A simplified longitudinal model for the development of Type 2 Diabetes Mellitus

Obesity and diabetes are a progressively more and more deleterious hallmark of modern, well fed societies. In order to study the potential impact of strategies designed to obviate the pathological consequences of detrimental lifestyles, a model for the development of Type 2 diabetes geared towards large population simulations would be useful. The present work introduces such a model, representing in simplified fashion the interplay between average glycemia, average insulinemia and functional beta-cell mass, and incorporating the effects of excess food intake or, conversely, of physical activity levels. Qualitative properties of the model are formally established and simulations are shown as examples of its use.

Recruitment-to-inflation Ratio Assessed through Sequential End-expiratory Lung Volume Measurement in Acute Respiratory Distress Syndrome

BACKGROUND

Positive end-expiratory pressure (PEEP) benefits in acute respiratory distress syndrome are driven by lung dynamic strain reduction. This depends on the variable extent of alveolar recruitment. The recruitment-to-inflation ratio estimates recruitability across a 10-cm H2O PEEP range through a simplified maneuver. Whether recruitability is uniform or not across this range is unknown. The hypotheses of this study are that the recruitment-to-inflation ratio represents an accurate estimate of PEEP-induced changes in dynamic strain, but may show nonuniform behavior across the conventionally tested PEEP range (15 to 5 cm H2O).

METHODS

Twenty patients with moderate-to-severe COVID-19 acute respiratory distress syndrome underwent a decremental PEEP trial (PEEP 15 to 13 to 10 to 8 to 5 cm H2O). Respiratory mechanics and end-expiratory lung volume by nitrogen dilution were measured the end of each step. Gas exchange, recruited volume, recruitment-to-inflation ratio, and changes in dynamic, static, and total strain were computed between 15 and 5 cm H2O (global recruitment-to-inflation ratio) and within narrower PEEP ranges (granular recruitment-to-inflation ratio).

RESULTS

Between 15 and 5 cm H2O, median [interquartile range] global recruitment-to-inflation ratio was 1.27 [0.40 to 1.69] and displayed a linear correlation with PEEP-induced dynamic strain reduction (r = -0.94; P < 0.001). Intraindividual recruitment-to-inflation ratio variability within the narrower ranges was high (85% [70 to 109]). The relationship between granular recruitment-to-inflation ratio and PEEP was mathematically described by a nonlinear, quadratic equation (R2 = 0.96). Granular recruitment-to-inflation ratio across the narrower PEEP ranges itself had a linear correlation with PEEP-induced reduction in dynamic strain (r = -0.89; P < 0.001).

CONCLUSIONS

Both global and granular recruitment-to-inflation ratio accurately estimate PEEP-induced changes in lung dynamic strain. However, the effect of 10 cm H2O of PEEP on lung strain may be nonuniform. Granular recruitment-to-inflation ratio assessment within narrower PEEP ranges guided by end-expiratory lung volume measurement may aid more precise PEEP selection, especially when the recruitment-to-inflation ratio obtained with the simplified maneuver between PEEP 15 and 5 cm H2O yields intermediate values that are difficult to interpret for a proper choice between a high and low PEEP strategy.

EDITOR’S PERSPECTIVE

Bariatric-metabolic surgery versus lifestyle intervention plus best medical care in non-alcoholic steatohepatitis (BRAVES): a multicentre, open-label, randomised trial

BACKGROUND

Observational studies suggest that bariatric-metabolic surgery might greatly improve non-alcoholic steatohepatitis (NASH). However, the efficacy of surgery on NASH has not yet been compared with the effects of lifestyle interventions and medical therapy in a randomised trial.

METHODS

We did a multicentre, open-label, randomised trial at three major hospitals in Rome, Italy. We included participants aged 25-70 years with obesity (BMI 30-55 kg/m2), with or without type 2 diabetes, with histologically confirmed NASH. We randomly assigned (1:1:1) participants to lifestyle modification plus best medical care, Roux-en-Y gastric bypass, or sleeve gastrectomy. The primary endpoint of the study was histological resolution of NASH without worsening of fibrosis at 1-year follow-up. This study is registered at ClinicalTrials.gov, NCT03524365.

FINDINGS

Between April 15, 2019, and June 21, 2021, we biopsy screened 431 participants; of these, 103 (24%) did not have histological NASH and 40 (9%) declined to participate. We randomly assigned 288 (67%) participants with biopsy-proven NASH to lifestyle modification plus best medical care (n=96 [33%]), Roux-en-Y gastric bypass (n=96 [33%]), or sleeve gastrectomy (n=96 [33%]). In the intention-to-treat analysis, the percentage of participants who met the primary endpoint was significantly higher in the Roux-en-Y gastric bypass group (54 [56%]) and sleeve gastrectomy group (55 [57%]) compared with lifestyle modification (15 [16%]; p<0·0001). The calculated probability of NASH resolution was 3·60 times greater (95% CI 2·19-5·92; p<0·0001) in the Roux-en-Y gastric bypass group and 3·67 times greater (2·23-6·02; p<0·0001) in the sleeve gastrectomy group compared with in the lifestyle modification group. In the per protocol analysis (236 [82%] participants who completed the trial), the primary endpoint was met in 54 (70%) of 77 participants in the Roux-en-Y gastric bypass group and 55 (70%) of 79 participants in the sleeve gastrectomy group, compared with 15 (19%) of 80 in the lifestyle modification group (p<0·0001). No deaths or life-threatening complications were reported in this study. Severe adverse events occurred in ten (6%) participants who had bariatric-metabolic surgery, but these participants did not require re-operations and severe adverse events were resolved with medical or endoscopic management.

INTERPRETATION

Bariatric-metabolic surgery is more effective than lifestyle interventions and optimised medical therapy in the treatment of NASH.

FUNDING

Fondazione Policlinico Universitario A Gemelli, Policlinico Universitario Umberto I and S Camillo Hospital, Rome, Italy.

Modeling outcome trajectories in patients with acquired brain injury using a non-linear dynamic evolution approach

This study describes a dynamic non-linear mathematical approach for modeling the course of disease in acquired brain injury (ABI) patients. Data from a multicentric study were used to evaluate the reliability of the Michaelis-Menten (MM) model applied to well-known clinical variables that assess the outcome of ABI patients. The sample consisted of 156 ABI patients admitted to eight neurorehabilitation subacute units and evaluated at baseline (T0), 4 months after the event (T1) and at discharge (T2). The MM model was used to characterize the trend of the first Principal Component Analysis (PCA) dimension (represented by the variables: feeding modality, RLAS, ERBI-A, Tracheostomy, CRS-r and ERBI-B) in order to predict the most plausible outcome, in terms of positive or negative Glasgow outcome score (GOS) at discharge. Exploring the evolution of the PCA dimension 1 over time, after day 86 the MM model better differentiated between the time course for individuals with a positive and negative GOS (accuracy: 85%; sensitivity: 90.6%; specificity: 62.5%). The non-linear dynamic mathematical model can be used to provide more comprehensive trajectories of the clinical evolution of ABI patients during the rehabilitation period. Our model can be used to address patients for interventions designed for a specific outcome trajectory.

Accurate liquid biopsy for the diagnosis of non-alcoholic steatohepatitis and liver fibrosis

OBJECTIVE

Clinical diagnosis and approval of new medications for non-alcoholic steatohepatitis (NASH) require invasive liver biopsies. The aim of our study was to identify non-invasive biomarkers of NASH and/or liver fibrosis.

DESIGN

This multicentre study includes 250 patients (discovery cohort, n=100 subjects (Bariatric Surgery Versus Non-alcoholic Steato-hepatitis - BRAVES trial); validation cohort, n=150 (Liquid Biopsy for NASH and Liver Fibrosis - LIBRA trial)) with histologically proven non-alcoholic fatty liver (NAFL) or NASH with or without fibrosis. Proteomics was performed in monocytes and hepatic stellate cells (HSCs) with iTRAQ-nano- Liquid Chromatography - Mass Spectrometry/Mass Spectrometry (LC-MS/MS), while flow cytometry measured perilipin-2 (PLIN2) and RAB14 in peripheral blood CD14⁺CD16^- monocytes. Neural network classifiers were used to predict presence/absence of NASH and NASH stages. Logistic bootstrap-based regression was used to measure the accuracy of predicting liver fibrosis.

RESULTS

The algorithm for NASH using PLIN2 mean florescence intensity (MFI) combined with waist circumference, triglyceride, alanine aminotransferase (ALT) and presence/absence of diabetes as covariates had an accuracy of 93% in the discovery cohort and of 92% in the validation cohort. Sensitivity and specificity were 95% and 90% in the discovery cohort and 88% and 100% in the validation cohort, respectively.The area under the receiver operating characteristic (AUROC) for NAS level prediction ranged from 83.7% (CI 75.6% to 91.8%) in the discovery cohort to 97.8% (CI 95.8% to 99.8%) in the validation cohort.The algorithm including RAB14 MFI, age, waist circumference, high-density lipoprotein cholesterol, plasma glucose and ALT levels as covariates to predict the presence of liver fibrosis yielded an AUROC of 95.9% (CI 87.9% to 100%) in the discovery cohort and 99.3% (CI 98.1% to 100%) in the validation cohort, respectively. Accuracy was 99.25%, sensitivity 100% and specificity 95.8% in the discovery cohort and 97.6%, 99% and 89.6% in the validation cohort. This novel biomarker was superior to currently used FIB4, non-alcoholic fatty liver disease fibrosis score and aspartate aminotransferase (AST)-to-platelet ratio and was comparable to ultrasound two-dimensional shear wave elastography.

