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Growth Factors, IGF-1
Without growth factors no maintenance
Insulin-like growth factor 1 (IGF-1) that was once called somatomedin C, is a polypeptide protein hormone similar in molecular structure to insulin. It plays an important role in childhood growth and continues to have anabolic effects in adults. IGF-1 is the most important and easy to measure growth factor.
In a healthy person, every release of hGH stimulates release of growth factors, from which we have hundreds of different types. HGH-stimulation can be done by hGH releasers, such as RecoveryMatrix and VitalityMatrix. If the pituitary cannot release hGH, the only way is to inject hGH. This is a prescription drug, costly and not free of side effects. However, if managed well, it can be very effective. It still is effective as well, and very economic to use a growth hormone releaser. These are products with a very specific blend of amino acids and other stimulating ingredients.
hGh stimulates IGF-1 secretion
IGF-1 consists of 79 amino acids in a single chain with three intramolecular disulfide bridges. IGF-1 has a molecular weight of 7649 daltons. IGF-1 is produced primarily by the liver as an endocrine hormone as well as target tissues in a paracrine/autocrine fashion. Production is stimulated by growth hormone and can be retarded by undernutrition, growth hormone insensitivity, lack of growth hormone receptors, or failures of the downstream signalling pathway post GH receptor including SHP2 and STAT5b. Approximately 98% of IGF-1 is always bound to one of 6 binding proteins (IGF-BP). IGFBP-3, the most abundant protein, accounts for 80% of all IGF binding. IGF-1 binds to IGFBP-3 in a 1:1 molar ratio.Primary action and importance during life
Its primary action is mediated by binding to specific IGF receptors present on many cell types in many tissues. The signal is transduced by intracellular events. IGF-1 is one of the most potent natural activators of the AKT signaling pathway, a stimulator of cell growth and multiplication and a potent inhibitor of programmed cell death.
Almost every cell in the human body is affected by IGF-1, especially cells in muscle, cartilage, bone, liver, kidney, nerves, skin, and lungs. In addition to the insulin-like effects, IGF-1 can also regulate cell growth and development, especially in nerve cells, as well as cellular DNA synthesis.
Biogerontology. 2003;4(1):1-8.
Interplay of IGF-I and 17beta-estradiol at age-specific levels in human sebocytes and fibroblasts in vitro.
Exp Gerontol. 2008 Aug 12. Makrantonaki E, Vogel K, Fimmel S, Oeff M, Seltmann H, Zouboulis CC.
Laboratory for Biogerontology, Dermato-Pharmacology and Dermato-Endocrinology, Institute of Clinical Pharmacology and Toxicology, Charité Universitaetsmedizin Berlin, Garystrasse 5, 14195 Berlin, Germany; Departments of Dermatology and Immunology, Dessau Medical Center, Auenweg 38, 06847 Dessau, Germany.
In order to obtain greater insights into the molecular mechanisms accompanying hormonal aging the effects of growth hormone (GH), insulin-like growth factor-I (IGF-I), 17beta-estradiol, progesterone and dehydroepiandrosterone were tested as single agents in concentrations corresponding to 20- and 60-year-old females on human SZ95 sebocytes and fibroblasts. Cell proliferation and viability were measured by 4-methylumbelliferyl heptanoate and lactate dehydrogenase microassays, respectively, whereas lipid accumulation was documented via nile red microassay and fluorescence microscopy. mRNA and protein expression was evaluated via real-time RT-PCR and Western blotting or ELISA, accordingly.
Our results depict the importance of IGF-I for the lipid synthesis in SZ95 sebocytes and demonstrate the lack of 17beta-estradiol, dehydroepiandrosterone and progesterone activity on lipid synthesis and SZ95 sebocytes proliferation suggesting that the action of these hormones in vivo may be implemented through indirect pathways. Fibroblasts showed to be more susceptible to 17beta-estradiol treatment, while IGF-I could significantly stimulate fibroblasts proliferation in a dose-dependent manner. Furthermore, an interplay between the 17beta-estradiol and IGF-I signaling pathway was documented in both cell types. In conclusion, IGF-I is a key regulator of human skin aging and declining IGF-I levels with age may play a significant role in the reduction of skin surface lipids and thickness.
Insulin-like growth factor 1 (IGF-1) and aging: controversies and new insights.
Bartke A, Chandrashekar V, Dominici F, Turyn D, Kinney B, Steger R, Kopchick JJ.
Department of Physiology, Southern Illinois University School of Medicine, Carbondale, IL 62901-6512, USA. abartke@siumed.edu
Insulin/insulin-like growth factor (IGF) signaling plays a major role in the control of aging and life span in invertebrates. Major extension of life span in growth hormone receptor knock out (GHR-KO) mice that are GH resistant, and subsequently, IGF-I-deficient indicates that similar mechanisms may operate in mammals. This conclusion is supported by association of reduced IGF-I levels and delayed aging in three different GH-deficient mutant mice and in animals subjected to caloric restriction, but is difficult to reconcile with neuroprotective effects of IGF-I and with the suspected role of declining GH levels during aging. We suggest that the role of IGF in the regulation of growth and adult body size is important in mediating the effects of longevity genes on aging and life span. Suspected mechanisms of IGF-I action in aging also include reduced insulin signaling, enhanced sensitivity to insulin, and reduced thermogenesis with diminished oxidative damage of macromolecules being the likely final common pathway of these effects. We suspect that IGF-I is important in evolutionarily conserved mechanisms that link life history, including development, reproduction, and aging with availability of energy resources.
Studies:
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