Increased lipolysis in adipose tissues is associated with elevation of systemic free fatty acids and insulin resistance in perilipin null mice

Elevated plasma levels of free fatty acids (FFAs) are thought to restrict glucose utilization and induce insulin resistance. Plasma FFA concentrations are primarily governed by lipolysis in adipocytes. Perilipin surrounds the lipid droplet in adipocytes and has a dual role in lipolysis regulation. Perilipin null mice studied by two independent laboratories exhibited similar phenotypes of reduced adipose mass and resistance to diet-induced obesity, but have inconsistent metabolic parameters such as plasma levels of FFA, glucose, and insulin. This discrepancy may be due to differences in genetic background, generation, and nutritional status of the animals examined. In this study, we examined the major metabolic parameters in 129/SvEv perilipin null mice fasted for 4 h and observed increased plasma concentrations of FFA, glycerol, glucose, and insulin. An increase in the score for the homeostasis model assessment of insulin resistance index confirmed the insulin resistance in perilipin null mice, which may be attributed to the plasma FFA elevation. Basal lipolysis was increased in adipose tissues or primary adipocytes isolated from perilipin null mice with increased mass and activity of hormone-sensitive lipase and adipose triglyceride lipase. The increased lipolytic action may accelerate FFA efflux from the adipose tissues to the bloodstream, thereby accounting for systemic FFA elevation and, hence, insulin resistance in perilipin null mice.

Efficacy and safety of sitagliptin when added to insulin therapy in patients with type 2 diabetes

OBJECTIVE

To evaluate the efficacy and tolerability of sitagliptin when added to insulin therapy alone or in combination with metformin in patients with type 2 diabetes.

METHODS

After a 2 week placebo run-in period, eligible patients inadequately controlled on long-acting, intermediate-acting or premixed insulin (HbA1c > or = 7.5% and < or = 11%), were randomised 1:1 to the addition of once-daily sitagliptin 100 mg or matching placebo over a 24-week study period. The study capped the proportion of randomised patients on insulin plus metformin at 75%. Further, the study capped the proportion of randomised patients on premixed insulin at 25%. The metformin dose and the insulin dose were to remain stable throughout the study. The primary endpoint was HbA1c change from baseline at week 24.

RESULTS

Mean baseline characteristics were similar between the sitagliptin (n = 322) and placebo (n = 319) groups, including HbA1c (8.7 vs. 8.6%), diabetes duration (13 vs. 12 years), body mass index (31.4 vs. 31.4 kg/m(2)), and total daily insulin dose (51 vs. 52 IU), respectively. At 24 weeks, the addition of sitagliptin significantly (p < 0.001) reduced HbA1c by 0.6% compared with placebo (0.0%). A greater proportion of patients achieved an HbA1c level < 7% while randomised to sitagliptin as compared with placebo (13 vs. 5% respectively; p < 0.001). Similar HbA1c reductions were observed in the patient strata defined by insulin type (long-acting and intermediate-acting insulins or premixed insulins) and by baseline metformin treatment. The addition of sitagliptin significantly (p < 0.001) reduced fasting plasma glucose by 15.0 mg/dl (0.8 mmol/l) and 2-h postmeal glucose by 36.1 mg/dl (2.0 mmol/l) relative to placebo. A higher incidence of adverse experiences was reported with sitagliptin (52%) compared with placebo (43%), due mainly to the increased incidence of hypoglycaemia (sitagliptin, 16% vs. placebo, 8%). The number of hypoglycaemic events meeting the protocol-specified criteria for severity was low with sitagliptin (n = 2) and placebo (n = 1). No significant change from baseline in body weight was observed in either group.

CONCLUSION

In this 24-week study, the addition of sitagliptin to ongoing, stable-dose insulin therapy with or without concomitant metformin improved glycaemic control and was generally well tolerated in patients with type 2 diabetes.

