Relationship between GLP-1 levels and dipeptidyl peptidase-4 activity in different glucose tolerance conditions.

AIM: The reduced levels of glucagon-like peptide 1 (GLP-1) after an oral glucose load in Type 2 diabetic patients could be dependent either on a reduced synthesis or an increased degradation; but GLP-1 and dipeptidyl peptidase IV (DPP-IV) levels during an oral glucose tolerance test (OGTT) have not been studied together. The aim of the present study was to investigate GLP-1 and DPP-IV levels during an OGTT in patients with different degrees of glucose tolerance. METHODS: Fifty six subjects (34 female, 22 male) matched for sex, age, body mass index (BMI) and waist circumference underwent a 75 g oral glucose tolerance test. Twenty-eight had normal glucose tolerance, 15 had impaired glucose tolerance and 13 had Type 2 diabetes mellitus. GLP-1 assay was performed with an ELISA kit, and DPP-IV assay using a colorimetric method. RESULTS: At 30 min GLP-1 levels were significantly lower in subjects with impaired glucose tolerance and type 2 diabetes mellitus compared to those with normal glucose tolerance. The area under the GLP-1 curve was significantly different among the three groups; there was a significant decrease between subjects with normal and impaired glucose tolerance(P = 0.004) and between those with normal glucose tolerance and type 2 diabetes mellitus. (P < 0.001), while the area under the curve for DPP-IV showed no significant difference between the groups. CONCLUSIONS: These results suggest that an increase of GLP-1 degradation does not play a role in the early stages of diabetes mellitus.

Glucagon-like peptide-1 response to meals and post-prandial hyperglycemia in Type 2 diabetic patients.

BACKGROUND: The impaired response of glucagonlike peptide-1 (GLP-1) to meals in diabetic patients can contribute to the pathogenesis of impaired insulin secretion and post-prandial hyperglycemia. This study is aimed at the assessment of the relationship between meal-induced GLP-1 and post-prandial hyperglycemia in Type 2 diabetic patients. METHODS: Twenty-one drug-naïve Type 2 diabetic patients were studied. Blood glucose and active GLP-1 levels were measured 0, 30, 60, 90, and 120 min after a standard test meal. A continuous glucose monitoring (CGM) system was applied for the following 3 days. Nutrient intake at each meal was calculated on the basis of patients' food records. For each patient, post-prandial 120-min glucose incremental area under the curve (iAUC) was included in linear regression model exploring its relationship with total energy and carbohydrate intake, and the angular coefficient for total energy (EAC) and carbohydrate (CAC) was calculated. RESULTS: GLP-1 levels peaked 30 min after the test meal. Logarithmically transformed 60-min GLP-1 iAUC showed a significant inverse correlation with glycated hemoglobin (HbA1c) (p<0.01). A significant inverse correlation of 60-min GLP-1 iAUC was also observed with EAC and CAC (both p<0.01), meaning that patients with a lower GLP-1 response to the test meal had a higher increment of post-prandial glucose for each additional unit of total energy or carbohydrate intake. CONCLUSIONS: In Type 2 diabetic patients, a lower GLP-1 response to meals is associated with a higher HbA1c, and with a greater degree of meal-induced hyperglycemia, both in a meal test and during CGM in "real-life" conditions.

Effects of internal Na+ on the Ca channel outward current in mouse neoplastic B lymphocytes.

The whole-cell configuration of the patch-clamp technique was used to study the outward Na+ current through Ca channels in hybridoma cell lines (202B and 206), constructed by fusion of S194 myeloma cells with murine splenic B lymphocytes. The concentration of Na+ in the electrode solution, [Na+]p, was changed by isosmotic replacement of Na+ with N-methyl-D-glucamine+ ions. When 2.5 mM calcium was present in the bath, neither the current nor the reversal potential was significantly altered by changes in the level of external Na+ [( Na+]o. By contrast, both of those properties were strongly affected by [Na+]p. At fixed depolarizing potentials, the outward current increased approximately as the square power of [Na+]p, a feature that cannot be easily explained by one-ion models for a channel or by "continuum" theories based on electrodiffusion. Instead, all the data could be well described by a "single-file" model for a two-site pore that admits up to two ions. Although double occupancy of the Ca channel by divalent cations has been proposed previously (Hess and Tsien. 1984. Nature. 309: 453-456; Almers et al., 1984. J. Physiol. 353: 585-608), this study indicates that, in our system, states of the channel with two Na+ ions must also be considered in order to explain the dependence of the outward current on [Na+]p. A good fit to the data could be obtained by assuming that both sites in the channel are "electrically" close to its cytoplasmic end and that most of the voltage dependence pertains to the rates for ion exit to the external medium. The values of the parameters suggest that: (a) Ca2+ is bound most strongly by the site nearest to the cytoplasm (in both singly and doubly occupied channels); (b) in channels with two Ca2+ ions, the dissociation constant of the site close to the external mouth must be greater than 2.5 mM; and (c) in pores occupied by two Na+ ions, the rate constant for Na+ exit to the external solution is larger than the rate constant for Na+ exit to the cytoplasm.

