Does seasonality of births in diabetes mellitus reflect pathogenetic differences?

OBJECTIVES: This study indicates that the seasonality of births of patients with DM1 and DM2 has occurred in their adolescence or adulthood. BACKGROUND: Patients with Diabetes mellitus type 2 (DM2) with the maturity onset have different seasonal birth patterns from those with Diabetes mellitus type 1 (DM1) with the maturity onset, or DM1children. METHODS: Monthly numbers of births of 81 and 236 children with DM1 and DM2, respectively, in adolescent or adult age, were adapted to different actual length of calendar months. The 12- and 6-month rhythm was tested using the cosinor regression with 95% confidence interval versus the hypothesis of null seasonality. RESULTS: Regarding DM1 with maturity onset, annual and semiannual rhythm was significant in both genders, with the increase in birth numbers from November to January and decrease in March, April and August. In DM2, only female data displayed a significant annual rhythm, with an increase in birth from April to August and decrease from October to December.  CONCLUSION: The birth seasonality related to DM1 in adolescent or adult age appears to be reciprocal, compared to DM1 in childhood. For DM2, the seasonality of births was found only in females. The increase in female fecundity seems to be related to an increase in the risk of DM2 in female offspring. The outcomes could help in identifying environmental and endogenous factors related to seasonality cycle (Tab. 1, Fig. 1, Ref. 18).

The nonskeletal effects of vitamin D3 and the threshold limit associated with the risk of health complications.

OBJECTIVE: To evaluate the threshold limit of vitamin D3 associated with the risk of nonskeletal health complications in humans. BACKGROUND: Vitamin D3 deficiency is primary caused by a reduced sun exposure, consequent limiting of vitamin D3 production in the skin, and low intake of food with this vitamin. METHODS: Ninety-two adults (25-95 years old) were admitted to III. Internal clinic or examined in outpatient department of The University hospital in Bratislava. Vitamin D3 levels were determined using electrochemical luminescence immunoassay. The least square method for the results processing was used. RESULTS: Vitamin D3 level 16 ng/ml may be threshold limit for the risk of hypertension, ischaemic heart disease, renal insufficiency and diabetes mellitus. A higher occurrence of the observed diseases was in female and male patients with vitamin D3 levels<16 ng/ml.The highest increase of occurrence of diabetes mellitus in women for vitamin D3<16 ng/ml (160%) compared to vitamin D3≥16 ng/ml (40%) was observed. Concerning the men, the highest increase refers to ischaemic heart disease (67%). CONCLUSION: The limit value of vitamin D3, 16 ng/ml, confirmed the association between vitamin D3 insufficiency and the presence of hypertension, ischaemic heart disease, renal insufficiency and diabetes mellitus. Its relation to age, sex and other variables was detected (Tab. 1, Fig. 5, Ref. 27).

Influence of Circulation System on Estimation of Absorption and Elimination Constant after per oral Drug Administration: A Reanalysis.

This study aimed to identify the cause of atypical shape of measured concentration-time profile in the peak area by one compartment open model with a lag time (Bateman function with a lag) after single dose oral administration of drug published in "Pharmacokinetic and Pharmacodynamic Data Analysis: Concepts and Application" by Gabrielsson and Weiner (1997) and two concentration profiles after frequent sampling oral glucose tolerance test. Following the oral administration of 100 µg of substance A to human volunteer, frequent sampling was carried out and concentration-time profiles were obtained. Our hemodynamic circulatory structural model capable of parameters estimation of circulation and gastrointestinal subsystem to explain the plateau within the interval 40-100 min (substance A) and 15-30 min (glucose) of the measured concentration-time profile was developed. The mean residence time, the rate constants of absorption and elimination parameters of our model were calculated. Comparing to the Bateman function, our results demonstrate better approximation of the substance A and glucose concentration-time profile and estimation of absorption rate constant by our structural model. Obtained model results indicate that the atypical shape of measured concentration-time profile of single dose oral administration of drug was probably caused by the gastrointestinal and circulation system with deep compartment. This applies to the substances with high coefficient of absorption.

Effect of gastric emptying and entero-hepatic circulation on bioequivalence assessment of ranitidine.

