Height Gaining with mTor(leucine)?

mTor regulates growth plate autophagy.  Without mTor autophagy cannot be induced.  mTor can increase the translation of Myc.  It also increases the availability of free eIF4E.  Inhibition of PTEN increases mTor and induces skeletal overgrowth.  Cadherin 13 activates mTor.

Leucine may increase mTor levels and Leucine is available for sale: Source Naturals L-Leucine 500mg, 120 Capsules

As is Isoleucine: Supplement Direct L-isoleucine Powder 250 Grams

ENDOCRINE AND NUTRITIONAL CONTROL OF LONG BONE GROWTH

"The objective of this study is to identify mechanisms by which nutrient availability, specifically leucine which is the most abundant essential amino acids, affects chondrocyte proliferation, differentiation, deposition of extracellular matrix (ECM) and their interactions. Nutritional status effect linear growth by modulating GH/IGF-I axis. Recently signaling mechanism by which nutrients directly regulate cells via mammalian Target Of Rapamycin (mTOR) has been elucidated. We hypothesize that leucine directly regulates chondrogenesis directly by affecting chondrocyte proliferation, differentiation and ECM deposition, 3 key components of bone growth. Our hypothesis is based on our observations. First, mTOR directly regulates chondrogenesis. MTOR inhibition results in decreased expression of Indian hedgehog (Ihh), a key regulator of chondrogenesis. Decreased Ihh could be central to mTOR action. Second, leucine restriction and mTOR inhibition result in significant reduction of ECM mRNA expression likely via miRNA regulation. Lastly, we utilized an ex vivo metatarsal explant system to demonstrate the physiological relevance of observations we made in the chondrogenic ATDC5 cell line.

Specific Aim 1: Identify the molecular mechanisms that mediate the effect of mTOR inhibition and leucine restriction on Ihh regulation and, as a consequence, chondrocyte growth and differentiation. .
Specific Aim 2: Determine the effect of mTOR inhibition and leucine restriction on miRNA-29 regulation resulting in altered ECM expression and functional role in chondrocyte growth and differentiation Specific Aim 3: Utilizing a fetal metatarsal explant model, we will study the effect of mTOR inhibition and leucine restriction on bone growth, growth plate dynamics and chondrogenic markers, in particular Ihh and miRNA-29. We will study the effect of restoring Ihh and miRNA-29 expression in bones subjected to mTOR inhibition and leucine restriction."

Isoleucine and leucine independently regulate mTOR signaling and protein synthesis in MAC-T cells and bovine mammary tissue slices.

"Omission of L-arginine, L-isoleucine, L-leucine, or all EAA[Essential amino acids] reduced (P < 0.05) mammalian target of rapamycin (mTOR; Ser2448) and ribosomal protein S6 (rpS6; Ser235/236)[LSJL upregulates rpS6ka6 and downregulates rpSKa3] phosphorylation in MAC-T cells. Phosphorylation of mTOR and rpS6 kinase 1 (S6K1; Thr389) decreased (P < 0.05) in the absence of L-isoleucine, L-leucine, or all EAA in lactogenic mammary tissue slices. Omission of L-tryptophan also reduced S6K1 phosphorylation (P = 0.01). Supplementation of L-leucine to media depleted of EAA increased mTOR and rpS6 and decreased eukaryotic elongation factor 2 (Thr56) phosphorylation (P < 0.05) in MAC-T cells. Supplementation of L-isoleucine increased mTOR, S6K1, and rpS6 phosphorylation (P < 0.05). No single EAA considerably affected eukaryotic initiation factor 2-α (eIF2α; Ser51) phosphorylation[LSJL reduces eIF2a phosphorylation], but phosphorylation was reduced in response to provision of all EAA (P < 0.04). FSR[protein synthesis rates] declined when L-isoleucine (P = 0.01), L-leucine (P = 0.01), L-methionine (P = 0.02), or L-threonine (P = 0.07) was depleted in media and was positively correlated (R = 0.64, P < 0.01) with phosphorylation of mTOR and negatively correlated (R = -0.42, P = 0.01) with phosphorylation of eIF2α. Such regulation of protein synthesis will result in variable efficiency of transfer of absorbed EAA to milk protein and is incompatible with the assumption that a single nutrient limits protein synthesis that is encoded in current diet formulation strategies."

Leucine nutrition in animals and humans: mTOR signaling and beyond.