CONCLUSIONS

The proposed novel liquid biopsy is accurate, sensitive and specific in diagnosing the presence and severity of NASH or liver fibrosis and is more reliable than currently used biomarkers.

CLINICAL TRIALS

Discovery multicentre cohort: Bariatric Surgery versus Non-Alcoholic Steatohepatitis, BRAVES, ClinicalTrials.gov identifier: NCT03524365.Validation multicentre cohort: Liquid Biopsy for NASH and Fibrosis, LIBRA, ClinicalTrials.gov identifier: NCT04677101.

High-Flow Versus VenturiMask Oxygen Therapy to Prevent Reintubation in Hypoxemic Patients after Extubation: A Multicenter Randomized Clinical Trial

Rationale: When compared with VenturiMask after extubation, high-flow nasal oxygen provides physiological advantages. Objectives: To establish whether high-flow oxygen prevents endotracheal reintubation in hypoxemic patients after extubation, compared with VenturiMask. Methods: In this multicenter randomized trial, 494 patients exhibiting Pa_O2:Fi_O2 ratio ⩽ 300 mm Hg after extubation were randomly assigned to receive high-flow or VenturiMask oxygen, with the possibility to apply rescue noninvasive ventilation before reintubation. High-flow use in the VenturiMask group was not permitted. Measurements and Main Results: The primary outcome was the rate of reintubation within 72 hours according to predefined criteria, which were validated a posteriori by an independent adjudication committee. Main secondary outcomes included reintubation rate at 28 days and the need for rescue noninvasive ventilation according to predefined criteria. After intubation criteria validation (n = 492 patients), 32 patients (13%) in the high-flow group and 27 patients (11%) in the VenturiMask group required reintubation at 72 hours (unadjusted odds ratio, 1.26 [95% confidence interval (CI), 0.70-2.26]; P = 0.49). At 28 days, the rate of reintubation was 21% in the high-flow group and 23% in the VenturiMask group (adjusted hazard ratio, 0.89 [95% CI, 0.60-1.31]; P = 0.55). The need for rescue noninvasive ventilation was significantly lower in the high-flow group than in the VenturiMask group: at 72 hours, 8% versus 17% (adjusted hazard ratio, 0.39 [95% CI, 0.22-0.71]; P = 0.002) and at 28 days, 12% versus 21% (adjusted hazard ratio, 0.52 [95% CI, 0.32-0.83]; P = 0.007). Conclusions: Reintubation rate did not significantly differ between patients treated with VenturiMask or high-flow oxygen after extubation. High-flow oxygen yielded less frequent use of rescue noninvasive ventilation. Clinical trial registered with www.clinicaltrials.gov (NCT02107183).

Validation of a simplified-geometry model of inhaled formoterol pharmacodynamics in asthmatic patients

PharmacoKinetics (PK) and PharmacoDynamics (PD) mathematical models of inhaled bronchodilators represent useful tools for understanding the mechanisms of drug action and for the individuation of therapy regimens. A PK/PD model for inhaled bronchoactive compounds was previously proposed, incorporating a simplified-geometry approach: the key feature of that model is a mixed compartmental and spatially distributed representation of the kinetics, with the direct computation of representative flow rates from Ohm's law and bronchial diameter profiles. The aim of the present work is the enrichment and validation of this simplified geometry modeling approach against clinical efficacy data. The improved model is used to compute airflow response to treatment for each single virtual patient from a simulated population and it is found to produce very good fits to observed FEV₁ profiles. The model provides a faithful quantitative description of the increasing degree of improvement with respect to basal conditions with continuing administration and with increasing drug dosages, as clinically expected.

[Hyperphosphatemic pseudotumoral calcinosis due to FGF23 mutation with secondary amyloidosis]

A 44 years old man was admitted for nephrotic syndrome and rapidly progressive renal failure. Two firm, tumour-like masses were localized around the left shoulder and the right hip joint. Since the age of 8 years old, the patient had a history of metastatic calcification of the soft tissues suggesting hyperphosphatemic pseudotumoral calcinosis. Despite treatment for a long time with phosphate binders the metastatic calcinosis had to be removed with several surgeries. The patient had also a history of recurrent fever associated with pain localized toward the two masses and underwent multiple antibiotic courses. Laboratory findings at admission confirmed nephrotic syndrome. S-creatinine was 2.8 mg/dl. Calcium was 8.4 mg/dl, Phosphorus 8.2 mg/dl, PTH 80 pg/ml, 25 (OH)VitD 8 ng/ml. Serum amyloid A was slightly increased. We performed renal biopsy and we found AA amyloid deposits involving the mesangium and the tubules. The bone marrow biopsy revealed the presence of AA amyloid in the vascular walls. During the next two months renal failure rapidly progressed and the patient started hemodialysis treatment. We performed genetic analysis that confirmed homozygous mutation of the FGF23 gene. After 14 months on hemodialysis, the patient's lesions are remarkably and significantly reduced in dimension. The current phosphate binder therapy is based on sevelamer and lanthanum carbonate. Serum amyloid A is persistently slightly increased as well as C reactive protein. Proteinuria is in the nephrotic range without nephrotic syndrome.

A Mathematical Model of In Vitro Cellular Uptake of Zoledronic Acid and Isopentenyl Pyrophosphate Accumulation

The mevalonate pathway is an attractive target for many areas of research, such as autoimmune disorders, atherosclerosis, Alzheimer’s disease and cancer. Indeed, manipulating this pathway results in the alteration of malignant cell growth with promising therapeutic potential. There are several pharmacological options to block the mevalonate pathway in cancer cells, one of which is zoledronic acid (ZA) (an N-bisphosphonate (N-BP)), which inhibits the farnesyl pyrophosphate (FPP) synthase enzyme, inducing cell cycle arrest, apoptosis, inhibition of protein prenylation, and cholesterol reduction, as well as leading to the accumulation of isopentenyl pyrophosphate (IPP). We extrapolated the data based on two independently published papers that provide numerical data on the uptake of zoledronic acid (ZA) and the accumulation of IPP (Ag) and its isomer over time by using in vitro human cell line models. Two different mathematical models for IPP kinetics are proposed. The first model (Model 1) is a simpler ordinary differential equation (ODE) compartmental system composed of 3 equations with 10 parameters; the second model (Model 2) is a differential algebraic equation (DAE) system with 4 differential equations, 1 algebraic equation and 13 parameters incorporating the formation of the ZA+enzyme+Ag complex. Each of the two models aims to describe two different experimental situations (continuous and pulse experiments) with the same ZA kinetics. Both models fit the collected data very well. With Model 1, we obtained a prevision accumulation of IPP after 24 h of 169.6 pmol/mgprot/h with an IPP decreasing rate per (pmol/mgprot) of ZA (kXGZ) equal to 13.24/h. With Model 2, we have comprehensive kinetics of IPP upon ZA treatment. We calculate that the IPP concentration was equal to 141.6 pmol/mgprot/h with a decreasing rate/percentage of 0.051 (kXGU). The present study is the first to quantify the influence of ZA on the pharmacodynamics of IPP. While still incorporating a small number of parameters, Model 2 better represents the complexity of the biological behaviour for calculating the IPP produced in different situations, such as studies on γδ T cell-based immunotherapy. In the future, additional clinical studies are warranted to further evaluate and fine-tune dosing approaches.

A comparison among three maximal mathematical models of the glucose-insulin system

The most well-known and widely used mathematical representations of the physiology of a diabetic individual are the Sorensen and Hovorka models as well as the UVAPadova Simulator. While the Hovorka model and the UVAPadova Simulator only describe the glucose metabolism of a subject with type 1 diabetes, the Sorensen model was formulated to simulate the behaviour of both normal and diabetic individuals. The UVAPadova model is the most known model, accepted by the FDA, with a high level of complexity. The Hovorka model is the simplest of the three models, well documented and used primarily for the development of control algorithms. The Sorensen model is the most complete, even though some modifications were required both to the model equations (adding useful compartments for modelling subcutaneous insulin delivery) and to the parameter values. In the present work several simulated experiments, such as IVGTTs and OGTTs, were used as tools to compare the three formulations in order to establish to what extent increasing complexity translates into richer and more correct physiological behaviour. All the equations and parameters used for carrying out the simulations are provided.

A mathematical model of cardiovascular dynamics for the diagnosis and prognosis of hemorrhagic shock

A variety of mathematical models of the cardiovascular system have been suggested over several years in order to describe the time-course of a series of physiological variables (i.e. heart rate, cardiac output, arterial pressure) relevant for the compensation mechanisms to perturbations, such as severe haemorrhage. The current study provides a simple but realistic mathematical description of cardiovascular dynamics that may be useful in the assessment and prognosis of hemorrhagic shock. The present work proposes a first version of a differential-algebraic equations model, the model dynamical ODE model for haemorrhage (dODEg). The model consists of 10 differential and 14 algebraic equations, incorporating 61 model parameters. This model is capable of replicating the changes in heart rate, mean arterial pressure and cardiac output after the onset of bleeding observed in four experimental animal preparations and fits well to the experimental data. By predicting the time-course of the physiological response after haemorrhage, the dODEg model presented here may be of significant value for the quantitative assessment of conventional or novel therapeutic regimens. The model may be applied to the prediction of survivability and to the determination of the urgency of evacuation towards definitive surgical treatment in the operational setting.