The aim of study was to compare the bioavailability of ranitidine obtained from either Ranitidine (300 mg tablet; LPH® S.C. LaborMed Pharma S.A. Romania: the test formulation) and Zantac® (300 mg tablet; GlaxoSmithKline, Austria: the reference formulation). Twelve, Romanian, healthy volunteers were enrolled in the study. An open-label, two-period, crossover, randomized design was used. Plasma levels of ranitidine were determined using the validated, high-pressure liquid chromatography (HPLC) method. The physiologically motivated time-delayed model was used for the data evaluation and a paired Student's t-test and Schuirmann's two one-sided tests were carried out to compare parameters. Nonmodeling parameters (AUC(t), AUC, C(max), T(max)) were tested by the paired Student's t-test and the 90 confidence intervals of the geometric mean ratios were determined by Schuirmann's tests. Paired Student's t-test showed no significant differences between nonmodeling and modeling parameters. The results of the Schuirmann's tests however indicated significant statistical differences with reference to AUC(t), AUC, C(max), T(max) and other modeling parameters, especially MT(c) and τ(c). Schuirmann's tests revealed significant bioequivalence between ranitidine formulations using the modeling parameters MRT and n. The presented model can be useful as an additional tool to assess drug bioequivalence, by screening for disruptive parameters.

Mathematical model indicates nonlinearity of noradrenaline effect on rat renal artery.

The aim of this work is to present the efficacy of a previously introduced computational procedure, developed for evaluation of vascular responsiveness. On this reason, as an example a common study of noradrenaline (NA) effect on a rat renal artery under in vitro conditions was arbitrarily selected. The response of the arterial segment to NA doses (0.1-10 microg) was digitally recorded on a PC and employed to develop mathematical model of NA effect. Using the model, the following NA effect variables were determined: the vessel sensitivity parameter, mean effect time and rate constant, respectively, characterizing the effect intensity, duration, and regression and also classic response variables: the maximal effect and time of the maximal effect. The two-way analysis of variance followed by Bonferroni's test revealed a significant influence of the increasing NA dose on the vessel sensitivity parameter and mean effect time. These findings indicated nonlinearity of processes underlying NA effect on the rat renal artery over the given range of NA doses. The procedure exemplified has the potential for use as an effective adjunct to routine studies of vascular responsiveness as it enables the extraction of meaningful information which cannot by obtained by common manual evaluation procedures.

Attenuated insulin response and normal insulin sensitivity in lean patients with ankylosing spondylitis.

Chronic low-grade inflammation is associated with insulin resistance. The aim of this study was to determine insulin response to intravenous glucose load and insulin sensitivity in patients with ankylosing spondylitis (AS). Fourteen nonobese male patients with AS and 14 matched healthy controls underwent frequent-sampling intravenous glucose tolerance test (FSIVGTT). Insulin secretion and insulin sensitivity were calculated using the computer-minimal and homeostasis-model assessment 2 (HOMA2) models. Fasting glucose, insulin, cholesterol, high-density lipoprotein and low-density lipoprotein cholesterol, triglyceride levels, HOMA2, glucose effectiveness, insulin sensitivity and insulin response to FSIVGTT did not differ between patients and controls. Tumor necrosis factor-alpha and interleukin (IL)-6 concentrations tended to be higher in AS patients than in controls. Second-phase beta-cell responsiveness was 37% lower (p = 0.05) in AS patients than in controls. A negative correlation was found between the percentage of beta-cell secretion and IL-6 in all subjects (r = -0.54, p = 0.006). We found normal insulin sensitivity but attenuated glucose utilization in the second phase of FSIVGTT in AS patients. Our results indicate that elevated IL-6 levels may play a pathophysiological role in attenuating beta-cell responsiveness, which may explain the association between elevated IL-6 levels and increased risk for type 2 diabetes.

Computer-based methods for measurement, recording and modeling vessel responses in vitro: a pilot study with noradrenaline.

