Progress Toward the Development of an Implantable Sensor for Glucose

The development of an electrochemically based implantable sensor for glucose is described. The sensor is needle-shaped, about the size of a 28-gauge needle. It is flexible and must be implanted subcutaneously by using a 21-gauge catheter, which is then removed. When combined with a monitoring unit, this device, based on the glucose oxidase-catalyzed oxidation of glucose, reliably monitors glucose concentrations for as long as 10 days in rats. Various design considerations, including the decision to monitor the hydrogen peroxide produced in the enzymatic reaction, are discussed. Glucose constitutes the most important future target analyte for continuous monitoring, but the basic methodology developed for glucose could be applied to several other analytes such as lactate or ascorbate. The success in implementation of such a device depends on a reaction of the tissue surrounding the implant so as not to interfere with the proper functioning of the sensor. Histochemical evidence indicates that the tissue response leads to enhanced sensor performance.

Temporality in chronic diseases and adherence to long-term therapies: From philosophy to science and back

This narrative review exhibits the construction and validation of a hypothesis to explain how treatment non-adherence in people with chronic disease, a major issue in contemporary medicine, occurs. I propose that non-adherence to long-term therapies is at least in part due to failure to prioritize the future, which is caused by a condition I dub disruption in time projection. This article gives the rationale for this hypothesis, which is largely grounded on philosophical arguments. Then, it demonstrates the plausibility of the hypothesis: on the one hand, it is consistent with certain epidemiological data found in the literature. On the other, it is possible to predict the underlying mechanisms of this lack of prioritization from recent achievements of neuro-economics and neuroscience. Next, it reviews empirical data that provide an experimental verification for this explanatory hypothesis. Finally, a general evolutionary and philosophical meaning for adherence is proposed, considering the advantages of its preconditions, namely, patience and foresight.

Holistic psychosocial determinants of adherence to medication in people with type 2 diabetes

BACKGROUND

The aim of this study was to determine whether adherent and non-adherent patients with type 2 diabetes can be differentiated according to psychosocial characteristics.

METHODS

A total of 1214 patients were included in the analysis. Data were derived from a cross-sectional observational study of adults with diabetes of the Access Santé (Access Health) panel of Kantar Health France. Patients completed a questionnaire on adherence to medication, psychological determinants (trust in physicians, constancy of habits, patience, temporal horizon, health locus of control, obedience, psychological reactivity, prevention vs promotion, optimism vs pessimism) and social deprivation.

RESULTS

Of these 1214 subjects, 46.2% were considered strictly adherent to antidiabetic medication, as reflected by negative answers to all six questions suggesting a non-adherent behaviours, whereas 48.9% provided 1-2 positive answers and 4.9% provided 3-6 positive answers, and were considered non-adherent. In addition to the effect of younger age (P=0.03), multivariate logistic regression analysis demonstrated the following psychosocial determinants of non-adherence: chance locus of control (P=0.02); lack of trust in physicians (P=0.010); and pessimism (P=0.021). Multiple factor analysis identified adherence and social deprivation as dimensions separating three distinct patient populations: (i) non-adherent; (ii) adherent and socially deprived; and (iii) adherent and non-socially deprived. It also revealed that patience, obedience, cautious behaviour, optimism, trust in physicians and constancy of habits were associated with adherence.

CONCLUSION

Of the multiple determinants of adherence, trust in physicians and constancy of habits represent modifiable factors, and constitute targets to prevent non-adherence because they can be reinforced through patient education and improved physician - patient relationship. Also, psychosocial determinants of adherence differ widely between socially deprived and non-deprived patients.

