Dexfenfluramine treatment of obesity: a double blind trial with post trial follow up

OBJECTIVE

As successful weight management demands a long term approach, a better understanding of weight changes during and for significant periods after cessation of dexfenfluramine therapy is essential to the evaluation of the drug's effectiveness in clinical practice. This study aimed to investigate additional benefits to weight loss during 6 months treatment with dexfenfluramine in 60 patients enrolled in a weight loss programme.

DESIGN

Sixty obese subjects (21 males; 39 females) were randomised to dexfenfluramine (15 mg twice daily) or placebo for six months. Fifty one (27 dexfenfluramine; 24 placebo) subjects completed the double blind, randomised, placebo controlled clinical trial.

RESULTS

After a one month 'run in' phase and six months treatment, weight loss in the dexfenfluramine group was significantly greater than placebo, 9.7 +/- 1.1 kg vs 4.9 +/- 0.9 kg (mean +/- s.e.m.); P = 0.002. Reduction in body fat, 5.0 +/- 0.7 kg vs 1.0 +/- 0.9 kg; P = 0.002 and waist circumference, 10.5 +/- 1.9 cm vs 5.7 +/- 1.1 cm; P = 0.04 was also greater in the dexfenfluramine group. Despite significant weight loss, waist to hip ratio (WHR) did not change in either group. The dexfenfluramine group reported a significantly greater incidence of nausea, dry mouth and dizziness which tended to decrease as treatment progressed. No subjects withdrew due to drug induced side effects. Reduction in serum triglyceride levels and an increase in HDL cholesterol (in female subjects) in conjunction with a reduction in fasting insulin, collectively support an improved cardiovascular risk profile in the dexfenfluramine group. Despite significant weight loss, these risk factor measurements worsened in the placebo group. After cessation of dexfenfluramine therapy, there was a significantly greater weight regain indicating a loss of treatment effect. By 5 months after cessation of dexfenfluramine, the treatment effect was negated with weight loss in the dexfenfluramine (6.0 +/- 1.6 kg) and placebo (6.2 +/- 1.3 kg) group, similar.

CONCLUSION

The results of this study support the longer term use of dexfenfluramine therapy for patients with chronic obesity.

Tissue differences in the response of the pyruvate dehydrogenase complex to a glucose load during the development of obesity in gold-thioglucose-obese mice

The activity of pyruvate dehydrogenase (PDHC), a key enzyme complex in the oxidative disposal of glucose, was measured after an oral glucose load in the heart, liver, quadriceps muscle, white adipose tissue (WAT) and brown adipose tissue (BAT) of gold-thioglucose (GTG)-obese mice at different stages during the development of obesity and in age-matched controls. Significant responses to the glucose load were seen 30 min post-gavage in heart, WAT and BAT of control mice but no change was observed in quadriceps muscle. The increase in activity of the active form of PDHC (PDHCa) in response to glucose in heart was reduced 2 weeks after the induction of GTG-obesity with no response in 5 or 10 week obese mice. A 2-3-fold increase in the PDHCa response in both WAT and BAT of 2 week obese mice was absent in 5 and 10 week obese animals. Basal PDHCa activity in quadriceps muscle was increased in 2 week obese mice but subsequently returned to control levels as obesity progressed. The glucose load produced no change in the activity of PDHCa in quadriceps muscle of obese mice. These results demonstrate that changes in the capacity for oxidative glucose disposal in different tissues, as indicated by changes in PDHCa activity, may contribute to glucose-intolerance and insulin-resistance in GTG-obese mice and that the response of the PDHC to insulin during the development of obesity varies in different tissues.

