New strategy for the treatment of type 2 diabetes mellitus with incretin-based therapy

Steatosis is involved in the progression of kidney disease in a high-fat-diet-induced non-alcoholic steatohepatitis mouse model

Chronic kidney disease (CKD) and non-alcoholic steatohepatitis (NASH) are major health issues associated with the metabolic syndrome. Although NASH is a known risk factor of CKD, the mechanisms linking these two diseases remain poorly understood. We aimed to investigate alterations in the kidney complicated with dyslipidemia in an established NASH mouse model. Male C57BL6/J mice were fed with control diet or high-fat diet (HFD), containing 40% fat, 22% fructose, and 2% cholesterol for 16 weeks. Metabolic characteristics, histological changes in the kidney, endoplasmic reticulum (ER) stress, apoptosis, and fibrosis were evaluated by histological analysis, immunoblotting, and quantitative reverse transcription-polymerase chain reaction. Levels of serum aspartate aminotransferase, alanine aminotransferase, alkali-phosphatase, total cholesterol, and urinary albumin were significantly higher in mice fed with HFD. Remarkable steatosis, glomerular hypertrophy, and interstitial fibrosis were also shown in in the kidney by leveraging HFD. Furthermore, HFD increased the mRNA expression levels of Casp3, Tgfb1, and Nfe2l2 and the protein level of BiP. We observed the early changes of CKD and speculate that the underlying mechanisms that link CKD and NASH are the induction of ER stress and apoptosis. Further, we observed the activation of Nfe2l2 in the steatosis-induced CKD mouse model. This NASH model holds implications in investigating the mechanisms linking dyslipidemia and CKD.

Liraglutide improves insulin sensitivity in high fat diet induced diabetic mice through multiple pathways

Glucagon like peptide-1 (GLP-1) promotes postprandial insulin secretion. Liraglutide, a full agonist of the GLP-1 receptor, reduces body weight, improve insulin sensitivity, and alleviate Non Alcoholic Fatty Liver Disease (NAFLD). However, the underlying mechanisms remain unclear. This study aims to explore the underlying mechanisms and cell signaling pathways involved in the anti-obesity and anti-inflammatory effects of liraglutide. Mice were fed a high fat high sucrose diet to induce diabetes, diabetic mice were divided into two groups and injected with liraglutide or vehicle for 14 days. Liraglutide treatment improved insulin sensitivity, accompanied with reduced expression of the phosphorylated Acetyl-CoA carboxylase-2 (ACC2) and upregulation of long chain acyl CoA dehydrogenase (LCAD) in insulin sensitive tissues. Furthermore, liraglutide induced adenosine monophosphate-activated protein kinase-α (AMPK-α) and Sirtuin-1(Sirt-1) protein expression in liver and perigonadal fat. Liraglutide induced elevation of fatty acid oxidation in these tissues may be mediated through the AMPK-Sirt-1 cell signaling pathway. In addition, liraglutide induced brown adipocyte differentiation in skeletal muscle, including induction of uncoupling protein-1 (UCP-1) and PR-domain-containing-16 (PRDM-16) protein in association with induction of SIRT-1. Importantly, liraglutide displayed anti-inflammation effect. Specifically, liraglutide led to a significant reduction in circulating interleukin-1 β (IL-1 β) and interleukin-6 (IL-6) as well as hepatic IL-1 β and IL-6 content. The expression of inducible nitric oxide synthase (iNOS-1) and cyclooxygenase-2 (COX-2) in insulin sensitive tissues was also reduced following liraglutide treatment. In conclusion, liraglutide improves insulin sensitivity through multiple pathways resulting in reduction of inflammation, elevation of fatty acid oxidation, and induction of adaptive thermogenesis.

Liraglutide induces beige fat development and promotes mitochondrial function in diet induced obesity mice partially through AMPK-SIRT-1-PGC1-α cell signaling pathway

PURPOSE

Glucagon like peptide-1 (GLP-1) is produced to induce postprandial insulin secretion. Liraglutide, a full agonist of the GLP-1 receptor, has a protective effect on weight gain in obese subjects. Brown adipose tissue plays a major role in the control of energy balance and is known to be involved in the weight loss regulated by liraglutide. The putative anti-obesity properties of liraglutide and the cell signaling pathways involved were examined.

