Beta-cell mass dynamics in Zucker diabetic fatty rats. Rosiglitazone prevents the rise in net cell death

Beta-Cell Tipe1 Orchestrates Insulin Secretion and Cell Proliferation by Promoting Gαs/cAMP Signaling via USP5

Inadequate β-cell mass and insulin secretion are essential for the development of type 2 diabetes (T2D). TNF-α-induced protein 8-like 1 (Tipe1) plays a crucial role in multiple diseases, however, a specific role in T2D pathogenesis remains largely unexplored. Herein, Tipe1 as a key regulator in T2D, contributing to the maintenance of β cell homeostasis is identified. The results show that the β-cell-specific knockout of Tipe1 (termed Ins2-Tipe1BKO) aggravated diabetic phenotypes in db/db mice or in mice with high-fat diet-induced diabetes. Notably, Tipe1 improves β cell mass and function, a process that depends on Gαs, the α subunit of the G-stimulating protein. Mechanistically, Tipe1 inhibited the K48-linked ubiquitination degradation of Gαs by recruiting the deubiquitinase USP5. Consequently, Gαs or cAMP agonists almost completely restored the dysfunction of β cells observed in Ins2-Tipe1BKO mice. The findings characterize Tipe1 as a regulator of β cell function through the Gαs/cAMP pathway, suggesting that Tipe1 may emerge as a novel target for T2D intervention.

Unlocking β-cell restoration: The crucial role of PDX1 in diabetes therapy

Diabetes has been a significant healthcare problem worldwide for a considerable period. The primary objective of diabetic treatment plans is to control the symptoms associated with the pathology. To effectively combat diabetes, it is crucial to comprehend the disease's etiology, essential factors, and the relevant processes involving β-cells. The development of the pancreas, maturation, and maintenance of β-cells, and their role in regular insulin function are all regulated by PDX1. Therefore, understanding the regulation of PDX1 and its interactions with signaling pathways involved in β-cell differentiation and proliferation are crucial elements of alternative diabetes treatment strategies. The present review aims to explore the protective role of PDX1 in β-cell proliferation through signaling pathways. The main keywords chosen for this review include "PDX1 for β-cell mass," "β-cell proliferation," "β-cell restoration via PDX1," and "mechanism of PDX1 in β-cells." A comprehensive literature search was conducted using various internet search engines, such as PubMed, Science Direct, and other publication databases. We summarize several approaches to generating β-cells from alternative cell sources, employing PDX1 under various modified growth conditions and different transcriptional factors. Our analysis highlights the unique potential of PDX1 as a promising target in molecular and cell-based therapies for diabetes.

Anti-Diabetic and Anti-Adipogenic Effect of Harmine in High-Fat-Diet-Induced Diabetes in Mice

One of the most important health issues facing the world today is obesity. It is an important independent risk factor for developing type 2 diabetes. Harmine offers various pharmacological effects, such as anti-inflammatory and anti-tumor effects. The current study aims to investigate Harmine's anti-diabetic and anti-adipogenic properties in albino mice after inducing low-grade inflammation with a high-fat diet (HFD). About forty-eight male albino mice were divided into four groups. Group 1: control mice were injected with daily saline and fed a normal chow diet of 21% protein for 5 months. Group 2: mice were treated daily with IP-injected Harmine (30 mg/kg body weight) and were fed a normal chow diet for 5 months. Group 3: mice were fed HFD to induce type 2 Diabetes Mellitus (T2DM) for 5 months. Group 4: mice were fed HFD for 14 weeks and treated with Harmine for the last 6 weeks. A figh-fat diet caused a significant increase in body and organ weight, lipid profiles, and destructive changes within the pancreas, kidney, and liver tissue. The administration of Harmine led to a remarkable improvement in the histological and ultrastructural changes induced by HFD. The findings indicate that mice cured using Harmine had lower oxidative stress, a higher total antioxidant capacity, and a reduced lipid profile compared to HFD mice. Harmine led to the hepatocytes partly restoring their ordinary configuration. Furthermore, it was noticed that the pathological incidence of damage in the structure of both the kidney and pancreas sections reduced in comparison with the diabetic group. Additional research will be required to fully understand Harmine and its preventive effects on the two forms of diabetes.

Zhx2 maintains islet β-cell mass and function by transcriptionally regulating Pax6

Emerging evidence shows that pancreatic β-cell function and quality are key determinants in the progression of type 2 diabetes (T2D). The transcription factor zinc finger homeobox 2 (Zhx2) is involved in proliferation and development of multiple cells. However, the exact role of Zhx2 in β-cells and T2D remains completely unknown. Here, we report that Zhx2 orchestrates β-cell mass and function by regulating paired box protein pax-6 (Pax6). We found that β-cell-specific knockout Zhx2 (Zhx2BKO) mice showed a decrease in β-cell proliferation and glucose homeostasis. Under prediabetic and diabetic conditions, we discovered glucose intolerance in both Zhx2BKO-HFD mice and Zhx2BKO-db/db mice, with reduced β-cell mass and insulin secretion. Mechanistically, we demonstrated that Zhx2 targeted the Pax6 promoter region (-1740∼-1563; -862∼-559; -251∼+75), enhanced promoter activity. Overall, Zhx2 maintains β-cell function by transcriptionally regulating Pax6, which provides a therapeutic target for diabetes intervention.

Yunpi Heluo decoction reduces ectopic deposition of lipids by regulating the SIRT1-FoxO1 autophagy pathway in diabetic rats

CONTEXT

Yunpi Heluo (YPHL) decoction is a Chinese herbal formula with particular advantages for treating type 2 diabetes. Yet, its exact mechanism of action is not fully understood.

OBJECTIVE

To examine the therapeutic effect of YPHL on ectopic lipid deposition (EDL) in Zucker diabetic fatty (ZDF) rats and the underlying mechanism.

MATERIALS AND METHODS

The ZDF Rats were randomized into five groups, including model, YPHL (200 mg/kg/d for 10 weeks), SIRT1-overexpression (injected with HBAAV2/9-r-SIRT1-3'-flag-GFP), NC (injected with HBAAV2/9-CMV-GFP as blank control) and control group. Pancreatic β-cells obtained from high-lipid-high-glucose fed rats were treated with YPHL (10 mg/mL) for 48 h. Lipid deposition and autophagosomes were analyzed by transmission electron microscopy. Intracellular H₂O₂ and ROS concentrations were measured by flow cytometry. SIRT1, FOXO1, LC3 and P62 mRNA and protein levels were analyzed using qRT-PCR and Western blots.

RESULTS

Compared with the model group, blood glucose levels in YPHL and si-SIRT1 groups were reduced by 19.3% and 27.9%, respectively. In high-lipid-high-glucose cells treated with YPHL, lipid droplets were reduced and decrease in apoptosis rate (38.6%), H₂O₂ (31.2%) and ROS (44.5%) levels were observed. After YPHL intervention or SIRT1 overexpression, LC3 and p62 expression increased. Protein expression of SIRT1 and LC3 in model, si-SIRT1, si-NC and si-SIRT1 + YPHL groups was lower than those in control group, while FoxO1 expression was increased. All of these protein level alterations were reversed in the si-NC + YPHL group.

DISCUSSION AND CONCLUSIONS

YPHL reduced EDL by regulating the SIRT1-FoxO1 autophagy pathway in diabetic rats, which could lead to future perspectives for the treatment of diabetes.

Rosiglitazone protects INS-1E cells from human islet amyloid polypeptide toxicity

Human islet amyloid polypeptide (hIAPP or amylin) is a hormone co-secreted with insulin by pancreatic β-cells, and is the main component of islet amyloid. Islet amyloid is found in the pancreas of patients with type 2 diabetes and may be involved in β-cell dysfunction and death, observed in this disease. Thus, counteracting islet amyloid toxicity represents a therapeutic approach to preserve β-cell mass and function. In this sense, thiazolidinediones (TZDs), as rosiglitazone, have shown protective effects against other harmful insults to β-cells. For this reason, we investigated whether rosiglitazone could protect β-cells from hIAPP-induced cell death and the underlying mechanisms mediating such effect. Here, we show that rosiglitazone improved the viability of hIAPP-exposed INS-1E cells. This benefit is not dependent on the insulin-degrading enzyme (IDE) since rosiglitazone did not modulate IDE protein content and activity. However, rosiglitazone inhibited hIAPP fibrillation and decreased hIAPP-induced expression of C/EBP homologous protein (CHOP) (CTL 100.0 ± 8.4; hIAPP 182.7 ± 19.1; hIAPP + RGZ 102.8 ± 9.5), activating transcription factor-4 (ATF4) (CTL 100.0 ± 3.1; hIAPP 234.9 ± 19.3; hIAPP + RGZ 129.6 ± 3.0) and phospho-eukaryotic initiation factor 2-alpha (p-eIF2α) (CTL 100.0 ± 31.1; hIAPP 234.1 ± 36.2; hIAPP + RGZ 150.4 ± 18.0). These findings suggest that TZDs treatment may be a promising approach to preserve β-cell mass and function by inhibiting islet amyloid formation and decreasing endoplasmic reticulum stress hIAPP-induced.

