Relationships among serum triacylglycerol, fat pad weight, and lipolysis in iron-deficient rats

The Importance of Iron Administration in Correcting Anaemia After Major Surgery

INTRODUCTION

Postoperative anaemia can affect more than 90% of patients undergoing major surgeries. Patients develop an absolute iron deficiency in the face of significant blood loss or preoperative anaemia and major surgery. Studies have shown the negative impact of these factors on transfusion requirements, infections, increased hospitalisation and long-term morbidities.

AIM OF THE STUDY

The research was performed to determine the correlation between intravenous iron administration in the postoperative period and improved haemoglobin correction trend.

MATERIAL AND METHODS

A prospective study was conducted to screen and treat iron deficiency in patients undergoing major surgery associated with significant bleeding. For iron deficiency anaemia screening, in the postoperative period, the following bioumoral parameters were assessed: haemoglobin, serum iron, transferrin saturation (TSAT), and ferritin, direct serum total iron-binding capacity (dTIBC), mean corpuscular volume (MCV) and mean corpuscular haemoglobin (MCH). In addition, serum glucose, fibrinogen, urea, creatinine and lactate values were also collected.

RESULTS

Twenty-one patients undergoing major surgeries (52,38% were emergency and 47,61% elective interventions) were included in the study. Iron deficiency, as defined by ferritin 100-300 μg/L along with transferrin saturation (TSAT) < 20 %, mean corpuscular volume (MVC) < 92 fL, mean corpuscular haemoglobin (MCH) < 33 g/dL, serum iron < 10 μmol/L and direct serum total iron-binding capacity (dTIBC) > 36 μmol/L, was identified in all cases. To correct the deficit and optimise the haematological status, all patients received intravenous ferric carboxymaltose (500-1000 mg, single dose). Using Quadratic statistical analysis, the trend of haemoglobin correction was found to be a favourable one.

CONCLUSION

The administration of intravenous ferric carboxymaltose in the postoperative period showed the beneficial effect of this type of intervention on the haemoglobin correction trend in these groups of patients.

Iron deficiency attenuates catecholamine‑stimulated lipolysis via downregulation of lipolysis‑related proteins and glucose utilization in 3T3‑L1 adipocytes

Iron deficiency has been associated with obesity and related metabolic disorders. The aim of the present study was to evaluate the effect of iron deficiency on fat metabolism, particularly regarding the lipolytic activity, lipolysis‑related protein expression, and glucose utilization of adipocytes. Differentiated 3T3‑L1 adipocytes were incubated with an iron chelator, deferoxamine mesylate (DFO), for 48 h. Subsequently, basal and isoproterenol‑stimulated lipolytic activities, the proteins involved in lipolysis and glucose utilization were compared with a control (CON). The results revealed that treatment with DFO significantly decreased the free iron content but did not affect total protein and lipid contents in adipocytes. Iron deprivation caused a significant reduction in isoproterenol‑stimulated lipolysis, but not basal lipolysis. Lipolysis‑related proteins, including perilipin A, adipose triglyceride lipase, hormone sensitive lipase and comparative gene identification‑58, were decreased in the DFO compared with the CON group. Furthermore, glucose utilization, a major precursor of 3‑glycerol phosphate for micro‑lipid droplet synthesis during lipolysis and the expression of glucose transporter (GLUT) 4 were significantly lower in the DFO group when compared with the CON group. However, hypoxia‑inducible factor‑1α and GLUT1 expressions were upregulated in DFO‑treated adipocytes. In conclusion, the results indicated that low iron availability attenuated catecholamine‑stimulated lipolysis by downregulating lipolytic enzymes and glucose utilization in 3T3‑L1 adipocytes.

Iron deficiency as energetic insult to skeletal muscle in chronic diseases

Specific skeletal myopathy constitutes a common feature of heart failure, chronic obstructive pulmonary disease, and type 2 diabetes mellitus, where it can be characterized by the loss of skeletal muscle oxidative capacity. There is evidence from in vitro and animal studies that iron deficiency affects skeletal muscle functioning mainly in the context of its energetics by limiting oxidative metabolism in favour of glycolysis and by alterations in both carbohydrate and fat catabolic processing. In this review, we depict the possible molecular pathomechanisms of skeletal muscle energetic impairment and postulate iron deficiency as an important factor causally linked to loss of muscle oxidative capacity that contributes to skeletal myopathy seen in patients with heart failure, chronic obstructive pulmonary disease, and type 2 diabetes mellitus.

