Pancreatic beta-cell mass in European subjects with type 2 diabetes

Teplizumab's immunomodulatory effects on pancreatic β-cell function in type 1 diabetes mellitus

This review explores the immunomodulatory potential of Teplizumab and its impact on pancreatic β-cell function in T1D. Characterized by the autoimmune destruction of insulin-producing beta cells, T1D's management involves maintaining glycemic control through exogenous insulin. Teplizumab, a humanized monoclonal antibody targeting the CD3 antigen, has shown promise in delaying T1D onset and preserving residual β-cell function. The review employs a narrative approach, synthesizing evidence from diverse clinical trials and studies gathered through a meticulous literature search. It scrutinizes Teplizumab's mechanisms of action, including its influence on autoreactive CD8 + T cells and regulatory T cells, offering insights into its immunological pathways. The synthesis of findings from various trials demonstrates Teplizumab's efficacy in preserving C-peptide levels and reducing exogenous insulin requirements, particularly in recent-onset T1D. Considering Teplizumab's real-world implications, the paper addresses potential obstacles, including side effects, patient selection criteria, and logistical challenges. It also emphasizes exploring combination therapies and personalized treatment strategies to maximize Teplizumab's benefits. The review contributes a nuanced perspective on Teplizumab's clinical implications and future directions in T1D management, bridging theoretical understanding with practical considerations.

cGAS suppresses β-cell proliferation by a STING-independent but CEBPβ-dependent mechanism

AIMS/HYPOTHESIS

cGAS (cyclic GMP-AMP synthase) has been implicated in various cellular processes, but its role in β-cell proliferation and diabetes is not fully understood. This study investigates the impact of cGAS on β-cell proliferation, particularly in the context of diabetes.

METHODS

Utilizing mouse models, including cGAS and STING (stimulator of interferon genes) knockout mice, we explored the role of cGAS in β-cell function. This involved β-cell-specific cGAS knockout (cGASβKO) mice, created by breeding cGAS floxed mice with transgenic mice expressing Cre recombinase under the insulin II promoter. We analyzed cGAS expression in diabetic mouse models, evaluated the effects of cGAS deficiency on glucose tolerance, and investigated the molecular mechanisms underlying these effects through RNA sequencing.

RESULTS

cGAS expression is upregulated in the islets of diabetic mice and by high glucose treatment in MIN6 cells. Both global cGAS deficiency and β-cell-specific cGAS knockout mice lead to improved glucose tolerance by promoting β-cell mass. Interestingly, STING knockout did not affect pancreatic β-cell mass, suggesting a STING-independent mechanism for cGAS's role in β-cells. Further analyses revealed that cGAS- but not STING-deficiency leads to reduced expression of CEBPβ, a known suppressor of β-cell proliferation, concurrently with increased β-cell proliferation. Moreover, overexpression of CEBPβ reverses the upregulation of Cyclin D1 and D2 induced by cGAS deficiency, thereby regulating β-cell proliferation. These results confirm that cGAS regulation of β-cell proliferation via a CEBPβ-dependent but STING-independent mechanism.

CONCLUSIONS/INTERPRETATION

Our findings highlight the pivotal role of cGAS in promoting β-cell proliferation and maintaining glucose homeostasis, potentially by regulating CEBPβ expression in a STING-independent manner. This study uncovers the significance of cGAS in controlling β-cell mass and identifies a potential therapeutic target for enhancing β-cell proliferation in the treatment of diabetes.

The age-dependent regulation of pancreatic islet landscape is fueled by a HNF1a-immune signaling loop

Animal longevity is a function of global vital organ functionality and, consequently, a complex polygenic trait. Yet, monogenic regulators controlling overall or organ-specific ageing exist, owing their conservation to their function in growth and development. Here, by using pathway analysis combined with wet-biology methods on several dynamic timelines, we identified Hnf1a as a novel master regulator of the maturation and ageing in the adult pancreatic islet during the first year of life. Conditional transgenic mice bearing suboptimal levels of this transcription factor in the pancreatic islets displayed age-dependent changes, with a profile echoing precocious maturation. Additionally, the comparative pathway analysis revealed a link between Hnf1a age-dependent regulation and immune signaling, which was confirmed in the ageing timeline of an overly immunodeficient mouse model. Last, the global proteome analysis of human islets spanning three decades of life largely backed the age-specific regulation observed in mice. Collectively, our results suggest a novel role of Hnf1a as a monogenic regulator of the maturation and ageing process in the pancreatic islet via a direct or indirect regulatory loop with immune signaling.

Receptors and Signaling Pathways Controlling Beta-Cell Function and Survival as Targets for Anti-Diabetic Therapeutic Strategies

Preserving the function and survival of pancreatic beta-cells, in order to achieve long-term glycemic control and prevent complications, is an essential feature for an innovative drug to have clinical value in the treatment of diabetes. Innovative research is developing therapeutic strategies to prevent pathogenic mechanisms and protect beta-cells from the deleterious effects of inflammation and/or chronic hyperglycemia over time. A better understanding of receptors and signaling pathways, and of how they interact with each other in beta-cells, remains crucial and is a prerequisite for any strategy to develop therapeutic tools aimed at modulating beta-cell function and/or mass. Here, we present a comprehensive review of our knowledge on membrane and intracellular receptors and signaling pathways as targets of interest to protect beta-cells from dysfunction and apoptotic death, which opens or could open the way to the development of innovative therapies for diabetes.

Loss of β-cell identity and dedifferentiation, not an irreversible process?

Type 2 diabetes (T2D) is a polygenic metabolic disorder characterized by insulin resistance in peripheral tissues and impaired insulin secretion by the pancreas. While the decline in insulin production and secretion was previously attributed to apoptosis of insulin-producing β-cells, recent studies indicate that β-cell apoptosis rates are relatively low in diabetes. Instead, β-cells primarily undergo dedifferentiation, a process where they lose their specialized identity and transition into non-functional endocrine progenitor-like cells, ultimately leading to β-cell failure. The underlying mechanisms driving β-cell dedifferentiation remain elusive due to the intricate interplay of genetic factors and cellular stress. Understanding these mechanisms holds the potential to inform innovative therapeutic approaches aimed at reversing β-cell dedifferentiation in T2D. This review explores the proposed drivers of β-cell dedifferentiation leading to β-cell failure, and discusses current interventions capable of reversing this process, thus restoring β-cell identity and function.

Pancreatic beta-cell mass and function and therapeutic implications of using antidiabetic medications in type 2 diabetes

Nowadays, the focus of diabetes treatment has switched from lowering the glucose level to preserving glycemic homeostasis and slowing the disease progression. The main pathophysiology of both type 1 diabetes and long-standing type 2 diabetes is pancreatic β-cell mass loss and dysfunction. According to recent research, human pancreatic β-cells possess the ability to proliferate in response to elevated insulin demands. It has been demonstrated that in insulin-resistant conditions in humans, such as obesity or pregnancy, the β-cell mass increases. This ability could be helpful in developing novel treatment approaches to restore a functional β-cell mass. Treatment strategies aimed at boosting β-cell function and mass may be a useful tool for managing diabetes mellitus and stopping its progression. This review outlines the processes of β-cell failure and detail the many β-cell abnormalities that manifest in people with diabetes mellitus. We also go over standard techniques for determining the mass and function of β-cells. Lastly, we provide the therapeutic implications of utilizing antidiabetic drugs in controlling the mass and function of pancreatic β-cells.

Comparison of β-Cell Function and Insulin Sensitivity Between Normal-Weight and Obese Chinese With Young-Onset Type 2 Diabetes

Normal-weight individuals with usual-onset type 2 diabetes have reduced β-cell function and greater insulin sensitivity compared with their obese counterparts. The relative contribution of β-cell dysfunction and insulin resistance to young-onset type 2 diabetes (YOD) among normal-weight individuals is not well established. In 44 individuals with YOD (24 with normal weight and 20 with obesity) and 24 healthy control individuals with normoglycemia (12 with normal weight and 12 with obesity), we conducted 2-h 12 mmol/L hyperglycemic clamps to measure acute (0-10 min) and steady-state (100-120 min) insulin and C-peptide responses, as well as insulin sensitivity index. Normal-weight individuals with YOD had lower acute insulin response, steady-state insulin and C-peptide responses, and a higher insulin sensitivity index compared with their obese counterparts with YOD. Compared with BMI-matched healthy control individuals, normal-weight individuals with YOD had lower acute and steady-state insulin and C-peptide responses but a similar insulin sensitivity index. The impairment of steady-state β-cell response relative to healthy control individuals was more pronounced in normal-weight versus obese individuals with YOD. In conclusion, normal-weight Chinese with YOD exhibited worse β-cell function but preserved insulin sensitivity relative to obese individuals with YOD and BMI-matched healthy individuals with normoglycemia. The selection of glucose-lowering therapy should account for pathophysiological differences underlying YOD between normal-weight and obese individuals.

