A comparison of insulin lispro and buffered regular human insulin administered via continuous subcutaneous insulin infusion pump.

This study compared glycemic control achieved with insulin lispro or buffered regular human insulin in patients with Type 1 diabetes treated with continuous subcutaneous insulin infusion (CSII) using an external insulin pump. In this 24-week multicenter, randomized, two-way crossover, open-label trial, 58 patients on CSII with adequate glycemic control received either insulin lispro or buffered regular human insulin for 12 weeks, followed by the alternate treatment for another 12 weeks. Efficacy and safety measures included hemoglobin A(1c) (HbA(1c)) at baseline and endpoint, home blood glucose monitoring, hypoglycemia, and frequency of pump catheter occlusion. Patients consumed a standard test meal on three occasions, with determinations of fasting, 1- and 2-h postprandial glucose values. Insulin lispro use was associated with a significantly lower HbA(1c) than was buffered regular human insulin (7.41+/-0.97 vs. 7.65+/-0.85 mmol/l; P=.004). Fasting serum glucose values before the test meal were similar between the two therapies. The 1-h (11.16+/-4.29 vs. 13.20+/-4.68 mmol/l; P=.012) and 2-h (9.64+/-4.10 vs. 12.53+/-4.64 mmol/l; P=.001) postprandial glucose concentrations were significantly lower during treatment with insulin lispro. No differences between treatments were observed in basal or bolus insulin doses, weight gain, or the incidence and rate of hypoglycemia, hyperglycemia, or pump occlusions. When used in external pumps, insulin lispro provides better glycemic control than buffered regular human insulin with a similar adverse event profile.

Prevalence and significance of retinopathy in subjects with type 1 diabetes of less than 5 years' duration screened for the diabetes control and complications trial.

OBJECTIVE: The Diabetes Control and Complications Trial (DCCT) demonstrated the powerlul impact of glycemic control on the progression of diabetic retinopathy. A large number of individuals (2,771) underwent stereoscopic color photography and fluorescein angiography as part of screening for participation in the DCCT. A subgroup of those individuals screened participated in the DCCT and underwent evaluation of their retinal vasculature semiannually for 4-9 years. These data were evaluated to determine how the 2000 American Diabetes Association position statement would apply to the DCCT experience. Specifically, the position statement indicates that the first dilated eye examination should be performed after 3-5 years' duration of diabetes because vision-threatening retinopathy virtually never develops in patients with type 1 diabetes during that interval RESEARCH DESIGN AND METHODS: We examined the experience of the DCCT in evaluating retinal photographs in 1,613 patients with type 1 diabetes of <5 years' duration and follow-up photographs every 6 months for 4-9 years in 855 members of that group. RESULTS: Of 1,613 subjects with type 1 diabetes of <5 years' duration screened for the DCCT, 716 (44.4%) had stereo-color photographic evidence of diabetic retinopathy, and 6 had preproliferative or worse pathology. Fluorescein angiography revealed retinopathy in 158 of 713 subjects with no evidence of retinopathy on color photographs. Thus, 874 (54.2%) of the original 1,613 subjects had retinopathy at baseline. DCCT follow-up identified 341 additional individuals in whom retinopathy was developing before 5 years; 1,083 of 1,613 (67.1%) individuals screened for the DCCT had retinopathy before 5 years' duration of diabetes. Those with retinopathy before 5 years had more rapid three-step progression of vascular pathology than those with no retinopathy. CONCLUSIONS: Dilated eye examinations and retinal photography should be included in the routine management of type 1 diabetes during the first 5 years to identify the individuals at greatest risk for vision-threatening problems.

Diabetic cardiomyopathy and carnitine deficiency.

This study was designed to study the pathogenesis of cardiomyopathy in animals with longstanding (6 months) diabetes mellitus. Male Wistar rats were made diabetic by the injection of streptozotocin (35 mg/kg) intraperitoneal at 6 months of age. Myocardial contractility was evaluated at 1 year of age by an echocardiogram. Blood was collected at that time to measure blood glucose and hemoglobin A1c as an indicator of metabolic control. Serum carnitine was also measured on the same sample to evaluate the availability of this substance so essential for fatty acid metabolism in the myocardium. Myocardial anatomy was evaluated by both light and electron microscopy after the animals had diabetes for 6 months. It was found that the left ventricular volume was greater at the end of systole and diastole. There was the suggestion of left ventricular fractional shortening and calculated reduced ejection fraction indicating decreased contractility consistent with cardiomyopathy. The hearts had no evidence of coronary vascular occlusion, and the serum cholesterol was normal. Myocardial ultrastructure revealed abnormal-appearing mitochondria consistent with carnitine deficiency. Serum and myocardial carnitine levels in the animals with diabetes and reduced myocardial function were low. Carnitine levels and metabolism could be important in the pathogenesis of diabetic cardiomyopathy.

