Glucose monitoring by microdialysis: performance in a multicentre study

AIMS

The aim of this study was to assess the performance of the Continuous Research Tool (CRT) in a multicentre clinical-experimental study.

METHODS

Three patient groups totalling 28 subjects with diabetes [group A 10 Type 1 (Ulm), group B 10 Type 1 (Neuss), group C eight Type 2 (Aarhus)] participated in this trial. Two CRT microdialysis probes were inserted in parallel in the abdominal subcutaneous tissue for 120 h in each subject. In subjects in group A, glucose excursions were induced on one study day and those in group B underwent a glucose clamp (eu-, hypo- or hyperglycaemic) on one study day. CRT data were calibrated once with a retrospective calibration model based on a run-in time of 24 h and three blood glucose measurements per day.

RESULTS

All analysable experiments, covering a broad range of blood glucose values, yielded highly accurate data for the complete experimental time with a mean relative absolute difference of 12.8 +/- 6.0% and a predictive residual error sum of squares of 15.6 +/- 6.3 (mean +/- SD). Of all measurement results, 98.2% were in zones A and B of the error grid analysis. The average absolute differences were 1.14 mmol/l for Type 1 and 0.88 mmol/l for Type 2 diabetic patients. Relative absolute differences were 16.0% for Type 1 and 12.6% for Type 2 diabetic patients.

CONCLUSIONS

These results demonstrate that this microdialysis system allows reliable continuous glucose monitoring in patients with diabetes of either type.

Leptin decreases postprandially in people with type 2 diabetes, an effect reduced by the cooking method

Leptin modulates satiety and increases in obesity and type 2 diabetes mellitus in parallel with leptin resistance. Postprandial leptin regulation has been previously postulated to depend on meal composition, but data are controversial. The hypothesis of our study was that in people with type 2 diabetes mellitus, a postprandial leptin regulation exists that can be regulated not only by meal composition but also by the cooking method. In 20 inpatients with type 2 diabetes (mean age: 55.9 years), the acute effects of 2 meals, a high-heat-processed meal HHPM or a low-heat-processed meal LHPM, on leptin levels were studied on 2 different days in a randomized, crossover design. Both test meals had similar ingredients and differed only in the cooking method used. Parameters were measured after an overnight fast and at 2, 4, and 6 h postprandially. The HHPM induced a marked decrease in leptin levels, from 8 717+/-2 079 pg/ml at baseline to 6 788+/-1 598 pg/ml at 2 h postprandially (-1 929 pg/ml, -22%*), an effect significantly reduced by the LHPM, where values were 8 563+/-1 900 pg/ml at baseline and 7 425+/-1 591 pg/ml at 2 h postprandially (-1 138 pg/ml, -13%* (double dagger)) (*p<0.05 vs. baseline, (double dagger)p<0.05 vs. HHPM). Parameters of oxidative stress and blood AGEs increased only following the HHPM, while postprandial glucose, triglycerides, and insulin excursions were similar between meals. Postprandial leptin decreases following a HHPM meal in people with T2DM, an effect reduced by the cooking method.

Glucose monitoring at the thenar: evaluation of upper dermal blood glucose kinetics during rapid systemic blood glucose changes

OBJECTIVE

We compared blood glucose measurements at the thenar with those at the fingertip during glucose increase and decrease that was rapid enough to induce glucose differences between the forearm and the fingertip.

METHODS

A rapid glucose increase was induced by oral glucose; subsequently, a rapid glucose decrease was induced by intravenous insulin in 16 insulin-treated patients with diabetes. Capillary samples were taken in parallel from the thenar and fingertip. Different glucose monitors (FreeStyle, OneTouch Ultra, Soft-Sense) were used. Additional samples were taken from the forearm (n = 10 patients) in order to demonstrate that the blood glucose change achieved was rapid enough to principally induce glucose differences at alternative sites.

RESULTS

Neither blood glucose at baseline (135 +/- 34 vs. 136 +/- 41 mg/dl, p = 0.86) nor glucose amplitude during increase (190 +/- 35 vs. 188 +/- 41 mg/dl, p = 0.65) or decrease (255 +/- 32 vs. 257 +/- 45 mg/dl, p = 0.83) differed significantly between the fingertip and the thenar. Intra-individual average thenar-fingertip glucose difference was - 2 +/- 12 (p = 1.00) and + 5 +/- 9 mg/dl (p = 0.11). In the subgroup, intra-individual average forearm-finger difference was - 50 +/- 19 (p < 0.01) and + 45 +/- 11 mg/dl (p < 0.01) during glucose-increase and decrease, respectively. There were no obvious device-specific differences.

CONCLUSIONS

Blood glucose measurements at the thenar are a safe alternative to measurements at the fingertip at steady state as well as during blood glucose change that is sufficiently rapid to induce clinically relevant differences between forearm and fingertip.

