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L M Laffel

Publications and source records attributed to L M Laffel.

26 records · Page 2Linked to original sources
PubMed1992

Sodium activation kinetics of red blood cell Na+/Li+ countertransport in diabetes: methodology and controversy.

Although many studies report an elevated Vmax of red blood cell Na/Li countertransport (CTT) activity in patients with insulin-dependent diabetes mellitus (IDDM) complicated by renal disease, divergent reports exist. This article reviews the technical issues and selection criteria that fuel this controversy. In addition, new studies from this laboratory indicate that insulin in vitro and in the nonfasted state modulate CTT activity and may contribute to the discrepant findings. Incubation of red blood cells from fasted controls with physiologic concentrations of insulin induced a twofold increase in the Km for external Na+. Similarly, Na+ activation kinetics of Li+ efflux showed saturation between 50 and 150 mM Na+ in fasted controls whereas saturation, postprandially, occurred between 100 and 150 mM Na+ as a result of an increase in Km. To clarify the role of prandial status on the measurement of Na+/Li+ CTT activity in diabetes, Na+ activation kinetics were investigated in 34 nonfasting patients with IDDM. Li+ efflux was fully saturated between 80 and 150 mM Na+ in the normoalbuminuric subjects (N = 22), whereas saturation occurred between 150 and 280 mM Na+ in the patients with diabetic nephropathy (N = 14). Patients with nephropathy have higher values of Km for Na+ than do the patients free of renal complications (86 +/- 9.5 versus 41.3 +/- 3.4 mM Na+, respectively; P < 0.000012). The higher Km prevented complete saturation of Li+ efflux at 150 mM extracellular Na+ concentration and contributed to the underestimation of Vmax at 150 mM Na+ selectively in persons with renal complications.(ABSTRACT TRUNCATED AT 250 WORDS)

Antiporters↗
PubMed1991

Evolving natural history of coronary artery disease in diabetes mellitus.

White diabetic patients are at high risk of developing coronary artery disease (CAD). The natural history of CAD in insulin-dependent (ID) and noninsulin-dependent (NID) diabetes mellitus (DM) is reviewed to gain insight into the mechanisms responsible for the development of premature or accelerated atherosclerosis in diabetic patients. In both IDDM and NIDDM, the risk of CAD increases with lengthening duration of diabetes; the risk, however, does not grow as a constant multiple of the nondiabetic risk of CAD, suggesting that the cumulative exposure to diabetes plays a significant role as a risk factor for CAD only in a subset of patients. This is consistent with the hypothesis that the diabetic milieu has an impact on the progression of atherosclerotic lesions but not on their initiation. This hypothesis is corroborated further by the observation that CAD does not occur in diabetic patients in populations with a low risk of CAD among nondiabetic patients. The component of the diabetic milieu responsible for promotion of atherosclerotic lesions is unknown. There is evidence, however, of a direct or indirect role of hyperinsulinemia in this process.

Adolescent↗
PubMed1991

Split-mixed insulin regimen with human ultralente before supper and NPH (isophane) before breakfast in children and adolescents with IDDM.

