Iron restriction improves type 2 diabetes mellitus in Otsuka Long-Evans Tokushima fatty rats

The Role of Iron Overload in Diabetic Cognitive Impairment: A Review

It is well documented that diabetes mellitus (DM) is strongly associated with cognitive decline and structural damage to the brain. Cognitive deficits appear early in DM and continue to worsen as the disease progresses, possibly due to different underlying mechanisms. Normal iron metabolism is necessary to maintain normal physiological functions of the brain, but iron deposition is one of the causes of some neurodegenerative diseases. Increasing evidence shows that iron overload not only increases the risk of DM, but also contributes to the development of cognitive impairment. The current review highlights the role of iron overload in diabetic cognitive impairment (DCI), including the specific location and regulation mechanism of iron deposition in the diabetic brain, the factors that trigger iron deposition, and the consequences of iron deposition. Finally, we also discuss possible therapies to improve DCI and brain iron deposition.

Fatty infiltration of the pancreas: a systematic concept analysis

Fatty infiltration of the pancreas (FIP) has been recognized for nearly a century, yet many aspects of this condition remain unclear. Regular literature reviews on the diagnosis, consequences, and management of FIP are crucial. This review article highlights the various disorders for which FIP has been established as a risk factor, including type 2 diabetes mellitus (T2DM), pancreatitis, pancreatic fistula (PF), metabolic syndrome (MS), polycystic ovary syndrome (PCOS), and pancreatic duct adenocarcinoma (PDAC), as well as the new investigation tools. Given the interdisciplinary nature of FIP research, a broad range of healthcare specialists are involved. This review article covers key aspects of FIP, including nomenclature and definition of pancreatic fat infiltration, history and epidemiology, etiology and pathophysiology, clinical presentation and diagnosis, clinical consequences, and treatment. This review is presented in a detailed narrative format for accessibility to clinicians and medical students.

Effect of small peptide chelated iron on growth performance, immunity and intestinal health in weaned pigs

BACKGROUND

Small peptide chelated iron (SPCI), a novel iron supplementation in pig diets, owns growth-enhancing characteristics. Although a number of researches have been performed, there is no clear-cut evidence to show the exact relationship between the dose and effects of small peptide chelated minerals. Therefore, we investigated the effect of dietary supplementation of SPCI at different doses in the growth performance, immunity, and intestinal health in weaned pigs.

METHODS

Thirty weaned pigs were randomly assigned into five groups and feed with basal diet or the basal diet containing 50, 75, 100, or 125 mg/kg Fe as SPCI diets. The experiment lasted for 21 d and on day 22, blood samples were collected 1 h later. The tissue and intestinal mucosa samples were collected following.

RESULTS

Our results showed that the feed to gain ratio (F:G) decreased with different levels of SPCI addition (P < 0.05). The average daily gain (ADG) (P < 0.05) and digestibility of crude protein (P < 0.01) decreased with 125 mg/kg SPCI addition. With dietary different levels of SPCI addition, the serum concentrations of ferritin (quadratic, P < 0.001), transferrin (quadratic, P < 0.001), iron content in liver (quadratic, P < 0.05), gallbladder (quadratic, P < 0.01) and fecal (quadratic, P < 0.01) increased quadraticly. While the iron content in tibia (P < 0.01) increased by 100 mg/kg SPCI supplementation. Dietary 75 mg/kg SPCI addition increased the serum insulin-like growth factor I (IGF-I) (P < 0.01) and SPCI (75 ~ 100 mg/kg) addition also increased the serum content of IgA (P < 0.01). The serum concentrations of IgG (quadratic, P < 0.05) and IgM (quadratic, P < 0.01) increased quadraticly by different levels of SPCI supplementation. Moreover, different levels of SPCI supplementation decreased the serum concentration of D-lactic acid (P < 0.01). The serum glutathione peroxidase (GSH-Px) (P < 0.01) elevated but the malondialdehyde (MDA) (P < 0.05) decreased by 100 mg/kg SPCI addition. Interestingly, SPCI supplementation at 75 ~ 100 mg/kg improved the intestinal morphology and barrier function, as suggested by enhanced villus height (P < 0.01) and villus height/crypt depth (V/C) (P < 0.01) in duodenum, as well as jejunum epithelium tight-junction protein ZO-1 (P < 0.01). Moreover, SPCI supplementation at 75 ~ 100 mg/kg increased the activity of duodenal lactase (P < 0.01), jejunal sucrase (P < 0.01) and ileal maltase (P < 0.01). Importantly, the expression levels of divalent metal transporter-1(DMT1) decreased with different levels of SPCI addition (P < 0.01). In addition, dietary SPCI supplementation at 75 mg/kg elevated the expression levels of critical functional genes such as peptide transporter-1(PePT1) (P = 0.06) and zinc transporter 1 (ZnT1) (P < 0.01) in ileum. The expression levels of sodium/glucose co-transporter-1 (SGLT1) in ileum (quadratic, P < 0.05) increased quadraticly by different levels of SPCI addition and amino acid transporter-1 (CAT1) in jejunum(P < 0.05) also increased by 100 mg/kg SPCI addition.

CONCLUSIONS

Dietary SPCI supplementation at 75 ~ 100 mg/kg improved growth performance by elevated immunity and intestinal health.

Iron and the Pathophysiology of Diabetes

High iron is a risk factor for type 2 diabetes mellitus (T2DM) and affects most of its cardinal features: decreased insulin secretion, insulin resistance, and increased hepatic gluconeogenesis. This is true across the normal range of tissue iron levels and in pathologic iron overload. Because of iron's central role in metabolic processes (e.g., fuel oxidation) and metabolic regulation (e.g., hypoxia sensing), iron levels participate in determining metabolic rates, gluconeogenesis, fuel choice, insulin action, and adipocyte phenotype. The risk of diabetes related to iron is evident in most or all tissues that determine diabetes phenotypes, with the adipocyte, beta cell, and liver playing central roles. Molecular mechanisms for these effects are diverse, although there may be integrative pathways at play. Elucidating these pathways has implications not only for diabetes prevention and treatment, but also for the pathogenesis of other diseases that are, like T2DM, associated with aging, nutrition, and iron.

The role of iron metabolism in chronic diseases related to obesity

Obesity is one of the major public health problems threatening the world, as well as a potential risk factor for chronic metabolic diseases. There is growing evidence that iron metabolism is altered in obese people, however, the highly refined regulation of iron metabolism in obesity and obesity-related complications is still being investigated. Iron accumulation can affect the body’s sensitivity to insulin, Type 2 diabetes, liver disease and cardiovascular disease. This review summarized the changes and potential mechanisms of iron metabolism in several chronic diseases related to obesity, providing new clues for future research.

Ferroptosis Signaling in Pancreatic β-Cells: Novel Insights & Therapeutic Targeting

Metabolic stress impairs pancreatic β-cell survival and function in diabetes. Although the pathophysiology of metabolic stress is complex, aberrant tissue damage and β-cell death are brought on by an imbalance in redox equilibrium due to insufficient levels of endogenous antioxidant expression in β-cells. The vulnerability of β-cells to oxidative damage caused by iron accumulation has been linked to contributory β-cell ferroptotic-like malfunction under diabetogenic settings. Here, we take into account recent findings on how iron metabolism contributes to the deregulation of the redox response in diabetic conditions as well as the ferroptotic-like malfunction in the pancreatic β-cells, which may offer insights for deciphering the pathomechanisms and formulating plans for the treatment or prevention of metabolic stress brought on by β-cell failure.

Adipose tissue macrophages exert systemic metabolic control by manipulating local iron concentrations

Iron is essential to many fundamental biological processes, but its cellular compartmentalization and concentration must be tightly controlled. Although iron overload can contribute to obesity-associated metabolic deterioration, the subcellular localization and accumulation of iron in adipose tissue macrophages is largely unknown. Here, we show that macrophage mitochondrial iron levels control systemic metabolism in male mice by altering adipocyte iron concentrations. Using various transgenic mouse models to manipulate the macrophage mitochondrial matrix iron content in an inducible fashion, we demonstrate that lowering macrophage mitochondrial matrix iron increases numbers of M2-like macrophages in adipose tissue, lowers iron levels in adipocytes, attenuates inflammation and protects from high-fat-diet-induced metabolic deterioration. Conversely, elevating macrophage mitochondrial matrix iron increases M1-like macrophages and iron levels in adipocytes, exacerbates inflammation and worsens high-fat-diet-induced metabolic dysfunction. These phenotypes are robustly reproduced by transplantation of a small amount of fat from transgenic to wild-type mice. Taken together, we identify macrophage mitochondrial iron levels as a crucial determinant of systemic metabolic homeostasis in mice.