Monitoring the Kinetics of Glucose Transfer across a Bioreactor Membrane with a Glucose Sensor

Bioreactors for cell culture, in which hollow fibers are sealed into a protective jacket, cells are seeded in the fibers’ outer surface and a culture medium circulates through the fibers, have been proposed as a bioartificial pancreas. We used a needle-type glucose sensor to study the kinetics of glucose transfer across the membrane of one such device. The glucose transfer was found to be dependent on the flow rate of the circulating medium, which suggests the involvement of an ultrafiltration flux across the membrane. The glucose concentration was heterogeneous within the cell compartment. This heterogeneity, and the delay in transmission of changes in glucose concentration from the circulating medium to the cell compartment, can be ascribed to the large volume of the compartment. The design of these bioreactors should therefore be modified, in order to meet the requirements of glucose transfer kinetics of a bioartificial pancreas.

Clinical inertia and its impact on treatment intensification in people with type 2 diabetes mellitus

Many people with type 2 diabetes mellitus (T2DM) fail to achieve glycaemic control promptly after diagnosis and do not receive timely treatment intensification. This may be in part due to 'clinical inertia', defined as the failure of healthcare providers to initiate or intensify therapy when indicated. Physician-, patient- and healthcare-system-related factors all contribute to clinical inertia. However, decisions that appear to be clinical inertia may, in fact, be only 'apparent' clinical inertia and may reflect good clinical practice on behalf of the physician for a specific patient. Delay in treatment intensification can happen at all stages of treatment for people with T2DM, including prescription of lifestyle changes after diagnosis, introduction of pharmacological therapy, use of combination therapy where needed and initiation of insulin. Clinical inertia may contribute to people with T2DM living with suboptimal glycaemic control for many years, with dramatic consequences for the patient in terms of quality of life, morbidity and mortality, and for public health because of the huge costs associated with uncontrolled T2DM. Because multiple factors can lead to clinical inertia, potential solutions most likely require a combination of approaches involving fundamental changes in medical care. These could include the adoption of a person-centred model of care to account for the complex considerations influencing treatment decisions by patients and physicians. Better patient education about the progressive nature of T2DM and the risks inherent in long-term poor glycaemic control may also reinforce the need for regular treatment reviews, with intensification when required.

Use of Polyethyleneglycol for Porcine Islet Cryopreservation

The aim of this work was to determine whether polyethylene glycol 20000 Da (PEG) could be used as protective agent in porcine islet cryopreservation. Cryopreservation was performed on 1-wk cultured pig islets and consisted in an overnight storage in liquid nitrogen. In a first set of experiments, we compared the in vitro function of PEG-cryopreserved islets to that of porcine islets cryopreserved under the standard procedure using dimethylsulfoxide (DMSO), by incubating the islets over 45 min in Krebs buffer containing either 2.8 or 10 mmol/L glucose. Insulin secretion of both types of islets reached a maximum at day 10 postthawing and had stimulation indices above 2 up to 3 wk after thawing. PEG-cryopreserved islets secreted more insulin than DMSO-treated islets and showed glucose-dependency insulin secretion in a 0-16.6 mmol/L glucose range. We also established that PEG-cryopreserved islets were as functional in vitro as nonfrozen tissue and that they could reverse experimental diabetes of the mouse for longer periods of time than noncryopreserved islets (p < 0.005 3 wk after transplantation) when implanted in the peritoneal cavity, being immunoprotected in a semipermeable hollow fiber. PEG can, therefore, be considered as a suitable cryoprotective compound for porcine islet storage.

[Factors associated with medication non-adherence in uncontrolled hypertensive males and females: ODACE study]

OBJECTIVES

The aim of this study was (1) to measure adherence in males and females with uncontrolled hypertension, and (2) to identify factors associated with non-adherence to antihypertensive medication.

PATIENTS AND METHODS

Each general practitioner (GP) should include the first two male and the first two female patients with uncontrolled treated hypertension. Adherence to antihypertensive treatment was estimated by the GP and using the French League Against High blood pressure (FLAH) self-administered questionnaire. A stepwise logistic regression analysis was used to identify factors associated with non-adherence on the FLAH scale, independently in males and in females.

