Insulin enhances leukocyte-endothelial cell adhesion in the retinal microcirculation through surface expression of intercellular adhesion molecule-1

Feeding enhances fibronectin adherence of quiescent lymphocytes through non-canonical insulin signalling

Nutritional availability during fasting and refeeding affects the temporal redistribution of lymphoid and myeloid immune cells among the circulating and tissue-resident pools. Conversely, nutritional imbalance and impaired glucose metabolism are associated with chronic inflammation, aberrant immunity and anomalous leukocyte trafficking. Despite being exposed to periodic alterations in blood insulin levels upon fasting and feeding, studies exploring the physiological effects of these hormonal changes on quiescent immune cell function and trafficking are scanty. Here, we report that oral glucose load in mice and healthy men enhances the adherence of circulating peripheral blood mononuclear cells (PBMCs) and lymphocytes to fibronectin. Adherence to fibronectin is also observed upon regular intake of breakfast following overnight fasting in healthy subjects. This glucose load-induced phenomenon is abrogated in streptozotocin-injected mice that lack insulin. Intra-vital microscopy in mice demonstrated that oral glucose feeding enhances the homing of PBMCs to injured blood vessels in vivo. Furthermore, employing flow cytometry, Western blotting and adhesion assays for PBMCs and Jurkat-T cells, we elucidate that insulin enhances fibronectin adherence of quiescent lymphocytes through non-canonical signalling involving insulin-like growth factor-1 receptor (IGF-1R) autophosphorylation, phospholipase C gamma-1 (PLCγ-1) Tyr783 phosphorylation and inside-out activation of β-integrins respectively. Our findings uncover the physiological relevance of post-prandial insulin spikes in regulating the adherence and trafficking of circulating quiescent T-cells through fibronectin-integrin interaction.

Tryptophol Acetate and Tyrosol Acetate, Small-Molecule Metabolites Identified in a Probiotic Mixture, Inhibit Hyperinflammation

Probiotic fermented foods are perceived as contributing to human health; however, solid evidence for their presumptive therapeutic systemic benefits is generally lacking. Here we report that tryptophol acetate and tyrosol acetate, small-molecule metabolites secreted by the probiotic milk-fermented yeast Kluyveromyces marxianus, inhibit hyperinflammation (e.g., "cytokine storm"). Comprehensive in vivo and in vitro analyses, employing LPS-induced hyperinflammation models, reveal dramatic effects of the molecules, added in tandem, on mice morbidity, laboratory parameters, and mortality. Specifically, we observed attenuated levels of the proinflammatory cytokines IL-6, IL-1α, IL-1β, and TNF-α and reduced reactive oxygen species. Importantly, tryptophol acetate and tyrosol acetate did not completely suppress proinflammatory cytokine generation, rather brought their concentrations back to baseline levels, thus maintaining core immune functions, including phagocytosis. The anti-inflammatory effects of tryptophol acetate and tyrosol acetate were mediated through downregulation of TLR4, IL-1R, and TNFR signaling pathways and increased A20 expression, leading to NF-kB inhibition. Overall, this work illuminates phenomenological and molecular details underscoring anti-inflammatory properties of small molecules identified in a probiotic mixture, pointing to potential therapeutic avenues against severe inflammation.

Neutrophils as a source of branched-chain, aromatic and positively charged free amino acids

Neutrophils release branched-chain (valine, isoleucine, leucine), aromatic (tyrosine, phenylalanine) and positively charged free amino acids (arginine, ornithine, lysine, hydroxylysine, histidine) when adhere and spread onto fibronectin. In the presence of agents that impair cell spreading or adhesion (cytochalasin D, fMLP, nonadhesive substrate), neutrophils release the same amino acids, except for a sharp decrease in hydroxylysine and an increase in phenylalanine, indicating their special connection with cell adhesion. Plasma of patients with diabetes is characterized by an increased content of branched-chain and aromatic amino acids and a reduced ratio of arginine/ornithine compared to healthy human plasma. Our data showed that the secretion of neutrophils, regardless of their adhesion state, can contribute to this shift in the amino acid content.

Abbreviations: BCAAs: branched-chain amino acids; Е2: 17β-estradiol; LPS: lipopolysaccharide from Salmonella enterica serovar Typhimurium; fMLP: N-formylmethionyl-leucyl-phenylalanine.

Relationship between modified homeostasis model assessment/correlative serum factors and diabetic retinopathy among type 2 diabetics with insulin therapy in Guangzhou, China

AIM

To explore the related risk factors for diabetic retinopathy (DR) in type 2 diabetes with insulin therapy.

METHODS

We studied the relationships among blood glucose, serum C-peptide, plasma insulin, beta-cell function and the development of DR. Beta-cell function was assessed by a modified homeostasis model assessment (modified HOMA) which was gained by using C-peptide to replace insulin in the homeostasis model assessment (HOMA) of beta-cell function. We also studied the relationships between modified HOMA index and serum C-peptide response to 100g tasteless steamed bread to determine the accuracy of modified HOMA.

