Fasting Plasma Proinsulin Research Articles

2105-P: Beta Cell PCSK1 Deficiency Increases Diabetes Susceptibility in Male Mice

Proinsulin (PI) is processed to mature insulin by prohormone convertases 1/3 (Pcsk1) and 2 (Pcsk2). In individuals with T1D and T2D, there is an increase in the circulating PI:insulin ratio. We hypothesized that beta-cell Pcsk1 deletion would result in beta-cell dysfunction and hyperglycemia. Male and female Pcsk1flox/flox Ins1cre/+ (Pcsk1beta-KO) and Pcsk1+/+ Ins1cre/+ (Pcsk1beta-WT) mice were fed either a chow or a high fat diet (HFD; 45% fat) and monitored until 30 weeks of age. Despite an approximately 150-fold increase in fasting plasma PI (p < 0.001) and only immature insulin granules detectable by electron microscopy, chow-fed Pcsk1beta-KO male mice had normal glucose tolerance early in life and only developed glucose intolerance by 26 weeks of age (AUC: 934±294 vs. 597±223; p = 0.008). Histological analysis showed that male Pcsk1beta-KO mice displayed a trend toward increased beta-cell area (1.3±0.6 vs. 0.8±0.4%; p = 0.08). The unexpectedly mild hyperglycemia in Pcsk1beta-KO mice is likely due to incomplete disruption of proinsulin processing, as mass spectrometry and western blot analysis of Pcsk1beta-KO islets confirmed markedly elevated proinsulin, but detectable mature insulin. In HFD-fed cohorts, 3/10 Pcsk1beta-KO male mice developed sustained fasting hyperglycemia (>16 mM) after 19 weeks of diet. Chow and HFD-fed female Pcsk1beta-KO mice displayed no differences in glycemia or body weight from Pcsk1beta-WT controls. Deletion of both Pcsk1 and Pcsk2 in beta cells (Pcsk1flox/flox Pcsk2flox/flox Ins1cre/+) resulted in undetectable mature insulin in islets (western blot), and impaired glucose tolerance at 10 weeks of age in both chow-fed male and female mice. Our results suggest that beta-cell Pcsk1 deficiency is not sufficient to drive diabetes development, but increases diabetes susceptibility in conditions of increased insulin secretory demand. Our data in mice support the idea that beta-cell prohormone processing errors likely contribute to pathogenesis of diabetes but not obesity. Disclosure A. Taylor: None. Y. Chen: None. B. Verchere: Advisory Panel; Self; Integrated Nanotherapeutics Inc., Sirona Biochem. Stock/Shareholder; Self; Integrated Nanotherapeutics Inc. Funding Canadian Institutes of Health Research (PJT153156)

P4663Hyperinsulinemia, hypertension and two clusters of biomarkers predict aortic stenosis in 10,144 Finnish men

Abstract BACKROUND Recent studies show that hypertension predicts aortic stenosis (AS). Other predictors of AS are not established. Purpose To investigate a large panel of biomarkers as predictors of AS in the population-based METSIM cohort. Methods Anthropometric, metabolic and inflammatory biomarkers were measured at baseline in the cohort of 10,197 Finnish men. Subjects with AS at baseline (n=53) were excluded from the analyses. Cases of AS were identified from the medical records. Cox regression analysis was used to identify variables predicting AS. Principal components analysis was applied to investigate clustering of variables predicting AS. Uni- and multivariate logistic regression analysis were used to investigate the clusters of biomarkers as predictors of AS. Results Over a mean follow-up time of 10.8 years, incident AS was diagnosed in 116 (1.1%) men. In Cox regression analysis, fasting plasma insulin (9.8±12.8 in men without AS vs. 14.5±18.2 mU/l in men with incident AS; P=6.13 x 10–6) and systolic blood pressure (138.2±16.7 vs. 146.3±19.4 mmHg; P=3.8 x 10–7) were associated with higher risk of AS (HR 1.44 (95% CI 1.23–1.68); P=4.04 x 10–5 and HR 1.54 (1.30–1.83); P=3.01 x 10–7, respectively). Other biomarkers, which significantly predicted AS were age, body mass index, waist, waist/hip ratio, body fat mass percentage, urine albumin, CRP, blood GHbA1C, fasting plasma glucose and proinsulin, oral glucose tolerance test (OGTT) 30 min plasma insulin and proinsulin, OGTT 120 min plasma insulin and proinsulin, and serum C-peptide. Glucose tolerance (ADA 2003), and insulin resistance and insulin secretion indices based on HOMA were significant predictors of AS. After adjusting for age, the same biomarkers except for OGTT 120 min plasma proinsulin, blood GHbA1C and fasting plasma glucose significantly predicted AS. After exclusion of diabetic subjects, all biomarkers mentioned above except for GHbA1C, fasting plasma glucose and glucose tolerance predicted AS in unadjusted Cox models. Two clusters of risk factors were found in principal components analysis, one consisting of fasting plasma insulin, HOMA insulin resistance index, waist/hip ratio, GHbA1c and CRP, and another consisting of age, systolic blood pressure and urine albumin, explaining 38.33 and 15.37% of the total variance, respectively. In univariate logistic regression analysis both clusters predicted AS (HR 1.35 (1.15–1.59); P=2.47 x 10–4 and HR 1.73 (1.46–2.04); P=1.53 x 10–10, respectively), and were statistically significant when entered in the multivariate model (HR 1.30 (1.11–1.52); P=1.01 x 10–3 and HR 1.69 (1.43–1.99); P=5.84 x 10–10, respectively). Conclusion In the present large-scale population-based study, several biomarkers, particularly hyperinsulinemia and systolic blood pressure, predicted AS. In addition, two clusters of biomarkers, one with high loading on insulin and another on systolic blood pressure, independently predicted AS. Acknowledgement/Funding Kuopio University Hospital ja Academy of Finland