RESULTS

A total of 1630 males and 1612 females were included in the analysis. Adherence to treatment was significantly better in females or when estimated by the GP. Lack of motivation was the first factor associated with poor adherence in both sexes. Considering hypertension as a simple anomaly and not a disease that can lead to cardiac or cerebral disorders was the second common parameter in both sexes. Other common factors were: having monthly periods of financial difficulties in facing his/her needs and absence of regular screening for colon cancer.

CONCLUSION

Adherence to treatment is better in uncontrolled hypertensive females. Poor adherence is mainly associated with non-clinical factors. The lack of motivation is the most important element.

Improving postpartum glucose screening after gestational diabetes mellitus: a cohort study to evaluate the multicentre IMPACT initiative

AIMS

To evaluate a mobilization campaign, the IMPACT initiative, which included multidisciplinary meetings, provision of information and a systematic prescription of an oral glucose tolerance test to improve the rate of glucose screening in women with gestational diabetes mellitus in the four largest maternity units in our area, starting in March 2011.

METHODS

We retrospectively compared the level of self-reported screening during the first 6 months postpartum of women who gave birth after having been diagnosed with gestational diabetes before (January 2009 to December 2010) and after the IMPACT campaign (April 2011 to February 2012).

RESULTS

We included 961 women (589 in the period before and 372 in the period after the campaign was initiated) with a mean ± SD age of 33.2 ± 5.3 years and BMI of 27.8 ± 5.3 kg/m². Multivariate analysis, stratified using a propensity score in order to limit bias caused by imbalance between both periods, showed that the postpartum screening rate was higher after the campaign began (48.9 vs 33.3%, odds ratio 1.7, 95% CI 1.1-2.5; P = 0.019) and higher in women who received insulin treatment during pregnancy (odds ratio 2.3, 95% CI 1.5-3.6; P < 0.001), consumed fruit and vegetables daily (odds ratio 1.6, 95% CI 1.1-2.4; P = 0.035) and did not smoke (smoking vs non-smoking: odds ratio 0.3, 95% CI 0.1-0.7; P = 0.01). There was no interaction between the campaign effect and these particular conditions. The proportion of oral glucose tolerance tests performed in women who underwent screening increased from 6.3 to 33.0%.

CONCLUSIONS

The IMPACT campaign increased postpartum screening, and the use the oral glucose tolerance test in particular. The effect of this initiative might be reinforced in women who are non-daily consumers of fruit and vegetables, smokers and those who do not receive insulin treatment during pregnancy.

Factors associated with screening for glucose abnormalities after gestational diabetes mellitus: baseline cohort of the interventional IMPACT study

INTRODUCTION

Although it is important to screen women who have had gestational diabetes mellitus (GDM) for abnormal post-partum glucose levels, such testing is rarely performed. The aim of this study was to use data from the first observational phase of the IMPACT study to determine rates of screening within 6 months of delivery in a multiethnic cohort, focusing in particular on the effects of social deprivation and the risk of future diabetes.

PATIENTS AND METHODS

To investigate the frequency of post-partum screening, charts were analyzed, and all women attending four centres located in a deprived area who had had GDM between January 2009 and December 2010 were contacted by phone. The Evaluation of Precarity and Inequalities in Health Examination Centres (EPICES) deprivation index and Finnish Diabetes Risk Score (FINDRISK) questionnaire were also evaluated.

RESULTS

Data were evaluable for 589 of the 719 women contacted (mean age: 33.4 ± 5.2 years; mean body mass index: 27.6 ± 5.4 kg/m(2)), and 196 (33.3%) reported having been screened. On multivariate analysis, factors associated with a lack of screening were smoking [odds ratio (OR): 0.42 (0.20-0.90), P<0.05], low consumption of fruit and vegetables [OR: 0.58 (0.39-0.82), P<0.01] and heavier offspring birth weight (P<0.05), although there were no differences in FINDRISK and EPICES scores between screened and unscreened women.

CONCLUSION

One-third of women who had had GDM reported having been screened for dysglycaemia at 6 months post-partum. However, it is expected that the interventional phase of the IMPACT study will increase screening rates, especially in women with the risk factors associated with lower screening rates during this observational phase.

