Soluble FLT1 binds lipid microdomains in podocytes to control cell morphology and glomerular barrier function.

Vascular endothelial growth factor and its receptors, FLK1/KDR and FLT1, are key regulators of angiogenesis. Unlike FLK1/KDR, the role of FLT1 has remained elusive. FLT1 is produced as soluble (sFLT1) and full-length isoforms. Here, we show that pericytes from multiple tissues produce sFLT1. To define the biologic role of sFLT1, we chose the glomerular microvasculature as a model system. Deletion of Flt1 from specialized glomerular pericytes, known as podocytes, causes reorganization of their cytoskeleton with massive proteinuria and kidney failure, characteristic features of nephrotic syndrome in humans. The kinase-deficient allele of Flt1 rescues this phenotype, demonstrating dispensability of the full-length isoform. Using cell imaging, proteomics, and lipidomics, we show that sFLT1 binds to the glycosphingolipid GM3 in lipid rafts on the surface of podocytes, promoting adhesion and rapid actin reorganization. sFLT1 also regulates pericyte function in vessels outside of the kidney. Our findings demonstrate an autocrine function for sFLT1 to control pericyte behavior.

Synchronous Health Care Delivery for the Optimization of Cardiovascular and Renal Care in Patients with Type 2 Diabetes.

PURPOSE OF REVIEW: The current care model of type 2 diabetes (T2D) and its complications appears to be "asynchronous" with patient care divided by specialty. This model is associated with low use of guideline-directed medical therapies. RECENT FINDINGS: The use of integrated care models has been well described in the management of patients with T2D; this usually includes an endocrinologist coupled with a nutritionist and nurse. However, physician-based care models are largely "asynchronous," whereby the patient requires multiple different siloed specialties to manage their health care. To date, there has been limited exploration of synchronous care delivery, i.e., whereby multi-comorbid patients with T2D are seen simultaneously by health care providers from endocrinology, cardiology, and nephrology to optimize use of guideline-directed medical therapies (GDMT). Given the rising complexity of patients with T2D, further research is needed on the role of synchronous health care delivery in optimizing the use of GDMT and improving patient outcomes.

Curcumin and other dietary polyphenols: potential mechanisms of metabolic actions and therapy for diabetes and obesity.

Recent controversy regarding the therapeutic potential of curcumin indicates the challenges to research in this field. Here, we highlight the investigations of curcumin and other plant-derived polyphenols that demonstrate their application to metabolic diseases, in particular, obesity and diabetes. Thus, a number of preclinical and clinical investigations have shown the beneficial effect of curcumin (and other dietary polyphenols) in attenuating body weight gain, improving insulin sensitivity, and preventing diabetes development in rodent models and prediabetic subjects. Other intervention studies with dietary polyphenols have also found improvements in insulin resistance. Recent studies suggest that the metabolic effects of curcumin/polyphenols are linked to changes in the gut microbiota. Thus, research into curcumin continues to provide novel insights into metabolic regulation that may ultimately translate into effective therapy.

The bradykinin-cGMP-PKG pathway augments insulin sensitivity via upregulation of MAPK phosphatase-5 and inhibition of JNK.

Bradykinin (BK) promotes insulin sensitivity and glucose uptake in adipocytes and other cell types. We demonstrated that in rat adipocytes BK enhances insulin-stimulated glucose transport via endothelial nitric oxide synthase, nitric oxide (NO) generation, and decreased activity of the mitogen-activated protein kinase (MAPK) JNK (c-Jun NH2-terminal kinase). In endothelial cells, NO increases soluble guanylate cyclase (sGC) activity, which, in turn, activates protein kinase G (PKG) by increasing cGMP levels. In this study, we investigated whether BK acts via the sGC-cGMP-PKG pathway to inhibit the negative effects of JNK on insulin signaling and glucose uptake in rat adipocytes. BK augmented cGMP concentrations. The BK-induced enhancement of insulin-stimulated glucose uptake was mimicked by the sGC activator YC-1 and a cell-permeable cGMP analog, CPT-cGMP, and inhibited by the sGC inhibitor ODQ and the PKG inhibitor KT 5823. Transfection of dominant-negative PKG reduced the BK augmentation of insulin-induced Akt phosphorylation. The activation of JNK and ERK1/2 by insulin was attenuated by BK, which was mediated by the sGC-cGMP-PKG pathway. Whereas insulin-stimulated phosphorylation of upstream activators of JNK and ERK, i.e., MKK4 and MEK1/2, was unaffected, BK augmented insulin-mediated induction of MKP-5 mRNA and protein levels. Furthermore, zaprinast, a phosphodiesterase inhibitor, enhanced cGMP and MKP-5 and prolonged the action of BK. These data indicate that BK enhances insulin action by inhibition of negative feedback by JNK and ERK via upregulation of MKP-5, mediated by the sGC-cGMP-PKG signaling pathway.

