Pancreatic polypeptide revisited: Potential therapeutic effects in obesity-diabetes

NPYR modulation: Potential for the next major advance in obesity and type 2 diabetes management?

The approval of the glucagon-like peptide 1 (GLP-1) mimetics semaglutide and liraglutide for management of obesity, independent of type 2 diabetes (T2DM), has initiated a resurgence of interest in gut-hormone derived peptide therapies for the management of metabolic diseases, but side-effect profile is a concern for these medicines. However, the recent approval of tirzepatide for obesity and T2DM, a glucose-dependent insulinotropic polypeptide (GIP), GLP-1 receptor co-agonist peptide therapy, may provide a somewhat more tolerable option. Despite this, an increasing number of non-incretin alternative peptides are in development for obesity, and it stands to reason that other hormones will take to the limelight in the coming years, such as peptides from the neuropeptide Y family. This narrative review outlines the therapeutic promise of the neuropeptide Y family of peptides, comprising of the 36 amino acid polypeptides neuropeptide Y (NPY), peptide tyrosine-tyrosine (PYY) and pancreatic polypeptide (PP), as well as their derivatives. This family of peptides exerts a number of metabolically relevant effects such as appetite regulation and can influence pancreatic beta-cell survival. Although some of these actions still require full translation to the human setting, potential therapeutic application in obesity and type 2 diabetes is conceivable. However, like GLP-1 and GIP, the endogenous NPY, PYY and PP peptide forms are subject to rapid in vivo degradation and inactivation by the serine peptidase, dipeptidyl-peptidase 4 (DPP-4), and hence require structural modification to prolong circulating half-life. Numerous protective modification strategies are discussed in this regard herein, alongside related impact on biological activity profile and therapeutic promise.

Novel enzyme-resistant pancreatic polypeptide analogs evoke pancreatic beta-cell rest, enhance islet cell turnover, and inhibit food intake in mice

Pancreatic polypeptide (PP) is a postprandial hormone secreted from pancreatic islets that activates neuropeptide Y4 receptors (NPY4Rs). PP is known to induce satiety but effects at the level of the endocrine pancreas are less well characterized. In addition, rapid metabolism of PP by dipeptidyl peptidase-4 (DPP-4) limits the investigation of the effects of the native peptide. Therefore, in the present study, five novel amino acid substituted and/or fatty acid derivatized PP analogs were synthesized, namely [P3]PP, [K13Pal]PP, [P3,K13Pal]PP, [N-Pal]PP, and [N-Pal,P3]PP, and their impact on pancreatic beta-cell function, as well as appetite regulation and glucose homeostasis investigated. All PP analogs displayed increased resistance to DPP-4 degradation. In addition, all peptides inhibited alanine-induced insulin secretion from BRIN-BD11 beta cells. Native PP and related analogs (10-8 and 10-6 M), and especially [P3]PP and [K13Pal]PP, significantly protected against cytokine-induced beta-cell apoptosis and promoted cellular proliferation, with effects dependent on the NPY4R for all peptides barring [N-Pal,P3]PP. In mice, all peptides, except [N-Pal]PP and [N-Pal,P3]PP, evoked a dose-dependent (25, 75, and 200 nmol/kg) suppression of appetite, with native PP and [P3]PP further augmenting glucagon-like peptide-1 (GLP-1) and cholecystokinin (CCK) induced reductions of food intake. The PP peptides had no obvious detrimental effect on glucose tolerance and they did not noticeably impair the glucose-regulatory actions of GLP-1 or CCK. In conclusion, Pro3 amino acid substitution of PP, either alone or together with mid-chain acylation, creates PP analogs with benefits on beta-cell rest, islet cell turnover, and energy regulation that may be applicable to the treatment of diabetes and obesity.

Differential diagnosis of post pancreatitis diabetes mellitus based on pancreatic and gut hormone characteristics

PURPOSE

Distinguishing different types of diabetes is important in directing optimized treatment strategies and correlated epidemiological studies. Through detailed analysis of hormone responses to mixed meal tolerance test (MMTT), we aimed to find representing characteristics of post-acute pancreatitis diabetes mellitus (PPDM-A) and post-chronic pancreatitis diabetes mellitus (PPDM-C).

METHODS

Participants with PPDM-A, PPDM-C, type 1 diabetes, type 2 diabetes and normal controls underwent MMTT. Fasting and postprandial responses of serum glucose, C-peptide, insulin, glucagon, pancreatic polypeptide (PP), ghrelin, gastric inhibitory peptide (GIP), glucagon like peptide-1 (GLP-1) and peptide YY (PYY) were detected and compared among different groups. Focused analysis on calculated insulin sensitivity and secretion indices were performed to reason major causes of hyperglycemia in different conditions.

