Minimum Effective Dose of DPP-4 Inhibitors for Treating Early Stages of Diabetic Retinopathy in an Experimental Model

Diabetic retinopathy features in lund MetS rats

The Lund MetS rat (BBDR.cg-Leprdb/db.cp/LundRj) is a novel animal model that has a congenic leptin receptor deficiency (LepR-/-) and males exhibit a variety of metabolic abnormalities mimicking the human metabolic syndrome, including hyperglycemia, dyslipidemia, severe obesity, and a type 2 diabetes-like condition from 14 weeks of age. However, whether Lund MetS rats (LM rats) develop diabetic retinopathy is still unknown. The purpose is to investigate the features of diabetic retinopathy in this model. In this study, male LM rats aged 15 and 30 weeks were analyzed for pathological retinal changes, including vasculopathy, inflammation, reactive gliosis, oxidative stress, and neurodegeneration features on the retinas by histological, immunohistochemical, and gene and protein expression analysis. Compared with the non-diabetic LM rats, diabetic LM rats, mainly at 30 weeks of age, had a decrease in retinal thickness and loss of retinal ganglion cells and photoreceptors, indicating retinal neurodegeneration. They also presented an increase in VEGF-A expression, Endra, Icam-1, Vcam-1, and Endrb vascular genes, and albumin suggesting neurovascular unit dysfunction. Furthermore, retinas presented reactive gliosis and infiltration of microglia, TNF-α-positive vessels and expressed elevated levels of inflammatory genes Tnf-α, IL-18 and IL-6, and oxidative stress markers Sod2 and 8-hydroxy-2-deoxyguanosine (8-OHdG). Our results suggest that diabetic LM rats reproduce the early neurodegenerative and altered neuro-vascular features that also occur in the human diabetic eye.

An update on ocular effects of antidiabetic medications

The global increase in the prevalence of type 2 diabetes has led to the development and implementation of new classes of antidiabetic medications, introducing advanced therapeutic options for the management of the disease. These new medications, though primarily designed to regulate blood glucose levels, also have applications in weight management, potentially transforming the current approaches to diabetes treatment. Newer medications, however, have ophthalmic side effects with controversies in trials and real-life data. We comprehensively assessed the ocular benefits and adverse effects of traditional and newer-generation anti-diabetic drugs. Our primary focus is on how these newer medications affect the stage of diabetic retinopathy. Additionally, we explore the associations between these medications and other ocular conditions, including age-related macular degeneration, glaucoma, orbital conditions, and diseases impacting the ocular surface. Furthermore, we provide contextual background by discussing the ocular effects of traditional anti-diabetic drugs.

Ocular and Plasma Pharmacokinetics of Sitagliptin Eye Drops: Preclinical Data

Background/Objectives: Early stages of diabetic retinopathy are currently considered an unmet medical need due to the lack of effective treatments beyond proper monitoring and control of glycemia and blood pressure. Sitagliptin eye drops have emerged as a new therapeutic approach against early stages of the disease, as they can prevent its main hallmarks, including both neurodegeneration and microvascular impairment. Interestingly, all of these effects occur without any glycemic systemic improvement. In the present study, we aimed to investigate the pharmacokinetics and distribution of the drug within the eye and plasma. Methods: A total of 48 male New Zealand rabbits were treated with topical administration (eye drops) of sitagliptin at two concentrations: 5 mg/mL and 10 mg/mL. Blood, iris/ciliary body, retina/choroid, aqueous humor, and vitreous humor samples were collected at specific intervals post-administration (10 and 30 min and 1, 3, 6, 15, and 24 h), processed, and analyzed using an LC-MS/MS method. The pharmacokinetics of sitagliptin were then calculated, and statistical comparisons were performed. Results: Our findings indicate that sitagliptin reaches the retina prior to the aqueous and vitreous humors, suggesting that its absorption follows the transscleral route. Additionally, systemic absorption was minimal and below pharmacologically active concentrations. Conclusions: These results support the use of an eye drop formulation for the treatment of diabetic retinopathy and other retinal diseases.

Dipeptidyl peptidase 4 inhibitors, sodium glucose cotransporter 2 inhibitors, and glucagon-like peptide 1 receptor agonists do not worsen diabetic macular edema

AIMS

There are limited studies on dipeptidyl-peptidase 4 inhibitor (DPP-4i), sodium glucose cotransporter 2 inhibitor (SGLT2-i), and glucagon-like peptide 1 (GLP-1) receptor agonist use and occurrence of diabetic macular edema (DME). The objective of this study was to determine the association between DPP-4i, SGLT2-i, and GLP-1 receptor agonist use and occurrence of DME.

METHODS

Proportional hazard models were used to evaluate the change in hazard of developing DME associated with DPP-4i, SGLT2-i, or GLP-1 receptor agonist use. Models accounted for age at DR diagnosis, DR severity (proliferative vs non-proliferative stage), time-weighted average of HbA1c level, sex, and self-reported race/ethnicity. A p-value ≤ 0.05 was considered statistically significant.

RESULTS

The hazard ratio of developing DME after diagnosis of DR was 1.2 (CI = 0.75 to 1.99; p = 0.43) for DPP-4i use, 0.93 (CI = 0.54 to 1.61; p = 0.81) for GLP-1 receptor agonist use, 0.82 (CI = 0.20 to 3.34; p = 0.78) for SGLT2-i use, 1.1 (CI = 0.75 to 1.59; p = 0.66) for any one medication use, 1.1 (CI = 0.62 to 2.09; p = 0.68) and for any two or more medications use.

CONCLUSIONS

We did not find an association between DPP-4i, SGLT2-i, or GLP-1 receptor agonist use and increased hazard of development of DME among patients with DR.

