Enantioselective carbenoid insertion into C(sp(3))-H bonds

The enantioselective carbenoid insertion into C(sp(3))-H bonds is an important tool for the synthesis of complex molecules due to the high control of enantioselectivity in the formation of stereogenic centers. This paper presents a brief review of the early issues, related mechanistic studies and recent applications on this chemistry area.

New advances in insulin treatment of diabetes: overcoming barriers

OBJECTIVE

To discuss the optimal role of insulin in the treatment of patients with diabetes mellitus.

METHODS

We review the complications of diabetes, highlight the attempts to improve control of plasma glucose, and summarize current recommendations for use of insulin in clinical practice.

RESULTS

With the strict new guidelines for the diagnosis of diabetes issued by the American Diabetes Association in July 1997--a plasma glucose level of 126 mg/dL (7 mmol/L) rather than 140 mg/dL (7.8 mmol/L)--an additional 8 million persons will be diagnosed this year, and diabetes and its complications will be at the forefront of public health concerns. Strong evidence indicates that with reduction of plasma glucose levels and tight control of glycohemoglobin, the rate of complications can be considerably decreased. Although insulin replacement therapy is well known to be both the best and the most cost-effective way to control glucose levels in patients with type 1 diabetes, studies have no shown that those with type 2 diabetes can likewise benefit from appropriate insulin therapy. Other investigations have indicated that coronary events are as likely to occur in patients with recently discovered impaired glucose tolerance as in patients with known diabetes (at a 2-hour postprandial glucose threshold of 96 mg/dL [5.3 mmol/L]). Such finding suggest that there may be no such thing as "borderline diabetes" and give impetus to the search for improved types of insulin to treat all patients with diabetes. A recent candidate is the new insulin analogue lispro, which was developed by recombinant DNA techniques, with its design influenced by the structural analogy to another endogenous hormone, insulin-like growth factor I. Lispro is a fast-acting, rapidly dissipating insulin formulation. This profile allows lispro to be given less than 15 minutes before a meal, yet with little risk of postprandial hypoglycemia because its high mealtime peak is followed by rapid disappearance from the bloodstream.

CONCLUSION

Lispro has been shown to improve postprandial control of plasma glucose and to decrease the occurrence of hypoglycemia episodes in comparison with regular insulin. Because of its stability and pharmacokinetic properties, lispro can also be used in insulin pump therapy.

Leptin concentrations in Prader-Willi syndrome before and after growth hormone replacement

OBJECTIVE

This study explored leptin concentrations in Prader-Willi syndrome (PWS), a genetic disorder characterized by significant obesity and presumed hypothalamic dysfunction. The potential interaction of leptin metabolism with the growth hormone (GH) axis was also studied.

STUDY DESIGN

Plasma leptin concentrations and percent body fat were determined by radioimmunoassay and dual energy x-ray absorptionmetry, respectively, in 23 children with Prader-Willi syndrome and 23 children with exogenous obesity.

RESULTS

Log plasma leptin concentrations were positively correlated with percentage body fat in PWS (r = 0.844) and exogenous obesity (r = 0.869). When the regression lines for the two groups were compared, there were no differences in their slopes (P = 0.737) or intercepts (P = 0.701). Administration of recombinant human growth hormone to PWS children for 12 months significantly reduced both percentage body fat and plasma leptin concentrations, but the relationship of log plasma leptin to percentage body fat was unchanged.

CONCLUSION

Prader-Willi syndrome is not accompanied by deranged leptin concentrations and there was no evidence of an interaction of the GH axis with leptin metabolism in these GH-deficient children.

Robustness of protein folding kinetics to surface hydrophobic substitutions

We use both combinatorial and site-directed mutagenesis to explore the consequences of surface hydrophobic substitutions for the folding of two small single domain proteins, the src SH3 domain, and the IgG binding domain of Peptostreptococcal protein L. We find that in almost every case, destabilizing surface hydrophobic substitutions have much larger effects on the rate of unfolding than on the rate of folding, suggesting that nonnative hydrophobic interactions do not significantly interfere with the rate of core assembly.

Experiment and theory highlight role of native state topology in SH3 folding

We use a combination of experiments, computer simulations and simple model calculations to characterize, first, the folding transition state ensemble of the src SH3 domain, and second, the features of the protein that determine its folding mechanism. Kinetic analysis of mutations at 52 of the 57 residues in the src SH3 domain revealed that the transition state ensemble is even more polarized than suspected earlier: no single alanine substitution in the N-terminal 15 residues or the C-terminal 9 residues has more than a two-fold effect on the folding rate, while such substitutions at 15 sites in the central three-stranded beta-sheet cause significant decreases in the folding rate. Molecular dynamics (MD) unfolding simulations and ab initio folding simulations on the src SH3 domain exhibit a hierarchy of folding similar to that observed in the experiments. The similarity in folding mechanism of different SH3 domains and the similar hierarchy of structure formation observed in the experiments and the simulations can be largely accounted for by a simple native state topology-based model of protein folding energy landscapes.

Important role of hydrogen bonds in the structurally polarized transition state for folding of the src SH3 domain

Experimental and theoretical studies on the folding of small proteins such as the chymotrypsin inhibitor 2 (CI-2) and the P22 Arc repressor suggest that the folding transition state is an expanded version of the native state with most interactions partially formed. Here we report that this picture does not hold generally: a hydrogen bond network involving two beta-turns and an adjacent hydrophobic cluster appear to be formed in the folding transition state of the src SH3 domain, while the remainder of the polypeptide chain is largely unstructured. Comparison with data on other small proteins suggests that this structural polarization is a consequence of the topology of the SH3 domain fold. The non-uniform distribution of structure in the folding transition state provides a challenging test for computational models of the folding process.

Development of proliferative diabetic retinopathy in African-Americans and whites with type 1 diabetes

OBJECTIVE

To investigate the comparable risk of developing proliferative diabetic retinopathy (PDR) in African-Americans and whites with type 1 diabetes.

RESEARCH DESIGN AND METHODS

Using a cohort design with the sample drawn from medical records, the sample consisted of 312 people with type 1 diabetes (97 African-Americans, 215 whites) having at least two visits to a Model Demonstration Unit with gradeable fundus photographs (stereo, color, 7 standard fields). Excluded were subjects with preexisting or treated PDR or hemoglobinopathy. Masked grading of the fundus photographs was conducted at the Wisconsin Reading Center.

