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Dipeptidyl peptidase (DPP)-4 and neprilysin (NEP) rapidly degrade glucagon-like peptide 1 (GLP-1) in mice. Commercially available sandwich ELISA kits may not accurately detect the degradation products, leading to potentially misleading results. We aimed to stabilize GLP-1 in mice allowing reliable measurement with sensitive commercially available ELISA kits. Non-anesthetized male C57Bl/6JRj mice were subjected to an oral glucose tolerance test (OGTT; 2 g/kg glucose), and plasma total and intact GLP-1 were measured (Mercodia and Alpco ELISA kits, respectively). No GLP-1 increases were seen in samples taken beyond 15 minutes after the glucose load. Samples taken at 5 and 10 minutes after the OGTT showed a minor increase in total, but not intact GLP-1. We then administered saline (control), or a DPP-4 inhibitor (valine pyrrolidide or sitagliptin) with or without a NEP-inhibitor (sacubitril) 30 minutes before the OGTT. In the inhibitor groups only, intact GLP-1 increased significantly during the OGTT. After injecting male C57Bl/6JRj mice with a known dose of GLP-1(7-36)NH2, peak GLP-1 levels were barely detectable after saline, but 5-10-fold higher during sitagliptin and the combination of sitagliptin/sacubitril. The half-life of the GLP-1 plasma disappearance increased up to 7-fold during inhibitor treatment. We conclude that reliable measurement of GLP-1 secretion is not possible in mice in vivo with commercially available sandwich ELISA kits, unless degradation is prevented by inhibition of DPP-4 and perhaps neprilysin. The described approach allows improved estimates of GLP-1 secretion for future studies, although it is a limitation that these inhibitors additionally influence levels of insulin and glucagon.

Objective: Fiber-free diet impairs intestinal and colonic health in mice, in parallel with a reduction in glucagon like peptide-1 (GLP-1) levels. Endogenous GLP-1 is important for intestinal growth and maintenance of the intestinal integrity. We aimed to investigate whether fiber-free diet reduces luminal content of metabolites which, upon supplementation, could increase GLP-1 secretion and restore the adverse effects of fiber-free diet. Methods: Untargeted metabolomics (LC-MS) was performed on colonic content of mice fed a fiber-free diet, identifying a metabolite of particular interest: indole-3-carboxyaldehyde (I3A). We exposed cultured GLUTag cells to I3A, and measured cumulative GLP-1 secretion. Isolated colon perfusions were performed in male C57BL/6JRj mice and Wistar rats. I3A was administered luminally or vascularly, and GLP-1 was measured in portal vein effluent. Finally, female C57BL/6JRJ mice were fed chow or fiber-free diet, with I3A or vehicle by oral gavage. After 10 days, plasma GLP-1 (ELISA) and intestinal permeability (FITC-dextran) were measured, animals were sacrificed and organs removed for histology. Results: Mice fed a fiber-free diet had significantly lower I3A in their colonic content compared to a control diet (7883 ± 3375 AU, p=0.04). GLP-1 secretion from GLUTag cells was unchanged after five minutes of exposure to I3A. However, GLP-1 levels increased after 120 minutes of exposure to 1 mM (60% increase, p=0.016) and 5 mM (89% increase, p=0.0025) I3A. In contrast, 48 h exposure to 1 mM decreased GLP-1 secretion (51% decrease, p<0.001) and viability. In isolated perfused mouse and rat colon, I3A applied into the luminal or vascular side did not affect GLP-1 secretion. Mice fed a fiber-free diet tended to weigh less compared to chow fed mice; and the small intestine and colon were significantly smaller. No differences were seen in crypt depth, villus length, mucosal area, and intestinal permeability. Supplementing I3A did not affect bod

Aim: To study the effects of the sodium-glucose co-transporter-2 (SGLT2) inhibitor empagliflozin, the angiotensin receptor blocker (ARB) losartan, and their combination on blood pressure, while studying the mechanisms potentially involved. Methods: A total of 24 people with type 2 diabetes (T2D) (age: 66 ± 6 years; body mass index: 31.0 ± 3 kg/m2; estimated glomerular filtration rate: 90 ml/min/1.73m2) received a 1-week treatment with empagliflozin 10 mg once daily, losartan 50 mg once daily, their combination, and placebo, in a randomized double-blind crossover design, with 4-week washout periods in between. Blood pressure, arterial stiffness, autonomic nervous system activity and plasma volume, extracellular fluid and serum albumin were assessed. Results: Versus placebo (139 mmHg), empagliflozin reduced systolic blood pressure (SBP) by 8 mmHg (P =.001), losartan by 12 mmHg (P =.001) and empagliflozin + losartan by 15 mmHg (P <.001). Combination therapy had a larger SBP-lowering effect versus empagliflozin monotherapy (-7 [95% CI -12; -2] mmHg) and numerically larger effects versus losartan monotherapy (-3 [-8; 2] mmHg). Empagliflozin reduced sympathetic nervous system (SNS) activity, arterial stiffness and extracellular fluid, while increasing serum albumin. Losartan reduced SNS activity and arterial stiffness. Combination therapy induced volume contraction variables, together with a reduction in SNS activity and arterial stiffness. Conclusion: In people with T2D, SGLT2 inhibition in combination with an ARB had a larger blood pressure-lowering effect versus placebo than either of the drugs alone. Our data further suggest that the mechanisms underlying these blood pressure reductions at least partially differ between these agents.