This paper reports the first results of an ongoing methodological pilot study aimed at designing techniques for the automatic measurement and digital recording of vessel responses to biologically active substances under in vitro conditions and for the mathematical modeling of the underlying processes. The techniques presented in this pilot study allowed us to determine model-based estimates of the parameters characterizing vasoconstrictor responses, i.e., the vessel sensitivity parameter, the mean time of vasoconstrictor response and the rate constant of vessel relaxation. The given parameters are not dependent on doses of biologically active substances, provided that the underlying processes satisfy the principle of superposition. Use of these techniques is shown in the classic study of vasoconstrictor responses to noradrenaline in the rat renal artery.

System approach to modeling metabolite formation from parent drug: a working example with methotrexate.

The aim of this methodological study was to present and exemplify a system-approach-based technology in modeling the formation of the metabolite from the parent drug. To represent this process, the parent-metabolite dynamic system was defined in such a way that the concentration-time profile of the parent drug was considered the input, while the concentration-time profile of the metabolite the output, of this system. The system-approach-based modeling technology was used to determine the model of the parent-metabolite dynamic system and to obtain the model-based estimates of the rate of metabolite formation, the rate of metabolic ratio and the mean time of metabolite formation. The technology was applied to concentration data for methotrexate and 7-hydroxymethotrexate in patients with psoriasis after a single oral methotrexate dose. Third-order linear models were selected as optimal to approximate the parent-metabolite dynamic systems representing the formation of 7-hydroxymethotrexate from methotrexate of these patients. The model-based estimates of the metabolic ratios ranged from 0.53 to 0.95. The model-based estimates of the mean times of formation of 7-hydroxymethotrexate from methotrexate ranged from 9.13 to 25.13 h. The model-based estimates of the rates of formation of 7-hydroxymethotrexate from methotrexate reached peak values (ranging from 0.03 to 0.11 h-1) in the time interval 1.5-4.5 h after administration of methotraxate. This study does not only introduce the method that may be useful in gaining insight into metabolite formation, but also presents a new example of the methodological, conceptual and computational uniformity of the system-approach-based technology in modeling various biomedical systems.

Modeling drug absorption from enteric-coated granules.

A system-approach-based method is proposed for modeling drug absorption from enteric-coated granules. This method was exemplified using enteric-coated granules of aspirin given to healthy subjects. Based on the results obtained, it can be concluded that absorption of salicylate from the granules can be sufficiently described using a first-order linear model with an absorption rate constant of salicylate similar to that reported for an aqueous solution of aspirin administered orally to healthy subjects. The method proposed in this study may contribute to the working library of modeling techniques in pharmacokinetics since it allows direct modeling of the drug absorption process and estimates the absorption rate constant of a drug when its behavior in the body is significantly influenced by a gastric emptying process. i.e., when the absorption rate constant of the drug cannot be estimated on the basis of its cumulative absorption-time profile.

Retrolective cohort study of an additive therapy with an oral enzyme preparation in patients with multiple myeloma.

PURPOSE: To evaluate the impact of an additive therapy with an oral enzyme (OE) preparation given for more than 6 months additionally to standard combination chemotherapy (vincristine/melphalan/cyclophosphamide/prednisone (VMCP)- or methylprednisolone/ vincristine/CCNU/cyclophosphamide/melphalan (MOCCA)-regimen) in the primary treatment of patients with multiple myeloma stages I-III. METHODS: A cohort of 265 patients with multiple myeloma stages I-III was consecutively treated at our institution in two parallel groups (control group (n = 99): chemotherapy +/-OE for less than 6 months; OE-group (n = 166): chemotherapy + OE for more than 6 months). The median follow-up time in the stages I, II, and III for the OE-group was 61, 37, and 46.5 months, respectively; for the control group the respective values were 33, 51.5, and 31.5 months. The primary endpoint of the study was disease-specific survival. Secondary endpoints were response to therapy, duration of first response and side effects. The chosen method for evaluation was the technique of a retrolective cohort analysis with a concurrent control group. Survival analysis was performed by the Kaplan-Meier method and multivariate analysis was done with the Cox proportional hazards model. RESULTS: Significantly higher overall response rates and longer duration of remissions were observed in the OE-group. Primary responders showed a longer mean survival time than non-responders. Additive therapy with OE given for more than 6 months decreased the hazard of death for patients at all stages of disease by approximately 60%. Observation time was not long enough to estimate the median survival for patients at stages I and II; for stage III patients it was 47 months in the control group versus 83 months for the patients treated with OE (P = 0.0014) which means a 3-year gain of survival time. Significant prognostic factors for survival, in the Cox regression analysis, were stage of disease and therapy with OE. The OE-therapy was generally well tolerated (3.6% of patients with mild to moderate gastrointestinal symptoms). CONCLUSION: OEs represent a promising new additive therapy in multiple myeloma which will be further evaluated in a randomized phase III trial in the USA.