METHODS

Four groups of C57/BL6 mice fed with chow or HFHS diet were injected with either liraglutide or vehicle for four weeks. Western blotting was used to analyze protein expression.

RESULTS

Liraglutide significantly attenuated the weight gain in mice fed with HFHS diet and was associated with significant reductions of epididymal fat and inguinal fat mass. Furthermore, liraglutide significantly upregulated the expression of brown adipose-specific markers in perigonadal fat in association with upregulation of AMPK-SIRT-1-PGC1-α cell signaling. However, elevation of brown fat markers in skeletal muscle was only observed in HFHS diet fed mice after liraglutide treatment, and AMPK-SIRT-1 cell signaling is not involved in this process.

CONCLUSIONS

the anti-obesity effect of liraglutide occurs through adaptive thermogenesis and may act through different cell signaling pathways in fat and skeletal muscle tissue. Liraglutide induces beige fat development partially through the AMPK-SIRT-1-PGC1-α cell signaling pathway. Therefore, liraglutide is a potential medication for obesity prevention and in targeting pre-diabetics.

New Insights in Cardiac β-Adrenergic Signaling During Heart Failure and Aging

Heart failure (HF) has become increasingly common within the elderly population, decreasing their survival and overall quality of life. In fact, despite the improvements in treatment, many elderly people suffer from cardiac dysfunction (HF, valvular diseases, arrhythmias or hypertension-induced cardiac hypertrophy) that are much more common in an older fragile heart. Since β-adrenergic receptor (β-AR) signaling is abnormal in failing as well as aged hearts, this pathway is an effective diagnostic and therapeutic target. Both HF and aging are characterized by activation/hyperactivity of various neurohormonal pathways, the most important of which is the sympathetic nervous system (SNS). SNS hyperactivity is initially a compensatory mechanism to stimulate contractility and maintain cardiac output. Unfortunately, this chronic stimulation becomes detrimental and causes decreased cardiac function as well as reduced inotropic reserve due to a decrease in cardiac β-ARs responsiveness. Therapies which (e.g., β-blockers and physical activity) restore β-ARs responsiveness can ameliorate cardiac performance and outcomes during HF, particularly in older patients. In this review, we will discuss physiological β-adrenergic signaling and its alterations in both HF and aging as well as the potential clinical application of targeting β-adrenergic signaling in these disease processes.

New Insights in Cardiac β-Adrenergic Signaling During Heart Failure and Aging

Heart failure (HF) has become increasingly common within the elderly population, decreasing their survival and overall quality of life. In fact, despite the improvements in treatment, many elderly people suffer from cardiac dysfunction (HF, valvular diseases, arrhythmias or hypertension-induced cardiac hypertrophy) that are much more common in an older fragile heart. Since β-adrenergic receptor (β-AR) signaling is abnormal in failing as well as aged hearts, this pathway is an effective diagnostic and therapeutic target. Both HF and aging are characterized by activation/hyperactivity of various neurohormonal pathways, the most important of which is the sympathetic nervous system (SNS). SNS hyperactivity is initially a compensatory mechanism to stimulate contractility and maintain cardiac output. Unfortunately, this chronic stimulation becomes detrimental and causes decreased cardiac function as well as reduced inotropic reserve due to a decrease in cardiac β-ARs responsiveness. Therapies which (e.g., β-blockers and physical activity) restore β-ARs responsiveness can ameliorate cardiac performance and outcomes during HF, particularly in older patients. In this review, we will discuss physiological β-adrenergic signaling and its alterations in both HF and aging as well as the potential clinical application of targeting β-adrenergic signaling in these disease processes.