Serum Activities of Ferritin Among Controlled and Uncontrolled Type 2 Diabetes Mellitus Patients

Background

Diabetes mellitus (DM) is a metabolic disorder characterized by the cells' inefficient utilization of blood glucose. DM occurs in two types: type 1 DM (T1DM) and type 2 DM (T2DM). DM results in increased blood sugar levels attributed to the non-functioning of the insulin-producing islet cells of the pancreas (type 1 DM) and insulin resistance, among other causes. Despite the initiation of treatment, in some people, diabetes remains uncontrolled and, over some time, could cause damage to other organs of the body, including the eyes, heart, and kidneys, among others. Recently, it was observed that iron metabolism and increased activity of serum ferritin (hyperferritinemia) could influence the development of T2DM. This study aims to assess the activities of ferritin among controlled and uncontrolled T2DM patients and compare them with the control group who were non-diabetic.

Methods

The study included 30 controlled and uncontrolled T2DM patients and an equal number of controls. The study was conducted between September and October 2021, and all patients included were those attending the General Medicine outpatient department attached to the RVM Institute of Medical Sciences and Research Centre, Siddipet, Telangana, South India. Blood glucose activities were estimated by the glucose oxidase-peroxidase (GOD-POD) method using the Randox Daytona plus analyzer, and serum ferritin was measured by the chemiluminescence method using the Beckmann Coulter Access 2 instrument.

Results

The mean age of the cases and the controls was 56.5 years and 46.7 years, respectively. Serum ferritin activities among people with controlled diabetes (73.3±56.6 ng/ml) (p=0.0003) and uncontrolled diabetes (269.8±347.1 ng/ml) (p=0.0006) varied significantly as compared to the controls (40.853±15.55). Glucose activities among controls (82.9±7.4 mg/dl), controlled T2DM patients (120.9±28.6 mg/dl), and uncontrolled T2DM patients (316.06±145.41 mg/dl) also showed significant differences.

Conclusion

Hyperferritinemia is evident among uncontrolled T2DM patients. However, increased serum ferritin activities were also noted among controlled T2DM patients as compared to normal activities observed in the non-diabetic control group.

The role of iron in obesity and diabetes

Iron is an essential trace metal for all life, but excess iron causes oxidative stress through catalyzing the toxic hydroxy-radical production via the Fenton reaction. The number of patients with obesity and diabetes has been increasing worldwide, and their onset and development are affected by diet. In both clinical and experimental studies, a high body iron content was associated with obesity and diabetes, and the reduction of body iron content to an appropriate level can ameliorate the status and development of obesity and diabetes. Macrophages play an essential role in the pathophysiology of obesity and diabetes, and in the metabolism and homeostasis of iron in the body. Recent studies demonstrated that macrophage polarization is related to adipocyte hypertrophy and insulin resistance through their capabilities of iron handling. Control of iron in macrophages is a potential therapeutic strategy for obesity and diabetes. J. Med. Invest. 69 : 1-7, February, 2022.

Dietary Iron Restriction Improves Muscle Function, Dyslipidemia, and Decreased Muscle Oxidative Stress in Streptozotocin-Induced Diabetic Rats

Diabetes mellitus is a chronic degenerative disease characterized by hyperglycemia and oxidative stress. Iron catalyzes free radical overproduction. High iron concentrations have previously been reported to promote an increase in oxidative stress; however, the effect of iron restriction in diabetes has not yet been explored, so we tested to see if iron restriction in diabetic rats reduces oxidative damage and improved muscle function. Wistar rats were assigned to 4 groups: Control; Diabetic; Diabetic rats with a high iron diet, and Diabetic with dietary iron restriction. After 8 weeks the rats were sacrificed, the muscles were extracted to prepare homogenates, and serum was obtained for biochemical measurements. Low iron diabetic rats showed an increase in the development of muscle strength in both muscles. Dietary iron restriction decreased triglyceride concentrations compared to the untreated diabetic rats and the levels of extremely low-density lipoproteins. Aggravation of lipid peroxidation was observed in the diabetic group with a high iron diet, while these levels remained low with iron restriction. Iron restriction improved muscle strength development and reduced fatigue times; this was related to better lipid profile control and decreased oxidant stress markers.

The Role of Estrogen Signaling in Cellular Iron Metabolism in Pancreatic β Cells

ABSTRACT

Several lines of evidence suggest that estrogen (17-β estradiol; E2) protects against diabetes mellitus and plays important roles in pancreatic β-cell survival and function. Mounting clinical and experimental evidence also suggest that E2 modulates cellular iron metabolism by regulating the expression of several iron regulatory genes, including hepcidin (HAMP), hypoxia-inducible factor 1-α, ferroportin (SLC40A1), and lipocalin (LCN2). However, whether E2 regulates cellular iron metabolism in pancreatic β cells and whether the antidiabetic effects of E2 can be, at least partially, attributed to its role in iron metabolism is not known. In this context, pancreatic β cells express considerable levels of conventional E2 receptors (ERs; mainly ER-α) and nonconventional G protein-coupled estrogen receptors and hence responsive to E2 signals. Moreover, pancreatic islet cells require significant amounts of iron for proper functioning, replication and survival and, hence, well equipped to manage cellular iron metabolism (acquisition, utilization, storage, and release). In this review, we examine the link between E2 and cellular iron metabolism in pancreatic β cells and discuss the bearing of such a link on β-cell survival and function.

The Interplay between Insulin Resistance, Inflammation, Oxidative Stress, Base Excision Repair and Metabolic Syndrome in Nonalcoholic Fatty Liver Disease

One of the most common chronic liver disorders, affecting mainly people in Western countries, is nonalcoholic fatty liver disease (NAFLD). Unfortunately, its pathophysiological mechanism is not fully understood, and no dedicated treatment is available. Simple steatosis can lead to nonalcoholic steatohepatitis and even to fibrosis, cancer, and cirrhosis of the liver. NAFLD very often occurs in parallel with type 2 diabetes mellitus and in obese people. Furthermore, it is much more likely to develop in patients with metabolic syndrome (MS), whose criteria include abdominal obesity, elevated blood triacylglycerol level, reduced high-density lipoprotein cholesterol level, increased blood pressure, and high fasting glucose. An important phenomenon in MS is also insulin resistance (IR), which is very common in NAFLD. Liver IR and NAFLD development are linked through an interaction between the accumulation of free fatty acids, hepatic inflammation, and increased oxidative stress. The liver is particularly exposed to elevated levels of reactive oxygen species due to a large number of mitochondria in hepatocytes. In these organelles, the main DNA repair pathway is base excision repair (BER). The present article will illustrate how impairment of BER may be related to the development of NAFLD.

Iron loading induces cholesterol synthesis and sensitizes endothelial cells to TNFα-mediated apoptosis

In plasma, iron is normally bound to transferrin, the principal protein in blood responsible for binding and transporting iron throughout the body. However, in conditions of iron overload when the iron-binding capacity of transferrin is exceeded, non-transferrin-bound iron (NTBI) appears in plasma. NTBI is taken up by hepatocytes and other parenchymal cells via NTBI transporters and can cause cellular damage by promoting the generation of reactive oxygen species. However, how NTBI affects endothelial cells, the most proximal cell type exposed to circulating NTBI, has not been explored. We modeled in vitro the effects of systemic iron overload on endothelial cells by treating primary human umbilical vein endothelial cells (HUVECs) with NTBI (ferric ammonium citrate [FAC]). We showed by RNA-Seq that iron loading alters lipid homeostasis in HUVECs by inducing sterol regulatory element-binding protein 2-mediated cholesterol biosynthesis. We also determined that FAC increased the susceptibility of HUVECs to apoptosis induced by tumor necrosis factor-α (TNFα). Moreover, we showed that cholesterol biosynthesis contributes to iron-potentiated apoptosis. Treating HUVECs with a cholesterol chelator hydroxypropyl-β-cyclodextrin demonstrated that depletion of cholesterol was sufficient to rescue HUVECs from TNFα-induced apoptosis, even in the presence of FAC. Finally, we showed that FAC or cholesterol treatment modulated the TNFα pathway by inducing novel proteolytic processing of TNFR1 to a short isoform that localizes to lipid rafts. Our study raises the possibility that iron-mediated toxicity in human iron overload disorders is at least in part dependent on alterations in cholesterol metabolism in endothelial cells, increasing their susceptibility to apoptosis.

