Glucose Levels at the Site of Subcutaneous Insulin Administration and Their Relationship to Plasma Levels

OBJECTIVE

To examine insulin''s effect on the tissue glucose concentration at the site of subcutaneous insulin administration.

RESEARCH DESIGN AND METHODS

A CMA-60 microdialysis (MD) catheter and a 24-gauge microperfusion (MP) catheter were inserted into the subcutaneous adipose tissue of fasting, healthy subjects (n = 5). Both catheters were perfused with regular human insulin (100 units/ml) over a 6-h period and used for glucose sampling and simultaneous administration of insulin at sequential rates of 0.33, 0.66, and 1.00 units/h (each rate was used for 2 h). Before and after the insulin delivery period, both catheters were perfused with an insulin-free solution (5% mannitol) for 2 h and used for glucose sampling only. Blood plasma glucose was clamped at euglycemic levels during insulin delivery.

RESULTS

Start of insulin delivery with MD and MP catheters resulted in a decline of the tissue glucose concentration and the tissue-to-plasma glucose ratio (TPR) for ∼60 min (P < 0.05). However, during the rest of the 6-h period of variable insulin delivery, tissue glucose concentration paralleled the plasma glucose concentration, and the TPR for MD and MP catheters remained unchanged at 83.2 ± 3.1 and 77.1 ± 4.8%, respectively. After subsequent switch to insulin-free perfusate, tissue glucose concentration and TPR increased slowly and reattained preinsulin delivery levels by the end of the experiments.

CONCLUSIONS

The results show the attainment of a stable TPR value at the site of insulin administration, thus indicating that insulin delivery and glucose sensing may be performed simultaneously at the same adipose tissue site.When insulin is secreted from the pancreas, the resulting rise in the blood insulin level acts to lower the blood glucose concentration by both suppressing glucose production in the liver and enhancing glucose uptake in insulin-sensitive tissues (mainly muscle and adipose tissue) (1). Studies (2,3) investigating insulin''s effect on glucose uptake in isolated muscle and fat cells have shown that the cellular response to increasing insulin concentration is a continuous increase in glucose uptake until a maximal response is reached. Further increases in the prevailing insulin concentrations beyond this threshold level does not further increase glucose uptake. Similar saturation-type concentration-response characteristics were found for insulin-stimulated arteriovenous glucose difference, blood flow, and glucose uptake (4,5) in the forearm and leg as well as for insulin-stimulated whole-body glucose uptake (1,4,5). In these in vivo studies, the maximal response to insulin in healthy humans was observed to occur at a blood plasma concentration of 300–1,000 μU/ml (1,4,5). Most notably, this maximally effective insulin level is ∼100,000 times lower than the insulin concentration in preparations currently used in the replacement therapy of diabetic patients (100 units/ml) (6). Thus, given the observed saturation-type relationship between insulin concentration and insulin''s effect on arteriovenous glucose difference, blood flow, and glucose uptake in human peripheral tissues, we reasoned that a similar saturation-type concentration-response characteristic for the insulin-stimulated difference between arterial blood glucose levels and interstitial fluid (ISF) glucose concentrations might exist in these tissues (online appendix Fig. 1 [available at http://care.diabetesjournals.org/cgi/content/full/dc09-1531/DC1]). An interstitial infusion of insulin into adipose tissue at rates used in the replacement therapy of diabetic patients might therefore evoke insulin concentrations at the infusion site that are much higher than the maximally effective insulin level of this tissue and, in turn, might ensure an essentially maximal and stable blood-to-ISF glucose concentration gradient in the tissue at this infusion site. If this were the case, then despite the presence of variable insulin delivery rates, reliable estimation of blood glucose concentrations from glucose concentrations measured in the ISF at the insulin delivery site would be possible.The present study was undertaken to investigate this possibility in the subcutaneous adipose tissue of healthy subjects. Microperfusion and microdialysis techniques were utilized to perform glucose sampling and simultaneous insulin delivery at the same adipose tissue site. Using these techniques, ISF glucose samples from the site of insulin delivery were obtained in the presence of variable insulin delivery rates. The observed ISF glucose levels were then compared with plasma glucose concentrations as well as to glucose levels in ISF samples from insulin-unexposed adipose tissue.     

Impact of Baseline Insulin Regimen on Glycemic Response to a Group Medical Clinic Intervention

OBJECTIVE

Group medical clinics (GMC) combine medication management and self-management training, and may improve diabetes outcomes. It remains unclear which patients benefit most from GMC. This secondary analysis examined the impact of baseline insulin regimen on GMC response.

RESEARCH DESIGN AND METHODS

We analyzed a trial of 239 veterans with type 2 diabetes randomized to GMC or usual care (UC). We categorized baseline insulin regimen as the following: no insulin; basal insulin only; or complex insulin (basal–prandial or mixed regimens). Using linear mixed models adjusted for clustering within GMC, we evaluated the differential impact of GMC relative to UC on hemoglobin A_1c (HbA_1c) and self-efficacy among patients on different baseline insulin regimens.

RESULTS

From linear mixed models, the effect of GMC on HbA_1c differed by baseline insulin regimen versus UC (P = 0.05); there was no differential effect on self-efficacy (P = 0.29). Among those using complex insulin regimens at baseline, GMC reduced HbA_1c by study end compared with UC (−1.0%; 95% CI −1.8 to −0.2; P = 0.01). We found no such HbA_1c difference between GMC and UC patients using no insulin (P = 0.65) or basal insulin only (P = 0.71). There were no clinically significant differences in hypoglycemia by baseline insulin regimen and intervention group.

