As potential activators of brown adipose tissue (BAT), mild cold exposure and sympathomimetic drugs have been considered as treatments for obesity and diabetes, but whether they activate the same pathways is unknown. In 10 healthy human volunteers, we found that the sympathomimetic ephedrine raised blood pressure, heart rate, and energy expenditure, and increased multiple circulating metabolites, including glucose, insulin, and thyroid hormones. Cold exposure also increased blood pressure and energy expenditure, but decreased heart rate and had little effect on metabolites. Importantly, cold increased BAT activity as measured by 18 F-fluorodeoxyglucose PET-CT in every volunteer, whereas ephedrine failed to stimulate BAT. Thus, at doses leading to broad activation of the sympathetic nervous system, ephedrine does not stimulate BAT in humans. In contrast, mild cold exposure stimulates BAT energy expenditure with fewer other systemic effects, suggesting that cold activates specific sympathetic pathways. Agents that mimic cold activation of BAT could provide a promising approach to treating obesity while minimizing systemic effects.metabolism | thermogenesis | respiratory quotient | norepinephrine | white adipose tissue B rown adipose tissue (BAT) is a type of fat that consumes calories to generate heat. Multiple recent studies have shown that adult humans have functional BAT that can be activated in response to cold exposure in a process called nonshivering thermogenesis (1-4). In both small and large population studies (1, 2, 4, 5), there is an inverse correlation between BAT activity and obesity, suggesting that activating BAT, through pharmacological, environmental, or potentially nutritional interventions, could become a therapeutic means to treat obesity and diabetes. Indeed, human BAT energy expenditure may be a critical counterbalance to the weight gain and metabolic dysregulation caused by excess energy storage in white adipose tissue.Human BAT has a high density of both nerves and blood vessels (6), providing two general approaches to activate BAT. Based on studies in rodents, it is known that the sensation of cold by the skin and body core sends signals via peripheral neurons to the spinal cord and then up to the preoptic area of the hypothalamus for processing. From the hypothalamus, some signals go to the cerebral cortex for conscious thermal perception and localization, and others go to premotor neurons in the rostral raphe pallidus of the brainstem, projecting to neurons of the peripheral sympathetic nervous system (SNS) (reviewed in ref. 7). Ultimately, postganglionic SNS nerves release norepinephrine to activate BAT via induction of uncoupling protein-1, the tissue-specific protein that allows BAT to generate heat by uncoupling aerobic respiration from the generation of ATP.Because the endogenous pathways by cold exposure are complex and indirect, an attractive alternative for stimulation of BAT has been the use of pharmacological agents. As norepinephrine itself has too many adverse effects on the ...

4-Anilinoquinazoline- and 4-anilinopyrido[3,2-d]pyrimidine-6-acrylamides substituted with solubilizing 7-alkylamine or 7-alkoxyamine side chains were prepared by reaction of the corresponding 6-amines with acrylic acid or acrylic acid anhydrides. In the pyrido[3,2-d]pyrimidine series, the intermediate 6-amino-7-alkylamines were prepared from 7-bromo-6-fluoropyrido[3,2-d]pyrimidine via Stille coupling with the appropriate stannane under palladium(0) catalysis. This proved a versatile method for the introduction of cationic solubilizing side chains. The compounds were evaluated for their inhibition of phosphorylation of the isolated EGFR enzyme and for inhibition of EGF-stimulated autophosphorylation of EGFR in A431 cells and of heregulin-stimulated autophosphorylation of erbB2 in MDA-MB 453 cells. Quinazoline analogues with 7-alkoxyamine solubilizing groups were potent irreversible inhibitors of the isolated EGFR enzyme, with IC(50[app]) values from 2 to 4 nM, and potently inhibited both EGFR and erbB2 autophosphorylation in cells. 7-Alkylamino- and 7-alkoxyaminopyrido[3,2-d]pyrimidines were also irreversible inhibitors with equal or superior potency against the isolated enzyme but were less effective in the cellular autophosphorylation assays. Both quinazoline- and pyrido[3,2-d]pyrimidine-6-acrylamides bound at the ATP site alkylating cysteine 773, as shown by electrospray ionization mass spectrometry, and had similar rates of absorptive and secretory transport in Caco-2 cells. A comparison of two 7-propoxymorpholide analogues showed that the pyrido[3,2-d]pyrimidine-6-acrylamide had greater amide instability and higher acrylamide reactivity, being converted to glutathione adducts in cells more rapidly than the corresponding quinazoline. This difference may contribute to the observed lower cellular potency of the pyrido[3,2-d]pyrimidine-6-acrylamides. Selected compounds showed high in vivo activity against A431 xenografts on oral dosing, with the quinazolines being superior to the pyrido[3,2-d]pyrimidines. Overall, the quinazolines proved superior to previous analogues in terms of aqueous solubility, potency, and in vivo antitumor activity, and one example (CI 1033) has been selected for clinical evaluation.

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