Haemodynamic, metabolic and endocrine effects of short-term dexfenfluramine treatment in young, obese women

Visceral obesity: a "civilization syndrome"

The controversial question of the relationship between obesity and disease has been considerably clearer after the demonstration in several prospective, epidemiological studies that the subgroup of central, visceral obesity is particularly prone to develop cardiovascular disease, stroke, and non-insulin dependent diabetes mellitus. Visceral obesity is associated with multiple central endocrine aberrations. The hypothalamo-adrenal axis is apparently sensitive to stimuli, sex steroid hormone secretion blunted, and hyperandrogenicity is found in women. In addition, there seem to be signs of central dysfunctions in the regulation of hemodynamic factors after stress, and growth hormone secretion appears to be particularly blunted. Several of these endocrine abnormalities are associated with insulin resistance, particularly glycogen synthesis in muscle. Fiber composition with low type I/type II ratio might be secondary to the prevailing hyperinsulinemia, but low capillary density in muscle may well be of importance. In combination with elevated turn-over of free fatty acids (FFA) this will probably provide powerful mechanisms whereby insulin resistance is created. Portal FFA, from the highly lipolytic visceral depots may, in addition, affect hepatic metabolism to induce increased gluconeogenesis, production of very low density lipoproteins as well as to perhaps inhibit clearance of insulin. By these mechanisms a Metabolic Syndrome Visceral adipocytes seem to have a high density of several steroid hormone receptors, directing steroid hormone effects particularly to these depots. The net effect of cortisol is apparently a stimulation of lipid storage, with opposing effects of sex steroid hormones which also facilitate lipid mobilization, regulations most often found at the gene transcription level. Growth hormone inhibits cortisol effects on lipid accumulation, and amplifies the lipid mobilizing effects of steroid hormones. The combined perturbations of hormonal secretions will therefore probably direct triglycerides toward visceral depots. Circulatory and nervous regulatory mechanisms require, however, more attention. The multiple central endocrine and nervous aberrations of visceral obesity suggest neuroendocrine dysregulations, and have features characteristic of the hypothalamic arousal seen after certain types of stress, alcohol intake, and smoking. Such factors can be traced to subjects with visceral fat accumulation. Standardized stress, eliciting a "defeat reaction" in primates is followed by an apparently identical syndrome. This integrated picture of the multiple symptoms of visceral obesity is based on epidemiological, clinical, experimental, cellular, and molecular evidence. The ingredients of positive energy balance, including physical inactivity, stress, smoking, and alcohol consumption are frequent features of modern, urbanized society. Visceral obesity may therefore be an expression of a "Civilization Syndrome."

Screening the receptorome reveals molecular targets responsible for drug-induced side effects: focus on ‘fen–phen’

The in vitro pharmacological profiling of drugs using a large panel of cloned receptors (e.g., G protein-coupled receptors, ligand-gated ion channels, Na(+)-dependent monoamine transporters), an approach that has come to be known as 'receptorome screening', has unveiled novel molecular mechanisms responsible for the actions and/or side effects of certain drugs. For instance, receptorome screening has been employed to uncover novel molecular targets involved in the actions of antipsychotic medications and the hallucinogenic mint extract salvinorin A. This review highlights the recent application of receptorome screening to discover why the anorexigen fenfluramine causes serious cardiopulmonary side effects. Receptorome screening has implicated N-deethylation of fenfluramine and serotonin 5-hydroxy-t-ryptamine 2B receptors in the adverse effects of the drug; subsequent studies corroborated this finding. The results discussed highlight the utility of determining the potential activity of drugs -- and, importantly, of their in vivo metabolites -- at as many molecular targets as possible in order to reliably predict side effect profiles. Receptorome screening represents one of the most effective methods for identifying potentially serious drug-related side effects at the preclinical stage, thereby avoiding significant economic and human health consequences.