CONCLUSIONS

We found that compared with UC, GMC lowered HbA_1c specifically among patients using complex insulin regimens at study baseline, which may relate to this group’s demanding medication and self-management requirements. Implementing GMC among patients using complex insulin regimens may maximize this care delivery strategy’s potential.Diabetes is increasingly prevalent (1), and the costs of poor glycemic control are increasing (2,3). Because improving hemoglobin A_1c (HbA_1c) leads to reduction in diabetes complications (4,5), addressing poor glycemic control is vital. Good self-care is a key predictor for attaining improved HbA_1c in patients with suboptimal glycemic control (6), so interventions that target deficiencies in diabetes self-management hold substantial promise.Group medical clinics (GMC) offer an opportunity to provide patients with diabetes with both individualized medical management and self-management education in a manner that could potentially improve access and decrease costs compared with usual care (UC) (7). Randomized controlled trials (RCT) of GMC have reported conflicting results among patients with diabetes, with some studies showing a greater improvement in HbA_1c with GMC relative to UC, and with some studies showing no difference (8–19). It remains unclear whether certain subgroups of patients may derive greater benefit from diabetes GMC than others; for example, a recent systematic review demonstrated that baseline HbA_1c does not appear to be a significant predictor of GMC response (20). Selection of high-yield patient subgroups will be essential to efficiently implementing GMC.Relative to patients using oral diabetes agents and/or basal insulin, patients using complex insulin regimens (defined for this study as multiple daily injections of either basal and prandial insulin or mixed basal–prandial insulin preparations) require careful insulin titration, which some primary care providers lack comfort in overseeing (21–25). Further, these patients have demanding self-management requirements, including regular blood glucose monitoring, frequent insulin administration, and nutritional restrictions (26). Consequently, self-management adherence is more challenging for patients using complex insulin regimens than for patients using simpler diabetes medication regimens (27). Because diabetes GMC appear to exert positive effects by providing both tailored medication management and self-management training (20), it is possible that GMC may have the greatest potential for impact among patients using complex insulin regimens.Using data from a published randomized trial (16), we sought to evaluate the effect of a GMC intervention among patients with poorly controlled type 2 diabetes who at study baseline were prescribed no insulin (oral diabetes medications only), basal insulin only (in addition to any oral medications), or complex insulin regimens (in addition to any oral medications). Because of their higher medication complexity and more demanding self-management, we hypothesized that patients using complex insulin regimens at study baseline would derive greater benefit from GMC relative to UC than would patients using simpler diabetes treatment regimens.     

Complementing Insulin Therapy to Achieve Glycemic Control

Introduction

Most patients with type 2 diabetes mellitus (T2DM) will need incrementally more complex therapeutic regimens to control hyperglycemia as the disease progresses. Insulin is very effective in reducing hyperglycemia and may improve β-cell function in patients with T2DM. However, insulin therapy is associated with weight gain and increased risk of hypoglycemia. Adding other antidiabetes medications to insulin can improve glycemic control and potentially lower the required insulin dose, resulting in less weight gain and lower risk for hypoglycemia. This article summarizes the advantages and disadvantages of different classes of commonly used antidiabetes agents, with emphasis on newer classes, for use as add-on therapy to insulin in patients with T2DM inadequately controlled on insulin therapy.

Methods

A PubMed search from July 1, 2003 to April 15, 2013 for peer-reviewed clinical and review articles relevant to insulin combination or add-on therapy in T2DM was conducted. Search terms included “insulin combination therapy,” “add-on therapy diabetes,” “dipeptidyl peptidase-4 (DPP-4) inhibitors,” “glucagon-like peptide-1 (GLP-1) receptor agonist,” “sodium-glucose cotransporter 2 (SGLT2) inhibitors”, “insulin metformin,” “insulin sulfonylurea,” and “insulin thiazolidinedione.” Bibliographies from retrieved articles were also searched for relevant articles. Study design, clinical relevance, and effect on insulin combination therapy were analyzed.

Results

Therapies used as add-on to insulin include agents associated with weight gain (thiazolidinediones and sulfonylureas) and/or hypoglycemia (sulfonylureas), which, therefore, may exacerbate risks already present with insulin. GLP-1 receptor agonists, DPP-4 inhibitors, and SGLT2 inhibitors improve glycemic control when added to insulin and have a low propensity for hypoglycemia and cause no change (DPP-4 inhibitors) or a reduction (GLP-1 receptor agonists, SGLT2 inhibitors) in body weight.

Conclusion

GLP-1 receptor agonists, DPP-4 inhibitors, and SGLT2 inhibitors improve glycemic control when combined with insulin. They also have low propensity for weight gain and hypoglycemia and so may be preferred treatment options for insulin combination when compared with traditional therapies.     

The Significance of Basal Insulin Levels in the Evaluation of the Insulin Response to Glucose in Diabetic and Nondiabetic Subjects

The level of insulin after an overnight fast (basal) in 37 obese and nonobese male subjects with normal and abnormal carbohydrate tolerance was directly related to the increase in insulin concentration during a 3 hr 100 g oral glucose tolerance test. Obesity, but not diabetes, was associated with an elevation of this basal insulin level. Thus obesity predicted with the magnitude of the insulin response to glucose ingestion. When the individual insulin values were expressed as per cent change from the basal level, this effect of obesity was excluded. The insulin levels of all subjects with normal carbohydrate tolerance promptly rose 5-7-fold, and reached peak values 1 hr after oral glucose. In contrast, the diabetic response (as per cent increase) was markedly reduced during the 1st hr, and maximal (but still subnormal) insulin levels were not attained until 2 hr. In all subjects the insulin response (quantitated by calculation of the area circumscribed by a plot of the per cent change in insulin with time) showed a significant inverse correlation with the glucose response. Thus increasing degrees of carbohydrate intolerance were associated with decreasing insulin responses. Elevated levels of insulin, in both the basal state and in response to glucose, were related to obesity.     

