Diurnal Rhythm in Anticoagulant Effect of Heparin during a Low Dose Constant Rate Infusion

The objective of the study was to investigate possible diurnal rhythms in coagulation tests during a continuous intravenous infusion of unfractionated heparin. Six volunteers participated in the study, which was divided in a treatment (500 U heparin/h for 30 h) and a control experiment. Under basal conditions, no rhythm was found in coagulation tests. During heparin treatment, APTT, thrombin clotting time and anti-Xa activity showed a greater anticoagulant effect at night, with a striking decrease in the morning.

In a search for the explanation of this phenomenon we looked for diurnal variations in the urinary excretion of heparin, in the plasma concentrations of antithrombin III and platelet factor 4, and in the effect of heparin added to the plasma samples in vitro. None of these studies provided the explanation.

HDL functionality in South Asians as compared to white Caucasians

BACKGROUND AND AIMS

South Asians have an exceptionally high risk of developing cardiovascular disease compared to white Caucasians. A contributing factor might be dysfunction of high density lipoprotein (HDL). We aimed to compare HDL function in different age groups of both ethnicities.

METHODS AND RESULTS

HDL functionality with respect to cholesterol efflux, anti-oxidation and anti-inflammation was determined using fasting, apoB-depleted, plasma samples from South Asian and white Caucasian neonates (n = 14 each), adolescent healthy men (n = 12 each, 18-25 y), and adult overweight men (n = 12 each, 40-50 y). Adolescents were subjected to a 5-day high fat high calorie diet (HCD) and adults to an 8-day very low calorie diet (LCD). Additionally, HDL composition was measured in adolescents and adults using (1)H-NMR spectroscopy. Anti-oxidative capacity was lower in South Asian adults before LCD (19.4 ± 2.1 vs. 25.8 ± 1.2%, p = 0.045, 95%-CI = [0.1; 12.7]) and after LCD (16.4 ± 2.4 vs. 27.6 ± 2.7%, p = 0.001, 95%-CI = [4.9; 17.5]). Anti-inflammatory capacity was reduced in South Asian neonates (23.8 ± 1.2 vs. 34.9 ± 1.3%, p = 0.000001, 95%-CI = [-14.6; -7.5]), and was negatively affected by an 8-day LCD only in South Asian adults (-12.2 ± 4.3%, p = 0.005, 95%-CI = [-5.9; -1.2]). Cholesterol efflux capacity was increased in response to HCD in adolescents (South Asians: +6.3 ± 2.9%, p = 0.073, 95%-CI = [-0.02; 0.46], Caucasians: +11.8 ± 3.4%, p = 0.002, 95%-CI = [0.17;0.65]) and decreased after LCD in adults (South Asians: -10.3 ± 2.4%, p < 0.001, 95%-CI = [-0.57; -0.20], Caucasians: -13.7 ± 1.9%, p < 0.00001, 95%-CI = [-0.67; -0.33]). Although subclass analyses of HDL showed no differences between ethnicities, cholesterol efflux correlated best with cholesterol and phospholipid within small HDL compared to other HDL subclasses and constituents.

CONCLUSION

Impaired HDL functionality in South Asians may be a contributing factor to their high CVD risk.

CLINICAL TRIAL REGISTRATION

NTR 2473 (URL: http://www.trialregister.nl/).

Cardiovascular flexibility in middle-aged overweight South Asians vs. white Caucasians: response to short-term caloric restriction

BACKGROUND AND AIMS

South Asians have a higher risk of developing cardiovascular disease than white Caucasians. The underlying cause is unknown, but might be related to higher cardiac susceptibility to metabolic disorders. Short-term caloric restriction (CR) can be used as a metabolic stress test to study cardiac flexibility. We assessed whether metabolic and functional cardiovascular flexibility to CR differs between South Asians and white Caucasians.

METHODS AND RESULTS

Cardiovascular function and myocardial triglycerides were assessed using a 1.5T-MRI/S-scanner in 12 middle-aged overweight male South Asians and 12 matched white Caucasians before and after an 8-day very low calorie diet (VLCD). At baseline South Asians were more insulin resistant than Caucasians. Cardiac dimensions were smaller, despite correction for body surface area, and pulse wave velocity (PWV) in the distal aorta was higher in South Asians. Systolic and diastolic function, myocardial triglycerides and pericardial fat did not differ significantly between groups. After the VLCD body weight reduced on average by 4.0 ± 0.2 kg. Myocardial triglycerides increased in both ethnicities by 69 ± 18%, and diastolic function decreased although this was not significant in South Asians. However, pericardial fat and PWV in the proximal and total aorta were reduced in Caucasians only.

CONCLUSION

Myocardial triglyceride stores in middle-aged overweight and insulin resistant South Asians are as flexible and amenable to therapeutic intervention by CR as age-, sex- and BMI-matched but less insulin resistant white Caucasians. However, paracardial fat volume and PWV showed a differential effect in response to an 8-day VLCD in favor of Caucasians.

CLINICAL TRIAL REGISTRATION

NTR 2473 (URL: http://www.trialregister.nl/trialreg/admin/rctsearch.asp?Term=2473).

Ectopic fat and insulin resistance: pathophysiology and effect of diet and lifestyle interventions

The storage of triglyceride (TG) droplets in nonadipose tissues is called ectopic fat storage. Ectopic fat is associated with insulin resistance and type 2 diabetes mellitus (T2DM). Not the triglycerides per se but the accumulation of intermediates of lipid metabolism in organs, such as the liver, skeletal muscle, and heart seem to disrupt metabolic processes and impair organ function. We describe the mechanisms of ectopic fat depositions in the liver, skeletal muscle, and in and around the heart and the consequences for each organs function. In addition, we systematically reviewed the literature for the effects of diet-induced weight loss and exercise on ectopic fat depositions.

Physiologic hyperleptinemia in obesity does not affect vasopressin secretion in acute hypo- or hyperosmolality

PURPOSE

Abnormal water excretion after ingestion of a water load has been described in obesity. We hypothesized that AVP secretion is abnormal in obese subjects in acute hypo- and hyperosmolality and that the hormone leptin is partly responsible for this.

METHODS

We studied the relation between leptin, AVP and serum osmolality in two separate tests: (1) after ingestion of a water load (20 ml/kg lean body mass plus 5 ml /kg of adipose tissue) and (2) after iv hypertonic saline (5% NaCl) at a rate of 0.1 ml/kg lean body mass/minute for 120 min in ten subjects of normal weight (BMI > 20 and < 25 kg/m2; controls) and ten obese females (BMI > 30 kg/m2). Obese subjects were tested before (98.6 +/- 9.3 kg) and after weight loss (90.2 +/- 8.5 kg).

RESULTS

In the water load experiment, obese subjects excreted a smaller percentage of the water load than controls. Weight loss restored the ability to excrete the water load in the obese. In the water load and hypertonic saline infusion experiment, plasma AVP concentrations and the area under the curve (AUC) for AVP concentration were not different in obese from normal weight women. Baseline leptin concentration was not correlated with baseline AVP or the change in AVP during the experiment in any of the groups. Weight loss did not change AVP responses in obese subjects.

CONCLUSION

AVP secretion in response to acute hypo- and hyperosmolality is not different in normal weight and obese subjects. There is no correlation between leptin and AVP in normal weight or obese subjects.