Sensors for glucose monitoring: technical and clinical aspects

The aim of this article is to critically discuss the technical and clinical aspects of glucose sensors and to briefly review current technical developments. This includes sensors for spot glucose measurements as well as those used for continuous glucose monitoring. Continuous glucose monitoring in particular should supply the diabetic patient with all the information required to optimize insulin therapy and metabolic control. Such systems should also allow hypo- and hyperglycemic episodes to be avoided. During the last 30 years numerous attempts have been made to develop glucose sensors, and new major breakthroughs have been announced repeatedly. However, up until now no glucose sensor has been available that can be used by diabetic patients in daily life conditions. Also one type of glucose sensor, a glucose electrode, recently received approval by the Food and Drug Administration (USA) and is commercially available. Other glucose sensors employing the transdermal, microdialysis or open tissue microperfusion technique are currently under clinical development and may also become available in the near future. The types of glucose sensors referred to so far are not truly non-invasive, but only minimally invasive. They measure glucose concentration in the interstitial fluid of the skin or the subcutis. Non-invasive optical glucose sensors are designed to monitor glucose changes in the skin by directing light through it. They measure the characteristics of the reflected light that are changed as the result of an interaction with glucose. However, none of the attempts with optical glucose sensors have resulted thus far in the development of a sensor that allows monitoring of glucose with sufficient accuracy and precision within the clinically relevant glucose range in daily life conditions. Nevertheless, more minimal-invasive glucose sensors systems will become available for practical use in the near future, whereas it is still uncertain if this can be said for any non-invasive glucose sensor.

Presence of diabetic complications in type 1 diabetic patients correlates with low expression of mononuclear cell AGE-receptor-1 and elevated serum AGE

BACKGROUND

Receptors for advanced glycation endproducts (AGE-R) mediate AGE turnover, but can also trigger inflammatory genes that promote diabetic tissue injury and diabetic complications (DC). High AGE levels and reduced AGE-R sites in kidneys of NOD mice prone to type 1 diabetes (T1D) and to renal disease (RD) suggested that impaired AGE-R function may contribute to RD in these mice.

MATERIALS AND METHODS

In this study, after confirming reduced AGE-R1 expression in NOD mouse peritoneal macrophages, we tested for differences in AGE-R1, -R2, and -R3 gene expression in 54 human subjects by RT-PCR and Western analysis. Fresh peripheral blood mononuclear cells (PBMN) were isolated from 36 persons: 18 T1D patients with severe RD (DC); 11 age-and DM-duration matched patients without DC (n-DC); and 7 normal volunteers (NL). EBV-transformed lymphoblasts were obtained from an additional 18 subjects (12 T1D patients, 6 with and 6 without DC, and 6 nondiabetics).

RESULTS

AGE-R1 mRNA and protein of PBMN from n-DC patients were enhanced (p < .05 versus NL) in proportion to serum AGE levels (sAGE) (p < .005 versus NL). In contrast, PBMN from DC patients exhibited no up-regulation of AGE-R1 mRNA or protein, despite higher sAGE levels (p < .005 versus NL). A similar unresponsiveness in AGE-R1 gene expression was observed in EBV-transformed lymphoblasts from DC patients versus NL (p < .01), but not in n-DC (p = NS). AGE-R2 and -R3 mRNA and protein levels were enhanced in both T1D groups (DC > n-DC) (n-DC AGE-R3, p < .05, DC AGE-R3, p < .05) compared to NL. AGE-R2 mRNA levels correlated with sAGE levels (r = .61, p < .05), and with creatinine clearance (r = -.63, p < .05). No differences were noted in AGE-R2 and -R3 mRNA expression in cultured cells.

CONCLUSIONS

The consistent pattern of elevated serum AGE and low expression of AGE-R1 gene in macrophages from T1D mice (NOD), fresh PBMN and EBV-transformed cells from T1D patients with advanced DC suggests ineffective regulation of R1-mediated AGE turnover, possibly of genetic basis.

High dose supplementation of RRR-alpha-tocopherol decreases cellular hemostasis but accelerates plasmatic coagulation in type 2 diabetes mellitus

BACKGROUND

Diabetes mellitus is associated with increased generation of free oxygen radicals and depleted scavenging potential (oxidative stress), leading to increased LDL oxidation and platelet hyperreactivity, the major components of atherothrombotic vascular lesions. A main goal of antioxidant therapy is to protect the LDL particle from atherogenic oxidation and to reduce the activated cellular hemostasis.

METHODS

We evaluated the influence of a high dose supplementation with 800 IU of the natural antioxidant RRR-alpha-tocopherol (vitamin E) per day for six months on serum levels, vitamin E load of LDL particles (HPLC), lag phase of LDL oxidation (Esterbauer's assay), platelet adhesion molecules, leukocyte-platelet coaggregation (flow cytometry, D-III protocol) and coagulation (INR/PTT) in a group of 36 patients with type 2 diabetes (f/m 22/14; age 58+/-8.0; HbA1 at baseline 10.25+/-1.7).