Changes in glycogen metabolism in liver of gold thioglucose injected mice during the development of obesity

A study of glycogen metabolism in the liver has been carried out in gold thioglucose (GTG) injected mice during the development of obesity. In GTG obese mice, overt obesity, hyperglycaemia and hyperinsulinaemia had developed by 6 weeks after the injection of GTG. Beyond 6 weeks after GTG injection, the gain of body weight and increment in serum glucose and insulin levels with age in obese mice were not obvious when compared with those of age-matched control animals. The glycogen concentration, total glycogen storage, activity of glycogen synthase R and activity of phosphorylase a in the liver from GTG obese mice were significantly greater than those in lean mice from 2-4 weeks after GTG injection and remained higher thereafter. These results demonstrate that the increased liver glycogen storage and increased activity of glycogen synthase and phosphorylase occur early in the development of obesity and at a similar time to previously reported increases in pyruvate dehydrogenase activity (Caterson et al. (1987) Biochem. J. 243, 549-553) and lipid synthesis in liver (Cooney et al. (1989) Biochem. J. 259, 651-657). The emergence of these abnormalities in glycogen metabolism early in the development of obesity may contribute to the establishment of glucose intolerance and insulin resistance in this model of obesity which became apparent at approximately the same time after GTG injection.

Effect of adrenalectomy on glucose tolerance and lipid metabolism in gold-thioglucose obese mice

The effect of adrenalectomy (ADX) on body weight, lipogenesis, and glucose tolerance was investigated in mice made obese by a single intraperitoneal injection of gold-thioglucose (GTG). Five weeks after ADX the weight of GTG-obese mice was significantly decreased (GTG-obese+sham-ADX: 39.8 +/- 0.8 g; GTG-obese+ADX: 27.6 +/- 1.1 g; P < 0.05). ADX also reduced serum glucose (GTG-obese+sham-ADX: 16.5 +/- 0.6 mmol/l; GTG-obese+ADX: 10.8 +/- 0.5 mmol/l; P < 0.05) and serum insulin concentrations (GTG-obese+sham-ADX: 197 +/- 36 microU/ml; GTG-obese+ADX: 38 +/- 7 microU/ml; P < 0.05) of fed GTG-obese mice and greatly improved glucose tolerance. ADX lowered liver glycogen content and reduced the fatty acid content of liver, epididymal white adipose tissue (WAT), and interscapular brown adipose tissue (BAT) of fed GTG-obese mice. Lipid synthesis in liver and WAT of GTG-obese mice was decreased by ADX, but lipogenesis in BAT was increased, possibly to provide substrate for increased thermogenesis in this tissue. Effects of ADX on metabolism were not confined to GTG-injected mice, as ADX also reduced body weight and altered the glucose tolerance of age-matched control mice. ADX increased lipid synthesis in liver, WAT, and BAT of fed control mice without an increase in lipid deposition, indicating that there was increased lipid turnover in these lipogenic tissues of ADX mice. ADX reduced the fasting blood glucose concentration of both control and GTG-obese mice to a level below that of sham-ADX control mice (sham-ADX control: 6.0 +/- 0.4 mM; ADX control: 2.9 +/- 0.5 mM; ADX GTG-obese: 3.3 +/- 0.2 mM).(ABSTRACT TRUNCATED AT 250 WORDS)

Tissue [1-14C] 2-deoxyglucose metabolism in the gold thioglucose obese mouse: effects of 'dieting'

Glucose uptake into heart and skeletal muscle and white and brown adipose tissue is reduced in mice with gold thioglucose-induced obesity. After acute dieting (40% of lean control uptake) for 18 days, glucose uptake into tissues remains low despite consistently elevated serum insulin levels. This reduced glucose uptake may be a consequence of the raised serum fatty acid levels produced by dieting. When the reduced weight obese mice are pair-fed with lean controls, they gain weight. Glucose uptake into both muscle and adipose tissues is markedly increased, and the insulin resistance of both previous obesity and recent relative starvation is rapidly overcome at the level of the glucose uptake, but serum insulin levels and insulin secretion from islets of Langerhans isolated from these animals remain high. To maintain reduced weight, previously obese animals were fed 80% of lean control intake. In this situation, glucose uptake into the four tissues studied remained reduced (compared to lean controls), consistent with relative starvation. While tissue glucose uptake increases after dieting and re-feeding of obese animals, serum insulin levels remain high, indicating persistence of a degree of insulin resistance. Reduced-weight obese animals are energy-efficient in that they gain excess weight on the control intake.

