Haysook Choi

Determinants of reversibility of β-cell dysfunction in response to short-term intensive insulin therapy in patients with early type 2 diabetes

Short-term intensive insulin therapy (IIT) can improve pancreatic β-cell function when administered early in the course of type 2 diabetes mellitus (T2DM). However, the degree of improvement in response to this therapy varies between patients. Thus, we sought to characterize the determinants of improvement in β-cell function in response to short-term IIT in early T2DM. Sixty-three patients with mean 3.0 ± 2.1 yr duration of T2DM and Hb A1c of 6.8 ± 0.8% underwent 4 wk of IIT consisting of basal insulin detemir and premeal insulin aspart, with oral glucose tolerance test administered at baseline and 1 day post-IIT. β-Cell function before and after IIT was assessed by Insulin Secretion Sensitivity Index-2 (ISSI-2). Reversibility of β-cell dysfunction was defined as percentage change in ISSI-2 of ≥25%. Overall, the study population experienced an increase in ISSI-2 from baseline to post-IIT (P = 0.01), with one-third of participants achieving ≥25% improvement in ISSI-2. Compared with their peers, those with increases in ISSI-2 of ≥25% had greater decrements in fasting glucose (P < 0.0001), Hb A1c (P = 0.001), ALT (P = 0.04), AST (P = 0.02), and HOMA-IR (P < 0.0001). On logistical regression analysis, baseline Hb A1c (OR = 2.83, 95% CI 1.16-6.88, P = 0.02) and change in HOMA-IR (OR = 0.008, 95%CI 0.0004-0.16, P = 0.001) emerged as independent predictors of reversibility of β-cell dysfunction. Indeed, reversibility of β-cell dysfunction was achieved in only those participants in whom IIT yielded an improvement in HOMA-IR. In conclusion, decline in HOMA-IR may be a key determinant of improvement of β-cell function in response to short-term IIT, suggesting a fundamental contribution of insulin resistance to the reversible component of β-cell dysfunction in early T2DM.

Glycemic Variability in Patients With Early Type 2 Diabetes: The Impact of Improvement in β-Cell Function

OBJECTIVE Increased glycemic variability has been reported to be associated with the risk of hypoglycemia and possibly diabetes complications and is believed to be due to β-cell dysfunction. However, it is not known whether improvement in β-cell function can reduce glycemic variability. Because short-term intensive insulin therapy (IIT) can improve β-cell function in early type 2 diabetes (T2DM), our objective was to determine whether the β-cell functional recovery induced by this therapy is associated with decreased glycemic variability. RESEARCH DESIGN AND METHODS Sixty-one patients with T2DM of 3.0 years mean duration underwent 4 weeks of IIT, which consisted of basal insulin detemir and premeal insulin aspart. Glucose variability was assessed in both the first and the last week by the coefficient of variation of capillary glucose on daily 6-point self-monitoring profiles. β-Cell function before and after IIT was assessed with the Insulin Secretion-Sensitivity Index-2 (ISSI-2). RESULTS Between the first and the last week on IIT, 55.7% of patients had a reduction in glucose variability. Change in glucose variability was negatively correlated with the change in β-cell function (ISSI-2) (r = −0.34, P = 0.008). On multiple linear regression analyses, percentage change in ISSI-2 emerged as the only factor independently associated with the change in glucose variability (standardized β = −0.42, P = 0.03). Moreover, patients with an increase in ISSI-2 ≥25% experienced a reduction in glucose variability compared with their peers who had almost no change (−0.041 ± 0.06 vs. −0.0002 ± 0.04, respectively; P = 0.006). CONCLUSIONS In early T2DM, glycemic variability is a modifiable parameter that can be reduced by improving β-cell function with short-term IIT.

Emerging parameters of the insulin and glucose response on the oral glucose tolerance test: Reproducibility and implications for glucose homeostasis in individuals with and without diabetes

AIMS Recent studies have suggested that novel parameters of the insulin and glucose response on the oral glucose tolerance test (OGTT) can provide metabolic insight beyond glucose tolerance, but have not evaluated their reproducibility. Thus, our aim was to evaluate the reproducibility of these parameters and, if confirmed, characterize their clinical/pathophysiologic relevance in healthy and diabetic individuals. METHODS Thirty healthy adults each underwent 3 replicate OGTTs, enabling assessment of the reproducibility of the following 5 parameters: time to insulin peak, shape of the glucose curve, glucose nadir below baseline, 1-h post-challenge glucose, and time to glucose peak. The only reproducible parameter was then further evaluated in 63 patients with early type 2 diabetes (T2DM) before and after 4-weeks of intensive insulin therapy (IIT) designed to improve beta-cell function (measured by Insulin Secretion-Sensitivity-Index-2 (ISSI-2)). RESULTS Of the five parameters, only time to glucose peak displayed reliable reproducibility on replicate testing (κ=0.76). Over 80% of controls had their glucose peak at 30-min post-load, whereas all but one of the diabetic patients had their peak at 60-min or later. ISSI-2 was lower in T2DM patients with peak at ≥90-min than in those with peak at ≤60-min (P=0.012). In patients in whom IIT improved beta-cell function by ≥20% from baseline, 39.1% had glucose peak on the post-therapy OGTT shift to an earlier timepoint, as compared to 15.4% with similar shift in those without such improvement(P=0.03). CONCLUSION Time to glucose peak is a reproducible characteristic on the OGTT and associated with beta-cell function in early T2DM.

