Diabetic regulation and its relationship to microangiopathy

Design and baseline characteristics for the aminoguanidine Clinical Trial in Overt Type 2 Diabetic Nephropathy (ACTION II)

Advanced glycosylation endproduct (AGE) formation has been implicated in the development and progression of nephropathy in type 2 diabetes mellitus. In diabetic animals, aminoguanidine inhibits AGE-mediated cross-linking of proteins in vascular and renal tissue and slows the progression of renal disease. ACTION II is a randomized, double-blind, placebo-controlled trial comparing two dose levels of aminoguanidine with placebo on the progression of nephropathy in 599 type 2 diabetic patients with renal disease from 84 centers in the United States and Canada. The primary endpoint is time to doubling of serum creatinine concentration. Secondary endpoints include the effect of aminoguanidine on time to all-cause mortality, end-stage renal disease (ESRD), cardiovascular morbidity and mortality, rate of change in indices of renal function (iothalamate, Cockcroft and Gault [C&G] calculated creatinine and measured creatinine clearances), proteinuria, retinopathy, circulating and urinary AGE levels, and estimation of the relationship between plasma aminoguanidine concentrations and primary and secondary efficacy endpoints and adverse events. Progression of macrovascular disease was monitored and fundus photography performed. Type 2 diabetic patients aged 30 to 70 years were eligible for the trial if their blood pressure was < or =180 mm Hg systolic and < or =120 mm Hg diastolic, serum creatinine concentration > or =1.0 mg/dL (in women) or > or =1.2 mg/dL (in men), C&G clearance > or =40 mL/min, and proteinuria > or =500 mg/d with diabetic retinopathy or diabetic nephropathy on renal biopsy. Recruitment began in July 1995 and terminated in December 1996. The trial randomized a total of 599 subjects. At baseline, the mean (standard deviation [SD]) age was 58 (7.7) years, diabetes duration 16.5 (7.5) years, body mass index 32 kg/m2 (10-90% range 2642), arterial blood pressure 105 (12) mm Hg, C-peptide concentration 2.55 (1.71) ng/mL, serum glucose concentration 201 (89) mg/dL, hemoglobin A1c 8.7% (1.6), serum creatinine concentration 1.6 (0.5) mg/dL, iothalamate clearance 52 (25) mL/min/1.73 m2, proteinuria 4.1 (4.2) g/d, triglycerides 259 (214) mg/dL, and LDL cholesterol 144 (40) mg/dL. Patients are 72% male, 68% white, 16% black, and 16% Asian American and Native American. At baseline, 76% were receiving concomitant angiotensin-converting enzyme (ACE) inhibitors and 43% lipid-lowering agents. Follow-up in ACTION II was scheduled to continue through December 1998, so that follow-up was to be 2 years after the date of randomization of the final enrolled patient. The trial in fact ended in March 1998. This trial will contribute to our understanding of the natural history of type 2 diabetes mellitus-associated nephropathy and determine whether aminoguanidine will slow the progression of established diabetic renal disease.

Management of diabetic neuropathy

The only strategy shown to be consistently beneficial in the treatment of diabetic neuropathy is meticulous control of blood glucose. The largest study of the effects of glycemic control on progression of neuropathy was the Diabetes Control and Complications Trial, which enrolled 1,500 patients. Meticulous control of blood glucose by multiple injections or continuous subcutaneous infusion both delayed the onset of neuropathy and slowed its progression. A weakness of this and other studies of the effect of glycemic control is that they used surrogate measures of improvement (or slowing of progression) of neurologic function. Most used sensory and motor nerve conduction studies and some used vibration perception thresholds. Whether such measures correlate reliably with neuropathy symptom scores, neurologic examination, quality-of-life measures, neuropathic complications (foot ulcers and amputation), and mortality remains controversial. Also, most studies of tight glycemic control do not address the complications of more intensive therapy, among them severe hypoglycemia. Severe hypoglycemia can precipitate acute painful neuropathy, and it markedly increases axonal degeneration in experimental diabetic neuropathy. Finally, all studies have been confined to patients with mild neuropathy; some patients had no clinical evidence of neuropathy. Whether benefit can accrue to patients with more advanced neuropathy is not known. The most physiologic means of achieving glycemic control is through pancreas transplantation; this can result in significant improvement in clinical and electrophysiologic measures of motor and sensory function and slightly improve autonomic function. Strategies to reduce the metabolic consequences of hyperglycemia on nerves and to enhance axonal regeneration are needed to supplement careful glycemic control. Aldose reductase inhibitors hold promise for reducing metabolic nerve injury, but further study is needed.

