Korean J Nutr.  2011 Oct;44(5):355-365. 10.4163/kjn.2011.44.5.355.

Effects of Different Types of Dietary Fat on Muscle Atrophy According to Muscle Fiber Types and PPARdelta Expression in Hindlimb-Immobilized Rats

• Lee HU
• Park MN
• Lee YS

• KMID: 2268559
• DOI: http://doi.org/10.4163/kjn.2011.44.5.355

Abstract

This study investigated how dietary fat affects muscle atrophy and lipid metabolism in various muscles during hindlimb immobilization in rats. Twenty-four male Sprague-Dawley rats had their left hindlimb immobilized and were divided into four groups by dietary fat content and composition. The contralateral hindlimb (control) was compared with the immobilized limb in all dietary groups. Rats (n = 6/group) were fed a 4% corn oil diet (CO), 2.6% corn oil + 1.4% fish oil diet (FO), 30% corn oil diet (HCO), or a 30% beef tallow diet (HBT)after their hind limbs were immobilized for 10 days. Data were collected for the gastrocnemius, plantaris and soleus muscles. Muscle atrophy was induced significantly after 10 days of hindlimb immobilization, resulting in significantly decreased muscle mass and total muscle protein content. The protein levels of peroxisome proliferator activated receptor delta (PPARdelta) in the plantaris, gastrocnemius, and soleus increased following hindlimb immobilization irrespective of dietary fat intake. Interestingly, the PPARdelta mRNA level in the plantaris decreased significantly in all groups and that in the FO group was lower than that in the other groups. The soleus PPARdelta mRNA level decreased significantly following hindlimb immobilization in the FO group only. Muscle carnitine palmitoyl transferase 1 (mCPT1) mRNA level was not affected by hindlimb immobilization. However, the mCPT1 mRNA level in the FO group was significantly lower in the plantaris but higher in the soleus than that in the other groups. The pyruvate dehydrogenase kinase 4 (PDK4) mRNA level in the plantaris decreased significantly, whereas that in the soleus increased significantly following hindlimb immobilization. The plantaris, but not soleus, PDK4 mRNA level was significantly higher in the FO group than that in the CO group. The increased PPARdelta protein level following hindlimb immobilization may have suppressed triglyceride accumulation in muscles and different types of dietary fat may have differentially affected muscle atrophy according to muscle type. Our results suggest that omega-3 polyunsaturated fatty acids may suppress muscle atrophy and lipid accumulation by positively affecting the expression level and activity of PPARdelta and PPARdelta-related enzymes, which are supposed to play an important role in muscle lipid metabolism.

Keyword

skeletal muscle atrophy; hindlimb immobilization; fish oil; high-fat diet; PPARdelta

MeSH Terms

Animals
Carnitine
Corn Oil
Diet
Diet, High-Fat
Dietary Fats
Extremities
Fats
Fatty Acids, Unsaturated
Hindlimb
Hindlimb Suspension
Humans
Lipid Metabolism
Male
Muscle Proteins
Muscles
Muscular Atrophy
Oxidoreductases
Phosphotransferases
PPAR delta
Protein Kinases
Pyruvic Acid
Rats
Rats, Sprague-Dawley
RNA, Messenger
Transferases
Carnitine
Corn Oil
Dietary Fats
Fats
Fatty Acids, Unsaturated
Muscle Proteins
Oxidoreductases
PPAR delta
Phosphotransferases
Protein Kinases
Pyruvic Acid
RNA, Messenger
Transferases

Figure

• 

  Fig. 1 Effects of hindlimb immobilization on skeletal muscle weight. Muscle weights normalized to body weights were assessed immediately after ten days of immobilization in the soleus (SOL), plantaris (PL) and gastrocnemius in rats fed corn oil (CO), fish oil (FO), high corn oil (HCO) or high beef tallow (HBT) diet. The data for contralateral and immobilized muscles are represented by black bars and open bars, respectively. Values are expressed as the mean ± SE (n = 6). Statistical significance: *: p <0.01 immobilized vs. diet-matched contralateral muscle. The data for immobilized muscles among diet groups is not significantly different at (p <0.05) by Duncan's multiple range test.

• 

  Fig. 2 Increased protein expressions of peroxisome proliferator activated receptor (PPAR) δ by hiindlimb immobilization. Protein levels of PPARδ were determined by western blotting immediately after ten days of immobilization in plantaris (PL) (A), gastrocnemius (GAST) (B) and soleus (SOL) (C) in rats fed corn oil (CO), fish oil (FO), high corn oil (HCO) or high beef tallow (HBT) diet. The data for contralateral and immobilized muscles are represented by black bars and open bars, respectively. The representative western blot bands are displayed with Coomassie Blue Stained gel to verify equal loading. Values are expressed as the mean ± SE [n = 6 (PL, GAST) or 3 (SOL)]. Statistical significance: *: p <0.05 immobilized vs. diet-matched contralateral muscle.

• 

  Fig. 3 Effects of hindlimb immobilization on gene expression of peroxisome proliferator activated receptor (PPAR) δ and PPARα. mRNA levels were determined by real time-polymerase chain reaction immediately after ten days of immobilization in plantaris (PL) (A) and soleus (SOL)(B) for PPARδ, and in PL (C) and SOL (D) for PPARα in rats fed corn oil (CO), fish oil (FO), high corn oil (HCO) or high beef tallow (HBT) diet. The data for contralateral and immobilized muscles are represented by black bars and open bars, respectively. Values are expressed as the mean ± SE (n = 6). Statistical significance: *: p < 0.05, **: p < 0.01 immobilized vs. dietmatched contralateral muscle, respectively; capital letters denote comparisons among contralateral muscles of all diet groups at p <0.05; small letters denote comparison among immobilized muscles of all diet groups at p <0.05.

• 

  Fig. 4 Effects of hindlimb immobilization on gene expression of key enzymes in lipid metabolism. mRNA levels were determined by real time-polymerase chain reaction immediately after ten days of immobilization in plantaris (PL)(A, C) and soleus (SOL)(B, D) for muscle carnitine palmitoyltransperase (mCPT) 1 (A, B), pyruvate dehydrogenase kinase (PDK) 4 (C, D) in rats fed corn oil (CO), fish oil (FO), high corn oil (HCO) or high beef tallow (HBT) diet. The data for contralateral and immobilized muscles are represented by black bars and open bars, respectively. Values are expressed as the mean ± SE (n = 6). Statistical significance: *: p < 0.05, **: p < 0.01 immobilized vs. diet-matched contralateral muscle, respectively; capital letters denote comparisons among contralateral muscles of all diet groups at p <0.05; small letters denote comparison among immobilized muscles of all diet groups at p <0.05.

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