Two-year trial of intermittent insulin therapy vs metformin for the preservation of β-cell function after initial short-term intensive insulin induction in early type 2 diabetes

To test the hypothesis that “induction” intensive insulin therapy (IIT) needs to be followed by “maintenance therapy” to preserve β‐cell function, and to evaluate the impact on β‐cell function over 2 years of two approaches to maintenance therapy: intermittent short‐term IIT every 3 months vs daily metformin.

Effect of short-term intensive insulin therapy on the incretin response in early type 2 diabetes

AIMS Short-term intensive insulin therapy (IIT) and gastric bypass surgery are both interventions that can improve beta-cell function, reduce insulin resistance and induce remission of type 2 diabetes. Whereas gastric bypass yields an enhanced glucagon-like peptide-1 (GLP-1) response that may contribute to its metabolic benefits, the effect of short-term IIT on the incretin response is unclear. Thus, we sought to evaluate the impact of IIT on GLP-1 and glucose-dependent insulinotropic polypeptide (GIP) secretion in early type 2 diabetes. METHODS In this study, 63 patients (age 59±8.3 years, baseline A1c 6.8±0.7%, diabetes duration 3.0±2.1 years) underwent 4 weeks of IIT (basal insulin detemir and pre-meal insulin aspart). GLP-1, GIP and glucagon responses were assessed by the area-under-the-curve (AUC) of these hormones on oral glucose tolerance tests at baseline and 1-day after the completion of therapy. Beta-cell function was assessed by Insulin Secretion-Sensitivity Index-2 (ISSI-2), with insulin resistance measured by Homeostasis Model Assessment (HOMA-IR). RESULTS As expected, comparing the post-therapy oral glucose tolerance test to that at baseline, IIT increased ISSI-2 (P=0.02), decreased HOMA-IR (P<0.001), and reduced AUCglucagon (P<0.001). Of note, however, IIT had no significant impact on AUCGLP-1 (P=0.24) and reduced AUCGIP (P=0.02). CONCLUSION Despite improving beta-cell function, insulin resistance and glucagonemia, short-term IIT does not change GLP-1 secretion and decreases the GIP response to an oral glucose challenge in early type 2 diabetes. Thus, the beneficial impact of this therapy on glucose homeostasis is not attributable to its effects on incretin secretion.

Impact of the Glucagon Assay when Assessing the Effect of Chronic Liraglutide Therapy on Glucagon Secretion.

Context Glucagon-like peptide-1 agonists acutely lower serum glucagon. However, in the Liraglutide and β-Cell Repair (LIBRA) Trial, 48-week treatment with liraglutide yielded lower/unchanged fasting glucagon but, surprisingly, enhanced postchallenge glucagonemia [measured by R&D Systems (Minneapolis, MN) assay]. Objective Because differences between glucagon assays potentially could explain these unexpected findings, we have remeasured glucagon in all 1222 samples from this trial using the highly-sensitive/specific Mercodia assay to compare the findings between assays. Design/Setting/Participants/Intervention In LIBRA, 51 patients with type 2 diabetes of 2.6 ± 1.9 years duration were randomized to daily subcutaneous liraglutide or placebo injection and followed for 48 weeks, with serial oral glucose tolerance test (OGTT) every 12 weeks (with liraglutide/placebo last administered ∼24 hours earlier). Outcome Serum glucagon was measured every 30 minutes on each OGTT, enabling determination of the area under the glucagon curve (AUCglucagon). Results With the Mercodia assay, fasting glucagon was higher in the liraglutide arm than placebo at 12 weeks (P = 0.01), with no between-group differences at 24, 36, and 48 weeks. There was no difference in AUCglucagon between the groups at any visit. Mercodia and R&D Systems glucagon measurements correlated at postchallenge time points but not at fasting. Conclusion The Mercodia assay did not replicate the R&D Systems glucagon findings. Although neither assay demonstrated lower postchallenge glucagonemia with chronic liraglutide last administered ∼24 hours earlier, the differential response reported by these assays precludes definitive conclusion and highlights the critical role of assay selection when measuring glucagon in clinical studies.

Effect of chronic liraglutide therapy and its withdrawal on time to postchallenge peak glucose in type 2 diabetes

Delayed timing of peak serum glucose following an oral glucose challenge can predict declining β-cell function and worsening glucose tolerance over time. Accordingly, postchallenge peak glucose is typically delayed in patients with type 2 diabetes (T2DM). However, little is known about the capacity of antidiabetic medications to reverse this delay. Thus, we sought to evaluate the effect of the glucagon-like peptide-1 agonist liraglutide on time to peak glucose in early T2DM. In this secondary analysis of a double-blind placebo-controlled trial, 51 patients with T2DM of 2.6 ± 1.9 yr duration were randomized to daily subcutaneous liraglutide or placebo injection for 48 wk, with oral glucose tolerance test (OGTT) performed every 12 wk while on therapy and after a 2-wk washout. On each OGTT, time to peak glucose was determined from venous glucose measurements at 0, 10, 20, 30, 60, 90, and 120 min. At randomization, most patients in both arms exhibited peak glucose at 90 min postchallenge. By 12 wk, 65.4% of the liraglutide arm had shifted to an earlier peak (vs. 36% on placebo; P = 0.19), with little change thereafter at 24, 36, and 48 wk. After the 2-wk washout, however, 57.7% of those who had been on liraglutide reverted to a later peak (vs. 4.5% on placebo; P < 0.001). This shift was associated with declining β-cell function ( P = 0.001), resulting in higher 2-h blood glucose at washout in the liraglutide arm compared with placebo ( P = 0.001). Thus, although liraglutide possibly might improve the delay in peak glucose, its cessation yielded a worsening thereof and higher glycemia. The mechanisms underlying these observations and their clinical implications warrant further investigation.