Improved Glycemic Control With Intraperitoneal Versus Subcutaneous Insulin in Type 1 Diabetes: A randomized controlled trial

OBJECTIVE

Continuous intraperitoneal insulin infusion (CIPII) with an implantable pump has been available for the past 25 years. CIPII, with its specific pharmacodynamic properties, may be a viable treatment alternative to improve glycemic control in patients with type 1 diabetes for whom other therapies have failed. There have been few studies in which CIPII was compared with subcutaneous insulin treatment for patients with type 1 diabetes with poor glycemic control.

RESEARCH DESIGN AND METHODS

In an open-label, prospective, crossover, randomized, 16-month study, the effects of CIPII and subcutaneous insulin were compared in 24 patients. The primary outcome measure was the incidence of hypoglycemia. Secondary outcome measures were A1C, and glucose profile, including time in euglycemia, as measured by continuous glucose monitoring.

RESULTS

The incidence of grade 1 hypoglycemic events was 4.0 ± 2.6 per week with subcutaneous insulin compared with 3.5 ± 2.3 per week during CIPII (P = 0.13). The absolute mean difference in A1C with CIPII compared with subcutaneous treatment was −0.76% (95% CI −1.41 to −0.11) (P = 0.03). Baseline time spent in euglycemia was 45.2 ± 12.6% and increased 10.9% (4.6–17.3) with CIPII compared with subcutaneous treatment (absolute value; P = 0.003). There were no differences in the occurrence rate for severe hypoglycemic events, daily insulin use, or BMI. No pump or catheter malfunction was observed during the study.

CONCLUSIONS

Although we did not observe a significant reduction in hypoglycemic events, improved glycemic control was achieved with the use of CIPII. We saw a 0.8% decrease in A1C and an 11% increase in the time spent in euglycemia.Meta-analyses conclude that continuous subcutaneous insulin infusion (CSII) is somewhat better than multiple daily injections (MDIs) for obtaining glycemic control in patients with type 1 diabetes (1–4). These differences tend to be smaller when synthetic insulin analogs are used. The absorption of subcutaneous infused insulin is influenced by many factors, sometimes responsible for unexpected hypo- and hyperglycemic events (5,6). In some patients with type 1 diabetes, this form of therapy does not yield acceptable and stable long-term glycemic control (7).The intraperitoneal administration of insulin allows blood glucose values to normalize more rapidly after a meal with more predictable insulin profiles than with subcutaneous insulin (8–10). Much of the intraperitoneal insulin is absorbed through the portal system, which more closely mimics normal physiological action, resulting in improved hepatic uptake and lower peripheral plasma insulin levels (11). Intraperitoneal insulin may lead to improved glucagon secretion and hepatic glucose production in response to hypoglycemia (12).The effects of continuous intraperitoneal insulin infusion (CIPII) in type 1 diabetes have been investigated in few randomized controlled trials, and all were done before the era of rapidly acting insulin analogs. The objective of our study was to assess the safety and efficacy of CIPII compared with intensified subcutaneous insulin therapy in patients with inadequately controlled type 1 diabetes.     

Basal Plasma Glucagon Levels of Man

The isolated perfused rat liver can serve as a bioassay system for glucagon, capable of detecting 10 mmug of this agent. Seven 15-ml plasma specimens obtained from different healthy volunteers after an overnight fast were assayed in this system; glucagon could not be detected in any of them, indicating concentrations significantly below 0.67 mmug per ml in all subjects. The effects of administering small doses of glucagon to patients were consistent with these results; imposition of increments to plasma glucagon concentration below 1 mmug per ml induced distinct and sustained increases in blood glucose.Observations of the biologic effects of glucagon, together with data on the rate of its inactivation by the liver, suggest that the basal concentration of this hormone in peripheral plasma probably does not exceed 0.1 mmug per ml.     

Lack of Association Between Residual Insulin Production and Glucagon Response to Hypoglycemia in Youth With Short Duration of Type 1 Diabetes

OBJECTIVE

To examine the loss of glucagon response to hypoglycemia and its relationship with residual β-cell function early in the course of type 1 diabetes (T1D) in youth.

RESEARCH DESIGN AND METHODS

Twenty-one youth with T1D duration <1 year (ages 8–18 years, T1D duration 6–52 weeks) underwent mixed-meal tolerance tests (MMTTs) to assess residual β-cell function and hypoglycemic clamps to assess glucagon responses to hypoglycemia. Glucagon responses to hypoglycemia in T1D subjects were compared with those in 12 nondiabetic young adults (ages 19–25 years).

RESULTS

Peak MMTT-stimulated C-peptide levels (range 0.12–1.43) were ≥0.2 nmol/L in all but one T1D subject. As expected, the median of glucagon responses to hypoglycemia in the T1D subjects (18 pg/mL [interquartile range 7–32]) was significantly reduced compared with the responses in nondiabetic control subjects (38 pg/mL [19–66], P = 0.02). However, there was no correlation between the incremental increase in plasma glucagon during the hypoglycemic clamp and the incremental increase and peak plasma C-peptide level during the MMTT. Similarly, the seven T1D subjects who failed to achieve an increase in glucagon ≥12 pg/mL (i.e., 3 SD above baseline values) had C-peptide response ≥0.2 nmol/L (0.54–1.12), and the one T1D subject with peak stimulated <0.2 nmol/L had a 14 pg/mL increase in plasma glucagon in response to hypoglycemia.

