Tero Varimo, Leo Dunkel, Kirsi Vaaralahti, Päivi J Miettinen, Matti Hero, and Taneli Raivio
Makorin ring finger protein 3 (MKRN3) gene restrains the hypothalamic–pituitary–gonadal axis. In girls, peripheral levels of MKRN3 decline prior to the onset of puberty. We described longitudinal changes in serum MKRN3 levels in boys before and during puberty and assessed the effect of inhibition of estrogen biosynthesis on MKRN3 levels.
Longitudinal serum samples from a double-blind, randomized controlled study in 30 boys (age range: 9.1–14.2years) with idiopathic short stature who received placebo (Pl; n=14) or aromatase inhibitor letrozole (Lz; 2.5mg/day; n=16) for 2years.
We analyzed the relationships between serum MKRN3 and clinical and biochemical markers of puberty by using summary measures.
Serum MKRN3 declined by 669±713 pg/mL per year (P<0.001). This change was biphasic, as the levels decreased during Tanner genital stage G1 (–2931±2750 pg/mL per year) and plateaued thereafter (–560±1510 pg/mL per year) (P<0.05). During G1, MKRN3 levels in Lz-treated subjects decreased slower than in Pl-treated boys (–782±3190 vs –2030±821 pg/mL per year, P<0.05). The decrease in serum MKRN3 levels in G1 was associated with increases in LH (r=–0.5, P<0.01), testosterone (r=–0.6, P<0.01), and inhibin B (r=–0.44, P<0.05) (n=26).
Peripheral MKRN3 levels in boys appear to serve as a readout of the diminishing central inhibition that controls the onset of puberty.
Tero Varimo, Yafei Wang, Päivi J Miettinen, Kirsi Vaaralahti, Matti Hero, and Taneli Raivio
The role of miRNA as endocrine regulators is emerging, and microRNA mir-30b has been reported to repress Mkrn3. However, the expression of miR-30b during male puberty has not been studied.
Design and methods
Circulating relative miR-30b expression was assessed in sera of 26 boys with constitutional delay of growth and puberty (CDGP), treated with low-dose testosterone (T) (n =11) or aromatase inhibitor letrozole (Lz) (n =15) for 6 months and followed up to 12 months (NCT01797718). The associations between the relative expression of miR-30b and hormonal markers of puberty were evaluated.
During the 12 months of the study, circulating miR-30b expression increased 2.4 ± 2.5 (s.d.) fold (P = 0.008) in all boys, but this change did not correlate with corresponding changes in LH, testosterone, inhibin B, FSH, or testicular volume (P = 0.25-0.96). Lz-induced activation of the hypothalamic–pituitary–gonadal (HPG) axis was associated with more variable miR-30b responses at 3 months (P < 0.05), whereas those treated with T exhibited significant changes in relative miR-30b levels in the course the study (P < 0.01–0.05).
Circulating miR-30b expression in boys with CDGP increases in the course of puberty, and appears to be related to the activity of the HPG axis.