Enzyme activity of rat tibialis anterior muscle differs between treatment with triamcinolone and prednisolone and nutritional deprivation

Abstract

The maximal activity of a selection of enzymes involved in muscle carbohydrate handling, citric acid cycle and fatty acyl β-oxidation were studied after treatment with the fluorinated corticosteroid triamcinolone and compared to a similar treatment of the non-fluorinated corticosteroid prednisolone in an equipotent anti-inflammatory dose. Furthermore, because triamcinolone causes loss of body mass and muscle wasting, the effects of triamcinolone were investigated relative to a control group, with the same loss of body mass, due to nutritional deprivation. The study was performed in male Wistar rats in the following treatment groups: TR, triamcinolone treatment (0.25 mg · kg⁻¹ · day⁻¹ for 2 weeks), which resulted in a reduction of body mass (24%); ND, nutritional deprivation (30% of normal daily food intake for 2 weeks) resulting in a similar (24%) decrease of body mass as TR; PR, prednisolone treatment (0.31 mg · kg⁻¹ · day⁻¹ for 2 weeks), with a 10% increase in body mass; FF, free-fed control group, with a 12% increase in body mass in 2 weeks. Compared to FF, TR induced an increase in phosphofructokinase (PFK) activity (P < 0.01), glycogen synthase [GS(i + d)] activity (P < 0.05) and glycogen content (P < 0.01) in the tibialis anterior muscle. The PR and ND caused no alterations in PFK or citrate synthase (CS) activity compared to FF. Compared to PR, TR induced an increase in PFK (P < 0.01), CS (P < 0.05) and GS(i + d) activity (P < 0.01). Both TR and PR caused an increased muscle glycogen content, being more pronounced in TR (P < 0.05). Compared to ND, TR induced an increased CS (P < 0.05) and GS(i + d) activity (P < 0.01) and glycogen content (P < 0.01). The ND resulted in a decreased glycogen content compared to FF (P < 0.05). None of the treatments affected the activity of glycogen phosphorylase, β-hydroxyacyl coenzyme A dehydrogenase and lactate dehydrogenase. It was concluded that corticosteroids led to an increased muscle glycogen content; however, the changes in the enzymes of carbohydrate metabolism were corticosteroid type specific and did not relate to undernutrition, which accompanied the triamcinolone treatment.