The effects of BTS 54,505, a metabolite of sibutramine, on monoamine and excitatory amino acid-evoked responses in the rat dorsolateral geniculate nucleus in vivo

Distinct subsets of hypothalamic genes are modulated by two different thermogenesis-inducing stimuli

Obesity results from an imbalance between food intake and energy expenditure, two vital functions that are tightly controlled by specialized neurons of the hypothalamus. The complex mechanisms that integrate these two functions are only beginning to be deciphered. The objective of this study was to determine the effect of two thermogenesis-inducing conditions, i.e., ingestion of a high-fat (HF) diet and exposure to cold environment, on the expression of 1,176 genes in the hypothalamus of Wistar rats. Hypothalamic gene expression was evaluated using a cDNA macroarray approach. mRNA and protein expressions were determined by reverse-transcription PCR (RT-PCR) and immunoblot. Cold exposure led to an increased expression of 43 genes and to a reduced expression of four genes. HF diet promoted an increased expression of 90 genes and a reduced expression of 78 genes. Only two genes (N-methyl-D-aspartate (NMDA) receptor 2B and guanosine triphosphate (GTP)-binding protein G-alpha-i1) were similarly affected by both thermogenesis-inducing conditions, undergoing an increment of expression. RT-PCR and immunoblot evaluations confirmed the modulation of NMDA receptor 2B and GTP-binding protein G-alpha-i1, only. This corresponds to 0.93% of all the responsive genes and 0.17% of the analyzed genes. These results indicate that distinct environmental thermogenic stimuli can modulate predominantly distinct profiles of genes reinforcing the complexity and multiplicity of the hypothalamic mechanisms that regulate energy conservation and expenditure.

The discovery and status of sibutramine as an anti-obesity drug

Sibutramine is a serotonin-norepinephrine reuptake inhibitor indicated for the management of obesity in conjunction with a reduced calorie diet. Though sibutramine was originally evaluated for possible use as an antidepressant, its research development was eventually redirected to evaluate it as an anorexiant. The pharmacological mechanisms by which sibutramine exerts its weight loss effect are likely due to a combination of reduced appetite, feelings of satiety, and possibly the induction of thermogenesis. Its efficacy for inducing an initial weight-loss and the subsequent maintenance of the weight-loss is well proven in short- and long-term clinical trials of up to 2 years duration. In general, sibutramine has been well tolerated. Increases in blood pressure and heart rate are possible adverse effects that require regular monitoring. Sibutramine is one of the few established and well-proven agents for obesity available for use today and should be considered effective in the management of patients requiring pharmacotherapy as part of the multi-modal approach to weight-loss.

Sibutramine: a serotonin-norepinephrine reuptake-inhibitor for the treatment of obesity

OBJECTIVE

To review the pharmacology, pharmacokinetics, efficacy data, adverse effects, and drug interactions of sibutramine as a treatment for obesity.

DATA SOURCES

English-language clinical studies, abstracts, and review articles were identified using MEDLINE, EMBASE, and a manual search from January 1980 through December 1998. References were also obtained from the reference section of published articles.

STUDY SELECTION AND DATA EXTRACTION

All articles identified were evaluated for possible inclusion in this review. Evaluative and comparative data from prospective, open-label, double-blind, and controlled studies were reviewed.

DATA SYNTHESIS

Sibutramine is a serotonin-norepinephrine reuptake-inhibitor effective in the treatment of obesity. It does not act as a releasing agent of these neurotransmitters. Sibutramine undergoes extensive metabolism in the liver via CYP3A4, forming two pharmacologically active metabolites. This agent has demonstrated efficacy superior to placebo in reducing weight when used as part of an integrated regimen involving behavior modification, physical activity, and a reduced-calorie intake. The most frequently reported adverse effects include dry mouth, anorexia, headache, insomnia, and constipation. Sibutramine has also been shown to substantially increase blood pressure and heart rate in some patients.

CONCLUSIONS

Based on anorectic efficacy data, sibutramine, a serotonin-norepinephrine reuptake-inhibitor, is a viable therapeutic option for the treatment of obesity. Recommended candidates for this medication are patients with a body mass index (BMI) > or = 30 kg/m2 without concomitant risk factors or patients with a BMI > or = 27 kg/m2 with concomitant risk factors. Sibutramine should be used with caution in patients with a history of hypertension and should not be used in those with uncontrolled hypertension and concomitant cardiovascular disease. Further studies need to be conducted in order to identify long-term outcomes beyond one year.