The prevalence of obstructive sleep apnoea in an obese female population

Obstructive sleep apnoea (OSA) has been estimated to affect between 1 and 4% of the total population. OSA may be more frequent among women than studies based on subjects presenting for treatment would indicate. The aim of this study was to determine the prevalence of OSA in an obese female population (BMI > 30 kg/m2, age > 18 years) who presented to a hospital-based obesity clinic. The women were screened by an overnight ambulatory sleep study (MESAM) to detect OSA. Subjective sleep quality and sleep disturbance were assessed by a 19-item questionnaire, the Pittsburg sleep quality index (PSQI). From a population of 108 women, 29 were screened by MESAM. OSA was determined on the basis of respiratory disturbance index (RDI). The prevalence of OSA, defined as five or more respiratory disturbances per hour, was 37.9%. The mean age of the women was 43.6 +/- 2.57 years (mean +/- s.e.m.) and they had a mean BMI of 40.7 +/- 1.40 kg/m2. There was a significant positive correlation for RDI and BMI (r = 0.71; P < 0.001). Our findings indicate that over one third of women had OSA, yet they did not complain of symptoms even though the PSQI questionnaire indicated that they were poor sleepers. Non-specific symptomatology of OSA may be important diagnostically, particularly in women, and obese women should be considered at risk of OSA.

Liver and peripheral tissue glycogen metabolism in obese mice: effect of a mixed meal

Glycogen metabolism in the liver, skeletal muscle, cardiac muscle, and white adipose tissue was studied in gold thioglucose (GTG) obese mice after fasting and during refeeding. Prolonged (48 h) fasted control and GTG mice were refed with standard laboratory diet for 24 h. During fasting and refeeding, the changes in glycogen content and the activity of glycogen synthase I and R and phosphorylase alpha in the liver were similar in lean and GTG mice. However, the glycogen storage in the livers from GTG mice was always greater than that in lean animals. In GTG mice the activity of liver glycogen synthase I and R was significantly higher than that in lean animals 3 and 6 h after refeeding. The activity of liver phosphorylase alpha in GTG mice was higher than that in lean mice after refeeding. There were no significant differences in the glycogen content of white adipose tissue, cardiac muscle, and skeletal muscle from lean and GTG mice during the entire study. The results of this study suggest that increased glycogen storage in the liver is a major alteration in nonoxidative glucose metabolism and contributes to the development of insulin resistance and glucose intolerance in GTG obese mice.

Diurnal patterns of cardiac and hepatic pyruvate dehydrogenase complex activity in gold-thioglucose-obese mice

The diurnal pattern of the activity of the pyruvate dehydrogenase complex (PDHC) was studied in the heart and liver of gold-thioglucose (GTG)-obese mice and age-matched controls. The diurnal pattern of lipogenesis was also measured in the liver. Both lean and obese mice had one main eating period, from 20:00 to 24:00 h. Eating produced no change in serum glucose of control mice but there was a significant rise in serum insulin and triacylglycerols. There was also a 3-fold increase in cardiac PDHC activity and a 3-fold increase in hepatic lipogenesis in the control mice, but little change in hepatic PDHC activity. GTG-obese mice were hyperglycaemic, hyperinsulinaemic and hypertriglyceridaemic at all times studied, with significant increases in these parameters being seen in response to eating. Eating produced little change in cardiac PDHC activity, but there was a 5-fold increase in hepatic PDHC activity, paralleled by a 10-fold increase in hepatic lipogenesis. Hepatic PDHC activity was significantly higher in GTG-obese mice at all times except 16:00 h. The simultaneous rise of hepatic PDHC activity, lipogenesis and serum triacylglycerols in GTG-obese mice suggests an increased utilization of glucose for lipogenesis. The lack of change in heart PDHC activity in GTG-obese mice over 24 h suggests that a general decrease in PDHC activity may contribute to the development of the glucose intolerance and insulin resistance of obesity and non-insulin-dependent diabetes. However, it appears that a different level of metabolic control allows hepatic PDHC activity of the same obese animals to increase in response to hyperinsulinaemia and contribute to the higher rates of lipogenesis seen in obese mice.

