Protein glycation in diabetes mellitus

Diabetes mellitus is the ninth leading cause of mortality worldwide. It is a complex disease that manifests as chronic hyperglycemia. Glucose exposure causes biochemical changes at the proteome level as reflected in accumulation of glycated proteins. A prominent example is hemoglobin A1c (HbA1c), a glycated protein widely accepted as a diabetic indicator. Another emerging biomarker is glycated albumin which has demonstrated utility in situations where HbA1c cannot be used. Other proteins undergo glycation as well thus impacting cellular function, transport and immune response. Accordingly, these glycated counterparts may serve as predictors for diabetic complications and thus warrant further inquiry. Fortunately, modern proteomics has provided unique analytic capability to enable improved and more comprehensive exploration of glycating agents and glycated proteins. This review broadly covers topics from epidemiology of diabetes to modern analytical tools such as mass spectrometry to facilitate a better understanding of diabetes pathophysiology. This serves as an attempt to connect clinically relevant questions with findings of recent proteomic studies to suggest future avenues of diabetes research.

Dependence of Retinopathy (and other Complications) on Glycaemic Control and on Weight over 5/10 Years from Diagnosis of Type II Diabetes

Glycosylated haemoglobins and weights were recorded for 200 consecutive diabetic clinic attendere seen yearly for 5 years, 76 of whom were also seen up to 10 years from diagnosis of type 2 diabetes, representing 1380 patient years. Weight fluctuation (≥3 kg) was associated with increased final prevalence of hypertension, macroalbuminaemia and a raised creatinine (P≤ 0.002) but this relationship was abolished by correction for higher initial weight. Average giycaemia over 5/10 years [itself related to initial weight in women on tablets (N=53) but not others, and to waist but not waist/hip ratio], correlated with prevalence and severity of retinopathy (N=200; r=0.38, P≤0.0006) seen also in the subgroup of patients on tablets (N=145, P≤0.006). At HbA1 levels ≥10.5% an increased prevelance of retinopathy was seen in those on insulin (W=37, P≤0.001) and an increased prevalence of peripheral vascular disease was seen in men but not women (x2=2.87, P≤0.01) as well as in the prevalence of neuropathy. These findings suggest that good glycaemic control is of value in type 2 diabetes and less easily achieved in obesity.

Optical detection of glucose and glycated hemoglobin using etched fiber Bragg gratings coated with functionalized reduced graphene oxide

An enhanced optical detection of D-glucose and glycated hemoglobin (HbA1c ) has been established in this study using etched fiber Bragg gratings (eFBG) coated with aminophenylboronic acid (APBA)-functionalized reduced graphene oxide (RGO). The read out, namely the shift in Bragg wavelength (ΔλB ) is highly sensitive to changes that occur due to the adsorption of glucose (or HbA1c ) molecules on the eFBG sensor coated with APBA-RGO complex through a five-membered cyclic ester bond formation between glucose and APBA molecules. A limit of detection of 1 nM is achieved with a linear range of detection from 1 nM to 10 mM in the case of D-glucose detection experiments. For HbA1c , a linear range of detection varying from 86 nM to 0.23 mM is achieved. The observation of only 4 pm (picometer) change in ΔλB even for the 10 mM lactose solution confirms the specificity of the APBA-RGO complex coated eFBG sensors to glucose molecules.

Predictive value of albuminuria in American Indian youth with or without type 2 diabetes

OBJECTIVE

To examine the prognostic significance of elevated albuminuria in youth with type 2 diabetes.

PATIENTS AND METHODS

Cross-sectional and prospective studies were conducted on Pima Indian youth aged 5 to 19 years at baseline who were examined between July 1, 1982, and December 31, 2007. Prevalence and sequential changes in the level of microalbuminuria (30 < or = albumin-to-creatinine ratio [ACR] < 300 mg/g) and macroalbuminuria (ACR > or = 300 mg/g) and incidence of macroalbuminuria were computed according to the presence or absence of type 2 diabetes.

RESULTS

The prevalence of microalbuminuria and macroalbuminuria was 6.5% and 0.6% in the 3856 nondiabetic youth and 18.5% and 2.9% in the 103 youth with diabetes, respectively. One hundred forty-one of 187 (75.4%) nondiabetic youth, but only 1 of 14 (7.1%) diabetic youth with an elevated ACR (> or =30 mg/g) regressed to an undetectable or normal ACR (<30 mg/g) on subsequent examination. In a subset of 2666 youth with a median follow-up of 8.1 years, 36 nondiabetic and 30 diabetic youth with baseline ACRs of <300 mg/g developed macroalbuminuria. For a given ACR, the incidence of macroalbuminuria was 15.9-fold (95% confidence interval: 11.1-22.6) higher in the diabetic than in the nondiabetic youth.

CONCLUSIONS

Elevated albuminuria is infrequent and largely transient in nondiabetic youth, but it is relatively frequent and largely persistent in those with diabetes. Microalbuminuria in youth with type 2 diabetes strongly predicts progression to macroalbuminuria, which supports annual screening for albuminuria.

Change in the distribution of albuminuria according to estimated glomerular filtration rate in Pima Indians with type 2 diabetes

OBJECTIVE

We examined secular trends in the frequency distribution of albuminuria and estimated glomerular filtration rate (eGFR) in subjects with type 2 diabetes in 1982-1988 and 2001-2006, two periods associated with major changes in the management of diabetes.

RESEARCH DESIGN AND METHODS

The cross-sectional study included Pima Indians > or =15 years old with type 2 diabetes and measures of serum creatinine and urinary albumin-to-creatinine ratios (ACR). The continuous probability density distributions of ACR and eGFR were compared for the two time periods. eGFR was calculated using the Modification of Diet in Renal Disease Study equation.

RESULTS

The overall standardized distribution of ACR shifted toward lower values between time periods (P = 0.001), whereas the standardized distribution of eGFR did not (P = 0.45). In the first period, eGFR was <60 ml/min per 1.73 m(2) in 6.5% of the 837 subjects. Of these, 9.3% had normal ACR, 7.4% had microalbuminuria, and 83.3% had macroalbuminuria. In the second period, the prevalence of low eGFR was similar (6.6% of the 1,310 subjects). Among those with low eGFR, normal ACR prevalence doubled to 17.2%, microalbuminuria prevalence nearly tripled to 19.5%, and macroalbuminuria prevalence declined to 63.2%. Twice as many subjects in the second period received antihypertensive medicines and 30% more received hypoglycemic medicines than in the first period.

