Insulin-like modulation of Akt/FoxO signaling by copper ions is independent of insulin receptor

Essential and Non-Essential Metals and Metalloids and Their Role in Atherosclerosis

Peripheral arterial disease (PAD) is becoming more prevalent in the aging developed world and can have significant functional impacts on patients. There is a recent recognition that environmental toxicants such as circulating metals and metalloids may contribute to the pathogenesis of atherosclerotic disease, but the mechanisms are complex. While the broad toxic biologic effects of metals in human systems have been extensively reviewed, the role of non-essential exposure and essential metal aberrancy in PAD specifically is less frequently discussed. This review of the literature describes current scientific knowledge regarding the individual roles several major metals and metalloids play in atherogenesis and highlights areas where a dearth of data exist. The roles of lead (Pb), arsenic (As), cadmium (Cd), iron (Fe), copper (Cu), selenium (Se) are included. Contemporary outcomes of therapeutic trials aimed at chelation therapy of circulating metals to impact cardiovascular outcomes are also discussed. This review highlights the supported notion of differential metal presence within peripheral plaques themselves, although distinguishing their roles within these plaques requires further illumination.

A prospective study of early pregnancy metal concentrations and gestational diabetes mellitus based on a birth cohort in Northwest China

BACKGROUND

Exposure to metals during early pregnancy may affect maternal glucose metabolism. We were aimed to assess the associations between early pregnancy whole blood concentrations of copper (Cu), zinc (Zn), calcium (Ca), iron (Fe), and magnesium (Mg) with GDM later in the second trimester among pregnant women in Northwest China.

METHODS

This study included 5478 first-trimester pregnant women who participated in the birth cohort of the Northwest Women's and Children's Hospital between July 2018 and December 2023. Metal concentrations, basic demographic characteristics, lifestyle and behavior patterns were collected. An oral glucose tolerance test was performed in the second trimester. A generalized linear model was used to analyze the effects of metal concentrations on GDM. A two-piecewise regression model was adopted to examine the threshold effect and find out the turning point. Weighted Quantile Sum (WQS) regression was conducted using a dataset randomly split into training and validation sets at a 4:6 ratio to investigate the association between metal mixtures and GDM.

RESULTS

Compared to the lowest tertile, the middle (RR = 0.82, 95%CI = 0.71, 0.95) and highest (RR = 0.84, 95%CI = 0.73, 0.97) tertiles of Ca concentrations could decrease the risk of GDM. However, the highest tertile of Cu concentration could increase the risk of GDM (RR = 1.18, 95%CI = 1.01, 1.39). Additionally, a non-linear relationship between Ca concentration with GDM and FPG was observed. The risk of GDM (RR = 0.08, 95%CI: 0.02, 0.31) and FPG (β=-0.56, 95%CI: -0.99, -0.12) decreased with 1 unit increase in ln-transformed Ca concentration below the turning point. However, the WQS index of maternal mixed metals was not correlated with the incidence of GDM (RR = 1.08, 95%CI = 0.98, 1.19).

CONCLUSIONS

Higher Cu concentration during early pregnancy may increase the risk of GDM in mothers. Increased Ca concentration may reduce the risk of GDM and lower the concentration of FPG below the turning point. Our findings could provide an early marker for potentially modifiable risk factors associated with maternal glucose dysregulation during pregnancy.

Dysfunctional copper homeostasis in Caenorhabditis elegans affects genomic and neuronal stability

While copper (Cu) is an essential trace element for biological systems due to its redox properties, excess levels may lead to adverse effects partly due to overproduction of reactive species. Thus, a tightly regulated Cu homeostasis is crucial for health. Cu dyshomeostasis and elevated labile Cu levels are associated with oxidative stress and neurodegenerative disorders, but the underlying mechanisms have yet to be fully characterized. Here, we used Caenorhabditis elegans loss-of-function mutants of the Cu chaperone ortholog atox-1 and the Cu binding protein ortholog ceruloplasmin to model Cu dyshomeostasis, as they display a shifted ratio of total Cu towards labile Cu. We applied highly selective and sensitive techniques to quantify metabolites associated to oxidative stress with focus on mitochondrial integrity, oxidative DNA damage and neurodegeneration all in the context of a disrupted Cu homeostasis. Our novel data reveal elevated oxidative stress, compromised mitochondria displaying reduced ATP levels and cardiolipin content. Cu dyshomeostasis further induced oxidative DNA damage and impaired DNA damage response as well as neurodegeneration characterized by behavior and neurotransmitter analysis. Our study underscores the essentiality of a tightly regulated Cu homeostasis as well as mitochondrial integrity for both genomic and neuronal stability.