In vitro inhibition of glucose phosphorylation by an aldose-reductase inhibitor (Tolrestat) in some non-insulin-sensitive rabbit tissues

We have previously demonstrated that in some non-insulin-sensitive tissues (capillaries of eel swimbladder Rete mirabile, and rabbit eye choroidocapillary lamina, optic nerve, retina, and lens) glucose phosphorylation increases with the increase in the concentration of glucose, a characteristic relevant to the hyperglycemia of diabetes. In the present research we demonstrate an effect of the aldose reductase inhibitor, Tolrestat, on the glucose-phosphorylating activity of rabbit lens and optic nerve, by assaying the enzyme activity of tissue homogenates (in the presence of 10 mmol/L glucose) without or with 10 min preincubation with increasing concentrations of Tolrestat (2, 4, and 8 micromol/L). In the lens, a 18% inhibition (p < 0.01) was observed in the presence of 8 micromol/L Tolrestat. In the optic nerve, a 12% (p < 0.05) and a 21% (p < 0.01) reduction was recorded at 4 and 8 micromol/L Tolrestat, respectively. Significant inverse correlations existed between the concentration of Tolrestat and the phosphorylation rate of glucose of rabbit lens and optic nerve. The dose-dependent inhibition of glucose phosphorylation observed by us suggests that the inhibitory action of Tolrestat on glucose metabolism extends beyond the well-known effects of this compound on the polyol pathway, and might contribute to the refraining action of Tolrestat on the development and progression of late diabetic complications in non-insulin-sensitive tissues.

Rabbit lens and retina phosphorylate glucose through a glucokinase-like enzyme: study in normal and spontaneously hyperglycemic animals

After having previously shown that some noninsulin-sensitive tissues (capillaries and optic nerve) phosphorylate glucose in a concentration-dependent manner through a glucokinase-like enzyme, here, we report data on glucose phosphorylation in rabbit lens and retina at various glucose concentrations (1, 5, 10, 25, 50, and 100 mmol/L). In the 3000 g supernatant of lens and retina homogenates from two separate groups of female albino rabbits ten animals in each group; 1.8-2.0 kg body weight; mean +/- SEM morning glycemia: 8.19 +/- 0.28 and 8.12 +/- 0.24 mmol/L, respectively) was assayed glucose phosphorylating activity (NADP reduction measured as change in optical density at 366 nm at pH 7.5). The enzyme activity did not reach the maximum at low glucose concentration (1 mmol/L), as it occurs in several tissues, but increased progressively in both tissues with the increase in glucose concentration. Values (mean +/- SEM) for lens were 0.197 +/- 0.031 nmol/min/mg protein at 1 mmol/L and 0.327 +/- 0.051 (the highest value) at 50 mmol/L glucose (+65.99%, p < 0.01; r = 0.31, p < 0.05). Values for retina were 36.02 +/- 2.12 at 1 mmol/L glucose and 42.48 +/- 2.79 (the highest value) at 25 mmol/L glucose (+17.93%, p < 0.001; r = 0.32, p < 0.05). These kinetic characteristics, somewhat reminiscent of those shown by hepatic glucokinase, are still more pronounced when we calculated the "glucokinase component," obtained by subtracting the activity at 1 mmol/L glucose (hexokinase component) from that at the highest glucose concentration (total glucose phosphorylating activity). In five rabbits of similar age and weight, with spontaneous hyperglycemia (mean +/- SEM morning glycemia: 11.71 +/- 0.60) glucose phosphorylation in the retina was lower than normal, value at pH 7.5 and 1 mmol/L glucose being 24.52 +/- 2.20 versus 36.02 +/- 2.12 of normal animals (-31.93%, p < 0.01). This, if occurs also in other tissues, could contribute to the hyperglycemia by reducing glucose utilization. In these animals, however, the glucose phosphorylating activity retained the responsivity to increasing glucose concentrations, with value at 100 mmol/L of 28.65 +/- 2.10, corresponding to + 16.84% over the value at 1 mmol/L (p < 0.01). Therefore, the actual glucose phosphorylation in the retina of these animals would depend both upon the enzyme level (which is reduced) and glucose concentration (which is increased). Due to the in vivo inhibition of the hexokinase component by glucose 6-phosphate, the glucokinase component in retina and lens may be predominant in vivo, making the stimulating effect of hyperglycemia much more important than it would appear from our in vitro data. This might play a role in the chronic diabetic complications.

Intensive insulin therapy in insulin-dependent diabetes mellitus, the results of the diabetes control and complications trial

Long term complications are the first causes of mortality and morbidity in diabetic patients. In Europe, many diabetologists speculated for a long time that a tight blood glucose control was the best way to avoid these complications, but without any complete evidence. In 1993, the results of the Diabetes Control and Complications Trial (DCCT), the first controlled, randomized, long term trial designed to study the link between metabolic control and complications in a large cohort of patients, has confirmed this hypothesis: in insulin-dependent diabetes mellitus, intensive insulin-therapy, as compared with conventional therapy, significantly reduces the risk of developing microvascular and neuropathic complications. Nevertheless, in some patients, the risk of hypoglycemia may outweight the benefit of intensive insulin therapy, and the results of the DCCT raises some questions about indications, the risk/benefit ratio and the cost/benefit ratio of intensive treatment.

