Muscle capillary basement membrane width and its relationship to diabetes mellitus in monozygotic twins

Quadriceps (Q) and gastrocnemius (G) muscle capillary basement membrane width (CBMW) were measured in 18 pairs of monozygotic (MZ) twins. Thirteen of these twin pairs were discordant for insulin-dependent diabetes (IDD) and five pairs were concordant for either IDD (two pairs) or for non-insulin-dependent diabetes (NIDD). In 12 of the 13 nondiabetic (ND) twin mates of IDD, 50 oral glucose tolerance tests performed in the years before or after determination of CBMW revealed mean blood glucose levels in the 36-52 percentile range, compared with normal controls. The mean (+/-SD) age at the onset of IDD in discordant twins was 18.7 +/- 10.1 (range 8-37) yr and the mean duration of discordance at the time of biopsy was 13.6 +/- 8.3 (range 3-32) yr. CBMW data were compared within each twin (Q versus G) and between twin mates and age- and sex-matched controls. Overall, CBMW of IDD twins was greater than that of their ND twin mates. Differences between IDD and ND twins, however, were much more marked in gastrocnemius (1859 +/- 643 versus 1222 +/- 307 A, P less than 0.0003) than in quadriceps (1291 +/- 319 versus 1112 +/- 302 A; P less than 0.04). CBMW in gastrocnemius was significantly thicker than that in the quadriceps of IDD twins (t = 4.55, P less than 0.0008) but not in their ND twin mates (t = 1.15, P less than 0.27). CMBW was significantly thicker in IDD than in their ND twin mates (in quadriceps and/or gastrocnemius) in 10 of the 12 twin pairs.(ABSTRACT TRUNCATED AT 250 WORDS)