Increased adipose tissue heme levels and exportation are associated with altered systemic glucose metabolism

Unearthing FLVCR1a: tracing the path to a vital cellular transporter

The Feline Leukemia Virus Subgroup C Receptor 1a (FLVCR1a) is a member of the SLC49 Major Facilitator Superfamily of transporters. Initially recognized as the receptor for the retrovirus responsible of pure red cell aplasia in cats, nearly two decades since its discovery, FLVCR1a remains a puzzling transporter, with ongoing discussions regarding what it transports and how its expression is regulated. Nonetheless, despite this, the substantial body of evidence accumulated over the years has provided insights into several critical processes in which this transporter plays a complex role, and the health implications stemming from its malfunction. The present review intends to offer a comprehensive overview and a critical analysis of the existing literature on FLVCR1a, with the goal of emphasising the vital importance of this transporter for the organism and elucidating the interconnections among the various functions attributed to this transporter.

The role of iron in host-microbiota crosstalk and its effects on systemic glucose metabolism

Iron is critical for the appearance and maintenance of life on Earth. Almost all organisms compete or cooperate for iron acquisition, demonstrating the importance of this essential element for the biological and physiological processes that are key for the preservation of metabolic homeostasis. In humans and other mammals, the bidirectional interactions between the bacterial component of the gut microbiota and the host for iron acquisition shape both host and microbiota metabolism. Bacterial functions influence host iron absorption, whereas the intake of iron, iron deficiency and iron excess in the host affect bacterial biodiversity, taxonomy and function, resulting in changes in bacterial virulence. These consequences of the host-microbial crosstalk affect systemic levels of iron, its storage in different tissues and host glucose metabolism. At the interface between the host and the microbiota, alterations in the host innate immune system and in circulating soluble factors that regulate iron (that is, hepcidin, lipocalin 2 and lactoferrin) are associated with metabolic disease. In fact, patients with obesity-associated metabolic dysfunction and insulin resistance exhibit dysregulation in iron homeostasis and alterations in their gut microbiota profile. From an evolutionary point of view, the pursuit of two important nutrients - glucose and iron - has probably driven human evolution towards the most efficient pathways and genes for human survival and health.

Phenylhydrazine-induced anemia reduces subcutaneous white and brown adipose tissues in hypothalamic obese rats

NEW FUNDINGS

What is the central question of this study? This study aims to assess whether an anemic state could modify adiposity and metabolic parameters in hypothalamic obese rats. What is the main finding and its importance? Our results indicate that hypothalamic obese rats do not display iron deficiency. However, the pharmacological induction of anemia in hypothalamic-obese rats resulted in reduced adiposity, characterized by a decrease in subcutaneous white and brown adipose tissue depots. These findings suggest that iron imbalance in obesity may elevate lipolysis.

ABSTRACT

Iron imbalance is frequent in obesity. Herein, we evaluated the impact of anemia induced by phenylhydrazine on adiposity and metabolic state of hypothalamic obese rats. Hypothalamic obesity was induced by high doses of glutamate monosodium (MSG; 4g/Kg) administered to neonatal male rats (n = 20). Controls (CTL; non-obese rats) received saline equimolar (n = 20). Rats were weaned at 21 days of life. At 70 days, half of the rats received three intraperitoneal doses of phenylhydrazine (PHZ; 40mg/Kg/dose) or saline solution. Body weight and food intake were accompanied for four weeks after PHZ administration. At 92 days, rats were euthanized, blood was collected for microcapillary hematocrit (Hct) analysis and plasma quantification of glucose, triglycerides, total cholesterol, and iron levels. The liver, the spleen, and the white (WAT) and brown (BAT) adipose tissues were excised, weighed, and used for histology. MSG-treated rats developed obesity, hypertriglyceridemia, and insulin resistance, compared to CTL rats, without changes in iron levels and Hct. PHZ administration reduced iron plasma levels and promoted similar tissue injuries in the spleen and liver from MSG and CTL rats. However, in MSG-treated rats, PHZ decreased fasting glucose levels and Hct, as well as diminished the subcutaneous WAT and BAT mass. Although MSG-obesity does not affect iron plasma levels and Hct by itself, PHZ-induced anemia associated with obesity induces a marked drop in subcutaneous WAT and BAT mass, suggesting that iron imbalance may lead to increased lipolytic responses in obese rats, compared to lean rats. This article is protected by copyright. All rights reserved.

