Complications of diabetes therapy

Analyzing Gene Expression After Administration of Low-Intensity Therapeutic Ultrasound in Human Islet Cells

OBJECTIVES

Diabetes mellitus is a complex heterogenous metabolic disease that significantly affects the world population. Although many treatments exist, including medications such as metformin, sulfonylureas, and glucagon-like peptide-1 (GLP) receptor agonist, there is growing interest in finding alternative methods to noninvasively treat this disease. It has been previously shown that low-intensity ultrasound stimulation of pancreatic β-cells in mice can elicit insulin secretion as a potential treatment for this disease. This is desirable as therapeutic ultrasound has the ability to induce bioeffects while selectively focusing deep within tissues, allowing for modulation of hormone secretion in the pancreas to mitigate insufficient levels of insulin.

METHODS

Exactly 800 kHz ultrasound with intensity 0.5 W/cm2 was administered 5 minutes continuously, that is, 100% duty cycle, to donor pancreatic human islets, followed by 1 hour incubation and RT-qPCR to assess the effect of ultrasound stimulation on gene expression. The genes were insulin (INS), glucagon (Glu), amylin (Amy), and binding immunoglobulin protein (BiP). Nine donor pancreatic human islets were used to assess insulin and glucagon secretion, while eight samples were used for amylin and BiP. Fold change (FC) was calculated to analyze the effect of ultrasound stimulation on the gene expression of the donor islet cells. High-glucose and thapsigargin-treated islets were utilized as positive controls. Cell viability testing was done using a Trypan Blue Exclusion Test.

RESULTS

Ultrasound stimulation did not cause a statistically significant upregulation in any of the tested genes (INS FC = 1.15, P-value = .5692; Glu FC = 1.60, P-value = .2231; Amy FC, P-value = .2863; BiP FC = 2.68, P-value = .3907).

CONCLUSIONS

The results of this study show that the proposed ultrasound treatment parameters do not appear to significantly affect gene expression of any gene tested.

New-Generation Glucokinase Activators: Potential Game-Changers in Type 2 Diabetes Treatment

Achieving glycemic control and sustaining functional pancreatic β-cell activity remains an unmet medical need in the treatment of type 2 diabetes mellitus (T2DM). Glucokinase activators (GKAs) constitute a class of anti-diabetic drugs designed to regulate blood sugar levels and enhance β-cell function in patients with diabetes. A significant progression in GKA development is underway to address the limitations of earlier generations. Dorzagliatin, a dual-acting GKA, targets both the liver and pancreas and has successfully completed two phase III trials, demonstrating favorable results in diabetes treatment. The hepato-selective GKA, TTP399, emerges as a strong contender, displaying clinically noteworthy outcomes with minimal adverse effects. This paper seeks to review the current literature, delve into the mechanisms of action of these new-generation GKAs, and assess their efficacy and safety in treating T2DM based on published preclinical studies and recent clinical trials.

Protective potential of fish oil supplementation against insulin resistance and pancreatic islet damage in STZ-induced Wistar rats

Background

Fish oil, which is regarded as the primary source of omega-3 fatty acids, has been long studied for its potential as an antidiabetic therapy. However, its protective ability against insulin resistance and pancreatic islet alteration remains unclear and controversial.

Aim

To investigate the beneficial effects of fish oil consumption on the progression of insulin resistance and pancreatic islet dysfunction in a rat model of diabetes.

Methods

Diabetic rats model (n = 30) were divided into five groups and received; 1) NS injection + NS oral (normal control); 2) NS injection + 3 g/kg fish oil (fish oil control); 3) streptozotocin (STZ) injection + NS oral [diabetes control (DC)]; 4) STZ injection + 1 g/kg fish oil (DFO1); and 5) STZ injection + 3 g/kg fish oil (DFO3). Fasting blood insulin was analyzed by commercial rat insulin enzyme-linked immunosorbent assay; meanwhile, the determination of insulin sensitivity was calculated by homeostatic model assessment of insulin resistance (HOMA-IR) and homeostatic model assessment of beta-cell function. A histological study was conducted on pancreas tissue using H and E staining.

Results

Fish oil supplementation reduced hyperglycemia and ameliorated HOMA-IR in STZ-induced animal models indicating that fish oil supplementation improved insulin sensitivity. Furthermore, animals treated with fish oil at a dose of 3 g/kg (DFO3) showed an enhancement in pancreatic islets, which was displayed by less abnormal structures than DC animals. This could imply that the administration of fish oil, especially rich in bioactive omega-3 fatty acids effectively inhibits insulin resistance and restore islet of Langerhans alteration in rats injected with STZ.