Adipose Tissue Secretion Pattern Influences β-Cell Wellness in the Transition from Obesity to Type 2 Diabetes

The dysregulation of the β-cell functional mass, which is a reduction in the number of β-cells and their ability to secure adequate insulin secretion, represents a key mechanistic factor leading to the onset of type 2 diabetes (T2D). Obesity is recognised as a leading cause of β-cell loss and dysfunction and a risk factor for T2D. The natural history of β-cell failure in obesity-induced T2D can be divided into three steps: (1) β-cell compensatory hyperplasia and insulin hypersecretion, (2) insulin secretory dysfunction, and (3) loss of β-cell mass. Adipose tissue (AT) secretes many hormones/cytokines (adipokines) and fatty acids that can directly influence β-cell function and viability. As this secretory pattern is altered in obese and diabetic patients, it is expected that the cross-talk between AT and pancreatic β-cells could drive the maintenance of the β-cell integrity under physiological conditions and contribute to the reduction in the β-cell functional mass in a dysmetabolic state. In the current review, we summarise the evidence of the ability of the AT secretome to influence each step of β-cell failure, and attempt to draw a timeline of the alterations in the adipokine secretion pattern in the transition from obesity to T2D that reflects the progressive deterioration of the β-cell functional mass.

Nutrient Regulation of Pancreatic Islet β-Cell Secretory Capacity and Insulin Production

Pancreatic islet β-cells exhibit tremendous plasticity for secretory adaptations that coordinate insulin production and release with nutritional demands. This essential feature of the β-cell can allow for compensatory changes that increase secretory output to overcome insulin resistance early in Type 2 diabetes (T2D). Nutrient-stimulated increases in proinsulin biosynthesis may initiate this β-cell adaptive compensation; however, the molecular regulators of secretory expansion that accommodate the increased biosynthetic burden of packaging and producing additional insulin granules, such as enhanced ER and Golgi functions, remain poorly defined. As these adaptive mechanisms fail and T2D progresses, the β-cell succumbs to metabolic defects resulting in alterations to glucose metabolism and a decline in nutrient-regulated secretory functions, including impaired proinsulin processing and a deficit in mature insulin-containing secretory granules. In this review, we will discuss how the adaptative plasticity of the pancreatic islet β-cell's secretory program allows insulin production to be carefully matched with nutrient availability and peripheral cues for insulin signaling. Furthermore, we will highlight potential defects in the secretory pathway that limit or delay insulin granule biosynthesis, which may contribute to the decline in β-cell function during the pathogenesis of T2D.

Chlorogenic acid and β-glucan from highland barley grain ameliorate β-cell dysfunction via inhibiting apoptosis and improving cell proliferation

Recent studies have reported that highland barley as a whole grain diet has anti-hyperglycemic effects, however little information is available about the active compounds that ameliorate pancreatic β-cell dysfunction and the related mechanisms. In this study, chlorogenic acid (CA) and β-glucan (BG) were identified as the active compounds that ameliorated β-cell dysfunction. CA ameliorated β-cell dysfunction by inhibiting cell apoptosis and improving glucose-stimulated insulin secretion via targeting G protein-coupled receptor 40 (GPR40) and regulating the phospholipase C β (PLCβ) pathway. BG ameliorated β-cell dysfunction by improving cell proliferation via targeting mammalian target of rapamycin (mTOR) and regulating the protein kinase B (Akt)/glycogen synthase kinase-3β (GSK-3β) pathway. Furthermore, CA and BG improved β-cell sensitivity and pancreatic insulin secretion, and inhibited β-cell apoptosis in impaired glucose tolerance (IGT) mice. Notably, CA restored homeostasis model assessment (HOMA)-β values and Ca²⁺-ATP and K⁺-ATP levels back to normal levels, and BG at 300 mg per kg BW restored β-cell insulin contents back to normal levels in IGT mice. Additionally, the combination of CA and BG had an additive effect on ameliorating β-cell dysfunction. These results help develop whole highland barley grain as a functional food for preventing type 2 diabetes by ameliorating pancreatic β-cell damage.

The role of autoimmunity in the pathophysiology of type 2 diabetes: Looking at the other side of the moon

Efforts to unravel the pathophysiological mechanisms of type 2 diabetes (T2D) have been traditionally trapped into a metabolic perspective. However, T2D is a phenotypically and pathophysiologically heterogenous disorder, and the need for a tailored approach in its management is becoming increasingly evident. There is emerging evidence that irregular immune responses contribute to the development of hyperglycemia in T2D and, inversely, that insulin resistance is a component of the pathogenesis of autoimmune diabetes. Nevertheless, it has not yet been fully elucidated to what extent the presence of conventional autoimmune markers, such as autoantibodies, in subjects with T2D might affect the natural history of the disease and particularly each response to various treatments. The challenge for future research in the field is the discovery of novel genetic, molecular, or phenotypical indicators that would enable the characterization of specific subpopulations of people with T2D who would benefit most from the addition of immunomodulatory therapies to standard glucose-lowering treatment. This narrative review aims to discuss the plausible mechanisms through which the immune system might be implicated in the development of metabolic disturbances in T2D and obesity and explore a potential role of immunotherapy in the future management of the disorder and its complications.

Yunpi Heluo decoction attenuates insulin resistance by regulating SIRT1-FoxO1 autophagy pathway in skeletal muscle of Zucker diabetic fatty rats

ETHNOPHARMACOLOGICAL RELEVANCE

Diabetes is a serious chronic metabolic disorder, and type 2 diabetes mellitus (T2DM) accounts for more than 90% of all diabetes cases. Insulin resistance (IR) is an early symptom, typical feature and main pathogenesis of T2DM due to the combined effects of genetic and environmental factors. Current evidence shows that IR is mainly caused by nutrient overload, systemic fatty acid excess, fatty tissue inflammation, endoplasmic reticulum stress, oxidative stress and abnormal autophagy. Autophagy plays an important role in the development of IR and decreased autophagy activity can cause IR through various ways.

AIM OF THE STUDY

Yunpiheluo (YPHL) decoction is a Chinese herbal formula with unique advantages for the treatment of T2DM. The aim of the present study was to investigate the regulatory mechanism of YPHL on the autophagy pathway in the skeletal muscle of IR Zucker diabetic fatty (ZDF) rats.

METHODS

T2DM ZDF rats were treated with YPHL or transfected with SIRT1 adeno-associated virus. Serum total cholesterol (TC), triglyceride (TG), high-density lipoprotein (HDL), low-density lipoprotein (LDL), insulin resistance index (IRI) and skeletal muscle TG levels were detected in a T2DM ZDF rat model. The skeletal muscle morphology was observed by histological analysis and Oil Red O Staining. Autophagosomes were observed by transmission electron microscopy (TEM). The skeletal muscle morphology and fat deposition were observed by histological examination and Oil Red O Staining. A rat skeletal muscle IR cell model was established and transfected with SIRT1 overexpression plasmids. Cell apoptosis was observed by DAPI staining. SIRT1 levels in skeletal muscle tissues and cells were detected by qRT-PCR. The protein expressions of SIRT1, FOXo1, LC3B and P62 were detected by Western blotting.

RESULTS

Large numbers of lipid droplets and swollen mitochondria were observed in the skeletal muscle in both model group and negative control (NC) group receiving blank plasmid. Autophagosomes were seen in the skeletal muscle of YPHL and SIRT1 groups, with no significant structural abnormality. In addition, the protein expression of LC3B was decreased and the protein expression of p62 was increased significantly in the model group as compared with the NC group. After intervention with YPHL and SIRT1 overexpression, the protein expression of LC3B was significantly increased and p62 was significantly decreased. However, there was no significant difference in cell apoptosis between the two groups.

CONCLUSION

The SIRT1-FoxO1 autophagy pathway may play a significant role in the pathogenesis of IR. YPHL could increase the autophagy level by regulating the SIRT1-FoxO1 signaling pathway in the skeletal muscle and improving the lipid metabolism, thereby attenuating IR.