Metformin in women with type 2 diabetes in pregnancy (MiTy): a multi-center randomized controlled trial.

BACKGROUND: The incidence of type 2 diabetes in pregnancy is rising and rates of serious adverse maternal and fetal outcomes remain high. Metformin is a biguanide that is used as first-line treatment for non-pregnant patients with type 2 diabetes. We hypothesize that metformin use in pregnancy, as an adjunct to insulin, will decrease adverse outcomes by reducing maternal hyperglycemia, maternal insulin doses, maternal weight gain and gestational hypertension/pre-eclampsia. In addition, since metformin crosses the placenta, metformin treatment of the fetus may have a direct beneficial effect on neonatal outcomes. Our aim is to compare the effectiveness of the addition of metformin to insulin, to standard care (insulin plus placebo) in women with type 2 diabetes in pregnancy. METHODS: The MiTy trial is a multi-centre randomized trial currently enrolling pregnant women with type 2 diabetes, who are on insulin, between the ages of 18-45, with a gestational age of 6 weeks 0 days to 22 weeks 6 days. In this randomized, double-masked, parallel placebo-controlled trial, after giving informed consent, women are randomized to receive either metformin 1,000 mg twice daily or placebo twice daily. A web-based block randomization system is used to assign women to metformin or placebo in a 1:1 ratio, stratified for site and body mass index. The primary outcome is a composite neonatal outcome of pregnancy loss, preterm birth, birth injury, moderate/severe respiratory distress, neonatal hypoglycemia, or neonatal intensive care unit admission longer than 24 h. Secondary outcomes are large for gestational age, cord blood gas pH < 7.0, congenital anomalies, hyperbilirubinemia, sepsis, hyperinsulinemia, shoulder dystocia, fetal fat mass, as well as maternal outcomes: maternal weight gain, maternal insulin doses, maternal glycemic control, maternal hypoglycemia, gestational hypertension, preeclampsia, cesarean section, number of hospitalizations during pregnancy, and duration of hospital stays. The trial aims to enroll 500 participants. DISCUSSION: The results of this trial will inform endocrinologists, obstetricians, family doctors, and other healthcare professionals caring for women with type 2 diabetes in pregnancy, as to the benefits of adding metformin to insulin in this high risk population. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: no. NCT01353391 . Registered February 6, 2009.

Is metformin ready for prime time in pregnancy? Probably not yet.

Metformin is one of the most commonly used drugs to treat type 2 diabetes and is safe and effective. Its main mechanism of action is thought to be the activation of AMP-activated protein kinase (AMPK) via inhibition of mitochondrial ATP generation. Recent use of metformin as an 'insulin sensitizer' in women with polycystic ovarian syndrome to increase fertility has been successful and resulted in the chance observation that continued use during pregnancy appeared to be safe. There are few studies of metformin in animal models of diabetic pregnancy. However, some data have implicated fetal AMPK activation in neural tube defects. While a recent report suggests that metformin may not activate fetal AMPK, which is reassuring, studies in pregnant woman with gestational diabetes and type 2 diabetes, which are ongoing, require completion before we can conclude that its use in pregnancy is safe. Furthermore, follow-up of the offspring will be critical to determine whether such treatment decreases or increases the development of obesity and diabetes.

Short-Term Curcumin Gavage Sensitizes Insulin Signaling in Dexamethasone-Treated C57BL/6 Mice.