RESULTS

At baseline, African-Americans had poorer glycemic control (mean HbA1 of 11.3 vs. 10.0%, P < 0.0001), higher systolic blood pressure (mean of 117 vs. 110 mmHg, P < 0.001), and were older (mean of 26.8 vs. 19.3 years, P < 0.0001) than the white subjects. African-Americans also tended to have slightly longer duration of diabetes and length of follow-up. In the African-Americans, 17.5% developed PDR, compared with 10.2% in the 215 whites, for an odds ratio (OR) of 1.86 (95% CI 0.93-3.70). When adjusted for baseline glycemic control, retinopathy grade, and length of follow-up, race was not a significant risk factor (OR = 0.73, 95% CI 0.30-1.78).

CONCLUSIONS

African-Americans with type 1 diabetes may have a higher rate of developing PDR. The observed racial difference, however, is attributable to the presence of a worse risk factor profile, especially to poorer glycemic control. Efforts should be expanded to improve the care for all individuals with poor glycemic control.

Disparity in glycemic control and adherence between African-American and Caucasian youths with diabetes. Family and community contexts

OBJECTIVE

To describe sociodemographic, family, and community factors that contribute to the glycemic control of African-American and Caucasian youths with diabetes, we investigated two questions: 1) Is there a disparity in glycemic control between African-American and Caucasian youths with diabetes, and if so, what sociodemographic, family, and community factors explain the disparity? and 2) Is there a difference in the adherence to treatment between African-American and Caucasian youths with diabetes, and if so, what sociodemographic, family, and community factors explain the difference?

RESEARCH DESIGN AND METHODS

This cross-sectional study included 146 youths with diabetes (95 Caucasians and 51 African-Americans) and their mothers. The youths were invited to participate if they had been diagnosed with diabetes at least 1 year before the study, did not have another chronic illness, and were < 18 years of age.

RESULTS

The findings indicate that African-American youths with diabetes are in significantly poorer metabolic control than their Caucasian counterparts (1.5% difference in HbA1c levels). Single-parent household status and lower levels of adherence partially account for the poorer glycemic control. Examination of the adherence subscales indicates that African-Americans report significantly lower adherence to diet and glucose testing than Caucasian youths.

CONCLUSIONS

This study suggests that African-American youths with diabetes may be at greater risk for poor glycemic control due to the higher prevalence of single parenting and lower levels of adherence found in this population.

Functional rapidly folding proteins from simplified amino acid sequences

Early protein synthesis is thought to have involved a reduced amino acid alphabet. What is the minimum number of amino acids that would have been needed to encode complex protein folds similar to those found in nature today? Here we show that a small beta-sheet protein, the SH3 domain, can be largely encoded by a five letter amino acid alphabet but not by a three letter alphabet. Furthermore, despite the dramatic changes in sequence, the folding rates of the reduced alphabet proteins are very close to that of the naturally occurring SH3 domain. This finding suggests that despite the vast size of the search space, the rapid folding of biological sequences to their native states is not the result of extensive evolutionary optimization. Instead, the results support the idea that the interactions which stabilize the native state induce a funnel shape to the free energy landscape sufficient to guide the folding polypeptide chain to the proper structure.

Pathophysiology of type 2 diabetes and modes of action of therapeutic interventions

At least 90% of the 12 to 15 million persons with diabetes mellitus in the United States, half of whose condition remains undiagnosed, have type 2 diabetes. Type 2 diabetes is preceded by a long period of impaired glucose tolerance, a reversible metabolic state associated with increased prevalence of macrovascular complications. Thus, at the time of diagnosis, long-term complications have developed in almost one fourth of patients. Susceptibility to type 2 diabetes requires genetic (most likely polygenic) and acquired factors, and its pathogenesis involves an interplay of progressive insulin resistance and beta-cell failure. The ideal treatment of type 2 diabetes should reverse insulin resistance and beta-cell dysfunction in most treated patients and prevent, delay, or reverse long-term complications. Current strategies are aimed at amelioration of insulin resistance (diet, exercise, weight loss, and metformin and troglitazone therapy), augmentation of insulin supply (sulfonylurea and insulin therapy), or limitation of postprandial hyperglycemia (acarbose therapy). Future therapies probably will target (1) insulin resistance, using a multifaceted approach; (2) hepatic glucose production, using gluconeogenesis inhibitors; (3) excess nonesterified fatty acid production, using lipolysis inhibitors; and (4) fat oxidation, using carnitine palmitoyltransferase I and II inhibitors. Attempts also could be made to stimulate energy expenditure and increase nonoxidative glucose disposal by means of beta 3-adrenoceptor agonists. One promising strategy is an attack on multiple pathophysiological processes by combining antidiabetic agents with disparate mechanisms of action. Thus, we now have unprecedented resources for drug therapy for diabetes, with great opportunity for innovative combinations. It is hoped that these expanded choices will provide the tools necessary for a more efficient management of type 2 diabetes and prevention of its long-term complications.

Mothers' satisfaction with medical care: perceptions of racism, family stress, and medical outcomes in children with diabetes

Patient satisfaction is an important indicator of medical outcomes. This study used an ecological framework to identify sociodemographic, family, and community predictors of mothers' satisfaction with their children's medical care and to determine the extent to which satisfaction is associated with medical outcomes such as adherence to treatment and health status of children with diabetes. Although individual demographics have little influence on satisfaction, family and community stressors are significant predictors of mothers' satisfaction with medical care. Mothers who reported greater perceptions of racism and family stress were significantly less satisfied with their children's medical care than those from less stressful environments. Mothers' satisfaction with medical care was significantly associated with adherence but was not significantly related to the children's health status.

Research on social support in adolescents with IDDM: a critical review

This article provides a review of the findings of 32 scientific studies that examined the relationship between social support and adherence/metabolic control in adolescents with insulin-dependent diabetes mellitus. Social support included qualitative family support characteristics, communication patterns, sibling and peer relationships, and regimen-specific support behaviors. The literature was examined in the context of adolescent development. Although the results of these studies were somewhat inconsistent, some general patterns emerged that are described and discussed in detail. Methodological limitations and suggestions for future research are provided.