Menin-regulated Pbk controls high fat diet-induced compensatory beta cell proliferation

Pancreatic beta cells undergo compensatory proliferation in the early phase of type 2 diabetes. While pathways such as FoxM1 are involved in regulating compensatory beta cell proliferation, given the lack of therapeutics effectively targeting beta cell proliferation, other targetable pathways need to be identified. Herein, we show that Pbk, a serine/threonine protein kinase, is essential for high fat diet (HFD)‐induced beta cell proliferation in vivo using a Pbk kinase deficiency knock‐in mouse model. Mechanistically, JunD recruits menin and HDAC3 complex to the Pbk promoter to reduce histone H3 acetylation, leading to epigenetic repression of Pbk expression. Moreover, menin inhibitor (MI) disrupts the menin–JunD interaction and augments Pbk transcription. Importantly, MI administration increases beta cell proliferation, ameliorating hyperglycemia, and impaired glucose tolerance (IGT) in HFD‐induced diabetic mice. Notably, Pbk is required for the MI‐induced beta cell proliferation and improvement of IGT. Together, these results demonstrate the repressive role of the menin/JunD/Pbk axis in regulating HFD‐induced compensatory beta cell proliferation and pharmacologically regulating this axis may serve as a novel strategy for type 2 diabetes therapy.

Beneficial effects of proximal intestinal bypass reconstruction on glucose metabolism in a type 2 diabetes animal model: a possible reconstruction strategy for diabetic gastric cancer patients

Purpose

Proximal intestinal bypass (PIB), such as Billroth II or Roux-en-Y gastrojejunostomy after curative distal gastrectomy for gastric cancer induces beneficial effects on glycemic control in patients with type 2 diabetes. We aimed to characterize the long-term evolution of pancreatic beta cells and insulin signaling in target tissue after a PIB procedure.

Methods

Zucker diabetic fatty rats were randomly assigned to the PIB, sham-operated PIB pair-fed, and ad libitum fed groups. Oral glucose tolerance (GT) and plasma insulin levels were measured periodically at 16 weeks postoperatively. Histomorphometric analyses were performed to evaluate changes in islet architectures and intranuclear pancreatic duodenal homeobox 1 (PDX1) expression in beta cells. Insulin signaling changes in visceral adipocytes were measured by the phosphorylated Akt/Akt ratio.

Results

Contrary to the progressively deteriorating GT and plasma insulin levels in sham-operated animals, these were preserved in PIB animals (P < 0.01) at 16 weeks postoperatively. The proportion of the islets having asteroid-like expanding projection was higher in PIB animals than in sham-operated animals (P < 0.01). PIB animals had 3-fold wider fractional area of beta cells (P < 0.01) and 3-fold higher proportion of beta-cell nuclear PDX1 expression (P < 0.01) than sham-operated animals. PIB animals had significantly higher levels of Akt phosphorylation in the visceral adipocytes (P < 0.05). The PIB did not substantially affect weight and food intake postoperatively.

Conclusion

The PIB preserved the plasma insulin levels and the wider beta-cell area over time and facilitated insulin signaling in the visceral fats. It could be considered as a possible reconstruction strategy for diabetic gastric cancer patients.

Innate immune receptors in type 1 diabetes: the relationship to cell death-associated inflammation

The importance of innate immunity in host defense and inflammatory responses has been clearly demonstrated after the discovery of innate immune receptors such as Toll-like receptors (TLRs) or Nucleotide-binding oligomerization domain-containing protein (Nod)-like receptors (NLRs). Innate immunity also plays a critical role in diverse pathological conditions including autoimmune diseases such as type 1 diabetes (T1D). In particular, the role of a variety of innate immune receptors in T1D has been demonstrated using mice with targeted disruption of such innate immune receptors. Here, we discuss recent findings showing the role of innate immunity in T1D that were obtained mostly from studies of genetic mouse models of innate immune receptors. In addition, the role of innate immune receptors involved in the pathogenesis of T1D in sensing death-associated molecular patterns (DAMPs) released from dead cells or pathogen-associated molecular patterns (PAMPs) will also be covered. Elucidation of the role of innate immune receptors in T1D and the nature of DAMPs sensed by such receptors may lead to the development of new therapeutic modalities against T1D.

AKT1 Regulates Endoplasmic Reticulum Stress and Mediates the Adaptive Response of Pancreatic β Cells

Isoforms of protein kinase B (also known as AKT) play important roles in mediating insulin and growth factor signals. Previous studies have suggested that the AKT2 isoform is critical for insulin-regulated glucose metabolism, while the role of the AKT1 isoform remains less clear. This study focuses on the effects of AKT1 on the adaptive response of pancreatic β cells. Using a mouse model with inducible β-cell-specific deletion of the Akt1 gene (βA1KO mice), we showed that AKT1 is involved in high-fat-diet (HFD)-induced growth and survival of β cells but is unnecessary for them to maintain a population in the absence of metabolic stress. When unchallenged, βA1KO mice presented the same metabolic profile and β-cell phenotype as the control mice with an intact Akt1 gene. When metabolic stress was induced by HFD, β cells in control mice with intact Akt1 proliferated as a compensatory mechanism for metabolic overload. Similar effects were not observed in βA1KO mice. We further demonstrated that AKT1 protein deficiency caused endoplasmic reticulum (ER) stress and potentiated β cells to undergo apoptosis. Our results revealed that AKT1 protein loss led to the induction of eukaryotic initiation factor 2 α subunit (eIF2α) signaling and ER stress markers under normal-chow-fed conditions, indicating chronic low-level ER stress. Together, these data established a role for AKT1 as a growth and survival factor for adaptive β-cell response and suggest that ER stress induction is responsible for this effect of AKT1.

S. Ferreira KC, Neto JCR. Pharmacological Strategies for Insulin Sensitivity in Obesity and Cancer: Thiazolidinediones and Metformin

Background:

Chronic diseases, such as obesity and cancer, have high prevalence rates. Both diseases have hyperinsulinemia, hyperglycemia, high levels of IGF-1 and inflammatory cytokines in common. Therefore, these can be considered triggers for cancer development and growth. In addition, low-grade inflammation that modulates the activation of immune cells, cellular metabolism, and production of cytokines and chemokines are common in obesity, cancer, and insulin resistance. Pharmacological strategies are necessary when a change in lifestyle does not improve glycemic homeostasis. In this regard, thiazolidinediones (TZD) possess multiple molecular targets and regulate PPARγ in obesity and cancer related to insulin resistance, while metformin acts through the AMPK pathway.

Objective:

The aim of this study was to review TZD and metformin as pharmacological treatments for insulin resistance associated with obesity and cancer.

Conclusions:

Thiazolidinediones restored adiponectin secretion and leptin sensitivity, reduced lipid droplets in hepatocytes and orexigen peptides in the hypothalamus. In cancer cells, TZD reduced proliferation, production of reactive oxygen species, and inflammation by acting through the mTOR and NFκB pathways. Metformin has similar effects, though these are AMPK-dependent. In addition, both drugs can be efficient against certain side effects caused by chemotherapy.

Therapeutic approaches for latent autoimmune diabetes in adults: One size does not fit all

Recent advances in the understanding of latent autoimmune diabetes in adults (LADA) pathophysiology make it increasingly evident that people with LADA comprise a heterogenous group of patients. This makes the establishment of a standard treatment algorithm challenging. On top of its glucose-lowering action, insulin may exert anti-inflammatory effects, rendering it an attractive therapeutic choice for a type of diabetes in which autoinflammation and beta cell insufficiency play major pathogenetic roles. However, there is growing evidence that other antidiabetic drugs, such as metformin, dipeptidyl peptidase-4 inhibitors, glucagon-like peptide-1 receptor agonists, and thiazolidinediones, might have a role in optimizing glycemic control and preserving beta cell function in individuals with LADA, either alone or in combination with insulin. Although most of these drugs have been routinely used in the daily clinical setting for years, large prospective randomized trials are needed to assess whether they are capable of delaying progression to insulin dependence as well as their effects on diabetic complications. The aim of the present review is to discuss the current state and future perspectives of LADA therapy, emphasizing the need for individualized and patient-centered therapeutic approaches.