The Use of Natural Compounds as a Strategy to Counteract Oxidative Stress in Animal Models of Diabetes Mellitus

Diabetes mellitus (DM) is a chronic metabolic disease characterised by insulin deficiency, resulting in hyperglycaemia, a characteristic symptom of type 2 diabetes mellitus (DM2). DM substantially affects numerous metabolic pathways, resulting in β-cell dysfunction, insulin resistance, abnormal blood glucose levels, impaired lipid metabolism, inflammatory processes, and excessive oxidative stress. Oxidative stress can affect the body’s normal physiological function and cause numerous cellular and molecular changes, such as mitochondrial dysfunction. Animal models are useful for exploring the cellular and molecular mechanisms of DM and improving novel therapeutics for their safe use in human beings. Due to their health benefits, there is significant interest in a wide range of natural compounds that can act as naturally occurring anti-diabetic compounds. Due to rodent models’ relatively similar physiology to humans and ease of handling and housing, they are widely used as pre-clinical models for studying several metabolic disorders. In this review, we analyse the currently available rodent animal models of DM and their advantages and disadvantages and highlight the potential anti-oxidative effects of natural compounds and their mechanisms of action.

Effects of dietary iron level on growth performance, hematological status, and intestinal function in growing-finishing pigs

This study investigated the different addition levels of iron (Fe) in growing-finishing pigs and the effect of different Fe levels on growth performance, hematological status, intestinal barrier function, and intestinal digestion. A total of 1,200 barrows and gilts ([Large White × Landrace] × Duroc) with average initial body weight (BW; 27.74 ± 0.28 kg) were housed in 40 pens of 30 pigs per pen (gilts and barrows in half), blocked by BW and gender, and fed five experimental diets (eight replicate pens per diet). The five experimental diets were control diet (basal diet with no FeSO4 supplementation), and the basal diet being supplemented with 150, 300, 450, or 600 mg/kg Fe as FeSO4 diets. The trial lasted for 100 d and was divided into the growing phase (27 to 60 kg of BW) for the first 50 d and the finishing phase (61 to 100 kg of BW) for the last 50 d. The basal diet was formulated with an Fe-free trace mineral premix and contained 203.36 mg/kg total dietary Fe in the growing phase and 216.71 mg/kg in the finishing phase based on ingredient contributions. And at the end of the experiment, eight pigs (four barrows and four gilts) were randomly selected from each treatment (selected one pig per pen) for digesta, blood, and intestinal samples collection. The results showed that the average daily feed intake (P = 0.025), average daily gain (P = 0.020), and BW (P = 0.019) increased linearly in the finishing phase of pigs fed with the diets containing Fe. On the other hand, supplementation with different Fe levels in the diet significantly increased serum iron and transferrin saturation concentrations (P < 0.05), goblet cell numbers of duodenal villous (P < 0.001), and MUC4 mRNA expression (P < 0.05). The apparent ileal digestibility (AID) of amino acids (AA) for pigs in the 450 and 600 mg/kg Fe groups was greater (P < 0.05) than for pigs in the control group. In conclusion, dietary supplementation with 450 to 600 mg/kg Fe improved the growth performance of pigs by changing hematological status and by enhancing intestinal goblet cell differentiation and AID of AA.

Starch composition, glycemic indices, antioxidant properties and carbohydrate hydrolyzing enzymes activities of African star apple fruit parts

Background

African star apple (Chrysophyllum albidum) is a traditonal fruit, which is predominant in tropical regions with the fruit parts consumed by the populace and used in folklore to manage diabetes. However, the likely activity mechanism is still undetermined. The current study examined and compared the inhibitory abilities of African star apple fruit parts on selected key enzymes related to diabetes mellitus in the pancreas tissue of rat.

Methods

Inhibitory effect of aqueous extract (1:10 w/v) of African star apple fruit parts (pulp, cotyledon, seed coat and pulp coat) on the activities of α-amylase, α-glucosidase, as well as their starch composition, phenolic constituents, estimated glycemic index, and antioxidant properties were assessed.

Results

The fruit parts showed low sugar, eGI, amylose, and amylopectin contents. The analysis also showed that the fruit parts inhibited α-glucosidase and α-amylase activities and exhibited antioxidant properties. Furthermore, the fruit parts contain high concentrations of beta-amyrin acetate, eleagine, epicatechin, epigallocatechin, skatole, stigmasterol and tetrahydro − 2- methylharman as revealed by HPLC-DAD.

Conclusion

The fruit part low estimated glycemic indices, strong antioxidant properties, inhibition of α-amylase and α-glucosidase activities exhibited might be related to the bioactive compounds contained in the extract. This could also be a potential mechanism for the use in the prevention and management of type-2 diabetes. Nevertheless, the African star apple pulp coat displayed the highest property in comparison to other parts of the fruit.

Deletion of H-ferritin in macrophages alleviates obesity and diabetes induced by high-fat diet in mice

AIMS/HYPOTHESIS

Iron accumulation affects obesity and diabetes, both of which are ameliorated by iron reduction. Ferritin, an iron-storage protein, plays a crucial role in iron metabolism. H-ferritin exerts its cytoprotective action by reducing toxicity via its ferroxidase activity. We investigated the role of macrophage H-ferritin in obesity and diabetes.

METHODS

Conditional macrophage-specific H-ferritin (Fth, also known as Fth1) knockout (LysM-Cre Fth KO) mice were used and divided into four groups: wild-type (WT) and LysM-Cre Fth KO mice with normal diet (ND), and WT and LysM-Cre Fth KO mice with high-fat diet (HFD). These mice were analysed for characteristics of obesity and diabetes, tissue iron content, inflammation, oxidative stress, insulin sensitivity and metabolic measurements. RAW264.7 macrophage cells were used for in vitro experiments.

RESULTS

Iron concentration reduced, and mRNA expression of ferroportin increased, in macrophages from LysM-Cre Fth KO mice. HFD-induced obesity was lower in LysM-Cre Fth KO mice than in WT mice at 12 weeks (body weight: KO 34.6 ± 5.6 g vs WT 40.1 ± 5.2 g). mRNA expression of inflammatory cytokines and infiltrated macrophages and oxidative stress increased in the adipose tissue of HFD-fed WT mice, but was not elevated in HFD-fed LysM-Cre Fth KO mice. However, WT mice fed an HFD had elevated iron concentration in adipose tissue and spleen, which was not observed in LysM-Cre Fth KO mice fed an HFD (adipose tissue [μmol Fe/g protein]: KO 1496 ± 479 vs WT 2316 ± 866; spleen [μmol Fe/g protein]: KO 218 ± 54 vs WT 334 ± 83). Moreover, HFD administration impaired both glucose tolerance and insulin sensitivity in WT mice, which was ameliorated in LysM-Cre Fth KO mice. In addition, energy expenditure, mRNA expression of thermogenic genes, and body temperature were higher in KO mice with HFD than WT mice with HFD. In vitro experiments showed that iron content was reduced, and lipopolysaccharide-induced Tnf-α (also known as Tnf) mRNA upregulation was inhibited in a macrophage cell line transfected with Fth siRNA.

CONCLUSIONS/INTERPRETATION

Deletion of macrophage H-ferritin suppresses the inflammatory response by reducing intracellular iron levels, resulting in the prevention of HFD-induced obesity and diabetes. The findings from this study highlight macrophage iron levels as a potential therapeutic target for obesity and diabetes.

Surgical Mouse Models of Vertical Sleeve Gastrectomy and Roux-en Y Gastric Bypass: a Review

Reviewed here are multiple mouse models of vertical sleeve gastrectomy (VSG) and Roux-en Y gastric bypass (RYGB) that have emerged over the past decade. These models use diverse approaches to both operative and perioperative procedures. Scrutinizing the benefits and pitfalls of each surgical model and what to expect in terms of post-operative outcomes will enhance our assessment of studies using mouse models, as well as advance our understanding of their translational potential. Two mouse models of bariatric surgery, VSG-lembert and RYGB-small pouch, demonstrate low mortality and most closely recapitulate the human forms of surgery. The use of liquid diets can be minimized, and in mice, RYGB demonstrates more reliable and longer lasting effects on weight loss compared to that of VSG.