Exercise training and metformin, but not exercise training alone, decreases insulin production and increases insulin clearance in adults with prediabetes.

Adding metformin to exercise does not augment the effect of training alone to boost whole body insulin sensitivity and lower circulating insulin concentrations. Although lower insulin concentrations (lower supply) following lifestyle and/or pharmacological interventions are primarily attributed to reductions in insulin secretion that match increases in peripheral insulin sensitivity (lower demand), it is unclear whether exercise and/or metformin exert direct effects on insulin production, extraction, or clearance. Thirty-six middle-aged, obese, sedentary adults with prediabetes were randomized to placebo (P), metformin (M), exercise and placebo (E+P), or exercise and metformin (E+M) for 12 wk. Fasting plasma proinsulin (an indicator of insulin production), C-peptide, insulin, and glucose were collected before and after the intervention. Peripheral insulin sensitivity (euglycemic clamp), hepatic insulin extraction, insulin clearance, body weight, and cardiorespiratory fitness were also measured. Fasting proinsulin was unchanged following P (19.4 ± 10.1 vs. 22.6 ± 15.0 pmol/l), E+P (15.1 ± 7.4 vs. 15.5 ± 7.4 pmol/l), or M (24.8 ± 18.9 vs. 16.7 ± 20.3 pmol/l) but was significantly reduced after E+M (18.6 ± 11.9 vs. 13.9 ± 6.7 pmol/l; P = 0.04). Insulin clearance was significantly greater following M (384.6 ± 19.4 vs. 477.4 ± 49.9; P = 0.03) and E+M (400.1 ± 32.0 vs. 482.9 ± 33.9; P = 0.02) but was unchanged in P or E+P. In this study, metformin combined with exercise training reduced circulating proinsulin, and both groups taking metformin increased insulin clearance. This suggests that adding metformin to exercise may augment or attenuate training effects depending on the outcome or organ system being assessed.NEW & NOTEWORTHY Exercise is increasingly viewed as medication, creating a need to understand its interactions with other common medications. Research suggests metformin, a widely prescribed diabetes medication, may diminish the benefits of exercise when used in combination. In this study, however, metformin combined with exercise training, but not exercise alone, lowered proinsulin concentrations and increased insulin clearance in adults with prediabetes. This may directly influence personalized prescriptions of lifestyle and/or pharmacology to reduce diabetes risk.

Proinsulin in Healthy Pregnancy, Pregnancy with Gestational Diabetes and after Delivery

