Disturbances of basal and postprandial insulin secretion and clearance in obese patients with type 2 diabetes mellitus.

Hyperinsulinemia of nondiabetic overweight and obese subjects is associated with weight-dependent increased insulin secretion and decreased insulin clearance. The present analysis examines whether similar effects can be observed in overweight and obese patients with type 2 diabetes mellitus (DM2). Additionally basal and postprandial insulin secretion and clearance were analyzed in relation to duration of disease. In a random sample of 348 DM2 patients basal plasma insulin concentrations were significantly higher in most BMI groups compared to matched nondiabetic (ND) controls. The weight-dependent increase of basal insulin in DM2 was primarily the result of reduced clearance rather than augmented secretion. Postprandial insulin concentrations were lower in DM2 patients and did not show any BMI-related increase. The weight-dependent reduction of postprandial insulin clearance was absent in DM2. At the time of diagnosis basal insulin concentration was higher and secretion was comparable to ND subjects and this did not change with duration of diabetes. The early postprandial insulin response was still comparable between DM2 and ND subjects at the time of diagnosis but deteriorated with longer duration of disease. The later postprandial response at diagnosis (AUC 90-180) was characterized by significantly greater insulin secretion and concentration while later on the 3-fold higher secretion was paralleled by comparable peripheral plasma concentrations due to a significantly greater postprandial insulin clearance in DM2. In conclusion, the present data indicate that apart from disturbances of insulin secretion substantial changes of insulin clearance contribute to inadequate peripheral insulin concentrations in obese DM2 patients.

Effect of GABA-ergic mechanisms on synaptosomal NO synthesis and the nitrergic component of NANC relaxation in rat ileum.

BACKGROUND: γ-Aminobutyric acid (GABA) acts on specific neural receptors [A, B and C(Aρ)] to modulate gastrointestinal function. The precise role of GABA receptor activation in the regulation of presynaptic nitric oxide (NO) synthesis in nerve terminals is unknown. METHODS: Rat ileal nerve terminals were isolated by differential centrifugation. Nitric oxide synthesis was analysed using a L-[(3) H]arginine assay. In vitro studies were performed under non-adrenergic non-cholinergic (NANC) conditions on isolated ileal segments. KEY RESULTS: γ-Aminobutyric acid inhibited NO synthesis significantly (n = 6, P < 0.05) [(fmol mg(-1) min(-1)) control: 27.7 ± 1.5, 10(-6) mol L(-1): 19.7 ± 1.3; 10(-5) mol L(-1): 17.5 ± 3.0]. This effect was antagonized by the GABA A receptor antagonist bicuculline and the GABA C receptor antagonist (1,2,5,6-tetrahydropyridin-4-yl)methylphosphinic acid (TPMPA), but not by the GABA B receptor antagonist SCH 50911. The GABA A receptor agonist muscimol [(fmol mg(-1) min(-1)) control: 27.6 ± 1.0, 10(-6) mol L(-1): 19.1 ± 1.7, n = 5, P < 0.05] and the GABA C receptor agonist cis-4-aminocrotonic acid (CACA) [(fmol mg(-1) min(-1)) control: 29.5 ± 3.2, 10(-3) mol L(-1): 20.3 ± 2.5, n = 6, P < 0.05], mimicked the GABA-effect, whereas the GABA B agonist baclofen was ineffective. Bicuculline reversed the inhibitory effect of muscimol, TPMPA antagonized the effect of CACA. In functional experiments the GABA A and C receptor agonists reduced the NANC relaxation induced by electrical field stimulation in rat ileum by about 40%. After NOS-inhibition by Nε-nitro-L-arginine methyl ester (L-NAME) the GABA A receptor agonist had no effect, whereas the GABA C receptor agonist still showed a residual response. CONCLUSIONS & INFERENCES: γ-Aminobutyric acid inhibits neural NO synthesis in rat ileum by GABA A and GABA C(Aρ) receptor-mediated mechanisms.

Effect of carbohydrate- and protein-rich meals on exercise-induced activation of lipolysis in obese subjects.