RESULTS

Average vitamin E levels increased 2.65-fold accompanied by a 1.83-fold increase of LDL-associated vitamin E and a 12.3 min prolongation of the lag-phase of LDL oxidation (p<0.001 for all parameters at six months). Platelet expression of PECAM-1 (CD31) (-30.2% positive cells, p<0.001; antigen density -25%, p<0.001), ICAM-2 (CD102) (-2.9% positive cells, p<0.01; antigen density -10.6%, p<0.001) and fibrinogen (-1.6% positive cells, p<0.001; antigen density - 16.1 %, p<0.001) decreased. Concomitantly, platelet-leukocyte-coaggregation increased by 44% (p<0.001), correlating to an INR reduction of 10.4% (1.06+/-0.09 to 0.95+/-0.09, p<0.001, r = - 0.34). The PTT remained constant.

CONCLUSION

The antioxidant protection from the increased vitamin E was accompanied by a decreased expression of constitutive and function-dependent platelet adhesion molecules. However, increases in platelet-leukocyte coaggregates and a shortened INR time suggest extrinsic coagulation activation, possibly by induction of a leukocyte tissue factor dependent mechanism. High dose supplements of alpha-tocopherol may override the available redox balance in well controlled type 2 diabetes. However, intrinsic effects of alpha-tocopherol must be discussed.

[Long-term management of the diabetic patient: what is important?]

Diabetes mellitus ist a typical example of a chronic disease that requires life-long treatment by a team of various specialists including physicians. It is essential for optimal quality of life to develop an individually tailored treatment programme together with the diabetic patient and his/her social partner(s). The problems, that have to be taken into account include the various clinical symptoms of diabetes related as well as non-diabetic diseases typical for the multimorbid Type 2 diabetic patient with increasing age. In addition, problems of the active cooperation by the diabetic patient and inadequate reactions and acceptance by the social environment have to be resolved. For the necessary interactions of all persons involved in the diabetes longterm treatment altered organisational structures with new requirements for the quality of care of diabetic out- and inpatients are being developed.

Orally absorbed reactive glycation products (glycotoxins): an environmental risk factor in diabetic nephropathy

Endogenous advanced glycation endproducts (AGEs) include chemically crosslinking species (glycotoxins) that contribute to the vascular and renal complications of diabetes mellitus (DM). Renal excretion of the catabolic products of endogenous AGEs is impaired in patients with diabetic or nondiabetic kidney disease (KD). The aim of this study was to examine the oral absorption and renal clearance kinetics of food AGEs in DM with KD and whether circulating diet-derived AGEs contain active glycotoxins. Thirty-eight diabetics (DM) with or without KD and five healthy subjects (NL) received a single meal of egg white (56 g protein), cooked with (AGE-diet) or without fructose (100 g) (CL-diet). Serum and urine samples, collected for 48 hr, were monitored for AGE immunoreactivity by ELISA and for AGE-specific crosslinking reactivity, based on complex formation with 125I-labeled fibronectin. The AGE-diet, but not the CL-diet, produced distinct elevations in serum AGE levels in direct proportion to amount ingested (r = 0.8, P < 0.05): the area under the curve for serum ( approximately 10% of ingested AGE) correlated directly with severity of KD; renal excretion of dietary AGE, although normally incomplete (only approximately 30% of amount absorbed), in DM it correlated inversely with degree of albuminuria, and directly with creatinine clearance (r = 0.8, P < 0.05), reduced to <5% in DM with renal failure. Post-AGE-meal serum exhibited increased AGE-crosslinking activity (two times above baseline serum AGE, three times above negative control), which was inhibited by aminoguanidine. In conclusion, (i) the renal excretion of orally absorbed AGEs is markedly suppressed in diabetic nephropathy patients, (ii) daily influx of dietary AGEs includes glycotoxins that may constitute an added chronic risk for renal-vascular injury in DM, and (iii) dietary restriction of AGE food intake may greatly reduce the burden of AGEs in diabetic patients and possibly improve prognosis.

Correlation between blood glucose concentration in diabetics and noninvasively measured tissue optical scattering coefficient

Diabetics would benefit greatly from a device capable of providing continuous noninvasive monitoring of their blood glucose levels. The optical scattering coefficient of tissue depends on the concentration of glucose in the extracellular fluid. A feasibility study was performed to evaluate the sensitivity of the tissue reduced scattering coefficient in response to step changes in the blood glucose levels of diabetic volunteers. Estimates of the scattering coefficient were based on measurements of the diffuse reflectance on the skin at distances of 1-10 mm from a point source. A correlation was observed between step changes in blood glucose concentration and tissue reduced scattering coefficient in 30 out of 41 subjects measured.