Summary The aim of the present study was to evaluate the levels of pro-insulin and pro-insulin/ insulin ratio (PIR) in pregnant with normal glucose tolerance (NGT), pregnant with gestational diabetes mellitus (GDM) and women after delivery with GDM history. Normal pregnancy is characterized by progressive insulin resistance, which is physiologically compensated by an increase in insulin secretion. The higher secretion of the insulin precursor pro-insulin has been associated with β-cell dysfunction. A total of 102 pregnant women between 24-28 gestational weeks (53 GDM pregnant, 49 with NGT) and 22 postpartum with GDM history, as assessed by a 2h oral glucose tolerance test, were included in the study. Fasting plasma insulin and pro-insulin (PI) concentrations at the basal state were measured in all women. The ratio pro-insulin/insulin was calculated. BMI was significantly higher in GDM pregnant compared to NGT weight-matched group (30.56 ± 6.9 vs. 30.56 ± 6.9; p < 0, 011) and compared to the levels after delivery (30.56 ± 6.9vs. 27.9 ± 6, 27; p < 0, 001). Significant differences in the levels of PI between NGT and GDM pregnant (3.94 ± 2.78 vs. 7.59 ± 5.27; p = 0.006), between GDM and postpartum women (7.59 ± 5.27 vs. 4.46 ± 1.14; p = 0.022) were established. No signifi cant difference in the level of PIR between two pregnant groups was observed. Separately NGT and GDM showed signifi cant difference compared to young mothers (0.41 ± 0.14 vs. 0.148 ± 0.031, p < 0.02; 0.46 ± 0.16 vs. 0.148 ± 0.031, p = 0.009). Fasting insulin was statistically higher in GDM pregnant compare to NGT and women after delivery (13.84 ± 8.43 vs. 11.35 ± 7.38, p = 0.02; 13.84 ± 8.43 vs. 10.60 ± 7.53, p < 0.01). The correlation between PIR and BMI in the three groups studied were r = 0.416; r = 0,741; r = 0,556 (with statistical significance p = 0.01 between NGT and GDM pregnancy, p = 0.02 between GDM pregnancy and postpartum, p < 0.0001 between NGT pregnancy and young mother with GDM history). In our study, comparison of PI levels between pregnant with NGT and GDM demonstrated that the OR of developing GDM was 1.194 (95% CI, 1.028-1.329, P = 0.001). Increasing the value of PI with 10 pmol/l increases the risk for development of GDM with 19.4%. According to our results, pregnant with GDM have elevated levels of pro-insulin and PIR which could serve as a markers for this condition. These results support our findings about relationship and influence of BMI on β-cell functions, established in this study with normotolerant, gestational diabetes pregnant and women postpartum with GDM history. These results demonstrate that gestational diabetics have abnormalities in pancreatic beta-cell secretion, which are likely to be important both in the etiology of gestational diabetes and non-insulin dependent diabetes.

Vildagliptin compared to glimepiride on post-prandial lipemia and on insulin resistance in type 2 diabetic patients

ObjectivesTo evaluate the effects of vildagliptin compared to glimepiride on glycemic control, insulin resistance and post-prandial lipemia. Material and Methods167 type 2 diabetic patients, not adequately controlled by metformin, were randomized to vildagliptin 50mg twice a day or glimepiride 2mg three times a day for 6months, in a double blind, randomized clinical trial. We evaluated: body mass index (BMI), glycemic control, fasting plasma insulin (FPI), homeostasis model assessment insulin resistance index (HOMA-IR), fasting plasma proinsulin (FPPr), glucagon, lipid profile, resistin, retinol binding protein-4 (RBP-4), visfatin and vaspin. Furthermore, at the randomization and at the end of the study all patients underwent an euglycemic hyperinsulinemic clamp to evaluate M value and an oral fat load. ResultsDespite a similar decrease of glycated hemoglobin, there were an increase of body weight with glimepiride+metformin and a decrease with vildagliptin+metformin. Fasting plasma insulin increased with glimepiride+metformin, while it did not change with vildagliptin+metformin. Vildagliptin+metformin improved lipid profile. Regarding insulin sensitivity, vildagliptin+metformin increased M value. Resistin, RBP-4, vaspin and visfatin were decreased by vildagliptin+metformin, but in group to group comparison, only vaspin reduction resulted statistically significant. Vildagliptin+metformin reduced post-prandial lipemia and insulinemia compared to glimepiride+metformin. ConclusionVildagliptin, in addition to metformin, was more effective than glimepiride+metformin in reducing insulin resistance and post-prandial lipemia.

Variation in Inflammatory Markers and Glycemic Parameters After 12 Months of Exenatide Plus Metformin Treatment Compared with Metformin Alone: A Randomized Placebo-Controlled Trial

To evaluate the effects of exenatide on some inflammatory markers and to quantify the effect of exenatide on β-cell function. A randomized, double-blind, placebo-controlled trial. Seven hospitals in Italy. A total of 174 white treatment-naive adults with type 2 diabetes and a glycated hemoglobin (HbA(1c)) level higher than 7.5%. After an open-label run-in period of 8 ± 2 months with metformin, patients were randomized to take exenatide (5 μg twice/day for the first 4 weeks, 10 μg twice/day thereafter) or a placebo volume equivalent for 12 months. Body mass index, HbA(1c), fasting plasma glucose, postprandial plasma glucose, fasting plasma insulin (FPI), homeostasis model assessment insulin resistance index, homeostasis model assessment β-cell function index (HOMA-β), fasting plasma proinsulin (FPPr), proinsulin-to-fasting plasma insulin ratio (Pr:FPI ratio), C-peptide, glucagon, vaspin, chemerin, and resistin were evaluated at baseline, at randomization, and at 3, 6, 9, and 12 months. Patients also underwent a combined euglycemic, hyperinsulinemic, and hyperglycemic clamp with subsequent arginine stimulation to assess insulin sensitivity and insulin secretion. HbA(1c) was significantly improved with exenatide plus metformin compared with placebo plus metformin. Exenatide plus metformin was also significantly more effective than placebo plus metformin in increasing HOMA-β C-peptide, and all measures of β-cell function after the euglycemic hyperinsulinemic and hyperglycemic clamp. We observed that exenatide plus metformin also reduced resistin compared with placebo plus metformin. No variations in vaspin and chemerin were noted in group-to-group comparisons. We observed a significant correlation between M value increase, an index of insulin sensitivity, and a decrease in inflammatory parameters in the exenatide plus metformin group. The combination of exenatide plus metformin was more effective than metformin alone in improving glycemic control, β-cell function, and inflammatory parameters.