Serum leptin concentrations in human immunodeficiency virus-infected men with low adiposity

The product of the obese gene (ob) is the protein leptin, which is synthesized in and secreted from adipocytes. Fasting serum leptin concentrations are closely related to body fat content and are higher in obese than in normal-weight individuals. Leptin may contribute to body weight regulation. Overproduction of leptin in certain pathologic conditions such as acquired immunodeficiency syndrome (AIDS) might in principle contribute to the low body fat content associated with body wasting. We measured fasting serum leptin levels by radioimmunoassay in individuals infected with the human immunodeficiency virus (HIV) and in a group of healthy lean men to determine whether HIV infection increases leptin levels. Thirteen HIV-infected men aged 26 to 50 years with a body mass index (BMI) of 15 to 26 kg/m2 and 4 to 24 kg body fat (7% to 29% body fat) had serum leptin levels (3.4 +/- 1.6 ng/mL) that were not elevated compared with the levels in 17 healthy men (4.0 +/- 1.4 ng/mL) matched for age (23 to 47 years), BMI (18 to 26 kg/m2), and body fat (5 to 21 kg; 9% to 28%). In both groups of men, serum leptin concentrations were correlated with percent body fat and body fat content (P < .001), and these relationships were not different between the two groups. In both groups, leptin concentrations were not correlated with lean body mass (P > or = .24). Energy intake in the HIV-infected men, assessed from 3-day intake records, was within the normal range. These findings extend the hypothesis that circulating leptin concentrations directly reflect adipose tissue mass, even in HIV-infected men with low body fat content. These findings do not support the hypothesis that HIV infection is associated with high circulating leptin concentrations, and suggest that low leptin levels do not stimulate food intake in HIV-infected individuals.

Increased plasma leptin concentration in end-stage renal disease

Leptin is a 16-kDa protein recently identified as the obese gene product involved in body weight regulation. Administration of recombinant leptin to ob/ob mice, which have a genetic defect in leptin production, reduces food intake and increases energy expenditure. Leptin is synthesized by fat cells, and in normal humans, plasma concentrations are proportional to adiposity. The physiological actions and the degradation pathways of leptin in humans are unknown. We investigated renal elimination of leptin by comparing plasma leptin concentrations in end-stage renal disease (ESRD) patients with normal controls. Our hypothesis was that if renal filtration is a significant route of elimination, the hormone would accumulate in ESRD patients. Mean plasma levels in 141 ESRD patients (26.8 +/- 5.7 and 38.3 +/- 5.6 micrograms/L for males and females, respectively) were significantly higher (P < 0.001) than mean values obtained in normal controls (11.9 +/- 3.1 and 21.2 +/- 3.0 micrograms/L for males and females, respectively). Leptin concentrations in ESRD patients correlated directly with body mass index (BMI; r = 0.77 for men and 0.78 for women). The rate of increase in leptin concentrations with BMI was significantly greater in ESRD patients (5.5 and 6.6 micrograms/L/U BMI for men and women, respectively) than in normal controls (1.4 and 2.6 micrograms/L/U for men and women, respectively). Pre- and postdialysis leptin levels in hemodialysis patients were similar. Western blot of plasma from ESRD patients with high leptin levels showed bands corresponding to the intact protein (16 kDa) with no lesser or greater molecular mass species observed. Leptin concentrations in patients with ESRD did not correlate with measures of residual renal function (serum creatinine, beta 2-microglobulin, PTH, or GH levels). Similarly, we found no correlation between leptin levels and the number of years patients had been on dialysis or with recent weight changes. We conclude that intact leptin is increased in ESRD patients, but does not appear to cause decreased weight. As leptin levels did not correlate with residual renal function, increased production may account for the high levels observed.

Radioimmunoassay of leptin in human plasma

Recent studies suggest that leptin, the ob gene product absent in ob/ob mice, is a negative regulator of adiposity. We developed an RIA to measure human leptin in plasma or serum. The minimum detectable concentration by the assay is 0.5 microg/L leptin and the limit of linearity is 100 microg/L. Recovery of leptin added to serum was 99-104% over by the linear range of the assay. The RIA agreed reasonably well with rough quantification by Western blot (RIA = 0.90 blot + 3.7 microg/L, Sy/x = 10.9 microg/L). CVs within- and between-run ranged from 3.4% to 8.3% and from 3.6% to 6.2%, respectively. Variation in plasma leptin concentrations in specimens collected on consecutive mornings was large (CVs of 10.9% and 22.5%). After an overnight fast, leptin concentrations were similar to those 1-2 h after 1-2 meals. Plasma leptin concentrations in specimens from 83 lean and obese adults correlated directly with body mass index (BMI; kg/m2): r = 0.72, P <0.001. Correlations were significantly improved by separating results by gender (men r = 0.84, women r = 0.87; p <0.001). The increase in leptin concentrations with increasing BMI was greater in women than in men (slope 2.53 vs 0.97 microg/L per unit BMI, respectively). Leptin concentrations determined in lean subjects (BMI between 18 and 25) were higher in women (7.36 +/- 3.73 microg/L) than in men (3.84 +/- 1.79 microg/L) (P <0.001). Plasma leptin varied little with age and no significant difference was observed between whites and blacks. We conclude that: (a) plasma leptin concentrations are accurately and precisely measured by this new RIA; (b) leptin concentrations vary little due to short-term fasting, age, or race; but (c) plasma leptin concentrations are gender specific.

Radioimmunoassay of leptin in human plasma

Recent studies suggest that leptin, the ob gene product absent in ob/ob mice, is a negative regulator of adiposity. We developed an RIA to measure human leptin in plasma or serum. The minimum detectable concentration by the assay is 0.5 microg/L leptin and the limit of linearity is 100 microg/L. Recovery of leptin added to serum was 99-104% over by the linear range of the assay. The RIA agreed reasonably well with rough quantification by Western blot (RIA = 0.90 blot + 3.7 microg/L, Sy/x = 10.9 microg/L). CVs within- and between-run ranged from 3.4% to 8.3% and from 3.6% to 6.2%, respectively. Variation in plasma leptin concentrations in specimens collected on consecutive mornings was large (CVs of 10.9% and 22.5%). After an overnight fast, leptin concentrations were similar to those 1-2 h after 1-2 meals. Plasma leptin concentrations in specimens from 83 lean and obese adults correlated directly with body mass index (BMI; kg/m2): r = 0.72, P &lt;0.001. Correlations were significantly improved by separating results by gender (men r = 0.84, women r = 0.87; p &lt;0.001). The increase in leptin concentrations with increasing BMI was greater in women than in men (slope 2.53 vs 0.97 microg/L per unit BMI, respectively). Leptin concentrations determined in lean subjects (BMI between 18 and 25) were higher in women (7.36 +/- 3.73 microg/L) than in men (3.84 +/- 1.79 microg/L) (P &lt;0.001). Plasma leptin varied little with age and no significant difference was observed between whites and blacks. We conclude that: (a) plasma leptin concentrations are accurately and precisely measured by this new RIA; (b) leptin concentrations vary little due to short-term fasting, age, or race; but (c) plasma leptin concentrations are gender specific.