CONCLUSIONS

The distribution of albuminuria changed significantly among diabetic Pima Indians over the past 20 years, as treatment with medicines to control hyperglycemia and hypertension increased. The distribution of eGFR, however, remained unchanged. Consequently, the frequency of chronic kidney disease characterized by normoalbuminuria and low eGFR doubled.

Falsely low HbA1c value due to a rare variant of hemoglobin J-Baltimore

HbA1c values are heavily relied on to assess glycemic control. Hemoglobin variants may interfere with measurements of HbA1c resulting in falsely low values. We present the first report of a rare variant of Hb in a patient with type 2 diabetes, which lead to a falsely low HbA1c.

An enzymatic method for the rapid measurement of the hemoglobin A1c by a flow-injection system comprised of an electrochemical detector with a specific enzyme-reactor and a spectrophotometer

A flow-injection analytical (FIA) system, comprised of an electrochemical detector with a fructosyl-peptide oxidase (FPOX-CET) reactor and a flow-type spectrophotometer, was proposed for the simultaneous measurement of glycohemoglobin and total hemoglobin in blood cell. The blood cell samples were hemolyzed with a surfactant and then treated with protease. In the first stage of operation, total hemoglobin in digested sample was determined spectrophotometrically. In the second stage, fructosyl valyl histidine (FVH) released from glycohemoglobin by the selective proteolysis was determined specifically using the electrochemical detector with the FPOX-CET reactor. The FIA system could be automatically processed at an analytical speed of 40 samples per hour. The proposed assay method could determine selectively only the glycated N-terminal residue of beta-chain in glycohemoglobin and total hemoglobin in blood cell. The enzymatic hemoglobin A1c (HbA1c) value calculated by the concentration ratio of the FVH to total hemoglobin, was closely correlated with the HbA1c values certified by the Japan Diabetic Society (JDS) and the International Federation of Clinical Chemistry (IFCC).

Improved haemorrheological properties by Ginkgo biloba extract (Egb 761) in type 2 diabetes mellitus complicated with retinopathy

BACKGROUND & AIMS

Abnormal haemorrheological property changes in erythrocyte deformability, plasma and blood viscosity, and blood viscoelasticity may play very important roles in the development of microangiopathies in diabetes mellitus (DM). In this study, we demonstrate the improvement in abnormal haemorrheological parameters in DM with ingestion of Ginkgo biloba extract 761 (Egb 761).

METHODS

Haemorrheological parameters before and 3 months after Egb 761 oral ingestion were determined in 25 type 2 DM patients with retinopathy. These parameters included lipid peroxidation stress of erythrocytes, erythrocyte deformability, plasma and blood viscosity, blood viscoelasticity, and retinal capillary blood flow velocity.

RESULTS

After taking Egb 761 orally for 3 months, the blood viscosity was significantly reduced at different shear rates, by 0.44 +/- 0.10 (gamma = 400), 0.52 +/- 0.09 (gamma = 150) and 2.88 +/- 0.57 (gamma = 5). Viscoelasticity was significantly reduced in diabetic patients by 3.08 +/- 0.78 (0.1 Hz). The level of erythrocyte malondialdehyde (MDA) was reduced by 30%; however, the deformability of erythrocyte was increased by 20%. And lastly, retinal capillary blood flow rate was increased from 3.23 +/- 0.12 to 3.67 +/- 0.24 cm min(-1).

CONCLUSION

In this preliminary clinical study, 3 months of oral administration of Egb 761 significantly reduced MDA levels of erythrocytes membranes, decreased fibrinogen levels, promoted erythrocytes deformability, and improved blood viscosity and viscoelasticity, which may facilitate blood perfusion. Furthermore, it effectively improved retinal capillary blood flow rate in type 2 diabetic patients with retinopathy.

Periodontal disease and mortality in type 2 diabetes

OBJECTIVE

Periodontal disease may contribute to the increased mortality associated with diabetes.

RESEARCH DESIGN AND METHODS

In a prospective longitudinal study of 628 subjects aged > or =35 years, we examined the effect of periodontal disease on overall and cardiovascular disease mortality in Pima Indians with type 2 diabetes. Periodontal abnormality was classified as no or mild, moderate, and severe, based on panoramic radiographs and clinical dental examinations.

RESULTS

During a median follow-up of 11 years (range 0.3-16), 204 subjects died. The age- and sex-adjusted death rates for all natural causes expressed as the number of deaths per 1,000 person-years of follow-up were 3.7 (95% CI 0.7-6.6) for no or mild periodontal disease, 19.6 (10.7-28.5) for moderate periodontal disease, and 28.4 (22.3-34.6) for severe periodontal disease. Periodontal disease predicted deaths from ischemic heart disease (IHD) (P trend = 0.04) and diabetic nephropathy (P trend < 0.01). Death rates from other causes were not associated with periodontal disease. After adjustment for age, sex, duration of diabetes, HbA1c, macroalbuminuria, BMI, serum cholesterol concentration, hypertension, electrocardiographic abnormalities, and current smoking in a proportional hazards model, subjects with severe periodontal disease had 3.2 times the risk (95% CI 1.1-9.3) of cardiorenal mortality (IHD and diabetic nephropathy combined) compared with the reference group (no or mild periodontal disease and moderate periodontal disease combined).

CONCLUSIONS

Periodontal disease is a strong predictor of mortality from IHD and diabetic nephropathy in Pima Indians with type 2 diabetes. The effect of periodontal disease is in addition to the effects of traditional risk factors for these diseases.

Haemoglobin A1c: Analysis and Standardisation

The measurement of glycated haemoglobin has become centrally important in the monitoring of glycaemic control in the patient with diabetes. A number of analytical techniques have been described to measure this important haemoglobin fraction, and the fraction measured depends on the technique used; this has resulted in laboratories reporting different fractions i.e., HbA1, HbA1c and total glycated haemoglobin. This paper outlines methods currently used in clinical laboratories for the measurement of this glycated fraction. It describes the principles behind these methods and goes on to describe the new IFCC reference method, which will be used in the future to standardise methods used in the clinical laboratory. Analytical goals and factors that interfere with methods are also discussed.