RETRACTED: Evaluation of the positive effects on insulin-resistance and β-cell measurements of vildagliptin in addition to metformin in type 2 diabetic patients

We evaluated the positive effects of vildagliptin in addition to metformin on glycemic control and β-cell function in type 2 diabetic patients. One hundred and seventy-one type 2 diabetic patients were instructed to add vildaglipin 50mg twice a day or placebo to metformin for 12 months. Body mass index (BMI), glycemic control, fasting plasma insulin (FPI), HOMA-IR, HOMA-β, fasting plasma proinsulin (FPPr), proinsulin/fasting plasma insulin ratio (Pr/FPI ratio), C-peptide, glucagon, vaspin, visfatin, and omentin-1 were evaluated. Before, and after 12 months since the addition of vildagliptin, patients underwent a combined euglycemic hyperinsulinemic and hyperglycemic clamp, with subsequent arginine stimulation. Vildagliptin+metformin were more effective than placebo+metformin in reducing body weight and BMI, glycemic control, HOMA-IR, glucagon and insulin resistance measurements. Vildagliptin+metformin gave also a better increase of HOMA-β, and of all β-cell parameters after the clamp. We also recorded a significant correlation between M value increase and the decrease of vaspin, visfatin, and omentin-1 obtained with vildagliptin+metformin. Vildagliptin, in addition to metformin, proved to be effective in improving β-cell function and in reducing insulin resistance measurements.

Effects of exenatide and metformin in combination on some adipocytokine levels: a comparison with metformin monotherapy

The aim of this study was to evaluate the effects of exenatide on levels of serum adipocytokines and on β-cell function. The study was conducted between 2008 and 2012. After a run-in period with metformin, 174 patients with type-2 diabetes were randomly distributed to either a group receiving exenatide at 10 μg twice daily, or a group receiving the placebo, for 12 months. We evaluated body mass index (BMI), blood pressure, glycemic control, lipid profile, fasting plasma insulin (FPI), HOMA-IR, HOMA-β, fasting plasma proinsulin (FPPr), proinsulin : fasting plasma insulin ratio (Pr/FPI ratio), C-peptide, glucagon, retinol binding protein-4 (RBP-4), visfatin, omentin-1, and microalbuminuria. We used ELISA methods to assess the various parameters. Patients also underwent a combined euglycemic-hyperinsulinemic and hyperglycemic clamp, with subsequent arginine stimulation. After 12 months, a combination of exenatide and metformin produced a better decrease in body mass, BMI, glycemic control, FPI, FPPr, FPPr/FPI ratio, HOMA-IR, and glucagon level. Treatment with exenatide + metformin was superior to the placebo + metformin in increasing HOMA-β, C-peptide, and β-cell function. Significant negative correlations were found between M value, an index of insulin sensitivity, and measured adipocytokines. In conclusion, the combination of exenatide + metformin plays a role in improving some adipocytokine levels, and is better than metformin alone. The significant negative correlation between M value and measured adipocytokines is another confirmation of the positive effects linked to the improvement in insulin sensitivity.

A comparison between sitagliptin or glibenclamide in addition to metformin + pioglitazone on glycaemic control and β‐cell function: the triple oral therapy

To evaluate which triple oral therapy between metformin + pioglitazone + sitagliptin and metformin + pioglitazone + glibenclamide can be more useful in improving glycaemic control and should be preferred in clinical practice. During the 2-year run-in period, patients were instructed to take metformin monotherapy for the first year, then a combination of metformin and pioglitazone for the second year, then patients were randomized to add glibenclamide or sitagliptin to the dual combination of metformin and pioglitazone for another year. Body weight reached with sitagliptin at 36 months was lower than that reached with glibenclamide. Fasting plasma insulin and homeostasis model assessment of insulin resistance were significantly increased by triple therapy with glibenclamide and decreased by that with sitagliptin. While sitagliptin did not change homeostasis model assessment of β-cell function, this value was significantly increased by glibenclamide. Fasting plasma proinsulin was not influenced by triple oral therapy including glibenclamide, while it was decreased by the therapy including sitagliptin compared to glibenclamide. Triple oral therapy with sitagliptin better improved β-cell function measures compared with the glibenclamide therapy. Sitagliptin should be preferred to glibenclamide as an addition to the metformin + pioglitazone combination for its better protection of β-cell secretion and its neutral effect on body weight.