ATP mediates both activation and inhibition of K(ATP) channel activity via cAMP-dependent protein kinase in insulin-secreting cell lines.

The single-channel recording technique was employed to investigate the mechanism conferring ATP sensitivity to a metabolite-sensitive K channel in insulin-secreting cells. ATP stimulated channel activity in the 0-10 microM range, but depressed it at higher concentrations. In inside-out patches, addition of the cAMP-dependent protein kinase inhibitor (PKI) reduced channel activity, suggesting that the stimulatory effect of ATP occurs via cAMP-dependent protein kinase-mediated phosphorylation. Raising ATP between 10 and 500 microM in the presence of exogenous PKI progressively reduced the channel activity; it is proposed that this inactivation results from a reduction in kinase activity owing to an ATP-dependent binding of PKI or a protein with similar inhibitory properties to the kinase. A model describing the effects of ATP was developed, incorporating these two separate roles for the nucleotide. Assuming that the efficacy of ATP in controlling the channel activity depends upon the relative concentrations of inhibitor and catalytic subunit associated with the membrane, our model predicts that the channel sensitivity to ATP will vary when the ratio of these two modulators is altered. Based upon this, it is shown that the apparent discrepancy existing between the sensitivity of the channel to low ATP concentrations in the excised patch and the elevated intracellular level of ATP may be explained by postulating a change in the inhibitor/kinase ratio from 1:1 to 3:2 owing to the loss of protein kinase after patch excision. At a low concentration of ATP (10-20 microM), a nonhydrolyzable ATP analogue, AMP-PNP, enhanced the channel activity when present below 10 microM, whereas the analogue blocked the channel activity at higher concentrations. It is postulated that AMP-PNP inhibits the formation of the kinase-inhibitor complex in the former case, and prevents phosphate transfer in the latter. A similar mechanism would explain the interaction between ATP and ADP which is characterized by enhanced activity at low ADP concentrations and blocking at higher concentrations.

Metabolic regulation of the K(ATP) and a maxi-K(V) channel in the insulin-secreting RINm5F cell.

K channels in the cell membrane of the insulin-secreting RINm5F cell line were studied using the patch-clamp technique in cell-attached patch mode. With 140 mM K in the pipette, two channels displaying different conductive and kinetics properties were observed. A voltage-independent, inward-rectifying, 55-pS channel was active at rest (no glucose, -70 mV), but was almost completely inhibited by 5 mM glucose. A 140-pS channel was seen in the absence of glucose only after cell membrane depolarization with high (30 mM) K. This channel was voltage dependent, with a linear slope conductance between -60 and +60 mV, and was completely inhibited only by greater than 15 mM glucose. The former channel we identify as an ATP-sensitive channel previously described in excised patches and refer to it as the K(ATP) channel. The latter, because of its large conductance and voltage-dependent kinetics, will be referred to as the maxi-K(V) channel, adopting a nomenclature previously used to classify highly conductive K channels (Latorre, R., and C. Miller, 1983, Journal of Membrane Biology, 71:11-30). In addition to glucose, mannose and 2-ketoisocaproate, which also initiate insulin secretion and electrical activity in the islet beta cell, reduced the activity of both the K(ATP) and the maxi-K(V) channel. Lactate and arginine, which potentiate but do not initiate insulin secretion or beta cell electrical activity in normal islets, each caused a large reduction in maxi-K(V) channel activity, without consistently affecting the activity of K(ATP) channels. Another agonist that potentiates insulin secretion and electrical activity in normal cells, the tumor-promoting phorbol ester TPA, blocked maxi-K(V) channel activity while stimulating the activity of the K(ATP) channel, thereby implicating phosphorylation in the control of channel activity. These results indicate that metabolic substrates that initiate electrical activity and insulin secretion in normal beta cells reduce the activity of both the K(ATP) and the maxi-K(V) channel, while potentiating agents reduce only the maxi-K(V) channel. The possible role of these two channels in the processes of initiation and potentiation of the beta cell response is discussed.

