Drp1 controls complex II assembly and skeletal muscle metabolism by Sdhaf2 action on mitochondria.

The dynamin-related guanosine triphosphatase, Drp1 (encoded by ), plays a central role in mitochondrial fission and is requisite for numerous cellular processes; however, its role in muscle metabolism remains unclear. Here, we show that, among human tissues, the highest number of gene correlations with is in skeletal muscle. Knockdown of Drp1 (Drp1-KD) promoted mitochondrial hyperfusion in the muscle of male mice.

The mitochondrial biliverdin exporter ABCB10 in hepatocytes mitigates neutrophilic inflammation in alcoholic hepatitis.

Acute liver failure caused by alcoholic hepatitis (AH) is only effectively treated with liver transplantation. Livers of patients with AH show a unique molecular signature characterized by defective hepatocellular redox metabolism, concurrent to hepatic infiltration of neutrophils that express myeloperoxidase (MPO) and form neutrophil extracellular traps (NETs). Exacerbated NET formation and MPO activity contribute to liver damage in mice with AH and predicts poor prognosis in AH patients.

Mitochondria isolated from lipid droplets of white adipose tissue reveal functional differences based on lipid droplet size.

Recent studies in brown adipose tissue (BAT) described a unique subpopulation of mitochondria bound to lipid droplets (LDs), which were termed PeriDroplet Mitochondria (PDM). PDM can be isolated from BAT by differential centrifugation and salt washes. Contrary to BAT, this approach has so far not led to the successful isolation of PDM from white adipose tissue (WAT).

Quantifying mitochondrial redox and bilirubin content in intact primary hepatocytes of obese mice using fluorescent reporters.

Assessing the physiological role of HO requires sensitive techniques to quantify HO and antioxidants in live cells. Here, we present a protocol to assess the mitochondrial redox state and unconjugated bilirubin levels in intact live primary hepatocytes from obese mice. We described steps to quantify HO, GSSG/GSH, and bilirubin content in the mitochondrial matrix and the cytosol using the fluorescent reporters roGFP2-ORP1, GRX1-roGFP2, and UnaG, respectively.

Restoration of lysosomal acidification rescues autophagy and metabolic dysfunction in non-alcoholic fatty liver disease.

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease in the world. High levels of free fatty acids in the liver impair hepatic lysosomal acidification and reduce autophagic flux. We investigate whether restoration of lysosomal function in NAFLD recovers autophagic flux, mitochondrial function, and insulin sensitivity.

Measuring Mitochondrial Uncoupling in Mouse Primary Brown Adipocytes Differentiated Ex Vivo.

Measuring the mitochondrial respiratory capacity of brown adipocytes ex vivo is an essential approach to understand the cell-autonomous regulators of mitochondrial uncoupling in brown adipose tissue. Here, we describe two protocols to isolate brown preadipocytes from mice, their ex vivo differentiation to mature brown adipocytes and the quantification of their mitochondrial uncoupling capacity by respirometry.

A novel approach to measure complex V ATP hydrolysis in frozen cell lysates and tissue homogenates.

Mitochondrial depolarization can initiate reversal activity of ATP synthase, depleting ATP by its hydrolysis. We have recently shown that increased ATP hydrolysis contributes to ATP depletion leading to a maladaptation in mitochondrial disorders, where maximal hydrolytic capacity per CV content is increasing. However, despite its importance, ATP hydrolysis is not a commonly studied parameter because of the limitations of the currently available methods.

Inhibition of ATP synthase reverse activity restores energy homeostasis in mitochondrial pathologies.

The maintenance of cellular function relies on the close regulation of adenosine triphosphate (ATP) synthesis and hydrolysis. ATP hydrolysis by mitochondrial ATP Synthase (CV) is induced by loss of proton motive force and inhibited by the mitochondrial protein ATPase inhibitor (ATPIF1). The extent of CV hydrolytic activity and its impact on cellular energetics remains unknown due to the lack of selective hydrolysis inhibitors of CV.

ISG15 Is a Novel Regulator of Lipid Metabolism during Infection.

Interferon-stimulated gene 15 (ISG15) is a 15-kDa ubiquitin-like modifier that binds to target proteins in a process termed ISGylation. ISG15, first described as an antiviral molecule against many viruses, participates in numerous cellular processes, from immune modulation to the regulation of genome stability. Interestingly, the role of ISG15 as a regulator of cell metabolism has recently gained strength.

The mitochondrial fission protein Drp1 in liver is required to mitigate NASH and prevents the activation of the mitochondrial ISR.

Objective: The mitochondrial fission protein Drp1 was proposed to promote NAFLD, as inhibition of hepatocyte Drp1 early in life prevents liver steatosis induced by high-fat diet in mice. However, whether Drp1-knockdown in older mice can reverse established NASH is unknown.