Comparative efficacy of different weight loss treatments on knee osteoarthritis: A network meta-analysis

The lifetime risk of developing symptomatic knee osteoarthritis is 60% in subjects with obesity. It is unclear which is the best weight loss interventions leading to a meaningful improvement of osteoarthritis symptoms and clinical conditions in subjects with obesity. Our network meta-analysis compares different weight loss interventions on the improvement of osteoarthritis symptoms and clinical conditions in subjects affected by obesity. PubMed, Embase, and Cochrane databases were systematically searched for eligible studies until November 2020. Thirty eligible studies comprising 4651 adults (74.6% women) were included. The most effective interventions reducing pain were bariatric surgery, low-calorie diet and exercise, and intensive weight loss and exercise (-62.7 [95% CrI: -74.6, -50.6]; -34.4 [95% CrI: -48.1, -19.5]; -27.1 [95% CrI: -40.4, -13.6] respectively). For every 1% weight loss Western Ontario and McMaster Universities Osteoarthritis (WOMAC) pain, function, and stiffness scores decreased by about 2% points. In conclusion, our meta-analysis shows that a substantial weight loss is necessary to reduce significantly knee pain and joint stiffness and to improve physical function: 25% weight reduction from baseline is necessary to obtain a 50% reduction of each subscale of the WOMAC score. However, performing physical exercise is essential to preserve the lean body mass and to avoid sarcopenia. Our results apply to a large spectrum of body mass index (BMI), from overweight to severe obesity.

Modeling continuous glucose monitoring with fractional differential equations subject to shocks

Continuous Glucose Monitoring (CGM) produces long time-series of noisy observations of a single variable (tissue glucose concentration), whose evolution may be explained by a dynamical model. In order to represent the unknown mixture of possible control mechanisms of different orders affecting the measured variable, a fractional differential approach seems justified. In any case, variations in food intake and/or physical activity ought to be taken into account if a plausible interpretation of the dynamics is to be obtained. In the present work, the mathematical construction and the numerical implementation of a Fractional Differential Equations (FDE) initial value problem are systematically reviewed, with the intent of offering the reader a concise and mathematically rigorous description of this approach. An FDE model for CGM is formulated: the model includes compartments for stomach and intestinal glucose contents and for blood and tissue (subcutaneous) glucose concentrations, as well as the shock effects of food ingestion and of increased glucose consumption due to physical activity. The model parameters, including the (non-integer) order of differentiation, are estimated from CGM observations on six Type 1 diabetic patients. The best-fit fractional orders for the six subjects range from 1.59 to 2.13. For comparison, best fits have also been computed for all subjects using an average fractional order of 1.9 and integer orders of 1 and 2.The results indicate that in the case of CGM the fractional differential model, which should be physiologically more appropriate, in fact fits the data much better than the first-order model and also better than the 2nd-order model.

Pioglitazone and bariatric surgery are the most effective treatments for non-alcoholic steatohepatitis: A hierarchical network meta-analysis

AIMS

To compare different treatments for non-alcoholic steatohepatitis (NASH) and to determine an effectiveness hierarchy.

MATERIALS AND METHODS

We conducted a systematic review and Bayesian network meta-analysis including randomized controlled trials or prospective trials with at least 6 months' follow-up and histologically proven NASH in adult participants. Monte Carlo simulations were performed, each generating 10 000 data points, and results are reported as medians and 95% credibility intervals (CrIs). A meta-regression was conducted to find the effects of body mass index (BMI) decrement or reduction of homeostatic model assessment of insulin resistance (HOMA-IR) index on non-alcoholic fatty liver disease activity score (NAS) change.

RESULTS

The review identified 48 eligible trials comprising 2356 adults (55.6% men). Data were pooled using a random-effects model. The most effective treatments in terms of NAS reduction per semester were pioglitazone and Roux-en-Y gastric bypass (RYGB; -1.50 [95% CrI -2.08, -1.00] for pioglitazione and -1.00 [95% CrI -1.70, -0.32] for RYGB). Pioglitazone was also the best therapy for steatosis and lobular inflammation reduction. RYGB was the best treatment for hepatocellular ballooning reduction, whereas antioxidants appeared to be best for fibrosis improvement. For each 1% decrement in BMI, NAS was reduced by 1.3% (β = 1.28%, P = 0.01). Conversely, a 1% reduction of HOMA-IR index reduced NAS by 0.3% (β = 0.31%, P < 0.001). Treatments that were regarded as promising, such as elafibranor, simtuzumab, selonsertib, cenicriviroc, obeticholic acid and liraglutide, did not reduce either NAS or liver fibrosis significantly.

CONCLUSIONS

Pioglitazione and RYGB are the most effective therapies for NASH. Antioxidants may be effective in reducing liver fibrosis. Weight loss and improvement of hepatic insulin resistance are promising approaches in the treatment of NASH.

A quasi-equilibrium reduced model of pancreatic insulin secretion

Much attention has been devoted in the last few decades to mathematical models of insulin secretion, in order to better understand the regulation of glycemia and its derangements. The glucose-insulin homeostatic mechanism is so complex and gives rise to such diverse behavior following perturbations that different models had been published, which reproduced the results of single experiments. More recently, a unifying model of pancreatic insulin secretion was proposed, which is able to account, with a single value of the (meta)parameters, for the wide array of clinically observed behavior. This model explicitly represented the pulsatile nature of the many pancreatic hormone-secreting firing units: the price to pay for its flexibility and performance is the very high dimensionality (hundreds of thousand equations) of the corresponding dynamical system. Clearly, it would be desirable to reduce this model to a much simpler form while retaining its power to reproduce heterogeneous phenomena. The present work reviews the qualitative behavior of this pancreas pulsatile model and offers some insight into its reduction in equilibrium and quasi-equilibrium conditions, also considering single-shot (non-repeated) glucose jumps from an approximately resting condition (such as would occur in standard Intra-Venous bolus dosing of glucose during diabetes diagnostic maneuvers). The resulting quasi-steady-state model can be further endowed with additional lower-order dynamics to also approximate transient behavior. Although a more accurate reduction of the original pulsatile model is left to further investigation, numerical results confirm the biomedical applicability of the formulation already obtained.

Metabolic surgery versus conventional medical therapy in patients with type 2 diabetes: 10-year follow-up of an open-label, single-centre, randomised controlled trial

BACKGROUND

No data from randomised controlled trials of metabolic surgery for diabetes are available beyond 5 years of follow-up. We aimed to assess 10-year follow-up after surgery compared with medical therapy for the treatment of type 2 diabetes.

METHODS

We did a 10-year follow-up study of an open-label, single-centre (tertiary hospital in Rome, Italy), randomised controlled trial, in which patients with type 2 diabetes (baseline duration >5 years; glycated haemoglobin [HbA_1c] >7·0%, and body-mass index ≥35 kg/m²) were randomly assigned (1:1:1) to medical therapy, Roux-en-Y gastric bypass (RYGB), or biliopancreatic diversion (BPD) by a computerised system. The primary endpoint of the study was diabetes remission at 2 years (HbA_1c <6·5% and fasting glycaemia <5·55 mmol/L without ongoing medication for at least 1 year). In the 10-year analysis, durability of diabetes remission was analysed by intention to treat (ITT). This study is registered with ClinicalTrials.gov, NCT00888836.

FINDINGS

Between April 30, 2009, and Oct 31, 2011, of 72 patients assessed for eligibility, 60 were included. The 10-year follow-up rate was 95·0% (57 of 60). Of all patients who were surgically treated, 15 (37·5%) maintained diabetes remission throughout the 10-year period. Specifically, 10-year remission rates in the ITT population were 5·5% for medical therapy (95% CI 1·0-25·7; one participant went into remission after crossover to surgery), 50·0% for BPD (29·9-70·1), and 25·0% for RYGB (11·2-46·9; p=0·0082). 20 (58·8%) of 34 participants who were observed to be in remission at 2 years had a relapse of hyperglycaemia during the follow-up period (BPD 52·6% [95% CI 31·7-72·7]; RYGB 66·7% [41·7-84·8]). All individuals with relapse, however, maintained adequate glycaemic control at 10 years (mean HbA_1c 6·7% [SD 0·2]). Participants in the RYGB and BPD groups had fewer diabetes-related complications than those in the medical therapy group (relative risk 0·07 [95% CI 0·01-0·48] for both comparisons). Serious adverse events occurred more frequently among participants in the BPD group (odds ratio [OR] for BPD vs medical therapy 2·7 [95% CI 1·3-5·6]; OR for RYGB vs medical therapy 0·7 [0·3-1·9]).

INTERPRETATION

Metabolic surgery is more effective than conventional medical therapy in the long-term control of type 2 diabetes. Clinicians and policy makers should ensure that metabolic surgery is appropriately considered in the management of patients with obesity and type 2 diabetes.

FUNDING

Fondazione Policlinico Universitario Agostino Gemelli IRCCS.