Ginsenoside Re Attenuates High Glucose-Induced RF/6A Injury via Regulating PI3K/AKT Inhibited HIF-1α/VEGF Signaling Pathway

Hyperglycaemia-induced retinal microvascular endothelial cell apoptosis is a critical and principle event in diabetic retinopathy (DR), which involves a series of complex processes such as mitochondrial dysfunction and oxidative stress. Ginsenoside Re (Re), a key ingredients of ginseng, is considered to have various pharmacologic functions, such as antioxidative, inhibition of inflammation and anti-apoptotic properties. However, the effects of Re in DR and the related mechanisms of endothelial cell injury induced by high glucose (HG) exposure remain unclear. The present study was designed to investigate and evaluate the ability of Re to ameliorate HG-induced retinal endothelial RF/6A cell injury and the potential mechanisms involved in the hypoxia-inducible factor-1-alpha (HIF-1α)/vascular endothelial growth factor (VEGF) signaling regulated by phosphoinositide 3-kinase (PI3K)/AKT pathway. Our results showed that preincubation with Re exerted cytoprotective effects by reversing the HG-induced decrease in RF/6A cell viability, downregulation of apoptosis rate and inhibition of oxidative-related enzymes, thereby reducing the excess intracellular reactive oxygen species (ROS) and HG-triggered RF/6A cell injury. In addition, Western blot analysis results showed ginsenoside Re significantly increased HIF-1α expression in the cytoplasm but decreased its expression in the nucleus, suggesting that it reduced the translocation of HIF-1α from the cytoplasm to the nucleus, and downregulated VEGF level. Moreover, this effect is involved in the activation of the PI3K/Akt pathway. LY294002, a PI3K inhibitor, was used to block the Akt pathway. Afterwards, the effects of Re on the regulation of apoptotic related proteins, VEGF and HIF-1α nuclear transcription was partially reversed. These findings suggested the exerting protective effects of ginsenoside Re were associated with regulating of PI3K/AKT and HIF-1α/VEGF signaling pathway, which indicates that ginsenoside Re may ameliorates HG-induced retinal angiogenesis and suggests the potential for the development of Re as a therapeutic for DR.

Trace Elements, PPARs, and Metabolic Syndrome

Metabolic syndrome (MetS) is a constellation of metabolic derangements, including central obesity, insulin resistance, hypertension, glucose intolerance, and dyslipidemia. The pathogenesis of MetS has been intensively studied, and now many factors are recognized to contribute to the development of MetS. Among these, trace elements influence the structure of proteins, enzymes, and complex carbohydrates, and thus an imbalance in trace elements is an independent risk factor for MetS. The molecular link between trace elements and metabolic homeostasis has been established, and peroxisome proliferator-activated receptors (PPARs) have appeared as key regulators bridging these two elements. This is because on one hand, PPARs are actively involved in various metabolic processes, such as abdominal adiposity and insulin sensitivity, and on the other hand, PPARs sensitively respond to changes in trace elements. For example, an iron overload attenuates hepatic mRNA expression of Ppar-α; zinc supplementation is considered to recover the DNA-binding activity of PPAR-α, which is impaired in steatotic mouse liver; selenium administration downregulates mRNA expression of Ppar-γ, thereby improving lipid metabolism and oxidative status in the liver of high-fat diet (HFD)-fed mice. More importantly, PPARs' expression and activity are under the control of the circadian clock and show a robust 24 h rhythmicity, which might be the reasons for the side effects and the clinical limitations of trace elements targeting PPARs. Taken together, understanding the casual relationships among trace elements, PPARs' actions, and the pathogenesis of MetS is of great importance. Further studies are required to explore the chronopharmacological effects of trace elements on the diurnal oscillation of PPARs and the consequent development of MetS.

Possible dysmetabolic hyperferritinemia in hyperinsulinemic horses

Background

Hyperinsulinemia associated with equine metabolic syndrome and pituitary pars intermedia dysfunction is a risk factor for laminitis. Research in other species has shown elevated body iron levels as both a predictor and consequence of insulin resistance. In humans, this is known as dysmetabolic hyperferritinemia.

Aim

To explore the relationship between equine hyperinsulinemia and body iron levels.

Methods

We reviewed case histories and laboratory results from an open access database maintained by the Equine Cushing's and Insulin Resistance Group Inc. (ECIR). We identified 33 horses with confirmed hyperinsulinemia and laboratory results for serum iron, total iron binding capacity, and ferritin. Pearson correlation was used to test the relationship between insulin and iron indices. Additionally, we performed a secondary analysis of a previously reported controlled trial that was originally designed to test the correlation between iron status and the insulin response in horses. Here, we used a t-test to compare the mean values of insulin and ferritin between horses we categorized as normal or hyperinsulinemic based on their response to an oral challenge.

Results

Serum ferritin exceeded published reference range in 100% of the horses identified from the ECIR database. There were no statistically significant associations between insulin indices (RISQI, log insulin) and iron indices (log serum iron, log TSI%, log ferritin). There were trends for a negative association between RISQI and log iron [r(31) = -0.33, p = 0.058] and a positive association between age and ferritin [r(30) = 0.34, p = 0.054]. From the secondary data analysis of published data, we found significantly elevated ferritin (p = 0.05) in horses considered hyperinsulinemic by dynamic insulin testing compared to horses with a normal response.

Conclusion

These results suggest the potential for iron overload in hyperinsulinemic horses, a feature documented in other species and should stimulate further study into the relationship between insulin and iron dysregulation in the horse.

[Body iron accumulation in obesity, diabetes and its complications, and the possibility of therapeutic application by iron regulation]

Iron is an essential trace metal element for maintaining vital functions, and it is involved in hemoglobin synthesis, redox reaction, enzyme activity, cell proliferation and apoptosis in various cells. Iron deficient-related diseases represented anemia are well-known, on the other hand, iron overload disease has attracted little attention. Excessive iron produces hydroxyl radicals via Fenton/Haber-Weiss reaction, causing organ damage in hereditary iron overload diseases. Additionally, it has been clarified that iron accumulation is involved in the pathological conditions even in metabolic diseases thought to be unrelated to iron so far. Therefore, the role of iron in the living body has been raised attention again. Recent studies have reported that body iron content is associated with both obesity and diabetes, and iron might be an aggravating factor of obesity and diabetes. We have revealed that iron chelating agent reduced oxidative stress and inflammation, suppressing the development of adipose hypertrophy in KKAy mice. Dietary iron restriction also diminishes oxidative stress, leading to the inhibition of increased albuminuria excretion and glomerular lesions in db/db mice. In this review, we give an outline of the role of iron on obese and diabetes, and diabetic kidney disease, and present the possibility of application to treatment with iron regulation in those disorders.

Role of Oxidative Stress in Pathophysiology of Nonalcoholic Fatty Liver Disease

Liver steatosis without alcohol consumption, namely, nonalcoholic fatty liver disease (NAFLD), is a common hepatic condition that encompasses a wide spectrum of presentations, ranging from simple accumulation of triglycerides in the hepatocytes without any liver damage to inflammation, necrosis, ballooning, and fibrosis (namely, nonalcoholic steatohepatitis) up to severe liver disease and eventually cirrhosis and/or hepatocellular carcinoma. The pathophysiology of fatty liver and its progression is influenced by multiple factors (environmental and genetics), in a “multiple parallel-hit model,” in which oxidative stress plays a very likely primary role as the starting point of the hepatic and extrahepatic damage. The aim of this review is to give a comprehensive insight on the present researches and findings on the role of oxidative stress mechanisms in the pathogenesis and pathophysiology of NAFLD. With this aim, we evaluated the available data in basic science and clinical studies in this field, reviewing the most recent works published on this topic.

Increased intracellular iron in mouse primary hepatocytes in vitro causes activation of the Akt pathway but decreases its response to insulin

BACKGROUND

An iron-overloaded state has been reported to be associated with insulin resistance. On the other hand, conditions such as classical hemochromatosis (where iron overload occurs primarily in the liver) have been reported to be associated with increased insulin sensitivity. The reasons for these contradictory findings are unclear. In this context, the effects of increased intracellular iron per se on insulin signaling in hepatocytes are not known.