BACKGROUND: Long-term dietary curcumin (>12 wk) improves metabolic homeostasis in obese mice by sensitizing insulin signaling and reducing hepatic gluconeogenesis. Whether these occur only secondary to its chronic anti-inflammatory and antioxidative functions is unknown. OBJECTIVE: In this study, we assessed the insulin sensitization effect of short-term curcumin gavage in a rapid dexamethasone-induced insulin resistance mouse model, in which the chronic anti-inflammatory function is eliminated. METHODS: Six-week-old male C57BL/6 mice received an intraperitoneal injection of dexamethasone (100 mg/kg body weight) or phosphate-buffered saline every day for 5 d, with or without simultaneous curcumin gavage (500 mg/kg body weight). On day 7, insulin tolerance tests were performed. After a booster dexamethasone injection and curcumin gavage on day 8, blood glucose and insulin concentrations were measured. Liver tissues were collected on day 10 for quantitative polymerase chain reaction and Western blotting to assess gluconeogenic gene expression, insulin signaling, and the expression of fibroblast growth factor 21 (FGF21). Primary hepatocytes from separate, untreated C57BL/6 mice were used for testing the in vitro effect of curcumin treatment. RESULTS: Dexamethasone injection impaired insulin tolerance (P < 0.05) and elevated ambient plasma insulin concentrations by ~2.7-fold (P < 0.01). Concomitant curcumin administration improved insulin sensitivity and reduced hepatic gluconeogenic gene expression. The insulin sensitization effect of curcumin was demonstrated by increased stimulation of S473 phosphorylation of protein kinase B (P < 0.01) in the dexamethasone-treated mouse liver, as well as the repression of glucose production in primary hepatocytes (P < 0.001). Finally, curcumin gavage increased FGF21 expression by 2.1-fold in the mouse liver (P < 0.05) and curcumin treatment increased FGF21 expression in primary hepatocytes. CONCLUSION: These observations suggest that the early beneficial effect of curcumin intervention in dexamethasone-treated mice is the sensitization of insulin signaling, involving the stimulation of FGF21 production, a known insulin sensitizer.

Thioredoxin-interacting protein mediates high glucose-induced reactive oxygen species generation by mitochondria and the NADPH oxidase, Nox4, in mesangial cells.

Thioredoxin-interacting protein (TxNIP) is up-regulated by high glucose and is associated with oxidative stress. It has been implicated in hyperglycemia-induced ß-cell dysfunction and apoptosis. As high glucose and oxidative stress mediate diabetic nephropathy (DN), the contribution of TxNIP was investigated in renal mesangial cell reactive oxygen species (ROS) generation and collagen synthesis. To determine the role of TxNIP, mouse mesangial cells (MC) cultured from wild-type C3H and TxNIP-deficient Hcb-19 mice were incubated in HG. Confocal microscopy was used to measure total and mitochondrial ROS production (DCF and MitoSOX) and collagen IV. Trx and NADPH oxidase activities were assayed and NADPH oxidase isoforms, Nox2 and Nox4, and antioxidant enzymes were determined by immunoblotting. C3H MC exposed to HG elicited a significant increase in cellular and mitochondrial ROS as well as Nox4 protein expression and NADPH oxidase activation, whereas Hcb-19 MC showed no response. Trx activity was attenuated by HG only in C3H MC. These defects in Hcb-19 MC were not due to increased antioxidant enzymes or scavenging of ROS, but associated with decreased ROS generation. Adenovirus-mediated overexpression of TxNIP in Hcb-19 MC and TxNIP knockdown with siRNA in C3H confirmed the specific role of TxNIP. Collagen IV accumulation in HG was markedly reduced in Hcb-19 cells. TxNIP is a critical component of the HG-ROS signaling pathway, required for the induction of mitochondrial and total cell ROS and the NADPH oxidase isoform, Nox4. TxNIP is a potential target to prevent DN.

FFA-induced hepatic insulin resistance in vivo is mediated by PKCδ, NADPH oxidase, and oxidative stress.

Fat-induced hepatic insulin resistance plays a key role in the pathogenesis of type 2 diabetes in obese individuals. Although PKC and inflammatory pathways have been implicated in fat-induced hepatic insulin resistance, the sequence of events leading to impaired insulin signaling is unknown. We used Wistar rats to investigate whether PKCδ and oxidative stress play causal roles in this process and whether this occurs via IKKß- and JNK-dependent pathways. Rats received a 7-h infusion of Intralipid plus heparin (IH) to elevate circulating free fatty acids (FFA). During the last 2 h of the infusion, a hyperinsulinemic-euglycemic clamp with tracer was performed to assess hepatic and peripheral insulin sensitivity. An antioxidant, N-acetyl-L-cysteine (NAC), prevented IH-induced hepatic insulin resistance in parallel with prevention of decreased IκBα content, increased JNK phosphorylation (markers of IKKß and JNK activation, respectively), increased serine phosphorylation of IRS-1 and IRS-2, and impaired insulin signaling in the liver without affecting IH-induced hepatic PKCδ activation. Furthermore, an antisense oligonucleotide against PKCδ prevented IH-induced phosphorylation of p47(phox) (marker of NADPH oxidase activation) and hepatic insulin resistance. Apocynin, an NADPH oxidase inhibitor, prevented IH-induced hepatic and peripheral insulin resistance similarly to NAC. These results demonstrate that PKCδ, NADPH oxidase, and oxidative stress play a causal role in FFA-induced hepatic insulin resistance in vivo and suggest that the pathway of FFA-induced hepatic insulin resistance is FFA → PKCδ → NADPH oxidase and oxidative stress → IKKß/JNK → impaired hepatic insulin signaling.