[Walking in the International Four Days Marches Nijmegen: an estimation of the risks]

In 2006, the annual Four Days Marches in Nijmegen, the Netherlands, were cancelled after the first day because two participants had died, and many had become unwell while walking in unusually high ambient temperatures. During the 2007 edition, an observational study of the physiological impact and health risks for walkers was carried out. This time, the ambient conditions were mild. Most participants (90.7%) finished the march without serious complaints or clinical complications, despite significant disturbances in fluid balance and electrolytes. The training level of the participants varied considerably. If we compare the results of this physiological study with studies during marathons, similarities in physiological adaptions are found, most probably due to the same biological mechanisms. However, the participants of the Four Days Marches are incomparable with long-distance runners. There is as yet no well-founded advice concerning the fluid intake of Four Days Marches participants. Increase or decrease in body weight may be an interesting diagnostic tool to measure the risk of dehydration or overhydration.

Loss of 50% of excess weight using a very low energy diet improves insulin-stimulated glucose disposal and skeletal muscle insulin signalling in obese insulin-treated type 2 diabetic patients

AIMS/HYPOTHESIS

Both energy restriction (ER) per se and weight loss improve glucose metabolism in obese insulin-treated type 2 diabetic patients. Short-term ER decreases basal endogenous glucose production (EGP) but not glucose disposal. In contrast the blood glucose-lowering mechanism of long-term ER with substantial weight loss has not been fully elucidated. The aim of this study was to investigate the effect of loss of 50% of excess weight [50% excess weight reduction (EWR)] on EGP, whole-body insulin sensitivity and the disturbed myocellular insulin-signalling pathway in ten obese insulin-treated type 2 diabetic patients.

METHODS

A euglycaemic-hyperinsulinaemic clamp with stable isotopes ([6,6-(2)H2]glucose and [2H5]glycerol) combined with skeletal muscle biopsies was performed during a very low energy diet (VLED; 1,883 kJ/day) on day 2 and again after 50% EWR. Oral blood glucose-lowering agents and insulin were discontinued 3 weeks prior to the VLED and at the start of the VLED, respectively.

RESULTS

Loss of 50% EWR (20.3+/-2.2 kg from day 2 to day of 50% EWR) normalised basal EGP and improved insulin sensitivity, especially insulin-stimulated glucose disposal (18.8+/-2.0 to 39.1+/-2.8 micromol kg fat-free mass(-1) min(-1), p=0.001). The latter was accompanied by improved insulin signalling at the level of the recently discovered protein kinase B/Akt substrates AS160 and PRAS40 along with a decrease in intramyocellular lipid (IMCL) content.

CONCLUSIONS/INTERPRETATION

Considerable weight loss in obese, insulin-treated type 2 diabetic patients normalises basal EGP and improves insulin sensitivity resulting from an improvement in insulin signal transduction in skeletal muscle. The decrease in IMCL might contribute to this effect.

[Measures to prevent or delay type 2 diabetes mellitus]

--The incidence of type 2 diabetes mellitus is increasing, as is the rate of related long-term complications. --Increased body weight and lack of exercise are the major non-genetic factors that are responsible for the increased incidence of type 2 diabetes mellitus. --People predisposed to developing type 2 diabetes mellitus can be identified easily by taking a patient history (e.g. genetic predisposition, gestational diabetes, medication), performing a physical examination (e.g. body-mass index, fat distribution) and laboratory tests (e.g. impaired fasting and post-load blood glucose levels). --Intensive lifestyle modifications reduce the risk of type 2 diabetes mellitus by 42-58%. --Drug therapy is less effective than lifestyle modifications in the prevention of type 2 diabetes mellitus. Moreover, the disease course after treatment is discontinued is unknown. --Successful intervention resulting in a sustained effect is expected to have a preventive effect on the long-term complications of type 2 diabetes mellitus.

Plasma arginine vasopressin and atrial natriuretic peptide concentration in patients with hyponatremia at diagnosis and following treatment

BACKGROUND

Much evidence for arginine vasopressin (AVP) and atrial natriuretic peptide (ANP) in the pathogenesis of hyponatremia in humans is based on single measurements. To study the roles of AVP and ANP in the pathogenesis and recovery of hyponatremia, sequential measurements of ANP and AVP were taken during treatment in a group of hyponatremic patients with different etiologies.

METHODS

Consecutive adult patients with hyponatremia (serum Na <130 mmol/l) and healthy controls were studied. Volume status was determined by clinical and laboratory criteria. Plasma AVP and ANP, fractional sodium excretion, and urine osmolality were determined daily until serum Na was above 135 mmol/l or for at most 7 days.

RESULTS

A total of 16 controls and 40 hyponatremic patients (12 normovolemic, 9 hypervolemic, and 19 hypovolemic) were studied. Patients' plasma AVP on the first day [1.0 (0.3-2.3) ng/l] and on the last day [1.1 (0.3-2.5) ng/l] of the study did not differ from that of controls [0.7 (0.5-1.0) ng/l]. Serum sodium concentration increased significantly in patients between the first and the last day. Patients had significantly lower ANP concentrations, both on the first day [25 (15-46) ng/l] and on the last day [29 (17-46) ng/l], than controls [41 (28-51) ng/l]. Plasma AVP was elevated relative to serum osmolality on the first day and to a lesser extent on the last day of the study.

CONCLUSIONS

AVP is inappropriately high in a majority of hyponatremic patients. Plasma AVP and ANP concentrations do not change during treatment in hyponatremic patients despite a significant increase in serum osmolality. A low ANP concentration in clinically normovolemic and hypovolemic patients indicates volume depletion, which may lead to baroreceptor-stimulated AVP secretion.

[Hyponatraenmia during a long-distance run: due to excessive fluid intake]

Hyponatraemia during a long-distance run, such as a marathon, is usually mild and asymptomatic. However, in runners who present with symptoms at a healthcare station, the diagnosis of hyponatraemia can have significant consequences. The complaints are usually aspecific, but in more severe hyponatraemia, signs of cerebral dysfunction due to incipient to severe cerebral oedema predominate. The most important aetiological factor is an excessive electrolyte-free fluid intake. The most important risk factors for the development of hyponatraemia are: a long duration of the run, female gender, recent use of NSAIDs, lower body weight and environmental factors like high temperature and high humidity. In the presence of symptoms, rapid correction must be started by administration ofhypertonic saline, sometimes in combination with a loop diuretic in cases of eu- and hypervolaemia. Isotonic saline must be added in case of dehydration. Prevention consists primarily of advice to moderate the fluid intake.

Cardiovascular risk factors after bariatric surgery: Do patients gain more than expected from their substantial weight loss?

BACKGROUND

While it has been established that even limited weight loss (5-10%) improves obesity-associated cardiovascular risk factors, it is not known if considerable weight loss following laparoscopic adjustable silicone gastric banding (LASGB) results in a cardiovascular risk profile that is comparable, worse, or even better than that of matched control subjects.

METHODS

Cardiovascular risk factors were compared in three groups of 24 women each: an index group that had lost considerable weight following LASGB for morbid obesity (BMI>40 kg/m(2)), a control group with the same BMI that the index group achieved after weight loss, and a pre-weight loss group of women with a BMI above 40 kg/m(2). Anthropometric measures, fasting serum glucose, insulin, lipids, C-reactive protein, and homocysteine levels were determined and insulin sensitivity was estimated using a homeostasis model assessment index (HOMA-IR).

RESULTS

After bariatric surgery, the index group had a BMI of 32.0+/-0.8 kg/m(2). This resulted in a significantly better cardiovascular risk profile than that of the pre-weight loss group (BMI 42.8+/-0.6 kg/m(2)). Unexpectedly, after weight loss, the index group had significantly lower systolic blood pressure, fasting serum insulin, and HOMA-IR than the BMI-matched (32.8+/-0.9 kg/m(2)) control group. Although not significant, diastolic blood pressure, LDL-cholesterol, and CRP levels were also lower.

CONCLUSION

Considerable weight loss following bariatric surgery leads to a greater improvement in cardiovascular risk factors than might be expected from the weight loss.