ARTICLE HIGHLIGHTS

A new histopathological phenomenon: Pancreatic islet cell loss in the elderly population

BACKGROUND

We observed the phenomenon of pancreatic islet cell loss (ICL) in our previous histopathological study. Multiple studies have reported that a decrease in β-cells is correlated with diabetes or chronic pancreatitis. Few studies have reported ICL in a healthy population.

METHODS

Thirty-three pancreatic tissue samples were obtained from cadavers (age: 65-104 years) who had never been diagnosed with any pancreatic diseases before death. The pancreatic body sections were used for an immunohistochemical study of pancreatic islet cells, and area calculations were performed using ImageJ to determine the degree of ICL and islet cell proportions.

RESULTS

The proportion of β-cells showed a downward trend as the degree of ICL increased (r=-0.414, P = 0.011), and the proportion of women with severe ICL was significantly higher than that of men with severe ICL (P = 0.016). The probability of severe ICL decreased with age in the population over 70 years of age (P = 0.069, linear correlation). Severe ICL may be associated with higher pancreatic intraepithelial neoplasia lesions (P = 0.059).

CONCLUSION

The phenomenon of ICL in the elderly population was mainly due to pancreatic β-cell reduction. It may be one of the direct causes of age-related diabetes.

Select DYRK1A Inhibitors Enhance Both Proliferation and Differentiation in Human Pancreatic Beta Cells

The small molecule DYRK1A inhibitor, harmine, induces human beta cell proliferation, expands beta cell mass, enhances expression of beta cell phenotypic genes, and improves human beta cell function i n vitro and in vivo . It is unknown whether the "pro-differentiation effect" is a DYRK1A inhibitor class-wide effect. Here we compare multiple commonly studied DYRK1A inhibitors. Harmine, 2-2c and 5-IT increase expression of PDX1, MAFA, NKX6.1, SLC2A2, PCSK1, MAFB, SIX2, SLC2A2, SLC30A8, ENTPD3 in normal and T2D human islets. Unexpectedly, GNF4877, CC-401, INDY, CC-401 and Leucettine fail to induce expression of these essential beta cell molecules. Remarkably, the pro-differentiation effect is independent of DYRK1A inhibition: although silencing DYRK1A induces human beta cell proliferation, it has no effect on differentiation; conversely, harmine treatment enhances beta cell differentiation in DYRK1A-silenced islets. A careful screen of multiple DYRK1A inhibitor kinase candidate targets was unable to identify pro-differentiation pathways. Overall, harmine, 2-2c and 5-IT are unique among DYRK1A inhibitors in their ability to enhance both beta cell proliferation and differentiation. While beta cell proliferation is mediated by DYRK1A inhibition, the pro-differentiation effects of harmine, 2-2c and 5-IT are distinct, and unexplained in mechanistic terms. These considerations have important implications for DYRK1A inhibitor pharmaceutical development.

Diabetes and the fabkin complex: A dual-edged sword

The Fabkin complex, composed of FABP4, ADK, and NDPKs, emerges as a novel regulator of insulin-producing beta cells, offering promising prospects for diabetes treatment. Our approach, which combines literature review and database analysis, sets the stage for future research. These findings hold significant implications for both diabetes treatment and research, as they present potential therapeutic targets for personalized treatment, leading to enhanced patient outcomes and a deeper comprehension of the disease. The multifaceted role of the Fabkin complex in glucose metabolism, insulin resistance, anti-inflammation, beta cell proliferation, and vascular function underscores its therapeutic potential, reshaping diabetes management and propelling advancements in the field.

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.

Intermittent fasting protects β-cell identity and function in a type-2 diabetes model

Type 2 diabetes (T2DM) is caused by the interaction of multiple genes and environmental factors. T2DM is characterized by hyperglycemia, insulin secretion deficiency and insulin resistance. Chronic hyperglycemia induces β-cell dysfunction, loss of β-cell mass/identity and β-cell dedifferentiation. Intermittent fasting (IF) a commonly used dietary regimen for weight-loss, also induces metabolic benefits including reduced blood glucose, improved insulin sensitivity, reduced adiposity, inflammation, oxidative-stress and increased fatty-acid oxidation; however, the mechanisms underlying these effects in pancreatic β-cells remain elusive. KK and KKAy, mouse models of polygenic T2DM spontaneously develop hyperglycemia, glucose intolerance, glucosuria, impaired insulin secretion and insulin resistance. To determine the long-term effects of IF on T2DM, 6-weeks old KK and KKAy mice were subjected to IF for 16 weeks. While KKAy mice fed ad-libitum demonstrated severe hyperglycemia (460 mg/dL) at 6 weeks of age, KK mice showed blood glucose levels of 230 mg/dL, but progressively became severely diabetic by 22-weeks. Strikingly, both KK and KKAy mice subjected to IF showed reduced blood glucose and plasma insulin levels, decreased body weight gain, reduced plasma triglycerides and cholesterol, and improved insulin sensitivity. They also demonstrated enhanced expression of the β-cell transcription factors NKX6.1, MAFA and PDX1, and decreased expression of ALDH1a3 suggesting protection from loss of β-cell identity by IF. IF normalized glucose stimulated insulin secretion in islets from KK and KKAy mice, demonstrating improved β-cell function. In addition, hepatic steatosis, gluconeogenesis and inflammation was decreased particularly in KKAy-IF mice, indicating peripheral benefits of IF. These results have important implications as an optional intervention for preservation of β-cell identity and function in T2DM.

Exercise induces tissue-specific adaptations to enhance cardiometabolic health

The risk associated with multiple cancers, cardiovascular disease, diabetes, and all-cause mortality is decreased in individuals who meet the current recommendations for physical activity. Therefore, regular exercise remains a cornerstone in the prevention and treatment of non-communicable diseases. An acute bout of exercise results in the coordinated interaction between multiple tissues to meet the increased energy demand of exercise. Over time, the associated metabolic stress of each individual exercise bout provides the basis for long-term adaptations across tissues, including the cardiovascular system, skeletal muscle, adipose tissue, liver, pancreas, gut, and brain. Therefore, regular exercise is associated with a plethora of benefits throughout the whole body, including improved cardiorespiratory fitness, physical function, and glycemic control. Overall, we summarize the exercise-induced adaptations that occur within multiple tissues and how they converge to ultimately improve cardiometabolic health.

Bridging the Gap: Pancreas Tissue Slices From Organ and Tissue Donors for the Study of Diabetes Pathogenesis

Over the last two decades, increased availability of human pancreatic tissues has allowed for major expansions in our understanding of islet biology in health and disease. Indeed, studies of fixed and frozen pancreatic tissues, as well as efforts using viable isolated islets obtained from organ donors, have provided significant insights toward our understanding of diabetes. However, the procedures associated with islet isolation result in distressed cells that have been removed from any surrounding influence. The pancreas tissue slice technology was developed as an in situ approach to overcome certain limitations associated with studies on isolated islets or fixed tissue. In this Perspective, we discuss the value of this novel platform and review how pancreas tissue slices, within a short time, have been integrated in numerous studies of rodent and human islet research. We show that pancreas tissue slices allow for investigations in a less perturbed organ tissue environment, ranging from cellular processes, over peri-islet modulations, to tissue interactions. Finally, we discuss the considerations and limitations of this technology in its future applications. We believe the pancreas tissue slices will help bridge the gap between studies on isolated islets and cells to the systemic conditions by providing new insight into physiological and pathophysiological processes at the organ level.

ARTICLE HIGHLIGHTS

Human pancreas tissue slices represent a novel platform to study human islet biology in close to physiological conditions. Complementary to established technologies, such as isolated islets, single cells, and histological sections, pancreas tissue slices help bridge our understanding of islet physiology and pathophysiology from single cell to intact organ. Diverse sources of viable human pancreas tissue, each with distinct characteristics to be considered, are available to use in tissue slices for the study of diabetes pathogenesis.