CONCLUSIONS

Impaired plasma glucagon responses to hypoglycemia are evident in youth with T1D during the first year of the disease. Moreover, defective and absent glucagon responses to hypoglycemia were observed in patients who retained clinically important residual endogenous β-cell function.There are a number of defects in counterregulatory hormone responses that make patients with type 1 diabetes (T1D) especially vulnerable to hypoglycemia (1). Unlike healthy nondiabetic subjects, patients with T1D on exogenous insulin are unable to suppress endogenous insulin secretion in response to falling plasma glucose levels, and excess exogenous insulin may result in inappropriately elevated insulin levels. In addition, plasma epinephrine responses are impaired in intensively treated patients (2,3) as a result of recurrent episodes of biochemical hypoglycemia (4) and at night during sleep (5,6). Perhaps most importantly, plasma glucagon responses to hypoglycemia are completely lost in almost all patients with long-standing T1D (7,8).Despite their central role in glucose counterregulation, the natural history and pathophysiology of the loss of the responsiveness of the α-cell to hypoglycemia in T1D patients have not been established in adults or children. In youth with T1D, previous studies that examined counterregulatory hormone responses to hypoglycemia were carried out in patients who already manifested absent plasma glucagon responses (9–12) and in subjects shortly after diagnosis in which glucagon response did not differ from those with long-standing disease (13). Siafarikas et al. (14) recently reported the loss of glucagon response to hypoglycemia occurring at a median of 8 months’ disease duration in adolescents with T1D. In that study of 28 subjects, roughly one-half of the subjects were diagnosed in the past year; however, disease duration ranged from 0.01 to 9.9 years. Although the β-cell is targeted by autoimmune destruction, the same is not true for the α-cells, as secretion of glucagon is preserved to other stimuli such as mixed-meal ingestion (15) or arginine infusion and may even be exaggerated in response to a mixed-meal feeding (16,17). Therefore, dysregulation of α-cell function rather than α-cell destruction appears to be the cause of the loss of glucagon responses to hypoglycemia in patients with T1D.The intraislet insulin hypothesis postulates that a reduction in insulin levels within the islet resulting from a decrease in insulin secretion in response to falling plasma glucose levels is needed to stimulate increases in glucagon secretion and circulating plasma glucagon concentrations (1,18). A number of animal and human studies have been conducted that support this hypothesis (1,17,19–24). The hypothesis also suggests that if patients maintained residual β-cell function, they would retain their ability to mount a glucagon response to hypoglycemia. In order to examine the natural history of the loss of glucagon response to hypoglycemia and its relationship to residual β-cell function early in the course of T1D, we performed one-step hypoglycemic clamps and mixed-meal tolerance tests (MMTTs) in children and adolescents with T1D with a disease duration that ranged between 6 and 52 weeks. The changes in plasma glucagon in our youth with T1D were also compared with those in healthy young-adult subjects who underwent a similar one-step hypoglycemic clamp study.     

Hepatic Autophagy in Uncontrolled Experimental Diabetes and Its Relationships to Insulin and Glucagon

Exogenous glucagon is known to increase hepatic lysosomes, but the relationships between endogenous glucagon and insulin levels and hepatic lysosomes have not been examined. To determine if the hormones of the pancreatic islets influence the development of these organelles glycogenosomes, dense bodies, and autophagosomes were morphometrically quantitated in normal rats, in rats with mild streptozotocin diabetes with normal hormone levels, and in rats with severe streptozotocin diabetes with hyperglucagonemia, hypo-insulinemia, and clinical evidence of uncontrolled diabetes and ketoacidosis. In the latter volume density of lysosomes averaged 222.8x10(-4) (SEM +/-19.8x10(-4)), significantly above the control value of 75x10(-4) (SEM +/-7.0x10(-4)) (P<0.0005); glycogenosomes were absent in the diabetics, the increase being largely the result of increased autophagosomes. Insulin treatment corrected the hyperglucagonemia, hypoinsulinemia, and other manifestations of uncontrolled diabetes and reduced the volume density of lysosomes to 37.4x10(-4) (SEM +/-2.0x10(-4)), significantly below both the untreated diabetic rats and the nondiabetic controls (P<0.0025). In mild streptozotocin diabetes, in which hyperglucagonemia, hypoinsulinemia, and other evidence of uncontrolled diabetes were absent, lysosomes averaged 77.6x10(-4) (SEM +/-5.5x10(-4)), not different from the controls. A statistically significant correlation between all measurements of lysosomal volume density and plasma glucagon was observed (r=0.79; P<0.001). It is concluded that uncontrolled streptozotocin diabetes in rats is accompanied by hepatic autophagy which may be related to the increased plasma glucagon level and/or the decreased insulin and which is corrected by insulin therapy.     

Glucagon and Insulin Binding to Liver Membranes in a Partially Nephrectomized Uremic Rat Model