Physical activity and type 2 diabetes. Recommandations of the SFD (Francophone Diabetes Society) diabetes and physical activity working group

Although regular physical activity is an integral part of T2D management, few diabetic patients have a sufficient level of physical activity. However over the past decade or so, the beneficial effects of regular physical activity have been well demonstrated, both in T2D prevention (50% reduction in the incidence of T2D in subjects with high metabolic risk) as well as T2D management for the improvement of glycaemic control (mean 0.7% improvement of HbA1c) and the reduction of T2D-related comorbidities (improvement in blood pressure values and lipid profile, decrease in insulin resistance). Physical activity has both acute effects (effects of one exercise session) and more prolonged effects of exercise when it is repeated on a regular basis (training effect). In addition, the physical activity recommendations have been extended to a wide range of physical activities (by combining both endurance and muscle strengthening exercises), thus varying the physical activity practiced according to the patient's available time, practice sites, preferences and interests. Following a pathophysiology review, the effects of physical activity will be discussed and presented in terms of evidence-based medicine. The recommendations will be defined and practical prescribing information will be suggested, while taking into account that clinicians are concerned with answering questions regarding how, where and with whom: how can patients be motivated to practice a physical activity over the long-term? And how can qualified exercise trainers and appropriate practice settings be found?

A psychophysical account of patient non-adherence to medical prescriptions. The case of insulin dose adjustment

AIM

Diabetic patients often do not adjust their insulin doses using the algorithms that they have been taught. While this behavior may intuitively have a number of causes, such as the complexity of the decision or the fear of hypoglycaemia, we propose in this article a more general, "psychophysical", explanation based on behavioral economics concepts used to describe decisions made under uncertainty and risk. The concepts discussed herein may not be familiar to clinicians, who will find here an introduction to theories that may be helpful in understanding some aspects of non-adherence to medical prescriptions.

RESULTS

1) The Prospect Theory of Kahneman and Tversky proposes that choices made in the context of risk are subject to loss aversion. 2) Decisions under uncertainty use mental short cuts called "heuristics", which can lead to biases; for instance, overestimating the probability of the risk. 3) To understand the very concept of risk, emotions must be considered with a special focus on anticipated regret. 4) Finally, selection difficulty is an important determinant of the preference for the status quo.

CONCLUSION

These concepts may be relevant for understanding a preference for the status quo in decisions made in a context of uncertainty and risk, such as insulin dose adjustment. We suggest that these mental mechanisms may also be involved in other aspects of patients' non-adherence. As other common human behaviors, non-adherence may actually often be a consequence of biases resulting from our ways of thinking, being both cognitive and emotional, and, according to Kahneman, more often "fast" than "slow". Empirical studies are needed to support this hypothesis.

Weight loss after sleeve gastrectomy in super superobesity

Objective. This prospective study evaluated laparoscopic sleeve gastrectomy for its safety and efficiency in excess weight loss (%EWL) in super superobese patients (BMI >60 Kg/m(2)). Results. Thirty patients (33 women and 7 men) were included, with mean age of 35 years (range 18 to 59). Mean preoperative BMI was 66 Kg/m(2) (range 60 to 85). The study included one patient with complete situs inversus and 4 (14%) with previous restrictive gastric banding. The mean operative time was 120 minutes (range 80 to 220 min) and the mean hospital stay was 7.5 days (4 to 28 days). There was no postoperative mortality or need for a laparotomy conversion. Two subphrenic hematomas, one gastric fistula, and one pulmonary embolism, were the major complications. After 18 months 17 (77%) had sufficient weight loss and six had insufficient results, leading to either re-sleeve gastrectomy (3), or gastric bypass (2). Three years after the initial laparoscopic sleeve gastrectomy, the mean EWL was 51% (range 21 to 82). Conclusion. The laparoscopic sleeve gastrectomy is a safe and efficient operating procedure for treating super superobesity. In the case of insufficient weight loss, a second-stage operation like resleeve gastrectomy or gastric bypass can be proposed.