Immunological evidence for the presence of advanced glycosylation end products in atherosclerotic lesions of euglycemic rabbits

Atherosclerosis is known to be accelerated in diabetic patients, but the mechanisms of this acceleration are poorly understood. Nonenzymatic glycosylation of long-lived proteins results in the formation of advanced glycosylation end products (AGEs), which are extensively cross-linked and could contribute to atherogenesis. Oxidative modification of LDL is also an important process in atherogenesis. In vitro evidence suggests that hyperglycemia may enhance lipid peroxidation, and conversely, that increased lipid peroxidation may enhance AGE formation. If such interactions occur in vivo, we hypothesized that AGE should be found in atherosclerotic lesions of euglycemic LDL receptor-deficient rabbits in areas rich in lipids and oxidized lipoproteins. To demonstrate the presence of AGEs, we developed antisera against a specific "model" compound of AGE, 2-furoyl-4(5)-(2-furanyl)-1H-imidazole (FFI) by using FFI-hexanoic acid (FFI-HA)-protein adducts as the antigen and against AGEs in general by using AGE-albumin as the antigen. Antisera generated with FFI-HA-protein adducts recognized FFI-HA alone as well as FFI-protein adducts. Native proteins or proteins conjugated with aldehydes formed during lipid peroxidation in vitro were not recognized by these antisera. Immunocytochemistry with both FFI-specific and AGE-specific antisera revealed the presence of these epitopes in atherosclerotic lesions of euglycemic LDL receptor-deficient rabbits but not in normal aortic tissues. AGE epitopes within atherosclerotic lesions were predominantly found in similar locations as epitopes generated during modification of the lipoproteins by oxidation, consistent with the hypothesized interactions between oxidation and glycosylation. Indirect evidence in support of the in vivo presence of FFI-like structures was also obtained by the observation that both diabetic and euglycemic human subjects contained autoantibodies that recognize FFI-protein adducts. Taken together, these data provide immunological evidence for the in vivo presence of FFI-like structures and other AGE-protein adducts in atherosclerotic lesions, even in euglycemic conditions.

Modification of low density lipoprotein by advanced glycation end products contributes to the dyslipidemia of diabetes and renal insufficiency

Atherosclerosis develops rapidly in patients with diabetes or renal insufficiency. Plasma lipoprotein profiles are frequently abnormal in these conditions and reflect an elevation in the level of the apoprotein B (ApoB)-containing components very low density lipoprotein (VLDL) and low density lipoprotein (LDL). High levels of circulating advanced glycation end products (AGEs) also occur in diabetes and end-stage renal disease (ESRD). These products arise from glucose-derived Amadori products and include AGE-modified peptides (AGE-peptides) which result from the catabolism of AGE-modified tissue proteins. AGE-peptides have been shown to crosslink protein amino groups and to accumulate in plasma as a consequence of renal insufficiency. To address potential mechanisms for the dyslipidemia of diabetes and ESRD, we investigated the possibility that circulating AGEs react directly with plasma lipoproteins to prevent their recognition by tissue LDL receptors. AGE-specific ELISA showed a significantly increased level of AGE-modified LDL in the plasma of diabetic or ESRD patients compared with normal controls. AGE-LDL formed readily in vitro when native LDL was incubated with either synthetic AGE-peptides or AGE-peptides isolated directly from patient plasma. LDL which had been modified by AGE-peptides in vitro to the same level of modification as that present in the plasma of diabetics with renal insufficiency exhibited markedly impaired clearance kinetics when injected into transgenic mice expressing the human LDL receptor. These data indicate that AGE modification significantly impairs LDL-receptor-mediated clearance mechanisms and may contribute to elevated LDL levels in patients with diabetes or renal insufficiency. This hypothesis was further supported by the observation that the administration of the advanced glycation inhibitor aminoguanidine to diabetic patients decreased circulating LDL levels by 28%.

Noninvasive blood glucose sensors based on near-infrared spectroscopy

Research into noninvasive devices for self-monitoring of blood glucose is mainly based on near-infrared spectroscopy. Such a device is particularly desirable in the intensive therapy of patients with diabetes mellitus to achieve optimal metabolic control through frequent glucose testing. The state of noninvasive assay technology is presented. Using diffuse reflectance spectra of mucous lip tissue has advantages and drawbacks compared with tissue transmittance experiments. Different approaches have been proposed in the patent literature; however, current technology requires further significant improvements, particularly within the lower normal and hypoglycemic glucose concentration ranges.