Deciphering the Role of Copper Homeostasis in Atherosclerosis: From Molecular Mechanisms to Therapeutic Targets

Cardiovascular disease (CVD) is a leading cause of death globally, with atherosclerosis (AS) playing a central role in its pathogenesis as a chronic inflammatory condition. Copper, an essential trace element in the human body, participates in various biological processes and plays a significant role in the cardiovascular system. Maintaining normal copper homeostasis is crucial for cardiovascular health, and dysregulation of copper balance is closely associated with the development of CVD. When copper homeostasis is disrupted, it can induce cell death, which has been proposed to be a novel form of "cuproptosis", distinct from traditional programmed cell death. This new form of cell death is closely linked to the occurrence and progression of AS. This article elaborately describes the physiological mechanisms of copper homeostasis and explores its interactions with signaling pathways related to AS. Additionally, we focus on the process and mechanism of cell death induced by imbalances in copper homeostasis and summarize the relationship between copper homeostasis-related genes and AS. We also emphasize potential therapeutic approaches, such as copper balance regulators and nanotechnology interventions, to adjust copper levels in the body, providing new ideas and strategies for the prevention and treatment of CVD.

Selective activation of cellular stress response pathways by fumaric acid esters

The cellular response to oxidants or xenobiotics comprises two key pathways, resulting in modulation of NRF2 and FOXO transcription factors, respectively. Both mount a cytoprotective response, and their activation relies on crucial protein thiol moieties. Using fumaric acid esters (FAEs), known thiol-reactive compounds, we tested for activation of NRF2 and FOXO pathways in cultured human hepatoma cells by dimethyl/diethyl as well as monomethyl/monoethyl fumarate. Whereas only the diesters caused acute glutathione depletion and activation of the stress kinase p38MAPK, all four FAEs stimulated NRF2 stabilization and upregulation of NRF2 target genes. However, no significant FAE-induced activation of FOXO-dependent target gene expression was observed. Therefore, while both NRF2 and FOXO pathways are responsive to oxidants and xenobiotics, FAEs selectively activate NRF2 signaling.

Copper Homeostasis in the Model Organism C. elegans

Cellular and organismic copper (Cu) homeostasis is regulated by Cu transporters and Cu chaperones to ensure the controlled uptake, distribution and export of Cu ions. Many of these processes have been extensively investigated in mammalian cell culture, as well as in humans and in mammalian model organisms. Most of the human genes encoding proteins involved in Cu homeostasis have orthologs in the model organism, Caenorhabditis elegans (C. elegans). Starting with a compilation of human Cu proteins and their orthologs, this review presents an overview of Cu homeostasis in C. elegans, comparing it to the human system, thereby establishing the basis for an assessment of the suitability of C. elegans as a model to answer mechanistic questions relating to human Cu homeostasis.

FOXO3a deregulation in uterine smooth muscle tumors

OBJECTIVE

The present study aimed to investigate FOXO3a deregulation in Uterine Smooth Muscle Tumors (USMT) and its potential association with cancer development and prognosis.

METHODS

The authors analyzed gene and protein expression profiles of FOXO3a in 56 uterine Leiomyosarcomas (LMS), 119 leiomyomas (comprising conventional and unusual leiomyomas), and 20 Myometrium (MM) samples. The authors used techniques such as Immunohistochemistry (IHC), FISH/CISH, and qRT-PCR for the present analyses. Additionally, the authors conducted an in-silico analysis to understand the interaction network involving FOXO3a and its correlated genes.