Identification of reversible and druggable pathways to improve beta-cell function and survival in Type 2 diabetes

Targeting β-cell failure could prevent, delay or even partially reverse Type 2 diabetes. However, development of such drugs is limited as the molecular pathogenesis is complex and incompletely understood. Further, while β-cell failure can be modeled experimentally, only some of the molecular changes will be pathogenic. Therefore, we used a novel approach to identify molecular pathways that are not only changed in a diabetes-like state but also are reversible and can be targeted by drugs. INS1E cells were cultured in high glucose (HG, 20 mM) for 72 h or HG for an initial 24 h followed by drug addition (exendin-4, metformin and sodium salicylate) for the remaining 48 h. RNAseq (Illumina TruSeq), gene set enrichment analysis (GSEA) and pathway analysis (using Broad Institute, Reactome, KEGG and Biocarta platforms) were used to identify changes in molecular pathways. HG decreased function and increased apoptosis in INS1E cells with drugs partially reversing these effects. HG resulted in upregulation of 109 pathways while drug treatment downregulated 44 pathways with 21 pathways in common. Interestingly, while hyperglycemia extensively upregulated metabolic pathways, they were not altered with drug treatment, rather pathways involved in the cell cycle featured more heavily. GSEA for hyperglycemia identified many known pathways validating the applicability of our cell model to human disease. However, only a fraction of these pathways were downregulated with drug treatment, highlighting the importance of considering druggable pathways. Overall, this provides a powerful approach and resource for identifying appropriate targets for the development of β-cell drugs.

Benefits and risks of drug combination therapy for diabetes mellitus and its complications: a comprehensive review

Diabetes is a chronic metabolic disease, and its therapeutic goals focus on the effective management of blood glucose and various complications. Drug combination therapy has emerged as a comprehensive treatment approach for diabetes. An increasing number of studies have shown that, compared with monotherapy, combination therapy can bring significant clinical benefits while controlling blood glucose, weight, and blood pressure, as well as mitigating damage from certain complications and delaying their progression in diabetes, including both type 1 diabetes (T1D), type 2 diabetes (T2D) and related complications. This evidence provides strong support for the recommendation of combination therapy for diabetes and highlights the importance of combined treatment. In this review, we first provided a brief overview of the phenotype and pathogenesis of diabetes and discussed several conventional anti-diabetic medications currently used for the treatment of diabetes. We then reviewed several clinical trials and pre-clinical animal experiments on T1D, T2D, and their common complications to evaluate the efficacy and safety of different classes of drug combinations. In general, combination therapy plays a pivotal role in the management of diabetes. Integrating the effectiveness of multiple drugs enables more comprehensive and effective control of blood glucose without increasing the risk of hypoglycemia or other serious adverse events. However, specific treatment regimens should be tailored to individual patients and implemented under the guidance of healthcare professionals.

Pancreatic Beta-cell Dysfunction in Type 2 Diabetes

Pancreatic β-cells produce and secrete insulin to maintain blood glucose levels within a narrow range. Defects in the function and mass of β-cells play a significant role in the development and progression of diabetes. Increased β-cell deficiency and β-cell apoptosis are observed in the pancreatic islets of patients with type 2 diabetes. At an early stage, β-cells adapt to insulin resistance, and their insulin secretion increases, but they eventually become exhausted, and the β-cell mass decreases. Various causal factors, such as high glucose, free fatty acids, inflammatory cytokines, and islet amyloid polypeptides, contribute to the impairment of β-cell function. Therefore, the maintenance of β-cell function is a logical approach for the treatment and prevention of diabetes. In this review, we provide an overview of the role of these risk factors in pancreatic β-cell loss and the associated mechanisms. A better understanding of the molecular mechanisms underlying pancreatic β-cell loss will provide an opportunity to identify novel therapeutic targets for type 2 diabetes.

Genetic risk converges on regulatory networks mediating early type 2 diabetes

Type 2 diabetes mellitus (T2D), a major cause of worldwide morbidity and mortality, is characterized by dysfunction of insulin-producing pancreatic islet β cells1,2. T2D genome-wide association studies (GWAS) have identified hundreds of signals in non-coding and β cell regulatory genomic regions, but deciphering their biological mechanisms remains challenging3-5. Here, to identify early disease-driving events, we performed traditional and multiplexed pancreatic tissue imaging, sorted-islet cell transcriptomics and islet functional analysis of early-stage T2D and control donors. By integrating diverse modalities, we show that early-stage T2D is characterized by β cell-intrinsic defects that can be proportioned into gene regulatory modules with enrichment in signals of genetic risk. After identifying the β cell hub gene and transcription factor RFX6 within one such module, we demonstrated multiple layers of genetic risk that converge on an RFX6-mediated network to reduce insulin secretion by β cells. RFX6 perturbation in primary human islet cells alters β cell chromatin architecture at regions enriched for T2D GWAS signals, and population-scale genetic analyses causally link genetically predicted reduced RFX6 expression with increased T2D risk. Understanding the molecular mechanisms of complex, systemic diseases necessitates integration of signals from multiple molecules, cells, organs and individuals, and thus we anticipate that this approach will be a useful template to identify and validate key regulatory networks and master hub genes for other diseases or traits using GWAS data.

A data-driven computational model for obesity-driven diabetes onset and remission through weight loss

Obesity is a major risk factor for the development of type 2 diabetes (T2D), where a sustained weight loss may result in T2D remission in individuals with obesity. To design effective and feasible intervention strategies to prevent or reverse T2D, it is imperative to study the progression of T2D and remission together. Unfortunately, this is not possible through experimental and observational studies. To address this issue, we introduce a data-driven computational model and use human data to investigate the progression of T2D with obesity and remission through weight loss on the same timeline. We identify thresholds for the emergence of T2D and necessary conditions for remission. We explain why remission is only possible within a window of opportunity and the way that window depends on the progression history of T2D, individual's metabolic state, and calorie restrictions. These findings can help to optimize therapeutic intervention strategies for T2D prevention or treatment.

A review: Mechanism and prospect of gastrodin in prevention and treatment of T2DM and COVID-19

Gastrodin is an extract from the dried tuber of the Chinese herb Gastrodia elata (Tian ma), with anti-inflammatory, antioxidant, and antiviral properties. Recent studies have shown that, compared to commonly used diabetes drugs, gastrodin has antidiabetic effects in multiple ways, with characteristics of low cost, high safety, less side effects, protection of β-cell function, relieving insulin resistance and alleviating multiple complications. In addition, it is confirmed that gastrodin can protect the function of lung and other organs, enhance antiviral activity via upregulating the type I interferon (IFN-I), and inhibit angiotensin II (AngII), a key factor in "cytokine storm" caused by COVID-19. Therefore, we reviewed the effect and mechanism of gastrodin on type 2 diabetes mellitus (T2DM), and speculated other potential mechanisms of gastrodin in alleviating insulin resistance from insulin signal pathway, inflammation, mitochondrial and endoplasmic reticulum and its potential in the prevention and treatment of COVID-19. We hope to provide new direction and treatment strategy for basic research and clinical work: gastrodin is considered as a drug for the prevention and treatment of diabetes and COVID-19.