Lipid advanced glycosylation: pathway for lipid oxidation in vivo

To address potential mechanisms for oxidative modification of lipids in vivo, we investigated the possibility that phospholipids react directly with glucose to form advanced glycosylation end products (AGEs) that then initiate lipid oxidation. Phospholipid-linked AGEs formed readily in vitro, mimicking the absorbance, fluorescence, and immunochemical properties of AGEs that result from advanced glycosylation of proteins. Oxidation of unsaturated fatty acid residues, as assessed by reactive aldehyde formation, occurred at a rate that paralleled the rate of lipid advanced glycosylation. Aminoguanidine, an agent that prevents protein advanced glycosylation, inhibited both lipid advanced glycosylation and oxidative modification. Incubation of low density lipoprotein (LDL) with glucose produced AGE moieties that were attached to both the lipid and the apoprotein components. Oxidized LDL formed concomitantly with AGE-modified LDL. Of significance, AGE ELISA analysis of LDL specimens isolated from diabetic individuals revealed increased levels of both apoprotein- and lipid-linked AGEs when compared to specimens obtained from normal, nondiabetic controls. Circulating levels of oxidized LDL were elevated in diabetic patients and correlated significantly with lipid AGE levels. These data support the concept that AGE oxidation plays an important and perhaps primary role in initiating lipid oxidation in vivo.

Modified low density lipoprotein from diabetic patients causes cholesterol accumulation in human intimal aortic cells

Fifty-five serum samples from 99 Type 1 and 71 serum samples from 81 Type 2 diabetic patients (56% and 88%, respectively) brought about a 1.5-3.5-fold increase in total cholesterol content of cultured human intimal aortic cells. This atherogenic effect did not correlate with patient's age, diabetes duration or plasma lipid levels, and was mainly due to low density lipoprotein (LDL). Cholesterol accumulation in cells incubated with LDL highly correlated with that in cells exposed to corresponding patient's serum (r = 0.872 and r = 0.811, P < 0.0001, in Type 1 and Type 2 diabetic patients, respectively). In LDL from diabetic patients the sialic acid content was decreased by an average of 30% (P < 0.05), as compared with healthy subjects, and the fructosyl lysine content was increased by an average of 25% (P < 0.05). Atherogenic effect of patients' LDL significantly correlated with their fructosyl lysine content (P < 0.0001) and negatively correlated with sialic acid content (P < 0.0001). Two LDL fractions were further separated from the total LDL preparation by affinity chromatography on Ricinus communis agglutinin-agarose. The bound (desialylated) LDL fraction was characterized by an increased fructosyl lysine content and the altered neutral lipid and phospholipid composition, while non-bound (sialylated) LDL fraction did not differ from normal LDL. Desialylated, but not sialylated, LDL fraction induced massive cholesterol accumulation in cultured cells. In conclusion, the cholesterol accumulating effect of diabetic patients' blood sera is mainly related to atherogenic low density lipoprotein fraction, which is modified in various ways--by increased non-enzymatic glycosylation, desialylation and alterations in lipid composition. This multiple-modified LDL may contribute to the premature atherosclerosis development in diabetes mellitus.

Oral antidiabetic combination therapy with sulphonylureas and metformin

In a multicentre trial in general practice, a total of 1823 type 2 diabetics, not adequately controlled by diet and maximal sulphonylurea therapy, were treated with additional metformin 850--2 550 mg/d for 12 weeks. The average postprandial blood sugar decreased from 15.48 mmol/l to 10.43 mmol/l, HbA1 fell from 11.0% to 9.1%. Serum triglycerides decreased from an initial level of 2.87 mmol/l to 2.41 mmol/l an mean total cholesterol from 6.76 mmol/l to 6.16 mmol/l. In addition, body weight and blood pressure declined steadily. All the described changes were statistically significant. The metformin-sulphonylurea combination therapy was generally well tolerated. Gastrointestinal side effects occurred in about 7% of patients, but mainly in the first week of treatment, generally disappearing spontaneous as therapy was continued. Side effects led to a discontinuation of the treatment in 4.2% of patients.

Diabetes and arterial disease

Macroangiopathy (or atherosclerosis) is a common and chronic complication in diabetic patients. Unlike other diabetic complications, atherosclerosis is not unique to diabetes, confounding analysis of its relationship with the diabetic condition. Evidence of an independent role for diabetes in the development of atherosclerosis remains equivocal. The main determinant of macrovascular disease may be an interaction between diabetes and the aging process. Similarly the question of a relationship between macrovascular disease and good metabolic control remains unanswered. Macroangiopathy in diabetic populations seems to be related to similar predictors and pathological mechanisms operating in the general population. However, after analysis of these common risk factors for macroangiopathy, a diabetes-specific risk remains. Low-density lipoprotein metabolism is markedly disturbed in poorly controlled diabetic patients. This is manifest as a concert of actions which increase formation of foam cells and fatty streaks. The next step in the atherosclerotic process, the formation of fibrous plaques, may be associated with the platelet hyperactivity seen in diabetes. This may promote overshooting of repair mechanisms at the vessel wall. Release of a specific diabetic serum growth factor from the platelets may be responsible for the later stages of fibrous plaque development and the increased atherosclerotic risk in diabetes.