RESULTS

This investigation revealed distinct expression patterns of the FOXO3a gene and protein, including both normal and phosphorylated forms. Expression levels were notably elevated in LMS, and Unusual Leiomyomas (ULM) compared to conventional Leiomyomas (LM) and Myometrium (MM) samples. This upregulation was significantly associated with metastasis and Overall Survival (OS) in LMS patients. Intriguingly, FOXO3a deregulation did not seem to be influenced by EGF/HER-2 signaling, as there were minimal levels of EGF and VEGF expression detected, and HER-2 and EGFR were negative in the analyzed samples. In the examination of miRNAs, the authors observed upregulation of miR-96-5p and miR-155-5p, which are known negative regulators of FOXO3a, in LMS samples. Conversely, the tumor suppressor miR-let7c-5p was downregulated.

CONCLUSIONS

In summary, the outcomes of the present study suggest that the imbalance in FOXO3a within Uterine Smooth Muscle Tumors might arise from both protein phosphorylation and miRNA activity. FOXO3a could emerge as a promising therapeutic target for individuals with Unusual Leiomyomas and Leiomyosarcomas (ULM and LMS), offering novel directions for treatment strategies.

The Link between Trace Metal Elements and Glucose Metabolism: Evidence from Zinc, Copper, Iron, and Manganese-Mediated Metabolic Regulation

Trace metal elements are of vital importance for fundamental biological processes. They function in various metabolic pathways after the long evolution of living organisms. Glucose is considered to be one of the main sources of biological energy that supports biological activities, and its metabolism is tightly regulated by trace metal elements such as iron, zinc, copper, and manganese. However, there is still a lack of understanding of the regulation of glucose metabolism by trace metal elements. In particular, the underlying mechanism of action remains to be elucidated. In this review, we summarize the current concepts and progress linking trace metal elements and glucose metabolism, particularly for the trace metal elements zinc, copper, manganese, and iron.

Copper in the suprachiasmatic circadian clock: A possible link between multiple circadian oscillators

The mammalian circadian clock in the suprachiasmatic nucleus (SCN) is very robust, able to coordinate our daily physiological and behavioral rhythms with exquisite accuracy. Simultaneously, the SCN clock is highly sensitive to environmental timing cues such as the solar cycle. This duality of resiliency and sensitivity may be sustained in part by a complex intertwining of three cellular oscillators: transcription/translation, metabolic/redox, and membrane excitability. We suggest here that one of the links connecting these oscillators may be forged from copper (Cu). Cellular Cu levels are highly regulated in the brain and peripherally, and Cu affects cellular metabolism, redox state, cell signaling, and transcription. We have shown that both Cu chelation and application induce nighttime phase shifts of the SCN clock in vitro and that these treatments affect glutamate, N-methyl-D-aspartate receptor, and associated signaling processes differently. More recently we found that Cu induces mitogen-activated protein kinase-dependent phase shifts, while the mechanisms by which Cu removal induces phase shifts remain unclear. Lastly, we have found that two Cu transporters are expressed in the SCN, and that one of these transporters (ATP7A) exhibits a day/night rhythm. Our results suggest that Cu homeostasis is tightly regulated in the SCN, and that changes in Cu levels may serve as a time cue for the circadian clock. We discuss these findings in light of the existing literature and current models of multiple coupled circadian oscillators in the SCN.

Nuclear trapping of inactive FOXO1 by the Nrf2 activator diethyl maleate

Diethyl maleate (DEM), a thiol-reactive α,β-unsaturated carbonyl compound, depletes glutathione (GSH) in exposed cells and was previously shown by us to elicit a stress response in Caenorhabditis elegans that, at lower concentrations, results in enhanced stress resistance and longer lifespan. This hormetic response was mediated through both the Nrf2 ortholog, SKN-1, and the forkhead box O (FOXO) family transcription factor DAF-16. As FOXO signaling is evolutionarily conserved, we analyzed here the effects of DEM exposure on FOXO in cultured human cells (HepG2, HEK293). DEM elicited nuclear accumulation of GFP-coupled wild-type human FOXO1, as well as of a cysteine-deficient FOXO1 mutant. Despite the nuclear accumulation of FOXO1, neither FOXO1 DNA binding nor FOXO target gene expression were stimulated, suggesting that DEM causes nuclear accumulation but not activation of FOXO1. FOXO1 nuclear exclusion elicited by insulin or xenobiotics such as arsenite or copper ions was attenuated by DEM, suggesting that DEM interfered with nuclear export. In addition, insulin-induced FOXO1 phosphorylation at Thr-24, which is associated with FOXO1 nuclear exclusion, was attenuated upon exposure to DEM. Different from FOXO-dependent expression of genes, Nrf2 target gene mRNAs were elevated upon exposure to DEM. These data suggest that, different from C. elegans, DEM elicits opposing effects on the two stress-responsive transcription factors, Nrf2 and FOXO1, in cultured human cells.