A mathematical model of food intake

The metabolic, hormonal and psychological determinants of the feeding behavior in humans are numerous and complex. A plausible model of the initiation, continuation and cessation of meals taking into account the most relevant such determinants would be very useful in simulating food intake over hours to days, thus providing input into existing models of nutrient absorption and metabolism. In the present work, a meal model is proposed, incorporating stomach distension, glycemic variations, ghrelin dynamics, cultural habits and influences on the initiation and continuation of meals, reflecting a combination of hedonic and appetite components. Given a set of parameter values (portraying a single subject), the timing and size of meals are stochastic. The model parameters are calibrated so as to reflect established medical knowledge on data of food intake from the National Health and Nutrition Examination Survey (NHANES) database during years 2015 and 2016.

A revised Sorensen model: Simulating glycemic and insulinemic response to oral and intra-venous glucose load

In 1978, Thomas J. Sorensen defended a thesis in chemical engineering at the University of California, Berkeley, where he proposed an extensive model of glucose-insulin control, model which was thereafter widely employed for virtual patient simulation. The original model, and even more so its subsequent implementations by other Authors, presented however a few imprecisions in reporting the correct model equations and parameter values. The goal of the present work is to revise the original Sorensen's model, to clearly summarize its defining equations, to supplement it with a missing gastrio-intestinal glucose absorption and to make an implementation of the revised model available on-line to the scientific community.

Comparison between two different cardiovascular models during a hemorrhagic shock scenario

Hemorrhagic shock is a form of hypovolemic shock determined by rapid and large loss of intravascular blood volume and represents the first cause of death in the world, whether on the battlefield or in civilian traumatology. For this, the ability to prevent hemorrhagic shock remains one of the greatest challenges in the medical and engineering fields. The use of mathematical models of the cardiocirculatory system has improved the capacity, on one hand, to predict the risk of hemorrhagic shock and, on the other, to determine efficient treatment strategies. In this paper, a comparison between two mathematical models that simulate several hemorrhagic scenarios is presented. The models considered are the Guyton and the Zenker model. In the vast panorama of existing cardiovascular mathematical models, we decided to compare these two models because they seem to be at the extremes as regards the complexity and the detail of information that they analyze. The Guyton model is a complex and highly structured model that represents a milestone in the study of the cardiovascular system; the Zenker model is a more recent one, developed in 2007, that is relatively simple and easy to implement. The comparison between the two models offers new prospects for the improvement of mathematical models of the cardiovascular system that may prove more effective in the study of hemorrhagic shock.

Insulin sensitivity depends on the route of glucose administration

AIMS/HYPOTHESIS

The small intestine plays an important role in hepatic and whole-body insulin sensitivity, as shown by bariatric surgery. Our goal was to study whether routes and dose of glucose administration have an acute impact on insulin sensitivity. The primary endpoint of this proof-of-concept study was the difference in insulin-mediated metabolic clearance rate (MCR/I) of glucose between the oral and intravenous routes of glucose administration. Secondary endpoints were differences in insulin effect on proteolysis, ketogenesis, lipolysis and glucagon levels.

METHODS

In this parallel cohort study, we administered multiple oral glucose loads to 23 participants (aged between 18 and 65 years) with morbid obesity and with normal or impaired glucose tolerance or type 2 diabetes. In a different session, we administered isoglycaemic intravenous glucose infusions (IGIVI) to match the plasma glucose levels observed during the oral challenges. Glucose rate of appearance (R_a) and disappearance (R_d) and endogenous glucose production (EGP) were calculated by infusing [6,6-²H₂]glucose with or without oral [U-¹³C₆]glucose. Plasma small polar metabolites were measured by gas chromatography and time-of-flight mass spectrometry. Lipids were measured by ultra-HPLC and quadrupole mass spectrometry. Glucagon-like peptide-1, insulin, C-peptide and glucagon were also measured. Participants, caregivers, people doing measurements or examinations, and people assessing the outcomes were unblinded to group assignment.

RESULTS

Glucose MCR/I was significantly higher during IGIVI than during oral glucose administration, independently of glycaemic status (12 ± 6 for IGIVI vs 7.4 ± 3 ml min^-1 kg^-1 per nmol/l for oral, p< 0.001 from paired t test). Insulin secretion was higher during oral administration than during IGIVI (p< 0.001). The disposition index was significantly lower during the oral procedure: 4260 ± 1820 vs 5000 ± 2360 (ml min^-1 kg^-1 (nmol/l)^-1 pmol/min; p = 0.005). Insulin clearance was significantly higher when glucose was infused rather than ingested (2.53 ± 0.82 vs 2.16 ± 0.49 l/min in intravenous and oral procedure, respectively, p = 0.006). The efficacy of insulin in inhibiting lipolysis and proteolysis was decreased after oral glucose loads. A heat map diagram showed a different pattern for the metabolites between the two routes of glucose administration.

CONCLUSIONS/INTERPRETATION

Our study shows that insulin sensitivity depends on the route of glucose administration, the oral route leading to increased insulin secretion and compensatory insulin resistance compared with the intravenous route. The efficacy of insulin in blocking lipolysis and protein breakdown is lower after oral glucose loads vs the intravenous route. Our findings suggest that, while the glucose-mediated incretin release is followed by an increase in insulin release, the effect of the released insulin is limited by an increase in insulin resistance.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03223129. Graphical abstract.

A novel fast-slow model of diabetes progression: Insights into mechanisms of response to the interventions in the Diabetes Prevention Program

Several models for the long-term development of T2DM already exist, focusing on the dynamics of the interaction between glycemia, insulinemia and β-cell mass. Current models consider representative (fasting or daily average) glycemia and insulinemia as characterizing the compensation state of the subject at some instant in slow time. This implies that only these representative levels can be followed through time and that the role of fast glycemic oscillations is neglected. An improved model (DPM15) for the long-term progression of T2DM is proposed, introducing separate peripheral and hepatic (liver and kidney) insulin actions. The DPM15 model no longer uses near-equilibrium approximation to separate fast and slow time scales, but rather describes, at each step in slow time, a complete day in the life of the virtual subject in fast time. The model can thus represent both fasting and postprandial glycemic levels and describe the effect of interventions acting on insulin-enhanced tissue glucose disposal or on insulin-inhibited hepatic glucose output, as well as on insulin secretion and β-cell replicating ability. The model can simulate long-term variations of commonly used clinical indices (HOMA-B, HOMA-IR, insulinogenic index) as well as of Oral Glucose Tolerance or Euglycemic Hyperinsulinemic Clamp test results. The model has been calibrated against observational data from the Diabetes Prevention Program study: it shows good adaptation to observations as a function of very plausible values of the parameters describing the effect of such interventions as Placebo, Intensive LifeStyle and Metformin administration.

Consistency of compact and extended models of glucose-insulin homeostasis: The role of variable pancreatic reserve

Published compact and extended models of the glucose-insulin physiologic control system are compared, in order to understand why a specific functional form of the compact model proved to be necessary for a satisfactory representation of acute perturbation experiments such as the Intra Venous Glucose Tolerance Test (IVGTT). A spectrum of IVGTT’s of virtual subjects ranging from normal to IFG to IGT to frank T2DM were simulated using an extended model incorporating the population-of-controllers paradigm originally hypothesized by Grodsky, and proven to be able to capture a wide array of experimental results from heterogeneous perturbation procedures. The simulated IVGTT’s were then fitted with the Single-Delay Model (SDM), a compact model with only six free parameters, previously shown to be very effective in delivering precise estimates of insulin sensitivity and secretion during an IVGTT. Comparison of the generating, extended-model parameter values with the obtained compact model estimates shows that the functional form of the nonlinear insulin-secretion term, empirically found to be necessary for the compact model to satisfactorily fit clinical observations, captures the pancreatic reserve level of the simulated virtual patients. This result supports the validity of the compact model as a meaningful analysis tool for the clinical assessment of insulin sensitivity.

Incidence of Hypoglycemia After Gastric Bypass vs Sleeve Gastrectomy: A Randomized Trial

CONTEXT

We compared the incidence of hypoglycemia after Roux-en-Y gastric bypass (RYGB) vs sleeve gastrectomy (SG).

DESIGN, SETTING, AND MAIN OUTCOME MEASURES

Randomized, open-label trial conducted at the outpatient obesity clinic in a university hospital in Rome, Italy. The primary aim was the incidence of reactive hypoglycemia (<3.1 mmol/L after 75-g oral glucose load) at 1 year after surgery. Secondary aims were hypoglycemia under everyday life conditions, insulin sensitivity, insulin secretion, and lipid profile.

RESULTS

Of 175 eligible patients, 120 were randomized 1:1 to RYGB or SG; 117 (93%) completed the 12-month follow-up. Reactive hypoglycemia was detected in 14% and 29% of SG and RYGB patients (P = 0.079), respectively, with the effect of treatment in multivariate analysis significant at P = 0.018. Daily hypoglycemic episodes during continuous glucose monitoring did not differ between groups (P = 0.75). Four of 59 RYGB subjects (6.8%) had 1 to 3 hospitalizations for symptomatic hypoglycemia vs 0 in SG. The static β-cell glucose sensitivity index increased after both treatments (P < 0.001), but the dynamic β-cell glucose sensitivity index increased significantly in SG (P = 0.008) and decreased in RYGB (P = 0.004 for time × treatment interaction). Whole-body insulin sensitivity increased about 10-fold in both groups.

