Cardiovascular Autonomic Neuropathy and Risk of Kidney Function Decline in Type 1 and Type 2 Diabetes: Findings From the PERL and ACCORD Cohorts

Results of previous studies have suggested that cardiovascular autonomic neuropathy (CAN) may predict rapid kidney function decline among people with diabetes. We analyzed the association between baseline CAN and subsequent glomerular filtration rate (GFR) decline among individuals with type 1 diabetes (T1D) from the Preventing Early Renal Loss in Diabetes (PERL) study (N = 469) and with type 2 diabetes (T2D) from Action to Control Cardiovascular Risk in Diabetes (ACCORD) (N = 7,973). Baseline CAN was ascertained with electrocardiogram-derived heart rate variability indices. Its association with GFR slopes, rapid kidney function decline (GFR loss of ≥5 mL/min/1.73 m2/year), and ≥40% GFR loss was evaluated by linear mixed-effects, logistic, and Cox regression, respectively. Participants with CAN experienced more rapid GFR decline, by an excess 1.15 mL/min/1.73 m2/year (95% CI -1.93 to -0.37; P = 4.0 × 10-3) in PERL and 0.34 mL/min/1.73 m2/year (95% CI -0.49 to -0.19; P = 6.3 × 10-6) in ACCORD. This translated to 2.11 (95% CI 1.23-3.63; P = 6.9 × 10-3) and 1.39 (95% CI 1.20-1.61; P = 1.1 × 10-5) odds ratios of rapid kidney function decline in PERL and ACCORD, respectively. Baseline CAN was also associated with a greater risk of ≥40% GFR loss events during follow-up (hazard ratio 2.60 [95% CI 1.15-5.45], P = 0.02, in PERL and hazard ratio 1.54 [95% CI 1.28-1.84], P = 3.8 × 10-6, in ACCORD). These associations remained significant after adjustment for potential confounders, including baseline GFR and albuminuria. Our findings indicate that CAN is a strong, independent predictor of rapid kidney function decline in both T1D and T2D. Further studies of the link between these two complications may help with development of new therapies to prevent kidney function decline in patients with diabetes.

ARTICLE HIGHLIGHTS

Correlation of Iron Status and Micronutrients With Anaemia of Childhood Haematopoietic Malignancies: A Study From Northern India

BACKGROUND

Most cancer patients undergoing chemotherapy develop anemia during their course of treatment. There is a need for early treatment for chemotherapy-induced anemia to prevent morbidity and mortality.

MATERIAL AND METHOD

This is a hospital-based study, conducted over one year and included 59 children who are known cases of hematological malignancy aged up to 18 years. Standard methods were used to measure micronutrients and complete blood count. Statistical analysis was done using SPSS for Windows, Version 15.0 (Released 2006; SPSS Inc., Chicago, United States).

RESULTS

The majority of subjects (n=21; 35.6%) were aged six to nine years with male dominance. Micronutrient deficiency and significant anemia were noted in 40-50% and 64.4% of cases, respectively. Both malignancy and blood indices showed no association with micronutrients.

CONCLUSION

Anemia with micronutrient deficiency is common in children with hematopoietic malignancies receiving chemotherapy. However, no significant association was noted between red cell indices and levels of micronutrients.

Clinical Correlation and Role of Cyclin D1 Expression in Glioblastoma Patients: A Study From North India

Background/Aims

Glioblastoma multiforme (GBM) is the most aggressive primary brain tumor. Cyclin D1 is a protein that in humans is encoded by the CCND1 gene. Cyclin D1 protein is frequently overexpressed in malignant gliomas.

Methods

It is an observational study comprising 40 biopsy-proven cases of GBM in a span of one and half years. Immunohistochemistry (IHC) was used with Cyclin D1 monoclonal antibody. Cyclin D1 on the outcome was assessed using the Kaplan-Meier survival estimate and compared by log-rank test.

Results

Cyclin D1 was expressed in 60% of patients. The majority (72.5%) of patients expired during the study period, out of which 69% showed immune-expression in contrast to living subjects, out of which only 45.5% of patients exhibited expression. The maximum number of glioblastoma patients were aged between 41 and 50 years (40%), followed by those aged between 31 and 40 years (20%). The male to female ratio of study subjects was 3.44:1.

Conclusion

The study concluded that there is no significant association between Cyclin D1 expression status and different demographic, clinical, and outcome variables.

123. Treatment Patterns and Prevalence of Inappropriate and Suboptimal Antibiotic Use Among Females with Uncomplicated Urinary Tract Infection in the US

Background

Urinary tract infections (UTIs) are the most common bacterial infection requiring medical care. Despite Infectious Diseases Society of America (IDSA) 2011 guidelines on antimicrobial agent selection and duration of therapy for uncomplicated UTI (uUTI), prescribing practices vary. Few studies have used real-world data (RWD) to evaluate inappropriate and suboptimal antibiotic use among patients treated for uUTI. We examined the prevalence of potentially inappropriate and suboptimal use of antibiotics among females with uUTI.

Methods

This retrospective cohort study examined the first-line use of antibiotics in females (age ≥ 12 years) with diagnosed uUTI in the US, identified using RWD from IBM MarketScan (commercial and Medicare claims) Jan 1, 2013–Dec 31, 2017. Index date was the date of uUTI diagnosis. Patients were included based on criteria in Table 1 and assigned to one of two groups: appropriate and optimal; or inappropriate or suboptimal antibiotic use. As uUTI is often treated empirically, appropriate use was defined based on IDSA 2011 guidelines on drug class, dose and therapy duration; antibiotic use was considered suboptimal if there was evidence of treatment failure (Table 2).

Table 1. Key inclusion and exclusion criteria

Results

In total, 557,669 patients with uUTI were included in the study; see Table 3 for baseline characteristics. Overall, 88.7% had inappropriate or suboptimal antibiotic use (Table 4). Of these, 86.1% had inappropriate use only, 2.1% had suboptimal use only, and 11.9% had both. Inappropriate drug class assignment was observed in 53.4% of patients with inappropriate use, 83.7% of whom were administered fluoroquinolones (a second-line agent) as first-line therapy. Among patients with inappropriate therapy duration: most given trimethoprim/sulfamethoxazole received 5- (27.2%), 7- (42.1%) or 10- (27.8%) days’ supply rather than the recommended 3 days; the majority given nitrofurantoin were provided a 7- (80.5%) or 10- (13.4%) day supply rather than the recommended 5 days; and 46.2% given fosfomycin received 3-days’ supply instead of the recommended 1 day.

Table 3. Baseline characteristics

Conclusion

In the treatment of uUTI, the prevalence of inappropriate and/or suboptimal antibiotic use is very high which may have subsequent implications for patient health outcomes.

Disclosures

Yuexi Wang, M.Econ, GlaxoSmithKline plc. (Other Financial or Material Support, Funding)STATinMED Research (Employee) Fanny S. Mitrani-Gold, MPH, GlaxoSmithKline plc. (Employee, Shareholder) Lin Xie, MS, MA, GlaxoSmithKline plc. (Other Financial or Material Support, Funding)STATinMED Research (Employee) Mamta Jaiswal, PhD, GlaxoSmithKline plc. (Other Financial or Material Support, Funding)STATinMED Research (Employee) Xiaoxi Sun, MA, GlaxoSmithKline plc. (Other Financial or Material Support, Funding)STATinMED Research (Employee) Ashish V. Joshi, PhD, GlaxoSmithKline plc. (Employee, Shareholder)

Morphology of enteric glia in colorectal carcinoma: A comparative study of tumor site and its proximal normal margin

OBJECTIVE

Colorectal carcinoma (CRC) is the third most common cancer in the world and fifth most common cancer in India. To understand the extent of perineural invasion (PNI) in CRC it is essential to study the morphology of enteric glial cells (EGCs). The aim of the study was to analyze the numerical density of EGCs and area of myenteric ganglia (MG) in the colonic tissue samples collected from CRC patients.