New approach to technical and clinical evaluation of devices for self-monitoring of blood glucose

Despite the wide distribution of devices for self-monitoring of blood glucose (SMBG), there is no internationally accepted agreement on a standardized procedure for their evaluation. This is due to incomplete or even inappropriate technical evaluation and to inadequate evaluation criteria for their clinical acceptability. To provide adequate information on the performance of these devices over the whole clinically relevant range for SMBG (30-350 mg/dl), a standardized test procedure has been established for technical (accuracy, precision, and total deviation) and clinical (acceptance analysis) evaluation. To demonstrate the potency of this new approach, the following SMBG devices and test strips were evaluated: Chemstrip bG batch (n = 10), Glucostix batch (n = 2), Accu-Check II (n = 5), Diascan (n = 5), Diascan strip batch (n = 4), Glucocheck SC (n = 4), and Glucometer II (n = 4). The devices and test strips were examined by trained technicians, and in addition, 1 Chemstrip bG batch and 2 Accu-Check II meters were examined by 10 and 5 trained diabetic patients, respectively. Even the best-performing device did not achieve the American Diabetes Association's goal that SMBG measurements should be within 15% of the reference value. Instead, the maximal total deviation within the clinically relevant blood glucose range reached values that equalled deviations from the reference value between 16 and 108%. Three of 36 devices were classified as good, 29 as acceptable, and 4 as unacceptable for clinical use. In conclusion, this new approach to the technical and clinical evaluation of devices for SMBG is easy to perform and provides more realistic and comparable information for clinical use and approval than commonly used methods.

Vascular growth factors and the development of macrovascular disease in diabetes mellitus

The pathogenesis of macrovascular disease in diabetes mellitus is still incompletely understood. Within the various pathomechanisms abnormal growth of vascular cells is well established as an intrinsic part of the angiopathic process. In this regard, there are different groups of vascular growth factors that are of potential relevance for the development of macrovascular disease in diabetes : hormones, locally released growth factors of platelet and of arterial wall cell origin. The following hormones whose blood levels could increase under various conditions in diabetes have to be considered : growth hormone, insulin-like growth factor I and II and insulin. Human platelets contain at least eight growth peptides or proteins that all stimulate in vitro growth of arterial wall cells : platelet-derived-, epidermal-, fibroblast-, diabetic serum-, endothelial- and transforming growth factor, vascular endothelial cell proliferation factor and platelet-derived endothelial cell mitogen. In serum and plasma from type II diabetics only the diabetic serum growth factor has been shown to be increased. Platelets from type I and II diabetic patients contain increased growth stimulating activity. This increased growth activity returned to normal levels in both types of diabetes after strict metabolic control. Arterial endothelial and smooth muscle cells, fibroblasts and monocyte/macrophages of different species release at least in culture a variety of growth factors that could participate in an autocrine or paracrine manner in the growth regulation of the arterial wall. Diabetes may affect the release of these factors, but direct evidence to which degree this would contribute to the development of macrovascular disease is lacking.(ABSTRACT TRUNCATED AT 250 WORDS)

[Clinical testing of a new blood glucose measuring system. A cooperative study at 8 centers]

The glucometer II system is a small measurement device with built-in batch-specific pressbutton calibration. The corresponding test strip "Glucostix" uses a two-color system. The blood glucose test strip can be evaluated both visually and by instrument. The precision determined in series was between 2.0% and 6.7% using control sera. The day-to-day precision was between 1.5% and 7.9%. Comparison of the methods on the basis of 781 and 109 capillary blood samples respectively revealed a good agreement between the hexokinase method or the glucose oxidase method (Beckman analyser) and the glucometer II values. The precision of measurement by the system was comparable in the two test strip batches employed. Visual reading of the test strips revealed a good agreement with the laboratory method in the hypoglycemic and normoglycemic range; at higher concentrations of blood glucose, a trend to underestimation of the measurement values was shown. The easy handling and small size of the instrument facilitates measurement of blood glucose by the patient under everyday conditions.

Increased growth stimulation of human vascular cells by serum from patients with primary hyper-LDL-cholesterolemia

Premature atherosclerosis in hypercholesterolemic patients may be due, in part, to increased growth of vascular cells. Therefore, the growth stimulating effect of serum and serum fractions from patients with primary hyper-LDL-cholesterolemia (LDL-cholesterol: 7.5 +/- 1.7 mmol/l) and from healthy subjects on human arterial smooth muscle cells and fibroblasts has been investigated over 5-7 days in culture. Human hypercholesterolemic sera increased the growth of both cell types up to a mean of 133% compared with normal sera (100%) (P less than 0.001). Removal of the dialyzable serum fraction (m.w. less than 3,500 daltons) reduced the growth effect of the hypercholesterolemic sera by 32% (P less than 0.001) and of the normal sera by 11% (P less than 0.01). Readdition of the hypercholesterolemic serum dialysate to its dialyzed serum restored completely the original growth effect. There was no significant difference in growth stimulation between the dialyzed hypercholesterolemic and normal sera excluding a major additional growth effect by LDL-cholesterol. The low molecular weight growth factor(s) of hypercholesterolemic serum (m.w. less than 3,500 daltons) showed a linear dependence of growth stimulation over a 20-fold concentration range. Increased amounts of this factor(s) might easily penetrate the arterial wall, thus contributing to atherogenesis.

