Repaglinide: a new short-acting insulinotropic agent for the treatment of type 2 diabetes

Repaglinide, a carbamoylmethyl benzoic acid derivative, is rapidly absorbed, metabolized by the liver and eliminated primarily via the bile. It has a short duration of action and is taken immediately before each main meal. This regimen has been shown to provide superior glycaemic control compared with regular morning and evening dosing. A flexible preprandial only dosing regimen of repaglinide significantly lowers the risk of hypoglycaemia if a meal is missed or postponed. Combination therapy with metformin improves glycaemic control significantly compared with therapy with either drug alone in overweight patients. Repaglinide has an equivalent safety and efficacy profile to the sulphonylureas, although it is superior to glipizide in maintaining long-term glycaemic control The postprandial glucose levels are significantly lower with repaglinide compared with glibenclamide. In naive patients with Type 2 diabetes, repaglinide lowers fasting glucose concentrations and functions also as a prandial glucose regulator.

Day-to-day variability of fasting plasma glucose in newly diagnosed type 2 diabetic subjects

OBJECTIVE

To determine the day-to-day intraindividual variability of fasting plasma glucose (FPG) in newly diagnosed Caucasian type 2 diabetic subjects.

RESEARCH DESIGN AND METHODS

A total of 193 newly diagnosed, previously untreated, Caucasian type 2 diabetic subjects (135 men, 58 women) had FPG measured on two consecutive days (FPG1, FPG2). Ethical approval and subjects' full informed consent were obtained. Subjects fasted for 12 h before each study day and rested for at least 30 min before blood was taken. Plasma glucose was analyzed by a glucose oxidase method with intra- and interassay coefficients of variation (CVs) < 2%. Variability of FPG was assessed by comparison of percentage differences (PDs): PD = 100 (FPG2 - FPG1)/FPG1, with averaged FPG (FPGaver = [FPG1 + FPG2]/2). Biological and analytical variability were determined by use of SD2total = SD2biological + SD2analytical, where SD2analytical approximately equal to 2 x (CVglucose measurement)2. Given normally distributed data with zero mean, 95% of daily percentage differences will be expected to fall within a range of +/- 2 SDtotal.

RESULTS

Subjects were age 54 +/- 10 years (mean +/- SD) and had BMI of 29.3 +/- 5.3 kg/m2. FPG values for both days were 12.2 +/- 3.4 mmol/l (FPG1) and 12.1 +/- 3.3 mmol/l (FPG2), with a mean paired difference (95% CI) of 0.1 (0.0 to 0.3) mmol/l. The variance of these differences increased with increasing FPGaver. The PDs did not exhibit this effect and were normally distributed (mean -0.6% [-1.7 to 0.4]; SD 7.4% [6.8 to 8.3]), giving a 95% variability (2 SD) of 14.8%. Biological variability (2 SDbiological) was 13.7%. No significant difference in PD was found between men and women (mean difference 1.3% [-1.0 to 3.6]; SDmale 7.4%, SDfemale 7.3%; P = 0.62).

CONCLUSIONS

A total of 95% of the FPG values for this group of newly diagnosed type 2 diabetic subjects varied within approximately +/- 15% on a daily basis, with approximately 14% caused by biological variability. As these results are expressed in percentage terms, subjects in the group with higher FPG values are likely to experience larger changes in FPG values measured from day to day. This variability should be considered when using FPG for the diagnosis and/or monitoring of response to treatment in patients with type 2 diabetes.

Determining true glomerular filtration status in newly presenting type 2 diabetic subjects using age and sex adjustment

OBJECTIVE

To determine age- and sex-adjusted reference ranges (ASARRs) for glomerular filtration status using data from nondiabetic subjects and to apply these to newly presenting type 2 diabetic subjects.

RESEARCH DESIGN AND METHODS

Glomerular filtration rate corrected for body surface area (cGFR) was determined using a radionuclide (51Cr-EDTA) method in 75 non-diabetic subjects (37 men, 38 women) and 219 type 2 diabetic subjects (157 men, 62 women). The 95% constant reference ranges (CRRs) were calculated as mean nondiabetic cGFR+/-1.96 SD. The 95% ASARRs were calculated by Altman's method from the nondiabetic cGFR versus age regression residuals for both male and female subjects.