Effects of blockade of fatty acid oxidation on whole body and tissue-specific glucose metabolism in rats

We examined the effect of the long-chain fatty acid oxidation blocker methyl palmoxirate (methyl 2-tetradecyloxiranecarboxylate, McN-3716) on glucose metabolism in conscious rats. Fasted animals [5 h with or without hyperinsulinemia (100 mU/l) and 24 h] received methyl palmoxirate (30 or 100 mg/kg body wt po) or vehicle 30 min before a euglycemic glucose clamp. Whole body and tissue-specific glucose metabolism were calculated from 2-deoxy-[3H]-glucose kinetics and accumulation. Oxidative metabolism was assessed by respiratory gas exchange in 24-h fasted animals. Pyruvate dehydrogenase complex activation was determined in selected tissues. Methyl palmoxirate suppressed whole body lipid oxidation by 40-50% in 24-h fasted animals, whereas carbohydrate oxidation was stimulated 8- to 10-fold. Whole body glucose utilization was not significantly affected by methyl palmoxirate under any conditions; hepatic glucose output was suppressed only in the predominantly gluconeogenic 24-h fasted animals. Methyl palmoxirate stimulated glucose uptake in heart in 24-h fasted animals [15 +/- 5 vs. 220 +/- 28 (SE) mumol x 100 g-1 x min-1], with smaller effects in 5-h fasted animals with or without hyperinsulinemia. Methyl palmoxirate induced significant activation of pyruvate dehydrogenase in heart in the basal state, but not during hyperinsulinemia. In skeletal muscles, methyl palmoxirate suppressed glucose utilization in the basal state but had no effect during hyperinsulinemia; pyruvate dehydrogenase activation in skeletal muscle was not affected by methyl palmoxirate under any conditions. The responses in skeletal muscle are consistent with the operation of a mechanism similar to the Pasteur effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Insulin response to an intravenous glucose load during development of obesity in gold thioglucose-injected mice

The insulin secretory response to an intravenous glucose load was examined in chronically catheterized, conscious mice 2, 5, and 10 wk after induction of obesity by a single injection of gold thioglucose. At 2 wk after administration of gold thioglucose, a significant increase in both the insulinemia and incremental area under the curve of insulin release after intravenous glucose were observed (incremental area under the curve for 2-wk control mice, 852 +/- 54 min/pM; incremental area under the curve for 2-wk GTG-injected mice, 1140 +/- 114 min/pM; P < 0.05). At this stage, no significant difference existed in the glucose tolerance or body weight of control and gold thioglucose-injected mice. By 5 wk, the gold thioglucose-injected mice were approximately 33% heavier than their lean controls and showed a marked glucose intolerance. This was accompanied by overt hyperinsulinemia in both the basal state and also in response to an intravenous glucose bolus as indicated by the increase in the incremental area under the curve of insulin (5-wk control mice, 816 +/- 114 min/pM; 5-wk gold thioglucose-injected mice, 1374 +/- 156 min/pM; P < 0.05). At 10 wk after gold thioglucose administration, body weight and the degree of glucose intolerance were increased. Although 10-wk gold thioglucose-injected mice showed basal hyperinsulinemia, an intravenous glucose bolus elicited a smaller insulin secretory response than that observed in the age-matched lean control animals (10-wk control mice, 672 +/- 54 min/pM; 10-wk gold-thioglucose-injected mice 186 +/- 42 min/pM; P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

In vivo insulin sensitivity of the pyruvate dehydrogenase complex in tissues of the rat