National Differences in Remission of Type 2 Diabetes Mellitus After Roux-en-Y Gastric Bypass Surgery-Subgroup Analysis of 2-Year Results of the Diabetes Surgery Study Comparing Taiwanese with Americans with Mild Obesity (BMI 30-35 kg/m2)

Background

The purpose of this study is to compare effects of different nations on Roux-en-Y gastric bypass (RYGB) vs. intensive medical management (IMM) in achieving remission of type 2 diabetes mellitus (T2DM).

Materials and Methods

Between April 2008 and December 2011, this randomized, controlled clinical trial was conducted at four teaching hospitals in the United States and Taiwan involving 71 participants with mild obesity (BMI 30–35 kg/m²). Thirty-six of 71 participants were randomly assigned to the RYGB group, and the others were in IMM group. Partial or complete remission of T2DM was defined as blood HbA1c < 6.5 % (48 mmol/mol) or <6 % (42 mmol/mol) without any antihyperglycemic medication for at least 1-year duration, respectively.

Results

At baseline, Taiwanese participants had a lower BMI, younger age, and shorter duration of T2DM than American participants. At 24 months, weight loss was greater in the RYGB group in both populations than in the IMM group. No IMM participant of either population had partial or complete remission of T2DM. In the RYGB group, a substantial proportion of the subjects achieved complete or partial remission (57 % in Taiwanese and 27 % in American participants, P = 0.08). Logistic regression revealed stimulated C-peptide (Odds ratio 2.22, P = 0.02) but not nationality as a significant predictor of diabetes remission.

Conclusion

Adding RYGB to lifestyle and medical management was associated with a greater likelihood of remission of T2DM in both Taiwanese and American subjects with mild obesity with type 2 diabetes. Residual beta-cell function at baseline appears to be the major factor predicting remission of T2DM.

Trial registry number: clinicaltrials.gov Identifier: NCT00641251

Effects of vildagliptin as add-on treatment in patients with type 2 diabetes mellitus: insights from long-term clinical studies in Japan

BACKGROUND

Vildagliptin, a dipeptidyl peptidase-4 (DPP-4) inhibitor, is wildly used to treat type 2 diabetes mellitus (T2DM) with mono- or combination-therapy. We review two previously published open-label studies to extract insights on the long-term efficacy and safety of vildagliptin.

METHODS

Two studies were conducted in Japan to assess the efficacy and safety of vildagliptin as an add-on to other oral antidiabetes drugs (OADs) for 52 weeks. These studies were performed under the similar protocol in Japanese patients with T2DM who were inadequately controlled with OAD monotherapy [excluding other dipeptidyl peptidase-4 (DPP-4) inhibitors].

RESULTS

Addition of vildagliptin (50 mg twice daily) to other OAD monotherapy [sulfonylurea (SU), metformin, thiazolidinedione, alpha-glucosidase inhibitor and glinide] reduced glycated hemoglobin (HbA1c) levels by -0.64 %,-0.75 %,-0.92 %,-0.94 % and - 0.64 %, respectively, over 52 weeks of treatment. Overall, the incidence of hypoglycemia was low and was slightly higher in the add-on to SU treatment group compared with the other groups. The incidences of adverse events were comparable among the treatment groups, and vildagliptin was well-tolerated as add-on therapy to other OADs.

CONCLUSIONS

The evidence from the two studies indicates that vildagliptin as an add-on therapy to other OADs is a clinically reasonable option for Japanese patients with T2DM who respond inadequately to other OAD monotherapy.

Efficacy and Safety of Vildagliptin as an Add-on to Insulin with or without Metformin in Japanese Patients with Type 2 Diabetes Mellitus: A 12-week, Double-Blind, Randomized Study

INTRODUCTION

To assess the efficacy and safety of vildagliptin as add-on therapy in Japanese patients with type 2 diabetes mellitus (T2DM), inadequately controlled on stable long-acting, intermediate-acting, or pre-mixed insulin, with or without concomitant metformin.