To investigate the role of glucagon and insulin receptor binding in the glucagon hypersensitivity and insulin resistance which characterize the glucose intolerance of uremia, liver plasma membranes were prepared from control rats (blood urea nitrogen [BUN] 15+/-1 mg/100 ml, creatinine 0.7+/-0.2 mg/100 ml), and from 70% nephrectomized rats (BUN 30+/-2 mg/100 ml, creatinine 2.2+/-0.2 mg/100 ml), and from 90% nephrectomized rats (BUN 46+/-3 mg/100 ml, creatinine 4.20+/-0.7 mg/100 ml), 4 wk after surgery. As compared to controls, the 90% nephrectomized rats had significantly higher levels of plasma glucose (95+/-4 vs. 125+/-11 mg/100 ml), plasma insulin (28+/-9 vs. 52+/-11 muU/ml), and plasma glucagon (28+/-5 vs. 215+/-18 pg/ml). Similar, but less marked, elevations were observed in the 70% nephrectomized animals.In liver plasma membranes from nephrectomized rats, specific binding of (125)I-glucagon was increased by 80-120%. Furthermore, glucagon (2 muM)-stimulated adenylate cyclase activity in nephrectomized rats was twofold higher than in controls. In contrast, fluoridestimulated adenylate cyclase activity was similar in both groups of rats. In marked contrast to glucagon binding, specific binding of (125)I-insulin to liver membranes from nephrectomized rats was reduced by 40-50% as compared to controls. Data analysis suggested that the changes in both glucagon and insulin binding are a consequence of alterations in binding capacity rather than changes in affinity. Liver plasma membranes from nephrectomized rats degraded (125)I-glucagon and (125)I-insulin to the same extent as control rats.THESE RESULTS DEMONSTRATE THAT: (a) the 70 and 90% nephrectomized rats simulate the hyperglycemia, hyperinsulinemia, and hyperglucagonemia observed in clinical uremia; (b) in these animals specific binding of glucagon to liver membranes is increased and is accompanied by higher glucagon-stimulated adenylate cyclase activity; and (c) specific binding of insulin is markedly decreased. These findings thus provide evidence of oppositely directed, simultaneous changes in glucagon and insulin receptor binding in partially nephrectomized rats. Such changes may account for the hypersensitivity to glucagon and may contribute to resistance to insulin observed in the glucose intolerance of uremia.     

Opposing Actions of Glucagon and Insulin on Splanchnic D Cell Function

The effect of glucagon at various infusion rates on plasma levels of somatostatin-like immunoreactivity (SLI) was examined in conscious normal and chronic alloxan diabetic dogs. In normal dogs glucagon infused at 6, 36, and 120 ng/kg per min did not affect the peripheral venous plasma SLI levels. In diabetic dogs, however, peripheral venous plasma SLI levels in inferior vena cava rose significantly from a mean base-line value of 181±9 pg/ml to a peak value of 279±38 pg/ml during the infusion of 120 μg/kg per min of glucagon, which raised plasma immunoreactive glucagon to >5,000 pg/ml. This glucagon-mediated increase was completely abolished by coinfusion of 7 mU/kg per min of insulin, a rate that maintained the ratio of insulin to glucagon at approximately the baseline value.     

Genome-Wide Meta-analysis Identifies Genetic Variants Associated With Glycemic Response to Sulfonylureas

OBJECTIVESulfonylureas, the first available drugs for the management of type 2 diabetes, remain widely prescribed today. However, there exists significant variability in glycemic response to treatment. We aimed to establish heritability of sulfonylurea response and identify genetic variants and interacting treatments associated with HbA_1c reduction.RESEARCH DESIGN AND METHODSAs an initiative of the Metformin Genetics Plus Consortium (MetGen Plus) and the DIabetes REsearCh on patient straTification (DIRECT) consortium, 5,485 White Europeans with type 2 diabetes treated with sulfonylureas were recruited from six referral centers in Europe and North America. We first estimated heritability using the generalized restricted maximum likelihood approach and then undertook genome-wide association studies of glycemic response to sulfonylureas measured as HbA_1c reduction after 12 months of therapy followed by meta-analysis. These results were supported by acute glipizide challenge in humans who were naïve to type 2 diabetes medications, cis expression quantitative trait loci (eQTL), and functional validation in cellular models. Finally, we examined for possible drug-drug-gene interactions.RESULTSAfter establishing that sulfonylurea response is heritable (mean ± SEM 37 ± 11%), we identified two independent loci near the GXYLT1 and SLCO1B1 genes associated with HbA_1c reduction at a genome-wide scale (P < 5 × 10⁻⁸). The C allele at rs1234032, near GXYLT1, was associated with 0.14% (1.5 mmol/mol), P = 2.39 × 10⁻⁸), lower reduction in HbA_1c. Similarly, the C allele was associated with higher glucose trough levels (β = 1.61, P = 0.005) in healthy volunteers in the SUGAR-MGH given glipizide (N = 857). In 3,029 human whole blood samples, the C allele is a cis eQTL for increased expression of GXYLT1 (β = 0.21, P = 2.04 × 10⁻⁵⁸). The C allele of rs10770791, in an intronic region of SLCO1B1, was associated with 0.11% (1.2 mmol/mol) greater reduction in HbA_1c (P = 4.80 × 10⁻⁸). In 1,183 human liver samples, the C allele at rs10770791 is a cis eQTL for reduced SLCO1B1 expression (P = 1.61 × 10⁻⁷), which, together with functional studies in cells expressing SLCO1B1, supports a key role for hepatic SLCO1B1 (encoding OATP1B1) in regulation of sulfonylurea transport. Further, a significant interaction between statin use and SLCO1B1 genotype was observed (P = 0.001). In statin nonusers, C allele homozygotes at rs10770791 had a large absolute reduction in HbA_1c (0.48 ± 0.12% [5.2 ± 1.26 mmol/mol]), equivalent to that associated with initiation of a dipeptidyl peptidase 4 inhibitor.CONCLUSIONSWe have identified clinically important genetic effects at genome-wide levels of significance, and important drug-drug-gene interactions, which include commonly prescribed statins. With increasing availability of genetic data embedded in clinical records these findings will be important in prescribing glucose-lowering drugs.     

Predicting the Glycemic Response to Gastric Bypass Surgery in Patients With Type 2 Diabetes

OBJECTIVE

To find clinically meaningful preoperative predictors of diabetes remission and conversely inadequate glycemic control after gastric bypass surgery. Predicting the improvement in glycemic control in those with type 2 diabetes after bariatric surgery may help in patient selection.

RESEARCH DESIGN AND METHODS

Preoperative details of 154 ethnic Chinese subjects with type 2 diabetes were examined for their influence on glycemic outcomes at 1 year after gastric bypass. Remission was defined as HbA_1c ≤6%. Analysis involved binary logistic regression to identify predictors and provide regression equations and receiver operating characteristic curves to determine clinically useful cutoff values.