CONCLUSIONS

We show that reactive hypoglycemia is no less common after SG and is not a safer option than RYGB, but RYGB is associated with more severe hypoglycemic episodes. This is likely due to the lack of improvement of β-cell sensitivity to changes in circulating glucose after RYGB, which determines an inappropriately high insulin secretion.

A Simple, Realistic Stochastic Model of Gastric Emptying

Several models of Gastric Emptying (GE) have been employed in the past to represent the rate of delivery of stomach contents to the duodenum and jejunum. These models have all used a deterministic form (algebraic equations or ordinary differential equations), considering GE as a continuous, smooth process in time. However, GE is known to occur as a sequence of spurts, irregular both in size and in timing. Hence, we formulate a simple stochastic process model, able to represent the irregular decrements of gastric contents after a meal. The model is calibrated on existing literature data and provides consistent predictions of the observed variability in the emptying trajectories. This approach may be useful in metabolic modeling, since it describes well and explains the apparently heterogeneous GE experimental results in situations where common gastric mechanics across subjects would be expected.

Determinants of Diabetes Remission and Glycemic Control After Bariatric Surgery

OBJECTIVE

Eligibility criteria for bariatric surgery in diabetes include BMI ≥35 kg/m(2) and poorly controlled glycemia. However, BMI does not predict diabetes remission, and thus, predictors need to be identified.

RESEARCH DESIGN AND METHODS

Seven hundred twenty-seven patients were included in a database merged from the Swedish Obese Subjects (SOS) study and two randomized controlled studies, with 415 surgical and 312 medical patients in total. Bariatric operations were divided into gastric only (GO) and gastric plus diversion (GD).

RESULTS

Sixty-four percent of patients in the surgical arm and 15.0% in the medical arm experienced diabetes remission (P < 0.001). GO yielded 60% remission, and GD yielded 76% remission. The best predictors of diabetes remission were lower baseline glycemia and shorter diabetes duration. However, when operation type was considered, GD predicted a higher likelihood of remission and greater weight loss. Patients in remission (responders) lost more weight (25% vs. 17%) and waist circumference (18% vs. 13%) and experienced better insulin sensitivity than nonresponders.

CONCLUSIONS

Surgery is more effective than medical treatment in achieving diabetes remission and tighter glycemic control. Shorter diabetes duration, lower fasting glycemia before surgery, and GD versus GO procedures independently predict higher rates of remission, whereas baseline HbA1c and waist circumference predict improved glycemic control. The results show the advantage of an early operation together with better controlled glycemia on diabetes remission independently of BMI.

A Unifying Organ Model of Pancreatic Insulin Secretion

The secretion of insulin by the pancreas has been the object of much attention over the past several decades. Insulin is known to be secreted by pancreatic β-cells in response to hyperglycemia: its blood concentrations however exhibit both high-frequency (period approx. 10 minutes) and low-frequency oscillations (period approx. 1.5 hours). Furthermore, characteristic insulin secretory response to challenge maneuvers have been described, such as frequency entrainment upon sinusoidal glycemic stimulation; substantial insulin peaks following minimal glucose administration; progressively strengthened insulin secretion response after repeated administration of the same amount of glucose; insulin and glucose characteristic curves after Intra-Venous administration of glucose boli in healthy and pre-diabetic subjects as well as in Type 2 Diabetes Mellitus. Previous modeling of β-cell physiology has been mainly directed to the intracellular chain of events giving rise to single-cell or cell-cluster hormone release oscillations, but the large size, long period and complex morphology of the diverse responses to whole-body glucose stimuli has not yet been coherently explained. Starting with the seminal work of Grodsky it was hypothesized that the population of pancreatic β-cells, possibly functionally aggregated in islets of Langerhans, could be viewed as a set of independent, similar, but not identical controllers (firing units) with distributed functional parameters. The present work shows how a single model based on a population of independent islet controllers can reproduce very closely a diverse array of actually observed experimental results, with the same set of working parameters. The model's success in reproducing a diverse array of experiments implies that, in order to understand the macroscopic behaviour of the endocrine pancreas in regulating glycemia, there is no need to hypothesize intrapancreatic pacemakers, influences between different islets of Langerhans, glycolitic-induced oscillations or β-cell sensitivity to the rate of change of glycemia.

A glycemia-structured population model

Structured models are population models in which the individuals are characterized with respect to the value of some variable of interest, called the structure variable. In the present paper, we propose a glycemia-structured population model, based on a linear partial differential equation with variable coefficients. The model is characterized by three rate functions: a new-adult population glycemic profile, a glycemia-dependent mortality rate and a glycemia-dependent average worsening rate. First, we formally analyze some properties of the solution, the transient behavior and the equilibrium distribution. Then, we identify the key parameters and functions of the model from real-life data and we hypothesize some plausible modifications of the rate functions to obtain a more beneficial steady-state behavior. The interest of the model is that, while it summarizes the evolution of diabetes in the population in a completely different way with respect to previously published Monte Carlo aggregations of individual-based models, it does appear to offer a good approximation of observed reality and of the features expected in the clinical setting. The model can offer insights in pharmaceutical research and be used to assess possible public health intervention strategies.

Bariatric-metabolic surgery versus conventional medical treatment in obese patients with type 2 diabetes: 5 year follow-up of an open-label, single-centre, randomised controlled trial

BACKGROUND

Randomised controlled trials have shown that bariatric surgery is more effective than conventional treatment for the short-term control of type-2 diabetes. However, published studies are characterised by a relatively short follow-up. We aimed to assess 5 year outcomes from our randomised trial designed to compare surgery with conventional medical treatment for the treatment of type 2 diabetes in obese patients.

METHODS

We did our open-label, randomised controlled trial at one diabetes centre in Italy. Patients aged 30-60 years with a body-mass index of 35 kg/m(2) or more and a history of type 2 diabetes lasting at least 5 years were randomly assigned (1:1:1), via a computer-generated randomisation procedure, to receive either medical treatment or surgery by Roux-en-Y gastric bypass or biliopancreatic diversion. Participants were aware of treatment allocation before the operation and study investigators were aware from the point of randomisation. The primary endpoint was the rate of diabetes remission at 2 years, defined as a glycated haemaglobin A1c (HbA1c) concentration of 6·5% or less (≤47·5 mmol/mol) and a fasting glucose concentration of 5·6 mmol/L or less without active pharmacological treatment for 1 year. Here we analyse glycaemic and metabolic control, cardiovascular risk, medication use, quality of life, and long-term complications 5 years after randomisation. Analysis was by intention to treat for the primary endpoint and by per protocol for the 5 year follow-up. This study is registered with ClinicalTrials.gov, number NCT00888836.

FINDINGS

Between April 27, 2009, and Oct 31, 2009, we randomly assigned 60 patients to receive either medical treatment (n=20) or surgery by gastric bypass (n=20) or biliopancreatic diversion (n=20); 53 (88%) patients completed 5 years' follow-up. Overall, 19 (50%) of the 38 surgical patients (seven [37%] of 19 in the gastric bypass group and 12 [63%] of 19 in the bilipancreatic diversion group) maintained diabetes remission at 5 years, compared with none of the 15 medically treated patients (p=0·0007). We recorded relapse of hyperglycaemia in eight (53%) of the 15 patients who achieved 2 year remission in the gastric bypass group and seven (37%) of the 19 patients who achieved 2 year remission in the biliopancreatic diversion group. Eight (42%) patients who underwent gastric bypass and 13 (68%) patients who underwent biliopancreatic diversion had an HbA1c concentration of 6·5% or less (≤47·5 mmol/mol) with or without medication, compared with four (27%) medically treated patients (p=0·0457). Surgical patients lost more weight than medically treated patients, but weight changes did not predict diabetes remission or relapse after surgery. Both surgical procedures were associated with significantly lower plasma lipids, cardiovascular risk, and medication use. Five major complications of diabetes (including one fatal myocardial infarction) arose in four (27%) patients in the medical group compared with only one complication in the gastric bypass group and no complications in the biliopancreatic diversion group. No late complications or deaths occurred in the surgery groups. Nutritional side-effects were noted mainly after biliopancreatic diversion.

INTERPRETATION

Surgery is more effective than medical treatment for the long-term control of obese patients with type 2 diabetes and should be considered in the treatment algorithm of this disease. However, continued monitoring of glycaemic control is warranted because of potential relapse of hyperglycaemia.

FUNDING

Catholic University of Rome.

A stochastic delay differential model of cerebral autoregulation

Mathematical models of the cardiovascular system and of cerebral autoregulation (CAR) have been employed for several years in order to describe the time course of pressures and flows changes subsequent to postural changes. The assessment of the degree of efficiency of cerebral auto regulation has indeed importance in the prognosis of such conditions as cerebro-vascular accidents or Alzheimer. In the quest for a simple but realistic mathematical description of cardiovascular control, which may be fitted onto non-invasive experimental observations after postural changes, the present work proposes a first version of an empirical Stochastic Delay Differential Equations (SDDEs) model. The model consists of a total of four SDDEs and two ancillary algebraic equations, incorporates four distinct delayed controls from the brain onto different components of the circulation, and is able to accurately capture the time course of mean arterial pressure and cerebral blood flow velocity signals, reproducing observed auto-correlated error around the expected drift.