Melatonin: Regulation of Prion Protein Phase Separation in Cancer Multidrug Resistance

The unique ability to adapt and thrive in inhospitable, stressful tumor microenvironments (TME) also renders cancer cells resistant to traditional chemotherapeutic treatments and/or novel pharmaceuticals. Cancer cells exhibit extensive metabolic alterations involving hypoxia, accelerated glycolysis, oxidative stress, and increased extracellular ATP that may activate ancient, conserved prion adaptive response strategies that exacerbate multidrug resistance (MDR) by exploiting cellular stress to increase cancer metastatic potential and stemness, balance proliferation and differentiation, and amplify resistance to apoptosis. The regulation of prions in MDR is further complicated by important, putative physiological functions of ligand-binding and signal transduction. Melatonin is capable of both enhancing physiological functions and inhibiting oncogenic properties of prion proteins. Through regulation of phase separation of the prion N-terminal domain which targets and interacts with lipid rafts, melatonin may prevent conformational changes that can result in aggregation and/or conversion to pathological, infectious isoforms. As a cancer therapy adjuvant, melatonin could modulate TME oxidative stress levels and hypoxia, reverse pH gradient changes, reduce lipid peroxidation, and protect lipid raft compositions to suppress prion-mediated, non-Mendelian, heritable, but often reversible epigenetic adaptations that facilitate cancer heterogeneity, stemness, metastasis, and drug resistance. This review examines some of the mechanisms that may balance physiological and pathological effects of prions and prion-like proteins achieved through the synergistic use of melatonin to ameliorate MDR, which remains a challenge in cancer treatment.

Early Changes in Immune Cell Count, Metabolism, and Function Following Sleeve Gastrectomy: A Prospective Human Study

OBJECTIVE

To characterize longitudinal changes in blood biomarkers, leukocyte composition, and gene expression following laparoscopic sleeve gastrectomy (LSG).

BACKGROUND

LSG is an effective treatment for obesity, leading to sustainable weight loss and improvements in obesity-related comorbidities and inflammatory profiles. However, the effects of LSG on immune function and metabolism remain uncertain.

METHODS

Prospective data were collected from 23 enrolled human subjects from a single institution. Parameters of weight, comorbidities, and trends in blood biomarkers and leukocyte subsets were observed from preoperative baseline to 1 year postsurgery in 3-month follow-up intervals. RNA sequencing was performed on pairs of whole blood samples from the first 6 subjects of the study (baseline and 3 months postsurgery) to identify genome-wide gene expression changes associated with undergoing LSG.

RESULTS

LSG led to a significant decrease in mean total body weight loss (18.1%) at 3 months and among diabetic subjects a reduction in hemoglobin A1c. Improvements in clinical inflammatory and hormonal biomarkers were demonstrated as early as 3 months after LSG. A reduction in neutrophil-lymphocyte ratio was observed, driven by a reduction in absolute neutrophil counts. Gene set enrichment analyses of differential whole blood gene expression demonstrated that after 3 months LSG induced transcriptomic changes not only in inflammatory cytokine pathways but also in several key metabolic pathways related to energy metabolism.

CONCLUSIONS

LSG induces significant changes in the composition and metabolism of immune cells as early as 3 months postoperatively. Further evaluation is required of bariatric surgery's effects on immunometabolism and the consequences for host defense and metabolic disease.

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

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

Early changes in immune cell metabolism and function are a hallmark of sleeve gastrectomy: a prospective human study

OBJECTIVE

To characterize longitudinal changes in blood biomarkers, leukocyte composition, and gene expression following laparoscopic sleeve gastrectomy (LSG).

BACKGROUND

LSG is an effective treatment for obesity, leading to sustainable weight loss and improvements in obesity-related co-morbidities and inflammatory profiles. However, the effects of LSG on immune function and metabolism remain uncertain.

METHODS

Prospective data was collected from 23 enrolled human subjects from a single institution. Parameters of weight, co-morbidities, and trends in blood biomarkers and leukocyte subsets were observed from pre-operative baseline to one year in three-month follow-up intervals. RNA-sequencing was performed on pairs of whole blood samples from the first six subjects of the study (baseline and three months post-surgery) to identify genome-wide gene expression changes associated with undergoing LSG.

RESULTS

LSG led to a significant decrease in mean total body weight loss (18.1%) at three months and among diabetic subjects a reduction in HbA1c. Improvements in clinical inflammatory and hormonal biomarkers were demonstrated as early as three months after LSG. A reduction in neutrophil-lymphocyte ratio was observed, driven by a reduction in absolute neutrophil counts. Gene set enrichment analyses of differential whole blood gene expression demonstrated that after three months, LSG induced transcriptomic changes not only in inflammatory cytokine pathways but also in several key metabolic pathways related to energy metabolism.

CONCLUSIONS

LSG induces significant changes in the composition and metabolism of immune cells as early as three months post-operatively. Further evaluation is required of bariatric surgery's effects on immunometabolism and consequences for host defense and metabolic disease.

