Gestational Diabetes Mellitus (GDM) is a risk factor for the development of Pregnancy Specific Urinary Incontinence (PSUI) [1] and skeletal muscle dysfunction, including rectus abdominis muscle, which is involved in urinary continence. Experimental study showed fiber type changes in the rectus abdominis of long-term mild Streptozotocin (STZ)-induced diabetic pregnant rats [2]. Swim exercise is effective in the prevention and treatment of GDM [3]. We hypothesized that swimming exercise would be capable of improving the fiber type changes in skeletal muscle. The aim of the study was to analyze the role of swim exercise on fiber type changes in the rectus abdominis muscle of long-term mild STZ-induced diabetic pregnant rats.

This is a multi-center, basic sciences/translational study. On the first day of life, Wistar female rats received Streptozotocin at a dose of 100 mg/kg, subcutaneously. At 90 days of age, every four females were mated overnight with one male rat for the maximum period of 15 days. The presence of spermatozoa in the vaginal smear was considered gestational day 0. The animals that presented glycemic level between 120-300 mg/dL and <120 mg/dL were included in the experimental groups: Control – Sedentary non-diabetic (C), Control – Exercised non-diabetic (Cex), Diabetic – Sedentary (D) and Diabetic – Exercised (Dex). The Cex and Dex groups started the swim exercise protocol on a gestational day 0 until gestational day 20 (60 minutes/day, 6 days/week). On gestational day 21, the lower third of rectus abdominis muscle were obtained to immunohistochemical analysis. Immunohistochemical analysis was used to stain fast and slow fiber type (2 samples/group) and images from 7 sections/animal were obtained and analyzed using cell Sens Standard software. The fast and slow fibers total area were quantified, as well as the area and diameter of each fiber (approximately 100 fibers/group). Comparisons between groups were performed by Two-way ANOVA followed by Tukey’s multiple comparison test.

The lower third of the rectus abdominis muscle showed a higher proportion of fast fibers compared to slow fibers. There was no difference between groups in fast and slow fibers total area. However, the analysis of each fiber type showed a reduction of the area and diameter of fast fibers in the D group compared to C group (p<0.05) and increased area and diameter of slow fibers in D group compared to C group (p<0.0001). Regarding the effect of exercise over these changes, the results showed that swim exercise increased area and diameter of fast fibers in the Dex group compared to D group (p<0.05 and p<0.001, respectively). There was no difference in the area and diameter of slow fibers in Dex group compared to other groups, but Cex group showed increased area and diameter of slow fibers compared to the C group (p<0.0001).

The results showed changes in the proportion of fiber type in the rectus abdominis muscle of pregnant rats caused by long-term mild diabetes. In addition, swim exercise was capable to improve this change through the increase in area and diameter of fast fibers, which is the most prevalent fiber type in the lower third of the rectus abdominis muscle. Our hypothesis is that the improvement of muscle fiber type may contribute to the improvement in muscle function as well.

We concluded that swim exercise improved the rectus abdominis muscle fiber type changes in long-term mild STZ-induced diabetic pregnant rats. Currently, the analysis is under progress to increase the sample size and to confirm these findings.

Hvidman L, Foldspang A, Mommsen S, Nielsen JB. Correlates of urinary incontinence in pregnancy. International Urogynecology Journal. 2002; 13(5), 278-283.
Vesentini G, Marini G, Piculo F, Damasceno DC, Matheus SMM, Felisbino SL. Morphological changes in rat rectus abdominis muscle induced by diabetes and pregnancy. Brazilian Journal of Medical and Biological Research. 2018; 51, 1–10.
Colberg SR, Castorino K, Jovanovic L. Prescribing physical activity to prevent and manage gestational diabetes. World journal of diabetes. 2013; 4(6), 256–262.