title: A Pilot Study of Age-Related Changes in the Sphingolipid Composition of the Rat Sarcoplasmic Reticulum.
abstract: BACKGROUND
  Muscle strength declines more rapidly than muscle size, manifesting as a loss of muscle quality. One putative contributor to this impairment of muscle quality is impaired sarcoplasmic reticulum (SR) function.
  
  
  OBJECTIVE
  The principal objective of this study was to characterize the sphingolipid composition of the SR in adult and aging rat muscles. A secondary, exploratory objective was to test for associations between SR sphingolipids and SR function (i.e., Ca2+ release).
  
  
  METHODS
  Using an animal model, the objectives were evaluated in a pre-clinical, cross-sectional study.
  
  
  METHODS
  Data were collected in an academic research laboratory.
  
  
  METHODS
  Medial gastrocnemius muscles of adult (n=8; 7-8 months) and aged (n=8; 24-25 months), male F344/BN hybrid rats were processed to extract SR.
  
  
  METHODS
  Sphingolipids in the SR were measured using tandem mass spectrometry. Fatty acid concentrations within the major sphingolipid classes were evaluated via Principal Component Analysis (PCA). In a subset of samples, SR Ca2+ release rates were determined using fluorometric methods, and associations with specific (based on results of PCA) fatty acid concentrations were evaluated.
  
  
  RESULTS
  Aging SR showed an overall decline in the ratio of unsaturated to saturated fatty acids. Age-specific differences were observed for hexosylceramide and ceramide-1-phosphate. Within subset of samples with SR Ca2+ release data, a significant negative association between Ca2+ release and C1P18:0 and trends for positive associations with hexCER24:0 and 24:1 were observed.
  
  
  CONCLUSIONS
  These preliminary, pre-clinical data suggest that changes in SR sphingolipids may play a role in age-related impairment of muscle function. Further work is needed to explore this hypothesis, as SR sphingolipids may prove a fruitful target for interventions, be they physical (i.e., exercise), nutritional or pharmacological.
authors.affiliation: David W. Russ, PT, Ph.D. Associate Professor, School of Rehabilitation and Communication Sciences, Division of Physical Therapy, Ohio University, W279 Grover Center, Athens, OH 45701, Phone: 740-566-0022, Fax: 740-593-0293, Email: russd@ohio.edu.
authors.forename: D W
authors.initials: DW
authors.lastname: Russ
authors.forename: M
authors.initials: M
authors.lastname: Nakazawa
authors.forename: I M
authors.initials: IM
authors.lastname: Boyd