Deletion of IRE1α in podocytes exacerbates diabetic nephropathy in mice.

Protein misfolding in the endoplasmic reticulum (ER) of podocytes contributes to the pathogenesis of glomerular diseases. Protein misfolding activates the unfolded protein response (UPR), a compensatory signaling network. We address the role of the UPR and the UPR transducer, inositol-requiring enzyme 1α (IRE1α), in streptozotocin-induced diabetic nephropathy in mice. Diabetes caused progressive albuminuria in control mice that was exacerbated in podocyte-specific IRE1α knockout (KO) mice. Compared to diabetic controls, diabetic IRE1α KO mice showed reductions in podocyte number and synaptopodin. Glomerular ultrastructure was altered only in diabetic IRE1α KO mice; the major changes included widening of podocyte foot processes and glomerular basement membrane. Activation of the UPR and autophagy was evident in diabetic control, but not diabetic IRE1α KO mice. Analysis of human glomerular gene expression in the JuCKD-Glom database demonstrated induction of genes associated with the ER, UPR and autophagy in diabetic nephropathy. Thus, mice with podocyte-specific deletion of IRE1α demonstrate more severe diabetic nephropathy and attenuation of the glomerular UPR and autophagy, implying a protective effect of IRE1α. These results are consistent with data in human diabetic nephropathy and highlight the potential for therapeutically targeting these pathways.

Overexpression of glutathione peroxidase 4 prevents ß-cell dysfunction induced by prolonged elevation of lipids in vivo.

We have shown that oxidative stress is a mechanism of free fatty acid (FFA)-induced ß-cell dysfunction. Unsaturated fatty acids in membranes, including plasma and mitochondrial membranes, are substrates for lipid peroxidation, and lipid peroxidation products are known to cause impaired insulin secretion. Therefore, we hypothesized that mice overexpressing glutathione peroxidase-4 (GPx4), an enzyme that specifically reduces lipid peroxides, are protected from fat-induced ß-cell dysfunction. GPx4-overexpressing mice and their wild-type littermate controls were infused intravenously with saline or oleate for 48 h, after which reactive oxygen species (ROS) were imaged, using dihydrodichlorofluorescein diacetate in isolated islets, and ß-cell function was assessed ex vivo in isolated islets and in vivo during hyperglycemic clamps. Forty-eight-hour FFA elevation in wild-type mice increased ROS and the lipid peroxidation product malondialdehyde and impaired ß-cell function ex vivo in isolated islets and in vivo, as assessed by decreased disposition index. Also, islets of wild-type mice exposed to oleate for 48 h had increased ROS and lipid peroxides and decreased ß-cell function. In contrast, GPx4-overexpressing mice showed no FFA-induced increase in ROS and lipid peroxidation and were protected from the FFA-induced impairment of ß-cell function assessed in vitro, ex vivo and in vivo. These results implicate lipid peroxidation in FFA-induced ß-cell dysfunction.

Outcomes in children of women with type 2 diabetes exposed to metformin versus placebo during pregnancy (MiTy Kids): a 24-month follow-up of the MiTy randomised controlled trial.

BACKGROUND: Metformin is increasingly being used during pregnancy, with potentially adverse long-term effects on children. We aimed to examine adiposity in children of women with type 2 diabetes from the Metformin in Women with Type 2 Diabetes in Pregnancy (MiTy) trial, with and without in-utero exposure to metformin, up to 24 months of age. METHODS: MiTy Kids is a follow-up study that included infants of women who participated in the MiTy randomised controlled trial, receiving either oral 1000 mg metformin twice daily or placebo. Caregivers and researchers remained masked to the type of medication (metformin or placebo) mothers received during their pregnancy. Anthropometric measurements, including weight, height, and skinfold thicknesses, were taken at 3, 6, 12, 18, and 24 months. At 24 months, linear regression was used to compare the BMI Z score and sum of skinfolds in the metformin versus placebo groups, adjusted for confounders. Fractional polynomials were used to assess growth trajectories. This study is registered with ClinicalTrials.gov, NCT01832181. FINDINGS: Of the 465 eligible children, 283 (61%) were included from 19 centres in Canada and Australia. At 24 months, there was no difference between groups in mean BMI Z score (0·84 [SD 1·52] with metformin vs 0·91 [1·38] with placebo; mean difference 0·07 [95% CI -0·31 to 0·45], p=0·72) or mean sum of skinfolds (23·0 mm [5·2] vs 23·8 mm [5·4]; mean difference 0·8 mm [-0·7 to 2·3], p=0·31). Metformin was not a predictor of BMI Z score at 24 months of age (mean difference -0·01 [95% CI -0·42 to 0·37], p=0·92). There was no overall difference in BMI trajectory but, in males, trajectories were significantly different by treatment (p=0·048); BMI in the metformin group was higher between 6 and 24 months. Children of women with type 2 diabetes were approximately 1 SD heavier than the WHO reference population. INTERPRETATION: Anthropometrics were similar in children exposed and those not exposed to metformin in utero; hence, overall, data are reassuring with regard to the use of metformin during pregnancy in women with type 2 diabetes and the long-term health of their children. FUNDING: Canadian Institute for Health Research.

