Niacin, also called nicotinic acid, is a water-soluble vitamin which belongs to the vitamin B complex and is essential for the metabolism of carbohydrates, fats and many other substances. At pharmacological doses, niacin has been shown to exert pronounced lipid-lowering activities.

A recent study showed that niacin supplementation counteracts the obesity-induced muscle fibre switching from oxidative type I to glycolytic type II and increases the number of type I fibres in skeletal muscle of obese Zucker rats, according to Muckta Khan and colleagues at Justus-Liebig-University Giessen in Germany.

They explain that these effects were likely mediated by the induction of key regulators of fibre transition, PGC-1α and PGC-1β, leading to muscle fibre switching and up-regulation of genes involved in mitochondrial fatty acid import and oxidation, citrate cycle, oxidative phosphorylation, mitochondrial biogenesis.

The aim of their study, published in BMC Veterinary Research, was to investigate whether niacin supplementation causes type II to type I muscle and changes the metabolic phenotype of skeletal muscles in growing pigs.

A total of 25 male, 11-week-old crossbred pigs (Danzucht × Pietrain) with an average body weight of 32.8 ± 1.3 (mean ± SD) kg were randomly allocated to two groups of 12 (control group) and 13 pigs (niacin group), which were fed either a control diet or a diet supplemented with 750mg niacin per kg diet.

After three weeks, the percentage number of type I fibres in three different muscles (M. longissismus dorsi, M. quadriceps femoris, M. gastrocnemius) was greater in the niacin group and the percentage number of type II fibres was lower in the niacin group than in the control group (P<0.05).

The mRNA levels of PGC-1β and genes involved in mitochondrial fatty acid catabolism (CACT, FATP1, OCTN2), citrate cycle (SDHA), oxidative phosphorylation (COX4/1, COX6A1), and thermogenesis (UCP3) in M. longissimus dorsi were greater in the niacin group than in the control group (P<0.05).

The study demonstrates that niacin supplementation induces type II to type I muscle fibre switching, and thereby an oxidative metabolic phenotype of skeletal muscle in pigs, concluded Khan and colleagues.

Given that oxidative muscle types tend to develop dark, firm and dry pork in response to intense physical activity and/or high psychological stress levels pre-slaughter, they added, a niacin-induced change in the muscle fibre type distribution may influence meat quality of pigs.

Reference

^{Khan M., R. Ringseis, F-C. Mooren, K. Krüger, E. Most and K. Eder. 2013. Niacin supplementation increases the number of oxidative type I fibres in skeletal muscle of growing pigs. BMC Veterinary Research. 9:177. doi:10.1186/1746-6148-9-177}

October 2013