[Thyroid function, activities of daily living and survival in extreme old age: the 'Leiden 85-plus Study']

OBJECTIVE

To determine the relationship between differences in thyroid function, changes in the activities of daily living and survival in the extremely-old segment of the general population in order to see whether screening for and treatment of subclinical thyroid-function disorders in the elderly will have a positive effect.

DESIGN

Prospective observational population study among 85-year-olds.

METHOD

As part of the 'Leiden 85-plus Study', all persons were followed who had their 85th birthday during the period from 1 September 1997 to 31 August 1999 (average length of time followed: 3.7 years; SD: 1.4). There were 558 participants. The thyroid function of these subjects was determined and the limitations in the activities of daily living, depressive symptoms, cognitive function and mortality were recorded annually.

RESULTS

At the age of 85, there was no relation between the serum levels of thyroid-stimulating hormone (TSH) or free thyroxine (FT4) and limitations in the activities of daily living, the occurrence of depressive symptoms and cognitive deterioration. Neither was any relationship found during the period of follow-up. A higher TSH-level was associated with a lower mortality, even after correction for the differences in performance and health during the base measurement (mortality risk: 0.77 per SD-increase in TSH; 95% CI: 0.63-0.94). The mortality risk per SD-increase in FT4 was 1.16 (95% CI: 1.04-1.30).

CONCLUSION

From the age of 85, there was no relationship between thyroid function and limitations in the activities of daily living, the occurrence of depressive symptoms or a deterioration in cognitive functions. Moreover, elderly persons with a less active thyroid gland lived longer. This raises the question whether the screening for and treatment of subclinical thyroid-function disorders in persons of extreme old age, as recommended, will have any positive effects.

A nasal squamous cell carcinoma complicated by a paraneoplastic syndrome consisting of a myositis and anti-Jo-1 autoantibodies

We report a female patient with the clinical features of a Jo-1-syndrome as a paraneoplastic phenomenon secondary to a nasal squamous cell carcinoma.

The metabolic syndrome: a vascular perspective

The metabolic syndrome (MS) is a clustering of cardiovascular risk factors. Current definitions of MS use hypertension, waist circumference, fasting glucose, triglyceride and HDL-cholesterol levels as defining variables. The prevalence of MS is increasing in our society due to lifestyle changes that result in decreased physical activity and increased body weight. Patients with MS have a three times greater risk of coronary heart disease and stroke, and a two to four times greater risk of dying from atherosclerotic coronary heart disease than those without MS. Imaging studies have shown an increased burden and progression of atherosclerosis. Also, MS patients seem to be more vulnerable to events at comparable levels of atherosclerosis. First-line treatment for MS is therapeutic lifestyle intervention, including exercise and weight reduction. Medical intervention strategies using blood pressure-lowering medication, statins, fibrates and metformin seem the most appropriate to date. The effects of thiazolidinediones on cardiovascular endpoints have not been studied to a large extent in the setting of MS. Evidence regarding risk assessment and optimal medical strategies will be an important aspect of vascular research in the coming years.

Vasopressin: physiology and clinical use in patients with vasodilatory shock: a review

Vasopressin is a nonapeptide synthesised in the hypothalamus and released upon stimulations such as hyperosmolality, hypotension and hypovolaemia. In acute shock states serum vasopressin levels increase rapidly and decrease in prolonged septic shock. The administration of vasopressin in healthy subjects has little effect, whereas in vasodilatory shock it increases the mean arterial pressure through V1 receptors and decreases the cardiac output. Vasopressin stimulates the V2 receptors in the kidney leading to reabsorption of water through aquaporin 2. However, in vasodilatory shock the antidiuretic effects are overcome by the effect vasopressin has on the kidneys: improvement of renal blood flow leading to water excretion. Twenty-four studies on the use of vasopressin in patients with vasodilatory shock are reviewed. They show that vasopressin potentiates norepinephrine effects, increases blood pressure significantly in patients with vasodilatory shock and may improve renal function. Side effects ranging from ischaemic skin lesions to possible intestinal ischaemia should not be underestimated. Above a dose of 0.04 U/min it may lead to cardiac arrest. Effects on mortality cannot be interpreted from these studies. Broad clinical use should await controlled trials to clarify its effects on clinical outcomes such as organ failure and mortality.

Factors predicting the blood glucose lowering effect of a 30-day very low calorie diet in obese Type 2 diabetic patients

OBJECTIVE

To identify factors which predict the blood glucose lowering effect of monotherapy with a 30-day very low calorie diet (VLCD) in obese Type 2 diabetic patients. A responder was a priori defined as a patient with a fasting plasma glucose (FPG) level < 10 mmol/l on day 30.

RESEARCH DESIGN AND METHODS

In 17 obese patients (BMI 37.6 +/- 5.6 (mean +/- SD) kg/m(2)) with Type 2 diabetes, all blood glucose lowering medication (including insulin) was discontinued on day -1 followed by a 30-day VLCD. On day 2 and 30 of the VLCD an intravenous glucose tolerance test (IVGTT) was performed.

RESULTS

Of the 14 patients who completed the 30-day VLCD, eight qualified as responder. Responders and non-responders could be distinguished by day 2. Responders had a shorter duration of Type 2 diabetes and higher fasting serum insulin, C-peptide and HOMA-beta-values. In addition, responders displayed a more prominent second-phase insulin response following i.v. glucose loading and higher k-values. In a stepwise discriminant analysis, the change in FPG from day 0 to day 2 (responders +0.64 +/- 2.3, non-responders +4.15 +/- 3.3 mmol/l, P = 0.035) in combination with the area under the curve of insulin (AUC) above baseline during an IVGTT on day 2 (responders 571 +/- 236, non-responders 88 +/- 65 mU*50 min, P < 0.001), distinguished responders completely from non-responders.

CONCLUSION

Preservation of the capacity of beta-cells to secrete insulin predicts a favourable metabolic response to a VLCD in obese Type 2 diabetic patients.

[The value and limitations of the body mass index (BMI) in the assessment of the health risks of overweight and obesity]

--The Body Mass Index (BMI) is used as a measure of overweight and obesity. In epidemiological studies age, sex and ethnic background all have to be taken into consideration, particularly when determining the health risk caused by the amount of body fat. --Caution should be observed when using the BMI as a measure for interpreting overweight and obesity as body composition can be highly variable yet have the same BMI. Therefore, BMI is not a reliable measurement of body composition in individuals particularly in older and younger people. --Excess body fat in the visceral depot poses a separate health risk. The BMI does not give any insight into regional body fat distribution. Waist circumference is a valid index of visceral fat accumulation and can therefore be used as an indicator of health risks associated with visceral obesity.

Pulsatile LH release is diminished, whereas FSH secretion is normal, in hypocretin-deficient narcoleptic men

Hypocretin (orexin) peptides are involved in the regulation of energy balance and pituitary hormone release. Narcolepsy is a sleep disorder characterized by disruption of hypocretin neurotransmission. Pituitary LH secretion is diminished in hypocretin-deficient animal models, and intracerebroventricular administration of hypocretin-1 activates the hypothalamo-pituitary-gonadal axis in rats. We evaluated whether hypocretin deficiency affects gonadotropin release in humans. To this end, we deconvolved 24-h serum concentrations of LH and FSH in seven hypocretin-deficient narcoleptic males (N) and seven controls (C) matched for age, body mass index, and sex. Basal plasma concentrations of testosterone, estradiol, and sex hormone-binding globulin were similar in both groups. Mean 24-h LH concentration was significantly lower in narcolepsy patients [3.0 +/- 0.4 (N) vs. 4.2 +/- 0.3 (C) U/l, P = 0.01], which was primarily due to a reduction of pulsatile LH secretion [23.5 +/- 1.6 (N) vs. 34.3 +/- 4.9 (C) U.l(-1).24 h(-1), P = 0.02]. The orderliness of LH and FSH secretion, quantitated by the approximate entropy statistic, was greater in patients than in controls. In contrast, all other features of FSH release were similar in narcoleptic and control groups. Also, LH and FSH secretions in response to intravenous administration of 100 microg of GnRH were similar in patients and controls. These data indicate that endogenous hypocretins are involved in the regulation of the hypothalamo-pituitary-gonadal axis activity in humans. In particular, reduced LH release in the face of normal pituitary responsivity to GnRH stimulation in narcoleptic men suggests that hypocretins promote endogenous GnRH secretion.