MATERIAL AND METHODS

Fifteen intraoperative tissue specimens were collected from the tumor site and 2cm proximal to the upper extent of tumor. The samples were divided into four groups: group 1 (n=15): proximal tumor free colonic tissue; group 2 (n=3): well-differentiated; group 3 (n=8): moderately differentiated; group 4 (n=4): poorly differentiated adenocarcinoma. After processing the tissues were subjected to hematoxylin and eosin staining. The anti-S100β and anti-GFAP antibodies were used to observe the EGCs.

RESULTS

In the H&E stained sections the number of myenteric ganglia appeared to be decreasing with increasing grade of adenocarcinoma. Immunostaining showed significant decreasing pattern in the numerical density of EGCs per myenteric ganglion and mean area of myenteric ganglia in relation to the thickness of circular muscle, corresponding to the increasing grades of adenocarcinoma. The morphology of the EGCs remained unaltered in the colonic tissue adjacent to the tumor site.

CONCLUSION

Significant loss of EGCs and neurodegeneration corresponded with the grade of tumor emphasizing on its prognostic value. The PNI was not seen in the clear margin proximal to the tumor site.

Cardiovascular risk and heart rate variability in young adults with type 2 diabetes and arterial stiffness: The SEARCH for Diabetes in Youth Study

AIMS

To evaluate cardiovascular risk factors and heart rate variability (HRV) in young adults with type 2 diabetes and arterial stiffness and to explore the relationship between HRV and arterial stiffness.

METHODS

We studied 185 young adults with youth-onset T2D enrolled in the SEARCH for Diabetes in Youth Study. Cardiovascular risk factors and HRV were compared between individuals with and without type 2 diabetes and arterial stiffness (defined as a pulse wave velocity greater than the 90th percentile of healthy controls, >6.767 m/s). Semiparametric regression evaluated the independent relationship between HRV and PWV.

RESULTS

Participants with T2D and arterial stiffness were more likely to be older, non-Hispanic Black, have higher systolic and diastolic blood pressure, greater adiposity and obesity-related dyslipidemia (higher triglycerides and lower HDLC). Participants with T2D and arterial stiffness also had lower overall HRV (lower SDNN) with parasympathetic loss (lower RMSSD and PNN50), p < 0.05. Lower HRV tended to be but was not significantly associated with arterial stiffness after adjustment for age, race/ethnicity, sex and cardiovascular risk factors (beta coefficient = -1.11, p = 0.08).

CONCLUSIONS

Youth with T2D and arterial stiffness have a worse cardiovascular risk profile, specifically risk factors related to the metabolic syndrome and lower HRV.

Impaired Amino Acid and TCA Metabolism and Cardiovascular Autonomic Neuropathy Progression in Type 1 Diabetes

While diabetes is characterized by hyperglycemia, nutrient metabolic pathways like amino acid and tricarboxylic acid (TCA) cycle are also profoundly perturbed. As glycemic control alone does not prevent complications, we hypothesized that these metabolic disruptions are responsible for the development and progression of diabetic cardiovascular autonomic neuropathy (CAN). We performed standardized cardiovascular autonomic reflex tests and targeted fasting plasma metabolomic analysis of amino acids and TCA cycle intermediates in subjects with type 1 diabetes and healthy control subjects followed for 3 years. Forty-seven participants with type 1 diabetes (60% female and mean ± SD age 35 ± 13 years, diabetes duration 13 ± 7 years, and HbA_1c 7.9 ± 1.2%) had lower fumarate levels and higher threonine, serine, proline, asparagine, aspartic acid, phenylalanine, tyrosine, and histidine levels compared with 10 age-matched healthy control subjects. Higher baseline fumarate levels and lower baseline amino acid levels-asparagine and glutamine-correlate with CAN (lower baseline SD of normal R-R interval [SDNN]). Baseline glutamine and ornithine levels also associated with the progression of CAN (lower SDNN at 3 years) and change in SDNN, respectively, after adjustment for baseline HbA_1c, blood glucose, BMI, cholesterol, urine microalbumin-to- creatinine ratio, estimated glomerular filtration rate, and years of diabetes. Therefore, significant changes in the anaplerotic flux into the TCA cycle could be the critical defect underlying CAN progression.

Therapeutic Lifestyle Changes Improve HDL Function by Inhibiting Myeloperoxidase-Mediated Oxidation in Patients With Metabolic Syndrome

OBJECTIVE

Phagocyte-derived myeloperoxidase (MPO) and proinflammatory HDL are associated with metabolic syndrome (MetS) and increased cardiovascular disease risk. Therapeutic lifestyle changes (TLCs), such as a Mediterranean diet and exercise, decrease this risk. However, the link among TLCs, HDL, and MPO-mediated oxidative stress remains unclear.

RESEARCH DESIGN AND METHODS

In this study, we characterized changes in cholesterol efflux capacity (CEC), a metric of HDL function; MPO-mediated oxidation; and the HDL proteomic profile in 25 patients with MetS who underwent 12 weeks of TLCs.

RESULTS

After 12 weeks, before significant changes to HDL levels, most MetS components improved as a result of the TLCs. CEC was significantly increased, and HDL MPO oxidation products, 3-chlorotyrosine and 3-nitrotyrosine, were decreased with TLCs. The changes in CEC were inversely related to the unit changes in 3-chlorotyrosine after we controlled for changes in the other MetS components. TLCs did not remodel the HDL proteome.

CONCLUSIONS

In summary, TLCs improved HDL function by inhibiting MPO-mediated oxidative stress even before appreciable changes in HDL levels.

Is there an association between non-dipping blood pressure and measures of glucose variability in type 1 diabetes?

AIM

To assess the relationship between glucose variability (GV) and non-dipping of blood pressure (BP) as a marker of cardiovascular autonomic neuropathy (CAN) among patients with type 1 diabetes (T1D).

METHODS

Forty-one subjects with T1D (age 34 ± 13 years, duration 13 ± 6 years, HbA1c 8 ± 1.2%) without cardiovascular disease, dyslipidemia, or hypertension at baseline were enrolled in a 3-year observational cohort study. Subjects were phenotyped for CAN with heart rate variability, cardiovascular autonomic reflex tests, and 24-h BP profiles at baseline and during follow-up. Non-dipping was defined as nocturnal systolic and diastolic BP fall of ≤10%. Reverse dipping BP was defined as a <0% change in the day to night for systolic and diastolic BP. Indices of GV were derived from 5-day continuous glucose monitoring obtained at 3-month intervals, and serum inflammatory biomarkers in all subjects.

RESULTS

At baseline 10% of the T1D subjects were non-dippers. The dippers and non-dippers were similar in age, diabetes duration, glucose control, traditional cardiovascular risk factors, GV and inflammatory markers. No significant correlations were found at baseline between non-dipping nocturnal blood pressure and measures of GV. At 3 years there were no differences in risk factor profile of subjects who were non-dippers over time (progressors) and those who were dippers (non-progressors).

CONCLUSION

In a cohort of contemporary patients with T1D following the current standard of care in diabetes, the prevalence of non-dipping is relatively low. There were no clear phenotypes that explained the difference in the risk for non-dipping, including GV. Ambulatory blood pressure monitoring could be used as a tool for improved CVD risk stratification and development of therapeutic interventions in these patients.

Cardiovascular autonomic neuropathy in adolescents and young adults with type 1 and type 2 diabetes: The SEARCH for Diabetes in Youth Cohort Study

OBJECTIVE

To estimate the prevalence of and risk factors for cardiovascular autonomic neuropathy (CAN) in adolescents and young adults with type 1 and type 2 diabetes enrolled in the SEARCH for Diabetes in Youth Study.

METHODS

The study included 1646 subjects with type 1 diabetes (age 18 ± 4 years, diabetes duration 8 ± 2 years, HbA1c 9.1 ± 1.9%, 76% non-Hispanic Whites) and 252 with type 2 diabetes (age 22 ± 4 years, diabetes duration 8 ± 2 years, HbA1c 9.2 ± 3.0%, 45% non-Hispanic Blacks). Cross-sectional and longitudinal risk factors were assessed at baseline and follow-up visits. Area under the curve (AUC) was used to assess the longitudinal glycemic exposure and cardiovascular risk factors. CAN was assessed by time and frequency domain indices of heart rate variability (HRV). CAN was defined as the presence of ≥3 of 5 abnormal HRV indices.