Effect of indoor nitrogen dioxide on lung function in urban environment

BACKGROUND

High levels of indoor NO2 are associated with increased asthma symptoms and decreased expiratory peak flows in children. We investigated the association of exposure to domestic indoor NO2, objectively measured in winter and spring, with respiratory symptoms and lung function in a sample of adolescents from a southern Mediterranean area.

METHODS

From a large school population sample (n=2150) participating in an epidemiological survey in the urban area of the City of Palermo (southern Italy), a sub-sample of 303 adolescents was selected which furnished an enriched sample for cases of current asthma. All subjects were evaluated by a health questionnaire, skin prick tests and spirometry. One-week indoor NO2 monitoring of their homes was performed by diffusive sampling during spring and again during winter.

RESULTS

We found that about 25% of subjects were exposed to indoor NO2 levels higher than the 40µg/m(3) World Health Organization limit, during both spring and winter. Moreover, subjects exposed to the highest indoor NO2 concentrations had increased frequency of current asthma (p=0.005), wheeze episodes in the last 12 months (p<0.001), chronic phlegm (p=0.013), and rhinoconjunctivitis (p=0.008). Finally, subjects with a personal history of wheeze ever had poorer respiratory function (FEF25-75%, p=0.01) when exposed to higher indoor NO2 concentrations.

CONCLUSIONS

Home exposure to high indoor NO2 levels frequently occurs in adolescents living in a southern Mediterranean urban area and is significantly associated with the risks for increased frequency of both respiratory symptoms and reduced lung function.

Mathematical modeling of renal tubular glucose absorption after glucose load

A partial differential Progressive Tubular Reabsorption (PTR) model, describing renal tubular glucose reabsorption and urinary glucose excretion following a glucose load perturbation, is proposed and fitted to experimental data from five subjects. For each subject the Glomerular Filtration Rate was estimated and both blood and urine glucose were sampled following an Intra-Venous glucose bolus. The PTR model was compared with a model representing the conventional Renal Threshold Hypothesis (RTH). A delay bladder compartment was introduced in both formulations. For the RTH model, the average threshold for glycosuria varied between 9.90 ± 4.50 mmol/L and 10.63 ± 3.64 mmol/L (mean ± Standard Deviation) under different hypotheses; the corresponding average maximal transport rates varied between 0.48 ± 0.45 mmol/min (86.29 ± 81.22 mg/min) and 0.50 ± 0.42 mmol/min (90.62 ± 76.15 mg/min). For the PTR Model, the average maximal transports rates varied between 0.61 ± 0.52 mmol/min (109.57 ± 93.77 mg/min) and 0.83 ± 0.95 mmol/min (150.13 ± 171.85 mg/min). The time spent by glucose inside the tubules before entering the bladder compartment varied between 1.66 ± 0.73 min and 2.45 ± 1.01 min. The PTR model proved much better than RTH at fitting observations, by correctly reproducing the delay of variations of glycosuria with respect to the driving glycemia, and by predicting non-zero urinary glucose elimination at low glycemias. This model is useful when studying both transients and steady-state glucose elimination as well as in assessing drug-related changes in renal glucose excretion.

Routine OGTT: a robust model including incretin effect for precise identification of insulin sensitivity and secretion in a single individual

In order to provide a method for precise identification of insulin sensitivity from clinical Oral Glucose Tolerance Test (OGTT) observations, a relatively simple mathematical model (Simple Interdependent glucose/insulin MOdel SIMO) for the OGTT, which coherently incorporates commonly accepted physiological assumptions (incretin effect and saturating glucose-driven insulin secretion) has been developed. OGTT data from 78 patients in five different glucose tolerance groups were analyzed: normal glucose tolerance (NGT), impaired glucose tolerance (IGT), impaired fasting glucose (IFG), IFG+IGT, and Type 2 Diabetes Mellitus (T2DM). A comparison with the 2011 Salinari (COntinuos GI tract MOdel, COMO) and the 2002 Dalla Man (Dalla Man MOdel, DMMO) models was made with particular attention to insulin sensitivity indices IS_COMO, IS_DMMO and k_xgi (the insulin sensitivity index for SIMO). ANOVA on k_xgi values across groups resulted significant overall (P<0.001), and post-hoc comparisons highlighted the presence of three different groups: NGT (8.62×10⁻⁵±9.36×10⁻⁵ min⁻¹pM⁻¹), IFG (5.30×10⁻⁵±5.18×10⁻⁵) and combined IGT, IFG+IGT and T2DM (2.09×10⁻⁵±1.95×10⁻⁵, 2.38×10⁻⁵±2.28×10⁻⁵ and 2.38×10⁻⁵±2.09×10⁻⁵ respectively). No significance was obtained when comparing IS_COMO or IS_DMMO across groups. Moreover, k_xgi presented the lowest sample average coefficient of variation over the five groups (25.43%), with average CVs for IS_COMO and IS_DMMO of 70.32% and 57.75% respectively; k_xgi also presented the strongest correlations with all considered empirical measures of insulin sensitivity. While COMO and DMMO appear over-parameterized for fitting single-subject clinical OGTT data, SIMO provides a robust, precise, physiologically plausible estimate of insulin sensitivity, with which habitual empirical insulin sensitivity indices correlate well. The k_xgi index, reflecting insulin secretion dependency on glycemia, also significantly differentiates clinically diverse subject groups. The SIMO model may therefore be of value for the quantification of glucose homeostasis from clinical OGTT data.

Double-blind, randomized study evaluating the glycemic and anti-inflammatory effects of subcutaneous LY2189102, a neutralizing IL-1β antibody, in patients with type 2 diabetes

OBJECTIVE

Inflammation is associated with pancreatic β-cell apoptosis and reduced insulin sensitivity. Literature suggests that interleukin (IL)-1β may contribute to the pathogenesis of type 2 diabetes mellitus (T2DM). This study aimed to determine the efficacy, safety, and tolerability of LY2189102, a neutralizing IL-1β antibody, in T2DM patients.

RESEARCH DESIGN AND METHODS

Phase II, randomized, double-blind, parallel, placebo-controlled study of subcutaneous LY2189102 (0.6, 18, and 180 mg) administered weekly for 12 weeks in T2DM patients on diet and exercise, with or without approved antidiabetic medications.

RESULTS

LY2189102 reduced HbA1c at 12 weeks (adjusted mean differences versus placebo: -0.27, -0.38 and -0.25% for 0.6, 18 and 180 mg doses, respectively), and fasting glucose at multiple time points compared with placebo. LY2189102 also reduced postprandial glycemia, and inflammatory biomarkers, including hs-CRP and IL-6. LY2189102 was generally well tolerated.

CONCLUSIONS

Weekly subcutaneous LY2189102 for 12 weeks was well tolerated, modestly reduced HbA1c and fasting glucose, and demonstrated significant anti-inflammatory effects in T2DM patients. Neutralizing IL-1β holds promise as a convenient adjuvant treatment for T2DM.

Effects of transoral gastroplasty on glucose homeostasis in obese subjects

CONTEXT AND OBJECTIVE

Transoral gastroplasty (TOGA) is a safe and less invasive procedure than traditional bariatric surgery. We studied the effects of TOGA on the risk of progression from prediabetes to overt type 2 diabetes mellitus (T2DM) or on regression from diabetes or prediabetes to a lower risk category.

DESIGN AND SETTING

Prospective, observational study (October 2008 to October 2010) performed at Catholic University, Rome, Italy. Fifty consecutive subjects 18-60 years old, 35 ≥ body mass index < 55 kg/m², were enrolled. Glucose tolerance, insulin sensitivity, and secretion were studied at baseline and 1 week and 1, 6, and 12 months after TOGA. Plasma glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic peptide (GIP), and ghrelin levels were measured.

RESULTS

Forty-three patients (86%) completed the 1-year postoperative follow-up. Patients lost 16.90% of baseline weight (P level × factor time <0.001). Body mass index decreased from 42.24 ± 3.43 to 34.65 ± 4.58 kg/m² (P < .001). Twenty-three patients (53.5%) were diagnosed as normal glucose tolerance (NGT) before treatment, 2 (4.6%) were impaired fasting glucose (IFG), 12 (27.9%) were impaired glucose tolerance (IGT), 1 (2.3%) had both IFG and IGT, and 5 (11.6%) had T2DM. At 1-year posttreatment, the percentages changed to 86.0% NGT, 2.3% IFG, 11.6% IGT, 0% IFG plus IGT, and 0% T2DM, respectively. Peripheral insulin resistance and homeostasis model of assessment-insulin resistance improved significantly. Fasting glucose-dependent insulinotropic peptide and ghrelin decreased from 316.9 ± 143.1 to 156.2 ± 68.2 pg/mL (P < .001) and from 630.6 ± 52.1 to 456.7 ± 73.1 pg/mL (P < .001), respectively, whereas GLP-1 increased from 16.2 ± 4.9 to 23.7 ± 9.5 pg/mL (P < .001).

CONCLUSIONS

TOGA induced glucose disposal improvement with regression of diabetes to NGT or IGT and regression of IGT and IFG to NGT in half of the cases. Regressors showed a much larger increase of GLP-1 levels than progressors.