A Randomized, Double-Blind, Comparative Therapy Evaluating Sitagliptin Versus Glibenclamide in Type 2 Diabetes Patients Already Treated with Pioglitazone and Metformin: A 3-Year Study

This study evaluated if triple oral therapy can be useful in improving glycemic control compared with metformin monotherapy and with a metformin and pioglitazone combination. Furthermore, we also compared a triple metformin+pioglitazone+glibenclamide combination with a metformin+pioglitazone+sitagliptin one. After a 2-year run-in therapy-augmenting phase with metformin and pioglitazone, 453 overweight, type 2 diabetes patients were randomized to 1 year of sitagliptin versus 1 year of glibenclamide to evaluate, as the primary outcome, the variation of β-cell function both in a fasting state and after an euglycemic hyperinsulinemic and hyperglycemic clamp. As secondary outcomes we evaluated glycemic control and insulin resistance. Both the triple therapy combinations were more effective in reducing glycated hemoglobin compared with metformin monotherapy and with dual therapy metformin+pioglitazone. Fasting plasma insulin level and the homeostasis model assessment insulin resistance index were significantly increased by triple therapy with glibenclamide and decreased by the one with sitagliptin. Although sitagliptin did not change the homeostasis model assessment β-function index, this value was significantly increased by glibenclamide. The fasting plasma proinsulin level was decreased by sitagliptin. Triple therapy with sitagliptin greatly improved β-cell function measures compared with the glibenclamide one and also compared with metformin monotherapy and with the metformin+pioglitazone combination. Dual combination therapy is more effective than monotherapy in improving glycemic control. When double therapy is not enough to reach an adequate glycemic control, sitagliptin should be preferred to glibenclamide as the third agent because of its positive effect on β-cells.

Exenatide plus metformin compared with metformin alone on β‐cell function in patients with Type 2 diabetes

To quantify how much exenatide added to metformin improves β-cell function, and to evaluate the impact on glycaemic control, insulin resistance and inflammation compared with metformin alone. A total of 174 patients with Type 2 diabetes with poor glycaemic control were instructed to take metformin for 8 ± 2 months, then they were randomly assigned to exenatide (5 μg twice a day for the first 4 weeks and forced titration to 10 μg twice a day thereafter) or placebo for 12 months. At 12 months we evaluated anthropometric measurements, glycaemic control, insulin resistance and β-cell function variables, glucagon, adiponectin, high sensitivity-C reactive protein and tumour necrosis factor-α. Before and after 12 months, patients underwent a combined euglycaemic hyperinsulinaemic and hyperglycaemic clamp, with subsequent arginine stimulation. Exenatide + metformin gave a greater decrease in body weight, glycaemic control, fasting plasma proinsulin and insulin and their ratio, homeostasis model assessment for insulin resistance (HOMA-IR), and glucagon values and a greater increase in C-peptide levels, homeostasis model assessment β-cell function index (HOMA-β) and adiponectin compared with placebo + metformin. Exenatide + metformin decreased waist and hip circumference, and reduced concentrations of high sensitivity-C reactive protein and tumour necrosis factor-α. Exenatide + metformin gave a greater increase in M value (+34%), and disposition index (+55%) compared with placebo + metformin; first (+21%) and second phase (+34%) C-peptide response to glucose and C-peptide response to arginine (+25%) were also improved by exenatide + metformin treatment, but not by placebo + metformin. Exenatide is effective not only on glycaemic control, but also in protecting β-cells and in reducing inflammation.

Vildagliptin action on some adipocytokine levels in type 2 diabetic patients: a 12-month, placebo-controlled study

Objective: To evaluate the action of vildagliptin + metformin on some adipocytokine levels, glycemic control, and β-cell function in type 2 diabetic patients.Research design and methods: A total of 171 patients with poor glycemic control were instructed to add after a 8 ± 2 month-run-in period with metformin, vildagliptin 50 mg twice a day or placebo for 12 months.Main outcome measures: We evaluated at 3, 6, 9, and 12 months, the body mass index (BMI), glycemic control, fasting plasma insulin (FPI), homeostasis model assessment insulin resistance index (HOMA-IR), homeostasis model assessment β-cell function index (HOMA-β), fasting plasma proinsulin (FPr), proinsulin/fasting plasma insulin ratio (Pr/FPI ratio), C-peptide, glucagon, resistin, retinol-binding protein-4 (RBP-4), chemerin, and tumor necrosis factor-α (TNF-α). Patients also underwent a combined euglycemic hyperinsulinemic and hyperglycemic clamp, with subsequent arginine stimulation to assess insulin sensitivity and insulin secretion.Results: After 12 months of vildagliptin + metformin, we observed a better decrease of body weight, glycemic control, HOMA-IR, and glucagon, and a better increase of HOMA-β, and of all the measures of β-cell function, compared to placebo + metformin. Vildagliptin + metformin also decreased resistin, RBP-4, and chemerin better.Conclusion: Vildagliptin seems to have a positive action on some adipocytokines related to inflammation.

