Diabetic retinopathy is characterized by early onset of neuronal cell death. We previously showed that insulin mediates a prosurvival pathway in retinal neurons and that normal retina expresses a highly active basal insulin receptor/Akt signaling pathway that is stable throughout feeding and fasting. Using the streptozotocin-induced diabetic rat model, we tested the hypothesis that diabetes diminishes basal retinal insulin receptor signaling concomitantly with increased diabetes-induced retinal apoptosis. The expression, phosphorylation status, and/or kinase activity of the insulin receptor and downstream signaling proteins were investigated in retinas of age-matched control, diabetic, and insulin-treated diabetic rats. Four weeks of diabetes reduced basal insulin receptor kinase, insulin receptor substrate (IRS)-1/2-associated phosphatidylinositol 3-kinase, and Akt kinase activity without altering insulin receptor or IRS-1/2 expression or tyrosine phosphorylation. After 12 weeks of diabetes, constitutive insulin receptor autophosphorylation and IRS-2 expression were reduced, without changes in p42/p44 mitogen-activated protein kinase or IRS-1. Sustained systemic insulin treatment of diabetic rats prevented loss of insulin receptor and Akt kinase activity, and acute intravitreal insulin administration restored insulin receptor kinase activity. Insulin treatment restored insulin receptor-␤ autophosphorylation in rat retinas maintained ex vivo, demonstrating functional receptors and suggesting loss of ligand as a cause for reduced retinal insulin receptor/Akt pathway activity. These results demonstrate that diabetes progressively impairs the constitutive retinal insulin receptor signaling pathway through Akt and suggests that loss of this survival pathway may contribute to the initial stages of diabetic retinopathy.

Dopaminergic and cholinergic amacrine cells are lost during the early stages of retinal neuropathy in diabetes. Loss of these neurons may play a critical role in the development of visual deficits in diabetes.

Nearly all renal tubular epithelial cells express insulin receptor. The insulin receptor in the distal tubule appears to modulate BP, but the role of the insulin receptor in the proximal tubule is unknown. Here, we selectively knocked out the insulin receptor from the proximal tubules of mice. Western blotting confirmed a two-to three-fold reduction in renal cortical homogenate insulin receptor-b among knockout mice compared with wild-type littermates. Young knockout mice exhibited a mildly diabetic phenotype, evidenced by higher fasting plasma glucose levels than wild-type mice. Assessments by hyperinsulinemic-euglycemic clamp and a glucose tolerance test revealed no differences in insulin sensitivity or overt pancreatic function, respectively. Renal cortical mRNA expression and enzyme activity of glucose-6-phosphatase, which catalyzes the final step of glucose production, were significantly higher in knockout mice. Taken together, these results support a role for insulin receptor in the proximal tubule in the modulation of systemic glucose levels. Downregulation of the insulin receptor in the proximal tubule, which occurs in insulinresistant states, may promote hyperglycemia through enhanced gluconeogenesis.

The relationship between fat and bone mass at distinct trabecular and cortical skeletal compartments in a high-fat diet (HFD) model was studied. For this, C57BL/6 mice were assigned to four groups of eight animals each. Two groups, each of males and females, received a standard chow diet while the remaining other two groups received the HFD for a period of 10 weeks. Male mice on the HFD were heavier and gained more weight (15·8 %; P, 0·05) v. those on the control diet or when compared with the female rats fed the HFD. We observed an increased lipid profile in both males and females, with significantly higher lipid levels (about 20 -25 %; P, 0·01) in males. However, glucose intolerance was more pronounced in females than males on the HFD (about 30 %; P,0·05). The micro-architectural assessment of bones showed that compared with female mice on the HFD, male mice on the HFD showed more deterioration at the trabecular region. This was corroborated by plasma osteocalcin and carboxy-terminal collagen crosslinks (CTx) levels confirming greater loss in males (about 20 %; P, 0·01). In both sexes cortical bone parameters and strength remained unchanged after 10 weeks of HFD treatment. The direct effect of the HFD on bone at the messenger RNA level in progenitor cells isolated from femoral bone marrow was a significantly increased expression of adipogenic marker genes v. osteogenic genes. Overall, the present data indicate that obesity induced by a HFD aggravates bone loss in the cancellous bone compartment, with a greater loss in males than females, although 10 weeks of HFD treatment did not alter cortical bone mass and strength in both males and females.