RESULTS

Using Altman's method, the intercepts, but not the gradients, of the cGFR versus age regressions were significantly different between male and female subjects (intercept difference [95% CI] 8.2 [1.3-15.1], gradient difference -0.4 [-1.1 to 0.3]). Fitting a common gradient, 95% ASARRs for normofiltration were found to be from 123.9 - (0.89 X age) to 181.7 - (0.89 x age) for male subjects, and from 116.0 - (0.89 X age) to 173.2 - (0.89 X age) for female subjects. The 95% CRR for normofiltration was 70.2-138.1 ml x min(-1) x (1.73 m)(-2). When applied to the diabetic cGFRs, the CRRs and ASARRs gave, respectively, 17% (37/219) versus 21% (46/219) hyperfiltrators and 83% (181/219) versus 79% (172/219) normofiltrators. Using the ASARRs, 14 normofiltrators (6 men, 8 women) were reclassified as hyperfiltrators (change [n/total n] [95% CI] 8% [14/181] [4-12]), and 5 hyperfiltrators (5 men, 0 women) were reclassified as normofiltrators (change 14% [5/37] [5-30]).

CONCLUSIONS

We conclude that age and sex adjustment are essential to assess glomerular filtration status.

Aspects of oligonucleotide and peptide sequencing with MALDI and electrospray mass spectrometry

Biopolymer sequencing with mass spectrometry has become increasingly important and accessible with the development of matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI). Here we examine the use of sequential digestion for the rapid identification of proteolytic fragments, in turn highlighting the general utility of enzymatic MALDI ladder sequencing and ESI tandem mass spectrometry. Analyses were performed on oligonucleotides ranging in size from 2 to 50 residues, on peptides ranging in size from 7 to 44 residues and on viral coat proteins. MALDI ladder sequencing using exonuclease digestion generated a uniform distribution of ions and provided complete sequence information on the oligonucleotides 2-30 nucleic acid residues long. Only partial sequence information was obtained on the longer oligonucleotides. C-terminal peptide ladder sequencing typically provided information from 4 to 7 amino acids into the peptide. Sequential digestion, or endoprotease followed by exoprotease exposure, was also successfully applied to a trypsin digest of viral proteins. Analysis of ladder sequenced peptides by LCMS generated less information than in the MALDI-MS analysis and ESI-MS2 normally provided partial sequence information on both the small oligonucleotides and peptides. In general, MALDI ladder sequencing offered information on a broader mass range of biopolymers than ESI-MS2 and was relatively straightforward to interpret, especially for oligonucleotides.

A comparison of digital retinal images and 35 mm colour transparencies in detecting and grading diabetic retinopathy

We compared digital retinal images and 35 mm colour transparencies taken with the Canon CR5 retinal camera for the detection and grading of diabetic retinopathy in a clinical setting, in a randomized, blinded study of diabetic patients with a spectrum of severity of diabetic retinopathy. Forty patients were photographed, giving a total of 75 eyes including non-diabetic eyes as controls. Images were graded according to the validated European guidelines. There was exact agreement between grades obtained from both the 2 field 45 degrees 35 mm colour transparencies and digital images in 93.3% (70/75) of eyes, with Cohen's Kappa statistic for the comparison being 0.92. Overall, when grading from the digital images 5.3% (4/75) eyes were undergraded with three cases of sight threatening diabetic retinopathy (STDR) graded as non-sight threatening (NSTDR) (3/48, 6.3%). One eye was overgraded (1/75, 1.3%). Two of the three cases of STDR undergraded as NSTDR had small numbers of intra-retinal microvascular abnormalities (IRMA) discernible on the colour transparencies but which were not visible from the digital image. The third had multiple small cotton wool spots graded as laser photocoagulation scars from the digital images. In conclusion there is good to excellent agreement between retinopathy grades using the Canon CR5 digital retinal imaging system compared to 35 mm colour transparencies.

Pancreatic beta-cell responsiveness during meal tolerance test: model assessment in normal subjects and subjects with newly diagnosed noninsulin-dependent diabetes mellitus