A randomized, double-blind, placebo-controlled trial evaluating sitagliptin action on insulin resistance parameters and β-cell function

Aim:To evaluate the impact on glycemic control, insulin secretion and on insulin resistance of a sitagliptin + metformin combination compared to metformin monotherapy in type 2 diabetic, naïve to treatment, patients.Materials and methods: A total of 178 Caucasian type 2 diabetic patients were randomized to take sitagliptin 100 mg once a day or placebo in addition to previously taken metformin, for 12 months. The authors evaluated at 3, 6, 9, and 12 months: body mass index (BMI), glycemic control, fasting plasma insulin (FPI), HOMA-IR, HOMA-β, fasting plasma proinsulin (FPPr), proinsulin/fasting plasma insulin ratio (Pr/FPI ratio), C-peptide, glucagon, retinol binding protein-4 (RBP-4), visfatin, and chemerin. Before and 12 months after the addition of sitagliptin, patients underwent tests to assess insulin sensitivity and insulin secretion.Results: Sitagliptin + metformin gave a better decrease of glycemic control, HOMA-IR and glucagon levels compared to placebo + metformin; sitagliptin + metformin also better increased HOMA-β and all β-cell measurements recorded after the clamp. Regarding adipocytokines, sitagliptin + metformin better reduced RBP-4, visfatin and chemerin levels, compared to placebo + metformin.Conclusion: When metformin alone is not enough to reach an adequate glycemic control, sitagliptin can be a valid option, because of its effects in reducing insulin resistance and in preserving β-cell function.

Effects of a combination of sitagliptin plus metformin vs metformin monotherapy on glycemic control, β-cell function and insulin resistance in type 2 diabetic patients

AimsTo evaluate the impact on glycemic control, insulin resistance, and insulin secretion of sitagliptin+metformin compared to metformin in type 2 diabetic patients. MethodsPatients were instructed to take metformin for 8±2 months, then they were randomly assigned to sitaglipin 100mg or placebo for 12 months. We evaluated at 3, 6, 9, and 12 months: body mass index (BMI), glycemic control, fasting plasma insulin (FPI), HOMA-IR, HOMA-β, fasting plasma proinsulin (FPPr), proinsulin/fasting plasma insulin ratio (Pr/FPI ratio), C-peptide, glucagon, adiponectin (ADN), and high sensitivity-C reactive protein (Hs-CRP). Before, and after 12 months since the addition of sitagliptin, patients underwent a combined euglycemic hyperinsulinemic and hyperglycemic clamp, with subsequent arginine stimulation. ResultsBoth treatments similarly decreased body weight, and BMI; on the other hand, they both improved glycemic control, glucagon and HOMA-IR, but sitagliptin+metformin were more effective in reducing these parameters. Sitagliptin+metformin, but not placebo+metformin, decreased FPPr, FPPR/FPI ratio, and increased C-peptide values, even if no differences between the groups were recorded. Sitaglitin+metformin gave also a greater increase of HOMA-β, M value, C-peptide response to arginine and disposition index compared to placebo+metformin group. ConclusionsOther than improving glycemic control, sitagliptin+metformin also improved β-cell function better than metformin alone.

Vildagliptin Added to Metformin on β-Cell Function After a Euglycemic Hyperinsulinemic and Hyperglycemic Clamp in Type 2 Diabetes Patients

This study evaluated the effect of vildagliptin + metformin on glycemic control and β-cell function in type 2 diabetes patients. One hundred seventy-one type 2 diabetes patients, naive to antidiabetes therapy and with poor glycemic control, were instructed to take metformin for 8±2 months up to a mean dosage of 2,500±500 mg/day; then they were randomly assigned to add vildaglipin 50 mg twice a day or placebo for 12 months. We evaluated at 3, 6, 9, and 12 months: body mass index, glycemic control, fasting plasma insulin, homeostasis model assessment insulin resistance index (HOMA-IR), homeostasis model assessment β-cell function index (HOMA-β), fasting plasma proinsulin, proinsulin/fasting plasma insulin ratio, C-peptide, glucagon, adiponectin, and high-sensitivity C-reactive protein. Before and at 12 months after the addition of vildagliptin, patients underwent a combined euglycemic hyperinsulinemic and hyperglycemic clamp, with subsequent arginine stimulation, to assess insulin sensitivity and insulin secretion. After 12 months of treatment, vildagliptin + metformin gave a better decrease of body weight, glycemic control, HOMA-IR, and glucagon and a better increase of HOMA-β compared with placebo + metformin. Regarding the measures of β-cell function, treatment-induced changes in M-value, first- and second-phase C-peptide response to glucose, and C-peptide response to arginine were significantly higher in the vildagliptin + metformin group compared with the placebo + metformin group. The addition of vildagliptin to metformin gave a better improvement of glycemic control, insulin resistance, and β-cell function compared with metformin alone.

