Expression Of The SCD1 Gene And Its Relationship With The Palmitoleic Acid And Oleic Acid Composition Of Tianfu Goat Muscles

Stearoyl-CoA desaturase (SCD), a membrane-bound protein of the endoplasmic reticulum, is a rate-limiting enzyme in the biosynthesis of monounsaturated fatty acids (MUFAs) from saturated fatty acids (SFAs) synthesized de novo or obtained from the diet. SCD introduces a single double bond between carbons 9 and 10 into SFAs. SCDs catalyze the synthesis of C16:1 and C18:1 acids using palmitic (C16:0) and stearic (C18:0) acids as substrates. SCD also plays a key role in the maintenance of membrane fluidity and lipid metabolism according to the ratio of SFAs and MUFAs. Changes in SFA and MUFA ratios have been connected with a variety of conditions and diseases, such as obesity, hypertension, diabetes, immune disorders, cardiovascular diseases and cancer. MUFAs have positive influence in production of healthy meat because of its positive role in many diseases. Furthermore, the SNPs of SCD1 gene significantly affected the meat quality, such as pH, marble grade, driage, cooked meat, intramuscular fat content and muscle color.This study was carried out by the used RT-PCR, cloning, RT-qPCR, Western blotting and gas chromatography on Tianfu goat SCD1 and the fatty acids of muscles. The main results of this study are as follows:1. This study obtained Tianfu goat SCD1 cDNA that was shown to be 1198 bp in length and to contain an ORF of 1080 bp encoding 359 amino acids, GeneBank access number: KT315581. SCD1 is a hydrophobic protein, containing 12 phosphorylation sites, four transmembrane domain and a possible N-glycosylation site, but no signal peptide sequence. The result of multiple sequence alignment revealed that the high identity shares with mammals. The phylogenetic tree revealed that the highest sequence homology for SCD1 AA from Tianfu goat was shared with SCD1 of Ovis aries and Bos Taurus, and the lowest homology was shared with SCD1 of Tachysurus fulvidraco.2. RT-qPCR analyses revealed that SCD1 gene expressed in all the tested muscles, and that day-old, muscles and the interaction of day-old and muscle significantly affected the SCD1 gene expression levels. Notably, a high SCD1 expression level was found in deltoid muscle from all three ages (P< 0.01). Particularly high SCD1 expression levels were found in the triceps muscle compared with those of the semimembranosus muscle and gastrocnemius muscle from the 90-day-old Tianfu goats (P< 0.01). Also, higher SCD1 expression levels were found in the gastrocnemius, triceps and biceps femoris muscles compared with the quadriceps femoris muscle from the 180-day-old Tianfu goats (P< 0.01). In the 270-day-old Tianfu goats, notably higher SCD1 expression levels were found in the biceps femoris muscle compared with the other muscles, except the triceps muscle (P< 0.01), and markedly higher SCD1 expression levels were found in the triceps, semimembranosus and longissimus dorsi muscles compared with the gluteus medius, gastrocnemius muscle and quadriceps femoris (P< 0.01). The temporal expression of SCD1 mRNA in all the muscles tested followed an age-related trend in the Tianfu goats. During muscle development, SCD1 mRNA expression increased from days 90 to 180, but then decreased by day 270. The highest expression was found in day 180 (P< 0.01) and the lowest expression in day 90 (P< 0.01) for the deltoid, biceps femoris, quadriceps femoris and gastrocnemius muscles, while for longissimus dorsi and semimembranosus muscles the p value was< 0.05.3. Western blotting analyses revealed that SCD1 protein expressed in all the tested muscles. Notably, a lowest SCD1 expression level was found in semimembranosus muscle from all three ages (P< 0.01). Particularly high SCD1 expression levels were found in the longissimus dorsi and deltoid muscle compared with those of the other six muscles from the 90-day-old Tianfu goats (P< 0.01). Also, higher SCD1 expression levels were found in the deltoid muscle compared with the other seven muscles from the 180-day-old Tianfu goats (P< 0.01). In the 270-day-old Tianfu goats, notably higher SCD1 expression levels were found in the gluteus medius (P< 0.01).4. The palmitoleic and oleic acids compositions in eight muscles of 90-,180- and 270-day-old Tianfu goat were detected by gas chromatographic. The results revealed that the day-old significantly affected the palmitoleic and oleic acids composition, but the muscles and the interaction of day-old and muscles did not affected them. Comparatively higher percentage composition of palmitoleic acid was found in the longissimus dorsi muscle and triceps muscle than in the gluteus medius from the 180-day-old Tianfu goats (P< 0.05), and a comparatively higher percentage of oleic acid was found in the semimembranosus muscle than in the quadriceps femoris from 270-day-old Tianfu goats (P< 0.05). Beyond that, hardly any significant differences in palmitoleic and oleic acids compositions were found in the eight muscles from the 90-,180-or 270-day-old Tianfu goats. During muscle development, the palmitoleic acid composition decreased from month 3 to 9, and the oleic acid composition increased from day 90 to 270. In particular, palmitoleic acid compositions in the gluteus medius, triceps, quadriceps femoris and gastrocnemius muscles were higher on day 90 than on day 270 (P< 0.01), and comparatively higher palmitoleic acid compositions in the longissimus dorsi, deltoid, biceps femoris and semimembranosus muscles were found on day 90 than on day 270 (P< 0.05). Comparatively higher oleic acid compositions in the longissimus dorsi, deltoid, biceps femoris and semimembranosus muscles were found on day 270 than on day 90 (P< 0.05). No significantly higher oleic acid compositions in the gluteus medius, triceps muscle, quadriceps femoris and gastrocnemius muscle were found on day 270 than on day 90.5. The correlation analyses revealed that palmitoleic and oleic acids compositions have no correlation with SCD1 gene relative expression; palmitoleic acid composition was negative correlation with SCD1 protein relative expression (r=-0.644) and oleic acid composition was positive correlation with SCD1 protein relative expression (r= 0.675), (P<0.01).