Activity of the insulin-activated pyruvate dehydrogenase complex (PDHC) is necessary for the complete oxidation of glucose to carbon dioxide or the conversion of glucose to fatty acids in lipogenic tissues. To determine the in vivo insulin sensitivity of PDHC activity in rat tissues, we measured the amount of PDHC in the active form in heart, diaphragm, red quadriceps, white adipose tissue (WAT), and brown adipose tissue (BAT) of rats exposed to five different circulating insulin concentrations under euglycemic clamp conditions. PDHC was measured in mitochondrial extracts of tissues rapidly dissected from rats in the starved state or after euglycemic clamp (4 mM) at insulin infusion rates of 0, 0.125, 0.25, and 2.0 U.kg-1.h-1. Increasing the insulin concentration increased the PDHC activity in all tissues, but the magnitude of this activation was different in different tissues (heart: 3.5-fold; diaphragm: 2.5-fold; red quadriceps: 1.8-fold; WAT: 3.4-fold; and BAT: 10.5-fold). Calculation of the half-maximal effective dose (ED50) for the activation of PDHC produced values that were similar in all tissues (heart: 112 pM; diaphragm: 108 pM; red quadriceps: 146 pM; WAT: 120 pM; and BAT: 118 pM). The insulin sensitivity of PDHC in these tissues correlated particularly well with the ED50 for the insulin effect of decreasing circulating nonesterified fatty acids (NEFA; 122 pM). The differences in the magnitude of the effect of increasing insulin on PDHC activity implies a tissue difference in the requirement for an increased capacity for glucose oxidation after insulin stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Diurnal rhythms of glycogen metabolism in the liver and skeletal muscle in gold thioglucose induced-obese mice with developing insulin resistance

The circadian rhythm of glycogen metabolism in liver and skeletal muscle was studied in lean and gold thioglucose (GTG) induced-obese mice. The active forms of glycogen synthase (GSI) and phosphorylase (GPa) and the total activity of these enzymes were measured every three hours over a 24 h period in mice fed ad libitum. Hepatic and muscle glycogen content displayed a marked diurnal rhythm that was similar in lean and obese mice. In skeletal muscle the glycogen content, GSI and GPa were not significantly different in lean and obese animals over the 24 h period. The activities of muscle GSI and GPa were constant in both groups despite the diurnal variation in the muscle glycogen content. The absence of an increase in the glycogen content of skeletal muscle despite the pronounced hyperinsulinemia and hyperglycemia in the obese mice, may indicate the degree of insulin resistance in this tissue or the maximal capacity of muscle tissue to store glycogen. In liver, glycogen concentration and total glycogen storage were higher in obese mice. Unlike muscle, both hepatic GSI and GPa underwent significant changes in activity over the 24 h period. Hepatic GSI was lower and GPa was higher in obese mice. The circadian rhythm in enzyme activities was independent of both blood glucose and insulin levels. The total glycogen storage and the activities of total phosphorylase and GPa were significantly increased in the liver from GTG obese mice over a 24 h period and could be implicated in the development of insulin resistance and glucose intolerance in this model of obesity.

Severe obesity: the use of very low energy diets or standard kilojoule restriction diets

OBJECTIVES

To determine the efficacy of two dietary therapies in both the short term (hospitalisation) and the longer term treatment of severe obesity.

DESIGN

A descriptive study of two patient groups with obesity defined by a body mass index of greater than 30 kg/m2.

SETTING

A multidisciplinary weight control program in a tertiary care hospital.

PATIENTS

All admissions to hospital of patients on the weight control program for initiation of weight loss during a period of 48 months.

INTERVENTION

A standard kilojoule reduction regimen or the use of complete, followed by partial, long term meal substitution with a very low energy liquid diet (VLED), coupled with an exercise and a behavioural modification program.

OUTCOME MEASURES

Weight loss during and after hospitalisation was measured in both dietary regimen groups.

RESULTS

Both diets induced weight loss in hospital. Men prescribed VLED lost significantly more weight, 8.3 +/- 0.8 kg (mean +/- SEM) than women prescribed this diet (5.5 +/- 0.5 kg) or standard kilojoule restriction (5.1 +/- 0.8 kg).

CONCLUSIONS

VLED and standard kilojoule restriction are both effective for the treatment of severe obesity, particularly in a controlled environment (hospitalisation). In the longer term, VLED is an effective method of maintaining weight loss. Lack of continuing weight loss may reflect the patients who were initially placed on this regimen--small eaters with a presumed high metabolic efficiency.