The protective role of shenqi compound in type 2 diabetes: A comprehensive investigation of pancreatic β-cell function and mass

Type 2 diabetes (T2D) is a prevalent metabolic disorder characterized by impaired insulin secretion and insulin resistance, resulting in elevated blood glucose levels. The dysfunction and loss of pancreatic β-cells, responsible for producing insulin, contribute to the development of T2D. Traditional Chinese medicine (TCM) has emerged as a potential source of innovative therapeutic interventions. However, limited research exists on Chinese herbal formulations specifically targeting the protection of pancreatic β-cell function and mass. One such formulation is the Shenqi compound (SQC), widely used in China and consisting of Panax Ginseng, Astragali Radix, Rhizoma Dioscoreae, Corni Fructus, Rehmanniae Radix, Salviae Miltiorrhizae Radix et Rhizoma, Radix Trichosanthis, and Rhei Radix et Rhizoma. Understanding the mechanisms underlying the therapeutic effects of SQC is crucial for developing novel treatment strategies for T2D. This study aims to comprehensively investigate the scientific evidence supporting the role of SQC in alleviating T2D by targeting the protection of pancreatic β-cell function and mass. Spontaneously diabetic GK rats were used as the animal model, receiving SQC (14.4 g/kg/d) for 8 weeks. The results demonstrate multiple beneficial effects of SQC, including significant control of blood glucose levels (P < 0.05), inhibition of insulin resistance (measured by Western Blot), reduction of hyperinsulinemia (P < 0.05), attenuation of oxidative stress (P < 0.05), suppression of inflammation (P < 0.05), protection against islet hypertrophy and beta cell proliferation (evaluated through pathological staining), and inhibition of β-cell apoptosis and senescence (also assessed through pathological staining). These findings indicate the promotion of β-cell survival and function. In vitro experiments using isolated islets further support these results, revealing improvements in insulin secretion (P < 0.05) and β-cell function following SQC therapy (P < 0.05). This represents a significant breakthrough in addressing β-cell dysfunction and preserving mass within the context of TCM. Overall, SQC shows promise as a natural therapeutic approach for T2D, with potential benefits in preserving pancreatic β-cell function and mass. This enhances the practical applicability and significance of the research by bridging the gap between experimental findings and clinical practice, thereby providing important clinical value in TCM treatment of T2D. Further research is necessary to elucidate its precise mechanisms of action and optimize its clinical application.

Unraveling the mysteries of hepatic insulin signaling: deconvoluting the nuclear targets of insulin

Over 100 years have passed since insulin was first administered to a diabetic patient. Since then great strides have been made in diabetes research. It has determined where insulin is secreted from, which organs it acts on, how it is transferred into the cell and is delivered to the nucleus, how it orchestrates the expression pattern of the genes, and how it works with each organ to maintain systemic metabolism. Any breakdown in this system leads to diabetes. Thanks to the numerous researchers who have dedicated their lives to cure diabetes, we now know that there are three major organs where insulin acts to maintain glucose/lipid metabolism: the liver, muscles, and fat. The failure of insulin action on these organs, such as insulin resistance, result in hyperglycemia and/or dyslipidemia. The primary trigger of this condition and its association among these tissues still remain to be uncovered. Among the major organs, the liver finely tunes the glucose/lipid metabolism to maintain metabolic flexibility, and plays a crucial role in glucose/lipid abnormality due to insulin resistance. Insulin resistance disrupts this tuning, and selective insulin resistance arises. The glucose metabolism loses its sensitivity to insulin, while the lipid metabolism maintains it. The clarification of its mechanism is warranted to reverse the metabolic abnormalities due to insulin resistance. This review will provide a brief historical review for the progress of the pathophysiology of diabetes since the discovery of insulin, followed by a review of the current research clarifying our understanding of selective insulin resistance.

Longitudinal changes in pancreatic volume and pancreatic fat with weight gain in Japanese without diabetes: An analysis using health check-up data

Aims/introduction

There have been few reports about the longitudinal changes in pancreas volume (PV) or pancreatic steatosis (PS) in response to obesity. In this longitudinal analysis using health check-up data, we explored changes in PV, PS and glucose metabolic indices that occurred after weight gain in Japanese without diabetes.

Materials/methods

Clinical data on 37 Japanese subjects with a ≥1 kg/m² increase in body mass index between two health check-ups and without diabetes were collected. PV, pancreas attenuation (PA) and splenic attenuation (SA) were evaluated using computed tomography (CT) images. The pancreas area was outlined by hand in multiple images with slice thickness of 2 mm, and the PV was computed by summing these areas. PS was defined as the difference between SA and PA (SA-PA). Medical records were collected, including findings on immunoreactive insulin (IRI), homeostasis model assessment of insulin resistance (HOMA-R) and beta cell function (HOMA-β). Paired t-test and Spearman's correlation coefficient were used in the analyses.

Results

The median follow-up period was 21.1 months and the mean BMI was increased from 25.5 ± 3.3 kg/m² to 27.0 ± 3.3 kg/m². PV (53.5 ± 15.9 cm³ vs. 56.2 ± 16.4 cm³) and SA-PA (8.7 ± 9.1 HU vs. 13.6 ± 10.9 HU) increased significantly after weight gain (both, P < 0.001). There were significant increases of IRI and HOMA-R with the weight gain (both, P < 0.05), whereas HOMA-β exhibited only a nonsignificant trend of increase (55.4％ (41.5-65.5) vs. 56.8％ (46.2-83.7), P = 0.07).

Conclusions

Both PV and PS were increased longitudinally with weight gain in Japanese without diabetes.

Immune cell infiltration in the pancreas of type 1, type 2 and type 3c diabetes

The different types of diabetes differ in disease pathogenesis but share the impairment or loss of β-cell function leading to chronic hyperglycaemia. While immune cells are present throughout the whole pancreas in normality, their number and activation is increased in diabetes. Different patterns and composition of inflammation could be observed in type 1, type 2 and type 3c diabetes. Immune cells, pancreatic stellate cells and fibrosis were present in the islet microenvironment and could add to β-cell dysfunction and therefore development and progression of diabetes. First studies investigating the use of anti-inflammatory drugs demonstrate their ability to rescue remaining β-cell function and their potential benefit in diabetes treatment. This article provides an overview of immune cell infiltrates in different types of diabetes, highlights the knowledge of their impact on β-cell function and introduces the potential of immunomodulatory strategies.

Type 2 diabetes mellitus in obesity promotes prolongation of cardiomyocyte contractile function, impaired Ca2+ handling and protein carbonylation damage

AIMS

To investigate whether the obesity associated to T2DM presented cardiomyocyte myocardial contractility dysfunction due to damage in Ca²⁺ handling, concomitantly with increased biomarkers of oxidative stress.

METHODS

Male Wistar rats were randomized into two groups: control (C): fed with standard diet; and obese (Ob) that fed a saturated high-fat. After the characterization of obesity (12 weeks), the Ob animals were submitted to T2DM induction with a single dose of intraperitoneal (i.p.) injection of streptozotocin (30 mg/kg). Thus, remained Ob rats that were characterized as to the presence (T2DMOb; n = 8) and/or absence (Ob; n = 10) of T2DM. Cardiac remodeling was measured by post-mortem morphological, isolated cardiomyocyte contractile function, as well as by intracellular Ca²⁺-handling analysis.

RESULTS

T2DMOb presented a significant reduction of all fat pads, total body fat and adiposity index. T2DMOb group presented a significant increase in protein carbonylation and superoxide dismutase (SOD) activity, respectively. T2DMOb promoted elevations in fractional shortening (15.6 %) and time to 50 % shortening (5.8 %), respectively. Time to 50 % Ca²⁺ decay was prolonged in T2DMOb, suggesting a possible impairment in Ca²⁺recapture and/or removal.

CONCLUSION

Type 2 diabetes mellitus in obesity promotes prolongation of cardiomyocyte contractile function with protein carbonylation damage and impaired Ca²⁺ handling.

β Cell function after Roux-en-Y gastric bypass surgery or reduced energy intake alone in people with obesity

BackgroundThe effects of diet-induced weight loss (WL) and WL after Roux-en-Y gastric bypass (RYGB) surgery on β cell function (BCF) are unclear because of conflicting results from different studies, presumably because of differences in the methods used to measure BCF, the amount of WL between treatment groups, and baseline BCF. We evaluated the effect of WL after RYGB surgery or reduced energy intake alone on BCF in people with obesity with and without type 2 diabetes.MethodsBCF (insulin secretion in relationship to plasma glucose) was assessed before and after glucose or mixed-meal ingestion before and after (a) progressive amounts (6%, 11%, 16%) of WL induced by a low-calorie diet (LCD) in people with obesity without diabetes, (b) ~20% WL after RYGB surgery or laparoscopic adjustable gastric banding (LAGB) in people with obesity without diabetes, and (c) ~20% WL after RYGB surgery or LCD alone in people with obesity and diabetes.ResultsDiet-induced progressive WL in people without diabetes progressively decreased BCF. Marked WL after LAGB or RYGB in people without diabetes did not alter BCF. Marked WL after LCD or RYGB in people with diabetes markedly increased BCF, without a difference between groups.ConclusionMarked WL increases BCF in people with obesity and diabetes but not in people with obesity without diabetes. The effect of RYGB-induced WL on BCF is not different from the effect of matched WL after LAGB or LCD alone.trial registrationNCT00981500, NCT02207777, NCT01299519.FundingNIH grants R01 DK037948, P30 DK056341, P30 DK020579, UL1 TR002345.