Impact of Meal Timing and Frequency on the Twenty-Four-Hour Leptin Rhythm

OBJECTIVE

To study the influence of changes in meal timing and frequency on the diurnal rhythm of leptin and on the 24-hour profile of insulin and glucose.

PATIENTS AND METHODS

Five obese women were studied twice during a weight-maintaining diet in either 3 daily or 8 day and night equal portions. Blood was sampled for 24-hour profiles of leptin and insulin.

RESULTS

During the 8-meal intervention, the 24-hour rhythm of leptin changed significantly: the amplitude decreased (p = 0.0089) and the acrophase was delayed by 168 min (p = 0.021). Also, 8 small insulin secretion peaks occurred instead of the 3 postprandial high insulin peaks.

CONCLUSION

The dispersion of food intake over 24 h affects the diurnal leptin rhythm. These changes could not be attributed to changes in circadian timing or energy balance. Instead, changes in daily insulin secretion profiles might play a role.

Effect of atorvastatin on impaired vascular function in healthy old men

OBJECTIVE

This study was initiated to examine the effect of cholesterol-lowering therapy with 40 mg atorvastatin on vascular function in healthy old and young men.

METHODS

We selected healthy normolipidaemic, elderly subjects (n = 8, mean age 80.1 years) and young subjects (n = 7, mean age 21.8 years). All had a normal electrocardiograph and blood pressure, and signs or symptoms of cardiovascular disease were absent. The subjects were studied for 2 days, with 6 weeks of atorvastatin treatment in between. Forearm blood flow (FBF) was measured by computerized venous occlusion plethysmography upon intra-arterial infusion of acetylcholine (ACh; 30 and 90 ng/kg/min) and 5-hydroxytryptamine (5-HT; 0.3 and 0.9 ng/kg/min) as endothelium-dependent vasodilators, and sodium nitroprusside (SNP; 30 and 90 ng/kg/min) as an endothelium-independent vasodilator.

RESULTS

At baseline, the mean absolute FBF in the elderly was 2.6 mL/min/100 mL and in the young 4.3 mL/min/100 mL tissue (P = 0.01). The mean serum total cholesterol levels were 5.2 and 3.8 mmol/L, respectively (P = 0.007). The endothelium-dependent vasodilatation induced by ACh and 5-HT was significantly lower in the elderly compared with the young (both P < 0.01), whereas the endothelium-independent vasodilatation induced by SNP was not significantly lower in the elderly compared with the young. Atorvastatin treatment decreased the serum total cholesterol level with a mean of 38 and 28% in the elderly and the young, respectively (P < 0.001). Impaired endothelium-dependent vasodilatation, however, was not modified (P > 0.65).

CONCLUSIONS

Healthy old men have an impaired endothelium-dependent vascular response but this impairment is not restored by treatment with atorvastatin.

Glucose homeostasis in abdominal obesity: hepatic hyperresponsiveness to growth hormone action

It has been suggested that (abdominally) obese individuals are hypersensitive to growth hormone (GH) action. Because GH affects glucose metabolism, this may impact glucose homeostasis in abdominal obesity. Therefore, we studied the effect of GH on glucose metabolism in abdominally obese (OB) and normal-weight (NW) premenopausal women. A 1-h intravenous infusion of GH or placebo was randomly administered to six NW [body mass index (BMI) 21.1 +/- 1.9 kg/m(2)] and six OB (BMI 35.5 +/- 1.5 kg/m(2)) women in a crossover design. Insulin, glucagon, and GH secretion were suppressed by concomitant infusion of somatostatin. Glucose kinetics were measured using a 10-h infusion of [6,6-(2)H(2)]glucose. In both groups, similar physiological GH peaks were reached by infusion of GH. GH strongly stimulated endogenous glucose production (EGP) in both groups. The percent increase was significantly greater in OB than in NW women (29.8 +/- 11.3 vs. 13.3 +/- 7.4%, P = 0.014). Accordingly, GH responsiveness, defined as the maximum response of EGP per unit GH, was increased in OB vs. NW subjects (6.0 +/- 2.1 vs. 2.2 +/- 1.5 micromol.min(-1).mU(-1).l(-1), P = 0.006). These results suggest that the liver is hyperresponsive to GH action in abdominally obese women. The role of the somatotropic ensemble in the control of glucose homeostasis in abdominal obesity is discussed.

[Tetany due to excessive use of alcohol: a possible magnesium deficiency]

Two alcoholic patients, a woman aged 64 and a man aged 69 years, were admitted with tetany. Both had severe electrolyte disorders, with low plasma levels of calcium, magnesium and potassium. Following mineral supplementation both patients recovered. Hypomagnesaemia plays a central role in the pathophysiology of this syndrome. Chronic alcohol abuse results in hypomagnesaemia in 30% of patients by decreasing renal tubular reabsorption. Hypomagnesaemia leads to suppression of parathyroid-hormone secretion, parathyroid-hormone resistance and vitamin-D suppression, resulting in hypocalcaemia. Hypomagnesaemia also causes kaliuresis leading to hypokalaemia. Supplementation with magnesium is crucial in the treatment of this combined electrolyte disorder.

Exophthalmos in Obesity

AIMS

To establish the relationship between exophthalmos and obesity.

METHODS

A group of 19 obese patients (body mass index, BMI >/=30 kg/m(2)) was compared with a control group of 45 nonobese individuals (26 > BMI >/= 20 kg/m(2)). Both groups underwent Hertel's exophthalmometry, Goldmann applanation tonometry and measurement of the medial rectus muscle by echography.

RESULTS

Obese patients had higher Hertel values and enlarged medial rectus muscle diameter (p < 0.05). Indeed, bilateral exophthalmos was observed in 33% of obese subjects. However, this did not cause any ocular morbidity. In some cases the difference in intraocular pressure was enlarged but together with the exophthalmos not statistically significant.

CONCLUSIONS

Standard values for exophthalmometry and orbital echography may have to be adapted for obese individuals. In several cases the eye signs had a remarkable resemblance to patients with Graves' orbitopathy. So in each patient with bilateral exophthalmos and eye signs suspicious of Graves' orbitopathy obesity should be considered as a possible cause.

[Overweight and obesity; recommendations from the National Health Council]

The Health Council of the Netherlands has issued a report on overweight and obesity. These are considered major threats to personal health, the public health care services and economic welfare. Overweight and obesity are no longer considered variations of the norm, but as a disease. As genetically predisposing factors cannot be influenced, major initiatives to contain further deterioration of the problem must be on environmental factors i.e. on macronutrient intake and physical exercise. Special target groups (young people, people of low socioeconomic status and immigrants) need to be defined. Government, health care organisations, industry and the general public should work together to combat overweight and obesity. The chances of success are not predictable but are certainly big enough to justify action.

Decrease of hemostatic cardiovascular risk factors by aggressive vs. conventional atorvastatin treatment in patients with Type 2 diabetes mellitus

BACKGROUND

Patients with Type 2 diabetes mellitus have increased levels of hemostatic risk variables for cardiovascular disease, such as fibrinogen, von Willebrand factor (VWF), factor (F)VIIa, d-dimer and plasminogen activator inhibitor-1 (PAI-1).