Sera from type 2 (non-insulin-dependent) diabetic and healthy subjects contain different amounts of a very low molecular weight growth peptide for vascular cells

Diabetic angiopathy may be due, in part, to increased growth in vascular cells. We have investigated serum growth factors in Type 2 (non-insulin-dependent) diabetic and healthy subjects and their effect on cultured human arterial smooth muscle cells and fibroblasts. Removal of the dialyzable serum fraction (mol. wt. less than 12,000) reduced the growth effect of the diabetic sera by 37% (2p less than 0.005) and of the non-diabetic sera by only 8% (2p less than 0.01). In contrast, there was no difference in growth stimulation between the dialyzed diabetic or non-diabetic sera. Complete recovery of the dialyzable serum growth fraction was also obtained at a mol. wt. below 3,500. Ten times the concentration of the low molecular weight growth factor (mol. wt. less than 3,500) from diabetic sera stimulated growth of fibroblasts or arterial smooth muscle cells by a mean of 243% or 174% and from non-diabetic sera by a mean of 146% or 137%, respectively (2p less than 0.01). The growth stimulating potency of this serum fraction (mol. wt. less than 3,500) contained in 10% diabetic sera, was two to ten times higher than that of human growth hormone or insulin, added in amounts equivalent to 10% or physiological serum concentrations. This diabetic serum growth factor was further characterized by: (1) linear dependence of growth stimulation over a concentration range of twenty times and by (2) reduction of the growth stimulating activity to control levels by pretreatment: (a) at 95 degrees C for 30 min, or (b) with two different proteases: Serva pronase E (Streptomyceus griseus) or Calbiochem protease (Subtilisin calsberg).(ABSTRACT TRUNCATED AT 250 WORDS)

[Reflolux--a new test system for the self control of blood glucose for diabetics]

Correctness and accuracy of Reflolux, a new microprocessor-controlled minireflectometer for measuring blood-glucose concentrations, were tested in ten instruments. There was good agreement between the Reflolux values and those obtained in the laboratory with the hexokinase method, over the entire range of 40-350 mg/dl with a relatively small margin of error. Thus the Reflolux provides even in the hypoglycaemic range values accurate enough for everyday use by a diabetic. An important advantage of this test system lies in the use of Haemo-Glukotest 20-800 test strips which, in conjunction with the Reflolux, provide a visual color comparison for blood-glucose levels in the range of 20-800 mg/dl.

[Improved metabolic state in insulin-tested diabetes. Self-testing of blood or urine glucose on 2 days per week]

Randomized serial tests of their metabolic state over four weeks, without self-testing and during daily urinary glucose-profile testing (4 tests) with the Diabur-Test or blood-glucose levels with the Haemo-Gluco-test 20-800 (5 tests daily) on two days weekly were undertaken on 27 unselected insulin-treated outpatient diabetes. HbA1, blood glucose, serum cholesterol, triglycerides and VLDL, LDL and HDL cholesterol were the target values. The following metabolic values were significantly reduced (P less than 0.05) during blood-glucose self-testing, compared with the results during the non-testing phase: HbA1 on average by 11%, blood-glucose (starving) by 20%, serum cholesterol by 9%, serum triglycerides by 13%. Self-testing of urinary glucose (compared with the test-free phase) brought little improvement in the metabolic state. The results of self-testing were the more impressive the worse the metabolic state during the phase without self-testing. Except for VLDL and HDL cholesterol, changes in HbA1 correlated well during all phases with changes in the other metabolic values (P less than 0.05).

[New instrument for blood glucose determination. Results of a clinical trial of the Reflocheck]

Reflocheck, a new microprocessor-regulated apparatus determining blood sugar levels was tested in six laboratories. In the range of 20-450 mg/dl the apparatus gave precise results (co-efficient of variance 0.8%-6.4%), in good agreement with results by the hexokinase method. Reflocheck is an accurate and reliable instrument for the measuring of blood glucose levels.

[Inborn and acquired metabolic disorders in human vascular cells in diabetes mellitus and hyperlipoproteinemia]

Fibroblast growth from diabetics with poor metabolic control is increased in vitro by 15-92% as compared to healthy age matched controls. In contrast, fibroblast growth from patients with different types of familial hyperlipoproteinemia is decreased by 9-83%. In these fibroblasts the activity of lysosomal cathepsin D, the key enzyme for LDL-apo B degradation, was decreased by 12-31% too. These cell associated alterations could be related to different stages of premature aging. Serum from type II diabetics with poor metabolic control (DS) and from hypercholesterolemics (HS) stimulated growth of human arterial smooth muscle cells and fibroblasts in vitro by 6-64% as compared to serum from healthy controls or to serum from diabetics with good metabolic control. DS increased in these vascular cells LDL- and HDL-binding up to 260%, but decreased LDL-apo B degradation by cathepsin D by 16-39% similar to HS that decreased it by 29-42%. These serum effects depend on the metabolic control and could stimulate the cell turnover. This growth effect of DS is mainly related to at least two new peptides of very low molecular weight (less than 2000 daltons), which might easily penetrate the arterial wall and could contribute to the increased angiopathic risk in diabetes.