RESULTS

Remission was achieved in 107 subjects (69.5%) at 12 months. Diabetes duration <4 years, body mass >35 kg/m², and fasting C-peptide concentration >2.9 ng/mL provided three independent preoperative predictors and three clinically useful cutoffs. The regression equation classification plot derived from continuous data correctly assigned 84% of participants. A combination of two or three of these predictors allows a sensitivity of 82% and specificity of 87% for remission. Duration of diabetes (with different cutoff points) and C-peptide also predicted those cases in which HbA_1c ≤7% was not attained. Percentage weight loss after surgery was also predictive of remission and of less satisfactory outcomes.

CONCLUSIONS

The glycemic response to gastric bypass is related to BMI, duration of diabetes, fasting C-peptide (influenced by insulin resistance and residual β-cell function), and weight loss. These data support and refine previous findings in non-Asian populations. Specific ethnic and procedural regression equations and cutoff points may vary.Surgery is the most effective treatment for clinically severe obesity. Although most patients display a dramatic improvement in type 2 diabetes, not every patient has remission of diabetes after surgery, with some not seeing substantial improvement and many having recurrence at a later date, sometimes in association with weight regain (1–5). Bariatric surgery, now often referred to as “metabolic surgery,” has been recommended as an effective treatment option for type 2 diabetes for those obese patients who do not have satisfactory control with lifestyle change (1). Optimal outcomes of surgical treatment of diabetes will be obtained if the patients best suited to the surgery are selected, but a clinically relevant grading system to categorize and predict outcomes of metabolic surgery is lacking (1). To develop such a grading system, the responses of patients to metabolic surgery need to be carefully observed, and the characteristics of responders that may have predicted their successful outcomes must be identified. Perhaps even more important is the identification of a group that does not respond well to metabolic surgery, so that such patients are not exposed to the unnecessary risk of surgery without expectation of clear benefit.Many preoperative patient factors have been associated with outcomes, including age, diabetes duration, glycemic control (HbA_1c), fasting C-peptide concentration, BMI, ethnicity, and medications used to manage blood glucose, including oral hypoglycemic agents and insulin (6–10). There are a number of weaknesses in many of these studies, and these include insufficient numbers to identify all independent clinically relevant factors, dealing in a univariate manner with a number of factors that are clearly related to one another, use of varying criteria for remission, and failure to record potentially important clinical predictors.The primary aim of this study was to seek, in a clinically meaningful way, the preoperative predictors of diabetes remission (HbA_1c ≤6.0%) at 12 months after gastric bypass surgery in a cohort of ethnic Chinese patients with type 2 diabetes who reside in Taiwan. Secondary aims included the identification of preoperative predictors of HbA_1c ≤7.0% at 12 months, a comparison of the effectiveness of mini gastric bypass (MGB) and Roux-en-Y gastric bypass (RYGB) for weight loss and glycemic control, and examination of the relevance of weight loss after gastric bypass as a predictor of diabetes remission.     

Use of an Insulin Bolus Advisor Improves Glycemic Control in Multiple Daily Insulin Injection (MDI) Therapy Patients With Suboptimal Glycemic Control: First results from the ABACUS trial

OBJECTIVE

Use of automated bolus advisors is associated with improved glycemic control in patients treated with insulin pump therapy. We conducted a study to assess the impact of using an insulin bolus advisor embedded in a blood glucose (BG) meter on glycemic control and treatment satisfaction in patients treated with multiple daily insulin injection (MDI) therapy. The study goal was to achieve >0.5% A1C reduction in most patients.

RESEARCH DESIGN AND METHODS

This was a 26-week, prospective, randomized, controlled, multinational study that enrolled 218 MDI-treated patients with poorly controlled diabetes (202 with type 1 diabetes, 16 with type 2 diabetes) who were 18 years of age or older. Participants had mean baseline A1C of 8.9% (SD, 1.2 [74 mmol/mol]), mean age of 42.4 years (SD, 14.0), mean BMI of 26.5 kg/m² (SD, 4.2), and mean diabetes duration of 17.7 years (SD, 11.1). Control group (CNL) patients used a standard BG meter and manual bolus calculation; intervention group (EXP) patients used the Accu-Chek Aviva Expert meter with an integrated bolus advisor to calculate insulin dosages. Glucose data were downloaded and used for therapy parameter adjustments in both groups.

RESULTS

A total of 193 patients (CNL, n = 93; EXP, n = 100) completed the study. Significantly more EXP than CNL patients achieved >0.5% A1C reduction (56.0% vs. 34.4%; P < 0.01). Improvement in treatment satisfaction (Diabetes Treatment Satisfaction Questionnaire scale) was significantly greater in EXP patients (11.4 [SD, 6.0] vs. 9.0 [SD, 6.3]; P < 0.01). Percentage of BG values <50 mg/dL was <2% in both groups during the study.

