Insulin insensitivity in type 1 diabetes

Beta cell mass in diabetes: a realistic therapeutic target?

Beta cell deficiency underlies both type 1 and type 2 diabetes, and restoration or replacement of beta cell function is therefore the logical long-term solution to therapy. This review sets out to describe the defects in beta cell mass and function in both forms of diabetes, summarises current understanding of the underlying causes of beta cell death, and the methodological limitations of determining beta cell mass in vivo. Finally, the potential effects of current and future treatment regimens on beta cell mass and turnover are considered.

Natural history and risk factors for microalbuminuria in adolescents with type 1 diabetes: a longitudinal study

OBJECTIVE

To describe the natural history and risk factors for persistent microalbuminuria in children and adolescents with type 1 diabetes followed for up to 15 years.

RESEARCH DESIGN AND METHODS

This study contained a longitudinal cohort of 972 patients; analysis of baseline risk factors was performed using logistic regression and predictors over time using survival analysis. Albumin excretion rate was measured on three consecutive timed overnight urine collections on at least two occasions. Normoalbuminuria was defined as a median albumin excretion rate < 7.5 microg/min, borderline microalbuminuria as 7.5-20 microg/min, and microalbuminuria as 20-200 microg/min. Microalbuminuria was further classified as persistent if its duration was >12 months. Median age was 12.7 years (interquartile range 11.5-14.4) and diabetes duration 6.5 years (4.1-9.3) at first assessment, and median follow-up was 6.2 years (range 1-15.3).

RESULTS

The incidence of persistent microalbuminuria was 4.6 (95% CI 3.3-6.1) per 1,000 patient-years. Predictors of persistent microalbuminuria from the first assessment using multiple logistic regression were high cholesterol (odds ratio 2.2 [95% CI 1.2-4.0]) and borderline microalbuminuria (2.5 [1.2-5.2]). Predictors using Cox regression were HbA(1c) (hazard ratio 1.4 [95% CI 1.1-1.7]), age at diagnosis (1.2 [1.1-1.3]), obesity (3.6 [0.8-15.5]), and insulin dose (2.7 [1.0-7.5]).

CONCLUSIONS

Children and adolescents with type 1 diabetes who have borderline microalbuminuria are more than twice as likely to develop persistent microalbuminuria. In addition to poor glycemic control, clinical markers of insulin resistance were associated with an increased risk of microalbuminuria.

Insulin resistance in children and adolescents with type 1 diabetes mellitus: relation to obesity

BACKGROUND

Insulin resistance is well recognized both in type 1 diabetes mellitus (T1DM) and in obesity. Studies concerning the relation between insulin resistance and overweight in T1DM have not yet been carried out.

METHODS

Degree of overweight [standard deviation score-body mass index (SDS-BMI)] and daily insulin doses per weight (ID/kg), per body surface (ID/m2), and per ideal body weight (ID/IW) were recorded in 4124 children aged between 5 and 20 yr with a duration of T1DM of 4-5 yr and an adequate metabolic control [hemoglobin A1c (HbA1c) <8.0%]. SDS-BMI was compared between insulin-resistant (ID/kg > or = 1.0) and insulin-sensitive (ID/kg <1.0) children. The ID/kg, ID/m2, and ID/IW were compared between obese (SDS-BMI >1.9) and non-obese children. Multivariate linear regression analysis was conducted for the dependent variables ID/kg, ID/m2, and ID/IW, including age, gender, SDS-BMI, and HbA1c as independent variables.

RESULTS

The 882 insulin-resistant children did not differ significantly (p = 0.447) with respect to SDS-BMI (median +0.38) compared to the 3242 insulin-sensitive children (median SDS-BMI +0.42). The ID/kg was significantly (p = 0.031) lower in the obese children compared to the non-obese children (median 0.80 vs. 0.83), while ID/m2 (median 31.0 vs. 26.2) and ID/IW (median 1.17 vs. 0.85) were significantly (p < 0.001) increased in the obese children. In multivariate linear regression analysis, SDS-BMI was significantly (p < 0.001) associated with an increase in ID/m2 and ID/IW and a decrease in ID/kg.

CONCLUSIONS

T1DM children with insulin resistance based on ID/kg are not more overweight than insulin-sensitive children with T1DM. ID/m2 and ID/IW seem to reflect a better tool than ID/kg to describe the influence of overweight on insulin resistance in T1DM.

Insulin action and skeletal muscle blood flow in patients with Type 1 diabetes and microalbuminuria

Our objective was to determine whether Type 1 diabetic patients with microalbuminuria are less sensitive to the effects of insulin on glucose metabolism and skeletal muscle blood flow, compared to those with normal albumin excretion, after careful matching for confounding variables. We recruited 10 normotensive Type 1 diabetic patients with microalbuminuria and 11 with normoalbuminuria matched for age, sex, body mass index, duration of diabetes and HbA(1c). Peripheral and hepatic insulin action was assessed using a two-step euglycaemic hyperinsulinaemic clamp (2 h at 0.4 mU x kg(-1) x min(-1), 2 h at 2.0 mU x kg(-1) x min(-1)) combined with isotope dilution methodology. Skeletal muscle blood flow was determined by venous occlusion plethysmography. During the clamps, glucose infusion rates required to maintain euglycaemia were similar in the microalbuminuric subjects and controls (step 1, 8.2+/-1.4 (SE) vs 9.2+/-1.3 micromol x kg(-1) x min(-1): step 2, 30.9+/-2.7 vs 32.0+/-3.8 micromol x kg(-1) x min(-1)), as was hepatic glucose production basally and at steady state in step 1. In step 2, hepatic glucose production was lower in the microalbuminuric group (2.9+/-0.9 vs 6.4+/-0.7 micromol x kg(-1) x min(-1), P=0.005). During step 2, skeletal muscle blood flow increased significantly above baseline in the normoalbuminuric group (4.1+/-0.5 vs 3.2+/-0.4 ml x 100-ml(-1) x min(-1), P=0.01) but not in the microalbuminuric group (2.4+/-0.3 vs 2.3+/-0.4 ml x 100-ml(-1) x min(-1)). In conclusion, microalbuminuria in Type 1 diabetes was found to be associated with impairment of insulin-mediated skeletal muscle blood flow, but not with insulin resistance.