Variations in Inflammatory Biomarkers Following the Addition of Sitagliptin in Patients with Type 2 Diabetes not Controlled with Metformin

The effects of dipeptidyl peptidase-4 (DPP-4) inhibition on adipose tissue inflammation remain obscure. The aim of this study was to evaluate the effects of the addition of sitagliptin on the β-cell function and various inflammatory biomarkers in type 2 diabetic patients. After a run-in period of taking metformin, 178 diabetic patients with poor glycemic control were randomized to take sitagliptin at a dose of 100 mg once a day or a placebo in addition to metformin for 12 months. We evaluated the following parameters at three, six, nine and twelve months: body mass index (BMI), glycemic control, the homeostasis model assessment insulin resistance index (HOMA-IR), the homeostasis model assessment β-cell function index (HOMA-β), the proinsulin/fasting plasma insulin ratio (Pr/FPI ratio) and the levels of fasting plasma insulin (FPI), fasting plasma proinsulin (FPPr), C-peptide, glucagon, resistin, vaspin, omentin-1 and tumor necrosis factor-α (TNF-α). Before and twelve months after the addition of sitagliptin, the patients underwent combined euglycemic hyperinsulinemic and hyperglycemic clamping with subsequent arginine stimulation to assess insulin sensitivity and secretion. Treatment with sitagliptin + metformin was more effective than placebo + metformin in improving glycemic control, the HOMA-IR and the glucagon level and increasing the HOMA-β and all β-cell measurements after combined euglycemic hyperinsulinemic and hyperglycemic clamping with subsequent arginine stimulation. Regarding inflammatory biomarkers, sitagliptin + metformin more effectively reduced the levels of resistin, vaspin and omentin-1 than placebo + metformin. When treatment with metformin alone is not adequate for obtaining glycemic control, the addition of sitagliptin can be considered due to its actions in preserving the β-cell function and reducing the levels of biomarkers of inflammation.

Islet Cholesterol Accumulation Due to Loss of ABCA1 Leads to Impaired Exocytosis of Insulin Granules

OBJECTIVEThe ATP-binding cassette transporter A1 (ABCA1) is essential for normal insulin secretion from β-cells. The aim of this study was to elucidate the mechanisms underlying the impaired insulin secretion in islets lacking β-cell ABCA1.RESEARCH DESIGN AND METHODSCalcium imaging, patch clamp, and membrane capacitance were used to assess the effect of ABCA1 deficiency on calcium flux, ion channel function, and exocytosis in islet cells. Electron microscopy was used to analyze β-cell ultrastructure. The quantity and distribution of proteins involved in insulin-granule exocytosis were also investigated.RESULTSWe show that a lack of β-cell ABCA1 results in impaired depolarization-induced exocytotic fusion of insulin granules. We observed disturbances in membrane microdomain organization and Golgi and insulin granule morphology in β-cells as well as elevated fasting plasma proinsulin levels in mice in the absence of β-cell ABCA1. Acute cholesterol depletion rescued the exocytotic defect in β-cells lacking ABCA1, indicating that elevated islet cholesterol accumulation directly impairs granule fusion and insulin secretion.CONCLUSIONSOur data highlight a crucial role of ABCA1 and cellular cholesterol in β-cells that is necessary for regulated insulin granule fusion events. These data suggest that abnormalities of cholesterol metabolism may contribute to the impaired β-cell function in diabetes.

Effects of One Year Treatment of Vildagliptin Added to Pioglitazone or Glimepiride in Poorly Controlled Type 2 Diabetic Patients

The aim of the study was to compare the effects of vildagliptin added to pioglitazone or glimepiride on metabolic and insulin resistance related-indices in poorly controlled type 2 diabetic patients (T2DM). 168 patients with T2DM were randomized to take either pioglitazone 30 mg once a day plus vildagliptin 50 mg twice a day or glimepiride 2 mg 3 times a day plus vildagliptin 50 mg twice a day. We evaluated body weight, body mass index (BMI), glycated hemoglobin (HbA1c), fasting plasma glucose (FPG), postprandial plasma glucose (PPG), fasting plasma insulin (FPI), homeostasis model assessment insulin resistance index (HOMA-IR), homeostasis model assessment beta-cell function index (HOMA-beta), fasting plasma proinsulin (FPPr), proinsulin/fasting plasma insulin ratio (Pr/FPI ratio), adiponectin (ADN), resistin (R), tumor necrosis factor-alpha (TNF-alpha), and high sensitivity C-reactive protein (Hs-CRP) at their baseline values, and after 3, 6, 9, and 12 months of treatment. We observed a similar improvement of HbA1c, FPG, PPG, and Hs-CRP compared to baseline in the 2 groups. Fasting plasma insulin, FPPr, Pr/FPI ratio, R, and TNF-alpha were significantly decreased and ADN was significantly increased with pioglitazone plus vildagliptin, but not with glimepiride plus vildagliptin. HOMA-IR, and HOMA-beta values obtained with pioglitazone plus vildagliptin were significantly better than the values obtained with glimepiride plus vildagliptin. Pioglitazone plus vildagliptin were found to be more effective in preserving beta-cell function, and in reducing insulin resistance, and inflammatory state parameters.