Exercise is an important part of obesity treatment concepts to support fat mobilisation from adipose tissue and also fat oxidation nolich is impaired in obese subjects. In normal weight subjects it is well known that stimulation of plasma insulin levels by a carbohydrate meal can inhibit lipolysis and subsequent fat oxidation. Since obese subjects frequently have elevated basal and postprandial insulin levels the effect of carbohydrate- and protein-rich test meals on exercise-induced activation of lipolysis is of special interest. Twenty obese subjects performed bicycle exercise for 30 min in the fasted state, 30 min after a carbohydrate-or a protein-rich meal, and 120 min after the carbohydrate meal (n=12), respectively, at low intensity. Activation of lipolysis was assessed by plasma glycerol levels. In addition, plasma insulin, glucose, and lactate concentrations were determined. In comparison to the fasted state, the carbohydrate meal suppressed activation of lipolysis. Following the protein meal, exercise led to an attenuated but significant increase of glycerol levels. A similar rise was observed when the carbohydrate meal was ingested 2 h prior to the exercise bout. To improve exercise-induced lipolysis and subsequent fat oxidation during low-intensity exercise obese subjects should not ingest carbohydrates immediately before exercise. Hunger sensations should be satisfied with protein-rich food. When carbohydrates are consumed 2 h prior to exercise its lipolytic effect is comparable to the protein meal. These data are useful in every day dietary counselling and might help to improve weight loss during obesity treatment.

Impaired postprandial response of active ghrelin and prolonged suppression of hunger sensation in the elderly.

BACKGROUND: The role of the orexigenic hormone ghrelin is of major interest in the altered appetite regulation of the elderly. METHODS: Basal and postprandial levels of active and total ghrelin were measured in 15 younger (mean age 35.4 years) and 19 older (80.7 years) participants following a carbohydrate-rich test meal. RESULTS: Our results showed that older participants felt postprandially less hungry and more full. Although basal levels were not significantly different, active and total ghrelin levels declined postprandially only in the younger study participants. Highly significant differences between the two age groups were shown for the changes of the area under the curve for active ghrelin (p = .024). CONCLUSIONS: Our study demonstrates for the first time that differences in hunger and satiety sensations in relation to age are paralleled by a substantially different response of acylated and total ghrelin, that is, the absence of a postprandial decline in ghrelin levels.

Differential stimulatory effects of cannabinoids on VIP release and NO synthase activity in synaptosomal fractions from rat ileum.

Cannabinoid-1 (CB1) and CB2 receptors are present on neurons of the enteric nervous system. Our aim was to study whether cannabinoid receptor activation is involved in the regulation of VIP release and NO synthesis in isolated fractions of nerve terminals from rat ileum. VIP was measured by RIA and NO synthesis was analyzed using a L-[3H]arginine assay. Anandamide stimulated VIP release (basal: 245.9+/-12.4pg/mg, 10(-6)M: 307.6+/-11.7pg/mg, [n=6, P<0.05], 10(-7)M: 367.0+/-26.1pg/mg, [n=6, P<0.01]). The cannabinoid receptor agonist WIN 55,212-2 had similar effects (basal: 250.5+/-37.4pg/mg, 10(-6)M: 320.9+/-34.7pg/mg; [n=4, P<0.05]). The stimulatory effect of anandamide was blocked by the selective CB2 receptor antagonist, SR144528 (10(-7)M) (anandamide 10(-6)M: 307.6+/-11.7pg/mg; +SR144528: 249.0+/-26.3pg/mg, [n=6, P<0.05]), whereas the selective CB1 receptor antagonist SR141716 A had no effect. NO synthesis was stimulated by anandamide ([fmol/mg/min] basal: 0.08+/-0.01, 10(-6)M: 0.16+/-0.03; 10(-7)M: 0.13+/-0.02, n=4, P<0.05) and WIN 55,212-2 ([fmol/mg/min] basal: 0.05+/-0.01, 10(-6)M: 0.1+/-0.02, n=4, P<0.05). The anandamide reuptake inhibitor, AM 404 increased basal NOS activity ([fmol/mg/min] control: 0.1+/-0.04, 10(-6)M: 0.28+/-0.08, n=7, P<0.05). The stimulatory effect of anandamide on NO synthase was not antagonized by antagonists at the CB1, CB2 or TRPV1 receptor, respectively. In conclusion, in enteric nerves anandamide stimulates VIP release by activation of a CB2 receptor specific pathway, while the stimulation of NO production suggests the existence of an additional type of cannabinoid receptor in the enteric nervous system.

