title: Lipid droplet-associated proteins in high-fat fed mice with the effects of voluntary running and diet change.
abstract: OBJECTIVE
  The relation between lipid accumulation and influence of exercise on insulin sensitivity is not straightforward. A proper balance between lipid droplet synthesis, lipolysis, and oxidative metabolism would ensure low local intramyocellular fatty acid levels, thereby possibly protecting against lipotoxicity-associated insulin resistance. This study investigated whether the accumulation of triglycerides and lipid droplets in response to high availability of fatty acids after high-fat feeding would parallel the abundance of intramyocellular perilipin proteins, especially PLIN5. The effects on these variables after diet change or voluntary running exercise intervention in skeletal muscle were also investigated.
  
  
  METHODS
  During a 19-week experiment, C57BL/6J mice were studied in six different groups: low-fat diet sedentary, low-fat diet active, high-fat diet sedentary, high-fat diet active and two groups which were high-fat sedentary for nine weeks, after which divided into low-fat sedentary or low-fat active groups. Myocellular triglyceride concentration and perilipin protein expression levels were assessed.
  
  
  RESULTS
  We show that, concurrently with impaired insulin sensitivity, the expression level of PLIN5 and muscular triglyceride concentration increased dramatically after high-fat diet. These adaptations were reversible after the diet change intervention with no additional effect of exercise.
  
  
  CONCLUSIONS
  After high-fat diet, lipid droplets become larger providing more surface area for PLIN5. We suggest that PLIN5 is an important regulator of lipid droplet turnover in altered conditions of fatty acid supply and consumption. Imbalances in lipid droplet metabolism and turnover might lead to lipotoxicity-related insulin resistance.
authors: Neuromuscular Research Center, Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland.
authors: Rita
authors: R
authors: Rinnankoski-Tuikka
authors: Neuromuscular Research Center, Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland.
authors: Juha J
authors: JJ
authors: Hulmi
authors: Neuromuscular Research Center, Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland.
authors: Sira
authors: S
authors: Torvinen
authors: Neuromuscular Research Center, Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland.
authors: Mika
authors: M
authors: Silvennoinen
authors: LIKES Research Center for Sport and Health Sciences, Jyväskylä, Finland.
authors: Maarit
authors: M
authors: Lehti
authors: Neuromuscular Research Center, Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland.
authors: Riikka
authors: R
authors: Kivelä
authors: Department of Biological and Environmental Sciences, University of Jyväskylä, Jyväskylä, Finland.
authors: Hilkka
authors: H
authors: Reunanen
authors: Department of Health Sciences, University of Jyväskylä, Jyväskylä, Finland.
authors: Urho M
authors: UM
authors: Kujala
authors: Neuromuscular Research Center, Department of Biology of Physical Activity, University of Jyväskylä, Jyväskylä, Finland. Electronic address: heikki.kainulainen@sport.jyu.fi.
authors: Heikki
authors: H
authors: Kainulainen
mesh_terms: D000818:Animals; D015153:Blotting, Western; D059305:Diet, High-Fat; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D011506:Proteins / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D012420:Running
chemical_list: D011506:Proteins
keywords: Insulin resistance; Perilipins; Physical activity; Skeletal muscle