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  • 1
    Publication Date: 2016-03-17
    Description: The energetic burden of continuously concentrating solutes against gradients along the tubule may render the kidney especially vulnerable to ischaemia. Acute kidney injury (AKI) affects 3% of all hospitalized patients. Here we show that the mitochondrial biogenesis regulator, PGC1alpha, is a pivotal determinant of renal recovery from injury by regulating nicotinamide adenine dinucleotide (NAD) biosynthesis. Following renal ischaemia, Pgc1alpha(-/-) (also known as Ppargc1a(-/-)) mice develop local deficiency of the NAD precursor niacinamide (NAM, also known as nicotinamide), marked fat accumulation, and failure to re-establish normal function. Notably, exogenous NAM improves local NAD levels, fat accumulation, and renal function in post-ischaemic Pgc1alpha(-/-) mice. Inducible tubular transgenic mice (iNephPGC1alpha) recapitulate the effects of NAM supplementation, including more local NAD and less fat accumulation with better renal function after ischaemia. PGC1alpha coordinately upregulates the enzymes that synthesize NAD de novo from amino acids whereas PGC1alpha deficiency or AKI attenuates the de novo pathway. NAM enhances NAD via the enzyme NAMPT and augments production of the fat breakdown product beta-hydroxybutyrate, leading to increased production of prostaglandin PGE2 (ref. 5), a secreted autacoid that maintains renal function. NAM treatment reverses established ischaemic AKI and also prevented AKI in an unrelated toxic model. Inhibition of beta-hydroxybutyrate signalling or prostaglandin production similarly abolishes PGC1alpha-dependent renoprotection. Given the importance of mitochondrial health in ageing and the function of metabolically active organs, the results implicate NAM and NAD as key effectors for achieving PGC1alpha-dependent stress resistance.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Tran, Mei T -- Zsengeller, Zsuzsanna K -- Berg, Anders H -- Khankin, Eliyahu V -- Bhasin, Manoj K -- Kim, Wondong -- Clish, Clary B -- Stillman, Isaac E -- Karumanchi, S Ananth -- Rhee, Eugene P -- Parikh, Samir M -- K08-DK090142/DK/NIDDK NIH HHS/ -- K08-DK101560/DK/NIDDK NIH HHS/ -- P30-DK079337/DK/NIDDK NIH HHS/ -- R01 DK095072/DK/NIDDK NIH HHS/ -- R01-DK095072/DK/NIDDK NIH HHS/ -- Howard Hughes Medical Institute/ -- England -- Nature. 2016 Mar 24;531(7595):528-32. doi: 10.1038/nature17184. Epub 2016 Mar 16.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Nephrology and Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA. ; Center for Vascular Biology Research, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA. ; Division of Clinical Chemistry, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA. ; Department of Pathology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA. ; Bioinformatics and Systems Biology Core, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA. ; Nephrology and Endocrine Divisions, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts 02114, USA. ; Broad Institute of MIT and Harvard, Cambridge, Massachusetts 02139, USA. ; Howard Hughes Medical Institute, Chevy Chase, Maryland 20815, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26982719" target="_blank"〉PubMed〈/a〉
    Keywords: 3-Hydroxybutyric Acid/metabolism ; Acute Kidney Injury/drug therapy/*metabolism ; Adipose Tissue/drug effects/metabolism ; Amino Acids/metabolism ; Animals ; Cytokines/metabolism ; Dinoprostone/biosynthesis/metabolism ; Humans ; Ischemia/drug therapy/metabolism ; Kidney/drug effects/*metabolism/physiology/physiopathology ; Male ; Mice ; Mice, Inbred C57BL ; Mitochondria/metabolism ; NAD/*biosynthesis ; Niacinamide/deficiency/pharmacology/therapeutic use ; Nicotinamide Phosphoribosyltransferase/metabolism ; Oxidation-Reduction ; Signal Transduction/drug effects ; Stress, Physiological ; Transcription Factors/deficiency/*metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2011-08-24
    Description: The response of skeletal muscle to unweighting was studied in six healthy males who were subjected to four weeks of lowerlimb suspension. They performed three bouts of 30 consecutive maximal concentric knee extensions, before unloading and the day after (POST 1), 4 days after (POST 2) and 7 weeks after (REC) resumed weight-bearing. Peak torque of each contraction was recorded and work was calculated as the mean of the average peak torque for the three bouts and fatigability was measured as the decline in average peak torque over bouts. Needle biopsies were obtained from m. vastus lateralis of each limb before and at POST 1. Muscle fibre type composition and area, capillarity and the enzyme activities of citrate synthase (CS) and phosphofructokinase (PFK) were subsequently analysed. Mean average peak torque for the three bouts at POST1, POST2 and REC was reduced (P 〈 0.05) by 17, 13 and 7%, respectively. Fatigability was greater (P 〈 0.05) at POST2 than before unloading. Type I, IIA and IIB percentage, Type I and II area and capillaries per fibre of Type I and II did not change (P 〉 0.05) in response to unloading. The activity of CS, but not PFK, decreased (P 〈 0.05) after unloading. The weight-bearing limb showed no changes in the variables measured. The results of this study suggest that this human lowerlimb suspension model produces substantial impairments of work and oxidative capacity of skeletal muscle. The performance decrements are most likely induced by lack of weight-bearing.
    Keywords: Aerospace Medicine
    Type: Clinical physiology (Oxford, England) (ISSN 0144-5979); Volume 13; 4; 337-47
    Format: text
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