Treatment with α-Methylparatyrosine Inhibits Sympathetic but Not Thyroidal Responses to Diet-Induced Thermogenesis in Lean Cafeteria-Overfed Rats

Abstract

The sympathoplegic drug α-methylparatyrosine (α-MPT) was administered to lean, normally fed rats or rats overfed to induce diet induced thermogenesis (DIT) with a highly palatable Cafeteria diet regimen (Café) for twelve weeks, and measures of resting thermogenesis under thermoneutral conditions (VO2 at ambient 30°C), serum T3 and 24-hour urinary vanilmandelic acid (VMA) excretion determined before and after the α-MPT treatment. The café diet resulted in significant increases in VO2, serum T3, and VMA excretion. The α-MPT resulted in approximately fifty percent decrease in the Café-induced increase in VO2 after 24hours, while thyroidal function appeared clinically unaffected. These observations suggest that the sympathetic contributions to diet-induced thermogenesis (DIT) following chronic overfeeding with the Café diet regimen represent only about half of the reported dietary induced thermic response to overfeeding and non-sympathetic contributions including the thyroidal actions that likely account for the remaining proportion of the increased DIT and sympathetic component may decrease further over time spent since feeding.