Methods: N-acetylgalactosamine-siRNA conjugates, an FDA approved method to deliver siRNA selectively to hepatocytes, were used to knockdown hepatocyte-Drp1 in mice (NAG-Drp1si).

The goodies of chelated fat: iron-regulated lipid droplet biogenesis precedes and preserves mitophagy.

The role of iron-regulated mitophagy in lipid metabolism is unclear. Recent work by Long, Sanchez-Martinez et al (2022) shows that iron chelation induces a primary change in lipid metabolism that promotes fat accumulation and precedes mitophagy.

Mitoquinone mesylate targets SARS-CoV-2 infection in preclinical models.

Unlabelled: To date, there is no effective oral antiviral against SARS-CoV-2 that is also anti-inflammatory. Herein, we show that the mitochondrial antioxidant mitoquinone/mitoquinol mesylate (Mito-MES), a dietary supplement, has potent antiviral activity against SARS-CoV-2 and its variants of concern and . Mito-MES had nanomolar antiviral potency against the Beta and Delta SARS-CoV-2 variants as well as the murine hepatitis virus (MHV-A59).

ABCB10 Loss Reduces CD4 T Cell Activation and Memory Formation.

T cells must shift their metabolism to respond to infections and tumors and to undergo memory formation. The ATP-binding cassette transporter ABCB10 localizes to the mitochondrial inner membrane, where it is thought to export a substrate important in heme biosynthesis and metabolism, but its role in T cell development and activation is unknown. In this article, we use a combination of methods to study the effect of ABCB10 loss in primary and malignantly transformed T cells.

Determining Basal Energy Expenditure and the Capacity of Thermogenic Adipocytes to Expend Energy in Obese Mice.

Energy expenditure measurements are necessary to understand how changes in metabolism can lead to obesity. Basal energy expenditure can be determined in mice by measuring whole-body oxygen consumption, CO2 production, and physical activity using metabolic cages. Thermogenic brown/beige adipocytes (BA) contribute significantly to rodent energy expenditure, particularly at low ambient temperatures.

Deletion of ABCB10 in beta-cells protects from high-fat diet induced insulin resistance.

Objective: The contribution of beta-cell dysfunction to type 2 diabetes (T2D) is not restricted to insulinopenia in the late stages of the disease. Elevated fasting insulinemia in normoglycemic humans is a major factor predicting the onset of insulin resistance and T2D, demonstrating an early alteration of beta-cell function in T2D. Moreover, an early and chronic increase in fasting insulinemia contributes to insulin resistance in high-fat diet (HFD)-fed mice.

ATP-consuming futile cycles as energy dissipating mechanisms to counteract obesity.

Obesity results from an imbalance in energy homeostasis, whereby excessive energy intake exceeds caloric expenditure. Energy can be dissipated out of an organism by producing heat (thermogenesis), explaining the long-standing interest in exploiting thermogenic processes to counteract obesity. Mitochondrial uncoupling is a process that expends energy by oxidizing nutrients to produce heat, instead of ATP synthesis.

Recruitment and remodeling of peridroplet mitochondria in human adipose tissue.

Beige adipocyte mitochondria contribute to thermogenesis by uncoupling and by ATP-consuming futile cycles. Since uncoupling may inhibit ATP synthesis, it is expected that expenditure through ATP synthesis is segregated to a disparate population of mitochondria. Recent studies in mouse brown adipocytes identified peridroplet mitochondria (PDM) as having greater ATP synthesis and pyruvate oxidation capacities, while cytoplasmic mitochondria have increased fatty acid oxidation and uncoupling capacities.

High-Throughput Image Analysis of Lipid-Droplet-Bound Mitochondria.

Changes to mitochondrial architecture are associated with various adaptive and pathogenic processes. However, quantification of changes to mitochondrial structures is limited by the yet unmet challenge of defining the borders of each individual mitochondrion within an image. Here, we describe a novel method for segmenting primary brown adipocyte (BA) mitochondria images.

ABCB10 exports mitochondrial biliverdin, driving metabolic maladaptation in obesity.

Although the role of hydrophilic antioxidants in the development of hepatic insulin resistance and nonalcoholic fatty liver disease has been well studied, the role of lipophilic antioxidants remains poorly characterized. A known lipophilic hydrogen peroxide scavenger is bilirubin, which can be oxidized to biliverdin and then reduced back to bilirubin by cytosolic biliverdin reductase. Oxidation of bilirubin to biliverdin inside mitochondria must be followed by the export of biliverdin to the cytosol, where biliverdin is reduced back to bilirubin.