(+)-Fenfluramine and its major metabolite, (+)-norfenfluramine, are potent substrates for norepinephrine transporters

(+/-)-Fenfluramine is an amphetamine analog that was once widely prescribed as an appetite suppressant. Although (+/-)-fenfluramine is no longer clinically available, the mechanisms underlying its anorectic properties are still of interest. Upon peripheral administration, stereoisomers of (+/-)-fenfluramine are N-deethylated to form the metabolites, (+)- and (-)-norfenfluramine. It is well accepted that isomers of (+/-)-fenfluramine and (+/-)-norfenfluramine interact with 5-hydroxytryptamine (serotonin, 5-HT) transporters to release 5-HT from neurons. However, the effects of these drugs on other monoamine transporters are not well characterized. In this study, we examined the interaction of stereoisomers of (+/-)-fenfluramine and (+/-)-norfenfluramine with transporters for 5-HT, norepinephrine (NE), and dopamine (DA). Results from in vitro assays confirmed these drugs are potent substrates for 5-HT transporters: (+)-fenfluramine, (-)-fenfluramine, (+)-norfenfluramine, and (-)-norfenfluramine released [3H]5-HT from synaptosomes with EC50 values of 52, 147, 59, and 287 nM, respectively. Importantly, (+)-fenfluramine and (+)-norfenfluramine released [3H]NE with EC50 values of 302 and 73 nM. Results from in vivo microdialysis experiments showed that intravenous injection of (+)-norfenfluramine elevates extracellular levels of 5-HT, NE, and DA in rat frontal cortex. The effects of (+)-norfenfluramine on NE and DA were antagonized by pretreatment with the NE uptake blocker nisoxetine. In summary, administration of fenfluramines can increase synaptic levels of 5-HT, NE, and DA in the cortex, and (+)-norfenfluramine likely contributes to these effects. Release of NE and DA evoked by (+)-norfenfluramine is at least partly mediated via NE transporters. Our results emphasize the potential involvement of noradrenergic mechanisms in the actions of fenfluramines.

Therapeutic and adverse actions of serotonin transporter substrates

A variety of drugs release serotonin (5-HT, 5-hydroxytryptamine) from neurons by acting as substrates for 5-HT transporter (SERT) proteins. This review summarizes the neurochemical, therapeutic, and adverse actions of substrate-type 5-HT-releasing agents. The appetite suppressant (+/-)-fenfluramine is composed of (+) and (-) isomers, which are N-de-ethylated in the liver to yield the metabolites (+)- and (-)-norfenfluramine. Fenfluramines and norfenfluramines are potent 5-HT releasers. (+/-)-3,4-Methylenedioxymethamphetamine ((+/-)-MDMA, "ecstasy") and m-chlorophenylpiperazine (mCPP) are substrate-type 5-HT releasers. Fenfluramines, (+/-)-MDMA, and mCPP release neuronal 5-HT by a common non-exocytotic diffusion-exchange mechanism involving SERTs. (+)-Norfenfluramine is a potent 5-HT(2B) and 5-HT(2C) receptor agonist. The former activity may increase the risk of valvular heart disease, whereas the latter activity is implicated in the anorexic effect of systemic fenfluramine. Appetite suppressants that increase the risk for developing primary pulmonary hypertension (PPH) are all SERT substrates, but these drugs vary considerably in their propensity to increase this risk. For example, fenfluramine and aminorex are clearly linked to the occurrence of PPH, whereas other anorectics are not. Similarly, some SERT substrates deplete brain tissue 5-HT in animals (e.g., fenfluramine), while others do not (e.g., mCPP). In addition to the established indication of obesity, 5-HT releasers may help treat psychiatric disorders, such as drug and alcohol dependence, depression, and premenstrual syndrome. Viewed collectively, we believe new medications can be developed that selectively release 5-HT without increasing the risk for adverse effects of valvular heart disease, PPH, and neurotoxicity. Such agents may be useful for treating a variety of psychiatric disorders.