OBJECTIVE: Fasting hyperglycemia is common in patients with insulin-dependent diabetes mellitus (IDDM) treated with twice-daily subcutaneous insulin regimens. We postulated that substituting human ultralente insulin for the presupper dose of intermediate-acting insulin would improve overnight glycemic control in children and adolescents with IDDM. RESEARCH DESIGN AND METHODS: This 6-mo double-blind crossover study compared a conventional insulin regimen, a mixture of human NPH and regular given before both breakfast and supper (NPH), with a novel twice-daily regimen in which human ultralente replaced NPH before the evening meal (ultralente). This study was comprised of 20 children and adolescents (mean age and duration of IDDM 11.3 +/- 2.9 and 2.4 +/- 1.3 yr, respectively) from the Youth Clinic of the Joslin Diabetes Center, all of whom regularly performed self-monitoring of blood glucose (SMBG) and had been treated exclusively with human insulin (mean daily dose 0.75 +/- 0.22 U/kg). Subjects performed SMBG on a prescribed schedule with a glucose meter with an electronic memory, and recorded results of blood glucose measurements, insulin dosages, and episodes of hypoglycemia. Monthly measurements were obtained for height, weight, and HbA1, and mean daily insulin dosages and average blood glucose level before breakfast, lunch, supper, bedtime snack, and between 0200 and 0300 were calculated. Nonfasting serum lipids were measured at entry, crossover, and the end of the study. RESULTS: After 3 mo, mean HbA, did not differ significantly (9.1 +/- 1.7 vs. 9.5 +/- 1.4%, NPH and ultralente, respectively). Mean fasting blood glucose was significantly lower on ultralente (9.6 +/- 1.9 vs. 10.3 +/- 2.2 mM, P less than 0.05, and blood glucose showed a similar trend (0.05 less than P less than 0.1) before lunch (8.9 +/- 1.7 vs. 9.8 +/- 2.6 mM. Mean blood glucose before bedtime snack was significantly lower (P less than 0.01) on NPH (8.4 +/- 1.9 vs. 10.0 +/- 2.1 mM) but did not differ significantly before supper or between 0200 and 0300. On the two regimens, growth and serum lipids were normal and similar, and no differences were observed in the incidence or severity of hypoglycemia. CONCLUSIONS: Compared with a mixed dose of regular and NPH, a similar dose of a mixture of regular and human ultralente insulin before supper caused a modest reduction in fasting blood glucose levels but was associated with higher blood glucose levels before the bedtime snack. Overall glycemic control, reflected in HbA1 values, was not significantly improved.

Child↗
PubMed1991

Excess mortality associated with diuretic therapy in diabetes mellitus.

OBJECTIVE: To determine whether the high mortality among diabetic patients receiving treatment for hypertension can be explained by associated risk factors or must be attributed to a deleterious effect of antihypertensive treatment. DESIGN: Cohort analytic study with a median follow-up of 4.5 years. SETTING: Outpatients with diabetes and severe retinopathy who were enrolled in a multicenter, randomized clinical trial of laser treatment to prevent blindness had ophthalmologic examinations every 4 months and annual medical examinations that included measurement of blood pressure and recording of anti-hypertensive treatment. Only 5.5% of the patients were unavailable for follow-up. When a patient died, the circumstances surrounding the death were reviewed and classified by a mortality review committee. PARTICIPANTS: --There were 759 participants in the study; they were white, were aged 35 to 69 years, and had normal serum creatinine levels at the baseline examination. MEASUREMENTS AND MAIN RESULTS: --Patients were classified into five groups according to information recorded at the baseline and first annual follow-up examinations: normotensive (diastolic blood pressure less than 90 mm Hg), untreated hypertensive, hypertensive treated by diuretics alone, hypertensive treated by other agents alone, and hypertensive treated by both agents. Cardiovascular mortality was higher in patients treated for hypertension than in patients with untreated hypertension. The excess was primarily found in patients treated with diuretics alone, although that group had the lowest blood pressure with treatment. After adjusting for differences in risk factors, cardiovascular mortality was 3.8 times higher in patients treated with diuretics alone than in patients with untreated hypertension (P less than .001). CONCLUSIONS: --In individuals with diabetes, intervention with diuretics to reduce hypertension is associated with excess mortality. Until there is a clinical trial showing a beneficial effect of diuretic treatment in diabetic patients, there is urgent need to reconsider its continued usage in this population.

Adult↗
PubMed1990

Continuous glucose for treatment of patients with type 1 glycogen-storage disease: comparison of the effects of dextrose and uncooked cornstarch on biochemical variables.