Major decrements in glycated hemoglobin levels between 1978 and 1989 in patients with insulin-dependent diabetes mellitus

The Diabetes Control and Complications Trial has shown that intensive treatment can deter the development and progression of diabetic complications. Integral to intensive treatment is improved glycemic control. To describe the trend in glycemic control for subjects with insulin-dependent diabetes mellitus, we examined the medical records of 662 subjects seen between 1978 and 1989 at the Model Demonstration Unit of the Diabetes Research and Training Center (Washington University School of Medicine). Mean value of glycated hemoglobin showed steady decline from a peak of 11.5% in 1979 to 9.0% in 1989. This decline was observed both in subjects evaluated only once (annual rate of decline estimated from linear regression, -0.17 +/1 0.03; p = 0.0001) and in subjects evaluated more than once (annual rate of decline estimated from growth curves, -0.18 +/- 0.06; p = 0.0001). These results suggest that substantial lowering of glycated hemoglobin has occurred during the last decade. This reduction should result in a lowered risk of diabetic complications.

I get by with a little help from my family and friends: adolescents' support for diabetes care

Evaluated and compared the support provided by family members and friends for adolescents' diabetes care. Family and friend support also were examined in relation to other measures of social support, to demographic variables (age, gender, duration of diabetes) and to adherence. Using a structured interview, 74 adolescents with diabetes described the ways that family members and friends provided support for diabetes management (insulin shots, blood glucose monitoring, eating proper meals, exercise), and for helping them to "feel good about their diabetes." Families provided more support than friends for three management tasks (insulin injections, blood glucose monitoring, meals); this support was largely instrumental. In contrast, friends provided more emotional support for diabetes than families. Greater family support was related to younger age, shorter disease duration, and better treatment adherence. Implications of the findings include encouraging parents to remain involved in adolescents' treatment management, and involving peers as supportive companions for meals and exercise.

Retinopathy in African Americans and whites with insulin-dependent diabetes mellitus

BACKGROUND

The development and progression of diabetic retinopathy in African Americans with insulin-dependent diabetes mellitus is not known.

METHODS

Two hundred subjects with insulin-dependent diabetes mellitus with duration of diabetes 16 years or less at first visit were studied; 58 were African Americans and 142 were whites. All had gradable stereoscopic color fundus photographs (seven standard fields) from at least two visits (mean time between first and second visit was 4.1 years). Subjects with hemoglobinopathy or proliferative retinopathy or subjects who had evidence of treatment for proliferative retinopathy at first visit were excluded. Masked grading of photographs was conducted using the modified Airlie House classification scheme.

RESULTS

African Americans were older, heavier, had higher systolic blood pressure (all P < .05), and marginally higher hemoglobin A1 (HbA1) values (P = .06) than the whites at first visit. African Americans had a lower rate of two steps or more progression from preexistent retinopathy (19%) than whites (43%). Progression to proliferative retinopathy or treatment was similar by race. Multivariate analysis predicting development oe progression of retinopathy, while controlling for length of follow-up, found higher HbA1 (odds ratio [OR] = 2.15), longer duration of insulin-dependent diabetes mellitus (OR = 1.69), higher serum creatinine concentration (OR = 1.59), and white race (OR = 2.62) to be independent risk factors.

CONCLUSIONS

These data suggest a previously unsuspected reduction in the adjusted risk for development and progression of retinopathy in African Americans. The reason for this apparently reduced risk are not known.

The relationship between eating patterns and metabolic control in patients with non-insulin-dependent diabetes mellitus (NIDDM)

The most important element in the therapeutic plan of patients with non-insulin-dependent diabetes mellitus (NIDDM) is dietary modification. Dietary instructions target patient behaviors in two areas: following an exchange-based diet and adhering to the same basic eating pattern every day. However, there is little empirical data that addresses the relationship between dietary instruction and metabolic control. Fifty patients with NIDDM were enrolled in an 8-week study to ascertain if either dietary approach was more predictive of improved metabolic control. The effect on metabolic control was determined by changes in HbA1c over a 2- to 3-month period. Patients added or deleted almost half of all prescribed exchanges, and added or deleted an average of one prescribed meal or snack per day. Deviations in prescribed eating patterns, particularly breakfast-skipping and snack additions and deletions, were related to poorer metabolic control. Maintaining consistent eating patterns should be further evaluated as an important component of dietary instruction for patients with NIDDM.

Potential autoantigens in IDDM. Expression of carboxypeptidase-H and insulin but not glutamate decarboxylase on the beta-cell surface

Insulin, carboxypeptidase-H (CP-H), and glutamate decarboxylase (GAD) have been identified as potential autoantigens in insulin-dependent diabetes mellitus (IDDM). Previous studies have described immunoreactive insulin as a surface molecule on the plasma membrane of rat islet cells and suggested that cell-surface insulin was derived during exocytosis by the fusion of insulin secretory granules with the beta-cell plasma membrane. These findings predict that insulin and other secretory granule-derived proteins such as the putative autoantigen CP-H may be colocalized with insulin at specific sites of exocytosis on the beta-cell surface. In studies to test this hypothesis, cell-surface staining of dispersed rat islet cells occurred in a granule-like pattern with antibodies for CP-H and insulin. The specificity of the CP-H antiserum was confirmed by immunoblotting and indicated that the antiserum was essentially monospecific for CP-H. Confocal laser microscopy confirmed that immunoreactive staining for CP-H and insulin was confined to the beta-cell surface. Colocalization of CP-H and insulin on the cell surface of beta-cells was demonstrated by double staining with antibodies to CP-H and insulin, and the percentage of beta-cells positive for both of these autoantigens increased twofold with increases in insulin secretion. In contrast, islet cells failed to reveal cell-surface staining for GAD65, another putative autoantigen in IDDM, under either basal or insulin stimulatory conditions or following exposure of islet cells to the cytokines interleukin-1 beta, tumor necrosis factor-alpha, and recombinant human interferon-gamma.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of the carbohydrase inhibitor miglitol in sulfonylurea-treated NIDDM patients

OBJECTIVE

To examine the effects of the carbohydrase inhibitor miglitol (BAY m 1099) on the metabolic profiles of non-insulin-dependent diabetes mellitus (NIDDM) patients suboptimally controlled on maximal daily doses of sulfonylurea (SFU) agents.