CONCLUSIONS

Use of an automated bolus advisor resulted in improved glycemic control and treatment satisfaction without increasing severe hypoglycemia.Intensive insulin therapy using multiple daily insulin injections (MDI) is efficacious in achieving and maintaining optimal glycemic control (1,2). Effective use of MDI therapy requires patients to use several factors, including insulin-to-carbohydrate (CHO) ratios, insulin sensitivity factors (ISFs), target blood glucose (BG) range, current BG values, anticipated physical activity, and general health status, to accurately determine their appropriate insulin doses.Because manual calculation of insulin boluses is complex and time-consuming, patients may rely on empirical estimates, which can limit their ability to achieve treatment goals (3). Moreover, many patients are limited in their ability to perform these calculations because of inadequate literacy and inadequate numeracy, which are common among patients with diabetes and are associated with poor glycemic control (4,5).In addition to the potential for computation errors, manual bolus calculation does not take into account the effect of the active insulin that remains from the initial bolus (“insulin on-board”). This can create a high potential for errors when determining a correction bolus, potentially resulting in severe hypoglycemia, which can be debilitating, frightening, and socially aversive (6).Automated bolus advisors integrated into BG meters may help overcome these challenges, improve self-care behaviors, and reduce the risk for long-term complications. Bolus advisors automatically calculate bolus insulin doses to cover CHO intake and address out-of-range BG levels based on individualized insulin parameter estimates. Several studies with patients treated with insulin pump therapy have shown that use of automated bolus advisors facilitates improvements in glycemic control and reductions in hypoglycemic events (7–10).Although a number of small studies have shown that the use of these devices is also beneficial in improving glycemic control (11,12), treatment satisfaction (11), and overall accuracy in bolus insulin calculation (13) in MDI-treated patients, no large randomized trials have been conducted to fully assess the impact and utility of automated bolus advisor use in this population.We hypothesized that use of an automated bolus advisor would enable more MDI-treated patients to achieve clinically significant improvements in glycemic control compared with patients who calculated their bolus insulin doses manually. To test this hypothesis, we designed a large randomized trial using a new automated bolus advisor system that integrates bolus calculations into a BG meter.     

Glucose Modulation of Amino Acid-Induced Glucagon and Insulin Release in the Isolated Perfused Rat Pancreas

Interactions between glucose and arginine and a mixture of 20 amino acids found in normal rat serum were studied in the isolated perfused rat pancreas of normal rats, with release of immunoreactive glucagon and insulin as parameters. Secretion of both pancreatic hormones was low during the steady state, whether glucose (5 mM) was included in the perfusion medium or not. This glucose concentration significantly stimulated insulin release twofold and resulted in an 80% inhibition of basal glucagon release. Arginine and the amino acid mixture were potent stimulants of both hormones. Secretion of both hormones followed identical biphasic response patterns after addition of arginine or the amino acid mixture. However, stimulation of insulin release occurred only when glucose was included, whereas both phases of glucagon release were elicited in the absence of glucose and markedly reduced in its presence. The dose-dependency curves of hormone release due to arginine on one hand and the amino acid mixture on the other differed substantially: with arginine, release of insulin and glucagon was linear between a concentration of 0.3 and 20 mM. In contrast, the amino acid mixture resulted in half-maximal release for both hormones between a concentration of 3 and 4.5 mM, and maximal release between 6 and 8 mM. The dose-dependencies of glucose modulation of alpha- and beta-cell activity were also different: when the amino acid mixture was maintained at 15 mM and glucose varied (0-6.25 nM), no insulin release occurred until glucose was above 2.5 mM, whereas incremental inhibition of glucagon occurred through the complete dose range. It was also observed that glucose inhibition of amino acid-stimulated glucagon release was dissociated from glucose-dependent increase of insulin release.THESE STUDIES INDICATE THAT: (a) the alpha-cell, like the beta-cell, secretes at a low basal rate; (b) hypoglycemia per se is a weak stimulus for glucagon secretion compared to the high efficacy of a physiologic amino acid mixture; (c) glucose plays opposite roles in the mechanisms leading to amino acid-induced hormone release from the alpha- and beta-cells, functioning as an inhibitor in the first case and a permissive agent in the second, and (d) the data are compatible with the postulated existence of glucose and amino acid receptors in both the alpha- and beta-cells.     

Insulin and Glucagon Release from Monolayer Cell Cultures of Pancreas from Newborn Rats

Abstract. Monolayer culture of pancreatic cells from newborn rats has been shown to yield ultrastructurally normal endocrine cells, virtual absence of differentiated exocrine cells, and the maintenance of the capacity to synthesize immuno-reactive insulin (IRI) and glucagon (ERG). Such a preparation has potential advantages for the study of mechanisms of hormone synthesis and release. Therefore, a survey of factors influencing hormone content and release from cultured cells was undertaken. The following general features were demonstrated: (1) highly reproducible responses within a given preparation of cells despite (2) some variations of absolute hormone content and release between preparations, (3) suitability for preparing sufficient quantities of cells to permit the simultaneous comparison of several factors within a given preparation, and (4) persistence of physiological responses to known modulators of IRI and IRG release. Thus, IRI release was stimulated in concentration-related fashion by glucose. Amino acids, tolbutamide and glucagon augmented release, and 2-deoxy-D-glucose, mannoheptulose and diazoxide inhibited glucose-induced release. Epinephrine inhibited glucose-induced IRI release through stimulation of an α-adrenergic receptor mechanism, and the presence of probable β-receptor stimulation of release was also demonstrated. Agents affecting the microtubular-microfilamentous system exerted effecte similar to those demonstrated in other preparations. Ouabain, as well as the absence or augmented potassium in the medium increased IRI release in the presence of non-stimulatory 2.75 mM glucose, whereas absence of calcium inhibited the response to 11 mM glucose without affecting baseline, non-stimulated release. IRG release was shown to be inversely related to the glucose concentration in the medium. It was stimulated by epinephrine, arginine, alanine, lactate and pyruvate, and inhibited by β-hydroxybutyrate. Diazoxide alone had no effect on IRG release. The monolayer culture employed in these studies provides a convenient, reproducible system for the further study of adult-type IRI and IRG secretory behaviour. In addition to acute or short-term regulation it may be especially suited for the study of long-term modulating effects during the culture period.     

