Optogenetic stimulation of vagal nerves for enhanced glucose-stimulated insulin secretion and ß cell proliferation.

The enhancement of insulin secretion and of the proliferation of pancreatic ß cells are promising therapeutic options for diabetes. Signals from the vagal nerve regulate both processes, yet the effectiveness of stimulating the nerve is unclear, owing to a lack of techniques for doing it so selectively and prolongedly. Here we report two optogenetic methods for vagal-nerve stimulation that led to enhanced glucose-stimulated insulin secretion and to ß cell proliferation in mice expressing choline acetyltransferase-channelrhodopsin 2. One method involves subdiaphragmatic implantation of an optical fibre for the photostimulation of cholinergic neurons expressing a blue-light-sensitive opsin. The other method, which suppressed streptozotocin-induced hyperglycaemia in the mice, involves the selective activation of vagal fibres by placing blue-light-emitting lanthanide microparticles in the pancreatic ducts of opsin-expressing mice, followed by near-infrared illumination. The two methods show that signals from the vagal nerve, especially from nerve fibres innervating the pancreas, are sufficient to regulate insulin secretion and ß cell proliferation.

Phagocytosis by macrophages promotes pancreatic ß cell mass reduction after parturition in mice.

Elucidating the mechanism(s) modulating appropriate tissue size is a critical biological issue. Pancreatic ß cells increase during pregnancy via cellular proliferation, but how ß cells promptly decrease to the original amount after parturition remains unclear. Herein, we demonstrate the role and mechanism of macrophage accumulation in this process. In the final stage of pregnancy, HTR1D signaling upregulates murine ß cell CXCL10, thereby promoting macrophage accumulation in pancreatic islets via the CXCL10-CXCR3 axis. Blocking this mechanism by administering an HTR1D antagonist or the CXCR3 antibody and depleting islet macrophages inhibited postpartum ß cell mass reduction. ß cells engulfed by macrophages increased in postpartum islets, but Annexin V administration suppressed this engulfment and the postpartum ß cell mass reduction, indicating the accumulated macrophages to phagocytose ß cells. This mechanism contributes to both maintenance of appropriate ß cell mass and glucose homeostasis promptly adapting to reduced systemic insulin demand after parturition.

A highly sensitive strategy for monitoring real-time proliferation of targeted cell types in vivo.

Cell proliferation processes play pivotal roles in timely adaptation to many biological situations. Herein, we establish a highly sensitive and simple strategy by which time-series showing the proliferation of a targeted cell type can be quantitatively monitored in vivo in the same individuals. We generate mice expressing a secreted type of luciferase only in cells producing Cre under the control of the Ki67 promoter. Crossing these with tissue-specific Cre-expressing mice allows us to monitor the proliferation time course of pancreatic ß-cells, which are few in number and weakly proliferative, by measuring plasma luciferase activity. Physiological time courses, during obesity development, pregnancy and juvenile growth, as well as diurnal variation, of ß-cell proliferation, are clearly detected. Moreover, this strategy can be utilized for highly sensitive ex vivo screening for proliferative factors for targeted cells. Thus, these technologies may contribute to advancements in broad areas of biological and medical research.

A case of fulminant type 1 diabetes and protein C deficiency complicated by deep vein thrombosis.

A 25-year-old man was diagnosed with diabetic ketoacidosis (DKA) at the onset of fulminant type 1 diabetes. After acute-phase DKA treatment including placement of a central venous catheter, a massive deep vein thrombosis (DVT) and pulmonary embolism (PE) were detected on hospital day 15. His protein C (PC) activity and antigen levels were low even 33 days after completing the DKA treatment, indicating partial type I PC deficiency. Severe PC dysfunction, due to overlapping of partial PC deficiency and hyperglycemia-induced PC suppression, concomitant with dehydration and catheter treatment, may have induced the massive DVT with PE. This case suggests that anti-coagulation therapy should be combined with acute-phase DKA treatment in patients with PC deficiency, even those who have been asymptomatic. As patients with partial PC deficiency should perhaps be included among those with severe DVT complications of DKA, venous thrombosis should always be considered as a potential complication of DKA.

Inter-organ insulin-leptin signal crosstalk from the liver enhances survival during food shortages.

