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Obesity is epidemic; new medications and therapeutic options are urgently needed to reduce the associated health care burden. The initial clinical strategy for weight loss is lifestyle modification involving a combination of diet, exercise, and behavior change. However, it is difficult for many to achieve and maintain weight loss solely through this approach. Only two drugs, orlistat and sibutramine, have been approved by the US Food and Drug Administration (FDA) to treat obesity long term, and both medications have undesirable side effects, leaving an enormous unmet need for efficacious and safe therapy for obesity. Other medications with weight-loss effects have been approved by the FDA for short-term treatment of obesity or for disorders other than obesity, but these also have potential adverse effects. This article discusses the perceived benefits and risks of these approved medications along with emerging drugs that have shown weight-loss effects.
We previously reported that inhaled isobutyl nitrite inhibited macrophage tumoricidal activity by inhibiting inducible nitric oxide (NO) production. In the present study, a much shorter inhalant exposure regimen (five daily exposures) inhibited inducible NO and the NO synthase (NOS2). One of the ways in which NO and NOS2 are regulated is by ubiquitin-dependent NOS2 degradation. Immunoprecipitated NOS2 showed increased poly-ubiquitination, following exposure to the inhalant. In addition, Western blots of macrophage nuclear extracts for the NFkappaB subunit, p65, showed that exposure to the inhalant inhibited NFkappaB signaling, necessary for induction of NOS2. The inhalant blocked phosphorylation of the NFkappaB inhibitor, IkappaBalpha. The inhibition of NFkappaB signaling following inhalant exposure was confirmed using mice transgenic for the kappaB-dependent promoter of the HIV 5' LTR linked to luciferase. The data suggested that inhalant exposure likely inhibited macrophage NO production by blocking NFkappaB-mediated activation signaling and promoting poly ubiquitination of NOS2.
BACKGROUND - Sibutramine, a serotonin and norepinephrine transporter blocker, is widely used as an adjunctive obesity treatment. Norepinephrine reuptake inhibition with sibutramine conceivably could exacerbate arterial hypertension and promote cardiovascular disease.
METHODS AND RESULTS - In 11 healthy subjects (7 men, age 27+/-2 years, body mass index 23.1+/-0.7 kg/m2), we compared the effect of sibutramine or matching placebo (ingested 26, 14, and 2 hours before testing) on cardiovascular responses to autonomic reflex tests and to a graded head-up tilt test. In addition, we tested sibutramine in combination with metoprolol. Testing was conducted in a double-blind and crossover fashion. Supine systolic blood pressure was 113+/-3 mm Hg with placebo, 121+/-3 mm Hg with sibutramine (P<0.001 versus placebo), and 111+/-2 mm Hg with the combination of sibutramine and metoprolol. Similarly, sibutramine increased upright blood pressure. Sibutramine substantially increased upright heart rate. This effect was abolished with metoprolol. The blood pressure response to cold pressor and handgrip testing was attenuated with sibutramine compared with placebo. Furthermore, sibutramine decreased low-frequency oscillations of blood pressure and plasma norepinephrine concentrations in the supine position.
CONCLUSIONS - The cardiovascular effect of the antiobesity drug sibutramine results from a complex interaction of peripheral and central nervous system effects. The inhibitory clonidine-like action of sibutramine on the central nervous system attenuates the peripheral stimulatory effect. Our findings strongly suggest that current concepts regarding the action of sibutramine on the sympathetic nervous system should be reconsidered.
Amyloid beta (Abeta) peptides play an important role in the pathogenesis of Alzheimer's disease. Free radical generation by Abeta peptides was suggested to be a key mechanism of their neurotoxicity. Reports that neurotoxic free radicals derived from Abeta-(1-40) and Abeta-(25-35) peptides react with the spin trap N-tert-butyl-alpha-phenylnitrone (PBN) to form a PBN/.Abeta peptide radical adduct with a specific triplet ESR signal assert that the peptide itself was the source of free radicals. We now report that three Abeta peptides, Abeta-(1-40), Abeta-(25-35), and Abeta-(40-1), do not yield radical adducts with PBN from the Oklahoma Medical Research Foundation (OMRF). In contrast to OMRF PBN, incubation of Sigma PBN in phosphate buffer without Abeta peptides produced a three-line ESR spectrum. It was shown that this nitroxide is di-tert-butylnitroxide and is formed in the Sigma PBN solution as a result of transition metal-catalyzed auto-oxidation of the respective hydroxylamine present as an impurity in the Sigma PBN. Under some conditions, incubation of PBN from Sigma with Abeta-(1-40) or Abeta-(25-35) can stimulate the formation of di-tert-butylnitroxide. It was shown that Abeta peptides enhanced oxidation of cyclic hydroxylamine 1-hydroxy-4-oxo-2,2,6, 6-tetramethylpiperidine (TEMPONE-H), which was strongly inhibited by the treatment of phosphate buffer with Chelex-100. It was shown that ferric and cupric ions are effective oxidants of TEMPONE-H. The data obtained allow us to conclude that under some conditions toxic Abeta peptides Abeta-(1-40) and Abeta-(25-35) enhance metal-catalyzed oxidation of hydroxylamine derivatives, but do not spontaneously form peptide-derived free radicals.