Sympathetic activity, age, sucrose preference, and diet-induced obesity.
Only half the adult male Sprague-Dawley rats which are placed on a diet relatively high in calories, fat, and sucrose (HE diet) develop diet-induced obesity (DIO). The rest are diet-resistant (DR). Some chow-fed rats prone to develop DIO on an HE diet have greater initial food intake of this diet and all have greater glucose-induced plasma norepinephrine (NE) increases than DR-prone rats. Here we looked for a relationship of sucrose preference or 24-hour urinary catecholamine excretion as possible phenotypic markers of the DIO- and DR-prone states before HE diet exposure as a function of age. When begun on an HE diet at 3 months of age, DIO-prone rats gained 30% more weight over 3 months than DR-prone rats and had 35% heavier retroperitoneal fat pads. While still on chow, sucrose preferences were similar, but 24 hour urine NE levels were 29% higher in DIO- than in DR-prone rats. The slope of the curve of urine NE versus body weight gain after 3 months on HE diet was 4-fold greater in DIO- than in DR-prone rats. After 3 months on the HE diet, there was no statistical relationship between 24-hour urine NE and body weight or prior body weight gain in DIO or DR rats. Six-month-old DIO-prone rats had 126% and 128% more urine NE and gained 112% and 232% more weight after 3 months on HE diet than DR-prone and chow-fed rats, respectively. Only DIO-prone rats showed a correlation (r=0.879; p=0.05) between urine NE levels and subsequent weight gain on HE diet. Thus, 3- or 6-month-old DIO- and DR-prone rats can be identified by their 24-hour basal urine NE levels but not sucrose preference prior to HE diet exposure. While this may suggest higher basal sympathetic activity in DIO-prone rats, other explanations are possible.
Levin
B E
BE
Neurology Service, Department of Veterans Affairs Medical Center, E. Orange, NJ 07018, USA.
D000273:Adipose Tissue / Q000378:metabolism; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight; D002395:Catecholamines / Q000652:urine; D004032:Diet; D002149:Energy Intake; D004777:Environment; D005247:Feeding Behavior; D005947:Glucose; D008297:Male; D009043:Motor Activity; D009638:Norepinephrine / Q000097:blood; D009752:Nutritional Status; D009765:Obesity / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology* / Q000378:metabolism; D010641:Phenotype; D051381:Rats; D017207:Rats, Sprague-Dawley; D013395:Sucrose / Q000378:metabolism*; D013564:Sympathetic Nervous System / Q000473:pathology*; D013997:Time Factors; D015430:Weight Gain
D001786:Blood Glucose; D002395:Catecholamines; D013395:Sucrose; D005947:Glucose; D009638:Norepinephrine