RESULTS

Participants with PPDM-A were characterized by increased C-peptide, insulin, glucagon and PP, while decreased ghrelin, GIP and PYY compared with controls. Patients with PPDM-C showed secretion insufficiency of C-peptide, insulin, ghrelin and PYY, higher postprandial responses of glucagon and PP than controls. In particular, both fasting and postprandial levels of ghrelin in PPDM-C were significantly lower than other diabetes groups. PYY responses in patients with PPDM-A and PPDM-C were markedly reduced. Besides, the insulin sensitivity of PPDM-A was decreased, and the insulin secretion for PPDM-C was decreased.

CONCLUSIONS

Along with the continuum from acute to chronic pancreatitis, the pathological mechanism of PPDM changes from insulin resistance to insulin deficiency. Insufficient PYY secretion is a promising diagnostic marker for distinguishing PPDM from type 1 and type 2 diabetes. Absent ghrelin secretion to MMTT may help identify PPDM-C.

Polyagonists in Type 2 Diabetes Management

PURPOSE OF THE REVIEW

This review summarizes the new developments in polyagonist pharmacotherapy for type 2 diabetes.

RECENT FINDINGS

Several dual- and triple-agonists targeting different pathogenic pathways of type 2 diabetes have entered clinical trials and have led to significant improvements in glycaemia, body weight, fatty liver, and cardio-renal risk factors, with variable adverse event profiles but no new serious safety concerns. Combining agents with complementary and synergistic mechanisms of action have enhanced efficacy and safety. Targeting multiple pathogenic pathways simultaneously has led to enhanced benefits which potentially match those of bariatric surgery. Tirzepatide, cotadutide, BI456906, ritatrutide, and CagriSema have entered phase 3 clinical trials. Outcomes from published clinical studies are reviewed. Efficacy-safety profiles are heterogeneous between agents, suggesting the potential application of precision medicine and need for personalized approach in pharmacological management of type 2 diabetes and obesity. Polyagonism has become a key strategy to address the complex pathogenesis of type 2 diabetes and co-morbidities and increasing number of agents are moving through clinical trials. Heterogeneity in efficacy-safety profiles calls for application of precision medicine and need for judicious personalization of care.

Islet Dimensions and Its Impact on the Cellular Composition and Insulin-Secreting Capacity: Insights Into the Role of Non-beta Cells

Studies have underscored the significance of islet dimensions, encompassing i) the necessity for islets to maintain an optimal diameter to sustain functional activity; ii) larger islets exhibit an intermingled architecture of alpha and beta cells, enhancing functional activity through paracrine effects; iii) non-alpha/beta (NAB) cells play a significant role in regulating beta cells; and iv) there is a preferential loss of larger islets in cases of type 2 diabetes mellitus. To delve deeper into these aspects, the authors documented the cellular composition in islets of various dimensions and regions of the pancreas, along with their secreting capacity, using the expression of the myosin Va motor protein in nine non-diabetic adult human pancreases. The proportion of NAB cells was found to be higher in intermediate islets and significantly lower in smaller and larger islets. By comparing the differences in islet composition, where NAB cells increase from smaller to intermediate islets, leading to a decrease in the proportion of alpha and beta cells, and in larger islets, there is a higher proportion of beta and alpha cells similar to smaller islets, we propose the hypothesis that NAB cells proliferate as islets increase in size. Furthermore, in larger islets, these NAB cells convert into alpha and beta cells, resulting in the scattered, intermingled arrangement observed in larger islets. The higher intensity of myosin Va expression in the islets of the tail region, along with a similar proportion of NAB cells in intermediate islets of the tail region compared to larger islets, leads to decreased inhibitory stimuli to beta cells and an increased insulin-secreting capacity.

Associations of Adipocytokines with The Development of Cardiovascular Events in Young People

The research was aimed to study the associations of adipocytokines with the risk of cardiovascular events and to determine the threshold values of adipocytes for the prognosis of cardiovascular events in a young population.

MATERIALS AND METHODS

The study is an epidemiological cohort study. The analysis included 1240 people aged 25-44 years. The endpoint was combined and included: death from cardiovascular disease, myocardial infarction, probable myocardial infarction, acute cerebrovascular accident, hospitalization for cardiovascular disease, and revascularization. Adipocytokines were determined with a MILLIPLEX panel.

RESULTS

In the examined population, 1.7% of cases of cardiovascular events were detected during cohort observation, of which 28.6% were fatal events. In men, cardiovascular endpoints were recorded 4.3 times more often than in women (17 (81%) vs. 4 (19%), p = 0.003). In individuals with cardiovascular events, arterial hypertension (2.6 times), diabetes mellitus (8.6 times), and overweight/obesity (1.5 times) were more often recorded compared to individuals without cardiovascular events. For tumor necrosis factor-alpha (TNFa), the threshold value was 2.5 pg/mL, with sensitivity assessment (Se) at 85.7% and specificity (Sp) at 83.3%. For amylin, the threshold value was 10.5 pg/mL, with Se at 73.7% and Sp at 67.0%. For pancreatic polypeptide (PP), the threshold value was 43.7 pg/mL, with Se at 85.7% and Sp at 56.7%.