METHODS

In this 12-week placebo-controlled study, patients were randomized to receive either vildagliptin 50 mg twice daily (bid) or placebo treatment in a 1:1 ratio. The primary endpoint was change in glycated hemoglobin A1c (HbA1c) from baseline to 12-week endpoint. Secondary endpoints included proportion of patients achieving pre-defined HbA1c targets of ≤6.5%, <7.0%, and HbA1c <7.0% in patients with baseline HbA1c ≤8.0% and change in fasting plasma glucose (FPG) after 12 weeks of treatment. Regular monitoring was performed to record any treatment-emergent adverse events (AEs) and serious adverse events or hypoglycemic episodes.

RESULTS

Of the 156 patients randomized, 96.8% completed the study (vildagliptin, n = 76; placebo, n = 75). Patient demographics and clinical characteristics were comparable between the groups at baseline. Addition of vildagliptin resulted in statistically significant reductions in HbA1c after 12 weeks (-1.01 ± 0.06%), with a between-treatment difference of -0.91 ± 0.09% (p < 0.001). FPG levels reduced from baseline to 12 weeks in the vildagliptin group (-1.2 ± 0.2 mmol/L), with a between-treatment difference of -1.2 ± 0.3 mmol/L which was significant (p < 0.001). The proportion of patients achieving HbA1c targets was higher with vildagliptin treatment for all pre-defined responder rate categories. The overall incidence of AEs was comparable between groups (vildagliptin, 46.2% vs. placebo, 43.6%). The overall incidence of hypoglycemic events was low and all events were self-treatable without using drug therapy. No severe hypoglycemic events were reported.

CONCLUSION

Treatment with vildagliptin 50 mg bid as add-on to insulin with or without metformin resulted in statistically significant reductions in HbA1c in Japanese patients with T2DM. Overall, vildagliptin was well tolerated with a safety profile similar to that of placebo in this patient population. ClinicalTrials.gov Identifier, NCT02002221 FUNDING: Novartis Pharma K.K.

Long-term efficacy of vildagliptin in patients with type 2 diabetes undergoing hemodialysis

BACKGROUND

There are few studies evaluating long-term glycemic control using a dipeptidyl peptidase-4 inhibitor in type 2 diabetes patients with end-stage renal disease (ESRD). The aim of this study was to evaluate the safety and efficacy of vildagliptin therapy over 2 years in type 2 diabetes with ESRD.

METHODS

Patients with ESRD resulting from type 2 diabetes requiring dialysis who had ≥20 % glycated albumin (GA) were enrolled. Vildagliptin 50 mg once daily was administered for 2 years. Changes in GA and dry weight were evaluated.

RESULTS

In 32 patients (24 men and 8 women) aged 68.3 ± 1.9 years, vildagliptin 50 mg once daily was administered for 2 years, but the dose was increased to 50 mg twice daily in 15 patients. GA was significantly reduced by 2.6 ± 0.6 %, from 22.4 ± 0.6 % at baseline to 19.8 ± 0.4 % at 2 years. After 2 years of vildagliptin therapy, 15 (46.9 %) of 32 patients achieved a GA level of <20 %. Dry weight changed slightly, with an increase of 1.3 ± 0.8 kg at 2 years. No adverse drug reactions related to treatment with vildagliptin were seen.

CONCLUSIONS

Vildagliptin is a promising therapeutic option for safe, effective glycemic control in type 2 diabetic patients with ESRD.

Long-term safety of once-daily lixisenatide in Japanese patients with type 2 diabetes mellitus: GetGoal-Mono-Japan

AIMS

This 76-week, open-label, parallel-group study assessed the long-term safety of once-daily lixisenatide monotherapy in Japanese patients with type 2 diabetes mellitus.

METHODS

Patients were randomized to receive lixisenatide in a 2-step or a 1-step dose-increase regimen. The primary objective was to assess the safety of lixisenatide at week 24 by a descriptive comparison of the 2- and 1-step groups.