Conclusion

Thus, the current study suggested that fish oil supplementation could support the treatment of diabetes but should not be considered as an alternative therapy.

Functionalized Collagen/Poly(ethylene glycol) Diacrylate Interpenetrating Network Hydrogel Enhances Beta Pancreatic Cell Sustenance

Three-dimensional matrices are a new strategy used to tackle type I diabetes, a chronic metabolic disease characterized by the destruction of beta pancreatic cells. Type I collagen is an abundant extracellular matrix (ECM), a component that has been used to support cell growth. However, pure collagen possesses some difficulties, including a low stiffness and strength and a high susceptibility to cell-mediated contraction. Therefore, we developed a collagen hydrogel with a poly (ethylene glycol) diacrylate (PEGDA) interpenetrating network (IPN), functionalized with vascular endothelial growth factor (VEGF) to mimic the pancreatic environment for the sustenance of beta pancreatic cells. We analyzed the physicochemical characteristics of the hydrogels and found that they were successfully synthesized. The mechanical behavior of the hydrogels improved with the addition of VEGF, and the swelling degree and the degradation were stable over time. In addition, it was found that 5 ng/mL VEGF-functionalized collagen/PEGDA IPN hydrogels sustained and enhanced the viability, proliferation, respiratory capacity, and functionality of beta pancreatic cells. Hence, this is a potential candidate for future preclinical evaluation, which may be favorable for diabetes treatment.

Evaluation of antihyperglycemic activity of aqueous stem bark extract of Boswellia dalzielii in alloxan-induced diabetic Wistar rats

Background

Diabetes mellitus is one of the leading causes of morbidity and mortality globally. Although synthetic hypoglycemic agents are commonly used to manage this disorder, such medications, besides being unable to cure the disease, are expensive and associated with side effects. Conversely, medicinal plants have emerged as effective, safe and affordable alternative treatments. Boswellia dalzielii plant has been reported to possess ethnomedicinal properties for the treatment of various health conditions; however, scientific studies exploring this plant as antihyperglycemic agent are still limited. Thus, this study evaluated the antihyperglycemic activity of aqueous stem bark extract (ASBE) of B. dalzielii in alloxan-induced diabetic Wistar albino rats.

Methods

Phytochemical screening of the ASBE of B. dalzielii was conducted. Twenty male Wistar albino rats weighing 100–150 g divided into 4 groups (A–D) of five rats were used for the study. Group A served as the normal control and received neither ASBE of B. dalzielii nor glibenclamide. The treatment for the other three groups was as follows: Group B, 10 mg/kg of glibenclamide (diabetic control); Group C, 500 mg/kg ASBE of B. dalzielii; and Group D, 1000 mg/kg ASBE of B. dalzielii. Treatments were administered orally every 24 h for a period of 2 weeks. Blood glucose level and body weight were evaluated at weeks 0, 1 and 2. Histomorphological features of the rats’ pancreas in all the groups were compared.

Results

The phytochemical analysis revealed the presence of alkaloids, saponins, tannins, cardiac glycosides, flavonoids, carbohydrates, steroids and triterpenes. The two different doses of the plant extract significantly reduced blood glucose level at weeks 1 and 2 (all p < 0.05), with the 1000 mg/kg dose demonstrating a greater reduction compared with glibenclamide at week 2 (p = 0.014). However, only the 500 mg/kg dose led to restoration, albeit slight, of the pancreatic islet cells.

Conclusion

This study suggests that B. dalzielii plant exhibits a potent antihyperglycemic activity evidenced by reduced blood glucose levels and slight restoration of pancreatic islet cells. This plant could be, therefore, considered in the treatment of diabetes mellitus.

Graphical Abstract

Antidiabetic effect of aqueous stem bark extract of Parinari macrophylla in alloxan-induced diabetic Wistar rats

Background

Diabetes is a major public health problem with increasing prevalence globally. Plant-based medicines for diabetes are gaining popularity across the world due to perceptions of efficacy, safety and cost-effectiveness. The plant, Parinari macrophylla, has been widely reported to possess potent ethnomedicinal properties especially in the northern part of Nigeria. However, there has been no scientific documentation of this plant to be used as an antidiabetic agent. The objective of this study was to investigate the antidiabetic effect of aqueous stem bark extract of P. macrophylla in alloxan-induced diabetic Wistar rats. Phytochemical screening and acute toxicity studies were conducted. Wistar rats weighing between 100 and 150 g were used for the study and diabetes was induced using alloxan monohydrate (150 mg/kg) intraperitoneally. The animals were treated with different doses of aqueous stem bark extract of P. macrophylla (1000 mg/kg and 2000 mg/kg) for 2 weeks. Blood glucose levels and body weight were then monitored. Histopathological investigation of pancreatic tissue was also conducted.

