a variety of func tionally diverse myofibre types, mainly the red and the white fibers. Red skeletal muscles, such as the psoas major muscles, have a higher percentage of capillaries, myoglobin, lipids and mitochondria, making them a better aerobic machine than the these paler appearing white muscle. White skel etal muscles, such as the longissimus doris muscles, are required for anaerobic glycolytic meta bolism to support the high transient energy demand. Deciphering the different gene expression patterns be tween the different tissues would aid in our understand ing of their distinct metabolic features. Mo et al. identified various candidate genes involved in cell adhe sion, energy balance, muscle atrophy and myogenesis by comparing patterns of gene expression in three in dependent mouse models of Kennedy disease spinal bulbar muscular atrophy.

Wolfs et al. reported that coexpressed immune and metabolic genes are as sociated with plasma high density lipoprotein and glu cose levels by comparing genome wide transcription profiling of subcutaneous and visceral adipose tissues obtained from obese patients. Previous reports also suggested that ethnic group and sex are also the important factors that affect physiological and biochemical features of skeletal muscles in mammals. Pigs are important agricultural animals and ideal biomedical models. In the modern pig industry, pigs have undergone strong artificial selection for lean meat or adipose production, which has led to remark able phenotypic variations, making these different breeds a perfect model for comparative studies.

Using a microarray approach, Bai et al. noted that most differentially expressed genes between porcine PMM and LDM were of mitochondrial origin. Li et al. reported that the differentially expressed genes between the LDM and soleus muscle of Chinese Meishan pigs were Anacetrapib mainly over represented in various signaling pathways. Nonetheless, the different gene expression profiles associated with breed and sex in skeletal muscle tissues has been long overdue, and elucidation of this information will benefit the development of strategies for skeletal muscle manipulation. Here, using a microarray technology, we present a comprehensive survey of gene expression profiles be tween two phenotypically distinct skeletal muscles and sexes of three well defined pig breeds displaying distinct muscle phenotypes.

This study will contribute to our un derstanding of the molecular process of muscle fiber type formulation and provide a theoretical basis for breed most and meat quality improvement in pigs. Results and discussion Phenotypic measurements Our previous report, based on the same individuals, demonstrated that the myofibre cross sectional area and myofibre ratio were significant different be tween the two skeletal tissues, between the male and fe male and among the three breeds. In addition, 24 representative metabolism in dicators in serum also revealed the same ranking from the leaner Landrace, the wild