The Dual Amylin and Calcitonin Receptor Agonist, KBP-066, Induces an Equally Potent Weight Loss Across a Broad Dose Range While Higher Doses May Further Improve Insulin Action

Pharmacological treatment with dual amylin and calcitonin receptor agonists (DACRAs) cause significant weight loss and improvement of glucose homeostasis. In this study, the maximally efficacious dose of the novel DACRA, KeyBiosciencePeptide (KBP)-066, was investigated. Two different rat models were used: high-fat diet (HFD)-fed male Sprague-Dawley rats and male Zucker diabetic fatty (ZDF, fa/fa) rats to determine the maximum weight loss and glucose homeostatic effect, respectively. One acute study and one chronic study was performed in HFD rats. Two chronic studies were performed in ZDF rats: a preventive and an interventive. All studies covered a dose range of 5, 50, and 500 µg/kg KBP-066 delivered by subcutaneous injection. Treatment with KBP-066 resulted in a significant weight reduction of 13%-16% and improved glucose tolerance in HFD rats, which was independent of dose concentration. Dosing with 50 and 500 µg/kg led to a transient but significant increase in blood glucose, both in the acute and the chronic study in HFD rats. All doses of KBP-066 significantly improved glucose homeostasis in ZDF rats, both in the preventive and interventive study. Moreover, dosing with 50 and 500 µg/kg preserved insulin secretion to a greater extent than 5 µg/kg when compared with ZDF vehicle rats. Taken together, these results show that maximum weight loss is achieved with 5 µg/kg, which is within the range of previously reported DACRA dosing, whereas increasing dosing concentration to 50 and 500 µg/kg may further improve preservation of insulin secretion compared with 5 µg/kg in diabetic ZDF rats. SIGNIFICANCE STATEMENT: Here we show that KeyBiosciencePeptide (KBP)-066 induces an equally potent body weight loss across a broad dose range in obese rats. However, higher dosing of KBP-066 may improve insulin action in diabetic rats both as preventive and interventive treatment.

PPARs and the Development of Type 1 Diabetes

Peroxisome proliferator-activated receptors (PPARs) are a family of transcription factors with a key role in glucose and lipid metabolism. PPARs are expressed in many cell types including pancreatic beta cells and immune cells, where they regulate insulin secretion and T cell differentiation, respectively. Moreover, various PPAR agonists prevent diabetes in the non-obese diabetic (NOD) mouse model of type 1 diabetes. PPARs are thus of interest in type 1 diabetes (T1D) as they represent a novel approach targeting both the pancreas and the immune system. In this review, we examine the role of PPARs in immune responses and beta cell biology and their potential as targets for treatment of T1D.

A Fermented Food Product Containing Lactic Acid Bacteria Protects ZDF Rats from the Development of Type 2 Diabetes

Type 2 diabetes (T2D) is a complex metabolic disease, which involves a maintained hyperglycemia due to the development of an insulin resistance process. Among multiple risk factors, host intestinal microbiota has received increasing attention in T2D etiology and progression. In the present study, we have explored the effect of long-term supplementation with a non-dairy fermented food product (FFP) in Zucker Diabetic and Fatty (ZDF) rats T2D model. The supplementation with FFP induced an improvement in glucose homeostasis according to the results obtained from fasting blood glucose levels, glucose tolerance test, and pancreatic function. Importantly, a significantly reduced intestinal glucose absorption was found in the FFP-treated rats. Supplemented animals also showed a greater survival suggesting a better health status as a result of the FFP intake. Some dissimilarities have been observed in the gut microbiota population between control and FFP-treated rats, and interestingly a tendency for better cardiometabolic markers values was appreciated in this group. However, no significant differences were observed in body weight, body composition, or food intake between groups. These findings suggest that FFP induced gut microbiota modifications in ZDF rats that improved glucose metabolism and protected from T2D development.

Inventing Liraglutide, a Glucagon-Like Peptide-1 Analogue, for the Treatment of Diabetes and Obesity

Glucagon-like peptide-1 (GLP-1) has been in focus since the early 1980s as a long looked for incretin hormone, released from the gastrointestinal tract and with an important effect on glucose-dependent insulin secretion, providing efficient glucose lowering, with little risk for hypoglycemia. The enzyme dipeptidyl peptidase-4 (DPP-4) degrades GLP-1 very fast, and the remaining metabolite is cleared rapidly by the kidneys. Liraglutide is a fatty acid acylated analogue of GLP-1 that provides efficacy for 24 h/day. The mechanism of action for liraglutide is reviewed in detail with focus on pancreatic efficacy and safety, thyroid safety, and weight loss mechanism. Evolving science hypothesizes that GLP-1 has important effects on atherosclerosis, relevant for the cardiovascular benefit seen in the treatment of diabetes and obesity. Also, GLP-1 may be relevant in neurodegenerative diseases.

Central and Peripheral Administration of Fibroblast Growth Factor 1 Improves Pancreatic Islet Insulin Secretion in Diabetic Mouse Models

Fibroblast growth factor 1 (FGF1) has been shown to reverse hyperglycemia in diabetic rodent models through peripheral and central administration routes. Previous studies demonstrated that insulin is required for central and peripheral FGF1 metabolic improvements; however, it is unknown if FGF1 targets insulin secretion at the islet level. Here we show for the first time that FGF1 increases islet insulin secretion in diabetic mouse models. FGF1 was administered via a single intracerebroventricular or multiple subcutaneous injections to leptin receptor-deficient (db/db), diet-induced obese, and control mice; pancreatic islets were isolated 7 days later for analysis of insulin secretion. Central and peripheral FGF1 significantly lowered blood glucose in vivo and increased ex vivo islet insulin secretion from diabetic, but not control, mice. FGF1 injections to the cisterna magna mimicked intracerebroventricular outcomes, pointing to a novel therapeutic potential. Central effects of FGF1 appeared dependent on reductions in food intake, whereas peripheral FGF1 had acute actions on islet function prior to significant changes in food intake or blood glucose. Additionally, peripheral, but not central, FGF1 increased islet β-cell density, suggesting that peripheral FGF1 may induce long-term changes in islet structure and function that are not present with central treatment.

Effect of heat-killed Streptococcus thermophilus on type 2 diabetes rats

BACKGROUND AND AIMS

The link between gut microbiota and type 2 diabetes (T2D) has been addressed by numerous studies. Streptococcus thermophilus from fermented milk products, has been used as a probiotic in previous research. However, whether heat-killed S. thermophilus can improve the glycemic parameters of diabetic rats remains unanswered. In this study, we evaluated the effect of heat-killed S. thermophilus on T2D model rats and the potential mechanisms of the effect.

METHODS

Zucker diabetic fatty (ZDF) rats were used to generate a diabetic rat model induced by feeding a high-fat diet. Heat-killed S. thermophilus were orally administered to normal and diabetic rats for 12 weeks. Intestinal microbiota analysis, histology analysis, oral glucose tolerance test and measurement of inflammatory factors were performed.

RESULTS

We found that heat-killed S. thermophilus treatment reduced fasting blood glucose levels and alleviated glucose intolerance and total cholesterol in diabetic ZDF rats. Additionally, heat-killed S. thermophilus increased the interleukin 10 while reducing the levels of lipopolysaccharide, interleukin 6, and tumor necrosis factor-α in diabetic ZDF rats. The heat-killed S. thermophilus treatment can normalize the structure of the intestinal and colon mucosal layer of diabetic rats. The characteristics of the gut microbiota in heat-killed S. thermophilus-treated and control rats were similar. At the genus level, the abundances of beneficial bacteria, including Ruminococcaceae, Veillonella, Coprococcus, and Bamesiella, were all significantly elevated by heat-killed S. thermophilus treatment in ZDF diabetic rats.

CONCLUSION

Our study supports the hypothesis that treatment with heat-killed S. thermophilus could effectively improve glycemic parameters in T2D model rats. In addition, the potential mechanisms underlying the protection maybe include changing the composition of gut microbiota, reinforcing the intestinal epithelial barrier and the immunity of the intestinal mucosa, decreasing the level of inflammation, and then reducing the insulin resistance.

Modulatory effect of empagliflozin on cellular parameters of endocrine pancreas in experimental pre-diabetes

The effect of empagliflozin (EMPA), a sodium-glucose cotransporter 2 inhibitor (SGLT2i), on the structure of endocrine pancreas in pre-diabetes (Pre-DM) is not yet elucidated. In the current study the relatively enlarged islets of Langerhans seen in the Pre-DM group was restored to control size by administration of EMPA. In addition the disbalance in the percentage of β-cells and α-cells in islets of the Pre-DM was corrected in the Pre-DM + EMPA group with reversal of the significantly increased islet mass, β-cell mass and neogenesis. Administrating EMPA in Pre-DM decreased level of caspase-3, increased that of Bcl-2 to control level and reduced the significantly increased inflammatory cytokines to levels approximated to those of the control group. In Pre-DM + EMPA group, EMPA had efficiently restored the significantly impaired glucose hemostasis to levels nearly similar to those of the control animals. This may indicate that the modulatory effect of EMPA on cells of the islets in Pre-DM is associated with a local pleotropic effect on inflammatory cytokines.