[Small reflectometers, independent of the electric current, for home blood glucose monitoring. Testing for correctness and precision]

Thirty small reflectometers not requiring mains electricity (23 Glucosemeter and 7 individual appliances of various makes) were tested under standardised laboratory conditions as to their relative and absolute accuracy in the measurement of blood glucose. The hexokinase method delivered the reference values. The investigation demonstrated systematic deviations of 1 to 97%, coincidental deviations of 8 to 24% and total deviations of between 25 and 153%. If one accepts a value of up to 50% for the total deviation only 13 out of 30 reflectometers are acceptable. The results show that each individual meter must be assessed by the doctor before it can be given to the patient for glucose monitoring at home.

Studies on inherited and acquired metabolic disorders in cultured arterial smooth muscle cells and fibroblasts

Cultured mesenchymal cells from insulin- and non-insulin-dependent diabetics with poor long-term control showed an increased growth rate as compared to age matched normal cells independent of the serum type used. These growth changes occurred independent of the genetic background as mesenchymal cells, (a) from four pancreatectomized diabetics with poor long-term metabolic control showed similar increased growth rates and (b) from two diabetics with good metabolic long-term control showed no growth changes as compared to age matched controls. There is no evidence (a) for the specific impact of obesity on these cell associated growth changes, and (b) for cell associated differences between cultured mesenchymal cells from diabetics and normal controls as far as protein and lipoprotein metabolism are concerned. The metabolic control of diabetes is of primary importance for the regulation of growth, protein synthesis and for lipoprotein binding and degradation in cultured mesenchymal cells independent of their origin, as serum from diabetics with poor metabolic control increased in these cells growth, protein synthesis and lipoprotein metabolism. Serum from well controlled diabetics did not differ from normal serum in its growth stimulating effects. As far as obesity could effect the metabolic control of diabetes, probably this could also affect indirectly the metabolism of mesenchymal cells. The interaction of cell associated and serum factors can further increase the observed growth and metabolic changes of mesenchymal cells. As far as these cell and serum related changes also occur in vivo they could contribute to the accelerated atherogenic development in diabetics as well as to an increased basal lamina layering in different tissues.

Effect of neomycin sulphate alone and in combination with D-thyroxine on serum lipoproteins in hypercholesterolaemic subjects

Treatment with neomycin sulphate 1.5 g/d for 8 weeks significantly lowered total serum cholesterol by an average of 19% in 15 out of 19 patients with primary hypercholesterolaemia and LDL-cholesterol by 21%, without significantly changing the corresponding triglyceride and HDL-cholesterol concentrations. Combined treatment with neomycin sulphate 1.5 g/d and d-thyroxine 6 mg/d for 8 weeks lowered total serum cholesterol in the same patients by an average of 30%, LDL-cholesterol by 27% and serum triglycerides by 18%, without significantly changing the HDL-cholesterol concentration. Continued treatment for 10 patients with neomycin sulphate 1.5 g/d for up to 13 months did not further change the reduced serum cholesterol level. 10 of 19 patients complained of side effects after 4-8 weeks of treatment with neomycin: 8 of recurrent diarrhoea, abdominal pain or poor appetite, and 4 of acute attacks of vertigo with nystagmus. All side effects were reversed a few days after stopping the neomycin treatment. No additional serious side effects due to d-thyroxine were observed. These serious side effects of neomycin sulphate limit its use to selected high risk patients with hypercholesterolaemia, who have failed to respond successfully to other LDL-cholesterol-lowering drugs. They stress the necessity for frequent monitoring for the side effects described.

Regulation of diabetic serum growth factors for human vascular cells by the metabolic control of diabetes mellitus

Serum factors from non-ketotic poorly controlled non-insulin-dependent diabetic patients stimulated growth and protein synthesis of human arterial smooth muscle cells and fibroblasts by 15-42%, compared to serum factors from well controlled diabetics. In contrast, the growth stimulating effect of pooled sera from well controlled diabetics did not differ from the effect of normal sera. Single sera from the same diabetics before and after improvement of the metabolic control stimulated cell growth to a similar degree as the respective pooled sera from different diabetic populations. As far as increased growth stimulation of vascular cells is related to increased angiopathic risk in diabetics, this metabolic regulation of growth factors supports the demand for a continuous optimal control of diabetic metabolism.