Histochemical and biochemical changes in human skeletal muscle with age in sedentary males, age 22–65 years

TLDR

Muscle biopsies from the vastus lateralis of 55 untrained healthy men aged 22–65 were used for histochemical and biochemical analyses. Older men showed a selective loss of type II fibers and their cross‑sectional area, an inverse relationship between type II/IIA ratio and type I fibers, and a shift in lactate dehydrogenase isozyme distribution toward reduced muscle‑specific activity, while Mg²⁺‑stimulated ATPase, myokinase, and heart‑specific LDH remained unchanged.

Abstract

Biopsies for histochemical and biochemical analyses were taken from the vastus lateralis muscle of 55 untrained, healthy male subjects from 22 to 65 years of age. Fibre type distribution changed towards a decrease in the percentage of type II fibres, both in type IIA and type IIB fibres, whereas type IIB/IIA fibre ratio and type IIC percentage did not change with increasing age. It was found that the type IIB/IIA fibre ratio was inversely related to type I fibres, i.e. subjects rich in type I fibres had a relatively smaller proportion of type IIB fibres. Fibre area determinations revealed a selective decrease in type II fibre area. Consequently, the type II/I fibre area ratio and relative type II fibre area decreased. No changes in the specific activities of Mg2+ stimulated ATPase and myokinase were observed, while the activity of lactate dehydrogenase (LDH) was higher in the youngest groups than in the oldest. LDH isozyme pattern shifted towards a decrease in percentage distribution of the muscle specific isozymes and a corresponding decrease in muscle specific activity while the activity of the heart specific isozymes did not change.