The direct effect of lobeglitazone, a new thiazolidinedione, on pancreatic beta cells: A comparison with other thiazolidinediones

AIMS

The direct effects of thiazolidinediones (TZDs) on pancreatic beta cells have been controversial. The aim of this study was to find out whether a novel TZD, lobeglitazone, has beneficial effects on pancreatic beta cells and db/db mice compared to those of other TZDs.

METHODS

INS-1 cells were incubated at a high-glucose concentration with various concentrations of troglitazone, rosiglitazone, pioglitazone, and lobeglitazone. Apoptosis and proliferation of beta cells, markers for ER stress and glucose-stimulated insulin secretion (GSIS) were assessed. In addition, C57BL/6 db/db mice were treated with pioglitazone or lobeglitazone for 4 weeks, and metabolic parameters and the configuration of pancreatic islets were also examined.

RESULTS

Lobeglitazone and other TZDs decreased INS-1 cell apoptosis in high-glucose conditions. Lobeglitazone and other TZDs significantly decreased hyperglycemia-induced increases in ER stress markers and increased GSIS. Metabolic parameters showed greater improvement in db/db mice treated with pioglitazone and lobeglitazone than in control mice. Islet size, cell proliferation, and beta cell mass were increased, and collagen surrounding the islets was decreased in treated mice.

CONCLUSIONS

Lobeglitazone showed beneficial effects on beta cell survival and function against hyperglycemia. The prosurvival and profunction effects of lobeglitazone were comparable to those of other TZDs.

Whole Egg Consumption Impairs Insulin Sensitivity in a Rat Model of Obesity and Type 2 Diabetes

BACKGROUND

The literature regarding the relation between egg consumption and type 2 diabetes (T2D) is inconsistent and there is limited evidence pertaining to the impact of egg consumption on measures of insulin sensitivity.

OBJECTIVES

The aim of this study was to investigate the effect of dietary whole egg on metabolic biomarkers of insulin resistance in T2D rats.

METHODS

Male Zucker diabetic fatty (ZDF) rats (n = 12; 6 wk of age) and age-matched lean controls (n = 12) were randomly assigned to be fed a casein- or whole egg-based diet. At week 5 of dietary treatment, an insulin tolerance test (ITT) was performed on all rats and blood glucose was measured by glucometer. After 7 wk of dietary treatment, rats were anesthetized and whole blood was collected via a tail vein bleed. Following sedation, the extensor digitorum longus muscle was removed before and after an intraperitoneal insulin injection, and insulin signaling in skeletal muscle was analyzed by Western blot. Serum glucose and insulin were analyzed by ELISA for calculation of the homeostatic model assessment of insulin resistance (HOMA-IR).

RESULTS

Mean ITT blood glucose over the course of 60 min was 32% higher in ZDF rats fed the whole egg-based diet than in ZDF rats fed the casein-based diet. Furthermore, whole egg consumption increased fasting blood glucose by 35% in ZDF rats. Insulin-stimulated phosphorylation of key proteins in the insulin signaling pathway did not differ in skeletal muscle of ZDF rats fed casein- and whole egg-based diets. In lean rats, no differences were observed in insulin tolerance, HOMA-IR and skeletal muscle insulin signaling, regardless of experimental dietary treatment.

CONCLUSIONS

These data suggest that whole body insulin sensitivity may be impaired by whole egg consumption in T2D rats, although no changes were observed in skeletal muscle insulin signaling that could explain this finding.

WITHDRAWN: HM47118A, a novel insulinotropic GPR119 agonist and potential oral antidiabetic agent

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Pancreatic β-Cell Rest Replenishes Insulin Secretory Capacity and Attenuates Diabetes in an Extreme Model of Obese Type 2 Diabetes

The onset of common obesity-linked type 2 diabetes (T2D) is marked by exhaustive failure of pancreatic β-cell functional mass to compensate for insulin resistance and increased metabolic demand, leading to uncontrolled hyperglycemia. Here, the β-cell-deficient obese hyperglycemic/hyperinsulinemic KS db/db mouse model was used to assess consequential effects on β-cell functional recovery by lowering glucose homeostasis and/or improving insulin sensitivity after treatment with thiazolidinedione therapy or glucagon-like peptide 1 receptor agonism alone or in combination with sodium/glucose cotransporter 2 inhibition (SGLT-2i). SGLT-2i combination therapies improved glucose homeostasis, independent of changes in body weight, resulting in a synergistic increase in pancreatic insulin content marked by significant recovery of the β-cell mature insulin secretory population but with limited changes in β-cell mass and no indication of β-cell dedifferentiation. Restoration of β-cell insulin secretory capacity also restored biphasic insulin secretion. These data emphasize that by therapeutically alleviating the demand for insulin in vivo, irrespective of weight loss, endogenous β-cells recover significant function that can contribute to attenuating diabetes. Thus, this study provides evidence that alleviation of metabolic demand on the β-cell, rather than targeting the β-cell itself, could be effective in delaying the progression of T2D.

A metabolome-wide characterization of the diabetic phenotype in ZDF rats and its reversal by pioglitazone

Type 2 diabetes (T2D) is a complex metabolic disease associated with alterations in glucose, lipid and protein metabolism. In order to characterize the biochemical phenotype of the Zucker diabetic fatty (ZDF) rat, the most common animal model for the study of T2D, and the impact of the insulin sensitizer pioglitazone, a global, mass spectrometry-based analysis of the metabolome was conducted. Overall, 420 metabolites in serum, 443 in the liver and 603 in the intestine were identified at study end. In comparison to two control groups, obese diabetic ZDF rats showed characteristic metabolic signatures that included hyperglycemia, elevated β-oxidation, dyslipidemia—featured by an increase in saturated and monounsaturated fatty acids and a decrease of medium chain and of polyunsaturated fatty acids in serum–and decreased amino acid levels, consistent with their utilization in hepatic gluconeogenesis. A 13-week treatment with the PPARγ agonist pioglitazone reversed most of these signatures: Pioglitazone improved glycemic control and the fatty acid profile, elevated amino acid levels in the liver, but decreased branched chain amino acids in serum. The hitherto most comprehensive metabolic profiling study identified a biochemical blueprint for the ZDF diabetic model and captured the impact of genetic, nutritional and pharmacological perturbations. The in-depth characterization on the molecular level deepens the understanding and further validates the ZDF rat as a suitable preclinical model of diabetes in humans.

Discovering the Health Promoting Potential of Fermented Papaya Preparation—Its Future Perspectives for the Dietary Management of Oxidative Stress During Diabetes

The simplistic morphological characteristics of Carica papaya fruit or “pawpaw” should not be the cause for underestimating its potential as a nutraceutical. The market for papaya has been expanding at a staggering rate, partly due to its applicability as a biofortified product, but also due to its phytochemical properties and traditional health benefits. Papaya or formulations of fermented papaya promotion (FPP) display effective free radical scavenging abilities thought to be influenced by its phenolic, carotenoid, flavonoid, or amino acid profile. The antioxidant properties of FPP have been extensively reported in literature to potently target a broad spectrum of free radical-induced diseases ranging from neurological impairments, such as senile dementia, to systemic diseases, to its interference at the cellular level and the support of normal biological ageing processes. FPP has thus been extensively investigated for its ability to exert cellular protective effects and reduce oxidative stress via the mitigation of genetic damage, reduction of lipid peroxidation, and enzymatic inactivation in specific diseases. The focus of this review is to appraise the potential of oxidative stress reduction strategies of FPP and discuss its holistic approach in disease prevention and management, with a particular focus on diabetes and cancer. However, with the current lack of information surrounding its mechanism of action, this review wishes to set the stage and aspire researchers to more profoundly investigate molecular pathways related to how FPP can unequivocally contribute to wellness in an aging population.

Pioglitazone Attenuates Palmitate-Induced Inflammation and Endoplasmic Reticulum Stress in Pancreatic β-Cells

BACKGROUND

The nuclear receptor peroxisome proliferator-activator gamma (PPARγ) is a useful therapeutic target for obesity and diabetes, but its role in protecting β-cell function and viability is unclear.

METHODS

To identify the potential functions of PPARγ in β-cells, we treated mouse insulinoma 6 (MIN6) cells with the PPARγ agonist pioglitazone in conditions of lipotoxicity, endoplasmic reticulum (ER) stress, and inflammation.