The effects of acetyl-L-carnitine and sorbinil on peripheral nerve structure, chemistry, and function in experimental diabetes.

Nerve conduction velocity (NCV) increased with age in nondiabetic male Wistar rats for the first 26 weeks of life. The NCV of animals made hyperglycemic at age 6 weeks by administration of streptozotocin (STZ) also increases, but at a slower rate. Animals with 4 weeks of hyperglycemia and reduced NCV treated with an aldose reductase inhibitor (sorbinil) or a short-chain acyl-carnitine (acetyl-L-carnitine [ALC]) daily for 16 weeks showed an improvement in NCV. Morphometric studies of tibial nerves collected from animals after 20 weeks of hyperglycemia (age 26 weeks) showed a consistent reduction in the width of the myelin sheath and little change in axon area. The number of large myelinated fibers (>6.5 microns) found in nerves collected from hyperglycemic animals was less than the number found in nondiabetic animals. Treatment of hyperglycemic rats with either sorbinil or ALC was associated with increased NCV, myelin width, and large myelinated fibers. The apparent metabolic effect of these agents was similar for fatty acid metabolism, but different for polyol pathway activity. We conclude that in animals hyperglycemic long enough to slow NCV, sorbinil and/or ALC treatment reduces the functional, structural, and biochemical changes associated with hyperglycemia that occur in the myelin sheath.

The effect of hyperglycemia on nerve conduction and structure is age dependent.

The nerve conduction velocity (NCV) of nondiabetic male Wistar rats continues to increase until approximately 26 weeks of age. Rats made hyperglycemic at 6 weeks of age manifest reduced NCV by 10 weeks of age and show morphological differences in the sciatic tibial nerve after 5 months of hyperglycemia when compared with age-matched controls. Fiber diameter, myelin width, and the number of large myelinated fibers were decreased in the tibial nerves of the hyperglycemic animals. Rats made hyperglycemic at 26 weeks of age had elevated glycosylated hemoglobin and sciatic nerve sorbitol levels but maintained normal NCVs and had little change in morphology after 7 months of hyperglycemia. Thus, animals with maturing peripheral nerve structure and function exposed to chronic hyperglycemia manifest greater pathological alterations than those that occur when more matured nerves are exposed to similarly elevated glucose concentrations for an even greater duration. We suggest that immature animal models commonly used to study diabetic peripheral neuropathy may not be appropriate for understanding a process that commonly develops in humans who become hyperglycemic after maturation of the peripheral nerves.

Acetyl-L-carnitine corrects the altered peripheral nerve function of experimental diabetes.

Acetyl-L-carnitine (ALC) has been shown to facilitate the repair of transected sciatic nerves. The effect of ALC (50 mg/kg/d) on the diminished nerve conduction velocity (NCV) of rats with streptozotocin (STZ)-induced hyperglycemia of 3 weeks' duration was evaluated. The aldose reductase inhibitor, sorbinil, which is reported to normalize the impaired NCV associated with experimental diabetes, was used as a positive control. Aldose reductase inhibitors are thought to have an effect by decreasing peripheral nerve sorbitol content and increasing nerve myo-inositol. Treatment of STZ-diabetic rats with either ALC or sorbinil resulted in normal NCV. Sorbinil treatment was associated with normalized sciatic nerve sorbitol and myo-inositol; ALC treatment did not reduce the elevated sorbitol levels, but sciatic nerve myo-inositol content was no different from nondiabetic levels. Both ALC and sorbinil treatment of STZ-diabetic rats were associated with a reduction in the elevated malondialdehyde (MDA) content of diabetic sciatic nerve, indicating reduced lipid peroxidation. The beneficial effects of sorbinil and ALC on the altered peripheral nerve function associated with diabetes were similar, but their effects on the polyol pathway (frequently implicated in the pathogenesis of peripheral neuropathy) were different.

Acetyl-L-carnitine corrects electroretinographic deficits in experimental diabetes.

Acetyl-L-carnitine reduces the latencies of electroretinogram oscillatory potentials in healthy humans. The effect of acetyl-L-carnitine (50 mg.kg-1.day-1) on the increased electroretinogram latencies found in rats with STZ-induced hyperglycemia of 3-wk duration was evaluated. The aldose reductase inhibitor sorbinil, which has been shown to normalize abnormal electroretinogram tracings associated with STZ-induced diabetes, was used as a positive control. Aldose reductase inhibitors are thought to lower tissue sorbitol while increasing myo-inositol. The electroretinograms of the STZ-induced diabetic rats in this study were abnormal; treatment with acetyl-L-carnitine as well as sorbinil significantly improved electroretinogram b-wave amplitude and decreased the latencies of oscillatory potentials 2 and 3. Acetyl-L-carnitine treatment of STZ-induced diabetic rats did not affect hyperglycemia or erythrocyte polyol pathway activity as reflected by erythrocyte sorbitol levels. In contrast, sorbinil did reduce elevated erythrocyte sorbitol levels. This suggests that the impaired electroretinograms associated with STZ-induced diabetes may not be caused solely by increased polyol pathway activity.

