Advancing Diabetes Research: A Novel Islet Isolation Method from Living Donors.

Pancreatic islet isolation is critical for type 2 diabetes research. Although -omics approaches have shed light on islet molecular profiles, inconsistencies persist; on the other hand, functional studies are essential, but they require reliable and standardized isolation methods. Here, we propose a simplified protocol applied to very small-sized samples collected from partially pancreatectomized living donors. Islet isolation was performed by digesting tissue specimens collected during surgery within a collagenase P solution, followed by a Lympholyte density gradient separation; finally, functional assays and staining with dithizone were carried out. Isolated pancreatic islets exhibited functional responses to glucose and arginine stimulation mirroring donors' metabolic profiles, with insulin secretion significantly decreasing in diabetic islets compared to non-diabetic islets; conversely, proinsulin secretion showed an increasing trend from non-diabetic to diabetic islets. This novel islet isolation method from living patients undergoing partial pancreatectomy offers a valuable opportunity for targeted study of islet physiology, with the primary advantage of being time-effective and successfully preserving islet viability and functionality. It enables the generation of islet preparations that closely reflect donors' clinical profiles, simplifying the isolation process and eliminating the need for a Ricordi chamber. Thus, this method holds promises for advancing our understanding of diabetes and for new personalized pharmacological approaches.

Why do some glucose-lowering agents improve non-alcoholic fatty liver disease whereas others do not? A narrative review in search of a unifying hypothesis.

Non-alcoholic fatty liver disease (NAFLD) and type 2 diabetes (T2D) are metabolic disorders connected by common pathophysiological mechanisms. Since insulin resistance (IR) and metabolic alterations are common to both conditions, almost all glucose-lowering agents which improve IR have also been studied in patients with NAFLD. Some have shown great efficacy, others none. Thus, the mechanisms behind the efficacy of these drugs in improving hepatic steatosis, steatohepatitis, and eventually fibrosis remain controversial. Glycaemic control improves T2D, but probably has limited effects on NAFLD, as all glucose-lowering agents ameliorate glucose control but only a few improve NAFLD features. In contrast, drugs that either improve adipose tissue function, reduce lipid ingestion, or increase lipid oxidation are particularly effective in NAFLD. We therefore hypothesise that improved free fatty acid metabolism may be the unifying mechanism behind the efficacy of some glucose-lowering agents on NAFLD and may represent the key to NAFLD treatment.

Adipose tissue remodelling in obese subjects is a determinant of presence and severity of fatty liver disease.

AIMS: Experimental data suggest that visceral adipose tissue (VAT) dysfunction contributes to non-alcoholic fatty liver disease (NAFLD) development in obesity, however, data on humans are limited. Aims of this study were to investigate the relationship between NAFLD and VAT morphofunctional impairment and to determine whether the extent of VAT remodelling is associated with liver damage and metabolic alterations in obesity. METHODS: We analysed data from 40 obese individuals candidate to bariatric surgery in whom paired intraoperative liver and omental biopsies were performed for diagnosing NAFLD and VAT inflammation by immunohistochemistry and mRNA expression studies. RESULTS: Within our study population, NAFLD was significantly associated with greater VAT CD68+ macrophages infiltration (P = .04), fibrosis (P = .04) and impaired microvascular density (P = .03) as well as increased expression of markers of local hypoxia, apoptosis and inflammation (UNC5B, CASP7, HIF1-α, IL-8, MIP2, WISP-1, all P < .01). The degree of VAT inflammation correlated with the severity of hepatic injury (steatosis, inflammation, fibrosis; all P < .01) and impaired gluco-metabolic profile. CONCLUSIONS: In obese patients, NAFLD is associated in a dose-dependent manner with signs of VAT remodelling, which reflect more severe clinical metabolic impairment. Our study depicts morphological alterations and novel mediators of VAT dysfunction, adding knowledge for future therapeutic approaches to NAFLD and its metabolic complications.

Greater circulating DPP4 activity is associated with impaired flow-mediated dilatation in adults with type 2 diabetes mellitus.