Prevalence and risk factors of diabetic retinopathy among noninsulin-dependent diabetic subjects

In a population-based study in Taiwan, 11,478 subjects aged 40 years or older were screened for diabetes in one urban and five rural areas. Among the 715 subjects proven to have diabetes, 527 subjects underwent ophthalmoscopy. Diabetic retinopathy was present in 184 of the 527 subjects (35.0%), including background diabetic retinopathy in 157 subjects (30.0%), preproliferative diabetic retinopathy in 15 subjects (2.8%), and proliferative diabetic retinopathy in 12 subjects (2.2%). Diabetic retinopathy was correlated with the duration of diabetes and age at onset of diabetes, type of diabetes treatment, higher serum creatinine levels, and lower serum cholesterol levels. Several other factors, including gender, age, residential area, family income, educational level, control and family history of diabetes, body mass index, physical activity, exercise, cigarette smoking, stroke, ischemic heart disease, leg vessel disease, hypertension, and proteinuria, had no significant association with retinopathy. By multiple logistic regression analysis, duration of diabetes was the most important risk factor related to retinopathy. Diabetic subjects treated with insulin had a higher risk of developing retinopathy than those treated with dietary control (relative risk, 1.57; .05 < P < .10). The univariate analysis disclosed that proliferative diabetic retinopathy was related to older age at examination, older age at onset of diabetes, type of diabetes treatment, and presence of leg vessel disease. Insulin-treated diabetic subjects also had a higher risk of proliferative diabetic retinopathy than patients in whom diabetes was controlled by diet, with a relative risk of 2.51 (.05 < P < .10) in the multiple logistic regression analysis.

Blood glucose control and albuminuria in type 1 diabetes mellitus

The relationship between long-term blood glucose control and albuminuria in type 1 diabetes was investigated in 42 male and 58 female patients who had had diabetes mellitus for more than 7 years. Their mean (+/- SD) age and diabetes duration were 18.6 +/- 3.6 and 12.1 +/- 3.5 years, respectively. For periods of observation ranging from 1 to 6 years (mean 4.4 +/- 1.5), hemoglobin A1c (HbA1c) was measured two to six times yearly (mean of 8.8 +/- 3.9 determinations per patient). Albumin excretion rate (AER) was measured in single-void urine samples two to four times in 93 patients and once in the other seven patients. The 52 patients with mean HbA1c no more than 9.0% had significantly lower mean AER than those whose HbA1c was greater than 9.0% (20.1 +/- 24.6 vs 265 +/- 1005 mg/gm Cr, p less than 0.001). Only five (9.6%) of these 52 patients had elevated AER values (greater than 40 mg/gm Cr), whereas 21 (43.7%) of 48 patients whose mean HbA1c was greater than 9.0% had elevated AER values (p less than 0.001). Six male but no female patients had mean AER values greater than 300 mg/gm Cr. The 74 patients with normal AER had significantly lower mean HbA1c values than the 26 with elevated AER (8.6 +/- 1.5 vs 10.1 +/- 1.6%, p less than 0.001). These results support the contention that maintenance of HbA1c levels at no more than 9% (one and one-half times the upper limit of normal) will significantly decrease the likelihood that diabetic nephropathy will develop.

The effect of aldose reductase inhibition with ponalrestat on the width of the capillary basement membrane in diabetes mellitus

There is evidence to suggest that hyperglycemia is required for the development of the microvascular complications of diabetes. However, the precise mechanism by which hyperglycemia might cause diabetic complications is not completely clear. One possibility is the increased activity of the polyol pathway. Capillary basement membrane thickness is a hallmark histological finding in diabetic microangiopathy. Previous studies in experimental models of diabetes have related the polyol pathway with the thickness of basement membrane in retinal capillaries. To study the effect of aldose reductase inhibition with ponalrestat on the width of the skeletal muscle capillary basement membrane in subjects with diabetes, we measured the capillary basement membrane width in 55 subjects with diabetes in a double masked, placebo controlled randomized trial over a period of 18 months. Twenty-nine patients received ponalrestat (two 300 mg tablets daily) and twenty-six received placebo tablets. The age, sex distribution, type and duration of diabetes were similar in both groups. The glycosylated hemoglobin remained at a constant level throughout the study in both groups. The baseline capillary basement membrane width of the ponalrestat group was 3134 +/- 146 A, it was 3074 +/- 226 A at month 12 and 2548 +/- 182 A at month 18 (P less than 0.001 vs baseline value). The placebo group also had a significant reduction in the width of the capillary basement membrane, from a baseline value of 3026 +/- 147 A to 2818 +/- 144 A at month 12 and 2618 +/- 156 A at month 18 (P less than 0.001 vs baseline value). There was no statistical difference in the capillary basement membrane width between the two groups at any time point.(ABSTRACT TRUNCATED AT 250 WORDS)

High prevalence of proliferative retinopathy in diabetic patients with low pancreatic B-cell capacity