Weighting function used for adjustment of multiple-bolus drug dosing.

This paper presents a new method for the adjustment of the multiple-bolus dosing of a drug. The method is based on the weighting function of the system describing the behavior (absorption, distribution and elimination) of the drug in the patient, identified employing a test dose administration of the drug to a patient. This method can be employed for the adjustment of the multiple-bolus dosing of the drugs whose behavior in the patient can be sufficiently described by linear time invariant models. The method allows to estimate loading and maintenance bolus doses of the drug, necessary to reach and maintain prescribed trough levels of the drug in a patient at desired time-points, both (the levels and time-points) specified by treatment requirements. The method is particularly suitable for the adjustment of multiple-bolus dosing of drugs with narrow therapeutical windows or of very expensive products such as the clotting factors. The method is exemplified by the adjustment of the multiple-bolus dosing of factor VIII in postoperative treatment of hemophilia A.

Model of lymphocyte migration in Merino ewes under physiological conditions.

The paper presents an example of a new type of a structured model containing time delays in parallel branches. This model was selected as optimal to describe mathematically the lymphocyte migration between the venous blood and prescapular lymph in Merino ewes under physiological conditions. The model allowed to identify and quantify several lymphocyte fractions exhibiting different migration dynamics.

Numerical simulations of stochastic circulatory models.

Properties of two of the stochastic circulatory models theoretically introduced by Smith et al., 1997, Bull. Math. Biol. 59, 1-22 were investigated. The models assumed the gamma distribution of the cycle time under either the geometric or Poisson elimination scheme. The reason for selecting these models was the fact that the probability density functions of the residence time of these models are formally similar to those of the Bateman and gamma-like function models, i.e., the two common deterministic models. Using published data, the analytical forms of the probability density functions of the residence time and the distributions of the simulated values of the residence time were determined on the basis of the deterministic models and the stochastic circulatory models, respectively. The Kolmogorov-Smirnov test revealed that even for 1000 xenobiotic particles, i.e., a relatively small number if the particles imply drug molecules, the probability density functions of the residence time based on the deterministic models closely matched the distributions of the simulated values of the residence time obtained on the basis of the stochastic circulatory models, provided that parameters of the latter models fulfilled selected conditions.

Pharmacokinetics of factor VIII in hemophilia A patients assessed by frequency response method.

The frequency response method, having its mathematical underpinnings in the theory of linear dynamic systems, was utilized to model pharmacokinetic systems describing the fate of factor VIII (F VIII) administered to hemophilia A patients before surgery. The pharmacokinetic system was defined on the basis of the patient's data in such a way that the injection of F VIII during 5-15 min was considered the input, and the corresponding plasma F VIII concentration profile consisting of both the injection and post-injection part the output of this system. The approach is an alternative to routine procedures based only on evaluation of the post-injection part of the F VIII concentration profile. With respect to the common sampling schedule of F VIII, simple second-order models were found acceptable for all the patients involved in the study. However, in the patients whose plasma F VIII concentration profiles did not decrease monotonously after the injection, these models failed to approximate secondary peaks indicating the presence of time delays in F VIII kinetics. The results obtained were discussed with respect to applications of pharmacokinetic models for the adjusted dose continuous infusion of F VIII in hemophilia A patients during and after surgical interventions.

[Osteoporosis in multiple myeloma]. / Problém osteoporózy pri mnohopocetnom myelóme.