BACKGROUND AND AIM: Dipeptidyl peptidase 4 (DPP4) is a key enzyme involved in the regulation of the incretin system exerted by cleaving the glucagon-like peptide 1 (GLP-1); the blockage of DPP4, exerted by the antidiabetic agents DPP4-inhibitors (DPP4-I), results in greater GLP-1 concentration and improved glycaemic control. DPP4 acts also as a pro-inflammatory molecule and mediates vascular damage in experimental models. The relationship between DPP4 activity and endothelial function in diabetes has not been explored yet. Aim of this study was to investigate systemic plasma DPP4 activity in relation to endothelial function in patients with type 2 diabetes mellitus (T2DM). METHODS AND RESULTS: Sixty-two T2DM individuals were recruited in our Diabetes outpatient clinics, Sapienza University, Rome, Italy. All participants underwent complete clinical work-up; endothelial function was evaluated by flow-mediated dilatation (FMD) test; plasma DPP4 activity was assessed by measuring the 7-amino-4-methylcoumarin (AMC) cleavage rate from the synthetic substrate H-glycyl-prolyl-AMC and compared with DPP4 activity measured in sixty-two age-, sex-, BMI-matched non-diabetic subjects. Patients with T2DM had significantly higher DPP4 activity than non-diabetic individuals (211,466 ± 87657 vs 158,087 ± 60267 nmol/min/ml, p < 0.001); in T2DM patients, greater DPP4 activity significantly correlated with lower FMD whereas was not associated with BMI and metabolic control. Greater systemic DPP4 activity was an independent predictor of reduced FMD after adjusting for age, gender and other confounders. CONCLUSIONS: Circulating DPP4 activity is increased in individuals with T2DM and associated with signs of endothelial dysfunction such as impaired FMD. DPP4 may negatively affect endothelial function through mechanisms beyond glucose homeostasis and metabolic control.

Dapagliflozin-Induced Myocardial Flow Reserve Improvement is not Associated with HDL Ability to Stimulate Endothelial Nitric Oxide Production.

BACKGROUND: Sodium-glucose cotransporter-2 (SGLT2) inhibitors have shown controversial results in modulating plasma lipids in clinical trials. Most studies found slight increases in high-density lipoprotein (HDL) cholesterol but few have provided evidence on HDL functionality with disappointing results. However, there is broad agreement that these drugs provide cardiovascular protection through several mechanisms. Our group demonstrated that dapagliflozin improves myocardial flow reserve (MFR) in patients with type 2 diabetes (T2D) with coronary artery disease (CAD). The underlying mechanisms are still unknown, although in vitro studies have suggested the involvement of nitric oxide (NO). AIM: To investigate changes in HDL-mediated modulation of NO production with dapagliflozin and whether there is an association with MFR. METHODS: Sixteen patients with CAD-T2D were enrolled and randomized 1:1 to dapagliflozin or placebo for 4 weeks. Blood samples were collected before and after treatment for each group. The ability of HDL to stimulate NO production in endothelial cells was tested in vitro by incubating human umbilical vein endothelial cells (HUVEC) with apoB-depleted (apoB-D) serum of these patients. The production of NO was assessed by fluorescent assay, and results were expressed as fold versus untreated cells. RESULTS: Change in HDL-mediated NO production remained similar in dapagliflozin and placebo group, even after adjustment for confounders. There were no significant correlations between HDL-mediated NO production and MFR either at baseline or after treatment. No changes were found in HDL cholesterol in either group, while low-density lipoprotein cholesterol (LDL cholesterol) significantly decreased compared to baseline only in treatment group (p = 0.043). CONCLUSIONS: In patients with T2D-CAD, beneficial effects of dapagliflozin on coronary microcirculation seem to be unrelated to HDL functions. However, HDL capacity to stimulate NO production is not impaired at baseline; thus, the effect of drug treatments would be negligible. To conclude, we can assume that HDL-independent molecular pathways are involved in the improvement of MFR in this population. TRIAL REGISTRATION: EudraCT No. 2016-003614-27; ClinicalTrials.gov Identifier: NCT03313752.

The interplay of extracellular vesicles in the pathogenesis of metabolic impairment and type 2 diabetes.

