Astragalus Extract Mixture HT042 Increases Longitudinal Bone Growth Rate by Upregulating Circulatory IGF‐1 in Rats

Astragalus extract mixture HT042 is a standardized ingredient of health functional food approved by Korean FDA with a claim of “height growth of children.” HT042 stimulates bone growth rate and increases local IGF‐1 expression in growth plate of rats which can be considered as direct stimulation of GH and its paracrine/autocrine actions. However, it remains unclear whether HT042 stimulates circulatory IGF‐1 which also plays a major role to stimulate bone growth. To determine the effects on circulatory IGF‐1, IGF‐1 and IGFBP‐3 expressions and phosphorylation of JAK2/STAT5 were evaluated in the liver after 10 days of HT042 administration. HT042 upregulated liver IGF‐1 and IGFBP‐3 mRNA expression, IGF‐1 protein expression, and phosphorylation of JAK2/STAT5. HT042 also increased bone growth rate and proliferative zonal height in growth plate. In conclusion, HT042 stimulates bone growth rate via increment of proliferative rate by upregulation of liver IGF‐1 and IGFBP‐3 mRNA followed by IGF‐1 protein expression through phosphorylation of JAK2/STAT5, which can be regarded as normal functioning of GH‐dependent endocrine pathway.