Lecithin cholesterol acyltransferase null mice are protected from diet-induced obesity and insulin resistance in a gender-specific manner through multiple pathways.

Complete lecithin cholesterol acyltransferase (LCAT) deficiency uniformly results in a profound HDL deficiency. We recently reported unexpected enhanced insulin sensitivity in LCAT knock-out mice in the LDL receptor knock-out background (Ldlr(-/-)×Lcat(-/-); double knock-out (DKO)), when compared with their Ldlr(-/-)×Lcat(+/+) (single knock-out (SKO)) controls. Here, we report that LCAT-deficient mice (DKO and Lcat(-/-)) are protected against high fat high sucrose (HFHS) diet-induced obesity without hypophagia in a gender-specific manner compared with their respective (SKO and WT) controls. The metabolic phenotypes are more pronounced in the females. Changes in endoplasmic reticulum stress were examined as a possible mechanism for the metabolic protection. The female DKO mice developed attenuated HFHS-induced endoplasmic reticulum stress as evidenced by a lack of increase in mRNA levels of the hepatic unfolded protein response (UPR) markers Grp78 and CHOP compared with SKO controls. The DKO female mice were also protected against diet-induced insulin resistance. In white adipose tissue of chow-fed DKO mice, we also observed a reduction in UPR, gene markers for adipogenesis, and markers for activation of Wnt signaling. In skeletal muscles of female DKO mice, we observed an unexpected increase in UCP1 in association with increase in phospho-AMPKα, PGC1α, and UCP3 expressions. This increase in UCP1 was associated with ectopic islands of brown adipocytes between skeletal muscle fibers. Our findings suggest that LCAT deficiency confers gender-specific protection against diet-induced obesity and insulin resistance at least in part through regulation in UPR, white adipose tissue adipogenesis, and brown adipocyte partitioning.

Insulin's discovery: new insights on its ninetieth birthday.

2012 marks the 90th year since the purification of insulin and the miraculous rescue from death of youngsters with type 1 diabetes. In this review, we highlight several previously unappreciated or unknown events surrounding the discovery. (i) We remind readers of the essential contributions of each of the four discoverers--Banting, Macleod, Collip, and Best. (ii) Banting and Best (each with his own inner circle) worked not only to accrue credit for himself but also to minimize credit to the other discoverers. (iii) Banting at the time of the insulin research was very likely suffering from post-traumatic stress disorder (PTSD) that originated during his heroic service as a surgeon in World War I on the Western Front in 1918, including an infected shrapnel wound that threatened amputation of his arm. His war record along with the newly discovered evidence of a suicide threat goes along with his paranoia, combativeness, alcohol excess, and depression, symptoms we associate with PTSD. (iv) Banting's eureka idea, ligation of the pancreatic duct to preserve the islets, while it energized the early research, was unnecessary and was bypassed early. (v) Post discovery, Macleod uncovered many features of insulin action that he summarized in his 1925 Nobel Lecture. Macleod closed by raising the question--what is the mechanism of insulin action in the body?--a challenge that attracted many talented investigators but remained unanswered until the latter third of the 20th century.

Combined Central Hypothyroidism and Adrenal Insufficiency Associated with Retinoic Acid Therapy for Cutaneous T-Cell Lymphoma.

