High-fat diet-induced ultradian leptin and insulin hypersecretion are absent in obesity-resistant rats.
OBJECTIVE
Sprague-Dawley rats fed a high-fat diet (HFD) are either obesity prone (OP) or obesity resistant (OR). We tested the hypothesis that differences in the ultradian rhythmic patterns of insulin and ghrelin in OP vs. OR rats promote obesity in OP rats.


METHODS
Rats were fed regular chow or an HFD, and ultradian fluctuations in leptin, insulin, and ghrelin were analyzed in blood samples collected at 5-minute intervals from intrajugular cannulae of freely moving rats.


RESULTS
Regular chow feeding resulted in a slow weight gain accompanied by small increases in insulin and leptin and a decrease in ghrelin discharge, with only the pulse amplitude significantly altered. Similar changes were observed in OR rats, despite HFD consumption. In contrast, OP rats exhibited a high rate of weight gain and marked hyperinsulinemia, hyperleptinemia, and hypoghrelinemia; amplitude was altered, but frequency was stable. In a short-term experiment, HFD elicited similar secretory patterns of smaller magnitude even in the absence of weight gain.


CONCLUSIONS
We showed that three hormonal signals of disparate origin involved in energy homeostasis were secreted in discrete episodes, and only the pulse amplitude component was vulnerable to age and HFD consumption. Increases in insulin and leptin and decreases in ghrelin pulse amplitude caused by HFD were exaggerated in OP rats relative to OR rats and preceded the weight increase. These findings show that a distinct genetic predisposition in the endocrine organs of OR rats confers protection against high-fat intake-induced ultradian hypersecretion of obesity-promoting hormonal signals.
Department of Neuroscience, University of Florida, College of Medicine, PO Box 100244, Gainesville, FL 32610-0244, USA.
Effiong E
EE
Otukonyong
Michael G
MG
Dube
Rita
R
Torto
Pushpa S
PS
Kalra
Satya P
SP
Kalra
D000818:Animals; D001835:Body Weight / Q000502:physiology; D002940:Circadian Rhythm / Q000502:physiology; D016000:Cluster Analysis; D004041:Dietary Fats / Q000008:administration & dosage*; D004435:Eating / Q000502:physiology; D005246:Feedback / Q000502:physiology; D005260:Female; D054439:Ghrelin; D007328:Insulin / Q000097:blood / Q000378:metabolism*; D000078790:Insulin Secretion; D020738:Leptin / Q000097:blood / Q000378:metabolism*; D009765:Obesity / Q000097:blood*; D036361:Peptide Hormones / Q000097:blood / Q000378:metabolism*; D010507:Periodicity; D051381:Rats; D017207:Rats, Sprague-Dawley; D018709:Statistics, Nonparametric
D004041:Dietary Fats; D054439:Ghrelin; D007328:Insulin; D020738:Leptin; D036361:Peptide Hormones