Serotonin releasing agents. Neurochemical, therapeutic and adverse effects

This review summarizes the neurochemical, therapeutic and adverse effects of serotonin (5-HT) releasing agents. The 5-HT releaser (plus minus)-fenfluramine is composed of two stereoisomers, (+)-fenfluramine and (minus sign)-fenfluramine, which are N-de-ethylated to yield the metabolites, (+)-norfenfluramine and (minus sign)-norfenfluramine. Fenfluramines and norfenfluramines are 5-HT transporter substrates and potent 5-HT releasers. Other 5-HT releasing agents include m-chlorophenylpiperazine (mCPP), a major metabolite of the antidepressant drug trazodone. Findings from in vitro and in vivo studies support the hypothesis that fenfluramines and mCPP release neuronal 5-HT via a non-exocytotic carrier-mediated exchange mechanism involving 5-HT transporters. (+)-Norfenfluramine is a potent 5-HT(2B) and 5-HT(2C) receptor agonist. The former activity may increase the risk of developing valvular heart disease (VHD), whereas the latter activity is implicated in the anorectic effect of systemic fenfluramine. Anorectic agents that increase the risk of developing primary pulmonary hypertension (PPH) share the common property of being 5-HT transporter substrates. However, these drugs vary considerably in their propensity to increase the risk of PPH. In this regard, neither trazodone nor mCPP is associated with PPH. Similarly, although some 5-HT substrates can deplete brain 5-HT (fenfluramine), others do not (mCPP). In addition to the established indication of obesity, 5-HT releasers may be helpful in treating psychiatric problems such as drug and alcohol dependence, depression and premenstrual syndrome. Viewed collectively, it seems possible to develop new medications that selectively release 5-HT without the adverse effects of PPH, VHD or neurotoxicity. Such agents may have utility in treating a variety of psychiatric disorders.

The effects of drugs used to treat obesity on the autonomic nervous system

OBJECTIVE

Body fatness is partly under hypothalamic control with effector limbs, which include the endocrine system and the autonomic nervous system (ANS). In previous studies we have shown, in both obese and never-obese subjects, that weight increase leads to increased sympathetic and decreased parasympathetic activity, whereas weight decrease leads to decreased sympathetic and increased parasympathetic activity. We now report on the involvement of such ANS mechanisms in the action of anti-obesity drugs, independent of change in weight.

RESEARCH METHODS AND PROCEDURES

Normal weight males (ages 22 to 38 years) were fed a solid food diet, carefully measured to maintain body weight, for at least 2 weeks, as inpatients at the Rockefeller University General Clinical Research Center. In a single-blind, placebo/drug/placebo design, eight subjects received dexfenfluramine, seven phentermine (PHE), and seven sibutramine (SIB). ANS measures of parasympathetic and sympathetic activity included: determination of amount of parasympathetic control (PC) and sympathetic control (SC) of heart period (interbeat interval), using sequential pharmacological blockade by intravenous administration of atropine and esmolol. These autonomic controls of heart period are used to estimate the overall level of parasympathetic and sympathetic activities. Norepinephrine, dopamine, and epinephrine levels in 24-hour urine collections were measured and also resting metabolic rate (RMR).

RESULTS

Sufficient food intake maintained constant body weight in all groups. PHE and SIB produced significant increases in SC but no change in PC or in RMR. In contrast, dexfenfluramine produced marked decreases in SC, PC, and RMR. For all three drugs, the effects on urine catecholamines directly paralleled changes in cardiac measures of SC.

DISCUSSION

ANS responses to PHE and SIB were anticipated. The large, and unanticipated, response to dexfenfluramine suggests further study to determine whether there could be any relation of these ANS changes to the adverse cardiovascular effects of treatment with dexfenfluramine.

Antiobesity pharmacotherapy in the management of type 2 diabetes

Obesity is a well-known risk factor for the development of Type 2 diabetes mellitus. The management of the obese diabetic patient remains a challenge for the clinician but, in any case, weight reduction should be considered as a key objective. In this respect, several antiobesity drugs have demonstrated potential. However, while fenfluramine and dexfenfluramine have been shown to promote weight loss and to directly improve insulin sensitivity, being two mechanisms contributing to better blood glucose control in obese Type 2 diabetic patients, they were recently withdrawn due to safety problems. Sibutramine, a new selective norepinephrine and serotonin reuptake inhibitor, promotes weight loss by decreasing food intake, an effect which leads to a mild improvement (significant in patients losing > or =5% of initial body weight) of blood glucose control in obese diabetic patients. Similarly, orlistat, a selective gastrointestinal lipase inhibitor which increases faecal fat losses, enhances diet-induced weight reduction and improves both blood glucose control and vascular risk profile, especially dyslipidaemia, in obese Type 2 diabetic patients. Further studies are required to better identify good responders to pharmacotherapy and specify the role of antiobesity agents in the overall long-term management of obese subjects with Type 2 diabetes. Other novel pharmacological approaches deserve further consideration, for instance beta-3 agonists aiming to increase energy expenditure, drugs interfering with tumor necrosis factor-alpha (TNF-alpha) or free fatty acid release by the adipose tissue or agents that slow gastric emptying. However, until now, results regarding efficacy and/or safety have been disappointing or preliminary in humans.