Iron Metabolism in Obesity and Metabolic Syndrome

Obesity is an excessive adipose tissue accumulation that may have detrimental effects on health. Particularly, childhood obesity has become one of the main public health problems in the 21st century, since its prevalence has widely increased in recent years. Childhood obesity is intimately related to the development of several comorbidities such as nonalcoholic fatty liver disease, dyslipidemia, type 2 diabetes mellitus, non-congenital cardiovascular disease, chronic inflammation and anemia, among others. Within this tangled interplay between these comorbidities and associated pathological conditions, obesity has been closely linked to important perturbations in iron metabolism. Iron is the second most abundant metal on Earth, but its bioavailability is hampered by its ability to form highly insoluble oxides, with iron deficiency being the most common nutritional disorder. Although every living organism requires iron, it may also cause toxic oxygen damage by generating oxygen free radicals through the Fenton reaction. Thus, iron homeostasis and metabolism must be tightly regulated in humans at every level (i.e., absorption, storage, transport, recycling). Dysregulation of any step involved in iron metabolism may lead to iron deficiencies and, eventually, to the anemic state related to obesity. In this review article, we summarize the existent evidence on the role of the most recently described components of iron metabolism and their alterations in obesity.

The Differential Expression of Long Noncoding RNAs in Type 2 Diabetes Mellitus and Latent Autoimmune Diabetes in Adults

BACKGROUND

Long noncoding RNAs (lncRNAs) were previously found to be closely related to the pathogenesis of diabetes.

OBJECTIVES

To reveal the differentially expressed lncRNAs and messenger RNAs (mRNAs) involved in type 2 diabetes mellitus (T2DM) and latent autoimmune diabetes in adults (LADA) and predict the lncRNA target genes to derive their expression profiles for the diagnosis of T2DM and LADA and their differential diagnosis.

METHODS

Twelve venous blood samples were collected from T2DM patients, LADA patients, and nondiseased subjects to obtain total RNAs. After removing rRNA from total RNAs to establish the desired library for sequencing, quality control and quantification analyses were carried out. The fragments per kilobase of exon model per million reads mapped (FPKM) of lncRNAs were calculated to construct the gene expression profiles of lncRNAs and mRNAs. Fold changes (fold change: 2.0) and p values (p values (.

RESULTS

Compared to nondiseased controls, 68,763 versus 28,523 lncRNAs and 133 versus 1035 mRNAs were significantly upregulated and significantly downregulated, respectively, in T2DM patients. For LADA patients, 68,748 versus 28,538 lncRNAs and 219 versus 805 mRNAs were significantly upregulated and significantly downregulated, respectively, relative to nondiseased controls. Compared to T2DM patients, 74,207 versus 23,079 lncRNAs and 349 versus 137 mRNAs were significantly upregulated and significantly downregulated, respectively, in LADA patients. Based on the correlation analysis, seven lncRNA-mRNA pairs (BTG2, A2M, HECTD4, MBTPS1, DBH, FLVCR1, and NCBP2) were significantly coexpressed, and two lncRNAs (ENST00000608916 and ENST00000436373) were newly discovered.

CONCLUSION

Significant differences in lncRNA expression were discovered among the three groups. Furthermore, after predicting lncRNA expression profiles, GO/KEGG pathway analysis could deduce the target gene function.

Haptoglobin phenotype influences the effectiveness of diet-induced weight loss in middle-age abdominally obese women with metabolic abnormalities

BACKGROUND & AIMS

Haptoglobin (Hp) is associated with risks of obesity and cardiometabolic dysfunction; however, the role of the Hp phenotype in diet-induced weight loss remains to be elucidated. This study investigated whether the Hp phenotype contributes to inter-individual variations in body weight reduction as well as changes in the metabolic profile.

METHODS

Secondary data analysis from a randomized controlled trial. In total, 151 abdominally obese Taiwanese women with ≥2 metabolic components were randomized to each of four dietary programs [calorie restriction (CR), calorie restriction plus fish oil supplementation (CRF), calorie restricted meal replacement (CRMR), and calorie restricted meal replacement with fish oil supplementation (CRMRF)] for 12 weeks. Abdominal obesity was defined as a waist circumference (WC) ≥ 80 cm in women. Hp phenotyping was performed by plasma gel electrophoresis.

RESULTS

The prevalence of the Hp 1-1, 2-1, and 2-2 phenotypes were 12.58%, 41.06% and 46.35%, respectively. The mean age was 50.59 ± 12.22 years, and mean reduction in the percent body weight was 4.7% ± 3.8%. The Hp 1-1 phenotype exhibited significant decreases in the WC, body fat mass, plasma insulin levels, free hemoglobin and homeostatic model assessment of insulin resistance (HOMA-IR) compared to the Hp 2-1 or Hp 2-2 phenotypes after adjusting for the baseline age, WC, metabolic syndrome (MetS), and dietary programs (all adjusted p < 0.05). A greater improvement in the prevalence of central obesity and, to a lesser extent, MetS was also found in women with the Hp 1-1 phenotype.

CONCLUSIONS

Obese women with the Hp 1-1 phenotype might obtain greater benefits in terms of reducing abdominal fat and improving insulin sensitivity in response to hypocaloric diet-induced weight reduction. The findings from this study support potential gene-diet interactions affecting weight loss. This trial was registered at ClinicalTrials.gov as NCT01768169.

CLINICAL TRIAL REGISTRY

This trial was registered at ClinicalTrials.gov as NCT01768169.