A retrospective study on the role of pancreatic B-cell insulin secretory capacity in the development of proliferative diabetic retinopathy was performed in 160 diabetic patients with a duration of diabetes of more than 10 years (mean 19.5 +/- 7.9 years). Pancreatic B-cell insulin secretory capacity was assessed in terms of the quantity of C-peptide excreted into urine per day (24-h urinary C-peptide). When the patients were divided into three groups according to the quantity of 24-h urinary C-peptide (group I, C-peptide less than 30 micrograms, n = 49; group II, 30 micrograms less than or equal to C-peptide less than 80 micrograms, n = 76; and group III, C-peptide greater than or equal to 80 micrograms, n = 35), the prevalence of proliferative diabetic retinopathy was much higher in group I (26.5%) than in group II (5.3%) or group III (2.9%). The incidence of proliferative diabetic retinopathy during the follow-up period (mean 9.8 +/- 4.8 years) was also highest in group I (20.0%, 2.7%, and 2.9% in groups I, II, and III, respectively). Other factors which might affect the development of proliferative diabetic retinopathy, including duration of diabetes and past glycemic control, were comparable in these three groups. In contrast, a division of the patients according to glycemic control revealed a strong correlation between glycemic control and background diabetic retinopathy whereas no such correlation was apparent with proliferative diabetic retinopathy. These data are consistent with the view that low pancreatic B-cell insulin secretory capacity may be a risk factor for the development of proliferative diabetic retinopathy.

The relationship between metabolic control and vascular complications of diabetes mellitus

Animal studies strongly support the notion that the microvascular complications of diabetes are a consequence of the metabolic derangements. The evidence from human studies is not nearly as persuasive, but controlled prospective clinical trials are examining this issue more incisively than has been possible previously.

Improved diabetes control reduces skeletal muscle capillary basement membrane width in insulin-dependent diabetes mellitus

We studied the relationship between the control of blood glucose and the width of skeletal muscle capillary basement membrane in 54 insulin-dependent diabetic patients. After initial measurement of levels of glycosylated hemoglobin and the width of skeletal muscle capillary basement membrane, the patients were divided into two groups: an intensive treatment group of 30 patients who were treated with continuous subcutaneous insulin infusion and a control group of 24 patients who continued to receive conventional treatment, usually two daily injections of insulin. Both groups have been followed prospectively for periods of time up to 4 years. Within 1 year the intensive treatment group had a significant decrease in glycosylated hemoglobin levels as compared to baseline values reflecting improved control of blood glucose. This level of glycosylated hemoglobin was stable over the remainder of the follow-up period. This group also had a significant reduction in the width of skeletal muscle capillary basement membrane within 1 year and it persisted for the 4 years of observation. The control group of patients had no significant change in their level of glycosylated hemoglobin and the width of the skeletal muscle capillary basement membrane tended to increase with time. It this result in skeletal muscle capillaries applies to those of retinal and renal tissue, meticulous diabetic control for a prolonged period of time may be beneficial in preventing the progression of the microvascular complications of diabetes mellitus.

Subepidermal capillary basement membrane thickness of the skin obtained by punch biopsy in patients with non insulin dependent diabetes mellitus

Thickening and proliferation of the capillary basement membrane is a generalized phenomenon in diabetes mellitus and has been described in many organs including the heart, kidney, pancreas, retina etc. While such changes are specific, it is difficult to obtain specimens from those organs. Tissue samples were obtained from the medial surface of the thigh of 33 diabetics and 4 healthy controls by means of punch biopsy. Measurements carried out by normogram obtained from electron microscopic pictures. HbA1c values were also determined at time of muscle biopsy. 1. The HbA1c values are higher in diabetics than in the control group (p<0.01). 2. The subepidermal capillary basement membrane thickness of the diabetics: 30% of the 5’th decade population, 53.9% of the 6’th decade population and 83.3% of the 7’th decade population was greater than 3,000 A°. Whereas that of the controls was less than 3,000 A°. 3. The subepidermal capillary basement membrane thickness was not significantly increased with the duration of the disease. 4. In cases of greater subepidermal capillary besement membrane thickness, HbA1c showed a significant increase. (p<0.01).

Effect of glycemic control on microvascular complications in patients with type I diabetes mellitus

The relation between the control of blood glucose levels and the progression of early diabetic retinopathy and the width of skeletal muscle capillary basement membrane was studied in 54 insulin-dependent diabetic patients. After initial ophthalmologic evaluation including seven-field fundus photography and fluorescein angiography and measurement of levels of glycosylated hemoglobin and width of skeletal muscle capillary basement membrane, the patients were divided into two groups: an experimental group of 30 patients who were treated with continuous subcutaneous insulin infusion and a control group of 24 patients who continued to receive conventional treatment--usually two injections of insulin daily. After a mean follow-up period of 31.4 months, the experimental group had a significant decrease in glycosylated hemoglobin levels as compared with baseline values (mean +/- SEM, 7.2 +/- 0.3 percent versus 10.1 +/- 0.4 percent), reflecting improved control of blood glucose levels. The conventional treatment group had no change in glycosylated hemoglobin levels after a mean of 33.5 months of follow-up. With use of either a modified Early Treatment Diabetic Retinopathy Study grading system or macular microaneurysm counts, the experimental treatment group showed significantly less progression of retinopathy (p less than 0.05). The skeletal muscle capillary basement membrane width was significantly reduced only in the experimental treatment group with stable or improved retinopathy and was unchanged in the control group. There was a tendency for skeletal muscle capillary basement membrane width to increase in thickness over time in those patients whose retinopathy worsened irrespective of treatment. It is concluded that meticulous diabetic control may slow the progression of early diabetic retinopathy. Changes in skeletal muscle capillary basement membrane width may reflect the course of diabetic retinopathy.