RESEARCH DESIGN AND METHODS

Multicenter, double-blind, randomized, placebo-controlled 14-week clinical trial with six-week, single-blind placebo lead-in and run-out periods. NIDDM volunteers (192) with fasting plasma glucose (FPG) 140-250 mg/dl and hemoglobin A1c (HbA1c) 6.5-12.0% after at least 4 weeks of treatment with SFU at maximal dose were stratified by baseline HbA1c (above and below 9.0%) and then randomly assigned within strata to placebo (n = 63), 50 mg miglitol 3 times a day (n = 61), or 100 mg miglitol 3 times a day (n = 68). Efficacy was assessed by HbA1c, FPG, insulin, and lipid concentrations, and by plasma glucose and serum insulin responses to a standard meal.

RESULTS

In the 50 and 100 mg miglitol treatment groups, the mean changes from baseline in HbA1c (with placebo values subtracted) were 0.82 and 0.74%, respectively, and were highly significant (P = 0.0001 in each case). Mean peak plasma glucose levels after a standard test meal were comparably lowered by 57 mg/dl with the 50 mg miglitol dose, and by 64 mg/dl with the 100 mg miglitol dose compared with placebo (P = 0.0001 for each), with associated reductions in integrated serum insulin response (P < 0.05). No significant drug-associated changes in FPG, insulin, or cholesterol levels were noted, but fasting triglyceride levels were lowered significantly with the 50 mg miglitol dose. Miglitol's side effects were limited to flatulence, loose stools, and abdominal discomfort, which were dose-related, rapidly resolved on drug discontinuation, and led to withdrawal from the study of 5 and 15% of patients taking 50 and 100 mg miglitol, respectively.

CONCLUSIONS

Miglitol may be indicated as effective adjuvant therapy in NIDDM patients with suboptimal metabolic control despite conventional treatment with diet and maximal daily doses of SFU. The dose of 50 mg miglitol 3 times a day may be preferable to 100 mg miglitol 3 times a day because of comparable efficacy and substantially reduced side effects.

D-chiro-inositol metabolism in diabetes mellitus

D-chiro-inositol is a rare inositol isomer present in inositol phosphoglycans which are proposed mediators of insulin action. To study D-chiro-inositol metabolism in diabetes mellitus, a sensitive and specific assay was developed using negative-ion chemical ionization gas chromatography/mass spectrometry. Median urinary D-chiro-inositol excretion, which was 2.1 mumol/day in nondiabetics, was substantially increased to 12 mumol/day in non-insulin-dependent diabetes (P < 0.0001) and to 74 mumol/day in insulin-dependent diabetes (P < 0.0001). Urinary D-chiro-inositol was strongly correlated with fasting plasma glucose (r = 0.568, P < 0.0001), glycated hemoglobin (r = 0.529, P < 0.0001), and urinary glucose (r = 0.368, P = 0.01). The renal clearance of D-chiro-inositol was selectively elevated in both non-insulin-dependent and insulin-dependent diabetes when compared with the clearances of L-chiro-inositol or myo-inositol and exceeded the glomerular filtration rate in 71% of the diabetics but in none of the nondiabetics. In poorly controlled diabetic patients insulin treatment reduced urinary D-chiro-inositol losses by 63% and increased plasma levels by 8.8-fold. The metabolism of D-chiro-inositol is abnormal in diabetes and appears to be influenced by short- and long-term metabolic control.

The relationship among six psychosocial domains, age, health care adherence, and metabolic control in adolescents with IDDM

This pilot study examined the relationship among six psychosocial factors, age, health care compliance, and metabolic control in adolescents with IDDM. Four objectives were identified: 1) to determine whether specific compliance areas predict metabolic control; 2) to determine whether specific psychosocial factors predict metabolic control; 3) to determine whether compliance and psychosocial issues change with age; and 4) to determine whether the parent or the youth is the more accurate predictor of metabolic control. Twenty-one adolescents age 13 through 18 years participated in this study. Dietary compliance was found to be the best predictor of metabolic control. Parents more accurately predicted metabolic control for youths younger than 16 years old, while the reverse was true for older youths. A negative relationship was identified among strong self-concept, high knowledge of IDDM, parental support, and poor metabolic control. Several possible explanations are discussed, including power struggles, coping difficulties, and fear of peer reactions.

Withdrawal of the aldose reductase inhibitor tolrestat in patients with diabetic neuropathy: effect on nerve function. The Tolrestat Study Group

A double-blind, placebo-controlled clinical trial was conducted to study the effects of discontinuing tolrestat, an aldose reductase inhibitor, on peripheral sensorimotor diabetic neuropathy. After an average of 4.2 years of continuous tolrestat use, 372 patients were randomly assigned to either placebo or continued tolrestat therapy and were followed for 52 weeks. After 3 months, patients who perceived worsening of symptoms of neuropathy were allowed to switch once to the alternate treatment group while maintaining the double-blind. Patients assigned to placebo had significant deterioration in motor nerve conduction velocity (MNCV) while those maintained on tolrestat did not (p < 0.05). The 28 patients who were randomly assigned to tolrestat and elected to switch to placebo had a significant deterioration in MNCV while the 36 assigned to placebo who switched to tolrestat had a significant improvement (p < 0.05). Treatment differences in favor of tolrestat were observed for sensation in the toes as well as for pain (p < 0.05). These data indicate that withdrawal from long-term treatment with tolrestat has a detrimental effect on several measures of diabetic neuropathy, whereas continuation of treatment is associated with stabilization of these measures, suggesting a continued role for polyol pathway activity in late neuropathy.

Family stress and resources: potential areas of intervention in children recently diagnosed with diabetes

This article examines the relationships among family stress, family capabilities, and the health status of 53 children diagnosed with insulin-dependent diabetes mellitus. Assessments were done at an outpatient diabetes clinic of family coping, resources, and stress; disease-related knowledge; metabolic control (HbA1); and endogenous insulin (C peptide). Results indicated that higher levels of family stress and lower levels of family resources as reported by fathers were significantly associated with poor metabolic control. Multiple regression analyses revealed that levels of family stress and resources were more strongly related to metabolic control than were disease variables such as C peptide levels. Moreover, family stress was directly associated with metabolic control, and family resources showed indirect linkages. Findings suggest that family stress and resources are potential areas for social work intervention in children recently diagnosed with diabetes.