Growth and sexual maturation in children with insulin-dependent diabetes mellitus.

Prediabetes, the interval preceding the clinical recognition of diabetes mellitus, is believed to consist of several months or years of beta-cell destruction associated with no clinically recognized signs other than possible increased growth velocity. This increased growth rate may be the result of increased insulin, increased growth hormone, or both. As insulin-dependent diabetes approaches clinical recognition, insulin deficiency becomes manifest as slowing of growth velocity and more obvious weight loss. If a prepubertal child has insulin-dependent diabetes mellitus, sexual maturation is frequently delayed and physical growth is adversely affected. Insulin is an anabolic hormone that regulates metabolic pathways involved in the production of protein, glycogen, and fat. The normal release of growth hormone and the hepatic production of insulin-like growth factor I is modulated by the action of insulin. The absence of physiologic insulin response leads to dysfunctional quantities of growth hormone, insulin-like growth factor I, and sex hormones, resulting in growth impairment and delayed sexual maturation. Delayed sexual maturation may cause concern because it has a major impact on growth and maturation of children. However, there is evidence that sex hormones have a stimulating effect on the tissue damage associated with chronic hyperglycemia. The loss of physiologic insulin release significantly affects physical growth, sexual maturation, and the chronic complications associated with insulin-dependent diabetes mellitus.

Taurine prevents galactose-induced cataracts.

Intact lenses from New Zealand white rabbits were incubated in tissue culture media containing either 5 mM glucose or 5 mM glucose plus 30 mM galactose. The standard media did not contain taurine. Lenses were also cultured in a third medium containing 30 mM galactose plus 0.2 mM taurine. The frequency of cataract formation was evaluated as a function of the culture media. One lens (1/10), in media containing 5 mM glucose, developed a lenticular opacification during a 72-h incubation. Lenses (12/15) incubated in 30 mM galactose, without taurine, developed cataracts; fewer lenses (2/13) exposed to 30 mM galactose plus 0.2 mM taurine developed cataracts (p < 0.005). Galactose cataracts have been associated with lens edema attributed to the osmotic stress of tissue polyol (galactitol) accumulation. The water content of the noncataractous and cataractous lenses in this experiment did not differ. Lens edema, therefore, was not thought to be important in cataract pathogenesis. Taurine, an organic osmolyte was lower (5.1 +/- 1.5 mumol/g protein) in cataractous lenses than in control lenses (10.0 +/- 1.0 mumol/g protein). Malondialdehyde, an indicator of lipid peroxidation, was higher (36.6 +/- 5.0 mumol/g protein) in lens-containing opacifications than in noncataractous lenses (10.1 +/- 1.9 mumol/gm protein) (p < 0.01). The levels of malondialdehyde suggest that lipid peroxidation was increased in the process of sugar cataractogenesis. The malondialdehyde content of all the lenses correlated inversely (r = -0.53, p < 0.01) with the coincident lens taurine levels. Taurine appears to protect the lens against the development of sugar cataracts; its inverse relationship with lens malondialdehyde suggests this is an antioxidant effect.

Measurements of tissue sorbitol in diabetes mellitus: enzyme method versus gas-liquid chromatography.

Two methods are commonly used to measure sorbitol in mammalian tissues. The first uses sorbitol dehydrogenase for a coupled enzymatic reaction; unfortunately, other polyols are also substrates for this enzyme. The second uses gas-liquid chromatography (GLC) for separation of polyols and mass quantitation of sorbitol. A comparison of these two methods for the measurement of sorbitol in duplicate samples of lens, nerve, and erythrocytes indicates that GLC of polyol acetates consistently finds less sorbitol than measured by sorbitol dehydrogenase. Erythritol, threitol, ribitol, arabitol, and galactitol are polyols found in variable quantities in these tissues, which have a variable influence on the activity of sorbitol dehydrogenase and therefore alter sorbitol quantitation with this enzyme. Moreover, there is an unidentified substance(s) that reacts with sorbitol dehydrogenase which seems to increase in association with hyperglycemia in the lens and nerve, but not in erythrocytes. The quantity of this unknown substance(s) seems to be reduced by the aldose reductase inhibitor sorbinil in erythrocytes and to a lesser extent sciatic nerve and lens. Since enzymatic sorbitol quantitation in the lens, nerve, and erythrocytes is influenced by many known and unknown factors other than sorbitol, we recommend that GLC of polyol acetates be used to measure sorbitol in biologic tissues.