Effect of HbE and HbH on HbA1C level by ionic exchange HPLC comparing to immunoturbidimetry

BACKGROUND

The hemoglobin (Hb)A1C level is widely used to monitor diabetes mellitus patients. The N-terminal amino acid valine of its beta chain is glycated. The assay of HbA1C is based on differences in the charge, chemical and structural properties of the protein.

METHODS

There are fully automated instruments available in clinical chemistry laboratory to assay HbA1C level. The effect of hemoglobinopathies was studied between an ionic exchange high-pressure liquid chromatography (HPLC) (Bio-Rad Laboratories, USA) and immunoturbidimetry (BM/Hitachi 912 with Roche HBA1CII, Germany-Japan) assay. The influence of high level HbF relative to the HbA1C level by ionic exchange HPLC is known. The effect of HbE and HbH to the HbA1C level by ionic exchange HPLC comparing to immunoturbimetry was examined. The evaluation was performed on 34 normal controls (A2A), 17 beta thalassemia traits (A2 upward arrow A), 36 HbE heterozygotes (EA), 37 HbE homozygotes (EE), 36 beta thalassemia/HbE (EF/EFA), 11 EABart's diseases (EABart's), 34 Hb H diseases (A2/CSAH) and 13 cord blood samples (FA).

CONCLUSIONS

Hemoglobinopathies can impact on the assay of HbA1C level such as HbE and HbH to ionic exchange HPLC. Although not studied as yet, this effect may influence the other methods such as affinity chromatography.

Impact of glycemic control on serum lipoprotein (a) in Arab children with type 1 diabetes

BACKGROUND

Lipoprotein (a) (Lp (a)) is an independent risk factor for coronary artery disease (CAD), a major cause of death in patients with type 1 diabetes mellitus. Both type 1 diabetes and CAD represent major problems in Kuwait. Data on the effect of metabolic control on Lp (a) in diabetic children are limited and this is particularly true for Arab children. The objectives of the present study were to analyze serum Lp (a) levels in patients with type 1 diabetes compared with non-diabetic children, taking into account the effect of glycemic control.

METHODS

Circulating lipids, including Lp (a), were measured in serum samples from 60 prepubertal non-diabetic children and 58 prepubertal children with type 1 diabetes. Comparisons of Lp (a) concentrations were made between the non-diabetic and diabetic children with good to fair control (glycosylated hemoglobin (GHb) <11%) and a group of diabetic children with poor control (GHb > or = 11%).

RESULTS

The mean serum Lp (a) level in all diabetic children was 187.62+160.43 mg/L, compared with 162.88+156.06 mg/L in the control group. The group of children with poor glycemic control had higher median Lp (a) levels (147.50 mg/L) than either the group of diabetic children with good to fair control (95 mg/L; P<0.028) or the group of non-diabetic children (125 mg/L; P<0.04). Moreover, 38.3% of poorly controlled diabetic children had elevated Lp (a) levels > or = 250 mg/L, compared with 12.5% of diabetic children with good to fair control and 16.7% of non-diabetic children (P<0.025 and P<0.039, respectively). No association was found between Lp (a), diabetes duration and insulin dose.

CONCLUSIONS

In Arab children, highest Lp (a) levels are associated with poorest metabolic control. The prevalence of Lp (a) levels associated with cardiovascular risk is higher in poorly controlled diabetic children. Increased levels of Lp (a) may be another contributing factor to the high risk for CAD in diabetic patients.

The effect of Indian or Anglo dietary preference on the incidence of diabetes in Pima Indians

OBJECTIVE

In short-term studies, adoption of a traditional diet is associated with reduction in metabolic abnormalities often found in populations experiencing rapid lifestyle changes. We examined the long-term effects of a self-assessed traditional or nontraditional dietary pattern on the development of type 2 diabetes in 165 nondiabetic Pima Indians.

RESEARCH DESIGN AND METHODS

Dietary intake was assessed in 1988 by a quantitative food frequency method, and subjects were asked to classify their diet as "Indian," "Anglo," or "mixed." The Indian diet reflects a preference for Sonoran-style and traditional desert foods. The Anglo diet reflects a preference for non-Sonoran-style foods typical of the remaining regions of the U.S.

RESULTS

In women, the intake of complex carbohydrates, dietary fiber, insoluble fiber, vegetable proteins, and the proportion of total calories from complex carbohydrate and vegetable proteins were significantly higher (P < 0.05) in the Indian than in the Anglo diet. The mixed diet was intermediate in of all these constituents. In men, the intake for these nutrients was also higher in the Indian than in the Anglo group, but not significantly. Diabetes developed in 36 subjects (8 men and 28 women) during 6.2 years of follow-up (range 0.9-10.9). The crude incidence rates of diabetes were 23. 35, and 63 cases per 1,000 person-years in the Indian. mixed, and Anglo groups, respectively. After adjustment for age, sex, BMI, and total energy intake in a proportional hazards model, the risk of developing diabetes in the Anglo-diet group was 2.5 times as high (95%) CI 0.9-7.2) and the rate in the mixed-diet group was 1.3 times as high (0.6-3.3) as in the Indian-diet group.

CONCLUSIONS

This study suggests that the adoption of an Anglo diet may increase the risk of developing diabetes in Pima Indians, but it does not provide unequivocal evidence for or against this hypothesis.

Glycemic control and major depression in patients with type 1 and type 2 diabetes mellitus

The current study evaluated the association of glycemic control and major depression in 33 type 1 and 39 type 2 diabetes mellitus patients. Type 1 patients with a lifetime history of major depression showed significantly worse glycemic control than patients without a history of psychiatric illness (t = 2.09; df = 31, p < 0.05). Type 2 diabetes patients with a lifetime history of major depression did not have significantly worse control than those with no history of psychiatric illness. Findings from this study indicate different relationships between lifetime major depression and glycemic control for patients with type 1 and type 2 diabetes. Treatment implications for glycemic control in type 1 and type 2 diabetes patients are discussed.