RESULTS

The prevalence of CAN was 12% in adolescents and young adults with type 1 diabetes and 17% in those with type 2 diabetes. Poor long-term glycemic control (AUC HbA1c), high blood pressure, and elevated triglyceride levels were correlates of CAN in subjects with type 1 diabetes. In those with type 2 diabetes, CAN was associated with elevated triglycerides and increased urinary albumin excretion.

CONCLUSIONS

The prevalence of CAN in this multiethnic cohort of adolescents and young adults with type 1 and type 2 diabetes are comparable to those reported in adults with diabetes. Suboptimal glycemic control and elevated triglycerides were the modifiable risk factors associated with CAN.

Structured lifestyle intervention in patients with the metabolic syndrome mitigates oxidative stress but fails to improve measures of cardiovascular autonomic neuropathy

AIMS

To assess the role of oxidative stress in mediating adverse outcomes in metabolic syndrome (MetS) and resultant cardiovascular autonomic neuropathy (CAN), and to evaluate the effects of lifestyle interventions on measures of oxidative stress and CAN in subjects with MetS.

METHODS

Pilot study in 25 non-diabetic subjects with MetS (age 49±10years, 76% females) participating in a 24-week lifestyle intervention (supervised aerobic exercise/Mediterranean diet), and 25 age-matched healthy controls. CAN was assessed by cardiovascular reflex tests, heart rate variability (HRV) and PET imaging with sympathetic analog [¹¹C] meta-hydroxyephedrine ([¹¹C]HED). Specific oxidative fingerprints were measured by liquid-chromatography/mass-spectrometry (LC/MS).

RESULTS

At baseline, MetS subjects had significantly higher oxidative stress markers [3-nitrotyrosine (234±158 vs. 54±47μmol/mol tyrosine), ortho-tyrosine (59±38 vs. 18±10μmol/molphenylalanine, all P<0.0001], and impaired HRV at rest and during deep breathing (P=0.039 and P=0.021 respectively) compared to controls. Twenty-four-week lifestyle intervention significantly reduced all oxidative stress markers (all P<0.01) but did not change any of the CAN measures.

CONCLUSIONS

Subjects with MetS present with signs of CAN and increased oxidative stress in the absence of diabetes. The 24-week lifestyle intervention was effective in ameliorating oxidative stress, but did not improve measures of CAN. Larger clinical trials with longer duration are required to confirm these findings.

Prevalence of and Risk Factors for Diabetic Peripheral Neuropathy in Youth With Type 1 and Type 2 Diabetes: SEARCH for Diabetes in Youth Study

OBJECTIVE

We assessed the prevalence of and risk factors for diabetic peripheral neuropathy (DPN) in youth with type 1 diabetes (T1D) and type 2 diabetes (T2D) enrolled in the SEARCH for Diabetes in Youth (SEARCH) study.

RESEARCH DESIGN AND METHODS

The Michigan Neuropathy Screening Instrument (MNSI) was used to assess DPN in 1,734 youth with T1D (mean ± SD age 18 ± 4 years, T1D duration 7.2 ± 1.2 years, and HbA_1c 9.1 ± 1.9%) and 258 youth with T2D (age 22 ± 3.5 years, T2D duration 7.9 ± 2 years, and HbA_1c 9.4 ± 2.3%) who were enrolled in the SEARCH study and had ≥5 years of diabetes duration. DPN was defined as an MNSI exam score of >2. Glycemic control over time was estimated as area under the curve for HbA_1c.

RESULTS

The prevalence of DPN was 7% in youth with T1D and 22% in youth with T2D. Risk factors for DPN in youth with T1D were older age, longer diabetes duration, smoking, increased diastolic blood pressure, obesity, increased LDL cholesterol and triglycerides, and lower HDL cholesterol (HDL-c). In youth with T2D, risk factors were older age, male sex, longer diabetes duration, smoking, and lower HDL-c. Glycemic control over time was worse among those with DPN compared with those without for youth with T1D (odds ratio 1.53 [95% CI 1.24; 1.88]) but not for youth with T2D (1.05 [0.7; 1.56]).

CONCLUSIONS

The high rates of DPN among youth with diabetes are a cause of concern and suggest a need for early screening and better risk factor management. Interventions in youth that address poor glycemic control and dyslipidemia may prevent or delay debilitating neuropathic complications.

Sudomotor dysfunction as a measure of small fiber neuropathy in type 1 diabetes

BACKGROUND

This study evaluated whether measuring the electrochemical skin conductance (ESC), as an indirect measure of sudomotor function, may be also a reliable surrogate for early cardiovascular autonomic neuropathy (CAN).

METHODS

Longitudinal study included 37 type 1 diabetes (T1D) subjects (mean age 38±13years, duration 15±7years, HbA1c 7.9±1.1%, no known complications at baseline), and 40 age-matched healthy control (HC) subjects. Mean hands ESC (ESChands) and feet (ESCfeet) were measured with the SUDOSCAN (Impeto Medical, France). CAN was assessed with heart rate variability (HRV) studies (ANSAR Inc., PA), cardiovascular autonomic reflex tests (deep-breathing, Valsalva, postural test), and positron emission tomography with sympathetic analogue [11C]meta-hydroxyephedrine. Associations between measures of CAN and ESC were estimated using Spearman correlations. Longitudinal changes were analyzed using paired t-test.

RESULTS

At baseline, there were no differences between T1D and HC in ESChands (69±14 vs. 69±13μS; P=0.84) or ESCfeet (82±8 vs. 78±9μS; P=0.12), while some indices of HRV and Valsalva ratio were significantly lower in T1D vs. HC. T1D subjects experienced a significant decline in both ESChands and ESCfeet at 12months (mean change -7.2±11.6µS, P=0.0006; -2.8±7.3µS, P=0.023 respectively). No significant correlations were consistently found between ESC and measures of CAN at baseline or at 12months.

CONCLUSION

Comparing patients with T1D to controls, no differences in ESC were observed at baseline. The associations between ESC and established measures of CAN were inconsistent, which does not support ESC as a reliable surrogate for CAN. While both hands and feet ESC declined over time, the significance of this finding is unclear and warrants further reliability testing.

Left ventricular metabolism, function, and sympathetic innervation in men and women with type 1 diabetes

BACKGROUND

In type I diabetes (T1DM), alterations in LV function may occur due to changes in innervation, metabolism, and efficiency.

OBJECTIVES

We evaluated the association between sympathetic nerve function, oxidative metabolism, resting blood flow, LV efficiency and function in healthy diabetics, and assessed gender differences.

METHODS

Cross-sectional study of 45 subjects with T1DM, 60% females, age 34 ± 13 years, and 10 age-matched controls. Positron emission tomography (PET) imaging with [(11)C]acetate and [(11)C]meta-hydroxyephedrine was performed, in addition to cardiac magnetic resonance imaging.

RESULTS

There were no significant differences in LV function, innervation, or oxidative metabolism between T1DM and controls. Cardiac oxidative metabolism was positively associated with higher levels of sympathetic activation, particularly in women. Diabetic women had significantly lower efficiency compared with diabetic men. Resting flow was significantly higher in diabetic women compared with diabetic men, and tended to be higher in female controls as well.

CONCLUSIONS

Measures of myocardial function, metabolism, blood flow, and sympathetic activation were preserved in young, otherwise healthy, T1DM patients. However, T1DM women presented with greater myocardial oxidative metabolism requirements than men. Ongoing studies are evaluating changes over time.

