HF diets increase hypothalamic PTP1B and induce leptin resistance through both leptin-dependent and -independent mechanisms.
Protein tyrosine phosphatase 1B (PTP1B) contributes to leptin resistance by inhibiting intracellular leptin receptor signaling. Mice with whole body or neuron-specific deletion of PTP1B are hypersensitive to leptin and resistant to diet-induced obesity. Here we report a significant increase in PTP1B protein levels in the mediobasal hypothalamus (P = 0.003) and a concomitant reduction in leptin sensitivity following 28 days of high-fat (HF) feeding in rats. A significant increase in PTP1B mRNA levels was also observed in rats chronically infused with leptin (3 microg/day icv) for 14 days (P = 0.01) and in leptin-deficient ob/ob mice infused with leptin (5 microg/day sc for 14 days; P = 0.003). When saline-infused ob/ob mice were placed on a HF diet for 14 days, an increase in hypothalamic PTP1B mRNA expression was detected (P = 0.001) despite the absence of circulating leptin. In addition, although ob/ob mice were much more sensitive to leptin on a low-fat (LF) diet, a reduction in this sensitivity was still observed following exposure to a HF diet. Taken together, these data indicate that hypothalamic PTP1B is specifically increased during HF diet-induced leptin resistance. This increase in PTP1B is due in part to chronic hyperleptinemia, suggesting that hyperleptinemia is one mechanism contributing to the development of leptin resistance. However, these data also indicate that leptin is not required for the increase in hypothalamic PTP1B or the development of leptin resistance. Therefore, additional, leptin-independent mechanisms must exist that increase hypothalamic PTP1B and contribute to leptin resistance.
White
Christy L
CL
Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA 70808, USA.
Whittington
Amy
A
Barnes
Maria J
MJ
Wang
Zhong
Z
Bray
George A
GA
Morrison
Christopher D
CD
D000818:Animals; D004036:Diet, Atherogenic; D004041:Dietary Fats / Q000494:pharmacology; D004351:Drug Resistance / Q000187:drug effects; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D020738:Leptin / Q000378:metabolism / Q000494:pharmacology* / Q000502:physiology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008820:Mice, Obese; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1 / Q000235:genetics* / Q000378:metabolism; D051381:Rats; D020318:Rats, Long-Evans; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
D004041:Dietary Fats; D020738:Leptin; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; C516609:Ptpn1 protein, mouse