An in vitro study of urea and ammonia production and transport by the intestinal tract of fed and fasted rainbow trout: responses to luminal glutamine and ammonia loading

Digestion of dietary protein in teleosts results in high ammonia levels within the intestinal chyme that may reach concentrations that are many-fold greater than blood plasma levels. We used in vitro gut sac preparations of the ammoniotelic rainbow trout (Oncorhynchus mykiss) to investigate the role of the intestine in producing and transporting ammonia and urea, with specific focus on feeding versus fasting, and on responses to loading of the lumen with 2 mmol L^-1 glutamine or 2 mmol L^-1 ammonia. Feeding increased not only ammonia production and both mucosal and serosal fluxes, but also increased urea production and serosal fluxes. Elevated urea production was accompanied by an increase in arginase activity but minimal CPS III activity, suggesting that urea may be produced by direct arginolysis. The ammonia production and serosal fluxes increased in fasted preparations with glutamine loading, indicating an ability of the intestinal tissue to deaminate glutamine and perhaps use it as an energy source. However, there was little evidence of urea production or transport resulting from the presence of glutamine. Furthermore, the intestinal tissues did not appear to convert surplus ammonia to urea as a detoxification mechanism, as urea production and serosal flux rates decreased in fed preparations, with minimal changes in fasted preparations. Nevertheless, there was indirect evidence of detoxification by another pathway, as ammonia production rate decreased with ammonia loading in fed preparations. Overall, our study suggests that intestinal tissues of rainbow trout have the ability to produce urea and detoxify ammonia, likely via arginolysis.

Concentrated insulins in current clinical practice

New concentrated insulins (exceeding 100 units/mL) and dedicated devices have recently become available, offering new treatment options for people with diabetes, for basal and prandial insulin supplementation. The concentrated insulin formulations range from 2-fold concentration (insulin lispro 200 units/mL) with rapid-acting prandial action to 5-fold concentration (human regular insulin, 500 units/mL) with basal and short-acting prandial actions. Long-acting basal insulins include degludec 200 units/mL and glargine 300 units/mL. Concentrated insulins have been developed with the goal of easing insulin therapy by reducing the volume and number of injections and in some cases making use of altered pharmacokinetic and pharmacodynamic properties. This review summarizes the unique characteristics of each concentrated insulin to help healthcare providers and people with diabetes understand how to best use them.

Insulin sensitivity predicts brain network connectivity following a meal

There is converging evidence that insulin plays a role in food-reward signaling in the brain and has effects on enhancing cognition. Little is known about how these effects are altered in individuals with insulin resistance. The present study was designed to identify the relationships between insulin resistance and functional brain connectivity following a meal. Eighteen healthy adults (7 male, 11 female, age: 41-57 years-old) completed a frequently-sampled intravenous glucose tolerance test to quantify insulin resistance. On separate days at least one week apart, a resting state functional magnetic resonance imaging scan was performed: once after a mixed-meal and once after a 12-h fast. Seed-based resting state connectivity of the caudate nucleus and eigenvector centrality were used to identify relationships between insulin resistance and functional brain connectivity. Individuals with greater insulin resistance displayed stronger connectivity within reward networks following a meal suggesting insulin was less able to suppress reward. Insulin resistance was negatively associated with eigenvector centrality in the dorsal anterior cingulate cortex following a meal. These data suggest that individuals with less sensitivity to insulin may fail to shift brain networks away from reward and toward cognitive control following a meal. This altered feedback loop could promote overeating and obesity.

Postprandial Glucagon Reductions Correlate to Reductions in Postprandial Glucose and Glycated Hemoglobin with Lixisenatide Treatment in Type 2 Diabetes Mellitus: A Post Hoc Analysis

INTRODUCTION

The extent to which postprandial glucagon reductions contribute to lowering of postprandial glucose in patients with type 2 diabetes mellitus (T2DM) is currently unknown. The aim of this analysis was to determine whether a reduction in postprandial glucagon following treatment with the glucagon-like peptide-1 receptor agonist lixisenatide correlates with a reduction in postprandial glucose and glycated hemoglobin (HbA1c) in patients with T2DM.

METHODS

A post hoc analysis was performed on pooled data from the modified intent-to-treat populations of two lixisenatide Phase 3 trials: GetGoal-M (lixisenatide versus placebo as add-on to metformin) and GetGoal-S (lixisenatide versus placebo as add-on to sulfonylurea [SU] ± metformin). Glucagon levels were assessed 2 h after a standardized meal test performed at baseline and Week 24 and were examined for correlation with changes in 2-h postprandial glucose and HbA1c.

RESULTS

Lixisenatide reduced 2-h postprandial glucagon at Week 24 compared with placebo (P < 0.00001). The mean change in postprandial glucagon significantly correlated with reductions in postprandial glucose (P < 0.00001) and HbA1c (P < 0.00001).

CONCLUSION

A reduction in postprandial glucagon following lixisenatide administration correlated with a decrease in postprandial glucose and HbA1c in patients with T2DM insufficiently controlled on metformin and/or SU. This suggests that lowering of postprandial glucagon contributes to the overall glycemic improvement observed with lixisenatide.

FUNDING

Sanofi.

CLINICAL TRIAL NUMBERS

NCT00712673 (GetGoal-M) and NCT00713830 (GetGoal-S).