Iron deficiency anemia and glucose metabolism

Iron deficiency anemia (IDA) is a global public health problem affecting both developing and developed countries with major consequences for human health as well as social and economic development. It occurs at all stages of the life cycle, but is more prevalent in pregnant women and young children. IDA appears to be more common in diabetic patients compared to non-diabetic population. Iron deficiency (ID) and IDA can impair glucose homeostasis in animals and human and may negatively affect glycemic control and predispose to more complications in diabetic patients. On the other hand diabetes and its complications are associated with anemia and its correction improves diabetes control and may prevent or delay the occurrence of complications. Physicians treating this form of anemia should be aware of its negative effect on glycemic control in normal and diabetic patients (both type 1 and type 2). They should prevent ID and treat early all those with IDA.This brief review aims to enlighten the different effects of IDA on glucose metabolism in normal and diabetic patients.

Neurobehavioural analysis of developmental iron deficiency in Oreochromis aureus × Oreochromis niloticus

The objective of this study was to examine the association between brain iron measurements of monoamine function and behavioural measurements of learning and memory. Male hybrid tilapias Oreochromis aureus × Oreochromis niloticus were fed either an iron-deficient (ID) diet or an iron-adequate (IA) diet for 8 weeks. The ID fishes showed significantly lower iron content in brain and decreasing learning and memory capacity. The fishes that showed increased learning and memory capacity had higher levels of iron and monoamine oxidase activity in brain. In addition, the results showed that learning and memory behaviours were related to monoamine (dopamine and noradrenaline) concentration in the brain. This suggests that iron can enhance learning and memory capacity in fishes and that the effect may have monoaminergic mediation in discrimination learning and memory tasks. The experimental data suggest that the properties and neural basis of learning and memory of teleosts are notably similar to those of land vertebrates.

Iron and diabetes risk

Iron overload is a risk factor for diabetes. The link between iron and diabetes was first recognized in pathologic conditions-hereditary hemochromatosis and thalassemia-but high levels of dietary iron also impart diabetes risk. Iron plays a direct and causal role in diabetes pathogenesis mediated both by β cell failure and insulin resistance. Iron also regulates metabolism in most tissues involved in fuel homeostasis, with the adipocyte in particular serving an iron-sensing role. The underlying molecular mechanisms mediating these effects are numerous and incompletely understood but include oxidant stress and modulation of adipokines and intracellular signal transduction pathways.

Iron loading impairs lipoprotein lipase activity and promotes hypertriglyceridemia

Iron loading is associated with altered lipid metabolism, but underlying mechanisms remain unknown. We compared serum iron and triglycerides (TGs) in Belgrade rats, a genetic model of iron-loading anemia. Homozygous b/b rats had greater serum iron (68 vs. 28 μM; P=0.0004) and TG levels (180 vs. 84 mg/dl; P=0.014) compared to +/b controls. To confirm the association between iron loading and high TGs, Fischer rats were fed chow containing 1% carbonyl iron. Compared to controls pair-fed normal chow, carbonyl iron-fed rats had elevated serum iron (42 vs. 21 μM; P=0.007) and TGs (190 vs. 115 mg/dl; P=0.009). Despite normal hepatic production and secretion, TG clearance was lower in b/b than +/b rats due to reduced serum lipoprotein lipase (LPL) activity (3.1 vs. 5.0 mM/min; P=0.026). Likewise, LPL was lower in carbonyl iron-fed rats compared to controls (2.4 vs. 3.7 mM/min; P=0.017). Direct addition of iron to serum ex vivo or recombinant LPL in vitro decreased enzymatic activity in a dose-dependent manner. Lowering serum iron in Belgrade rats reduced TG levels (274 to 67 mg/dl, P=0.001). This study explains the relationship between iron status and lipid metabolism and provides mechanistic support for interventions that reduce serum iron levels in individuals at risk for hypertriglyceridemia.

