Volume 6 Issue 2, February 2024

The prevailing notion that mitochondrial diseases arise from ATP deficiency is challenged by recent evidence that oxidative phosphorylation defects trigger maladaptive stress responses consuming excess energy. We argue that this chronic state of hypermetabolism imposes energetic constraints, thus causing mitochondrial disease pathophysiology, calling for careful translational studies from organelle to organism.

Electron transfer flavoprotein dehydrogenase (ETFDH), respiratory chain complex III and the coenzyme Q10 synthesis regulator COQ2 interact as a protein complex that is disrupted in ETFDH deficiency, with potential implications for disease therapy.

High-fat diet (HFD) causes mitochondrial dysfunction in white adipocytes. A study in Nature Metabolism identifies the small GTPase RalA as a culprit in mice. Upon HFD, RalA activates the fission protein Drp1 to cause mitochondrial fragmentation and dysfunction, linking mitochondrial fuel utilization in white adipocytes to systemic lipid metabolism.

Selenium is usually incorporated into selenoproteins, with important functions in redox regulation. A new study in Nature Metabolism reveals a previously unappreciated role for selenium-based chemical species as direct electron donors to reduce ubiquinone, thus contributing to redox homeostasis by preventing lipid peroxidation.

Although obesity is associated with higher risk of cardiometabolic disease, high-protein diets can reduce fatness but still promote cardiometabolic disease. Zhang et al. address this contradiction and show that high-protein diets, and subsequently higher blood leucine levels, promote mTORC1 activation in macrophages in humans and mice, and that an increase in dietary leucine raises the risk of atherosclerosis in a mouse model.

Glycerol-3-Phosphate (G3P) and phosphoethanolamine (pEtN) biosynthetic pathways are modulated during senescence establishment to sustain lipid droplet accumulation and senescence-associated secretome. These findings reveal new targets for an immunomodulatory approach against senescent cells.

Here, we reveal functional heterogeneity among β cells and discover that readily releasable β cells (RRβs) are a subpopulation that disproportionally contributes to biphasic glucose-stimulated insulin secretion. We further show that the dysfunction of RRβs has a crucial role in the progression of diabetes.

Electron-transfer flavoprotein dehydrogenase (ETFDH) is shown to associate with mitochondrial complex III (CIII) physically and functionally, thereby promoting electron channelling to increase CIII efficiency.

Kwak et al. identify a mixture of monogenic, rare and common genetic variants of youth-onset type 2 diabetes (T2D), highlighting the heterogeneity of youth-onset T2D and positioning it on a genetic spectrum between monogenic diabetes and adult-onset T2D.

This study reveals functional heterogeneity at the level of exocytosis among β cells and identifies a subpopulation of β cells that make a disproportionally large contribution to insulin release from mouse islets.

Miotto et al. show that in mice, liver-derived extracellular vesicles act on skeletal muscle and the pancreas and increase glucose effectiveness and insulin secretion, thereby modulating glycaemic control.

Xia et al. show that the activity of the small GTPase RalA is increased in white adipocytes in diet-induced obese mice. RalA enhances mitochondrial fission and therefore reduces energy expenditure, which contributes to weight gain.

Veniant et al. report here on a GIPR antagonist conjugated to GLP-1 analogues that reduces body weight and improves metabolic markers in preclinical and phase 1 clinical settings.

Ramachandran et al. identify a previously unappreciated function for transcriptional repressor B cell lymphoma 6 (BCL6) in muscle proteostasis and strength, and provide mechanistic insight into the molecular underpinnings of this function.

Tighanimine et al. perform integrative time-resolved transcriptome and metabolome analysis in senescent cells and find that glycerol-3-phosphate and phosphoethanolamine accumulate and rewire lipid metabolism to promote senescence.

Lee, Park et al. show that selenium has the ability to directly regulate the redox state of ubiquinone by donating electrons from hydrogen selenide via sulfide quinone oxidoreductase, thus preventing lipid peroxidation.

Zhang et al. use human studies and mechanistic work in mouse models to describe how leucine serves as the key amino acid derived from dietary protein to drive deleterious macrophage mTORC1 signalling and promote cardiovascular disease.