In recent years, we have witnessed the many beneficial effects of glucagon-like peptide (GLP)-1 receptor agonists, including the reduction in cardiovascular risk in patients with type 2 diabetes, and the reduction of body weight in those with obesity. Increasing evidence suggests that these agents differ considerably from endogenous GLP-1 when it comes to their routes of action, although their clinical effects appear to be the same. Given the limitations of the GLP-1 receptor agonists, could it be useful to develop agents which stimulate GLP-1 release? Here we will discuss the differences and similarities between GLP-1 receptor agonists and endogenous GLP-1, and will detail how endogenous GLP-1—when stimulated appropriately—could have clinically relevant effects.

AIMS: To determine the effect of dipeptidyl-peptidase (DPP)-4-inhibitor linagliptin on postprandial glomerular hyperfiltration compared to the sulfonylurea glimepiride in adults with type 2 diabetes (T2DM).MATERIALS AND METHODS: In this pre-defined sub-study within a randomized, double-blind, parallel-group, intervention-trial, overweight people with T2DM without renal-impairment were treated with once-daily linagliptin 5 mg (N = 10) or glimepiride 1 mg (N = 13) as add-on to metformin for 8 weeks. After a standardized liquid protein-rich meal, GFR and effective renal plasma flow were determined by inulin and para-aminohippuric acid clearance, respectively, based on timed urine-sampling. Intrarenal hemodynamics were estimated using Gomez'-equations. Glucoregulatory/vasoactive hormones, urinary-pH and fractional excretions (FE) of sodium, potassium and urea were measured.RESULTS: Linagliptin compared to glimepiride increased postprandial filtration fraction (FF; mean-difference 2.1%; P = 0.016) and estimated glomerular hydraulic pressure (mean-difference 3.0 mmHg; P = 0.050), and tended to increase GFR (P = 0.08) and estimated efferent renal arteriolar resistance (RE ; P = 0.08) from baseline to Week-8. No differences in FE were noted. Glimepiride reduced HbA1c more than linagliptin (mean-difference - 0.40%; P = 0.004), without between-group differences in time-averaged postprandial glucose-levels. In the linagliptin-group, change in FF correlated with change in mean arterial pressure (R = 0.807; P = 0.009) and time-averaged-mean glucagon (R = 0.782; P = 0.008), but not with changes in glucose, insulin, intact GLP-1, renin or FENa . Change in glucagon was associated with change in RE (R = 0.830; P = 0.003).CONCLUSIONS: In contrast to our hypothesis, linagliptin compared to glimepiride does not reduce postprandial hyperfiltration, yet seems to increase FF after meal-ingestion by increasing blood pressure or RE . This article is protected by copy

Aim: To determine the effect of the dipeptidyl peptidase-4 inhibitor linagliptin on postprandial glomerular hyperfiltration compared with the sulphonylurea glimepiride in adults with type 2 diabetes (T2D). Materials and Methods: In this predefined substudy within a randomized, double-blind, parallel-group, intervention trial, overweight people with T2D without renal impairment were treated with once-daily linagliptin 5 mg (N = 10) or glimepiride 1 mg (N = 13) as an add-on to metformin for 8 weeks. After a standardized liquid protein-rich meal, the glomerular filtration rate (GFR) and effective renal plasma flow were determined by inulin and para-aminohippuric acid clearance, respectively, based on timed urine sampling. Intrarenal haemodynamics were estimated using the Gomez equations. Glucoregulatory/vasoactive hormones, urinary pH and fractional excretions (FE) of sodium, potassium and urea were measured. Results: Compared with glimepiride, linagliptin increased the postprandial filtration fraction (FF; mean difference 2.1%-point; P =.016) and estimated glomerular hydraulic pressure (mean difference 3.0 mmHg; P =.050), and tended to increase GFR (P =.08) and estimated efferent renal arteriolar resistance (RE; P =.08) from baseline to week 8. No differences in FE were noted. Glimepiride reduced HbA1c more than linagliptin (mean difference −0.40%; P =.004), without between-group differences in time-averaged postprandial glucose levels. In the linagliptin group, change in FF correlated with change in mean arterial pressure (R = 0.807; P =.009) and time-averaged mean glucagon (R = 0.782; P =.008), but not with changes in glucose, insulin, intact glucagon-like peptide-1, renin or FENa. Change in glucagon was associated with change in RE (R = 0.830; P =.003). Conclusions: In contrast to our hypothesis, compared with glimepiride, linagliptin does not reduce postprandial hyperfiltration, yet appears to increase FF after meal ingestion by