Anomalous permeabilities of the egg cell membrane of a starfish in K+-Tl+ mixtures.

The electrical properties of "inward" rectifying egg cell membranes of the starfish mediastera aequalis have been studied in the presence of K(+)-Tl(+) mixtures. When the ratio of the external concentrations of these ions is changed while their sum is kept constant, both the conductance and the zero-current membrane potential go through a minimum, showing clear discrepancies from theoretical results based on conventional electrodiffusion models (E.g., Goldman's equation). By contrast, when the ration of the two concentrations is fixed and their sum varied, the potential follows an ideal Nernst slope, consistent with Goldman's equation. The membrane conductance which, according to previous studies on similar membranes, is to be viewed as a function of the displacement of the membrane potential from its resting value deltaV, shows marked differences between the cases in which K(+) or Tl(+) are the predominant ions: when K(+) is the predominant permeant ion in solution, the addition of small amounts of Tl(+) inhibits the current, while corresponding blocking effects of K(+) on the current are not observed when Tl(+) is the predominant permeant ion. Also, the time course of the conductance during voltage clamp is different in the two cases, being much faster in Tl(+) than in K(+) solution for comparable values of deltaV. Most of the above features are accounted for by a model in which it is assumed that the ionic channels have external binding sites for cations and that their permeability properties depend on the species of the cation bound (K(+)or Tl(+) in the present experiments).

Pure testicular carcinoid associated with intratubular germ cell neoplasia.

This case report describes for the first time a case of pure testicular carcinoid pre-aortic lymph node metastases in a 25 year old patient with carcinoid syndrome. The simultaneous occurrence of intratubular germ cell neoplasia in the surrounding testicular tissue was identified by OCT4 and placental-like alkaline phosphatase positivity. This confirmed that the tumour had a germ cell origin in the testis, rather than being a metastasis from an extragenital carcinoid.

Effect of metformin on glucagon-like peptide 1 (GLP-1) and leptin levels in obese nondiabetic subjects.

OBJECTIVE: To evaluate the effects of metformin on glucagon-like peptide 1 (GLP-1) and leptin levels. RESEARCH DESIGN AND METHODS: A total of 10 obese nondiabetic male patients were studied before and after a 14-day treatment with 2,550 mg/day metformin and were compared with 10 untreated obese control subjects. On days 0 and 15, leptin and GLP-1(7-36)amide/(7-37) levels were assessed before and after an oral glucose load during a euglycemic hyperinsulinemic clamp to avoid the interference of variations of insulinemia and glycemia on GLP-1 and leptin secretion. The effects of metformin on GLP-1(7-36)amide degradation in human plasma and in a buffer solution containing dipeptidyl peptidase IV (DPP-IV) were also studied. RESULTS: Leptin levels were not affected by the oral glucose load, and they were not modified after metformin treatment. Metformin induced a significant (P < 0.05) increase of GLP-1(7-36)amide/(7-37) at 30 and 60 min after the oral glucose load (63.8 +/- 29.0 vs. 50.3 +/- 15.6 pmol/l and 75.8 +/- 35.4 vs. 46.9 +/- 20.0 pmol/l, respectively), without affecting baseline GLP-1 levels. No variations of GLP-1 levels were observed in the control group. In pooled human plasma, metformin (0.1-0.5 microg/ml) significantly inhibited degradation of GLP-1(7-36)amide after a 30-min incubation at 37 degrees C; similar results were obtained in a buffer solution containing DPP-IV. CONCLUSIONS: Metformin significantly increases GLP-1 levels after an oral glucose load in obese nondiabetic subjects; this effect could be due to an inhibition of GLP-1 degradation.