The effects of fasting and refeeding on liver glycogen synthase and phosphorylase in obese and lean mice

The responses of hepatic glycogen synthase and phosphorylase to fasting and refeeding were assessed as part of an investigation into possible sites of insulin resistance in gold thioglucose (GTG) obese mice. The active forms glycogen synthase and phosphorylase (synthase I and phosphorylase a) and the total activity of these enzymes were estimated in lean and GTG mice over 48 h of food deprivation, and for 120 min after glucose gavage (1 g/kg wt). In lean mice there was a maximal reduction in hepatic glycogen content after 12 h of starvation and the activity of phosphorylase a decreased from 23.8 +/- 1.9 to 6.8 +/- 0.7 mumol/g protein/min. These changes were accompanied by an increase in the activity of synthase I (from 0.14 +/- 0.01 to 0.46 +/- 0.04 mumol/g protein/min). In obese mice, similar changes in enzyme activity occurred after 48 h of starvation. These changes were accompanied by a significant reduction in the hyperinsulinemia and hyperglycemia of the GTG mice. After glucose gavage in both lean and obese mice, the activity of synthase I further increased over the first 30 min and declined thereafter. The activity of phosphorylase a increased progressively after refeeding. Results from this study suggest that despite increased hepatic glycogen deposition, the responses of glycogen synthase and phosphorylase, in livers of obese mice, to fasting and refeeding are similar to those of control mice even in the presence of insulin resistance.

Differences in lipogenesis in tissues of control and gold-thioglucose obese mice after an isocaloric meal

Lipogenesis was measured in 2 and 5 week gold-thioglucose (GTG) obese mice after a single meal of 0.5 g of standard chow. Compared to control mice the rate of lipogenesis in GTG obese mice, was 4-fold higher in liver and 10-fold higher in white adipose tissue (WAT). In brown adipose tissue (BAT) of GTG-injected mice the lipogenic rate was only 50% of that of controls. These results indicate that the increased lipid synthesis observed in GTG-injected mice is not due solely to hyperphagia and that some other stimuli, such as increased basal insulin levels and/or decreased thermogenesis and insulin resistance in BAT, contribute to the high rates of fat synthesis in this animal model of obesity.

Heterogeneity of response to exercise of rat muscle pyruvate dehydrogenase complex

Muscle glucose uptake is greatly stimulated by moderate exercise, but full oxidation of the glucose to CO2 depends on the activity of the pyruvate dehydrogenase (PDH) complex. Our aim was to determine how PDH complex in different muscle groups responds to varying periods of moderate exercise. Rats were run on a motor-driven treadmill for 5-30 min and muscle PDH complex activity was determined in heart, diaphragm and red quadriceps muscles after isolation of mitochondria in the presence of inhibitors of PDH complex interconversion. In heart and diaphragm muscle, exercise caused an increase in PDH complex activity after 5 min, but this was followed by a significant decrease in activity as exercise progressed. In red quadriceps muscle, PDH complex activity was reduced after 5 min of exercise and was decreased further as exercise continued. We conclude that increased duration of exercise can lead to reduced PDH complex activity in rat muscles. We propose that this is a consequence of elevated fatty acid oxidation, the products of which stimulate PDH kinase. This implies that increased glycolysis to lactate and increased fatty acid oxidation can simultaneously provide energy for contracting muscle.