Induction of remission in diabetes by lowering blood glucose

As diabetes continues to grow as major health problem, there has been great progress in understanding the important role of pancreatic beta-cells in its pathogenesis. Diabetes develops when the normal interplay between insulin secretion and the insulin sensitivity of target tissues is disrupted. With type 2 diabetes (T2D), glucose levels start to rise when beta-cells are unable to meet the demands of insulin resistance. For type 1 diabetes (T1D) glucose levels rise as beta-cells are killed off by autoimmunity. In both cases the increased glucose levels have a toxic effect on beta-cells. This process, called glucose toxicity, has a major inhibitory effect on insulin secretion. This beta-cell dysfunction can be reversed by therapies that reduce glucose levels. Thus, it is becoming increasingly apparent that an opportunity exists to produce a complete or partial remission for T2D, both of which will provide health benefit.

A highly sensitive strategy for monitoring real-time proliferation of targeted cell types in vivo

Cell proliferation processes play pivotal roles in timely adaptation to many biological situations. Herein, we establish a highly sensitive and simple strategy by which time-series showing the proliferation of a targeted cell type can be quantitatively monitored in vivo in the same individuals. We generate mice expressing a secreted type of luciferase only in cells producing Cre under the control of the Ki67 promoter. Crossing these with tissue-specific Cre-expressing mice allows us to monitor the proliferation time course of pancreatic β-cells, which are few in number and weakly proliferative, by measuring plasma luciferase activity. Physiological time courses, during obesity development, pregnancy and juvenile growth, as well as diurnal variation, of β-cell proliferation, are clearly detected. Moreover, this strategy can be utilized for highly sensitive ex vivo screening for proliferative factors for targeted cells. Thus, these technologies may contribute to advancements in broad areas of biological and medical research.

Complete remission of diabetes with a transient HDAC inhibitor and insulin in streptozotocin mice

Despite the growing epidemic worldwide, diabetes is an incurable disease. We have been focusing on why diabetes manifests refractoriness to any therapy. We recently found that abnormal bone marrow-derived cells (BMDCs), namely, Vcam-1⁺ST-HSCs, was a key mechanism for diabetic complications. We then hypothesize that those aberrant BMDCs sustainedly impair pancreatic β cells. Here we show that eliminating abnormal BMDCs using bone marrow transplantation results in controlling serum glucose in diabetic mice, in which normoglycemia is sustained even after cessation of insulin therapy. Alternatively, abnormal BMDCs exhibiting epigenetic alterations are treated with an HDAC inhibitor, givinostat, in diabetic mice. As a result, those mice are normoglycemic along with restored insulin secretion even following the cessation of both insulin and givinostat. Diabetic cell fusion between abnormal BMDCs and resident cells is significantly blocked by the combination therapy in the pancreatic islets and thymus while surgical ablation of the thymus completely eliminates therapeutic protection in diabetic mice. In conclusion, diabetes is an epigenetic stem cell disorder with thymic disturbances. The combination may be applied to patients aiming at complete remission from diabetes in clinical medicine.

The therapeutic mechanism of Yuye decoction on type 2 diabetes mellitus based on network pharmacology and experimental verification

ETHNOPHARMACOLOGICAL RELEVANCE

Yuye decoction (YYD) has been widely used as a folk Chinese herbal formula in clinical treatment of type 2 diabetes mellitus(T2DM) for many years. However, its mechanism is still unclear.

AIM OF THE STUDY

The aim of this study was to explore the potential mechanism of YYD against T2DM initially by UHPLC-MS/MS combining with network pharmacology, molecular docking techniques and experimental validation.

MATERIALS AND METHODS

The main ingredients in the water extract of YYD were initially identified using UHPLC-MS/MS analysis. Combined with network pharmacology and molecular docking techniques, the YYD key compounds-core targets-key signaling pathways network was constructed and the binding activity of key components to core targets was validated. The T2DM rat model was induced by Streptozotocin combined with high glucose and high fat diets. The apoptosis cell model of mouse islet β-cell of Min6 was induced by high-glucose and palmitic acid. Histopathological and immunofluorescence satining were used to evaluate pancreatic islet β-cell function and apoptosis in rats. Min6 cell viability and apoptosis ratio were evaluated by CCK-8 and TUNEL staining. The predicted targets and pathways were validated by experiments in vitro and in vivo.

RESULTS

The 56 compounds from YYD were identified by UHPLC-MS/MS. The potential targets of the above compounds were predicted by online compound target database, among of which 362 targets were associated with T2DM. Protein-protein interaction analysis identified the main targets such as SRC, MAPK1, PIK3R1, AKT1, HRAS and HSP90AA1, which were considered as the therapeutic targets of YYD on against T2DM. Functional enrichment analysis revealed that PI3K/AKT, FoxO and apoptosis signaling pathways were significantly enriched. Molecular docking results showed that compounds of monolinolein, neomangiferin, mangiferin, pelargonidin-3-O-glucoside and acacetin from YYD had high binding activities to PIK3R1, AKT1, Sirt1 and FoxO1. Therefore, PI3K/AKT1, Sirt1/FoxO1 and apoptotic signaling pathways were considered as predicted targets for experimental validation study. Animal experiments showed that YYD reduced blood glucose levels, improved pancreatic dysfunction and pancreatic islet β-cells apoptosis in T2DM rats which contributed to the activation of AKT1 and FoxO1 and their related signaling molecules. These results were confirmed in Min6 cell model induced by high-glucose and palmitic acid.

CONCLUSIONS

In summary, this study systematically visualized the possible therapeutic effects and mechanisms of YYD on T2DM through the network pharmacology approach and experimental study. The results indicated that YYD could prevent pancreatic islet dysfunction and reverse islet of β-cells apoptosis possibly via PI3K/AKT1, Sirt1/FoxO1 signaling pathways.

Beta Cell Dysfunction in Youth- and Adult-Onset Type 2 Diabetes: An Extensive Narrative Review with a Special Focus on the Role of Nutrients

Traditionally a disease of adults, type 2 diabetes (T2D) has been increasingly diagnosed in youth, particularly among adolescents and young adults of minority ethnic groups. Especially, during the recent COVID-19 pandemic, obesity and prediabetes have surged not only in minority ethnic groups but also in the general population, further raising T2D risk. Regarding its pathogenesis, a gradually increasing insulin resistance due to central adiposity combined with a progressively defective β-cell function are the main culprits. Especially in youth-onset T2D, a rapid β-cell activity decline has been observed, leading to higher treatment failure rates, and early complications. In addition, it is well established that both the quantity and quality of food ingested by individuals play a key role in T2D pathogenesis. A chronic imbalance between caloric intake and expenditure together with impaired micronutrient intake can lead to obesity and insulin resistance on one hand, and β-cell failure and defective insulin production on the other. This review summarizes our evolving understanding of the pathophysiological mechanisms involved in defective insulin secretion by the pancreatic islets in youth- and adult-onset T2D and, further, of the role various micronutrients play in these pathomechanisms. This knowledge is essential if we are to curtail the serious long-term complications of T2D both in pediatric and adult populations.

Biomarkers of aging

Aging biomarkers are a combination of biological parameters to (i) assess age-related changes, (ii) track the physiological aging process, and (iii) predict the transition into a pathological status. Although a broad spectrum of aging biomarkers has been developed, their potential uses and limitations remain poorly characterized. An immediate goal of biomarkers is to help us answer the following three fundamental questions in aging research: How old are we? Why do we get old? And how can we age slower? This review aims to address this need. Here, we summarize our current knowledge of biomarkers developed for cellular, organ, and organismal levels of aging, comprising six pillars: physiological characteristics, medical imaging, histological features, cellular alterations, molecular changes, and secretory factors. To fulfill all these requisites, we propose that aging biomarkers should qualify for being specific, systemic, and clinically relevant.

Systematic review and meta-analysis of teneligliptin for treatment of type 2 diabetes

BACKGROUND AND AIM

There are efficacy and safety concerns related to teneligliptin treatment. A systematic review of randomized controlled trials (RCTs) was undertaken to comprehensively profile the efficacy and safety of teneligliptin in the treatment of type 2 diabetes mellitus (T2DM).