Crosstalk among organs/tissues is important for regulating systemic metabolism. Here, we demonstrate inter-organ crosstalk between hepatic insulin and hypothalamic leptin actions, which maintains survival during food shortages. In inducible liver insulin receptor knockout mice, body weight is increased with hyperphagia and decreased energy expenditure, accompanied by increased circulating leptin receptor (LepR) and decreased hypothalamic leptin actions. Additional hepatic LepR deficiency reverses these metabolic phenotypes. Thus, decreased hepatic insulin action suppresses hypothalamic leptin action with increased liver-derived soluble LepR. Human hepatic and circulating LepR levels also correlate negatively with hepatic insulin action indices. In mice, food restriction decreases hepatic insulin action and energy expenditure with increased circulating LepR. Hepatic LepR deficiency increases mortality with enhanced energy expenditure during food restriction. The liver translates metabolic cues regarding energy-deficient status, which is reflected by decreased hepatic insulin action, into soluble LepR, thereby suppressing energy dissipation and assuring survival during food shortages.

Roles of FoxM1-driven basal ß-cell proliferation in maintenance of ß-cell mass and glucose tolerance during adulthood.

AIMS/INTRODUCTION: Whether basal ß-cell proliferation during adulthood is involved in maintaining sufficient ß-cell mass, and if so, the molecular mechanism(s) underlying basal ß-cell proliferation remain unclear. FoxM1 is a critical transcription factor which is known to play roles in 'adaptive' ß-cell proliferation, which facilitates rapid increases in ß-cell mass in response to increased insulin demands. Therefore, herein we focused on the roles of ß-cell FoxM1 in 'basal' ß-cell proliferation under normal conditions and in the maintenance of sufficient ß-cell mass as well as glucose homeostasis during adulthood. MATERIALS AND METHODS: FoxM1 deficiency was induced specifically in ß-cells of 8-week-old mice, followed by analyzing its short- (2 weeks) and long- (10 months) term effects on ß-cell proliferation, ß-cell mass, and glucose tolerance. RESULTS: FoxM1 deficiency suppressed ß-cell proliferation at both ages, indicating critical roles of FoxM1 in basal ß-cell proliferation throughout adulthood. While short-term FoxM1 deficiency affected neither ß-cell mass nor glucose tolerance, long-term FoxM1 deficiency suppressed ß-cell mass increases with impaired insulin secretion, thereby worsening glucose tolerance. In contrast, the insulin secretory function was not impaired in islets isolated from mice subjected to long-term ß-cell FoxM1 deficiency. Therefore, ß-cell mass reduction is the primary cause of impaired insulin secretion and deterioration of glucose tolerance due to long-term ß-cell FoxM1 deficiency. CONCLUSIONS: Basal low-level proliferation of ß-cells during adulthood is important for maintaining sufficient ß-cell mass and good glucose tolerance and ß-cell FoxM1 underlies this mechanism. Preserving ß-cell FoxM1 activity may prevent the impairment of glucose tolerance with advancing age.

Continuous glucose monitoring in patients with remission of type 2 diabetes after laparoscopic sleeve gastrectomy without or with duodenojejunal bypass.

Bariatric surgery is associated with a high remission rate of type 2 diabetes mellitus. However, it is unclear whether patients showing remission of diabetes actually have normal blood glucose levels throughout the day. We therefore performed continuous glucose monitoring (CGM) in 15 ambulatory patients showing remission of diabetes after laparoscopic sleeve gastrectomy (LSG) without or with duodenojejunal bypass (DJB) at the time of diabetic remission (12.9 ± 1.8 months after bariatric surgery). The definition of remission of diabetes was based on the American Diabetes Association criteria. The mean, SD, and coefficient of variation (CV) of glucose calculated from CGM were 6.2 ± 0.6 mmol/L, 1.5 ± 0.4 mmol/L, and 23.7 ± 6.2%, respectively. These values were higher than those of healthy participants without diabetes previously reported. The percentages of time spent above 10.0 mmol/L and below 3.9 mmol/L were 2.6 (IQR 0-5.0)% and 0 (IQR 0-8.0)%, respectively. Thus, patients with remission of diabetes after LSG or LSG/DJB still had substantial periods of hyperglycemia and hypoglycemia throughout the day. Therefore, we must manage patients with diabetes carefully, even after apparent remission of type 2 diabetes in response to bariatric surgery.

Inhibition of Plasminogen Activator Inhibitor-1 Activation Suppresses High Fat Diet-Induced Weight Gain via Alleviation of Hypothalamic Leptin Resistance.

