Divergent effects of lycopene on pancreatic alpha and beta cells / 生理学报

Lycopene is an antioxidant which has potential anti-diabetic activity, but the cellular mechanisms have not been clarified. In this study, different concentrations of lycopene were used to treat pancreatic alpha and beta cell lines, and the changes of cell growth, cell apoptosis, cell cycle, reactive oxygen species (ROS), ATP levels and expression of related cytokines were determined. The results exhibited that lycopene did not affect cell growth, cell apoptosis, cell cycle, ROS and ATP levels of alpha cells, while it promoted the growth of beta cells, increased the ratio of S phase, reduced the ROS levels and increased the ATP levels of beta cells. At the same time, lycopene treatment elevated the mRNA expression levels of tnfα, tgfβ and hif1α in beta cells. These findings suggest that lycopene plays cell-specific role and activates pancreatic beta cells, supporting its application in diabetes therapy.

Efficacy of ranolazine in lowering HbA1c in patients with type 2 diabetes mellitus: A meta-analysis

@#<p style="text-align: justify;"><strong>INTRODUCTION:</strong> Cardiovascular diseases and diabetes mellitus (DM) are two disease entities that commonly coexist in a single patient. Ranolazine is an active piperazine derivative approved by FDA in 2006 as an anti-anginal medication. It was noted to have HbA1c lowering effects in the trials on angina. The proposed mechanism of action is the inhibition of glucagon secretion by blocking the Na v1.3 isoform of sodium channels in pancreatic alpha cells leading to glucagon- and glucose-lowering effects. HbA1c lowering to a target of 6.5% in type 2 diabetes patients has been shown to reduce risk of microvascular complications. The objective of this study is to determine the efficacy and safety of Ranolazine in HbA1c lowering as an add-on therapy to existing anti-diabetic regimen.</p><p style="text-align: justify;"><strong>METHODS:</strong> A comprehensive literature search in PubMed, The Cochrane Central Register of Controlled Trials, the ClinicalTrials.gov website, Google Scholar databases and EMBASE databases were made using the search terms "Randomized controlled trial", "Ranolazine," "HbA1c," and "glycosylated hemoglobin", as well as various combinations of these, was done to identify randomized control trials. No restriction on language and time were done. The authors extracted data for characteristics, quality assessment and mean change in HbA1c after at least eight weeks of treatment with ranolazine. The program RevMan 5.3 was used to generate the statistical analysis of the data.</p><p style="text-align: justify;"><strong>RESULTS:</strong> Six RCTs were included to make up a total of 1,650 diabetic patients. Five studies had moderate risk of bias assessment while one had low risk of bias assessment and hence was not included in the analysis. The overall analysis showed an HbA1c reduction of 0.35% 0.68 to -0.03, p-value=0.03) however, the population was heterogenous (I2=100%). The heterogeneity was not eliminated by sensitivity analysis.</p><p style="text-align: justify;"><strong>DISCUSSION:</strong> The results showed a statistically significant lowering of HbA1c with ranolazine. However, the population was heterogenous. The sources of heterogeneity could be the (1) differences in the level of glycemic control among subjects as indicated by baseline HbA1c levels, (2) the current anti-diabetic regimen of the study patients, i.e. whether or not they are on insulin therapy, (3) the presence or absence of ischemic heart disease and (5) duration of ranolazine therapy, and (4) the presence or absence of chronic kidney disease. When the analysis excluded the population with combination insulin therapy and ranolazine, the effect becomes non-significant. Thus, the HbA1c lowering effect may have been from the insulin therapy rather than the ranolazine.</p><p style="text-align: justify;"><strong>CONCLUSION:</strong> Ranolazine as anti-diabetic therapy shows statistically significant HbA1c lowering effect. It can be a potential treatment option for patients with both DM and angina pectoris. However, well-designed, prospective trials are still recommended to determine the effect on a less heterogenous population. Likewise, more studies are needed to determine its safety.</p>

Pancreatic alpha-Cell Dysfunction in Type 2 Diabetes: Old Kids on the Block

Type 2 diabetes (T2D) has been known as 'bi-hormonal disorder' since decades ago, the role of glucagon from alpha-cell has languished whereas beta-cell taking center stage. Recently, numerous findings indicate that the defects of glucagon secretion get involve with development and exacerbation of hyperglycemia in T2D. Aberrant alpha-cell responses exhibit both fasting and postprandial states: hyperglucagonemia contributes to fasting hyperglycemia caused by inappropriate hepatic glucose production, and to postprandial hyperglycemia owing to blunted alpha-cell suppression. During hypoglycemia, insufficient counter-regulation response is also observed in advanced T2D. Though many debates still remained for exact mechanisms behind the dysregulation of alpha-cell in T2D, it is clear that the blockade of glucagon receptor or suppression of glucagon secretion from alpha-cell would be novel therapeutic targets for control of hyperglycemia. Whereas there have not been remarkable advances in developing new class of drugs, currently available glucagon-like peptide-1 and dipeptidyl peptidase-IV inhibitors could be options for treatment of hyperglucagonemia. In this review, we focus on alpha-cell dysfunction and therapeutic potentials of targeting alpha-cell in T2D.