Relation of plasma obestatin levels to bmi, gender, age and insulin.

Obestatin is supposed to be involved in nutrient homeostasis. Therefore, basal plasma obestatin levels were investigated in 321 normal weight and obese subjects in relation to body mass index, gender, age, insulin concentrations, and type 2 diabetes mellitus. Additionally, postprandial obestatin levels were determined in 20 normal weight subjects. Basal obestatin levels in females were higher compared to males (193.6+/-5.8 vs. 140.6+/-5.1 pg/ml). Obestatin levels correlated inversely and significantly with body mass index (f: r=-0.632, p<0.001; m: r=-0.487, p<0.001) and basal insulin levels (f: r=-0.536, p<0.001; m: r=-0.320, p=0.008) in females and males. However, in a multiple regression analysis as well as in a matched comparison of a low and high insulin group no significant relationship between insulin and obestatin levels was observed in nondiabetics. On the other hand, inclusion of type 2 diabetics with higher insulin levels resulted in a significant inverse correlation. Obestatin levels were independent of age in both sexes. In patients with type 2 diabetes mellitus basal obestatin levels were not different compared to nondiabetic subjects when matched for gender, body mass index, and insulin. In normal weight subjects, postprandial obestatin levels showed a significant decrease between 60 and 90 minutes rising to basal levels thereafter. The present data demonstrate a relation of plasma obestatin levels to body weight, gender and food intake, but not to age. The inverse relationship with insulin might depend on the level of hyperinsulinemia. The present data are compatible with a potential role of obestatin in nutrient regulation.

Ghrelin, anthropometry and nutritional assessment in geriatric hospital patients.

UNLABELLED: Loss of appetite is an important causal factor for malnutrition in the elderly, and age-associated changes of hormone levels seem to be of great relevance in this regard. At present there has been no study exploring the role of the appetite stimulating hormone ghrelin in geriatric hospital patients. STUDY POPULATION: 121 (f 82, m 39) patients from two geriatric wards of our hospital. Mean age was 80.2+/-7.7 years. RESULTS: The basal ghrelin level (mean 158.43+/-144.02 pg/ml) showed no gender difference. No association with the age of the patients could be demonstrated. There was an inverse correlation of basal ghrelin with BMI, upper arm circumference, triceps skin fold, basal leptin and insulin. No correlation between established screening/assessment tools for malnutrition - Mini Nutritional Assessment (MNA), Subjective Global Assessment (SGA), Nutritional Risk Screening (NRS) - could be shown. Even after grouping the ghrelin levels into six different disease categories, no significant difference could be shown between them. CONCLUSION: For our patients aged 67 to 94, no correlation with age could be shown. Nevertheless the basal level of ghrelin is substantially lower when compared to a younger population with similar BMI, while the anorectic hormone leptin shows no substantial difference. This causes a more anorectic hormonal constellation which may contribute to the loss of appetite in geriatric patients.

Patient selection for surgical treatment of obesity.

A successful reduction of body weight in patients with morbid obesity (BMI >40 kg/m2) is difficult and in the majority of patients it is impossible with non-interventional treatment modalities. Surgical therapy is an efficient alternative for these patients. Potential surgical intervention, however, should be carefully evaluated during a six month preoperative treatment phase. During this time period indications and contraindications must be evaluated.

[Bariatric surgery. Patient selection and indication]. / Adipositaschirurgie: Patientenselektion und Indikationsstellung.

Successful reduction of body weight in patients with morbid obesity (BMI >40 kg/m(2)) is difficult and on a long-term basis nearly impossible with non-interventional treatment modalities. Surgical therapy is an efficient alternative for these patients. Potential surgical treatment should be carefully evaluated during a 6-month preoperative treatment phase during which indications and contraindications should be evaluated. Qualified postoperative care must be provided.

