Effects of Prolonged Food Deprivation on the Ultradian Growth Hormone Rhythm and Immunoreactive Somatostatin Tissue Levels in the Rat*

Increased Expression of Fibroblast Growth Factor 21 (FGF21) during Chronic Undernutrition Causes Growth Hormone Insensitivity in Chondrocytes by Inducing Leptin Receptor Overlapping Transcript (LEPROT) and Leptin Receptor Overlapping Transcript-like 1 (LEPROTL1) Expression

“…In many experimental models food restriction is associated with reduced skeletal growth, with such association primarily resulting from impaired growth hormone action (7)(8)(9)(10)(11)(12)(13)(14)(15)(16). In a previous study we demonstrated that mice undergoing 4 weeks of food restriction exhibited increased expression of Fgf21 (both in the liver and in the growth plate), growth hormone (GH) 3 insensitivity, and a concomitant reduction of their body linear growth and growth plate chondrogenesis (17).…”

Leptin increases in vivo GH responses to GHRH and GH-releasing peptide-6 in food-deprived rats

“…Although contradictory findings (29,30) deprivation on GH responses to GHRH in the rat, there is a general agreement that it elicits a marked decrease in spontaneous GH secretion (17,29,31,32). This later effect is due to a suppression of high-amplitude GH secretory bursts and a decrease in the duration of secretory episodes (31).…”

“…Although the mechanisms mediating these alterations remain unclear, several possibilities have been put forward. Increased somatostatinergic tone has been implicated, because passive immunization of food-deprived rats with somatostatin antiserum restored spontaneous GH secretion to values similar to those in normally fed rats (31). Nevertheless, hypothalamic prepro-somatostatin mRNA levels and peptide content did not differ between food-deprived and control rats, and somatostatin immunostaining in middle and caudal regions of the median eminence has been reported to be decreased (33,34).…”

“…This later effect is due to a suppression of high-amplitude GH secretory bursts and a decrease in the duration of secretory episodes (31). Although the mechanisms mediating these alterations remain unclear, several possibilities have been put forward.…”

Fasting vs dietary restriction in cellular protection and cancer treatment: from model organisms to patients

“…In non-obese subjects GH levels eventually level off and drop between 3-10 days of fasting (Cahill et al, 1966;Merimee and Fineberg, 1974;Palmblad et al, 1977). In mice, a shortterm starvation (24-72 h) decreases IGF-I production by 70% and causes an 11-fold increase in its inhibitory partner IGF-binding protein 1 (IGFBP-1) (Tannenbaum et al, 1979;Frystyk et al, 1999;Lee et al, 2010). In response to fasting, mice also show reduced protein synthesis, reduced AKT activity via TRB3, a mammalian homolog of Drosophila tribbles (Du et al, 2003), reduced mTOR/S6K, increased 4E-BP1 activity (Sans et al, 2004) and increases FOXO-1, -3, -4 (Imae et al, 2003).…”