Non-separation assay for glycohemoglobin

The determination of glycohemoglobin [HbA1c, HbA1, or total glycohemoglobin (GHb)] has become an established procedure in the management of diabetes mellitus. Here, we describe the development of a simple, fluorescence, non-separation assay for the percentage of GHb (%GHb). The fluorescence of an eosin-boronic acid derivative when it was mixed with hemolysates of unwashed erythrocytes was quenched in proportion to the percentage of glycohemoglobin. Measurement of the fluorescence intensity gave an estimate of GHb in the sample, and measurement of light absorbance gave an estimate of total hemoglobin. A combination of the two measurements gave the assay response. Comparison with HPLC (Menarini-Arkray HA-8140 fully automated analyzer) for the percentage of HbA1 (%HbA1) gave %GHb(NETRIA) = 1.1(SD ±0.03)%HbA1 +0.6(SD ±0.3), Sy‖x = 0.821, r = 0.972, n = 80; comparison for HbA1c gave %GHb(NETRIA) = 1.3(SD ±0.04)%HbA1c + 1.8(SD ±0.3), Sy‖x = 0.813, r = 0.973, n = 80. Precision, estimated as the percentage of the CV of the %GHb assay results, was &lt;2% (intraassay, range 5–22% GHb) and &lt;4.2% (interassay, range 4–16% GHb). Dilution of a high-percentage GHb sample lysate showed that the assay was linear, and addition of glucose (60 mmol/L), bilirubin (250 μmol/L), and triglycerides (14 mmol/L) to low, medium, and high %GHb samples showed no clinical interference in assay results.

The effects of diabetes on placental aromatase activity

Diabetes complicates 2-3% of all pregnancies and is associated with an increase in both perinatal morbidity and mortality, though reasons for these adverse outcomes are unknown. Estrogen biosynthesis is a critical factor during pregnancy and is carried out in the placenta via aromatase (cytochrome P450 19A1), which catalyzes the conversion of C-19 androgens to C-18 estrogens. Previous studies have shown that hormones such as insulin-like growth factors and insulin regulate aromatase activity when studied in vitro. Interestingly, levels of these hormones are altered in patients with diabetes. Thus, we hypothesized that the presence of maternal diabetes may alter placental aromatase activity and thus estrogen biosynthesis, possibly serving as one factor in the adverse outcomes of babies born to mothers with diabetes. To this end, we measured the production of 19-hydroxyandrostenedione, 19-oxoadrostenedione and estrone in 30 placental tissues from diabetic patients, using [7-3H]androst-4-ene-3,17-dione as a model substrate for aromatase (P450 19A1). A statistical difference was detected in the percentage of 19-oxoandrostenedione formed between the overt and control groups (P < 0.05). Additionally, NADPH P450-reductase levels were measured in these same tissues to determine whether alterations in this enzyme necessary for aromatase activity could be affected by diabetes. No differences in reductase levels were detected among the patient groups. However, a statistical correlation was found between NADPH P450-reductase activity and the formation velocities of all three estrogen products (P < 0.05). Thus, it appears that the presence of diabetes does not affect placental aromatase activity.

Degradation of glycated hemoglobin. Role of erythrocytic proteolytic enzymes and oxidant damage

Glycated hemoglobin can be degraded by proteolytic enzyme(s) in the erythrocyte. The enzyme(s) co-elutes with glycated hemoglobin when the latter is separated from erythrocyte lysates using the cation-exchanger Bio Rex-70. A further purification of the Bio Rex eluant on DEAE Sephadex A-50 separated the enzyme(s) from glycated hemoglobin. Studies with the Bio Rex eluant showed that degradation of glycated hemoglobin is maximum at 37 degrees C at pH 8.6. Proteolytic degradation is inhibited by 5 mM N-ethylmaleimide (NEM), 5 mM ethylenediamine tetraacetic acid (EDTA) and 0.6 mM n-p-tosyl-L-lysine choromethyl ketone (TLCK) (100-87 and 76% inhibition respectively). This study also examines the possibility that oxidative-damage to glycated hemoglobin increases its susceptibility to proteolytic degradation. When incubated with various anti-oxidants like DTPA, uric acid, mannitol and butylated hydroxy toluene (BHT), proteolytic degradation of glycated hemoglobin decreased by 66.1, 50.7 and 38% respectively.

Evaluation of the Menarini–Arkray HA 8140 hemoglobin A1c analyzer

We describe a multinational evaluation of the Menarini– Arkray HA 8140 hemoglobin (Hb) A1canalyzer, which utilizes a high degree of automation, including bar code reading, cap piercing, and whole-blood sampling. Within- and between-batch CVs were &lt;2%. Linearity was confirmed throughout the working range of the analyzer. Common Hb variants, including Hb S, Hb C, and Hb F, did not interfere with the Hb A1c separation, and the potentially interfering labile Schiff base was effectively removed during the chromatographic procedure. The HA 8140 analyzer displayed good correlation to the Bio-Rad Variant analyzer, Tinaquant immunoassay, affinity chromatography, and an optimized “in-house” HPLC Hb A1c method. The methods when compared by Altman and Bland plots showed bias (upper, lower 95% confidence limits) of: Variant minus HA 8140 = 0.99 (0.23, 1.74), Tinaquant minus HA 8140 = 0.14 (−0.71, 0.98); affinity minus HA 8140 (after log transformation) = 1.13 (0.90, 1.41), and “in house” HPLC minus HA 8140 (after log transformation) = 0.91 (0.82, 1.01).