Twenty-four hour energy expenditure and skeletal muscle gene expression changes after bariatric surgery

CONTEXT

Obesity is characterized by decreased insulin-stimulated glucose uptake in muscle and shift from glucose to lipid oxidation, the so-called metabolic inflexibility. Biliopancreatic diversion (BPD), a mainly malabsorptive bariatric operation, determines a prompt improvement of insulin resistance, but the mechanisms are still unclear.

OBJECTIVE

We aimed to estimate the response of glucose transporter 4 (GLUT4) and hexokinase-II (HKII) gene expression to hyperinsulinemia before and after surgical treatment with a BPD or dietary-induced weight loss. The association with 24-hour energy expenditure and its different components-diet-induced thermogenesis (DIT), resting energy expenditure, physical activity (PA) of daily living, and physical exercise-was also determined. DESIGN, SETTING, AND MAIN OUTCOME MEASURES: Case-control study: 20 subjects, BPD vs diet-induced weight loss. Four subjects withdrew in the surgical arm and 1 subject withdrew in the dietary arm. Insulin sensitivity was measured by the euglycemic-hyperinsulinemic clamp. Energy expenditure was assessed by indirect calorimetry over 24 hours. Muscle biopsies were obtained during the clamp to measure gene expression: GLUT4 and HKII.

RESULTS

Insulin sensitivity increased significantly (P < .01) only after BPD (0.101 ± 0.012 to 0.204 ± 0.033 μmol/kg/min/pM). Enhanced GLUT4 and HKII mRNA levels were observed after surgery (P < .0001 and P = .021, respectively), whereas they were not affected by diet-induced weight loss. Carbohydrate oxidation (P = .0027), DIT (P = .033), PA (P = .036), and energy expenditure during the exercise (P = .017) increased only in the BPD group.

CONCLUSIONS

BPD improved impaired glucose metabolism and insulin resistance through increased glucose uptake, glycogen synthesis, and glucose oxidation. Furthermore, the concomitant increase in DIT, PA, and exercise in BPD patients may partly explain their ability to sustained long-term weight loss and may contribute to the improved insulin sensitivity.

A geometrical approach to the PKPD modelling of inhaled bronchodilators

The present work introduces a new method to model the pharmacokinetics (PK) and pharmacodynamics (PD) of an inhaled dose of bronchodilator, alternative to classic compartmental representations or computational fluid dynamics. A five compartment PK model comprising alimentary tract absorption (gut), bronchial tree mucosa, bronchial muscles, plasma, and elimination/excretion pathways has been developed. Many anatomical and physiological features of the bronchial tree depend on bronchial generation or on mean distance from the larynx. Among these are diameters, resistances, and receptor density, which determine together the local response to the inhaled drug; integrating these local responses over the whole bronchial tree allows an approximation of total bronchodilator response and airflow resistance. While the PK part of the model reflects classical compartmental assumptions, the PD part adds a simplified geometrical and functional description of the bronchial tree to a typical empirical model of local effect on bronchial muscle, leading to the direct computation of the approximate forced expiratory volume in 1 s (FEV(1)). In the present work the construction of the model is detailed, with reference to literature data. Simulation of a hypothetical asthmatic subject is employed to illustrate the behaviour of the model in representing the evolution over time of the distribution and pharmacological effect of an inhaled dose of a bronchodilator. The relevance of particle size and drug formulation diffusivity on therapeutic efficacy is discussed.

Evaluation of a mathematical model of diabetes progression against observations in the Diabetes Prevention Program

The seminal publication of the Diabetes Prevention Program (DPP) results in 2002 has provided insight into the impact of major therapies on the development of diabetes over a time span of a few years. In the present work, the publicly available DPP data set is used to calibrate and evaluate a recently developed mechanistic mathematical model for the long-term development of diabetes to assess the model's ability to predict the natural history of disease progression and the effectiveness of preventive interventions. A general population is generated from which virtual subject samples corresponding to the DPP enrollment criteria are selected. The model is able to reproduce with good fidelity the observed time courses of both diabetes incidence and average glycemia, under realistic hypotheses on evolution of disease and efficacy of the studied therapies, for all treatment arms. Model-based simulations of the long-term evolution of the disease are consistent with the transient benefits observed with conventional therapies and with promising effects of radical improvement of insulin sensitivity (as by metabolic surgery) or of β-cell protection. The mechanistic diabetes progression model provides a credible tool by which long-term implications of antidiabetic interventions can be evaluated.

Modeling rejection immunity

Background

Transplantation is often the only way to treat a number of diseases leading to organ failure. To overcome rejection towards the transplanted organ (graft), immunosuppression therapies are used, which have considerable side-effects and expose patients to opportunistic infections. The development of a model to complement the physician’s experience in specifying therapeutic regimens is therefore desirable. The present work proposes an Ordinary Differential Equations model accounting for immune cell proliferation in response to the sudden entry of graft antigens, through different activation mechanisms. The model considers the effect of a single immunosuppressive medication (e.g. cyclosporine), subject to first-order linear kinetics and acting by modifying, in a saturable concentration-dependent fashion, the proliferation coefficient. The latter has been determined experimentally. All other model parameter values have been set so as to reproduce reported state variable time-courses, and to maintain consistency with one another and with the experimentally derived proliferation coefficient.

Results

The proposed model substantially simplifies the chain of events potentially leading to organ rejection. It is however able to simulate quantitatively the time course of graft-related antigen and competent immunoreactive cell populations, showing the long-term alternative outcomes of rejection, tolerance or tolerance at a reduced functional tissue mass. In particular, the model shows that it may be difficult to attain tolerance at full tissue mass with acceptably low doses of a single immunosuppressant, in accord with clinical experience.

Conclusions

The introduced model is mathematically consistent with known physiology and can reproduce variations in immune status and allograft survival after transplantation. The model can be adapted to represent different therapeutic schemes and may offer useful indications for the optimization of therapy protocols in the transplanted patient.

Bariatric surgery and T2DM improvement mechanisms: a mathematical model

Background

Consensus exists that several bariatric surgery procedures produce a rapid improvement of glucose homeostasis in obese diabetic patients, improvement apparently uncorrelated with the degree of eventual weight loss after surgery. Several hypotheses have been suggested to account for these results: among these, the anti-incretin, the ghrelin and the lower-intestinal dumping hypotheses have been discussed in the literature. Since no clear-cut experimental results are so far available to confirm or disprove any of these hypotheses, in the present work a mathematical model of the glucose-insulin-incretin system has been built, capable of expressing these three postulated mechanisms. The model has been populated with critically evaluated parameter values from the literature, and simulations under the three scenarios have been compared.

Results

The modeling results seem to indicate that the suppression of ghrelin release is unlikely to determine major changes in short-term glucose control. The possible existence of an anti-incretin hormone would be supported if an experimental increase of GIP concentrations were evident post-surgery. Given that, on the contrary, collected evidence suggests that GIP concentrations decrease post-surgery, the lower-intestinal dumping hypothesis would seem to describe the mechanism most likely to produce the observed normalization of Type 2 Diabetes Mellitus (T2DM) after bariatric surgery.

Conclusions

The proposed model can help discriminate among competing hypotheses in a context where definitive data are not available and mechanisms are still not clear.

Bariatric surgery versus conventional medical therapy for type 2 diabetes

BACKGROUND

Roux-en-Y gastric bypass and biliopancreatic diversion can markedly ameliorate diabetes in morbidly obese patients, often resulting in disease remission. Prospective, randomized trials comparing these procedures with medical therapy for the treatment of diabetes are needed.

METHODS

In this single-center, nonblinded, randomized, controlled trial, 60 patients between the ages of 30 and 60 years with a body-mass index (BMI, the weight in kilograms divided by the square of the height in meters) of 35 or more, a history of at least 5 years of diabetes, and a glycated hemoglobin level of 7.0% or more were randomly assigned to receive conventional medical therapy or undergo either gastric bypass or biliopancreatic diversion. The primary end point was the rate of diabetes remission at 2 years (defined as a fasting glucose level of <100 mg per deciliter [5.6 mmol per liter] and a glycated hemoglobin level of <6.5% in the absence of pharmacologic therapy).

RESULTS

At 2 years, diabetes remission had occurred in no patients in the medical-therapy group versus 75% in the gastric-bypass group and 95% in the biliopancreatic-diversion group (P<0.001 for both comparisons). Age, sex, baseline BMI, duration of diabetes, and weight changes were not significant predictors of diabetes remission at 2 years or of improvement in glycemia at 1 and 3 months. At 2 years, the average baseline glycated hemoglobin level (8.65±1.45%) had decreased in all groups, but patients in the two surgical groups had the greatest degree of improvement (average glycated hemoglobin levels, 7.69±0.57% in the medical-therapy group, 6.35±1.42% in the gastric-bypass group, and 4.95±0.49% in the biliopancreatic-diversion group).

CONCLUSIONS

In severely obese patients with type 2 diabetes, bariatric surgery resulted in better glucose control than did medical therapy. Preoperative BMI and weight loss did not predict the improvement in hyperglycemia after these procedures. (Funded by Catholic University of Rome; ClinicalTrials.gov number, NCT00888836.).