RESULTS

As expected with treatment with a glucagon-like peptide-1 agonist, nausea was the most common treatment-emergent adverse event (2-step group: n=12/33 [36.4%] vs 1-step group: n=18/36 [50.0%] up to week 24). In total, 5/33 patients (15.2%; 2-step group) and 2/36 patients (5.6%; 1-step group) prematurely discontinued treatment up to week 24, mainly due to adverse events. Serious treatment-emergent adverse events occurred in 2/33 patients (6.1%; 2-step group) versus 0/36 patients (0%; 1-step group) up to week 24. Symptomatic hypoglycemia occurred in 2/33 patients (6.1%; 2-step group) versus 1/36 patients (2.8%; 1-step group) up to week 24, with no severe events reported. Glycated hemoglobin, fasting plasma glucose, and body weight were reduced from baseline at weeks 24 and 76.

CONCLUSION

In Japanese patients with type 2 diabetes mellitus, once-daily lixisenatide monotherapy was well tolerated, with less nausea with the 2-step regimen.

Effects and molecular mechanisms of the antidiabetic fraction of Acorus calamus L. on GLP-1 expression and secretion in vivo and in vitro

ETHNOPHARMACOLOGICAL RELEVANCE

The radix of Acorus calamus L. (AC) is widely used in diabetes therapies in traditional folk medicine from America and Indonesia, and we have previously reported that the ethyl acetate fraction of AC (ACE) acts as an antidiabetic through insulin sensitizing, insulin releasing and alpha-glucosidase inhibitory activities. The present study is designed to investigate the effects and molecular mechanisms of ACE on glucagon-like peptide-1 (GLP-1) expression and secretion related to its hypoglycemic effects.

MATERIALS AND METHODS

The hypoglycemic effect of ACE (100mg/kg, i.g.) was confirmed by testing blood glucose levels or via oral glucose tolerance test (OGTT) in streptozotocin (STZ) induced hyperglycemic mice, db/db diabetic mice and diet-induced obese (DIO) mice. Plasma insulin, GLP-1 levels and intestinal GLP-1 related gene expression were determined in STZ-induced and db/db diabetic mice. The in vitro effects of ACE (12.5μg/ml) on the expression and secretion of GLP-1 were detected in NCI-H716 intestinal L-cells, and the correlation between ACE and molecules in the Wnt signaling pathway was further explored.

RESULTS

ACE (100mg/kg) significantly lowered fasting blood glucose in STZ-induced and db/db diabetic mice and improved the OGTT in DIO mice. Insulin releasing and islet protective effects, along with the increased secretion of GLP-1, were observed. The expression of proglucagon gene (gcg) and post-translational processing gene prohormone convertase 3 (pc3) and the GLP-1 content in the culture medium of L-cells notably increased after the ACE treatment (12.5μg/ml). At the same time, β-catenin nuclear translocation occurred, and its downstream protein cyclin D1 was activated, showing the involvement of Wnt signaling.

CONCLUSIONS

ACE might activate Wnt signaling to increase the gene expression of gcg and pc3 and exert incretin effects, including insulinotropic and islet protection, to lower blood glucose levels via elevated GLP-1 secretion either directly or indirectly.

Asymmetric dimethylarginine, a biomarker of cardiovascular complications in diabetes mellitus

Cardiovascular (CV) complications are an essential causal element of prospect in diabetes mellitus (DM), with carotid atherosclerosis being a common risk factor for prospective crisis of coronary artery diseases and/or cerebral infarction in DM subjects. From another point of view, asymmetric dimethylarginine (ADMA) has been established as an inhibitor of endogenous nitric oxide synthesis and the relationship between ADMA and arteriosclerosis has been reported. In our study with 87 type 2 DM (T2DM) patients, we have examined whether ADMA and other CV risk factors are the useful predictors of DMCV complications. After the measurement of the respective CV risk factors, we have followed the enrolled T2DM patients for 5 years. We have finally analyzed 77 patients. DMCV complications developed in 15 cases newly within 5 years, and 4 cases recurred. The concentrations of ADMA in plasma were markedly more elevated in 19 DM patients with CV complications than in 58 DM patients without CV complications. Urinary albumin (U-Alb), mean intimal-medial thickness (IMT) and ankle brachial index (ABI) were also higher in patients with CV complications. Multiple regression analyses showed that U-Alb had an influence on the high level of ADMA (standardized β = 6.59, P = 0.00014) independently of age, systolic BP, fibrinogen, mean IMT, plaque score, and ABI. The review indicates what is presently known regarding plasma ADMA that might be a new and meaningful biomarker of CV complications in DM subjects.