Background/Objective: Although retinoid-associated central hypothyroidism has been reported on several occasions, there are very few studies on retinoid-associated central adrenal insufficiency. Here, we present the case of a patient with alitretinoin-induced central hypothyroidism and adrenal insufficiency. Case Report: An 86-year-old man with a diagnosis of cutaneous T-cell lymphoma, treated with oral alitretinoin 30 mg po daily, topical steroids, and ultraviolet light therapy presented to the emergency department with generalized weakness, decreased energy, orthostasis, and unexplained falls. Thyroid-stimulating hormone (TSH) was 0.31 mIU/L (normal range: 0.4-4.4) from 1.93 before alitretinoin therapy, whereas free thyroxine was 5.7 pmol/L (normal range: 8-18) and the AM cortisol was 40 nmol/L (normal range: 120-535); these values were suggestive of central hypothyroidism and adrenal insufficiency. Adrenocorticotropic hormone (ACTH) was not measured because of a laboratory error. Alitretinoin was stopped, and one dose of hydrocortisone 100mg IV was initiated, followed by maintenance doses of oral hydrocortisone 20mg qam and 10mg qpm. Levothyroxine (50µg ) daily was started 24 hours later. After stopping hydrocortisone for 24 hours, the AM cortisol and ACTH levels were 406 nmol/L and 2.18 pmol/L (normal range:1.6-13.9), respectively. He was discharged on thyroid hormone replacement therapy and glucocorticoids. Repeat thyroid function tests 6 weeks later showed a TSH of 0.4 mIU/L, and free thyroxine of 9.7 pmol/L. Discussion: Alitretinoin activates nuclear receptors called retinoic acid receptors and retinoid X-receptors. Retinoic acid receptors and retinoid X-receptors are widely expressed in the anterior pituitary gland. RXR-selective ligands such as retinoids can suppress TSH secretion, resulting in central hypothyroidism. Retinoids have also been shown to decrease ACTH secretion, which can result in central adrenal insufficiency. Conclusion: Although central adrenal insufficiency and hypothyroidism have not been commonly reported in patients taking retinoids, they should always be considered when caring for these patients.

O-linked ß-N-acetylglucosamine supports p38 MAPK activation by high glucose in glomerular mesangial cells.

Hyperglycemia augments flux through the hexosamine biosynthetic pathway and subsequent O-linkage of single ß-N-acetyl-d-glucosamine moieties to serine and threonine residues on cytoplasmic and nuclear proteins (O-GlcNAcylation). Perturbations in this posttranslational modification have been proposed to promote glomerular matrix accumulation in diabetic nephropathy, but clear evidence and mechanism are lacking. We tested the hypothesis that O-GlcNAcylation enhances profibrotic signaling in rat mesangial cells. An adenovirus expressing shRNA directed against O-GlcNAc transferase (OGT) markedly reduced basal and high-glucose-stimulated O-GlcNAcylation. Interestingly, O-GlcNAc depletion prevented high-glucose-induced p38 mitogen-activated protein kinase (MAPK) and c-Jun NH(2)-terminal kinase phosphorylation. Downstream of p38, O-GlcNAc controlled the expression of plasminogen activator inhibitor-1, fibronectin, and transforming growth factor-ß, important factors in matrix accumulation in diabetic nephropathy. Treating mesangial cells with thiamet-G, a highly selective inhibitor of O-GlcNAc-specific hexosaminidase (O-GlcNAcase), increased O-GlcNAcylation and p38 phosphorylation. The high-glucose-stimulated kinase activity of apoptosis signal-regulating kinase 1 (ASK1), an upstream MAPK kinase kinase for p38 that is negatively regulated by Akt, was inhibited by OGT shRNA. Akt Thr(308) and Ser(473) phosphorylation were enhanced following OGT shRNA expression in high-glucose-exposed mesangial cells, but high-glucose-induced p38 phosphorylation was not attenuated by OGT shRNA in cells pretreated with the phosphatidylinositol 3-kinase inhibitor LY-294002. OGT shRNA also reduced high-glucose-stimulated reactive oxygen species (ROS) formation. In contrast, diminished O-GlcNAcylation caused elevated ERK phosphorylation and PKCδ membrane translocation. Thus, O-GlcNAcylation is coupled to profibrotic p38 MAPK signaling by high glucose in part through Akt and possibly through ROS.

Glomerular structure and function require paracrine, not autocrine, VEGF-VEGFR-2 signaling.