Comparisons of the iron deficient metabolic response in rats fed either an AIN-76 or AIN-93 based diet

Background

Previous studies examining the metabolic consequences of dietary iron deficiency have reported elevated serum glucose concentrations in iron-deficient animals. Importantly, the majority of these findings were observed using an earlier version of a laboratory animal diet (AIN-76A) in which the primary carbohydrate source was sucrose – a disaccharide known to negatively impact both glucose and lipid homeostasis. The AIN-76A diet formula was improved in 1993 (AIN-93) to optimize animal nutrition with a major change being the substitution of cornstarch for sucrose. Therefore, we sought to examine the effects of iron deficiency on steady-state glucose homeostasis and the hepatic expression of glucose- and lipid-related genes in rats fed an iron-deficient diet based on either an AIN-76A or AIN-93 diet.

Methods

The study design consisted of 6 treatment groups: control (C; 40 mg Fe/kg diet), iron deficient (ID; ≤ 3 mg Fe/kg diet), or pair-fed (PF; 40 mg Fe/kg) fed either an AIN-76A or AIN-93 diet for 21 d. Hemoglobin and hematocrit were measured in whole blood. Serum insulin and cortisol were measure by ELISA. Serum glucose and triacylglycerols were measured by standard colorimetric enzyme assays. Alterations in hepatic gene expression were determined by real-time qPCR.

Results

Hemoglobin and hematocrit were significantly reduced in both ID groups compared to the C and PF groups. Similarly, animals in the both ID groups exhibited elevated steady-state levels of blood glucose and insulin, and significantly decreased levels of circulating cortisol compared to their respective PF controls. Serum triacyglycerols were only increased in ID animals consuming the AIN-76A diet. Hepatic gene expression analyses revealed a ~4- and 3-fold increase in the expression of glucokinase and pyruvate dehydrogenase kinase-4 mRNA, respectively, in the ID group on either diet compared to their respective PF counterparts. In contrast, the expression of lipogenic genes was significantly elevated in the AIN-76 ID group, while expression of these genes was unaffected by iron status in the AIN-93 ID group.

Conclusions

These results indicate that an impaired iron status is sufficient to alter glucose homeostasis, though alterations in lipid metabolism associated with ID are only observed in animals receiving the AIN-76A diet.

Adipocyte iron regulates adiponectin and insulin sensitivity

Iron overload is associated with increased diabetes risk. We therefore investigated the effect of iron on adiponectin, an insulin-sensitizing adipokine that is decreased in diabetic patients. In humans, normal-range serum ferritin levels were inversely associated with adiponectin, independent of inflammation. Ferritin was increased and adiponectin was decreased in type 2 diabetic and in obese diabetic subjects compared with those in equally obese individuals without metabolic syndrome. Mice fed a high-iron diet and cultured adipocytes treated with iron exhibited decreased adiponectin mRNA and protein. We found that iron negatively regulated adiponectin transcription via FOXO1-mediated repression. Further, loss of the adipocyte iron export channel, ferroportin, in mice resulted in adipocyte iron loading, decreased adiponectin, and insulin resistance. Conversely, organismal iron overload and increased adipocyte ferroportin expression because of hemochromatosis are associated with decreased adipocyte iron, increased adiponectin, improved glucose tolerance, and increased insulin sensitivity. Phlebotomy of humans with impaired glucose tolerance and ferritin values in the highest quartile of normal increased adiponectin and improved glucose tolerance. These findings demonstrate a causal role for iron as a risk factor for metabolic syndrome and a role for adipocytes in modulating metabolism through adiponectin in response to iron stores.