Influences of hypoxia on hatching performance in chickens with different genetic adaptation to high altitude

The experiments were conducted to assess how hatching performance is affected by chicken breeds and environment of high altitude and to analyze the vital factor of the low hatchability at a 2,900-m altitude. Eggs of Tibetan and Dwarf chickens were incubated at conditions of normobaric normoxia, normobaric hypoxia, hypobaric hypoxia, and supplemental O2 at high altitude (hypobaric normoxia) during the whole incubation or at 0 to 7, 8 to 14, and 15 to 22 d of incubation, respectively. The results showed that the Tibetan chickens had greater hatchability (79.72%), lower water loss (12.90%), greater relative embryo weight (38.08%), and relative chick weight (68.41%) compared with the Dwarf chickens (31.69, 15.79, 30.71, and 65.21%, respectively) when both of them were incubated at a 2,900-m altitude. The hatchability was 71.60% in Tibetan chicken and 36.23% in Dwarf chicken under the normobaric hypoxia condition. The hatchability of chicken was efficiently increased with supplemental O2. The previous results indicated that the O2 deficit is the main factor resulting in the low hatchability and the poor chick quality of the lowland chicken breed when incubated at a 2,900-m altitude. Breeding chickens for adaptability to hypoxia and supplemental O2 is a good way to improve the hatchability and chick quality at that altitude.

A SNP in the ACT gene associated with astrocytosis and rapid cognitive decline in AD

There is biochemical and animal model evidence supporting a pathological role of the ACT gene in AD. However, direct genetic evidence remains controversial and has been mostly limited to individual single nucleotide polymorphism (SNP) analysis. To resolve this apparent conflict we have used a high-density ACT SNP map, constructed haplotypes and explored correlations with phenotype. SNPs were identified by sequencing and used to construct haplotypes in 668 AD patients and 419 controls and a case-control association study was performed. Five SNPs, comprising five common haplotypes, represented 93% of ACT gene variation. Although no single SNP or haplotype was associated with AD status, a SNP in intron 2 was associated with later onset and more rapid cognitive decline (P=0.04). This SNP was both individually associated with severe astrocytosis (P=0.004) in AD patients and when combined with the signal sequence SNP (P=0.002). This suggests that astrocytosis may have a protective function for a limited period in some patients. These SNP associations either support a direct role for the ACT gene, in AD pathology or alternatively reflect linkage with polymorphisms in other genes nearby.

ERCC1 mRNA levels and survival of advanced gastric cancer patients treated with a modified FOLFOX regimen

Molecular markers involved in DNA repair can help to predict survival in gastric cancer patients treated with 5-FU plus platinum chemotherapy. Excision repair cross-complementing 1 (ERCC1) and thymidylate synthase (TS) mRNA expression levels were assessed in advanced gastric cancer tumour samples using real-time quantitative PCR in 76 patients treated with a modified FOLFOX (biweekly oxaliplatin plus 5-FU and folinic acid) regimen. Median survival time in patients with low ERCC1 levels was significantly longer than in those with high levels (15.8 vs 6.2 months; P<0.0001). Patients with high TS levels had longer survival than those with low levels (12.2 vs 10.1 months; P=0.01). Forty-eight patients with low ERCC1 and high TS levels had a median survival of 16.1 months (P<0.0001). The hazard ratio for patients with high ERCC1 expression was 9.4 (P<0.0001). In patients with high mRNA levels of ERCC1, alternative chemotherapy regimens should be considered.

Cell-specific effects of insulin receptor substrate-1 deficiency on normal and IGF-I-mediated colon growth