METHODS

Mouse primary hepatocytes were loaded with iron in vitro by incubation with ferric ammonium citrate (FAC). Intracellular events related to insulin signaling, as well as changes in gene expression and hepatocyte glucose production (HGP), were studied in the presence and absence of insulin and/or forskolin (a glucagon mimetic).

RESULTS

In vitro iron-loading of hepatocytes resulted in phosphorylation-mediated activation of Akt and AMP-activated protein kinase. This was associated with decreased basal and forskolin-stimulated HGP. Iron attenuated forskolin-mediated induction of the key gluconeogenic enzyme, glucose-6-phosphatase. It also attenuated activation of the Akt pathway in response to insulin, which was associated with decreased protein levels of insulin receptor substrates 1 and 2, constituting insulin resistance.

CONCLUSIONS

Increased intracellular iron has dual effects on insulin sensitivity in hepatocytes. It increased basal activation of the Akt pathway, but decreased activation of this pathway in response to insulin.

GENERAL SIGNIFICANCE

These findings may help explain why both insulin resistance and increased sensitivity have been observed in iron-overloaded states. They are of relevance to a variety of disease conditions characterized by hepatic iron overload and increased risk of diabetes.

Urinary exosomes reveal protein signatures in hypertensive patients with albuminuria

Albuminuria is an indicator of cardiovascular risk and renal damage in hypertensive individuals. Chronic renin-angiotensin system (RAS) suppression facilitates blood pressure control and prevents development of new-onset-albuminuria. A significant number of patients, however, develop albuminuria despite chronic RAS blockade, and the physiopathological mechanisms are underexplored. Urinary exosomes reflect pathological changes taking place in the kidney. The objective of this work was to examine exosomal protein alterations in hypertensive patients with albuminuria in the presence of chronic RAS suppression, to find novel clues underlying its development. Patients were followed-up for three years and were classified as: a) patients with persistent normoalbuminuria; b) patients developing de novo albuminuria; and c) patients with maintained albuminuria. Exosomal protein alterations between groups were identified by isobaric tag quantitation (iTRAQ). Confirmation was approached by target analysis (SRM). In total, 487 proteins were identified with high confidence. Specifically, 48 proteins showed an altered pattern in response to hypertension and/or albuminuria. Out of them, 21 proteins interact together in three main functional clusters: glycosaminoglycan degradation, coagulation and complement system, and oxidative stress. The identified proteins constitute potential targets for drug development and may help to define therapeutic strategies to evade albuminuria progression in hypertensive patients chronically treated.

High serum ferritin levels are associated with insulin resistance but not with impaired glucose tolerance in a healthy people population

AIM

To assess the association between elevated serum ferritin levels and the presence of insulin resistance (IR) or impaired glucose tolerance (IGT) in a population of individuals with no endocrine or metabolic disorders background.

METHODS

Analytical cross-sectional study, carried out in adults of both sexes with no medical history of type 2 diabetes mellitus (T2DM) or other metabolic or endocrine disorder, who attended the outpatient service of a private clinic in Lima-Peru during 2012-2014 period. Impaired serum ferritin levels were defined as serum ferritin values >300μg/L in men and >200μg/L in women. IR was defined as a Homeostasis Model Assessment (HOMA-IR) value ≥3.8 and IGT was defined as an oral glucose tolerance test (OGTT) value between 126mg/dL and 199mg/dL. The reported association measure was the prevalence ratio (PR) with their respective 95% confidence intervals (95% CI).

RESULTS

We analyzed 213 participants, the average age was 35.8±11.1years and 35.7% were males. The prevalence of impaired serum ferritin levels, IR and IGT in the population was 12.7%, 33.3% and 9.9% respectively. In the adjusted Poisson regression models, the prevalence of IR was higher among the group with impaired serum ferritin levels (PR=1.74; 95%CI:1.18-2.56); however, we found no association between impaired serum ferritin levels and IGT (PR=1.42; 95%CI:0.47-4.30).

CONCLUSIONS

Impaired levels of serum ferritin are associated with IR, nevertheless, not with IGT in a metabolically healthy population. Serum ferritin could be considered as an early marker of IR prior to the onset of glycaemia disorders.

Iron elevation and adipose tissue remodeling in the epididymal depot of a mouse model of polygenic obesity

Background

Iron dysregulation is a potential contributor to the pathology of obesity-related metabolic complications. KK/HIJ (KK) mice, a polygenic obese mouse model, have elevated serum iron levels. A subset of KK male mice display a bronzing of epididymal adipose tissue (eAT) associated with >100-fold (p<0.001) higher iron concentration.

Methods

To further phenotype and characterize the adipose tissue iron overload, 27 male KK mice were evaluated. 14 had bronzing eAT and 13 had normal appearing eAT. Fasting serum and tissues were collected for iron content, qPCR, histology and western blot.

Results

High iron levels were confirmed in bronzing eAT (High Iron group, HI) versus normal iron level (NI) in normal appearing eAT. Surprisingly, iron levels in subcutaneous and brown adipose depots were not different between the groups (p>0.05). The eAT histology revealed iron retention, macrophage clustering, tissue fibrosis, cell death as well as accumulation of HIF-2α in the high iron eAT. qPCR showed significantly decreased Lep (leptin) and AdipoQ (adiponectin), whereas Tnfα (tumor necrosis factor α), and Slc40a1 (ferroportin) were up-regulated in HI (p<0.05). Elevated HIF-2α, oxidative stress and local insulin signaling loss was also observed.

Significance

Our data suggest that deposition of iron in adipose tissue is limited to the epididymal depot in male KK mice. A robust adipose tissue remodeling is concomitant with the high iron concentration, which causes local adipose tissue insulin resistance.

Iron and non-alcoholic fatty liver disease

The mechanisms that promote liver injury in non-alcoholic fatty liver disease (NAFLD) are yet to be thoroughly elucidated. As such, effective treatment strategies are lacking and novel therapeutic targets are required. Iron has been widely implicated in the pathogenesis of NAFLD and represents a potential target for treatment. Relationships between serum ferritin concentration and NAFLD are noted in a majority of studies, although serum ferritin is an imprecise measure of iron loading. Numerous mechanisms for a pathogenic role of hepatic iron in NAFLD have been demonstrated in animal and cell culture models. However, the human data linking hepatic iron to liver injury in NAFLD is less clear, with seemingly conflicting evidence, supporting either an effect of iron in hepatocytes or within reticulo-endothelial cells. Adipose tissue has emerged as a key site at which iron may have a pathogenic role in NAFLD. Evidence for this comes indirectly from studies that have evaluated the role of adipose tissue iron with respect to insulin resistance. Adding further complexity, multiple strands of evidence support an effect of NAFLD itself on iron metabolism. In this review, we summarise the human and basic science data that has evaluated the role of iron in NAFLD pathogenesis.

Genetics of nonalcoholic fatty liver disease

Epidemiological, familial, and twin studies indicate that non-alcoholic fatty liver disease, now the leading cause of liver damage in developed countries, has a strong heritability. The common I148M variant of PNPLA3 impairing hepatocellular lipid droplets remodeling is the major genetic determinant of hepatic fat content. The I148M variant has a strong impact on the full spectrum of liver damage related to fatty liver, encompassing non-alcoholic steatohepatitis, advanced fibrosis, and hepatocellular carcinoma, and influences the response to therapeutic approaches. Common variants in GCKR enhance de novo hepatic lipogenesis in response to glucose and liver inflammation. Furthermore, the low-frequency E167K variant of TM6SF2 and rare mutations in APOB, which impair very low-density lipoproteins secretion, predispose to progressive fatty liver.

CONCLUSIONS

These and other recent findings reviewed here indicate that impaired lipid handling by hepatocytes has a major role in the pathogenesis of non-alcoholic fatty liver disease by triggering inflammation, fibrogenesis, and carcinogenesis. These discoveries have provided potential novel biomarkers for clinical use and have revealed intriguing therapeutic targets.

The Effects of Dietary Iron and Capsaicin on Hemoglobin, Blood Glucose, Insulin Tolerance, Cholesterol, and Triglycerides, in Healthy and Diabetic Wistar Rats

Objective

Our aim was to assess the effects of dietary iron, and the compound capsaicin, on hemoglobin as well as metabolic indicators including blood glucose, cholesterol, triglycerides, insulin, and glucose tolerance.