Investigation of the mechanism underlying the variability of glycated haemoglobin in non-diabetic subjects not related to glycaemia

The Islington Diabetes Survey identified two groups of non-diabetic individuals, low and high glycators, who remained consistently classified 4.4 +/- 0.2 years after the original study. To investigate the mechanism for this grouping, 12 original subjects, 5 with low and 7 with high levels of glycated haemoglobin relative to their 2 h blood glucose, were studied. Glycated albumin and fructosamine measurements gave comparable classifications, with three individuals being misclassified for each measurement; in addition glycated albumin was positively correlated with mean blood-glucose concentration (r = 0.53; P < 0.05). Fasting plasma glucose concentration was greater than the intra-erythrocyte concentration (P < 0.05), but their ratio was reduced in low compared to high glycators (0.77 +/- 0.12 and 0.94 +/- 0.13, P < 0.0001). No differences between groups were found for plasma insulin, urea or non-esterified fatty acids; plasma or intra-erythrocyte inorganic phosphate or vitamin C; nor plasma, erythrocyte or urinary total amino acids. Erythrocyte 2,3-diphosphoglycerate, a catalyst of glycation, was elevated in high compared to low glycators (5.61 +/- 0.26 and 4.81 +/- 0.24 mmol/l, P < 0.001). Mean centile glycated haemoglobin was positively correlated with intra-erythrocyte pH (r = 0.55; P < 0.05) and negatively with plasma total amino acids (r = -0.57, P < 0.05). These data indicate that the intra-erythrocyte environment of high glycators favours glycation of haemoglobin. This could have important consequences for diabetic patients in terms of monitoring their glycaemic control and in the progression of those complications related to non-enzymic glycation of intracellular proteins.

Development and progression of renal disease in Pima Indians with non-insulin-dependent diabetes mellitus. Diabetic Renal Disease Study Group

BACKGROUND

Non-insulin-dependent diabetes mellitus (NIDDM) is a major cause of end-stage renal disease. However, the course and determinants of renal failure in this type of diabetes have not been clearly defined.

METHODS

We studied glomerular function at intervals of 6 to 12 months for 4 years in 194 Pima Indians selected to represent different stages in the development and progression of diabetic renal disease. Initially, 31 subjects had normal glucose tolerance, 29 had impaired glucose tolerance, 30 had newly diagnosed diabetes, and 104 had had diabetes for five years or more; of these 104, 20 had normal albumin excretion, 50 had microalbuminuria, and 34 had macroalbuminuria. The glomerular filtration rate, renal plasma flow, urinary albumin excretion, and blood pressure were measured at each examination.

RESULTS

Initially, the mean (+/-SE) glomerular filtration rate was 143+/-7 ml per minute in subjects with newly diagnosed diabetes, 155+/-7 ml per minute in those with microalbuminuria, and 124+/-7 ml per minute in those with macroalbuminuria; these values were 16 percent, 26 percent, and 1 percent higher, respectively, than in the subjects with normal glucose tolerance (123+/-4 ml per minute). During four years of follow-up, the glomerular filtration rate increased by 18 percent in the subjects who initially had newly diagnosed diabetes (P=0.008); the rate declined by 3 percent in those with microalbuminuria at base line (P=0.29) and by 35 percent in those with macroalbuminuria (P<0.001). Higher base-line blood pressure predicted increasing urinary albumin excretion (P=0.006), and higher base-line urinary albumin excretion predicted a decline in the glomerular filtration rate (P<0.001). The initial glomerular filtration rate did not predict worsening albuminuria.

CONCLUSIONS

The glomerular filtration rate is elevated at the onset of NIDDM and remains so while normal albumin excretion or microalbuminuria persists. It declines progressively after the development of macroalbuminuria.

Severe periodontitis and risk for poor glycemic control in patients with non-insulin-dependent diabetes mellitus

This study tested the hypothesis that severe periodontitis in persons with non-insulin-dependent diabetes mellitus (NIDDM) increases the risk of poor glycemic control. Data from the longitudinal study of residents of the Gila River Indian Community were analyzed for dentate subjects aged 18 to 67, comprising all those: 1) diagnosed at baseline with NIDDM (at least 200 mg/dL plasma glucose after a 2-hour oral glucose tolerance test); 2) with baseline glycosylated hemoglobin (HbA1) less than 9%; and 3) who remained dentate during the 2-year follow-up period. Medical and dental examinations were conducted at 2-year intervals. Severe periodontitis was specified two ways for separate analyses: 1) as baseline periodontal attachment loss of 6 mm or more on at least one index tooth; and 2) baseline radiographic bone loss of 50% or more on at least one tooth. Clinical data for loss of periodontal attachment were available for 80 subjects who had at least one follow-up examination, 9 of whom had two follow-up examinations at 2-year intervals after baseline. Radiographic bone loss data were available for 88 subjects who had at least one follow-up examination, 17 of whom had two follow-up examinations. Poor glycemic control was specified as the presence of HbA, of 9% or more at follow-up. To increase the sample size, observations from baseline to second examination and from second to third examinations were combined. To control for non-independence of observations, generalized estimating equations (GEE) were used for regression modeling. Severe periodontitis at baseline was associated with increased risk of poor glycemic control at follow-up. Other statistically significant covariates in the GEE models were: 1) baseline age; 2) level of glycemic control at baseline; 3) having more severe NIDDM at baseline; 4) duration of NIDDM; and 5) smoking at baseline. These results support considering severe periodontitis as a risk factor for poor glycemic control and suggest that physicians treating patients with NIDDM should be alert to the signs of severe periodontitis in managing NIDDM.

Quantitative analysis of myelinated nerve fibers of peripheral nerve in streptozotocin-induced diabetes mellitus

The purpose of this study was to examine morphometric changes of myelinated fibers in early stages of experimental diabetes mellitus. Adult male Wistar rats aged 17 wk were used in this study. Diabetes mellitus was induced by streptozotocin. Samples of common peroneal nerve from diabetic rats (4 and 8 wk after induction of diabetes mellitus) and age-matched control animals were removed and processed. The semithin cross sections were stained with toluidine blue and used for myelinated fiber computer-aided morphometric analysis. There were no significant changes in diabetic animals after 4 wk duration of the disease. There was significant reduction in myelinated nerve fiber caliber in diabetic rats 8 wk after induction of diabetes as compared to age-matched controls. There was no significant reduction of axonal area in this group of diabetic rats, so diminution of fiber area was caused predominantly by reduction of myelin sheath area. The study demonstrates that the induction of diabetes mellitus in rat by streptozotocin is accompanied by early changes of the morphometric indices of myelinated nerve fibers of peripheral nerve.