Novel ligands specific for mitochondrial benzodiazepine receptors: 6-arylpyrrolo[2,1-d][1,5]benzothiazepine derivatives. Synthesis, structure-activity relationships, and molecular modeling studies.

A novel class of ligands specific for MBR receptors has been identified: 6-arylpyrrolo[2,1-d][1,5]benzothiazepine derivatives. The majority of newly synthesized esters 37-64 as well as some intermediate ketones showed micro- or nanomolar affinity for [3H]PK 11195 binding inhibition. A SAR study on 42 compounds and a molecular modeling approach led to a preliminary structural selectivity profile: the 6,7-double bond, the carbamoyloxy, alcanoyloxy, and mesyloxy side chains at the 7-position, and the prospective chloro substitution at the 4-position seemed to be the most important structural features improving affinity. Therefore, 7-[(dimethylcarbamoyl)oxy]- and 7-acetoxy-4-chloro-6-phenylpyrrolo[2,1-d][1,5]benzothiazepine (43 and 57) were synthesized. With 7-[(dimethylcarbamoyl)oxy]-6-(p-methoxyphenyl)pyrrolo[2,1- d][1,5]benzothiazepine (65), these were the most promising compounds with IC50s of respectively 9, 8, and 9 nM, under conditions where PK 11195 had an IC50 of 2 nM.

A comparative molecular field analysis model for 6-arylpyrrolo[2,1-d] [1,5]benzothiazepines binding selectively to the mitochondrial benzodiazepine receptor.

A series of 42 6-arylpyrrolo[2,1-d][1,5]benzothiazepines, which we have recently described as selective ligands of the mitochondrial benzodiazepine receptor (MBR) (Fiorini I.; et al. J. Med. Chem. 1994, 37, 1427-1438), have been investigated using the comparative molecular field analysis (CoMFA) approach. The resulting 3D-QSAR model rationalizes the steric and electronic factors which modulate affinity to the MBR with a cross-validation standard error of 0.648 pIC50 unit. A set of seven novel pyrrolobenzothiazepine congeners has successively been synthesized and tested. The CoMFA model forecasts the binding affinity values of these new compounds with a prediction standard error of 0.536.

New antipsychotic agents with serotonin and dopamine antagonist properties based on a pyrrolo[2,1-b][1,3]benzothiazepine structure.

The development of a synthetic approach to the novel pyrrolo[2, 1-b][1,3]benzothiazepine and its derivatives and their biological evaluation as potential antipsychotic drugs are described. In binding studies these compounds proved to be potent 5-HT2, D2, and D3 receptor ligands. The more potent benzothiazepine (+/-)-3b was resolved into its enantiomers by using HPLC techniques. In vitro testing confirmed that (-)-3b is a more potent D2 receptor ligand, maintaining high affinity for 5-HT2 receptors. In contrast, the (+)-3b enantiomer presents a 35 times higher affinity for 5-HT2 than for dopamine D2 receptors with a similar dopamine D1 receptor affinity to that of (-)-3b. Overall, (+)-3b shows an "atypical" neuroleptic binding profile, while (-)-3b has a more "classical" profile. Furthermore pharmacological and biochemical testing displayed that the novel benzothiazepine (+/-)-3b is able to increase the extracellular levels of dopamine in the rat striatum and causes a dose-related suppression of apomorphine-induced locomotor activity. At low doses (+/-)-3b does not induce catalepsy, showing atypical antipsychotic properties similar to those of olanzapine. These heterocyclic compouds represent new leads for the development of novel antipsychotic drugs with atypical properties.

Cardiovascular characterization of pyrrolo[2,1-d][1,5]benzothiazepine derivatives binding selectively to the peripheral-type benzodiazepine receptor (PBR): from dual PBR affinity and calcium antagonist activity to novel and selective calcium entry blockers.