The pathogenesis of type 2 diabetes (T2D) involves dysfunction in multiple organs, including the liver, muscle, adipose tissue, and pancreas, leading to insulin resistance and ß cell failure. Recent studies highlight the significant role of extracellular vesicles (EVs) in mediating inter-organ communication in T2D. This review investigates the role of EVs, focusing on their presence and biological significance in human plasma and tissues affected by T2D. We explore specific EV cargo, such as miRNAs and proteins, which affect insulin signaling and glucose metabolism, emphasizing their potential as biomarkers. By highlighting the diagnostic and therapeutic potential of EVs, we aim to provide new insights into their role in early detection, disease monitoring, and innovative treatment strategies for T2D.

Beta-cell function and glucose metabolism in patients with chronic pancreatitis.

AIMS: Chronic pancreatitis (CP) is - along with acute pancreatitis - the most frequent cause of diabetes of the exocrine pancreas (DEP). Although insulin deficiency is widely accepted as the major feature of DEP, it is still unclear whether diabetes associated with CP is characterized by additional or different functional defects of the insulin secretory machinery. To identify possible functional defects specifically induced by CP, we performed a cross-sectional study in individuals with normal glucose tolerance (NGT), impaired glucose tolerance (IGT) and diabetes mellitus (DM) comparing patients with and without CP (CP vs. NCP). METHODS: We administered an oral glucose tolerance test (OGTT) to all participants and, according to their glucose tolerance, classified them as NGT, IGT and DM. Insulin sensitivity and beta-cell functional parameters were derived from OGTT, hyperglycemic clamp and hyperinsulinemic euglycemic clamp. RESULTS: Studying 146 subjects, we found that beta-cell function and insulin secretion were significantly lower in CP compared to NCP patients. However, when we classified the subjects according to OGTT-derived glucose tolerance, we found no differences in beta-cell function or in insulin sensitivity between CP and NCP with the same glucose tolerance status. Of note, we found that arginine-stimulated insulin secretion is reduced only in subjects with CP and DM compared to NCP subjects with DM. CONCLUSIONS: Patients with CP had no specific alterations in insulin secretion and beta-cell function. However, in patients diagnosed with diabetes, we found a lower arginine-stimulated insulin secretion, a marker of reduced functional mass.

First-phase insulin secretion: can its evaluation direct therapeutic approaches?

Our work is aimed at unraveling the role of the first-phase insulin secretion in the natural history of type 2 diabetes mellitus (T2DM) and its interrelationship with insulin resistance and with ß cell function and mass. Starting from pathophysiology, we investigate the impact of impaired secretion on glucose homeostasis and explore postmeal hyperglycemia as the main clinical feature, underlining its relevance in the management of the disease. We also review dietary and pharmacological approaches aimed at improving early secretory defects and restoring residual ß cell function. Furthermore, we discuss possible approaches to detect early secretory defects in clinical practice. By providing a journey through human and animal data, we attempt a unification of the recent evidence in an effort to offer a new outlook on ß cell secretion.

Effects of PCSK9 inhibition on glucose metabolism and ß-cell function in humans: a pilot study.

Background: Anti-PCSK9 monoclonal antibodies are effective in reducing LDL-C and cardiovascular events by neutralizing circulating PCSK9. PCSK9, however, is also expressed in tissues, including the pancreas, and studies on PCSK9 KO mice have shown impaired insulin secretion. Statin treatment is already known to affect insulin secretion. Our aim was to conduct a pilot study to evaluate the effect of anti-PCSK9 mAb on glucose metabolism and ß-cell function in humans. Methods: Fifteen non-diabetic subjects, candidates for anti-PCSK9 mAb therapy, were enrolled. All underwent OGTT at baseline and after 6 months of therapy. During OGTT, insulin secretion parameters were derived from C-peptide by deconvolution (ß cell glucose sensitivity). Surrogate insulin sensitivity indices were also obtained from OGTT (Matsuda). Results: Glucose levels during OGTT were unchanged after 6 months of anti-PCSK9 mAb treatment, as well as insulin and C-peptide levels. The Matsuda index remained unchanged, while ß-cell glucose sensitivity improved post-therapy (before: 85.3 ± 65.4; after: 118.6 ± 70.9 pmol min-1m-2mM-1; p<0.05). Using linear regression, we found a significant correlation between ßCGS changes and BMI (p=0.004). Thus, we compared subjects with values above and below the median (27.6 kg/m2) and found that those with higher BMI had a greater increase in ßCGS after therapy (before: 85.37 ± 24.73; after: 118.62 ± 26.83 pmol min-1m-2mM-1; p=0.007). There was also a significant correlation between ßCGS change and Matsuda index through linear regression (p=0.04), so we analyzed subjects who had values above and below the median (3.8). This subgroup analysis showed a slight though not significant improvement in ßCGS in more insulin resistant patients, (before: 131.4 ± 69.8; after: 170.8 ± 92.7 pmol min-1m-2mM-1; p=0.066). Conclusions: Our pilot study demonstrates that six-month treatment with anti-PCSK9 mAb improves ß-cell function, and does not alter glucose tolerance. This improvement is more evident in patients with greater insulin-resistance (low Matsuda) and higher BMI.