"After structural roles are satisfied, the ability of leucine to function as signal and oxidative substrate is based on a sufficient intracellular concentration. Therefore, leucine level must be sufficiently high to play the signaling and metabolic roles. Leucine is not only a substrate for protein synthesis of skeletal muscle, but also plays more roles beyond that. Leucine activates signaling factor of mammalian target of rapamycin (mTOR) to promote protein synthesis in skeletal muscle and in adipose tissue{and bone and growth plates}. It is also a major regulator of the mTOR sensitive response of food intake to high protein diet. Meanwhile, leucine regulates blood glucose level by promoting gluconeogenesis and aids in the retention of lean mass in a hypocaloric state."

"activation of mTOR/S6K1 pathway by AA has been shown to phosphorylate serine (Ser-1101) of insulin receptor substrate 1 (IRS-1) and suppress tyrosine phosphorylation, which results in impaired phosphatidylinositol 3-kinase (PI3K) activity"

IRS1 which inhibits PI3K is downregulated by LSJL.

So increase in p-mTor(in conjunction with increase in p-Akt) has been shown to induce overgrowth by inhibition of PTEN.  However, p-mTor has a negative feedback mechanisms where it inhibits p-Akt.


The effect of rapamycin on bone growth in rabbits.

"[Rapamycin is an mTOR inhibitor]i. [We directly infused] rapamycin into the proximal tibial growth plates of rabbits. Rapamycin or DMSO vehicle was infused directly into growth plates by an osmotic minipump for 8 weeks. At the end of the experiment, growth plates were recovered for histological analysis. Six animals were studied. Bone growth of limbs exposed to rapamycin was slower than control limbs, particularly during the period of most rapid growth. Histological analysis revealed that growth plate height in the rapamycin-infused limbs was reduced. Both the hypertrophic and proliferative zones were significantly smaller in the rapamycin-infused limbs. Direct infusion of rapamycin into proximal tibial growth plates decreased the size of the growth plate and inhibited overall long bone growth. Rapamycin appears to affect both the proliferative and hypertrophic zones of the tibial growth plate."

"One animal was excluded from these data because closure of the growth plate had occurred on the rapamycin infused side but not the control side."<-So mTor inhibition may cause adult height reduction and not just growth rate reduction.

"rapamycin affects the expression of Indian Hedgehog (Ihh)"

Chondrogenic differentiation of growth factor-stimulated precursor cells in cartilage repair tissue is associated with increased HIF-1alpha activity.

"Scaffold-bound autologous periosteal cells, which had been activated by Insulin-like Growth Factor 1 (IGF-1) or Bone Morphogenetic Protein 2 (BMP-2) gene transfer using both adeno-associated virus (AAV) and adenoviral (Ad) vectors, were applied to chondral lesions in the knee joints of miniature pigs. Six weeks after transplantation, the repair tissues were investigated for collagen type I and type II content as well as for HIF-1alpha expression. The functional role of phosphatidylinositol 3-kinase (PI3K)/mammalian target of rapamycin (mTOR) and mitogen-activated protein kinase (MEK)/extracellular signal-regulated kinase (ERK) signaling on BMP-2/IGF-1-induced HIF-1alpha expression was assessed in vitro by employing specific inhibitors.

Unstimulated periosteal cells formed a fibrous extracellular matrix in the superficial zone and a fibrocartilaginous matrix in deep zones of the repair tissue. This zonal difference was reflected by the absence of HIF-1alpha staining in superficial areas{so maybe HIF-1a isn't need to induce chondrogenesis}, but moderate HIF-1alpha expression in deep zones. In contrast, Ad/AAVBMP-2-stimulated periosteal cells, and to a lesser degree Ad/AAVIGF-1-infected cells, adopted a chondrocyte-like phenotype with strong intracellular HIF-1alpha staining throughout all zones of the repair tissue and formed a hyaline-like matrix. In vitro, BMP-2 and IGF-1 supplementation increased HIF-1alpha protein levels in periosteal cells, which was based on posttranscriptional mechanisms rather than de novo mRNA synthesis, involving predominantly the MEK/ERK pathway.

This pilot experimental study on a relatively small number of animals indicated that chondrogenesis by precursor cells is facilitated in deeper hypoxic zones of cartilage repair tissue and is stimulated by growth factors which enhance HIF-1alpha activity."

"Application of Wortmannin or Rapamycin, inhibiting PI3K or mTOR, respectively, only moderately decreased the HIF-1α levels following BMP-2 and IGF-1 stimulation. However, treatment with the MEK inhibitor UO126 nearly completely abolished HIF-1α induction by either growth factor"

"HIF-1 was shown to transactivate Sox9. The HIF-1 subunit HIF-1α [directly binds] to the Sox9 promotor region"

Leucine may increase height via activation of mTor.  However:

1) We don't know the optimal dosage of Leucine

2) p-mTor inhibits p-Akt(although LSJL increases p-Akt)