Results

The phytochemical analysis revealed the presence of alkaloids, saponins, tannins, cardiac glycosides, carbohydrates, steroids, and triterpenes as secondary metabolites. The acute toxicity test revealed no mortality with a median lethal dose determined to be above 5000 mg/kg. Although the two different doses of aqueous stem bark extract of P. macrophylla decreased blood glucose levels at weeks 1 and 2, a statistically significant difference (P < 0.05) was only observed for the group treated with 2000 mg/kg dose compared to the diabetic control group at week 2. The histological investigation revealed that the two different doses of aqueous stem bark extract of P. macrophylla caused regeneration of pancreatic islet cells, with the 2000 mg/kg dose being more evident.

Conclusion

This study suggests that the stem bark extract of P. macrophylla possesses a potent antidiabetic effect and may potentially be used to treat diabetes and associated complications.

Graphical Abstract

Centella asiatica alleviates diabetes-induced changes in fatty acid profile and oxidative damage in rat testis

The in vivo effects of Centella asiatica L. Urban (Family: Apiaceae; CA) on diabetes-induced testicular fatty acid misdistribution and oxidative injury were investigated. Diabetic rats were treated with vehicle, CA or metformin daily for 14 days by oral gavage. Fatty acid (FA) content in testis was analysed using gas chromatography-flame ionisation detection while redox indices were measured as peroxide value (PV), malondialdehyde (MDA), oxygen radical antioxidant capacity (ORAC), reduced glutathione (GSH), glutathione S-transferase (GST) and glutathione peroxidase (GPx) activities. Diabetes increased omega-6 (61%), and decreased omega-3 (23%) and monounsaturated fatty acids (MUFA; 18%) compared to non-diabetic controls. Oxidative injury in diabetic rats was confirmed by increases in PV (112%) and MDA (77%) in addition to decreases in GSH (41%) and activities of GST (19%) & GPx (24%) compared to non-diabetic controls. CA treatment led to 17% reduction in omega-6 and 33% rise in MUFA compared to diabetic controls. Additionally, CA ameliorated the oxidative injury and improved antioxidant capacity by increasing GSH (49%), GST (16%) and GPx (23%) when compared to diabetic controls. Data suggest CA potential in alleviating the alterations caused by diabetes in testes through effects on omega-6 and MUFA; and via increased GSH level and dependent enzyme activities.

In vivo generation and regeneration of β cells in zebrafish

The pathological feature of diabetes, hyperglycemia, is a result of an inadequate number and/or function of insulin producing β cells. Replenishing functional β cells is a strategy to cure the disease. Although β-cell regeneration occurs in animal models under certain conditions, human β cells are refractory to proliferation. A better understanding of both the positive and the negative regulatory mechanisms of β-cell regeneration in animal models is essential to develop novel strategies capable of inducing functional β cells in patients. Zebrafish are an attractive model system for studying β-cell regeneration due to the ease to which genetic and chemical-genetic approaches can be used as well as their high regenerative capacity. Here, we highlight the current state of β-cell regeneration studies in zebrafish with an emphasis on cell signaling mechanisms.

Glucagon-like peptide-1 receptor agonists and risk of bone fracture in patients with type 2 diabetes: A meta-analysis of randomized controlled trials

AIMS

To evaluate the association between glucagon-like peptide-1 receptor agonists (GLP-1 RAs) and the risk of bone fracture in patients with type 2 diabetes mellitus (T2DM).

MATERIALS AND METHODS

We conducted a systematic literature search in PubMed, Embase, the Cochrane Library, and Web of Science from inception to 28 February 2018 and identified eligible randomized controlled trials. The following data were extracted from each study: first author, year of publication, sample size, patient characteristics, study design, intervention drug, control drug, follow-up time, and incident bone fracture events. A meta-analysis was conducted using Review Manager 5.3 software to calculate the odds ratio (OR) and 95% confidence intervals (CI) for dichotomous variables.

RESULTS

A total of 38 studies with 39 795 patients with T2DM were included. There were 241 incident bone fracture cases (107 in the GLP-1 RAs group and 134 in the control group). Compared with patients who received placebo and other anti-diabetic drugs, those who received GLP-1 RAs treatment showed a pooled OR of 0.71 (95% CI, 0.56-0.91) for bone fracture. Subgroup analysis showed that treatments with liraglutide and lixisenatide were associated with significantly reduced risk of bone fractures (ORs, 0.56; 95% CI, 0.38-0.81 and 0.55; 95% CI, 0.31-0.97, respectively). However, other GLP-1 RAs did not show superiority to placebo or other anti-diabetic drugs. Moreover, these beneficial effects were dependent on the duration of GLP-1 RAs treatment, only a GLP-1 RAs treatment period of more than 52 weeks could significantly lower the risk of bone fracture in patients with T2DM (OR, 0.71; 95% CI, 0.56-0.91).

