Turnover and oxidation rates of plasma-free fatty acids in obese patients treated 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being two mechanisms contributing to better blood glucose control in obese Type 2 diabetic patients, they were recently withdrawn due to safety problems.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.

Elevated diet-induced thermogenesis and lipid oxidation rate in Crohn disease

BACKGROUND

Although malnutrition is frequently observed in Crohn disease (CD), its cause is not clear. Regulation of energy metabolism and diet-induced thermogenesis (DIT) have not been adequately studied in CD.

OBJECTIVE

The aim was to study DIT and substrate oxidation in patients with inactive ileal CD.

DESIGN

After a test meal providing 50.2 kJ/kg body wt, DIT was assessed by indirect calorimetry performed over 360 min in 18 CD patients and 12 healthy volunteers matched for age, sex, weight, and height. Body composition was evaluated with the labeled-water-bolus injection technique.

RESULTS

Fat-free mass did not differ significantly between groups, but CD patients had markedly lower fat mass than control subjects (13.8+/-5.63 compared with 19.0+/-3.49 kg; P < 0.001). Nonprotein respiratory quotient was lower in CD patients than control subjects (0.80+/-0.04 compared with 0.86+/-0.03; P < 0.001). Average respiratory quotient between 75 and 150 min after the test meal was 0.85+/-0.03 in CD patients and 0.91+/-0.02 in control subjects (P < 0.001). Lipid oxidation rate was higher in CD patients than in control subjects (2.26+/-1.13 compared with 1.50+/-0.75 kJ/min; P < 0.05). DIT was higher in CD patients than in control subjects (9.89+/-1.93% compared with 5.67+/-0.91% of energy intake; P < 0.001).

CONCLUSIONS

Patients with inactive ileal CD had significantly higher DIT and lipid oxidation rate than do healthy volunteers. These results may explain why CD patients have difficulty maintaining adequate nutritional status, and the findings also suggest that a diet relatively rich in fat may attain better energy balance.

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.

Changes in energy metabolism and metabolite patterns of obese rats after application of dexfenfluramine

Serotonergic neuronal networks are important for food intake and body weight regulation. Dexfenfluramine (dF), a serotonin releaser and reuptake inhibitor, was used to investigate changes in food intake, body weight development, energy expenditure, respiratory quotient, and substrate oxidation rates for 12 days. Rats, which had been made obese by early postnatal overfeeding, received an energy-controlled mash diet and water ad lib and were intraperitoneally injected daily with either saline, 5 or 10 mg dF/kg. Compared to controls, food intake, body weight development, and energy expenditure were decreased in a dose-dependent manner, especially during the first 6 days. Lipid oxidation was increased while oxidation of carbohydrates was decreased. Pair-feeding experiments over 2 days revealed that this was not solely a result of diminished food intake but also an additional metabolic effect of dF, different from its anorectic effect. At the end of these experiments, plasma glucose and liver glycogen were unchanged after dF, but plasma free fatty acids were significantly decreased. Insulin-sensitivity was probably improved, indicated by decreased insulin levels and increases in muscle glycogen contents and activities of muscle pyruvate kinase. Liver-glutamine and contents of valine, leucine, and isoleucine in the muscle were significantly decreased after dF-treatment, the latter indicating a diminished proteolysis. The plasma tryptophan/large neutral amino acids ratio of the dF-rats was unchanged but that of the paired-fed rats was changed, despite similar changes in food intake. It is concluded that both increased oxidation of endogenous fat and reduced food intake could mediate the body weight reducing effect of dF.

Effects of dexfenfluramine on free fatty acid turnover and oxidation in obese patients with type 2 diabetes mellitus

To test the potential effects of dexfenfluramine (dF) on enhancing free fatty acid (FFA) turnover and oxidation rates, 11 obese female non-insulin-dependent diabetes mellitus (NIDDM) outpatients (age, 52.5 +/- 1.5 years; weight, 81.3 +/- 3.2 kg; height, 158 +/- 3.04 cm; body mass index, 32.4 +/- 0.7 kg/m2) received a primed-constant infusion of 1-14C-palmitate. The waist to hip ratio (WHR) was 0.91 +/- 0.04. Fat body mass and lean body mass, assessed by dual-energy x-ray densitometry, were 32.0 +/- 1.5 and 49.30 +/- 2.67 kg, respectively. All patients had an average hemoglobin A1 of 6.3% +/- 0.3% in the month preceding the study and had not received oral hypoglycemic agents. Gas exchange was measured both basally and during a ventilated-hood system, indirect-calorimetry session. The protocol was a randomized, placebo-controlled, single-blind design. Subjects received dF 30 mg acutely (n = 6) or a placebo (n = 5). A dose of dF 15 mg twice daily or placebo was then administered over 15 days (chronic). To obtain serum peak level of the drug, dF was administered 2 hours before starting palmitate infusion. A free diet was allowed throughout the study, and the group treated with dF lost approximately 0.5 kg body weight. Acute and chronic dF administration resulted in a significant increase in FFA oxidation, expressed as a percentage of the dose of radiocarbon (respectively, 11.47% +/- 0.46% v 9.50% +/- 0.46% [P < .01] and 12.06% +/- 0.71% v 9.88% +/- 0.62% [P < .01]). FFA turnover rate was higher after both acute and chronic dF administration (respectively, 10.71 +/- 2.18 v 7.79 +/- 1.48 mumol/kg/min [P < .05] and 11.92 +/- 2.74 v 8.43 +/- 1.86 mumol/kg/min [P < .05]). Serum FFA concentration during both acute and chronic dF administration increased, but not significantly. Mean serum glucose level decreased after acute dF from 114.3 +/- 8.6 to 86.5 +/- 5.1 mg/dL (P < .001) and after chronic dF from 120.3 +/- 7.3 to 89.8 +/- 5.8 mg/dL (P < .001). Serum insulin was not affected by dF administration. In conclusion, oral acute and chronic dF administration increase FFA turnover and oxidation rates in NIDDM obese patients. This may play an important role in weight reduction. In addition, dF shows a weight-independent effect on glucose metabolism, reducing serum glucose levels without acting on insulin secretion.