Abnormal myocardial acoustic properties in diabetic patients and their correlation with the severity of disease

Although patients with diabetes mellitus may be afflicted by cardiomyopathy, its prevalence and nature are controversial. Studies have shown that fibrosis alters the acoustic properties of the heart in animals and humans and that the changes are detectable by cardiac tissue characterization with ultrasound. The present study was performed to characterize myocardial acoustic properties in patients with insulin-dependent diabetes to determine whether ultrasound tissue characterization could detect changes potentially indicative of occult cardiomyopathy. The magnitude of cyclic variation of myocardial ultrasound integrated backscatter and its phase delay with respect to the onset of the cardiac cycle in the septum and posterior wall of the left ventricle were measured in 54 patients with diabetes who had no overt cardiac disease. Conventional echocardiography documented normal ventricular systolic function in 96%. As compared with results in age-matched patients without diabetes studied previously, cyclic variation of integrated backscatter was reduced (4.6 +/- 0.8 vs. 3.6 +/- 1.4 dB; p less than 0.001). In addition, delay was significantly increased (0.86 +/- 0.09 vs. 0.99 +/- 0.15). The primary analysis of the data focused on differences among the diabetic patients. Reduction of cyclic variation of backscatter was greatest in patients with diabetes who had neuropathy (3.2 +/- 1.0 dB; p less than 0.001) as was the increase in delay (1.04 +/- 0.16, p less than 0.001 vs. values in patients without neuropathy). Retinopathy and nephropathy were associated with abnormal myocardial acoustic properties as well. Thus, abnormalities that may reflect fibrosis or other occult cardiomyopathic changes in diabetic patients without overt heart disease are readily detectable by myocardial tissue characterization with ultrasound and parallel the severity of noncardiac diabetic complications.

Effects of cyclosporine on insulin secretion and insulin sensitivity in dogs with intrasplenic islet autotransplants

Concern about cyclosporine causing adverse effects on glucose metabolism is based mainly on in vitro studies and in vivo data in rodents. However, data on large mammals and humans are much more controversial. Because the drug is used as therapy accompanying pancreatic or isolated islet transplantations, studies in large animals are needed to assess whether cyclosporine inhibits beta-cell function and causes glucose intolerance. To address these issues, we examined intravenous glucose tolerance, islet beta-cell function, and insulin sensitivity in a group of adult mongrel dogs with intrasplenic islet autografts, with and without cyclosporine treatment. Similar fasting plasma glucose and insulin values were found before and after pancreatectomy and islet transplantation. After intravenous glucose, plasma glucose values decreased more slowly in dogs that had undergone transplantation, but no additional adverse effect as a result of cyclosporine was observed. During euglycemic clamp studies, performed at both physiologic and pharmacologic insulin concentrations, the drug had no effect on the total amount of metabolized glucose, and glucose production was unaffected by cyclosporine treatment. Thus intramuscular cyclosporine therapy does not seem to inhibit insulin secretion from heterotopic islets or to affect peripheral and hepatic insulin sensitivity in dogs with intrasplenic islet autografts.

Absence of the dawn phenomenon and abnormal lipolysis in type 1 (insulin-dependent) diabetic patients with chronic growth hormone deficiency

To determine the role of growth hormone in overnight insulin requirements and lipolysis, five patients with chronic growth hormone deficiency and Type 1 (insulin-dependent) diabetes mellitus and six control patients with diabetes were each studied on two separate nights. Insulin was infused at a variable rate throughout one night to maintain euglycaemia and fixed at 04.00 hours on another. During the variable infusion, euglycaemia was maintained in control patients by a 36% increase in insulin infusion rate between 03.00 and 08.00 hours while a 46% decrease in the rate was required in growth hormone deficient patients (p less than 0.02). Despite this difference, mean free insulin values were equivalent. This finding is suggestive of increased insulin clearance in growth hormone sufficient patients. Glucose levels rose in control and fell in growth hormone deficient patients when insulin infusion rates were fixed at 04.00 hours. Glycerol production and non-esterified fatty acid concentrations were significantly lower in the growth hormone deficient diabetic patients, p less than 0.001, and when normalized with a heparin infusion, had no effect on insulin requirements. We conclude that: (1) growth hormone contributes to the development of the "dawn phenomenon," possibly by increasing insulin clearance (2) growth hormone helps sustain nocturnal lipolysis in Type 1 diabetes and (3) non-esterified fatty acids are not involved in the dawn phenomenon.

Predictors of diabetes knowledge in newly diagnosed children and parents

Utilizing standardized instruments, family and demographic predictors of general and problem-solving knowledge pertaining to diabetes were identified in 53 newly diagnosed children. Mothers, fathers, and children scored significantly higher on the general information component than on the problem-solving knowledge test. Parents of youth ages 15-18 scored significantly lower on both components of the knowledge test than parents of younger youth. Multivariate analyses identified 5 predictors of general information and problem-solving knowledge: child's age, family socioeconomic levels, family stress, family communication abilities, and financial resources. Results suggest that education programs should emphasize problem-solving ability as well as general knowledge, and target parents of older teenagers. Moreover, assessment of family stressors and resources should be routinely performed in families of newly diagnosed children.

Learned helplessness in diabetic youths

Determined the relationships among the learned helplessness attributional style, depression, regimen adherence, and metabolic control in a sample of diabetic youth. Fifty children (20 male and 30 female) between the ages of 10 and 16 completed the Children's Attributional Style Questionnaire and the Children's Depression Inventory. Regimen adherence was assessed with three 24-hr recall interviews conducted separately with patients and their mothers over a 1-week period. Metabolic control was measured by glycosylated hemoglobin A1 (HbA1). Learned helplessness was significantly associated with depression (p less than .001) and HbA1 (p less than .02), but was not associated with regimen adherence. Depression was unrelated to regimen adherence and metabolic control. The adherence measures together accounted for 24% of the variance of HbA1. Significant correlations were obtained between HbA1 and the exercise (p less than .05) and eating/testing frequency (p less than .05) adherence factors, indicating that lower levels of adherence were associated with worse metabolic control. Age, pubertal status, sex, disease duration, and SES were unrelated to regimen adherence and metabolic control. These results support the notion that the learned helplessness attributional style for negative events is related to both depression and long-term metabolic control problems in diabetic youths.

Assessing family sharing of diabetes responsibilities

This study examined sharing of diabetes responsibilities between mothers and their diabetic children and the relationship between patterns of mother-child sharing of responsibility for diabetes tasks and demographic variables, adherence, and metabolic functioning in children with insulin-dependent diabetes mellitus (IDDM). A factor analysis of the Diabetes Family Responsibility Questionnaire (DFRQ), a 17-item questionnaire developed for the present study, resulted in a meaningful three-factor solution. Factors included responsibilities related to regimen tasks, General Health Maintenance, and Social Presentation of Diabetes. Analysis indicated that the DFRQ had adequate internal consistency and concurrent validity. One hundred and twenty-one children with IDDM, 6-21 years of age, and their mothers completed the DFRQ. Glycosylated hemoglobin (HbA1c) was used to index the child's level of metabolic control. Results of multiple regression analyses indicated that the child's age, disease duration, and sex are significant predictors of mother and child patterns of sharing diabetes responsibilities. Disagreements between mothers and children in perceptions of who is assuming responsibility and adherence level were significant predictors of HbA1c. Results indicated that children assume increasing responsibility with increasing age. Clinicians should not assume that mothers and children communicate about the sharing of diabetes responsibilities in the family or about changes in expectations of who is responsible as children develop. To foster better control and adherence in diabetic children, members of the health care team can help to identify diabetes tasks for which no one in the family takes responsibility.