The Effect of DPT-1 Intravenous Insulin Infusion and Daily Subcutaneous Insulin on Endogenous Insulin Secretion and Postprandial Glucose Tolerance

OBJECTIVETo investigate the effect of parenteral insulin therapy on endogenous insulin secretion in the Diabetes Prevention Trial–Type 1 (DPT-1).RESULTSIV-I suppressed fasting and OGTT-stimulated C-peptide (62% and 40%, respectively), and it significantly lowered fasting glucose (67.4 ± 4.5 mg/dL during IV-I vs. 90.9 ± 1.8 mg/dL off insulin; P < 0.05). By contrast, post-OGTT glucose levels were significantly higher during IV-I: Glucose during IV-I versus off insulin at 120 min was 203.9 ± 15.1 vs. 151.6 ± 10.2 mg/dL, respectively (P < 0.05); 49% of OGTTs became transiently diabetic (>200 mg/dL at 120 min) when receiving IV-I. Fasting glucose was significantly lower when receiving SC-I versus when off insulin (85 ± 3 vs. 94 ± 2 mg/dL, respectively; P < 0.05), but SC-I did not significantly alter fasting or OGTT-stimulated C-peptide compared with being off insulin.CONCLUSIONSThese data demonstrate that the IV-I used in the DPT-1 markedly suppressed endogenous insulin secretion, which was frequently associated with postprandial glucose intolerance. SC-I, however, did not.     

胰岛素泵治疗2型糖尿病患者的临床疗效观察

[目的]评价胰岛素泵在2型糖尿病病人中的治疗效果.[方法]68例2型糖尿病患者分为两组进行胰岛素强化治疗,胰岛素泵持续皮下胰岛素输注(CSII)组32例,多次皮下胰岛素注射(MSII)组36例.[结果]两组达到目标血糖时,CSII组所需的治疗时间,胰岛素量以及低血糖发生率明显比MSII减少(P＜0.01或P＜0.05).[结论]CSII比MSII可以更快、更有效地控制高血糖,降低低血糖的发生率.     

Varicella-Zoster Virus and Subcutaneous Cytarabine: Correlation of In Vitro Sensitivities to Blood Levels

The susceptibility of 26 strains of varicella-zoster virus to cytarabine was tested in vitro by measuring reduction in number and size of plaques using human foreskin fibroblast cells. Most strains showed 50% reduction of plaque number by 0.125 mug of cytarabine per ml or less. Cytarabine levels in sera of 12 patients after a single subcutaneous injection of 50 mg/M(2) exceeded this inhibitory level for a period of 75 min. Thus, the subcutaneous route is a potentially useful method of administration of cytarabine for antiviral drug trials.     

Childhood Predictors of Adult Acute Insulin Response and Insulin Action

OBJECTIVE

Because declines in acute insulin response (AIR) and insulin action (M) predict development of type 2 diabetes, we sought to determine childhood factors that predict insulin action and AIR using longitudinal data from young Pima Indian adults with normal glucose regulation.

RESEARCH DESIGN AND METHODS

Predictors of adult M, measured by the euglycemic-hyperinsulinemic clamp, and AIR, measured after a 25-g glucose bolus, were assessed in 76 individuals from a set of childhood data (BMI, systolic blood pressure [sBP] and diastolic blood pressure, cholesterol, fasting and 2-h insulin, and glucose levels during an oral glucose tolerance test).

RESULTS

After adjustment for sex, adult percent body fat, adult and childhood age, childhood BMI, and sBP were negative and independent predictors of adult M. A 5 kg/m² increase in childhood BMI was associated with a 7.4% decrease in adult insulin action (95% CI −12.7 to −1.8%, P = 0.01) and a 10-mmHg increase in childhood sBP with a 5.0% decrease in adult M (95% CI −8.4 to −1.4%, P = 0.007). After a similar adjustment with M as an additional covariate, childhood 2-h insulin was a positive predictor of adult AIR such that a 25% increase predicted a 7.3% increase in adult AIR (95% CI 1.5–13.5%, P = 0.014).

CONCLUSIONS

Childhood insulin response during an oral glucose challenge predicts adult AIR, indicating that β-cell capacity may be set early in life. Childhood measures related to adiposity predict adult insulin action, which may reflect common underlying mechanisms that may be amenable to modification through programs targeting prevention or treatment of childhood obesity.Type 2 diabetes is a lifelong process progressing from normal glucose regulation to impaired glucose regulation and ultimately to diabetes (1). If lifestyle interventions are initiated in people with impaired glucose regulation, type 2 diabetes can be prevented, at least in the short term (2). However, over longer periods, once impaired glucose regulation has occurred, a large proportion of people may eventually develop type 2 diabetes despite preventive efforts (3). Development of type 2 diabetes is preceded by declines in insulin release from pancreatic islet cells and insulin sensitivity such that even in people with normal glucose regulation, these two measures predict subsequent type 2 diabetes (4). It has been shown that defects in these two factors occur early in the natural history of diabetes before clinically apparent changes in glucose handling (1).Risk factors including obesity, dyslipidemia, hypertension, and glucose intolerance are known to predict type 2 diabetes (5). Many of these also track from childhood into adulthood (6–8), and it has been shown that early life events such as in utero exposure to diabetes and childhood obesity predict future risk of type 2 diabetes (9,10). The relation of these risk factors during childhood to later adult measures of acute insulin release (AIR) and insulin sensitivity before the development of diabetes is not well defined but may lead to greater understanding of the pathogenesis of type 2 diabetes and point to targets for early intervention.We evaluated a subset of childhood metabolic measures including blood pressure, BMI, cholesterol, and fasting and 2-h glucose (2hG) and insulin (2hIns) levels during an oral glucose tolerance test in the Pima Indians of the Gila River Community of Arizona, a population with a high prevalence of type 2 diabetes. These measures were assessed as potential predictors of insulin action (M) and AIR in adults with normal glucose regulation, before potential pathologic declines in β-cell function.