A model-based method was developed to quantify pancreatic beta-cell responsiveness during a meal tolerance test (MTT). C peptide secretion was related in a linear fashion to glucose concentration, whereas the standard population model was used to derive transfer rate constants of the two compartmental model of C peptide kinetics. Two indexes of pancreatic beta-cell responsiveness were defined: 1) postprandial sensitivity M(I) (ability of postprandial glucose to stimulate beta-cell), and 2) basal sensitivity M0 (ability of fasting glucose to stimulate beta-cell). The method was evaluated using plasma glucose and C peptide measured over 180 min with a 10- to 30-min sampling interval during a MTT (75 g carbohydrates; 500 Cal) performed in 16 normal subjects (7 men and 9 women; age, 50 +/- 10 yr; body mass index, 29.2 +/- 3.6 kg/m2; fasting plasma glucose, 5.1 +/- 0.5 mmol/L; mean +/- SD) and 16 body mass index-matched subjects with newly diagnosed noninsulin-dependent diabetes mellitus (NIDDM; 15 men and 1 woman; age, 50 +/- 9 yr; body mass index, 29.3 +/- 3.7 kg/m2; fasting plasma glucose, 12.6 +/- 3.2 mmol/L). M(I) and M0 indexes were estimated with very good precision (coefficient of variation, < 15%). Subjects with NIDDM demonstrated lower postprandial sensitivity M(I) (17.7 +/- 11.4 vs. 90.0 +/- 43.3 x 10(-9)/min; NIDDM vs. normal, P < 0.001) and basal sensitivity M0 (5.4 +/- 2.2 vs. 10.3 +/- 4.9 x 10(-9)/min; P < 0.005). Deconvolution analysis documented that the relationship between C peptide secretion and glucose concentration is approximately linear during MTT in both normal subjects (plasma glucose range, 5-8 mmol/L) and subjects with NIDDM (12-17 mmol/L). We conclude that pancreatic responsiveness during glucose stimulation (M(I)) and under basal conditions (M0) can be obtained from this novel method during MTT in healthy and disease states.

Screening for diabetic retinopathy by general practitioners: ophthalmoscopy or retinal photography as 35 mm colour transparencies?

In order to assess the relative ability of general practitioners (GPs) to detect diabetic retinopathy (DR), especially sight-threatening diabetic retinopathy (STDR) by direct ophthalmoscopy or by examining, on a separate occasion, retinal images as 35 mm colour transparencies, a South and Mid Wales primary care-based study was performed in four general practices (six GPs). The participating GPs were provided with standardized training and equipment. Both methods were compared to the 'reference' grade of DR provided by the Diabetic Retinopathy Reading Centre (London), based on the same retinal images. Ophthalmoscopy and retinal photography (Canon CR4 45NM) with mydriasis were all practice based. The clinical assessments were based on a protocol developed for screening for DR in Europe. A total of 996 people with diabetes were identified, representing a prevalence of known diabetes of 2.1%. After exclusions on medical grounds, 897 patients were available for screening, of whom 605 (68%) were photographed. Based on the retinal images, the reference centre identified DR in 43% and STDR in 14.4%. In total, 597 valid comparisons between GPs and the reference centre were obtained; of these, 462 (77%) were high quality photographs which were used in subsequent analysis. The sensitivity for detecting any DR increased from 62.6% (95% CI 55.9-69.4) with ophthalmoscopy to 79.2% (95% CI 73.6-84.9) using retinal photographs, specificity remaining essentially unchanged at 75.0 (95% CI 69.5-80.5) and 73.5% (95% CI 68.0-79.1) with the positive predictive value (PPV) increasing from 67.2 (95% CI 60.4-74.0) to 71.0% (95% CI 65.0-77.0), respectively. The detection of STDR sensitivity increased from 65.7 (95% CI 54.4-77.1) with ophthalmoscopy alone to 87.3% (95% CI 79.4-95.2) based on retinal photographs with specificity falling from 93.8 (95% CI 91.4-96.3) to 84.8% (95% CI 81.2-88.5) and PPV from 65.7 (95% CI 54.4-77.1) to 51.2% (95% CI 42.1-60.3), respectively. We conclude that the use of standardized 35 mm colour transparency retinal photographs for screening by trained GPs in a primary care setting achieves an acceptable detection rate (>87%) for STDR, contrasting with ophthalmoscopy alone (66%), which was below the proposed UK standard of 80%.