The problem of osteoporosis is world-wide in people above 50 years of age. As this period is also a risk period for the development of multiple myeloma or other malignant processes, comprehensive differential diagnosis of malignant and benign osteoporosis is essential. By retrospective analysis of a 12-year group of 270 patients treated by chemotherapy on account of multiple myeloma the authors selected a group of 151 patients treated in addition to chemotherapy and immunomodulating drugs (mixture of proteolytic enzymes-Wobe Mugos) for 2-3 years, also with biphosphonates. At the time ofdiagnosis osteoporosis was in 24.5% patients the only finding on bones. When biphosphonates (Bonefos, Ibandronate) and chemotherapy were administered during a three-year observation period the bone process was stable in 61.59%, osseous changes disappeared in 11.26% and progression of osteolysis was recorded in 27.15%. The objective of the work was to emphasize the importance of a correct diagnosis of osseous changes which can progress even in clinically asymptomatic myelomas.

Modeling in frequency domain used for assessment of in vivo dissolution profile.

PURPOSE: To present a model-dependent approach for the assessment of the in vivo drug dissolution profile based on in vitro data for the multiple unit dosage form, as an alternative to the numerical method proposed in the study by Hayashi et al., Pharm Res. 12:1333-1337 (1995). METHODS: The data for aspirin granules administered to healthy subjects obtained in the above mentioned study were re-evaluated. The subject dissolution system was considered to consist of two subsystems connected in series, i.e. the subsystem describing the gastric-emptying process and the subsystem describing the intestinal dissolution process. The frequency response method was used to model the subject dissolution system. RESULTS: The model in vivo dissolution profile of aspirin, assessed as the integral of the model weighting function of the subject dissolution system, was in agreement with the in vivo cumulative absorption profile calculated by the Wagner-Nelson method. CONCLUSIONS: Comparison of dynamic properties of the subject dissolution system with the subsystem describing the gastric-emptying process yielded quantitative confirmation of the decisive role of the gastric-emptying process in the in vivo drug dissolution after administration in the multi unit dosage form.

CXT-MAIN: a software package for determination of the analytical form of the pharmacokinetic system weighting function.

A new procedure specific for the determination of the analytical form of the model weighting function of a complex multicomponent pharmacokinetic system with or without a shunt and time delays is described. The procedure is based on the theory of linear dynamic systems and on a circulatory pharmacokinetic model of the living body. The model transfer function of the system under study was obtained by the frequency response method in the form of the ratio of two frequency dependent polynomials. Subsequently, the technique of the partial fraction inversion was employed to determine the analytical form of the model weighting function. Two examples from bioavailability studies in pharmacokinetics are given. The first example presents two estimates of the model weighting function of a pharmacokinetic system obtained by the new procedure and by a polyexponential deconvolution method. To compare these results, two models of the measured system output were determined using the two estimates of the model weighting function, the actual system input and a convolution method. The model weighting function obtained by the new procedure yielded a better model approximation of the output data than that obtained by the polyexponential deconvolution method. The second example, using the new procedure, presents the determination of the model weighting function of such a system that the deconvolution methods, commonly used in pharmacokinetics, cannot be applied to.

Determination of analytical form of system weighting function.

This paper presents the determination of the analytical form of the weighting function of the three following complex multicomponent systems: 1) the system describing human pharmacokinetics of pentacaine after oral administration; 2) the system describing the hepatal elimination of indocyanine green in pig, and 3) the system describing the fate of indocyanine green in human esophageal varixes. The determination of the weighting function is based on the system transfer function and the technique of the partial-fraction inversion.

Building a structured model of a complex pharmacokinetic system with time delays.

This paper presents a description of the procedure for building a structured model of a complex pharmacokinetic system on using its transfer function. The example employed is that of the pharmacokinetic system based on gentamicin plasma concentrations after intravenous and intratracheal administration to guinea pigs, describing the pathway of the drug into the systemic circulation after the extravascular injection mentioned. The structured model selected consisted of a submodel of a proportional linear subsystem, two submodels of simple linear dynamic subsystems with time constants of 0.135 +/- 0.065 hr (95% I.C.) and 0.052 +/- 0.049 hr, and two submodels of parallel subsystems with time delays of 0.25 +/- 0.046 hr and 1.135 +/- 0.288 hr, connected in serial. Two estimates of the mean residence time of the total amount of gentamicin in the system, i.e., 0.347 and 0.335 hr, were obtained, based on the system frequency and structured model, respectively. From the methodological point of view, our paper demonstrates the efficiency of combination of modelling in the frequency and in the time domain, designed to facilitate studies of pharmacokinetic systems.