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Biology subjects

Knutson, J. R.

Publications and source records attributed to Knutson, J. R..

3 recordsLinked to original sources

The non-steroidal mineralocorticoid receptor (MR) antagonist (FINERENONE) reverses Western diet-induced kidney disease by enhancing mitochondrial metabolism and decreasing lipid accumulation and inflammation

Mineralocorticoid receptor (MR) overactivation plays a crucial role in the pathogenesis of chronic kidney disease, as well as several cardiovascular and arterial diseases. Current studies determined the mechanisms of the beneficial kidney effects of the non-steroidal MR antagonist Finerenone (FN) in a mouse model of western diet-induced obesity and insulin resistance. 10-week-old male C57BL/6J mice were fed a low fat (LF) or a western diet (WD) for 12 weeks followed by treatment with either vehicle or finerenone (FN) for another 14 weeks (intervention studies) until they were 36 weeks old. Finerenone treatment prevented a) the increased albuminuria and kidney injury molecule 1 (KIM1), b) the expanded extracellular mesangial matrix, and podocyte injury, c) fibronectin, collagen IV, CD45 and CD68 immunostaining, d) glomerular basement membrane disruption, podocyte foot process loss, and mitochondrial structural abnormalities, e) the pro-inflammatory cytokines (MCP1), innate immunity pathways (TLR2, STING, STAT3), and fibrosis markers fibronectin, TGF{beta} and Pai1, and f) the increased kidney cholesterol levels. There was also reduced expression of nuclear receptor ERR{gamma} without changes in ERR in WD-fed mice whereas both ERR and ERR{gamma} expression levels increased after Finerenone treatment. NADH lifetime analysis showed decreased bound NADH, compatible with decreased mitochondrial OXPHOS in the kidneys of WD-fed mice compared to controls, which was prevented by finerenone treatment. In conclusion, Finerenone treatment exhibits a renal protective role and prevents the progression of kidney disease by regulating mitochondrial function, most likely via ERR{gamma}, and reducing lipid accumulation and inflammation.

pharmacology and toxicology↗

Impact of Capillary and Sarcolemmal Proximity on Mitochondrial Structure and Energetic Function in Skeletal Muscle

Mitochondria within skeletal muscle cells are considered to be located either between the muscle contractile apparatus (interfibrillar mitochondria, IFM) or in large pools beneath the cell membrane (subsarcolemmal mitochondria, SSM), with several structural and functional differences reported between IFM and SSM. However, recent 3D imaging studies suggest that proximity to capillaries embedded in sarcolemmal grooves, rather than proximity to the sarcolemma itself, may drive the accumulation of mitochondria near the cell periphery (paravascular mitochondria, PVM). To evaluate the impact of capillary versus sarcolemmal proximity, we compared the structure and function of skeletal muscle mitochondria located either in large pools lateral to embedded capillaries (PVM), adjacent to the sarcolemma but not in PVM pools (SSM), or interspersed between sarcomeres (IFM). Mitochondrial morphology and interactions were assessed by 3D electron microscopy coupled with machine learning segmentation while mitochondrial energy conversion was assessed by two-photon microscopy of mitochondrial membrane potential, content, calcium, NADH redox and flux in live, intact cells. Structurally, while PVM and SSM were similarly larger than IFM, PVM were more compact and had greater mitochondrial connectivity compared to both IFM and SSM. Functionally, PVM had similar or greater basal NADH flux compared to SSM and IFM, respectively, despite a more oxidized NADH pool and a greater membrane potential, signifying a greater activation of the electron transport chain in PVM. Together, these data indicate proximity to capillaries has a greater impact on mitochondrial energy conversion and distribution in skeletal muscle than the sarcolemma alone.

physiology↗

High resolution spatial investigation of intracellular oxygen in muscle cells.

Molecular oxygen (O2) is one of the most functionally relevant metabolites. O2 is essential for mito-chondrial aerobic respiration. Changes in O2 affect muscle metabolism and play a critical role in the maintenance of skeletal muscle mass, with lack of sufficient O2 resulting in detrimental loss of muscle mass and function. How exactly O2 is used by muscle cells is less known, mainly due to the lack of tools to address O2 dynamics at the cellular level. Here we discuss a new imaging method for the real time quantification of intracellular O2 in muscle cells based on a genetically encoded O2-responsive sensor, Myoglobin-mCherry. We show that we can spatially resolve and quantify intracellular O2 concentration in single muscle cells and that the spatiotemporal O2 gradient measured by the sensor is linked to, and reflects, functional metabolic changes occurring during the process of muscle differentiation. HighlightsO_LIReal time quantitation of intracellular oxygen with spatial resolution C_LIO_LIIdentification of metabolically active sites in single cells C_LIO_LIOxygen metabolism is linked to muscle differentiation C_LI

cell biology↗