The acute effects of dexfenfluramine on human and porcine pulmonary vascular tone and resistance

STUDY OBJECTIVES

Treatment with anorectics has become an important aspect of care for the severely obese. One such anorectic, the phenylethylamine dexfenfluramine (dFen), has been associated with the development of pulmonary hypertension. It works by reducing the neuronal uptake of 5-hydroxytryptamine (5-HT; serotonin) through inhibition of the 5-HT transporter. In this study we investigated whether dFen has a direct vasoconstrictor action on human and porcine pulmonary vasculature.

DESIGN

For the human study, tissue was obtained from patients who had undergone lung and heart-lung transplantation. The effect of dFen was studied in seven isolated colloid perfused human lungs and in rings of human pulmonary artery (PA) dissected from the lungs of a further 19 patients. For the porcine study, regional pulmonary vascular resistances (PVRs) were measured in isolated perfused porcine lungs. Vasoconstriction was assessed following dFen alone and in combination with hypoxia, cyclo-oxygenase blockade (indomethacin, 10(-5) mol/L), or nitric oxide synthase (NOS) blockade (N(G)-nitro-L-arginine, 10(-5) mol/L).

RESULTS

In the human study, 5-HT and dFen caused only limited increases in tension of isolated rings of PA. The concentration of dFen, 10(-4) mol/L, that was needed to increase tension was higher than that found normally in treated patients where peak levels are 3. 3 x 10(-7) mol/L. Other vasoconstrictors such as prostaglandin F(2)alpha, 10(-5) mol/L, and the thromboxane analog U46619, 10(-6) mol/L, produced far greater increases in tension. Ketanserin, 10(-4) mol/L, attenuated the constrictor response to 5-HT but had no effect on the constrictor response to dFen. Removal of the endothelium did not influence the response to dFen. In the isolated ventilated and perfused lungs, dFen caused an increase in PVR again only at a comparatively high concentration, 10(-4) mol/L. In the porcine study, dFen, 10(-4) mol/L, did not increase any PVR during normoxia or following NOS blockade. Small insignificant increases in PVR occurred during hypoxia and after cyclo-oxygenase blockade.

CONCLUSION

These results do not support the view that dFen would act as a direct vasoconstrictor when given in the usual doses. However, delayed elimination of dFen could raise tissue concentrations to high levels and give rise to vasoconstriction and pulmonary hypertension.

A comparison of sibutramine and dexfenfluramine in the treatment of obesity

OBJECTIVE

Because long-term weight reduction is often unsuccessful with dietary restriction alone, pharmacological agents have been used to promote weight loss. We have compared the novel (multiple monoamine neurotransmitter reuptake inhibitor) antiobesity drug sibutramine (10 mg once daily) with the extensively studied serotonin-releasing antiobesity agent dexfenfluramine (15 mg twice daily).

RESEARCH METHODS AND PROCEDURES

226 healthy outpatients (aged 18 to 65 years; body mass index > or =27 kg/m2) were included in a 12-week, randomized, double-blind, parallel group study. The main outcome measures were changes in weight, body mass index, waist and hip circumference and ratio, and safety profiles.

