Sex-Specific Alterations on Muscle Plasticity and Myogenesis in Offspring Rats from Vitamin D Deficient Mothers

Objective To analyze the impact of maternal Vitamin D deficiency (VDD) on offspring muscle development in adulthood of male and female rats. Methods Twelve 5‐week‐old female Wistar Hannover rats were fed either a Vit. D3 + diet (AIN93G with 1000 IU vitamin D3/kg diet) or Vit. D3 − diet (AIN93G without vitamin D3) for six weeks and then bred to male rats. Mothers were maintained on the diets throughout gestation and lactation. At weaning, male and female offsprings were separated in four groups: male and female offspring control (M‐CTRL and F‐CTRL, respectively) pups of dams with Vit. D3 + diet; male and female offspring VDD (M‐VDD and F‐VDD, respectively) pups of dams with Vit. D3 − diet. Offspring received a standard diet (Nuvilab) until 180 days of age, at which point tissues were harvested for analysis. *P≤0,05 (CEUA 052/2018). Results Both male and female VDD groups showed a reduction in the calcidiol serum concentration (23±1 vs 40±2 ng/ml in M‐CTRL and 23±2.2 ng/ml vs 36.6±0.9 ng/ml in F‐CTRL) without affecting Ca +2 serum. At weaning, M‐VDD weighed less than M‐CTRL rats but recovered weight in the 60 days post weaning and acquired a greater body weight accompanied by a higher mass of white and brown adipose tissue at 180 days. Extensor digitorum longus (EDL) muscles from the M‐VDD showed a decrease (20 %; p<0.05) in the number of total fibers and an increase in the cross sectional area of IIB (17 %), IIA (19 %) and IIAX (21%; p<0.05) fibers. VDD also deregulated myogenesis as indicated by the higher levels of MyoD (43%; p<0.05) and Myogenin (160%; p<0.05) and in the number of satellite cells (128.8±14 vs 91±7.6 nuclei Pax7+ in the MO‐CTRL). To further investigate the signaling pathways involved in the muscle hypertrophy effect in the M‐VDD group, p‐IGF‐1/insulin receptor levels, and different insulin downstream targets related to protein synthesis including Ser 473 p‐Akt, Ser 21/9 p‐GSK‐3β and Ser 209 p‐eIF4e were measured. VDD increased all these parameters and in parallel increased plasma insulin and muscle IGF‐1 mRNA levels, but did not affect mTOR signaling. These changes were not found in Soleus from the M‐VDD group and in both EDL and Soleus from the female offspring. Conclusion Maternal VDD selectively affect the development of glycolytic muscle in male offspring characterized by hypoplasia, hypertrophy and deregulated myogenesis. The muscle hypertrophy is a compensatory mechanism probably due to the greater insulin sensitivity and activation of the Akt pathway. Muscles from female offspring seem to be protected from this metabolic disturbance showing a clear sex‐specific effect induced by maternal VDD. Support or Funding Information FAPESP (19/06517‐1; 18/10089‐2)