Muscle proteolytic enzyme activities in diabetic rats

Area of Science:

• Biochemistry
• Physiology

Background:

• Diabetes mellitus is associated with altered protein metabolism.
• The role of proteolytic enzymes in diabetic muscle wasting is not fully understood.

Purpose of the Study:

• To investigate the activity and origin of proteolytic enzymes in skeletal muscle of diabetic rats.

Main Methods:

• Streptozotocin-induced diabetes in Sprague-Dawley rats.
• Assay of alkaline serine protease and lysosomal cathepsin activities in muscle homogenates.
• Analysis of myofibril-associated protease activity.
• Investigation of mast cell involvement using compound 48/80.

Main Results:

• Diabetic rat muscle showed significantly increased alkaline serine protease activity compared to controls and insulin-treated rats.
• Lysosomal cathepsin activities remained unchanged in diabetic muscle.
• The alkaline serine protease was associated with myofibrils and originated from mast cells, as evidenced by its abolition after compound 48/80 treatment.

Conclusions:

• Alkaline serine proteases are not involved in muscle protein breakdown in diabetes.
• The observed serine protease activity in diabetic muscle is of mast cell origin.