RESULTS

Palmitate-treated cells incubated with pioglitazone exhibited significant improvements in glucose-stimulated insulin secretion and the repression of apoptosis, as shown by decreased caspase-3 cleavage and poly (adenosine diphosphate [ADP]-ribose) polymerase activity. Pioglitazone also reversed the palmitate-induced expression of inflammatory cytokines (tumor necrosis factor α, interleukin 6 [IL-6], and IL-1β) and ER stress markers (phosphor-eukaryotic translation initiation factor 2α, glucose-regulated protein 78 [GRP78], cleaved-activating transcription factor 6 [ATF6], and C/EBP homologous protein [CHOP]), and pioglitazone significantly attenuated inflammation and ER stress in lipopolysaccharide- or tunicamycin-treated MIN6 cells. The protective effect of pioglitazone was also tested in pancreatic islets from high-fat-fed KK-Ay mice administered 0.02% (wt/wt) pioglitazone or vehicle for 6 weeks. Pioglitazone remarkably reduced the expression of ATF6α, GRP78, and monocyte chemoattractant protein-1, prevented α-cell infiltration into the pancreatic islets, and upregulated glucose transporter 2 (Glut2) expression in β-cells. Moreover, the preservation of β-cells by pioglitazone was accompanied by a significant reduction of blood glucose levels.

CONCLUSION

Altogether, these results support the proposal that PPARγ agonists not only suppress insulin resistance, but also prevent β-cell impairment via protection against ER stress and inflammation. The activation of PPARγ might be a new therapeutic approach for improving β-cell survival and insulin secretion in patients with diabetes mellitus.

Mechanisms of β-cell dedifferentiation in diabetes: recent findings and future research directions

Like all the cells of an organism, pancreatic β-cells originate from embryonic stem cells through a complex cellular process termed differentiation. Differentiation involves the coordinated and tightly controlled activation/repression of specific effectors and gene clusters in a time-dependent fashion thereby giving rise to particular morphological and functional cellular features. Interestingly, cellular differentiation is not a unidirectional process. Indeed, growing evidence suggests that under certain conditions, mature β-cells can lose, to various degrees, their differentiated phenotype and cellular identity and regress to a less differentiated or a precursor-like state. This concept is termed dedifferentiation and has been proposed, besides cell death, as a contributing factor to the loss of functional β-cell mass in diabetes. β-cell dedifferentiation involves: (1) the downregulation of β-cell-enriched genes, including key transcription factors, insulin, glucose metabolism genes, protein processing and secretory pathway genes; (2) the concomitant upregulation of genes suppressed or expressed at very low levels in normal β-cells, the β-cell forbidden genes; and (3) the likely upregulation of progenitor cell genes. These alterations lead to phenotypic reconfiguration of β-cells and ultimately defective insulin secretion. While the major role of glucotoxicity in β-cell dedifferentiation is well established, the precise mechanisms involved are still under investigation. This review highlights the identified molecular mechanisms implicated in β-cell dedifferentiation including oxidative stress, endoplasmic reticulum (ER) stress, inflammation and hypoxia. It discusses the role of Foxo1, Myc and inhibitor of differentiation proteins and underscores the emerging role of non-coding RNAs. Finally, it proposes a novel hypothesis of β-cell dedifferentiation as a potential adaptive mechanism to escape cell death under stress conditions.

Beneficial Effects of Aerobic Exercise Training Combined with Rosiglitazone on Glucose Metabolism in Otsuka Long Evans Tokushima Fatty Rats

BACKGROUND

Regular aerobic exercise is essential for the prevention and management of type 2 diabetes mellitus and may be particularly beneficial for those treated with thiazolidinediones, since it may prevent associated weight gain. This study aimed to evaluate the effect of combined exercise and rosiglitazone treatment on body composition and glucose metabolism in obese diabetes-prone animals.

METHODS

We analyzed metabolic parameters, body composition, and islet profiles in Otsuka Long Evans Tokushima Fatty rats after 28 weeks of aerobic exercise, rosiglitazone treatment, and combined exercise and rosiglitazone treatment.

RESULTS

Combined exercise with rosiglitazone showed significantly less increase in weight and epididymal fat compared to rosiglitazone treatment. Aerobic exercise alone and combined rosiglitazone and exercise treatment led to similar retention of lean body mass. All experimental groups showed a decrease in fasting glucose. However, the combined exercise and rosiglitazone therapy group showed prominent improvement in glucose tolerance compared to the other groups. Rescue of islet destruction was observed in all experimental groups, but was most prominent in the combined therapy group.

CONCLUSION

Regular aerobic exercise combined with rosiglitazone treatment can compensate for the adverse effect of rosiglitazone treatment and has benefit for islet preservation.

Effect of curcumin on glucose and lipid metabolism, FFAs and TNF-α in serum of type 2 diabetes mellitus rat models

Objective

To investigate how curcumin affects the glucose and lipid metabolism in type 2 diabetes mellitus (DM) rat models, and to explore its effect on the free fatty acid (FFA) and tumor necrosis factor α (TNF-α) in serum.

Methods

Successfully established type 2 DM rats were divided into three groups, i.e. the normal control group, model group and curcumin group, and received the medication for consecutive 8 weeks. Thereafter, we detected the level of fasting blood glucose (FBG), and the blood glucose at 30 min, 60 min and 120 min; besides, we also carried out the insulin tolerance tests to measure the levels of fasting serum insulin (FINS) and blood glucose at 40 min and 90 min; additionally, we also detected the levels of TC, TG, HDL-C, LDL-C, FFA and TNF-α in serum. The results were expected to discover the mechanism of curcumin in decreasing the blood glucose level in DM rats.

Results

Compared with the model group, AUCs of FBG, blood glucose at 30 min, 60 min and 120 min, and glucose were decreased in varying degrees in the curcumin group, and the differences had statistical significance (p < .05). After subcutaneous injection of insulin, we found that the blood glucose at 40 min and 90 min in the curcumin group was decreased, while AUC of glucose level was also decreased (p < .05 or .01). Eight weeks after medication, compared with the rats in the normal group, the levels of HDL-C, LDL-C, TC and TG in rats of the model group and the curcumin group were obviously increased (p < .05). In comparison with the model group, the level of LDL-C in rats of the curcumin group was also decreased significantly (p < .05). In comparison with the normal control group in the same period, we found that the content of FFAs and TNF-α in serum of rats of the model group were elevated significantly, and the differences had statistical significance (p < .05 or .01); the levels in the curcumin group were significantly decreased in comparison with the model group in the same period, and the difference had statistical significance (p < .05 or .01).

Conclusion

Treatment with curcumin can significantly improve the metabolic disorder of glucose and lipid, enhance the sensitivity to the insulin, and ameliorate the resistance to insulin of the type II DM rats. Meanwhile, this treatment method can also significantly decrease the level of FFA and TNF-α in serum of type II DM rats. Thus, we inferred that the mechanism of curcumin to improve the insulin resistance might be correlated with the decreases of FFA and TNF-α in serum.

mTORC1 inhibitors rapamycin and metformin affect cardiovascular markers differentially in ZDF rats

Mammalian target for rapamycin complex 1 (mTORC1) is a common target for the action of immunosuppressant macrolide rapamycin and glucose-lowering metformin. Inhibition of mTORC1 can exert both beneficial and detrimental effects in different pathologies. Here, we investigated the differential effects of rapamycin (1.2 mg/kg per day delivered subcutaneously for 6 weeks) and metformin (300 mg/kg per day delivered orally for 11 weeks) treatments on male Zucker diabetic fatty (ZDF) rats that mimic the cardiorenal pathology of type 2 diabetic patients and progress to insulin insufficiency. Rapamycin and metformin improved proteinuria, and rapamycin also reduced urinary gamma glutamyl transferase (GGT) indicating improvement of tubular health. Metformin reduced food and water intake, and urinary sodium and potassium, whereas rapamycin increased urinary sodium. Metformin reduced plasma alkaline phosphatase, but induced transaminitis as evidenced by significant increases in plasma AST and ALT. Metformin also induced hyperinsulinemia, but did not suppress fasting plasma glucose after ZDF rats reached 17 weeks of age, and worsened lipid profile. Rapamycin also induced mild transaminitis. Additionally, both rapamycin and metformin increased plasma uric acid and creatinine, biomarkers for cardiovascular and renal disease. These observations define how rapamycin and metformin differentially modulate metabolic profiles that regulate cardiorenal pathology in conditions of severe type 2 diabetes.

Impaired glucose tolerance: do pharmacological therapies correct the underlying metabolic disturbance?

Lifestyle intervention prevents or delays the conversion from impaired glucose tolerance (IGT) to type 2 diabetes. However, many subjects fail to achieve and/or maintain long-term weight loss and to follow a regular exercise regimen may require pharmacologic therapy. Insulin resistance in liver, muscle and fat, along with impaired beta-cell function, plays a central role in the pathogenesis of type 2 diabetes. Insulin sensitising drugs, including metformin and the thiazolidinediones, have significantly reduced the conversion rate of IGT to type 2 diabetes in subjects in several large, well designed clinical trials. Insulin-sensitising drugs are likely to play an important role in future strategies for diabetes prevention.