Deciphering the Molecular and Functional Basis of RHOGAP Family Proteins: A SYSTEMATIC APPROACH TOWARD SELECTIVE INACTIVATION OF RHO FAMILY PROTEINS

RHO GTPase-activating proteins (RHOGAPs) are one of the major classes of regulators of the RHO-related protein family that are crucial in many cellular processes, motility, contractility, growth, differentiation, and development. Using database searches, we extracted 66 distinct human RHOGAPs, from which 57 have a common catalytic domain capable of terminating RHO protein signaling by stimulating the slow intrinsic GTP hydrolysis (GTPase) reaction. The specificity of the majority of the members of RHOGAP family is largely uncharacterized. Here, we comprehensively investigated the sequence-structure-function relationship between RHOGAPs and RHO proteins by combining our in vitro data with in silico data. The activity of 14 representatives of the RHOGAP family toward 12 RHO family proteins was determined in real time. We identified and structurally verified hot spots in the interface between RHOGAPs and RHO proteins as critical determinants for binding and catalysis. We have found that the RHOGAP domain itself is nonselective and in some cases rather inefficient under cell-free conditions. Thus, we propose that other domains of RHOGAPs confer substrate specificity and fine-tune their catalytic efficiency in cells.

Novel Biochemical and Structural Insights into the Interaction of Myristoylated Cargo with Unc119 Protein and Their Release by Arl2/3

Primary cilia are highly specialized small antenna-like cellular protrusions that extend from the cell surface of many eukaryotic cell types. The protein content inside cilia and cytoplasm is very different, but details of the sorting process are not understood for most ciliary proteins. Recently, we have shown that prenylated proteins are sorted according to their affinity to the carrier protein PDE6δ and the ability of Arl3 but not Arl2 to release high affinity cargo inside the cilia (Fansa, E. K., Kösling, S. K., Zent, E., Wittinghofer, A., and Ismail, S. (2016) Nat. Commun. 7, 11366). Here we address the question whether a similar principle governs the transport of myristoylated cargo by the carrier proteins Unc119a and Unc119b. We thus analyzed the binding strength of N-terminal myristoylated cargo peptides (GNAT1, NPHP3, Cystin1, RP2, and Src) to Unc119a and Unc119b proteins. The affinity between myristoylated cargo and carrier protein, Unc119, varies between subnanomolar and micromolar. Peptides derived from ciliary localizing proteins (GNAT1, NPHP3, and Cystin1) bind with high affinity to Unc119 proteins, whereas a peptide derived from a non-ciliary localizing protein (Src) has low affinity. The peptide with intermediate affinity (RP2) is localized at the ciliary transition zone as a gate keeper. We show that the low affinity peptides are released by both Arl2·GppNHp and Arl3·GppNHp, whereas the high affinity peptides are exclusively released by only Arl3·GppNHp. Determination of the x-ray structure of myristoylated NPHP3 peptide in complex with Unc119a reveals the molecular details of high affinity binding and suggests the importance of the residues at the +2 and +3 positions relative to the myristoylated glycine for high and low affinities. The mutational analysis of swapping the residues at the +2 and +3 positions between high and low affinity peptides results in reversing their affinities for Unc119a and leads to a partial mislocalization of a low affinity mutant of NPHP3.

Cardiovascular autonomic neuropathy associates with nephropathy lesions in American Indians with type 2 diabetes

AIMS

Cardiovascular autonomic neuropathy (CAN) predicts clinical diabetic nephropathy (DN). We investigated the relationship between DN structural lesions and CAN.

METHODS

Sixty three Pima Indians with type 2 diabetes underwent kidney biopsies following a 6-year clinical trial testing the renoprotective efficacy of losartan vs. placebo. CAN was assessed a median 9.2years later. CAN variables included expiration/inspiration ratio (E/I), standard deviation of the normal R-R interval (sdNN), and low and high frequency signal power and their ratio (LF, HF, LF/HF); lower values reflect more severe neuropathy. Associations of CAN with renal structural variables were assessed by linear regression adjusted for age, sex, diabetes duration, blood pressure, HbA1c, glomerular filtration rate, and treatment assignment during the trial.

RESULTS

Global glomerular sclerosis was negatively associated with sdNN (partial r=-0.35, p=0.01) and LF (r=-0.32, p=0.02); glomerular basement membrane width was negatively associated with all measures of CAN except for LF/HF (r=-0.28 to -0.42, p<0.05); filtration surface density was positively associated with sdNN, LF, and HF (r=0.31 to 0.38, p<0.05); and cortical interstitial fractional volume was negatively associated with HF (r=-0.27, p=0.04).

CONCLUSIONS

CAN associates with DN lesions.

Effects of exenatide on measures of diabetic neuropathy in subjects with type 2 diabetes: results from an 18-month proof-of-concept open-label randomized study

OBJECTIVE

Experimental studies have reported potential benefit of glucagon-like peptide-1(GLP-1) receptor agonists in preventing diabetic peripheral neuropathy (DPN). We therefore performed a proof-of-concept pilot study to evaluate the effect of exenatide, a GLP-1 agonist, on measures of DPN and cardiovascular autonomic neuropathy (CAN) in patients with type 2 diabetes (T2D).

RESEARCH DESIGN AND METHODS

Forty-six T2D subjects (age 54±10years, diabetes duration 8±5years, HbA1c 8.2±1.3%) with mild to moderate DPN at baseline were randomized to receive either twice daily exenatide (n=22) or daily insulin glargine (n=24). The subjects, with similar HbA1c levels, were followed for 18months. The primary end point was the prevalence of confirmed clinical neuropathy (CCN). Changes in measures of CAN, other measures of small fiber neuropathy such as intra-epidermal nerve fiber density (IENFD), and quality of life were also analyzed.

RESULTS

Glucose control was similar in both groups during the study. There were no statistically significant treatment group differences in the prevalence of CCN, IENFD, measures of CAN, nerve conductions studies, or quality of life indices.

CONCLUSIONS

In this pilot study of patients with T2D and mild to moderate DPN, 18months of exenatide treatment had no significant effect on measures of neuropathy compared with glargine treatment.

Specificity of Lipoprotein Chaperones for the Characteristic Lipidated Structural Motifs of their Cognate Lipoproteins

Lipoprotein-binding chaperones mediate intracellular transport of lipidated proteins and determine their proper localisation and functioning. Understanding of the exact structural parameters that determine recognition and transport by different chaperones is of major interest. We have synthesised several lipid-modified peptides, representative of different lipoprotein classes, and have investigated their binding to the relevant chaperones PDEδ, UNC119a, UNC119b, and galectins-1 and -3. Our results demonstrate that PDEδ recognises S-isoprenylated C-terminal peptidic structures but not N-myristoylated peptides. In contrast, UNC119 proteins bind only mono-N-myristoylated, but do not recognise doubly lipidated and S-isoprenylated peptides at the C terminus. For galectins-1 and -3, neither binding to N-acylated, nor to C-terminally prenylated peptides could be determined. These results shed light on the specificity of the chaperone-mediated cellular lipoprotein transport systems.

New insight into the molecular switch mechanism of human Rho family proteins: shifting a paradigm

Major advances have been made in understanding the structure, function and regulation of the small GTP-binding proteins of the Rho family and their involvement in multiple cellular process and disorders. However, intrinsic nucleotide exchange and hydrolysis reactions, which are known to be fundamental to Rho family proteins, have been partially investigated in the case of RhoA, Rac1 and Cdc42, but for others not at all. Here we present a comprehensive and quantitative analysis of the molecular switch functions of 15 members of the Rho family that enabled us to propose an active GTP-bound state for the rather uncharacterized isoforms RhoD and Rif under equilibrium and quiescent conditions.

Association between impaired cardiovascular autonomic function and hypoglycemia in patients with type 1 diabetes

OBJECTIVE

We studied the association between glycemic variability (GV) reflecting hypoglycemic stress and cardiovascular autonomic function in subjects with type 1 diabetes.

RESEARCH DESIGN AND METHODS

Forty-four type 1 diabetic patients (mean age 34 ± 13 years, 40% male, 86% Caucasian, mean diabetes duration 13 ± 6 years, mean hemoglobin A1c [HbA1c] 8.0 ± 1.2% [64 ± 5 mmol/mol]) without cardiovascular disease, dyslipidemia, or hypertension participated in this pilot study. Indices of GV reflective of hypoglycemic stress (low blood glucose index [LBGI] and area under the curve [AUC] for hypoglycemia) were computed using data obtained during 5-day continuous glucose monitoring. Cardiovascular autonomic neuropathy (CAN) was assessed using standardized cardiovascular reflex testing and measures of heart rate variability (HRV), which were analyzed as time and frequency domain measures.