OBJECTIVES

To evaluate the effect of aggressive vs. standard dose atorvastatin on hemostatic cardiovascular risk factors in patients with Type 2 diabetes mellitus.

PATIENTS AND METHODS

The effect of 30 weeks of treatment with atorvastatin 10 and 80 mg on hemostatic cardiovascular risk factors was assessed in a randomized double-blind placebo-controlled trial on 217 patients with Type 2 diabetes mellitus and dyslipidemia.

RESULTS AND CONCLUSIONS

Atorvastatin 10 and 80 mg dose-dependently reduced d-dimer (7.4% and 8.5%, respectively, P for trend = 0.004) and PAI-1 antigen levels (9.0% and 18%, respectively, P for trend = 0.021). Levels of fibrinogen, VWF, tissue-type plasminogen activator and FVIIa were not influenced by atorvastatin. In conclusion, in patients with Type 2 diabetes mellitus, atorvastatin dose-dependently improved the levels of the hemostatic risk variables d-dimer and PAI-1.

Adipose tissue as an endocrine organ: impact on insulin resistance

It is well known that obesity is associated with insulin resistance and an increased risk for type 2 diabetes mellitus. Formerly it was postulated that increased lipolysis and consequently free fatty acid (FFA) production, from with triglycerides overloaded fat cells, would disrupt glucose homeostasis via Randle's hypothesis. Lipodystrophy, however, also leads to insulin resistance. Recently it has become clear that adipose tissue functions as an endocrine organ and secretes numerous proteins in response to a variety of stimuli. These secreted proteins exert a pleiotropic effect. The proteins that are involved in glucose and fat metabolism and hence can influence insulin resistance are discussed in this paper. They include leptin, resistin, adiponectin, acylation-stimulating protein, tumour necrosis factor-alpha and interleukin-6. The stimuli for production and the site and mechanism of action in relation to insulin resistance will be discussed. None of these proteins are, however, without controversy with regard to their mechanism of action. Furthermore, some of these proteins may influence each other via common signalling pathways. A theory is presented to link the interrelationship between these adipocyte secretory products and their effect on insulin resistance.

Effects of recombinant human leptin treatment as an adjunct of moderate energy restriction on body weight, resting energy expenditure and energy intake in obese humans

We explored the effects of recombinant human leptin (rL) as an adjunct of mild energy restriction (2092 kJ/day less than needed) in the treatment of obese humans as part of a larger multicentre trial. In a double blind, randomised, placebo (P)-controlled design, the effects of 10 mg of rL once daily vs twice daily (rL OD/BID, by s.c. injection) upon body weight, resting energy expenditure (REE) and energy intake were compared. The study groups comprised 9 (P), 15 (rL OD) and 6 (rL BID) healthy subjects (body mass index 27.5-35 kg/m2). We observed in both groups treated with rL a decline of body weight. [2.8+/-1.1 kg (P), 5.2+/-0.9 kg (rL OD), 7.9+/-1.4 kg (rL BID), p < 0.035]. No significant effects of rL treatment upon energy intake or REE were observed. However, rL tended to reduce the decline of energy expenditure associated with energy restriction, whereas the tendency of energy intake to increase back to baseline levels in placebo-treated subjects was largely prevented in subjects treated with rL. Thus, rL appears to enhance the loss of body weight in obese humans in a dose-dependent fashion if prescribed as an adjunct of energy restriction. This effect might be mediated by rL ability to counteract the behavioural and metabolic adaptations that accompany weight loss attempts.

Statins in type 2 diabetes mellitus: target on lipids and vascular wall function

The typical dyslipidaemia in type 2 diabetes mellitus shows high levels of triglycerides, low levels of highdensity lipoprotein cholesterol (HDL-c) and small dense low-density lipoprotein (LDL) particles. In these patients low-dose atorvastatin (10 mg) results in a significant and relevant reduction in triglycerides and LDL-c. High-dose atorvastatin (80 mg) results in a better LDL-c reduction. The endothelial dysfunction is likely to be caused by factors related to insulin resistance and not by dyslipidaemia alone. The results from the DALI study (Diabetes Atorvastatin Lipid Intervention) on lipids and endothelial function are discussed, together with two invasive endothelial function studies in diabetics and hypertriglyceridaemic patients. The subgroup of diabetics in the large secondary prevention trials using statins are analysed with respect to total cholesterol lowering and death due to coronary heart disease and nonfatal myocardial infarction.

[Atherosclerosis and inflammation: the role of C-reactive protein]

C-reactive protein (CRP) is an acute phase protein, the serum concentration of which can increase up to a 1000-fold after the onset of a stimulus. It plays a role in the aspecific immune response to bacteria and fungi and the clearance of apoptotic cell material. Inflammation plays an important role in the aetiology and pathogenesis of atherosclerosis and plaque formation. Approximately fifty percent of acute coronary syndromes are the consequence of unstable plaques rupturing, followed by thrombus formation. A characteristic of these unstable plaques is an increase in inflammatory cells (macrophages and T lymphocytes). The serum concentration of CRP might reflect the amount of inflammation within atherosclerotic plaques and thus might provide an indirect measurement of the instability of the plaques. CRP could therefore have a predictive value for the occurrence of plaque rupture. Furthermore, there are indications that CRP itself is active in the inflammatory process. Prospective studies have shown that so-called high-sensitivity CRP (hsCRP) measurements could be used as a tool for determining the risk for acute coronary syndromes. The inflammation-inhibiting characteristics of statins and acetylsalicylic acid (especially the reduction of the hsCRP level) might contribute to reducing the risk of plaque rupture.

Gall bladder dysmotility: a risk factor for gall stone formation in hypertriglyceridaemia and reversal on triglyceride lowering therapy by bezafibrate and fish oil

BACKGROUND AND AIM

The aim of this study was to unravel the mechanisms responsible for the increased risk of gall stone disease in hypertriglyceridaemia (HTG) and to compare the effects of triglyceride lowering therapy by bezafibrate and fish oil on determinants of cholelithiasis (biliary lipid composition and gall bladder motility) in HTG patients.

PATIENTS AND METHODS

Gall bladder motility (ultrasonography) was studied postprandially and during infusion of cholecystokinin (CCK). Determinants of cholelithiasis and serum lipids were compared between nine HTG patients and 10 age, sex, and body mass index matched normolipidaemic controls. The effects of bezafibrate and fish oil in HTG patients were studied in a randomised cross over trial.

RESULTS

HTG patients showed 14-fold higher serum triglyceride (TG) levels than controls. Biliary lipid composition, fasting gall bladder volumes, and CCK levels did not differ between HTG patients and controls. Gall bladder emptying was reduced in HTG patients compared with controls during CCK infusion (-22%) as well as in response to a meal (-37%; both p<0.001). Postprandial CCK levels were significantly higher in HTG patients. Both bezafibrate and fish oil reduced serum TG levels (-68% and -51% v baseline, respectively; both p<0.01). Fasting CCK levels were not affected whereas CCK induced gall bladder emptying increased during bezafibrate (+29%; p<0.001) and tended to increase on fish oil therapy (+13%; p=0.07). Postprandial gall bladder motility improved on bezafibrate and fish oil (+47 and +25% v baseline, respectively; both p<0.02) at least partly due to increased gall bladder sensitivity to CCK (both p<0.05 v baseline). Bezafibrate but not fish oil increased the molar ratio of cholesterol to bile acids (+40%; p</=0.05) but no effects on cholesterol saturation index were seen with either treatment.

CONCLUSIONS

We suggest that impaired gall bladder motility occurs in HTG patients due to decreased sensitivity to CCK, which may add to the enhanced risk of gall stone disease in HTG patients. Triglyceride lowering therapy by both fish oil and bezafibrate improve gall bladder dysmotility without adversely affecting biliary cholesterol saturation.

