Seasonally inappropriate body weight induced by food restriction: effect on hypothalamic gene expression in male Siberian hamsters.
Male Siberian hamsters undergo physiological weight change in changing photoperiod. Weight loss was induced by food restriction in long days to mimic short-day weight loss, or by food restriction superimposed on short-day weight loss, to test the hypothesis that the hypothalamus differentiates between weight change induced by imposed negative energy balance (inappropriate body weight) and seasonal, appropriate, body weight change, even when these are of similar magnitude. Short-day weight loss was accompanied by reduced POMC and leptin receptor (OB-Rb) mRNA in the arcuate nucleus but elevated cocaine- and amphetamine-regulated transcript. Melanocortin 3-receptor gene expression was reduced in the arcuate nucleus but elevated in the ventromedial nucleus compared with ad libitum-fed long-day controls. Weight loss in long-day restricted animals generated a gene expression profile typical of negative energy balance with low cocaine- and amphetamine-regulated transcript mRNA and elevated OB-Rb. Melanocortin 3-receptor mRNA levels were indistinguishable in short-day and long-day food-restricted hamsters. The hypothalamic correlates of food restriction in short days included up-regulated anabolic neuropeptides and increased OB-Rb mRNA. Low plasma leptin is integrated differently in short-day and long-day restricted animals, and seasonally-inappropriate body weight in either photoperiod engages the compensatory neuropeptide systems involved in the defense of body weight.
Mercer
J G
JG
Molecular Neuroendocrinology Group, Aberdeen Centre for Energy Regulation and Obesity, Rowett Research Institute, Bucksburn, Aberdeen, Scotland AB21 9SB, United Kingdom. jgm@rri.sari.ac.uk
Moar
K M
KM
Logie
T J
TJ
Findlay
P A
PA
Adam
C L
CL
Morgan
P J
PJ
D000818:Animals; D001835:Body Weight / Q000502:physiology; D002352:Carrier Proteins / Q000502:physiology; D006224:Cricetinae; D004734:Energy Metabolism / Q000502:physiology; D005508:Food Deprivation; D005786:Gene Expression Regulation / Q000502:physiology*; D007031:Hypothalamus / Q000502:physiology*; D008297:Male; D011956:Receptors, Cell Surface; D054411:Receptors, Leptin; D012621:Seasons
D002352:Carrier Proteins; D011956:Receptors, Cell Surface; D054411:Receptors, Leptin