RESULTS

Both LBGI and AUC hypoglycemia had a significant negative association with the low-frequency power of HRV (r = -0.47, P = 0.002; r = -0.43, P = 0.005, respectively) and with the high-frequency power of HRV (r = -0.37, P = 0.018; r = -0.38, P = 0.015, respectively). These inverse associations persisted after adjusting for HbA1c, although they were attenuated in multivariable analysis after adjustment for age, diabetes duration, and several other covariates.

CONCLUSIONS

Increased GV promoting hypoglycemic stress was associated with reduced HRV independent of glycemic control as assessed by HbA1c. These pilot data suggest that glucose variability may contribute to cardiovascular autonomic dysfunction among adults with type 1 diabetes.

Activating mutations in RRAS underlie a phenotype within the RASopathy spectrum and contribute to leukaemogenesis

RASopathies, a family of disorders characterized by cardiac defects, defective growth, facial dysmorphism, variable cognitive deficits and predisposition to certain malignancies, are caused by constitutional dysregulation of RAS signalling predominantly through the RAF/MEK/ERK (MAPK) cascade. We report on two germline mutations (p.Gly39dup and p.Val55Met) in RRAS, a gene encoding a small monomeric GTPase controlling cell adhesion, spreading and migration, underlying a rare (2 subjects among 504 individuals analysed) and variable phenotype with features partially overlapping Noonan syndrome, the most common RASopathy. We also identified somatic RRAS mutations (p.Gly39dup and p.Gln87Leu) in 2 of 110 cases of non-syndromic juvenile myelomonocytic leukaemia, a childhood myeloproliferative/myelodysplastic disease caused by upregulated RAS signalling, defining an atypical form of this haematological disorder rapidly progressing to acute myeloid leukaemia. Two of the three identified mutations affected known oncogenic hotspots of RAS genes and conferred variably enhanced RRAS function and stimulus-dependent MAPK activation. Expression of an RRAS mutant homolog in Caenorhabditis elegans enhanced RAS signalling and engendered protruding vulva, a phenotype previously linked to the RASopathy-causing SHOC2(S2G) mutant. Overall, these findings provide evidence of a functional link between RRAS and MAPK signalling and reveal an unpredicted role of enhanced RRAS function in human disease.

Lipids and lipid management in diabetes

Cardiovascular disease is more prevalent in type 1 and type 2 diabetes, and continues to be the leading cause of death among adults with diabetes. Although atherosclerotic vascular disease has a multi-factorial etiology, disorders of lipid metabolism play a central role. The coexistence of diabetes with other risk factors, in particular with dyslipidemia, further increases cardiovascular disease risk. A characteristic pattern, termed diabetic dyslipidemia, consists of increased levels of triglycerides, low levels of high density lipoprotein cholesterol, and postprandial lipemia, and is mostly seen in patients with type 2 diabetes or metabolic syndrome. This review summarizes the trends in the prevalence of lipid disorders in diabetes, advances in the mechanisms contributing to diabetic dyslipidemia, and current evidence regarding appropriate therapeutic recommendations.

Baseline extracellular potassium level as an indicator of the rate of increase of the same on further storage in CPDA-1 whole blood units: a potential approach to complement FIFO system for prioritisation of blood bags for release from blood-banks

BACKGROUND

Potassium levels in stored blood bags increases as they age. Hyperkalemia in transfused blood has undesirable cardiac effects.

MATERIALS AND METHODS

Within a 19-month period, baseline and weekly samples from 15 CPDA-1 whole blood bags were collected till 28 days of storage and analysed for potassium, sodium, uric acid, albumin and whole blood haemoglobin.

RESULTS

One unit increase in baseline (0 day) potassium in extracellular fluid of blood units was associated with the following increases in potassium levels on later days of storage: around two unit increase at 1 week (r2 = 0·50, P < 0·01) of storage; four units increase at 2 weeks (r2 = 0·64, P < 0·001) and 3 weeks (r2 = 0·51, P < 0·01) of storage; six units at 4 weeks (r2 = 0·53, P < 0·01) of storage. Baseline whole blood haemoglobin showed a moderate association with baseline potassium (r2 = 0·36, P < 0·05) and 2-week potassium (r2 = 0·35, P < 0·05) values.

CONCLUSION

For CPDA-1 blood bags (i) low baseline potassium blood bags might be preferred for transfusion in cases demanding a low potassium load and (ii) coordinating the ‘first-in-first-out’ (FIFO) policy with ‘early release of blood-bags with high initial potassium’ might be helpful in improving the release of suitable blood units from blood-banks.

Effect of pain in pediatric inherited neuropathies

OBJECTIVE

Assess the prevalence and impact of pain in children with Charcot-Marie-Tooth (CMT) disease.

METHODS

In this prospective cross-sectional study on children with CMT disease seen at study sites of the Inherited Neuropathy Consortium, we collected standardized assessments of pain (Wong-Baker FACES Pain Rating Scale) from 176 patients (140 children aged 8-18 years, and 36 children aged 2-7 years through parent proxies), along with standardized clinical assessments and quality-of-life (QOL) outcomes. We then developed a series of multivariate regression models to determine whether standardized measures of neuropathy severity, functional impact, or structural changes to the feet explained the observed pain scores.

RESULTS

The mean score on the Wong-Baker FACES Pain Rating Scale was 2 (range 0-5). Increased pain strongly correlated with worse QOL scores but not with more severe neuropathy. Independent determinants of increased pain in children with CMT disease included measures of ankle inflexibility.

CONCLUSION

Pain is present in children with CMT disease and negatively affects QOL. Pain scores do not positively correlate with neuropathy severity but do correlate in limited univariate analyses with measures of ankle inflexibility. Further studies to elucidate the mechanisms of pain may help identify treatments that can reduce pain and improve QOL in patients with CMT disease.

Functional cross-talk between ras and rho pathways: a Ras-specific GTPase-activating protein (p120RasGAP) competitively inhibits the RhoGAP activity of deleted in liver cancer (DLC) tumor suppressor by masking the catalytic arginine finger

The three deleted in liver cancer genes (DLC1-3) encode Rho-specific GTPase-activating proteins (RhoGAPs). Their expression is frequently silenced in a variety of cancers. The RhoGAP activity, which is required for full DLC-dependent tumor suppressor activity, can be inhibited by the Src homology 3 (SH3) domain of a Ras-specific GAP (p120RasGAP). Here, we comprehensively investigated the molecular mechanism underlying cross-talk between two distinct regulators of small GTP-binding proteins using structural and biochemical methods. We demonstrate that only the SH3 domain of p120 selectively inhibits the RhoGAP activity of all three DLC isoforms as compared with a large set of other representative SH3 or RhoGAP proteins. Structural and mutational analyses provide new insights into a putative interaction mode of the p120 SH3 domain with the DLC1 RhoGAP domain that is atypical and does not follow the classical PXXP-directed interaction. Hence, p120 associates with the DLC1 RhoGAP domain by targeting the catalytic arginine finger and thus by competitively and very potently inhibiting RhoGAP activity. The novel findings of this study shed light on the molecular mechanisms underlying the DLC inhibitory effects of p120 and suggest a functional cross-talk between Ras and Rho proteins at the level of regulatory proteins.

Glucose control and diabetic neuropathy: lessons from recent large clinical trials

Diabetic peripheral and autonomic neuropathies are common complications of diabetes with broad spectrums of clinical manifestations and high morbidity. Studies using various agents to target the pathways implicated in the development and progression of diabetic neuropathy were promising in animal models. In humans, however, randomized controlled studies have failed to show efficacy on objective measures of neuropathy. The complex anatomy of the peripheral and autonomic nervous systems, the multitude of pathogenic mechanisms involved, and the lack of uniformity of neuropathy measures have likely contributed to these failures. To date, tight glycemic control is the only strategy convincingly shown to prevent or delay the development of neuropathy in patients with type 1 diabetes and to slow the progression of neuropathy in some patients with type 2 diabetes. Lessons learned about the role of glycemic control on distal symmetrical polyneuropathy and cardiovascular autonomic neuropathy are discussed in this review.