VEGF is a potent vascular growth factor produced by podocytes in the developing and mature glomerulus. Specific deletion of VEGF from podocytes causes glomerular abnormalities including profound endothelial cell injury, suggesting that paracrine signaling is critical for maintaining the glomerular filtration barrier (GFB). However, it is not clear whether normal GFB function also requires autocrine VEGF signaling in podocytes. In this study, we sought to determine whether an autocrine VEGF-VEGFR-2 loop in podocytes contributes to the maintenance of the GFB in vivo. We found that induced, whole-body deletion of VEGFR-2 caused marked abnormalities in the kidney and also other tissues, including the heart and liver. By contrast, podocyte-specific deletion of the VEGFR-2 receptor had no effect on glomerular development or function even up to 6 months old. Unlike cell culture models, enhanced expression of VEGF by podocytes in vivo caused foot process fusion and alterations in slit diaphragm-associated proteins; however, inhibition of VEGFR-2 could not rescue this defect. Although VEGFR-2 was dispensable in the podocyte, glomerular endothelial cells depended on VEGFR-2 expression: postnatal deletion of the receptor resulted in global defects in the glomerular microvasculature. Taken together, our results provide strong evidence for dominant actions of a paracrine VEGF-VEGFR-2 signaling loop both in the developing and in the filtering glomerulus. VEGF produced by the podocyte regulates the structure and function of the adjacent endothelial cell.

Evidence for a tumor promoting effect of high-fat diet independent of insulin resistance in HER2/Neu mammary carcinogenesis.

The mechanism of the association between breast cancer and obesity remains unknown. To investigate this mice over-expressing HER2/Neu in the mammary gland (MMTV-HER2/Neu) were fed either a high-fat diet (45% of calories) (HFD) or low-fat diet (10%) (LFD) from 4 weeks of age and followed for up to 1 year, or sacrificed when a mammary tumor reached 1.5 cm. There was a small but significant increase in body weight on HFD (P < 0.05) and the HFD mice displayed a greater fat mass determined by MRI (P < 0.01). Mild glucose intolerance was observed from 3 months of age on HFD, but insulin levels were not elevated. While the time of onset of a first tumor and tumor growth rates were not altered, mice on HFD had an earlier onset of a second tumor and a twofold greater incidence (LFD 25%, HFD 54%) and a greater absolute number of multiple tumors (tumors/mouse, LFD 1.5 +/- 0.25 vs. HFD 2.7 +/- 0.23, P < 0.01). Consistent with a lack of hyperinsulinemia, immunoblotting of skeletal muscle lysates from mice injected with insulin showed no insulin resistance determined by the phosphorylation of Akt/PKB. Similarly, there was no difference in basal or maximum insulin-stimulated phosphorylation of IRS-1/2, Akt/PKB, or p70 S6K in tumor cell lysates from HFD and LFD groups. Immunohistochemistry revealed no difference in tumor tissue staining for the proliferative marker, Ki67, between diets. These data indicate that HFD, in the absence of significant insulin resistance, mediates a tumor promoting, but not a tumor growth effect in this model of mammary carcinogenesis.

Metformin in women with type 2 diabetes in pregnancy (MiTy): a multicentre, international, randomised, placebo-controlled trial.