CONCLUSIONS

Compared with placebo and other anti-diabetic drugs, liraglutide and lixisenatide were associated with a significant reduction in the risk of bone fractures, and the beneficial effects were dependent on the duration of treatment.

A novel high-performance liquid chromatographic method combined with fluorescence detection for determination of ertugliflozin in rat plasma: Assessment of pharmacokinetic drug interaction potential of ertugliflozin with mefenamic acid and ketoconazole

Ertugliflozin (ERTU) is a novel, potent, and highly selective sodium glucose cotransporter 2 inhibitor that has been recently approved for the treatment of type 2 diabetes mellitus. We describe a novel bioanalytical method using high-performance liquid chromatography (HPLC) coupled with fluorescence detection for quantitative determination of ERTU in rat plasma. Acetonitrile-based protein precipitation method was used for sample preparation, and chromatographic separation was performed on a Kinetex® C18 column with an isocratic mobile phase comprising acetonitrile and 10 mM potassium phosphate buffer (pH 6.0). The eluent was monitored by a fluorescence detector at an optimized excitation/emission wavelength pair of 277/320 nm. The method was validated to demonstrate the selectivity, linearity (ranging from 4 to 2000 ng/mL), precision, accuracy, recovery, matrix effect, and stability in line with the current FDA guidelines. The newly developed method was successfully applied to investigate the pharmacokinetic interactions of ERTU with mefenamic acid (MEF) and ketoconazole (KET). The findings of the present study revealed that the pharmacokinetics of ERTU may be altered by concurrent administration of MEF and KET in rats. To our knowledge, the present study is the first to develop a validated bioanalytical method for quantification of ERTU using HPLC coupled with fluorescence detection and to assess the drug interaction potential of ERTU with non-steroidal anti-inflammatory (MEF) and azole antifungal (KET) drugs.

Suppression of Prolactin Secretion Partially Explains the Antidiabetic Effect of Bromocriptine in ob/ob Mice

Previous studies have shown that bromocriptine mesylate (Bromo) lowers blood glucose levels in adults with type 2 diabetes mellitus; however, the mechanism of action of the antidiabetic effects of Bromo is unclear. As a dopamine receptor agonist, Bromo can alter brain dopamine activity affecting glucose control, but it also suppresses prolactin (Prl) secretion, and Prl levels modulate glucose homeostasis. Thus, the objective of the current study was to investigate whether Bromo improves insulin sensitivity via inhibition of Prl secretion. Male and female ob/ob animals (a mouse model of obesity and insulin resistance) were treated with Bromo and/or Prl. Bromo-treated ob/ob mice exhibited lower serum Prl concentration, improved glucose and insulin tolerance, and increased insulin sensitivity in the liver and skeletal muscle compared with vehicle-treated mice. Prl replacement in Bromo-treated mice normalized serum Prl concentration without inducing hyperprolactinemia. Importantly, Prl replacement partially reversed the improvements in glucose homeostasis caused by Bromo treatment. The effects of the Prl receptor antagonist G129R-hPrl on glucose homeostasis were also investigated. We found that central G129R-hPrl infusion increased insulin tolerance of male ob/ob mice. In summary, our findings indicate that part of Bromo effects on glucose homeostasis are associated with decrease in serum Prl levels. Because G129R-hPrl treatment also improved the insulin sensitivity of ob/ob mice, pharmacological compounds that inhibit Prl signaling may represent a promising therapeutic approach to control blood glucose levels in individuals with insulin resistance.

Tube Feeding with a Diabetes-Specific Enteral Formula Improves Glycemic Control in Severe Acute Ischemic Stroke Patients

BACKGROUND

Glycemic control is essential for managing acute stroke. This study evaluated the impact of a diabetes-specific formula (DSF) on glycemic control in severe acute ischemic stroke patients.

METHODS

A randomized, prospective controlled trial was conducted in Nanjing Drum Tower Hospital. Acute ischemic stroke patients who scored > 10 on the National Institutes of Health Stroke Scale as well as had swallowing problems were randomized to group A, which received a diabetes-specific enteral formula, and group B, which received a standard formula. Glycemic parameters were assessed at baseline and 7 days after admission.

