MitoNEET prevents iron overload-induced insulin resistance in H9c2 cells through regulation of mitochondrial iron

MitoNEET preserves muscle insulin sensitivity during iron overload by regulating mitochondrial iron, reactive oxygen species and fission

Iron overload (IO) is known to contribute to metabolic dysfunctions such as type 2 diabetes and insulin resistance. Using L6 skeletal muscle cells overexpressing the CDGSH iron-sulfur domain-containing protein 1 (CISD1, also known as mitoNEET) (mitoN) protein, we examined the potential role of MitoN in preventing IO-induced insulin resistance. In L6 control cells, IO resulted in insulin resistance which could be prevented by MitoN as demonstrated by western blot of p-Akt and Akt biosensor cells. Mechanistically, IO increased; mitochondrial iron accumulation, mitochondrial reactive oxygen species (ROS), Fis1-dependent mitochondrial fission, mitophagy, FUN14 domain-containing protein 1 (FUNDC1) expression, and decreased Parkin. MitoN overexpression was able to reduce increases in mitochondrial iron accumulation, mitochondrial ROS, mitochondrial fission, mitophagy and FUNDC1 upregulation due to IO. MitoN did not have any effect on the IO-induced downregulation of Parkin. MitoN alone also upregulated peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC1α) protein levels, a master regulator of mitochondrial biogenesis. The use of mitochondrial antioxidant, Skq1, or fission inhibitor, Mdivi-1, prevented IO-induced insulin resistance implying both mitochondrial ROS and fission play a causal role in the development of insulin resistance. Taken together, MitoN is able to confer protection against IO-induced insulin resistance in L6 skeletal muscle cells through regulation of mitochondrial iron content, mitochondrial ROS, and mitochondrial fission.

Ferrostatin-1 specifically targets mitochondrial iron-sulfur clusters and aconitase to improve cardiac function in Sirtuin 3 cardiomyocyte knockout mice

AIMS

Ferroptosis is a form of iron-regulated cell death implicated in ischemic heart disease. Our previous study revealed that Sirtuin 3 (SIRT3) is associated with ferroptosis and cardiac fibrosis. In this study, we tested whether the knockout of SIRT3 in cardiomyocytes (SIRT3cKO) promotes mitochondrial ferroptosis and whether the blockade of ferroptosis would ameliorate mitochondrial dysfunction.

METHODS AND RESULTS

Mitochondrial and cytosolic fractions were isolated from the ventricles of mice. Cytosolic and mitochondrial ferroptosis were analyzed by comparison to SIRT3loxp mice. An echocardiography study showed that SIRT3cKO mice developed heart failure as evidenced by a reduction of EF% and FS% compared to SIRT3loxp mice. Comparison of mitochondrial and cytosolic fractions of SIRT3cKO and SIRT3loxp mice revealed that, upon loss of SIRT3, mitochondrial, but not cytosolic, total lysine acetylation was significantly increased. Similarly, acetylated p53 was significantly upregulated only in the mitochondria. These data demonstrate that SIRT3 is the primary mitochondrial deacetylase. Most importantly, loss of SIRT3 resulted in significant reductions of frataxin, aconitase, and glutathione peroxidase 4 (GPX4) in the mitochondria. This was accompanied by a significant increase in levels of mitochondrial 4-hydroxynonenal. Treatment of SIRT3cKO mice with the ferroptosis inhibitor ferrostatin-1 (Fer-1) for 14 days significantly improved preexisting heart failure. Mechanistically, Fer-1 treatment significantly increased GPX4 and aconitase expression/activity, increased mitochondrial iron‑sulfur clusters, and improved mitochondrial membrane potential and Complex IV activity.

CONCLUSIONS

Inhibition of ferroptosis ameliorated cardiac dysfunction by specifically targeting mitochondrial aconitase and iron‑sulfur clusters. Blockade of mitochondrial ferroptosis may be a novel therapeutic target for mitochondrial cardiomyopathies.

Inhibition of CISD1 alleviates mitochondrial dysfunction and ferroptosis in mice with acute lung injury