Repaglinide--prandial glucose regulator: a new class of oral antidiabetic drugs

The highest demand on insulin secretion occurs in connection with meals. In normal people, following a meal, the insulin secretion increases rapidly, reaching peak concentration in the blood within an hour. The mealtime insulin response in patients with Type 2 diabetes is blunted and delayed, whereas basal levels often remain within the normal range (albeit at elevated fasting glucose levels). Restoration of the insulin secretion pattern at mealtimes (prandial phase)--without stimulating insulin secretion in the 'postabsorptive' phase--is the rationale for the development of 'prandial glucose regulators', drugs that are characterized by a very rapid onset and short duration of action in stimulating insulin secretion. Repaglinide, a carbamoylmethyl benzoic acid (CMBA) derivative is the first such compound, which recently has become available for clinical use. Repaglinide is very rapidly absorbed (t(max) less than 1 hour) with a t1/2 of less than one hour. Furthermore, repaglinide is inactivated in the liver and more than 90% excreted via the bile. The implications of tailoring repaglinide treatment to meals were examined in a study where repaglinide was dosed either morning and evening, or with each main meal (i.e. breakfast, lunch, dinner), with the total daily dose of repaglinide being identical. The mealtime dosing caused a significant improvement in both fasting and 24-hour glucose profiles, as well as a significant decrease in HbA1c. In other studies, repaglinide caused a decrease of 5.8 mmol x l(-1) in peak postprandial glucose levels, and a decrease of 3.1 mmol x l(-1) in fasting levels with a reduction in HbA1c of 1.8% compared with placebo. In comparative studies with either sulphonylurea or metformin, repaglinide caused similar or improved control (i.e. HbA1c, mean glucose levels) and the drug was well tolerated (e.g. reported gastrointestinal side-effects were more than halved when patients were switched from metformin to repaglinide). A hallmark of repaglinide treatment is that this medication follows the eating pattern, and not vice versa. Hence the risk of developing severe hypoglycaemia (BG < or = 2.5 mmol x l(-1)) in connection with flexible lifestyles should be reduced. This concept was examined in a study in which patients well controlled on repaglinide skipped their lunch on one occasion. When a meal (i.e. lunch) was skipped--so was the repaglinide dose, whereas in the comparative group on glibenclamide the recommended morning and evening doses were taken. Twenty-four per cent of the patients in the glibenclamide group developed severe hypoglycaemia, whereas no hypoglycaemic events occurred in the group receiving repaglinide. However, in long-term studies the overall prevalence of hypoglycaemia was similar to that found with other insulin secretagogues. In summary, current evidence shows that the concept of prandial glucose regulation offers good long-term glycaemic control combined with a low risk of severe hypoglycaemia with missed meals. The concept should meet the needs of Type 2 diabetic patients, allowing flexibility in their lifestyle.

Practical application of the European Field Guide in screening for diabetic retinopathy by using ophthalmoscopy and 35 mm retinal slides

The Welsh Community Diabetic Retinopathy Study was designed to assess the effectiveness of the Field Guide Book for screening for diabetic retinopathy in Europe. A community-based sample (prevalence 2%) of diabetic patients was recruited from four general practices. Standardised training and equipment were provided. All patients were invited to attend practice-based screening sessions on two occasions over 3 years (phases 1 and 2). After mydriasis, clinical ophthalmoscopy was performed by a study optometrist and general practitioners (GPs). 2 x 45 field 35 mm retinal slides were obtained according to EURODIAB protocol. Anonymised slides were assessed by GPs, diabetologists and the optometrist. All the findings were graded externally (reference standard). In phase 2 community optometrists also performed ophthalmoscopy and assessed photographs. For detecting sight threatening diabetic retinopathy using ophthalmoscopy, GPs achieved a sensitivity of 65.7%, specificity 93.8% and positive predictive value (PPV) 65.7%. Community optometrists achieved a sensitivity of 82.2% with a PPV of 50.7%; the study optometrist 79.2 and 55.9%, respectively. The use of 35 mm slides improved sensitivity for the detection of sight threatening retinopathy to 87.3, 91.1 and 97.2% for GPs, community optometrists and the study optometrist, respectively. PPV fell to 51.2% for GPs, 40.6% for community optometrists, but increased to 58.8% for the study optometrist. Diabetologists achieved a sensitivity of 88.7% and a PPV of 65.6%. It is concluded that the European field guide is an effective tool for screening for retinopathy in clinical practice.

Can digitised colour 35 mm transparencies be used to diagnose diabetic retinopathy?