METHODS

Thirteen studies were chosen from a search of scientific databases for RCTs using teneligliptin as a monotherapy or as an adjunct to other glycemic agents with pre-specified inclusion criteria. We calculated weighted mean differences (WMDs) and 95% confidence intervals (CIs) in each included trial and pooled the data using a random-effects model.

RESULTS

Thirteen studies enrolled 2853 patients were identified. Teneligliptin treatment was associated with weight gain (vs. placebo, weighted mean difference (WMD) 0.28 kg; 95% CI - 0.20-0.77 kg; I² = 86%; P = 0.25). Compared to monotherapy, add on therapy with teneligliptin showed significant improvement in FPG mg/dl levels (WMD - 16.75 mg/dl; 95% CI - 19.38 to - 14.13 mg/dl), HOMA-β (WMD 7.91; 95% CI 5.38-10.45) and HOMA-IR (WMD - 0.27; 95% CI - 0.46 to - 0.07). The improvement in HbA1c was greater with monotherapy (WMD - 8.88 mmol/mol; 95% CI - 9.59 to - 8.08 mmol/mol). There was no significant risk of any hypoglycemia with teneligliptin compared to placebo (OR 0.84; 95% CI 0.44-1.60; I² = 0%; P = 0.60). However, the risk was 1.84 times high when combined with other glycemic agents. The risk of cardiovascular events was comparable, regardless of treatment duration when compared to placebo or any other active comparator (OR 0.79; 95% CI 0.40-1.57; I² = 0%; P = 0.50). [PROSPERO, CRD42022360785].

CONCLUSIONS

Teneligliptin is an effective and safe therapeutic option for patients with T2DM, both as monotherapy and as add-on therapy. However, additional large-scale, high-quality, long-term follow-up clinical trials with diverse ethnic populations are required to confirm its long-term efficacy and safety.

Polymer-Based Nanostructures for Pancreatic Beta-Cell Imaging and Non-Invasive Treatment of Diabetes

Diabetes poses major economic, social, and public health challenges in all countries worldwide. Besides cardiovascular disease and microangiopathy, diabetes is a leading cause of foot ulcers and lower limb amputations. With the continued rise of diabetes prevalence, it is expected that the future burden of diabetes complications, early mortality, and disabilities will increase. The diabetes epidemic is partly caused by the current lack of clinical imaging diagnostic tools, the timely monitoring of insulin secretion and insulin-expressing cell mass (beta (β)-cells), and the lack of patients' adherence to treatment, because some drugs are not tolerated or invasively administrated. In addition to this, there is a lack of efficient topical treatment capable of stopping the progression of disabilities, in particular for treating foot ulcers. In this context, polymer-based nanostructures garnered significant interest due to their tunable physicochemical characteristics, rich diversity, and biocompatibility. This review article emphasizes the last advances and discusses the prospects in the use of polymeric materials as nanocarriers for β-cell imaging and non-invasive drug delivery of insulin and antidiabetic drugs in the management of blood glucose and foot ulcers.

PEPITEM modulates leukocyte trafficking to reduce obesity-induced inflammation

Dysregulation of leukocyte trafficking, lipid metabolism, and other metabolic processes are the hallmarks that underpin and drive pathology in obesity. Current clinical management targets alternations in lifestyle choices (e.g. exercise, weight loss) to limit the impact of the disease. Crucially, re-gaining control over the pathogenic cellular and molecular processes may offer an alternative, complementary strategy for obese patients. Here we investigate the impact of the immunopeptide, PEPITEM, on pancreas homeostasis and leukocyte trafficking in mice on high-fed obesogenic diet (HFD). Both prophylactic and therapeutic treatment with PEPITEM alleviated the effects of HFD on the pancreas, reducing pancreatic beta cell size. Moreover, PEPITEM treatment also limited T-cell trafficking (CD4+ T-cells and KLRG1+ CD3+ T-cells) to obese visceral, but not subcutaneous, adipose tissue. Similarly, PEPITEM treatment reduced macrophage numbers within the peritoneal cavity of mice on HFD diet at both 6 and 12 weeks. By contrast, PEPITEM therapy elevated numbers of T and B cells were observed in the secondary lymphoid tissues (e.g. spleen and inguinal lymph node) when compared to the untreated HFD controls. Collectively our data highlights the potential for PEPITEM as a novel therapy to combat the systemic low-grade inflammation experienced in obesity and minimize the impact of obesity on pancreatic homeostasis. Thus, offering an alternative strategy to reduce the risk of developing obesity-related co-morbidities, such as type 2 diabetes mellitus, in individuals at high risk and struggling to control their weight through lifestyle modifications.

Discovery of IHMT-MST1-39 as a novel MST1 kinase inhibitor and AMPK activator for the treatment of diabetes mellitus

Insulin-producing pancreatic β cell death is the fundamental cause of type 1 diabetes (T1D) and a contributing factor to type 2 diabetes (T2D). Moreover, metabolic disorder is another hallmark of T2D. Mammalian sterile 20-like kinase 1 (MST1) contributes to the progression of diabetes mellitus through apoptosis induction and acceleration of pancreatic β cell dysfunction. AMP-activated protein kinase (AMPK) is an energy sensing kinase and its activation has been suggested as a treatment option for metabolic diseases. Thus, pharmacological inhibition of MST1 and activation of AMPK simultaneously represents a promising approach for diabetes therapy. Here, we discovered a novel selective MST1 kinase inhibitor IHMT-MST1-39, which exhibits anti-apoptosis efficacy and improves the survival of pancreatic β cells under diabetogenic conditions, as well as primary pancreatic islets in an ex vivo disease model. Mechanistically, IHMT-MST1-39 activated AMPK signaling pathway in hepatocytes in vitro, combination of IHMT-MST1-39 and metformin synergistically prevented hyperglycemia and significantly ameliorated glucose tolerance and insulin resistance in diabetic mice. Taken together, IHMT-MST1-39 is a promising anti-diabetic candidate as a single agent or in combination therapy for both T1D and T2D.

The effects of early short-term insulin treatment vs. glimepiride on beta cell function in newly diagnosed type 2 diabetes with HbA1c above 9

BACKGROUND

Type 2 diabetes mellitus (T2D) is a complex metabolic impairment. Beta cell (BC) failure is the most challenging among its pathogenetic mechanisms. Recognizing reversible contributors to BC failure could guide individualized approach to early T2D treatment. The aim of this study was to compare early short-term insulin treatment vs. glimepiride, both added to metformin, on BC function, glycemic and lipid control, during 12-month follow-up.

METHODS

Eighty newly diagnosed T2D patients, 30-65 years of age, presenting with HbA1c ≥ 9% were enrolled in the study. They were randomly assigned to single-month initial insulin therapy (INS) added to metformin, or to glimepiride and metformin (OAD) as only treatment. Subjects assigned to initial insulin intervention were thereafter switched to OAD. C-peptide (C-Pep) was analyzed at baseline and 2 hours after standardized test meal (STM). All subjects were STM-retested after 3 and 12 months. HbA1c, serum lipids, BMI, HOMA IR, and HOMA B were assessed over follow-up.

RESULTS

HbA1c was lower in INS vs OAD at 3-months: 6.26 ± 0.18% vs 6.78 ± 0.10% (p = 0.016), remaining so by 12 months (p =0.056). BMI-adjusted ΔC-Pep was greater in INS vs. OAD at 3 months (4.60 ± 0.59 vs. 3.21 ± 0.34 m2 /kg; p = 0.044), persisting by 12months (4.57 ± 0.56 vs. 3.04 ± 0.34 m2/kg; p = 0.023). Average ΔC-Pep improvement from recruitment to 3 months was 100.8% in INS,vs. 51.3% in OAD. Prevalence of STM-ΔC-Pep response greater than 2.4 ng/mL had risen 3.2-fold by 12 months in the INS, vs. 2.4-fold only in the OAD group (p = 0.018).

DISCUSSION

Early short-term insulin intervention in newly diagnosed T2D improves beta cell function more than glimepiride, both added to metformin, resulting in a superior and longer lasting glycemic and lipid control.