Materials and Methods

Our animal model was the Wistar rat, fed a chow diet, with or without experimentally induced diabetes. Diabetic males were fed control, low, or high-iron diets, the latter, with or without capsaicin. Healthy rats were fed identical diets, but without the capsaicin supplement. We then measured the parameters listed above, using the Student t-test and ANOVA, to compare groups.

Results

Healthy rats fed a low-iron diet exhibited significantly reduced total cholesterol and triglyceride levels, compared with rats fed a control diet. Significantly reduced blood lipid was also provoked by low dietary iron in diabetic rats, compared with those fed a control diet. Insulin, and glucose tolerance was only improved in healthy rats fed the low-iron diet. Significant increases in total cholesterol were found in diabetic rats fed a high-iron diet, compared with healthy rats fed the same diet, although no statistical differences were found for triglycerides. Hemoglobin levels, which were not statistically different in diabetic versus healthy rats fed the high-iron diet, fell when capsaicin was added. Capsaicin also provoked a fall in the level of cholesterol and triglycerides in diabetic animals, versus diabetics fed with the high iron diet alone. In conclusion, low levels of dietary iron reduced levels of serum triglycerides, hemoglobin, and cholesterol, and significantly improved insulin, and glucose tolerance in healthy rats. In contrast, a high-iron diet increased cholesterol significantly, with no significant changes to triglyceride concentrations. The addition of capsaicin to the high-iron diet (for diabetic rats) further reduced levels of hemoglobin, cholesterol, and triglycerides. These results suggest that capsaicin, may be suitable for the treatment of elevated hemoglobin, in patients.

Long-term risk of type 2 diabetes in relation to habitual iron intake in women with a history of gestational diabetes: a prospective cohort study

BACKGROUND

An iron overload may induce pancreatic islet damage and increase risk of diabetes. Women with a history of gestational diabetes mellitus (GDM) are at high risk of developing type 2 diabetes mellitus (T2DM) after pregnancy.

OBJECTIVE

We aimed to examine the association of habitual iron intake with long-term risk of T2DM in this high-risk population.

DESIGN

We included 3976 women with a history of GDM from the Nurses' Health Study II cohort as part of the ongoing Diabetes & Women's Health Study. The women were followed up through 2009. Iron intake was assessed with the use of a validated food-frequency questionnaire in 1991 and every 4 y thereafter. We used Cox proportional hazards models to estimate HRs and 95% CIs.

RESULTS

We documented 641 incident T2DM cases during 57,683 person-years of observation. Adjusted HRs for T2DM for the highest quartile compared with the lowest quartile were 1.64 (95% CI: 1.20, 2.25; P-trend = 0.02) for total iron intake and 1.80 (95% CI: 1.18, 2.74; P-trend = 0.005) for dietary heme iron intake. In addition, women who consumed ≥30.0 mg supplemental Fe/d, compared with nonusers, had an adjusted HR of 1.83 (95% CI: 1.25, 2.70; P-trend = 0.002).

CONCLUSION

In women with a history of GDM, greater intakes of total iron, dietary heme iron, and supplemental iron were associated with higher risk of T2DM.

Garlic Influences Gene Expression In Vivo and In Vitro

There is a large body of preclinical research aimed at understanding the roles of garlic and garlic-derived preparations in the promotion of human health. Most of this research has targeted the possible functions of garlic in maintaining cardiovascular health and in preventing and treating cancer. A wide range of outcome variables has been used to investigate the bioactivity of garlic, ranging from direct measures of health status such as cholesterol concentrations, blood pressure, and changes in tumor size and number, to molecular and biochemical measures such as mRNA gene expression, protein concentration, enzyme activity, and histone acetylation status. Determination of how garlic influences mRNA gene expression has proven to be a valuable approach to elucidating the mechanisms of garlic bioactivity. Preclinical studies investigating the health benefits of garlic far outnumber human studies and have made frequent use of mRNA gene expression measurement. There is an immediate need to understand mRNA gene expression in humans as well. Although safety and ethical constraints limit the types of available human tissue, peripheral whole blood is readily accessible, and measuring mRNA gene expression in whole blood may provide a unique window to understanding how garlic intake affects human health.

Efficacy of alogliptin in preventing non-alcoholic fatty liver disease progression in patients with type 2 diabetes

Non-alcoholic fatty liver disease (NAFLD) represents one of the most common causes of chronic liver disease worldwide and is characterized by chronic liver inflammation and fibrosis leading to cirrhosis and increased risk of liver cancer in a proportion of patients. Effective anti-fibrotic agents have yet to be approved for the treatment of NAFLD. The present study aimed to evaluate the efficacy of dipeptidyl peptidase 4 inhibitors (DPP4-I) in the prevention of NAFLD progression in NAFLD patients with type 2 diabetes. The study was a single arm, multi-centre, non-randomised study of NAFLD patients with type 2 diabetes. NAFLD was diagnosed according to ultrasonographic findings. All the patients received 25 mg/day of alogliptin for 12 months. The efficacy of alogliptin in preventing NAFLD progression was assessed using overall NAFIC scores [non-alcoholic steatohepatitis (NASH), ferritin, insulin and type IV collagen 7S] and individual component scores according to baseline haemoglobin A1c (HbA1c) levels. Of the 39 patients enrolled in the study, 16 patients (40.3%) had NAFIC scores >2 points, indicating the presence of NASH. NAFIC scores markedly decreased following 12 months of alogliptin administration, but remained >2 points in 10 patients, indicating that NASH may have persisted in these patients. The relative risks for persistent NASH were 4.92 (95% confidence interval, 0.61-40.0) in the highest HbA1c tertile group compared with those in the lowest group. However, no statistically significant linear trend was observed across all HbA1c categories (P=0.145). DPP4-I may have efficacy against NAFLD progression in patients with type 2 diabetes with relatively lower HbA1c levels. DPP4-I may represent a potential new therapeutic strategy for the prevention of disease progression in NAFLD patients with type 2 diabetes.

Iron Deprivation May Enhance Insulin Receptor and Glut4 Transcription in Skeletal Muscle of Adult Rats

OBJECTIVES

Considering that phenotype related to iron overload associated with pathological conditions differs from that caused by dietary iron excess, our study set out to evaluate the impact of dietary iron restriction and dietary iron supplementation on oxidative stress and functional outcome in adult, healthy rats.

METHODS

adult rats were divided into the three groups and fed diets containing 10, 35 or 350 mg/kg iron (restricted-diet, control-diet and supplemented- diet groups, respectively) for 78 days. Hematological variables, fasting blood glucose, hepatic enzyme activity and C-reactive protein levels were analyzed. Iron and glycogen concentrations in liver and skeletal muscle were determined. The extent of tissue damage caused by either dietary iron restriction or iron supplementation was accessed by measuring malondialdehyde, carbonyl, NADPH oxidase, glutathione peroxidase, glutathione reductase and glutathione-s-transferase in various tissues. The mRNA expression levels of insulin receptor, glucose transporter 4 and p53 were also determined.

RESULTS

Fasting blood glucose values trended toward a decrease by dietary iron restriction, moreover, hepatic glycogen content decreased with concomitant increases in skeletal muscle. In addition, dietary iron restriction resulted in a twofold increase in mRNA expression of Insr and fourfold increase in Glut4 expression in skeletal muscle. Although the dietary iron restriction did not affect body iron status, it caused hepatic low oxidative damages. However, high liver NADPH oxidase activity and increased levels of protein oxidation in muscle were observed. Chronic feeding of high iron diet induces iron overload and resulted in elevated levels of stress markers in tissues.

CONCLUSION

Dietary iron deprivation may improve insulin receptor and glucose transporter transcription in muscle; however, our results show that dietary iron restriction can prevent and/or promote oxidative damage in a tissue-specific manner, emphasizing the importance of maintaining optimal iron intake.

