Comparison of Sodium Selenite and Selenium-Enriched Spirulina Supplementation Effects After Selenium Deficiency on Growth, Tissue Selenium Concentrations, Antioxidant Activities, and Selenoprotein Expression in Rats

Selenium contributes to physiological functions through its incorporation into selenoproteins. It is involved in oxidative stress defense. A selenium deficiency results in the onset or aggravation of pathologies. Following a deficiency, the repletion of selenium leads to a selenoprotein expression hierarchy misunderstood. Moreover, spirulina, a microalga, exhibits antioxidant properties and can be enriched in selenium.. Our objective was to determine the effects of a sodium selenite or selenium-enriched spirulina supplementation. Thirty-two female Wistar rats were fed for 12 weeks with a selenium-deficient diet. After 8 weeks, rats were divided into 4 groups and were fed with water, sodium selenite (20 μg Se/kg body weight), spirulina (3 g/kg bw), or selenium-enriched spirulina (20 μg Se/kg bw + 3 g spirulina/kg bw). Another group of 8 rats was fed with normal diet during 12 weeks. Selenium concentration and antioxidant enzyme activities were measured in plasma, urine, liver, brain, kidney, heart, and soleus. Expression of GPx (1, 3), Sel (P, S, T, W), SEPHS2, TrxR1, ApoER2, and megalin were quantified in liver, kidney, brain, and heart. We showed that a selenium deficiency leads to a growth delay, reversed by selenium supplementation despite a minor loss of weight in week 12 for SS rats. All tissues displayed a decrease in selenium concentration following deficiency. The brain seemed protected. We demonstrated a hierarchy in selenium distribution and selenoprotein expression. A supplementation of sodium selenite improved GPx activities and selenoprotein expression while a selenium-enriched spirulina was more effective to restore selenium concentration especially in the liver, kidney, and soleus.

Muscle development, insulin-like growth factor-I and myostatin mRNA levels in chickens selected for increased breast muscle yield

Insulin-like growth factor-I (IGF-I) and myostatin (MSTN) are paracrine regulators of muscle growth. The present study was conducted to relate their expression with muscle fibre development in chickens selected for high breast meat yield and their controls. Both mRNA levels were measured by real-time RT-PCR in the Pectoralis major (PM) muscle between 14 days in ovo and 6 weeks post-hatch and in the Sartorius (SART) muscle between 2 and 6 weeks. The data show that PM growth was slow during in ovo development and rapid in the early post-hatch period. Chickens from the selected genotype exhibited significantly higher breast muscle yields from 2 to 6 weeks of age, and muscle fibre hypertrophy. In the PM, IGF-I and MSTN mRNA levels decreased markedly around hatch, while the IGF-I/MSTN ratio increased, suggesting that it could contribute to the explosive growth observed in the early post-hatch period. Between 4 and 6 weeks of age in selected chickens, IGF-I mRNA levels were significantly higher (p=0.04) with a similar trend in MSTN mRNA levels (p=0.07) in the PM muscle but not in the SART muscle. Our results support the hypothesis that the relative levels of IGF-I and MSTN mRNA may participate to set muscle growth rate along development, while other factors are required to explain differences between genotypes.