Thymosin beta-4 (Tβ4) is a water-soluble, 43-amino acid, and 4.9 kDa protein that was originally isolated from bovine thymus . Since Tβ4 is the major actin-sequestering molecule in eukaryotic cells and is found in all cells , Tβ4 has multiple diverse cellular functions, including tissue development, migration, angiogenesis, and wound healing . We previously reported that Tβ4-overexpressing transgenic mice, using a construct on the skin-specific keratin-5 promoter, have abnormal tooth development and enhanced stimulation of hair growth . Moreover, exogenous Tβ4 has anti-inflammatory effects in the bleomycin-induced mouse model of lung fibrosis , tooth extraction sockets in rats , rat model of myocardial ischemia , corneal wound healing , wound healing of rat palatal mucosa , in vitro model of cultured human gingival fibroblasts , and cardiac fibroblasts . However, the effects of Tβ4 over expression or inhibition on differentiation are controversial. Exogenous β4 peptide inhibited osteogenic differentiation but facilitated adipogenic differentiation in human bone marrow-derived-mesenchymal stem cells (MSCs) . In contrast, Tβ4 inhibition by Tβ4 siRNA attenuated odontoblastic differentiation in the odontoblast-like cells, MDPC-23 . Moreover, we recently demonstrated that odontoblastic differentiation was enhanced by activation of Tβ4 by Tβ4 peptide but was decreased by Tβ4 siRNA in human dental pulp cells (HDPCs) . However, the effects of Tβ4 on osteoclastic differentiation have not been reported.
This current literature is notable for its apparent irrelevancy to an AFL footballer. It begs the question; did Tβ4 make a difference to the Essendon players? The only honest answer is that we don’t know. Most of our understanding exists on a molecular and cellular level, without any significant appreciation of how Tβ4 influences applicable outcomes such as exercise performance, endurance, muscle strength, and time to recovery. Furthermore, as the majority of research has been performed on mice, rat and pig models, any results are not directly translatable to a human, let alone an elite athlete. This is a stark contrast to a supplement such as EPO, which has been investigated thoroughly.
Melanotan II non-selectively mimics the action of melanocortin peptides. These are natural hormones involved with pigmentation, energy homeostasis, sexual functioning, the immune system, inflammation, and the cardiovascular system. Much like melanotan I (afamelanotide), melanotan II stimulates the production of eumelanin, causing the skin to go darker (tanning).
A 2002 review concluded that although the data evaluated suggests that 5-HTP is more effective than placebo in the treatment of depression, the evidence was insufficient to be conclusive due to a lack of clinical data meeting the rigorous standards of today. More and larger studies using current methodologies are needed to determine if 5-HTP is truly effective in treating depression. In small controlled trials 5-HTP has also been reported to augment the antidepressant efficacy of the antidepressant clomipramine.