Impact of the use of anti-diabetic drugs on survival of diabetic dialysis patients: a 5-year retrospective cohort study in Taiwan

BACKGROUND

Type 2 diabetes mellitus (DM) and associated complications are common in patients with chronic kidney disease (CKD) and can increase morbidity and mortality. A longitudinal 5-year observational study was conducted to investigate whether the use of anti-diabetic medications or not affected survival rates of diabetic dialysis patients.

METHODS

Using a data sample of a million patients from Taiwan's National Health Insurance Database, a retrospective cohort study surveyed patients with type 2 DM who began dialysis between 2002 and 2007. The study population was classified into groups using or not using anti-diabetic drugs. The group using anti-diabetic drugs was then categorized into 3 subgroups, including use of only oral hypoglycemic agents (OHAs), only insulin, and OHAs-combined insulin groups. Subjects of these four groups were followed 5 years or to date of death. Three major areas were analyzed: (1) demographic data and medical history; (2) survival prognosis and causes of death; and (3) effects on survival prognosis of different classes of OHAs.

RESULTS

A total of 912 patients fitting inclusion criteria were enrolled and followed-up for 5 years or to date of death. A total 465 patients died, and those not using anti-diabetic drugs (67.34 %) had a higher mortality rate than those using anti-diabetic drugs (46.42 %). After the multivariate analysis, group of OHAs-combined insulin had the lowest risk of death (HR 0.36, 95 % CI 0.27-0.47), followed by OHAs alone (HR 0.49, 95 % CI 0.38-0.63) and then insulin alone (HR 0.67, 95 % CI 0.51-0.88). To clarify four classes of OHAs (sulfonylurea, α-glucosidase inhibitors, meglitinide, and thiazolidinedione) are used in Taiwan for uremia patient with type 2 DM, and in our study, there were no significant differences in survival prognosis for the four drugs. Finally, the most common cause of death was infectious disease and there were no significant differences among the four groups.

CONCLUSION

This 5-year observational study results suggested that diabetic dialysis patients with anti-diabetic drugs had a lower risk of death compared with those without anti-diabetic drugs. Despite insulin therapy, appropriate OHAs should play an important role in treating these patients.

Alterations in β-Cell Calcium Dynamics and Efficacy Outweigh Islet Mass Adaptation in Compensation of Insulin Resistance and Prediabetes Onset

Emerging insulin resistance is normally compensated by increased insulin production of pancreatic β-cells, thereby maintaining normoglycemia. However, it is unclear whether this is achieved by adaptation of β-cell function, mass, or both. Most importantly, it is still unknown which of these adaptive mechanisms fail when type 2 diabetes develops. We performed longitudinal in vivo imaging of β-cell calcium dynamics and islet mass of transplanted islets of Langerhans throughout diet-induced progression from normal glucose homeostasis, through compensation of insulin resistance, to prediabetes. The results show that compensation of insulin resistance is predominated by alterations of β-cell function, while islet mass only gradually expands. Hereby, functional adaptation is mediated by increased calcium efficacy, which involves Epac signaling. Prior to prediabetes, β-cell function displays decreased stimulated calcium dynamics, whereas islet mass continues to increase through prediabetes onset. Thus, our data reveal a predominant role of islet function with distinct contributions of triggering and amplifying pathway in the in vivo processes preceding diabetes onset. These findings support protection and recovery of β-cell function as primary goals for prevention and treatment of diabetes and provide insight into potential therapeutic targets.

Cellular and molecular effects of yeast probiotics on cancer

The cancer is one of the main causes of human deaths worldwide. The exact mechanisms of initiation and progression of malignancies are not clear yet, but there is a common agreement about the role of colonic microbiota in the etiology of different cancers. Probiotics have been examined for their anti-cancer effects, and different mechanisms have been suggested about their antitumor functions. Nonpathogenic yeasts, as members of probiotics family, can be effective on gut microbiota dysbiosis. Generally safe yeasts have shown so many beneficial effects on human health. Probiotic yeasts influence physiology, metabolism, and immune homeostasis in the colon and contribute to cancer treatment due to possessing anti-inflammatory, anti-proliferative and anti-cancer properties. This study reviews some of the health-beneficial effects of probiotic yeasts and their biological substances like folic acid and β-glucan on cancer and focuses on the possible cellular and molecular mechanisms of probiotic yeasts such as influencing pathogenic bacteria, inactivation of carcinogenic compounds, especially those derived from food, improvement of intestinal barrier function, modulation of immune responses, antitoxic function, apoptosis, and anti-proliferative effects.

Intermittent hypoxia maintains glycemia in streptozotocin-induced diabetic rats

Increasing studies have shown protective effects of intermittent hypoxia on brain injury and heart ischemia. However, the effect of intermittent hypoxia on blood glucose metabolism, especially in diabetic conditions, is rarely observed. The aim of this study was to investigate whether intermittent hypoxia influences blood glucose metabolism in type 1 diabetic rats. Streptozotocin-induced diabetic adult rats and age-matched control rats were treated with intermittent hypoxia (at an altitude of 3 km, 4 h per day for 3 weeks) or normoxia as control. Fasting blood glucose, body weight, plasma fructosamine, plasma insulin, homeostasis model assessment of insulin resistance (HOMA-IR), pancreas β-cell mass, and hepatic and soleus glycogen were measured. Compared with diabetic rats before treatment, the level of fasting blood glucose in diabetic rats after normoxic treatment was increased (19.88 ± 5.69 mmol/L vs. 14.79 ± 5.84 mmol/L, p < 0.05), while it was not different in diabetic rats after hypoxic treatment (13.14 ± 5.77 mmol/L vs. 14.79 ± 5.84 mmol/L, p > 0.05). Meanwhile, fasting blood glucose in diabetic rats after hypoxic treatment was also lower than that in diabetic rats after normoxic treatment (13.14 ± 5.77 mmol/L vs. 19.88 ± 5.69 mmol/L, p<0.05). Plasma fructosamine in diabetic rats receiving intermittent hypoxia was significantly lower than that in diabetic rats receiving normoxia (1.28 ± 0.11 vs. 1.39 ± 0.11, p < 0.05), while there were no significant changes in body weight, plasma insulin and β-cell mass. HOMA-IR in diabetic rats after hypoxic treatment was also lower compared with diabetic rats after normoxic treatment (3.48 ± 0.48 vs. 3.86 ± 0.42, p < 0.05). Moreover, intermittent hypoxia showed effect on the increase of soleus glycogen but not hepatic glycogen. We conclude that intermittent hypoxia maintains glycemia in streptozotocin-induced diabetic rats and its regulation on muscular glycogenesis may play a role in the underlying mechanism.

The case for combination therapy as first-line treatment for the type 2 diabetic patient

The glycosylated hemoglobin (HbA(1c)) goal in patients with type 2 diabetes mellitus should be to achieve as low a value as can be obtained without causing significant or frequent hypoglycemia. This is best achieved by utilizing agents that lower glucose levels without causing hypoglycemia (thiazolidinediones and metformin). To maintain these low HbA(1c) values and avoid the utilization of insulin secretagogues or insulin, which are associated with hypoglycemia and suboptimal dosing leading to higher HbA(1c) values, drugs that maintain or improve pancreatic beta-cell function (thiazolidinediones and possibly incretin-based therapies) should be utilized. Restoration of first-phase insulin release, as has been shown with thiazolidinediones, will not only improve postprandial hyperglycemia but will also improve postprandial hyperlipidemia, both of which will decrease cardiac risk. Utilizing small doses of two drugs will also result in a decreased incidence of adverse effects compared with a large dose of a single drug. The use of fixed-dose combination oral antihyperglycemics will not only improve compliance but will often decrease costs compared with individual component dual therapy.

Microbubbles and Ultrasound: Therapeutic Applications in Diabetic Nephropathy

Diabetic nephropathy (DN) remains one of the most common causes of end-stage renal disease. Current therapeutic strategies aiming at optimization of serum glucose and blood pressure are beneficial in early stage DN, but are unable to fully prevent disease progression. With the limitations of current medical therapies and the shortage of available donor organs for kidney transplantation, the need for novel therapies to address DN complications and prevent progression towards end-stage renal failure is crucial. The development of ultrasound technology for non-invasive and targeted in-vivo gene delivery using high power ultrasound and carrier microbubbles offers great therapeutic potential for the prevention and treatment of DN. The promising results from preclinical studies of ultrasound-mediated gene delivery (UMGD) in several DN animal models suggest that UMGD offers a unique, non-invasive platform for gene- and cell-based therapies targeted against DN with strong clinical translation potential.