Glycosylated hemoglobin and the risk of microalbuminuria in patients with insulin-dependent diabetes mellitus

BACKGROUND

The risk of microalbuminuria in patients with insulin-dependent diabetes mellitus (IDDM) is thought to depend on the degree of hyperglycemia, but the relation between the degree of hyperglycemia and urinary albumin excretion has not been defined.

METHODS

We measured urinary albumin excretion in three random urine samples obtained at least one month apart from 1613 patients with IDDM. Microalbuminuria or overt albuminuria was considered to be present if the ratio of albumin (in micrograms) to creatinine (in milligrams) was 17 to 299 or > or = 300, respectively, for men and 25 to 299 or > or = 300, respectively, for women. Measurements of glycosylated hemoglobin (hemoglobin A1) obtained up to four years before the urine testing were used as an index of hyperglycemia. Twelve percent of the patients had overt albuminuria and were excluded from subsequent analyses.

RESULTS

The prevalence of microalbuminuria was 18 percent in patients with IDDM. It increased with increasing postpubertal duration of diabetes and, within each six-year interval of disease duration, it increased nonlinearly with the hemoglobin A1 value. For hemoglobin A1 values below 10.1 percent, the slope of the relation was almost flat, whereas for values above 10.1 percent, the prevalence of microalbuminuria rose steeply (P < 0.001). For example, as the hemoglobin A1 value increased from 8.1 to 10.1 percent, the odds of microalbuminuria increased by a factor of 1.3, but as the value increased from 10.1 to 12.1 percent, the odds were increased by a factor of 2.4.

CONCLUSIONS

The risk of microalbuminuria in patients with IDDM increases abruptly above a hemoglobin A1 value of 10.1 percent (equivalent to a hemoglobin A1c value of 8.1 percent), suggesting that efforts to reduce the frequency of diabetic nephropathy should be focused on reducing hemoglobin A1 values that are above this threshold.

Energy expenditure in type 2 diabetic patients on metformin and sulphonylurea therapy

Insulin and sulphonylurea therapies have both been reported to cause weight gain in Type 2 diabetic patients whereas metformin does not have this adverse effect. The mechanism for this difference is unclear. We have investigated in a cross-over study the effect of sulphonylurea and metformin therapy on energy expenditure and body composition in 10 Type 2 diabetic patients (7 females, 3 males) of various weights (mean body mass index 33.4 (SD 7.6 kg m-2)). Free living total energy expenditure was measured over 14 days by the doubly labelled water method adjusted for urinary glucose energy losses and resting energy expenditure by ventilated hood indirect calorimetry. Overall, total energy expenditure (12.88 +/- 4.17 vs 13.1 +/- 3.69 MJ 24 h-1) and resting metabolic rate (7.30 +/- 1.75 vs 7.23 +/- 1.74 MJ 24 h-1) were similar on metformin and sulphonylurea therapy, respectively. When adjusted for differences in fat free mass, resting metabolic rate on sulphonylurea therapy was slightly but significantly lower (mean difference -5.5 kJ 24 h-1 kg-1, 95% CI -1.2, -9.9 kJ 24 h-1 kg-1, p < 0.05). Fat free mass also increased significantly by 1.3 kg (95% CI 0.4, 2.4 kg, p < 0.05) when on sulphonylurea therapy, thus compensating for the lower resting metabolic rate per kg fat free mass to leave overall resting metabolic rate unchanged compared to metformin therapy. We also investigated the effect of adding metformin to six Type 2 diabetic patients already on insulin. This did not lead to any measurable changes in any of the components of energy expenditure.(ABSTRACT TRUNCATED AT 250 WORDS)

Microalbuminuria as identified by a spot morning urine specimen in non-insulin-treated diabetes: an eight-year follow-up study

This study followed up a cohort of patients with microalbuminuria identified on a spot morning urine sample 8 years earlier and aimed to determine if a spot morning urinary albumin concentration was able to identify patients with non-insulin treated diabetes at increased risk of mortality and progression to nephropathy. In 1984, 47 of 216 patients chosen by random selection from our teaching hospital-based diabetes clinic were identified as having microalbuminuria (urinary albumin concentration 35-300 micrograms ml-1). Subjects were compared with an age-matched control group from the 1984 cohort who did not have microalbuminuria. Eight years later, 22 of 47 (46.8%) patients with microalbuminuria had died compared to 10 of 47 (21.3%) patients without albuminuria (p < 0.05). The majority of deaths were from cardiovascular disease (53.1%). Logistic regression showed microalbuminuria to be an independent predictor of mortality, not influenced by age, duration of diabetes, blood pressure, glycosylated haemoglobin or creatinine at the initial examination. Eight years later, in the group with initial microalbuminuria, eight still had microalbuminuria and five patients had developed nephropathy. In the group without albuminuria in 1984, only one patient had progressed to microalbuminuria and no patients to nephropathy. In conclusion, a spot urinary albumin concentration is of value in identifying patients with an increased risk of mortality or progression to nephropathy, and is simple to obtain at a clinic.

Cognitive function in patients with insulin-dependent diabetes mellitus during hyperglycemia and hypoglycemia

BACKGROUND

To determine the impact of glycemic control, gender, and other relevant parameters on cognitive function during exposure to different blood glucose levels in patients with insulin-dependent diabetes mellitus (IDDM), we examined neuropsychologic function during experimentally induced periods of hyperglycemia and hypoglycemia.

METHODS

We studied 20 men and 22 women, aged 18 to 44 years, with IDDM duration of 3 to 14 years and HbA1 values ranging from 5.8% to 18.0% (nondiabetic range 5.4% to 7.4%). We used a controlled experimental setting involving tests of sensory perceptual processing, simple motor abilities, attention, learning and memory, language, and spatial and constructional abilities at plasma glucose levels of 2.2, 5.6, 8.9, 14.4, and 21.1 mmol/L. Patients were blind to the glucose level. Tests used at each glucose level included reaction time (simple and choice), digit vigilance, trail making part B, word recall, digit sequence learning, and verbal fluency.

RESULTS

All aspects of neuropsychologic function were diminished at 2.2 mmol/L when compared with basal levels of performance at 8.9 mmol/L, whereas no alterations were observed at 14.4 or 21.1 mmol/L. Tests involving associative learning, attention, and mental flexibility were the most affected during hypoglycemia. Glycemic control was not correlated with neuropsychologic function at any glucose level. Women demonstrated less of an impairment in neuropsychologic function than men at 2.2 mmol/L.