The synthesis and cardiovascular characterization of a series of novel pyrrolo[2,1-d][1,5]-benzothiazepine derivatives (54-68) are described. Selective peripheral-type benzodiazepine receptor (PBR) ligands, such as PK 11195 and Ro 5-4864, have recently been found to possess low but significant inhibitory activity of L-type calcium channels, and this property is implicated in the cardiovascular effects observed with these compounds. In functional studies both PK 11195 (1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxa mide) and Ro 5-4864 (4'-chlorodiazepam) did not display selectivity between cardiac and vascular tissue. Therefore, several 7-(acyloxy)-6-arylpyrrolo[2,1-d][1,5]benzothiazepines, potent and selective peripheral-type benzodiazepine receptor ligands recently developed by us (3, 7-20), were subjected to calcium channel receptor binding assay. Some of these compounds showed an unexpected potency in displacing the binding of [3H]nitrendipine from L-type calcium channels, much higher than that reported for PK 11195 and Ro 5-4864 and equal to or higher than that of reference calcium antagonists such as verapamil and (+)-cis-diltiazem. Specifically, in rat cortex homogenate, our prototypic PBR ligand 7-acetoxy-6-(p-methoxyphenyl)pyrrolo[2,1-d][1,5]benzothiazepine (3) showed an IC50 equal to 0.13 nM for inhibition of [3H]nitrendipine binding. Furthermore, in functional studies this compound displayed a clear-cut selectivity for cardiac over vascular tissue. Comparison of calcium antagonist activity on guinea pig aorta strips with the negative inotropic activity, determined by using isolated guinea pig left atria, revealed that 3 displayed higher selectivity than the reference (+)-cis-diltiazem. Thus, the pyrrolobenzothiazepine 3 might represent a new tool for characterizing the relationship between the PBR and cardiac function. Furthermore, we have also investigated the structural dependence of binding to PBR and L-type calcium channels, and this study allowed us to identify a new class of potent calcium channel blockers selective for cardiac over vascular tissue, with no affinity for PBR. A number of structure-activity relationship trends have been identified, and a possible explanation is advanced in order to account for the observed differences in selectivity. Three structural features, namely, (i) the saturation of the C(6)-C(7) double bond, with a consequent higher molecular flexibility, (ii) the presence of a substituent in the benzofused ring, and (iii) a basic side chain at C-10 of the pyrrolobenzothiazepine ring system, were found to be responsible for potent L-type calcium channel antagonism and clear-cut selectivity for cardiac over vascular tissue. Among the synthesized compounds the pyrrolobenzothiazepine 62 was found to be the most promising selective calcium channel blocker. Additionally, the molecular structure determination of the key intermediate 48 by X-ray diffraction, molecular modeling, and NMR analysis is reported.

Synthesis, biological activity, and SARs of pyrrolobenzoxazepine derivatives, a new class of specific "peripheral-type" benzodiazepine receptor ligands.

The "peripheral-type" benzodiazepine receptor (PBR) has been reported to play a role in many biological processes. We have synthesized and tested a novel series of PBR ligands based on a pyrrolobenzoxazepine skeleton, in order to provide new receptor ligands. Several of these new compounds proved to be high affinity and selective ligands for PBR, and benzoxazepines 17f and 17j were found to be the most potent ligands for this receptor to have been identified to date. The SAR and the molecular modeling studies detailed herein delineated a number of structural features required for improving affinity. Some of the ligands were employed as "molecular yardsticks" to probe the spatial dimensions of the lipophilic pockets L1 and L3 in the PBR cleft and to determine the effect of occupation of L1 and L3 with respect to affinity, while other C-7 modified analogues provided information specifically on the hydrogen bonding with a putative receptor site H1. The new pyrrolobenzoxazepines were tested in rat cortex, a tissue expressing high density of mitochondrial PBR, and exhibited IC50 and Ki values in the low nanomolar or subnanomolar range, as measured by the displacement of [3H]PK 11195 binding. A subset of the highest affinity ligands was also found to have high affinities for [3H]PK 11195 and [3H]Ro 5-4864 binding in rat adrenal mitochondria. All the ligands in this subset are stimulators of steroidogenesis having similar potency and extent of stimulation as PK 11195 and Ro 5-4864 of steroidogenesis in the mouse Y-1 adrenocortical cell line.

Endometrial coccidiosis.

This report describes a case of granulomatous endometritis caused by coccidiosis in an immunologically uncompromised 63 year old patient. The glandular epithelium of the endometrium contained numerous intracytoplasmic cysts, corresponding to periodic acid Schiff positive and methenamine silver negative sporoblasts. The endometrial glands revealed reactive phenomena, such as eosinophilic and squamous glandular metaplasia and intraluminal desquamation. Non-necrotising epithelioid granulomata, lacking the presence of parasites, were present in the stroma. Although not detected in the stool examination, the organisms were probably Isospora belli. There was no evidence of other foci of the disease. Coccidiosis should be differentiated from the more commonly occurring coccidiomycosis.