•

Diethyl maleate (DEM) causes FOXO1 nuclear accumulation in HepG2 or HEK293 cells.

•

DEM also elicits nuclear accumulation of the FOXO-ortholog, DAF-16, in C. elegans.

•

Nevertheless, DEM does not elicit expression of FOXO, but of Nrf2 target genes.

•

Insulin-induced FOXO1 phosphorylation and nuclear exclusion are attenuated by DEM.

•

Nuclear accumulation of FOXO1 is due to interference with nuclear export machinery.

Effects of life-time exposure to waterborne copper on the somatotropic axis of the viviparous fish Poecilia vivipara

Reduced fish growth following chronic exposure to dissolved copper (Cu) is well reported in the literature. Nevertheless, information on the mechanism(s) involved in this process is scarce. Therefore, we evaluated growth, gene expression and concentrations of proteins related to growth regulation in the viviparous guppy Poecilia vivipara chronically exposed to dissolved Cu. Newborn (<24 h after birth) fish were kept under control conditions or exposed to environmentally relevant concentrations of Cu (5 and 9 μg/L) in salt water (24 ppt) for 345 days. After exposure, fish growth was evaluated based on body weight and length. Also, growth hormone (gh) mRNA expression was evaluated in brain, while growth hormone receptor 1 (ghr1) and 2 (ghr2) mRNA expressions were analyzed in brain, skeletal muscle and liver. In turn, insulin-like growth factor 1 (igf1) and 2 (igf2) mRNA expressions were evaluated in skeletal muscle and liver. Additionally, Gh concentration was assessed in brain, while Ghr concentration was evaluated in skeletal muscle and liver. Exposure to 9 μg/L Cu reduced fish body weigh and length. Metal exposure affected mRNA expression only in skeletal muscle. Reduced ghr2 mRNA expression was observed in guppies exposed to 5 and 9 μg/L Cu. Additionally, reduced igf1 and igf2 mRNA expressions were observed in guppies exposed to 9 μg/L Cu. However, no significant change in Ghr concentration was observed. The reduced ghr2 mRNA expression suggests that chronic Cu exposure induced an insensitivity of the skeletal muscle to Gh, thus resulting in reduced igf1 and igf2 mRNA expression which lead to reduced fish growth. These findings indicate that chronic exposure to dissolved Cu disrupts the somatotropic axis regulation, thus helping to elucidate the mechanism underlying the Cu-dependent inhibition of growth observed in the viviparous fish P. vivipara.

Synthesis of cytochrome c oxidase 1 (SCO1) inhibits insulin sensitivity by decreasing copper levels in adipocytes

Dysregulation of insulin signaling leads to type 2 diabetes mellitus (T2DM) and other metabolic disorders. Obesity is an important contributor to insulin resistance, and although the understanding of this relationship has improved in recent years, the mechanism of obesity-induced insulin resistance is not completely understood. Disorders of copper metabolism tend to accompany the development of obesity, which increases the risk of insulin resistance. Synthesis of cytochrome c oxidase 1 (SCO1) functions in the assembly of cytochrome c oxidase (COX) and cellular copper homeostasis. However, the role of SCO1 in the regulation of metabolism remains unknown. Here, we found that obese mice had higher expression of SCO1 and lower levels of copper in white adipose tissue (WAT) than did the control mice. Overexpression of SCO1 in adipocytes was associated with copper deficiency. Copper increased insulin sensitivity by decreasing the level of phosphatase and tensin homolog (PTEN) protein. Ectopic expression of SCO1 led to insulin resistance and was accompanied by a decrease in intracellular copper level, and addition of copper abolished the inhibitory effect of SCO1 on insulin sensitivity. Our results demonstrated a novel role of SCO1 in modulating insulin sensitivity via the regulation of copper concentration in WAT and suggested a potential therapeutic target for T2DM.