RESULTS

Mean (+/-SEM) absolute weight loss was 4.5 +/- 0.4 kg in the sibutramine group (n = 112) and 3.2 +/- 0.3 kg in the dexfenfluramine group (n = 112) (endpoint analysis); 4.7 +/- 0.4 kg in the sibutramine group (n = 101); and 3.6 +/- 0.3 kg in the dexfenfluramine group (n = 94) (completers analysis). Comparing the two treatments under the conventional null hypothesis of equality as a secondary analysis, weight loss at endpoint in patients receiving sibutramine was significantly greater than that achieved with dexfenfluramine (p<0.05). Both drugs had similar adverse events profiles: 174 patients (77%) experienced adverse events; 17 patients withdrew due to adverse events (sibutramine, n = 6; dexfenfluramine, n = 11). Pulse rate increased significantly in sibutramine-treated patients (3.6 bpm), but decreased in dexfenfluramine-treated patients (-0.9 bpm).

DISCUSSION

Sibutramine (10 mg once daily) is at least as effective as dexfenfluramine (15 mg twice daily) in achieving weight loss in patients with obesity.

The pharmacologic approach to the treatment of obesity

Obesity is a major risk factor for morbidity and mortality, and a series of pharmacologic approaches are available for helping to manage the problem. Obesity is caused by an imbalance between caloric intake and energy expenditure, which is influenced by both environmental and genetic factors. Pharmacologic treatments include anorexigenic agents, which fall into two broad categories: those that act via brain catecholamine pathways and those that act via serotonin pathways. The most recent oral agents approved are dexfenfluramine, which is currently being marketed, and sibutramine. Both agents inhibit the control reuptake of serotonin but in addition may have effects on thermogenesis. Under investigation are agents that increase energy expenditure: the beta 3-adrenergic receptor agonists and drugs that prevent the intestinal absorption of free fatty acids and cholesterol. In development are innovative approaches to influence leptin and its receptors, various obesity genes, and biologic substances thought to influence satiety (neuropeptide Y, enterostatin, cholecystokinin, bombesin, and amylin). Obesity has now become a major target for drug development not only for affecting obesity per se but also for managing and preventing comorbid conditions such as diabetes and cardiovascular disease.

Dexfenfluramine. An updated review of its therapeutic use in the management of obesity

Dexfenfluramine increases serotonergic activity by stimulating serotonin (5-hydroxytryptamine; 5-HT) release into brain synapses, inhibiting its reuptake into presynaptic neurons and by directly stimulating postsynaptic serotonin receptors. On the basis of the serotonin hypothesis of appetite control, these actions would be expected to reduce appetite and, consequently, bodyweight. Studies conducted in animals and in overweight patients with and without associated disorders have confirmed the weight-reducing efficacy and good tolerability of dexfenfluramine. In 3-month clinical studies in obese patients, weight reductions with dexfenfluramine 15mg twice daily combined with dietary support were significantly higher than those achieved with placebo and similar to those with ephedrine/caffeine 20/20mg 3 times daily, sibutramine 10mg once daily and fluoxetine 60 mg/day. Furthermore, dexfenfluramine recipients with non-insulin-dependent diabetes mellitus, hyperlipidaemia or hypertension consistently show improvements in glycaemic control, blood lipid profiles and blood pressure. 12-month trial results indicate that most weight loss occurs in the initial 6 months and appears to be maintained for a further 6 months. Weight regain after withdrawal of treatment in 12-month studies demonstrates that dexfenfluramine is effective in maintaining a stable bodyweight at a lower level than placebo and in limiting food intake over this time period. Commonly reported adverse events with dexfenfluramine include diarrhoea, tiredness, dry mouth and somnolence; these symptoms are generally mild and transient. Approximately 7 and 10% of dexfenfluramine recipients in short and long term studies withdrew because of adverse events. Dexfenfluramine was better tolerated than ephedrine/caffeine and fluoxetine in short term studies. Obesity is a chronic condition that is accompanied by a number of metabolic complications. It is a significant health problem in developed countries, and as a major risk factor for many chronic diseases, including diabetes and cardiovascular disease, the economic burden of this condition is considerable. As with other chronic conditions, there is a role for pharmacological intervention in patients with severe obesity. However, drugs should be considered as only one component of a weight-control programme, since additional lifestyle modification is required to maintain weight loss. The promising data on the long term efficacy and tolerability of dexfenfluramine as well as its favourable effects on risk factors associated with obesity requires confirmation in long term studies. In the meantime, dexfenfluramine should be considered a valuable adjunct to a reduced-calorie diet in the management of severe obesity, particularly in patients with associated disorders and those unsuccessful with conventional weight loss measures. Available data support the use of the drug for up to 1 year to maintain weight loss and thus dexfenfluramine should be considered for long term administration.