RESULTS

One hundred four patients were enrolled in the study (group A, 53; group B, 51). Postprandial glucose parameters, including capillary glucose concentration from 8 hours to 16 hours after enteral nutrition (EN) consumption, incremental areas under the curve (iAUC_{0-16 h} ), peak value, and mean glucose concentration, were significantly lower in group A than in group B following a 7-day intervention period. Moreover, changes in HOMA_IR after the 7-day treatment were significantly higher in group A than in group B. No significant difference in the incidence of hypoglycemia, glycemic variability parameters, or nutrition parameters was found between the 2 groups, either at baseline or after treatment. There were no serious adverse events observed during the study.

CONCLUSION

A diabetes-specific formula may improve acute-term glycemic control in severe acute ischemic stroke patients.

Preclinical and Clinical Studies for Sodium Tungstate: Application in Humans

Diabetes is a complex metabolic disorder triggered by the deficient secretion of insulin by the pancreatic β-cell or the resistance of peripheral tissues to the action of the hormone. Chronic hyperglycemia is the major consequence of this failure, and also the main cause of diabetic problems. Indeed, several clinical trials have agreed in that tight glycemic control is the best way to stop progression of the disease. Many anti-diabetic drugs for treatment of type 2 diabetes are commercially available, but no ideal normoglycemic agent has been developed yet. Moreover, weight gain is the most common side effect of many oral anti-diabetic agents and insulin, and increased weight has been shown to worsen glycemic control and increase the risk of diabetes progression. In this sense, the inorganic salt sodium tungstate (NaW) has been studied in different animal models of metabolic syndrome and diabetes, proving to have a potent effect on normalizing blood glucose levels and reducing body weight, without any hypoglycemic action. Although the liver has been studied as the main site of NaW action, positive effects have been also addressed in muscle, pancreas, brain, adipose tissue and intestine, explaining the effective anti-diabetic action of this salt. Here, we review NaW research to date in these different target organs. We believe that NaW deserves more attention, since all available anti-diabetic treatments remain suboptimal and new therapeutics are urgently needed.

Benefits of healthy adipose tissue in the treatment of diabetes

The major malfunction in diabetes mellitus is severe perturbation of glucose homeostasis caused by deficiency of insulin. Insulin deficiency is either absolute due to destruction or failure of pancreatic β cells, or relative due to decreased sensitivity of peripheral tissues to insulin. The primary lesion being related to insulin, treatments for diabetes focus on insulin replacement and/or increasing sensitivity to insulin. These therapies have their own limitations and complications, some of which can be life-threatening. For example, exogenous insulin administration can lead to fatal hypoglycemic episodes; islet/pancreas transplantation requires life-long immunosuppressive therapy; and anti-diabetic drugs have dangerous side effects including edema, heart failure and lactic acidosis. Thus the need remains for better safer long term treatments for diabetes. The ultimate goal in treating diabetes is to re-establish glucose homeostasis, preferably through endogenously generated hormones. Recent studies increasingly show that extra-pancreatic hormones, particularly those arising from adipose tissue, can compensate for insulin, or entirely replace the function of insulin under appropriate circumstances. Adipose tissue is a versatile endocrine organ that secretes a variety of hormones with far-reaching effects on overall metabolism. While unhealthy adipose tissue can exacerbate diabetes through limiting circulation and secreting of pro-inflammatory cytokines, healthy uninflamed adipose tissue secretes beneficial adipokines with hypoglycemic and anti-inflammatory properties, which can complement and/or compensate for the function of insulin. Administration of specific adipokines is known to alleviate both type 1 and 2 diabetes, and leptin mono-therapy is reported to reverse type 1 diabetes independent of insulin. Although specific adipokines may correct diabetes, administration of individual adipokines still carries risks similar to those of insulin monotherapy. Thus a better approach is to achieve glucose homeostasis with endogenously-generated adipokines through transplantation or regeneration of healthy adipose tissue. Our recent studies on mouse models show that type 1 diabetes can be reversed without insulin through subcutaneous transplantation of embryonic brown adipose tissue, which leads to replenishment of recipients’ white adipose tissue; increase of a number of beneficial adipokines; and fast and long-lasting euglycemia. Insulin-independent glucose homeostasis is established through a combination of endogenously generated hormones arising from the transplant and/or newly-replenished white adipose tissue. Transplantation of healthy white adipose tissue is reported to alleviate type 2 diabetes in rodent models on several occasions, and increasing the content of endogenous brown adipose tissue is known to combat obesity and type 2 diabetes in both humans and animal models. While the underlying mechanisms are not fully documented, the beneficial effects of healthy adipose tissue in improving metabolism are increasingly reported, and are worthy of attention as a powerful tool in combating metabolic disease.