Is there an impatience genotype leading to non-adherence to long-term therapies?

In chronic diseases such as diabetes, adherence to therapy aims to preserve health, which is a long-term objective, whereas non-adherence tends to present an immediate 'reward'. We propose that non-adherence, like addiction, is at least in part due to the fact that, for physiological, and maybe genetic reasons described in a new field, neuroeconomics, a number of people have a taste for the present rather than the future. Thus, for 'impatient patients' it is natural not to adhere to therapeutic prescriptions that share the characteristic of being future-oriented. This hypothesis may apply to any disease requiring long-term therapy.

Linguistic barriers in diabetes care

For a message to be conveyed successfully, both the words (translation step) and the meaning (interpretation step) of what is said need to be understood. This holds true even when the patient and healthcare provider speak the same language, in that the message can be lost if the patient is unable to put it into context. Linguistic barriers can pose major problems. Patient education needs to avoid jargon, and when introducing a new concept to the patient, the healthcare provider needs to check that it is understood.

Prevalence of diabetic retinopathy in children and adolescents with type-1 diabetes attending summer camps in France

OBJECTIVE

To evaluate, using fundus photography, the prevalence of diabetic retinopathy (DR) in young diabetic subjects attending summer camps run by the Aide aux Jeunes Diabétiques Association (Aid to Young Diabetics).

RESEARCH DESIGN AND METHODS

Five hundred and four children and adolescents (250 boys and 254 girls), with type 1 diabetes mellitus, aged 10-18 years (mean:13+/-2), were screened for DR using non mydriatic photography, during their stay in a holiday camp. Demographic and clinical data recorded on subjects' arrival in the camp included date of birth, height, weight, treatment, blood pressure, and duration of diabetes. HbA(1c) was determined with a DCA 2000 kit.

RESULTS

Mean diabetes duration was 4.8+/-3.4 years and mean HbA(1c) was 8.5+/-1.3%. Mild non proliferative DR was diagnosed in 23 children (4.6%). Compared to subjects without DR, those with DR were significantly older (P<10(-3)), had a longer duration of diabetes (P=0.001), higher systolic blood pressure (P=0.04), and had higher (but not significantly so) HbA(1c) (P=0.15). After adjustment for age, only longer duration remained significantly associated with DR (P=0.01).

CONCLUSION

The prevalence of DR in these young patients was low compared to that reported in previous studies. The decrease may be due to modern diabetes care with multiple insulin injections. However, early detection of DR in adolescents, especially in their late teens, remains important, because it allows the identification of patients at high risk of progression towards severe stages of DR.

Innovative therapies: some ethical considerations

The purpose of this text is to try to understand why certain innovations are not permitted, although they are possible. Our guiding thread will be the four principles of biomedical ethics defined by Beauchamp and Childress: beneficence, non-maleficence, justice and autonomy. We shall show how they can guide the ethical inquiry in the field of pancreas or islet transplantation, leading to an analysis of the risks and benefits of the innovations epistemologically taking into account their historical context.

Role of habit in adherence to medical treatment

This paper presents an analysis, from a philosophical point of view, of three psychological models describing how one adopts a health behaviour. More specifically, this analysis makes it possible to explain the role of habit in therapeutic adherence. By clarifying the notions of intention and decision, this novel analysis may be useful for understanding the dynamics of diabetes care.

Accuracy of the continuous glucose monitoring system in inpatient and outpatient conditions

OBJECTIVE

To evaluate in inpatient and outpatient conditions, using only non-calibration data, the accuracy of the Continuous Glucose Monitoring System (CG-MS).

RESEARCH DESIGN AND METHODS

Twelve, 21 and 20 type 1 diabetic patients participated in 3- day inhospital, 6-day ambulatory (i.e., 2 sensors worn consecutively) and 3-day ambulatory studies. Capillary glucose tests (7-8/day) served as comparisons. Pairs of data (excluding the 4 daily pairs used automatically by the CGMS for calibrations) were analyzed using correlation coefficient, error -grid analysis, and mean of absolute differences.