Quantification of the mycotoxins patulin and ochratoxin A by stable isotope dilution assays.

For analysis of trace compounds, stable isotope dilution assays (SIDAs) have gained increasing importance in the past years. This methodology is based on the use of stable isotopically labelled analogues of the analytes as internal standards (IS). To take the mycotoxins patulin and ochratoxin A as examples, the benefits of SIDAs were demonstrated both for foods and for clinical analyses.Regarding PAT, an isotopomer labelled with(13)C was used as IS and enabled quantitation of the mycotoxin in tissues and blood. By applying this technology, a fast passive diffusion into tissue was proven with the model of the perfused rat stomach. Furthermore, rapid degradation of PAT was observed when it was reacted with blood, which was attributed to the formation of PAT-GSH adducts detected by LC-MS/MS.For OTA, a SIDA was based on the use of [(2)H5]-OTA as the IS and proved to be more accurate when compared to alternative methods such as HPLC-FD or ELISA. In contrast to PAT, OTA was detectable in human blood and urine samples. Under the assumption that the majority of OTA is circulating in blood, an urinary excretion rate of about 1% of the whole body content per day was calculated.

[Pharmacotherapy of obesity]. / Pharmakotherapie der Adipositas. Schlank auf Rezept?

While the intentional modification of eating habits remains the most important measure for losing weight, pharmacological support, in particular with regard to the long-term outcome, can be helpful. Catacholaminergic substances, such as diethylpropion and phenylpropanolamine are restricted by their side effects to short-term application only, and their use makes little sense. The serotoninergic substance sibutramine, which acts on the central nervous system to curb the appetite or enhance the feeling of saturation, and orlistat, which inhibits the assimilation of fat from the bowel, are approved for longer-term treatment of obesity, and lead to an additional loss of 3-5% of the patient's initial weight after one year of use. Thereafter, however, this benefit decreases. Further substances involving new, possibly combinable, approaches are currently under development.

Treatment of HCC with pravastatin, octreotide, or gemcitabine--a critical evaluation.

BACKGROUND/AIMS: New perspectives in the treatment of advanced hepatocellular carcinomas have recently been inaugurated with the application of hydroxymethylglutaryl coenzyme A reductase inhibitors i.e. pravastatin, the somatostatin analogue octreotide, or the cytidine analogue gemcitabine. The present study aimed to evaluate these substances in patients with progressive tumor growth. METHODOLOGY: A total of 58 patients either received 3 x 200 microg/day octreotide for 2 months followed by 20mg octreotide LAR every 4 weeks (n=30) or 40-80 mg pravastatin (n=20) or 80-90 mg/m2 gemcitabine over 24 hours weekly in cycles of 4 weeks (n=8). Kaplan-Meier survival curves and the log-rank test were used for univariate comparison of sur vival. RESULTS: The median overall survival of patients receiving octreotide was 5 months, of patients receiving pravastatin 7.2 months and of patients receiving gemcitabine 3.5 months. The difference between the pravastatin and the gemcitabine groups was significant. No WHO grade 3 or 4 side effects were seen in either group of patients. CONCLUSIONS: These results do not confirm those of former studies. Neither pravastatin, nor octreotide, nor gemcitabine did prolong the patients' median overall survival as compared to control groups reported by other authors. New therapeutic strategies have to be found for patients with advanced hepatocellular carcinomas.

Cholesterol lowering effect of dietary weight loss and orlistat treatment--efficacy and limitations.