Cation-induced restoration of insulin action in insulin-desensitized HTC cells

Insulin desensitization of amino acid uptake in HTC cells was induced by preincubation with 4 or 10 micrograms/ml insulin. Insulin binding after desensitisation was decreased by both insulin concentrations due to a 45-49% decrease in insulin receptor numbers. Desensitization with 4 micrograms/ml insulin increased the ED50 for half-maximal stimulation of amino acid uptake from 19.5 +/- 9.2 ng/ml in control cells to 84.0 +/- 8.3 ng/ml (P less than 0.0001). It also decreased the maximal insulin response of amino acid uptake from 1.40 +/- 0.10 to 1.14 +/- 0.10 nmol/mg protein, indicating the production of a mild postreceptor defect. Desensitization with 10 micrograms/ml insulin completely abolished this insulin response. When cellular receptors were down-regulated with 4 micrograms/ml insulin and restimulated with insulin in the presence of 0.03 mM ruthenium red (RR) or 10 mM Ca2+, both the insulin response and insulin binding were increased. Insulin binding was restored to levels comparable to those observed in control cells by an increase in receptor affinity. The ED50 of amino acid uptake decreased to 20.5 +/- 7.3 ng/ml insulin in the presence of RR and to 42.2 +/- 8.9 ng/ml in the presence of 10 mM Ca2+ (both P less than 0.0001 from down-regulated cells). In addition, the maximal insulin response increased from 1.14 +/- 0.10 to 1.40 +/- 0.10 and 1.45 +/- 0.10 nmol/mg protein, respectively. Preincubation with 10 micrograms/ml insulin prevented the effect of RR and Ca2+ on the recovery of insulin responses. These experiments suggest that insulin-desensitized cells undergo a progressive loss of their insulin response and that RR and Ca2+ provide useful reagents to investigate the mechanisms of this process because they can counteract the decrease in insulin response by increasing receptor affinity and receptor-effector coupling.

Effect of high plasma dexamethasone levels on DST sensitivity: dose-response study in depressed patients and controls

The aim of this study was to examine cortisol dynamics over a range of plasma dexamethasone (DEX) levels using a two-dose dexamethasone suppression test (DST). Two doses of DEX (0.5 and 1.5 mg) were administered in a randomized crossover design to 29 inpatients with major depression and 26 controls to identify the upper range of plasma DEX levels that would allow reliable interpretation of DST results. It was hypothesized that due to inappropriately high plasma DEX levels following 1.5 mg, several depressed patients would switch from suppressors after the 1.5 mg dose to nonsuppressors after 0.5 mg. In contrast, the nondepressed controls with high DEX levels following 1.5 mg would remain suppressors after the lower dose. Fourteen patients were identified as having high 4 p.m. DEX levels (greater than 4 nmol/l) after the 1.5 mg DST. Cortisol was suppressed in all of the subjects with high DEX levels. After 0.5 mg, five of the eight depressed patients with high DEX levels switched to nonsuppressors. In contrast, all six controls with high DEX levels remained suppressors. These results indicate that patients with high DEX levels after a 1 mg DST should be retested with a lower dose. This strategy enhances the sensitivity of the DST without loss of specificity.

High affinity insulin binding and insulin receptor-effector coupling: modulation by Ca2+

Insulin binding and insulin stimulated amino acid and glucose uptake were determined in cultured HTC hepatoma cells in the presence of Ca2+ and ruthenium red (RR) in order to further characterise the putative calcium binding site on the receptor. These ions increased insulin receptor high affinity binding and the sensitivity of these responses to insulin. The insulin concentration required to half-maximally stimulate amino acid uptake decreased significantly from 26.9 +/- 5.8 ng/ml to 6.0 +/- 1.3 ng/ml in the presence of 10 mM Ca2+ and to 1.3 +/- 0.5 ng/ml in the presence of RR. The effect of Ca2+ and RR was more pronounced on insulin stimulated glucose uptake. These agents also increased receptor-effector coupling, reducing the percentage of occupied receptors required for maximal insulin stimulation of amino acid uptake from 10.8% in control cells to 3.4 and 1.4% in the presence of Ca2+ and RR respectively. The receptor occupancy required to produce maximal insulin responses on glucose uptake decreased from 20% (control) to 3.8% (Ca2+ and RR). We hypothesize that since Ca2+ and RR have similar effects, that occupation of Ca2+ binding sites on the receptor produces a conformational change in the insulin receptor which increases insulin receptor affinity, insulin sensitivity and acts on an early post-receptor event responsible for coupling binding to insulin action.