Strong decrease of high sensitivity C-reactive protein with high-dose atorvastatin in patients with type 2 diabetes mellitus

OBJECTIVE

Statins are known to reduce CRP concentrations, but whether high doses are more effective is not known.

METHODS

In a prospective double-blind multicenter study in 186 DM2 patients without manifest coronary artery disease and with dyslipidemia, the effect of a 30-week treatment with 10 and 80 mg atorvastatin or placebo on the reduction of hs-CRP levels was measured.

RESULTS

Median CRP levels increased with 6.6% in the placebo group and were reduced by 15 and 47%, respectively, with atorvastatin 10 and 80 mg (P<0.001; significantly different from 10 mg atorvastatin and from placebo (P<0.001). Variation in IL-6 and plasma lipids associated for 21 and 8%, respectively, with variation in CRP levels (P<0.001 and P=0.01). Of patients with a baseline CRP level above an arbitrary threshold of 3.0 mg/l, 56% in the 80 mg atorvastatin group reached a level of less than 3.0 mg/l, versus 23% randomized to 10 mg atorvastatin (P<0.01) and 17% in the placebo group (P<0.005).

CONCLUSIONS

In DM2 patients high dose atorvastatin induced a strong reduction in CRP levels. The decrease in CRP was mainly independent of effects on lipid lowering and changes in IL-6 levels. The pleiotropic effect of high-dose atorvastatin on inflammation could add to its cardioprotective effect in high-risk patients.

Dynamics of the pituitary-adrenal ensemble in hypocretin-deficient narcoleptic humans: blunted basal adrenocorticotropin release and evidence for normal time-keeping by the master pacemaker

Narcolepsy is a sleep disorder caused by disruption of hypocretin (orexin) neurotransmission. It has been suggested that anomalous timing by the biological clock contributes to the symptomatology. Hypocretins stimulate the pituitary-adrenal (PA) axis in rodents. We explored whether hypocretin deficiency disrupts circadian timing and blunts PA hormone release. We deconvolved 24-h plasma profiles of ACTH and cortisol, and determined their circadian rhythm by cosinor analysis in seven hypocretin-deficient narcoleptic males and seven matched controls. Basal and total ACTH production were blunted in narcoleptics [310 +/- 86 vs. 760 +/-160 ng/liter.24 h (P = 0.02) and 920 +/- 147 vs. 1460 +/- 220 ng/liter.24 h (P = 0.04), respectively], whereas pulsatile release did not differ between groups. In contrast, basal, pulsatile and total cortisol secretion were similar in both groups. The cross-approximate entropy of the joint ACTH/cortisol time series was higher in narcoleptics (1.26 +/- 0.07 vs. 1.07 +/- 0.04; P = 0.04), reflecting reduced secretory process regularity. The acrophases of both ACTH and cortisol occurred at similar clock times (approximately 0830 h) in patients and controls, which supports the idea that the master pacemaker is intact in narcolepsy. The reduced (basal) ACTH secretion and the diminished secretory process regularity of the ACTH/cortisol ensemble conjointly suggest that hypocretin deficiency induces changes in the interplay between PA hormones.

Selection for the internal medicine residency programme in the Leiden region

BACKGROUND

The selection and the professional training for a resident in internal medicine requires a great investment of time, training effort and money. Drop-outs are therefore considered a failure of the selection procedure. To evaluate our selection model and outcome of the training programme, we determined the drop-out rate at the Leiden University Medical Centre with its affiliated hospitals.

METHODS

Data were collected from all files that have been kept from 1988 onwards of all internists trained and registered in Leiden. These files contained the application forms, the assessments of the trainers and references and the specifications of the programme. Also the first employment as board-certified internist is registered.

RESULTS

The drop-out percentage of the training programme was 8.5%. The drop-outs did not differ in study characteristics from those who successfully completed the programme. The reports from the training team members showed that the drop-outs were as suitable and motivated as the other candidates. During the training programme 8.5% of the residents moved to another university to complete their training as an internist. All board-certified internists who graduated at the Leiden University Medical Centre found a job.

CONCLUSIONS

The efficacy of the selection procedure for trainee internists is more than 90%. There are no studies in the literature for a comparison of data.

Insulin resistance but not hypertriglyceridemia per se is associated with endothelial dysfunction in chronic hypertriglyceridemia

OBJECTIVES

To infer the relative impact of elevated triglyceride levels and insulin resistance on endothelial dysfunction in patients with chronic hypertriglyceridemia (HTG).

METHODS

Endothelial function was studied in 11 HTG patients and 16 normolipidemic controls. Cumulative-dose infusions of 5-hydroxytryptamine (5HT) and sodium nitroprusside were infused locally into the brachial artery to study endothelium-dependent and endothelium-independent vasodilation, respectively. Data of the HTG patients were dichotomized around the median of insulin resistance, calculated as HOMA-index, forming HTG groups with mild (HTG-MIR) and severe insulin resistance (HTG-SIR).

RESULTS

HTG patients had higher triglyceride levels and smaller LDL particle size than controls (both P< or =0.001), whereas these parameters did not differ between both HTG groups. Insulin resistance was higher in both HTG groups than in controls (11.1 (7.0-14.5) and 4.9 (4.0-6.7) vs. 2.4 (4.9-5.2), respectively, both P<0.001). Similarly, free fatty acid levels, another indicator of insulin resistance, were highest in the HTG-SIR group, followed by those in the HTG-MIR and control group (0.7 (0.6-0.8), 0.5 (0.4-0.6) and 0.4 (0.3-0.4) mmol/l, respectively, all P<0.05). Endothelial-dependent vasodilation was similar in HTG-MIR and controls. In contrast, the response to 5HT was attenuated in the HTG-SIR group compared to controls (low and high dose by, respectively, -60 and -44%, both P<0.01), and tended to be lower than in the HTG-MIR group (-43%, P=0.068 and -41%, P=0.100, respectively). Endothelium-independent vasodilation did not differ between the three groups.

CONCLUSION

These findings indicate that chronic hypertriglyceridemia per se is not associated with endothelial dysfunction. In contrast, the presence of insulin resistance, characterized by hyperinsulinemia and FFA elevation, contributes to the induction of endothelial dysfunction in chronic HTG.

Reduction of plasma leptin levels and loss of its circadian rhythmicity in hypocretin (orexin)-deficient narcoleptic humans

Recent observations have implicated hypocretin deficiency in the pathogenesis of narcolepsy. Hypocretin neurotransmission also affects energy balance, and narcoleptic patients tend to become obese. Because hypocretins appear to have important neuroendocrine effects, we hypothesized that the neuroendocrine systems that regulate energy balance might be distinctly set in narcolepsy. As leptin is a pivotal part of these systems, we explored the 24-h plasma leptin (20-min sampling interval) concentration profile in six narcoleptic males and six normal controls, matched for age, sex, body mass index, waist/hip ratio, and fat mass. We thus demonstrated a reduction of the mean 24-h leptin concentration in narcoleptics to 52% of that in controls (5.9 microg/liter in narcolepsy vs. 11.4 microg/liter in controls; P < 0.05). Further, a nocturnal acrophase (clock time of the highest concentration), which is typical of normal leptin secretion, was observed in controls (mean, 2335 h; 95% confidence interval, 2105-0205 h), but not in narcoleptic patients. The mechanisms that potentially disturb the circadian rhythm of leptin levels in hypocretin-deficient narcoleptic humans include anomalies of the sleep-wake cycle and/or disruption of the circadian distribution of autonomic activity. As leptin deficiency clearly leads to morbid obesity in experimental animals and humans, we infer that the observed reduction of plasma leptin levels may predispose narcoleptic humans to weight gain.