Prolonged culture of human pancreatic islets under glucotoxic conditions changes their acute beta cell calcium and insulin secretion glucose response curves from sigmoid to bell-shaped

AIMS/HYPOTHESIS

The rapid remission of type 2 diabetes by a diet very low in energy correlates with a marked improvement in glucose-stimulated insulin secretion (GSIS), emphasising the role of beta cell dysfunction in the early stages of the disease. In search of novel mechanisms of beta cell dysfunction after long-term exposure to mild to severe glucotoxic conditions, we extensively characterised the alterations in insulin secretion and upstream coupling events in human islets cultured for 1-3 weeks at ~5, 8, 10 or 20 mmol/l glucose and subsequently stimulated by an acute stepwise increase in glucose concentration.

METHODS

Human islets from 49 non-diabetic donors (ND-islets) and six type 2 diabetic donors (T2D-islets) were obtained from five isolation centres. After shipment, the islets were precultured for 3-7 days in RPMI medium containing ~5 mmol/l glucose and 10% (vol/vol) heat-inactivated FBS with selective islet picking at each medium renewal. Islets were then cultured for 1-3 weeks in RPMI containing ~5, 8, 10 or 20 mmol/l glucose before measurement of insulin secretion during culture, islet insulin and DNA content, beta cell apoptosis and cytosolic and mitochondrial glutathione redox state, and assessment of dynamic insulin secretion and upstream coupling events during acute stepwise stimulation with glucose [NAD(P)H autofluorescence, ATP/(ATP+ADP) ratio, electrical activity, cytosolic Ca²⁺ concentration ([Ca²⁺]_c)].

RESULTS

Culture of ND-islets for 1-3 weeks at 8, 10 or 20 vs 5 mmol/l glucose did not significantly increase beta cell apoptosis or oxidative stress but decreased insulin content in a concentration-dependent manner and increased beta cell sensitivity to subsequent acute stimulation with glucose. Islet glucose responsiveness was higher after culture at 8 or 10 vs 5 mmol/l glucose and markedly reduced after culture at 20 vs 5 mmol/l glucose. In addition, the [Ca²⁺]_c and insulin secretion responses to acute stepwise stimulation with glucose were no longer sigmoid but bell-shaped, with maximal stimulation at 5 or 10 mmol/l glucose and rapid sustained inhibition above that concentration. Such paradoxical inhibition was, however, no longer observed when islets were acutely depolarised by 30 mmol/l extracellular K⁺. The glucotoxic alterations of beta cell function were fully reversible after culture at 5 mmol/l glucose and were mimicked by pharmacological activation of glucokinase during culture at 5 mmol/l glucose. Similar results to those seen in ND-islets were obtained in T2D-islets, except that their rate of insulin secretion during culture at 8 and 20 mmol/l glucose was lower, their cytosolic glutathione oxidation increased after culture at 8 and 20 mmol/l glucose, and the alterations in GSIS and upstream coupling events were greater after culture at 8 mmol/l glucose.

CONCLUSIONS/INTERPRETATION

Prolonged culture of human islets under moderate to severe glucotoxic conditions markedly increased their glucose sensitivity and revealed a bell-shaped acute glucose response curve for changes in [Ca²⁺]_c and insulin secretion, with maximal stimulation at 5 or 10 mmol/l glucose and rapid inhibition above that concentration. This novel glucotoxic alteration may contribute to beta cell dysfunction in type 2 diabetes independently from a detectable increase in beta cell apoptosis.

Venom Peptides, Polyphenols and Alkaloids: Are They the Next Antidiabetics That Will Preserve β-Cell Mass and Function in Type 2 Diabetes?

Improvement of insulin secretion by pancreatic β-cells and preservation of their mass are the current challenges that future antidiabetic drugs should meet for achieving efficient and long-term glycemic control in patients with type 2 diabetes (T2D). The successful development of glucagon-like peptide 1 (GLP-1) analogues, derived from the saliva of a lizard from the Helodermatidae family, has provided the proof of concept that antidiabetic drugs directly targeting pancreatic β-cells can emerge from venomous animals. The literature reporting on the antidiabetic effects of medicinal plants suggests that they contain some promising active substances such as polyphenols and alkaloids, which could be active as insulin secretagogues and β-cell protectors. In this review, we discuss the potential of several polyphenols, alkaloids and venom peptides from snake, frogs, scorpions and cone snails. These molecules could contribute to the development of new efficient antidiabetic medicines targeting β-cells, which would tackle the progression of the disease.

Expansion of human alpha-cell area is associated with a higher maximum body mass index before the onset of type 2 diabetes

Highlights: We examined whether maximum body mass index (BMI) before the onset of diabetes (MBBO) affects histological findings of islet cells. We divided patients into two groups according to an MBBO cutoff of 25 kg/m² or BMI cutoff of 21 kg/m². We compared immunohistochemical parameters between the MBBO groups or BMI groups. The relative alpha‐cell area in the high MBBO group was significantly higher than that in the low MBBO group. There was no difference in the other parameters between the MBBO groups or BMI groups.

Molecular Genetics of Abnormal Redox Homeostasis in Type 2 Diabetes Mellitus

Numerous studies have shown that oxidative stress resulting from an imbalance between the production of free radicals and their neutralization by antioxidant enzymes is one of the major pathological disorders underlying the development and progression of type 2 diabetes (T2D). The present review summarizes the current state of the art advances in understanding the role of abnormal redox homeostasis in the molecular mechanisms of T2D and provides comprehensive information on the characteristics and biological functions of antioxidant and oxidative enzymes, as well as discusses genetic studies conducted so far in order to investigate the contribution of polymorphisms in genes encoding redox state-regulating enzymes to the disease pathogenesis.

New-onset type 1 diabetes and severe acute respiratory syndrome coronavirus 2 infection

Type 1 diabetes (T1D) is a condition characterized by an absolute deficiency of insulin. Loss of insulin-producing pancreatic islet β cells is one of the many causes of T1D. Viral infections have long been associated with new-onset T1D and the balance between virulence and host immunity determines whether the viral infection would lead to T1D. Herein, we detail the dynamic interaction of pancreatic β cells with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and the host immune system with respect to new-onset T1D. Importantly, β cells express the crucial entry receptors and multiple studies confirmed that β cells are infected by SARS-CoV-2. Innate immune system effectors, such as natural killer cells, can eliminate such infected β cells. Although CD4⁺ CD25⁺ FoxP3⁺ regulatory T (T_REG ) cells provide immune tolerance to prevent the destruction of the islet β-cell population by autoantigen-specific CD8⁺ T cells, it can be speculated that SARS-CoV-2 infection may compromise self-tolerance by depleting T_REG -cell numbers or diminishing T_REG -cell functions by repressing Forkhead box P3 (FoxP3) expression. However, the expansion of β cells by self-duplication, and regeneration from progenitor cells, could effectively replace lost β cells. Appearance of islet autoantibodies following SARS-CoV-2 infection was reported in a few cases, which could imply a breakdown of immune tolerance in the pancreatic islets. However, many of the cases with newly diagnosed autoimmune response following SARS-CoV-2 infection also presented with significantly high HbA_1c (glycated hemoglobin) levels that indicated progression of an already set diabetes, rather than new-onset T1D. Here we review the potential underlying mechanisms behind loss of functional β-cell mass as a result of SARS-CoV-2 infection that can trigger new-onset T1D.

Nutritional strategies for intervention of diabetes and improvement of β-cell function

Diabetes mellitus, especially Type 2 diabetes (T2D), is caused by multiple factors including genetics, diets, and lifestyles. Diabetes is a chronic condition and is among the top 10 causes of death globally. Nutritional intervention is one of the most important and effective strategies for T2D management. It is well known that most of intervention strategies can lower blood glucose level and improve insulin sensitivity in peripheral tissues. However, the regulation of pancreatic β cells by dietary intervention is not well characterized. In this review, we summarized some of the commonly used nutritional methods for diabetes intervention. We then discussed the effects and the underlying mechanisms of nutritional intervention in improving the cell mass and function of pancreatic islet β cells. With emerging intervention strategies and in-depth investigation, we are expecting to have a better understanding about the effectiveness of dietary interventions in ameliorating T2D in the future.

GLUT4 degradation by GLUTFOURINH® in mice resembles moderate-obese diabetes of human with hyperglycemia and low lipid accumulation

BACKGROUNDS AND AIMS

Type 2 diabetes mellitus (T2D) is a chronic disease characterized by insulin resistance and hyperglycemia. To investigate T2D, genetic and chemical induced hyper-obese rodent models have been experimentally developed. However, establishment of moderate-obese diabetes model will confer diverse opportunities for translational studies. In this study, we found the chemical, GLUTFOURINH® (GFI), induces post-translational degradation of glucose transporter 4 (GLUT4). We aimed to establish novel diabetic model by using GFI.