CONCLUSIONS

Cognitive function in IDDM patients was generally well-preserved even at substantially elevated blood glucose levels. Deficits in all relevant areas of cognitive function occurred during hypoglycemia (2.2 mmol/L), irrespective of prior glycemic control, and women with IDDM were less cognitively impaired than men with IDDM during hypoglycemia.

Blood glucose estimation and symptoms during hyperglycemia and hypoglycemia in patients with insulin-dependent diabetes mellitus

PURPOSE

To investigate hypoglycemic and hyperglycemic symptoms, accuracy of estimating blood glucose, and their relation to glycemic control and counterregulatory hormone levels in insulin-dependent diabetes mellitus.

PATIENTS AND METHODS

During randomly ordered stepped hypoglycemic and hyperglycemic insulin clamps on two separate days, 42 patients with insulin-dependent diabetes mellitus rated the intensity of 40 moods and symptoms when glucose was 8.9, 5.6 and 2.2 mmol/L, and 8.9, 14.4 and 21.1 mmol/L. The subjects were blinded to their actual glucose levels and asked to estimate them at each step. Epinephrine, norepinephrine, cortisol, growth hormone, and glucagon were measured at each glucose plateau.

RESULTS

Cluster analysis yielded five symptom groups during hypoglycemia: autonomic symptoms, negative moods, positive moods, feeling weak/dizzy, and feeling relaxed. At 2.2 mmol/L, mean scores for all five symptom groups and 11 of 17 unclustered symptoms differed from those reported at the baseline glucose of 8.9 mmol/L (P < or = 0.05), but 34% of patients reported no awareness of autonomic symptoms. The intensity of autonomic symptoms correlated positively with HbA1 (r = .43, P < 0.01), epinephrine (r = .59, P < 0.001), norepinephrine (r = .45, P < 0.01) and cortisol (r = .62, P < 0.001), and negatively with glucose estimation error (r = -.45, P = 0.01). Six patients (15%) were unaware of both autonomic and neuroglycopenic symptoms during hypoglycemia. At 21.1 mmol/L, only 5 of 40 symptoms differed (P < 0.05) from baseline. Seventeen percent of subjects made potentially serious errors when estimating glucose at 2.2 mmol/L, and 66% at 21.1 mmol/L. Many patients experienced symptoms different from those they reported as their usual manifestations of changing glucose levels.

CONCLUSIONS

Since the majority of patients made clinically serious errors in glucose estimation, and many used symptoms that did not discriminate hyperglycemia and hypoglycemia, individualized training to increase awareness of glucose-related symptoms and glucose levels may help patients reduce the frequency or severity of hyperglycemic and hypoglycemic events.

Towards improving care for children with diabetes in Kuwait

Presents the results of a medical audit of the records of 199 children diagnosed as diabetic and admitted to Al-Amiri Hospital, Kuwait. Uses the measurement of glycosylated haemoglobin (HbA1) to indicate the levels of control achieved. Finds that the degree of glycaemic control compares favourably with studies done in other hospitals, but unfavourably with specialized diabetic clinics. Proposes that glycaemic control could be improved by provision of the services of specialized support staff such as dietitian, educator, psychologist and health visitor.

Pupil size in diabetes

Sympathetic function was studied in 101 diabetic children and 102 age and sex matched control children, as part of a longitudinal study of the evolution of microvascular disease in the population of diabetic children and adolescents in Avon County. The median (range) age of the diabetic population was 13.5 (6.0-17.2) years, the duration of diabetes was 4.0 (0.4-13.9) years, and glycated haemoglobin (HbA1) was 10.9 (7.0-18.1)%. Pupillary adaptation in darkness, as an index of sympathetic neuropathy, was measured using a Polaroid portable pupillometer. Diabetic children had a significantly smaller median pupillary diameter, measured as the pupil/iris ratio and expressed as a percentage, than control children (median (range) 62.9 (50.3-72.1) v 65.9 (52.2-73.8)). Pupillary diameter was significantly related to diabetes duration (r = -0.22), HbA1 (r = -0.34), systolic blood pressure (r = -0.25), diastolic blood pressure (r = -0.49), and mean albumin/creatinine ratio on random urine samples (r = -0.26). Pupillary diameter was not related to age (r = -0.1). Eight (7.9%) diabetic and four (3.9%) control children were identified as having abnormal pupillary dilation in darkness. In comparison with the rest of the diabetic population, these diabetic children had longer diabetes duration and poorer glycaemic control. Polaroid pupillometry has demonstrated subclinical autonomic neuropathy in a population of diabetic children and adolescents. These abnormalities were related to poor metabolic control, long diabetes duration, and also to other indices of microvascular disease.

Laboratory evaluation of the DCA 2000 clinic HbA1c immunoassay analyser

The DCA 2000 clinical analyser for the measurement of haemoglobin A1c was evaluated for analytical quality. The analyser, which utilises inhibition of latex agglutination immunoassay, demonstrated good within-batch (1.9-3.1% CV) and between-batch (2.2% CV) imprecision, and was not affected by haemoglobin concentration. The analyser was linear throughout the analytical range, and was found to correlate well with agar electroendosmosis (r = 0.93), affinity chromatography (r = 0.97), HPLC (r = 0.90) and EIA (r = 0.98). The analyser was found to give reliable analytical results, and with its ease of use, will provide the diabetologist with HbA1c results in the clinic; although an analysis time of 9 min will limit sample throughput.