RESULTS

Two third and half of the sensing days were qualified as "optimal", i.e., interpretable by the CGMS program in the inpatient and outpatient studies, respectively. Correlation coefficient was 0.92, 0.81 and 0.73 in the inpatient, 6 day outpatient and 3-day outpatient studies. 98%, 93% and 96% of the data fell in the A or B error-grid "clinically acceptable" zones. Mean absolute differences between sensor and glucometer values were 25 +/- 2, 34 +/- 5 and 32 +/- 5 mg/dl.

CONCLUSION

CGMS may be used for assessment of glycemic trends, though accuracy is more in the range of glucometers than of laboratory tests. Inhospital utilisation improved accuracy and 6-day rather than 3-day sessions may be more appropriate to evaluate day to day reproducibility of glucose profile.

[Continuous glucose monitoring: different systems, different ambitions]

This paper describes the current approaches towards the development of continuous glucose monitoring system, in which glucose is measured either in blood or in the subcutaneous tissue. These systems may be used as a glycemic holter, or to display continuously the changes in glucose level, to trigger an alarm in case of hypoglycemia, or of risk of hypoglycemia, or finally to pave the way to the development of an artificial beta cell.

Calibration of a subcutaneous amperometric glucose sensor. Part 1. Effect of measurement uncertainties on the determination of sensor sensitivity and background current

The calibration of a continuous glucose monitoring system, i.e. the transformation of the signal I(t) generated by the glucose sensor at time (t) into an estimation of glucose concentration G(t), represents a key issue. The two-point calibration procedure consists of the determination of a sensor sensitivity S and of a background current I(o) by plotting two values of the sensor signal versus the concomitant blood glucose concentrations. The estimation of G(t) is subsequently given by G(t) = (I(t)-I(o))/S. A glucose sensor was implanted in the subcutaneous tissue of nine type 1 diabetic patients during 3 (n = 2) and 7 days (n = 7). For each individual trial, S and I(o) were determined by taking into account the values of two sets of sensor output and blood glucose concentration distant by at least 1 h, the procedure being repeated for each consecutive set of values. S and I(o) were found to be negatively correlated, the value of I(o) being sometimes negative. Theoretical analysis demonstrates that this phenomenon can be explained by the effect of measurement uncertainties on the determination of capillary glucose concentration and of sensor output.

Calibration of a subcutaneous amperometric glucose sensor implanted for 7 days in diabetic patients. Part 2. Superiority of the one-point calibration method

Calibration, i.e. the transformation in real time of the signal I(t) generated by the glucose sensor at time t into an estimation of glucose concentration G(t), represents a key issue for the development of a continuous glucose monitoring system.

OBJECTIVE

To compare two calibration procedures. In the one-point calibration, which assumes that I(o) is negligible, S is simply determined as the ratio I/G, and G(t) = I(t)/S. The two-point calibration consists in the determination of a sensor sensitivity S and of a background current I(o) by plotting two values of the sensor signal versus the concomitant blood glucose concentrations. The subsequent estimation of G(t) is given by G(t) = (I(t)-I(o))/S.

RESEARCH DESIGN AND METHODS

A glucose sensor was implanted in the abdominal subcutaneous tissue of nine type 1 diabetic patients during 3 (n = 2) and 7 days (n = 7). The one-point calibration was performed a posteriori either once per day before breakfast, or twice per day before breakfast and dinner, or three times per day before each meal. The two-point calibration was performed each morning during breakfast.

RESULTS

The percentages of points present in zones A and B of the Clarke Error Grid were significantly higher when the system was calibrated using the one-point calibration. Use of two one-point calibrations per day before meals was virtually as accurate as three one-point calibrations.