Long-term effects of fluoxetine on glycemic control in obese patients with non-insulin-dependent diabetes mellitus or glucose intolerance: influence on muscle glycogen synthase and insulin receptor kinase activity

Fluoxetine (F) is a specific serotonin-reuptake inhibitor that has been shown to promote weight loss and improve glycemic control in obese diabetic patients. To study its long-term metabolic effect, 40 obese patients with non-insulin -dependent diabetes mellitus (NIDDM) or impaired glucose tolerance (IGT) were included in a 12-month, randomized, placebo controlled study. Patients were assigned to receive either 60 mg F or placebo (P) daily in conjunction with a 5.0-MJ/d diet (> 50% carbohydrate). Both groups showed a significant weight loss, with a nadir after 6 months without group differences (mean +/- SD: F, 10.1 +/- 10.0 kg; P, 9.4 +/- 11.5 kg). Fifteen patients from the F group and 14 from the P group completed the 12-month study without weight loss differences. Glycemic regulation improved along with the weight loss, but with a larger decline in plasma C-peptide and fasting glucose levels on the F group (P < .05). Total skeletal muscle glycogen synthase (GS) activity increased by 31% in the F group (P < .01) and by 17% in the P group (nonsignificant) after 6 months of treatment, but was still less than the activity in normal-weight controls (aged 28.0 +/- 6.3 years; body mass index, 23.5 +/- 2.2). After adjustment for fasting glucose, insulin, weight loss, and diabetic state, a positive effect of F remained on the total GS activity, which accounted for 27% of the variation (P < .05). The waist to hip ratio was reduced in P subjects as compared with F subjects (P < .05). Fat-free mass (FFM) tended to be more reduced in the F group as compared with P subjects (4.9 v 1.9 kg), although the difference did not reach statistical significance. In conclusion, F seems to improve insulin sensitivity beyond the effect mediated through weight loss by a possible effect on GS activity in skeletal muscle tissue.

The influence of chronic administration of the serotonin agonist dexfenfluramine on responsiveness to corticotropin releasing hormone and growth hormone-releasing hormone in moderately obese people

Evidence exists that the serotoninergic system influences the hypothalamo-pituitary-adrenal axis and pituitary GH secretion. The effect was investigated of chronic (9 weeks) administration of the serotonin receptor agonist dexfenfluramine (DF) (15 mg twice daily) versus placebo on both systems in 24 moderately obese patients with an overconsumption of snacks. Before as well as after treatment, 100 micrograms GHRH and 100 micrograms CRH was administered iv. Weight loss after 9 weeks was 3.1 +/- 2.3 kg in the DF group and 0.1 +/- 1.2 in the placebo group (p < 0.001). No significant difference between the changes in the apparently normal ACTH and cortisol response in both groups was found. The apparently low GH response did not increase or normalize, but on the contrary decreased further after DF. No changes were shown in urinary free cortisol excretion and serum IGF-I levels. It can be concluded that in moderately obese patients the use of DF during a 9-week period induced a significant weight loss, did not influence the responsiveness of the pituitary gland to CRH nor the overall activity of the pituitary adrenal axis and finally, did not normalize the blunted GH response after GHRH.

Clinical studies with dexfenfluramine: from past to future

d Fenfluramine (dF) (15 mg twice daily) has been studied in controlled trials in human obesity. It has been shown to increase adherence to weight lowering programs, to double the number of patients losing 10 kg or more when compared with a fairly efficient placebo plus dietary counselling, and to prevent weight regain when continued over a 1 year period. Weight loss after 1 month and 4 months is likely to predict subsequent outcome. Also, significant improvement in metabolic risk factors and blood pressure were clearly demonstrated, even more markedly in some obesity-associated diseases, when body weight is maintained at a lower level. Even moderate but sustained weight loss of some 10% of starting weight or less has been confirmed to be of medical value. Tolerance and safety of dF can be considered acceptable, even if longer term follow-up is clearly needed. These studies support the concept that long-term pharmacotherapy with this serotoninergic drug might help achieve better outcome in the management of many obese patients, particularly in preventing relapse. The long-term managerial strategies to be developed for each patient might thus include dF together with dietary advice, behavioral modification and physical exercise, either simultaneously or sequentially.