Retinal photography is an adjunct to ophthalmoscopy in screening for diabetic retinopathy (DR). Digital retinal cameras allow a retinal image to be displayed immediately on a high resolution video display monitor. We conducted a pilot study to investigate the agreement in retinopathy grading from digitized images in comparison to original colour transparencies as 35 mm slides. One hundred and fifty macula-centred, 45 degree, non-stereoscopic retinal images were digitized onto CD ROM by Kodak at base resolution of 768 x 512 pixels. The anonymized images were displayed on a 17" monitor running Windows at 800 x 600 resolution in 64,000 colours (PC images) and graded in random order. Alternatively the transparencies were graded on a Slidex viewer. A quality control set were also graded with exact agreement in 93% of cases (91% (73/80) of PC images and 94% (75/80) of slide images). Compared to colour transparencies, 95% (84/88) of sight threatening diabetic retinopathy (STDR) and 100% (62/62) of non-STDR cases were diagnosed using the PC. One case of pre-proliferative DR and three cases of non-proliferative DR were graded as non-STDR from the PC. There was good agreement between PC displayed digitized retinal images and 35 mm colour transparencies.

Visual function in young IDDM patients over 8 years of age. A 4-year longitudinal study

OBJECTIVE

To carry out a longitudinal study of visual functions in young patients over the age of 8 years with IDDM and to assess the impact of metabolic control on the presence of diabetic retinopathy.

RESEARCH DESIGN AND METHODS

There were 37 young IDDM patients from the Paediatric and Adolescent Clinic at the University Hospital of Wales studied annually for 4 years, with a control group of 24 healthy subjects observed over a 2-year period. Assessment of visual functions included visual acuity, color vision, and contrast sensitivity. Ophthalmoscopy and retinal photography were used to determine the presence or absence of diabetic retinopathy. In addition, pubertal status and metabolic control (glycosylated hemoglobin) were determined at each visit.

RESULTS

Patients with IDDM demonstrate abnormal color vision and contrast sensitivity compared with the control group (P < 0.05), but visual acuity was unaffected. Visual functions were not significantly different between those IDDM patients with and without retinopathy. After 4 years, diabetic retinopathy was present in 43% of the group and was related to diabetes duration and metabolic control (P < 0.05).

CONCLUSIONS

Visual function testing could not distinguish between those IDDM patients with and without retinopathy, but the color vision and contrast sensitivity in those with IDDM were significantly impaired compared with the control group. The presence of retinopathy was related to the duration of diabetes and metabolic control. It is important to ensure that good glycemic control and regular attendance for retinopathy screening is encouraged in the adolescent patients.

Estimation of glomerular filtration rate in type II (non-insulin dependent) diabetes mellitus patients

The aim of this research was to develop an estimation of glomerular filtration rates (GFRs) from a combination of simple parameters in a large group of type II diabetic patients. We selected 122 newly presenting, previously untreated, type II patients whose GFR was determined from the plasma clearance of 51Cr-ethylenediamine tetraacetic acid (51Cr-EDTA) and simultaneous measurements of demographic variables, including fasting plasma glucose concentration, HbA1c, blood pressure, lipids, age, weight, body-mass index, body surface area, urea, and plasma creatinine concentration. The actual GFR values were compared with estimated values obtained from multiple regression and the Cockroft-Gault equations. Out of all the demographic variables, only plasma creatinine concentration (r = -0.56, p < 0.001), age (r = -0.50, p < 0.001), urea (r = -0.28, p < 0.01), and systolic blood pressure (r = -0.21, p < 0.05) showed significant correlations with the actual GFR values, for which the mean and standard deviation were 117.5 +/- 22.0 ml min-1 x 1.73 m-2. The estimated values are highly correlated with the actual values (r = 0.70), having an identical mean value of 117 +/- 15.3 and an unbiased regression relation (y = 0.000 + 1.000x). As standard measurements of the GFR are very time consuming and expensive, the use of the simple equation GFR1 = 218.1 - 0.916 x Age - 0.635 x Creatinine is recommended. The classification of GFR values into three ranges has also revealed the nonlinear characteristics of GFR in relation to other demographic variables: age and creatinine are the dominant variables in the middle GFR range, while the body-mass index and urea are dominant in the high and low ranges, respectively.

Does hyperglycaemia have an influence upon colour vision of patients with diabetes mellitus?

It has been suggested that variations found in colour vision upon repeated testing may be due to fluctuations in the plasma glucose level, but the results of studies to date are conflicting. Therefore, the aim of this study was to investigate whether a short-term increase in plasma glucose concentration had an influence on colour vision in patients with non insulin-dependent diabetes mellitus (NIDDM) (n = 16). The colour vision and plasma glucose levels were monitored every 30 min for a total period of 4 h during three test conditions: two when the plasma glucose levels were increased by the administration of glucose, either orally (n = 8) or intravenously (n = 8), and one when the plasma glucose was relatively stable during fasting conditions (n = 8). The results indicate that the colour vision, as assessed by the Desaturated D15, appears to be unaffected by the short-lived increases in plasma glucose concentrations.