Histological features of resolving acute, non-complicated phlegmonous appendicitis.

The histological features of resolving acute appendicitis are described. Formalin-fixed, paraffin-embedded appendices of 200 cases with acute, non-complicated phlegmonous appendicitis were reviewed. In 80 out of 200 cases, a histological picture characterized by a predominantly lymphocytic infiltrate of the subserosa and muscularis propria or the subserosa alone was found. In the affected muscularis propria, eosinophils were admixed with lymphocytes, and the cellular infiltrate showed a lesser degree than that of the classic phlegmonous appendicitis. A multifocal, rather than a diffuse pattern of infiltration was observed. Cases were divided into three groups. Group 1: appendices with the typical features of phlegmonous appendicitis: 120 cases, 60%. Group 2: appendices with a predominantly lymphocytic infiltrate in the muscularis propria, subserosa, or both, and no granulation tissue: 65 cases, 32.5%. Group 3: appendices with granulation tissue: 15 cases, 7.5%. Complicated appendicitis was excluded. Data on the duration of the clinical symptoms were derived from the clinical history. The differences between the mean duration time of groups 1 and 2, and of groups 2 and 3 were statistically significant. The findings support the contention that a mixed infiltrate of lymphocytes and eosinophils represents a regression phase of acute appendicitis.

Permeation of organic cations and ammonium through the glutamate receptor channel in Drosophila larval muscle.

The inside-out configuration of the patch-clamp technique was used to study the effects of large organic cations on the single-channel current through the glutamate receptor channel in muscles of Drosophila larvae. Control experiments with symmetrical Na+ showed slightly supra-linear I-V curves. When external Na+ was equiosmolarly replaced with either arginine+ or N-methyl-D-glucamine+ (NMDG+), the reversal potential changed almost according to VNa, suggesting that both these ions are only slightly permeant through the channel. However, both ions strongly reduced the current amplitude in a voltage-dependent manner, the effect being most pronounced for the inward current. Tris+ had similar effects on the Na+ current, although the reversal potential indicated that this ion is somewhat permeant. All of these results could be fitted with a "one-ion" Eyring model for the channel with internal binding sites. The ion-channel dissociation constants for arginine+, NMDG+, and Tris+ were found to be 17, 27, and 23 mM, respectively. In order to acquire evidence for the "one-ion" hypothesis used in the model, I-V data were taken with different mixtures of Na+ and a comparably permeant ion, NH4+. All of the data could be accurately fitted with the results of the Eyring theory for singly occupied channels.

Relationship of the Southern California Sensory Integration Tests, the Southern California Postrotary Nystagmus Test, and clinical observations accompanying them to evaluations in otolaryngology, ophthalmology, and audiology: two descriptive case studies.

A preliminary investigation was conducted into the relationship of the Southern California Sensory Integration Tests (SCSIT), the Southern California Postrotary Nystagmus Test (SCPNT), and clinical observations accompanying these tests to evaluations in otolaryngolgoy, ophthalmology, and audiology, ophthalmology, and audiology. The subjects were two children with vestibularly based sensory integrative dysfunction. The results revealed that there was no agreement between the results of the SCPNT and the otolaryngological evaluation. There was some agreement between the ophthalmology evaluation and the clinical observations accompanying the SCSIT. Both subjects scored poorly in two areas of auditory processing. Possible reasons for these results are discussed as well as implications for occupational therapy reached and practice.

Corneal cross-linking for the treatment of keratoconus in a patient with ipsilateral myelinated retinal nerve fiber layer.

Keratoconus associated with myelinated retinal nerve fibers is not frequent and the relationship between the two pathologies is difficult to explain, therefore studies and further investigation are required. The etiology of each condition may suggest the role of genetic factors. Follow-up is important to evaluate the progression of keratoconus and myelination. Here we describe the unusual coexistence of keratoconus and ipsilateral myelinated retinal nerve fiber layer and, for the first time, the corneal cross-linking treatment in this condition.