Insulin-like growth factor I (IGF-I) potently stimulates intestinal growth. Insulin receptor substrate-1 (IRS-1) mediates proliferative and antiapoptotic actions of IGF-I in cell lines, but its in vivo relevance in intestine is not defined. This study tested the hypothesis that there is cell type-specific dependence on IRS-1 as a mediator of IGF-I action. Length, mass, crypt cell proliferation, and apoptosis were measured in small intestine and colon of IRS-1-null mice and wild-type (WT) littermates and in colon of IRS-1-null or WT mice expressing IGF-I transgenes. Expression of IGF-I receptor and signaling intermediates was examined in intestine of WT and IRS-1-null mice, cultured intestinal epithelial cells, and myofibroblasts. Absolute IRS-1 deficiency reduced mucosal mass in jejunum and colon, but effects were more pronounced in colon. Muscularis mass was decreased in both segments. In IGF-I transgenics, IRS-1 deficiency significantly attenuated IGF-I-stimulated growth of colonic mucosa and abolished antiapoptotic but not mitogenic effects of IGF-I transgene on crypt cells. IGF-I-induced muscularis growth was unaffected by IRS-1 deficiency. In intestinal epithelial cells, IRS-1 was expressed at higher levels than IRS-2 and was preferentially activated by IGF-I. In contrast, IGF-I activated both IRS-1 and IRS-2 in intestinal myofibroblasts and IRS-2 activation was upregulated in IRS-1-null myofibroblasts. We conclude that the intestinal epithelium but not the muscularis requires IRS-1 for normal trophic actions of IGF-I and that IRS-1 is required for antiapoptotic but not mitogenic effects of IGF-I in the intestinal crypts in vivo.

Blood characteristics for high altitude adaptation in Tibetan chickens

Tibetan chickens, a unique chicken breed native to high altitude, have good adaptation to hypoxia. The experiment was conducted to determine the adaptive blood characteristics in Tibetan chickens. Fertile eggs from Tibetan and Dwarf Recessive White chickens were incubated, and the chicks were reared until 10 wk of age at low altitude (100 m) and high altitude (2,900 m). At 1 d and 2, 6, and 10 wk of age, the hematological characteristics, blood gas value, and blood volume were measured. Tibetan chickens had more red blood cells (RBC), smaller mean cell volume, lower pH and partial pressure of oxygen, and higher partial pressure of carbon dioxide at high altitude and had lower blood volume, erythrocyte volume, and plasma volume at low and high altitude than Dwarf Recessive White chickens. Tibetan chickens reared at high altitude retained a high level of RBC and a stable level of hematocrit from younger to older, but Dwarf Recessive White chickens reared at high altitude presented an increase in RBC and hematocrit values. It was concluded the adaptation was achieved in Tibetan chickens by increase in RBC and blood oxygen affinity, decrease in mean cell volume, and reducing susceptivity to hypocapnia.

Steroids and immunosuppressive agents potentiate the cytotoxicity of the EGFR inhibitor erlotinib (E) in human skin keratinocytes whereas Vit K3 exerts a protective effect: Implications for the management of the skin rash

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Background: Skin toxicity secondary to EGFR inhibitors is treated symptomatically with topical and systemic combinations of steroids, antibiotics, antihistamines, and immunosuppressive agents with variable and often unsatisfactory results. Vit K3 prevents EGFR inhibition induced by E and cetuximab in human A431 tumor cells, probably through an effect on the phosphatase (Perez-Soler, ASCO 2006). We studied the cytotoxic effects of different agents used to treat the EGFR inhibitor-mediated skin rash on human immortalized skin keratinocytes exposed to the EGFR inhibitor E as well as the potential protective effect of Vit K3. Methods: The cytotoxicity of E in the presence of non cytotoxic concentrations of hydrocortisone, minocycline, cyclosporine-A, diphenhydramine, and Vit K3 was assessed by MTT assay in human HaCat cells, a cell line derived from human basal epidermal cells. Results: E cytotoxicity was enhanced by 2–5 fold by cyclosporine A and hydrocortisone, not affected by minocycline and diphenhydramine, and reduced by 5-fold by Vit K3. Vit K3 25–50 μM induced EGFR activation and prevented E's inhibitory effect on EGFR. Conclusions: Steroids and immunosuppressive agents may potentiate the cytotoxic effect of anti-EGFR agents in the skin, thus providing a possible explanation for the erratic and mixed therapeutic results often observed with the use of these agents. Vit K3 was the only agent capable of abrogating the cytotoxic effect of E in this clinically relevant model of normal human skin. A topical formulation of Vit K3 is undergoing preclinical evaluation. Supported by NCI CA 91784 and 113630 and a grant from Hana Biosciences.

No significant financial relationships to disclose.