Assessing family sharing of diabetes responsibilities

This study examined sharing of diabetes responsibilities between mothers and their diabetic children and the relationship between patterns of mother-child sharing of responsibility for diabetes tasks and demographic variables, adherence, and metabolic functioning in children with insulin-dependent diabetes mellitus (IDDM). A factor analysis of the Diabetes Family Responsibility Questionnaire (DFRQ), a 17-item questionnaire developed for the present study, resulted in a meaningful three-factor solution. Factors included responsibilities related to regimen tasks, General Health Maintenance, and Social Presentation of Diabetes. Analysis indicated that the DFRQ had adequate internal consistency and concurrent validity. One hundred and twenty-one children with IDDM, 6-21 years of age, and their mothers completed the DFRQ. Glycosylated hemoglobin (HbA1c) was used to index the child's level of metabolic control. Results of multiple regression analyses indicated that the child's age, disease duration, and sex are significant predictors of mother and child patterns of sharing diabetes responsibilities. Disagreements between mothers and children in perceptions of who is assuming responsibility and adherence level were significant predictors of HbA1c. Results indicated that children assume increasing responsibility with increasing age. Clinicians should not assume that mothers and children communicate about the sharing of diabetes responsibilities in the family or about changes in expectations of who is responsible as children develop. To foster better control and adherence in diabetic children, members of the health care team can help to identify diabetes tasks for which no one in the family takes responsibility.

Prevalence and consequences of nocturnal hypoglycemia among conventionally treated children with diabetes mellitus

To determine the prevalence and predictors of, and the glucose responses after, nocturnal hypoglycemia, we studied 135 pediatric patients with insulin-dependent diabetes mellitus on 388 nights. The frequencies of blood glucose values less than 60, 50, and 40 mg/dl (3.3, 2.8, and 2.2 mmol/L) at 2 AM were 14.4%, 7.0%, and 2.1%, and at 6 AM were 6.7%, 2.6%, and 0.5%, respectively. Longer duration of diabetes, higher daily insulin doses, and lower glycosylated hemoglobin values were all significant but weak predictors of 2 AM hypoglycemia (glucose less than or equal to 60 mg/dl (less than or equal to 3.3 mmol/L). A 10 PM glucose concentration less than or equal to 100 mg/dl (less than or equal to 5.6 mmol/L) was present on 48% of nights with 2 AM glucose values less than or equal to 60 mg/dl (less than or equal to 3.3 mmol/L), but only 24% of nights with 10 PM blood glucose values less than or equal to 100 mg/dl (less than or equal to 5.6 mmol/L) were followed by 2 AM hypoglycemia. After treatment of 70 episodes of 2 AM glucose concentrations less than or equal to 60 mg/dl (less than or equal to 3.3 mmol/L), mean 6 AM glucose concentration was 95 +/- 6 mg/dl (5.7 +/- 0.3 mmol/L) and less than or equal to 100 mg/dl in 68.6%. In only 4.3% of these cases was the 6 AM glucose concentration greater than 200 mg/dl (greater than 11.1 mmol/L). Among patients who experienced 2 AM hypoglycemia, after-breakfast glucose values were not greater on days with 2 AM hypoglycemia than on days without it. These data indicate that 2 AM hypoglycemia is relatively common in patients with insulin-dependent diabetes mellitus, is frequently preceded by a 10 PM glucose value less than or equal to 5.6 mmol/L, and is less well predicted by other factors. Appropriate treatment of 2 AM hypoglycemia seldom results in either before-breakfast or after-breakfast blood glucose values greater than 200 mg/dl (greater than 11.1 mmol/L). Early-morning hypoglycemia is an uncommon cause of otherwise unexplained, prebreakfast hyperglycemia in children with insulin-dependent diabetes mellitus.

Randomized prospective study of self-management training with newly diagnosed diabetic children

This study was designed to evaluate the effects of a self-management training (SMT) program on metabolic control of children with insulin-dependent diabetes mellitus (IDDM) in the first 2 yr after diagnosis. After standard in-hospital diabetes education, 36 children (mean age 9.3 yr, range 3-16 yr) were randomized to conventional follow-up, conventional and supportive counseling (SC), or conventional and SMT, which emphasized use of data obtained from self-monitoring of blood glucose. SC and SMT interventions consisted of seven outpatient sessions with a medical social worker during the first 4 mo after diagnosis and booster sessions at 6 and 12 mo postdiagnosis. Groups were similar with respect to age, sex, body mass index, socioeconomic status, C-peptide, and severity of illness at diagnosis. Metabolic control, measured quarterly by glycosylated hemoglobin (HbA1), improved substantially in all three treatment groups during the first 6 mo. SMT patients had significantly lower HbA1 levels than conventional patients at 1 yr (P less than 0.01) and 2 yr (P less than 0.05) postdiagnosis. SMT patients also had lower HbA1 levels than SC patients, but this did not reach statistical significance. The lower HbA1 levels of SMT patients were not explained by severity of illness at diagnosis, or insulin dose, body mass index, and C-peptide levels at 2 yr. These results suggest that an SMT program during the first few months after diagnosis helps avoid the deterioration in metabolic control often seen in children with IDDM between 6 and 24 mo after diagnosis.

