Dietary supplementation with cholesterol and docosahexaenoic acid increases the activity of the arginine-nitric oxide pathway in tissues of young pigs

Abstract

Nitric oxide (NO), synthesized from l-arginine by tetrahydrobiopterin (BH4)-dependent NO synthase (NOS), is critical for neurological and muscular development and function. This study was designed to test the hypothesis that cholesterol and docosahexaenoic acid (DHA) may modulate the arginine-NO pathway in tissues of the young pig. Sixteen newborn pigs were nursed by sows for 24h and then assigned to one of four treatment groups, representing supplementation with 0.0%, 0.2% cholesterol, 0.2% DHA, or cholesterol plus DHA to the basal milk-formula. All piglets were euthanized at 49 days of age. Brain, liver and gastrocnemius muscle were analyzed for BH4, NADPH and arginine, GTP cyclohydrolase-I (GTP-CH) and NOS activities, and NOS protein isoforms. Hepatic NOS activity was below the detection limit in all pigs. DHA supplementation (P<0.01) increased GTP-CH activities, as well as BH4 and NADPH concentrations in brain, liver, and muscle by 24-46%, while enhancing (P<0.05) NOS activities by 45-48% in brain and muscle. Dietary cholesterol supplementation increased (P<0.05) NOS and GTP-CH activities by 17-26% in brain but had no effect in liver or muscle. The enhanced NOS activity in the brain or muscle of cholesterol- or DHA-supplemented piglets was attributable to the combined effects of increased eNOS and nNOS activation (changes in phosphorylation levels) and total iNOS protein. Additionally, DHA and cholesterol enhanced (P<0.05) arginine concentrations in brain (35-42%), but not in liver or muscle. These tissue-specific effects of cholesterol and DHA on NO synthesis may play an important role in postnatal growth and development.

Regulation of glucose and protein metabolism in growing steers by long-chain n-3 fatty acids in muscle membrane phospholipids is dose-dependent

“…The regulation of membrane phospholipid composition would occur in accordance with membrane fluidity, carbohydrate and protein transmembrane motions and organelle reorganization, and these have been shown to impact ATPase, adenylate cyclase, cellular interaction, transmembrane transport and insulin action (Stubbs and Smith, 1984; Else and Hulbert, 2003). The arginine-activated nitric-oxide pathway in muscle could also be part of the basic regulation (Jobgen et al ., 2006; Li et al ., 2008a and 2008b). Previous studies showed a maximal LCn-3PUFA threshold of 22% in muscle membranes in newborn piglets (Bergeron et al ., 2007) and in rat liver plasma membranes (Abel et al ., 1997).…”

Impact of fatty acids on brain circulation, structure and function

“…Additionally, DHA may enhance CBF through increased activity of nitric oxide synthase (NOS) [40]. Increased NOS activity after DHA supplementation was observed in both piglets and rats [41,42] and may have led to enhanced production of nitric oxide (NO) [43]. NO, like extracellular potassium (K þ), is an important molecular regulator of mechanisms underlying both autoregulation of CBF and NVC [44].…”

N-acetylcysteine stimulates protein synthesis in enterocytes independently of glutathione synthesis

“…After a 3-day period of culture, cells were analyzed for total protein and specific proteins using the Western blotting technique (Li et al 2008;Yao et al 2012). Briefly, cells in 6-well culture plates were gently washed with Dulbecco's phosphate-buffered saline and viable cells were counted using an automated cell counter.…”