A new screening tool for diabetic retinopathy: the Canon CR5 45NM retinal camera with Frost Medical Software RIS-lite digital imaging system

The introduction of the Canon CR5 45NM non-mydriatic retinal camera with the Frost Medical Software RIS-Lite digital imaging system provides a new screening tool for diabetic retinopathy with potential for remote diagnosis and telemedicine. This paper presents a description and early evaluation of the system.

Insulin secretion and sensitivity in newly diagnosed NIDDM Caucasians in the UK

Beta-cell secretion and insulin sensitivity was studied in healthy subjects and newly diagnosed Caucasian (Welsh) NIDDM patients. A standardized meal tolerance test (MTT) and frequent sampled intravenous glucose tolerance tests (FSIVGTT) were employed and the patients stratified according to fasting plasma glucose (FPG). A deficient early (first hour) post-prandial (MTT) insulin secretion was demonstrated in all NIDDM patients, deteriorating with increasing fasting hyperglycaemia. For the patient group fasting and post-prandial hyperproinsulinaemia was evident with diminishing post-prandial excursions as fasting hyperglycaemia increased. The early phase (0-10 min) insulin secretion to intravenous glucose (300 mg kg-1) was severely impaired in NIDDM patients. A shortlived paradoxical fall in plasma insulin concentrations was observed in those with FPG > 9 mmol l-1. Insulin sensitivity utilizing the insulin modified FSIVGTT demonstrated that all NIDDM patients had marked insulin insensitivity. Characteristic of the newly diagnosed previously untreated Caucasian NIDDM is a dysfunctional beta cell, resulting in a deficit in insulin secretion with relative hyperproinsulinaemia. The quantitative and qualitative secretory status of the beta cell decreases with increasing fasting hyperglycaemia. Insulin sensitivity is markedly reduced when FPG exceeds 7.0 mmol l-1 with little or no further discernible fall with deteriorating glycaemic control.

Dominant risk factors for retinopathy at clinical diagnosis in patients with type II diabetes mellitus

A study of 270 newly presenting, previously untreated, type II diabetic patents revealed that 38 patients (14%) had already developed diabetic retinopathy (DR). Among this group, 26 patients had lesions of background diabetic retinopathy and 12 patients already had maculopathy or preproliferative changes. The aim of this study was to determine the risk factors influencing susceptibility to retinopathy, and to provide an accurate predictive value for diabetic retinopathy from a detailed multiple regression analysis that involved 27 demographic variables and the metabolic and hormonal responses during a meal tolerance test (MTT) at presentation. Compared to the nonretinopaths, the retinopaths had higher fasting plasma glucose levels (FPG) (mean +/- SD) (13.9 +/- 3.1 versus 11.6 +/- 3.2 mmol/L, p < 0.001), lower body-mass index values (BMI) (26.1 +/- 3.8 versus 29.3 +/- 5.0 kg/m2, p < 0.001) and higher plasma urea concentrations (6.0 +/- 1.9 versus 5.3 +/- 1.2 mmol/L, p 0.05). In contrast, gender and levels of blood pressure and other lipid levels did not influence the prevalence of diabetic retinopathy. A multiple regression formula for the prediction of diabetic retinopathy was derived and then used to categorize patients into high-risk and low-risk groups. The retinopaths also had higher HbA1c (p < 0.001), higher plasma glucose are under curve (0-2 h, p < 0.001), lower plasma insulin area under curve (0-22 h, p < 0.001), lower C-peptide area under curve (0-2 h, p < 0.01). They were also leaner (p < 0.001) and older (p < 0.05). However, these variables did not feature significantly in the multiple regression formula. The retinopaths were found to have higher risk probability values (25.1 +/- 11.5 versus 13.1 +/- 10.4%, p < 0.001). In the high risk group, 81.6% of retinopaths were identified. In the low-risk group, 63.8% of nonretinopaths were found. The incidence of diabetic retinopathy in type II diabetic patients at clinical diagnosis was found to be highly related to the degree of hyperglycemia, body-mass index, and to a lesser extent, renal impairment.

Proinsulin secretion during the first 3 years after diagnosis in diabetic patients with and without islet cell antibodies

OBJECTIVE

To evaluate proinsulin secretion in different types of NIDDM.