CONCLUSION

This study demonstrates the feasibility of a simple method for calibrating a continuous glucose monitoring system.

eNOS4 polymorphism of the endothelial nitric oxide synthase predicts risk for severe diabetic retinopathy

BACKGROUND

Genetic factors may be involved in the development, and particularly in the severity, of diabetic retinopathy (DR), in addition to chronic hyperglycaemia. Increased nitric oxide generation has been suggested to play a significant role in the pathogenesis of DR.

AIMS AND METHODS

To examine whether the eNOS4 is involved in the risk of severe DR, 200 unrelated Caucasian Type 1 diabetic patients of long duration were randomly selected (M/F 103/97, age 44.4 +/- 12.4 years, diabetes duration 27.7 +/- 10.0 years, body mass index 24.3 +/- 3.4 kg/m2, HbA1c 8.6 +/- 1.3%). The eNOS4 polymorphism was analysed by polymerase chain reaction, and DR by retinal angiography and classified as presence (n = 101) or absence (n = 99) of severe (proliferative or pre-proliferative) DR.

RESULTS

The genotype distribution of eNOS4b/b (wild-type), eNOS4b/a (heterozygous) and eNOS4a/a (homozygous) was 72%, 24.5% and 3.5%, respectively. Frequency of eNOS4a/a was significantly lower in patients with severe DR (n = 0) when compared with controls (n = 7, odds ratio (OR) = 0 (95% confidence interval (CI) = 0.5-0.74), P = 0.02). eNOS4b/b was more frequent in patients with severe DR (n = 80) when compared with controls (n = 64, OR = 2.1 (95% CI = 1.1-4.12), P = 0.032). Frequency of eNOS4b/a was not different between the study (n = 21) and control groups (n = 28, ns). The allelic frequencies between the study and control groups were different (4b: n = 181 vs. n = 156, respectively, OR = 2.3 (95% CI = 1.27-4.25), P = 0.005; 4a: n = 21 vs. n = 42, respectively, OR = 0.4 (95% CI = 0.24-0.79), P = 0.005).

CONCLUSIONS

We demonstrate in Caucasians with Type 1 diabetes that (i) eNOS4a/a is associated with absent or non-severe DR, and (ii) eNOS4b/b is associated with severe DR.

Taq I polymorphism of the vitamin D receptor and risk of severe diabetic retinopathy

AIMS/HYPOTHESIS

Vitamin D, a molecule with antiproliferative, antiangiogenic, antioxidant and immunosuppressive effects, could play a role in the pathogenesis of severe diabetic retinopathy. We examined whether Taq I polymorphism of the vitamin D receptor is involved in the development of severe diabetic retinopathy.

METHODS

200 unrelated C-peptide-negative French Type I diabetic patients were randomly selected (male:female, 103:97, age 44.4 +/- 12.4 years, diabetes duration: 27.7 +/- 10.0 years, BMI: 24.3 +/- 3.4 kg/m(2), HbA(1c): 8.6 +/- 1.3 %). The Taq I site was analysed by PCR followed by digestion with Taq I enzyme. Diabetic retinopathy was assessed by retinal angiography and classified as presence (n = 101) or absence (n = 99) of severe (preproliferative or proliferative) diabetic retinopathy.

RESULTS

Frequency of wild-type genotype TT was lower in patients with severe diabetic retinopathy (n = 27) when compared with control subjects (n = 42, OR = 0.5, p = 0.028). Allele frequencies were not different between patients (T: n = 112 and t: n = 90) and control subjects (T: n = 128, and t: n = 70, p = 0.075). Global chi(2) (df = 2): p = 0.064. In subjects with diabetes duration of more than 25 years, TT was lower in severe diabetic retinopathy (n = 14) than control subjects (n = 18, OR = 0.3, p = 0.01). Allele frequencies were different between patients (T: n = 68 and t: n = 66) and control subjects (T: n = 52, OR = 0.5, and t: n = 26, OR = 1.9, p = 0.034). Global chi(2) (df = 2): p = 0.024. In subjects with HbA(1c) over 9 %, Tt was higher in patients (n = 28) than control subjects (n = 15, OR = 3.1, p = 0.019). Allele frequencies were not different between patients (T: n = 52 and t: n = 38) and control subjects (T: n = 57, and t: n = 29, p = 0.31). Global chi(2) (df = 2): p = 0.035.