CONCLUSION

A method for assessing the risk of cardiovascular events in young people includes determining the levels of amylin, PP, and TNFa in blood serum. The cut-off points for predicting cardiovascular events were levels of amylin above 10.5 pg/mL, PP above 43.7 pg/mL, or a decrease in TNFa below 3.8 pg/mL.

Clinical Case Report of Non-Diabetic Hypoglycemia Due to a Combination of Germline Mutations in the MEN1 and ABCC8 Genes

INTRODUCTION

Non-diabetic hypoglycemia (NDH) is a collective term including the multiple causes of hypoglycemic syndrome not due to diabetes mellitus. NDH may result from insulinoma, IGF-2-omas, hypocorticism, Hirata's disease, genital disorders of glucose metabolism, etc. One of the most common causes of NDH faced by an endocrinologist is insulinoma, which in turn can be part of the hereditary syndrome of multiple endocrine neoplasia type 1 (MEN1). Congenital disorders of glucose metabolism in adult patients, on the contrary, are diagnosed extremely rarely, since they usually manifest in childhood. This article presents a unique clinical case of a patient with NDH and genetically verified MEN1 in combination with congenital hyperinsulinism due to an ABCC8 gene mutation.

CASE REPORT

A 43-year-old patient with hypoglycemic symptoms from childhood is presented, in whom multiple pancreatic tumors and fluctuations in glycemia from 38.7 mg/dL to 329.7 mg/dL (2.15 to 18.3 mmol/L) were detected in adulthood, but a mild course of hypoglycemic syndrome was noted. Numerous examinations that were performed to establish an accurate diagnosis are described, signs that served as a reason for expanding the complex of studies are indicated, possible pathogenetic mechanisms of the mild course of hypoglycemic syndrome and hyperglycemic conditions are discussed.

CONCLUSION

This case report is original and highlights that we must always remain intolerant of the inexplicable. Conducting an extended gene study can help perform a correct diagnosis in complex cases.

Neuropeptide Y Peptide Family and Cancer: Antitumor Therapeutic Strategies

Currently available data on the involvement of neuropeptide Y (NPY), peptide YY (PYY), and pancreatic polypeptide (PP) and their receptors (YRs) in cancer are updated. The structure and dynamics of YRs and their intracellular signaling pathways are also studied. The roles played by these peptides in 22 different cancer types are reviewed (e.g., breast cancer, colorectal cancer, Ewing sarcoma, liver cancer, melanoma, neuroblastoma, pancreatic cancer, pheochromocytoma, and prostate cancer). YRs could be used as cancer diagnostic markers and therapeutic targets. A high Y1R expression has been correlated with lymph node metastasis, advanced stages, and perineural invasion; an increased Y5R expression with survival and tumor growth; and a high serum NPY level with relapse, metastasis, and poor survival. YRs mediate tumor cell proliferation, migration, invasion, metastasis, and angiogenesis; YR antagonists block the previous actions and promote the death of cancer cells. NPY favors tumor cell growth, migration, and metastasis and promotes angiogenesis in some tumors (e.g., breast cancer, colorectal cancer, neuroblastoma, pancreatic cancer), whereas in others it exerts an antitumor effect (e.g., cholangiocarcinoma, Ewing sarcoma, liver cancer). PYY or its fragments block tumor cell growth, migration, and invasion in breast, colorectal, esophageal, liver, pancreatic, and prostate cancer. Current data show the peptidergic system's high potential for cancer diagnosis, treatment, and support using Y2R/Y5R antagonists and NPY or PYY agonists as promising antitumor therapeutic strategies. Some important research lines to be developed in the future will also be suggested.

The Bidirectional Relationship of NPY and Mitochondria in Energy Balance Regulation

Energy balance is regulated by several hormones and peptides, and neuropeptide Y is one of the most crucial in feeding and energy expenditure control. NPY is regulated by a series of peripheral nervous and humoral signals that are responsive to nutrient sensing, but its role in the energy balance is also intricately related to the energetic status, namely mitochondrial function. During fasting, mitochondrial dynamics and activity are activated in orexigenic neurons, increasing the levels of neuropeptide Y. By acting on the sympathetic nervous system, neuropeptide Y modulates thermogenesis and lipolysis, while in the peripheral sites, it triggers adipogenesis and lipogenesis instead. Moreover, both central and peripheral neuropeptide Y reduces mitochondrial activity by decreasing oxidative phosphorylation proteins and other mediators important to the uptake of fatty acids into the mitochondrial matrix, inhibiting lipid oxidation and energy expenditure. Dysregulation of the neuropeptide Y system, as occurs in metabolic diseases like obesity, may lead to mitochondrial dysfunction and, consequently, to oxidative stress and to the white adipose tissue inflammatory environment, contributing to the development of a metabolically unhealthy profile. This review focuses on the interconnection between mitochondrial function and dynamics with central and peripheral neuropeptide Y actions and discusses possible therapeutical modulations of the neuropeptide Y system as an anti-obesity tool.