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Biomedical subjects

G Reach

Publications and source records attributed to G Reach.

At least 19 recordsLinked to original sources
PubMed2006

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.

Diabetes Mellitus↗
PubMed2005

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.

Chronic Disease↗
PubMed2003

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.

Automation↗
PubMed2003

[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.

Blood Chemical Analysis↗
PubMed2002

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.

Adult↗
PubMed2002

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

UNLABELLED: 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.

Biosensing Techniques↗
PubMed2002

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.

Biosensing Techniques↗
PubMed2002

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.

Adult↗
PubMed2001

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.

1-Methyl-3-isobutylxanthine↗
PubMed2001

[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.

Adenoviridae↗
PubMed2001

[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.

Adipocytes↗
PubMed2000

[Application of the causal theory of action through analysis of therapeutic non-observance].

This paper presents an analysis of an aspect of non-observance in the treatment of type 1 diabetes mellitus, the absence of adaptation of insulin dosage in spite of hyperglycemia. The adaptation of insulin dosage by the patient is described as an intentional action, performed as a habit. The problem is analysed through the causal theory of action and the concept of akrasia. These considerations may be useful to understand other aspects of therapeutic non-observance.

Attitude to Health↗
PubMed2000

Inhibition of insulin gene expression by long-term exposure of pancreatic beta cells to palmitate is dependent on the presence of a stimulatory glucose concentration.

Long-term exposure of pancreatic beta cells to elevated levels of fatty acids (FAs) impairs glucose-induced insulin secretion. However, the effects of FAs on insulin gene expression are controversial. We hypothesized that FAs adversely affect insulin gene expression only in the presence of elevated glucose concentrations. To test this hypothesis, isolated rat islets were cultured for up to 1 week in the presence of 2.8 or 16.7 mmol/L glucose with or without 0.5 mmol/L palmitate. Insulin release, insulin content, and insulin mRNA levels were determined at the end of each culture period. Palmitate increased insulin release at each time point independently of the glucose concentration. In contrast, insulin content was unchanged in the presence of palmitate at 2.8 mmol/L glucose, but was markedly decreased in the presence of 0.5 mmol/L palmitate and 16.7 mmol/L glucose after 2, 3, and 7 days of culture. In the presence of a basal concentration of glucose, insulin mRNA levels were transiently increased by palmitate at 24 hours but were unchanged thereafter. In contrast, palmitate significantly inhibited the stimulatory effects of 16.7 mmol/L glucose on insulin mRNA levels after 2, 3, and 7 days. To determine whether the inhibitory effect of palmitate on glucose-stimulated insulin mRNA levels was associated with decreased insulin promoter activity, HIT-T15 cells were cultured for 24 hours in 11.1 mmol/L glucose in the presence or absence of palmitate, and insulin gene promoter activity was measured in transient transfection experiments using the insulin promoter-reporter construct INSLUC. INSLUC activity was decreased more than 2-fold after 24 hours of exposure to 0.5 mmol/L palmitate. We conclude that long-term exposure of pancreatic beta cells to palmitate decreases insulin gene expression only in the presence of elevated glucose concentrations, in part through inhibition of insulin gene promoter activity.

Animals↗
PubMed2000

Glucose-induced insulin mRNA accumulation is impaired in islets from neonatal streptozotocin-treated rats.

According to the "glucose toxicity" hypothesis, hyperglycemia contributes to defective beta-cell function in type 2, non-insulin-dependent diabetes mellitus. This concept is supported by substantial data in rodent models of diabetes. However, the ability of glucose to stimulate the accumulation of insulin mRNA, a critical feature of normal beta-cell physiology, has not been investigated in in vivo models with chronic hyperglycemia. The aim of this study was to determine whether glucose-induced insulin mRNA accumulation is impaired in the neonatal streptozotocin-treated rat (n0-STZ rat), a model of non-obese, non-insulin-dependent diabetes mellitus. Islets of Langerhans isolated from n0-STZ and control rats were cultured for 24 h in the presence of 2.8 or 16.7 mmol/l glucose, and insulin mRNA levels were measured by Northern analysis. Insulin mRNA levels were increased more than twofold by glucose in control islets. In contrast, no significant effect of glucose was found on insulin mRNA levels in n0-STZ islets. We conclude that insulin gene regulation by glucose is impaired in n0-STZ rat islets.

Animals↗