Physical Activity and Type 2 Diabetes: In Search of a Personalized Approach to Improving ß-Cell Function.

Type 2 diabetes mellitus (T2DM) is one of the most widespread diseases worldwide. Lifestyle interventions, including diet and physical activity (PA), are fundamental non-pharmacological components of T2DM therapy. Exercise interventions are strongly recommended for people with or at risk of developing or already with overt diabetes, but adherence to PA guidelines in this population is still challenging. Furthermore, the heterogeneity of T2DM patients, driven by differing residual ß-cell functionality, as well as the possibility of practicing different types and intensities of PA, has led to the need to develop tailored exercise and training plans. Investigations on blood glucose variation in response to exercise could help to clarify why individuals do not respond in the same way to PA, and to guide the prescription of personalized treatments. The aim of this review is to offer an updated overview of the current evidence on the effects of different regimens and modalities of PA regarding glucose sensing and ß-cell secretory dynamics in individuals with prediabetes or T2DM, with a special focus on ß-cell function.

An update on pancreatic regeneration mechanisms: Searching for paths to a cure for type 2 diabetes.

BACKGROUND: Over the last decades, various approaches have been explored to restore sufficient ß-cell mass in diabetic patients. Stem cells are certainly an attractive source of new ß-cells, but an alternative option is to induce the endogenous regeneration of these cells. SCOPE OF REVIEW: Since the exocrine and endocrine pancreatic glands have a common origin and a continuous crosstalk unites the two, we believe that analyzing the mechanisms that induce pancreatic regeneration in different conditions could further advance our knowledge in the field. In this review, we summarize the latest evidence on physiological and pathological conditions associated with the regulation of pancreas regeneration and proliferation, as well as the complex and coordinated signaling cascade mediating cell growth. MAJOR CONCLUSIONS: Unraveling the mechanisms involved in intracellular signaling and regulation of pancreatic cell proliferation and regeneration may inspire future investigations to discover potential strategies to cure diabetes.

Prediabetes: how pathophysiology drives potential intervention on a subclinical disease with feared clinical consequences.

INTRODUCTION: Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder whose rising incidence suggests the epidemic proportions of the disease. Impaired fasting glucose (IFG) and Impaired Glucose Tolerance (IGT) - alone or combined - represent two intermediate metabolic condition between Normal Glucose Tolerance (NGT) and overt T2DM. EVIDENCE ACQUISITION: Databases were systematically screened using the following MeSH terms combination as follows: 1. prediabetes, 2. prediabetic state, 3. prevention, 4. lifestyle, 5. diet, 6. nutrition, 7. pharmacotherapy, 8. metformin, 9. thiazolidinediones, 10. sodium glucose cotransporter 2 inhibitors, 11. GLP 1 receptor agonists, 12. alpha glucosidase inhibitors, 13. insulin, 14. DPP IV inhibitors. EVIDENCE SYNTHESIS: Several studies have demonstrated that insulin resistance and beta-cell impairment can be identified even in normoglycemic prediabetic individuals. Worsening of these two conditions may lead to progression of IGT and/or IFG status to overt diabetes. Starting from these assumptions, it seems logical to suppose that interventions aimed at improving metabolic conditions, even in prediabetes, could represent an effective target to halt transition from IGT/IFG to manifest T2DM. Starting from pathophysiological knowledge, in this review we evaluate two possible interventions (lifestyle modifications and pharmacological agents) eligible as prediabetes therapy since they have been demonstrated to improve insulin resistance and beta-cell impairment. CONCLUSIONS: Detecting high-risk people and treating them could represent an effective strategy to slow down progression to overt diabetes, normalize glucose tolerance, and even prevent micro- and macrovascular complications.