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Muscle fibre composition and glycogen synthase activity in hypertension-prone men
T Endre1, I Mattiasson, G Berglund
1Department of Medicine, Malmö University Hospital, Lund University, Sweden.
Objectives:
To study muscle fibre characteristics and glycogen synthase activity in relation to peripheral glucose disposal in skeletal muscle in hypertension-prone men.
Design:
The hyperinsuliemic euglycemic clamp method was used to calculate insulin sensitivity index (M/I). Muscle biopsies were performed for the analysis of slow-twitch (ST) and fast twitch (FT, low insulin sensitivity and low capillarisation compared to ST fibres) muscle fibres, capillarisation (number of capillaries per fibre) and diffusional index (mean area per fibre divided by capillarisation) of muscle fibres, capillary density (capillaries mm(-2) muscle fibre) and glycogen synthase activity.
Subjects:
Thirty-two young, healthy, normotensive men with a family history of hypertension (REL) were compared to 2 5 age-matched men with no family history of hypertension (CON) and similar body mass index (BMI).
Results:
REL had a lower M/I (P = 0.021), lower capillarisation (P = 0.04) and a tendency of a lower diffusional index of subgroup b of FT muscle fibres (P = 0.10) compared to CON. Glycogen synthase activity did not differ between the groups.
Conclusions:
Men with a family history of hypertension have less capillaries per FTb fibre and greater diffusion distance from the capillary to the muscle cell compared to controls, which may be a contributory factor to the lower insulin sensitivity in the former group. However, additional investigations are needed to study the causality in this association.