BACKGROUND: Orlistat reduces energy uptake by the impairment of fat digestion and some evidence indicates it also lowers plasma cholesterol. AIM: To examine total, low-density lipoprotein- and high-density lipoprotein cholesterol during a weight reducing regimen, and assess the effect of orlistat in lowering cholesterol levels independent of its weight reducing efficacy. METHODS: A total of 448 patients with elevated cholesterol according to cardiovascular risk factors entered a 2 week single-blind run-in period on a hypocaloric diet. Of 384 patients were subsequently assigned double-blind treatment with orlistat (3 x 120 mg/day) or placebo for 6 months in conjunction with the hypocaloric diet. RESULTS: Weight loss in the orlistat group was 7.4 kg vs. 4.9 kg with placebo. Total and low-density lipoprotein cholesterol decreased by 25-30 mg/dL vs. 10-15 mg/dL with placebo. Reduction of cholesterol with orlistat was significantly greater than anticipated from weight loss alone. In patients with cardiovascular risk factors entering the study with lower cholesterol values orlistat was also superior to placebo. On the contrary, reduction of cholesterol concentrations never exceeded 20%. CONCLUSION: Orlistat has a cholesterol lowering efficacy independent of its weight reducing effect. Because of the limited therapeutic effectiveness, patients at high cardiovascular risk should receive rather early additional cholesterol lowering medication during weight loss programmes.

Cannabinoid receptor type 1 modulates excitatory and inhibitory neurotransmission in mouse colon.

The effects of cannabinoid receptor agonists and antagonists on smooth muscle resting membrane potentials and on membrane potentials following electrical neuronal stimulation in a myenteric neuron/smooth muscle preparation of wild-type and cannabinoid receptor type 1 (CB1)-deficient mice were investigated in vitro. Double staining for CB1 and nitric oxide synthase (neuronal) was performed to identify the myenteric CB1-expressing neurons. Focal electrical stimulation of the myenteric plexus induced a fast (f) excitatory junction potential (EJP) followed by a fast and a slow (s) inhibitory junction potential (IJP). Treatment of wild-type mice with the endogenous CB1 receptor agonist anandamide reduced EJP while not affecting fIJP and sIJP. EJP was significantly higher in CB1-deficient mice than in wild-type littermate controls, and anandamide induced no effects in CB1-deficient mice. N-arachidonoyl ethanolamide (anandamide), R-[2,3-dihydro-5-methyl-3-(4-morpholinylmethyl)pyrrolo[1,2,3,-de]- 1,4-benzoxazin-6-yl]-1-naphtalenylmethanone, a synthetic CB1 receptor agonist, nearly abolished EJP and significantly reduced the fIJP in wild-type mice. N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-3-pyrazole-caroxamide (SR141716A), a CB1-specific receptor antagonist, was able to reverse the agonist effects induced in wild-type mice. SR141716A, when given alone, significantly increased EJP in wild-type mice without affecting IJP in wild-type and EJP in CB1-deficient mice. Interestingly, SR141716A reduced fIJP in CB1-deficient mice. In the mouse colon, nitrergic myenteric neurons do not express CB1, implying that CB1 is expressed in cholinergic neurons, which is in line with the functional data. Finally, excitatory and inhibitory neurotransmission in the mouse colon is modulated by activation of CB1 receptors. The significant increase in EJP in CB1-deficient mice strongly suggests a physiological involvement of CB1 in excitatory cholinergic neurotransmission.

Impact of carbohydrate and fat intake on weight-reducing efficacy of orlistat.

BACKGROUND: Orlistat treatment of obesity results in a poor long-term weight loss (< 5%) in about 30% of patients. AIM: Total energy and macronutrient intake were examined to assess the effect of a change in eating habits on weight loss. METHODS: Sixty-two patients consumed a hypocaloric diet, together with orlistat (3 x 120 mg/day), for 72 weeks, with a maximal fat allowance of 30% of the energy intake. At regular intervals, food diaries were recorded. RESULTS: Fifty-six patients completed the study and lost 8.5 +/- 0.88 kg (P < 0.001). Energy intake was approximately 1500 kcal/day during the entire study period. In three sub-groups established according to weight loss (1, < 5%; 2, > 5% and < 10%; 3, > 10%), fat intake was within the recommended range in all groups during the first 6 months, but thereafter only in group 3. All groups increased their carbohydrate consumption, with the greatest increase in group 1, which could account for the rapid regain of initially lost body weight in this group. CONCLUSION: At the beginning of a weight management programme in conjunction with orlistat, a low fat intake is advised for an efficient reduction in body weight. Subsequently, in patients with poor long-term weight loss, dietary recommendations must also consider carbohydrate restriction to ensure an adequate hypocaloric diet.

