Effects of peripheral muscle contraction and muscle sympathetic activity on the insulin sensitivity

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Using normal and high-fat-fed (HFF) rats, by means of the euglycemic insulin clamp technique, we investigated insulin sensitivity during hind-limb muscle contraction as well as at rest, with and without sciatic nerve innervation. In addition, we measured hepatic glycogen contents, with a method using phenol and sulfuric acid, to distinguish endogenous and exogenous glucose used during the clamp, and separated endogenous rat insulin and exogenous human insulin with simultaneous measurements using human and rat plasma insulin assays. The results obtained suggest; (1) We accumulated basic data on insulin sensitivity to be used as the control in various studies in the future; (2) Commencement of insulin infusion prior to glucose infusion makes euglycemic clamp maneuver easier; (3) We established how to make HFF rats; (4) In HFF rats, ED_<50> of insulin is higher than in normal rats; (5) No significant change was observed in the insulin sensitivity during titanic muscle contraction; (6) Rhythmic contraction made the sensitivity higher; (7) Denervation considerably affects the insulin sensitivity at rest; (8) Glucose uptake mechanism after denervation may be different from that observed in normal rats; (9) The insulin sensitivity of HFF rats at rest was similar to that of normal rats after dennervation; (10) During the euglycemic clamp, endogenous hepatic glucose output was considerably larger than we expected, which may mean the effects of euglycemic clamp on glucose metabolism is large.