CONCLUSION/INTERPRETATION

In French Type I (insulin-dependent) diabetic patients, we demonstrate an association between TT form (VDR) and low risk for severe diabetic retinopathy, especially in patients with long duration, and between Tt variant and high risk for severe diabetic retinopathy in subjects with poor glycaemic control.

PPAR-alpha-null mice are protected from high-fat diet-induced insulin resistance

Peroxisome proliferator-activated receptor (PPAR)-alpha controls the expression of genes involved in lipid metabolism. PPAR-alpha furthermore participates to maintain blood glucose during acute metabolic stress, as shown in PPAR-alpha-null mice, which develop severe hypoglycemia when fasted. Here, we assessed a potential role for PPAR-alpha in glucose homeostasis in response to long-term high-fat feeding. When subjected to this nutritional challenge, PPAR-alpha-null mice remained normoglycemic and normoinsulinemic, whereas wild-type mice became hyperinsulinemic (190%; P < 0.05) and slightly hyperglycemic (120%; NS). Insulin tolerance tests (ITTs) and glucose tolerance tests (GTTs) were performed to evaluate insulin resistance (IR). Under standard diet, the response to both tests was similar in wild-type and PPAR-alpha-null mice. Under high-fat diet, however, the efficiency of insulin in ITT was reduced and the amount of hyperglycemia in GTT was increased only in wild-type and not in PPAR-alpha-null mice. The IR index, calculated as the product of the areas under glucose and insulin curves in GTT, increased fourfold in high-fat-fed wild-type mice, whereas it remained unchanged in PPAR-alpha-null mice. In contrast, PPAR-alpha deficiency allowed the twofold rise in adiposity and blood leptin levels elicited by the diet. Thus, the absence of PPAR-alpha dissociates IR from high-fat diet-induced increase in adiposity. The effects of PPAR-alpha deficiency on glucose homeostasis seem not to occur via the pancreas, because glucose-stimulated insulin secretion of islets was not influenced by the PPAR-alpha genotype. These data suggest that PPAR-alpha plays a role for the development of IR in response to a Western-type high-fat diet.

[Towards a cell therapy for diabetes? An epistemiological perspective]

This text describes, in an epistemological perspective, the development of the concept of cellular therapy applied to the treatment of type 1 diabetes. Emphasis is put on three recent papers describing the success of islet allograft in diabetic patients, the development of neo-islets from stem cells isolated from the pancreas of adult mice, and the effect of hepatic cell transfection with an adenovirus bearing the gene coding for PDX-1, a transcription factor involved in the maturation of islets of Langerhans. This text tries to delineate some factors which may be involved in the chances for these techniques to reach the real world of human therapeutics.

[Does obesity protect against diabetes? A new controversy]

Obesity is a risk factor for the appearance of type 2 diabetes: this notion, largely based on clinical experience, dictates the essential principles of the treatment of type 2 diabetes. At odds with this conventional wisdom, Elliot Danforth Jr. has recently proposed that "too few adipocytes predisposes to type 2 diabetes". A further thought on this controversy is discussed herein. In the context of the "orthodox" view which links obesity and diabetes, and its relation to the controversy, we analyse on one hand the effects of thiazolidine-diones on insulin sensitivity and on adipogenesis and, on the other hand, those of extreme situations represented by lipoatrophic diabetes and morbid obesity. This analysis shows that fat tissue indeed favors the appearance of diabetes but is also able to be anti-diabetogenic, and a dynamic solution of this paradox is put forward. We propose a dual evolutionist hypothesis leading to the selection of an intermediary adipogenic genotype based on the limitation of both insulin secretion and adipogenic potential, which would explain both the necessity of the existence of adipose tissue in man and the limitations of its development.