Endogenous CCK depresses contractile activity within the ascending myenteric reflex pathway of rat ileum.

The ascending excitatory reflex is an important part of the myenteric reflex. In order to study the ascending neural pathways, isolated segments of rat ileum were stimulated by electrical stimulation of the gut wall (20 V, 3 pulses per second, 1 ms) using platinum electrodes. The excitatory contractile response was recorded using perfused manometric side-hole tubing located 2 and 4 cm orally to the stimulation site. The contractile response to electrical stimulation was abolished by atropine (10(-6) M) or hexamethonium (10(-4) M). The excitatory response increased after administration of the cholecystokinin A (CCK(A)) receptor antagonists lorglumide (3x10(-6) M: +44.1%), devazepide (10(-8) M: +19.4%; 10(-7) M: +30.0%) and SR-27897 (10(-10) M: +21.8%, 10(-8) M: +47.0%, P<0.05, n=8). However, the CCK(B) receptor antagonist L-365,260 also caused a significant increase in the oral excitation (10(-6) M: +27.4%). sCCK-8 caused a significant reduction in the ascending response (10(-8) M: -11.5%) and induced spontaneously occurring contractions at doses ranging from 10(-10)-10(-6) M. CCK-9 significantly increased the ascending response (10(-7) M: +10.9%, P<0.05). However, caerulein (10(-10) M: -25.9%, 10(-8) M: -26.8%; P<0.01) and pentagastrin (10(-10) M: -20.2%, P<0.05; 10(-8) M: -23.7%, P<0.01; 10(-6) M: -28.3%, P<0.001) reduced the ascending contractile response significantly. These data, obtained with potent and highly specific CCK receptor antagonists, demonstrate an inhibitory role of endogenously released CCK within the ascending neural pathway. The data further suggest that exogenously applied CCK-related peptides have different effects on the myenteric reflex which might be due to excitation of the different involved neurons (short and long ascending inter- and motorneurons) in an unphysiological order. Thus in experiments investigating more complex neuronal circuits, experiments with antagonists should be regarded as more specific.

Characterizing voltage-dependent Ca(2+) channels coupled to VIP release and NO synthesis in enteric synaptosomes.

In enteric synaptosomes of the rat, the role of voltage-dependent Ca(2+) channels in K(+)-induced VIP release and nitric oxide (NO) synthesis was investigated. Basal VIP release was 39 +/- 4 pg/mg, and cofactor-substituted NO synthase activity was 7.0 +/- 0.8 fmol. mg(-1). min(-1). K(+) depolarization (65 mM) stimulated VIP release Ca(2+) dependently (basal, 100%; K(+), 172.2 +/- 16.2%; P < 0.05, n = 5). K(+)-stimulated VIP release was reduced by blockers of the P-type (omega-agatoxin-IVA, 3 x 10(-8) M) and N-type (omega-conotoxin-GVIA, 10(-6) M) Ca(2+) channels by ~50 and 25%, respectively, but not by blockers of the L-type (isradipine, 10(-8) M), Q-type (omega-conotoxin-MVIIC, 10(-6) M), or T-type (Ni(2+), 10(-6) M) Ca(2+) channels. In contrast, NO synthesis was suppressed by omega-agatoxin-IVA, omega-conotoxin-GVIA, and isradipine by ~79, 70, and 70%, respectively, whereas Ni(2+) and omega-conotoxin-MVIIC had no effect. These findings are suggestive of a coupling of depolarization-induced VIP release primarily to the P- and N-type Ca(2+) channels, whereas NO synthesis is presumably dependent on Ca(2+) influx not only via the P- and N- but also via the L-type Ca(2+) channel. In contrast, none of the Ca(2+) channel blockers affected VIP release evoked by exogenous NO, suggesting that NO induces VIP secretion by a different mechanism, presumably involving intracellular Ca(2+) stores.