Blood gas, hemoglobin, and growth of Tibetan chicken embryos incubated at high altitude

Metabolism and hatchability are impaired when chicken eggs laid at sea level are incubated at high altitude. The Tibetan chicken is an excellent local poultry breed that inhabits altitudes of 2,900 m and has a hatchability of approximately 75% at that altitude. To understand how Tibetan chicken embryos develop successfully at high altitude, we compared blood gas, pH, hemoglobin concentrations and embryo mass for Tibetan chicken embryos (T) and for embryos from a dwarf breed (D) that normally is reared at sea level. The 2 breeds (T and D) and 2 incubation altitudes (2,900 m = high, H; and 100 m = low, L) were compared at 9, 12, 15, and 18 d of incubation. Embryo weights were lower for the high altitude groups (TH, DH) than for the low altitude groups at all stages of incubation. The embryo mass of TH appeared to increase more quickly than that of DH. Compared with DH, TH embryos had lower arterialized oxygen partial pressure on d 18, higher venous carbon dioxide partial pressure from d 12 to 18, and higher hemoglobin concentration and lower venous blood pH values on d 12 and 15. These findings indicate that the ability of the Tibetan chicken embryos to adapt to the high altitude may be due to the increase in hemoglobin concentration, which augments the blood oxygen-carrying capacity. In addition, the higher venous carbon dioxide partial pressure and lower venous blood pH promote unloading of oxygen from hemoglobin.

Pseudoretinoblastoma in enucleated eyes of Asian patients

INTRODUCTION

Retinoblastomas of the eye are a cause of childhood blindness and have a high rate of mortality, as well as a hereditary mode of transmission. Other conditions that mimic retinoblastomas are known as pseudoretinoblastomas, and are managed differently. Although pseudoretinoblastoma and the accuracy of retinoblastoma diagnosis have been reviewed in Caucasian patients, published studies in Asian patients are lacking. The purpose of this article is to report our experience with pseudoretinoblastomas in two major ophthalmological centres in Asia.

METHODS

A case series of 28 enucleations carried out for suspected retinoblastoma at the Singapore National Eye Centre and KK Women's and Children's Hospital, Singapore, between January 1991 and December 2002, is reported. All cases were subjected to a detailed history from parents, followed by external ocular examination, slit-lamp biomicroscopy and binocular indirect ophthalmoscopy. Ancillary studies, such as B-scan ultrasonography and computed tomography, were employed as necessary to confirm the diagnosis. Histology was obtained on all cases.

RESULTS

Of the 28 cases, 25 (89 percent) were found on histological analysis to be retinoblastomas. Three (11 percent) were pseudoretinoblastomas. There were two cases of Coat's disease and a case of presumed ocular toxocariasis. These three cases were described in detail.

CONCLUSION

Although our sample size is small, the percentage of confirmed retinoblastomas was found to be only slightly higher than that found in western countries. Our findings are consistent with their findings that Coat's disease and presumed ocular toxocariasis are the more common causes of pseudoretinoblastoma.

Topical vitamin K3 (Vit K3, Menadione) prevents erlotinib and cetuximab-induced EGFR inhibition in the skin

3036

Background: The EGFR inhibitors erlotinib and cetuximab cause skin toxicity in about 75% of patients. The occurrence of skin toxicity correlates with clinical benefit. About half the patients with skin toxicity report significant discomfort. There are currently no scientifically based or proven methods for preventing or treating effectively the skin toxicity secondary to EGFR inhibitors. Methods: We screened a number of EGFR activators and phosphatase inhibitors for their ability to abrogate EGFR inhibition secondary to erlotinib and cetuximab in A431 cells. P-EGFR expression was assessed by western blot analysis. Vit K3 was selected for further in vivo studies. The skin toxicity secondary to the topical application of Vit K3 was evaluated in nude mice. The highest non-toxic concentration was used to determine the ability of topical Vit K3 to prevent EGFR inhibition in the skin of nude mice treated with EGFR inhibitors. Results: Vit K3 was the most potent EGFR activator identified, the maximum effect being observed at concentrations of 0.1–0.5 mM. In the presence of erlotinib or cetuximab, 0.1- 0.5 mM Vit K3 completely prevented EGFR inhibition. The maximum non-toxic concentration of Vit K3 applied topically BID × 10 days to nude mice was 15 mM. At this concentration, topical Vit K3 caused P-EGFR upregulation in the skin. In animals treated with erlotinib (100 mg/kg daily × 5 days), there was no detectable P-EGFR expression in the skin not treated with topical Vit K3 whereas P-EGFR expression was completely restored in the skin treated BID x 5 days with topical Vit K3. Conclusions: Vit K3 is one of the first reported agents to prevent/reverse EGFR inhibition secondary to anti-EGFR agents. The results strongly justify the development of a topical formulation of Vit K3 to treat and prevent the cutaneous toxicity secondary to EGFR inhibitors.