RESEARCH DESIGN AND METHODS

Proinsulin and insulin were evaluated at diagnosis of diabetes and 3 years later (fasting and after stimulation with intravenous glucose and glucagon) in 10 NIDDM patients without islet cell antibodies (ICAs) at diagnosis (age 52 +/- 4 years), 11 NIDDM patients with ICAs at diagnosis (age 50 +/- 5 years), and 21 healthy control subjects (age 53 +/- 4 years).

RESULTS

At diagnosis, fasting proinsulin was higher in NIDDM patients without ICAs than in control subjects (39.6 +/- 10.0 vs. 12.8 +/- 1.6 pmol/l, P < 0.01). Proinsulin response to intravenous glucose decreased in NIDDM patients with ICAs (from 35.6 +/- 6.2 to 13.5 +/- 5.4 pmol/l, P < 0.05), but remained unchanged in those without ICAs. At 3 years after diagnosis, fasting proinsulin (10.0 +/- 3.7 vs. 59.1 +/- 17.0 pmol/l) and proinsulin responses to intravenous glucose (13.5 +/- 5.4 vs. 103.9 +/- 35.1 pmol/l) and to intravenous glucagon (7.4 +/- 3.9 vs. 36.0 +/- 7.7 pmol/l) were much lower (P < 0.01) in NIDDM patients with ICAs than in those without ICAs.

CONCLUSIONS

After diagnosis of diabetes, proinsulin secretion decreases significantly in NIDDM patients with ICAs and remains constant in those without.

Longitudinal evaluation of renal function in non-insulin-dependent diabetic patients with early nephropathy: effects of angiotensin-converting enzyme inhibition

A prospective self-controlled evaluation of renal function in non-insulin-dependent diabetic patients with early nephropathy, mild to moderate hypertension, and retinopathy was undertaken over a 1-year period. Thereafter, the effects of treatment with captopril on blood pressure, albumin excretion, and renal function were assessed. Glomerular filtration rate (GFR), effective renal plasma flow (ERPF), and systolic and diastolic blood pressures remained stable during the pretreatment period; 24-h urinary protein excretion increased progressively from 0.79 +/- 0.13 to 1.23 +/- 0.18 g/24 h (p < 0.05) (mean +/- standard error). Captopril (25 mg b.i.d.) for 3 months reduced systolic and diastolic blood pressures significantly (p < 0.01). Simultaneously, 24-h urinary protein excretion declined by 41 +/- 2.4%, to 0.70 +/- 0.12 g/24 h (p < 0.05) while GFR, ERPF, and fractional filtration demonstrated small but insignificant changes. Subsequently, increase in captopril to 50 mg b.i.d. for the remaining 6 months did not produce further significant changes in renal hemodynamics, blood pressure, or urinary protein excretion (0.48 +/- 0.10 g/24 h at the termination of the study). Non-insulin-dependent diabetic patients with early nephropathy and mild to moderate hypertension demonstrate a progressive increase in urinary protein excretion. Administration of captopril resulted in prompt control of hypertension and reversal of the increase in urinary protein excretion.

Comparison of estimates of insulin sensitivity from minimal model analysis of the insulin-modified frequently sampled intravenous glucose tolerance test and the isoglycemic hyperinsulinemic clamp in subjects with NIDDM

Minimal model (MINMOD) analysis of the frequently sampled intravenous glucose tolerance test (FSIVGTT) is dependent on an adequate insulin response to the glucose load. As this is characteristically deficient in subjects with non-insulin-dependent diabetes mellitus (NIDDM), the technique has been modified by the use of an intravenous bolus of insulin. Previous validation of this modification in humans has relied on agreement between insulin sensitivity indexes (SI) estimated from tolbutamide- and insulin-modified tests and not on direct comparison with estimates derived from the isoglycemic glucose clamp. We have compared estimates of insulin sensitivity derived from minimal modeling of a 4-h insulin-modified FSIVGTT and the glucose clamp in subjects with NIDDM. Twelve subjects underwent an insulin-modified FSIVGTT and an isoglycemic hyperinsulinemic clamp in random order 2-4 weeks apart. Fasting plasma glucose (8.4 vs. 9.0 mmol/l) and immunoreactive insulin (IRI) concentrations (104.5 vs. 101.5 pmol/l) were not different between the 2 study days. SI(clamp) was derived from the steady-state glucose infusion rate during the 3rd h of the clamp, corrected for the ambient insulin and glucose concentrations. SI(ivgtt) was derived using MINMOD. SI(ivgtt) was 1.06 +/- 0.18 min-1.mU-1.ml x 10(4), and mean SI(clamp) was 4.97 +/- 0.69 l.min-1/pmol.l-1 x 10(4) (mean +/- SE). SI(ivgtt) was positively correlated with SI(clamp) (r = 0.73, P = 0.004) and negatively correlated with body mass index (r = -0.7, P = 0.005) and fasting IRI(ivgtt) (r = -0.64, P = 0.008). In summary, MINMOD analysis of the insulin-modified FSIVGTT provides a valid measure of insulin sensitivity in subjects with NIDDM.

