Basement Membranes in Muscle Capillaries

Summary

Thickening of capillary basement membranes, including those of skeletal muscle, is now widely accepted as the ultrastructural hallmark of diabetic microangiopathy. Although muscle capillary basement membrane thickening has been reported in a limited number of collagen diseases, diabetes mellitus is by far the commonest disease associated with capillary basement membrane thickening. Muscle capillary basement membrane width increases in nondiabetic males essentially throughout life. In nondiabetic females, capillary basement membrane thickening tends to increase less rapidly until after the menopause. In both sexes basement membrane width increases linearly with increasing hydrostatic pressure in muscles below the heart level.

In a series of 138 juvenile-onset diabetics (age 10–24) recently examined, muscle capillary basement membrane width increased significantly with increasing age and with postpubertal duration, but not prepubertal or total duration, of diabetes. These observations indicate that: (1) some, as yet unidentified, puberty-related factor exerts an important permissive effect on muscle capillary basement membrane thickening in diabetic subjects and that (2) muscle capillary basement membrane thickening is, in some way, a consequence of the abnormal metabolic milieu and hormonal imbalances associated with the diabetic state. These interpretations and conclusions are supported by recent studies on monozygotic twins and triplets, discordant for diabetes, which document muscle capillary basement membrane thickening only in those individuals with diabetes.