Insulin independence after islet transplantation into type I diabetic patient

Effective clinical trials of islet transplantation have been limited by the inability to transplant enough viable human islets into patients with type I (insulin-dependent) diabetes mellitus to eliminate their exogenous insulin requirement. We report the first type I diabetic patient with an established kidney transplant on basal cyclosporin immunosuppression who was able to eliminate the insulin requirement after human islet transplantation into the portal vein. We successfully isolated approximately 800,000 islets that were 95% pure from 1.4 cadaver pancreases containing 121 U of insulin. Islets were proven viable by in vitro insulin response to glucose challenge. After 7 days of 24 degrees C culture, the islets were transplanted into the portal vein under local anesthesia. Seven days of Minnesota antilymphoblast globulin (20 mg/kg) administration followed the islet transplantation, with maintenance of the cyclosporin. Blood glucose was kept under strict control via intravenous insulin for 10 days posttransplantation, when all insulin therapy was stopped. Off insulin, the average 24-h blood glucose level remained less than 150 mg/dl, with the fasting glucose level at 115 +/- 6 mg/dl and the 2-h postprandial level at 141 +/- 8 mg/dl for 22 days posttransplantation (the time of this study). The C-peptide values post-Sustacal testing, although initially rising slower, exceeded the normal range, with peak values of 1.0-1.8 pmol/ml. This preliminary result represents the first essential step required to determine the feasibility of islet transplantation by future clinical trials.

In-hospital bedside blood glucose monitoring: the importance of a quality control program

This study examined the adequacy of a quality control program to assure accuracy of blood glucose monitoring performed at the bedside by nurses in a general pediatric hospital. A standard quality control program during which all nurses received inservice training and demonstrated proficiency resulted in accuracies (percentage of values within 15% of the laboratory) of only 68.6% and 69.2% over two successive 3-month periods. A standardized refresher course did not improve accuracy. Expansion of the program to include identification and reinstruction of individual nurses who had more than 20% of their blood glucose measurements more than 10% off the laboratory value or any one value more than 40% off the laboratory during the previous quarter resulted in improved accuracies (83%, 78%, and 91%) over three successive 3-month periods. These findings indicate that a systemic quality control program including individual monitoring and remedial retraining is required to improve the long-term accuracy of bedside blood glucose monitoring by nurses in a general pediatric hospital.

Prenatal fetal adrenal suppression following in utero diagnosis of congenital adrenal hyperplasia

Congenital adrenal hyperplasia due to 21-hydroxylase deficiency can result in marked virilization of the external genitalia of affected female subjects. Theoretically, suppression of the fetal pituitary-adrenal axis with glucocorticoid during gestational weeks 9 to 17 should prevent the development of ambiguous genitalia in the female fetus. Prenatal diagnosis of congenital adrenal hyperplasia can be made on elevated amniotic fluid 17-hydroxyprogesterone and adrenal androgen concentrations, and HLA typing of cultured amniotic fluid cells. However, these tests cannot be completed before 16 to 17 weeks of gestation, and maternal therapy would have to be instituted before the exact genetic status of the fetus is known. Chorionic villus sampling during the first trimester provides an alternative to second trimester diagnosis in patients who are at risk for bearing offspring with congenital adrenal hyperplasia. We report the use of dexamethasone suppression at 8 weeks of gestation in a 34-year-old woman whose son had congenital adrenal hyperplasia due to severe salt-losing 21-hydroxylase deficiency and whose biopsy revealed a 46XX chromosomal pattern. Cultured cells from the biopsy confirmed the fetus to be of identical HLA haplotype to the previous affected sibling. At 41 weeks the patient delivered a female neonate with minimal prominence of the clitoris, mildly rugated labia, a single perineal opening and minimal posterior labial fusion. Postnatal tapering of maternal steroids was performed with no long-term sequelae.

Self-monitoring of blood glucose by adolescents with diabetes: technical skills and utilization of data

Two studies of adolescent patients were conducted to determine their technical skills and utilization of data obtained by self-monitoring of blood glucose (SMBG). In Study 1, direct observations of 58 adolescents revealed an overall SMBG technical accuracy score of 82%. Most frequent errors were not cleaning fingers (45%), not placing blood on strips correctly (21%), and wiping strip at wrong time (14%). Technical performance was inversely correlated with blood glucose concentration, but was unrelated to other variables. In Study 2, a questionnaire was used to determine SMBG practices among 64 adolescents. Although the majority of patients reported doing daily SMBG, most did not record results in logbooks every time or utilize such data for self-management. No significant relationships were found between SMBG behaviors and other variables. We conclude that periodic evaluation and retraining are required for maintenance of SMBG skills and that methods to enhance utilization of SMBG data be developed for this patient population.

Retinocortical conduction time in diabetics with abnormal pattern reversal electroretinograms and visual evoked potentials

Clinically evident retinal vascular disease in patients with diabetes mellitus may be preceded by an increase in visual evoked potential latency in electrophysiologic testing. This increase may indicate either retinal or optic nerve dysfunction. To determine the origin of the latency increase we initiated a cross-sectional study of simultaneous pattern-reversal electroretinograms and visual evoked potentials. We recorded transient (3.8 reversals/second) pattern electroretinograms and visual evoked potentials using both 15' and 60' high-contrast black-white checks. Fifty-five diabetic patients (34 with no retinopathy and 21 with background retinopathy) and 34 age-matched visual normals (controls) were tested. Group data in diabetics showed significant latency increases in both tests, but not significant differences in retinocortical conduction time were noted. These results suggest that the increases in visual evoked potential latency exhibited by diabetic patients with little or no retinopathy usually reflect altered retinal function rather than optic neuropathy. Two patients with background retinopathy exhibited retinocortical conduction times that exceeded the normal mean by more than two standard deviations, suggesting that optic neuropathy may occasionally occur in diabetic patients with background retinopathy.

The relationship between hue discrimination and contrast sensitivity deficits in patients with diabetes mellitus

In an attempt to elucidate more fully the pathophysiologic basis of early visual dysfunction in patients with diabetes mellitus, color vision (hue discrimination) and spatial resolution (contrast sensitivity) were tested in diabetic patients with little or no retinopathy (n = 57) and age-matched visual normals (n = 35). Some evidence of visual dysfunction was observed in 37.8% of the diabetics with no retinopathy and 60.0% of the diabetics with background retinopathy. Although significant hue discrimination and contrast sensitivity deficits were observed in both groups of diabetic patients, contrast sensitivity was abnormal more frequently than hue discrimination. However, only 5.4% of the diabetics with no retinopathy and 10.0% of the diabetics with background retinopathy exhibited both abnormal hue discrimination and abnormal contrast sensitivity. Contrary to previous reports, blue-yellow (B-Y) and red-green (R-G) hue discrimination deficits were observed with approximately equal frequency. In the diabetic group, contrast sensitivity was reduced at all spatial frequencies tested, but for individual diabetic patients, significant deficits were only evident for the mid-range spatial frequencies. Among diabetic patients, the hue discrimination deficits, but not the contrast sensitivity abnormalities, were correlated with the patients' hemoglobin A1 level. A negative correlation between contrast sensitivity at 6.0 cpd and the duration of diabetes also was observed.