Neck Circumference as a Novel Measure of Cardiometabolic Risk: The Framingham Heart Study

Neck circumference, a proxy for upper-body sc fat, may be a unique fat depot that confers additional cardiovascular risk above and beyond central body fat. Participants with neck circumference measures who underwent multidetector computed tomography to assess visceral adipose tissue (VAT) were included [n=3307, 48% women; mean age=51 yr; mean body mass index (BMI)=27.8 kg/m2; mean neck circumference=40.5 cm (men) and 34.2 cm (women)]. Sex-specific linear regression models were used to assess the association between sd increase in neck circumference and cardiovascular disease (CVD) risk factors (systolic and diastolic blood pressure; total, low-density lipoprotein, and high-density lipoprotein cholesterol and triglycerides; and fasting plasma glucose, insulin, proinsulin, and homeostasis model assessment of insulin resistance). Neck circumference was correlated with VAT [r=0.63 (men); r=0.74 (women); P<0.001] and BMI [r=0.79 (men); r=0.80 (women); P<0.001]. After further adjustment for VAT, neck circumference was positively associated with systolic blood pressure, diastolic blood pressure in men only, triglycerides, fasting plasma glucose in women only, insulin, proinsulin, and homeostasis model assessment of insulin resistance and was inversely associated with high-density lipoprotein (all P values<0.01). Similar results were observed in models that adjusted for both VAT and BMI. In a secondary analysis of incident CVD as an outcome, there was no statistically significant association observed for neck circumference in multivariable-adjusted models. Neck circumference is associated with CVD risk factors even after adjustment for VAT and BMI. These findings suggest that upper-body sc fat may be a unique, pathogenic fat depot.

Effects of sitagliptin or metformin added to pioglitazone monotherapy in poorly controlled type 2 diabetes mellitus patients

The aim of the study was to compare the effects of the addition of sitagliptin or metformin to pioglitazone monotherapy in poorly controlled type 2 diabetes mellitus patients on body weight, glycemic control, β-cell function, insulin resistance, and inflammatory state parameters. One hundred fifty-one patients with uncontrolled type 2 diabetes mellitus (glycated hemoglobin [HbA 1c] >7.5%) in therapy with pioglitazone 30 mg/d were enrolled in this study. We randomized patients to take pioglitazone 30 mg plus sitagliptin 100 mg once a day, or pioglitazone 15 mg plus metformin 850 mg twice a day. We evaluated at baseline and after 3, 6, 9, and 12 months these parameters: body weight, body mass index, HbA 1c, fasting plasma glucose (FPG), postprandial plasma glucose (PPG), fasting plasma insulin (FPI), homeostasis model assessment insulin resistance index (HOMA-IR), homeostasis model assessment β-cell function index, fasting plasma proinsulin (Pr), Pr/FPI ratio, adiponectin, resistin (R), tumor necrosis factor- α (TNF- α), and high-sensitivity C-reactive protein. A decrease of body weight and body mass index was observed with metformin, but not with sitagliptin, at the end of the study. We observed a comparable significant decrease of HbA 1c, FPG, and PPG and a significant increase of homeostasis model assessment β-cell function index compared with baseline in both groups without any significant differences between the 2 groups. Fasting plasma insulin, fasting plasma Pr, Pr/FPI ratio, and HOMA-IR values were decreased in both groups even if the values obtained with metformin were significantly lower than the values obtained with sitagliptin. There were no significant variations of ADN, R, or TNF- α with sitagliptin, whereas a significant increase of ADN and a significant decrease of R and TNF- α values were recorded with metformin. A significant decrease of high-sensitivity C-reactive protein value was obtained in both groups without any significant differences between the 2 groups. There was a significant correlation between HOMA-IR decrease and ADN increase, and between HOMA-IR decrease and R and TNF- α decrease in pioglitazone plus metformin group after the treatment. The addition of both sitagliptin or metformin to pioglitazone gave an improvement of HbA 1c, FPG, and PPG; but metformin led also to a decrease of body weight and to a faster and better improvement of insulin resistance and inflammatory state parameters, even if sitagliptin produced a better protection of β-cell function.