Glucometers are also widely used in diabetes research conducted using animal models. However, the appropriateness of measuring blood glucose levels using glucometers in animal models remains unclear. In this study, we evaluated the consistency between the blood glucose levels measured by 11 models of glucometers and plasma glucose levels measured by a laboratory biochemical test in blood samples collected by retro-orbital sinus puncture or tail-tip amputation. In both blood samples obtained by retro-orbital sinus puncture and those obtained by tail-tip amputation, 10 of the 11 models of glucometers yielded higher glucose values, while 1 yielded lower glucose values, than the plasma glucose values yielded by the laboratory test, the differences being in direct proportion to the plasma glucose values. Most glucometers recorded higher blood glucose levels after glucose loading and lower blood glucose levels after insulin loading in retro-orbital sinus blood as compared to tail vein blood. Our data suggest that the blood glucose levels measured by glucometers in mice tended to be higher than the plasma glucose levels yielded by the biochemical test under the hyperglycemic state, and that differences in the measured levels were observed according to the blood collection method depending on the glycemia status.

Growth factor signaling via insulin receptor (IR) and IGF-1 receptor (IGF1R) plays several important roles in the pathogenesis of metabolic syndrome and diabetes. OSI-906 (linsitinib), an anti-tumor drug, is an orally bioavailable dual inhibitor of IR and IGF1R. To investigate the recovery from metabolic changes induced by the acute inhibition of IR and IGF1R in adult mice, mice were treated with OSI-906 or a vehicle for 7 days and the results were analyzed on the last day of injection (Day 7) or after 7 or 21 days of withdrawal (Day 14 or Day 28). On day 7, the visceral white fat mass was significantly reduced in mice treated with OSI-906 accompanied by a reduced expression of leptin and an increased expression of the lipolysis-related genes Lpl and Atgl. Interestingly, the lipoatrophy and the observed changes in gene expression were completely reversed on day 14. Similarly, liver steatosis and β cell proliferation were transiently observed on day 7 but had disappeared by day 14. Taken together, these results suggest that this model for the acute inhibition of systemic IR/IGF1R signaling may be useful for investigating the recovery from metabolic disorders induced by impaired growth factor signaling.

Metformin has been widely used for the treatment of type 2 diabetes. However, the effect of metformin on pancreatic β-cells remains controversial. In this study, we investigated the impacts of treatment with metformin on pancreatic β-cells in a mouse model fed a high-fat diet (HFD), which triggers adaptive β-cell replication. An 8-wk treatment with metformin improved insulin resistance and suppressed the compensatory β-cell hyperplasia induced by HFD-feeding. In contrast, the increment in β-cell mass arising from 60 wk of HFD feeding was similar in mice treated with and those treated without metformin. Interestingly, metformin suppressed β-cell proliferation induced by 1 wk of HFD feeding without any changes in insulin resistance. Metformin directly suppressed glucose-induced β-cell proliferation in islets and INS-1 cells in accordance with a reduction in mammalian target of rapamycin phosphorylation. Taken together, metformin suppressed HFD-induced β-cell proliferation independent of the improvement of insulin resistance, partly via direct actions.

Chronic low-grade inflammation in the pancreatic islets is observed in individuals with type 2 diabetes, and macrophage levels are elevated in the islets of these individuals. However, the molecular mechanisms underlying the interactions between the pancreatic β cells and macrophages and their involvement in inflammation are not fully understood. Here, we investigated the role of S100 calcium-binding protein A8 (S100A8), a member of the damage-associated molecular pattern molecules (DAMPs), in β-cell inflammation. Co-cultivation of pancreatic islets with unstimulated peritoneal macrophages in the presence of palmitate (to induce lipotoxicity) and high glucose (to induce glucotoxicity) synergistically increased the expression and release of islet-produced S100A8 in a Toll-like receptor 4 (TLR4)-independent manner. Consistently, a significant increase in the expression of the gene was observed in the islets of diabetic db/db mice. Furthermore, the islet-derived S100A8 induced TLR4-mediated inflammatory cytokine production by migrating macrophages. When human islet cells were co-cultured with U937 human monocyte cells, the palmitate treatment up-regulated S100A8 expression. This S100A8-mediated interaction between islets and macrophages evoked β-cell apoptosis, which was ameliorated by TLR4 inhibition in the macrophages or S100A8 neutralization in the pancreatic islets. Of note, both glucotoxicity and lipotoxicity triggered S100A8 secretion from the pancreatic islets, which in turn promoted macrophage infiltration of the islets. Taken together, a positive feedback loop between islet-derived S100A8 and macrophages drives β-cell apoptosis and pancreatic islet inflammation. We conclude that developing therapeutic approaches to inhibit S100A8 may serve to prevent β-cell loss in patients with diabetes.

Aims/Introduction Liraglutide and empagliflozin suppress cardiovascular events. However, reports on their long‐term combined use with insulin therapy or direct comparisons of these drugs are limited. Materials and Methods This open‐label, parallel‐group, randomized controlled trial compared the effects of liraglutide and empagliflozin combined with insulin therapy in type 2 diabetes patients . Adult type 2 diabetes outpatients undergoing stable insulin therapy with glycated hemoglobin levels of 7.0–9.5% were enrolled. Participants received 0.9 mg/day liraglutide or 10 mg/day empagliflozin for 24 weeks. The primary end‐point was the change in glycated hemoglobin levels from week 0 to 24. Body composition was assessed by dual‐energy X‐ray absorptiometry. Results A total of 64 insulin‐treated patients were randomized to receive liraglutide or empagliflozin. We analyzed 61 patients (30 liraglutide and 31 empagliflozin) who could be followed up. Liraglutide induced greater changes in glycated hemoglobin and glycated albumin than empagliflozin (glycated hemoglobin −1.24 ± 0.15% vs −0.35 ± 0.11%, P < 0.0001; glycated albumin −4.4 ± 0.6% vs −2.4 ± 0.5%, P < 0.01). Bodyweight (−1.3 ± 0.4 kg vs −1.5 ± 0.3 kg, P = 0.69) or body fat mass/lean tissue mass; urinary albumin excretion (median −5.3 mg/g‐creatinine [interquartile range −60.6, 9.9 mg/g‐creatinine] vs −12.9 mg/g‐creatinine [interquartile range −70.8, −2.0 mg/g‐creatinine], P = 0.23); and frequency of hypoglycemia did not differ significantly between the groups over a period of 24 weeks. There were no cases of study discontinuation owing to adverse effects. Conclusions Liraglutide addition to ongoing insulin therapy more effectively reduced glycated hemoglobin and glycated albumin levels than empagliflozin in patients with inadequately controlled type 2 diabetes.