Pharmacogenomics and pharmacogenetics of thiazolidinediones: role in diabetes and cardiovascular risk factors

The most important goal in the treatment of patients with diabetes is to prevent the risk of cardiovascular disease (CVD), the first cause of mortality in these subjects. Thiazolidinediones (TZDs), a class of antidiabetic drugs, act as insulin sensitizers increasing insulin-dependent glucose disposal and reducing hepatic glucose output. TZDs including pioglitazone, rosiglitazone and troglitazone, by activating PPAR-γ have shown pleiotropic effects in reducing vascular risk factors and atherosclerosis. However, troglitazone was removed from the market due to its hepatoxicity, and rosiglitazone and pioglitazone both have particular warnings due to being associated with heart diseases. Specific genetic variations in genes involved in the pathways regulated by TDZs have demonstrated to modify the variability in treatment with these drugs, especially in their side effects. Therefore, pharmacogenomics and pharmacogenetics are an important tool in further understand intersubject variability per se but also to assess the therapeutic potential of such variability in drug individualization and therapeutic optimization.

An Extended Minimal Physiologically Based Pharmacokinetic Model: Evaluation of Type II Diabetes Mellitus and Diabetic Nephropathy on Human IgG Pharmacokinetics in Rats

Although many studies have evaluated the effects of type 2 diabetes mellitus (T2DM) on the pharmacokinetics (PK) of low molecular weight molecules, there is limited information regarding effects on monoclonal antibodies. Our previous studies have reported significant increases in total (2-4 fold) and renal (100-300 fold) clearance of human IgG, an antibody isotype, in Zucker diabetic fatty (ZDF) rats. Pioglitazone treatment incompletely reversed the disease-related PK changes. The objective of this study was to construct a mechanistic model for simultaneous fitting plasma and urine data, to yield physiologically relevant PK parameters. We propose an extended minimal physiologically based PK (mPBPK) model specifically for IgG by classifying organs as either leaky or tight vascular tissues, and adding a kidney compartment. The model incorporates convection as the primary mechanism of IgG movement from plasma into tissues, interstitial fluid (ISF) in extravascular distribution space, and glomerular filtration rate (GFR), sieving coefficient and fraction reabsorbed in the kidney. The model captured the plasma and urine PK profiles well, and simulated concentrations in ISF. The model estimated a 2-4 fold increase in nonrenal clearance from plasma and 30-120 fold increase in renal clearance with T2DM, consistent with the experimental findings, and these differences in renal clearance were related to changes in GFR, sieving coefficient, and proximal tubular reabsorption. In conclusion, the mPBPK model offers a more relevant approach for analyzing plasma and urine IgG concentration-time data than conventional models and provides insight regarding alterations in distributional and elimination parameters occurring with T2DM.

Impact of glucose-lowering drugs on cardiovascular disease in type 2 diabetes

Type 2 diabetes mellitus (T2DM) is characterized by multiple pathophysiologic abnormalities. With time, multiple glucose-lowering medications are commonly required to reduce and maintain plasma glucose concentrations within the normal range. Type 2 diabetes mellitus individuals also are at a very high risk for microvascular complications and the incidence of heart attack and stroke is increased two- to three-fold compared with non-diabetic individuals. Therefore, when selecting medications to normalize glucose levels in T2DM patients, it is important that the agent not aggravate, and ideally even improve, cardiovascular risk factors (CVRFs) and reduce cardiovascular morbidity and mortality. In this review, we examine the effect of oral (metformin, sulfonylureas, meglitinides, thiazolidinediones, DPP4 inhibitors, SGLT2 inhibitors, and α-glucosidase inhibitors) and injectable (glucagon-like peptide-1 receptor agonists and insulin) glucose-lowering drugs on established CVRFs and long-term studies of cardiovascular outcomes. Firm evidence that in T2DM cardiovascular disease can be reversed or prevented by improving glycaemic control is still incomplete and must await large, long-term clinical trials in patients at low risk using modern treatment strategies, i.e., drug combinations designed to maximize HbA1c reduction while minimizing hypoglycaemia and excessive weight gain.

Effect of Type 2 Diabetes Mellitus and Diabetic Nephropathy on IgG Pharmacokinetics and Subcutaneous Bioavailability in the Rat

The objective of this research was to assess the effects of type 2 diabetes mellitus (T2DM) and diabetic nephropathy (DN) on the pharmacokinetics of human IgG (hIgG), an antibody isotype, in Zucker diabetic fatty (ZDF) rats. Furthermore, the specific role of T2DM in the altered disposition of hIgG was evaluated by treating diabetic rats with pioglitazone, while the role of chronic kidney disease (CKD) was assessed using 5/6 nephrectomized Sprague Dawley rats. ZDF male (lean non-diabetic control and obese diabetic) and pioglitazone-treated ZDF rats were studied at ages 12-13 weeks (only DM was present), and at ages 29-30 weeks (progression to DN). All animals were dosed with 1 mg/kg of hIgG intravenously (IV) or subcutaneously (SC). ZDF rats had significantly higher blood glucose concentrations and urinary albumin excretion compared to control rats. Significant increases in total clearance (2.5-fold) and renal clearance (100-fold) of hIgG were observed; however the major increase in total clearance was due to increased non-renal clearance. Greater changes in urinary albumin excretion and total and renal clearances of IgG (3.5-fold and 300-fold, respectively) were observed with progression to DN. SC bioavailability of hIgG in all animal groups was similar (>84%). With pioglitazone-treatment, diabetic animals remained euglycemic and treatment was able to reverse the clearance changes, although incompletely. In the CKD group, no difference in hIgG clearance was observed when compared with controls. In conclusion, the increased clearance of hIgG in ZDF diabetic animals, reversal by pioglitazone treatment and lack of effect of CKD, demonstrate the influence of T2DM on hIgG pharmacokinetics.

Characterization of the Prediabetic State in a Novel Rat Model of Type 2 Diabetes, the ZFDM Rat

We recently established a novel animal model of obese type 2 diabetes (T2D), the Zucker fatty diabetes mellitus (ZFDM) rat strain harboring the fatty mutation (fa) in the leptin receptor gene. Here we performed a phenotypic characterization of the strain, focusing mainly on the prediabetic state. At 6-8 weeks of age, fa/fa male rats exhibited mild glucose intolerance and severe insulin resistance. Although basal insulin secretion was remarkably high in the isolated pancreatic islets, the responses to both glucose stimulation and the incretin GLP-1 were retained. At 10-12 weeks of age, fa/fa male rats exhibited marked glucose intolerance as well as severe insulin resistance similar to that at the earlier age. In the pancreatic islets, the insulin secretory response to glucose stimulation was maintained but the response to the incretin was diminished. In nondiabetic Zucker fatty (ZF) rats, the insulin secretory responses to both glucose stimulation and the incretin in the pancreatic islets were similar to those of ZFDM rats. As islet architecture was destroyed with age in ZFDM rats, a combination of severe insulin resistance, diminished insulin secretory response to incretin, and intrinsic fragility of the islets may cause the development of T2D in this strain.

Cardiovascular pharmacotherapy: Innovation stuck in translation

Systematic reviews of animal studies have revealed serious limitations in internal and external validity strongly affecting the reliability of this research. In addition inter-species differences are likely to further limit the predictive value of animal research for the efficacy and tolerability of new drugs in humans. Important changes in the research process are needed to allow efficient translation of preclinical discoveries to the clinic, including improvements in the laboratory and publication practices involving animal research and early incorporation of human proof-of-concept studies to optimize the interpretation of animal data for its predictive value for humans and the design of clinical trials.

Development, growth and maintenance of β-cell mass: models are also part of the story

Pancreatic β-cells in the islets of Langerhans play a crucial role in regulating glucose homeostasis in the circulation. Loss of β-cell mass or function due to environmental, genetic and immunological factors leads to the manifestation of diabetes mellitus. The mechanisms regulating the dynamics of pancreatic β-cell mass during normal development and diabetes progression are complex. To fully unravel such complexity, experimental and clinical approaches need to be combined with mathematical and computational models. In the natural sciences, mathematical and computational models have aided the identification of key mechanisms underlying the behavior of systems comprising multiple interacting components. A number of mathematical and computational models have been proposed to explain the development, growth and death of pancreatic β-cells. In this review, we discuss some of these models and how their predictions provide novel insight into the mechanisms controlling β-cell mass during normal development and diabetes progression. Lastly, we discuss a handful of the major open questions in the field.