Enhanced expression of lipogenic genes may contribute to hyperglycemia and alterations in plasma lipids in response to dietary iron deficiency

Iron deficiency (ID) remains a public health concern affecting ~25% of the world's population. Metabolic consequences of ID include elevated plasma glucose concentrations consistent with increased reliance on glucose as a metabolic substrate, though the mechanisms controlling these responses remain unclear. To further characterize the metabolic response to ID, weanling male Sprague-Dawley rats were fed either a control (C; 40 mg Fe/kg diet) or iron-deficient (ID; 3 mg Fe/kg diet) diet or were pair-fed (PF) the C diet to the level of intake of the ID group for 21 days. In addition to reductions in hemoglobin, hematocrit, and plasma iron, the ID group also exhibited higher percent body fat and plasma triglycerides compared to the PF group. Steady-state levels of both plasma glucose and insulin increased 40 and 45%, respectively, in the ID group compared to the PF group. Plasma cortisol levels were decreased 67% in the ID group compared to the PF diet group. The systematic evaluation of the expression of genes involved in insulin signaling, glucose metabolism, and fatty acid metabolism in the liver and skeletal muscle revealed significant alterations in the expression of 48 and 52 genes in these tissues, respectively. A significant concurrent increase in lipogenic gene expression and decrease in gene expression related to β-oxidation in both the liver and skeletal muscle, in combination with differential tissue expression of genes involved in glucose metabolism, provides novel insight into the adaptive metabolic response in rodent models of severe iron deficiency anemia.

Effect of di(2-ethylhexyl) phthalate (DEHP) on lipolysis and lipoprotein lipase activities in adipose tissue of rats

The di(2-ethylhexyl) phthalate (DEHP) is an ubiquitous environmental chemical with detrimental health effects. The present work was designed to asses some potential mechanisms by which DEHP causes, among others, a reduced body fat retention. Since this effect could be related to an alteration of adipocyte triacylglycerol (TG) metabolism, we evaluated the effects of dietary DEHP in adipose tissues upon (1) the number and size of fat cells; (2) the basal and stimulated lipolysis and (3) the lipoprotein lipase (LPL) activity. Groups of male Wistar rats were fed for 21 days a control diet alone (control group) or the same control diet supplemented with 2% (w/w) of DEHP (DEHP group). The LPL activity of DEHP-fed rats was increased in lumbar and epididymal adipose tissues. These rats had significantly reduced weight in epididymal and lumbar tissues, together with reduced size of epididymal adipocytes. These alterations do not seem to be associated with higher lipid mobility because neither basal lipolysis nor 'in vitro' stimulated lipolysis by noradrenaline (NA) showed to be modified by DEHP. Based on these results, we concluded that the adipose tissue size reduction induced by DEHP intake is not due to changes in lipolysis nor to a decreased LPL activity. More research is needed to achieve a comprehensive understanding of the potential mechanisms by which DEHP causes, among others, a reduced body fat retention.

Hemochromatosis gene polymorphisms, mitochondrial haplogroups, and peripheral lipoatrophy during antiretroviral therapy

BACKGROUND

Antiretroviral therapy (ART)-associated lipoatrophy involves mitochondrial dysfunction. Iron metabolism impacts mitochondrial function and oxidative stress. Mitochondrial haplogroups and hemochromatosis gene (HFE) polymorphisms have been associated with ART-induced neuropathy. We assessed relationships between these variants and lipoatrophy.

METHODS

The AIDS Clinical Trials Group 384 study randomized ART-naive individuals to receive didanosine-stavudine or zidovudine-lamivudine, combined with efavirenz and/or nelfinavir. Substudy A5005s evaluated fat distribution by dual-energy X-ray absorptiometry (DEXA). We characterized HFE polymorphisms 845G>A and 187C>G and European mitochondrial haplogroups in A5005s participants who consented to genetic analyses.

RESULTS

Among 96 participants (58% were white, and 10% were female) with baseline and 48 or 64 week DEXA data, the median limb fat change was -8.8% (interquartile range, -28.7% to +15.6%). HFE 187C/G heterozygotes (n = 23) had less limb fat loss than 187C/C homozygotes (n = 71) (+6.1% vs. -12.5%; P = .02) and were less likely to develop lipoatrophy after adjustment for age, sex, race, and ART randomization (odds ratio, 0.31; 95% confidence interval, 0.10-0.95; P = .04). Among non-Hispanic white participants, median limb fat change was +26.1% among 5 participants with mitochondrial haplogroup J, compared with -9.7% among 49 participants with other mitochondrial haplogroups (P = .07).

CONCLUSIONS

HFE 187C>G and, possibly, mitochondrial haplogroup J gave relative protection against lipoatrophy during ART in A5005s. These associations should be replicated in other studies.