RESULTS

Our study group consisted of 170 type 2 diabetic inpatients with DR (age: 58.35±13.87y, mean±SD) and 205 type 2 diabetic inpatients with no DR (NDR) (age: 65.52±11.59y). DR patients had higher age, longer diabetic duration, higher hypertension grade, higher postprandial plasma glucose, higher fluctuation level of plasma glucose, lower body mass index (BMI), lower postprandial serum insulin and C-peptide, lower fluctuation level of serum insulin and C-peptide (P<0.05). In our logistic regression model, duration of diabetes, hypertension grade, fasting plasma insulin and glycosylated hemoglobin (HbA1C) were significantly associated with the presence of DR after adjustment for confounding factors (P<0.05).

CONCLUSION

Our results suggested although modified HOMA showed significant correlation to the occurrence of DR on Spearman's rank-correlation analysis, logistic regression showed no significant association between these two variables after adjustment for relevant confounding factors (such as age, sex, duration of diabetes, BMI, hypertension grade, HbA1C, plasma insulin). Duration of diabetes, hypertension grade, fasting plasma insulin and HbA1C were independently associated with the development of DR in Chinese type 2 diabetics.

Delivery of SAR 1118 to the retina via ophthalmic drops and its effectiveness in a rat streptozotocin (STZ) model of diabetic retinopathy (DR)

PURPOSE

To determine the pharmacokinetics of SAR 1118, a small-molecule antagonist of leukocyte function-associated antigen (LFA)-1, after administration of ophthalmic drops in normal rats, and to determine its pharmacologic activity by assessing the inhibition of retinal leukostasis and vascular leakiness in a streptozotocin (STZ)-induced diabetic retinopathy model.

METHODS

The ocular pharmacokinetics of SAR 1118 were studied in rats after a single topical dose of (14)C-SAR 1118 (1 mg/eye; 40 μCi; 15.5 μL). SAR 1118 concentration time profiles in plasma and ocular tissues were quantified by liquid scintillation counting (LSC). The pharmacologic activity of SAR 1118 eye drops administered thrice daily for 2 months at 1% (0.3 mg/eye/d) and 5% (1.5 mg/eye/d) was assessed in an STZ-induced diabetic rat model by determining retinal leukostasis and blood-retinal barrier breakdown. Diabetic rats treated with periocularly administered celecoxib microparticles served as the positive control, and vehicle-treated rats served as the negative control.

RESULTS

A single dose of 6.5% (14)C-radiolabeled SAR 1118 ophthalmic drops delivered retinal drug levels greater than 1 μM in less than 30 minutes and sustained levels greater than 100 nM for 8 hours. SAR 1118 eye drops significantly reduced leukostasis and blood-retinal barrier breakdown in a dose-dependent manner.

CONCLUSIONS

SAR 1118 ophthalmic drops administered thrice daily deliver therapeutic levels of SAR 1118 in the retina and can alleviate the retinal complications associated with diabetes.

Insulin may cause deterioration of proliferative diabetic retinopathy

Diabetes mellitus (DM) can cause many systemic complications, including proliferative diabetic retinopathy (PDR). Retinal neovascularization (RNV) is the typical symptom of PDR, representing an important risk factor for severe vision loss in patients with DM. Diabetic hyperglycemia plays a major role in the destruction of retinal capillary walls, resulting in retinal ischemia and up-regulation of vascular endothelial growth factor (VEGF), leading to neovascularization. The transcriptional regulation of VEGF is mediated by transcription factor hypoxia-inducible factor 1 (HIF-1). Insulin is the mainstay of treatment for DM, but some studies have demonstrated that insulin had the ability to stimulate VEGF and HIF-1 expression in retinal pigment epithelial cells, retinal epithelial cells and vascular smooth muscle cells. In addition to the mitogenic effect of insulin makes it as an assistant agent has long been used in vitro cell culture. Other studies confirmed that insulin increased leukostasis in retinal microcirculation. Based on these experimental results, we hypothesize that long-term insulin therapy maybe improves the expression of VEGF and increase the risk of RNV, eventually deteriorates PDR in patients with DM.

In vivo observation of pulmonary micrometastasis of colon cancer in normal rats

The initial kinetics of cancer cell metastasis to organs requires investigation to establish an effective strategy against malignant disease. In vivo observation of pulmonary micrometastasis at an extremely early stage is of particular importance, and it is desirable from a clinical perspective to use an animal model with a normal immune system. RCN-9 cells labeled with green fluorescent protein were injected into the liver parenchyma of Fischer F344 male rats and the lungs were observed using real-time confocal laser scanning microscopy from 3 to 10 weeks after injection. Metastasis at the single cell level was observed throughout this period, but the number of pulmonary micrometastases did not increase significantly with time. The largest metastasis was 300 mum in diameter, and the mean size of the metastases did not increase with time. There were two types of micrometastases in terms of shape: round and linear metastases, with the latter resembling the pulmonary microvasculature. The precise location of each pulmonary micrometastasis was revealed by acridine orange infusion. We could observe a single cancer cell and a small cancer mass in endothelial and interstitial locations in vivo, and we found proliferating cancer cells both inside and outside of microvessels. Most of the pulmonary micrometastases stayed dormant as a single cell or a cancer mass of less than 100 microm in diameter until 10 weeks after cancer-cell injection into the liver.