Diabetes pathology derives from the combination of hyperglycemia and hypoinsulinemia or insulin resistance leading to diabetic complications including diabetic neuropathy, nephropathy and retinopathy. Diabetic retinopathy is characterized by numerous retinal defects affecting the vasculature and the neuro-retina, but the relative contributions of the loss of retinal insulin signaling and hyperglycemia have never been directly compared. In this study we tested the hypothesis that increased retinal insulin signaling and glycemic normalization would exert differential effects on retinal cell survival and retinal physiology during diabetes. We have demonstrated in this study that both subconjunctival insulin administration and systemic glycemic reduction using the sodium-glucose linked transporter inhibitor phloridzin affected the regulation of retinal cell survival in diabetic rats. Both treatments partially restored the retinal insulin signaling without increasing plasma insulin levels. Retinal transcriptomic and histological analysis also clearly demonstrated that local administration of insulin and systemic glycemia normalization use different pathways to counteract the effects of diabetes on the retina. While local insulin primarily affected inflammation-associated pathways, systemic glycemic control affected pathways involved in the regulation of cell signaling and metabolism. These results suggest that hyperglycemia induces resistance to growth factor action in the retina and clearly demonstrate that both restoration of glycemic control and retinal insulin signaling can act through different pathways to both normalize diabetes-induced retinal abnormality and prevent vision loss.

Non-invasive renal signatures can help in serial monitoring of diabetic patients. We tested whether urinary exosomal (UE) microRNA (miR) analysis could non-invasively predict renal pathology in diabetic rats during the course of diabetes. Diabetes mellitus (DM) was induced in male Wistar rats by a single intraperitoneal injection of streptozotocin (STZ, 50 mg/kg body weight). Non-diabetic control (CTRL) rats were injected with vehicle. Insulin (INS) treatment (5U/d, s.c.) was provided to 50% of the DM rats. Urine samples were collected at weeks 3, 6, and 9 following injections and UE prepared. An increase in miR-451-5p and miR-16, observed by pilot small RNA sequencing of UE RNA, was confirmed by quantitative real-time polymerase chain reaction (qPCR) and selected for further study. Subsets of rats were euthanized after 3, 6, and 9 weeks of diabetes for renal pathology analysis, including determination of the tubulointerstitial fibrotic index (TFI) and glomerulosclerotic index (GI) scores. qPCR showed a substantial rise in miR-451-5p in UE from DM rats during the course of diabetes, with a significant rise (median fold change >1000) between 3 and 6 weeks. Moreover, UE miR-451-5p at 6 weeks predicted urine albumin at 9 weeks (r = 0.76). A delayed but significant rise was also observed for miR-16. In contrast, mean urine albumin only increased 21% between 3 and 6 weeks (non-significant rise), and renal TFI and GI were unchanged till 9 weeks. Renal expression of miR-451-5p and miR-16 (at 10 weeks) did not correlate with urine levels, and moreover, was negatively associated with indices of renal pathology (r≥-0.70, p = 0.005 for TFI and r≥-0.6, p≤0.02 for GI). Overall, a relative elevation in renal miR-451-5p and miR-16 in diabetes appeared protective against diabetes-induced kidney fibrosis; while UE miR-451-5p may hold prognostic value as an early and sensitive non-invasive indicator of renal disease.

US Centers for Disease Control and Prevention.

Venipuncture is the most common painful event for a hospitalized child. We evaluated the efficacy of balloon inflation for attenuating venipuncture pain in children. Seventy-five pediatric patients aged 6-12 yr, ASA physical status I-II, of either sex, undergoing elective surgery were included in this prospective and randomized study. Patients were randomly divided into 3 equal groups of 25 each; Group I (control), Group II (distraction) pressed a rubber ball, and Group III (balloon) inflated a balloon. A manual venous occlusion was applied on the forearm and venipuncture was performed with a 22-gauge venous cannula. Pain was self-reported by a pain face scale with a 10-cm visual analog scale (VAS) placed at its back, where 0 = "no pain" and 10 = "worst imaginable pain." VAS scores of 1-3 were rated as mild, 4-6 as moderate, and >6 as severe. Median (interquartile range) VAS score in the balloon group was 1 (3), which was reduced as compared with 2 (2) and 4 (2) observed in the distraction and control groups, respectively (P < 0.000). Significant reduction in the incidence and severity of venipuncture pain was also observed in the balloon group compared with the other 2 groups (P < 0.05).