Insulin-dependent diabetes mellitus: pathophysiology

Diabetes mellitus is a heterogeneous disorder. About 80% of the patients with this disease are categorized as having non-insulin-dependent diabetes mellitus, a disorder resulting from varied degrees of insulin resistance and impaired insulin secretion; the causes for these abnormalities are unknown. The remaining 15 to 20% of patients have insulin-dependent diabetes mellitus, a disorder caused by the destruction of insulin-producing endocrine cells within the pancreas and currently considered to be the result of an autoimmune process. During the course of both types of diabetes mellitus, the so-called long-term complications of diabetes invariably occur to some extent in all patients. These complications include retinopathy, nephropathy, neuropathy, and premature atherosclerosis. The molecular basis for these complications is not completely understood, but recent evidence obtained from both experiments in animals and prospective clinical studies indicates that metabolic derangements associated with poor glycemic control are a major determinant of the frequency and severity of these complications. Such evidence is the rationale for current attempts to maintain near-normal glycemia in patients with diabetes mellitus.

Assessment of long-term glycemia in type I diabetes using multiple blood glucose values stored in a memory-containing reflectometer

The relationship between repetitive hemoglobin A1 values and daily blood glucose tests performed by 20 insulin-dependent diabetic outpatients was assessed over a six-week period using a modified reflectance meter capable of storing blood glucose determinations automatically. An average of four and a half determinations per subject per day was recorded with a range of average blood glucose values between 82 +/- 2 mg/dl and 316 +/- 5 mg/dl (mean +/- SE). The relationship between average blood glucose and hemoglobin A1 values was significant when hemoglobin A1 values at the end of the six-week period were correlated with the mean blood glucose level over that period (r = 0.55, p less than 0.02), but improved when a more remote hemoglobin A1 value obtained at 10 weeks was used (r = 0.64, p less than 0.005). Hemoglobin A1 values covering two-week intervals were extremely poor in reflecting average glycemia. The average fasting blood glucose level in these subjects was highly correlated with the overall daily blood glucose values (r = 0.89, p less than 0.0001), although the coefficients of variation of these parameters averaged 43 +/- 3 percent and 47 +/- 2 percent, respectively, and were greater than that of the hemoglobin A1 values over six weeks (10 +/- 2 percent). It is concluded that labile blood glucose control in patients with insulin-dependent diabetes is accurately reflected by the average fasting blood glucose level, although multiple determinations must be employed. Satisfactory assessment may be made by use of hemoglobin A1 value provided that the hemoglobin A1 determination follows a sufficiently long period of time, presumably related to the turnover of glycosylated hemoglobin.

Fiber loss is primary and multifocal in sural nerves in diabetic polyneuropathy

Pathological, morphometric, and teased fiber studies of sural nerve from 36 diabetic patients with (n = 32) and without (n = 4) neuropathy and from 47 healthy subjects provide evidence that in diabetic polyneuropathy: (1) fiber loss is primary; (2) demyelination and remyelination with or without onion bulb formation are secondary; (3) remaining fibers, on average, have the same ratio of small to large fibers as in healthy individuals, but with a greatly increased variability; and (4) the spatial distribution of fiber loss is both diffuse and multifocal. Criteria developed during the study of experimental models of ischemic neuropathy were employed to assess whether ischemic nerve damage had occurred in diabetic polyneuropathy. We conclude that there is increasing evidence that microvascular pathological abnormality and ischemia may be involved in the pathogenesis of human diabetic polyneuropathy. Cases with selective loss of small or large afferent fibers are probably extremes of a normal distribution and not different disorders.

Blood glucose and diabetic retinopathy: a critical appraisal of new evidence

The relationship between blood glucose and diabetic retinopathy remains controversial. To obtain a proper perspective on this issue, a critical appraisal of clinical evidence published between 1974 and 1984 was done using standard methodologic criteria. Thirteen cohort studies and four intervention trials were found which provided the following new information: systolic hypertension, alcohol ingestion, female sex, and obesity were implicated as potential adverse prognostic factors related to retinopathy development. Although initial diagnostic blood glucose concentration was associated with subsequent retinopathy development, the reviewed studies did not provide evidence that tight glucose control prevented or retarded its development and progression. Some funduscopic and angiographic lesions deteriorated with tight control.