Pyruvate dehydrogenase-complex activity in brown adipose tissue of gold thioglucose-obese mice

The activity of pyruvate dehydrogenase (PDH) complex and PDH kinase were measured in brown adipose tissue (BAT) of 4-week-gold thioglucose (GTG)-obese mice. The proportion of PDH complex in the active dephosphorylated form was 2-fold higher in BAT of post-absorptive obese mice compared with lean controls. This result was consistent with the higher circulating insulin concentration observed in GTG-obese mice. In both obese and lean mice the PDH-complex activity in BAT decreased after 24 h starvation and increased in response to supraphysiological insulin injection, indicating that the PDH complex is insulin-responsive in BAT of GTG-obese mice. There was no difference in the PDH kinase activity of BAT in post-absorptive or insulin-injected lean and obese mice, suggesting that the higher PDH-complex activity in obese mice was not due to decreased PDH kinase activity. There is no evidence for a decreased activity of PDH complex contributing to insulin resistance in BAT of 4-week-GTG-obese mice.

Management strategies for weight control. Eating, exercise and behaviour

Obesity is a major health and social problem worldwide for which no single satisfactory treatment exists. Because of the prevalence of the disease, numerous therapeutic strategies have been attempted--often unsuccessfully. Weight loss programmes based on dietary restriction of caloric intake and nutritional education, exercise, surgical (gastroplasty, gastric bypass) and procedural (gastric balloon, waist cord, jaw wiring, liposuction) intervention and pharmacotherapy (appetite suppressants, thermogenic agents, bulking agents) used alone or in combination, have produced weight loss in the short to medium term; however, weight is generally regained on discontinuation of treatment. Behaviour modification programmes appear to offer the highest success rate in the long term. Weight loss is not rapid, although losses of 10 to 15 kg have been achieved after 6 months, and this may be increased when behaviour modification therapy is combined with more aggressive treatments such as severe caloric restriction or jaw wiring. Behaviour modification is particularly beneficial in special patient groups such as the obese elderly, children or adolescents, and disabled patients. Thus, although it appears that each of the treatments developed for the management of obese patients has its place, the cornerstone of therapy for most patients remains a programme of dietary restriction, combined with exercise and behaviour modification.

Hypercalcemia and lipoid pneumonia

A 49-year-old man with an 11 year history of NIDDM presented hypercalcemic and with acute on chronic renal failure. His only symptoms were mild anorexia and nausea. Four years previously he had been diagnosed as having lipoid pneumonia, with classical histological findings. On this admission, serum parathyroid hormone was suppressed and 1,25 dihydroxyvitamin D levels elevated. The cause of his hypercalcemia presumably was ectopic 1 hydroxylation of 25 hydroxyvitamin D in the chronic granulomata in his lungs. It should be emphasised that any chronic granulomatous disease, and not just sarcoidosis, may be a cause of hypercalcemia.

Effect of starvation and insulin in vivo on the activity of the pyruvate dehydrogenase complex in rat skeletal muscles

The in vivo responses of pyruvate dehydrogenase (PDH) complex to starvation and insulin was assessed in heart, diaphragm and red quadriceps muscle. PDH complex activity was decreased by starvation (3.4-10.2-fold), the magnitude of change depending on muscle type. Insulin increased PDH activity in all muscle types. In fed rats, this effect was relatively small (1.25-1.29-fold). In starved rats there were effects in heart (4.3-fold) and red quadriceps (1.7-fold) but no effect in diaphragm. These results demonstrate that PDH complex in different groups of muscle has different insulin sensitivity (particularly in tissues from starved animals).

The effect of age on cortisol and plasma dexamethasone concentrations in depressed patients and controls

The aim of this study was to identify any relationships between various patient factors such as age, gender and concurrent medication that may affect plasma cortisol or dexamethasone (DEX) concentrations. Multiple regression analysis was used to formulate an equation to predict plasma DEX levels to identify factors that may influence DEX bioavailability. Pre- and post-DST cortisol levels did not increase with age, but DEX levels were higher in elderly depressed patients. Neither gender nor psychotropic medication affected plasma cortisol or DEX levels. There was no indication that pre-DST cortisol levels influenced plasma DEX levels to account for the lower DEX values in non-suppressors. Age was the only significant factor found in this study to influence DEX levels and it could be argued that the dose of DEX should be lowered when administering the DST to elderly patients to reduce plasma DEX variability.