Responses to uncooked cornstarch (UCS), dextrose (Dex), and a 3:1 mixture (UCS:Dex) were determined in seven children with type 1 glycogen-storage disease (GSD-1). UCS maintained blood glucose (BG) and serum insulin concentrations between 3.5 +/- 0.3 and 4.0 +/- 0.4 mmol/L (mean +/- SEM) and 50 +/- 7 and 79 +/- 22 pmol/L, respectively, in six of the seven patients for 4 h. Only four of seven patients completed the 4-h test after UCS:Dex (BG 2.9 +/- 0.3 mmol/L): After Dex, tests had to be stopped in all patients by 150 min after initiation (BG 2.7 +/- 0.4 mmol/L). Two methods of providing dietary glucose overnight, continuous intragastric glucose infusion (COG) and intermittent UCS at 2100 and 0200, were compared by monitoring metabolites and glucoregulatory hormones. The use of UCS in amounts equal to the calculated glucose production rate is an effective method of providing a continuous dietary source of glucose overnight to patients with GSD-1.

Adolescent↗
PubMed1989

Elevated blood pressure predicts the development of persistent proteinuria in the presence of poor glycemic control, in patients with type I diabetes.

The risk of developing persistent proteinuria was studied prospectively in 376 patients, enrolled in the Diabetic Retinopathy Study, who did not have proteinuria at entry to the study. The subjects had insulin-dependent diabetes with onset before age 30, more than 5 years duration of diabetes, and a median of 3 years of follow-up for proteinuria. Persistent proteinuria developed in 55 patients, giving an overall incidence rate of 61/1000 person-years; however, the incidence rate decreased markedly after 20 years of diabetes, from 117/1000 to 23/1000 person-years. Regardless of duration, it also decreased after age 40. Among those with less than 20 years of diabetes, it decreased from 126/1000 to 28/1000 person-years; and among those with duration 20 or more years, it decreased from 44/1000 to 7/1000 person-years. High mean blood pressure quadrupled the risk of persistent proteinuria among patients with high plasma glucose levels but had little effect on the risk in patients with glucose levels below the median for the group. In conclusion, hypertension predicts the development of nephropathy particularly in those with poorly controlled diabetes. This is consistent with our hypothesis that, in individuals with predisposition to hypertension, severe hyperglycemia interacts with some mechanism underlying that predisposition and causes injury to the kidneys. The marked decrease in risk after age 40 suggests that the development of diabetic nephropathy may be limited to a window of vulnerability. While the mechanisms for these associations remain unclear, these findings have important implications for managing patients with Type I diabetes to prevent renal failure.

Adult↗
PubMed1988

Predisposition to hypertension and susceptibility to renal disease in insulin-dependent diabetes mellitus.

Only one third of patients with juvenile-onset insulin-dependent diabetes seem to be susceptible to diabetic nephropathy. To test whether this susceptibility is related to a predisposition to hypertension, we investigated the association of nephropathy with markers of risk for hypertension. We randomly selected 89 patients with insulin-dependent diabetes from a roster of children and adolescents who were seen between 1968 and 1972 at about the time the diagnosis was made. These 89 patients were recalled for examination, as young adults, in 1986 and 1987. Patients with nephropathy (cases, n = 33) were compared with controls without nephropathy (n = 56). Having a parent with hypertension tripled the risk of nephropathy (odds ratio, 3.7; 95 percent confidence interval, 1.4 to 10.1). Moreover, cases had significantly higher values for maximal velocity of lithium-sodium countertransport in red cells than controls (mean maximal velocity +/- SE, 0.51 +/- 0.04 vs. 0.38 +/- 0.02 mmol per liter of cells per hour; P less than 0.05). The excess risk associated with both these indicators of a predisposition to hypertension was evident principally in patients with poor glycemic control during their first decade of diabetes; the odds ratios were 4.5 (95 percent confidence interval, 1.1 to 18.7) for patients with a parental history of hypertension and 7.7 (95 percent confidence interval, 1.8 to 33.8) for patients with a maximal velocity of lithium-sodium countertransport greater than or equal to 0.35 mmol per liter of cells per hour. We conclude that the risk of renal disease in patients with juvenile-onset insulin-dependent diabetes is associated with a genetic predisposition to hypertension. Predisposition to hypertension appears to increase susceptibility for renal disease principally in patients with poor glycemic control.

Adult↗