Intranasal insulin: the effects of three dose regimens on postprandial glycaemic profiles in type II diabetic subjects

In both fasting normal and diabetic subjects, nasally administered insulin achieves significant falls in plasma glucose concentrations. Repeated administration before and during a meal has been necessary to lower postprandial glycaemic excursion in subjects with NIDDM. We have studied the use of Novolin Nasal which employs a non-irritant, lecithin-based enhancer as a vehicle for human insulin, on postprandial glucose profiles in NIDDM subjects to determine efficacy, optimal dose frequency, and tolerability. Seventeen NIDDM subjects (15 men, 2 women) participated in a randomized, partially blinded, placebo-controlled, crossover trial of three active treatment regimens (nasal insulin, 120 U at 0 min, 60 U at 0 and +20 min or 120 U at +20 min) in relation to a standardized mixed meal given at 0 min. All active treatments significantly reduced postprandial glucose concentrations compared to placebo. Intranasal insulin given at 0 min at a dose of 60 U or 120 U resulted in a 50% reduction in postprandial incremental glucose compared to placebo over the first 2 h, whereas treatment with 60 U both at 0 and 20 min lead to a 70% reduction over the 240 min postprandial period. Post-prandial intravenous insulin was the least effective. There were no episodes of symptomatic hypoglycaemia. Local tolerability was excellent with only four reports of transient nasal irritation out of a total of 68 doses. The delivery device was accurate with intra-device CV of delivered dose of 4.8%.(ABSTRACT TRUNCATED AT 250 WORDS)

A glimpse of the 'natural history' of established type 2 (non-insulin dependent) diabetes mellitus from the spectrum of metabolic and hormonal responses to a mixed meal at the time of diagnosis

The reported glucose and immunoreactive insulin (IRI) responses to oral and intravenous glucose in subjects with Type 2 diabetes have not always been consistent. This may have resulted from variations in the method of glucose administration, the ethnic backgrounds of subjects, the diagnostic criteria applied, the duration of the disease or IRI assay methods. The use of a mixed meal rather than glucose has been shown to provide a more physiological stimulus to the pancreatic beta-cell due to both glucose and non-glucose secretagogues. We have analysed the metabolic and hormonal responses of 188 newly diagnosed Caucasian subjects with Type 2 diabetes and 38 non-diabetic subjects to a 500 kcal mixed meal. The diabetic subjects were stratified according to fasting plasma glucose (FPG) (< 9, 9-12, 12-15 and > or = 15 mmol/l) and body mass index (BMI) (< 26.5, 26.5-30 and > or = 30 kg/m2). Increasing FPG was associated with higher peak glucose concentrations and increasing failure to achieve basal glucose levels by 4 h. Median fasting IRI concentrations were similar to those of normal subjects, but all diabetic subjects had reduced early-phase insulin secretion. Diabetic subjects with FPG < 9 mmol/l showed augmented IRI area under the curve (AUC) at 2 and 4 h, whereas those with FPG > 9 mmol/l had progressive falls in IRI AUC to below that of the normal subjects (P < 0.0001 for the trend). Peak IRI concentrations declined progressively with increasing FPG. Despite equivalent glucose exposure simple trends of increasing AUC, IRI with increasing BMI were statistically significant (P < 0.001, P < 0.02, P < 0.001 and P < 0.01, respectively for each FPG group). Both fasting and AUC non-esterified fatty acid concentrations increased significantly with FPG regardless of BMI (P < 0.001 for the trends). These results using a more physiological mixed meal challenge in a large number of recently diagnosed Type 2 diabetic subjects demonstrate a marked and increasing loss of beta-cell secretory function with increasing fasting hyperglycaemia aggravated by insulin resistance with increasing obesity.