Impact of glycemic control on heart rate variability in youth with type 1 diabetes: the SEARCH CVD study

AIM

This study explored the role of glycemic control on cardiac autonomic function, measured by heart rate variability (HRV), in youth with type 1 diabetes.

PATIENTS AND METHODS

A retrospective cohort of 345 youth with type 1 diabetes (mean age, 18.5 years; duration, 10 years) participating in the SEARCH for Diabetes in Youth study were enrolled in the ancillary SEARCH Cardiovascular Disease (CVD) study. Anthropometric, metabolic, and HRV parameters were collected at the current research visit. Glycemic control over time was assessed by the mean glycated hemoglobin (A1c) levels collected over the past 6 years. Multiple linear regression analysis assessed the association between A1c over time and HRV parameters, independent of demographic and CVD risk factors. Participants were categorized into four glycemic control categories based on their mean A1c over time: Group 1, optimal (mean A1c, ≤7.4%); Group 2 (mean A1c, 7.5-8.4%); Group 3 (mean A1c, 8.5-9.4%), and Group 4, poor (mean A1c, ≥9.5%), and a linear trend was explored across these categories.

RESULTS

For every 1% increase in the average A1c over 6 years there was a 5% decrease in the SD of the normal RR interval (SDNN) (P=0.02) and 7% decrease in the root mean square successive difference of the RR interval (RMSSD) (P=0.02), independent of demographic and traditional CVD risk factors. A dose-response relationship between worsening glucose control categories and measures of overall reduced HRV was found.

CONCLUSIONS

Chronic hyperglycemia is the main determinant of early cardiac autonomic dysfunction, manifested as reduced overall HRV and parasympathetic loss, among youth with type 1 diabetes.

Peripheral neuropathy in adolescents and young adults with type 1 and type 2 diabetes from the SEARCH for Diabetes in Youth follow-up cohort: a pilot study

OBJECTIVE

To estimate the prevalence of and risk factors for diabetic peripheral neuropathy (DPN) in a pilot study among youth participating in the SEARCH for Diabetes in Youth study.

RESEARCH DESIGN AND METHODS

DPN was assessed using the Michigan Neuropathy Screening Instrument (MNSI) (examination for foot abnormalities, distal vibration perception, and ankle reflexes). An MNSI exam (MNSIE) score >2 is diagnostic for DPN.

RESULTS

The MNSIE was completed in 399 subjects, including 329 youth with type 1 diabetes (mean age 15.7 ± 4.3 years, duration 6.2 ± 0.9 years) and 70 with type 2 diabetes (mean age 21.6 ± 4.1 years, duration 7.6 ± 1.8 years). Glycated hemoglobin (A1C) was similar in both groups (8.8 ± 1.8% for type 1 vs. 8.5 ± 2.9% for type 2). The prevalence of DPN was significantly higher in youth with type 2 compared with those with type 1 diabetes (25.7 vs. 8.2%; P < 0.0001). In unadjusted analyses, diabetes type, older age, longer duration of diabetes, increased waist circumference, elevated blood pressure, lower HDL cholesterol, and presence of microalbuminuria (urinary albumin-to-creatinine ratio >30 mg/g) were associated with DPN. The association between diabetes type and DPN remained significant after adjustment for age and sex (odds ratio 2.29 [95% CI 1.05-5.02], P = 0.03).

CONCLUSIONS

DPN prevalence among youth with type 2 diabetes approached rates reported in adult populations with diabetes. Our findings suggest not only that youth with diabetes are at risk for DPN but also that many already show measurable signs of DPN.

Depression among undergraduate medical students

BACKGROUND

Psychological stress is common in medical school and associated with depression. Medical education is grooming in Nepal, but only few studies are done concerning mental health of medical students.

OBJECTIVE

To assess the prevalence of depression among medical students at different levels of education and find about their stressors.

METHODS

A cross sectional, questionnaire-based survey was carried out among the undergraduate medical students of B.P.Koirala Institute of Health Sciences, Nepal. 50 students each from Bachelor of Medicine and Bachelor of Surgery (MBBS) first and third year were enrolled in the study conducted between November 2008 to January 2009. The depression levels were assessed using Zung depression scale. Students were asked to complete the questionnaire and then the depression levels calculated .The stress inducing factors during their course of medical education were also assessed.

RESULTS

The overall prevalence of depression among the students was 29.78 percent. The prevalence of depression in first and third year was 36.74and 22.22 percent respectively. The prevalence of depression was 32.43 percent among female students versus 28.07 percent in male students. Both first and third year students gave high ratings to academic stress and hectic lifestyle as the main stress inducing factors.

CONCLUSION

The prevalence of depression is seen especially in the first year medical students. So, attempts should be made to alleviate the stressors right from the time they join medical school. Since academic stress proved to be one of the major factors, measures to make the academic curriculum more student-friendly are suggested.

Reduced heart rate variability is associated with increased arterial stiffness in youth with type 1 diabetes: the SEARCH CVD study

OBJECTIVE

Reduced heart rate variability (HRV) and increased arterial stiffness (AS) are both present in youth with type 1 diabetes. However, it is unclear whether they are associated and whether their association is independent of cardiovascular disease (CVD) risk factors.

RESEARCH DESIGN AND METHODS

The SEARCH Cardiovascular Disease (SEARCH CVD) study explored the cross-sectional relationships between HRV and several measures of AS in youth with (n = 344) and without (n = 171) type 1 diabetes. The SphygmoCor device (AtCor Medical, Sydney, Australia) was used to measure HRV using SD of normal R-R interval (SDNN), as well as AS, using pulse wave velocity in the carotid to femoral segment (PWV-trunk) and augmentation index adjusted to a heart rate of 75 bpm (AIx75). Brachial distensibility (BrachD), another index of AS, was measured with a DynaPulse instrument (Pulse Metric, San Diego, CA). Multiple linear regression analyses explored the associations between HRV and each of the three AS measures, after adjusting for demographic characteristics and traditional CVD risk factors (blood pressure, lipids, obesity, microalbuminuria, and smoking) separately, for youth with and without type 1 diabetes.

RESULTS

Among youth with type 1 diabetes, lower SDNN was associated with peripheral AS (lower BrachD, P = 0.01; r(2) = 0.30) and central AS (higher PVW-trunk, P < 0.0001; r(2) = 0.37; and higher AIx75, P = 0.007; r(2) = 0.08). These associations were attenuated with adjustment for CVD risk factors, but remained statistically significant for BrachD and PWV-trunk. While a similar association between HRV and BrachD was present in control youth, lower HRV was not associated with increased central AS or with AIx75.

CONCLUSIONS

Longitudinal studies are needed to understand the pathways responsible for these associations.

Reduced heart rate variability among youth with type 1 diabetes: the SEARCH CVD study

OBJECTIVE

This study compared heart rate variability (HRV) parameters in youth with and without type 1 diabetes and explored potential contributors of altered HRV.

RESEARCH DESIGN AND METHODS

HRV parameters were measured among 354 youth with type 1 diabetes (mean age 18.8 years, diabetes duration 9.8 years, and mean A1C 8.9%) and 176 youth without diabetes (mean age 19.2 years) participating in the SEARCH CVD study. Multiple linear regression was used to assess the relationship between diabetes status and HRV parameters, adjusting for covariates.

RESULTS

Compared with control subjects, youth with type 1 diabetes had reduced overall HRV (10.09 ms lower SD of NN intervals [SDNN]) and markers of parasympathetic loss (13.5 ms reduced root mean square successive difference of NN intervals [RMSSD] and 5.2 normalized units (n.u.) reduced high frequency [HF] power) with sympathetic override (5.2 n.u. increased low frequency [LF] power), independent of demographic, anthropometric, and traditional cardiovascular risk factors. Older age, female sex, higher LDL cholesterol and triglyceride levels, and presence of microalbuminuria were independently associated with lower HRV but did not account for the observed differences between youth with and without diabetes. Youth with type 1 diabetes and A1C levels ≥7.5% had significantly worse HRV parameters than control subjects; however, in youth with optimal glycemic control (A1C <7.5%), HRV parameters did not differ significantly from control subjects.