Rationale for inhibition of growth hormone secretion in the management of the diabetic patient

Patients with diabetes mellitus, especially the insulin-dependent variety, have increased circulating levels of growth hormone. On the basis of currently available information, the potential advantages of inhibition of growth hormone secretion as an adjunct in the treatment of diabetes mellitus include improved metabolic control (less hyperglycaemia, greater stability), resulting from diminution of the insulin-antagonistic actions of this hormone, and reduced micro- and possibly macro-angiopathy, resulting not only from improved metabolic control but also from decreased direct effects of growth hormone on blood vessels.

Comparison of plasma insulin profiles after subcutaneous administration of insulin by jet spray and conventional needle injection in patients with insulin-dependent diabetes mellitus

The characteristics of plasma free insulin profiles after conventional subcutaneous injection of regular insulin (10 units) and after jet injection of this amount of insulin were compared in eight subjects with insulin-dependent diabetes mellitus. Although administration of insulin with the jet injector resulted in peak plasma free insulin concentrations (45 +/- 4 microU/ml) similar to those achieved after conventional injection (47 +/- 5 microU/ml), it produced more rapid increases in plasma free insulin concentrations (time to peak concentration, 76 +/- 11 minutes versus 152 +/- 16 minutes; P less than 0.01) and less prolonged hyperinsulinemia. Variability in the peak insulin concentrations and the time to peak concentration was comparable for both methods of administration of insulin. Thus, insulin administered by jet injector may improve control of postprandial hyperglycemia and diminish the risk for late hypoglycemia in some patients with insulin-requiring diabetes mellitus treated with conventional injections of insulin.

Juvenile diabetes and the heart

This article reviews the clinical features of heart disease in the diabetic in three categories: (1) coronary atherosclerosis (CAD), (2) autonomic neuropathy, and (3) cardiomyopathy. Particular attention is given to current methods of noninvasive assessment of cardiac function in juvenile diabetics.

Sustained reduction of proteinuria in type 2 (non-insulin-dependent) diabetes following diet-induced reduction of hyperglycaemia

To determine whether sustained control of hyperglycaemia in Type 2 (non-insulin-dependent) diabetic patients would diminish proteinuria, the effect of hypocaloric diet therapy (500 kcal/day) on proteinuria was assessed in obese, Type 2 diabetic patients (n = 24) and compared with results obtained for obese subjects with normal glucose tolerance (n = 7) and impaired glucose tolerance (n = 6). Diet therapy of similar mean duration resulted in similar percentage weight loss (mean percentage of original weight +/- SEM) in diabetic (13.6 +/- 1.6%), glucose intolerant (16.4 +/- 3.3%) and obese non-diabetic (11.0 +/- 1.0%) subjects. Following therapy, plasma glucose concentrations 2h after an oral glucose load declined in the diabetic (18.34 +/- 0.81 to 10.67 +/- 0.50 mmol/l, mean +/- SEM; p less than 0.001) and in the glucose intolerant subjects (10.2 +/- 0.3 to 7.3 +/- 0.4 mmol/l, p less than 0.01) while remaining unchanged in the obese non-diabetic subjects (7.09 +/- 0.23 to 6.77 +/- 0.32 mmol/l, NS). Concentrations of total protein of plasma origin and albumin in 24-h urine collections were quantified by a sensitive immunonephelometric assay using specific antisera. Initially, 24-h excretion of total protein and albumin were elevated in the diabetic [mg protein/24 h; (median +/- 95% confidence limits): 63 (42-138), p less than 0.05; albumin: 26 (14-56), p less than 0.05] and glucose intolerant subjects [protein: 52 (13-92), NS; albumin: 24 (3-61), NS] compared with the non-diabetic subjects [protein: 20 (5-38); albumin: 6.2 (3.5-9.5)].(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of diabetic control on the width of skeletal-muscle capillary basement membrane in patients with Type I diabetes mellitus

We studied the relation between the control of blood glucose and the width of skeletal-muscle capillary basement membrane in 23 insulin-dependent (Type I) diabetic patients. After initial measurement of levels of glycosylated hemoglobin and width of skeletal-muscle capillary basement membrane, the patients were divided into two groups: an experimental group of 13 patients who were treated with continuous subcutaneous insulin infusion, and a control group of 10 patients who continued to receive conventional treatment--usually two injections of insulin daily. After two years, the experimental group had a significant decrease in glycosylated hemoglobin levels as compared with base-line values (mean +/- S.E.M., 7.6 +/- 0.4 vs 10.2 +/- 0.7 per cent; P less than 0.001), reflecting improved control of blood glucose, and a significant reduction in the width of skeletal-muscle capillary basement membrane (1293 +/- 68 vs. 1717 +/- 182 A; P less than 0.05). The control group of patients had no significant change in their levels of glycosylated hemoglobin or in the width of their skeletal-muscle capillary basement membranes. If changes in the capillaries in skeletal muscle parallel those in the capillaries in retinal or renal tissue, then meticulous control of blood glucose may be beneficial over time in preventing the microvascular complications of diabetes.