The NET family member, CDGSH iron-sulfur domain-containing protein 1 (CISD1), is located in theoutermembrane of mitochondria, where it regulates energy and iron metabolism. CISD1 has vital functions in certain human diseases; however, its function in acute lung injury (ALI) is unknown. ALI pathogenesis critically involves mitochondrial dysfunction and ferroptosis, which might be regulated by CISD1. Therefore, we investigated CISD1's function in mitochondrial dysfunction and ferroptosis regulation in lipopolysaccharide (LPS)-induced ALI. We found that CISD1 was upregulated in LPS-induced ALI,and silencing Cisd1 prevented cell apoptosis and increased cell viability. When CISD1was inhibited by mitoNEET ligand-1 (NL-1) there was a significant mitigation of pathological injury and lung edema, and reduced numbers of total cells, polymorphonuclear leukocytes, and a decreased protein content in the bronchoalveolar lavage fluid (BALF). Moreover, inhibition of CISD1 markedly decreased the interleukin (IL)6, IL-1β, and tumor necrosis factor alpha (TNF-α) levels in the lungs and BALF of ALI-model mice. Silencing of Cisd1 prevented LPS-induced mitochondrial membrane potential depolarization, cellular ATP reduction, and reactive oxygen species (ROS) accumulation, suggesting mitochondrial protection. ALI activated ferroptosis, as evidenced by the increased lipid-ROS, intracellular Fe2+ level, reduced Gpx4 (glutathione peroxidase 4) expression, and the glutathione/glutathione disulfide ratio. Interestingly, inhibition of CISD1 reduced LPS-induced ferroptosis in vivo and in vitro. In conclusion, inhibition of CISD1 alleviated mitochondrial dysfunction and ferroptosis in LPS-induced ALI, identifying CISD1 as possible target for therapy of LPS-induced ALI.

Adipose knockout of H-ferritin improves energy metabolism in mice

OBJECTIVE

Ferritin, the principal iron storage protein, is essential to iron homeostasis. How iron homeostasis affects the adipose tissue is not well understood. We investigated the role of ferritin heavy chain in adipocytes in energy metabolism.

METHODS

We generated adipocyte-specific ferritin heavy chain (Fth, also known as Fth1) knockout mice, herein referred to as FthAKO. These mice were analyzed for iron homeostasis, oxidative stress, mitochondrial biogenesis and activity, adaptive thermogenesis, insulin sensitivity, and metabolic measurements. Mouse embryonic fibroblasts and primary mouse adipocytes were used for in vitro experiments.

RESULTS

In FthAKO mice, the adipose iron homeostasis was disrupted, accompanied by elevated expression of adipokines, dramatically induced heme oxygenase 1(Hmox1) expression, and a notable decrease in the mitochondrial ROS level. Cytosolic ROS elevation in the adipose tissue of FthAKO mice was very mild, and we only observed this in the brown adipose tissue (BAT) but not in the white adipose tissue (WAT). FthAKO mice presented an altered metabolic profile and showed increased insulin sensitivity, glucose tolerance, and improved adaptive thermogenesis. Interestingly, loss of ferritin resulted in enhanced mitochondrial respiration capacity and a preference for lipid metabolism.

CONCLUSIONS

These findings indicate that ferritin in adipocytes is indispensable to intracellular iron homeostasis and regulates systemic lipid and glucose metabolism.

MitoNEET Provides Cardioprotection via Reducing Oxidative Damage and Conserving Mitochondrial Function

Cardiometabolic diseases exert a significant health impact, leading to a considerable economic burden globally. The metabolic syndrome, characterized by a well-defined cluster of clinical parameters, is closely linked to an elevated risk of cardiovascular disease. Current treatment strategies often focus on addressing individual aspects of metabolic syndrome. We propose that exploring novel therapeutic approaches that simultaneously target multiple facets may prove more effective in alleviating the burden of cardiometabolic disease. There is a growing body of evidence suggesting that mitochondria can serve as a pivotal target for the development of therapeutics aimed at resolving both metabolic and vascular dysfunction. MitoNEET was identified as a binding target for the thiazolidinedione (TZD) class of antidiabetic drugs and is now recognized for its role in regulating various crucial cellular processes. Indeed, mitoNEET has demonstrated promising potential as a therapeutic target in various chronic diseases, encompassing cardiovascular and metabolic diseases. In this review, we present a thorough overview of the molecular mechanisms of mitoNEET, with an emphasis on their implications for cardiometabolic diseases in more recent years. Furthermore, we explore the potential impact of these findings on the development of novel therapeutic strategies and discuss potential directions for future research.

Recent Trends in the Antidiabetic Prominence of Natural and Synthetic Analogues of Aurones

Natural products are a boundless source for the development of pharmaceutical agents against a wide range of human diseases. Accordingly, naturally occurring aurones possess various biological benefits, such as anticancer, antioxidant, antimicrobial, antidiabetic, anti-inflammatory, antiviral and neuroprotective effects. In addition, various studies have revealed that aurones are potential templates for the regulation of diabetes mellitus and its associated complications. Likewise, certain aurones and their analogues have been found to be remarkable kinase inhibitors of DARK2, PPAR-γ, PTPM1, AGE, α-amylase and α-glucosidase, which represents a promising approach for the treatment of chronic metabolic disorders such as diabetes. Therefore, in our present study, we provide a detailed account of the advances in aurones as antidiabetic agents over the past decade.