Use of V-Go® Insulin Delivery Device in Patients with Sub-optimally Controlled Diabetes Mellitus: A Retrospective Analysis from a Large Specialized Diabetes System

INTRODUCTION

Tight glycemic control and timely treatment can improve outcomes in patients with diabetes yet many remain sub-optimally controlled. The objective of the current study was to evaluate the effect of switching patients with sub-optimally controlled diabetes to the V-Go® (Valeritas Inc., Bridgewater, NJ, USA) Disposable Insulin Delivery device.

METHODS

A retrospective analysis of electronic medical records was conducted to assess patients with sub-optimal glycemic control defined as a glycated hemoglobin (HbA1c) >7%, switched to V-Go. Blood glucose control defined as change from baseline in HbA1c, prescribed insulin doses, body weight, concomitant anti-hyperglycemic agents, and reported hypoglycemia were collected prior to switching to V-Go and during V-Go use.

RESULTS

Two-hundred and four patients were evaluated during the study period. Overall, there was a significant decrease in HbA1c after switching to V-Go at the 14- and 27-week follow-up visits. The least-squares mean (LSM) change in HbA1c (95% confidence interval) from baseline to 14 weeks was -1.53% (-1.69% to -1.37%; P < 0.001), and from baseline to 27 weeks was -1.79% (-1.97% to -1.61%; P < 0.001). Significant reductions in mean HbA1c were achieved at both visits in all patient subsets: Patients with type 2 and type 1/latent autoimmune diabetes in adults (LADA); patients using insulin at baseline and patients naïve to insulin at baseline. Patients administering insulin at baseline required significantly less insulin on V-Go (86-99 LSM units/day at baseline to 58 LSM units/day at 27 weeks; P < 0.001). Across all patients, reported hypoglycemic events were no more frequent on V-Go than on previous therapy.

CONCLUSION

V-Go is safe and effective in patients with sub-optimally controlled diabetes requiring insulin therapy. Glycemic control improved significantly, less insulin was required, and hypoglycemic events were similar after patients switched to insulin delivery by V-Go.

FUNDING

Valeritas, Inc.

Lixisenatide plus basal insulin in patients with type 2 diabetes mellitus: a meta-analysis

AIMS

The efficacy of the once-daily prandial GLP-1 receptor agonist lixisenatide plus basal insulin in T2DM was assessed by pooling results of phase III trials.

METHODS

A meta-analysis was performed of results from three trials in the GetGoal clinical program concerning lixisenatide or placebo plus basal insulin with/without OADs. The primary endpoint was change in HbA1c from baseline to week 24. Secondary endpoints were change in PPG, FPG, insulin dose, and weight from baseline to week 24. Hypoglycemia rates and several composite endpoints were assessed.

RESULTS

Lixisenatide plus basal insulin was significantly more effective than basal insulin alone at reducing HbA1c at 24 weeks. Composite and secondary endpoints were improved significantly with lixisenatide plus basal insulin, with the exception of FPG, which showed no significant difference between the groups. Lixisenatide plus basal insulin was associated with an increased incidence of hypoglycemia versus basal insulin alone.

CONCLUSIONS

Lixisenatide plus basal insulin resulted in significant improvement in glycemic control versus basal insulin alone, particularly in terms of controlling PPG. Prandial lixisenatide in combination with basal insulin is a suitable option for treatment intensification in patients with T2DM insufficiently controlled with basal insulin, as these agents have complementary effects on PPG and FPG, respectively.

Differential effects of GLP-1 receptor agonists on components of dysglycaemia in individuals with type 2 diabetes mellitus

Metabolic consequences of glucagon-like peptide-1 receptor agonists (GLP-1 RAs) are the result of enhanced glucose-stimulated insulin secretion, inhibition of glucagon release, delayed gastric emptying and increased satiety. These attributes make GLP-1 agonists a treatment option in type 2 diabetes mellitus (T2DM). To optimise treatment choice, a detailed understanding of the effects of GLP-1 RAs on glucose homeostasis in individuals with T2DM is necessary. Although the various GLP-1 RAs share the same basic mechanisms of action, differences in pharmacokinetic/pharmacodynamic characteristics translate into differential effects on parameters of glycaemia. Head-to-head comparisons between long-acting non-prandial (liraglutide once daily and exenatide once weekly) and shorter-acting prandial (exenatide twice daily and lixisenatide once daily prandial) GLP-1 RAs confirm their differential effects on fasting plasma glucose (FPG) and post-prandial glucose (PPG). Liraglutide once daily and exenatide once weekly demonstrate greater reductions in FPG but lesser impacts on PPG excursions plasma than exenatide twice daily. Prandial GLP-1 RAs have a profound effect on post-prandial glycaemia, mediated by delaying gastric emptying, which is not subject to the tachyphylaxis occurring due to the sustained elevated plasma GLP-1 concentrations after treatment with long-acting GLP-1 RAs. Lixisenatide once-daily prandial, in contrast to liraglutide, strongly suppresses post-prandial glucagon secretion, further contributing to the more pronounced PPG-lowering effect found with lixisenatide. Evidence suggests that the GLP-1 RAs that predominantly target the prandial glucose excursions, such as exenatide twice daily and lixisenatide once-daily prandial, are therefore best used as combination therapy with basal insulin and will form an important new treatment option for individuals with T2DM.