Diabetic nephropathy: clinical and histological study in 22 patients

Twenty-two patients with insulin-dependent diabetes mellitus and renal involvement were submitted to renal biopsy. Mean age was 42 years; 10 were males, 12 females. The mean interval between clinical manifestation of nephropathy and biopsy was about 2 years. At the time of biopsy, 4 groups were distinguished according to clinical conditions, depending on the presence or absence of nephrotic syndrome and renal failure. Renal lesions were semiquantitatively evaluated, a separate score being considered for glomerular and vascular lesions. Immunofluorescence most frequently showed a pattern of faint linear IgG deposits along glomerular basement membranes. Severity of histological lesions and pattern of urinary abnormalities were not correlated with the duration of diabetes or the patients' age. Both glomerular and vascular lesions were correlated with the presence of renal failure, while no relationship with the pattern of urinary abnormalities was found. Fourteen patients were followed for more than one year after biopsy: 5 had normal renal function, 4 were in chronic renal insufficiency and 5 in end-stage renal failure (3 were in dialysis, 2 died). There was no correlation between the 3 above-mentioned types of evolution and glomerular histological findings. Nevertheless a higher score of vascular impairment at biopsy was observed among patients who subsequently were found to have a more unfavorable prognosis. Therefore renal biopsy, by providing information on the degree of renal vascular damage, may have some value in predicting the clinical course of diabetic nephropathy.

N-Acetyl-beta-D-glucosaminidase levels and the onset of diabetic microangiopathy

N-Acetyl-beta-D-glucosaminidase (NAG) levels in serum and urine from diabetics have been measured over a three-year period to assess their potential as indicators of the onset of retinopathy and nephropathy. The presence of retinopathy and nephropathy was confirmed by fluorescein angiography performed at the end of the study and by proteinuria, respectively. Three groups of diabetics were investigated, those on insulin, on oral hypoglycaemics, or on diet only. There was no apparent correlation between total NAG activity in serum with the development of retinopathy, nor were serum isoenzyme variations useful in this context. However, urine total NAG activity demonstrated a striking difference between diabetics of all groups and normals. In particular the B isoenzyme doubled in diabetics. The potential use of this finding in relation to prediction of the onset of microangiopathy is discussed.

Structural and functional consequences of increased tubulin glycosylation in diabetes mellitus

The extent of in vitro nonenzymatic glycosylation of purified rat brain tubulin was dependent on time and glucose concentration. Tubulin glycosylation profoundly inhibited GTP-dependent tubulin polymerization. Electron microscopy and NaDodSO4/polyacrylamide gel electrophoresis showed that glycosylated tubulin forms high molecular weight amorphous aggregates that are not disrupted by detergents or reducing agents. The amount of covalently bound NaB3H4-reducible sugars in tubulin recovered from brain of streptozotocin-induced diabetic rats was dramatically increased as compared with tubulin recovered from normal rat brain. Moreover, tubulin recovered from diabetic rat brain exhibited less GTP-induced polymerization than tubulin from nondiabetic controls. The possible implications of these data for diabetic neuropathy are discussed.

Intensive attention improves glycaemic control in insulin-dependent diabetes without further advantage from home blood glucose monitoring: results of a controlled trial

Forty-six diabetics treated with twice-daily insulin were seen every two weeks for six months in an intensive education programme aided by regular home urine glucose testing. Control was improved with a decrease in 24-hour urinary glucose excretion (median 138 mmol/24 h (24.8 g/24 h) falling to 70 mmol/24 h (12.6 g/24 h); p less than 0.002), glycosylated haemoglobin concentration (mean 11.4 +/- SD 2.3% falling to 10.4 +/- 1.5%; p less than 0.001), and Diastix score (median 3.0 falling to 1.3; p less than 0.001). There was no reported increase in hypoglycaemia. Thirty-eight of the diabetics proceeded to a nine-month randomised cross-over study of the effect on blood glucose control of monitoring urinary glucose or blood glucose measured visually or by a reflectance meter using appropriate reagent strips. No further improvement in control was observed after home blood glucose monitoring. Nevertheless, 29 out of 37 patients preferred blood to urine glucose monitoring. During both the education and cross-over studies there was evidence of an initial improvement in control followed by deterioration. This was independent of the monitoring method used in the cross-over period and may have been due to waning enthusiasm. Despite patient enthusiasm and other reports to the contrary, home blood glucose monitoring offered no improvement in control over intensive attention and conventional urine glucose monitoring.

Pathogenesis of rheumatoid arthritis: a vascular hypothesis

Past research into the pathogenesis of RA has generally concerned itself with established inflammation. The present review summarizes alterations in microvascular anatomy and function which occur during the hypoxic state, in various experimental and disease conditions. It further shows that tissue hypoxia is a common finding in RA and that the microvascular alterations of RA are similar to those produced by experimental hypoxia. The available data suggest that microcirculatory compromise, concomitant with an increase in metabolic needs of synovial tissue, may initiate tissue injury via anoxia and acidosis, resulting in hydrolytic enzyme release, increased vascular permeability and acceleration of inflammatory processes. It is further believed that the microcirculatory abnormality may be generalized, accounting for the systemic manifestations often seen in RA. Factors effecting arteriolar blood flow obstruction are reviewed to identify areas for future investigation in RA and other disorders involving microvasculopathy. The multitude of longknown and newly recognized factors predisposing to vasospasm and vasodilatation have been outlined as a guide to possible mechanisms which may be operative in RA. An attempt has been made to gather and synthesize the available data in the hope that it may stimulate other investigators to pursue more definitive research into specific areas which may show early microvascular abnormalities in the pathophysiology of RA. Identification of factors operative early in the pathogenesis of RA, before it becomes self-perpetuating, may well be a step in the direction of preventing the ravages of this disease, or providing insight to more effective control.