Influence of Gegenqinlian decoction on pharmacokinetics and pharmacodynamics of saxagliptin in type 2 diabetes mellitus rats

Gegenqinlian decoction (GQD) is a classic prescription of traditional Chinese medicine (TCM), which originated from Shanghanlun. The combination of GQD and hypoglycemic drugs (saxagliptin, Sax, metformin) is often used to treat Type 2 diabetes mellitus (T2DM) in TCM clinics. However, the herb-drug interactions (HDIs) between GQD and hypoglycemic drugs are still unclear. In order to determine the safety of the combination, we assessed the influences of GQD on the pharmacokinetics and pharmacodynamics of Sax in T2DM rats. The plasma concentration of Sax (5 mg/kg) pretreated with GQD (freeze-dried powder, 1.35 g/kg) or not was determined by high-performance liquid chromatography (HPLC), and pharmacokinetics parameters were calculated. The influence of GQD on the pharmacodynamics of Sax was investigated by detecting the levels of weight, (see abbreviations list) OGTT, TC, TG, LDL-C, HDL-C, FBG, FINS, HOMA-IR, QUICKI, AST, ALT, and the liver coefficient. The Cmax , AUC0-t ,and AUC0-∞ of Sax increased significantly in the combination group whether in normal or T2DM rats. The results of pharmacodynamics showed that the weight of rats in each treatment group increased. FBG, TC, TG, LDL-C, and HOMA-IR decreased, HDL-C, FINS, and QUICKI increased significantly (p < 0.05) compared with the model control group. The result showed that the combination of GQD and Sax could not only improve the hypoglycemic effect but also increase the plasma exposure of Sax. The potential HDIs between GQD and Sax should be taken into consideration in clinics. Moreover, for the complexity of the human compared with experimental animals, as well as genetic differences, the in-depth study should be carried out to assess the uniformity of the pharmacokinetics and pharmacodynamics between rats and humans.

Continuous Glucose Monitoring as an Additional Tool in Early Cystic Fibrosis-Related Diabetes Monitoring and in Evaluation of Short-Term Sitagliptin Response

Cystic fibrosis-related diabetes (CFRD) is a complication associated with a negative prognosis in patients with cystic fibrosis (CF). Although the oral glucose tolerance test (OGTT) is the widely recommended screening test for CFRD diagnosis, continuous glucose monitoring (CGM) is increasingly considered a useful and easy-to-perform test for diagnosis and follow-up in clinical practice. Regarding CFRD treatment, although insulin is the classic approved pharmacological option, incretins could also be a helpful alternative in early stages. CGM could be also a useful tool to measure the early response to this therapy.

METHODS

We studied 25 CF patients with abnormal OGTT results and compared glucose and insulin levels during the OGTTs with CGM results as a tool for early CFRD diagnosis. In addition, we evaluated glycaemic control with CGM before and after treatment with sitagliptin.

RESULTS

A correlation was found between lower plasma insulin levels during the OGTTs and higher average sensor glucose (p = 0.009) and hyperglycaemic excursions (p = 0.017). The CGM data on sitagliptin treatment (n = 25) showed an average glycaemic improvement from 124.2 to 117.2 mg/dL (p = 0.002) with a 5.6-point standard deviation of glucose decrease (p < 0.001). Hyperglycaemic excursions ≥200 mg/dL diminished 57.1% (p = 0.021). Both time in range and time above 180 mg/dL improved during treatment (p = 0.036 and p = 0.006, respectively).

CONCLUSION

CGM is a useful tool that offers valuable information for both the diagnosis and the management of CFRD. Lower plasma insulin levels during OGTTs are associated with a poor ambulatory glucose profile in CGM. Sitagliptin could play an important role in the treatment of the early stages of CFRD.

Saxagliptin alleviates erectile dysfunction through increasing stromal cell-derived factor-1 in diabetes mellitus

BACKGROUND

Diabetes mellitus-induced erectile dysfunction (DMED) is one of the complications of diabetes and has a poor response to phosphodiesterase type 5 inhibitor, the first-line treatment for ED. Saxagliptin (Sax), a dipeptidyl peptidase-4 inhibitor (DPP-4i), has been officially used in the treatment of type 2 diabetes. Stromal cell-derived factor-1 (SDF-1) is one of the important substrates of DPP-4, and has been proven to be beneficial for several DM complications. However, it is unknown whether Sax contributes to the management of DMED.

OBJECTIVES

To explore the effect and possible underlying mechanisms of Sax in the treatment of DMED.

METHODS

The model of DM was established by intraperitoneal injection of streptozotocin. All rats were divided into three groups (n = 8 per group): control group, DMED group and DMED+Sax group. In cellular experiments, the corpus cavernosum smooth muscle cells (CCSMCs) were exposed to high glucose (HG), and treated with Sax and AMD3100 (SDF-1 receptor inhibitor). The penile tissue and CCSMCs were harvested for detection.

RESULTS

We found that erectile function was impaired in DMED rats compared with the control group, which was partially relieved by Sax. Decreased expression of DPP-4 and increased level of SDF-1 were also observed in DMED+Sax group, together with elevation of PI3K/AKT pathway and inhibition of endothelial dysfunction, oxidative stress and apoptosis in corpus cavernosum. Moreover, Sax could also regulate oxidative stress and apoptosis in CCSMCs under HG condition, which was blocked in part by AMD3100.

CONCLUSION

Sax could alleviate DMED through increasing SDF-1 and PI3K/AKT pathway, in company with moderation of endothelial dysfunction, oxidative stress and apoptosis. Our findings indicated that DPP-4 is may be beneficial to the management of DMED.