Cellular adaptation to xenobiotics: Interplay between xenosensors, reactive oxygen species and FOXO transcription factors

Cells adapt to an exposure to xenobiotics by upregulating the biosynthesis of proteins involved in xenobiotic metabolism. This is achieved largely via activation of cellular xenosensors that modulate gene expression. Biotransformation of xenobiotics frequently comes with the generation of reactive oxygen species (ROS). ROS, in turn, are known modulators of signal transduction processes. FOXO (forkhead box, class O) transcription factors are among the proteins deeply involved in the cellular response to stress, including oxidative stress elicited by the formation of ROS. On the one hand, FOXO activity is modulated by ROS, while on the other, FOXO target genes include many that encode antioxidant proteins – thereby establishing a regulatory circuit. Here, the role of ROS and of FOXOs in the regulation of xenosensor transcriptional activities will be discussed. Constitutive androstane receptor (CAR), pregnane X receptor (PXR), peroxisome proliferator-activated receptors (PPARs), arylhydrocarbon receptor (AhR) and nuclear factor erythroid 2-related factor 2 (Nrf2) all interact with FOXOs and/or ROS. The two latter not only fine-tune the activities of xenosensors but also mediate interactions between them. As a consequence, the emerging picture of an interplay between xenosensors, ROS and FOXO transcription factors suggests a modulatory role of ROS and FOXOs in the cellular adaptive response to xenobiotics.

•

Exposure of cells to xenobiotics may trigger formation of reactive oxygen species.

•

Xenosensors respond to xenobiotics by upregulation of xenobiotic metabolism.

•

FOXO transcription factors modulate the activities of several xenosensors.

•

ROS affect FOXO activity, and FOXO target genes include antioxidant proteins.

•

FOXOs bridge xenobiotic-induced ROS generation and xenosensor regulation.

The Inorganic Side of NGF: Copper(II) and Zinc(II) Affect the NGF Mimicking Signaling of the N-Terminus Peptides Encompassing the Recognition Domain of TrkA Receptor

The nerve growth factor (NGF) N-terminus peptide, NGF(1–14), and its acetylated form, Ac-NGF(1–14), were investigated to scrutinize the ability of this neurotrophin domain to mimic the whole protein. Theoretical calculations demonstrated that non-covalent forces assist the molecular recognition of TrkA receptor by both peptides. Combined parallel tempering/docking simulations discriminated the effect of the N-terminal acetylation on the recognition of NGF(1–14) by the domain 5 of TrkA (TrkA-D5). Experimental findings demonstrated that both NGF(1–14) and Ac-NGF(1–14) activate TrkA signaling pathways essential for neuronal survival. The NGF-induced TrkA internalization was slightly inhibited in the presence of Cu²⁺ and Zn²⁺ ions, whereas the metal ions elicited the NGF(1–14)-induced internalization of TrkA and no significant differences were found in the weak Ac-NGF(1–14)-induced receptor internalization. The crucial role of the metals was confirmed by experiments with the metal-chelator bathocuproine disulfonic acid, which showed different inhibitory effects in the signaling cascade, due to different metal affinity of NGF, NGF(1–14) and Ac-NGF(1–14). The NGF signaling cascade, activated by the two peptides, induced CREB phosphorylation, but the copper addition further stimulated the Akt, ERK and CREB phosphorylation in the presence of NGF and NGF(1–14) only. A dynamic and quick influx of both peptides into PC12 cells was tracked by live cell imaging with confocal microscopy. A significant role of copper ions was found in the modulation of peptide sub-cellular localization, especially at the nuclear level. Furthermore, a strong copper ionophoric ability of NGF(1–14) was measured. The Ac-NGF(1–14) peptide, which binds copper ions with a lower stability constant than NGF(1–14), exhibited a lower nuclear localization with respect to the total cellular uptake. These findings were correlated to the metal-induced increase of CREB and BDNF expression caused by NGF(1–14) stimulation. In summary, we here validated NGF(1–14) and Ac-NGF(1–14) as first examples of monomer and linear peptides able to activate the NGF-TrkA signaling cascade. Metal ions modulated the activity of both NGF protein and the NGF-mimicking peptides. Such findings demonstrated that NGF(1–14) sequence can reproduce the signal transduction of whole protein, therefore representing a very promising drug candidate for further pre-clinical studies.