A Case of Alpha-cell Nesidioblastosis and Hyperplasia with Multiple Glucagon-producing Endocrine Cell Tumor of the Pancreas / 대한소화기학회지

Nesidioblastosis is a term used to describe pathologic overgrowth of pancreatic islet cells. It also means maldistribution of islet cells within the ductules of exocrine pancreas. Generally, nesidioblastosis occurs in beta-cell and causes neonatal hyperinsulinemic hypoglycemia or adult noninsulinoma pancreatogenous hypoglycemia syndrome. Alpha-cell nesidioblastosis and hyperplasia is an extremely rare disorder. It often accompanies glucagon-producing marco- and mircoadenoma without typical glucagonoma syndrome. A 35-year-old female was referred to our hospital with recurrent acute pancreatitis. On radiologic studies, 1.5 cm sized mass was noted in pancreas tail. Cytological evaluation with EUS-fine-needle aspiration suggested serous cystadenoma. She received distal pancreatectomy. The histologic examination revealed a 1.7 cm sized neuroendocrine tumor positive for immunohistochemical staining with glucagon antibody. Multiple glucagon-producing micro endocrine cell tumors were scattered next to the main tumor. Additionally, diffuse hyperplasia of pancreatic islets and ectopic proliferation of islet cells in centroacinar area, findings compatible to nesidioblastosis, were seen. These hyperplasia and almost all nesidioblastic cells were positive for glucagon immunochemistry. Even though serum glucagon level still remained higher than the reference value, she has been followed-up without any evidence of recurrence or hormone related symptoms. Herein, we report a case of alpha-cell nesidioblastosis and hyperplasia combined with glucagon-producing neuroendocrine tumor with literature review.

Toll-like receptor 4 on islet beta cells senses expression changes in high-mobility group box 1 and contributes to the initiation of type 1 diabetes

Type 1 diabetes mellitus is caused by the autoimmune destruction of beta cells within the islets. In recent years, innate immunity has been proposed to play a key role in this process. High-mobility group box 1 (HMGB1), an inflammatory trigger in a number of autoimmune diseases, activates proinflammatory responses following its release from necrotic cells. Our aim was to determine the significance of HMGB1 in the natural history of diabetes in non-obese diabetic (NOD) mice. We observed that the rate of HMGB1 expression in the cytoplasm of islets was much greater in diabetic mice compared with non-diabetic mice. The majority of cells positively stained for toll-like receptor 4 (TLR4) were beta cells; few alpha cells were stained for TLR4. Thus, we examined the effects of anti-TLR4 antibodies on HMGB1 cell surface binding, which confirmed that HMGB1 interacts with TLR4 in isolated islets. Expression changes in HMGB1 and TLR4 were detected throughout the course of diabetes. Our findings indicate that TLR4 is the main receptor on beta cells and that HMGB1 may signal via TLR4 to selectively damage beta cells rather than alpha cells during the development of type 1 diabetes mellitus.

Role and mechanism of uncoupling protein 2 on the fatty acid-induced dysfunction of pancreatic alpha cells in vitro / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Uncoupling protein (UCP) 2 is related to the dysfunction of beta cells induced by fatty acids. However, whether UCP2 has similar effects on alpha cell is still not clear. This study aimed to investigate the effects of UCP2 and its possible mechanisms in lipotoxicity-induced dysfunction of pancreatic alpha cells.</p><p><b>METHODS</b>The alpha TC1-6 cells were used in this study to evaluate the effects of palmitate and/or UCP2 inhibit factors on the glucagon secretory function, glucagon content, the glucagon mRNA level and the nitrotyrosine level in the supernatant. Meantime, the expression levels of UCP2 and peroxisome proliferator-activated receptor-γ coactivator-1 alpha (PGC-1 alpha) were measured by real-time reverse transcription polymerase chain reaction (RT-PCR) and Western blotting. Furthermore, the possible relationship between UCP2 and insulin signal transduction pathway was analyzed.</p><p><b>RESULTS</b>Palmitate stimulated alpha cell glucagon secretion and the expression of UCP2 and PGC-1 alpha, which could be partially decreased by the inhibition of UCP2. Palmitate increased nitrotyrosine level and suppressed insulin signal transduction pathway in alpha cells. Inhibition of UCP2 influenced the effects of free fatty acid on alpha cells and may relate to glucagon secretion.</p><p><b>CONCLUSION</b>UCP2 played an important role on alpha cell dysfunction induced by free fatty acid in vitro, which may be related to its effects on oxidative stress and insulin signal transduction pathway.</p>