The Decline in Pulsatile Growth Hormone Secretion throughout Early Adulthood in Mice is Exacerbated by Dietary Induced Weight Gain (#9)
The pathological decline in growth hormone (GH) secretion in early adulthood is detrimental to attainment of peak lean muscle and bone mass, and promotes adiposity and susceptibility for the development of obesity. It is thus essential that we identify factors that may advance the age-associated decline in GH secretion throughout early adulthood.
To characterize the impact of dietary induced weight gain on the decline in GH secretion throughout early adulthood, we first characterized pulsatile GH secretion in C57BL/6J mice maintained on a standard diet at 12 and 16 weeks of age. We then assessed GH secretion in mice following 4 and 8 weeks of high fat feeding. In addition, circulating levels of IGF-1 and hepatic triglycerides were assessed.
We observed a significant decline in pulsatile GH secretion in mice from 12 to 16 weeks of age. This was characterized by a significant decline in total (725±136 vs 365±68.3ng/ml per 6h, p=0.014), pulsatile (594±129 vs 326±68.5ng/ml per 6h, p=0.022), and the mass of GH secreted per burst (143±17.0 vs 101±24.2ng/ml, p=0.005). Alongside an increase in body weight, we observed a suppression of total (873±160 vs 442±36.3ng/ml per 6h, p=0.015), pulsatile (732±140 vs 414±38.8ng/ml per 6h, p=0.040) and basal GH secretion (141±32.4 vs 26.7±6.02ng/ml per 6h, p=0.002) following 4 weeks of high fat feeding and a further decline in GH secretion by 8 weeks of dietary intervention. In addition, impaired GH secretion coincided with an elevation in hepatic triglycerides and an eventual reduction in circulating levels of IGF-1.
Observations suggest that dietary induced weight gain advances the age-associated decline in pulsatile GH secretion throughout early adulthood in mice. Whether the advanced decline in GH secretion following dietary induced weight gain will have long-term ramifications on adult health awaits further investigation.
This work was supported by the Australian National Health and Medical Research Council (NHMRC) and The University of Queensland. L. Huang receives an overseas postgraduate research scholarship from China Scholarship Council (CSC) and subsidy scholarship from The University of Queensland.