[Table: see text]

Pemetrexed overcomes primary and secondary resistance to erlotinib in human non-small cell lung cancer (NSCLC) cell lines

17040

Background: Erlotinib (E) and pemetrexed (P) have proven single agent activity in advanced NSCLC after first-line chemotherapy. The presence of K-Ras or EGFR T790M mutations in NSCLC tumors has been associated with primary or secondary resistance to erlotinib. We have previously reported that sequential administration of P followed by E results in synergistic cytotoxicity in NSCLC cells that contain the wild-type EGFR gene. In this study, we evaluate the cytotoxic effects of E and P in E-resistant human NSCLC cell lines that have either EGFR or K-Ras mutations and validate predictive biomarkers for drug sensitivity. Methods: E-resistant NSCLC cell lines [H1650 (EGFRdel E746-A750), H1975 (EGFRL858R/T790M), and A549 (K-RasG12S)] were exposed to E and P continuously for 72 hrs. Combinations of E and P were compared with E or P alone. Cellular effects assayed include cell survival by cell count and MTT assay, cell cycle distribution and apoptosis by flow cytometry after propidium iodide staining, and expression of different elements of the EGFR axis by immunoblots. The degree of cytotoxic synergism was expressed by the combination index (C.I.). Results: P and E have significant cytotoxic synergism (C.I. <1) in these E-resistant NSCLC cell lines. The cytotoxic synergism is, at least in part, mediated by the inhibitory effect of E on the P-induced activation of EGFR-mediated proliferation and/or survival responses (mainly via the PI3K/AKT pathway). Sensitivity of NSCLC cells to P and E might be predicted by the ratio of (p-EGFR:EGFR) to (p-AKT:AKT), reflecting tumor dependency on the EGFR axis for growth and survival. Conclusions: Together with our previous data, we have demonstrated that the combination of P and E is synergistic in E-resistant NSCLC cell lines that have either a wild-type or mutant EGFR gene, or a mutant K-Ras gene. This combination deserves further evaluation in a clinical trial for the treatment of advanced NSCLC.

No significant financial relationships to disclose.

Regeneration of dystrophin-expressing myocytes in the mdx heart by skeletal muscle stem cells

Cell transplantation holds promise as a potential treatment for cardiac dysfunction. Our group has isolated populations of murine skeletal muscle-derived stem cells (MDSCs) that exhibit stem cell-like properties. Here, we investigated the fate of MDSCs after transplantation into the hearts of dystrophin-deficient mdx mice, which model Duchenne muscular dystrophy (DMD). Transplanted MDSCs generated large grafts consisting primarily of numerous dystrophin-positive myocytes and, to a lesser degree, dystrophin-negative non-myocytes that expressed an endothelial phenotype. Most of the dystrophin-positive myocytes expressed a skeletal muscle phenotype and did not express a cardiac phenotype. However, some donor myocytes, located at the graft-host myocardium border, were observed to express cardiac-specific markers. More than half of these donor cells that exhibited a cardiac phenotype still maintained a skeletal muscle phenotype, demonstrating a hybrid state. Sex-mismatched donors and hosts revealed that many donor-derived cells that acquired a cardiac phenotype did so through fusion with host cardiomyocytes. Connexin43 gap junctions were not expressed by donor-derived myocytes in the graft. Scar tissue formation in the border region may inhibit the fusion and gap junction connections between donor and host cells. This study demonstrates that MDSC transplantation warrants further investigation as a potential therapy for cardiac dysfunction in DMD.