Food choice in hyperthyroidism: potential influence of the autonomic nervous system and brain serotonin precursor availability

We explored energy and macronutrient intake in patients with Graves' hyperthyroidism. We specifically hypothesized that hyperthyroidism is associated with increased appetite for carbohydrates, because of enhanced sympathetic tone and diminished serotonin mediated neurotransmission in the brain. To test this hypothesis, we measured food intake by dietary history and food selected for lunch in the laboratory in 14 patients with Graves' hyperthyroidism. Twenty-four-hour catecholamine excretion was used as a measure of activity of the sympathetic nervous system (SNS) and the plasma [Trp]/[NAA] ratio was measured to estimate (rate limiting) precursor availability for brain 5-hydroxytryptamine synthesis. All measurements were repeated after the subjects had been treated to establish euthyroidism. In addition, the effects of nonselective beta-adrenoceptor blockade upon these parameters were studied to evaluate the influence of beta-adrenergic hyperactivity on food intake. Hyperthyroidism was marked by increased SNS activity and reduced plasma [Trp]/[NAA] ratio. Accordingly, energy intake was considerably and significantly increased in hyper vs. euthyroidism, which was fully attributable to enhanced carbohydrate consumption, as protein and fat intake were not affected. These results suggest that hyperthyroidism alters the neurophysiology of food intake regulation. Increased SNS activity and reduced Trp precursor availability for 5-hydroxytryptamine synthesis in the brain may drive the marked hyperphagia and craving for carbohydrates that appears to characterize hyperthyroid patients. Because propranolol did not affect food intake in hyperthyroidism, the potential effect of catecholamines on food intake might be mediated by alpha-adrenoceptors.

Altered neuroregulation of GH secretion in viscerally obese premenopausal women

We used deconvolution analysis of 24-h plasma GH concentration profiles (10- min sampling intervals) to appraise GH secretion rates and elimination kinetics in obese (body mass index, approximately 34 kg/m2) premenopausal women with large visceral fat area (LVFA; n = 8) vs. small visceral fat area (SVFA; n = 8) as determined by magnetic resonance imaging. The subjects were matched for body mass index, body fat percentage, and age. The impact of the loss of 50% of prestudy weight excess induced by caloric restriction was assessed as well. The results were compared with those obtained in normal weight control women (n = 8). LVFA subjects manifested markedly (4-fold) reduced mean plasma GH levels, which was brought about by jointly diminished basal and pulsatile GH secretion. Moreover, visceral obesity was associated with loss of regularity of GH release, as established by the approximate entropy statistic. In contrast, SVFA subjects produced normal daily amounts of GH and exhibited mean 24-h plasma GH concentrations that were similar to those in normal weight controls. GH half-life and distribution volume were not different among the study groups. Importantly, weight loss did not affect the daily GH secretion rate in LVFA women, so that their mean plasma GH concentration remained considerably reduced (approximately 50%) compared with controls (despite the loss of approximately 40% of visceral fat). Normal GH kinetics in SVFA women were not significantly influenced by weight reduction. Thus, GH neuroregulation appears to be particularly altered in obese women with a tendency to store fat in their visceral adipose depot. Because weight loss did not reverse GH secretion rate in viscerally obese women, we speculate that relative hyposomatotropism is a primary feature of these women, which could be involved in their tendency to preferentially store excess fat in visceral adipose tissue.

Impaired endothelium-dependent vasodilation in type 2 diabetes mellitus and the lack of effect of simvastatin

OBJECTIVE

Although type 2 diabetes is recognized as an independent risk factor for cardiovascular disease and cardiovascular disease is associated with endothelial dysfunction, the influence of type 2 diabetes per se on the endothelial function is controversial. HMG-CoA-reductase inhibitors have been shown to have short-term beneficial effects on endothelial dysfunction among patients with dyslipidemia or cardiovascular disease. The effect of HMG-CoA reductase inhibitors on the endothelial function in diabetes is largely unknown.

METHODS

Seventeen patients with type 2 diabetes, free of cardiovascular disease and no other cardiovascular risk factors, except for dyslipidemia, were studied together with ten healthy volunteers. The effect of 5-hydroxytryptamine, as an endothelium-dependent vasodilator, and sodium nitroprusside, as an endothelium-independent vasodilator, on the forearm blood flow was measured using venous occlusion plethysmography.

RESULTS

5-Hydroxytryptamine and sodium nitroprusside, infused in the brachial artery, caused a dose-dependent vasodilation. The vasodilator response to 5-hydroxytryptamine was significantly lower among the diabetic patients, 42 and 56%, than among the controls, 73 and 103%, at a dose of 0.3 and 0.9 ng/kg/min, respectively (P<0.05 and P<0.001). Vasodilator responses to sodium nitroprusside were comparable among the diabetic patients and controls. A 6-week treatment with simvastatin 40 mg once daily did not change the vasodilator responses to 5-hydroxytryptamine or sodium nitroprusside among the patients with diabetes.

CONCLUSIONS

The results of this study indicate that the endothelial function is impaired in type 2 diabetes and is not restored after a 6-week treatment period with simvastatin 40 mg.

[Role of statins in prevention of stroke and dementia]

There is accumulating evidence that statins reduce stroke risk, even though total cholesterol is not a risk factor for stroke. The explanation for this discrepancy is subject to discussion. It should be realised that the beneficial effects of statins on stroke risk have only been demonstrated in a select population, i.e. middle-aged men with ischaemic heart disease. Several clinical trials are underway to examine the effects of statins on stroke risk in more characteristic groups of patients who are at increased risk of developing stroke. The results of these studies should be awaited before statins are recommended for the prevention of stroke. Recently it has been reported that statins lower the risk of developing dementia. These conclusions were drawn from two cross-sectional studies. Because of the nature of the studies, only an association between the use of statins and a lower risk of developing dementia was shown, and not a causal relationship. Experimentally-controlled studies have to be designed to investigate the effect of statins on dementia.

Pathogenesis of malignant ascites: Starling's law of capillary hemodynamics revisited

Peritonitis carcinomatosa, indicating the presence of malignant cells in the peritoneal cavity, is a well-known complication of malignant disease. As a result, so-called malignant ascites develops. Malignant ascites is a debilitating condition for which no effective anti-tumor therapy is available. Frequent draining may be necessary to relieve pain and discomfort. Most studies regarding malignant ascites focus on diagnosis and treatment. In this paper. we will address the subject from a pathophysiologic perspective, using the characteristics of malignant ascites, Starling's equation of capillary forces, and recent knowledge regarding biologically active peptides produced by tumor cells. Following this approach. apart from decreased lymphatic ascites absorption, increased net capillary fluid-production can be identified as a contributing feature of ascites formation. The increased net filtration is due to an increase of overall capillary membrane-surface, increased capillary permeability and a subsequent increase of intraperitoneal protein concentration leading to increased intraperitoneal oncotic pressure. This sequence might be the result of biologically active peptides produced by tumor cells such as vascular endothelial growth factor and basic fibroblast growth factor. Interference with these mediators may serve as a target in future therapeutic strategies.

[The thiazolidinedione derivates: a new class of oral blood glucose lowering agents]

The thiazolidine-dione derivatives are a new class of oral blood-glucose lowering drugs in type 2 diabetes. They increase the sensitivity of target tissues to insulin, thereby reducing insulin resistance. They act by activation of a specific nuclear receptor--the peroxisome proliferator-activated receptor gamma (PPAR-gamma)--which increases transcription of certain genes involved in adipocyte differentiation and lipid and glucose metabolism. They increase glucose disposal, reduce hepatic glucose output and reduce both plasma glucose and circulating insulin. By reducing insulin requirements the hypersecretion of the beta cell can be diminished, thereby sparing beta cell function. Thiazolidine-dione derivatives reduce plasma glycosylated haemoglobin (HbA1c) by about 1 to 2%. Combination therapy with sulphonylurea derivatives or metformin seems to be more effective, i.e. lower dosages of either agent or both are sufficient to achieve the same reduction in plasma glucose and HbA1c as monotherapy. The thiazolidine-dione derivatives are generally well tolerated and the new drugs such as rosiglitazone and pioglitazone do not seem to be associated with idiosyncratic hepatotoxicity.