Iron Deficiency Impairs Intra-Hepatic Lymphocyte Mediated Immune Response

Hepatic expression of iron homeostasis genes and serum iron parameters predict the success of immunosuppression withdrawal following clinical liver transplantation, a phenomenon known as spontaneous operational tolerance. In experimental animal models, spontaneous liver allograft tolerance is established through a process that requires intra-hepatic lymphocyte activation and deletion. Our aim was to determine if changes in systemic iron status regulate intra-hepatic lymphocyte responses. We used a murine model of lymphocyte-mediated acute liver inflammation induced by Concanavalin A (ConA) injection employing mice fed with an iron-deficient (IrDef) or an iron-balanced diet (IrRepl). While the mild iron deficiency induced by the IrDef diet did not significantly modify the steady state immune cell repertoire and systemic cytokine levels, it significantly dampened inflammatory liver damage after ConA challenge. These findings were associated with a marked decrease in T cell and NKT cell activation following ConA injection in IrDef mice. The decreased liver injury observed in IrDef mice was independent from changes in the gut microflora, and was replicated employing an iron specific chelator that did not modify intra-hepatic hepcidin secretion. Furthermore, low-dose iron chelation markedly impaired the activation of isolated T cells in vitro. All together, these results suggest that small changes in iron homeostasis can have a major effect in the regulation of intra-hepatic lymphocyte mediated responses.

Genetic Factors in the Pathogenesis of Nonalcoholic Fatty Liver and Steatohepatitis

Liver fat accumulation generally related to systemic insulin resistance characterizes nonalcoholic fatty liver disease (NAFLD), which in the presence of nonalcoholic steatohepatitis (NASH) can progress towards cirrhosis and hepatocellular carcinoma. Due to the epidemic of obesity, NAFLD is now the most frequent liver disease in Western countries. Epidemiological, familial, and twin studies provide evidence for a strong genetic component of NAFLD susceptibility. Recently, genome-wide association studies led to the identification of the major inherited determinants of hepatic fat accumulation: patatin-like phospholipase domain-containing 3 (PNPLA3) I148M gene and transmembrane 6 superfamily member 2 (TM6SF2) E167K gene variants, involved in lipid droplets remodelling and very low-density lipoproteins secretion, are the major determinants of interindividual differences in liver steatosis, and susceptibility to progressive NASH. In this review, we aimed to provide an overview of recent insights into the genetics of hepatic fat accumulation and steatohepatitis.

Higher ferritin levels, but not serum iron or transferrin saturation, are associated with Type 2 diabetes mellitus in adult men and women free of genetic haemochromatosis

CONTEXT

Iron overload predisposes to diabetes and higher ferritin levels have been associated with diabetes. However, it is unclear whether ferritin reflects differences in iron-related parameters between diabetic and nondiabetic persons. We examined associations of serum ferritin, iron and transferrin saturation with Type 2 diabetes in adults without genetic predisposition to iron overload.

DESIGN, PARTICIPANTS AND MEASUREMENTS

Cross-sectional analysis of community-dwelling men and women aged 17-97 years from the Busselton Health Survey, Western Australia. Men and women carrying genotypes associated with haemochromatosis (C282Y/C282Y or C282Y/H63D) were excluded. Serum ferritin, iron and transferrin saturation were assayed.

RESULTS

There were 1834 men (122 with diabetes, 6·6%) and 2351 women (141 with diabetes, 6%). In men, higher serum ferritin was associated with diabetes after adjusting for age, smoking, alcohol, cardiovascular history, body mass index (BMI), waist, blood pressure, lipids, C-reactive protein (CRP), adiponectin, alanine transaminase (ALT) and gamma-glutamyl transpeptidase (GGT) [odds ratio (OR): 1·29 per 1 unit increase log ferritin, 95% confidence interval (CI) = 1·01-1·65, P = 0·043]. In women, higher serum ferritin was associated with diabetes [fully adjusted OR: 1·31 per 1 unit increase log ferritin, 95% CI = 1·04-1·63, P = 0·020; 1·84 for tertile (T) 3 vs T1, 95% CI = 1·09-3·11]. Neither iron levels nor transferrin saturation were associated with diabetes risk in men or women. Higher ferritin was not associated with insulin resistance in nondiabetic adults.

CONCLUSIONS

In adults, higher ferritin levels are independently associated with prevalent diabetes while iron and transferrin saturation are not. Ferritin is a robust biomarker for diabetes risk, but further investigation is needed to clarify whether this relationship is mediated via iron metabolism.

In vitro inhibition activity of polyphenol-rich extracts from Syzygium aromaticum (L.) Merr. & Perry (Clove) buds against carbohydrate hydrolyzing enzymes linked to type 2 diabetes and Fe(2+)-induced lipid peroxidation in rat pancreas

OBJECTIVE

To investigate and compare the inhibitory properties of free and bound phenolic extracts of clove bud against carbohydrate hydrolyzing enzymes (alpha-amylase & alpha-glucosidase) and Fe(2+)-induced lipid peroxidation in rat pancreas in vitro.

METHODS

The free phenolics were extracted with 80% (v/v) acetone, while bound phenolics were extracted from the alkaline and acid hydrolyzed residue with ethyl acetate. Then, the interaction of the extracts with alpha-amylase and alpha-glucosidase was subsequently assessed. Thereafter, the total phenolic contents and antioxidant activities of the extracts were determined.

RESULTS

The result revealed that both extracts inhibited alpha-amylase and alpha-glucosidase in a dose-dependent manner. However, the alpha-glucosidase inhibitory activity of the extracts were significantly (P<0.05) higher than their alpha-amylase inhibitory activity. The free phenolics (31.67 mg/g) and flavonoid (17.28 mg/g) contents were significantly (P<0.05) higher than bound phenolic (23.52 mg/g) and flavonoid (13.70 mg/g) contents. Both extracts also exhibited high antioxidant activities as typified by their high reducing power, 1,1 diphenyl-2- picrylhydrazyl (DPPH) and 2, 2-azinobis-3-ethylbenzo-thiazoline-6-sulfonate (ABTS) radical scavenging abilities, as well as inhibition of Fe(2+)-induced lipid peroxidation in rat pancreas in vitro.

CONCLUSIONS

This study provides a biochemical rationale by which clove elicits therapeutic effect on type 2 diabetes.

Inhibitory effect of polyphenolic-rich extract from Cola nitida (Kolanut) seed on key enzyme linked to type 2 diabetes and Fe(2+) induced lipid peroxidation in rat pancreas in vitro

OBJECTIVE

To investigate the inhibitory effect of phenolic-rich extracts from Cola nitida (C. nitida) seeds on key enzymes linked with type-2 diabetes and Fe(2+) induced oxidative stress in rat pancreas.

METHODS

The phenolic extract was prepared with 80% acetone (v/v). Subsequently, the antioxidant properties and inhibitory effect of the extract on α - amylase and α - glucosidase as well as on Fe(2+) induced lipid peroxidation in rat pancreas were determined in vitro.

RESULTS

The result revealed that C. nitida extract inhibited α-amylase (EC50=0.34 mg/mL) and α-glucosidase (EC50=0.32 mg/mL) activities as well as Fe(2+) induced lipid peroxidation in rat pancreas in a dose dependent manner. In addition, the extract had high DPPH radical scavenging ability (EC50=2.2 mg/mL) and reducing power (8.2 mg AAE/g). Characterization of the main phenolic compounds of the extract using gas chromatography analysis revealed catechin (6.6 mg/100 g), epicatechin (3.6 mg/100 g), apigenin (5.1 mg/100 g) and naringenin (3.6 mg/100 g) were the main compounds in the extract.

CONCLUSIONS

This antioxidant and enzyme inhibition could be some of the possible mechanism by which C. nitida is use in folklore for the management/treatment of type-2 diabetes. However, the enzyme inhibitory properties of the extract could be attributed to the presence of catechin, epicatechin, apigenin and naringenin.

Iron increases diabetes-induced kidney injury and oxidative stress in rats

Diabetic nephropathy is both a common and a severe complication of diabetes mellitus. Iron is an essential trace element. However, excess iron is toxic, playing a role in the pathogenesis of diabetic nephropathy. The present study aimed to determine the extent of the interaction between iron and type 2 diabetes in the kidney. Male rats were randomly assigned into four groups: control, iron (300-mg/kg iron dextran), diabetes (a single dose of intraperitoneal streptozotocin), and iron + diabetes group. Iron supplementation resulted in a higher liver iron content, and diabetic rats showed higher serum glucose compared with control rats, which confirmed the model as iron overload and diabetic. It was found that iron + diabetes group showed a greater degree of kidney pathological changes, a remarkable reduction in body weight, and a significant increase in relative kidney weight and iron accumulation in rat kidneys compared with iron or diabetes group. Moreover, malondialdehyde values in the kidney were higher in iron + diabetes group than in iron or diabetes group, sulfhydryl concentration and glutathione peroxidase activity were decreased by the diabetes and iron + diabetes groups, and protein oxidation and nitration levels were higher in the kidney of iron + diabetes group as compared to iron or diabetes group. However, iron supplementation did not elevate the glucose level of a diabetic further. These results suggested that iron increased the diabetic renal injury probably through increased oxidative/nitrative stress and reduced antioxidant capacity instead of promoting a rise in blood sugar levels; iron might be a potential cofactor of diabetic nephropathy, and strict control of iron would be important under diabetic state.