BACKGROUND: Although metformin is increasingly being used in women with type 2 diabetes during pregnancy, little data exist on the benefits and harms of metformin use on pregnancy outcomes in these women. We aimed to investigate the effects of the addition of metformin to a standard regimen of insulin on neonatal morbidity and mortality in pregnant women with type 2 diabetes. METHODS: In this prospective, multicentre, international, randomised, parallel, double-masked, placebo-controlled trial, women with type 2 diabetes during pregnancy were randomly assigned from 25 centres in Canada and four in Australia to receive either metformin 1000 mg twice daily or placebo, added to insulin. Randomisation was done via a web-based computerised randomisation service and stratified by centre and pre-pregnancy BMI (<30 kg/m2 or ≥30 kg/m2) in a ratio of 1:1 using random block sizes of 4 and 6. Women were eligible if they had type 2 diabetes, were on insulin, had a singleton viable pregnancy, and were between 6 and 22 weeks plus 6 days' gestation. Participants were asked to check their fasting blood glucose level before the first meal of the day, before the last meal of the day, and 2 h after each meal. Insulin doses were adjusted aiming for identical glucose targets (fasting glucose <5·3 mmol/L [95 mg/dL], 2-h postprandial glucose <6·7 mmol/L [120 mg/dL]). Study visits were done monthly and patients were seen every 1-4 weeks as was needed for standard clinical care. At study visits blood pressure and bodyweight were measured; patients were asked about tolerance to their pills, any hospitalisations, insulin doses, and severe hypoglycaemia events; and glucometer readings were downloaded to the central coordinating centre. Participants, caregivers, and outcome assessors were masked to the intervention. The primary outcome was a composite of fetal and neonatal outcomes, for which we calculated the relative risk and 95% CI between groups, stratifying by site and BMI using a log-binomial regression model with an intention-to-treat analysis. Secondary outcomes included several relevant maternal and neonatal outcomes. The trial was registered with ClinicalTrials.gov, NCT01353391. FINDINGS: Between May 25, 2011, and Oct 11, 2018, we randomly assigned 502 women, 253 (50%) to metformin and 249 (50%) to placebo. Complete data were available for 233 (92%) participants in the metformin group and 240 (96%) in the placebo group for the primary outcome. We found no significant difference in the primary composite neonatal outcome between the two groups (40% vs 40%; p=0·86; relative risk [RR] 1·02 [0·83 to 1·26]). Compared with women in the placebo group, metformin-treated women achieved better glycaemic control (HbA1c at 34 weeks' gestation 41·0 mmol/mol [SD 8·5] vs 43·2 mmol/mol [-10]; 5·90% vs 6·10%; p=0·015; mean glucose 6·05 [0·93] vs 6·27 [0·90]; difference -0·2 [-0·4 to 0·0]), required less insulin (1·1 units per kg per day vs 1·5 units per kg per day; difference -0·4 [95% CI -0·5 to -0·2]; p<0·0001), gained less weight (7·2 kg vs 9·0 kg; difference -1·8 [-2·7 to -0·9]; p<0·0001) and had fewer caesarean births (125 [53%] of 234 in the metformin group vs 148 [63%] of 236 in the placebo group; relative risk [RR] 0·85 [95% CI 0·73 to 0·99]; p=0·031). We found no significant difference between the groups in hypertensive disorders (55 [23%] in the metformin group vs 56 [23%] in the placebo group; p=0·93; RR 0·99 [0·72 to 1·35]). Compared with those in the placebo group, metformin-exposed infants weighed less (mean birthweight 3156 g [SD 742] vs 3375 g [742]; difference -218 [-353 to -82]; p=0·002), fewer were above the 97th centile for birthweight (20 [9%] in the metformin group vs 34 [15%] in the placebo group; RR 0·58 [0·34 to 0·97]; p=0·041), fewer weighed 4000 g or more at birth (28 [12%] in the metformin group vs 44 [19%] in the placebo group; RR 0·65 [0·43 to 0·99]; p=0·046), and metformin-exposed infants had reduced adiposity measures (mean sum of skinfolds 16·0 mm [SD 5·0] vs 17·4 [6·2] mm; difference -1·41 [-2·6 to -0·2]; p=0·024; mean neonatal fat mass 13·2 [SD 6·2] vs 14·6 [5·0]; p=0·017). 30 (13%) infants in the metformin group and 15 (7%) in the placebo group were small for gestational age (RR 1·96 [1·10 to 3·64]; p=0·026). We found no significant difference in the cord c-peptide between groups (673 pmol/L [435] in the metformin group vs 758 pmol/L [595] in the placebo group; p=0·10; ratio of means 0·88 [0·72 to 1·02]). The most common adverse event reported was gastrointestinal (38 events in the metformin group and 38 events in the placebo group). INTERPRETATION: We found several maternal glycaemic and neonatal adiposity benefits in the metformin group. Along with reduced maternal weight gain and insulin dosage and improved glycaemic control, the lower adiposity and infant size measurements resulted in fewer large infants but a higher proportion of small-for-gestational-age infants. Understanding the implications of these effects on infants will be important to properly advise patients who are contemplating the use of metformin during pregnancy. FUNDING: Canadian Institutes of Health Research, Lunenfeld-Tanenbaum Research Institute, University of Toronto.

High insulin levels in newly diagnosed breast cancer patients reflect underlying insulin resistance and are associated with components of the insulin resistance syndrome.

BACKGROUND: High insulin levels have been associated with poor outcomes in breast cancer. Our goal was to investigate whether hyperinsulinemia was associated with insulin resistance in a cohort of newly diagnosed locoregional breast cancer patients and to examine associations of hyperinsulinemia with the broader insulin resistance syndrome (IRS). METHODS: Five hundred and four women with T1-3, N0-1, M0 breast cancer provided fasting blood that was analyzed for glucose, insulin and lipids. They underwent anthropomorphic measurements and provided information on diet, exercise and sleep. Relationships of insulin with three validated indices of insulin resistance and with attributes of the IRS were examined. RESULTS: High insulin levels were strongly correlated with insulin resistance calculated using the three indices of insulin resistance/sensitivity (Spearman r=0.83-0.98). Hyperinsulinemia was also associated with other components of the IRS (obesity, high waist-hip ratio, lipid profile). CONCLUSIONS: High insulin levels in women with locoregional breast cancer reflect the presence of insulin resistance and are associated with other components of the IRS. These observations have implications for the development of therapies that target hyperinsulinemia in early stage breast cancer and for the long-term management of breast cancer survivors.