Leptin resistance is an important mechanism underlying the development and maintenance of obesity and is thus regarded as a promising target of obesity treatment. Plasminogen activator inhibitor 1 (PAI-1), a physiological inhibitor of tissue-type and urokinase-type plasminogen activators, is produced at high levels in adipose tissue, especially in states of obesity, and is considered to primarily be involved in thrombosis. PAI-1 may also have roles in inter-organ tissue communications regulating body weight, because PAI-1 knockout mice reportedly exhibit resistance to high fat diet (HFD)-induced obesity. However, the role of PAI-1 in body weight regulation and the underlying mechanisms have not been fully elucidated. We herein studied how PAI-1 affects systemic energy metabolism. We examined body weight and food intake of PAI-1 knockout mice fed normal chow or HFD. We also examined the effects of pharmacological inhibition of PAI-1 activity by a small molecular weight compound, TM5441, on body weight, leptin sensitivities, and expressions of thermogenesis-related genes in brown adipose tissue (BAT) of HFD-fed wild type (WT) mice. Neither body weight gain nor food intake was reduced in PAI-1 KO mice under chow fed conditions. On the other hand, under HFD feeding conditions, food intake was decreased in PAI-1 KO as compared with WT mice (HFD-WT mice 3.98 ± 0.08 g/day vs HFD-KO mice 3.73 ± 0.07 g/day, P = 0.021), leading to an eventual significant suppression of weight gain (HFD-WT mice 40.3 ± 1.68 g vs HFD-KO mice 34.6 ± 1.84 g, P = 0.039). Additionally, TM5441 treatment of WT mice pre-fed the HFD resulted in a marked suppression of body weight gain in a PAI-1-dependent manner (HFD-WT-Control mice 37.6 ± 1.07 g vs HFD-WT-TM5441 mice 33.8 ± 0.97 g, P = 0.017). TM5441 treatment alleviated HFD-induced systemic and hypothalamic leptin resistance, before suppression of weight gain was evident. Moreover, improved leptin sensitivity in response to TM5441 treatment was accompanied by increased expressions of thermogenesis-related genes such as uncoupling protein 1 in BAT (HFD-WT-Control mice 1.00 ± 0.07 vs HFD-WT-TM5441 mice 1.32 ± 0.05, P = 0.002). These results suggest that PAI-1 plays a causative role in body weight gain under HFD-fed conditions by inducing hypothalamic leptin resistance. Furthermore, they indicate that pharmacological inhibition of PAI-1 activity is a potential strategy for alleviating diet-induced leptin resistance in obese subjects.

Vascular resistance of carotid and vertebral arteries is associated with retinal microcirculation measured by laser speckle flowgraphy in patients with type 2 diabetes mellitus.

AIMS: Evaluation of the retinal microcirculation is key to understanding retinal vasculopathies, such as diabetic retinopathy. Laser speckle flowgraphy (LSFG) has recently enabled us to directly evaluate the vascular resistance in both retinal vessels and capillaries, non-invasively. We therefore assessed whether retinal vessel blood flow and/or the capillary microcirculation are associated with blood flow in the cervical arteries in diabetic patients without severe retinopathy. METHODS: We enrolled 110 type 2 diabetes patients, with no or mild non-proliferative diabetic retinopathy, in this prospective cross-sectional study. We measured the resistivity indices (RIs) of the retinal vessel and capillaries by LSFG and those of cervical arteries by Doppler ultrasonography, followed by analyzing associations. RESULTS: The RIs of not only the carotid but also vertebral arteries were associated with those of retinal vessel blood flow and the retinal capillary microcirculation. Multiple regression analyses revealed these associations to be independent of other explanatory variables including age and diabetes duration. CONCLUSIONS: We obtained novel and direct evidence demonstrating a close association between the retinal microcirculation and cervical artery hemodynamics in diabetic patients. These findings suggest shared mechanisms to underlie micro- and macro-angiopathies. Thus, high vascular resistance of cervical arteries may be a risk of developing retinopathy.

MicroRNAs 106b and 222 Improve Hyperglycemia in a Mouse Model of Insulin-Deficient Diabetes via Pancreatic ß-Cell Proliferation.

Major symptoms of diabetes mellitus manifest, once pancreatic ß-cell numbers have become inadequate. Although natural regeneration of ß-cells after injury is very limited, bone marrow (BM) transplantation (BMT) promotes their regeneration through undetermined mechanism(s) involving inter-cellular (BM cell-to-ß-cell) crosstalk. We found that two microRNAs (miRNAs) contribute to BMT-induced ß-cell regeneration. Screening murine miRNAs in serum exosomes after BMT revealed 42 miRNAs to be increased. Two of these miRNAs (miR-106b-5p and miR-222-3p) were shown to be secreted by BM cells and increased in pancreatic islet cells after BMT. Treatment with the corresponding anti-miRNAs inhibited BMT-induced ß-cell regeneration. Furthermore, intravenous administration of the corresponding miRNA mimics promoted post-injury ß-cell proliferation through Cip/Kip family down-regulation, thereby ameliorating hyperglycemia in mice with insulin-deficient diabetes. Thus, these identified miRNAs may lead to the development of therapeutic strategies for diabetes.