Energy expenditure in lean and obese diabetic patients using the doubly labelled water method

Obesity is a common problem among Type 2 diabetic patients. To investigate the role of energy expenditure in the maintenance of obesity in diabetic subjects, total energy output was measured during weight stability in 23 diabetic patients: 8 lean, 5 overweight, and 10 obese. Free living total energy expenditure was measured over 14 days using doubly labelled water method, resting metabolic rate by indirect calorimetry, and urinary energy losses were assessed. Total energy output was higher in the obese (13.66 +/- SD 3.18 MJ 24 h-1) than normal weight patients (10.84 +/- 2.02 MJ 24 h-1; p < 0.05); 11.96 +/- 2.51 MJ 24 h-1 in the overweight. None of the lean but four of the obese had total energy output > 16 MJ 24 h-1. Urinary energy losses accounted for only 0.6% of total energy output in lean, 2.8% in overweight, and 3.1% in obese. Resting metabolic rate was significantly higher in obese (7.47 +/- 1.69 MJ 24 h-1) compared to lean (5.87 +/- 1.07; p < 0.05) and resting metabolic rate correlated with lean body mass (r = 0.8, p < 0.001). Thermogenesis plus physical activity was substantial and not lower in the obese (5.77 versus lean 4.97 MJ 24 h-1). The mean ratio of total energy expenditure to resting metabolic rate was in the moderate exercise category and similar in lean (1.87) and obese (1.80). Resting metabolic rate, total energy expenditure, and thermogenesis and physical activity were similar in all three groups when corrected for differences in lean body mass.(ABSTRACT TRUNCATED AT 250 WORDS)

Glycated haemoglobin, plasma glucose and diabetic retinopathy: cross-sectional and prospective analyses

Among Pima Indians with Type 2 (non-insulin-dependent) diabetes mellitus the relationships between glycated haemoglobin (HbA1), fasting or 2-h post-load plasma glucose and diabetic retinopathy were examined by cross-sectional and prospective analyses, and the strengths of the associations were directly compared by receiver operating characteristic analysis. In the cross-sectional analysis, HbA1, fasting and 2-h plasma glucose were each significantly related to retinopathy among 789 diabetic subjects by separate logistic models. In a stepwise multiple logistic model in which HbA1, fasting and 2-h plasma glucose were included, HbA1 was selected as having the strongest association with retinopathy and neither fasting nor 2-h plasma glucose contributed significantly to the model once HbA1 was entered. Similarly, in the prospective analysis, HbA1, fasting and 2-h plasma glucose all predicted retinopathy in 227 diabetic subjects by separate proportional-hazards models. In a stepwise proportional-hazards model with HbA1, fasting and 2-h plasma glucose available to the model, HbA1 was again selected as having the strongest association with the incidence of retinopathy, and neither fasting nor 2-h plasma glucose significantly added to the prediction of retinopathy. A receiver operating characteristic analysis was used to determine if HbA1 was statistically significantly better than fasting or 2-h plasma glucose in assessing the risk for retinopathy. In neither the cross-sectional nor the prospective data did the area under the receiver operating characteristic curve for HbA1 differ significantly from that for fasting or 2-h plasma glucose (p > 0.05 for each).(ABSTRACT TRUNCATED AT 250 WORDS)

Purified haemoglobin preparations in the evaluation of HbA1c determination by ion exchange chromatography

The use of ion exchange resins for the estimation of HbA1c in clinical samples rests on the assumption that HbA1c is effectively and efficiently separated from other N-terminally modified haemoglobins and from HbA0. To test this assumption, we applied highly purified preparations of HbA(1a+1b, HbA1c and HbA0 to ion exchange minicolumns, using conditions of application simulating actual blood samples and the first and second elution buffers provided by the manufacturer. The authenticity and purity of the applied haemoglobin preparations were documented by high performance liquid chromatography, gel electrophoresis and carbohydrate content. About 40% of the applied HbA(1a+1b) eluted in the first fraction; 45% eluted in the second fraction, and 10% to 15% required 1 mol/L NaCl to elute from the column. Of the applied HbA1c, 65-80% eluted where expected in the second fraction, about 20% required 1 mol/L NaCl to elute from the column, and the remainder eluted with HbA(1a+1b). Some 3-6% of pure HbA0 applied to minicolumns emerged in the second fraction, with the remainder eluting as expected after making the buffer 1 mol/L in NaCl. The results indicate that the fraction eluting from ion exchange minicolumn chromatography that is designated 'HbA1c' contains HbA(1a+1b), and that a substantial portion of the HbA1c in an applied sample does not elute in this fraction.

Use of fructosamine and glycated haemoglobin to verify self blood glucose monitoring data in diabetic pregnancy

Relationships between fructosamine and HbA1, and mean blood glucose over the previous 1-8 weeks, determined from self blood glucose monitoring with memory meters, were studied prospectively throughout 16 pregnancies in Type 1 diabetic women. Fructosamine correlated best (Spearman rank) with mean blood glucose over the previous 2 weeks in the first and second trimesters (0.5) and over the previous 1 week in the third trimester (0.39). HbA1 correlated best with mean blood glucose over the previous 8 weeks in the first and second trimesters (0.56), but over the previous 2 weeks in the third trimester (0.524) probably because of increased erythropoiesis in late pregnancy. From Deming regression models, 95% prediction intervals for mean blood glucose for fructosamine and HbA1 values were calculated, showing that fructosamine predicted levels of mean blood glucose more precisely than HbA1. These intervals can be used to estimate an individual pregnant diabetic woman's mean blood glucose from her fructosamine or HbA1 results and to verify self blood glucose monitoring data. In well-controlled diabetic pregnancy, both fructosamine and HbA1 reliably indicated trends in blood glucose but fructosamine estimated blood glucose levels more precisely.

Is diabetes always diabetes?

Diabetes is always taken to be a life-long diagnosis. In order to re-examine this question, 75 g glucose tolerance tests (OGTT) were performed twice on 37 previously confirmed diabetic patients (mean duration of diabetes of 4.6 years; range 1-15 years) with normal glycosylated haemoglobin levels on regular review. Weight loss since institution of a healthy diet was 7.6 +/- 4.8 kg (+/- SE). Normal glucose tolerance was found in 27% of patients and impaired glucose tolerance in 21% with no significant change on rechallenge. HbA1 was 6.3 +/- 1.5% (+/- SD) (normal < 7.5%) in patients with normal glucose tolerance compared to 7.0 +/- 0.9% (+/- SD) in those with impaired glucose tolerance, P < 0.05. The response of the OGTT in these patients varied with dietary intake and weight. Such individuals could be regarded as having perfectly controlled diabetes or alternatively to have been cured. The definition of diabetes should be reviewed to allow people to escape the diagnosis where permanent change in dietary habits is established.