CONCLUSIONS

Youth with type 1 diabetes have signs of early cardiac autonomic neuropathy: reduced overall HRV and parasympathetic loss with sympathetic override. The main driver of these subclinical abnormalities appears to be hyperglycemia.

Deciphering the molecular and functional basis of Dbl family proteins: a novel systematic approach toward classification of selective activation of the Rho family proteins

The diffuse B-cell lymphoma (Dbl) family of the guanine nucleotide exchange factors is a direct activator of the Rho family proteins. The Rho family proteins are involved in almost every cellular process that ranges from fundamental (e.g. the establishment of cell polarity) to highly specialized processes (e.g. the contraction of vascular smooth muscle cells). Abnormal activation of the Rho proteins is known to play a crucial role in cancer, infectious and cognitive disorders, and cardiovascular diseases. However, the existence of 74 Dbl proteins and 25 Rho-related proteins in humans, which are largely uncharacterized, has led to increasing complexity in identifying specific upstream pathways. Thus, we comprehensively investigated sequence-structure-function-property relationships of 21 representatives of the Dbl protein family regarding their specificities and activities toward 12 Rho family proteins. The meta-analysis approach provides an unprecedented opportunity to broadly profile functional properties of Dbl family proteins, including catalytic efficiency, substrate selectivity, and signaling specificity. Our analysis has provided novel insights into the following: (i) understanding of the relative differences of various Rho protein members in nucleotide exchange; (ii) comparing and defining individual and overall guanine nucleotide exchange factor activities of a large representative set of the Dbl proteins toward 12 Rho proteins; (iii) grouping the Dbl family into functionally distinct categories based on both their catalytic efficiencies and their sequence-structural relationships; (iv) identifying conserved amino acids as fingerprints of the Dbl and Rho protein interaction; and (v) defining amino acid sequences conserved within, but not between, Dbl subfamilies. Therefore, the characteristics of such specificity-determining residues identified the regions or clusters conserved within the Dbl subfamilies.

Probing mechanisms that underlie human neurodegenerative diseases in Drosophila

The fruit fly, Drosophila melanogaster, is an excellent organism for the study of the genetic and molecular basis of metazoan development. Drosophila provides numerous tools and reagents to unravel the molecular and cellular functions of genes that cause human disease, and the past decade has witnessed a significant expansion of the study of neurodegenerative disease mechanisms in flies. Here we review the interplay between oxidative stress and neuronal toxicity. We cover some of the studies that show how proteasome degradation of protein aggregates, autophagy, mitophagy, and lysosomal function affect the quality control mechanisms required for neuronal survival. We discuss how forward genetic screens in flies have led to the isolation of a few loci that cause neurodegeneration, paving the way for large-scale systematic screens to identify such loci in flies as well as promoting gene discovery in humans.

Biochemical assays to characterize Rho GTPases

Rho GTPases act as tightly regulated molecular switches governing a large variety of critical cellular functions. Their activity is controlled by two different biochemical reactions, the GDP/GTP exchange and the GTP hydrolysis. These very slow reactions require catalysis in cells by two kinds of regulatory proteins. While the guanine nucleotide exchange factors (GEFs) activate small GTPases by stimulating the exchange of bound GDP for the cellular abundant GTP, GTPase-activating proteins (GAPs) accelerate the intrinsic rate of GTP hydrolysis by several orders of magnitude, leading to their inactivation. There are a number of methods that can be used to characterize the specificity and activity of such regulators to understand the effect of binding on the protein structure and, ultimately, to gain insights into their biological functions. This chapter describes (1) detailed protocols for the expression and purification of Rho GTPases, of -effector-binding domains, and catalytic domains of GEFs and GAPs; (2) the preparation of nucleotide-free and fluorescent nucleotide-bound Rho GTPases; and (3) methods for monitoring the intrinsic and GEF-catalyzed nucleotide exchange, the intrinsic and GAP-stimulated GTP hydrolysis, and the effector interaction with active GTPase (three alternative approaches).

Observation of long spin-relaxation times in bilayer graphene at room temperature

We report on the first systematic study of spin transport in bilayer graphene (BLG) as a function of mobility, minimum conductivity, charge density, and temperature. The spin-relaxation time τ(s) scales inversely with the mobility μ of BLG samples both at room temperature (RT) and at low temperature (LT). This indicates the importance of D'yakonov-Perel' spin scattering in BLG. Spin-relaxation times of up to 2 ns at RT are observed in samples with the lowest mobility. These times are an order of magnitude longer than any values previously reported for single-layer graphene (SLG). We discuss the role of intrinsic and extrinsic factors that could lead to the dominance of D'yakonov-Perel' spin scattering in BLG. In comparison to SLG, significant changes in the carrier density dependence of τ(s) are observed as a function of temperature.

Mechanistic insights into specificity, activity, and regulatory elements of the regulator of G-protein signaling (RGS)-containing Rho-specific guanine nucleotide exchange factors (GEFs) p115, PDZ-RhoGEF (PRG), and leukemia-associated RhoGEF (LARG)

The multimodular guanine nucleotide exchange factors (GEFs) of the Dbl family mostly share a tandem Dbl homology (DH) and pleckstrin homology (PH) domain organization. The function of these and other domains in the DH-mediated regulation of the GDP/GTP exchange reaction of the Rho proteins is the subject of intensive investigations. This comparative study presents detailed kinetic data on specificity, activity, and regulation of the catalytic DH domains of four GEFs, namely p115, p190, PDZ-RhoGEF (PRG), and leukemia-associated RhoGEF (LARG). We demonstrate that (i) these GEFs are specific guanine nucleotide exchange factors for the Rho isoforms (RhoA, RhoB, and RhoC) and inactive toward other members of the Rho family, including Rac1, Cdc42, and TC10. (ii) The DH domain of LARG exhibits the highest catalytic activity reported for a Dbl protein till now with a maximal acceleration of the nucleotide exchange by 10(7)-fold, which is at least as efficient as reported for GEFs specific for Ran or the bacterial toxin SopE. (iii) A novel regulatory region at the N terminus of the DH domain is involved in its association with GDP-bound RhoA monitored by a fluorescently labeled RhoA. (iv) The tandem PH domains of p115 and PRG efficiently contribute to the DH-mediated nucleotide exchange reaction. (v) In contrast to the isolated DH or DH-PH domains, a p115 fragment encompassing both the regulator of G-protein signaling and the DH domains revealed a significantly reduced GEF activity, supporting the proposed models of an intramolecular autoinhibitory mechanism for p115-like RhoGEFs.

The tumor suppressor protein DLC1 is regulated by PKD-mediated GAP domain phosphorylation

Deleted in liver cancer 1 (DLC1) is a tumor suppressor protein that is frequently downregulated in various tumor types. DLC1 contains a Rho GTPase activating protein (GAP) domain that appears to be required for its tumor suppressive functions. Little is known about the molecular mechanisms that regulate DLC1. By mass spectrometry we have mapped a novel phosphorylation site within the DLC1 GAP domain on serine 807. Using a phospho-S807-specific antibody, our results identify protein kinase D (PKD) to phosphorylate this site in DLC1 in intact cells. Although phosphorylation on serine 807 did not directly impact on in vitro GAP activity, a DLC1 serine-to-alanine exchange mutant inhibited colony formation more potently than the wild type protein. Our results thus show that PKD-mediated phosphorylation of DLC1 on serine 807 negatively regulates DLC1 cellular function.

Structure of N-acetylglucosamine-1-phosphate uridyltransferase (GlmU) from Mycobacterium tuberculosis in a cubic space group

The structure of M. tuberculosisN-acetylglucosamine-1-phosphate uridyltransferase (GlmU) was determined by the molecular-replacement method to 3.4 Å resolution in space group I432 and was refined to a final R_work and R_free of 0.285 and 0.321, respectively.

