzheimer’s disease (AD), bipolar disorder (BD), schizophrenia, Parkinson’s disease and major depressive disorder. Single nucleotide polymorphisms (SNPs) that are independent (r² < 0.01) and are strongly related to minerals (p < 5 × 10⁻⁸) are selected as instrumental variables. Each standard deviation increase in magnesium (0.16 mmol/L) is associated with an 8.94-fold increase in the risk of RA (p = 0.044) and an 8.78-fold increase in BD (p = 0.040) but a 0.10 g/cm² increase in bone density related to OP (p = 0.014). Each per-unit increase in copper is associated with a 0.87-fold increase in the risk of AD (p = 0.050) and BD (p = 0.010). In addition, there is suggestive evidence that calcium is positively correlated (OR = 1.36, p = 0.030) and iron is negatively correlated with T2D risk (OR = 0.89, p = 0.010); both magnesium (OR = 0.26, p = 0.013) and iron (OR = 0.71, p = 0.047) are negatively correlated with gout risk. In the sensitivity analysis, causal estimation is not affected by pleiotropy. This study supports the long-standing hypothesis that magnesium supplementation can increase RA and BD risks and decrease OP risk and that copper intake can reduce AD and BD risks. This study will be helpful to address some controversial debates on the relationships between minerals and chronic diseases.