Lower obesity rate during residence at high altitude among a military population with frequent migration: a quasi experimental model for investigating spatial causation

We sought to evaluate whether residence at high altitude is associated with the development of obesity among those at increased risk of becoming obese. Obesity, a leading global health priority, is often refractory to care. A potentially novel intervention is hypoxia, which has demonstrated positive long-term metabolic effects in rats. Whether or not high altitude residence confers benefit in humans, however, remains unknown. Using a quasi-experimental, retrospective study design, we observed all outpatient medical encounters for overweight active component enlisted service members in the U.S. Army or Air Force from January 2006 to December 2012 who were stationed in the United States. We compared high altitude (>1.96 kilometers above sea level) duty assignment with low altitude (<0.98 kilometers). The outcome of interest was obesity related ICD-9 codes (278.00-01, V85.3x-V85.54) by Cox regression. We found service members had a lower hazard ratio (HR) of incident obesity diagnosis if stationed at high altitude as compared to low altitude (HR 0.59, 95% confidence interval [CI] 0.54–0.65; p<0.001). Using geographic distribution of obesity prevalence among civilians throughout the U.S. as a covariate (as measured by the Centers for Disease Control and Prevention and the REGARDS study) also predicted obesity onset among service members. In conclusion, high altitude residence predicts lower rates of new obesity diagnoses among overweight service members in the U.S. Army and Air Force. Future studies should assign exposure using randomization, clarify the mechanism(s) of this relationship, and assess the net balance of harms and benefits of high altitude on obesity prevention.

Iron: the hard player in diabetes pathophysiology

The interest in the role of ferrous iron in diabetes pathophysiology has been revived by recent evidence of iron as an important determinant of pancreatic islet inflammation and as a biomarker of diabetes risk and mortality. The iron metabolism in the β-cell is complex. Excess free iron is toxic, but at the same time, iron is required for normal β-cell function and thereby glucose homeostasis. In the pathogenesis of diabetes, iron generates reactive oxygen species (ROS) by participating in the Fenton chemistry, which can induce oxidative damage and apoptosis. The aim of this review is to present and discuss recent evidence, suggesting that iron is a key pathogenic factor in both type 1 and type 2 diabetes with a focus on inflammatory pathways. Pro-inflammatory cytokine-induced β-cell death is not fully understood, but may include iron-induced ROS formation resulting in dedifferentiation by activation of transcription factors, activation of the mitochondrial apoptotic machinery or of other cell death mechanisms. The pro-inflammatory cytokine IL-1β facilitates divalent metal transporter 1 (DMT1)-induced β-cell iron uptake and consequently ROS formation and apoptosis, and we propose that this mechanism provides the relay between inflammation and oxidative β-cell damage. Iron chelation may be a potential therapeutic approach to reduce disease severity and mortality among diabetes patients. However, the therapeutic effect and safety of iron reduction need to be tested in clinical trials before dietary interventions or the use of iron chelation therapy titrated to avoid anaemia.

Iron chelation by deferoxamine prevents renal interstitial fibrosis in mice with unilateral ureteral obstruction

Renal fibrosis plays an important role in the onset and progression of chronic kidney diseases (CKD). Although several mechanisms underlying renal fibrosis and candidate drugs for its treatment have been identified, the effect of iron chelator on renal fibrosis remains unclear. In the present study, we examined the effect of an iron chelator, deferoxamine (DFO), on renal fibrosis in mice with surgically induced unilateral ureter obstruction (UUO). Mice were divided into 4 groups: UUO with vehicle, UUO with DFO, sham with vehicle, and sham with DFO. One week after surgery, augmented renal tubulointerstitial fibrosis and the expression of collagen I, III, and IV increased in mice with UUO; these changes were suppressed by DFO treatment. Similarly, UUO-induced macrophage infiltration of renal interstitial tubules was reduced in UUO mice treated with DFO. UUO-induced expression of inflammatory cytokines and extracellular matrix proteins was abrogated by DFO treatment. DFO inhibited the activation of the transforming growth factor-β1 (TGF-β1)-Smad3 pathway in UUO mice. UUO-induced NADPH oxidase activity and p22^phox expression were attenuated by DFO. In the kidneys of UUO mice, divalent metal transporter 1, ferroportin, and ferritin expression was higher and transferrin receptor expression was lower than in sham-operated mice. Increased renal iron content was observed in UUO mice, which was reduced by DFO treatment. These results suggest that iron reduction by DFO prevents renal tubulointerstitial fibrosis by regulating TGF-β-Smad signaling, oxidative stress, and inflammatory responses.

Obesity alters adipose tissue macrophage iron content and tissue iron distribution

Adipose tissue (AT) expansion is accompanied by the infiltration and accumulation of AT macrophages (ATMs), as well as a shift in ATM polarization. Several studies have implicated recruited M1 ATMs in the metabolic consequences of obesity; however, little is known regarding the role of alternatively activated resident M2 ATMs in AT homeostasis or how their function is altered in obesity. Herein, we report the discovery of a population of alternatively activated ATMs with elevated cellular iron content and an iron-recycling gene expression profile. These iron-rich ATMs are referred to as MFe(hi), and the remaining ATMs are referred to as MFe(lo). In lean mice, ~25% of the ATMs are MFe(hi); this percentage decreases in obesity owing to the recruitment of MFe(lo) macrophages. Similar to MFe(lo) cells, MFe(hi) ATMs undergo an inflammatory shift in obesity. In vivo, obesity reduces the iron content of MFe(hi) ATMs and the gene expression of iron importers as well as the iron exporter, ferroportin, suggesting an impaired ability to handle iron. In vitro, exposure of primary peritoneal macrophages to saturated fatty acids also alters iron metabolism gene expression. Finally, the impaired MFe(hi) iron handling coincides with adipocyte iron overload in obese mice. In conclusion, in obesity, iron distribution is altered both at the cellular and tissue levels, with AT playing a predominant role in this change. An increased availability of fatty acids during obesity may contribute to the observed changes in MFe(hi) ATM phenotype and their reduced capacity to handle iron.

Microarray analysis of rat pancreas reveals altered expression of Alox15 and regenerating islet-derived genes in response to iron deficiency and overload

It is well known that iron overload can result in pancreatic iron deposition, beta-cell destruction, and diabetes in humans. Recent studies in animals have extended the link between iron status and pancreatic function by showing that iron depletion confers protection against beta-cell dysfunction and diabetes. The aim of the present study was to identify genes in the pancreas that are differentially expressed in response to iron deficiency or overload. Weanling male Sprague-Dawley rats (n = 6/group) were fed iron-deficient, iron-adequate, or iron-overloaded diets for 3 weeks to alter their iron status. Total RNA was isolated from the pancreases and pooled within each group for microarray analyses in which gene expression levels were compared to those in iron-adequate controls. In iron-deficient pancreas, a total of 66 genes were found to be differentially regulated (10 up, 56 down), whereas in iron-overloaded pancreas, 164 genes were affected (82 up, 82 down). The most up-regulated transcript in iron-deficient pancreas was arachidonate 15-lipoxygenase (Alox15), which has been implicated in the development of diabetes. In iron-overloaded pancreas, the most upregulated transcripts were Reg1a, Reg3a, and Reg3b belonging to the regenerating islet-derived gene (Reg) family. Reg expression has been observed in response to pancreatic stress and is thought to facilitate pancreatic regeneration. Subsequent qRT-PCR validation indicated that Alox15 mRNA levels were 4 times higher in iron-deficient than in iron-adequate pancreas and that Reg1a, Reg3a, and Reg3b mRNA levels were 17–36 times higher in iron-overloaded pancreas. The elevated Alox15 mRNA levels in iron-deficient pancreas were associated with 8-fold higher levels of Alox15 protein as indicated by Western blotting. Overall, these data raise the possibility that Reg expression may serve as a biomarker for iron-related pancreatic stress, and that iron deficiency may adversely affect the risk of developing diabetes through up-regulation of Alox15.