title: Supplementing healthy rats with a high-niacin dose has no effect on muscle fiber distribution and muscle metabolic phenotype.
abstract: OBJECTIVE
  It was recently shown that niacin prevents the obesity-induced type I to type II fiber switching in skeletal muscle of obese rats and favors the development of a more oxidative metabolic phenotype and thereby increases whole body utilization of fatty acids. Whether niacin also causes type II to type I fiber switching in skeletal muscle of healthy rats has not been investigated yet. Thus, the present study aimed to investigate whether niacin supplementation influences fiber distribution and metabolic phenotype of different skeletal muscles with a distinct type I-to-type II fiber ratio in healthy rats.
  
  
  METHODS
  Twenty-four male, 10-week-old Sprague-Dawley rats were randomly assigned into two groups of 12 rats each and fed either a control diet with 30 mg supplemented niacin/kg diet (control group) or a high-niacin diet with 780 mg supplemented niacin/kg diet (high-niacin group).
  
  
  RESULTS
  After 27 days of treatment, the percentage number of type I fibers in rectus femoris, gastrocnemius, and tibialis anterior muscles was 5-10% greater in the niacin group than in the control group, but did not differ between groups in soleus and vastus intermedius muscles. Transcript levels of genes encoding transcription factors regulating fiber switching, fiber-specific myosin heavy chain isoforms, and proteins involved in fatty acid utilization, oxidative phosphorylation, and angiogenesis did not differ between groups.
  
  
  CONCLUSIONS
  The results show that niacin has only negligible effects on fiber distribution and its regulation as well as the metabolic phenotype of skeletal muscle in healthy rats.
authors.affiliation: Institute of Animal Nutrition and Nutrition Physiology, Justus-Liebig-University Giessen, Heinrich-Buff-Ring 26-32, 35390, Giessen, Germany.
authors.forename: Kristen
authors.initials: K
authors.lastname: Scholz
authors.forename: Anna Marie
authors.initials: AM
authors.lastname: Kynast
authors.forename: Aline
authors.initials: A
authors.lastname: Couturier
authors.forename: Frank-Christoph
authors.initials: FC
authors.lastname: Mooren
authors.forename: Karsten
authors.initials: K
authors.lastname: Krüger
authors.forename: Erika
authors.initials: E
authors.lastname: Most
authors.forename: Klaus
authors.initials: K
authors.lastname: Eder
authors.forename: Robert
authors.initials: R
authors.lastname: Ringseis
mesh_terms: D000818:Animals; D019587:Dietary Supplements; D005227:Fatty Acids / Q000378:metabolism; D005786:Gene Expression Regulation; D008297:Male; D018485:Muscle Fibers, Skeletal / Q000187:drug effects* / Q000378:metabolism; D009525:Niacin / Q000494:pharmacology*; D010085:Oxidative Phosphorylation / Q000187:drug effects; D010641:Phenotype; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D005227:Fatty Acids; D014157:Transcription Factors; D009525:Niacin