Neuroendocrine abnormalities in human obesity

Recent research has indicated that visceral obesity is associated with multiple endocrine disturbances. Insulin resistance, as well as visceral fat accumulation, may be consequences of these abnormalities. The complex endocrine aberrations are probably of central origin, and suggest a neuroendocrine background with a "hypothalamic arousal" syndrome. Such a syndrome has been found after excess alcohol intake, tobacco smoking, and certain types of stress reactions. Subjects with visceral obesity might be characterized by a high prevalence of such factors, although only indirect evidence is available for the stress component, maybe caused by a poor socioeconomic and psychosocial situation. In primate experiments, a submissive stress reaction is followed by a syndrome essentially identical to that seen in humans with visceral obesity, including visceral fat accumulation. These observations strongly support a similar chain of events in humans. Recent studies have indicated several abnormalities in cerebrospinal fluid (CSF) concentrations of catecholamines and neuropeptides. In particular, serotonin metabolites and corticotropin-releasing factor (CRF) concentrations are apparently lower than normal. In women with visceral obesity, these low concentrations are associated with food choices that indicate a preference for carbohydrates. This finding emphasizes the importance of serotonin agonists in the treatment of human obesity. It seems possible that such drugs may have effects on metabolic and other symptoms particularly prevalent in abdominal obesity, and that these effects might be independent of the decrease in energy intake. It would seem highly desirable to explore these possibilities further. Such observations may also provide a link between the abnormalities of low serotonin and CRF concentrations in the central nervous system on one hand and peripheral metabolic and other abnormalities on the other.

The effects of dexfenfluramine on blood glucose control in patients with type 2 diabetes

Dexfenfluramine has been shown to promote weight loss in overweight people. The present double-blind study was designed to test whether the addition of dexfenfluramine to conventional oral hypoglycaemic treatment would promote weight loss and improve blood glucose control in overweight patients with Type 2 diabetes. The 34 patients studied were randomly assigned to dexfenfluramine or placebo therapy which was added for 12 weeks to their existing treatment regimens of metformin with or without a sulphonylurea. Dexfenfluramine treatment was associated with a significant reduction in weight (98.7 +/- 5.0 (+/- SE) vs 94.9 +/- 5.2 kg; p less than 0.001), BMI (35.0 +/- 1.2 vs 33.6 +/- 1.9 kg m-2; p less than 0.001), HbA1c (7.5 +/- 0.3 vs 6.3 +/- 0.2%; p less than 0.001), fructosamine (313.9 +/- 17.6 vs 274.3 +/- 10.4 mumol l-1; p less than 0.01), systolic (137 +/- 5 vs 128 +/- 6 mmHg; p less than 0.05), and diastolic blood pressure (85 +/- 2 vs 73 +/- 3 mmHg; p less than 0.001). At the end of the study period, the dexfenfluramine treated group had a significantly lower HbA1c (6.3 +/- 0.2 vs 7.2 +/- 0.4; p less than 0.05), fructosamine level (274.3 +/- 10.4 vs 313.3 +/- 16.1 mumol l-1; p less than 0.05) and diastolic blood pressure (73 +/- 3 vs 81 +/- 3 mmHg; p less than 0.03) when compared with the placebo group. In those patients treated with dexfenfluramine, the reduction in HbA1c and blood pressure did not correlate with the decrease in BMI (r = 0.44 and 0.12, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of chronic administration of dexfenfluramine on blood pressure in salt-sensitive rats

Chronic administration of dexfenfluramine, at a relatively low daily dose, slowed the development of salt-induced elevation of blood pressure in salt-sensitive (Dahl DS and Rapp SS) rats. This effect could not be accounted for by drug-related anorexia alone. Elevated serotonin activity, possibly in the brain, may underlie this antihypertensive action of dexfenfluramine.