Altered neuroexcitability in experimental diabetic neuropathy: effect of acetyl-L-carnitine.

Sciatic nerve conduction velocity (NCV) is reduced in rats made hyperglycaemic with streptozotocin (STZ). This neurophysiological dysfunction has been associated with increased nerve sorbitol and reduced nerve inositol. Treatment of STZ diabetic rats with aldose reductase inhibitors (ARIs) which reduce sorbitol and increase inositol in the nerve results in normalization of NCVs. Male Wistar rats were made diabetic with 50 mg/kg of streptozotocin given intraperitoneally. Those animals with blood glucose > 300 mg/dl two weeks later were included in this study. The STZ-diabetic rats were treated with either the ARI sorbinil (40 mg/kg per day), or acetyl-L-carnitine (ALC) (300 mg/kg per day) or sterile 0.15% aqueous NaCl for 16 weeks after 4 or 8 weeks of untreated hyperglycaemia. A control group of non-diabetic rats received no treatment during the interval. Sciatic-nerve sorbitol was elevated (1.08 +/- 0.13 nanomol/mg wet weight vs. 0.19 +/- 0.03 nm/mg wet weight) and inositol was reduced (1.21 +/- 0.12 nm/mg ww vs. 2.02 +/- 0.08 nm/mg ww) in the STZ diabetic rats, which were untreated for 4 weeks. Treatment with sorbinil was associated with normalization of the tissue sorbitol (0.10 +/- 0.05 nm/mg ww), while ALC treatment also significantly reduced the nerve sorbitol but only to a level (0.34 +/- 0.08 nm/mg ww) more elevated than the normal level. The nerves of STZ animals treated with sorbinil or ALC had inositol levels no different from untreated diabetic rats. Thus, hyperglycaemic animals treated with either ALC or sorbinil had similar improvements in NCVs as the diabetic, even though the effect on nerve sorbitol was different and nerve inositol was unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Continuous infusion of insulin in hyperglycemic low-birth weight infants receiving parenteral nutrition with and without lipid emulsion.

The efficiency of a continuous infusion of insulin in improving glucose tolerance was compared in two groups of very low-birth weight infants (mean +/- SEM birth weights 757 +/- 40 vs 828 +/- 80 g and gestational ages 27.6 +/- 0.7 vs. 27.2 +/- 0.5 weeks) receiving total parenteral nutrition with and without the addition of lipid emulsion to the nutrition regimen. The mean +/- SEM cumulative doses of insulin (0.87 +/- 0.1 vs 1.15 +/- 0.3 U/kg) and hours required to decrease the blood glucose level to 120 mg/dL (9.1 +/- 0.8 vs 9.5 +/- 1.0 hours) were similar. Insulin was delivered with a syringe pump used for other routine purposes in the neonatal intensive care unit. Continuous intravenous insulin infusion is an effective, inexpensive, safe method for maintaining glucose homeostasis in low-birth weight infants who develop hyperglycemia as a consequence of total parenteral nutrition.

Insulin resistance and hyperinsulinemia induce hyperandrogenism in a young type B insulin-resistant female.

An adolescent female with type B insulin resistance and hyperandrogenemia is described. Evidence presented suggests that hyperinsulinemia leads to an increase in serum total and free testosterone. Support for this hypothesis is noted during an in vivo experiment in which large doses of regular insulin (305 U/kg-day) were infused iv, and multiple serum total testosterone measurements obtained. After 35 days of iv insulin therapy, the serum total testosterone values rose from 4.9 nmol/L (142 ng/dL) to 22.8 nmol/L (660 ng/dL), and the ovarian volume increased 2-fold. Basal (9.8 nmol/L; 282 ng/dL) and stimulated (16.8 nmol/L; 481 ng/dL) androstenedione measurements were elevated, and the dehydroepiandrosterone/androstenedione ratio was low, suggesting increased 3 beta-hydroxysteroid dehydrogenase activity. After resolution of the insulin-resistant state and the concomitant hyperinsulinemia, the serum total testosterone values returned to normal. This case illustrates that long term hyperinsulinemia leads to elevation of serum total testosterone.

Florida newborn screening for galactosemia.

Galactosemia, an inborn error of metabolism characterized by the inability to transform galactose-1-phosphate into glucose-1-phosphate, occurs in 1:50,000 live births. If not diagnosed and treated within the newborn period, it can lead to severe morbidity and mortality within a few weeks of life. All children in Florida are screened for this disorder by a fluorescence assay system to measure galactose-1-phosphate uridyltransferase (GALT) activity in a dried blood spot. Genetic factors and external forces can affect the activity of the GALT enzyme and lead to confusing results. Parents of infants heterozygous for galactosemia should be offered the opportunity for carrier detection. If both are carriers, genetic counseling should be provided.