Profile of saxagliptin in the treatment of type 2 diabetes: focus on Japanese patients

Saxagliptin is a selective and potent dipeptidyl peptidase (DPP)-4 inhibitor, approved as an adjunct to diet and exercise to improve glycemic control in type 2 diabetes mellitus (T2DM) in the USA on July 2009, and had been launched globally in over 86 countries by September 2013. In patients with T2DM, once-daily administration of saxagliptin before breakfast achieves sustained inhibition of plasma DPP-4 activity and reduction of postprandial hyperglycemia, including after dinner, associated with an increase in plasma glucagon-like peptide-1 levels. This paper reviews the safety and efficacy of saxagliptin in Japanese patients with T2DM. The clinical development study in Japan supported its usefulness for the disease. Saxagliptin 1, 2.5, and 5 mg led to significant improvements in glycated hemoglobin (HbA_1c), and was generally well tolerated. Treatment with saxagliptin 5 mg induced a sustained reduction in HbA_1c over 52 weeks. Long-term combination therapy with saxagliptin and other oral hypoglycemic agents also provided sustained glycemic control and was well tolerated for up to 52 weeks. Saxagliptin as add-on to sulfonylureas or glinides has a tendency to increase hypoglycemia, but not with other oral antidiabetic agents, such as α-glucosidase inhibitors, metformin, or thiazolidinediones. The results of clinical trials have confirmed the long-term efficacy and safety of saxagliptin monotherapy as well as its use as add-on combination therapy, and support its usefulness as a therapeutic agent for T2DM. Saxagliptin has less concern for hypoglycemia and weight gain, which often becomes problematic in routine care of T2DM. Meta-analysis of clinical trials in the USA showed no evidence of increased risk of cardiovascular events associated with saxagliptin, suggesting the superior of saxagliptin in terms of safety. Recently, investigators in the SAVOR-TIMI (Saxagliptin Assessment of Vascular Outcomes Recorded in Patients with Diabetes Mellitus-Thrombolysis in Myocardial Infarction) 53 study suggested that DPP-4 inhibition with saxagliptin did not increase or decrease the rate of ischemic events, although the rate of hospitalization for heart failure was increased. Although saxagliptin improves glycemic control, other approaches are necessary to reduce cardiovascular risk in patients with diabetes. Saxagliptin is applicable for various pathological conditions, and is considered to be clinically significant as a new therapeutic option for Japanese patients with T2DM.

DPP-4 inhibitors repress foam cell formation by inhibiting scavenger receptors through protein kinase C pathway

Studies show that dipeptidyl peptidase-4 (DPP-4) inhibitors may have an anti-atherosclerotic effect. Since foam cells are key components of atherosclerotic plaque, we studied the effect of DPP-4 inhibitors on foam cell formation. Foam cell formation was studied by treatment of THP-1 macrophages with oxidized low-density lipoprotein in the absence or presence of DPP-4 inhibitors (sitagliptin and NVPDPP728). The expression of scavenger receptors SRA, CD36 and LOX-1 was measured, and their role in foam cell formation in the presence of DPP-4 inhibitors was examined. In additional studies, role of protein kinase C and A in the effect of DPP-4 inhibitors was examined. Foam cell formation was markedly reduced by both DPP-4 inhibitors, as was the expression of CD36 and LOX-1 (CD36 ≫ LOX-1), but not SRA. Simultaneously, there was a reduction in phosphorylated PKC, but not PKA, content. Recovery of phosphorylated PKC following treatment of cells negated the effect of DPP-4 inhibitors on foam cell formation. Further, overexpression of CD36 or LOX-1 blocked the effect of DPP-4 inhibitors on foam cell formation. DPP-4 inhibitors repress foam cell formation through the inhibition of SRs CD36 and LOX-1, most likely via the inhibition of PKC activity. This study provides novel insights into the mechanism of inhibition of atherosclerosis by DPP-4 inhibitors.