Protocol for a randomised clinical study comparing the effect of Roux-en-Y gastric bypass and sleeve gastrectomy on reactive hypoglycaemia in morbidly obese subjects

INTRODUCTION

Roux-en-Y gastric bypass (RYGB) is the most performed bariatric operation. Reactive hypoglycaemia is a frequent late complication occurring in about 72% of RYGB patients, which can present with various intensities up to the serious form of neuroglycopaenia. However, it seems to occur also after sleeve gastrectomy (SG) although much more rarely.

METHODS AND ANALYSIS

A single centre, open, 1-year randomised trial to compare the incidence of hypoglycaemia after RYGB or SG. A secondary objective is the assessment of the comparative ability of the two surgical procedures in determining the improvement or normalisation of insulin sensitivity, given the established relevance of insulin resistance in the cardiometabolic syndrome of obesity.

ETHICS AND DISSEMINATION

The study will be published and presented to international meetings and, due to the safety issue, it will represent a relevant information for national healthcare systems. The protocol was approved by the Catholic University Ethical Committee (A1534/CE/2012). Clinicaltrials.gov Registration n. NCT01581801.

The range of time delay and the global stability of the equilibrium for an IVGTT model

Diabetes mellitus has become a prevalent disease in the world. Diagnostic protocol for the onset of diabetes mellitus is the initial step in the treatments. The intravenous glucose tolerance test (IVGTT) has been considered as the most accurate method to determine the insulin sensitivity and glucose effectiveness. It is well known that there exists a time delay in insulin secretion stimulated by the elevated glucose concentration level. However, the range of the length of the delay in the existing IVGTT models are not fully discussed and thus in many cases the time delay may be assigned to a value out of its reasonable range. In addition, several attempts had been made to determine when the unique equilibrium point is globally asymptotically stable. However, all these conditions are delay-independent. In this paper, we discuss the range of the time delay and provide easy-to-check delay-dependent conditions for the global asymptotic stability of the equilibrium point for a recent IVGTT model through Liapunov function approach. Estimates of the upper bound of the delay for global stability are given in corollaries. In addition, the numerical simulation in this paper is fully incorporated with functional initial conditions, which is natural and more appropriate in delay differential equation systems.

Effects of bilio-pancreatic diversion on diabetic complications: a 10-year follow-up

OBJECTIVE

The surgical option could represent a valid alternative to medical therapy in some diabetic patients. However, no data are available on long-term effects of metabolic surgery on diabetic complications. We aimed to determine whether patients with newly diagnosed type 2 diabetes who underwent bilio-pancreatic diversion (BPD) had less micro- and macrovascular complications than those who received conventional therapy.

RESEARCH DESIGN AND METHODS

This was an unblinded, case-controlled trial with 10-years' follow-up, conducted from July 1998 through October 2009 at the Day Hospital of Metabolic Diseases, Catholic University, Rome, Italy. A consecutive sample of 110 obese patients (BMI >35 kg/m(2)) with newly diagnosed type 2 diabetes was enrolled. The study was completed by 50 subjects. The main outcome measure was long-term effects (10 years) of BPD versus those associated with conventional therapy on microvascular outcome, micro- and macroalbuminuria, and glomerular filtration rate (GFR). Secondary measures included macrovascular outcomes, type 2 diabetes remission, glycated hemoglobin, and hyperlipidemia.

RESULTS

Ten-year GFR variation was -45.7 ± 18.8% in the medical arm and 13.6 ± 24.5% in the surgical arm (P < 0.001). Ten-year hypercreatininemia prevalence was 39.3% in control subjects and 9% in BPD subjects (P = 0.001). After 10 years, all BPD subjects recovered from microalbuminuria, whereas microalbuminuria appeared or progressed to macroalbuminuria in control subjects. Three myocardial infarctions, determined by electrocardiogram, and one stroke occurred in control subjects. After the 10-year follow-up, coronary heart disease (CHD) probability was 0.22 ± 0.10 and 0.05 ± 0.04 in the medical and surgical groups, respectively (P < 0.001). Remission from type 2 diabetes was observed in all patients within 1 year of surgery. Surgical and medical subjects had lost 34.60 ± 10.25 and 0.38 ± 6.10% of initial weight at the 10-year follow-up (P < 0.001).

CONCLUSIONS

Renal and cardiovascular complications were dramatically reduced in the surgical arm, indicating long-term benefits of BPD on diabetic complications, at least in the case of morbid obesity with decompensated type 2 diabetes.

Resistant arterial hypertension: association with syncronous kidney cancer and adrenal adenoma

The coexistence of renal cancer and adrenal adenoma is rare. We report the case of a 60-year-old patient with synchronous hypernephroma and adrenal adenoma. The patient presented with resistant hypertension, high plasma renin activity and aldosterone and target organ damage. Removal of the affected kidney cured the hypertension and normalized the plasma renin activity (PRA) and circulating aldosterone. This suggests that the coexistence of kidney cancer and adrenal adenoma may be a curable cause of resistant hypertension. The potential mechanisms accounting for the lack of suppression of PRA are discussed.

Advantages of the single delay model for the assessment of insulin sensitivity from the intravenous glucose tolerance test

Background

The Minimal Model, (MM), used to assess insulin sensitivity (IS) from Intra-Venous Glucose-Tolerance Test (IVGTT) data, suffers from frequent lack of identifiability (parameter estimates with Coefficients of Variation (CV) less than 52%). The recently proposed Single Delay Model (SDM) is evaluated as a practical alternative.

Methods

The SDM was applied to 74 IVGTTs from lean (19), overweight (22), obese (22) and morbidly obese (11) subjects. Estimates from the SDM (K_xgI) were compared with the corresponding MM (S_I), 1/HOMA-IR index and Euglycemic-Hyperinsulinemic Clamp (M-EHC over 7 subjects) estimates.

Results

K_xgI was identifiable in 73 out of 74 subjects (CV = 69% in the 74^th subject) and ranged from 1.25 × 10^-5 to 4.36 × 10^-4min^-1pM^-1; S_I CV was >52% in 36 subjects (up to 2.36 × 10⁹%) and presented 18 extreme values (≤ 1.5 × 10^-12 or ≥ 3.99).

K_xgI correlated well with 1/HOMA-IR (r = 0.56, P < 0.001), whereas the correlations K_xgI-S_I and 1/HOMA-IR-S_I were high (r = 0.864 and 0.52 respectively) and significant (P < 0.001 in both cases) only in the non-extreme S_I sub-sample (56 subjects). Correlations K_xgI vs. M-EHC and S_I vs. M-EHC were positive (r = 0.92, P = 0.004 and r = 0.83, P = 0.02 respectively). K_xgI decreased for higher BMI's (P < 0.001), S_I significantly so only over the non-extreme-S_I sub-sample. The Acute Insulin Response Index was also computed and the expected inverse (hyperbolic) relationship with the K_xgI observed.

Conclusions

Precise estimation of insulin sensitivity over a wide range of BMI, stability of all other model parameters, closer adherence to accepted physiology make the SDM a useful alternative tool for the evaluation of insulin sensitivity from the IVGTT.

Blood pressure assessment in haemodialysis patients: comparison between pre-dialysis blood pressure and ambulatory blood pressure measurement

AIM

Hypertension is common in haemodialysis (HD) patients. Determining the most appropriate method of blood pressure (BP) measurement, representative of target organ damage, is still an issue. BP variations between pre- and post-HD treatment, or between on-dialysis day and off-dialysis day, are common. The aim of this study was to examine the possible differences between pre-HD office BP (OBP) levels, inter-HD (iHD) or HDday 24 h ambulatory BP measurement (ABPM) with 48 h ABPM, where the latter was considered the gold standard.

METHODS

163 HD patients were studied. BP was monitored consecutively for 48 h with a Takeda TM2421 device, then sub-analysed into two periods of 24 h: HD and iHD day. An average of 12 sessions pre-HD OBP measurements was determined.

RESULTS

OBP significantly overestimates systolic (SBP) and diastolic BP (DBP) when compared with 48 hABPM. SBP and DBP are significantly higher on iHD day than on HD day: 141.2 1 20.8 versus 137.9 1 20.9, and 77.1 1 11.1 versus 76.1 1 10.9 (P < 0.01). No differences of SBP night/day ratio were reported between 48 hABPM and iHD 24 h ABPM or HD 24 h ABPM. The highest correlations were reported between 48 h SBP/DBP with iHD or HD 24 h ABPM (r 2 = 0.95, P < 0.001), while the lowest between 48 h SBP/DBP and OBP (r 2 = 0.40,P < 0.01, r 2 = 0.12, P < 0.01). The narrowest limits of agreement using the Bland and Altman test were reported between 48 h SBP or DBP and 24 h iHD or HD day ABPM. Considering 48 h ABPM, 80.5% of patients had BP higher than the norm, compared with 61.7% of patients in the case of OBP (c2 = 13.28, P < 0.001). The sensibility for detecting hypertension for iHD day 24 h ABPM was 98.4%, with specificity of 90%. The sensibility of 24 h HDday ABPM was 90.3%, with specificity 96.6%. In the case of OBP, sensibility and specificity were considerably lower, that is, 72.6% and 83.3% respectively.

CONCLUSION

Significant differences are shown between OBP and 48 h ABPM in the recognition of a hypertensive state. OBP measurement has a lower sensibility and specificity than 24 h ABPM, which remains a valid alternative approach to 48 h ABPM in HD patients. Errors of OBP estimation should be taken into account, with possible negative impact on treatment strategies and epidemiology studies