Comparison of single- and split-dose insulin regimens with 24-hour monitoring

It has been asserted that twice daily injections of mixed insulin provide better blood glucose control than one. To compare the two regimens we conducted a random-order, double-crossover trial in ten diabetic children. Each regimen lasted for six weeks, concluding with a hospital evaluation. Control at home was assessed by a urine log and determination of glycosylated hemoglobin. Control in the hospital was assessed with measurements of quantitative urinary glucose, serum lipids, and by 24-hour blood sampling for glucose, C-peptide, and counterregulatory hormones. For the group as a whole, none of the indices of control demonstrated a significant advantage for either regimen. Individually, several children did appear to achieve better control on one regimen than the other. Indices of control at home did not consistently predict control in the hospital. In the hospital, the largest increases in glucose concentration followed breakfast (mean rise 148 mg/dl), and standardized exercise invariably reduced plasma glucose values (mean decrement 60 mg/dl). C-Peptide concentrations were low, but higher values were associated with better control. Although a split insulin regimen may improve metabolic control in some patients, this study did not demonstrate a substantial advantage for the majority of subjects over the short period of the trials.

A rise in ambient temperature augments insulin absorption in diabetic patients

The absorption rate of 125I-Actrapid insulin (6 U) from a subcutaneous injection site was examined in six insulin-dependent diabetic patients at ambient temperatures of 20 degrees C and 35 degrees C. During a 4-hr observation period, the insulin disappearance rate at 35 degrees C was 50%-60% greater than at 20 degrees C (p less than 0.01). Despite the small dose of insulin used, plasma glucose levels tended to be 1 to 2 mmole/liter lower at 35 degrees C than at 20 degrees C. These findings indicate that a rise in ambient temperature augments insulin absorption, in insulin-treated diabetic patients.

Future management of diabetes mellitus

A review of therapies for diabetes mellitus reveals little that is new for the diabetic today. Also, there is little evidence that progression of diabetic complications can be slowed or halted with currently available therapeutic modalities that are acceptable to patients and can be applied in an everyday clinical setting. Few new drugs are likely to be ready for marketing in the immediate future, and most of the pharmacologic approaches that are now under study do not address the basic problem of lost sensitivity of the beta cell to endogenous glucose. In the longer term, it is likely that an oral insulin, allowing more convenient management of diabetes, will be available, as well as several new drug classes that may offer therapy adjunctive to insulin. As more is learned of the cellular physiology of the islet cell and the pathology of diabetes mellitus, some additional therapeutic breakthrough may occur. It is highly likely that an implantable or portable infusion system, either of the closed- or open-loop type, will be available when technologic problems are overcome. Islet cell transplantation may provide a definitive treatment for diabetes. At the very least, the questions should be resolved relating to careful physiologic control of the metabolic aberrations of diabetes mellitus. Unfortunately, because of the relatively slow evolution of diabetic vascular pathology, it will be several decades before current studies can provide the answers. If present hypotheses are confirmed, future therapeutic approaches can be more clearly defined; if the hypotheses must be rejected, the therapeutic dilemmas will remain.

Treatment of diabetes mellitus: the future

For more than half a century the management of hyperglycemia in diabetes mellitus has included rigid diets and intermittent subcutaneous insulin administration. These methods have been totally unsuccessful in restoring glucose homeostasis to normal in most diabetic patients. This review focuses on techniques that offer promise as alternatives or adjuncts to the current modalities of treatment. Specific areas discussed include pancreatic transplantation, islet cell transplantation, artificial beta cell devices, and the glucagon-suppressing agent somatostatin. Although many of these show promise for the future, a cure for the metabolic abnormalities of diabetes is not imminent.

The effects of dietary fibre on glucose tolerance in healthy males

Previous studies have shown that the addition of non-absorbable carbohydrate (NAC) to test meals decreases the glucose and and insulin response both in normal and diabetic subjects. However, these studies appear to have used brain in the basic test meal without a knowledge of the effect of bran itself or of the added NAC alone. In the present investigation bran alone, pectin alone, guar alone and pectin with guar have been studied. Guar alone added to the test meal significantly lowered blood glucose at 90 minutes. Pectin alone did not have a significant effect. Pectin and guar together resulted in a blood glucose lower at 30 minutes and greater at 120 minutes. No significant changes in insulin response were noted to our study. It appears that NAC alters the glucose response to a given meal, but the extent to which this occurred in the present study was less than in previous studies. The differences may reflect synergism between bran and other NAC's to lower blood glucose response after a meal.