Impaired mitochondrial function has been implicated in the pathogenesis of age-associated metabolic diseases through regulation of cellular redox balance. Exercise training is known to promote mitochondrial biogenesis in part through induction of the transcriptional coactivator peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α). Recently, mitochondrial ADP sensitivity has been linked to reactive oxygen species (ROS) emission with potential impact on age-associated physiological outcomes, but the underlying molecular mechanisms remain unclear. Therefore, the present study investigated the effects of aging and exercise training on mitochondrial properties beyond biogenesis, including respiratory capacity, ADP sensitivity, ROS emission, and mitochondrial network structure, in myofibers from inducible muscle-specific PGC-1α-knockout mice and control mice. Aged mice displayed lower running endurance and mitochondrial respiratory capacity than young mice. This was associated with intermyofibrillar mitochondrial network fragmentation, diminished submaximal ADP-stimulated respiration, increased mitochondrial ROS emission, and oxidative stress. Exercise training reversed the decline in maximal respiratory capacity independent of PGC-1α, whereas exercise training rescued the age-related mitochondrial network fragmentation and the impaired submaximal ADP-stimulated respiration in a PGC-1α-dependent manner. Furthermore, lack of PGC-1α was associated with altered phosphorylation and carbonylation of the inner mitochondrial membrane ADP/ATP exchanger adenine nucleotide translocase 1. In conclusion, the present study provides evidence that PGC-1α regulates submaximal ADP-stimulated respiration, ROS emission, and mitochondrial network structure in mouse skeletal muscle during aging and exercise training.

Background: Idiopathic pulmonary fibrosis (IPF) is a rapidly progressing disease with challenging management. To find novel effective therapies, better preclinical models are needed for the screening of anti-fibrotic compounds. Activated fibroblasts drive fibrogenesis and are the main cells responsible for the accumulation of extracellular matrix (ECM). Here, a prolonged Scar-in-aJar assay was combined with clinically validated biochemical markers of ECM synthesis to evaluate ECM synthesis over time. To validate the model as a drug screening tool for novel antifibrotic compounds, two approved compounds for IPF, nintedanib and pirfenidone, and a compound in development, omipalisib, were tested. Methods: Primary human lung fibroblasts from healthy donors were cultured for 12 days in the presence of ficoll and were stimulated with TGF-β1 with or without treatment with an ALK5/TGF-β1 receptor kinase inhibitor (ALK5i), nintedanib, pirfenidone or the mTOR/PI3K inhibitor omipalisib (GSK2126458). Biomarkers of ECM synthesis were evaluated over time in cell supernatants using ELISAs to assess type I, III, IV, V and VI collagen formation (PRO-C1, PRO-C3, PRO-C4, PRO-C5, PRO-C6), fibronectin (FBN-C) deposition and α-smooth muscle actin (α-SMA) expression. Results: TGF-β1 induced synthesis of PRO-C1, PRO-C6 and FBN-C as compared with unstimulated fibroblasts at all timepoints, while PRO-C3 and α-SMA levels were not elevated until day 8. Elevated biomarkers were reduced by suppressing TGF-β1 signalling with ALK5i. Nintedanib and omipalisib were able to reduce all biomarkers induced by TGF-β1 in a concentration dependent manner, while pirfenidone had no effect on α-SMA. Conclusions: TGF-β1 stimulated synthesis of type I, III and VI collagen, fibronectin and α-SMA but not type IV or V collagen. Synthesis was increased over time, although temporal profiles differed, and was modulated pharmacologically by ALK5i, nintedanib, pirfenidone and omipalisib. This prolonged 12-day Scar-in-aJar assay utilising biochemical markers of ECM synthesis provides a useful screening tool for novel anti-fibrotic compounds.

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SUMMARY1. The characteristics of renal transport of ,-alanine by luminal membrane vesicles isolated from either the proximal convoluted part (pars convoluta) or the proximal straight part (pars recta) of rabbit proximal tubule were investigated.2. In vesicles from pars convoluta two transport systems have been characterized: (1) a Na+-dependent system with intermediate affinity (half-saturation 2-7 mM), and (2) a Na+-independent system, which in the presence of a H+ gradient (extravesicular > intravesicular) can drive the uphill transport of f,-alanine into these vesicles. This is the first demonstration of H+-,-alanine co-transport across luminal membrane of rabbit kidney proximal convoluted tubule.3. By contrast, in membrane vesicles from pars recta, transport of fi-alanine was strictly dependent on Na+ and occurred via a dual transport system, namely a highaffinity (half-saturation 0-16 mM) and a low-affinity system (half-saturation 9-3 mM).4. The demonstration of competition between the Na+-gradient-dependent uptake of 8i-alanine and taurine, without appreciable inhibition by a-amino acids in vesicles from pars convoluta as well as from pars recta, strongly suggests that the luminal membrane of proximal tubule has transport systems for the reabsorption of ,f-amino acids which are distinct from a-amino acid transport systems.

Background Idiopathic pulmonary fibrosis (IPF) is characterized by the accumulation of fibrillar collagens in the alveolar space resulting in reduced pulmonary function and a high mortality rate. Biomarkers measuring the turnover of type I and III collagen could provide valuable information for prognosis and treatment decisions in IPF. Methods Serological biomarkers reflecting the formation of type III collagen (PRO-C3) and degradation of type I (C1M) and III collagen (C3M) were evaluated in a real-world cohort of 178 newly diagnosed IPF patients. Blood samples and clinical data were collected at baseline, six, and 12 months. Baseline and longitudinal biomarker levels were related to disease progression of IPF (defined as ≥ 5% decline in forced vital capacity (FVC) and/or ≥ 10% decline in diffusing capacity for carbon monoxide (DLco) and/or all-cause mortality at 12 months). Furthermore, we analysed differences in percentage change of biomarker levels from baseline between patients receiving antifibrotic treatment or not. Results Increased baseline levels of type I and III collagen turnover biomarkers were associated with a greater risk of disease progression within 12 months compared to patients with a low baseline type I and III collagen turnover. Patients with progressive disease had higher serum levels of C1M (P = 0.038) and PRO-C3 (P = 0.0022) compared to those with stable disease over one year. There were no differences in biomarker levels between patients receiving pirfenidone, nintedanib, or no antifibrotics. Conclusion Baseline levels of type I and III collagen turnover were associated with disease progression within 12 months in a real-world cohort of IPF patients. Longitudinal biomarker levels of type I and III collagen turnover were related to progressive disease. Moreover, antifibrotic therapy did not affect type I and III collagen turnover biomarkers in these patients. PRO-C3 and C1M may be potential biomarkers for a progressive disease behavior in IPF.