Renal clearance of endogenous leptin in hypertensive humans with or without renal artery stenosis

In humans, the kidney is involved in leptin clearance from the body. The present study was performed to assess the renal extraction of leptin in hypertensive patients with or without renal artery stenosis. Sixty-five hypertensive subjects (39 males and 26 females) underwent catheterization of the renal artery and both renal veins with blood sampling for measuring leptin levels. Blood flow to both kidneys was measured by the xenon washout technique. From these data, renal leptin uptake and renal fractional extraction of leptin were calculated. Endogenous creatinine clearance ranged from 24 to 191 ml/min in the males and from 20 to 149 ml/min in the females. In 25 patients, radiological signs of renal artery stenosis were present. Total renal leptin uptake by both kidneys averaged 141 +/- 47 ng x min(-1) x 100 g(-1). No differences in leptin uptake were found between males and females or between patients with or without renal artery stenosis. The average renal extraction fraction of leptin was 6 +/- 2%. Renal leptin uptake and renal extraction fraction of leptin did not correlate with arterial leptin concentrations or with blood pressure, endogenous creatinine clearance, or the presence or absence of renal artery stenosis. In hypertensive patients with or without renal artery stenosis, the kidney removes only a small fraction of circulating leptin from the body within one passage. This fraction remains relatively constant despite wide variations in renal function or circulating leptin.

Sympathovagal imbalance in hyperthyroidism

We assessed sympathovagal balance in thyrotoxicosis. Fourteen patients with Graves' hyperthyroidism were studied before and after 7 days of treatment with propranolol (40 mg 3 times a day) and in the euthyroid state. Data were compared with those obtained in a group of age-, sex-, and weight-matched controls. Autonomic inputs to the heart were assessed by power spectral analysis of heart rate variability. Systemic exposure to sympathetic neurohormones was estimated on the basis of 24-h urinary catecholamine excretion. The spectral power in the high-frequency domain was considerably reduced in hyperthyroid patients, indicating diminished vagal inputs to the heart. Increased heart rate and mid-frequency/high-frequency power ratio in the presence of reduced total spectral power and increased urinary catecholamine excretion strongly suggest enhanced sympathetic inputs in thyrotoxicosis. All abnormal features of autonomic balance were completely restored to normal in the euthyroid state. beta-Adrenoceptor antagonism reduced heart rate in hyperthyroid patients but did not significantly affect heart rate variability or catecholamine excretion. This is in keeping with the concept of a joint disruption of sympathetic and vagal inputs to the heart underlying changes in heart rate variability. Thus thyrotoxicosis is characterized by profound sympathovagal imbalance, brought about by increased sympathetic activity in the presence of diminished vagal tone.

Atrial natriuretic peptide infusion and nitric oxide inhalation in patients with acute respiratory distress syndrome

Aim:

To study the effects of infusion of atrial natriuretic peptide (ANP) versus the inhalation of nitric oxide (NO) in patients with an early acute respiratory distress syndrome (ARDS).

Methods:

Ten patients with severe ARDS were studied in a crossover study design, within 72 hours after starting mechanical ventilation. We studied the effects of ANP infusion (10 ng/kg/min for 1 hour) and of inhalation of NO (20 ppm for 1 hour) on hemodynamic and respiratory patient parameters, as well as the effects on plasma levels of ANP, guanosine 3',5'-cyclic monophosphate, nitrate and endothelin-1.

Results:

Despite an approximate 50% increase in mixed venous ANP plasma concentration (from 86 ± 21 to 123 ± 33 ng/l, P < 0.05) during ANP infusion, there were no changes in mean pulmonary artery pressure, pulmonary vascular resistance index, extravascular lung water index, or in pulmonary gas exchange. NO inhalation, in contrast, lowered mean pulmonary artery pressure (from 26 ± 1.9 to 23.9 ± 1.7 mmHg, P < 0.01), pulmonary vascular resistance index (from 314 ± 37 to 273 ± 32 dynes/cm⁵/m², P < 0.05) and central venous pressure (from 8.2 ± 1.2 to 7.3 ± 1.1 mmHg, P < 0.02). Furthermore, NO inhalation improved pulmonary gas exchange, reflected by a decrease in alveolar-arterial oxygen gradient (from 41.9 ± 3.9 to 40.4 ± 3.6 kPa, P < 0.05), a small increase in oxygenation (PaO₂/FiO₂ from 17.7 ± 1.4 to 19.7 ± 1.1 kPa, P = 0.07) and a small decrease in venous admixture (Q_s/Q_t from 35.7 ± 2.0 to 32.8 ± 2.7%, P = 0.11).

Conclusion:

This study shows that, in contrast to NO inhalation, infusion of ANP neither improves oxygenation nor attenuates pulmonary hypertension or pulmonary edema in patients with severe ARDS.

Monitoring renal function in obese patients with type 2 diabetes mellitus in daily practice

BACKGROUND

Endogenous creatinine clearance (GFR(24-hr)) and the Cockcroft formula (GFR(Cockcroft)) are used for the assessment of the glomerular filtration rate (GFR) in daily practice. The influence of extreme obesity in Type 2 diabetes mellitus (T2DM) on the Cockcroft formula was evaluated.

METHODS

We compared GFR as calculated by GFR(Cockcroft) to GFR as determined by GFR(24-hr) in 210 patients with T2DM and normal serum creatinine levels. The influence of body mass index (BMI) on the difference between both methods was evaluated.

RESULTS

GFR(Cockcroft) was an overall good predictor for GFR(24-hr), but a large individual difference between both methods was observed. A significant correlation was found between the two methods (r=0.962, p<0.001). In T2DM patients with a BMI>35 kg/m2, mean GFR(Cockcroft) was 18% greater than GFR(24-hr). For every unit BMI in this patient group the GFR(Cockcroft) increased by 7.9% relative to the GFR(24-hr).

CONCLUSIONS

The major limitation of this evaluation is the lack of a gold standard for GFR measurement. This evaluation of daily practice shows the GFR estimation by the Cockcroft formula and the 24-hr creatinine clearance are in agreement, although a large individual variation was found between both methods making the interchangeability questionable. In view of the influence of BMI on the Cockcroft formula, this should not be used to estimate the GFR in T2DM patients with extreme obesity.

[From gene to disease; leptin and obesity]

Homozygous mutations of the ob gene, encoding leptin, are associated with severe obesity, hyperphagia and insulin resistance in humans. Leptin conveys a signal from adipose tissue to hypothalamic nuclei that integrate whole body fuel metabolism, informing those nuclei about the magnitude of fuel reserves. In the absence of leptin, the brain perceives energy availability as insufficient and therefore activates powerful mechanisms to restore fuel depots. If leptin synthesis or signal transduction is perturbed in the presence of food, a severely obese phenotype ensues.

Sixty-eight-year-old patient with hypokalemia

A 68-year-old patient with severe hypokalemia and metabolic alkalosis is described. Six years before admission he had been treated for a small cell bronchial carcinoma. We discuss the diagnostic approach of hypokalemia and the way in which we reached the diagnosis. The patient suffered from metastatic small cell carcinoma with a very high plasma adrenocorticotropic hormone concentration, possibly due to production of corticotropin-releasing hormone by the malignancy.