GlmU is a bifunctional enzyme that catalyzes the final two steps in the biosynthesis of UDP-GlcNAc. Crystals of GlmU from Mycobacterium tuberculosis obtained using ammonium sulfate as a precipitant diffracted poorly (to 3.4 Å resolution) and displayed an unusually high solvent content (>80%) with sparse crystal packing that resulted in large solvent channels. With one molecule per asymmetric unit, the monomers from three neighbouring asymmetric units related by the crystal threefold formed a biological trimer. Although this is the first report of the structure of GlmU determined in a cubic crystal form, the trimeric arrangement here is similar to that observed for other GlmU structures determined in hexagonal (H3, H32, P6₃22) space groups.

The mountain-lowland debate: deforestation and sediment transport in the upper Ganga catchment

The Himalaya-Gangetic Plain region is the iconic example of the debate about the impact on lowlands of upland land-use change. Some of the scientific aspects of this debate are revisited by using new techniques to examine the role of deforestation in erosion and river sediment transport. The approach is whole-of-catchment, combining a history of deforestation with a history of sediment sources from well before deforestation. It is shown that deforestation had some effect on one very large erosional event in 1970, in the Alaknanda subcatchment of the Upper Ganga catchment, but that both deforestation and its effects on erosion and sediment transport are far from uniform in the Himalaya. Large magnitude erosional events occur for purely natural reasons. The impact on the Gangetic Plain of erosion caused by natural events and land cover change remains uncertain.

Obstructed labour - a preventable entity

We present a clinical study of 204 cases of obstructed labour admitted over a period of 5 years between 1991-92 and 1996-97 in a rural institute in central India. They constituted 1.9% of births. Seventy-one per cent of the cases were from the rural area (similar to the overall patient population in this hospital), 31.4% women were primigravidae. Of the subjects, 64.7% were between 20 and 29 years. Malpresentation was the cause in 53.2%, followed by cephalopelvic disproportion, in 41.1%. Intraoperative incomplete rupture was detected in 5.9% cases. The commonest maternal morbidity was intraoperative extension of uterine incision at the time of caesarean section, mostly lateral (14.0%). Of the women, 12.5% had intrapartum or postpartum sepsis. The perinatal mortality was 160/1000. There was no maternal mortality. Timely diagnosis of malpresentation, pelvic contraction and use of a partogram at all levels could have prevented obstructed labour. In these unfortunate situations, judicious selection of subjects for caesarean section is appropriate, avoiding heroic vaginal procedures even with a dead baby. Infection devitalises tissues and attempts at vaginal delivery may be dangerous.

Nitric oxide in gastrointestinal epithelial cell carcinogenesis: linking inflammation to oncogenesis

Chronic inflammation of gastrointestinal tissues is a well-recognized risk factor for the development of epithelial cell-derived malignancies. Although the inflammatory mediators linking chronic inflammation to carcinogenesis are numerous, current information suggests that nitric oxide (NO) contributes to carcinogenesis during chronic inflammation. Inducible nitric oxide synthase (iNOS), expressed by both macrophages and epithelial cells during inflammation, generates the bioreactive molecule NO. In addition to causing DNA lesions, NO can directly interact with proteins by nitrosylation and nitosation reactions. The consequences of protein damage by NO appear to be procarcinogenic. For example, NO inhibits DNA repair enzymes such as human 8-oxodeoxyguanosine DNA glycosylase 1 and blocks apoptosis via nitrosylation of caspases. These cellular events permit DNA damage to accumulate, which is required for the numerous mutations necessary for development of invasive cancer. NO also promotes cancer progression by functioning as an angiogenesis factor. Strategies to inhibit NO generation during chronic inflammation or to scavenge reactive nitrogen species may prove useful in decreasing the risk of cancer development in chronic inflammatory gastrointestinal diseases.

Human Ogg1, a protein involved in the repair of 8-oxoguanine, is inhibited by nitric oxide

NO-mediated inhibition of base excision DNA repair may potentiate oxidativeDNA damage in cells and could be relevant to carcinogenesis associated with chronic inflammation. Because 8-oxoguanine, a ubiquitous oxidative DNA lesion, is repaired predominantly by human 8-oxoguanine glycosylase (hOgg1), our aim was to determine whether NO directly inhibits its repair activity. Neither induction of NO-generating enzyme inducible NO synthase nor treatment with S-nitroso-N-acetyl-D-L-pencillamine altered expression of hOgg1 in a human cholangiocarcinoma cell line (KMBC). In contrast, both treatments completely inhibited activity of hOgg1 immunoprecipitated from KMBC cells overexpressing hOgg1 and in a cell-free system. Both NO and peroxynitrite were capable of inhibiting hOgg1 activity. Inhibition of hOgg1 protein was characterized by formation of S-nitrosothiol adducts and loss/ejection of zinc ions. Our data indicate that NO, an inflammatory mediator, directly inhibits a key base excision repair enzyme (hOgg1) responsible for base excision repair of 8-oxoguanine. These data support the concept that NO-mediated inhibition of DNA contributes to the mutagenic environment of chronic inflammation.

Nitric oxide-mediated inhibition of DNA repair potentiates oxidative DNA damage in cholangiocytes

BACKGROUND & AIMS

Chronic inflammation, a risk factor for the development of bile duct cancer, induces inducible nitric oxide synthase (iNOS) with nitric oxide (NO) generation, which promotes oxidative damage of DNA, a process that probably is important in the initiation and progression of malignancies. Because inhibition of DNA repair is required for accumulation of oxidative DNA lesions, our aim was to determine if NO also inhibits repair of oxidative DNA damage.

METHODS

A cholangiocarcinoma cell line and a cholangiocyte cell line were transfected with iNOS.

RESULTS

Extracts from transfected but not untransfected cells were unable to repair 8-oxodeoxyguanine (8-oxodG); this effect was irreversible because addition of dithiothreitol to cell extracts had no effect. NO inhibition of 8-oxodG repair was blocked by NO scavengers but not by peroxynitrite scavengers or inhibitors of the soluble guanylyl cyclase/protein kinase G pathway. NO also potentiated hydrogen peroxide-induced DNA damage. Finally, immunohistochemistry in human liver samples uniformly demonstrated de novo expression of iNOS and the presence of 3-nitrotyrosine and 8-oxodG formation in the biliary epithelia of 30 patients with primary sclerosing cholangitis (a premalignant disease of the biliary tract) compared with controls.

CONCLUSIONS

Collectively, these data implicate NO-mediated inhibition of 8-oxodG base excision DNA repair processes as a mechanism potentiating DNA damage in human inflammatory diseases involving the biliary tract.

Inflammatory cytokines induce DNA damage and inhibit DNA repair in cholangiocarcinoma cells by a nitric oxide-dependent mechanism

Chronic infection and inflammation are risk factors for the development of cholangiocarcinoma, a highly malignant, generally fatal adenocarcinoma originating from biliary epithelia. However, the link between inflammation and carcinogenesis in these disorders is obscure. Because nitric oxide (NO) is generated in inflamed tissues by inducible nitric oxide synthase (iNOS) and because DNA repair proteins are potentially susceptible to NO-mediated nitrosylation, we formulated the hypothesis that inflammatory cytokines induce iNOS and sufficient NO to inhibit DNA repair enzymes leading to the development and progression of cholangiocarcinoma. iNOS and nitrotyrosine were demonstrated in 18/18 cholangiocarcinoma specimens. Furthermore, iNOS and NO generation could be induced in vitro by inflammatory cytokines (mixture of interleukin-1beta, IFN-gamma, and tumor necrosis factor alpha) in three human cholangiocarcinoma cell lines. NO-dependent DNA damage as assessed by the comet assay was demonstrated during exposure of the three cholangiocarcinoma cell lines to cytokines. Moreover, global DNA repair activity was inhibited by 70% by a NO-dependent process after exposure of cells to cytokines. Our data indicate that activation of iNOS and excess production of NO in response to inflammatory cytokines cause DNA damage and inhibit DNA repair proteins. NO inactivation of DNA repair enzymes may provide a link between inflammation and the initiation, promotion, and/or progression of cholangiocarcinoma.