METHODS AND RESULTS

Low plasma membrane GLUT4 (pmGLUT4) levels by GFI resulted in reduction of intracellular glucose uptake and TG, and increase of intracellular FFA in A204 cells. Likewise, GFI treatment decreased intracellular TG and increased intracellular FFA levels in Hep3B and 3T3-L1 cells. Mice were administered with GFI (16 mg/kg) for short-term (3-day) and long-term (28- and 31-day) to compared with vehicle injection, HFD model, and T2D model, respectively. Short-term and long-term GFI treatments induced hyperglycemia and hyperinsulinemia with low pmGLUT4 levels. Compared to HFD model, long-term GFI with HFD reduced adipose weight and intracellular TG accumulation, but increased plasma FFA. GFI treatment resulted in insulin resistance by showing low QUICKI and high HOMA-IR values, and low insulin response during insulin tolerance test. Additionally, low pmGLUT4 by GFI heightened hyperglycemia, hyperinsulinemia, and insulin resistance compared to T2D model.

CONCLUSIONS

In summary, we report GLUT4 degradation by novel chemical (GFI) induces moderate-obese diabetes representing hyperglycemia, insulin resistance and low intracellular lipid accumulation. The GLUT4 degradation by GFI has translational value for studying diseases related to moderate-obese diabetes.

Genetic evidence that high BMI in childhood has a protective effect on intermediate diabetes traits, including measures of insulin sensitivity and secretion

Determining how high body-mass index (BMI) at different time points influences the risk of developing type two diabetes (T2D), and affects insulin secretion and insulin sensitivity, is critical. By estimating childhood BMI in 441,761 individuals in the UK Biobank, we identified which genetic variants had larger effects on adulthood BMI than on childhood BMI, and vice-versa. All genome-wide significant genetic variants were then used to separate the independent genetic effects of high childhood BMI from high adulthood BMI on the risk of T2D and insulin related phenotypes using Mendelian randomisation and studies of T2D, and oral and intravenous measures of insulin secretion and sensitivity. We found that a 1.s.d. (= 1.97kg/m 2 ) higher childhood BMI, corrected for the independent genetic liability to adulthood BMI, was associated with a protective effect for seven measures of insulin sensitivity and secretion, including an increased insulin sensitivity index (β = 0.15 [0.067, 0.225], p = 2.79×10 -4 ), and reduced fasting glucose (β = -0.053 [-0.089, -0.017], p = 4.31×10 -3 ). There was however little to no evidence of a direct protective effect on T2D (OR = 0.94 [0.85 - 1.04], p = 0.228), independently of genetic liability to adulthood BMI. Our results thus cumulatively provide evidence of the protective effect of higher childhood BMI on insulin secretion and sensitivity, which are crucial intermediate diabetes traits. However, we stress that our results should not currently lead to any change in public health or clinical practice, given the uncertainty in biological pathway of these effects, and the limitations of this type of study.

Research in Context

High BMI in adulthood is associated with higher risk of type two diabetes, coupled with lower insulin sensitivity and secretion.Richardson et al [2020] used genetics to show that high BMI in childhood does not appear to increase the risk of type diabetes independently from its effect on adult BMI.We asked: does high childhood BMI affect insulin related traits such as fasting glucose and insulin sensitivity, independently of adulthood BMI?We used genetics to show that high childhood BMI has a protective effect on seven insulin sensitivity and secretion traits, including fasting glucose and measures of insulin sensitivity and secretion, independently of adulthood BMI.Our work has the potential to turn conventional understanding on its head - high BMI in childhood improves insulin sensitivity (when adjusting for knock on effects to high adult BMI) and opens up important questions about plasticity in childhood and compensatory mechanisms.

Glucokinase Inhibition: A Novel Treatment for Diabetes?

Chronic hyperglycemia increases pancreatic β-cell metabolic activity, contributing to glucotoxicity-induced β-cell failure and loss of functional β-cell mass, potentially in multiple forms of diabetes. In this perspective we discuss the novel paradoxical and counterintuitive concept of inhibiting glycolysis, particularly by targeted inhibition of glucokinase, the first enzyme in glycolysis, as an approach to maintaining glucose sensing and preserving functional β-cell mass, thereby improving insulin secretion, in the treatment of diabetes.

VGLL4 and MENIN function as TEAD1 corepressors to block pancreatic β cell proliferation

TEAD1 and the mammalian Hippo pathway regulate cellular proliferation and function, though their regulatory function in β cells remains poorly characterized. In this study, we demonstrate that while β cell-specific TEAD1 deletion results in a cell-autonomous increase of β cell proliferation, β cell-specific deletion of its canonical coactivators, YAP and TAZ, does not affect proliferation, suggesting the involvement of other cofactors. Using an improved split-GFP system and yeast two-hybrid platform, we identify VGLL4 and MENIN as TEAD1 corepressors in β cells. We show that VGLL4 and MENIN bind to TEAD1 and repress the expression of target genes, including FZD7 and CCN2, which leads to an inhibition of β cell proliferation. In conclusion, we demonstrate that TEAD1 plays a critical role in β cell proliferation and identify VGLL4 and MENIN as TEAD1 corepressors in β cells. We propose that these could be targeted to augment proliferation in β cells for reversing diabetes.

Reflections on the state of diabetes research and prospects for treatment

Research on the etiology and treatment of diabetes has made substantial progress. As a result, several new classes of anti-diabetic drugs have been introduced in clinical practice. Nonetheless, the number of patients achieving glycemic control targets has not increased for the past 20 years. Two areas of unmet medical need are the restoration of insulin sensitivity and the reversal of pancreatic beta cell failure. In this review, we integrate research advances in transcriptional regulation of insulin action and pathophysiology of beta cell dedifferentiation with their potential impact on prospects of a durable "cure" for patients suffering from type 2 diabetes.

Regeneration of Pancreatic β-Cells for Diabetes Therapeutics by Natural DYRK1A Inhibitors

The pathogenesis of diabetes mellitus is characterized by insulin resistance and islet β-cell dysfunction. Up to now, the focus of diabetes treatment has been to control blood glucose to prevent diabetic complications. There is an urgent need to develop a therapeutic approach to restore the mass and function of β-cells. Although exogenous islet cell transplantation has been used to help patients control blood glucose, it is costly and has very narrow application scenario. So far, small molecules have been reported to stimulate β-cell proliferation and expand β-cell mass, increasing insulin secretion. Dual-specificity tyrosine-regulated kinase 1A (DYRK1A) inhibitors can induce human β-cell proliferation in vitro and in vivo, and show great potential in the field of diabetes therapeutics. From this perspective, we elaborated on the mechanism by which DYRK1A inhibitors regulate the proliferation of pancreatic β-cells, and summarized several effective natural DYRK1A inhibitors, hoping to provide clues for subsequent structural optimization and drug development in the future.

The Role of Pancreatic Fatty Acid Synthesis in Islet Morphology and Function after Caloric Restriction or Roux-En-Y Gastric Bypass Surgery in Mice

BACKGROUND

Both caloric restriction (CR) and Roux-en-Y gastric bypass (RYGB) are practical interventions for type 2 diabetes mellitus (T2DM), while the molecular mechanisms of CR and RYGB regarding glycemic control are still poorly understood. Here, we explore the effects and underlying mechanisms of CR and RYGB on β-cell area and function.

METHODS

Average islet size was measured by histological analysis. The pancreatic lipid content was detected by using a commercial lipid assay kit. The expression levels of lipogenic transcription factors and enzymes in mouse pancreas were determined by quantitative PCR, Western blot, and immunofluorescence.

RESULTS

CR decreased the mean size of islets and pancreatic insulin production in both regular diet-fed and high-fat diet-fed mice. Increased β-cell apoptosis was detected in the calorie-restricted mice. Interestingly, the lipogenic transcription factors and enzymes such as SREBP1c, PPARγ, FASN and ACC were upregulated in the pancreas after CR. In contrast to CR, RYGB decreased the apoptosis of β-cells and the expression of fatty acid synthase.

CONCLUSIONS

Pancreatic fatty acid synthesis is critical to the β-cell function after CR and RYGB.